KR20140008664A - Adhesive composition for optical film - Google Patents

Abstract

The present invention provides an adhesive composition for an optical film. The adhesive composition includes 25 wt% or more of monomers containing hydrophilic functional groups relative to 100 wt% of (meth)acrylic ester monomers. Moreover, the present invention may include an adhesive layer which includes an adhesive composition including 25 wt% or more of monomers containing hydrophilic functional groups relative to 100 wt% of (meth)acrylic ester monomers. [Reference numerals] (AA) Before absorbing water; (BB) After absorbing water; (CC) Water particles; (DD) After a vacuum/high temperature condition

Description

Adhesive composition for optical films {ADHESIVE COMPOSITION FOR OPTICAL FILM}

The present invention relates to a pressure-sensitive adhesive composition for an optical film, and more particularly to a pressure-sensitive adhesive composition containing a hydrophilic functional group-containing monomer content is limited to a monomer of a certain component.

Conventionally, a liquid crystal cell in which both surfaces of a polarizing film such as a polyvinyl alcohol-based film imparted with polarization are sandwiched by a liquid crystal component in which a polarizing plate coated with a cellulose-based film such as a triacetic cellulose film is oriented between two glass plates. It is carried out by laminating | stacking on the surface of and making a liquid crystal display panel, and lamination | stacking on this liquid crystal cell surface is normally performed by contacting and pressing the adhesive layer formed in the polarizing plate surface to the said liquid crystal cell surface.

However, after the optical member on which the pressure-sensitive adhesive layer is formed is bonded to the liquid crystal cell and peeled again, foreign matters may be mixed or damaged, or adhesive miss may occur on the LCD surface, which has been adhered to the pressure-sensitive adhesive layer, and the LCD may be reworked. There was a difficulty. In addition, the Republic of Korea Patent No. 10-0988185 discloses a pressure-sensitive adhesive composition comprising an acrylic polymer composed of a certain component, although the pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition shows an excellent effect in peel force or durability, before and after peeling Due to the relationship between the pressure-sensitive adhesive layer and the adherend and the rework function of the adherend, nothing is described, which still implies the conventional problem of the remaining of foreign matter or residue after peeling off the pressure-sensitive adhesive layer.

In order to solve the above problems, the present invention is that the pressure-sensitive adhesive composition used for the optical film is neatly peeled off from the adherend of glass and plastic after water absorption, to impart a function that the adherent can be reworked (rework). The purpose.

In order to achieve the said one objective, the adhesive composition of this invention is characterized by including 25 weight part or more of hydrophilic functional group containing monomers with respect to 100 weight part of (meth) acrylic acid ester monomers.

In addition, in order to achieve the other object may include an adhesive layer formed by including the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition of the present invention can absorb a predetermined level or more water by containing a predetermined content or more of the hydrophilic functional group-containing monomer. Thereafter, moisture absorbed at high vacuum and high temperature is boiled, and volume expansion occurs, so that desorption with glass or plastic, to which the pressure-sensitive adhesive composition is attached, is facilitated, and the pressure-sensitive adhesive composition is neatly peeled back to the adhesive such as glass or plastic. Allow to have a rework function.

1 is a diagram showing the before and after the water absorption of the pressure-sensitive adhesive composition of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Hereinafter, the present invention will be described in detail.

This invention provides the adhesive composition characterized by including 25 weight part or more of hydrophilic functional group containing monomers with respect to 100 weight part of (meth) acrylic acid ester monomers.

The pressure-sensitive adhesive composition of the present invention includes a hydrophilic functional group-containing monomer to enable peeling of the pressure-sensitive adhesive composition that adheres to glass or plastic. More specifically, the hydrophilic functional group-containing monomer absorbs a certain level of water so that water exists through condensation in the pressure-sensitive adhesive composition.

Thereafter, the moisture absorbed at a high vacuum high temperature is boiled to cause volume expansion of the pressure-sensitive adhesive composition. The volume expansion enables the pressure-sensitive adhesive composition to be detached from the adherend such as glass or plastic without residue or foreign matter. As a result, liquid crystal displays, such as glass or plastic, specifically, LCDs, which are detached from the pressure-sensitive adhesive composition, may have a rework function.

