KR101922646B1 - Adhesive film for optical film of dispaly - Google Patents

Abstract

An adhesive film for an optical film, comprising: an uppermost pressure-sensitive adhesive layer; An intermediate pressure-sensitive adhesive layer; And the lowermost pressure-sensitive adhesive layer, wherein the uppermost pressure-sensitive adhesive layer and the lowermost pressure-sensitive adhesive layer occupy 15% or less of the total thickness of the pressure-sensitive adhesive film for an optical film, Sensitive adhesive film for an optical film satisfies the following formula (1).
[Formula 1]
G? 2.5
(G = G'_m / G'_s,
G'_m is a storage elastic modulus of an adhesive film for an optical film at -20 ° C,
G'_s is the storage modulus of the intermediate pressure-sensitive adhesive layer at -20 ° C.)
The adhesive film for an optical film has good stress relaxation characteristics under bending / folding conditions and is free from lifting, peeling, and bubbling under bending / folding conditions.

Description

[0001] The present invention relates to an adhesive film for an optical film,

The present invention relates to an adhesive film for an optical film, and more particularly, to an adhesive film for an optical film having a pressure-sensitive adhesive layer of a multi-layer structure and having excellent stress relaxation properties under bending / folding conditions of a display or a touch panel .

The display of the future society, especially the mobile display, is expected to evolve into a flexible display that is thinner, lighter and consumes less energy as informationization becomes more widespread and popularized. Such a display may include a polarizing plate, a retarder, and additional functional layers formed of a sheet-like material. These are adhered to an adherend inside the device through a pressure-sensitive adhesive, and can be manufactured in various shapes such as warping or folding.

The pressure-sensitive adhesive film used in the conventional flat panel display is hardly deformed by external force, but the pressure-sensitive adhesive film applied to the flexible display generates stress due to external bending or bending. In this case, it is difficult for the pressure-sensitive adhesive itself 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 transferred to the display,

Therefore, it is urgent to develop a pressure-sensitive adhesive film which can be used as a flexible and flexible display due to a small change of viscoelasticity in various temperature ranges and a cracking phenomenon under the condition that flexibility is required during display processing and operation.

KR 10-2016-0025050 A

It is an object of the present invention to provide an adhesive film for an optical film having a good stress relaxation property in a bending / folding condition of a display or a touch panel.

Another object of the present invention is to provide an adhesive film for an optical film free from lifting, peeling, and bubbling under bending / folding conditions.

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

According to an aspect of the present invention, there is provided an adhesive film for an optical film comprising: a top adhesive layer; An intermediate pressure-sensitive adhesive layer; And a lowermost pressure-sensitive adhesive layer; Wherein the uppermost pressure sensitive adhesive layer and the lowermost pressure sensitive adhesive layer occupy 15% or less of the total thickness of the pressure sensitive adhesive film, and the ratio of the storage elastic modulus of the pressure sensitive adhesive film and the intermediate pressure sensitive adhesive layer at- Is satisfied.

[Formula 1]

G? 2.5

(G = G'_m / G'_s,

G'_m is the storage elastic modulus of the pressure-sensitive adhesive film at -20 ° C,

G'_s is the storage modulus of the intermediate pressure-sensitive adhesive layer at -20 ° C.)

The uppermost pressure-sensitive adhesive layer and the lowermost pressure-sensitive adhesive layer include a (meth) acrylate-based polymer having a glass transition temperature (Tg) of from -20 ° C. to less than 10 ° C., and the intermediate pressure- .

Also, the (meth) acrylate polymer may include 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.

Also, at this time, the silicone-based polymer is characterized by comprising an MQ polymer, an organosiloxane polymer having a vinyl functional group, an organohydrogensilicon compound, and a hydrosilylation catalyst.

In this case, the adhesive film for an optical film has a thickness of 20 to 100 탆.

In this case, the adhesive film for an optical 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.

In this case, the uppermost pressure-sensitive adhesive layer and the lowermost pressure-sensitive adhesive layer have a storage elastic modulus of -10 MPa or more at -20 캜.

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

In this case, the adhesive film for an optical film has a haze of 3% or less, a total light transmittance of 90% or more, and a reflectance of 5% or less.

