JP2006282687A - Pressure-sensitive adhesive composition for polarizing film - Google Patents

Abstract

【Task】
Providing a pressure-sensitive adhesive composition for polarizing films that does not cause peeling or white spots even in a “heat shock” test, and has both reworkability, recyclability, and “durability”.
[Solution]
_A high molecular weight acrylic copolymer containing a repeating unit (a ₁ ) containing a carboxyl group in the molecule, having a weight average molecular weight (Mw _A ) of 800,000 or more and a glass transition temperature (Tg _A ) of −40 ° C. or less. A); low molecular weight acrylic copolymer (B) having a weight average molecular weight (Mw _B ) of less than 800,000 and a glass transition temperature (Tg _B ) of −40 ° C. or higher; and a crosslinked structure by reacting with a carboxyl group In the pressure-sensitive adhesive composition for a polarizing film, which contains, as an essential component, a polyfunctional compound (C) containing two or more functional groups capable of forming a carboxyl group contained in the repeating unit (a ₁ ) Is present at the end of the pendant side chain of the repeating unit (a ₁ ), and the number of carbon atoms contained in the pendant side chain is 4 or more.
[Selection] Figure 1

Description

  The present invention relates to a pressure-sensitive adhesive composition for a polarizing film for sticking a polarizing film used for a liquid crystal display panel or the like to a support substrate constituting a liquid crystal cell.

More specifically, it contains a repeating unit (a ₁ ) containing a carboxyl group in the molecule, has a weight average molecular weight (Mw _A ) of 800,000 or more, and a glass transition temperature (Tg _A ) of −40 ° C. or less. Copolymer (A); low molecular weight acrylic copolymer (B) having a weight average molecular weight (Mw _B ) of less than 800,000 and a glass transition temperature (Tg _B ) of −40 ° C. or higher; and reacting with a carboxyl group In the pressure-sensitive adhesive composition for a polarizing film, which contains, as an essential component, a polyfunctional compound (C) containing two or more functional groups capable of forming a crosslinked structure, the repeating unit (a ₁ ) A pressure-sensitive adhesive, wherein the contained carboxyl group is present at the end of the pendant side chain of the repeating unit (a ₁ ), and the number of carbon atoms contained in the pendant side chain is 4 or more. composition It relates.

  A liquid crystal display panel used in a wide range of fields as a display device is generally a liquid crystal cell in which a liquid crystal component oriented in a predetermined direction is sandwiched between two support substrates such as glass, and a support for the liquid crystal cell. It is comprised from the polarizing film stuck to the surface of the board | substrate using the pressure sensitive adhesive.

  In recent years, liquid crystal display panels have been used as display devices for personal computers, liquid crystal televisions, car navigation systems, and the like, and thus high pressure transparency is required for pressure-sensitive adhesives used. In addition, such a liquid crystal display panel is often used under severe conditions such as high temperature and high humidity, and in that case, peeling and bubbles are generated at the interface between the pressure sensitive adhesive layer and the support substrate, and pressure sensitive. There is a problem of the so-called white spot phenomenon, in which light leaks from the peripheral portion of the liquid crystal display panel which occurs because the adhesive layer cannot follow the contraction of the polarizing film and becomes white. The occurrence of such peeling, bubbles, and white spots is caused by insufficient adhesive force, insufficient cohesive force, insufficient flexibility, and the like of the pressure-sensitive adhesive for attaching the polarizing film to the support substrate.

  Furthermore, in this technical field, when a polarizing film having such a pressure-sensitive adhesive layer is stuck to a liquid crystal cell, if foreign matter is mixed, damaged, or an adhesion error occurs, the polarizing film is peeled off and re-applied. At that time, problems such as ease of operation and partial remaining of pressure-sensitive adhesive on the adherend surface such as glass cell after peeling of the polarizing film, generation of spider (reworkability) ) Exists. In addition, since liquid crystal cells are expensive recently, the polarizing film from the used liquid crystal display panel is often peeled off and the liquid crystal cell is often used again. At that time, it is easy to peel off, Properties (recyclability) such as no damage to the glass cell and no contamination of the glass cell surface have been demanded as a new problem to be solved.

