JPWO2005111167A1 - Adhesive composition - Google Patents

Abstract

Provided is a pressure-sensitive adhesive composition having a (meth) acrylic polymer capable of suppressing bleeding and detachment under severe conditions while eliminating bleed while maintaining good durability and light leakage prevention properties. For the purpose. The pressure-sensitive adhesive composition having the (meth) acrylic polymer is a pressure-sensitive adhesive composition comprising at least a (meth) acrylic polymer and a crosslinking agent, and the (meth) acrylic polymer is a requirement (a ) To (d) (a) The content of a component having a weight average molecular weight of 800,000 or more and (b) a molecular weight of 300,000 or less is 25% by mass or more based on the whole (meth) acrylic polymer. In the molecular weight distribution chart of the linear scale for the molecular weight, the slope of the single regression line fitted to the molecular weight distribution curve of the molecular weight of 300,000 or less is 0 or more. (D) The determination coefficient in the single regression line satisfies 0.8 or more. It is characterized by being.

Description

  The present invention relates to a pressure-sensitive adhesive composition, and more specifically, has excellent physical properties such as no bleeding of low molecular weight components while achieving both durability and light leakage prevention properties, an optical film, etc. The present invention relates to a pressure-sensitive adhesive composition that is advantageously used as a pressure-sensitive adhesive.

  The pressure-sensitive adhesive for an optical film flexibly follows the durability of the optical film to prevent foaming, floating, peeling, etc. even in a high-temperature and high-humidity atmosphere, and the dimensional change of the optical film in a high-temperature atmosphere. When the optical film is a polarizing film, it is necessary to prevent light leakage in order to prevent light leakage when the two polarizing films are adhered to each other with a pressure-sensitive adhesive at right angles and left under high temperature and high humidity. ing. In addition, even when the optical film is adhered to an adherend such as a liquid crystal panel, the optical member (having an adhesive on the optical film) can be used without contaminating the adherend even if the position is shifted. Reworkability for re-peeling from an adherend is also required.

  Conventionally, acrylic adhesives have been mainly used as such adhesives for optical films. And what satisfy | fills the said request | requirement is known the acrylic adhesive which blended the high molecular weight acrylic polymer and the medium and low molecular weight body, and bridge | crosslinked. This improves the cohesive force by crosslinking high molecular weight acrylic polymer, imparts durability to prevent floating and peeling, and does not cause light leakage by containing medium and low molecular weight substances. It is to make.

  However, with the recent increase in size of displays, light leakage due to dimensional changes of optical films, particularly polarizing films, in a high temperature atmosphere becomes a bigger problem, and the adhesive for optical films has more flexibility. It is getting demanded. Further, under severe conditions, there is a problem that the low molecular weight substance added for improving the light leakage prevention property bleeds, contaminates the adherend during re-peeling, and causes peeling.

  For example, in order to improve heat durability and stress relaxation properties, a technique is disclosed in which the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 4 or more (patent document) 1). However, without considering the molecular weight distribution, if Mw / Mn is merely 4 or more, it is possible to prevent contamination during re-peeling and peeling under severe use environments such as extremely large temperature differences. There wasn't. Further, depending on the molecular weight distribution, there is a problem that foaming tends to occur generally when Mw / Mn is 20 or more.

  In addition, as this (meth) acrylic polymer, a mixture having a weight average molecular weight of 200,000 or more and less than 200,000 is used to improve adhesion to plastics under high temperature and high humidity. Although it is also known (Patent Document 2), in this method, a component having a small weight average molecular weight bleeds on the surface, and the above-mentioned problems such as contamination due to re-peeling and peeling under severe use environment can be solved. There wasn't.

Furthermore, as a (meth) acrylic polymer that maintains the adhesiveness under high temperature and high humidity and gives an adhesive composition that does not easily peel off, it is prepared by mixing high molecular weight, medium molecular weight, and low molecular weight polymers. Although a method is also known (Patent Document 3), it has not yet been solved.
JP 2002-341141 A JP 2002-107507 A JP 2003-049141 A

  The present invention has been made in view of such a technical background, and the problem is that while maintaining good durability and light leakage prevention property, the bleed is eliminated, contamination during re-peeling and peeling in a harsh environment. It is providing the adhesive composition which has a (meth) acrylic-type polymer which can suppress this.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by selecting and using a (meth) acrylic polymer that satisfies a specific condition, and have reached the present invention. .