The adhesive film for an optical film of the present invention is excellent in stress relaxation characteristics under bending / folding conditions and has no lifting, peeling, or bubble formation under bending / folding conditions.

1 is a schematic cross-sectional view of an adhesive film for an optical film according to an embodiment of the present invention

The present invention will be described in detail with reference to the accompanying drawings. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

 In the present specification, 'upper' and 'lower' refer to the drawings for convenience, and 'upper' may be changed to 'lower' and 'lower' may be changed to 'upper' depending on viewing time.

As used herein, '(meth) acrylate' may mean acrylate and / or methacrylate.

As used herein, the term " polymer " may include oligomers, polymers or resins.

1 is a schematic cross-sectional view of an adhesive film 100 for an optical film according to an embodiment of the present invention. 1, the pressure-sensitive adhesive film 100 of the present invention comprises a top pressure-sensitive adhesive layer 110; A lowermost pressure-sensitive adhesive layer (130); And an intermediate pressure-sensitive adhesive layer (120) formed between the uppermost pressure-sensitive adhesive layer (110) and the lowermost pressure-sensitive adhesive layer (130).

1. The uppermost pressure-sensitive adhesive layer 110 and the lowermost pressure-

The thickness of the uppermost adhesive layer 110 and the lowermost adhesive layer 130 is preferably 15% or less of the total thickness of the adhesive film 100, and more preferably 5 to 12%. If it exceeds 15%, the storage elastic modulus of the adhesive film (100) is affected by the pressure-sensitive adhesive composition of the uppermost pressure-sensitive adhesive layer (110) and the lowermost pressure-sensitive adhesive layer (130), and flexibility is lowered at various temperatures, Lt; / RTI >

The storage elastic modulus of the uppermost pressure-sensitive adhesive layer 110 and the lowermost pressure-sensitive adhesive layer 130 is preferably 10 MPa or more at -20 캜. If the storage elastic modulus at -20 캜 is less than 10 MPa, the stiffness of the uppermost pressure-sensitive adhesive layer 110 and the lowermost pressure-sensitive adhesive layer 130 is low, and the high cohesive force at the interface can not be maintained.

The uppermost pressure sensitive adhesive layer 110 and the lowermost pressure sensitive adhesive layer 130 preferably include a (meth) acrylate based polymer having a glass transition temperature (Tg) of from -20 ° C to less than 10 ° C. If the glass transition temperature is lower than -20 占 폚, the storage elastic modulus of 10 MPa can not be induced and becomes soft. If the glass transition temperature is higher than 10 占 폚, the flexibility of the adhesive film 100 is lowered and cracks may be generated under the condition of bending.

The specific composition of the (meth) acrylate-based polymer is not particularly limited. For example, in the present invention, the (meth) acrylate-based polymer may be a polymer of a monomer mixture comprising 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.

The specific 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, one or more of the above- .

 The monomer mixture of the present invention may contain 80 to 99.9 parts by weight of the (meth) acrylic acid ester monomer as described above. If the content is less than 80 parts by weight, the initial adhesion of the pressure-sensitive adhesive may be deteriorated. If the content is more than 99.9 parts by weight, there is a fear of a problem of durability due to a decrease in cohesion.

The crosslinkable monomer contained in the monomer mixture of the present invention is a monomer capable of imparting to the (meth) acrylate-based polymer a crosslinkable functional group capable of reacting with a crosslinking agent component described later, and is excellent in durability, adhesion and cohesion Can play a role.

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 Acrylate, 8-hydroxyoctyl (meth) acrylate, 2-hydroxyethyleneglycol (meth) acrylate or 2-hydroxypropyleneglycol (meth) acrylate. Examples of the carboxyl group- (Meth) acryloyloxypropionic acid, 4- (meth) acryloyloxybutyric acid, acrylic acid dimer, itaconic acid, maleic acid, and Maleic anhydride and the like. 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-mentioned mixtures may be used.

The crosslinkable monomer in the monomer mixture of the present invention is preferably contained in an amount of 0.1 to 20 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 20 parts by weight, the cross-linking reaction may excessively proceed, thereby deteriorating the tackiness and / or peeling force.

