TWI534225B - Adhesive compositions, adhesives, and adhesive sheets - Google Patents

Description

Adhesive composition, adhesive and adhesive sheet

The present invention relates to an adhesive composition, an adhesive (a material crosslinked by an adhesive composition), and an adhesive sheet, and particularly, an adhesive composition, an adhesive, and an adhesive which are suitably used as an optical member such as a polarizing plate or the like. sheet.

In general, in a liquid crystal panel, a polarizer and a retardation film are adhered to a glass substrate of a liquid crystal cell or the like, and an adhesive layer formed of an adhesive composition is often used. However, the optical members such as the polarizing plate and the retardation plate are easily contracted by heat or the like. As a result, the adhesive layer stacked on the optical member is difficult to follow the shrinkage, and peeling occurs at the interface (so-called floating Light leakage (so-called white spot) occurs when the optical axis of the optical member causes a stress at the time of contraction of the optical member.

As a method of preventing the adhesion of the optical member, the adhesive layer having a high adhesiveness and excellent form stability is bonded to an optical member such as a polarizing plate, and the shrinkage of the optical member is suppressed. Or (2) an adhesive layer method using a small stress at the time of shrinkage of the optical member. As the method of (1), it is effective to use an adhesive layer having a high storage modulus as described in Patent Document 1. On the other hand, as the method of (2), it is effective to use an adhesive layer which is excellent in the stress relaxation rate which can soften the deformation of the optical member.

In the method of (2), Patent Document 2 describes an adhesive for a polarizing plate which comprises: (A) an alkyl (meth)acrylate and a functional group having a crosslinking agent; a copolymer of 0.5 to 20% by weight of a polymerizable monomer, 100 parts by weight of a high molecular weight (meth)acrylic copolymer having a weight average molecular weight of 1,000,000 or more; (B) a low molecular weight of a weight average molecular weight of 30,000 or less ( The methyl group (acrylic) (co)polymer is 20-200 parts by weight, and (C) the functional group capable of forming a crosslinked structure is composed of at least two polyfunctional compounds in the molecule of 0.005 to 5 parts by weight. The functional group distribution ratio of the functional group of the low molecular weight (meth)acrylic (co)polymer/[the functional group of the high molecular weight (meth)acrylic copolymer] is in the range of 0 to 15% by weight.

Similarly, in the implementation of the method of the above (2), Patent Document 3 describes an optical adhesive composition comprising a (meth) acrylate copolymer having a weight average molecular weight of 800,000 to 2,000,000 (a). 100 parts by mass and an acrylate copolymer mixture (A) having a weight average molecular weight of 50,000 or less (meth)acrylate copolymer (b) 20-100 parts by mass and a crosslinking agent (B), and the above copolymerization The substance (a) contains a monomer unit having a functional group having high reactivity with the crosslinking agent (B), and the copolymer (b) contains a reactivity with the crosslinking agent (B) as compared with the above copolymer (a) A monomer unit having a lower functional group of functional groups.

[Patent Literature]

[Patent Document 1] JP-A-2006-235568

Patent Document 2, Patent No. 3533589

[Patent Document 3] JP-A-2009-108122

The adhesive disclosed in Patent Documents 2 and 3 obtains a stress relaxation ratio by preferentially crosslinking a high molecular weight (meth)acrylic copolymer. However, the above-mentioned adhesive has poor durability, for example, peeling occurs at the adhesive interface under moist heat conditions. Further, the stress relaxation rate is not sufficient, and when it is used for an optical member such as a polarizing plate, light leakage may occur. Further, the adhesion tends to increase with time after attachment, and the reusability is insufficient.

The present invention has been made in view of such actual conditions. An object of the present invention is to provide an adhesive composition and an adhesive which are excellent in stress relaxation rate, prevent light leakage, and have excellent durability and are excellent in reusability when applied to an optical member such as a polarizing plate. And sticky sheets.

In order to achieve the above object, the first aspect of the present invention provides an adhesive composition comprising a first (meth) acrylate polymer (A) having a weight average molecular weight of 500,000 to 3,000,000 and a weight average molecular weight of 8,000 - An adhesive composition of a 300,000th (meth) acrylate polymer (B) and a crosslinking agent (C), characterized in that the first (meth) acrylate polymer (A) and the above Each of the (meth) acrylate polymer (B) contains substantially no acidic group, and contains a hydroxyl group-containing monomer as a constituent monomer unit of the polymer, and the first (meth) acrylate polymer ( A) The hydroxyl group-containing monomer is the same as the hydroxyl group-containing monomer contained in the second (meth) acrylate polymer (B), and is contained in the first (meth) acrylate polymer (A). Hydroxyl group, the above 2 (methyl) propyl The olefin polymer (B) has a molar ratio of hydroxyl groups of 1.0 to 40 (Invention 1).

The adhesive obtained by crosslinking the adhesive composition of the above invention (Invention 1) can exhibit an appropriate cohesive force and an excellent stress relaxation rate. When the adhesive having such an excellent stress relaxation rate is applied to an optical member such as a polarizing plate, it is possible to obtain an adhesive sheet which is excellent in both light leakage resistance and durability and which is excellent in reusability. Further, in the case where the polymer of the above-mentioned adhesive composition does not substantially contain an acidic group and the adherend is made of a metal or contains a metal, the corrosion of the metal can be suppressed.

In the above invention (Invention 1), the second (meth) acrylate polymer (B) preferably contains 10 to 40% by mass of the hydroxyl group-containing monomer as a constituent monomer unit of the polymer (invention) 2).

In the above invention (Invention 1 and 2), the ratio of the second (meth) acrylate polymer (B) to 100 parts by mass of the first (meth) acrylate polymer (A) is preferably 5 - 50 parts by mass (Invention 3).

In the above invention (Invention 1-3), the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) are preferably substantially not contained except for a hydroxyl group. A functional group reactive with the above crosslinking agent (C) (Invention 4).

In the above invention (Invention 1-4), the crosslinking agent (C) is preferably an isocyanate crosslinking agent (Invention 5).

