KR20190011460A - Adhesive composition and adhesive sheet prepared from the same - Google Patents

Abstract

Examples of the present invention provide an adhesive composition, which contains: an acrylic compound; a benzophenone-based photoreactive monomer; and a photopolymerization initiator. The storage elastic modulus of the composition by primary photocuring for forming an adhesive sheet is 1 to 10 MPa at the temperature of 25°C and 0.05 to 0.5 MPa at the temperature of 70°C, and the storage elastic modulus thereof at the temperature of 25°C by secondary photocuring is 1.1 to 2 times the storage elastic modulus at the temperature of 25°C by the primary photocuring. The adhesive sheet having improved step filling properties and adhesive reliability can be prepared by using the adhesive composition.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a pressure-sensitive adhesive composition and a pressure-

The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet produced therefrom. More specifically, the present invention relates to a pressure-sensitive adhesive composition having photo-curability and a pressure-sensitive adhesive sheet produced therefrom.

For example, a pressure-sensitive adhesive or a pressure-sensitive adhesive sheet can be used to bond various optical structures or circuit structures with a display panel of an image display device such as a liquid crystal display (LCD) device, an organic light emitting display (OLED) It is necessary that the pressure-sensitive adhesive has improved transparency so as not to deteriorate the optical characteristics of the image display device and at the same time has excellent adhesive force.

In recent years, flexible displays capable of folding or bending have been actively researched, and accordingly, structures coupled to the flexible display are also designed to have appropriate elasticity and flexibility. Therefore, the pressure-sensitive adhesive or pressure-sensitive adhesive sheet used for bonding the structure needs to be formed so as to prevent the structure from falling off and peeling off in spite of bending and folding operations.

Further, the pressure-sensitive adhesive or pressure-sensitive adhesive sheet may be formed to sufficiently cover the steps included on the display panel, in which case it may be provided as a substantially planarizing layer. When the gap-fill characteristic of the pressure-sensitive adhesive or the pressure-sensitive adhesive sheet is insufficient, delamination and bubble generation may occur in the vicinity of the step.

For example, Korean Patent Laid-Open Publication No. 2010-0039274 discloses a pressure-sensitive adhesive for a polarizing plate which is applied to an image display device and has improved storage stability and coating properties. However, there is a limit in sufficiently securing the above-mentioned characteristics required in the flexible display through the conventional known pressure-sensitive adhesive.

Korean Patent Publication No. 2010-0039274

An object of the present invention is to provide a pressure-sensitive adhesive composition having improved adhesion and durability.

An object of the present invention is to provide a pressure-sensitive adhesive sheet having improved adhesion and durability.

An object of the present invention is to provide a laminate using the pressure-sensitive adhesive sheet or a method of manufacturing an image display device.

1. Acrylic compounds; Benzophenone-based photoreactive monomers; And a photopolymerization initiator, wherein a storage modulus at 25 ° C is 1 to 10 MPa due to primary photocuring for forming a pressure-sensitive adhesive sheet, a storage modulus at 70 ° C is 0.05 to 0.5 MPa, Wherein the storage elastic modulus at 25 DEG C is 1.1 to 2 times the storage elastic modulus at 25 DEG C due to the primary photocuring.

2. The pressure-sensitive adhesive composition according to 1 above, wherein the benzophenone-based photoreactive monomer contains a (meth) acrylate end group.

3. The pressure-sensitive adhesive composition according to 1 above, wherein the benzophenone-based photoreactive monomer comprises a compound represented by the following formula (1):

[Chemical Formula 1]

(Wherein R ₁ and R ₂ are independently selected from the group consisting of hydrogen, halogen, a hydroxyl group, an alkyl group having 1 to 30 carbon atoms, an alkylsilyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, Group, a heteroaryl group having 6 to 30 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a trifluoroalkyl group having 1 to 10 carbon atoms, an amino group substituted or unsubstituted with an alkyl group having 1 to 10 carbon atoms, a nitro group or a cyano group, R ₃ is hydrogen or an alkyl group having 1 to 30 carbon atoms, and L is a single bond or an alkylene group having 1 to 30 carbon atoms.

4. The acrylic pressure-sensitive adhesive composition of claim 1, wherein the acrylic compound is an alkyl (meth) acrylate monomer; Hydrophilic copolymerizable monomers; And an acrylic polymer formed from at least one selected from the group consisting of the alkyl (meth) acrylate and the hydrophilic copolymerizable monomer.

