KR20190005427A - Adhesive composition and adhesive sheet prepared from the same - Google Patents

Abstract

Embodiments of the present invention comprise: alkyl methacrylate-based compounds; hydrophilic copolymerizable monomers; benzoyl group-containing photoreactive monomers, and photopolymerization initiators. Provided is an adhesive composition having a storage elastic modulus of 1 MPa or more at 25 deg. C after first photocuring for forming an adhesive sheet, and a tangent delta value at 100 deg. C after second photocuring reduced by at least 0.2 than that after the first photocuring. By using the adhesive composition, an adhesive sheet having improved gap filling ability and adhesion reliability can be produced.

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 to sufficiently securing the above-mentioned characteristics required in a flexible display through a 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. An alkyl (meth) acrylate-based compound; Hydrophilic copolymerizable monomers; A benzoyl group-containing photoreactive monomer; And a photopolymerization initiator,

Wherein the storage modulus at 25 ° C is 1 MPa or more after the first photocuring for forming the pressure sensitive adhesive sheet and the tangent delta value at 100 ° C after the second photocuring is decreased by 0.2 or more than the tentative delta value after the first photocuring. .

2. The pressure-sensitive adhesive composition according to 1 above, wherein the tentative delta value at 100 DEG C after the primary photocuring is 1.0 or more.

3. The pressure-sensitive adhesive composition according to 1 above, wherein the hydrophilic copolymerizable monomer contains at least one selected from the group consisting of a hydroxyl group, a carboxyl group and an amide group.

4. The pressure-sensitive adhesive composition according to 1 above, wherein the benzoyl group-containing photoreactive monomer contains an amide unit and an acrylate end group.

5. The pressure-sensitive adhesive composition according to 4 above, wherein the benzoyl group-containing photoreactive monomer comprises a compound represented by the following formula (1):

[Chemical Formula 1]

.

.

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 the crosslinking reaction between the alkyl (meth) acrylate ester compound and the hydrophilic copolymerizable monomer by the photopolymerization initiator is induced through the primary photocuring.

8. The pressure-sensitive adhesive composition according to 1 above, wherein the crosslinking reaction of the benzoyl group-containing photoreactive monomer is induced by the secondary photo-curing.

9. The pressure-sensitive adhesive composition according to 1 above, wherein said primary light curing is irradiated with ultraviolet light having a wavelength of 380 nm or more, and said secondary light curing is irradiated with ultraviolet light having a wavelength of 370 nm or less.

10. A pressure-sensitive adhesive sheet produced from the pressure-sensitive adhesive composition according to any one of the above 1 to 9.

11. preparing a first object having a stepped pattern formed thereon; Attaching one surface of the pressure sensitive adhesive sheet according to claim 10 to cover the step pattern on the first object; And performing a secondary photo-curing on the adhesive sheet.

12. The method of producing a laminate according to 11 above, wherein the first object comprises a window or a hard coating film of an image display apparatus.

13. The method of manufacturing a laminate according to 11 above, further comprising the step of attaching a second object on the other surface of the adhesive sheet.

14. The method of producing a laminate according to 13 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 manufactured as a pressure sensitive adhesive sheet having a predetermined tangent delta value through primary light curing, thereby achieving tackiness and step-coverage characteristics Can be improved. Also, the adhesive sheet may have a tacky structure or a laminate having improved tear resistance and high temperature durability due to tangent delta value dropping by a predetermined amount or more through second light curing after being attached to a target object.

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

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 may include an alkyl (meth) acrylate ester compound, a hydrophilic copolymerizable monomer, a benzoyl group-containing photoreactive monomer, and a photopolymerization initiator. According to exemplary embodiments, the pressure-sensitive adhesive composition may be made of a pressure-sensitive adhesive sheet having a predetermined storage elastic modulus and a tangent delta range through primary light curing. According to exemplary embodiments, the adhesive sheet can be manufactured with a laminate having a tangent delta value reduced through secondary photocuring after being adhered on a target object, and lined 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 may include an alkyl (meth) acrylate ester compound, a hydrophilic copolymerizable monomer, a benzoyl group-containing photoreactive monomer, and a photopolymerization initiator.

