KR100383092B1 - Acrylic pressure sensitive adhesives composition having superior residual stress relaxation effect - Google Patents

Abstract

The present invention relates to a high functional pressure sensitive adhesives composition used to prepare an adhesive for an optical film, in particular an acrylic pressure-sensitive adhesive composition that can minimize the residual stress caused by the difference in the dimensional change of the substrate and the pressure-sensitive adhesive It is about.

The present invention comprises a) i) 20 to 98.4 parts by weight of a (meth) acrylic acid ester monomer having an alkyl group having 4 to 12 carbon atoms; Ii) 1 to 30 parts by weight of (meth) acrylic acid ester having a high flexibility long chain structure; Iii) 1 to 30 parts by weight of (meth) acrylic acid ester having a homopolymer glass transition temperature (Tg) of a bulky structure or above room temperature; Iii) 0.1 to 5 parts by weight of a vinyl monomer containing a hydroxyl group; And iii) 100 parts by weight of an acrylic copolymer prepared by copolymerizing 0.5 to 10 parts by weight of an α, β unsaturated carboxylic acid monomer; b) 0.01 to 5 parts by weight of a crosslinking agent; And c) 0.01 to 2 parts by weight of a silane coupling agent.

The composition of the present invention not only has stress relaxation characteristics that can minimize the formation of residual stresses that can cause problems in display function when the liquid crystal panel is used for a long period of time, as well as initial adhesion, permanent adhesion, retention, and cutting characteristics. It is an acrylic adhesive composition excellent in various physical properties. In addition, the pressure-sensitive adhesive product using the acrylic pressure-sensitive adhesive composition of the present invention as an adhesive layer effectively improves the reliability.

Description

ACRYLIC PRESSURE SENSITIVE ADHESIVES COMPOSITION HAVING SUPERIOR RESIDUAL STRESS RELAXATION EFFECT}

[Industrial use]

The present invention relates to a high functional pressure sensitive adhesives composition used to prepare an adhesive for an optical film, in particular an acrylic pressure-sensitive adhesive composition that can minimize the residual stress caused by the difference in the dimensional change of the substrate and the pressure-sensitive adhesive It is about. Specifically, stress concentration phenomenon caused by thermal contraction and expansion of various types of substrates such as functional films having various chemical structures can be alleviated to the maximum, and at the same time, various properties such as initial adhesive strength, permanent adhesive strength, holding force, cutting characteristics, etc. It is related with this excellent acrylic adhesive composition.

[Prior art]

Adhesives are used for a wide variety of applications such as sheets, films, labels, and tapes because of their ease of use. Recently, optical adhesives for optical films, which require various high functionalities and durability, are also being applied to liquid crystal displays. It is expanding.

In general, a liquid crystal display panel requires a liquid crystal cell containing a liquid crystal and a polarizing plate, and an appropriate adhesive layer or adhesive layer is used to coalesce it. In addition, in order to improve the function of the liquid crystal panel, an additional retardation plate or a light recovery plate is attached and used.

The main structure of such a liquid crystal panel

a) a transparent glass plate comprising a liquid crystal layer and a transparent electrode layer which are constantly arranged

Or a liquid crystal cell comprising an acrylic plate-like material; And

b) a polarizing plate, a retardation plate, and a multilayered structure integrated into an adhesive layer or an adhesive layer, and

Additional functional film layer

And the like.

The polarizing plate includes an iodine-based compound or a dichroic polarizing material arranged in a predetermined direction, and in order to protect the polarizing plate, a polarizing plate is generally configured in a multilayered shape using a protective film on both sides, and the retardation film has a unidirectional molecular array. It is shaped.

Each of the films is made of a material having a different molecular structure and composition, each having different physical properties. In particular, when the liquid crystal panel is used for a long time, the molecular structure changes over time due to the aging characteristics of the material. For example, due to the difference in the coefficient of linear expansion of the material, the effect of continuous deformation stress between the film and the film due to the temperature change occurs, and the shrinkage due to the stress relaxation effect of the material having a unidirectional molecular arrangement after a long time elapses. do. Therefore, in order to manufacture the liquid crystal panel by incorporating each of these materials, an adhesive or a pressure-sensitive adhesive must be used.