  Various proposals have been made in order to prevent the occurrence of the above-described peeling, bubbles, white spots, etc. For example, Patent Document 1 described later discloses 15% by weight of a copolymer component having a weight average molecular weight of 100,000 or less. A polarizing film using a pressure-sensitive adhesive composed of a (meth) acrylic copolymer containing 10% by weight or more of a copolymer component having a weight average molecular weight of 1,000,000 or more is described below. However, in the pressure-sensitive adhesive type polarizing plate described in Patent Document 1, the occurrence of peeling or bubbles can be suppressed to some extent, but the occurrence of white spot phenomenon cannot be sufficiently prevented.

  Patent Document 2 discloses a combination of a high molecular weight acrylic copolymer and a low molecular weight acrylic copolymer as in the present invention. The invention described in Patent Document 2 is at least a low molecular weight copolymer. It differs from the present invention in that the weight average molecular weight of the acrylic copolymer is 30,000 or less, and the combination of monomers constituting the low molecular weight acrylic copolymer is also the technical idea of the present invention. In the examples which are specific embodiments of the invention described in Patent Document 2, the combination of monomers used for forming the low molecular weight acrylic copolymer is as follows. This is completely different from that of the present invention. And the polarizing film using the pressure-sensitive adhesive composition described in Patent Document 2 is not sufficient, although it is prevented to some extent from occurrence of bubbles and white spots, and has insufficient reworkability. In addition, there is a problem that the adherend is contaminated by bleed of the low molecular weight copolymer component, which is completely insufficient in terms of recyclability.

  The present inventors have earnestly provided a pressure-sensitive adhesive composition for a polarizing film that can sufficiently prevent the occurrence of the above-mentioned peeling, bubbles and white spots, and is excellent in reworkability and recyclability. I have been doing development research.

  As a result, a high molecular weight acrylic copolymer having a weight average molecular weight of 100 to 2,500,000 containing a reactive functional group and a low molecular weight acrylic copolymer having a glass transition point of 0 to -80 ° C and a weight average molecular weight of 3 to 100,000. By using in combination with a polymer, a pressure-sensitive adhesive composition that is soft and strong and has excellent viscoelasticity is obtained, and this pressure-sensitive adhesive composition has a suitable performance balance as a pressure-sensitive adhesive for polarizing films. As a result, it was found that it was a good one and a patent application was filed as a pressure-sensitive adhesive composition for polarizing film and a polarizing film (Patent Document 3).

  However, even the above-mentioned pressure-sensitive adhesive composition for polarizing film may cause peeling when used for, for example, a large-screen LCD having a size of 16 inches or more. Also, a polarizing film integrated with a viewing angle widening film having a discotic liquid crystal layer. It has been found that when a film is used, bubbles and peeling may occur, which is not always satisfactory.

The present inventors have, in order to solve the above problems of the polarizing film pressure-sensitive adhesive composition described in Patent Document 3, a weight average molecular weight of from 90 to 2,500,000, a glass transition temperature (Tg A) _-45 ℃ _A high molecular weight acrylic copolymer (A) containing a reactive functional group having a solubility parameter (SP _A ) in the range of 8.7 to 9.3; glass having a weight average molecular weight of 5 to 200,000, and glass An acrylic copolymer having a transition temperature (Tg _B ) of −40 to 0 ° C. and a solubility parameter (SP _B ) of 8.7 to 9.3, wherein the low molecular weight acrylic copolymer is The copolymer of the acrylic acid ester having a glass transition temperature (Tg) of the homopolymer of −50 ° C. or less, the monomer having a relatively low copolymerizability with the acrylic acid ester, and the acrylic acid ester At least with relatively large monomers Low molecular weight acrylic copolymer (B), which is a copolymer of three types of monomers; and two functional groups capable of forming a crosslinked structure by reacting with the reactive functional group of component (A). A pressure-sensitive adhesive composition containing the polyfunctional compound (C) as an essential component is peeled off from a support substrate such as a liquid crystal cell, bubbles are generated in the pressure-sensitive adhesive layer, and a liquid crystal display device The inventors have found that it is possible to prevent a white spot phenomenon during use in the present invention and that the reworkability and recyclability are excellent, and filed a patent application (Patent Document 4).