5. The pressure-sensitive adhesive composition according to 1 above, further comprising a thiol-based molecular weight modifier.

6. The pressure-sensitive adhesive composition according to 1 above, wherein the photopolymerization initiator comprises a compound generating free radicals by ultraviolet rays used in the primary photo-curing.

7. The pressure-sensitive adhesive composition according to 6 above, wherein said primary photo-curing irradiates light in the UVV band.

8. The pressure-sensitive adhesive composition according to 1 above, wherein the crosslinking reaction of the acrylic compound with the photopolymerization initiator is induced through the primary photocuring.

9. The pressure-sensitive adhesive composition according to 1 above, wherein the crosslinking reaction of the benzophenone-based photoreactive monomer is induced by the secondary photocuring.

10. The pressure-sensitive adhesive composition according to 1 above, wherein the primary light curing uses ultraviolet rays of wavelengths of 380 nm or more, and the secondary light curing uses ultraviolet rays of 370 nm or less.

11. A pressure-sensitive adhesive sheet produced from any one of the above 1 to 10 pressure-sensitive adhesive compositions.

12. A method comprising: preparing a first object on which a stepped pattern is formed; Attaching one side of the adhesive sheet along the top 11 to cover the step pattern on the first object; And performing a secondary photo-curing on the adhesive sheet.

13. The method of producing a laminate according to 12 above, wherein the first object comprises a window or a hard coating film of an image display apparatus.

14. The method of manufacturing a laminate according to 12 above, further comprising the step of attaching a second object on the other surface of the adhesive sheet.

15. The method of producing a laminate according to 14 above, wherein the second object comprises a display panel, a polarizing plate or a touch screen panel of an image display apparatus.

The pressure-sensitive adhesive composition according to the above-described embodiments of the present invention can be made into a pressure-sensitive adhesive sheet having a predetermined storage elastic modulus value at room temperature or high temperature through photo-curing. Accordingly, a tackiness and step- coverage property, and the adhesive property is maintained at room temperature or high temperature, and thus the reliability is excellent.

The laminate to which the pressure-sensitive adhesive composition or the pressure-sensitive adhesive sheet according to the exemplary embodiment is applied is improved in storage elasticity through additional secondary photo-curing after the primary photo-curing, thereby realizing a pressure-sensitive adhesive structure or laminate having improved peel resistance and high- .

The laminate to which the pressure-sensitive adhesive composition or the pressure-sensitive adhesive sheet according to the exemplary embodiment is applied has an excellent bending property and can be effectively applied to bonding various structures of the flexible display, for example, so that improved adhesive durability can be maintained even in an operation such as folding or bending .

The pressure-sensitive adhesive composition or pressure-sensitive adhesive sheet according to the exemplary embodiments can be applied on a target including a step or projection to prevent bubbling or floating, and to have excellent mechanical durability after curing.

Figs. 1 to 4 are sectional views for explaining a method of manufacturing a laminate according to exemplary embodiments. Fig.

According to embodiments of the present invention, the pressure-sensitive adhesive composition comprises an acrylic compound; Benzophenone-based photoreactive monomers; And a photopolymerization initiator. According to exemplary embodiments, the pressure-sensitive adhesive composition can be produced as a pressure-sensitive adhesive sheet having improved adhesion and durability by having a predetermined storage elastic modulus range at normal temperature or high temperature through photo-curing. According to exemplary embodiments, the pressure-sensitive adhesive sheet may be laminated on the object and then increased in storage elasticity through secondary light curing to be laminated with an additional layer or structure to improve durability.

Hereinafter, embodiments of the present invention will be described in detail.

≪ Pressure sensitive adhesive composition and pressure sensitive adhesive sheet &

The pressure-sensitive adhesive composition according to embodiments of the present invention includes an acrylic compound; Benzophenone-based photoreactive monomers; And a photopolymerization initiator.

The acrylic compound includes, for example, a polymer formed by including at least one selected from the group consisting of an alkyl (meth) acrylate monomer, a hydrophilic copolymerizable monomer and / or the alkyl (meth) acrylate monomer and the hydrophilic copolymerizable monomer .

