JP2015525808A - Adhesive composition for optical film - Google Patents

Abstract

A pressure-sensitive adhesive composition used for an optical film is exfoliated cleanly from glass and plastic adhesives after moisture absorption, and the function of reusing the adhesive is provided. A pressure-sensitive adhesive composition comprising 25 parts by weight or more of a hydrophilic functional group-containing monomer with respect to 100 parts by weight of a (meth) acrylic acid ester monomer. The hydrophilic functional group-containing monomer includes 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. It is preferably selected from the group consisting of monomers. In addition, the present invention includes an adhesive composition comprising 25 parts by weight or more of a hydrophilic functional group-containing monomer with respect to 100 parts by weight of a (meth) acrylic acid ester monomer. An adhesive layer can be included. [Selection] Figure 1

Description

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

  Conventionally, a polarizing film, for example, a liquid crystal in which a polarizing plate coated with a cellulose-based film, for example, a cellulose triacetate film, on both sides of a polarizing film such as a polyvinyl alcohol-based film is aligned between two glass plates. The liquid crystal cell is laminated on the surface of the liquid crystal cell sandwiched between the components to form a liquid crystal display panel. The liquid crystal cell surface is usually laminated with the pressure-sensitive adhesive layer formed on the surface of the polarizing plate as the liquid crystal. This is done by contacting and pressing the cell surface.

  However, since the optical member on which the pressure-sensitive adhesive layer is formed is bonded to the liquid crystal cell and peeled again, foreign matter mixing, damage, adhesion failure, etc. may occur on the pressure-sensitive adhesive layer and the LCD, etc. There were difficulties in reworking the LCD. Korean Patent No. 10-098185 discloses a pressure-sensitive adhesive composition containing an acrylic polymer composed of a certain component, and the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition has a peeling force or durability. However, there is no description about the relationship between the adhesive layer and the adhesive before and after the peeling and the reuse function of the adhesive, so after the peeling of the adhesive layer It still contains the conventional problem that foreign matter or residue remains.

Korean Registered Patent No. 10-098185

  In order to solve the above problems, the present invention provides a function in which the pressure-sensitive adhesive composition used for an optical film is cleanly peeled off from a glass and plastic adhesive after moisture absorption, and the adhesive is reused. The purpose is to grant.

  In order to achieve the one object, the pressure-sensitive adhesive composition of the present invention contains 25 parts by weight or more of a hydrophilic functional group-containing monomer with respect to 100 parts by weight of a (meth) acrylic acid ester monomer. It is characterized by that.

  In order to achieve the other object, the present invention includes a pressure-sensitive adhesive layer formed by including the pressure-sensitive adhesive composition.

  The pressure-sensitive adhesive composition of the present invention can absorb moisture at a certain level or more by containing a certain amount or more of the hydrophilic functional group-containing monomer. After that, the moisture absorbed at high vacuum and high temperature boils, and volume expansion occurs, but it becomes easy to desorb from the glass or plastic to which the adhesive composition is attached, and the adhesive composition is peeled cleanly. Accordingly, the adherend such as glass or plastic has a rework function.

It is the figure which showed schematically before and after the water | moisture-content absorption of the adhesive composition which concerns on this invention.

  Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described later in detail. However, the present invention is not limited to the embodiments disclosed below, and can be embodied in various different forms. However, this embodiment is provided in order to complete the disclosure of the present invention and to fully inform the person of ordinary skill in the technical field to which the present invention belongs the scope of the invention. They are 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.

  By including the hydrophilic functional group-containing monomer, the pressure-sensitive adhesive composition of the present invention enables 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 moisture and causes moisture to exist through condensation inside the pressure-sensitive adhesive composition.

  Thereafter, the moisture absorbed at high vacuum and high temperature boils, and the volume expansion of the pressure-sensitive adhesive composition occurs, but due to the volume expansion, the pressure-sensitive adhesive composition has no residue or foreign matter from the adherend such as glass or plastic. Detachable. Accordingly, glass or plastic desorbed from the pressure-sensitive adhesive composition, specifically, each liquid crystal display device such as an LCD has a reuse function.