However, the conventional pressure-sensitive adhesive is difficult to minimize the residual stress caused by the difference in the dimensional change of the base material and the pressure-sensitive adhesive, which has a number of problems in durability and reliability, especially when used for a long time.

On the other hand, Japanese Patent Application Laid-Open No. 57-195208 discloses an interfacial property between a glass plate and a polarizing plate by adding a silane coupling agent to the pressure-sensitive adhesive composition in order to improve the durability of the pressure-sensitive adhesive film under the heat and moisture resistance test conditions of the liquid crystal display panel with a polarizing plate. A technique for effectively improving is disclosed.

In addition, Japanese Patent Laid-Open Publication No. 64-66238 uses a high molecular weight acrylic resin from which a low molecular weight portion has been removed as an adhesive for the same purpose, and simultaneously improves the elastic modulus and adhesive properties of the adhesive layer, thereby producing minute fines generated between the glass plate and the adhesive layer. The technique which reduces generation | occurrence | production of a bubble and prevents peeling of an adhesion layer is disclosed.

In addition, Japanese Patent Application Laid-Open No. 3-12471 discloses a technique of improving durability by improving high temperature adhesive strength by controlling a crosslinking density in a specific range using a high molecular weight acrylic adhesive, but using a high molecular weight resin Since the crosslinking density is severely changed depending on the amount of used, it is very difficult to control the crosslinking density between molecules and it is difficult to uniformly control the stress concentration phenomenon between the substrates.

In addition, Japanese Patent Application Laid-open No. Hei 7-301792 discloses a technique for adjusting the deformation cohesion force of the pressure-sensitive adhesive to solve the problem of screen unevenness of the liquid crystal display panel caused by the concentration of stress between the pressure-sensitive adhesive film and the glass plate under heat and moisture resistance conditions. Depending on the pressure-sensitive adhesive used, there is a problem that it is difficult to maintain a constant deformation cohesion such as a change over time due to the continuous progress of the crosslinking reaction. In particular, when the pressure-sensitive adhesive layer is prepared using a copolymer prepared by introducing a certain amount of reactive functional groups into the non-reactive acrylic main monomer, it is difficult to effectively control the crosslinking structure exhibiting cohesion and cohesion. there is a problem.

In addition, Japanese Patent Application Laid-open No. Hei 8-120238 discloses a technique using an alcohol containing an epoxy functional group to reduce the effect on the durability of the change in adhesion properties between the film and the glass plate according to the cohesion of the pressure-sensitive adhesive and the time-dependent change of the adhesive force. As a means for adjusting the cohesive force and adhesive force of the pressure-sensitive adhesive, it is insufficient to provide uniform cohesive force and adhesive force, and it is very difficult to control, resulting in insufficient effectiveness. That is, since the crosslinking agent used for the pressure sensitive adhesive mainly contains 3 or more reactive functional groups, it is difficult to precisely control the molecular structure of the pressure sensitive adhesive due to the complexity of the resulting pressure sensitive adhesive layer crosslinked structure.

In consideration of the problems of the prior art, the present invention provides an acrylic pressure-sensitive adhesive composition having a stress relaxation property that can minimize the formation of residual stresses that can cause problems in display function when the liquid crystal panel is used for a long time. It aims to do it.

Another object of the present invention is to provide an adhesive product comprising a pressure-sensitive adhesive layer that can effectively improve the durability reliability of the adhesive product.

Still another object of the present invention is to mitigate the stress concentration phenomenon caused by thermal contraction and expansion of various types of substrates, such as functional films having various chemical structures to the maximum, while at the same time the initial adhesion, permanent adhesion, holding force, cutting characteristics It is to provide an acrylic pressure-sensitive adhesive composition excellent in various physical properties.