In the above invention (Invention 5), the content of the isocyanate crosslinking agent is the isocyanate group of the isocyanate crosslinking agent to the second The amount of the above hydroxyl group contained in the (meth) acrylate polymer (B) is 0.1 to 3.5 equivalents (Invention 6).

Secondly, the present invention provides an adhesive which is obtained by crosslinking the above-mentioned adhesive composition (Invention 1-6) (Invention 7).

Thirdly, the present invention is an adhesive sheet having a substrate and an adhesive layer, wherein the adhesive layer is composed of the above-mentioned adhesive (Invention 7) (Invention 8).

In the above invention (Invention 8), the substrate is preferably an optical member (Invention 9).

Fourthly, the present invention provides an adhesive sheet comprising two release sheets and a binder layer held by the two release sheets, whereby the adhesive layer is in contact with the release faces of the two release sheets, and is characterized in that The above-mentioned adhesive layer is composed of the above-mentioned adhesive (Invention 7) (Invention 10).

In the adhesive obtained by crosslinking the adhesive composition of the present invention, a low molecular weight polymer which has been conventionally used as a plasticizer is preferentially crosslinked, and the low molecular weight polymer forms a chemically crosslinked three-dimensional network structure. In the three-dimensional network structure, a plurality of high molecular weight polymers are inserted, and a high molecular weight polymer is bound, whereby a high molecular weight polymer forms a pseudocrosslinked structure (presumed). In this way, the obtained adhesive can exhibit an appropriate cohesive force and an excellent stress relaxation rate, and when applied to an optical member such as a polarizer, the light leakage can be effectively prevented, and the durability is also excellent. Reusability is also good. Further, since each polymer of the adhesive composition of the present invention does not substantially contain an acidic group, the adherend is made of a metal. In the case of a structure or a metal, corrosion of the above metal can be suppressed.

Hereinafter, embodiments of the present invention will be described.

[adhesive composition]

The adhesive composition of the present embodiment contains a first (meth) acrylate polymer (A) having a weight average molecular weight (Mw) of 500,000 to 3,000,000, a weight average molecular weight (Mw), and a weight of 8,000 to 300,000. The 2 (meth) acrylate polymer (B) and the crosslinking agent (C) preferably further contain a decane coupling agent (D). Further, in the present specification, the (meth) acrylate has both acrylate and methacrylate. The same is true for other similar terms. In addition, the concept of "copolymer" is also included in "polymer".

Each of the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) does not substantially contain an acidic group, and contains a hydroxyl group as a monomer unit constituting the polymer. a monomer (a monomer having a hydroxyl group in the molecule), preferably an alkyl (meth)acrylate having a carbon number of 1 to 20, a hydroxyl group-containing monomer, and, if necessary, not containing and cross-linking Agent (C) A copolymer of another monomer having a reactive functional group.

As the acidic group, a carboxyl group is mainly exemplified, and other examples thereof include a sulfonic acid group and a phosphoric acid group. When the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) do not substantially contain an acidic group and the adherend is made of a metal (for example, the adherend is oxidized) In the case of an electrode composed of indium tin (ITO) or a metal (for example, When the adherend contains a metal mesh, the above metal corrosion can be suppressed.

Here, the phrase "substantially does not contain an acidic group" means that the degree of corrosion to the metal is small and tolerable to the extent that the acid group is not contained at all. Specifically, it is a constituent unit of the polymer (A) or (B), and the content of the acid group-containing monomer is usually 1% by mass or less, preferably 0.5% by mass or less, and particularly preferably 0.1% by mass. % is not full.

The (meth)acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group may, for example, be methyl (meth)acrylate, ethyl (meth)acrylate or propyl (meth)acrylate. N-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, Isooctyl (meth)acrylate, n-aryl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, hexadecane (meth)acrylate A base ester and a stearyl (meth) acrylate. They may be used alone or in combination of two or more.

The hydroxyl group-containing monomer may, for example, be 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate or (meth)acrylic acid. Hydroxyalkyl (meth)acrylate such as 2-hydroxybutyl ester, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. These may be used alone or in combination of two or more.

In the adhesive composition of the present embodiment, the hydroxyl group-containing monomer and the second (meth)acrylic acid contained in the first (meth) acrylate polymer (A) The hydroxyl group-containing monomer contained in the ester polymer (B) is of the same type, and the second (meth) acrylate polymer (B) containing a hydroxyl group contained in the first (meth) acrylate polymer (A) is contained. The molar ratio of the hydroxyl groups is from 1.0 to 40, preferably from 3 to 30, particularly preferably from 5 to 20.

Further, the above molar ratio, in other words, the ratio of the number of moles of the hydroxyl group derived from the polymer (A) to the number of moles of the hydroxyl group derived from the polymer (B) in the adhesive composition. For example, in the adhesive composition, when 100 parts by mass of the polymer (A) and 20 parts by mass of the polymer (B) are blended, the ratio of the number of moles of the hydroxyl group in the above compounding amount is represented. In addition, the "same type" in the present specification means not only the same hydroxyl group-containing monomer but also a hydroxyl group-containing monomer having the same reactivity as the crosslinking agent (C) when it exists in the same polymer.

