JP2013213084A - Pressure-sensitive adhesive and pressure-sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet, having excellent follow-up capability to a rough surface and excellent heat resistance.SOLUTION: A pressure-sensitive adhesive shows that a gel fraction variation calculated from expression is within 3%, and the expression is as follows: gel fraction variation (%)=|(G2-G1)/G2|×100; wherein G1 represents a gel fraction immediately after the formation of a pressure-sensitive adhesive layer, and G2 represents a gel fraction after storage for 7 days in an environment at 23°C and 50% RH after the formation of the pressure-sensitive adhesive layer. Then, the pressure-sensitive adhesive shows that the rupture elongation rate by a tensile test is 100-250% and the rupture stress is 0.2-0.6 N/mm.

Description

  The present invention relates to an adhesive (a material obtained by curing an adhesive composition) and an adhesive sheet.

  In recent years, a pressure-sensitive adhesive excellent in unevenness followability, which is one of the properties of a pressure-sensitive adhesive, has been desired. For example, in a liquid crystal panel, a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition is often used to bond a polarizing plate or a retardation plate to a glass substrate of a liquid crystal cell. In recent years, liquid crystal panels have been made thinner, and for this reason, liquid crystal cells have been thinned by mechanical polishing. Although the surface of the liquid crystal cell is roughened by such mechanical polishing, in order to ensure the adhesion between the roughened liquid crystal cell and the pressure-sensitive adhesive layer, the unevenness of the pressure-sensitive adhesive layer with respect to the roughened surface It is desirable to improve followability.

  In addition, a pressure-sensitive adhesive layer is laminated on the surface of the transparent conductive film provided with the patterned transparent conductive layer without mixing bubbles or the like, and a printed layer having a patterned step on the hard coat film surface is provided. Adhesive layers with excellent irregularity followability are desired for various applications, such as laminating an adhesive layer on the surface without air bubbles, or filling a step with a light-shielding layer corresponding to the frame portion of a mobile phone monitor with an adhesive layer. It is rare.

  In order to improve the unevenness followability of the pressure-sensitive adhesive layer, for example, as in Patent Documents 1 and 2, a plasticizer or liquid paraffin may be added to the acrylic pressure-sensitive adhesive to moderately soften the resulting pressure-sensitive adhesive layer. Conceivable.

Japanese Patent Laid-Open No. 5-45517 Japanese Patent Laid-Open No. 9-137143

  However, the pressure-sensitive adhesive obtained by adding a plasticizer or liquid paraffin does not have sufficient cohesive strength, and when it is placed at a high temperature, the adhesive strength is reduced or foamed, resulting in low heat resistance. There's a problem. Also, there are concerns about various problems such as plasticizers and liquid paraffin bleed out from the pressure-sensitive adhesive layer over time, resulting in a decrease in adhesion durability and contamination of the adherend.

  This invention is made | formed in view of such an actual condition, and it aims at providing the adhesive and adhesive sheet which are excellent in uneven | corrugated followable | trackability and heat resistance.

In order to achieve the above object, first, the present invention is the gel fraction immediately after the pressure-sensitive adhesive layer is formed, G1, the gel after being stored for 7 days in an environment of 23 ° C. and 50% RH from the formation of the pressure-sensitive adhesive layer. When the fraction is G2, the following formula Gel fraction fluctuation rate (%) = | (G2-G1) / G2 | × 100
The gel fraction fluctuation rate calculated from the following is within 3%, the elongation at break by tensile test is 100 to 250%, and the stress at break is 0.2 to 0.6 N / mm ² An agent is provided (Invention 1).

  According to the pressure-sensitive adhesive according to the invention (Invention 1), it is possible to obtain the effect of being excellent in unevenness followability and heat resistance, which cannot be predicted at all from the above physical properties.

  The pressure-sensitive adhesive according to the invention (Invention 1) has a (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 600,000 to 2,000,000, a weight average molecular weight of 30,000 to 100,000, and a side chain. It is preferable that it is a pressure-sensitive adhesive obtained by curing a pressure-sensitive adhesive composition containing a reactive (meth) acrylic acid ester polymer (B) having a polymerizable double bond by irradiation with active energy rays (invention). 2).

  In the said invention (invention 2), the polymerizable double bond of the side chain of the said reactive (meth) acrylic acid ester polymer (B) is contained in the (meth) acryloyl group introduce | transduced into the side chain through isocyanate. (Invention 3).

  In the said invention (invention 2 and 3), the ratio of the said reactive (meth) acrylic acid ester polymer (B) with respect to 100 mass parts of said (meth) acrylic acid ester polymers (A) is 5-30 mass parts. It is preferable (Invention 4).

  In the said invention (invention 2-4), it is preferable that the said adhesive composition contains a photoinitiator (C) further (invention 5).

  In the said invention (invention 5), it is preferable that the ratio of the said photoinitiator (C) with respect to 100 mass parts of said reactive (meth) acrylic ester polymers (B) is 5-30 mass parts (invention). 6).

In the said invention (invention 2-6), it is preferable that the irradiation amount of the said active energy ray is 50-1000 mJ / cm < ² > (invention 7).

  In the said invention (invention 1), it is preferable that the said adhesive is an active energy ray hardening-type adhesive (invention 8).

  In the said invention (invention 1-8), it is preferable that the gel fraction immediately after the adhesive layer formation and the said 7-day storage is 30 to 60% (invention 9).

  In the said invention (invention 1-9), it is preferable that a haze value is 1.0% or less (invention 10).

  2ndly, this invention is an adhesive sheet provided with the base material and the adhesive layer, Comprising: The said adhesive layer consists of the said adhesive (invention 1-10), The adhesive sheet characterized by the above-mentioned is provided. (Invention 11).

  In the said invention (invention 11), it is preferable that the said base material is an optical member (invention 12).

  Thirdly, the present invention is an adhesive sheet comprising two release sheets and an adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets. A pressure-sensitive adhesive sheet, characterized in that the layer is composed of the pressure-sensitive adhesive (Invention 1 to 10) (Invention 13).

  The pressure-sensitive adhesive according to the present invention has a gel fraction fluctuation rate immediately after formation of the pressure-sensitive adhesive layer and after storage for 7 days within a predetermined range, and by setting the elongation at break and the stress at break within a predetermined range. From the physical properties, it is possible to obtain the effect of being excellent in unevenness followability and heat resistance, which cannot be predicted at all. By using this pressure-sensitive adhesive, a pressure-sensitive adhesive sheet excellent in unevenness followability and heat resistance can be obtained.

It is sectional drawing of the adhesive sheet which concerns on the 1st Embodiment of this invention. It is sectional drawing of the adhesive sheet which concerns on the 2nd Embodiment of this invention. It is a top view explaining the uneven | corrugated followable | trackability test of an adhesive layer. It is a schematic sectional drawing explaining the uneven | corrugated followable | trackability test of an adhesive layer.

Hereinafter, embodiments of the present invention will be described.
[Physical properties of adhesive]
The pressure-sensitive adhesive according to this embodiment is
When the gel fraction immediately after formation of the pressure-sensitive adhesive layer is G1, and the gel fraction after storage for 7 days in an environment of 23 ° C. and 50% RH from the formation of the pressure-sensitive adhesive layer is G2, the following formula Gel fraction Rate of change (%) = | (G2−G1) / G2 | × 100
The gel fraction fluctuation rate calculated from is within 3%,
The elongation at break by a tensile test is 100 to 250%, and the breaking stress is 0.2 to 0.6 N / mm ² .
Is. A pressure-sensitive adhesive satisfying such physical properties is excellent in unevenness followability and heat resistance. The reason for this is not clear, but it is considered that both the gel fraction fluctuation rate, the elongation at break and the stress at break are related to both the unevenness followability and the heat resistance.