The alkyl (meth) acrylate monomers may include, for example, alkyl (meth) acrylate monomers having 4 to 18 carbon atoms.

In some embodiments, non-limiting examples of the alkyl (meth) acrylate monomers having 4 to 18 carbon atoms include n-butyl (meth) acrylate, 2-butyl (meth) acrylate, (Meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, (Meth) acrylate, isobutyl (meth) acrylate, isodecyl (meth) acrylate, isobornyl acrylate, lauryl (meth) acrylate, cyclohexyl 2-methylbutyl (meth) acrylate, and the like. These may be used alone or in combination of two or more.

The alkyl (meth) acrylate monomer having 4 to 18 carbon atoms may be contained in an amount of about 75 to 98.5% by weight based on the total weight (100% by weight) of the monomers used in the pressure-sensitive adhesive composition. If the content of the alkyl (meth) acrylate monomer having 4 to 18 carbon atoms is less than about 75 wt%, it may be difficult to secure sufficient adhesion and durability. When the content exceeds about 98.5 wt%, a sufficient gap- Characteristic or step difference plugging property may not be ensured.

In some embodiments, the tackifier composition may comprise, for example, a hydrophilic copolymerizable monomer.

The hydrophilic copolymerizable monomer may form an acrylic copolymer with the alkyl (meth) acrylate monomer through, for example, primary photocuring. The cohesive force and the adhesive force of the composition are improved by the hydrophilic copolymerizable monomers, so that a pressure sensitive adhesive sheet having a predetermined physical property can be produced.

The hydrophilic copolymerizable monomer may contain, for example, a hydroxyl group, a carboxyl group and / or an amide group. Non-limiting examples of the hydrophilic copolymerizable monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (Meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropylene glycol (meth) acrylate, Itaconic acid, fumaric acid, (meth) acrylamide, N-isopropyl acrylamide, N-tert-butyl acrylamide and the like. These may be used alone or in combination of two or more.

In some embodiments, the hydrophilic copolymerizable monomer may be included in an amount of about 1 to 20% by weight of the total weight of monomers (100% by weight) used in the pressure-sensitive adhesive composition. If the content of the hydrophilic copolymerizable monomer is less than about 1% by weight, an acrylic copolymer having a sufficient molecular weight after the first photocuring is not formed, which may lower the durability of the adhesive sheet. If the content of the hydrophilic copolymerizable monomer exceeds about 20% by weight, peeling damage may occur at the time of peeling off the releasing film from the pressure-sensitive adhesive sheet, and a sufficient leveling plug or gap-fill property may not be secured.

The photopolymerization initiator can induce, for example, radical polymerization of the acrylic compound through the primary photocuring.

The photopolymerization initiator may include, for example, a compound capable of generating free radicals by ultraviolet (UV) irradiation and capable of selectively inducing polymerization of the acrylic compound. According to exemplary embodiments, the photopolymerization initiator may have selective activity for light above 380 nm wavelength. In one embodiment, the photopolymerization initiator may have selective activity for light in the UVV band, for example, light having a wavelength of 400 nm or more.

Non-limiting examples of the photopolymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, Dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 4- methoxyphenylacetophenone, dimethoxy-2-phenylacetophenone, 2-methyl-1-phenylpropan-1-one, 4-hydroxycyclophenyl ketone, 1-hydroxycyclohexyl phenyl ketone, 2 Methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, oligo [2-hydroxy- ) Propanone], 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4-diaminobenzophenone, '- diethylaminobenzophenone, dichlorobenzophenone, ant Quinone, 2-methyl anthraquinone, 2-ethyl anthraquinone, 2-t-butyl anthraquinone, 2-amino anthraquinone, , 4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethylketal, diphenylketone benzyldimethylketal, acetophenone dimethylketal, p-dimethylaminobenzoic acid ester, 2,4,6-trimethylbenzoyl di Phenyl phosphine oxide (TPO), fluorene, triphenylamine, carbazole, and the like. In addition, commercially available products such as Igacure 651, Igacure TPO, Igacure TPO-L (Basf), Darocur TPO, Darocur 1173, Igacure 184, Igracure 74, Igacure 819, Igacure 907, Igacure 1700 have. These may be used alone or in combination of two or more.