[Means for solving the problem]

The present invention to achieve the above object,

a) iii) a (meth) acrylic acid ester monomer having an alkyl group having 4 to 12 carbon atoms

20 to 98.4 parts by weight;

Ii) (meth) acrylic acid ester having a high flexibility and long chain structure

1 to 30 parts by weight;

Iii) having a homopolymer glass transition temperature (Tg) above the room temperature of the bulky structure

1 to 30 parts by weight of (meth) acrylic acid ester;

Iii) 0.1 to 5 parts by weight of a vinyl monomer containing a hydroxyl group; And

Viii) 0.5 to 10 parts by weight of an α, β unsaturated carboxylic acid monomer

100 parts by weight of an acrylic copolymer prepared by copolymerizing; And

b) 0.01 to 5 parts by weight of crosslinking agent

It provides an acrylic pressure-sensitive adhesive composition comprising a.

The present invention also relates to 100 parts by weight of the acrylic copolymer of a) in the composition

c) 0.01 to 2 parts by weight of silane coupling agent

It also provides an acrylic pressure-sensitive adhesive composition further comprising.

[Action]

The present invention is to use a specific acrylic copolymer resin to have a partial crosslinked structure of the pressure-sensitive adhesive composition, such a pressure-sensitive adhesive composition is to minimize the stress accumulated in the pressure-sensitive adhesive layer in the deformation state of the pressure-sensitive adhesive layer caused by shrinkage expansion between the substrates In particular, the balance of physical properties of the pressure-sensitive adhesive can be maintained, and the residual stress can be effectively reduced. The element necessary for minimizing the residual stress is to impart the flow characteristics of the polymer chains forming the adhesive layer, which enhances the stress relaxation of the polymer chains forming the adhesive as the substrate shrinks and expands.

In another aspect, the present invention is a high-functional display device such as a polarizing plate, an optical function addition film, or a light control film used for the purpose of controlling the optical properties of the pressure-sensitive adhesive layer prepared by depositing the pressure-sensitive adhesive composition interposed between the film and manufactured by plywood It provides an optical film.

The present invention controls the structure of the pressure-sensitive adhesive used in the pressure-sensitive adhesive sheet, the optical pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive under the control of the entanglement (physical structure) between physical chains while maintaining the crosslinking density by chemical bonding is required. It is intended to represent. In particular, by using an acrylic copolymer prepared using a copolymerizable monomer capable of controlling specific flow characteristics, after the pressure-sensitive adhesive composition is mixed, the crosslinking density of the pressure-sensitive adhesive is adjusted in the range of 5 to 90%, more preferably 15 to 80%. By using the pressure-sensitive adhesive was to minimize the residual stress of the product using the pressure-sensitive adhesive.

Preferred pressure-sensitive adhesive of the present invention is preferably used after sufficiently removing the components causing the bubbles such as volatile components and reaction residues in the interior of the pressure-sensitive adhesive. This is because when the crosslinking density or molecular weight is too low and the elastic modulus of the pressure sensitive adhesive is too low, small bubbles existing between the glass plate and the pressure sensitive adhesive layer may grow in high temperature to form scatterers inside the pressure sensitive adhesive layer. When the adhesive with too high elastic modulus is used, peeling may occur at the end portion of the adhesive sheet when used for a long time, which is often caused by excessive crosslinking reaction.

The viscoelastic properties of the pressure-sensitive adhesive according to the present invention mainly depend on the molecular weight and molecular weight distribution of the polymer chain, and the amount of branching structure present, and are mainly determined by the molecular weight. The preferred molecular weight of the acryl-based copolymer of a) is about 200,000 to 2 million, and is prepared by a well-known radical copolymerization process, in general solution polymerization, bulk polymerization, photopolymerization, suspension polymerization, or emulsion. It can manufacture using a legitimate method.

The residual stress generated by shrinkage expansion of the optical film used with the pressure-sensitive adhesive layer is very large. The pressure-sensitive adhesive prepared according to the present invention causes the stress relaxation effect to occur very effectively by the movement of the molecular units occurring in the non-crosslinked portion.

In addition, the crosslinking density may be lowered by using a plasticizer. In this case, a significant change in the adhesion characteristics is expected under heat and moisture resistance conditions due to the transition characteristics caused by a large amount of the plasticizer. In addition, the crosslinking density can be controlled downward by using a tackifier that is frequently used in pressure sensitive adhesive applications, but the glass transition temperature of the resin is increased to weaken the low temperature adhesive property, and the stability of the tackifying resin is poor when used for a long time. The change in adhesion characteristics with time may appear as a problem.