The pressure-sensitive adhesive composition of the present invention comprises a crosslinking agent component capable of reacting with the (meth) acrylate-based polymer described above 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, the use of a trifunctional or higher crosslinking agent, . 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 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. In the present invention, isocyanate-based compounds or epoxy-based compounds may be preferably used among the above compounds, and more preferably, isocyanate-based compounds may be used, but the present invention is not limited thereto.

2. The intermediate pressure-sensitive adhesive layer (120)

The intermediate pressure-sensitive adhesive layer 120 formed between the uppermost pressure-sensitive adhesive layer 110 and the lowermost pressure-sensitive adhesive layer 130 occupies 70 to 90% of the total thickness of the pressure-sensitive adhesive film 100 and the pressure- bending and folding characteristics.

The storage elastic modulus of the intermediate pressure-sensitive adhesive layer 120 is preferably 100 kPa or less at -20 캜 and 10 kPa or more at 80 캜. When the storage modulus exceeds-100 kPa at -20 캜, cracks or bubbles are generated in the pressure-sensitive adhesive film (100) in evaluation of low-temperature folding and bending properties and can not be applied to displays. If the storage elastic modulus is higher than 10 kPa at 80 캜, it will not be deformed at high temperature and reliability can be ensured. If it is less than 10 kPa, bubbles or wrinkles may occur.

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

Component A comprises a polymer having R3SiO1 _{/ 2} (M units) and SiO4 _{/ 2} (Q units), wherein R is a pre-determined alkyl group such as a methyl group. However, other aliphatic groups having up to 20 carbon atoms can be used in place of the methyl groups, without departing from the scope of the present invention. The molar ratio of M units to Q units may range from about 0.6: 1 to 4: 1. Component A may 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 (2). 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 2]

R ₁ R ₂ ViSiO (R ₃ R ₄ SiO) _n SiR ₅ R ₆ Vi

R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently a C 1-7 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, heptyl, cyclopentyl, cyclohexyl and cycloheptyl. When n is an integer of 1 or more and the molecular weight is 25,000 to 200,000, the intermediate pressure-sensitive adhesive layer 120 has good folding and bending properties.

Component C comprises at least one crosslinking organohydrogensiloxane compound having an average of at least two Si-H bonds per molecule, represented by the following formula 3: Organohydrogensiloxane compounds suitable for use as Component C may be linear, branched, or cyclic molecules and any mixtures or combinations thereof.

[Formula 3]

- (R ₇ HSiO) n-

In the formula 3, R ₇ is a C 1-7 alkyl group or a phenyl group. The alkyl group represented by R ₇ may be exemplified by methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, cyclopentyl, cyclohexyl and cycloheptyl.

Component D may comprise any catalyst known to those skilled in the art which is useful for promoting 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 in anhydrous form, and chloroplatinic acid or the chloroplatinic acid with an aliphatic unsaturated organosilicon compound. A specific example of component D in many examples is a platinum complex having a platinum concentration of about 5,200 ppm and a 1,3-diethenyl-1,1,2,2-tetramethyldisiloxane diluted with a vinyl-terminated polymer Lt; / RTI > catalyst.

3. Adhesive film

The adhesive film 100 is obtained by laminating the uppermost adhesive layer 110 and the lowermost adhesive layer 130 on the upper and lower adhesive layers 120 and 120, The adhesive film 100 having the layer 130 structure can be manufactured.

The thickness of the adhesive film 100 is preferably 20 to 100 mu m. When the thickness of the adhesive film (100) is less than 20 mu m, when the adhesive film (100) is applied to a flexible display formed by stacking various films, the adhesive force is insufficient and the stress between the films can not be buffered. If the thickness of the adhesive film (100) exceeds 100 탆, the thickness of the flexible display becomes thick, and a good display can not be obtained.

The storage elastic modulus of the adhesive film 100 is preferably 200 kPa or less at -20 캜 and 10 kPa or more at 80 캜. When the storage elastic modulus exceeds 200 kPa at -20 캜, the storage elasticity is high, so that when folding and bending are repeated, cracks or bubbles are introduced. If the storage elastic modulus is less than 10 kPa at 80 캜, the adhesive film (100) may have fluidity at high temperature, and the dimensions may not be stable, and the adhesive film (100)

It is preferable that the ratio of the storage modulus of the adhesive film 100 to the storage modulus of the intermediate pressure-sensitive adhesive layer 120 at -20 ° C satisfies the following formula (1).