In some embodiments, in order to enhance the selective activity of the UVV band, 2,4,6-trimethylbenzoyldiphenylphosphine oxide and / or 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholino-propan-1-one can be used.

The photopolymerization initiator may be included in an amount of about 0.01 to 1% by weight based on the total weight of the composition. If the content of the photopolymerization initiator is less than about 0.01 wt%, the primary photo-curing rate may be lowered and the initial durability of the pressure-sensitive adhesive sheet may be deteriorated. When the content of the photopolymerization initiator is more than about 1% by weight, deterioration of the properties of the pressure-sensitive adhesive sheet due to the residual components after the primary photo-curing and deterioration of transparency due to yellowing may occur.

The benzophenone-based photoreactive monomer may be further crosslinked with the acrylic copolymer by secondary or further photocuring following the first photocuring, for example, to form mechanical properties of the adhesive sheet after adhesion of the object, The durability and the heat resistance can be improved at the same time without deterioration. The benzophenone-based photoreactive monomer is not reacted or excited by the primary photocuring and may be activated by the secondary photocuring to induce additional crosslinking.

The benzophenone based photoreactive monomer comprises a benzophenone group, and in some embodiments, the benzophenone based photoreactive monomer may contain a (meth) acrylate end group for further crosslinking.

According to exemplary embodiments, the benzophenone based photoreactive monomer may include a compound represented by the following formula (1).

[Chemical Formula 1]

Wherein R ₁ and R ₂ are independently selected from the group consisting of hydrogen, halogen, a hydroxyl group, an alkyl group having 1 to 30 carbon atoms, an alkylsilyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, Group, a heteroaryl group having 6 to 30 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a trifluoroalkyl group having 1 to 10 carbon atoms, an amino group substituted or unsubstituted with an alkyl group having 1 to 10 carbon atoms, a nitro group or a cyano group, R ₃ is hydrogen or an alkyl group having 1 to 30 carbon atoms, and L is a single bond or an alkylene group having 1 to 30 carbon atoms.

For example, the compound represented by Formula 1 may include a compound represented by Formula 1-1, Formula 1-2, and / or Formula 1-3.

[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

The benzophenone-based photoreactive monomer may be included in an amount of about 0.2 to 3% by weight based on the total weight of the monomers used in the pressure-sensitive adhesive composition. When the content of the benzophenone-based photoreactive monomer is less than about 0.2 wt%, the effect of improving the elasticity and durability due to the secondary photo-curing may not be realized. When the content of the benzophenone-based photoreactive monomer exceeds about 3% by weight, the adhesion of the pressure-sensitive adhesive sheet after the secondary photo-curing may be lowered.

According to exemplary embodiments, the pressure-sensitive adhesive composition may further include a thiol-based molecular weight modifier, and the thiol-based molecular weight modifier may promote initiation and initiation of chain growth upon radical polymerization of the acrylic compound, The degree of radical polymerization can be controlled and the molecular weight of the acrylic copolymer can be controlled.

The thiol-based molecular weight modifier may include at least one thiol group, and preferably at least two or more functional polyfunctional thiol-based molecular weight modifiers.

For example, the thiol-based molecular weight modifier may be selected from the group consisting of 2-ethylhexyl 3-mercaptopropionate, n-octyl 3-mercaptopropionate, methoxybutyl 3-mercaptopropionate, tetraethylene glycol bis Mercaptopropionate), trimethylolpropane tris (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptopropionate), tris [(3-mercaptopropionyloxy) ] -Isocyanurate, which may be used alone or in combination of two or more.

The pressure-sensitive adhesive composition according to exemplary embodiments may further include additional agents to the extent that the above-described photocuring properties are not deteriorated. For example, solvents, silane coupling agents, light stabilizers, antifoaming agents, fillers. Lubricants, surfactants, corrosion inhibitors, and the like may be appropriately included depending on the characteristics of the object.

According to exemplary embodiments, the pressure-sensitive adhesive composition may have a storage elastic modulus at 25 ° C of about 1 to 10 MPa and a storage elastic modulus at 70 ° C of about 0.05 to 0.5 MPa have.

For example, the storage elastic modulus at 25 DEG C is the room temperature storage modulus of the pressure-sensitive adhesive sheet or pressure-sensitive adhesive layer, and the storage elastic modulus at 70 DEG C may be defined by the high temperature storage modulus of the pressure-sensitive adhesive sheet or adhesive layer, It can be used as an index showing the adhesive property or the mechanical property.