As described above, when the hydroxyl group derived from the same hydroxyl group-containing monomer contains the same amount or more as the second (meth)acrylate polymer (B) and the first (meth)acrylate polymer (A) When the above adhesive composition is crosslinked, the second (meth) acrylate polymer (B) (low molecular weight polymer) and the crosslinking agent (C) are preferentially reacted, and the crosslinker (C) forms a three-dimensional network. Structure (presumed). Therefore, the three-dimensional network structure is two or more molecules of the first (meth) acrylate polymer (A) (high molecular weight polymer), and is inserted without accompanying a direct chemical bond or with only a small number of chemical bonds. A) A state in which there is a certain degree of freedom is bound to form a pseudo-linked structure (presumed) (the structure thus estimated is hereinafter also referred to as "structure X"). Since the first (meth) acrylate polymer (A) has a small content of a hydroxyl group, it is considered to be favorable in the above three-dimensional network structure. insert. The adhesive having the above structure X can exert a suitable cohesive force and an excellent stress relaxation rate. When it is applied to an optical member such as a polarizing plate, the adhesive having such excellent stress relaxation rate is excellent in light leakage resistance and excellent in durability, and can be prevented from floating and peeling under conditions such as moist heat. . Further, when the second (meth) acrylate polymer (B) and the first (meth) acrylate polymer (A) contain the same amount of hydroxyl groups, compared with the high molecular weight polymer (A), The low molecular weight polymer (B) has a high density of hydroxyl groups, and the difficulty in contact with the crosslinking agent (C) due to the structure is also extremely small, whereby the polymer (B) and the crosslinking agent (C) Give priority to the reaction. Further, in the above-described structure X, since there is no uncrosslinked low molecular weight component or the like for imparting a stress relaxation ratio, bleeding of a low molecular weight component which is a problem in the conventional stress relaxation rate type adhesive is not As a result, the adhesive obtained from the adhesive composition of the present embodiment is excellent in recyclability.

The second (meth) acrylate polymer (B), as a constituent monomer unit, preferably contains 10 to 40% by mass, particularly preferably 10 to 30% by mass, more preferably 12%, based on the hydroxyl group-containing monomer. 20% by mass. When the hydroxyl group-containing monomer is contained in this range, the degree of crosslinking of the second (meth) acrylate polymer (B) is good, and the combination with the first (meth) acrylate polymer (A) The stress relaxation rate of the adhesive is more effectively improved. When the content of the hydroxyl group-containing monomer is less than 10% by mass, the crosslinking of the second (meth)acrylate polymer (B) is insufficient, the gel fraction is low, and durability may be deteriorated. On the other hand, if the content of the hydroxyl group-containing monomer exceeds 40% by mass, the crosslinking of the second (meth) acrylate polymer (B) is excessive, and the stress relaxation There is a possibility that the rate is deteriorated, and after crosslinking, the hydroxyl group remains, and durability under heat and humidity conditions is particularly deteriorated. Further, when the upper limit of the content of the hydroxyl group-containing monomer is 30% by mass, the light leakage resistance of the obtained pressure-sensitive adhesive sheet is further improved.

Further, the preferred content of the hydroxyl group-containing monomer in the first (meth) acrylate polymer (A) is contained in the hydroxyl group-containing monomer in the second (meth) acrylate polymer (B). The amount and the molar ratio of the above hydroxyl groups are automatically determined.

The other monomer may, for example, be an aliphatic ring-containing (meth)acrylate such as cyclohexyl (meth)acrylate or an aromatic ring (meth) having a (meth)acrylic acid phenyl group or the like. Acrylate; non-crosslinkable acrylamide such as acrylamide and methacrylamide; N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethyl (meth)acrylate A non-crosslinkable (meth) acrylate having a tertiary amino group such as aminopropyl ester, vinyl acetate, styrene or the like. They may be used alone or in combination of two or more.

Among the above other monomers, N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate have non-crosslinking properties. The tertiary amino group (meth) acrylate, especially N,N-dimethylaminoethyl (meth) acrylate, has a promoting touch to promote the reaction of the hydroxyl group in the polymer and the crosslinking agent (C) In the second (meth) acrylate polymer (B), the monomer component which is a constituent of the above polymer may be contained.

In this case, the above in the second (meth) acrylate polymer (B) The content of the non-crosslinkable (meth) acrylate having a tertiary amino group is preferably from 0.1 to 10% by mass, particularly preferably from 1 to 5% by mass.

Here, in order to form the above-described structure X, the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) are preferably substantially free of hydroxyl groups. A functional group reactive with the crosslinking agent (C). As the above functional group, for example, a crosslinkable primary or secondary amino group, as a monomer having the above functional group, for example, aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate Base ester and the like.

The phrase "substantially free of a functional group reactive with the crosslinking agent (C)" means that the reactivity containing the p-hydroxy group and the crosslinking agent (C) is not impaired, except that the functional group is not contained at all. The extent of the above-mentioned functional group can be tolerated. Specifically, in each of the polymers (A) and (B), the molar ratio of the functional group to the hydroxyl group is preferably 0.2 or less, and particularly preferably 0.1 or less.

The polymerization method of the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) may be a random copolymer or a block copolymer.

The weight average molecular weight of the first (meth) acrylate polymer (A) is from 500,000 to 3,000,000, preferably from 700,000 to 2,500,000, particularly preferably from 1,000,000 to 2,000,000. That is, the first (meth) acrylate polymer (A) is a high molecular weight polymer component. In addition, the weight average molecular weight in this specification is a polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

If the weight average molecular weight of the first (meth) acrylate polymer (A) is within the above range, the polymer (A) has a relatively large molecular weight, This above structure X can be formed well (presumed).

When the weight average molecular weight of the first (meth) acrylate polymer (A) is less than 500,000, the obtained adhesive may have a low gel fraction, and may have poor durability and reusability. When the weight average molecular weight of the first (meth) acrylate polymer (A) exceeds 3,000,000, the compatibility with the second (meth) acrylate polymer (B) or the like is deteriorated, and the obtained adhesive has The possibility that the stress relaxation rate will deteriorate.

On the other hand, the weight average molecular weight of the second (meth) acrylate polymer (B) is from 8,000 to 300,000, preferably from 10,000 to 200,000, particularly preferably from 50,000 to 100,000. That is, the second (meth) acrylate polymer (B) is a low molecular weight polymer component.

When the weight average molecular weight of the second (meth) acrylate polymer (B) is within the above range, the three-dimensional network structure peculiar to the adhesive composition of the present embodiment is formed, and contributes to excellent stress relaxation rate. . That is, when the weight average molecular weight of the second (meth) acrylate polymer (B) is less than 8,000, a good three-dimensional network structure is difficult to obtain. On the other hand, if the weight average molecular weight of the second (meth) acrylate polymer (B) exceeds 300,000, the compatibility with the first (meth) acrylate polymer (A) or the like is deteriorated, and the polymerization is progressed. The insertion of the polymer (A) in the three-dimensional network structure formed of the object (B) is insufficient, and as a result, the durability and reusability of the obtained adhesive are deteriorated.