That is, the present invention is a pressure-sensitive adhesive composition comprising at least a (meth) acrylic polymer and a crosslinking agent, and the (meth) acrylic polymer has requirements (a) to (d).
(A) The weight average molecular weight is 800,000 or more, and (b) the molecular weight of 300,000 or less is 25% by mass with respect to the entire (meth) acrylic polymer.
(C) In the molecular weight distribution chart in which the horizontal axis is a linear scale with respect to the molecular weight, the slope of the single regression line applied to the molecular weight distribution curve of the molecular weight of 300,000 or less is 0 or more. (D) The coefficient of determination in the single regression line is 0. The pressure-sensitive adhesive composition is characterized by satisfying .8 or more.
Moreover, the adhesive sheet which provided the adhesive layer obtained from the said adhesive composition on the at least single side | surface on a support body is provided.
Furthermore, the optical member which provided the adhesive layer obtained from the said adhesive composition on the at least single side | surface of an optical film is provided.

  According to the present invention, while maintaining both durability and light leakage prevention, there is no bleeding of low molecular weight components, contamination during re-peeling, suppression of peeling under harsh conditions, and excellent reworkability An agent composition can be provided.

  The pressure-sensitive adhesive composition of the present invention is prepared from a (meth) acrylic polymer that satisfies at least all the above conditions (a) to (d) and a crosslinking agent.

  The requirement (a) to be satisfied by this (meth) acrylic polymer is that its weight average molecular weight (hereinafter abbreviated as “Mw”) is 800,000 or more. Preferably, it is 900,000 or more. In particular, when using the adhesive composition of this invention for adhesion of a polarizing film, 800,000 to 1,500,000 are preferable. When Mw is less than 800,000, the cohesive force is insufficient and the durability may be insufficient.

  In addition, the requirement (b) to be satisfied by the (meth) acrylic polymer is that the content of the component having a molecular weight of 300,000 or less in the polymer is 25% by mass with respect to the entire (meth) acrylic polymer. That is all. Preferably, it is 30 mass% or more. On the other hand, if the content of the molecular weight of 300,000 or less is less than 25% by mass, there may be a problem in light leakage prevention properties. Here, light leakage refers to transmitted light that should not exist when two polarizing films are heated with adhesive applied to both surfaces of a substrate such as glass with the deflection surfaces perpendicular to each other. Is a phenomenon that can be observed, and the light leakage prevention property refers to a performance capable of preventing such light leakage. And when an adhesive cannot follow the shrinkage | contraction of the optical film by a heat | fever, the said light leak prevention property worsens.

  Furthermore, the requirement (c) to be satisfied by the (meth) acrylic polymer is that the slope of the single regression line fitted to the molecular weight distribution curve of the molecular weight portion of 300,000 or less in the molecular weight distribution chart with the horizontal axis being a linear scale with respect to the molecular weight. It is 0 or more.

  A method of obtaining a molecular weight distribution chart for judging the requirement (c) and the requirement (d) described later is obtained by gel permeation chromatography (hereinafter abbreviated as “GPC”). The shape of the molecular weight distribution chart generally varies depending on the measurement conditions such as the GPC column, but the slope of the single regression line, the determination coefficient, etc. in the present invention are defined based on the molecular weight distribution chart measured by the GPC measurement conditions of the examples. Is done.

  In the determination of requirement (c), the “molecular weight distribution chart with the horizontal axis being a linear scale with respect to molecular weight” means that the horizontal axis is not a logarithmic scale generally used for displaying molecular weight, but a molecular weight distribution scaled at regular intervals. A chart. In obtaining this molecular weight distribution chart, the molecular weight on the horizontal axis is calibrated with standard polystyrene or the like, and a single regression line is obtained as a straight line when the curve is approximated by a straight line using the least square method according to a conventional method. .

  In the present invention, it is essential that the slope of the single regression line obtained using the method of least squares in the molecular weight range is 0 or more. An inclination of less than 0 means that there is a further peak on the lower molecular weight side than the molecular weight of 300,000. When such a (meth) acrylic polymer is used, the low molecular weight component bleeds on the surface. In some cases, contamination during re-peeling or peeling during a cooling / heating cycle may occur.

Furthermore, the requirement (d) to be satisfied by the (meth) acrylic polymer is that the coefficient of determination in the single regression line is 0.8 or more. Here, the coefficient of determination means r ² in the following formula (1), and is a value indicating the degree of deviation from the actual molecular weight distribution curve of the single regression line obtained by the method of least squares with 1 as the upper limit.

Here, S _E is a residual sum of squares represented by Expression (2), and S _yy is a deviation sum of squares represented by Expression (3) for the measured value y _i .

  As is clear from equation (1), the larger the coefficient of determination, the smaller the deviation of the obtained single regression line from the actual molecular weight distribution curve, that is, the GPC chart curve having a molecular weight of 300,000 or less means that it is closer to a straight line. To do. In the present invention, it is essential that the determination coefficient defined by the equation (1) is 0.8 or more. If it is less than 0.8, the low molecular weight component may bleed and the adverse effect thereof may be at a level that cannot be ignored, which may cause problems such as contamination during re-peeling and peeling during the cooling and heating cycle.