  The content of the hydrophilic functional group-containing monomer is 25 parts by weight or more with respect to 100 parts by weight of the (meth) acrylic acid ester monomer, but when it is less than 25 parts by weight, the hydrophilic functional group Since the content of the monomer is insufficient, the area where moisture can stagnate is insufficient, and the cohesive force between the hydrophilic functional group-containing monomers is reduced. There is a possibility that peeling will not be easily performed. The upper limit of the hydrophilic functional group-containing monomer inclusion ratio is not limited, but is preferably 80 parts by weight or more in order to impart a strong cohesive force and peel at any one interface. .

  The hydrophilic functional group-containing monomer is 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, or a glycidyl group-containing monomer. It is one or more types selected from the body.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxy. Octyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl (meth) acrylate and other (meth) acrylic acid hydroxyalkyl esters, caprolactone modified 2-hydroxyethyl (meth) acrylate, etc. Contains primary hydroxyl groups such as caprolactone-modified monomer, 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, N-methylol (meth) acrylamide, N-hydroxyethyl (meth) acrylamide Nomer; 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, 2-hydroxy- There may be mentioned secondary hydroxyl group-containing monomers such as 3-phenoxypropyl (meth) acrylate; tertiary hydroxyl group-containing monomers such as 2,2-dimethyl-2-hydroxyethyl (meth) acrylate.

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

  Examples of the amino group-containing monomer may include dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate.

  Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid, acrylamide N-glycolic acid, cinnamic acid and (meth) acrylic acid Michael. Additives (eg, acrylic acid dimer, methacrylic acid dimer, acrylic acid trimer, methacrylic acid trimer, acrylic acid tetramer, methacrylic acid tetramer, etc.), 2- (meth) acryloyloxyethyl dicarboxylic acid monoester (eg, 2-acryloyloxy) Ethyl succinic acid monoester, 2-methacryloyloxyethyl succinic acid monoester, 2-acryloyloxyethyl phthalic acid monoester, 2-methacryloyloxyethyl phthalic acid monoester, 2-acryloyloxyethyl hexahydride Phthalic acid monoester, 2-methacryloyloxy such acryloyloxyethyl hexahydrophthalic acid mono ester) may be mentioned the like.

  Examples of the sulfone group-containing monomer may include olefin sulfones such as ethylene sulfone, allyl sulfone, and methallyl sulfone, 2-acrylamide-2-methylpropane sulfone, styrene sulfone, or a salt thereof. Examples of the morpholine group-containing monomer may include 4-methylmorpholine, and examples of the glycidyl group-containing monomer may include glycidyl (meth) acrylate and allyl glycidyl ether.

  The pressure-sensitive adhesive composition of the present invention achieves the object of the present invention by increasing the water absorption rate by including the hydrophilic functional group-containing monomer and reusing the adhesive after the pressure-sensitive adhesive composition is peeled off. can do.

  At this time, the polymer molecular weight of the (meth) acrylic acid ester monomer and the hydrophilic functional group-containing monomer is 1,000,000 to 1,200,000. When the polymer molecular weight exceeds 1,200,000, there is a problem that the specific gravity of the pressure-sensitive adhesive composition is increased, and when the polymer molecular weight is less than 1,000,000, durability may be weakened.

  The (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 may be used. At this time, if the alkyl group contained in the monomer is excessively long chain, the cohesive force of the pressure-sensitive adhesive composition is reduced, and it may be difficult to adjust the glass transition temperature (Tg) and the adhesiveness. It is preferable to use a (meth) acrylic acid ester monomer having an alkyl group having 1 to 14 carbon atoms.

  The (meth) acrylic acid ester monomers are 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) acrylate, isooctyl (meth) acrylate, isononyl One or more selected from the group consisting of (meth) acrylate, lauryl (meth) acrylate, and tetradecyl (meth) acrylate may be used.

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

  By further including a photopolymerization initiator, the pressure-sensitive adhesive composition of the present invention can be cured by irradiation of active energy rays such as ultraviolet rays for a very short time, and the molecular weight of the pressure-sensitive adhesive composition can be reduced. Can be adjusted. When the thermal polymerization initiator is used, the pressure-sensitive adhesive composition is cured by heating, so that the curing rate is slow and it is difficult to adjust the molecular weight of the pressure-sensitive adhesive composition, but both may be used together as necessary.