The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition mainly composed of a partially crosslinkable acrylic copolymer prepared by copolymerizing a specific flexible monomer and a monomer having a bulky structure, and easily balances cohesion and adhesive strength including stress relaxation characteristics. It can be adjusted, and can realize a stable and time-free adhesive properties without using additives such as a plasticizer and a tackifier resin, it can be prepared as a pressure-sensitive adhesive layer that can easily control the stress relaxation properties of the pressure-sensitive adhesive.

Hereinafter, the main raw material of the said adhesive composition is demonstrated.

In the raw materials used to prepare the acrylic copolymer of a), a (meth) acrylic acid ester monomer having an alkyl group having 4 to 12 carbon atoms of (i) is used as the main monomer. The alkyl (meth) acrylate is preferably selected from the range of 4 to 12 carbon atoms of the alkyl group in order to maintain the cohesive force under high temperature because the cohesive force of the pressure-sensitive adhesive is lowered when the alkyl group is in the long chain form.

The amount used is 20 to 98.4 parts by weight in 100 parts by weight of the acrylic copolymer of a), preferably 40 to 95 parts by weight, more preferably 60 to 90 parts by weight is effective to copolymerize. When the amount of use exceeds 90 parts by weight, the residual stress relaxation effect is relatively low. When the amount is less than 60 parts by weight, the cohesive force of the pressure-sensitive adhesive is lowered, and the cost increases.

Examples of the (meth) acrylic acid ester monomer having an alkyl group having 4 to 12 carbon atoms (i) include butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, t-butyl (meth) acrylate, and pentyl (meth). ) Acrylate, n-octyl (meth) acrylate, or isononyl (meth) acrylate. In addition, ethyl (meth) acrylate, methyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, acryl Copolymerizable monomers such as nitrile, styrene, glycidyl (meth) acrylate, or vinyl acetate may be additionally used. These monomers can be used individually or in mixture of 2 or more types.

In the raw materials used to prepare the acrylic copolymer of a), the (meth) acrylic acid ester having a long chain structure with high flexibility of ii) is for the purpose of enhancing the flexibility of the polymer chain and lowering the glass transition temperature. Used.

This component is preferably copolymerized by including 1 to 30 parts by weight, preferably 2 to 20 parts by weight, more preferably 3 to 15 parts by weight within 100 parts by weight of the acrylic copolymer of a). Less than 3 parts by weight does not significantly increase the flexibility of the polymer chains to reduce the residual stress, less than 20 parts by weight of cohesion is lowered may be a problem in durability reliability.

The (meth) acrylic acid ester having such a flexible long chain structure is typically a (meth) acrylic acid ester component of a compound in which 1-20 ethylene oxide or propylene oxide molecular units are added to an alkyl alcohol compound alone or randomly added. Can be used. Examples of this component are methoxydiethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, octyloxydiethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, ethoxydipropylene glycol (Meth) acrylate, octyloxydipropylene glycol (meth) acrylate, methoxy triethylene glycol (meth) acrylate, ethoxy triethylene glycol (meth) acrylate, octyloxy triethylene glycol (meth) acrylate, Methoxy tripropylene glycol (meth) acrylate, ethoxy tripropylene glycol (meth) acrylate, octyloxytripropylene glycol (meth) acrylate, methoxy tetraethylene glycol (meth) acrylate, ethoxy tetraethylene glycol ( Meta) acrylate, octyloxytetraethylene glycol (meth) acrylate, methoxytetrapropyleneglycol (Meth) acrylate, ethoxy tetrapropylene glycol (meth) acrylate, octyloxy tetrapropylene glycol (meth) acrylate, methoxy decaethylene glycol (meth) acrylate, ethoxy decaethylene glycol (meth) acrylate, Octyloxydecaethylene glycol (meth) acrylate, methoxy decapropylene glycol (meth) acrylate, ethoxy decapropylene glycol (meth) acrylate or octyloxydecapropylene glycol (meth) acrylate, and the like, and these are singly or mixed. Can be used.