  The (meth) acrylic polymer used in the present invention is not particularly limited as long as it satisfies all the above requirements (a) to (d). Such a (meth) acrylic polymer is obtained by (co) polymerizing a commonly used (co) polymerizable (meth) acrylic monomer by a method described later.

  Although there is no limitation in particular as a (meth) acrylic-type monomer used for manufacture of the (meth) acrylic-type polymer used for this invention, As a specific example, (meth) acrylic acid methyl, (meth) acrylic Ethyl acetate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, n-butyl (meth) acrylate, (meth) acrylic Isobutyl acid, tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, n-octyl (meth) acrylate 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, (meth) acrylic acid Decyl, (meth) acrylate, stearyl (meth) behenyl acrylate (meth) acrylic acid alkyl esters;

  Cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, benzyl (meth) acrylate, phenylethyl (meth) acrylate, phenoxyethyl (meth) acrylate, (meth) acrylic (Meth) acrylic acid esters such as dicyclopentenyloxyethyl acid and (meth) acrylic acid phenoxydiethylene glycol ester; (meth) acrylic acid aryl esters such as (meth) acrylic acid phenyl and (meth) acrylic acid methylphenyl;

  (Meth) acrylic acid, (meth) acrylic acid β-carboxyethyl, succinic acid mono (meth) acryloyloxyethyl ester, ω-carboxypolycaprolactone mono (meth) acrylate, 2- (meth) acryloyloxyethyl hydrogen phthalate, 2 -Carboxyl group-containing monomers such as (meth) acryloyloxypropyl hydrogen phthalate, 2- (meth) acryloyloxypropyl hexahydrohydrogen phthalate, 2- (meth) acryloyloxypropyl tetrahydrohydrogen phthalate; 2-hydroxyethyl (meth) acrylate , 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxy (meth) acrylate Hydroxyl group content such as -3-chloropropyl, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-hydroxy-3-allyloxypropyl (meth) acrylate, 2-acryloyloxyethyl-2-hydroxypropyl phthalate monomer;

  (Meth) acrylic acid 2-methoxyethyl, 1,3-butylene glycol methyl ether (meth) acrylate, (meth) acrylic acid butoxyethyl, methoxytriethylene glycol (meth) acrylate, methoxypolyethylene glycol # 400 (meth) acrylate, Methoxydipropylene glycol (meth) acrylate, methoxytripropylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, 2-ethylhexyl carbitol (meth) acrylate, (meth) acrylic acid tetrahydrofur Furyl, phenoxyethyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, phenoxypolyethyleneglycol Le (meth) acrylate, cresyl polyethylene glycol (meth) acrylate, p- nonyl phenoxyethyl (meth) acrylate, p- nonylphenoxy polyethylene glycol (meth) ether group-containing monomers such as acrylate;

  Epoxy group-containing monomers such as glycidyl (meth) acrylate; amino group-containing monomers such as N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate and morpholinoethyl (meth) acrylate; trimethyl Organosilicon group-containing monomers such as siloxyethyl (meth) acrylate and γ- (meth) acryloxypropyltrimethoxysilane; diphenyl-2- (meth) acryloyloxyethyl phosphate, 2- (meth) acryloyloxyethyl acid phosphate, caprolactone Modified 2-containing monomers such as (meth) acryloyloxyethyl acid phosphate; isocyanines such as (meth) acryloyl isocyanate and 2- (meth) acryloyloxyethyl isocyanate Preparative group-containing monomer, and the like. These may be used alone or in combination.

Among the above (meth) acrylic monomers, a (meth) acrylic monomer having a benzene ring such as phenoxyethyl acrylate or benzyl acrylate is 10 to 70% by mass, preferably 30%, based on the total amount of the (meth) acrylic monomer. Use at a ratio of ˜50 mass% is preferable because light leakage resistance is improved.

  The copolymer component of the (meth) acrylic polymer is preferably a combination of at least a (meth) acrylic acid alkyl ester and a functional group-containing (meth) acrylic monomer. Specifically, butyl acrylate, ethyl acrylate, benzyl acrylate, 2-phenoxyethyl acrylate, 2-hydroxyethyl acrylate, 4-hydroxybutyl (meth) acrylate, (meth) acrylic acid, (meth) 2-Carboxyethyl acrylate or the like is used.

  As a copolymer component of the (meth) acrylic polymer, when at least a (meth) acrylic acid alkyl ester and a functional group-containing (meth) acrylic monomer are used in combination, the (meth) acrylic acid alkyl ester is 59 to 99.5 mass. %, A functional group-containing (meth) acrylic monomer is preferably copolymerized in an amount of 0.5 to 40% by mass, (meth) acrylic acid alkyl ester 70 to 99.5% by mass, a functional group-containing (meth) acrylic monomer More preferably, 0.5 to 20% by mass is copolymerized.

