KR101924411B1 - Adhesive multi-layer film for Optical film of Display - Google Patents

Abstract

The present invention relates to a multilayer adhesive film comprising an uppermost layer adhesive; Intermediate layer adhesive; And a lowermost pressure-sensitive adhesive. The multi-layered pressure-sensitive adhesive film may be applied to a curved substrate by adjusting the thickness of the uppermost pressure-sensitive adhesive and the lowermost pressure-sensitive adhesive to a certain ratio or less and adjusting the storage elastic modulus of the multi-layer pressure- By having excellent flexibility in the conditions, there is no occurrence of cracks. Also disclosed is a multilayer pressure-sensitive adhesive film having an adhesive strength retention of 70% or more at a temperature change and having improved adhesion even at a high temperature.

Description

[0001] The present invention relates to a multi-layer adhesive film for an optical film,

More particularly, the present invention relates to a multi-layered pressure-sensitive adhesive film for an optical film, and more particularly, to a multi-layer pressure-sensitive adhesive film for optical films, which is excellent in flexibility when applied to a curved base material and thus has no cracking, has little change in viscoelasticity at various temperatures, To a multilayer adhesive film for a film.

Future displays, especially mobile displays, are expected to evolve into flexible displays that are thinner, lighter, and consume less energy as information becomes more widespread, popularized, and popularized. Such a display may include a polarizer, a retarder, and other functional layers of a sheet material. These are attached to the adhesive agent inside the device via a pressure-sensitive adhesive, and can be manufactured in various forms such as warping or folding.

In the case of an adhesive film used in a conventional flat panel display, there is almost no deformation due to an external force, but in the case of an adhesive film applied to a flexible display, stress is generated by external bending or bending. In this case, it is difficult for the pressure-sensitive adhesive to be deformed into a curved surface due to the viscoelasticity of the pressure-sensitive adhesive itself, and there arises a problem that it can not be applied to a flexible display because stress is transmitted to the display or external stress is exerted.

Therefore, there is an urgent need to develop a pressure-sensitive adhesive that can be used as a flexible and flexible display due to a small change in viscoelasticity at various temperatures and a low flexibility in display processing or in a condition requiring flexibility during operation.

An object of the present invention is to provide a multilayer adhesive film for an optical film having excellent flexibility at the time of application to a curved substrate or under conditions requiring flexibility during display processing or operation so that cracks are not generated and adhesion at high temperature is excellent.

It is still another object of the present invention to provide a pressure-sensitive adhesive composition for the pressure-sensitive adhesive film.

The multilayered pressure-sensitive adhesive film for an optical film of the present invention is an uppermost pressure-sensitive adhesive; Intermediate layer adhesive; Wherein the thickness of the uppermost adhesive layer or the lowermost layer adhesive is 15% or less of the total thickness of the adhesive film, and the adhesive force retention ratio expressed by the following [formula 1] is 70% or more.

[Formula 1]

? F (%) = F _f / F _o * 100

(F _o is the initial cohesive force measured at room temperature for any substrate film, F _f is the cohesive force measured after being left in a thermo-hygrostat at 85 ° C and 85% RH for 120 hours)

The storage elastic modulus of the multilayered pressure-sensitive adhesive film and the storage modulus ratio of the intermediate pressure-sensitive adhesive satisfy the following formula (2).

[Formula 2]

G?? 2.5

(G'_m / G'_s, G'_m is the storage elastic modulus of the multi-layered pressure-sensitive adhesive film at -20 ° C, G'_s is the storage elastic modulus of the intermediate pressure-

The multi-layered pressure-sensitive adhesive film has an initial adhesive strength of 85 g / 85% RH and an adhesive strength of at least 700 gf / in after 120 hours.

Wherein the acrylic resin comprises 80 to 99.9 parts by weight of a (meth) acrylic acid ester monomer and 0.1 to 20 parts by weight of a crosslinkable monomer, wherein the acrylic resin has a Tg of -20 DEG C to 10 DEG C, And the like.