In the present embodiment, the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) may be used alone or in combination of two or more. .

The ratio of the second (meth) acrylate polymer (B) to 100 parts by mass of the first (meth) acrylate polymer (A) is preferably 5 to 50 parts by mass, particularly 5 to 40 parts by mass. Preferably, it is further preferably 10-30 parts by mass.

The above-described structure X can be favorably formed from the adhesive obtained by the adhesive composition containing the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) in the above ratio ( Speculated).

Examples of the crosslinking agent (C) include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, and a metal complexing compound crosslinking agent, among which a polymer (A) is used. Further, an isocyanate crosslinking agent having excellent reactivity of the hydroxyl group of (B) is preferred.

The isocyanate crosslinking agent includes at least a polyisocyanate compound. The polyisocyanate compound may, for example, be an aromatic polyisocyanate such as toluene diisocyanate, diphenylmethane diisocyanate or p-xylylene diisocyanate, or an aliphatic polyisocyanate such as hexamethylene diisocyanate or isophorone. An alicyclic polyisocyanate such as an isocyanate or a hydrogenated diphenylmethane diisocyanate, and a biuret or isocyanurate thereof, and further, they may be exemplified by ethylene glycol, propylene glycol, and neopentyl An adduct of a compound containing a low molecular weight active hydrogen such as an alcohol, trimethylolpropane or castor oil.

The above-mentioned crosslinking agent (C) may be used alone or in combination of two or more.

The content of the crosslinking agent (C) is such that the crosslinking group (for example, isocyanate group) of the crosslinking agent (C) and the hydroxyl group of the second (meth) acrylate polymer (B) are usually 0.05. -5 equivalents, preferably 0.1-3.5 The amount of the equivalent is particularly preferably an amount of from 0.3 to 1.0 equivalent. When the amount of the crosslinkable group is 0.05 equivalent or less, the gel fraction of the obtained adhesive is low, and the cohesive force may not be sufficiently exhibited. Further, the amount of the crosslinkable group is 0.1 equivalent or more, particularly 0.3 equivalent or more, and the durability of the obtained adhesive is further excellent. On the other hand, if the amount of the crosslinkable group is 3.5 equivalents or less, the adhesive strength of the obtained adhesive can be sufficiently ensured. Further, the amount of the crosslinkable group is 1.0 equivalent or less, and the crosslinking agent (C) contributes only to the formation of the three-dimensional network structure of the polymer (B), and can effectively prevent crosslinking of the polymer (A). (presumed). As a result, the obtained adhesive has excellent stress relaxation rate.

The adhesive composition of the present embodiment preferably further contains a decane coupling agent (D). When the decane coupling agent (D) is contained, the alkoxy fluorenyl group of the decane coupling agent (D) acts on the surface of the adherend such as a glass substrate, and for example, the polarizing plate is bonded to a liquid crystal glass unit or the like. In this case, the adhesion between the adhesive and the liquid crystal glass unit becomes better.

The decane coupling agent (D) is an organic ruthenium compound containing at least one alkoxy fluorenyl group in the molecule, and is compatible with an adhesive component and has a light-transmitting property. For example, a substantially transparent substance is preferable. . The amount of the decane coupling agent (D) to be added is preferably 0.01 to 0.5 parts by mass, particularly preferably 0.05 to 0.3 parts by mass, per 100 parts by mass of the first (meth) acrylate polymer (A).

Specific examples of the decane coupling agent (D) include polymerizable unsaturated groups such as vinyl trimethoxy decane, vinyl triethoxy decane, and methacryloxypropyl trimethoxy decane. Bismuth compound; 3-shrinkage An anthracene compound having an epoxy structure such as glyceryl ether propyl trimethoxy decane or 2-(3,4-epoxycyclohexyl)ethyltrimethoxy decane; 3-aminopropyltrimethoxydecane, N-( Aminoguanidine compound such as 2-aminoethyl)-3-aminopropyltrimethoxydecane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxydecane; 3-chloropropane Trimethoxy decane; 3-isocyanate propyl triethoxy decane, and the like. These may be used alone or in combination of two or more.

The adhesive composition may be added with various additives commonly used in acrylic adhesives, such as a charge preventive agent, an adhesion-imparting agent, an oxidation preventive agent, an ultraviolet absorber, a light stabilizer, a softener, a filler, and the like, as needed. Refractive index modifier, etc.

[Method for Producing Adhesive Composition]

The above adhesive composition, the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) are separately produced, and they may be mixed at any stage. A crosslinking agent (C) and a desired decane coupling agent (D) are added.

As a preferable specific example, the (meth) acrylate polymers (A) and (B) are each produced by a usual radical polymerization method. The polymerization of the (meth) acrylate polymers (A) and (B) can be carried out by a solution polymerization method or the like, if necessary, by using a polymerization initiator. The polymerization solvent may, for example, be ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane or methyl ethyl ketone, and may be used in combination of two or more kinds.

The polymerization initiator may, for example, be an azo compound or an organic peroxide, and may be used in combination of two or more kinds. As an azo compound, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutylcyano), 1,1'-azobis(cyclohexane-1-carbonitrile), 2 , 2'-azobis(2,4-dimethylcarbonitrile), 2,2'-azobis(2,4-dimethyl-4-methoxy nitrile), dimethyl 2,2'- Azobis(2-methylpropionate), 4,4'-azobis(4-cyanoshikimate), 2,2'-azobis(2-hydroxymethylpropanyl) and 2, 2'-Azobis[2-(2-imidazolin-2-yl)propane].