  The photopolymerization initiator is not particularly limited, and examples thereof include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 4- (2-hydroxyethoxy ) Phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexylphenylketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino- Acetophenones such as 1- (4-morpholinophenyl) butanone, 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone oligomers; benzoyl, benzoin methyl ether, benzoin ethyl ether, benzoin Isopropyl ether, benzoin isobuty Benzoins such as ether; benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) Benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N, N-dimethyl-N- [2- (1-iodine-2-propenyloxy) ethyl] benzenemethanaminium bromide, (4-benzoylbenzyl) ) Benzophenones such as trimethylammonium chloride; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2- (3-dimethylamino- -Hydroxy) -3,4-dimethyl-9H-thioxanthone-9-one mesochloride and other thioxanthones; 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4 , 4-trimethyl-pentylphosphine oxide, acylphosphon oxides such as bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide; Moreover, only one of these photopolymerization initiators may be used alone, or one or more of them may be used in combination.

  These preparations include triethanolamine, triisopropanolamine, 4,4′-dimethylaminobenzophenone (Michler's ketone), 4,4′-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, and ethyl 4-dimethylaminobenzoate. Use in combination with ethyl 4-dimethylaminobenzoate (n-butoxy), isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, etc. Is also possible.

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

  In the content of the photopolymerization initiator, the pressure-sensitive adhesive composition of the present invention is a photopolymerization initiator of 0.5 part by weight to 1.0 part with respect to 100 parts by weight of the (meth) acrylate monomer. A weight part may be further included. When the photopolymerization initiator deviates from the above range, many molecules having a short bond length are generated, and durability may be weakened.

  In curing the pressure-sensitive adhesive composition of the present invention, in addition to electromagnetic waves such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays and infrared rays, X-rays and γ rays, an electron beam, a proton beam, a neutron beam or the like may be used. However, curing by irradiation with ultraviolet rays is advantageous from the viewpoint of curing speed, availability of an irradiation device, price, and the like.

And as a light source at the time of performing the said ultraviolet irradiation, a high pressure mercury lamp, an electrodeless lamp, a super high pressure mercury lamp carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light etc. are used. Wherein in the case of a high-pressure mercury lamp, for ^{example, 5mJ / cm 2 ~3000mJ / cm} 2, is preferably carried out irradiation under conditions of ^{10mJ / cm 2 ~1000mJ / cm 2} . Also, the case of the electrodeless lamp, for ^{example, 2mJ / cm 2 ~1500mJ / cm} 2, is preferably carried out irradiation under conditions of ^{5mJ / cm 2 ~500mJ / cm 2} mJ.

  The irradiation time varies depending on the type of light source, the distance between the light source and the coating surface, the coating thickness, and other conditions, but is usually several seconds to several tens of seconds, and in some cases, a fraction of a second. There may be.

  The pressure-sensitive adhesive composition of the present invention absorbed moisture for 48 hours in an environment of a temperature of 25 ° C. and a humidity of 50%, and was dried at a temperature of 100 ° C. for 1 hour. It can absorb more than wt% water. Specifically, the amount of moisture absorbed by the pressure-sensitive adhesive composition may be 7.0% by weight or more. When the pressure-sensitive adhesive composition contains 25 parts by weight or more of the hydrophilic functional group-containing monomer with respect to 100 parts by weight of the acrylate monomer, the hydrophilic functional group-containing monomer has a certain level. Water absorption can be ensured.

  When the amount of moisture absorbed by the pressure-sensitive adhesive composition is less than 5.0% by weight, it is in a range where moisture is not sufficiently moistened. Insufficient moisture particles are sufficient, and as a result, there is a problem that peeling becomes difficult after moisture absorption of the pressure-sensitive adhesive composition, and there is a possibility that moisture condensation is induced in use for the pressure-sensitive adhesive composition. The water absorption amount of the pressure-sensitive adhesive composition is preferably 5.0% by weight or more, and most preferably 7.0% by weight or more, but is limited to the upper limit of the water absorption amount of the pressure-sensitive adhesive composition. There is no reason.