The interlayer pressure sensitive adhesive may comprise one or more MQ resins [A]; At least one organosiloxane polymer [B] having a vinyl functional group; At least one organohydrogensilicon compound [C]; And an addition curable silicone pressure sensitive adhesive (PSA) resin comprising a hydrosilylation catalyst [D].

And the thickness of the multilayered adhesive film is 20 to 100 占 퐉.

The multilayered adhesive film has a storage elastic modulus at -20 캜 of 200 kPa or less and a storage elastic modulus at 80 캜 of 10 kPa or more.

Wherein the uppermost layer adhesive and the lowermost layer adhesive have a storage elastic modulus at -20 캜 of 10 MPa or more.

The intermediate layer pressure-sensitive adhesive has a storage elastic modulus at -20 캜 of 100 kPa or less and a storage elastic modulus at 80 캜 of 10 kPa or more.

INDUSTRIAL APPLICABILITY The multilayered adhesive film for an optical film of the present invention has excellent flexibility in application to a curved substrate or in a condition requiring flexibility during display processing or operation so that cracks are not generated and the change of viscoelasticity is small in various temperature ranges, Is excellent.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view showing the overall constitution of a multilayer adhesive film for an optical film. Fig.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a multilayer adhesive film for an optical film of the present invention will be described with reference to the accompanying drawings. 1 is a schematic cross-sectional view showing a configuration of a multilayer adhesive film 100 according to an embodiment of the present invention. 1, the multi-layer adhesive film 100 according to the present invention comprises an uppermost adhesive 110, a lowermost adhesive 130, and an intermediate adhesive 120 formed between the uppermost adhesive 110 and the lowermost adhesive 130 do.

The multilayered adhesive film 100 has a storage elastic modulus at -20 캜 of 200 kPa or less and a value of 10 kPa or more at 80 캜. When the storage elastic modulus at -20 ° C exceeds 200 kPa, cracks or bubbles are generated when folding and bending are repeated due to excessive storage elasticity, and when the storage elastic modulus at 80 ° C does not reach 10 kPa, So that the dimension can not be stabilized and can be removed from the interface at the time of repeated folding. The multi-layered adhesive film (100) has fluidity in the range of -20 캜 to 80 캜 and has excellent adhesion at high temperature.

The thickness of the multilayered adhesive film 100 is 20 to 100 탆. When the thickness of the multilayered adhesive film 100 is less than 20 占 퐉, when the adhesive film 100 is applied to a flexible display formed by stacking several films, the adhesive force is insufficient and the stress between the films is not buffered, . If the thickness of the multilayer adhesive film 100 is more than 100 mu m, the thickness of the flexible display becomes excessively thick, which may limit the thinning of the display.

The initial adhesion of the multilayered adhesive film 100 and the adhesive strength of the prepared sample after being left in a thermo-hygrostat at 85 ° C and 85% RH for 120 hours is 700 gf / in or more, and the adhesive force maintenance rate ΔF expressed by the following formula 1 is 70% or more. When the adhesive force is less than 700 gf / in, it is composed of a multilayer film, and interlayer adhesion of the flexible display which is folded or bent can not be maintained. When the adhesive force maintenance ratio? F is less than 70%, the interlaminar adhesion in the reliability is lowered, which may lead to a failure in delamination.

[Formula 1]

? F (%) = F _f / F _o * 100

(F _o is the initial cohesive force measured at room temperature for any substrate film, F _f is the cohesive force measured after being left in a thermo-hygrostat at 85 ° C and 85% RH for 120 hours)

1. The uppermost adhesive layer 110 and the lowermost adhesive layer 130

The thicknesses of the uppermost adhesive layer 110 and the lowermost adhesive layer 130 are 15% or less, preferably 5 to 12%, of the thickness of the multilayered adhesive film 100, respectively. When the thickness of the uppermost adhesive layer 110 or the lowermost layer adhesive 130 exceeds 15% of the total thickness of the multilayered adhesive film 100, flexibility is reduced and cracks are generated when applied to a curved substrate.

If the storage elastic modulus of the uppermost adhesive layer 110 and the lowermost layer adhesive 130 is less than 10 MPa at -20 캜, the rigidity of the uppermost pressure-sensitive adhesive layer and the lowermost pressure- Adhesion can not be maintained.