  Here, the term “immediately after the formation of the pressure-sensitive adhesive layer” refers to the first stage in which no additional artificial treatment is performed until the time of use after the formation of the pressure-sensitive adhesive layer. For example, in the case of an active energy ray-curable adhesive, it means immediately after irradiation with active energy rays. In actual measurement, due to the fact that it takes a certain amount of time from sample preparation to the start of various measurements, immediately after the formation of the pressure-sensitive adhesive layer is about a half day from the state in which the above-mentioned artificial treatment is no longer performed. To do.

  The method for measuring the gel fraction is as shown in the test examples described later. As described above, the gel fraction fluctuation rate of 3% or less indicates that the curing of the pressure-sensitive adhesive is substantially completed immediately after the pressure-sensitive adhesive layer is formed. That is, the physical properties of the adhesive are stabilized immediately after the formation of the adhesive layer. Therefore, the pressure-sensitive adhesive according to the present embodiment does not require aging, which has been conventionally required, and can thereby quickly carry out shipment of a member having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive or the next process, This is very advantageous in terms of the stock burden and productivity of intermediate materials.

  The gel fraction G1 immediately after formation of the pressure-sensitive adhesive layer and the gel fraction G2 after storage for 7 days are each preferably 30 to 60%, particularly preferably 32 to 56%, and more preferably 35 to 50%. % Is preferred. When the gel fraction is less than 30%, the cohesive force of the pressure-sensitive adhesive is insufficient, and durability (heat resistance) at high temperatures may be reduced. Moreover, when the gel fraction exceeds 60%, the unevenness followability of the pressure-sensitive adhesive may be lowered.

  In the tensile test, a pressure-sensitive adhesive piece (single pressure-sensitive adhesive layer without a substrate or the like) having a width of 10 mm, a length of 20 mm, and a thickness of 500 μm by lamination or the like is stretched at a speed of 200 mm / min by a tensile test. Do it. The elongation at break by the tensile test of the pressure-sensitive adhesive according to this embodiment is 100 to 250%. When the elongation at break is less than 100%, the unevenness followability may be lowered, and when it exceeds 250%, the heat resistance may be lowered. From such a viewpoint, the elongation at break is preferably 110 to 240%, particularly preferably 115 to 230%, and further preferably 130 to 200%.

Moreover, the breaking stress by the said tension test is 0.2-0.6 N / mm < ² >. When rupture stress is less than 0.2 N / mm ^2, there is the heat resistance is lowered, and when it exceeds 0.6 N / mm ^2, unevenness follow-up properties there is a case of decrease. From such a viewpoint, the breaking stress is preferably 0.2 to 0.5 N / mm ² .

  The haze value (value measured according to JIS K7105) of the pressure-sensitive adhesive according to this embodiment is preferably 1.0% or less, particularly preferably 0.7% or less, and more preferably 0.5. % Or less is preferable. When the haze value is 1.0% or less, the transparency is very high, and it is suitable even when considering application to optical applications and the like.

[Adhesive composition]
The pressure-sensitive adhesive according to this embodiment is preferably an active energy ray-curable pressure-sensitive adhesive. In addition, an active energy ray hardening-type adhesive means the adhesive with which use as an adhesive is performed after active energy ray irradiation.

  The pressure-sensitive adhesive having the above physical properties is preferably a (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 600,000 to 2,000,000 (hereinafter simply referred to as “polymer (A)”). ) And a reactive (meth) acrylic acid ester polymer (B) having a weight average molecular weight of 30,000 to 100,000 and having a polymerizable double bond in the side chain (hereinafter simply referred to as “polymer (B)”) In some cases, a pressure-sensitive adhesive composition (hereinafter, referred to as “pressure-sensitive adhesive composition P”) is cured by irradiation with active energy rays. In this specification, (meth) acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same applies to other similar terms. Further, the “polymer” includes the concept of “copolymer”.

  Conventionally, low molecular weight polymers have been used as plasticizers. However, in the pressure-sensitive adhesive obtained from the above-mentioned pressure-sensitive adhesive composition P, a plurality of low-molecular weight polymers (B) are produced by irradiation with active energy rays. They are bonded to each other by cleavage of the polymerizable double bond in the side chain to form a three-dimensional network structure. A plurality of high molecular weight polymers (A) are inserted into the three-dimensional network structure and constrained, and a pseudo-crosslinked structure (constrained but covalently bonded between the high molecular weight polymers (A)). It is presumed that an unstructured structure is formed (the entire structure is hereinafter referred to as “structure X”). With such a structure X, it is considered that the pressure-sensitive adhesive exhibits excellent unevenness followability and heat resistance. Hereinafter, the said adhesive composition P is demonstrated.

  The (meth) acrylic acid ester polymer (A) is a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms, an alkoxyalkyl group-containing (meth) acrylic acid ester optionally used, and, if desired, A copolymer of a monomer having a functional group to be used (functional group-containing monomer) and another monomer used as desired is preferable. The (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms of the alkyl group and the alkoxyalkyl group-containing (meth) acrylic acid ester can impart desired adhesive strength to the resulting pressure-sensitive adhesive, and the functional group-containing monomer It is considered that the polymer (A) can be effectively inserted into the three-dimensional network structure of the polymer (B) depending on the polarity of the functional group.

  Examples of the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and (meth) acrylic acid n-. Butyl, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n- (meth) acrylate Examples include decyl, n-dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, and the like. These may be used alone or in combination of two or more.

  Examples of the alkoxyalkyl group-containing (meth) acrylic acid ester include methoxymethyl (meth) acrylate, methoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, methoxybutyl (meth) acrylate, (meth) Examples include ethoxymethyl acrylate, ethoxyethyl (meth) acrylate, ethoxypropyl (meth) acrylate, ethoxybutyl (meth) acrylate, and the like. These may be used alone or in combination of two or more. In addition, it is preferable that carbon number of an alkoxyalkyl group is about 20 or less.

  As functional group-containing monomers, monomers having a hydroxyl group in the molecule (hydroxyl group-containing monomer), monomers having a carboxyl group in the molecule (carboxyl group-containing monomer), monomers having an amino group in the molecule (amino group-containing monomer), etc. Are preferred.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, (meth And (meth) acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylate. These may be used alone or in combination of two or more.

  Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used alone or in combination of two or more. In addition, when the adhesive composition P contains an aziridine-based crosslinking agent described later, since the carboxyl group is excellent in reactivity with the aziridinyl group of the aziridine-based crosslinking agent, the (meth) acrylic acid ester polymer (A) is It is preferable to have at least a carboxyl group-containing monomer as a constituent monomer unit.

  Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, n-butylaminoethyl (meth) acrylate, and the like. These may be used alone or in combination of two or more.