The organic peroxide may, for example, be benzoyl peroxide, t-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate or di-n-propylperoxy Carbonate, bis(2-ethoxyethyl)peroxydicarbonate, t-butyl peroxy neopentate, t-butyl peroxypivalate, (3,5,5-trimethyl) A hexyl acyl) peroxide, a dipropionyl peroxide, a diacetyl peroxide, and the like.

Further, in the above polymerization process, the weight average molecular weight of the obtained polymer can be adjusted by blending a chain shifting agent such as 2-mercaptoethanol.

Then, the obtained solutions of the polymers (A) and (B) are mixed, and a diluted solvent is added. Thereafter, the crosslinking agent (C) and the desired decane coupling agent (D) are added and sufficiently mixed to obtain an adhesive composition (coating solution) diluted with a solvent.

The diluent solvent to be used for the coating solution obtained by diluting the adhesive composition may, for example, be an aliphatic hydrocarbon such as hexane, heptane or cyclohexane; an aromatic hydrocarbon such as toluene or xylene; or dichloromethane. And halogenated hydrocarbons such as dichloroethane; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; acetone, methyl ethyl ketone, 2-pentanone, and isophor Ketones such as ketones and cyclohexanone; esters of ethyl acetate, butyl acetate, etc.; ethyl cellosolve Solvent-based solvents such as the like.

The concentration of the prepared coating solution thus obtained. The viscosity is not particularly limited as long as it can be applied, and can be appropriately selected depending on the situation. For example, the concentration of the adhesive composition can be diluted to 10 to 40% by mass. Further, when a coating solution is obtained, the addition of a diluent solvent or the like is not a requirement, and the adhesive composition may have a viscosity to be applied, and the like, and a diluent solvent may not be added. In this case, the adhesive composition can be used as a coating solution as it is.

[adhesive]

The adhesive of the present embodiment is obtained by crosslinking the above-mentioned adhesive composition. The crosslinking of the above adhesive composition can be carried out by heat treatment. In addition, this heat treatment can also serve as a drying treatment at the time of volatilization of a diluted solvent or the like of the adhesive composition.

In the case of heat treatment, the heating temperature is preferably 50-150 ° C, and particularly preferably 70-120 ° C. In addition, the heating time is preferably from 30 seconds to 3 minutes, and is preferably from 50 seconds to 2 minutes. Further, after the heat treatment, it is particularly preferable to carry out the ripening at a normal temperature (for example, 23 ° C, 50% RH) for about 1-2 weeks.

By the above heat treatment (and aging), the crosslinking agent (C) is crosslinked with the second (meth) acrylate polymer (B), and has a first (meth) group in the three-dimensional network structure. The acrylate polymer (A) was inserted, and the above structure X was formed (presumed).

The adhesive of the present embodiment preferably has an adhesion to an alkali-free glass of 0.1 to 25 N/25 mm, more preferably 2 to 20 N/25 mm. In addition, in The adhesive force is a 180° peeling adhesive force (peeling speed 300 mm/min) in accordance with JIS Z0237, and is pressed at 0.5 MPa and 50 ° C for 20 minutes, and after being attached to the adherend, at 23 The measurement was carried out after standing at ° C for 50 hours under the conditions of 50% RH. When the adhesive force is within the above range and is applied to an optical member such as a polarizing plate, floating, peeling, or the like can be prevented.

The adhesive of the present embodiment is adhered to the adherend, and further adhered to the adherend for 14 days under conditions of 23 ° C and 50% RH (adhesive force after 14 days of attachment), and 0.1-25 N/ 25mm is preferred, and 2-20N/25mm is preferred. Thus, the increase in the adhesive force with time is suppressed, and the adhesive of the present embodiment can be evaluated as excellent in reusability.

The adhesive agent described above is preferably used as an optical member, for example, bonding between an optical member such as a polarizing plate (polarizing film) and a phase difference plate (phase difference film), or a polarizing plate (polarizing film). And the adhesion between the phase difference plate (phase difference film) and the glass substrate can be used satisfactorily. In the adhesive layer formed of the adhesive of the present embodiment, the stress relaxation rate is extremely excellent, and when the dimensional change of the adherend is large, the stress caused by the dimensional change is absorbed by the adhesive layer. Since it is moderated, it is difficult to peel off from the adherend even after long-term use, and at the same time, light leakage can be effectively prevented when used for an optical member as described above. That is, the adhesive of the present embodiment can achieve both light leakage resistance and durability as well as both. Further, the adhesive of the present embodiment has excellent reusability, and since it has no acid, it is excellent in corrosion resistance when the adherend is made of metal or contains a metal.

[adhesive sheet]

As shown in Fig. 1, the adhesive sheet 1A of the first embodiment is an adhesive layer 11 which is laminated on the release surface of the release sheet 12 in order from the bottom, and is laminated on the adhesive layer 11. The substrate 13 is placed to constitute.

Further, as shown in Fig. 2, the adhesive sheet 1B of the second embodiment has two peeling sheets 12a and 12b, and the two adhesive sheets 12a and 12b hold the adhesive 11 so that the adhesive is applied thereto. Layer 11 is in contact with the two peeling faces. In addition, the peeling surface of the peeling sheet in this specification is a surface which has peeling property in a peeling sheet, and the surface which has peeling process is not included in the surface of the peeling process, and the peeling surface is included in this concept. .

Regardless of the adhesive sheet 1A or 1B, the adhesive layer 11 is an adhesive obtained by crosslinking the above-mentioned adhesive composition.

The thickness of the adhesive layer 11 is appropriately determined depending on the purpose of use of the adhesive sheets 1A, 1B, and is usually in the range of 5 to 100 μm, preferably 10 to 60 μm, for example, as an optical member, particularly as an adhesive for a polarizing plate. In the case of a layer, it is preferably from 10 to 50 μm, particularly preferably from 10 to 30 μm.