Further, the pressure-sensitive adhesive top layer 110 and bottom layer pressure-sensitive adhesive 130 is formed by curing the composition of the glass transition temperature (T _g) that contains an acrylic resin in a range from -20 ℃ 10 ℃. If the glass transition temperature of the acrylic resin is less than -20 占 폚, the storage elastic modulus of 10 MPa can not be induced and becomes soft. If the glass transition temperature is more than 10 占 폚, the flexibility of the adhesive film is lowered.

The specific composition of the acrylic resin is not particularly limited. For example, in the present invention, the acrylic resin may be a polymer of a monomer mixture comprising 75 parts by weight to 99.9 parts by weight of a (meth) acrylic acid ester monomer and 0.1 to 25 parts by weight of a crosslinkable monomer.

The kind of the (meth) acrylic acid ester monomer contained in the monomer mixture in the present invention is not particularly limited and may be, for example, alkyl (meth) acrylate. In this case, if the alkyl group contained in the alkyl (meth) acrylate is excessively long, the cohesive force of the pressure-sensitive adhesive is lowered and the glass transition temperature (Tg) or tackiness may be difficult to control. (Meth) acrylate is preferably used. Examples of such monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n- (Meth) acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl Acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate and tetradecyl (meth) acrylate. In the present invention, .

The monomer mixture of the present invention may contain the above (meth) acrylic acid ester monomer in an amount of 75 parts by weight to 99.9 parts by weight. If the content is less than 75 parts by weight, the initial adhesive strength of the pressure-sensitive adhesive may be lowered. If the content is more than 99.9 parts by weight, a problem of durability may occur due to a decrease in cohesive strength.

The crosslinkable monomer contained in the monomer mixture of the present invention is a monomer capable of imparting a crosslinkable functional group capable of reacting with a crosslinking agent component to be described later to the acrylic resin and plays a role of controlling the durability, adhesion and cohesion of the pressure- .

Examples of the crosslinkable monomer that can be used in the present invention include, but are not limited to, a hydroxy group-containing monomer, a carboxyl group-containing monomer, and a nitrogen-containing monomer. Specific examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (Meth) acrylate, 2-hydroxyethyleneglycol (meth) acrylate or 2-hydroxypropyleneglycol (meth) acrylate, and examples of the carboxyl group- (Meth) acryloyloxypropionic acid, 4- (meth) acryloyloxybutyric acid, acrylic acid dimer, itaconic acid, maleic acid (meth) acrylate, And maleic anhydride. Examples of the nitrogen-containing monomer include (meth) acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, and the like, but are not limited thereto. In the present invention, one or more of the above compounds may be used in combination.

The crosslinkable monomer in the monomer mixture of the present invention is preferably contained in an amount of 0.1 to 25 parts by weight. If the content is less than 0.1 parts by weight, the endurance reliability of the pressure-sensitive adhesive may be deteriorated. If the content exceeds 25 parts by weight, the cross-linking reaction may excessively proceed and the tackiness and / or peelability may be deteriorated.

The pressure-sensitive adhesive composition of the present invention comprises a crosslinking agent component capable of reacting with the above acrylic resin to form a crosslinked structure. In the present invention, as the crosslinking agent component, a crosslinking agent component comprising a bifunctional crosslinking agent is used. As used herein, the term " crosslinking agent component comprising a bifunctional crosslinking agent " means a case where the crosslinking agent component contains only a bifunctional crosslinking agent, and the use of other polyfunctional crosslinking agent, that is, . That is, the meaning of the term does not include not only the case where the crosslinking agent component is a mixture of a trifunctional or higher crosslinking agent but also the case where the crosslinking agent is a mixture of a bifunctional crosslinking agent and a trifunctional or higher crosslinking agent. However, as long as the cross-linking agent component contains only the bifunctional cross-linking agent, it is not necessarily limited to the use of one kind of cross-linking agent but may also include the use of a mixture of two or more cross-linking agents.