[Formula 1]

G? 2.5

(G = G'_m / G'_s

 G'_m is the storage elastic modulus of the adhesive film 100 at -20 ° C

 G'_s is the storage elastic modulus of the intermediate pressure-sensitive adhesive layer 120 at -20 ° C.)

If the ratio of the storage elastic modulus exceeds 2.5, the storage elastic modulus of the intermediate pressure-sensitive adhesive layer 120 largely changes due to the uppermost pressure-sensitive adhesive layer 110 and the lowermost pressure-sensitive adhesive layer 130, and bubbles or cracks Thereby causing a problem in reliability.

The adhesive film 100 preferably has a haze of 3% or less, a total light transmittance of 90% or more, and a reflectance of 5% or less. In order to apply the adhesive film 100 to a display, the adhesive film 100 should not hinder the color and transmittance of the light emitting substrate. If the haze of the adhesive film (100) exceeds 3%, color reproduction is inhibited and if the transmittance is less than 90%, the luminance is lowered. If the reflectance exceeds 5%, the brightness of the display is hindered by external light.

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: Preparation of the uppermost pressure-sensitive adhesive layer 110 and the lowermost pressure-sensitive adhesive layer 130

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 acrylate To prepare a pressure-sensitive adhesive polymer. The pressure-sensitive adhesive polymer thus obtained has a weight average molecular weight of 200,000 g / mol to 1,000,000 g / mol.

Step 2: Preparation of intermediate pressure-sensitive adhesive layer (120) composition

40 g of a solid MQ polymer 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 of 50,000 51 g of a main polymer polymer having a vinyl functional group content of less than 0.1% and having an Si-H content of 0.5 to 1.5%, and 8.5 g of an organohydrogensilicon compound having an Si-H content of 0.5 to 1.5%. [Component C] 60 g of toluene as a solvent, The mixture is stirred for about 2 hours. To this mixture was added 0.5 g of a platinum complex of 1,3 diethenyl-1,1,2,2-tetramethyldisiloxane, which had a platinum content of 5,200 ppm and diluted with a vinyl-endblocked polymer [component D] Adjust to 100g.

Step 3: Production of adhesive film (100) for optical film

To 100 parts by weight of the acrylate-based copolymer for the uppermost pressure-sensitive adhesive layer 110 prepared in the step 1, 1.0 part by weight of methyl diphenyl diisocyanate adduct was added as a curing agent, and a thickness of 75 Mu] m PET film (trade name: ROH-751, manufactured by Toray Industries, Ltd.) to a thickness of 7 mu m and dried and cured in an oven at 120 DEG C for 3 minutes. Then, a PET film (trade name: ROH-751, manufactured by Toray Industries, Ltd.) having a thickness of 75 m and treated with silicone as a release sheet was laminated on the surface having the pressure-sensitive adhesive layer formed thereon to complete the uppermost pressure-sensitive adhesive layer 110. The lowermost pressure-sensitive adhesive layer 130 having the same thickness was produced in the same manner.

The pressure sensitive adhesive for the intermediate pressure-sensitive adhesive layer (120) was prepared by coating the composition prepared in the above step 2 with a fluorine-releasing coated PET film having a thickness of 75 占 퐉 so as to have a thickness of 50 占 퐉 and drying and curing in an oven at 150 占 폚 for 6 minutes .

Then, the uppermost pressure sensitive adhesive layer 110 and the lowermost pressure sensitive adhesive layer 130 are sequentially laminated on the upper and lower pressure sensitive adhesive layers 110, 120, and 130, respectively, To thereby produce an adhesive film (100).

≪ 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 5 g of acrylic acid was added in the step of preparing the pressure-sensitive adhesive composition of step 1 of Example 1.

≪ Comparative Example 1 &

The procedure of Example 1 was repeated, except that the coating thickness of the uppermost adhesive layer 110 and the lowermost adhesive layer 130 in the step 3 of Example 1 was 15 탆.