The substrate 13 is not particularly limited, and any of the substrates used as the adhesive sheet of the adhesive sheet can be used. For example, in addition to optical components, woven fabrics or nonwoven fabrics of rayon, acrylic polymer, and polyester fibers; papers such as upper paper, cellophane, impregnated paper, and copper paper; metal foils such as aluminum and copper; Polyurethane foam, foam of polyethylene foam, etc.; polyester film of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc. Polyurethane film, polyethylene film, polypropylene film, cellulose film such as triacetyl cellulose; Ethyl chloride film; polyvinylidene chloride film; polyvinyl alcohol film; ethylene vinyl acetate copolymer film; polystyrene film; polycarbonate film; acrylic film; borneol resin film; A plastic film such as a film; two or more of these stacked bodies. Plastic film, one-axis rolling or two-axis rolling can also be used.

Examples of the optical member include a polarizing plate (polarizing film), a polarizer, a retardation film (retardation film), a viewing angle compensation film, a brightness enhancement film, a contrast improving film, a liquid crystal polymer film, a diffusion film, and a half. Through a reflective film or the like. Among them, the polarizing plate (polarizing film) is easy to shrink and has a large dimensional change, and is most suitable as an object of use of the adhesive (the above-mentioned adhesive layer 11) of the present embodiment from the viewpoint of light leakage resistance.

The thickness of the substrate 13 varies depending on the type thereof, and for example, in the case of an optical member, it is usually 10 μm to 500 μm, preferably 50 μm to 300 μm.

Examples of the release sheets 12, 12a, and 12b include a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polydichloroethane-based film, and dichloroethane. Base copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, vinyl acetate film, ion exchange resin film , ethylene. (Meth)acrylic copolymer film, ethylene. (Meth) acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, and the like. In addition, these crosslinked films are also used. Further, these laminated films can also be used.

The release surface of the release sheet (particularly the adhesive layer 11 and the joined surface) is preferably subjected to a release treatment. Peeling used as a peeling treatment The agent may, for example, be a release agent of an alkyd, a siloxane, a fluorine, an unsaturated polyester, a polyolefin, or a wax.

The thickness of the release sheets 12, 12a, 12b is not particularly limited and is usually about 20 to 150 μm.

The pressure-sensitive adhesive sheet 1A is produced by applying a solution (coating solution) containing the above-mentioned adhesive composition to a peeling surface of the release sheet 12, and heat-treating the adhesive layer 11 after the adhesive layer 11 is formed on the adhesive layer 11. The substrate 13 is superposed on top. After that, it is better to set the ripening period.

In addition, the conditions of the heat treatment and the ripening are as described above.

Further, in order to manufacture the pressure-sensitive adhesive sheet 1B, a coating solution containing the above-mentioned adhesive composition is applied onto a release surface of one release sheet 12a (or 12b), and heat treatment is performed. After the pressure-sensitive adhesive layer 11 is formed, The adhesive layer 11 coincides with the peeling surface of the other release sheet 12b (or 12a).

The coating method of the coating solution may, for example, be a stick coating method, a doctor blade method, a roll coating method, a plate coating method, a die coating method, or a gravure coating method.

For example, in the production of a liquid crystal display device comprising a liquid crystal cell and a polarizer, a polarizing plate is used as the substrate 13 of the adhesive sheet 1A, and the release sheet 12 of the adhesive sheet 1A is peeled off to expose the exposed adhesive layer. 11 is bonded to the liquid crystal cell.

Further, for example, in the production of a liquid crystal display device in which a phase difference plate is disposed between a liquid crystal cell and a polarizer, as an example, first, one release sheet 12a (or 12b) of the adhesive sheet 1B is peeled off, and the adhesive sheet 1B is peeled off. The exposed adhesive layer 11 and the phase difference plate are bonded together. Then, as a substrate The release sheet 12 of the adhesive sheet 1A using the polarizing plate is peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1A is bonded to the phase difference plate. Further, the other release sheet 12b (or 12a) is peeled off from the adhesive layer 11 of the adhesive sheet B, and the exposed adhesive layer 11 of the adhesive sheet B is bonded to the liquid crystal cell.

The above adhesive sheets 1A, 1B and the adhesive layer 11 have excellent stress relaxation ratio. Therefore, when applied to, for example, adhesion of a polarizing plate, stress generated by deformation of the polarizing plate is absorbed by the adhesive layer 11. It is tempered (presumed), whereby excellent light leakage resistance and high durability can be exhibited.

The embodiments described above are described in order to facilitate understanding of the present invention, and the present invention is not limited at all. Therefore, each element disclosed in the above embodiments includes all design changes and equivalents belonging to the technical scope of the present invention.

For example, the release sheet 12 of the adhesive sheet 1A can be omitted, and one of the release sheets 12a, 12b in the adhesive sheet 1B can also be omitted.

[Examples]

Hereinafter, the present invention will be specifically described based on examples and the like, but the scope of the present invention is not limited to the examples and the like.

[Example 1] 1. Modulation of polymer (A)

To a reaction vessel having a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 99.0 parts by mass of n-butyl acrylate, 1.0 part by mass of 2-hydroxyethyl acrylate, and 200 mass of ethyl acetate were added. And 0.08 parts by mass of 2,2'-azobisisobutyronitrile, and the air in the above reaction vessel was replaced with nitrogen. The mixture was stirred under a nitrogen atmosphere, and the reaction solution was heated to 60 ° C for 16 hours, and then cooled to room temperature. Here, one part of the obtained solution was subjected to molecular weight measurement by the following method, and the formation of the polymer (A) having a weight average molecular weight of 1.57 million was confirmed.

2. Modulation of polymer (B)

In a reaction vessel having a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 85.0 parts by mass of n-butyl acrylate, 15.0 parts by mass of 2-hydroxyethyl acrylate, 200 parts by mass of ethyl acetate, and 2 0.08 parts by mass of 2'-azobisisobutyronitrile was added, and the air in the above reaction vessel was replaced with nitrogen. The reaction solution was heated to 60 ° C under stirring in a nitrogen atmosphere, and after 16 hours, the mixture was cooled to room temperature. Here, the molecular weight of the obtained solution was measured by the following method, and the formation of the polymer (B) having a weight average molecular weight of 60,000 was confirmed.