The specific type of crosslinking agent that can be used in the present invention is not particularly limited as long as it has bifunctionality and examples thereof include isocyanate compound, epoxy compound, aziridine compound, melamine compound, urea compound, dialdehyde compound, A general crosslinking agent such as a methylol polymer compound, a metal alkoxide, a metal salt and a metal chelate compound may be used. Preferably, isocyanate-based compounds or epoxy-based compounds can be used in the above compounds, and isocyanate-based compounds are more preferably used, but the present invention is not limited thereto.

2. Intermediate layer adhesive 120

The thickness of the intermediate layer adhesive 120 formed between the uppermost adhesive layer 110 and the lowest layer adhesive 130 is 70 to 90% of the total thickness of the multilayered adhesive film 100. The storage elastic modulus is 100 kPa or less at -20 캜, In the range of 10 kPa or more. When the storage elastic modulus exceeds-100 kPa at -20 캜, cracks or bubbles are generated when folding and bending are repeated due to excessive storage elasticity, and when the storage elastic modulus at 80 캜 does not reach 10 kPa, So that the dimension can not be stabilized and can be removed from the interface at the time of repeated folding.

The storage elastic modulus ratio of the multi-layered adhesive film (100) and the intermediate layer adhesive (120) satisfies the following formula (2).

[Formula 2]

G? 2.5

(G = G'_m / G'_s, G'_m is the storage elastic modulus of the multi-layered adhesive film at -20 ° C, G'_s is the storage elastic modulus of the middle-

If the storage elastic modulus ratio G is more than 2.5, the storage elastic modulus of the intermediate layer adhesive 120 is largely changed by the uppermost adhesive layer 110 and the lowermost layer adhesive 130, and bubbles or cracks are generated when the folding and bending properties are evaluated There is a problem with reliability.

The intermediate layer adhesive 120 includes a silicone resin and is formed from a silicone composition. The interlayer pressure sensitive adhesive 120 may comprise one or more MQ resins [A]; At least one organosiloxane polymer [B] having a vinyl functional group; At least one organohydrogensilicon compound [C]; And an addition curable silicone pressure sensitive adhesive (PSA) resin comprising a hydrosilylation catalyst [D].

Component A is R ₃ SiO _1/2 (M unit s) and SiO _4/2, and a resin having a (the Q units), where each R is a predetermined alkyl group such as methyl group. However, without departing from the scope of the present invention, other aliphatic groups having up to about 20 carbon atoms may be used in place of the methyl groups. The molar ratio of M units: Q units may range from about 0.6: 1 to 4: 1. Component A may also comprise up to 5% by weight of silanol functional groups, with less than about 1% by weight being alternatively used.

Component B is an organosiloxane polymer end-blocked with a vinyl functional group represented by the following formula (3). These components may also include additional vinyl functionality. These two or more organosiloxane polymers can control the viscosity and degree of cure after coating by varying the molecular weight.

[Formula 3]

R1R2ViSiO (R3R4SiO) nSiR5R6Vi

R 1, R 2, R 3, R 4, R 5, and R 6 are a C 1-6 alkyl group or a phenyl group, and may be the same or different. The alkyl group represented by R 1, R 2, R 3, R 4, R 5 and R 6 may be exemplified by methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopentyl and cyclohexyl. The n is an integer of 1 or more, and when the molecular weight is 25,000 to 200,000, the folding and bending properties of the intermediate layer adhesive 120 are good.

Component C comprises at least one crosslinking organohydrogensiloxane compound having an average of at least two Si-H bonds per molecule, represented by the formula 4. [ Suitable organohydrogensiloxane compounds for use as component D may be linear, branched, or cyclic molecules, and any mixtures or combinations thereof.

[Formula 4]

- (R7HSiO) n-

In the above formula 4, R7 is a C1-6 alkyl group or a phenyl group. The alkyl group represented by R7 may be exemplified by methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopentyl and cyclohexyl.