≪ Comparative Example 2 &

Except that the amount of n-butyl acrylate was 80 g, the amount of isobornyl acrylate was not added, and the amount of acrylamide was reduced to 5 g in the pressure-sensitive adhesive composition production process of step 1 of Example 1, 1.

≪ Comparative Example 3 &

In the step of preparing the intermediate pressure-sensitive adhesive layer (120) pressure-sensitive adhesive composition of the step 2 of Example 1, 50 g of a solid MQ polymer having an OH content of less than 5% (component A), a weight average molecular weight of 50,000 to 600,000 g / The procedure of Example 1 was repeated, except that the main polymer polymer [component B] having a functional group content of less than 0.1% was reduced to 41 g.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3
The uppermost pressure-
Preparation of Lowermost Pressure Sensitive Adhesive Layer Composition (g) n-BA 60 60 60 80 60 MMA 5 5 5 5 5 IBoA 10 10 10 0 10 2-HEA 10 5 10 10 10 Aamid 15 15 15 5 15 AA 0 5 0 0 0


Preparation of intermediate pressure-sensitive adhesive layer composition (g) MQ polymer
[Component A] 40 40 40 40 50 Note Polymer Polymer
[Component B] 51 51 51 51 41 Organohydrogensilicon compound
[Component C] 8.5 8.5 8.5 8.5 8.5 Platinum complex
[Component D] 0.5 0.5 0.5 0.5 0.5
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 adhesive film (100) prepared above were evaluated and are shown in Table 2.

(1) Storage modulus (kPa)

The viscoelasticity was measured at a frequency of 1 rad / sec in a shear mode (1 ㎐) using a dynamic viscoelasticity measuring device ARES (TA instruments). After removing the release film, the adhesive films 100 of Examples and Comparative Examples were laminated so as to have a thickness of 1 mm 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 rate of 10 DEG C / min in a temperature range of -70 to 150 DEG C, and the elastic modulus was recorded at -20 and 80 DEG C. [

(2) Adhesion (gf / in)

A PET film / adhesive film (100) / PET film structure sample was prepared and the sample was cut into 1 inch x 15 cm strips. Peeling force was measured with a T-peel test at a rate of 5 mm / sec (0.3 m / min) using a Texture Analyzer (TAXplus / 50, SMS) at 60 minutes after attachment.

(3) Folding and bending characteristics

Folding and bending tests were performed using samples of PET film / adhesive film (100) / PET film structure to determine whether delamination (unadhered), streaking or bubbles were generated. The folding and bending tests were carried out in the order of 50,000 times, and the bending radius was 2 mm. The delamination state was observed at or near the bending part, and the micro bubbles were regarded as bubbles and the elliptical bubbles as stripe.

O: No bubbles and stripes.

X: Bubbles and streaks, Delamination occurrence

(4) Reliability evaluation

A sample of the PET film / adhesive film (100) / PET film structure was heated at 85 DEG C, 85% R.H. After standing for 120 hours in a constant temperature and humidity condition, whether or not lifting, peeling or bubble formation on the surface of the substrate was visually observed was evaluated according to the following criteria.

O: No bubble or peeling phenomenon

X: Many bubbles or peeling phenomena occur

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Top pressure-sensitive adhesive layer thickness (占 퐉) 7 7 15 7 7 Medium Pressure Sensitive Adhesive Layer Thickness (占 퐉) 50 50 50 50 50 Thickness of the lowermost pressure-sensitive adhesive layer (占 퐉) 7 7 15 7 7 Percentage of thickness of topmost pressure-sensitive adhesive layer (%) 11 11 19 11 11 % Of the lowermost pressure-sensitive adhesive layer thickness (%) 11 11 19 11 11 The uppermost pressure-
The lowermost pressure-sensitive adhesive layer Tg (占 폚) -16 -9 -16 - 35 -16 The uppermost pressure-sensitive adhesive layer and the lowermost pressure-
Storage modulus (MPa)
-20 ° C
90
110
90
4
90 Adhesive film
Storage modulus (kPa) -20 ° C 100 146 250 50 370 80 ℃ 15 19 4 3 20 Intermediate pressure-sensitive adhesive layer
Storage modulus (kPa) -20 ° C 80 80 80 80 300 Storage modulus
Ratio (G, -20 C) Adhesive film /
Intermediate pressure-sensitive adhesive layer 1.13 1.38 3.13 0.63 1.23 Adhesion (gf / in) 1455 1568 1958 1225 1750 Folding / Bending Properties O O X X X responsibility O O O X X

As shown in Table 2, in Examples 1 and 2, folding / bending characteristics and reliability were excellent, thus satisfying the remarkable effect of the present invention.