As described above, free radicals are generated from the photopolymerization initiator by the first photocuring, and an acrylic copolymer can be produced in the pressure-sensitive adhesive composition by the crosslinking reaction of the acrylic compound. Thus, a pressure-sensitive adhesive sheet can be produced from the pressure-sensitive adhesive composition.

For example, by controlling the storage elastic modulus at 25 캜 of the pressure-sensitive adhesive sheet formed by the primary photo-curing to the above-mentioned range, the fluidity, the adhesive force and the elasticity at the time of applying or adhering to the object are improved together, have. Therefore, for example, even when the object includes a step or protrusion, peeling or lifting of the adhesive sheet can be prevented, so that an improved initial adhesive force can be secured. In addition, by controlling the storage elastic modulus at 70 캜 of the pressure-sensitive adhesive sheet formed by the primary photo-curing in the above-described range, it is possible to secure mechanical properties such as durability and heat resistance without excessively decreasing the adhesive force of the pressure-sensitive adhesive sheet.

According to exemplary embodiments, the storage modulus at 25 ° C due to secondary photocuring can be 1.1 to 2.0 times the storage modulus at 25 ° C due to the primary photocuring.

As described above, the benzophenone-based photoreactive monomer may be activated by the secondary photo-curing to induce further crosslinking with the acrylic copolymer. The storage elastic modulus of the pressure-sensitive adhesive sheet formed by the secondary photo-curing at 25 캜 is adjusted to the above-mentioned range, so that the mechanical durability can be further secured after the pressure-sensitive adhesive sheet having undergone the secondary photo-curing is adhered to the object In addition, the laminate formed through the pressure-sensitive adhesive sheet may have improved mechanical stability and bending stability under high temperature and high humidity conditions as well as at normal temperature conditions.

According to exemplary embodiments, an acrylic syrup may be prepared by mixing the above-mentioned acrylic compound and benzophenone-based photoreactive monomer. A photopolymerization initiator may be added to the acrylic syrup to form a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition is applied onto a release film to form a preliminary coating film, and the preliminary coating film is cured through primary light curing to produce a pressure-sensitive adhesive sheet.

In some embodiments, preliminary ultraviolet radiation may be further performed on the acrylic syrup prior to the primary photocuring. By the irradiation of the preliminary ultraviolet rays, the viscosity of the acrylic syrup is increased, and the ease of subsequent processing can be improved.

After the release film is peeled, the pressure-sensitive adhesive sheet may be adhered to the object and secondary light curing may be performed.

The primary photocuring and the secondary photocuring may each include ultraviolet irradiation at different wavelengths. In some embodiments, the ultraviolet light irradiation wavelength of the secondary light curing may be smaller than the ultraviolet light irradiation wavelength of the primary light curing.

In the exemplary embodiments, the primary photocuring may irradiate an ultraviolet ray having a wavelength of 380 nm or more, and the secondary photocuring may irradiate an ultraviolet ray having a wavelength of 370 nm or less. In some embodiments, ultraviolet light having a wavelength of about 400 nm or more is irradiated on the UV light as described above, and ultraviolet light having a wavelength of about 370 nm or less is irradiated on the secondary light curing You can investigate.

≪ Method for producing laminate >

Figs. 1 to 4 are schematic cross-sectional views for explaining a method of manufacturing a laminate according to exemplary embodiments. Fig.

Referring to FIG. 1, a first object 100 is prepared. The first object 100 may comprise, for example, a substrate, film or sheet of glass or plastic.

1, a step pattern 110 may be formed at an end of the upper surface of the first object 100.

In some embodiments, the first object 100 may be provided as a window film or a hard coating film of an image display apparatus. The stepped pattern 110 may be provided, for example, as a bezel of the image display device, a color pattern, a light shielding pattern, a decoration pattern, or the like.

Referring to FIG. 2, the adhesive sheet 120 may be attached to the upper surface of the first object 100.