The hydrophilic functional group-containing monomer includes 25 parts by weight or more based on 100 parts by weight of the (meth) acrylic acid ester monomer, and when less than 25 parts by weight, the hydrophilic functional group-containing monomer is insufficient to sufficiently retain water. This becomes insufficient and the cohesion force between hydrophilic functional group containing monomers becomes low, and there exists a possibility that a destruction of superposition | polymerization may occur and peeling may not become easy after high humidity conditions. The upper limit of the content ratio of the hydrophilic functional group-containing monomer is not limited, but in order to have a strong cohesive force and to be peeled off at any interface, it is preferable to include 80 parts by weight or more.

The said hydrophilic functional group containing monomer is 1 or more types chosen from a hydroxyl group containing monomer, an amino group containing monomer, a carboxyl group containing monomer, a sulfone group containing monomer, a morpholine group containing monomer, and a glycidyl group containing monomer.

As said hydroxyl-containing monomer, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, for example (Meth) acrylic acid hydroxyalkyl esters, such as 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate, and capro Caprolactone-modified monomers such as lactone-modified 2-hydroxyethyl (meth) acrylate, 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, N-methylol (meth) acrylamide, N-hydroxyethyl ( Primary hydroxyl group-containing monomers such as meta) acrylamide; 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) Secondary hydroxyl group-containing monomers such as acrylate and 2-hydroxy-3-phenoxypropyl (meth) acrylate; Tertiary hydroxyl group containing monomers, such as 2, 2- dimethyl- 2-hydroxyethyl (meth) acrylate, are mentioned.

Among the hydroxyl group-containing monomers, it is particularly preferable to use 2-hydroxyethyl (meth) acrylate because it contains little impurities such as di (meth) acrylate and is easy to manufacture.

As said amino-group containing monomer, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, etc. are mentioned, for example.

Examples of the carboxyl group-containing monomers include acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid, acrylamide N-glycolic acid, cinnamic acid, and Michael adducts of (meth) acrylic acid (e.g., acrylic acid). Dimer, methacrylic acid dimer, acrylic acid trimer, methacrylic acid trimer, acrylic acid tetramer, methacrylic acid tetramer and the like), 2- (meth) acryloyloxyethyldicarboxylic acid monoester (e.g. 2- Acryloyloxyethyl succinic acid monoester, 2-methacryloyloxyethyl succinic acid monoester, 2-acryloyloxyethyl phthalic acid monoester, 2-methacryloyloxyethyl phthalic acid monoester, 2-acryloyloxy Ethyl hexahydrophthalic acid monoester, 2-methacryloyloxyethyl hexahydrophthalic acid monoester, etc.) etc. are mentioned.

Examples of the sulfone group-containing monomers include olefin sulfones such as ethylene sulfone, allyl sulfone, and metaallyl sulfone, 2-acrylamide-2-methylpropane sulfone, styrene sulfone or salts thereof. 4-methylmorpholine (4-Methylmorpholine) and the said glycidyl-group containing monomer are glycidyl (meth) acrylate, allyl glycidyl ether, etc. are mentioned as said morpholine group containing monomer.

The pressure-sensitive adhesive composition of the present invention can achieve the object of the present invention that can increase the moisture absorption by containing the hydrophilic functional group-containing monomer to rework the adherend after peeling off the pressure-sensitive adhesive composition.

At this time, the polymer molecular weight of the said (meth) acrylic acid ester monomer and the said hydrophilic functional group containing monomer is 1 million-1.2 million, It is characterized by the above-mentioned. If the polymer molecular weight exceeds 1.2 million, there is a problem that the specific gravity of the pressure-sensitive adhesive composition is increased, and if the polymer molecular weight is less than 1 million, durability may be weak.

The kind of (meth) acrylic acid ester monomer contained in the pressure-sensitive adhesive composition of the present invention is not particularly limited, and for example, alkyl (meth) acrylate can be used. At this time, when the alkyl group contained in the monomer is too long, the cohesive force of the pressure-sensitive adhesive composition may be lowered, and the glass transition temperature (Tg) and the adhesion may be difficult to control, and thus the alkyl group having 1 to 14 carbon atoms ( It is preferable to use a meta) acrylic acid ester monomer.

The (meth) acrylic acid ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t -Butyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, n-octyl (meth) At least one selected from the group consisting of acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate and tetradecyl (meth) acrylate.

In forming the pressure-sensitive adhesive composition, a crosslinkable functional group may be provided, and in this case, the pressure-sensitive adhesive composition to be formed in the present invention may be a monomer mixture including a (meth) acrylic acid ester monomer, a hydrophilic functional group-containing monomer, and a crosslinkable monomer. May be a polymer of

By further including a photoinitiator, the adhesive composition of this invention makes it possible to harden an adhesive composition by active energy ray irradiation, such as an ultraviolet-ray for a very short time, and can adjust the molecular weight of an adhesive composition. In the case of using a thermal polymerization initiator, the pressure-sensitive adhesive composition is cured by heating, and the curing rate is slow, and there is difficulty in controlling the molecular weight of the pressure-sensitive adhesive composition.