Component D may include any catalyst known to those skilled in the art which is useful for catalyzing the hydrosilylation reaction. Component D may be a platinum group metal-containing catalyst. By definition, the platinum group metals refer to ruthenium, rhodium, palladium, osmium, iridium, and platinum metals as well as any mixtures or complexes thereof. Platinum group metals may include solid or hollow particles, a layer deposited on a carrier such as silica gel or powdered charcoal, or an organometallic compound or complex. Some examples of platinum-containing catalysts include platinum-containing catalysts obtained by reacting chloroplatinic acid in hexahydrate form or anhydrous form, and chloroplatinic acid or the chloroplatinic acid with an aliphatic unsaturated organosilicon compound. One specific example of component D, in many instances, is a polymer having a platinum concentration of about 5,200 ppm, 1,3-diethenyl-1,1,2,2-tetramethyldisiloxane diluted with a vinyl- Of a Pt 4000 catalyst (Dow Corning Corporation), which is described as a platinum complex.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is intended to more specifically illustrate the present invention, and the scope of the present invention is not limited to these embodiments.

≪ Example 1 >

Step 1: Top layer adhesive and bottom layer adhesive

In a 1000 ml chemical reactor equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen introducing apparatus, 60 g of n-butyl acrylate, 5 g of methyl methacrylate, 10 g of isobornyl acrylate, 10 g of 2-hydroxyethyl acrylate and 15 g of acrylamide Add 100g of the monomer. 300 g of ethyl acetate was added as a solvent and 0.05 part by weight of azobisisonitrile (AIBN) was added. The mixture was stirred at room temperature with a high-speed stirrer, refluxed with nitrogen gas for 1 hour, and polymerized at 70 DEG C for 8 hours to obtain an acrylic adhesive Resin. The adhesive resin thus obtained has a weight average molecular weight of 200,000 g / mol to 1,000,000 g / mol.

Step 2: Intermediate layer adhesive

40 g of a solid MQ resin having a weight average molecular weight of 2,000 to 20,000 g / mol and an OH content of less than 5% (component A), a weight average molecular weight , 51 g of a main polymer resin having a vinyl functional group content of less than 0.1% and a content of Si-H of 0.5 to 1.5% 60 g of toluene as a solvent is added, and stirring is carried out for about 2 hours to sufficiently mix at room temperature. To this mixture was added 0.5 g [component D] of platinum complex of 1,3 diethenyl-1,1,2,2-tetramethyldisiloxane diluted in a vinyl endblocked polymer with a platinum content of 5,200 ppm Make a total of 100g.

Step 3: Production of pressure-sensitive adhesive composition and multilayer adhesive film for optical film

To 100 parts by weight of the uppermost acrylic copolymer prepared in the above step 1, 1.0 part by weight of an MDI-based adisocyanate adduct was added as a curing agent, and a 75 mu m-thick PET film (trade name: ROH-751 , Manufactured by Toray Advanced Materials Co., Ltd.), and dried and cured in an oven at 120 캜 for 3 minutes. Thereafter, a 75 mu m thick PET film (trade name: ROH-751, manufactured by Toray Industries, Inc.) having a silicon release treatment as a release sheet was laminated on the surface on which the adhesive layer was formed to complete an adhesive film. The lowermost multilayer adhesive film of the same thickness was produced in the same manner.

The intermediate layer adhesive resin was coated on a PET film having a thickness of 75 탆 coated with a fluorine-releasing coating on the material prepared in Step 2, so that the thickness was 50 탆 and dried and cured in an oven at 150 캜 for 6 minutes. Then, the prepared uppermost layer adhesive and the lowermost layer adhesive were sequentially laminated to prepare a multilayered adhesive film for an optical film having an uppermost adhesive layer / an intermediate layer adhesive layer / a lowermost layer adhesive layer structure.

≪ Example 2 >

The procedure of Example 1 was repeated except that the amount of 2-hydroxyethyl acrylate was reduced from 10 g to 5 g and acrylic acid was added in an amount of 5 g in the adhesive resin manufacturing process of step 1 of Example 1.

≪ Comparative Example 1 &

The same procedure as in Example 1 was carried out except that the thickness of the uppermost layer and the lowermost layer of the pressure-sensitive adhesive coating in Step 3 of Example 1 was changed to 15 탆.