On the other hand, in Comparative Example 1 in which the thicknesses of the uppermost adhesive layer 110 and the lowermost pressure-sensitive adhesive layer 130 were out of the range of the present invention, the storage elastic modulus of the adhesive film was influenced and the storage modulus ratio G exceeded the range of the present invention Cracks occurred during folding / bending evaluation, and the effect of the present invention could not be realized.

In Comparative Example 2 in which the Tg of the uppermost pressure-sensitive adhesive layer 110 and the lowermost pressure-sensitive adhesive layer 130 were out of the range of the present invention, the storage elastic modulus of the pressure-sensitive adhesive film was out of the range of the present invention and the folding / The effect of the present invention could not be realized.

In Comparative Example 3 in which the storage modulus of the intermediate pressure-sensitive adhesive layer 120 exceeds the range of the present invention at -20 ° C, the storage modulus ratio G is satisfied but the folding / bending properties and reliability are not excellent.

While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims.

100: Adhesive film
110: uppermost pressure-sensitive adhesive layer
120: intermediate pressure-sensitive adhesive layer
130: Lowermost pressure-sensitive adhesive layer

Claims (9)

In the adhesive film for an optical film,
An uppermost pressure-sensitive adhesive layer; An intermediate pressure-sensitive adhesive layer; And a lowermost pressure-sensitive adhesive layer, wherein the uppermost pressure-sensitive adhesive layer and the lowermost pressure-sensitive adhesive layer occupy 5 to 12% of the total thickness of the pressure-sensitive adhesive film for an optical film, The ratio of the storage elastic modulus of the layer satisfies the following formula (1)
Wherein the uppermost pressure-sensitive adhesive layer and the lowermost pressure-sensitive adhesive layer comprise a (meth) acrylate-based polymer having a glass transition temperature (Tg) of from -16 ° C to less than 10 ° C, and the intermediate pressure- Adhesive film for optical film.
[Formula 1]
G? 2.5
(G = G'_m / G'_s,
G'_m is the storage elastic modulus of the pressure-sensitive adhesive film at -20 ° C,
G'_s is the storage modulus of the intermediate pressure-sensitive adhesive layer at -20 ° C.) delete The pressure-sensitive adhesive film for an optical film according to claim 1, wherein the (meth) acrylate-based polymer 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. The pressure sensitive adhesive film for an optical film according to claim 1, wherein the silicone-based polymer comprises an MQ polymer, an organic siloxane polymer having a vinyl functional group, an organohydrogensilicon compound, and a hydrosilylation catalyst. The pressure-sensitive adhesive film for an optical film according to claim 1, wherein the pressure-sensitive adhesive film for optical films has a thickness of 20 to 100 탆. The pressure-sensitive adhesive film for optical films according to claim 1, wherein the pressure-sensitive adhesive film for optical films has a storage elastic modulus at -20 캜 of not less than 100 kPa and not more than 200 kPa, and a storage elastic modulus at 80 캜 of not less than 10 kPa and not more than 19 kPa. The pressure sensitive adhesive film for an optical film according to claim 1, wherein the uppermost pressure sensitive adhesive layer and the lowermost pressure sensitive adhesive layer have a storage elastic modulus at -20 캜 of 10 MPa or more and 110 MPa or less. The pressure-sensitive adhesive film for optical films according to claim 1, wherein the intermediate pressure-sensitive adhesive layer has a storage elastic modulus at 80 deg. The adhesive film for an optical film according to claim 1, wherein the adhesive film for an optical film has a haze of 3% or less, a total light transmittance of 90% or more, and a reflectance of 5% or less.

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