It does not specifically limit as said photoinitiator, For example, diethoxy acetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 4- (2-hydroxyethoxy) Phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2- Acetophenones such as dimethylamino-1- (4-morpholinophenyl) butanone and 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone oligomer; Benzoin such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether; Benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenylsulfide, 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzo Phenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N, N-dimethyl-N- [2- (1-oxo-2-propenyloxy) ethyl] benzenemethanealuminum bromide, (4-benzoyl Benzophenones such as benzyl) trimethylammonium chloride; 2-isopropyl thioxanthone, 4-isopropyl thioxanthone, 2,4-diethyl thioxanthone, 2,4-dichloro thioxanthone, 1-chloro-4-propoxy thioxanthone, 2- ( Thioxanthones, such as 3-dimethylamino-2-hydroxy) -3,4-dimethyl-9H- thioxanthone-9-one mesochloride; 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, bis (2,4,6-trimethylbenzoyl Acyl phosphon oxides such as) -phenylphosphine oxide; And the like. Moreover, only one of these photoinitiators may be used independently, and one or more may be used together.

As these preparations, triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Mihiler ketone), 4,4'-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, 4-dimethyl Ethyl aminobenzoate, 4-dimethylaminobenzoic acid (n-butoxy) ethyl, 4-dimethylaminobenzoic acid isoamyl, 4-dimethylaminobenzoic acid 2-ethylhexyl, 2,4-diethylthioxanthone, 2,4- It is also possible to use diisopropyl thioxanthone together.

Among these, benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoyl isopropyl ether, 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2-propyl) ketone, 2-hydroxy- Preference is given to using 2-methyl-1-phenylpropan-1-one.

In content of the said photoinitiator, the adhesive composition of this invention can further contain 0.5-1.0 weight part of photoinitiators with respect to 100 weight part of said (meth) acrylic acid ester monomers. When the photopolymerization initiator is out of the above range, many molecules having a short bond length may be generated, and thus durability may be weak.

In curing the pressure-sensitive adhesive composition of the present invention, electron rays, proton rays, neutral magnetic rays, and the like may be used in addition to electromagnetic waves such as ultraviolet rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, and infrared rays, X-rays, and γ-rays. Curing by ultraviolet irradiation is advantageous from the ease of obtaining the apparatus, the price, and the like.

As the light source for the ultraviolet irradiation, a high pressure mercury lamp, an electrodeless lamp, an ultra high pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light, and the like are used. In the case of the said high pressure mercury lamp, it is performed on condition of 5-3000mJ / cm <2>, Preferably it is 10-1000mJ / cm <2>. In the case of the electrodeless lamp, for example, it is carried out under a condition of 2 to 1500 mJ / cm 2, preferably 5 to 500 mJ / cm 2.

The irradiation time varies depending on the type of light source, the distance between the light source and the coated surface, the coating thickness, and other conditions, but usually several seconds to several tens of seconds, and in some cases, one second of water.

The pressure-sensitive adhesive composition of the present invention may absorb water for 48 hours in an environment of temperature 25 ℃, humidity 50%, and dried for 1 hour at a temperature of 100 ℃ can absorb more than 5.0% by weight of water compared to the weight of the pressure-sensitive adhesive composition. . The amount of water absorbed by the pressure-sensitive adhesive composition may be specifically 7.0 wt% or more. By the pressure-sensitive adhesive composition containing 25 parts by weight or more of the hydrophilic functional group-containing monomer with respect to 100 parts by weight of the acrylic acid ester monomer, it is possible to ensure a certain level of water absorption due to the hydrophilic functional group-containing monomer.

If the amount of water absorbed by the pressure-sensitive adhesive composition is less than 5.0% by weight, the moisture moisture is not sufficiently ranged, so that there is not enough water particles to induce expansion in the inside under high temperature and vacuum conditions, resulting in the moisture of the pressure-sensitive adhesive composition. There exists a problem that peeling becomes difficult after absorption, and there exists a possibility of causing moisture condensation in use with an adhesive composition. Preferably at least 5.0% by weight, most preferably at least 7.0% by weight, but the upper limit of the water absorption of the pressure-sensitive adhesive composition is not limited.