  Moreover, as a copolymerization component which comprises a (meth) acrylic-type polymer, copolymerization components other than the said (meth) acrylic-type monomer can also be used. Examples of such copolymer components include styrene, hydroxystyrene, chlorostyrene, bromostyrene, methylstyrene, methoxystyrene, tert-butoxystyrene, tert-butoxycarbonylstyrene, tert-butoxycarbonyloxystyrene, 2,4-diphenyl-4- Styrenes such as methyl-1-pentene and α-methylstyrene; vinyl acetate, vinyl monochloroacetate, vinyl benzoate, vinyl pivalate, vinyl butyrate, vinyl laurate, divinyl adipate, vinyl methacrylate, vinyl crotonate, 2 -Vinyl compounds such as vinyl ethylhexanoate, N-vinylcarbazole and N-vinylpyrrolidone; allyl compounds such as allyl acetate and allyl glycidyl ether; carboxyl group-containing compounds such as itaconic acid, crotonic acid and fumaric acid Monomers; acid anhydride residue-containing monomers such as maleic anhydride; organosilicon group-containing monomers such as vinyltrimethoxysilane, allyltrimethoxysilane, trimethoxysilylpropylallylamine, 2-methoxyethoxytrimethoxysilane; acids such as acrylamide Examples thereof include amide compounds. These are preferably used in a proportion of 0 to 10% by mass in the (meth) acrylic polymer.

  The (meth) acrylic polymer having the above requirements (a) to (d) of the present invention is not limited to the following production method, but can be produced, for example, by the following method.

Method A:
According to a conventional method, polymers having a plurality of molecular weights are synthesized separately, and these are blended so as to satisfy the requirements (a) to (d). Although there will be no limitation in particular if the number of the polymers to mix | blend is two or more, 2-10 are preferable and 3-5 are especially preferable.
Specifically, for example, a polymer having a molecular weight peak at 1 million to 1.5 million, a polymer having a molecular weight peak at 50,000 to 300,000, a polymer having a molecular weight peak at 10,000 to 40,000, and a molecular weight peak at 500 to 5000 Examples include a method in which the polymer is mixed in the solution in each weight so as to finally satisfy the requirements (a) to (d).

  In this case, depending on the polymer components having different molecular weights (degrees of polymerization), the copolymerization component and the component ratio thereof may be different or may be substantially the same, but are preferably substantially the same.

Method B:
In the same polymerization apparatus, the reaction is carried out sequentially so as to satisfy the requirements (a) to (d) under a plurality of reaction conditions to obtain a (meth) acrylic polymer. For example, a method of changing the reaction conditions by adjusting the reaction temperature, the type and amount of the polymerization initiator, the type and amount of the chain transfer agent, the monomer concentration, and the polymerization time, and performing polymerization in multiple stages. Specifically, a monomer, an initiator and, if necessary, a solvent are charged into a reaction vessel, the reaction vessel is purged with nitrogen, and then the temperature is raised to the reaction temperature to start the reaction. When the monomer conversion rate (polymerization rate) reaches about 30% to 70%, an initiator is added, and if necessary, the reaction proceeds while dropping the solvent, and the monomer conversion rate (polymerization rate) is A method in which polymerization is performed in multiple stages by appropriately adding an initiator and a chain transfer agent, adjusting a reaction temperature, a reaction time, and the like until it becomes almost 100% can be mentioned.

  The (meth) acrylic polymer of the present invention can be synthesized by a conventional method. There is no particular limitation on the type of polymerization reaction in the polymerization, but radical solution polymerization is preferred. In addition, since a residual monomer hardly remains after polymerization, a method of polymerizing in a multistage is more preferable than a method of mixing polymers having a plurality of molecular weights.

  The polymerization initiator used in the polymerization reaction is not particularly limited as long as a desired polymerization rate and degree of polymerization can be obtained, and general-purpose ones can be preferably used. The polymerization initiators may be used alone or in combination of a plurality of types. However, in the case of performing polymerization in multiple stages, as an initial initiator, an azo-based initiator that forms a polymer structure having a relatively large molecular weight and no branching. As the additional initiator, it is preferable to use a peroxide-based initiator with good initiator efficiency for the purpose of improving the cohesive force and the polymerization rate.

  Furthermore, a general purpose chain transfer agent can also be used as needed. Further, the polymerization conditions such as polymerization temperature and nitrogen substitution are not particularly limited as long as those satisfying the requirements (a) to (d) can be obtained.

  In the present invention, the value Mw / Mn obtained by dividing the weight average molecular weight (Mw) of the (meth) acrylic polymer by the number average molecular weight (hereinafter abbreviated as “Mn”) is 20 or more. In order to prevent light leakage due to the inclusion of a low molecular weight substance, it is preferable to prevent contamination due to bleed and peeling during a cooling / heating cycle. Particularly preferably, it is 30 or more.