In the raw materials used to prepare the acrylic copolymer of a), the (meth) acrylic acid ester having a homopolymer glass transition temperature above the room temperature of the bulky structure of i) reduces the deformation cohesion of the polymer chain. It is used as a monomer that plays a role of increasing the glass transition temperature at the same time.

This component is effective to use 1 to 30 parts by weight, preferably 2 to 25 parts by weight, more preferably 3 to 20 parts by weight within 100 parts by weight of the acrylic copolymer of a).

Examples of (meth) acrylic acid esters having a homopolymer glass transition temperature of room temperature or more having such a bulky structure are isobornyl acrylate, isobornyl methacrylate, dicyclopentadiene ethylene glycol (meth) acrylate, and the like. . In addition, the glass transition temperature of the homopolymer is higher than room temperature, and a vinyl monomer having a bulky structure may also be used. These components may be used alone or in combination. In particular, in the present invention, since the structure of the polymer chain is controlled by a polymerization process, there is an advantage in that a reliable pressure-sensitive adhesive may be prepared by preventing problems such as phase separation due to excessive additives.

In the raw materials used to prepare the acrylic copolymer of a), the vinyl monomer including the hydroxyl group of iii) is a component which imparts cohesive force of the pressure-sensitive adhesive alone or by reacting with a crosslinking agent. It is preferable to copolymerize 0.1-5 weight part in 100 weight part of coalescing. The use of less than 0.1 parts by weight has a small effect of increasing the holding force, the use of more than 5 parts by weight is low in the stress relaxation effect.

Examples of vinyl monomers containing such hydroxyl groups include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate, or 2-hydroxy Propylene glycol (meth) acrylates and the like, and these may be used alone or in combination if necessary.

In the raw materials used to prepare the acrylic copolymer of a), the α, β unsaturated carboxylic acid monomer of i) is a component that imparts the adhesive strength or cohesion, within 100 parts by weight of the acrylic copolymer of a) Including 0.5 to 10 parts by weight of the copolymer is preferable. The use of less than 0.5 parts by weight lowers the adhesive force, and when used in excess of 10 parts by weight reduces the stress relaxation characteristics due to the increase in cohesive force.

Examples of such α, β unsaturated carboxylic monomers include acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, and the like, and these may be used alone or in combination if necessary.

Isocyanate-based, epoxy-based, or aziridine-based may be used as the crosslinking agent of b), of which isocyanate-based is easy to use. The crosslinking agent is used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the acrylic copolymer of a). These crosslinking agents enhance the holding strength of the pressure-sensitive adhesive through the crosslinking structure to improve reliability.

Examples of such crosslinking agents include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, or an adduct of tolylene diisocyanate of trimethylolpropane, and the epoxy type is ethylene glycol diglycidyl ether, triglycol. Cylyl ether, trimethol propane triglycidyl ether, or N, N, N ', N'- tetraglycidyl ethylenediamine, etc. are mentioned.

The pressure-sensitive adhesive composition of the present invention may use the silane coupling agent of c) to improve the adhesion stability when in contact with the glass plate to further improve the heat and moisture resistance characteristics. This component serves to improve the adhesion reliability, especially when left for a long time under high temperature and high humidity. This component can use vinyl silane, epoxy silane, methacryl silane, etc., and can use 0.01-2 weight part with respect to 100 weight part of acrylic copolymers of a).

Examples of such silane coupling agent compounds include vinyltrimethoxysilane, vinyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane, and these are singly or mixed. It can also be used.

The pressure-sensitive adhesive composition of the present invention may be used by adding an appropriate amount of antioxidant, pigment, filler, dye, coupling agent, tackifier resin, plasticizer, softener and the like as needed for a specific purpose in addition to the above components.

The pressure-sensitive adhesive composition of the present invention may be prepared by a photopolymerization curing method by the addition of a suitable photoinitiator, which is generally well known.

The pressure-sensitive adhesive composition of the present invention is used as a pressure-sensitive adhesive layer of other optical films such as a polarizing plate or a retardation film, and does not form residual stress, and has a good balance of adhesive strength and cohesion, so that a display function such as peeling or bubbles is achieved. This deterioration can be prevented.