Furthermore, the moisture permeability of the pressure-sensitive adhesive composition of the present invention is 110 g / m ² · 24 hr or less under conditions of a temperature of 40 ° C. and a relative humidity of 70%. Moisture permeability refers to the degree to which water vapor permeates through the paper, and refers to the amount of water vapor that permeates for 24 hours, which is the surface area of 1 m ² of paper under certain conditions, in g.

When the moisture permeability exceeds 110 g / m ² · 24 hr under conditions of a temperature of 40 ° C. and a relative humidity of 70%, there is a possibility that the network through which moisture can move is not dense, and in this case, a hydrophilic functional group-containing monomer The moisture permeability increases because there is almost no interaction with water particles due to the lack of the content of water, and on the contrary, the adhesive composition has a low cohesive force because the content of the hydrophilic functional group-containing monomer is low. There's a problem. The moisture permeability is preferably 100 g / m ² · 24 hr or more under conditions of a temperature of 40 ° C. and a relative humidity of 70%, but the lower limit is not limited.

  The pressure-sensitive adhesive composition of the present invention is characterized in that the peeling force after moisture absorption is smaller than the peeling force before moisture absorption. The pressure-sensitive adhesive composition is peeled cleanly from the adherend by the peeling force that has become smaller after moisture absorption, and as a result, the adherend can be reused. At this time, the adhesive of the pressure-sensitive adhesive composition may be glass or plastic, for example, between a touch screen panel (Touch Screen Panel, TSP) and a liquid crystal display device (Liquid Crystal Display, LCD). It may adhere.

  FIG. 1 is a diagram schematically showing before and after moisture absorption of the pressure-sensitive adhesive composition according to the present invention. Referring to FIG. 1, before moisture absorption, a pressure-sensitive adhesive composition is laminated between the TSP and the LCD to firmly adhere the adherend. At this time, the present invention provides a pressure-sensitive adhesive for removing the pressure-sensitive adhesive composition and the LCD and removing the pressure-sensitive adhesive composition without leaving any foreign matter or residue, and imparting a reuse function to the LCD. The composition includes a certain content of a hydrophilic functional group-containing monomer.

  Unlike before moisture absorption, the hydrophilic functional group-containing monomer can contain a certain level of moisture after high temperature and high humidity / low temperature and high humidity, and after vacuum / high temperature conditions, it becomes hydrophilic at low pressure. While vapor bubbles are generated and vaporized inside the moisture particles containing the functional functional group-containing monomer, volume expansion occurs, and the peeling force of the pressure-sensitive adhesive composition on the adherent is reduced.

  Unlike the adhesive composition attached to TSP or LCD before moisture absorption, the adhesive composition attached to the LCD can be detached without any residue or foreign matter due to the increased peeling force. Since the pressure-sensitive adhesive composition can be removed more easily than in the past, the LCD can be reused.

More specifically, the peeling force before moisture absorption of the pressure-sensitive adhesive composition is 1,500 g / in.
It can be characterized by ˜2,000 g / in, and peel strength after moisture absorption is 800 g / in˜1,100 g / in. When the peeling force before moisture absorption of the pressure-sensitive adhesive composition deviates from the above range, the pressure-sensitive adhesive composition may be detached from the adherend due to an external environment or impact. In addition, when the peeling force after moisture absorption of the pressure-sensitive adhesive composition deviates from the above range, the pressure-sensitive adhesive composition is not peeled off at the interface with the adherent, and therefore the adhesive is peeled off when twisted arbitrarily. There is a problem of tearing.

  The present invention provides a pressure-sensitive adhesive layer formed by including the pressure-sensitive adhesive composition, and the pressure-sensitive adhesive layer can be used for an optical member.

  The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 5 μm to 300 μm, particularly preferably 10 μm to 50 μm, and more preferably 12 μm to 30 μm. If the thickness of the pressure-sensitive adhesive layer is excessively thin, the adhesive physical properties tend to be difficult to stabilize. If the thickness of the pressure-sensitive adhesive layer is excessively large, the thickness of the entire optical member to which the pressure-sensitive adhesive layer can be applied. Tends to increase excessively.