  Further, in the present invention, the glass transition point of the (meth) acrylic polymer (hereinafter abbreviated as “Tg”) is not particularly limited as long as it exhibits good adhesiveness, but it is flexible during re-peeling. In order to ensure the properties, 0 ° C. or lower is preferable, and −70 ° C. to −20 ° C. is particularly preferable.

  On the other hand, the crosslinking agent, which is another essential component of the pressure-sensitive adhesive of the present invention, is a compound that can react or interact with the functional group of the (meth) acrylic polymer. Although there is no limitation in particular as this crosslinking agent, An isocyanate type crosslinking agent, an epoxy-type crosslinking agent, etc. are used preferably.

  Among these, the isocyanate-based crosslinking agent is a compound having two or more isocyanate groups in its molecule, specifically, tolylene diisocyanate, chlorophenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, Illustrative examples include isocyanate compounds such as hydrogenated diphenylmethane diisocyanate, isocyanate compounds obtained by subjecting them to addition reaction with dihydric or higher alcohol compounds such as trimethylolpropane, pentaerythritol, and glycerin, isocyanurates, and burette type compounds. The Moreover, the urethane prepolymer type isocyanate etc. which made the isocyanate compound addition reaction to well-known polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, polyisoprene polyol, etc. are mentioned.

  The epoxy-based crosslinking agent is a compound having two or more epoxy groups in the molecule, and specifically, bisphenol A epichlorohydrin type epoxy-based resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl. Ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamine glycidylamine, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N′-diamineglycidylaminomethyl) cyclohexane and the like can be mentioned. These crosslinking agents are used alone or in combination.

  The blending ratio of the (meth) acrylic polymer and the crosslinking agent in the production of the pressure-sensitive adhesive composition of the present invention is not particularly limited, but is 0.001 to 100 parts by weight of the (meth) acrylic polymer. 5 parts by weight is preferable, and 0.005 to 3 is particularly preferable. And especially in the case of an isocyanate type crosslinking agent, 0.01-5 weight part is preferable and 0.1-3 weight part is especially preferable. Moreover, in the case of an epoxy type crosslinking agent, 0.001-0.5 weight part is preferable and 0.005-0.3 weight part is especially preferable.

  For the production of the pressure-sensitive adhesive composition of the present invention, in addition to the above essential components, a tackifier, an inorganic or organic filler, a thickener, a foaming agent, a dye, a pigment, an antioxidant, a flame retardant, as necessary. Etc. can also be blended.

  The pressure-sensitive adhesive composition of the present invention obtained as described above can be applied to various uses, but for liquid crystal displays such as polarizing films, retardation films, optical compensation films, brightness enhancement films, and antiglare sheets. It is used suitably for the adhesive sheet for optical films used. Among them, it is particularly preferable to use it for an adhesive sheet for a polarizing film.

  Such a pressure-sensitive adhesive sheet is obtained by applying the pressure-sensitive adhesive composition of the present invention to an appropriate support, for example, a polyethylene terephthalate film, a nonwoven fabric or the like, if necessary. Obtainable.

  Furthermore, it can also be used as an optical member in which an adhesive layer obtained from the adhesive composition of the present invention is provided on at least one surface of the optical film. In this invention, an optical member means what has an adhesive on the surface of optical films, such as a polarizing film. The optical member can also be obtained by adhering an adhesive sheet to an optical film, and can also be obtained by applying a pressure-sensitive adhesive composition to the surface of the optical film, followed by a crosslinking reaction or the like.

  The pressure-sensitive adhesive composition of the present invention described above has both durability and light leakage prevention properties, has no bleed of low molecular weight components, can suppress contamination during re-peeling, and can prevent peeling under severe conditions. The reason for having the properties is not clear, but since the (meth) acrylic polymer satisfies the requirements (a) to (d), the high molecular weight to low molecular weight polymers are arranged without gaps, and thus the low molecular weight polymer It is easy to be retained in the system, and the compatibility of the entire (meth) acrylic polymer having such a wide molecular weight distribution has been improved, and bleeding of low molecular weight components under severe conditions has been suppressed. Conceivable. For this reason, it is possible to increase the ratio of medium to low molecular weight components, and to prevent peeling and light leakage under harsh conditions while maintaining durability and suppression of contamination during re-peeling (good reworkability). It is thought that.

  EXAMPLES Next, although an Example is given and this invention is further demonstrated, this invention is not limited to these Examples. In the examples, “part” represents “part by weight”.