The pressure-sensitive adhesive composition excellent in the stress relaxation characteristics of the present invention can be applied to the pressure-sensitive adhesive layer of high-precision optical, electrical and electronic products that is not limited to the case of the liquid crystal display panel, which is a problem due to shrinkage or expansion. In addition, it is not only applicable to the optical, but the concept of operation such as a general commercial adhesive sheet product, a medical patch, a heat active adhesive (heat atcivatable, pressure-sensitive adhesive), etc., which is a multilayer laminate product, can be applied to the same application field. .

The present invention will be described in detail through the following examples and comparative examples. However, the examples are only for illustrating the present invention and are not limited thereto.

EXAMPLE

Example 1

(Acrylic copolymer production)

79 parts by weight of n-butylacrylate (BA; n-butylacrylate), ethoxydipropylene glycol acrylate (as shown in Table 1) in a 1000 ml reactor equipped with a refrigeration system to facilitate nitrogen temperature reflux and temperature control. 7 parts by weight of EDPA; ethoxydipropyleneglycolacrylate, 8 parts by weight of isobonylmethacrylate (IBMA), 1 part by weight of 2-hydroxyethyl (meth) acrylate (2-HEMA; and 100 parts by weight of ethylacetate (EAc) was added to the monomer mixture and 5 parts by weight of acrylic acid (AA).

In order to remove oxygen, nitrogen gas was supplied for 20 minutes, maintained at 70 ° C., uniformed, and then diluted with ethyl acetate to 0.015 parts by weight of benzoylperoxide (BPO) as a reaction initiator at 50% concentration. The reaction was carried out for 10 hours to prepare a final acrylic copolymer.

The molecular weight of the prepared acrylic copolymer was measured using a polystyrene standard sample, and the results are shown in Table 1.

(Acrylic pressure-sensitive adhesive composition production)

As shown in Table 2, 2.0 parts by weight of tolylene diisocyanate adduct of isocyanate trimethylolpropane as a crosslinking agent was added to 100 parts by weight of the acryl-based copolymer obtained above as a solution diluted in 50% concentration in ethyl acetate solution. -0.05 parts by weight of glycidoxy propyl trimethoxysilane was added to a solution diluted to 50% concentration in ethyl acetate solution, and uniformly mixed to prepare an acrylic pressure-sensitive adhesive composition.

(Adhesive layer production)

The acrylic adhesive composition prepared above was coated on a release paper and dried to obtain a uniform adhesive layer having a thickness of 30 μm.

(Plywood processing)

The pressure-sensitive adhesive layer prepared above was tack-processed to a 150 μm thick iodine-based polarizing plate using a laminator.

(Durability evaluation)

The pressure-sensitive adhesive coated polarizing plate (90 mm x 170 mm size) was attached to a glass substrate (110 mm x 190 mm x 0.7 mm) in a state where the optical axis was cross on both sides. At this time, the applied pressure was 5 kg / ㎠ to clean room work so as not to generate bubbles or foreign matter.

The specimens were left for 1000 hours at 60 ° C. and 90% relative humidity to observe the heat and moisture resistance.

The heat resistance was observed after 1000 hours at 80 ℃ bubble or peeling occurred.

The specimens were used for the test after being left at room temperature for 24 hours immediately before use for measurement, and the reliability is shown in Table 2 evaluated by the following evaluation criteria.

The case where there is no bubble or peeling phenomenon is shown by (circle), the case where there is a little bubble or peeling phenomenon is shown by (triangle | delta), and the case where there exists a bubble or peeling phenomenon is shown by X.

(Transmission uniformity evaluation)

In order to determine the uniformity of the light transmittance with the same specimen used in the endurance reliability evaluation, it was observed whether the light leaks out of the dark room using the backlight. This light transmission uniformity evaluation is shown in Table 2 evaluated by the following evaluation criteria.

The case where there is no light transmittance nonuniformity phenomenon is represented by (circle), the case where there exists a light transmittance nonuniformity phenomenon to some extent is shown by (triangle | delta), and the case where there exists a light transmittance nonuniformity phenomenon is shown by X.

(Glass Substrate Warpage Evaluation)

The bending degree of the glass substrate was measured with the same specimen used in the durability evaluation. This light transmission uniformity evaluation is described in Table 2 by evaluating the following evaluation criteria according to the degree of warpage of the observed glass substrate.