According to exemplary embodiments, the adhesive sheet 120 formed from the above-described pressure-sensitive adhesive composition can be formed on the first object 100 so as to cover the step pattern 110. [ The adhesive sheet 120 may have a storage elastic modulus measured at 25 캜 through primary light curing of about 1 to 10 MPa and a storage elastic modulus measured at 70 캜 of about 0.05 to 0.5 MPa. As a result, the adhesive sheet 120 can be bonded onto the first object 100 without bubbling or lifting due to the improved leveling property and adhesive force.

In some embodiments, the adhesive sheet 120 may be pressed onto the first object 100 through an autoclave process to which a predetermined pressure is applied.

Referring to FIG. 3, secondary light curing can be performed on the adhesive sheet 120. FIG. The value of the storage modulus measured at 25 ° C of the adhesive sheet 120 through the secondary photocuring may be 1.1 to 2.0 times the storage modulus at 25 ° C due to the primary photocuring. Thus, the adhesion durability and reliability of the laminate can be improved through the secondary light curing.

Referring to FIG. 4, the second object 130 may be bonded to the upper surface side of the adhesive sheet 120. In some embodiments, the secondary photocuring may be performed after the attachment of the second object 130 as shown in FIG.

The second object 130 may include a display panel of the image display device. For example, the second object 130 may be a liquid crystal display (LCD) panel or an organic light emitting display (OLED) panel. The display panel may include a flexible resin substrate such as polyimide. In this case, the image display device may be provided as a flexible display.

As described above, the pressure-sensitive adhesive composition or the pressure-sensitive adhesive sheet may have excellent bending durability through physical properties change depending on the primary and secondary light curing. Therefore, the adhesive reliability in the laminate can be maintained even for repeated bending and folding operations for a long time.

In some embodiments, the second object 130 may include a structure coupled with an image display device, such as a polarizer, a touch sensor panel, or a touch sensor film.

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. It will be apparent to those skilled in the art that various changes and modifications can be made to the embodiments within the spirit and scope of the appended claims.

Examples and Comparative Examples

Example 1

45 parts by weight of ethylhexyl acrylate (EHA), 40 parts by weight of isobotyl acrylate (IBOA), 13 parts by weight of 2-hydroxyethyl acrylate (2-HEA) 2 parts by weight were mixed to prepare a monomer mixture. The monomer mixture was purged with nitrogen gas for 1 hour and maintained at 80 占 폚. The monomer mixture was added with 0.3 parts by weight of 1-hydroxy-cyclohexyl-phenylketone with a total weight of 100 parts by weight, and exposed to a UV lamp (10 mW) to give an acrylic syrup having a viscosity of about 2,000 cp.

Then, 0.5 part by weight of 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO) as a photopolymerization initiator and 2-ethylhexyl 3-mercaptopropionate (TMMP) as a molecular weight regulator were added to the acrylic syrup The preliminary coating film was formed on the release film after stirring and de-foaming to a thickness of 150 mu m. An additional releasing film was bonded onto the preliminary coating film and cured (primary light curing) with ultraviolet light of 380 nm or more (TL Lamp, UVV 0.5J) to produce a pressure-sensitive adhesive sheet.

Examples 2-6 and Comparative Examples 1-4

The pressure-sensitive adhesive sheets of Examples 2 to 6 and Comparative Examples 1 to 4 were prepared in substantially the same manner, except that the content of the monomers and the photopolymerization initiator was changed in Example 1 described above.

Experimental Example

1) Measurement of storage modulus

The storage elastic modulus was measured at 25 ° C and 70 ° C for the pressure-sensitive adhesive sheets of Examples and Comparative Examples. The value of the storage elastic modulus of the pressure-sensitive adhesive sheet was measured at 25 ° C and 70 ° C using a viscoelasticity measuring device (MCR-301, Anton Paar). More specifically, the adhesive layer sample size was 30 mm in length and 30 mm in width. After bonding the measurement sample to a glass plate, the adhesive was adhered to the measurement tip at a temperature of -30 to 100 캜 in a temperature range of 1.0 Hz, Temperature rise rate of 5 占 폚 / min, and reading the measured values at 25 占 폚 and 70 占 폚.

 The pressure-sensitive adhesive sheets of Examples and Comparative Examples were subjected to secondary light curing (365 nm wavelength, illuminance of 200 mW / cm 2), and then the storage modulus at 25 ° C was measured. The difference between the values was calculated. The results are shown in Tables 3 and 4 below.