  Examples of the other monomer include (meth) acrylic acid ester having an aliphatic ring such as cyclohexyl (meth) acrylate, (meth) acrylic acid ester having an aromatic ring such as phenyl (meth) acrylate, and acrylamide. Non-crosslinkable tertiary amino groups such as non-crosslinkable (meth) acrylamide such as methacrylamide, N, N-dimethylaminoethyl (meth) acrylate and N, N-dimethylaminopropyl (meth) acrylate Examples include (meth) acrylic acid ester, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

  The (meth) acrylic acid ester polymer (A) is a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms and an alkoxyalkyl group-containing (meth) acrylic acid as a monomer unit constituting the polymer. It is preferable to contain 70 to 99% by mass in combination with the ester, particularly preferably 70 to 95% by mass, and more preferably 80 to 95% by mass. When the total content of the (meth) acrylic acid alkyl ester and the alkoxyalkyl group-containing (meth) acrylic acid ester is within the above range, an appropriate adhesive force as an adhesive can be obtained. Moreover, if the total content of the (meth) acrylic acid alkyl ester and the alkoxyalkyl group-containing (meth) acrylic acid ester is less than 70% by mass, the adhesive strength may be too low. The (meth) acrylic acid ester polymer (A) may be composed of only a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms and an alkoxyalkyl group-containing (meth) acrylic acid ester. Good.

  Here, when using together the (meth) acrylic-acid alkylester whose carbon number of an alkyl group is 1-20, and the alkoxyalkyl group containing (meth) acrylic acid ester, the carbon number of the alkyl group in both is 1-20 (meta) ) The proportion of acrylic acid alkyl ester is preferably 50% by mass or more, particularly preferably 70% by mass or more, and further preferably 80% by mass or more. In addition, 100 mass% may be sufficient as (meth) acrylic-acid alkylester whose carbon number of an alkyl group is 1-20 as an upper limit of the said mixture ratio of both.

  The (meth) acrylic acid ester polymer (A) preferably contains 1 to 30% by mass, particularly 2 to 20% by mass of the functional group-containing monomer as a monomer unit constituting the polymer. It is preferable to contain 3 to 10% by mass. By containing the functional group-containing monomer in the above range, it is estimated that the compatibility with the polymer (B) described later is improved and the structure X can be efficiently formed. As a result, a low haze value is obtained. An adhesive having excellent heat resistance is obtained.

  When the adhesive composition P contains an aziridine-based crosslinking agent described later, the (meth) acrylic acid ester polymer (A) has a carboxyl group-containing monomer as a monomer unit constituting the polymer in an amount of 1.0 to It is preferable to contain 10.0 mass%, and it is preferable to contain 3.0-5.0 mass% especially. Thereby, the polymer (A) can favorably form a crosslinked structure via an aziridine-based crosslinking agent.

  The polymerization mode of the (meth) acrylic acid ester polymer (A) may be a random copolymer or a block copolymer.

  The (meth) acrylic acid ester polymer (A) has a weight average molecular weight of 600,000 to 2,000,000, preferably 700,000 to 1,800,000, particularly preferably 800,000 to 1,500,000. That is, the (meth) acrylic acid ester polymer (A) is a high molecular weight polymer component. In addition, the weight average molecular weight in this specification is the value of polystyrene conversion measured by the gel permeation chromatography (GPC) method.

  The (meth) acrylic acid ester polymer (A) has a weight average molecular weight within the above range, and the polymer (A) has a relatively large molecular weight, so that the structure X is presumably formed. The

  Here, when the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is less than 600,000, the gel fraction of the resulting pressure-sensitive adhesive may be low and heat resistance may be poor. Moreover, when the weight average molecular weight of (meth) acrylic acid ester polymer (A) exceeds 2 million, compatibility with a reactive (meth) acrylic acid ester polymer (B) etc. will deteriorate, and the adhesive obtained There is a possibility that the unevenness followability of the lowering.

  In the adhesive composition P, the (meth) acrylic acid ester polymer (A) may be used singly or in combination of two or more.

  The reactive (meth) acrylic acid ester polymer (B) having a polymerizable double bond in the side chain is a (meth) acrylic polymer (b1) having a functional group (x) -containing monomer as a constituent monomer unit; It can obtain preferably by making it react with the polymerizable double bond containing compound (b2) which has the substituent (y) which reacts with the functional group (x).

  The (meth) acrylic polymer (b1) is a functional group (x) -containing monomer, a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms, which is optionally used, and other optionally used Copolymers with monomers are preferred.

  The functional group (x) -containing monomer is a monomer having a polymerizable double bond and a functional group such as a hydroxyl group, a carboxyl group, an amino group, a substituted amino group, and an epoxy group in the molecule, preferably a hydroxyl group-containing monomer. An unsaturated compound and / or a carboxyl group-containing unsaturated compound is used.

  Specific examples of such functional group (x) -containing monomers include hydroxyl group-containing (meth) acrylates such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, Examples include carboxyl group-containing compounds such as acrylic acid, methacrylic acid, and itaconic acid, and these are used alone or in combination of two or more.

  As the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group and other monomers, those similar to the (meth) acrylic acid ester polymer (A) can be used.

  In the (meth) acrylic polymer (b1), as a monomer unit constituting the polymer, the functional group (x) -containing monomer is usually 3 to 100% by mass, preferably 5 to 40% by mass, and particularly preferably 10%. The proportion of the structural unit derived from a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group is usually 0 to 97% by mass, preferably 60 to 95% by mass, Preferably it contains in the ratio of 70-90 mass%.

  The functional group-containing monomer that is a constituent monomer of the (meth) acrylic acid ester polymer (A) and the functional group (x) -containing monomer that is a constituent monomer of the (meth) acrylic polymer (b1) are: For example, it is preferable to make the types different, for example, a carboxyl group-containing monomer and a hydroxyl group-containing monomer. Thereby, it is because a crosslinking agent (D) and a silane coupling agent (E) can be made to act only on a polymer (A).

  On the other hand, the substituent (y) of the polymerizable double bond-containing compound (b2) is the same as the functional group (x) of the functional group (x) -containing monomer unit of the (meth) acrylic polymer (b1). Depending on the situation, it can be appropriately selected. For example, when the functional group (x) is a hydroxyl group, an amino group or a substituted amino group, the substituent (y) is preferably an isocyanate group or an epoxy group, and when the functional group (x) is a carboxyl group, the substituent (y) Is preferably an aziridinyl group, an epoxy group or an oxazolinyl group. When the functional group (x) is an epoxy group, the substituent (y) is preferably an amino group, a carboxyl group or an aziridinyl group. One such substituent (y) is included for each molecule of the polymerizable double bond-containing compound (b2).

  The polymerizable double bond-containing compound (b2) usually contains 1 to 5 and preferably 1 to 2 polymerizable double bonds (carbon-carbon double bonds) per molecule. Examples of such a polymerizable double bond-containing compound (b2) include (meth) acryloyloxyethyl isocyanate, meta-isopropenyl-α, α-dimethylbenzyl isocyanate, (meth) acryloyl isocyanate, allyl isocyanate; Or (meth) acryloyl monoisocyanate compound obtained by reaction of polyisocyanate compound and hydroxyethyl (meth) acrylate; obtained by reaction of diisocyanate compound or polyisocyanate compound, polyol compound and hydroxyethyl (meth) acrylate (Meth) acryloyl monoisocyanate compound; glycidyl (meth) acrylate; (meth) acrylic acid, 2- (1-aziridinyl) ethyl (meth) acrylate And 2-vinyl-2-oxazoline, 2-isopropenyl-2-oxazoline and the like.