≪ Comparative Example 2 &

Except that the amount of n-butyl acrylate was added in an amount of 80 g, isobornyl acrylate was not added, and the amount of acrylamide was reduced to 5 g in the adhesive resin manufacturing step of the step 1 of Example 1 above. The procedure of Example 1 was repeated.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 The topmost pressure-
The lowest pressure-sensitive adhesive composition n-BA 60 60 60 80 MMA 5 5 5 5 IBoA 10 10 10 0 2-HEA 10 5 10 10 Aamid 15 15 15 5 AA 0 5 0 0 n-BA: n-butyl acrylate
MMA: methyl methacrylate
IBoA: isobornyl acrylate
2-HEA: 2-hydroxyethyl acrylate
Aamid: Acrylamide
AA: Acrylic acid

The following properties of the multi-layer pressure-sensitive adhesive film for a multilayer optical film thus produced were evaluated and are shown in Table 2.

(1) Storage modulus (kPa)

The viscoelasticity was measured in a shear mode (1 Hz) using a dynamic viscoelasticity measuring device ARES (TA instruments). (Frequency: 1 rad / sec) After removing the release film, the pressure- And the laminate was perforated with a perforator having a diameter of 8 mm and used as a specimen. The temperature was measured at a temperature rising rate of 5 DEG C / min in a temperature range of -70 to 150 DEG C, and the elastic modulus was recorded at -20 DEG C and 80 DEG C.

(2) Initial adhesion (gf / in)

Samples of PET film / adhesive layer / PET film structure were prepared and the samples were cut into 1 inch x 15 cm strips. Peeling force was measured by a T-peel test method at a rate of 5 mm / sec (0.3 m / min) using a Texture Analyzer (TAXplus / 50, SMS) at the point of 60 minutes after attachment.

(3) Later adhesion (gf / in)

Samples of the same structure and size as those of the sample having the initial adhesive strength were left in a thermo-hygrostat under the conditions of 85 ° C and 85% RH for 120 hours, and then subjected to a test using a Texture Analyzer (TAXplus / 50, SMS) m / min). The peel force was measured by a T-peel test method.

(4) Folding and bending characteristics

Folding and bending tests were performed using samples of PET film / adhesive layer / PET film structure to determine delamination, stripes and bubbles. The folding and bending tests were carried out in the order of 50,000 times in this order, with a bending radius of 2 mm. Delamination state was observed at or near the bending portion, and microbubbles were regarded as bubbles or elliptical bubbles as stripes.

O: No bubbles and stripes

X: delamination occurred

(5) Reliability evaluation

Samples of the PET film / adhesive layer / PET film structure were allowed to stand in a thermo-hygrostat under the conditions of 85 ° C and 85% RH for 120 hours. Visually observing the occurrence of lifting or peeling or bubbling on the adhered surface, Respectively.

O: No bubble or peeling phenomenon

X: Many bubbles or peeling phenomena occur

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Top layer Adhesive thickness (㎛) 7 7 15 7 Thickness of intermediate layer adhesive (탆) 50 50 50 50 Thickness of the Lowermost Adhesive (μm) 7 7 15 7 % Thickness of Topmost Adhesive Thickness (%) 11 11 19 11 Thickness% of Lowermost Adhesive Thickness (%) 11 11 19 11 The uppermost and lowermost tackiness agent T _g -16 -9 -16 -35 Top layer adhesive and bottom layer
The storage modulus (MPa) of the pressure- -20 ° C 90 110 90 4 The storage elastic modulus (kPa) of the multi- -20 ° C 100 146 250 50 80 ℃ 15 19 4 3 The storage elastic modulus (kPa) -20 ° C 80 80 80 80
The storage modulus ratio (G) Multilayer adhesive film
/ Intermediate layer adhesive
(-20 ° C) 1.25 1.83 3.13 0.63 Initial adhesion (F _o , gf / in) 1455 1568 1958 1225 Later adhesion (F _f , gf / in) 1121 1143 1621 613 Folding / Bending Characteristics O O X X responsibility O O O X

As shown in Table 2, in the case of Examples 1 and 2, the storage elastic modulus of each layer and the multilayer adhesive film as a whole was excellent, and the initial adhesive force / late adhesive force (ΔF) and folding / Both the characteristics and the reliability are excellent, thereby satisfying the remarkable effects of the present invention.