In addition, the water vapor transmission rate of the pressure-sensitive adhesive composition of the present invention is characterized in that 110g / m ² · 24hr or less under the conditions of temperature 40 ℃, relative humidity 70%. Moisture permeability refers to the degree of water vapor permeation through the paper, and refers to the amount of water vapor transmitted through the surface area of 1 m ² paper for 24 hours under a certain condition in g.

If the moisture permeability exceeds 110 g / m ² · 24hr at a temperature of 40 ° C. and a relative humidity of 70%, the network capable of moving moisture may not be dense. There is little interaction with and the moisture permeability is increased, on the contrary, the pressure-sensitive adhesive composition has a problem in that the cohesive force is low because the content of the hydrophilic functional group-containing monomer is low. Preferably, at 40 ° C. and 70% relative humidity, the water vapor transmission rate may be 100 g / m ² · 24hr or more, but the lower limit thereof is not limited.

The adhesive composition of the present invention is characterized in that the peel force after water absorption is smaller than the peel force before water absorption. Due to the reduced peel force after water absorption, the pressure-sensitive adhesive composition is neatly peeled from the adherend, whereby the adherend can be used again. At this time, the adhesive of the pressure-sensitive adhesive composition may be glass or plastic, for example, may be attached between a touch screen panel (TSP) and a liquid crystal display (LCD). .

1 is a schematic diagram showing before and after water absorption of the pressure-sensitive adhesive composition of the present invention. Referring to FIG. 1, before the water absorption, the pressure-sensitive adhesive composition is laminated between the TSP and the LCD to firmly adhere the adhesive. At this time, the present invention allows the adhesive composition to be removed without debris or residue after desorption of the adhesive composition and the LCD, containing a certain amount of hydrophilic functional group in the adhesive composition in order to give the LCD rework (rework) function Monomers.

Unlike before and after water absorption, after the high temperature, high temperature and low temperature and high humidity, the hydrophilic functional group-containing monomer can impregnate a certain level of water, and vapor bubbles inside the water particles in which the hydrophilic functional group-containing monomer is impregnated at low pressure after vacuum / high temperature conditions. Is generated and vaporized, the volume expansion occurs, the peeling force of the pressure-sensitive adhesive composition to the adherend becomes small.

Unlike the pressure-sensitive adhesive composition attached to TSP or LCD before water absorption, the pressure-sensitive adhesive composition attached to the LCD can be detached without residue or foreign matter due to the increased peeling force, and the pressure-sensitive adhesive composition can be easily removed compared to the conventional LCD. Can be reworked.

More specifically, the peeling force before water absorption of the pressure-sensitive adhesive composition may be characterized in that 1,500 ~ 2,000g / in, peeling force after water absorption is 800 ~ 1,100g / in. When the peeling force before water absorption of the pressure-sensitive adhesive composition is out of the above range, there is a fear of detachment from the adherend by the external environment or impact. In addition, when the peeling force after the water absorption of the pressure-sensitive adhesive composition is out of the above range does not peel the pressure-sensitive adhesive composition at the interface with the adhesive, there is a problem that the adhesive is torn when peeling off by twisting arbitrarily.

The present invention provides a pressure-sensitive adhesive layer characterized in that the pressure-sensitive adhesive composition is formed, and further, the pressure-sensitive adhesive layer can be used for the optical member.

Although the thickness of the said adhesive layer is not specifically limited, 5-300 micrometers is preferable, Especially 10-50 micrometers is preferable, Furthermore, 12-30 micrometers is preferable. When the thickness of the pressure-sensitive adhesive layer is too thin, there is a tendency that the adhesive physical properties are difficult to stabilize, and when too thick, the thickness of the entire optical member to which the pressure-sensitive adhesive layer can be applied tends to increase excessively.

As an optical member in this invention, it does not specifically limit, The optical film used suitably for image display apparatuses, such as a liquid crystal display device, an organic electroluminescence display, and a PDP, for example, a polarizing plate, a retardation plate, an elliptical polarizing plate, an optical compensation film, And luminance-enhanced films, and those in which they are laminated.

&Lt; Examples and Comparative Examples &

Example 1

30 parts by weight of 2-hydroxyethyl acrylate was thermally polymerized in a 1 liter glass reactor to 100 parts by weight of 2-ethylhexyl acrylate to obtain a polymer having a molecular weight of about 1 million. 0.5 parts by weight of Igacure-651 (a, a-methoxy-a-hydroxyacetophenone) as a photoinitiator, and 1,6-hexanediol diacrylate (HDDA) 0.35 as a crosslinking agent based on 100 parts by weight of the thermally polymerized resin. After adding the parts by weight, the mixture was sufficiently stirred to prepare an adhesive composition.