  As the polymerizable double bond-containing compound (b2), among them, the group having an isocyanate group as the substituent (y) and containing a polymerizable double bond, a group containing an ethylenic double bond, A compound having a (meth) acryloyl group is particularly preferable, and specifically, (meth) acryloyloxyethyl isocyanate, particularly methacryloyloxyethyl isocyanate is preferable.

  The amount of the polymerizable double bond-containing compound (b2) in the reactive (meth) acrylic acid ester polymer (B) as the substituent (y) is the functional group of the (meth) acrylic polymer (b1). (X) The amount of the functional group (x) of the containing monomer is preferably 0.05 to 0.8 molar equivalent, particularly preferably 0.1 to 0.6 molar equivalent, Is preferably 0.1 to 0.4 molar equivalent.

  The reaction between the (meth) acrylic polymer (b1) and the polymerizable double bond-containing compound (b2) is usually acetic acid under normal pressure and inert gas atmosphere at room temperature or at 40 to 70 ° C. The reaction is performed for 12 to 48 hours in an organic solvent such as ethyl. In the reaction, a catalyst, a polymerization inhibitor or the like can be appropriately used. For example, in the case of a reaction between an acrylic copolymer (b1) whose functional group (x) is a hydroxyl group and a polymerizable double bond-containing compound (b2) whose substituent (y) is an isocyanate group, dibutyltin It is preferable to use an organic tin-based catalyst such as laurate. Further, depending on the combination of the functional group (x) and the substituent (y), the reaction temperature, pressure, solvent, time, presence / absence of catalyst, and type of catalyst can be selected as appropriate. As a result, the functional group (x) present in the (meth) acrylic polymer (b1) reacts with the substituent (y) in the polymerizable double bond-containing compound (b2) to polymerize in the side chain. A reactive (meth) acrylic acid ester polymer (B) into which an ionic double bond is introduced is obtained. The reaction rate of the functional group (x) and the substituent (y) in this reaction is usually 70% or more, preferably 80% or more, and the unreacted functional group (x) is a reactive (meth) acrylate. It may remain in the polymer (B).

  The polymerization mode of the reactive (meth) acrylic acid ester polymer (B) ((meth) acrylic polymer (b1)) may be a random copolymer or a block copolymer. .

  The weight average molecular weight of the reactive (meth) acrylic acid ester polymer (B) is 10,000 to 100,000, preferably 30,000 to 80,000, particularly preferably 40,000 to 60,000. That is, the reactive (meth) acrylic acid ester polymer (B) is a polymer component having a low molecular weight as compared with the (meth) acrylic acid ester polymer (A).

  When the weight average molecular weight of the reactive (meth) acrylic acid ester polymer (B) is within the above range, a three-dimensional network structure peculiar to the pressure-sensitive adhesive according to the present embodiment is formed. It will contribute to heat resistance. That is, when the weight average molecular weight of the reactive (meth) acrylic acid ester polymer (B) is less than 10,000, a good three-dimensional network structure cannot be obtained, and heat resistance may deteriorate. On the other hand, when the weight average molecular weight of the reactive (meth) acrylic acid ester polymer (B) exceeds 100,000, the compatibility with the (meth) acrylic acid ester polymer (A) is lowered and the haze value is increased. There is a case. Moreover, the restraint state of the polymer (A) in the three-dimensional network structure formed by the polymer (B) becomes insufficient, and as a result, the resulting pressure-sensitive adhesive may be inferior in heat resistance.

  In the adhesive composition P, the reactive (meth) acrylic acid ester polymer (B) may be used alone or in combination of two or more.

  The blending ratio of the reactive (meth) acrylate polymer (B) to 100 parts by weight of the (meth) acrylate polymer (A) is preferably 5 to 30 parts by weight, particularly 7 to 25 parts by weight. It is preferable that it is 10-20 mass parts.

  The pressure-sensitive adhesive obtained from the pressure-sensitive adhesive composition P containing the (meth) acrylic acid ester polymer (A) and the reactive (meth) acrylic acid ester polymer (B) in the above proportions forms the structure X well. Presumed to be.

  Here, when using an ultraviolet-ray as an active energy ray irradiated with respect to the adhesive composition P, it is preferable that the adhesive composition P contains a photoinitiator (C) further. By containing the photopolymerization initiator (C) in this way, the reactive (meth) acrylic acid ester polymer (B) can be efficiently cured, and the aziridinyl propionate and the light irradiation amount can be reduced. Can be reduced.

  Specific examples of the photopolymerization initiator (C) include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin methyl benzoate, and benzoin. Dimethyl ketal, 2,4-diethylthioxanthone, 1-hydroxycyclohexyl phenyl ketone, benzyl diphenyl sulfide, tetramethyl thiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β-chloranthraquinone, (2 , 4,6-trimethylbenzyldiphenyl) phosphine oxide, 2-benzothiazole-N, N-diethyldithiocarbamate and the like.

  The photopolymerization initiator (C) may be used in an amount in the range of 1 to 50 parts by mass, particularly 5 to 30 parts by mass with respect to 100 parts by mass of the reactive (meth) acrylic acid ester polymer (B). preferable.

  The adhesive composition P contains a crosslinking agent (D) and a silane coupling agent (E) as desired, in addition to the polymer (A), the polymer (B) and the photopolymerization initiator (C). In addition, it contains various additives usually used for acrylic adhesives, such as tackifiers, antistatic agents, antioxidants, ultraviolet absorbers, light stabilizers, softeners, fillers, etc. Also good.

  As the crosslinking agent (D), any desired one can be used as long as the effects of the present invention are not hindered. However, when the (meth) acrylic acid ester polymer (A) has a carboxyl group as a reactive functional group. It is preferable to use an aziridine-based crosslinking agent that reacts well with the carboxyl group. Thus, by using the aziridine type crosslinking agent to crosslink the (meth) acrylic acid ester polymer (A), it is possible to improve the durability of the resulting pressure-sensitive adhesive, particularly the heat and moisture resistance.

  Examples of the aziridine-based crosslinking agent include diphenylmethane-4,4′-bis (1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethanetri-β-aziridinyl. Propionate, toluene-2,4-bis (1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1- (2-methylaziridine), tris-1- (2-methylaziridine) phosphine, And trimethylolpropane tri-β- (2-methylaziridine) propionate.

  The content of the crosslinking agent (D) in the adhesive composition P is such that the crosslinking group (for example, aziridinyl group) of the crosslinking agent (D) is a reactive functional group of the (meth) acrylate polymer (A). The amount is preferably 0.001 to 0.1 molar equivalent with respect to the amount of (e.g., carboxyl group), and particularly preferably 0.003 to 0.02 molar equivalent.

  When the adhesive composition P contains a silane coupling agent (E), the adhesiveness of the resulting adhesive to the glass substrate can be improved. For example, when the (meth) acrylic acid ester polymer (A) has a carboxyl group as a reactive functional group, the organic reactive group of the silane coupling agent (E) and the (meth) acrylic acid ester polymer (A) On the other hand, the alkoxysilyl group of the silane coupling agent (E) acts on the adherend surface such as a glass substrate. For this reason, when bonding a polarizing plate to a liquid crystal glass cell etc., the adhesiveness between an adhesive and a liquid crystal glass cell becomes more favorable, for example. In addition, when the reactive functional group of a polymer (A) is other than a carboxyl group, the silane coupling agent (E) which has the organic reactive group which acts with the said reactive functional group is selected suitably.