The alkyl (meth) acrylate ester-based compound may include, for example, an alkyl (meth) acrylate monomer or a polymer formed therefrom.

In some embodiments, alkyl (meth) acrylate monomers having from 4 to 18 carbon atoms may be used. Nonlimiting examples of the alkyl (meth) acrylate monomers having 4 to 18 carbon atoms include n-butyl (meth) acrylate, 2-butyl (meth) acrylate, (Meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, decyl (Meth) acrylate, cyclohexyl (meth) acrylate, phenylmethacrylate, benzylmethacrylate, isostearyl acrylate, 2-methylbutyl (meth) acrylate, 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 80 to 95% 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 80% by weight, it may be difficult to secure sufficient adhesion and durability, and when the content exceeds about 95% by weight, sufficient gap- Characteristic or step difference plugging property may not be ensured.

The hydrophilic copolymerizable monomer may form an acrylic copolymer with the alkyl (meth) acrylate ester compound through primary photocuring, for example. 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 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 may, for example, induce radical polymerization between the alkyl (meth) acrylate ester compound and the hydrophilic copolymerizable monomer via the primary photocuring.

The photopolymerization initiator may be, for example, a compound capable of generating free radicals by ultraviolet (UV) irradiation and capable of selectively inducing a reaction between the alkyl (meth) acrylate ester compound and the hydrophilic copolymerizable monomer .

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. Further, commercially available products such as Darocur 1173, Igacure 184, Igacure 907 and Igacure 1700 (manufactured by Ciba) can also be used. These may be used alone or in combination of two or more.

The photopolymerization initiator may be included in an amount of about 0.1 to 5% by weight based on the total weight of the composition. If the content of the photopolymerization initiator is less than about 0.1% by weight, the primary photo-curing rate may be lowered and the initial durability of the adhesive sheet may be lowered. When the content of the photopolymerization initiator is more than about 5% 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 benzoyl group-containing photoreactive monomer is further crosslinked with the acrylic copolymer by secondary photopolymerization, for example, to form the mechanical properties of the adhesive sheet after adhesion of the object. The benzoyl group-containing photoreactive monomer is not reacted or excited by the primary photocuring and can be activated by the secondary photocuring to induce additional crosslinking.

In some embodiments, the benzoyl group containing photoreactive monomer may contain a hydrophilic unit and an acrylate end group. In one embodiment, the hydrophilic unit may comprise an amide unit.

According to exemplary embodiments, the benzoyl group-containing photoreactive monomer may include a compound represented by the following formula (1).

[Chemical Formula 1]

The benzoyl group-containing photoreactive monomer may be formed through reaction of an isocyanate group and an acrylate group-containing compound with a benzoyl group and a carboxyl group-containing compound.

For example, the compound of formula (1) can be prepared by the following reaction formula (1).

[Reaction Scheme 1]

The benzoyl group-containing photoreactive monomer may be contained in an amount of about 1 to 5% by weight based on the total weight of the monomers used in the pressure-sensitive adhesive composition. When the content of the benzoyl group-containing photoreactive monomer is less than about 1% by weight, the effect of improving the elasticity and durability due to the secondary photo-curing may not be realized. When the content of the benzoyl group-containing photoreactive monomer exceeds about 5% by weight, the adhesion of the pressure-sensitive adhesive sheet after the secondary photo-curing may be lowered.

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 modulus of at least 1 MPa measured at 25 ^o C after the primary photocuring, and a tangent delta value measured at 100 ^o C of at least about 1.0.

The term " tangent delta " as used in the present application is utilized as an index indicating the stickiness or stickiness of the adhesive layer or the pressure-sensitive adhesive sheet and can be calculated as " loss modulus / storage modulus ". As described above, free radicals are generated from the photopolymerization initiator by the primary photo-curing and crosslinking reaction between the alkyl (meth) acrylate ester compound and the hydrophilic copolymerizable monomer causes the acrylic copolymer to react with the pressure- Lt; / RTI > Thus, a pressure-sensitive adhesive sheet can be produced from the pressure-sensitive adhesive composition.