Example 2

Except for obtaining a polymer having a molecular weight of about 1.2 million including 25 parts by weight of 2-hydroxyethyl acrylate in Example 1, a pressure-sensitive adhesive composition was prepared as in Example 1.

Example 3

A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except for obtaining a polymer having a molecular weight of about 1 million by including 30 parts by weight of acrylic acid based on 100 parts by weight of 2-ethylhexyl acrylate in Example 1.

Example 4

The pressure-sensitive adhesive composition was prepared in the same manner as in Example 3 except that 25 parts by weight of acrylic acid was obtained to obtain a polymer having a molecular weight of about 1.1 million.

Example 5

A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except for obtaining a polymer having a molecular weight of about 1.1 million by including 30 parts by weight of glycidyl methacrylate with respect to 100 parts by weight of 2-ethylhexyl acrylate in Example 1. .

Example 6

A pressure-sensitive adhesive composition was prepared in the same manner as in Example 5 except that 25 parts by weight of glycidyl methacrylate was obtained to obtain a polymer having a molecular weight of about 1.2 million.

Comparative Example 1

15 parts by weight of 2-hydroxyethyl acrylate was thermally polymerized in a 1 liter glass reactor with respect to 100 parts by weight of 2-ethylhexyl acrylate to obtain a polymer having a molecular weight of about 1 million. 0.5 parts by weight of Igacure-651 (a, a-methoxy-a-hydroxyacetophenone) as a photoinitiator, and 1,6-hexanediol diacrylate (HDDA) 0.35 as a crosslinking agent based on 100 parts by weight of the thermally polymerized resin. After adding the parts by weight, the mixture was sufficiently stirred to prepare an adhesive composition.

Comparative Example 2

A pressure-sensitive adhesive composition was prepared in the same manner as in Comparative Example 1 except that 20 parts by weight of 2-hydroxyethyl acrylate was obtained to obtain a polymer having a molecular weight of about 1.2 million.

polymer HEA content Polymer molecular weight Example 1 EHA / HEA 30 parts by weight 1 million Example 2 EHA / HEA 25 parts by weight 1.2 million Example 3 EHA / AA 30 parts by weight 1 million Example 4 EHA / AA 25 parts by weight 1.1 million Example 5 EHA / GMA 30 parts by weight 1.1 million Example 6 EHA / GMA 25 parts by weight 1.2 million Comparative Example 1 EHA / HEA 15 parts by weight 1 million Comparative Example 2 EHA / HEA 20 parts by weight 1.2 million

< Experimental Example >-Physical Properties of Adhesive Composition

The pressure-sensitive adhesive composition of Examples and Comparative Examples of Table 1 was cured to prepare a pressure-sensitive adhesive layer having a thickness of 100 μm, and then the pressure-sensitive adhesive layer was attached between the TSP and the LCD. At this time, the water absorption of the pressure-sensitive adhesive layer, moisture permeability, peel strength, and LCD reuse (rework) The availability was measured.

1) Moisture absorption amount: The pressure-sensitive adhesive layer containing moisture for 48 hours in an environment of temperature 25 ℃, 50% humidity is dried for 1 hour at 100 ℃ temperature weight of the adhesive layer through a moisture analyzer (Moisture analyzer Ohus MB45) The rate of reduction was calculated and the moisture uptake was measured.

2) water vapor permeability: to the obtained measured value is allowed to stand for 3 hours in a constant temperature and humidity chamber of the pressure-sensitive adhesive layer temperature 40 ℃, relative humidity 70% and, calculating the amount of water passing through the 1m ² per unit area, per 24 hours, the pressure-sensitive adhesive layer from the moisture increase The moisture permeability was measured.

3) Peeling force: A pressure of 300 g per 1 cm ² was applied to the pressure-sensitive adhesive layer adhered to the LCD surface to bring the adhesive force into close contact. Thereafter, some of the ends of the pressure-sensitive adhesive layer were peeled at a peel rate of 300 mm / min at a peel angle of 180 degrees to measure its peel strength.

4) LCD reworkability: Heat the product at 70 ℃ under 50 Torr vacuum for more than 30 minutes under 50 Torr vacuum after allowing it to be absorbed by high temperature, high humidity (85/85) for 2 days with adhesive layer attached between TSP and LCD. Then, the pressure-sensitive adhesive layer was taken out and twisted to observe whether the LCD could be reworked after desorption with the LCD.