2) Evaluation of the step filling

A stepped pattern having a width of 5 mm and a step height of 20 탆 was formed on a flat glass plate using printing ink

The release films on one side of the pressure-sensitive adhesive sheet of Examples and Comparative Examples were peeled off and attached to one surface of a 163 탆 m polarizing plate laminated with 250 탆 PET. The release film on the opposite side of the pressure-sensitive adhesive sheet was removed, and the exposed side of the pressure-sensitive adhesive sheet was attached to the surface of the glass plate on which the stepped pattern was formed.

Thereafter, the laminate was subjected to autoclave treatment (50 占 폚 for 30 minutes and 0.5 MPa), and then the laminate was irradiated under a light-convergence type high pressure mercury lamp (120 W / cm, (Wavelength: 365 nm, illumination: 200 mW / cm ² , cumulative light amount per one time: 500 mJ / cm ² ).

after. After standing at room temperature for 24 hours and at 85 ° C / 85% RH for 240 hours, the occurrence of bubbles in a stepped pattern was confirmed by an optical microscope (magnification: 100 times) and evaluated as follows.

Good: The adhesive sheet is bonded substantially without air bubbles.

B: Partial bubble generation around the stepped pattern

X: bubbles are distributed throughout the adhesive surface

3) Reliability evaluation after attachment of object including bend

One release film was peeled off from the pressure-sensitive adhesive sheet of Examples and Comparative Examples and attached to a PET film (cosmoshine A-4300, manufactured by Toyobo) having a thickness of 50 占 퐉 m. The release film on the opposite side of the pressure-sensitive adhesive sheet was peeled off, and the exposed surface of the pressure-sensitive adhesive sheet was adhered to a polycarbonate film (RASTA BANANA, manufactured by Panasonic ELUGA) having a curvature radius of 7 mm using a manual roller to prepare a laminate . The polycarbonate film of the laminate was irradiated with ultraviolet rays (secondary light curing) by passing the polycarbonate film upward four times at a conveyer speed of 5 m / min under a light-collecting type high-pressure mercury lamp (120 W / cm, one lamp, (Wavelength: 365 nm, illuminance: 200 mW / cm ² , cumulative light amount per one time: 500 mJ / cm ² ).

Thereafter, the film was allowed to stand at room temperature for 24 hours and 85 ° C / 85% RH (100 hours), or left at room temperature for 24 hours and 100 ° C. (100 hours) The results were evaluated.

○: No bubble and peeling occurred

B: Partial observation of bubbles or peeling in the vicinity of the bent portion

X: bubbles or peeling were distributed throughout the adhesive surface

4) Reliability evaluation after attaching display module with bent parts

One side of the pressure-sensitive adhesive sheet (first pressure-sensitive adhesive sheet) of Examples and Comparative Examples was attached to a touch screen panel sample (manufactured by Dongwoo Fine-Chem) including a COP substrate and an ITO electrode, The other side of the first adhesive sheet was attached through vacuum lamination to produce a first laminate. The first laminate was subjected to a first autoclave treatment at 0.5 MPa, 50 캜, and 20 minutes.

One side of the pressure sensitive adhesive sheet (second pressure sensitive adhesive sheet) of Examples and Comparative Examples was attached to a sample of a flexible display (OLED) panel through vacuum lamination to produce a second laminate.

The first laminate and the second laminate were joined by vacuum lamination, and subjected to a second autoclave treatment under conditions of 0.5 MPa, 50 DEG C, and 20 minutes. Thereafter, ultraviolet rays were irradiated (secondary light curing) by passing through the light-convergence type high pressure mercury lamp (120 W / cm, one lamp, lamp height 30 cm) at a conveyor speed of 5 m / min four times repeatedly (wavelength 365 nm, / cm < ² >, an integrated amount of light per one cycle of 500 mJ / cm < ² >).

The module thus prepared was allowed to stand at room temperature for 24 hours and 85 ° C / 85% RH (100 hours), or left at room temperature for 24 hours and 100 ° C. (100 hours) The results were evaluated as follows.

○: No bubble and peeling occurred

B: Partial observation of bubbles or peeling in the vicinity of the bent portion

X: bubbles or peeling were distributed throughout the adhesive surface

The evaluation results of the above-described experimental examples are shown in Tables 3 and 4 below.