Example 1
99 parts of butyl acrylate, 1 part of 2-hydroxyethyl acrylate, 120 parts of ethyl acetate, and azobisisobutyronitrile (manufactured by Otsuka Chemical Co., Ltd.) which is an azo polymerization initiator (hereinafter abbreviated as “AIBN”) ) 0.2 parts was charged into the reaction vessel, and the air in the reaction vessel was replaced with nitrogen gas. Next, the mixture was heated to 60 ° C. with stirring in a nitrogen atmosphere, and then reacted for 2 hours. Then, while adding 30 parts of ethyl acetate dropwise, 0.2 part of perhexyl PV (manufactured by Nippon Oil & Fats Co., Ltd.) (hereinafter abbreviated as “PHPV”) as a peroxide-based polymerization initiator is added and allowed to react for 20 minutes. Then, 0.3 part of PHPV was added and reacted for 40 minutes, and further 1.0 part of PHPV was added and reacted for 3 hours. After completion of the reaction, the reaction mixture was diluted with ethyl acetate to obtain a (meth) acrylic polymer solution having a weight average molecular weight of 980,000.

  For 100 parts of (meth) acrylic polymer (solid content) in the obtained (meth) acrylic polymer solution, 2 parts of isocyanate-based crosslinking agent L-45 (manufactured by Soken Chemical Co., Ltd.), silane coupling 0.05 part of the agent U-10 (manufactured by Soken Chemical Co., Ltd.) was added to obtain a solution of the pressure-sensitive adhesive composition.

  The pressure-sensitive adhesive composition solution was applied to the surface of the peeled polyester film and dried to obtain a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of 25 μm. This pressure-sensitive adhesive sheet was affixed to one side of a polarizing film and aged for 7 days under conditions of a temperature of 23 ° C. and a humidity of 65% to obtain an optical member.

Example 2
In Example 1, except that 99 parts of butyl acrylate and 1 part of 2-hydroxyethyl acrylate were replaced with 96 parts of butyl acrylate and 4 parts of acrylic acid, a weight average molecular weight of 1.1 million was obtained. A (meth) acrylic polymer solution was obtained.

  Using the obtained (meth) acrylic polymer solution, 0.8 parts of an isocyanate crosslinking agent L-45 (manufactured by Soken Chemical Co., Ltd.) as a crosslinking agent, and further an epoxy crosslinking agent E-5XM (Soken Chemical Co., Ltd.) Product) An optical member was obtained in the same manner as in Example 1 except that 0.02 part was added.

Example 3
Polymer solutions A to D separately prepared by the following methods were mixed at the following ratios to obtain a (meth) acrylic polymer solution having a weight average molecular weight of 1.32 million.
Polymer solution A: Amount equivalent to 100 parts as polymer (solid content) Polymer solution B: Amount equivalent to 2 parts as polymer (solid content) Polymer solution C: Amount equivalent to 4 parts as polymer (solid content) Polymer solution D: Polymer (solid content) ) As 2 parts

<Method for preparing polymer solution A>
96 parts of butyl acrylate, 4 parts of acrylic acid, 120 parts of ethyl acetate and 0.2 part of AIBN were charged into the reaction vessel, and the air in the reaction vessel was replaced with nitrogen gas. Next, the mixture was heated to 60 ° C. with stirring in a nitrogen atmosphere, and then reacted for 4 hours. After completion of the reaction, it was diluted with ethyl acetate to obtain a polymer solution A having a weight average molecular weight of 1.3 million.

<Method for Preparing Polymer Solution B>
96 parts of butyl acrylate, 4 parts of acrylic acid, 120 parts of toluene and 0.2 part of AIBN were charged into a reaction vessel, and the air in the reaction vessel was replaced with nitrogen gas. Next, the mixture was heated to 85 ° C. with stirring in a nitrogen atmosphere, and then reacted for 4 hours. After completion of the reaction, it was diluted with toluene to obtain a polymer solution B having a weight average molecular weight of 100,000.

<Method for preparing polymer solution C>
96 parts of butyl acrylate, 4 parts of acrylic acid, 100 parts of toluene, 2 parts of AIBN and 5 parts of α-methylstyrene dimer were charged into the reaction vessel, and the air in the reaction vessel was replaced with nitrogen gas. Next, the mixture was heated to 110 ° C. with stirring in a nitrogen atmosphere, and then reacted for 4 hours. After completion of the reaction, it was diluted with toluene to obtain a polymer solution C having a weight average molecular weight of 20,000.

<Method for preparing polymer solution D>
96 parts of butyl acrylate, 4 parts of acrylic acid, 100 parts of toluene, 3 parts of AIBN and 15 parts of α-methylstyrene dimer were charged into the reaction vessel, and the air in the reaction vessel was replaced with nitrogen gas. Next, the mixture was heated to 110 ° C. with stirring in a nitrogen atmosphere, and then reacted for 4 hours. After completion of the reaction, it was diluted with toluene to obtain a polymer solution D having a weight average molecular weight of 3000.

  Using the obtained (meth) acrylic polymer solution, 0.8 parts of an isocyanate crosslinking agent L-45 (manufactured by Soken Chemical Co., Ltd.) as a crosslinking agent, and further an epoxy crosslinking agent E-5XM (Soken Chemical Co., Ltd.) Product) An optical member was obtained in the same manner as in Example 1 except that 0.02 part was added.