Water absorption
(%) Moisture permeability
(g / m ² · 24hr) Peeling force before water absorption (g / in) Peeling force after water absorption (g / in) LCD
Reworkability Example 1 5.943 100 1,600 1,020 possible Example 2 5.582 105 1,700 1,000 possible Example 3 6.237 95 2,000 800 possible Example 4 6.012 102 1,000 1,000 possible Example 5 5.810 97 1,900 1,100 possible Example 6 5.365 100 1,800 900 possible Comparative Example 1 4.968 117 1,800 1,600 impossible Comparative Example 2 4.730 120 1,800 1,600 impossible

Table 2 shows the results of the above water absorption, water vapor permeability, peel strength, and LCD rework. As a result, in the pressure-sensitive adhesive composition of Examples 1 to 6 containing 25 parts by weight or more of the hydrophilic functional group-containing monomer, it was found that it had a water absorption of 5% or more and a water vapor transmission rate of 110 g / m ² · 24hr or less. The water absorption amount and the moisture permeability of the above values include a smaller peeling force after water absorption than before water absorption, so that the LCD and the pressure-sensitive adhesive composition can be easily detached and left without residue or impurities, resulting in reuse of the LCD. (rework) is possible.

On the contrary, in the pressure-sensitive adhesive compositions of Comparative Examples 1 and 2 containing less than 25 parts by weight of the hydrophilic functional group-containing monomer, moisture absorption of not less than 5% and moisture permeability of 110 g / m ² · 24hr or less were not obtained. Peeling force before absorption and peeling force after water absorption were measured similarly. Desorption of the pressure-sensitive adhesive composition that does not have a difference in peeling force due to water absorption is still difficult, and even if peeling, foreign substances and impurities still exist, so it is difficult to rework the LCD.

Therefore, by containing a certain amount of the hydrophilic functional group-containing monomer in the pressure-sensitive adhesive composition to ensure moisture absorption and moisture permeability, thereby controlling the peeling force before and after the absorption of water, through the process of condensation and volume expansion of the absorbed moisture Desorption with the optical member becomes possible, and as a result, it is possible to give a rework function to the adherend.

Although the above description has been made with reference to embodiments of the present invention, this is merely exemplary, and a person skilled in the art to which the present invention pertains will understand that various modifications and equivalent other embodiments are possible. . Accordingly, the true scope of the present invention should be determined by the following claims.

Claims (9)

The adhesive composition characterized by including 25 weight part or more of hydrophilic functional group containing monomers with respect to 100 weight part of (meth) acrylic acid ester monomers.
The method of claim 1,
The pressure-sensitive adhesive composition, characterized in that the hydrophilic functional group-containing monomer is at least one selected from the group consisting of a hydroxyl group-containing monomer, an amino group-containing monomer, a carboxyl group-containing monomer, a sulfone group-containing monomer, a morpholine group-containing monomer, a glycidyl group-containing monomer.
The method of claim 1,
The adhesive composition of the said (meth) acrylic-ester type monomer and the said hydrophilic functional group containing monomer has a polymer molecular weight of 1 million-1,20 million.
The method of claim 1,
The (meth) acrylic acid ester monomer is methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t -Butyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, n-octyl (meth) Pressure-sensitive adhesive composition, characterized in that at least one selected from the group consisting of acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate and tetradecyl (meth) acrylate.
The method of claim 1,
The adhesive composition, further comprising 0.5 to 1.0 parts by weight of the photopolymerization initiator with respect to 100 parts by weight of the (meth) acrylic acid ester monomer.
The method of claim 1,
The pressure-sensitive adhesive composition absorbs moisture for 48 hours in an environment of temperature 25 ℃, humidity 50%, and dried for 1 hour at a temperature of 100 ℃, absorbing more than 5.0% by weight of water relative to the weight of the pressure-sensitive adhesive composition Pressure-sensitive adhesive composition.
The method of claim 1,
The water vapor transmission rate of the said pressure-sensitive adhesive composition is an adhesive composition, characterized in that 110g / m ² · 24hr or less under the conditions of temperature 40 ℃, relative humidity 70%. .
The method of claim 1,
The pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition, characterized in that the peel force after water absorption is smaller than the peel force before water absorption.
The method of claim 1,
The pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition, characterized in that the peeling force before water absorption 1,500 ~ 2,000g / in, the peeling force after water absorption is 800 ~ 1,100g / in.

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