By adjusting the storage elastic modulus and tangent delta value of the pressure sensitive adhesive sheet by the primary photo-curing to the above-mentioned range, fluidity, adhesive force and elasticity can be improved together with application or adhesion to the object, and bubble discharge can be promoted. 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.

The tacky delta value of the pressure-sensitive adhesive composition or the pressure-sensitive adhesive sheet measured at 100 ^° C after the secondary photo-curing may be reduced as compared to the primary curing. According to exemplary embodiments, the difference between the tantalum delta value after the first light curing and the tantalum delta value after the second light curing can be about 0.2 or more.

As described above, the benzoyl group-containing photoreactive monomer may be activated by the secondary photo-curing to induce further crosslinking with the acrylic copolymer. Therefore, mechanical durability can be ensured after the adhesive sheet is attached to the object, and mechanical stability and bending stability in the high-temperature and high-humidity structure of the laminate formed through the adhesive sheet can be improved.

According to exemplary embodiments, an acrylic syrup may be prepared by mixing the alkyl (meth) acrylate ester compound, the hydrophilic copolymerizable monomer, and the benzoyl group-containing photoreactive monomer described above. 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 one embodiment, ultraviolet light of about 380 nm or more is used for the primary light curing, and ultraviolet light of about 370 nm or less may be used for the secondary light curing.

< Of the laminate  Manufacturing method>

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 of 1 MPa or more and a tangent delta value of about 1.0 or more as measured at 25 ^o C through primary photocuring. 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 tangent delta value measured at 100 ^° C of the adhesive sheet 120 through the secondary photo-curing can be reduced by about 0.2 or more as compared with the primary photo-curing. 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.

Example  And Comparative Example

Example  One

50 parts by weight of isodecylmethacrylate (IDMA), 40 parts by weight of isobornyl acrylate (IBOA), 10 parts by weight of 2-hydroxyethyl acrylate (2-HEA) And 2 parts by weight of the benzoyl-containing photoreactive monomer shown in Table 1 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 2,2-dimethoxy-2-phenylacetophenone as a photopolymerization initiator was added to the acrylic syrup, and the mixture was coated on the release film after stirring and deaeration to a thickness of 150 mu m to form a precoat film. 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.

Example  2-6, Comparative Example  1-3

The pressure-sensitive adhesive sheets of Examples 2 to 6 and Comparative Examples 1 to 3 were prepared in substantially the same manner, except that the contents of the monomers and the photopolymerization initiator were changed in Example 1 described above.

division Example Comparative Example One 2 3 4 5 6 One 2 3 acryl
syrup
(weight%) IDMA 50 - - - - - 65 - 50 EHA - 48 35 35 35 35 35 - EHMA - - 15 15 15 15 15 - IBOA 38 40 38 38 39 36 23 39.8 40 2-HEA 10 10 10 10 10 10 10 10 10 Formula 1 2 2 2 2 One 4 2 0.2 - Photopolymerization
Initiator
(weight%) 2,2-dimethoxy-
2-phenylacetophenone 0.5 0.5 0.5 - - - 0.5 - 0.5 TPO - - - 0.5 0.5 0.5 - 0.5 - EHA: Ethylhexyl acrylate
EHMA: Ethylhexyl methacrylate
TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide

Experimental Example

1) Measurement of storage modulus and tangent delta (tan δ)

The pressure-sensitive adhesive sheets of Examples and Comparative Examples were measured for storage elastic modulus at 25 캜 and tangent delta values at 100 캜. The storage modulus and tangent delta of the pressure-sensitive adhesive sheet were measured at 25 ° C and 100 ° C using a viscoelasticity measuring device (MCR-301, Anton Paar). Specifically, the adhesive layer sample size was 30 mm in length and 30 mm in width. After bonding the measurement specimen to the glass plate, the adhesive was adhered to the measurement tip. The temperature was -30 to 100 캜, , A temperature raising rate of 5 占 폚 / min, and reading the measured values at 25 占 폚 and 100 占 폚.

Secondary photosetting (365 nm wavelength, illuminance of 200 mW / cm ² ) was performed on the pressure sensitive adhesive sheets of Examples and Comparative Examples, and then tangent delta value at 100 ° C was measured. After primary light curing, The measured values and differences were calculated. The results are shown in Table 2 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 ).