The case where there is no warpage of the glass substrate is indicated by o, the case where the warpage phenomenon of the glass substrate is less than 2 mm is indicated by △, and the case where the warpage phenomenon of the glass substrate is 2 mm or more is indicated by X.

(Cutability evaluation)

The pressure sensitive adhesive was applied to the polarizing plate using a Thomson Carter test. The cut section of the pressure-sensitive adhesive layer was observed and evaluated in the following evaluation criteria.

The case where the adhesive residue of the cut surface and the degree to which the adhesive escapeed was less than 0.2 mm was indicated by o, the case where the defect was somewhat poor by 0.2 mm to 0.5 mm was indicated by Δ, and the severe case by 0.5 mm or more was indicated by X. .

Example 2, 3

An acrylic copolymer, an acrylic pressure-sensitive adhesive composition, and an adhesive layer were prepared in the same manner as in Example 1 except for changing the composition for preparing the acrylic copolymer shown in Table 1. The evaluation was performed in the same manner as in Example 1 to evaluate the durability reliability, light transmission uniformity, glass substrate warpage degree, and cutability, and are shown in Table 2.

Comparative Examples 1 to 3

Based on the composition of Example 1 for preparing the acrylic copolymer as in the composition ratio of Table 1, a part of each component is not added or partially added and copolymerized, and as shown in the composition ratio of Table 2, the crosslinking agent or the coupling agent An acrylic copolymer, an adhesive composition, and an adhesive layer were prepared in the same manner as in Example 1 except for changing the amount. The evaluation was performed in the same manner as in Example 1 to evaluate the durability reliability, light transmission uniformity, glass substrate warpage degree, and cutability, and are shown in Table 2.

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Acrylic copolymer blend composition (parts by weight) BA 79.0 70.3 79.0 94.0 87.0 86.0 EDPA 7.0 10.0 5.0 0 7.0 0 IBMA 8.0 13.0 10.0 0 0 8.0 2-HEMA 1.0 1.2 1.0 1.0 1.0 1.0 AA 5.0 5.5 5.0 5.0 5.0 5.0 BPO 0.015 0.012 0.02 0.015 0.015 0.015 Solvent (EAc) 100 100 100 100 100 100 Manufactured Acrylic Copolymer Molecular Weight 810,000 1.0 million 700,000 890,000 840,000 790,000

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Pressure Sensitive Composition Acrylic Copolymer 100 100 100 100 100 100 Crosslinking agent 2.0 2.5 2.0 1.0 1.0 1.0 Silane coupling agent 0.05 0.05 0.05 0.05 0.05 0.05 Property evaluation Durability Reliability ○ ○ ○ △-○ △ X Light transmission uniformity ○ ○ ○ X ○ X Machinability ○ ○ ○ ○ X ○

The composition of the present invention not only has stress relaxation characteristics that can minimize the formation of residual stresses that can cause problems in display function when the liquid crystal panel is used for a long period of time, as well as initial adhesion, permanent adhesion, retention, and cutting characteristics. It is an acrylic adhesive composition excellent in various physical properties.

In addition, the pressure-sensitive adhesive product using such an acrylic pressure-sensitive adhesive composition as an adhesive layer effectively improves durability.

Claims (13)