Referring to Tables 3 and 4, in Examples 1 to 6 that satisfied the storage elastic modulus according to the above-described exemplary embodiments, excellent results were obtained in the step filling property and the reliability evaluation.

On the other hand, in the case of Comparative Example 1 in which UVV light and UVA light were irradiated together to cure the adhesive layer, the storage elastic modulus at 25 ° C due to secondary photo-curing was out of the scope of the present invention, And the storage modulus at 25 ℃ did not change after the second photocuring.

In the case of Comparative Example 2 in which the storage modulus at 25 占 폚 due to secondary photo-curing deviates from the range of the present invention, a large number of bubbles or peeling occurred in the laminate or module, and a deterioration in reliability evaluation appeared. In particular, since the photoreactive monomer (compound of Formula 1) was not included in Comparative Example 2, the storage elastic modulus at 25 ° C did not change after the secondary photocuring.

In the case of Comparative Example 3, the curing did not progress during the primary photo-curing, making it impossible to produce a sheet.

100: first object
110: step pattern
120: Pressure sensitive adhesive sheet
130: second object

Claims (15)

Acrylic compounds;
Benzophenone-based photoreactive monomers; And
A photopolymerization initiator,
A storage elastic modulus at 25 DEG C of 1 to 10 MPa and a storage modulus at 70 DEG C of 0.05 to 0.5 MPa due to primary curing for forming a pressure-
Wherein the storage elastic modulus at 25 DEG C due to the secondary photocuring is 1.1 to 2 times the storage elastic modulus at 25 DEG C due to the primary photocuring.
The pressure-sensitive adhesive composition according to claim 1, wherein the benzophenone-based photoreactive monomer contains a (meth) acrylate end group.
The pressure-sensitive adhesive composition according to claim 1, wherein the benzophenone-based photoreactive monomer comprises a compound represented by the following formula (1):
[Chemical Formula 1]

(Wherein R ₁ and R ₂ are independently selected from the group consisting of hydrogen, halogen, a hydroxyl group, an alkyl group having 1 to 30 carbon atoms, an alkylsilyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, Group, a heteroaryl group having 6 to 30 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a trifluoroalkyl group having 1 to 10 carbon atoms, an amino group substituted or unsubstituted with an alkyl group having 1 to 10 carbon atoms, a nitro group or a cyano group,
R ₃ is hydrogen or an alkyl group having 1 to 30 carbon atoms,
L is a single bond or an alkylene group having 1 to 30 carbon atoms).
[2] The method according to claim 1, wherein the acrylic compound is an alkyl (meth) acrylate monomer; Hydrophilic copolymerizable monomers; And an acrylic polymer formed from at least one selected from the group consisting of the alkyl (meth) acrylate and the hydrophilic copolymerizable monomer.
The pressure-sensitive adhesive composition according to claim 1, further comprising a thiol-based molecular weight modifier.
The pressure-sensitive adhesive composition according to claim 1, wherein the photopolymerization initiator comprises a compound generating free radicals by ultraviolet rays used in the primary photo-curing.
7. The pressure-sensitive adhesive composition according to claim 6, wherein the primary photocuring irradiates light in the UVV band.
The pressure-sensitive adhesive composition according to claim 1, wherein a cross-linking reaction of the acrylic compound is induced by the photopolymerization initiator through the primary photo-curing.
The pressure-sensitive adhesive composition according to claim 1, wherein the crosslinking reaction of the benzophenone-based photoreactive monomer is induced by the secondary light curing.
2. The method of claim 1, wherein the primary light curing uses ultraviolet light having a wavelength of 380 nm or more,
Wherein said secondary light curing utilizes ultraviolet light of 370 nm or less.
A pressure-sensitive adhesive sheet produced from the pressure-sensitive adhesive composition according to any one of claims 1 to 10.
Preparing a first object on which a stepped pattern is formed;
Attaching one surface of the adhesive sheet according to claim 11 to cover the step pattern on the first object; And
And performing a second photocuring on the adhesive sheet.
The method according to claim 12, wherein the first object comprises a window or a hard coating film of an image display apparatus.
The method according to claim 12, further comprising the step of attaching a second object on the other side of the adhesive sheet.
15. The method according to claim 14, wherein the second object comprises a display panel, a polarizing plate or a touch screen panel of an image display apparatus.

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