  The silane coupling agent (E) is an organosilicon compound having at least one alkoxysilyl group in the molecule, having good compatibility with the pressure-sensitive adhesive component, and having light transmittance, for example, substantially transparent Are suitable. It is preferable that the compounding quantity of such a silane coupling agent (E) is 0.01-1.0 mass part with respect to 100 mass parts of (meth) acrylic acid ester polymer (A), and is especially 0.1. It is preferable that it is 05-0.5 mass part.

  Specific examples of the silane coupling agent (E) include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, (meth) acryloxypropyltrimethoxysilane, and 3-glycidoxypropyltri Silicon compounds having an epoxy structure such as methoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane And amino group-containing silicon compounds such as N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, and 3-isocyanatopropyltriethoxysilane. These may be used individually by 1 type and may be used in combination of 2 or more type.

[Method for producing adhesive composition]
The pressure-sensitive adhesive composition P is prepared by manufacturing each of the (meth) acrylic acid ester polymer (A) and the reactive (meth) acrylic acid ester polymer (B), mixing them, and if desired, any It can manufacture by adding a photoinitiator (C), a crosslinking agent (D), a silane coupling agent (E), etc. in a step.

  The (meth) acrylic acid ester polymer (A) can be produced by a normal radical polymerization method. The polymerization of the (meth) acrylic acid ester polymer (A) can be performed by a solution polymerization method or the like using a polymerization initiator as desired. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and the like. Two or more kinds may be used in combination.

  Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more kinds may be used in combination. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane 1-carbonitrile), 2 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2′-azobis (2-methylpropionate) 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-hydroxymethylpropionitrile), 2,2′-azobis [2- (2-imidazolin-2-yl) Propane] and the like.

  Examples of the organic peroxide include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples include dicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

  In addition, in the said superposition | polymerization process, the weight average molecular weight of the polymer obtained can be adjusted by mix | blending chain transfer agents, such as 2-mercaptoethanol.

  On the other hand, the reactive (meth) acrylic acid ester polymer (B) is produced by reacting the (meth) acrylic polymer (b1) with the polymerizable double bond-containing compound (b2) as described above. be able to. The (meth) acrylic polymer (b1) can be produced in the same manner as in the production method of the (meth) acrylic acid ester polymer (A).

  When the (meth) acrylic acid ester polymer (A) and the reactive (meth) acrylic acid ester polymer (B) are obtained, the solutions of the polymers (A) and (B) are mixed and a diluting solvent is added. Then, if desired, a photopolymerization initiator (C), a cross-linking agent (D), a silane coupling agent (E), etc. are added and mixed thoroughly to obtain a pressure-sensitive adhesive composition (coating solution) diluted with a solvent. )

  Examples of the dilution solvent for diluting the adhesive composition to form a coating solution include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, methylene chloride, and ethylene chloride. Halogenated hydrocarbons, alcohols such as methanol, ethanol, propanol, butanol and 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethyl cellosolve A cellosolve solvent such as is used.

  The concentration / viscosity of the coating solution thus prepared is not particularly limited as long as it can be coated, and can be appropriately selected depending on the situation. For example, it dilutes so that the density | concentration of an adhesive composition may be 10-40 mass%. In addition, when obtaining an application | coating solution, addition of a dilution solvent etc. is not a necessary condition, and if a viscosity etc. which can be coated with an adhesive composition, it is not necessary to add a dilution solvent. In this case, the adhesive composition becomes the coating solution as it is.

(Formation of adhesive)
The pressure-sensitive adhesive according to this embodiment can be preferably obtained by applying the pressure-sensitive adhesive composition P to a desired object and drying it, and then curing the pressure-sensitive adhesive composition P by irradiation with active energy rays.

  Although drying of the adhesive composition P may be performed by air drying, it is normally performed by heat processing (preferably hot air drying). When performing heat processing, it is preferable that heating temperature is 50-150 degreeC, and it is especially preferable that it is 70-120 degreeC. The heating time is preferably 10 seconds to 10 minutes, particularly preferably 50 seconds to 2 minutes. In addition, when (meth) acrylic acid ester polymer (A) has a reactive functional group and the adhesive composition P contains a crosslinking agent (D), (meth) acrylic acid is obtained by the above heat treatment. The ester polymer (A) is crosslinked.

As active energy rays, ultraviolet rays, electron beams and the like are usually used. The dose of the active energy ray varies depending on the type of the energy ray, for example, in the case of ultraviolet rays, preferably 50~1000mJ / cm ² in quantity, in particular 100 to 500 mJ / cm ² is preferred. In the case of an electron beam, about 10 to 1000 krad is preferable.

  By irradiation with the active energy ray, a plurality of reactive (meth) acrylate polymers (B) are bonded to each other by cleavage of a polymerizable double bond in a side chain to form a three-dimensional network structure. It is presumed that the (meth) acrylic acid ester polymer (A) is inserted into the three-dimensional network structure and the structure X is formed. At this time, since the adhesive composition P is cured quickly, there is no need for aging, and various physical properties of the obtained adhesive are stabilized from the initial stage. The pressure-sensitive adhesive is considered to exhibit excellent unevenness followability and heat resistance due to its structure X.

  The pressure-sensitive adhesive according to this embodiment can be preferably used for an optical member. For example, an adhesive between optical members such as a polarizing plate (polarizing film) and a retardation plate (retarding film), or a polarizing plate (polarizing film) ) Or a retardation plate (retardation film) and a glass substrate.

  Since the pressure-sensitive adhesive according to the present embodiment is excellent in unevenness followability, even when adhered to a liquid crystal cell having a rough surface, the adhesive adheres to the liquid crystal cell so as to fill the dimple, and superior optical characteristics are obtained. It is done. Moreover, the adhesive which concerns on this embodiment is excellent also in heat resistance. That is, the pressure-sensitive adhesive according to the present embodiment achieves both the unevenness followability and the heat resistance.

[Adhesive sheet]
As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 </ b> A according to the first embodiment is laminated on the pressure-sensitive adhesive layer 11, the pressure-sensitive adhesive layer 11 stacked on the release surface of the release sheet 12, and the pressure-sensitive adhesive layer 11. And the formed base material 13.

  In addition, as shown in FIG. 2, the adhesive sheet 1B according to the second embodiment includes the two release sheets 12a and 12b and the two release sheets 12a and 12b so as to be in contact with the release surfaces of the two release sheets 12a and 12b. And the pressure-sensitive adhesive layer 11 sandwiched between the release sheets 12a and 12b. In addition, the release surface of the release sheet in this specification refers to a surface having peelability in the release sheet, and includes both a surface that has been subjected to a release treatment and a surface that exhibits peelability without being subjected to a release treatment. .

  In any of the pressure-sensitive adhesive sheets 1A and 1B, the pressure-sensitive adhesive layer 11 is made of a pressure-sensitive adhesive formed by curing the above-described pressure-sensitive adhesive composition.

  The thickness of the pressure-sensitive adhesive layer 11 is appropriately determined according to the purpose of use of the pressure-sensitive adhesive sheets 1A and 1B, but is usually in the range of 5 to 100 μm, preferably 10 to 60 μm, for example, for optical members, particularly for polarizing plates. When used as a PSA layer, it is preferably 10 to 50 μm, particularly preferably 10 to 30 μm.