In the case of Comparative Example 1, when the thicknesses of the uppermost adhesive layer and the lowermost layer adhesive became thick, the storage elastic modulus and the storage modulus ratio (G) of the multilayered adhesive film were out of the range of the present invention, And the effect of the present invention can not be realized. In the case of Comparative Example 2, the Tg of the uppermost layer and the lowermost layer adhesive did not satisfy the storage elastic modulus and the later adhesive strength (F _f ) Delamination occurred and the effect of the present invention could not be realized.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art.

100 multi-layer adhesive film
110 top layer adhesive
120 intermediate layer adhesive
130 Lowermost Adhesive

Claims (9)

In the multilayer adhesive film for an optical film,
An uppermost layer adhesive 110; An intermediate layer adhesive 120; And a lowermost pressure-sensitive adhesive (130)
The thickness of the uppermost layer adhesive 100 or the lowermost layer adhesive 130 is 5 to 12% of the thickness of the entire multilayered adhesive film 100,
The uppermost layer adhesive 110 and the lowermost layer adhesive 130 each include an acrylic resin having a Tg of -16 ° C. to 10 ° C. The acrylic resin is composed of 75 to 99.9 parts by weight of a (meth) acrylate monomer, 0.1 to 25 parts by weight of a monomer,
Wherein the crosslinkable monomer comprises a nitrogen-containing monomer,
A multi-layer pressure-sensitive adhesive film for an optical film, characterized in that the adhesive force retention ratio indicated by the following [formula 1] is 70% or more.
[Formula 1]
? F (%) = F _f / F _o * 100
(F _o is the initial cohesive force measured at room temperature for any substrate film, F _f is the cohesive force measured after being left in a thermo-hygrostat at 85 ° C and 85% RH for 120 hours) The multi-layer pressure-sensitive adhesive film for optical films according to claim 1, wherein the storage elastic modulus of the multilayer adhesive film (100) and the storage modulus ratio of the intermediate layer adhesive (120) satisfy the following formula (2).
[Formula 2]
G? 2.5
(G = G'_m / G'_s, G'_m is the storage elastic modulus of the multi-layered pressure-sensitive adhesive film at -20 ° C, G'_s is the storage elastic modulus of the pressure- The multilayer adhesive film for an optical film according to claim 1, wherein the multilayered adhesive film (100) has an initial adhesive strength and an adhesive strength after lapse of 120 hours at 85 ° C and 85% RH of not less than 700 gf / in and not more than 1568 gf / in. delete The method of claim 1, wherein the interlayer pressure sensitive adhesive (120) comprises one or more MQ resins [A]; At least one organosiloxane polymer [B] having a vinyl functional group; At least one organohydrogensilicon compound [C]; (PSA) resin comprising an addition-curable silicone pressure-sensitive adhesive (PSA) resin comprising a hydrosilylation catalyst [D]. The multilayer adhesive film for an optical film according to claim 1, wherein the thickness of the multilayer adhesive film (100) is 20 to 100 占 퐉. The multilayer adhesive film (100) according to claim 1, wherein the multilayered adhesive film (100) has a storage elastic modulus at -20 캜 of 100 kPa or more to 200 kPa or less and a storage elastic modulus at 80 캜 of 10 kPa or more to 19 kPa or less film. The multi-layer pressure-sensitive adhesive film for optical films according to claim 1, wherein the uppermost adhesive layer (110) and the lowermost layer adhesive (130) have a storage modulus at -20 캜 of not less than 10 MPa and not more than 110 MPa. The multi-layer pressure-sensitive adhesive film for optical films according to claim 1, wherein the intermediate layer adhesive (120) has a storage elastic modulus at -20 캜 of 80 kPa or more and 100 kPa or less.

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