3. Modulation of adhesive composition

After mixing 100 parts by mass (solid content converted value) of the polymer (A) obtained in the above item (1) with 20 parts by mass (solid content converted value) of the polymer (B) obtained in the above item (2), The cross-linking agent (C) is a xylene diisocyanate adduct of trimethylolpropane in an amount of 0.6 equivalent of the hydroxyl group of the polymer (B) (manufactured by Mitsui Chemicals, Inc., trade name "TAKENATED-110N") 3.0 parts by mass added. Finally, as a decane coupling agent (D), 3-glycidyl ether propyl trimethoxy decane (trade name "KBM403", manufactured by Shin-Etsu Chemical Co., Ltd.) was added in an amount of 0.3 parts by mass, and the mixture was sufficiently stirred to obtain an adhesive composition. Dilute the solution.

Further, the ratio of the monomer to be blended was such that the amount of the hydroxyl group (H[OH]) in 100 g of the polymer (A) was 8.62 mmol, and the amount of the hydroxyl group (L[OH]) in 20 g of the polymer (B) was 25.84 mmol. . Therefore, the ratio (L[OH]/H[OH]) of the number of moles of the hydroxyl groups in 100 parts by mass of the polymer (A) to the number of moles of the hydroxyl groups in 20 parts by mass of the polymer (B) is 3.00.

Here, the adhesion of the above adhesive composition is shown in Table 1. In addition, the details of the abbreviations and the like described in Table 1 are as follows.

[Polymer (A) and (B)]

BA: n-butyl acrylate

AA: Acrylic

DM: N,N-dimethylaminoethyl methacrylate

HEA: 2-hydroxyethyl acrylate

H[OH] (mmol): the amount of the polymer (A) added (parts by mass) as the number of moles of the hydroxyl group calculated in (g)

L[OH] (mmol): the amount of the polymer (B) added (parts by mass) as the number of moles of the hydroxyl group calculated in (g)

[Isocyanate crosslinking agent (C)]

XDI-TMP: a xylene diisocyanate adduct of trimethylolpropane (manufactured by Mitsui Chemicals, Inc., under the trade name "TAKENATE D-110N")

TDI-TMP: toluene diisocyanate adduct of trimethylolpropane (manufactured by Nippon Polyurethane Co., Ltd., trade name "CORONET-L")

[decane coupling agent (D)]

KBM403: 3-glycidyl ether propyl trimethoxy decane (Xin Yue Chemical Industrial company, trade name "KBM403")

A peeling sheet obtained by peeling off a diluted solution of the obtained adhesive composition on one side of a polyethylene terephthalate film with a decane-based release agent (SP-PET3811, manufactured by Linde Co., Ltd.) The peel-treated surface of the thickness: 38 μm was subjected to blade coating to have a thickness of 25 μm after drying, and heat treatment was performed at 90 ° C for 1 minute to form an adhesive layer.

Then, a polarizing film composed of a disk-shaped polarizing film having a liquid crystal layer and a polarizing film integrated with a viewing angle expansion film are bonded together, and the exposed surface of the adhesive layer is in contact with the surface of the disk-shaped liquid crystal layer. The aging was carried out at 23 ° C, 50% RH for 7 days to obtain a polarizing plate with an adhesive layer.

[Examples 2-10, Comparative Examples 1-7]

In addition to the kind and ratio of each monomer constituting the adhesive composition, the type and amount of the crosslinking agent and the decane coupling agent, the blending of the polymer (A) and the polymer (B) is as shown in Table 1. The production of the polarizer having the adhesive layer was carried out in the same manner as in the first embodiment.

Here, the weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC) under the following conditions (GPC measurement).

<Measurement conditions>

. GPC measuring device: manufactured by TOSOH, HLC-8020

. GPC column (the following sequence is passed): TOSOH company

TSK guard columN HXL-H

TSK gel GMHXL (×2)

TSK gel G2000HXL

. Determination of solvent: tetrahydrofuran

. Measuring temperature: 40 ° C

[Experimental Example 1] (Light leakage test)

The polarizing plate having the adhesive layer obtained in the examples or the comparative examples was adjusted to a size of 233 mm × 309 mm by a cutting device (Super Knife, manufactured by Takino Seisakusho Co., Ltd., PN1-600). The peeling sheet was peeled off, and the exposed adhesive layer was adhered to an alkali-free glass (manufactured by Corning Co., Ltd., Eagle XG), and then pressurized in a kettle made by Kurihara Seisakusho Co., Ltd. at 0.5 MPa, 50 ° C for 20 minutes. Further, in the above-described bonding, the polarizing plate having the adhesive layer has a polarization axis in a Nicols cross state (polarizing axis: ∠45°, ∠135°). In this state, it was allowed to stand in an environment of drying at 80 ° C for 250 hours, and then placed in an environment of 23 ° C and 50% RH for 2 hours, and this was sampled, and the light leakage property was evaluated by the method shown below. The results are shown in Table 2.

<Light leakage evaluation: visual inspection>

The above sample was placed on a flat panel illumination lamp (HF-SL-A312LC, illuminance: 26,000 Lux, luminance: 10,000 cd), and a two-dimensional color luminance meter (manufactured by Konica Minolta, CA) -2000) Performing a shadow and performing luminance distribution image conversion using analysis software (CA-S20w, manufactured by Konica Minolta Co., Ltd.). The luminance distribution image of the obtained sample was evaluated in accordance with the evaluation basis shown in FIG.

[Experimental Example 2] (Durability Evaluation)

A bias having an adhesive layer obtained in the examples or the comparative examples The vibrating piece was adjusted to a size of 233 mm × 309 mm by a cutting device (Super Knife manufactured by Takino Seisakusho Co., Ltd., PN1-600). The release sheet was peeled off, and the exposed adhesive layer was attached to an alkali-free glass (Eagle XG, manufactured by Corning Co., Ltd.), and then the kettle made of Kurihara Co., Ltd. was pressurized at 0.5 MPa, 50 ° C, and 20 minutes.