Example 4
In Example 1, 99 parts of butyl acrylate were replaced with 59 parts of butyl acrylate and 40 parts of phenoxyethyl acrylate, and 120 parts of initial charged ethyl acetate was replaced with 140 parts of ethyl acetate. Thus, a (meth) acrylic polymer solution having a weight average molecular weight of 1.16 million was obtained.

  Using the obtained (meth) acrylic polymer solution, 2 parts of isocyanate crosslinking agent L-45 (manufactured by Soken Chemical Co., Ltd.) and 0.2 part of isocyanate crosslinking agent TD-75 (manufactured by Soken Chemical Co., Ltd.) An optical member was obtained in the same manner as in Example 1, except that

Example 5
In Example 1, 99 parts of butyl acrylate was replaced with 64 parts of butyl acrylate and 35 parts of benzyl acrylate, and 120 parts of initial charged ethyl acetate was replaced with 80 parts of ethyl acetate. A (meth) acrylic polymer solution having a weight average molecular weight of 950,000 was obtained.

  Using the obtained (meth) acrylic polymer solution, 2 parts of isocyanate crosslinking agent L-45 (manufactured by Soken Chemical Co., Ltd.) and 0.2 part of isocyanate crosslinking agent TD-75 (manufactured by Soken Chemical Co., Ltd.) An optical member was obtained in the same manner as in Example 1, except that

Comparative Example 1
In Example 1, the amount of ethyl acetate initially charged was changed from 120 parts to 140 parts, and 10 parts of toluene was further added, and the same procedure as in Example 1 was followed, and (meth) acrylic having a weight average molecular weight of 720,000. A system polymer solution was obtained.

  An optical member was obtained in the same manner as in Example 1 using the obtained (meth) acrylic polymer solution.

Comparative Example 2
99 parts of butyl acrylate, 1 part of 2-hydroxyethyl acrylate, 100 parts of ethyl acetate and 0.2 part of AIBN were charged into the reaction vessel, and the air in the reaction vessel was replaced with nitrogen gas. Next, the mixture was heated to 60 ° C. with stirring in a nitrogen atmosphere, and then reacted for 5 hours. Thereafter, while dropwise adding 30 parts of ethyl acetate, 0.2 part of PHPV is added and reacted for 20 minutes, then 0.3 part of PHPV is added and reacted for 40 minutes, and further 1.0 part of PHPV is added and reacted for 4 hours. It was. After completion of the reaction, the reaction mixture was diluted with ethyl acetate to obtain a (meth) acrylic polymer solution having a weight average molecular weight of 1.35 million.

  An optical member was obtained in the same manner as in Example 1 using the obtained (meth) acrylic polymer solution.

Comparative Example 3
99 parts of butyl acrylate, 1 part of 2-hydroxyethyl acrylate, 120 parts of ethyl acetate and 0.2 part of AIBN were charged into the reaction vessel, and the air in the reaction vessel was replaced with nitrogen gas. Next, the mixture was heated to 60 ° C. with stirring in a nitrogen atmosphere, and then reacted for 2 hours. Thereafter, while dropwise adding 30 parts of ethyl acetate, 0.2 part of PHPV and 5 parts of α-methylstyrene dimer were added and reacted for 5 hours. After completion of the reaction, the reaction mixture was diluted with ethyl acetate to obtain a (meth) acrylic polymer solution having a weight average molecular weight of 1.06 million.

  An optical member was obtained in the same manner as in Example 1 using the obtained (meth) acrylic polymer solution.

  The molecular weight distribution curves and the like were determined by measuring the (meth) acrylic polymers obtained in Examples 1 to 5 and Comparative Examples 1 to 3 under the following GPC measurement conditions.

<GPC measurement conditions>
Measuring device: HLC-8120GPC (manufactured by Tosoh Corporation)
GPC column configuration: The following five columns (all manufactured by Tosoh Corporation)
(1) TSK-GEL H _XL -H (guard column)
(2) TSK-GEL G7000H _XL
(3) TSK-GEL GMH _XL
(4) TSK-GEL GMH _XL
(5) TSK-GEL G2500H _XL
Diluted with tetrahydrofuran so that the sample concentration is 1.0 mg / cm ³ Mobile phase solvent: Tetrahydrofuran flow rate: 1.0 cm ³ / min
Column temperature: 40 ° C

  FIG. 1 shows a molecular weight distribution chart of only a part having a molecular weight of 300,000 or less of the (meth) acrylic polymer produced in Example 1. In addition, Table 1 shows numerical values obtained from GPC measurement of the (meth) acrylic polymers produced in Examples 1 to 5 and Comparative Examples 1 to 3.