a) iii) a (meth) acrylic acid ester monomer having an alkyl group having 4 to 12 carbon atoms 20 to 98.4 parts by weight; Ii) (meth) acrylic acid ester having a high flexibility and long chain structure 1 to 30 parts by weight; Iii) having a homopolymer glass transition temperature (Tg) above the room temperature of the bulky structure 1 to 30 parts by weight of (meth) acrylic acid ester; Iii) 0.1 to 5 parts by weight of a vinyl monomer containing a hydroxyl group; And Viii) 0.5 to 10 parts by weight of an α, β unsaturated carboxylic acid monomer 100 parts by weight of an acrylic copolymer prepared by copolymerizing; And b) 0.01 to 5 parts by weight of a crosslinking agent; Acrylic pressure-sensitive adhesive composition comprising a. The method of claim 1, 100 parts by weight of the acrylic copolymer of a) in the composition c) 0.01 to 2 parts by weight of silane coupling agent Acrylic pressure-sensitive adhesive composition further comprising. The method according to claim 1 or 2, The acrylic pressure-sensitive adhesive composition having a molecular weight of the acrylic copolymer of a) is 200,000 to 2 million. The method according to claim 1 or 2, The acrylic adhesive composition of the a) the acrylic copolymer is prepared by a polymerization method selected from the group consisting of solution polymerization, photopolymerization, bulk polymerization, suspension polymerization, and emulsion polymerization. The method according to claim 1 or 2, (Meth) acrylic acid ester monomer which has a C4-C12 alkyl group of said a) iii) is butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) ) Acrylic adhesive composition selected from the group consisting of acrylate, n-octyl (meth) acrylate, and isononyl (meth) acrylate. The method according to claim 1 or 2, (Meth) acrylic acid ester monomer which has a C4-C12 alkyl group of said a) iii) is ethyl (meth) acrylate, methyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acryl An acrylic copolymer composition prepared from an acrylic copolymer by mixing at least one monomer or copolymerization monomer selected from the group consisting of acrylate, acrylonitrile styrene, glycidyl (meth) acrylate, and vinyl acetate. The method according to claim 1 or 2, (Meth) acrylic acid esters having a long chain structure with high flexibility of a) ii) include methoxydiethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, octyloxydiethylene glycol (meth) acrylate, Methoxydipropylene glycol (meth) acrylate, ethoxydipropylene glycol (meth) acrylate, octyloxydipropylene glycol (meth) acrylate, methoxy triethylene glycol (meth) acrylate, ethoxy triethylene glycol (meth) Acrylate, octyloxytriethylene glycol (meth) acrylate, methoxy tripropylene glycol (meth) acrylate, ethoxy tripropylene glycol (meth) acrylate, octyloxy tripropylene glycol (meth) acrylate, methoxy tetra Ethylene glycol (meth) acrylate, ethoxy tetraethylene glycol (meth) acrylate, octyloxy tetraethylene Recall (meth) acrylate, methoxy tetrapropylene glycol (meth) acrylate, ethoxy tetrapropylene glycol (meth) acrylate, octyloxy tetrapropylene glycol (meth) acrylate, methoxy decarboxyethylene glycol (meth) acrylate , Ethoxy decaethylene glycol (meth) acrylate, octyl oxydecaethylene glycol (meth) acrylate, methoxy decapropylene glycol (meth) acrylate, ethoxy decapropylene glycol (meth) acrylate, and octyl oxydecapropylene Acrylic pressure-sensitive adhesive composition selected from the group consisting of glycol (meth) acrylate. The method according to claim 1 or 2, (Meth) acrylic acid esters having a homopolymer glass transition temperature above room temperature of the bulky structure of a) iii) isobornyl acrylate, isobornyl methacrylate, and dicyclopentadiene ethylene glycol (meth) acryl Acrylic pressure-sensitive adhesive composition selected from the group consisting of a rate. The method according to claim 1 or 2, The vinyl monomer containing the hydroxyl group of said a) iii) is 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate, and 2 -Acrylic pressure-sensitive adhesive composition selected from the group consisting of hydroxypropylene glycol (meth) acrylate. The method according to claim 1 or 2, The acrylic pressure-sensitive adhesive composition of the a) iii) wherein the α, β unsaturated carboxylic acid monomer is selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, and maleic anhydride. The method according to claim 1 or 2, The crosslinking agent of b) is selected from the group of isocyanates consisting of adducts of tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and tolylene diisocyanate of trimethylolpropane, ethylene glycol diglycidyl ether, triglycis An acrylic pressure-sensitive adhesive composition selected from the group consisting of diethyl ether, trimetholol propane triglycidyl ether, and N, N, N ', N'-tetraglycidylethylenediamine. The method of claim 2, The silane coupling agent of c) is one or more from the group consisting of vinyltrimethoxysilane, vinyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane Acrylic adhesive composition selected. The method according to claim 1 or 2, Acrylic pressure-sensitive adhesive composition having a crosslinking density of 5 to 90% of the pressure-sensitive adhesive composition.