  The optical member in the present invention is not particularly limited, and an optical film that is appropriately used for an image display device such as a liquid crystal display device, an organic EL display device, or a PDP, such as a polarizing plate, a retardation plate, or an elliptically polarized light. A plate, an optical compensation film, a brightness enhancement film, and those in which these are laminated may also be mentioned.

<Examples and Comparative Examples>

Example 1
30 parts by weight of 2-hydroxyethyl acrylate with respect to 100 parts by weight of 2-ethylhexyl acrylate was thermally polymerized in a 1 liter glass reactor to obtain a polymer having a molecular weight of about 1,000,000. With respect to 100 parts by weight of the thermally polymerized resin, 0.5 part by weight of Irgacure-651 (a, a-methoxy-a-hydroxyacetophenone) as a photoinitiator and 1,6-hexanediol diester as a crosslinking agent After adding 0.35 weight part of acrylate (HDDA), it fully stirred and manufactured the adhesive composition.

(Example 2)
A pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that a polymer containing 25 parts by weight of 2-hydroxyethyl acrylate and having a molecular weight of about 1,200,000 was obtained.

(Example 3)
A pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that a polymer containing 30 parts by weight of acrylic acid with respect to 100 parts by weight of 2-ethylhexyl acrylate and having a molecular weight of about 1,000,000 was obtained.

Example 4
A pressure-sensitive adhesive composition was produced in the same manner as in Example 3 except that a polymer containing 25 parts by weight of acrylic acid and having a molecular weight of about 1.1 million was obtained.

(Example 5)
A pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that a polymer containing 30 parts by weight of glycidyl methacrylate with respect to 100 parts by weight of 2-ethylhexyl acrylate and having a molecular weight of about 1.1 million was obtained. .

(Example 6)
A pressure-sensitive adhesive composition was produced in the same manner as in Example 5 except that a polymer containing 25 parts by weight of glycidyl methacrylate and having a molecular weight of about 1,200,000 was obtained.

(Comparative Example 1)
15 parts by weight of 2-hydroxyethyl acrylate with respect to 100 parts by weight of 2-ethylhexyl acrylate was thermally polymerized in a 1 liter glass reactor to obtain a polymer having a molecular weight of about 1,000,000. With respect to 100 parts by weight of the thermally polymerized resin, 0.5 part by weight of Irgacure-651 (a, a-methoxy-a-hydroxyacetophenone) as a photoinitiator and 1,6-hexanediol diester as a crosslinking agent After adding 0.35 weight part of acrylate (HDDA), it fully stirred and manufactured the adhesive composition.

(Comparative Example 2)
A pressure-sensitive adhesive composition was produced in the same manner as Comparative Example 1 except that a polymer containing 20 parts by weight of 2-hydroxyethyl acrylate and having a molecular weight of about 1,200,000 was obtained.

<Experimental Example> -Physical Properties of Adhesive Composition After the adhesive compositions of Examples and Comparative Examples in Table 1 were cured to produce an adhesive layer having a thickness of 100 μm, between the TSP and the LCD The pressure-sensitive adhesive layer was attached, and at this time, the water absorption amount, moisture permeability, peeling force and LCD reusability of the pressure-sensitive adhesive layer were measured.

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

2) Moisture permeability: Moisture that permeated the pressure-sensitive adhesive layer for 24 hours per 1 m ² area from the increased amount of water by leaving the pressure-sensitive adhesive layer in a constant temperature and humidity chamber at a temperature of 40 ° C. and a relative humidity of 70% for 3 hours. The amount was calculated, and the moisture permeability was measured with the obtained measured value.

3) Peeling force: The adhesive layer adhered to the LCD surface was brought into close contact with a load of 300 g per 1 cm ² area. Then, the partial end of the pressure-sensitive adhesive layer was peeled off at a peeling speed of 300 mm / min at a peeling angle of 180 degrees, and the peel strength was measured.