  The optical members obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were made 240 mm × 140 mm and 310 mm × 230 mm in size and evaluated by the following evaluation methods. The results for a size of 240 mm × 140 mm are shown in Table 2, and the results for a size of 310 mm × 230 mm are shown in Table 3.

<Durability evaluation method>
The optical member was attached to one side of an alkali-free glass plate using a laminator roll, and then held in an autoclave adjusted to 50 ° C. and 5 atm for 20 minutes to prepare a test plate.
Two similar test plates were prepared and left for 500 hours under the conditions of a temperature of 60 ° C. and a humidity of 95% RH and for 500 hours under a temperature of 85 ° C., respectively, and foamed and peeled according to the following criteria. The occurrence of cracks and the like were visually observed and evaluated.
○: Appearance defects such as foaming, peeling and cracking were not observed. ×: Appearance defects such as foaming, peeling and cracking were observed.

<Cooling cycle durability evaluation method>
The optical member was attached to one side of an alkali-free glass plate using a laminator roll, and then held in an autoclave adjusted to 50 ° C. and 5 atm for 20 minutes to prepare a test plate.
Using the thermal shock device TSA-71L-A manufactured by Espec Co., Ltd., the test plate thus prepared was repeated 200 times for a cooling cycle of -40 ° C. for 30 minutes and 80 ° C. for 30 minutes to foam the optical member. The presence or absence of floating or peeling was visually observed and evaluated according to the following criteria.
◯: No poor appearance such as foaming, floating, peeling, etc. ×: Foaming, floating, peeling was confirmed.

<Evaluation method for light leakage prevention>
Two optical members are attached to the front and back surfaces of an alkali-free glass plate using a laminator roll so that they are mutually orthogonal Nicols, and then held in an autoclave adjusted to 50 ° C. and 5 atm for 20 minutes. A test plate was prepared.
The prepared test plate was allowed to stand at 85 ° C. for 500 hours, visually observed for light leakage prevention properties, and evaluated according to the following criteria.
◎: No light leakage was observed ○: Light leakage was hardly observed ×: Clear light leakage was observed

<Re-peeling contamination evaluation method>
The optical member is attached to one surface of an alkali-free glass plate using a laminator roll, and then held for 20 minutes in an autoclave adjusted to 50 ° C. and 5 atm, for 24 hours in an atmosphere of 23 ° C. and 65% humidity. A test plate was prepared by standing.
The optical member was peeled from the test plate thus prepared, and the contamination of the adherend (non-alkali glass plate) was visually observed and evaluated according to the following criteria.
○: No contamination was observed on the adherend ×: Contamination was confirmed on the adherend

  As can be seen from Tables 2 and 3, the optical members of Examples 1 to 5 were excellent in all the performances evaluated in any size, whereas any one of the requirements (a) to (d) Any of the evaluated performances of the optical members of Comparative Examples 1 to 3 that did not satisfy the above conditions was inferior.

  According to the present invention, a pressure-sensitive adhesive that has both durability and light leakage properties, has no low molecular weight bleed, can suppress contamination during re-peeling, can be prevented from peeling under severe conditions, and has excellent reworkability Since the composition can be provided, it can be applied to various uses such as a pressure-sensitive adhesive sheet for optical films such as a polarizing film and a retardation film.

It is a figure which shows the single regression line fit to the molecular weight distribution curve of the part of molecular weight 300,000 or less of the (meth) acrylic-type polymer obtained in Example 1, and a molecular weight distribution curve.

Claims (7)

A pressure-sensitive adhesive composition comprising at least a (meth) acrylic polymer and a crosslinking agent, wherein the (meth) acrylic polymer has the requirements (a) to (d)
(A) The content of a component having a weight average molecular weight of 800,000 or more and (b) a molecular weight of 300,000 or less is 25 with respect to the entire (meth) acrylic polymer.
(C) In the molecular weight distribution chart in which the horizontal axis is a linear scale with respect to the molecular weight, the slope of the single regression line fitted to the molecular weight distribution curve of the molecular weight of 300,000 or less is 0 or more. (D) The coefficient of determination in the single regression line Is a pressure-sensitive adhesive composition characterized by satisfying 0.8 or more.   The pressure-sensitive adhesive composition according to claim 1, wherein the (meth) acrylic polymer contains at least an alkyl acrylate ester and a functional group-containing (meth) acrylic monomer as a copolymerization component.   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein a value obtained by dividing the weight average molecular weight of the (meth) acrylic polymer by the number average molecular weight is 20 or more.   The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the crosslinking agent is an isocyanate crosslinking agent or an epoxy crosslinking agent.   The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive composition is used for sticking an optical film.   A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition according to any one of claims 1 to 5 on at least one surface of a support. An optical member, wherein an adhesive layer obtained from the adhesive composition according to any one of claims 1 to 5 is provided on at least one surface of an optical film.

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