  There is no restriction | limiting in particular as the base material 13, What was used as a base material sheet of a normal adhesive sheet can be used. For example, in addition to desired optical members, woven or non-woven fabrics using fibers such as rayon, acrylic, polyester, etc .; papers such as fine paper, glassine paper, impregnated paper, coated paper; metal foils such as aluminum and copper; synthesis Paper: Foam such as urethane foam, polyethylene foam; polyester film such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyurethane film, polyethylene film, polypropylene film, cellulose film such as triacetyl cellulose, polyvinyl chloride film , Polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, acrylic resin film, norbornene resin film, cycloolefin Plastic film such as emission resin film; and the like of two or more kinds of those laminates. The plastic film may be uniaxially stretched or biaxially stretched.

  Examples of the optical member include a polarizing plate (polarizing film), a polarizer, a retardation plate (retarding film), a viewing angle compensation film, a brightness enhancement film, a contrast enhancement film, a liquid crystal polymer film, a diffusion film, and a transflective film. Etc.

  Although the thickness of the base material 13 changes with kinds, for example in the case of an optical member, they are 10 micrometers-500 micrometers normally, Preferably they are 50 micrometers-300 micrometers.

  As the release sheets 12, 12a, 12b, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, Polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polycarbonate film, polyimide film A fluororesin film or the like is used. These crosslinked films are also used. Furthermore, these laminated films may be sufficient.

  The release surface of the release sheet (particularly the surface in contact with the pressure-sensitive adhesive layer 11) is preferably subjected to a release treatment. Examples of the release agent used for the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax release agents. The release sheet is preferably active energy ray permeable.

  Although there is no restriction | limiting in particular about the thickness of the peeling sheets 12, 12a, 12b, Usually, it is about 20-150 micrometers.

  In order to manufacture the pressure-sensitive adhesive sheet 1A, a solution (coating solution) containing the pressure-sensitive adhesive composition P is applied to the release surface of the release sheet 12 and dried to obtain a coating film of the pressure-sensitive adhesive composition. The base material 13 is laminated on the exposed surface side of the coating film. Next, the adhesive layer 11 is formed by irradiating active energy rays through the release sheet 12. At this time, aging is unnecessary. The conditions for the active energy ray are as described above.

  Moreover, in order to manufacture the said adhesive sheet 1B, the coating solution of an adhesive composition is apply | coated to the peeling surface of one peeling sheet 12a (or 12b) by apply | coating the coating solution containing the said adhesive composition, and drying. The release sheet 12b is laminated on the exposed surface side of the coating film. Next, the adhesive layer 11 is formed by irradiating active energy rays from either side of the release sheet 12a or 12b.

  Moreover, it replaces with forming an adhesive layer 11 by irradiating an active energy ray through a peeling sheet as mentioned above, and forms the coating-film layer of the adhesive composition P on a peeling sheet, The coating-film layer With the exposed state, the active energy ray may be irradiated to form the pressure-sensitive adhesive layer 11, and then the base material 13 or the release sheet may be laminated on the pressure-sensitive adhesive layer 11. Furthermore, the adhesive layer 11 may be formed by directly forming a coating layer of the adhesive composition P on the substrate 13 and irradiating the coating layer with active energy rays.

  As a method for applying the coating solution, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.

  Here, for example, to manufacture a liquid crystal display device composed of a liquid crystal cell and a polarizing plate, a polarizing plate is used as the base material 13 of the pressure-sensitive adhesive sheet 1A, and the release sheet 12 of the pressure-sensitive adhesive sheet 1A is peeled off. What is necessary is just to bond the exposed adhesive layer 11 and a liquid crystal cell.

  For example, in order to manufacture a liquid crystal display device in which a retardation plate is disposed between a liquid crystal cell and a polarizing plate, as an example, first, one release sheet 12a (or 12b) of the adhesive sheet 1B is released. Then, the pressure-sensitive adhesive layer 11 exposed from the pressure-sensitive adhesive sheet 1B and the phase difference plate are bonded together. Next, the release sheet 12 of the pressure-sensitive adhesive sheet 1A using a polarizing plate as the base material 13 is peeled off, and the pressure-sensitive adhesive layer 11 exposed from the pressure-sensitive adhesive sheet 1A and the retardation plate are bonded. Furthermore, the other release sheet 12b (or 12a) is peeled from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet B, and the pressure-sensitive adhesive layer 11 exposed from the pressure-sensitive adhesive sheet B is bonded to the liquid crystal cell.

  According to the above pressure-sensitive adhesive sheets 1A and 1B, even when the adhesive layer 11 adheres to a liquid crystal cell having a rough surface due to the excellent conformability of the pressure-sensitive adhesive layer 11, the pressure-sensitive adhesive layer 11 reliably adheres to the liquid crystal cell. .

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include 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 may be omitted, or one of the release sheets 12a and 12b in the adhesive sheet 1B may be omitted.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples etc.

[Example 1]
1. Preparation of polymer (A1) In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen introduction tube, 76.5 parts by mass of n-butyl acrylate, 20 parts by mass of methoxyethyl acrylate, acrylic acid 3.0 parts by weight, 0.5 parts by weight of 2-hydroxyethyl acrylate, 200 parts by weight of ethyl acetate, and 0.08 parts by weight of 2,2′-azobisisobutyronitrile were charged, and the air in the reaction vessel Was replaced with nitrogen gas. While stirring in this nitrogen atmosphere, the reaction solution was heated to 60 ° C., reacted for 16 hours, and then cooled to room temperature. Here, the molecular weight of a part of the obtained solution was measured by the method described later, and production of a polymer (A1) having a weight average molecular weight of 800,000 was confirmed.

2. Preparation of polymer (B1) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device and nitrogen introduction tube, 85 parts by mass of n-butyl acrylate, 15 parts by mass of 2-hydroxyethyl acrylate (HEA) 200 parts by mass of ethyl acetate, 0.16 parts by mass of 2,2′-azobisisobutyronitrile, and 0.3 parts by mass of 2-mercaptoethanol were charged, and the air in the reaction vessel was replaced with nitrogen gas. While stirring in this nitrogen atmosphere, the reaction solution was heated to 70 ° C., reacted for 6 hours, cooled to room temperature, and a (meth) acrylic polymer (b1) having a hydroxyl group as the functional group (x). )

  Subsequently, 2-methacryloyloxyethyl isocyanate (MOI) as the polymerizable double bond-containing compound (b2) is set so that the amount of the isocyanate group of the MOI is 0.000 relative to the HEA of the (meth) acrylic polymer (b1). It added so that it might become 1 molar equivalent, Dibutyltin dilaurate was added as a catalyst, and it stirred at normal temperature (23 degreeC) normal pressure for 24 hours. Here, a molecular weight of a part of the obtained solution was measured by a method described later, and production of a polymer (B1) having a weight average molecular weight of 50,000 was confirmed.

3. Preparation of Adhesive Composition 100 parts by mass (solid content converted value) of the polymer (A1) obtained in the step (1) and 20 parts by mass (solid) of the polymer (B1) obtained in the step (2). 1. After mixing with benzophenone and 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator (C) at a mass ratio of 1: 1 (Ciba Specialty Chemicals, Irgacure 500). A diluted solution of the adhesive composition by adding 0 part by mass (a quantity corresponding to 10 parts by mass of the photopolymerization initiator (C) when the polymer (B1) is 100 parts by mass) and stirring sufficiently. Got.

4). Manufacture of polarizing plate with pressure-sensitive adhesive layer Release sheet (manufactured by Lintec Corporation, SP-PET3811) obtained by removing the diluted solution of the pressure-sensitive adhesive composition obtained in the above step (3) with a silicone release agent on one side of the polyethylene terephthalate film. , Thickness: 38 μm) was applied with a knife coater and heat-treated at 90 ° C. for 1 minute to obtain a coating film of an adhesive composition.