Thereafter, the environment was subjected to the following durability conditions, and after 500 hours, it was observed with a magnifying glass of 10 times. The appearance changes were observed with the following base. The results are shown in Table 2.

◎: 4 sides, no problem

○: There is no problem in the four sides from 0.6 mm or more from the outer peripheral end.

In the case where at least one of the four sides is 0.6 mm or more from the outer peripheral end portion, the appearance of the adhesive of 0.1 mm or more, such as floating, peeling, foaming, and streaking, is observed to be abnormal.

<endurance condition>

. 60 ° C, relative humidity 90% RH

[Experimental Example 3] (Reusability evaluation)

The polarizer having the adhesive layer obtained in the examples or the comparative examples was cut to prepare a sample having a width of 25 mm and a length of 100 mm. The release sheet was peeled off from the sample, and the sample was attached to the alkali-free glass (Eagle XG, manufactured by Corning Co., Ltd.), and the autoclave manufactured by Kurihara Co., Ltd. was placed at 0.5 MPa, 50 ° C, Perform 20 minutes of pressurization. Then, it was allowed to stand under the conditions of drying at 50 ° C for 48 hours, and humidity control was carried out for 3 hours under conditions of 23 ° C and 50% RH. Thereafter, the sample was peeled off from the alkali-free glass by hand, and the surface contamination of the above alkali-free glass was visually evaluated. The evaluation was carried out in the following bases. The results are shown in Table 2.

○: No glass pollution. Residual adhesive

△: There is very little pollution of the glass. Residual adhesive

×: The pollution of the glass. Significant residual of adhesive

[Experimental Example 4] (Evaluation of corrosion resistance)

The release sheet of the polarizing plate having the adhesive layer obtained in the examples or the comparative examples was peeled off, and the copper foil (thickness: 80 μm) was bonded, and then stored in an atmosphere of 60° C. and 90% RH for 500 hours. Thereafter, the polarizing plate having the adhesive layer was peeled off from the copper foil, and the surface of the exposed copper foil was visually observed to confirm the presence or absence of corrosion. The results are shown in Table 2.

○: no corrosion

×: corroded

[Experimental Example 5] (Evaluation of haze value)

A structure (a structure before the polarizing plate attachment) of the release sheet/adhesive layer (thickness: 25 μm) obtained in the production process of the example or the comparative example was prepared. The surface of the adhesive layer on which the structure was exposed was bonded to soda lime glass (haze value: 0%), and the release sheet was peeled off to prepare a measurement sample.

The measurement sample was measured by a haze value (%) (abbreviated as Hz (%)) in accordance with JIS K7105 using a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.). Further, the haze value is preferably in the range of 0 to 3%, and is represented by ○ in the range, and is represented by × outside the above range. The results are shown in Table 2.

As is clear from Table 2, in the polarizing plate having the adhesive layer obtained in the examples, the light leakage resistance and durability are excellent, and the reusability, corrosion resistance, and optical characteristics are also good.

The adhesive composition and the adhesive of the present invention can be suitably applied to an optical member, and can be suitably applied to, for example, a polarizing plate and a phase difference plate, and the adhesive sheet of the present invention is used as a polarizing plate. An adhesive sheet for an optical member such as a phase difference plate can be suitably used.

1A, 1B‧‧‧Adhesive tablets

11‧‧‧Adhesive layer

12,12a,12b‧‧‧ peeling film

13‧‧‧Substrate

Fig. 1 is a cross-sectional view showing an adhesive sheet according to a first embodiment of the present invention.

Fig. 2 is a cross-sectional view showing an adhesive sheet according to a second embodiment of the present invention.

Fig. 3 is a view showing a (visual) evaluation criterion of a light leakage test in a polarizing plate having an adhesive layer.

1A‧‧‧Adhesive tablets

11‧‧‧Adhesive layer

12‧‧‧ peeling layer

13‧‧‧Substrate

Claims (9)

An adhesive composition comprising a first (meth) acrylate polymer (A) having a weight average molecular weight of 500,000 to 3,000,000 and a second (meth) acrylate polymer having a weight average molecular weight of 8,000 to 300,000 (B) and the crosslinking agent (C), each of the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) substantially does not contain an acidic group, and The monomer unit constituting the polymer contains a hydroxyl group-containing monomer, and the hydroxyl group-containing monomer contained in the first (meth)acrylate polymer (A) and the second (meth)acrylate polymer (B) The hydroxyl group-containing monomer is contained in the same type, and is contained in the second (meth) acrylate polymer (B) which is a hydroxyl group contained in the first (meth) acrylate polymer (A). The molar ratio of the hydroxyl group is 1.0 to 40, and the second (meth) acrylate polymer (B) contains 10 to 40% by mass of the hydroxyl group-containing monomer as a monomer unit constituting the polymer. The adhesive composition according to the first aspect of the invention, wherein the second (meth) acrylate polymer (B) is 100 parts by mass of the first (meth) acrylate polymer (A). The ratio is 5 to 50 parts by mass. The adhesive composition according to claim 1, wherein the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) are in addition to a hydroxyl group. It does not substantially contain a functional group having reactivity with the above crosslinking agent (C). The adhesive composition according to claim 1, wherein the crosslinking agent (C) is an isocyanate crosslinking agent. The adhesive composition according to claim 4, wherein the content of the isocyanate crosslinking agent is the amount of the hydroxyl group contained in the second (meth) acrylate polymer (B). The isocyanate group of the above isocyanate crosslinking agent is in an amount of 0.1 to 3.5 equivalents. An adhesive which is obtained by crosslinking an adhesive composition according to any one of claims 1 to 5. An adhesive sheet having a substrate and an adhesive layer, wherein the adhesive layer is composed of the adhesive described in claim 6 of the patent application. The adhesive sheet according to claim 7, wherein the substrate is an optical member. An adhesive sheet comprising two release sheets and an adhesive layer held by the release sheet, wherein the adhesive layer is in contact with the release surface of the two release sheets, wherein the adhesive layer is patented The adhesive composition according to item 6.