4) LCD reusability: With a pressure-sensitive adhesive layer adhered between the TSP and the LCD, it was left at high temperature and high humidity (85/85) for 2 days to absorb moisture, and then under a vacuum of 50 Torr, 70 After heating at 30 ° C. for 30 minutes or more, the pressure-sensitive adhesive layer was taken out, twisted and detached from the LCD, and then the LCD was observed for reuse.

Table 2 shows experimental results of the moisture absorption amount, moisture permeability, peeling force, and LCD reusability measurement. As a result, in the case of the pressure-sensitive adhesive compositions of Examples 1 to 6 containing 25 parts by weight or more of the hydrophilic functional group-containing monomer, the moisture absorption amount is 5% or more and the permeability is 110 g / m ² · 24 hr or less. It was found to have humidity. Since the numerical value of moisture absorption and moisture permeability are included, it will have a smaller peel force after moisture absorption than before moisture absorption, making it easier to desorb the LCD from the adhesive composition, residues and impurities, etc. As a result, the LCD can be reused.

On the contrary, in the case of the pressure-sensitive adhesive compositions of Comparative Example 1 and Comparative Example 2 containing less than 25 parts by weight of the hydrophilic functional group-containing monomer, the water absorption amount is 5% or more and 110 g / m ² · 24 hr. Since the following moisture permeability cannot be secured, the peel force before moisture absorption and the peel force after moisture absorption were measured to be similar values. Desorption of the pressure-sensitive adhesive composition having no difference in peeling force due to moisture absorption is still difficult, and even if it is peeled off, foreign substances and impurities still exist, and it is difficult to reuse the LCD.

  Therefore, the moisture absorption capacity and moisture permeability can be ensured by including a certain amount of the hydrophilic functional group-containing monomer in the pressure-sensitive adhesive composition, thereby adjusting the peeling force before and after moisture absorption and absorbing the absorbed moisture. Desorption from the optical member becomes possible through processes such as condensation and volume expansion, and as a result, a reuse function can be imparted to the adherend.

  In the above, the embodiments of the present invention have been described mainly. However, this is merely an example, and various modifications and equivalents will be made by engineers having ordinary knowledge in the technical field to which the present invention belongs. It will be appreciated that other embodiments are possible. Accordingly, the true technical protection scope of the present invention should be determined by the claims set forth below.

Claims (9)

A pressure-sensitive adhesive composition comprising 25 parts by weight or more of a hydrophilic functional group-containing monomer with respect to 100 parts by weight of a (meth) acrylic acid ester monomer. The hydrophilic functional group-containing monomer includes 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. The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition is one or more selected from the group consisting of monomers. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the polymer molecular weight of the (meth) acrylic acid ester monomer and the hydrophilic functional group-containing monomer is 1,000,000 to 1,200,000. The (meth) acrylic acid ester monomers are 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) acrylate, isooctyl (meth) acrylate, isononyl The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition is one or more selected from the group consisting of (meth) acrylate, lauryl (meth) acrylate, and tetradecyl (meth) acrylate. The pressure-sensitive adhesive according to claim 1, further comprising 0.5 to 1.0 parts by weight of a photopolymerization initiator with respect to 100 parts by weight of the (meth) acrylic acid ester monomer. Composition. The pressure-sensitive adhesive composition absorbs moisture for 48 hours in an environment at a temperature of 25 ° C. and a humidity of 50% and is dried at a temperature of 100 ° C. for 1 hour. As a result, the pressure-sensitive adhesive composition is 5.0% by weight relative to the weight of the pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition according to claim 1, which absorbs the above moisture. The pressure-sensitive adhesive composition according to claim 1, wherein moisture permeability of the pressure-sensitive adhesive composition is 110 g / m ² · 24 hr or less under conditions of a temperature of 40 ° C and a relative humidity of 70%. The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition has a peeling force after moisture absorption that is smaller than a peeling force before moisture absorption. The pressure-sensitive adhesive composition has a peeling force before moisture absorption of 1,500 g / in to 2,000 g / in, and a peeling force after moisture absorption of 800 g / in to 1,100 g / in, The pressure-sensitive adhesive composition according to claim 1.

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