After standing at room temperature for 24 hours and 85 ° C / 85% RH (100 hours), the change in appearance of the laminate was observed, and 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

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 &lt; ² &gt;, an integrated amount of light per one cycle of 500 mJ / cm &lt; ² &gt;).

The fabricated module was allowed to stand at room temperature for 24 hours and 85 ° C / 85% RH (100 hours), and then the appearance change of the module was confirmed, and the result was 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 Table 2 below.

Example Comparative Example One 2 3 4 5 6 One 2 3 After the first photocuring
Storage elasticity (25 ℃)
(MPa) 2.1 1.8 2.3 2.2 2.1 1.7 0.7 1.7 1.8 After primary curing, tan? (100 占 폚) 0.75 0.72 0.80 0.78 0.74 0.79 0.6 0.62 0.58 After secondary curing, tan?
(100 DEG C) 0.42 0.45 0.50 0.41 0.52 0.38 0.39 0.63 0.58 tanδ difference
(100 DEG C) 0.33 0.27 0.30 0.37 0.22 0.41 0.21 0.1 0 Step filling property ○ ○ ○ ○ ○ ○ △ △ × Flexible object reliability ○ ○ ○ ○ ○ ○ △ × × Flexible Display Module Reliability ○ ○ ○ ○ ○ ○ △ × ×

Referring to Table 2, in Examples 1 to 6 satisfying the storage elastic modulus and tangent delta value according to the above-described exemplary embodiments, excellent results were obtained in the step filling property and the reliability evaluation.

On the other hand, Comparative Example 1 in which the storage elastic modulus after the first photocuring was less than 1 Mpa showed reduced step filling property and reliability compared to the embodiments. In the case of Comparative Example 2 and Comparative Example 3 in which the tangent delta value was not sufficiently decreased after the secondary light curing, a large number of bubbles or peeling occurred in the laminate or module, and a deterioration reliability evaluation appeared. In particular, in Comparative Example 3, since the benzoyl group-containing photoreactive monomer (compound of Formula 1) was not included, the tangent delta value did not change even after the secondary light curing.

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

Claims (14)

Alkyl (meth) acrylate compounds;
Hydrophilic copolymerizable monomers;
A benzoyl group-containing photoreactive monomer; And
A photopolymerization initiator,
Wherein the storage modulus at 25 ° C is 1 MPa or more after the first photocuring for forming the pressure sensitive adhesive sheet and the tangent delta value at 100 ° C after the second photocuring is decreased by 0.2 or more than the tentative delta value after the first photocuring. .
2. The pressure-sensitive adhesive composition of claim 1, wherein the tentative delta value at 100 DEG C after the primary photocuring is at least 1.0.
The pressure-sensitive adhesive composition according to claim 1, wherein the hydrophilic copolymerizable monomer contains at least one selected from the group consisting of a hydroxyl group, a carboxyl group and an amide group.
The pressure-sensitive adhesive composition according to claim 1, wherein the benzoyl group-containing photoreactive monomer contains an amide unit and an acrylate end group.
The pressure-sensitive adhesive composition according to claim 4, wherein the benzoyl group-containing photoreactive monomer comprises a compound represented by the following formula (1):
[Chemical Formula 1]

.
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.
The pressure-sensitive adhesive composition according to claim 6, wherein a cross-linking reaction between the alkyl (meth) acrylate ester compound and the hydrophilic copolymerizable monomer 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 benzoyl group-containing photoreactive monomer is induced by the secondary photocuring.
The pressure-sensitive adhesive composition according to claim 1, wherein the primary photocuring irradiates ultraviolet rays having a wavelength of 380 nm or more, and the secondary photocuring is irradiating ultraviolet rays having a wavelength 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 9.
Preparing a first object on which a stepped pattern is formed;
Attaching one surface of the pressure sensitive adhesive sheet according to claim 10 to cover the step pattern on the first object; And
And performing a second photocuring on the adhesive sheet.
12. The method according to claim 11, wherein the first object comprises a window or a hard coating film of an image display apparatus.
12. The method according to claim 11, further comprising the step of attaching a second object on the other side of the adhesive sheet.
14. The method according to claim 13, 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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