Next, a polarizing plate composed of a polarizing film with a discotic liquid crystal layer, in which the polarizing film and the viewing angle widening film are integrated, is so that the exposed surface of the coating film of the adhesive composition and the surface of the discotic liquid crystal layer are in contact with each other. And pasted with the coating film of the above-mentioned adhesive composition. Then, the polarizing plate with an adhesive layer was obtained by irradiating an ultraviolet-ray on the following conditions through a peeling sheet, and making the coating film of an adhesive composition into an adhesive layer. The pressure-sensitive adhesive layer had a thickness of 25 μm.
<Ultraviolet irradiation conditions>
Fusion Co. electrodeless lamp H bulb used, illuminance 600 mW / cm ^2, light quantity 150 mJ / cm ²
・ Use UV-illumination meter "UVPF-36" manufactured by iGraphics.

[Example 2]
As the polymerizable double bond-containing compound (b2), 2-methacryloyloxyethyl isocyanate (MOI) is used in which the amount of isocyanate group of the MOI is 0.2 mol with respect to HEA of the (meth) acrylic polymer (b1). A polymer in the same manner as the polymer (B1) of Example 1 except that the (meth) acrylic polymer (b1) and the polymerizable double bond-containing compound (b2) were reacted so as to be equivalent. (B2) was produced. Part of the resulting solution was measured for molecular weight by the method described later, and production of a polymer (B2) having a weight average molecular weight of 50,000 was confirmed.

  A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the polymer (B2) was used instead of the polymer (B1), and a polarizing plate with a pressure-sensitive adhesive layer was prepared using the pressure-sensitive adhesive composition. Manufactured. The pressure-sensitive adhesive layer had a thickness of 25 μm.

[Example 3, Comparative Examples 1-3]
A polarizing plate with an adhesive layer was produced in the same manner as in Example 1 except that the type and blending amount of the polymer (B) were changed as shown in Table 1. The pressure-sensitive adhesive layer had a thickness of 25 μm.

[Comparative Example 4]
1. Preparation of polymer (A2) In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen introduction tube, 76 parts by mass of n-butyl acrylate, 20 parts by mass of methyl acrylate, 4 parts by mass of acrylic acid 200 parts by mass of ethyl acetate and 0.08 part by mass of 2,2′-azobisisobutyronitrile were charged, and the air in the reaction vessel was replaced with nitrogen gas. While stirring in this nitrogen atmosphere, the reaction solution was heated to 60 ° C., reacted for 16 hours, and then cooled to room temperature. Here, a molecular weight of a part of the obtained solution was measured by a method described later, and production of a polymer (A2) having a weight average molecular weight of 800,000 was confirmed.

2. Preparation of adhesive composition Tolylene diisocyanate (TDI) adduct of trimethylolpropane as an isocyanate cross-linking agent was added to 100 parts by mass (in terms of solid content) of the polymer (A2) obtained in the above step (1) ( By adding 2.5 parts by mass of Nippon Polyurethane Co., Ltd. (Coronate L) and stirring sufficiently, a diluted solution of the adhesive composition was obtained.

3. Production of polarizing plate with pressure-sensitive adhesive layer A polarizing plate with a pressure-sensitive adhesive layer was produced in the same manner as in Example 1 using the diluted solution of the pressure-sensitive adhesive composition obtained in the above step (2). The pressure-sensitive adhesive layer had a thickness of 25 μm.

Here, the above-mentioned weight average molecular weight (Mw) is a polystyrene-reduced weight average molecular weight measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC).
<Measurement conditions>
GPC measurement device: manufactured by Tosoh Corporation, HLC-8020
GPC column (passed in the following order): TSK guard column HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (× 2)
TSK gel G2000HXL
・ Measurement solvent: Tetrahydrofuran ・ Measurement temperature: 40 ° C.

[Test Example 1] (Measurement of gel fraction)
Instead of the polarizing plate used for the production of the polarizing plate with the pressure-sensitive adhesive layer in the examples or comparative examples, a release sheet obtained by peeling one side of the polyethylene terephthalate film with a silicone release agent (manufactured by Lintec Corporation, SP-PET 3801, thickness) In the same manner as in Examples or Comparative Examples, a pressure-sensitive adhesive sheet composed of a release sheet / pressure-sensitive adhesive layer (thickness 25 μm) / release sheet corresponding to each example was prepared.

  Immediately after production (within half a day), the pressure-sensitive adhesive sheet prepared as described above was sampled to a size of 80 mm × 80 mm, and only the pressure-sensitive adhesive layer was wrapped in a polyester mesh (mesh size 200). The mass was weighed with a precision balance. Further, the pressure-sensitive adhesive sheet prepared as described above was stored for 7 days under the conditions of 23 ° C. and 50% RH, and then the mass of the pressure-sensitive adhesive alone was weighed in the same manner as described above. Let these masses be M1.

  Next, the pressure-sensitive adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23 ° C.) for 24 hours. In addition, after the ultraviolet-ray was irradiated to the coating film of the adhesive composition and the adhesive layer was formed, the time required for sampling and immersing in ethyl acetate was about a half day. Thereafter, the pressure-sensitive adhesive was taken out, air-dried for 24 hours in an environment of a temperature of 23 ° C. and a relative humidity of 50%, and further dried in an oven at 80 ° C. for 12 hours. The mass of only the pressure-sensitive adhesive after drying was weighed with a precision balance. The mass at this time is M2.

From the obtained M1 and M2, the following formula Gel fraction (%) = (M2 / M1) × 100
The gel fraction G1 (%) immediately after preparation of the pressure-sensitive adhesive sheet (immediately after formation of the pressure-sensitive adhesive layer) and after storage for 7 days in an environment of 23 ° C. and 50% RH from the production of the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer formation) The gel fraction G2 (%) was calculated.

Further, from the obtained G1 and G2, the following formula Gel fraction variation rate (%) = | (G2-G1) / G2 | × 100
Was used to calculate the gel fraction fluctuation rate (%). The results are shown in Table 2.

[Test Example 2] (Measurement of haze value)
As a measurement sample, an adhesive sheet (stored for 7 days) similar to the adhesive sheet used for measurement of the gel fraction was prepared. About the adhesive layer of the said adhesive sheet, haze value (%) was measured according to JISK7105 using the haze meter (the Nippon Denshoku Industries Co., Ltd. make, NDH2000). The results are shown in Table 2.

[Test Example 3] (Tensile test)
The adhesive composition prepared in Examples or Comparative Examples was applied to a release treatment surface of a release sheet (SP-PET3811, manufactured by Lintec Co., Ltd.) obtained by releasing one side of a polyethylene terephthalate film with a silicone release agent at 100 ° C. It heated for 1 minute and formed the coating film of the adhesive composition. The coating film and a release treatment surface of another release sheet (SP-PET 3801, manufactured by Lintec Corporation) on which one side of a polyethylene terephthalate film is release-treated with a silicone-based release agent are bonded together and irradiated with ultraviolet rays under the following conditions. Thus, an adhesive layer was formed to obtain an adhesive sheet. The pressure-sensitive adhesive layer had a thickness of 25 μm.
<Ultraviolet irradiation conditions>
Fusion Co. electrodeless lamp H bulb used, illuminance 600 mW / cm ^2, light quantity 150 mJ / cm ²
・ Use UV-illumination meter "UVPF-36" manufactured by iGraphics.

A plurality of the pressure-sensitive adhesive layers were laminated so that the total thickness of the pressure-sensitive adhesive layers in the pressure-sensitive adhesive sheet was 500 μm, and only the outermost release sheet of the laminate remained. After that (only Comparative Example 4 requires aging, it was left for 2 weeks in an atmosphere of 23 ° C. and 50% RH), and then a sample having a width of 10 mm × 75 mm from the pressure-sensitive adhesive sheet in which a plurality of the pressure-sensitive adhesive layers were laminated. And peel off the release sheet laminated on the outermost layer of the laminate, set the sample so that the sample measurement site is 10mm wide x 20mm long (extension direction), and pull in an environment of 23 ° C and 50% RH Using a tester (Orientec, Tensilon), the film was stretched at a tensile speed of 200 mm / min, and the breaking elongation (%) and breaking stress (N / mm ² ) were measured. The results are shown in Table 2.

[Test Example 4] (Heat resistance evaluation)
The pressure-sensitive adhesive layer-attached polarizing plate obtained in Examples or Comparative Examples was adjusted to a size of 233 mm × 309 mm using a cutting device (Super cutter manufactured by Hadano Seisakusho, PN1-600). After peeling off the release sheet and pasting it onto a polymethylmethacrylate (PMMA) plate (Mitsubishi Rayon Co., Ltd., Acrylite L001 transparent, thickness 2.0 mm) through the exposed adhesive layer, it was 0 with an autoclave manufactured by Kurihara Seisakusho. Pressurized at 5 MPa and 50 ° C. for 20 minutes.

Then, it put in the 80 degreeC dry environment, and the presence or absence of the float and peeling was confirmed using the 10 time loupe 100 hours afterward. The evaluation criteria are as follows. The results are shown in Table 2.
◯: No floating, peeling, foaming or the like was confirmed.
X: Floating, peeling, foaming, etc. were confirmed.

[Test Example 5] (Concavity and convexity followability test)
The adhesive composition prepared in Example or Comparative Example was applied to one side of a 100 μm thick polyethylene terephthalate (PET) film so that the coating thickness after drying was 50 μm, and heat-treated at 90 ° C. for 1 minute (drying Treatment) to obtain a coating film of the pressure-sensitive adhesive composition, followed by irradiation with ultraviolet rays under the following conditions to form a pressure-sensitive adhesive layer, thereby preparing a sample.
<Ultraviolet irradiation conditions>
Fusion Co. electrodeless lamp H bulb used, illuminance 600 mW / cm ^2, light quantity 150 mJ / cm ²
・ Use UV-illumination meter "UVPF-36" manufactured by iGraphics.

As shown in FIGS. 3 and 4, on a PMMA plate (Mitsubishi Rayon Co., Ltd., Acrylite L001 transparent) having a size of 125 mm × 125 mm and a thickness of 1.1 mm, PET of size 25 mm × 25 mm, thickness 25 μm or 50 μm The film was placed, and the sample was attached to a PMMA plate so that the pressure-sensitive adhesive surface of the sample sealed a PET film having a thickness of 25 μm or 50 μm. Subsequently, it pressurized for 20 minutes at 0.5 MPa and 50 degreeC with the autoclave by Kurihara Seisakusho. The length L of the pressure-sensitive adhesive layer floating generated near the edge of the sealed PET film (from the edge of the PET film having a thickness of 25 μm or 50 μm, the pressure-sensitive adhesive layer and the alkali-free glass plate) The distance to the adhesion part was arbitrarily measured at five points, and the average of them was measured. The evaluation criteria are as follows. The results are shown in Table 2.
◎: Floating length L is less than 0.1 mm ○: Floating length L is 0.1 mm or more and less than 0.5 mm Δ: Floating length L is 0.5 mm or more and less than 1.0 mm ×: Floating length L is 1.0mm or more

  As is clear from Table 2, the pressure-sensitive adhesives of the pressure-sensitive adhesive layers obtained in the examples satisfy the requirements of the present invention in terms of the gel fraction fluctuation rate, the breaking elongation rate, and the breaking stress. Was also excellent.

  The pressure-sensitive adhesive of the present invention is suitable for adhesion of optical members such as polarizing plates and retardation plates, and the pressure-sensitive adhesive sheet of the present invention is suitable as a pressure-sensitive adhesive sheet for optical members such as polarizing plates and retardation plates. is there.

1A, 1B ... Adhesive sheet 11 ... Adhesive layer 12, 12a, 12b ... Release sheet 13 ... Base material

Claims (13)

When the gel fraction immediately after formation of the pressure-sensitive adhesive layer is G1, and the gel fraction after storage for 7 days in an environment of 23 ° C. and 50% RH from the formation of the pressure-sensitive adhesive layer is G2, the following formula Gel fraction Rate of change (%) = | (G2−G1) / G2 | × 100
The gel fraction fluctuation rate calculated from is within 3%,
A pressure-sensitive adhesive having a breaking elongation rate of 100 to 250% by a tensile test and a breaking stress of 0.2 to 0.6 N / mm ² . (Meth) acrylic acid ester polymer (A) having a weight average molecular weight of 600,000 to 2,000,000,
The adhesive composition containing a reactive (meth) acrylic acid ester polymer (B) having a weight average molecular weight of 30,000 to 100,000 and having a polymerizable double bond in the side chain is irradiated with active energy rays. The pressure-sensitive adhesive according to claim 1, wherein the pressure-sensitive adhesive is cured by the method.   The polymerizable double bond in the side chain of the reactive (meth) acrylic acid ester polymer (B) is contained in a (meth) acryloyl group introduced into the side chain via isocyanate. The pressure-sensitive adhesive according to claim 2.   The ratio of the reactive (meth) acrylic acid ester polymer (B) to 100 parts by mass of the (meth) acrylic acid ester polymer (A) is 5 to 30 parts by mass. 3. The pressure-sensitive adhesive according to 3.   The pressure-sensitive adhesive composition according to any one of claims 2 to 4, wherein the pressure-sensitive adhesive composition further contains a photopolymerization initiator (C).   The pressure-sensitive adhesive according to claim 5, wherein a ratio of the photopolymerization initiator (C) to 100 parts by mass of the reactive (meth) acrylic acid ester polymer (B) is 5 to 30 parts by mass. . Adhesive according to any one of claims 2-6, wherein the dose of the active energy ray is an 50~1000mJ / cm ^2.   The pressure-sensitive adhesive according to claim 1, wherein the pressure-sensitive adhesive is an active energy ray-curable pressure-sensitive adhesive.   The pressure-sensitive adhesive according to any one of claims 1 to 8, wherein a gel fraction immediately after formation of the pressure-sensitive adhesive layer and after storage for 7 days is 30 to 60%.   The pressure-sensitive adhesive according to any one of claims 1 to 9, wherein a haze value is 1.0% or less. A pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer,
The said adhesive layer consists of an adhesive as described in any one of Claims 1-10, The adhesive sheet characterized by the above-mentioned.   The pressure-sensitive adhesive sheet according to claim 11, wherein the base material is an optical member. Two release sheets,
An adhesive sheet comprising an adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets,
The said adhesive layer consists of an adhesive as described in any one of Claims 1-10, The adhesive sheet characterized by the above-mentioned.

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