  However, recent technological progress and market expansion in the field of liquid crystal display devices are extremely dizzying, and large screen LCDs are increasingly used for liquid crystal display devices. When transporting these large-screen display devices in connection with export, they are often placed under extremely severe temperature conditions from low to high temperatures in shipping containers and aircraft cargo compartments. For this reason, recent pressure-sensitive adhesives for polarizing films have good results that do not cause peeling or white spots even in so-called “heat shock” tests (for example, repeated tests at −20 ° C. and + 60 ° C.). Unfortunately, the pressure-sensitive adhesive composition described in Patent Document 4 is unfortunately not always sufficient for such severe conditions.

  On the other hand, Patent Document 5 is used in the present invention as one capable of crosslinking and functioning efficiently as a crosslinking reaction point even at a low functional group concentration from the viewpoint of compatibility between heat resistance and optical function maintenance. The use of an acrylic copolymer copolymerized with carboxypentyl acrylate, which is a monomer having a carboxyl group at the end of a pendant side chain having 4 or more carbon atoms, as an adhesive for optical films is disclosed. This Patent Document 5 also states that “monomers having a functional group at the end of a relatively long methylene chain have a high degree of cross-linkability because of the high degree of movement of the functional group in the copolymer, and 0 “A sufficient crosslinking effect is exhibited with a small amount of copolymerization of about 5% by weight”.

However, Patent Document 5 does not have any description or suggestion about the low molecular weight acrylic copolymer which is an essential component in the present invention. In addition, the present inventors prepared a pressure-sensitive adhesive in which the crosslinking agent used in Example 2 was blended with the acrylic copolymer of Example 3 in Patent Document 5, and subjected to the same test as in the present invention. However, it has been found that harsh test conditions such as a heat shock test are quite insufficient in terms of various physical properties such as whiteness and durability.
JP-A-1-66283 (Claims) Japanese Patent Laid-Open No. 10-279907 (claims, detailed description of the invention) JP 2002-121521 A (claims, detailed description of the invention) Japanese Unexamined Patent Application Publication No. 2004-2784 (Claims, Full Description of the Invention) Japanese Patent Laid-Open No. 10-44291 (Claims, [0033], [0036], [0058] to [0072] [Example])

  The inventors of the present invention have further studied to develop an excellent pressure-sensitive adhesive composition for polarizing film that can withstand the “heat shock” test. In order to withstand the “heat shock” test and avoid peeling or white spots, the pressure-sensitive adhesive layer is “soft” —that is, the pressure-sensitive adhesive to the support substrate with a low degree of crosslinking. Increase the followability of the layer-necessary, but reducing the degree of crosslinking within the scope of the prior art reduces the reworkability and recyclability that occurs with the lack of cohesive strength of the pressure sensitive adhesive layer, After the pressure-sensitive adhesive layer is adhered to the support substrate, the so-called “durability” that is exposed to severe conditions such as high temperature and high humidity tends to be insufficient. On the other hand, if the pressure-sensitive adhesive layer is “hard” in order to improve durability and the like, the followability of the pressure-sensitive adhesive layer with respect to the support substrate is deteriorated, which tends to cause peeling or white spots. Thus, the pressure-sensitive adhesive for polarizing film is required to satisfy the conflicting properties at the same time.

As a result of development studies by the present inventors, the main component is a monomer that forms a very flexible polymer such as butyl acrylate (BA), particularly as a high molecular weight acrylic copolymer (A). _A weight average molecular weight (Mw _A ) of about 1.15 million obtained by copolymerizing about 5% by weight of a monomer having a carboxyl group at the end of a long pendant side chain (total carbon number of the pendant side chain is 10 or more, etc.) 100 parts by weight of an acrylic copolymer having a glass transition temperature (Tg) of about −55 ° C. is used as the low molecular weight acrylic copolymer (B). Polymer, ie, 44% by weight of n-butyl methacrylate (nBMA), which is a monomer having a relatively low copolymerization with BA, and a monomer having a relatively high copolymerization with BA, relative to 36% by weight of BA Of methyl acrylate (MA) 20% by weight is a weight average molecular weight (Mw _B) about 90,000, glass transition temperature (Tg _B) is an acrylic copolymer which is -15 ° C. were blended 30 parts by weight, more The inventors have found that the above problems can be remarkably improved by adding an appropriate amount of a hexamethylene diisocyanate polyisocyanate compound as a polyfunctional compound, and further research has been continued to complete the present invention.

Therefore, according to the present invention, the following (A) to (C):
(A) High molecular weight acrylic containing a repeating unit (a ₁ ) containing a carboxyl group in the molecule, having a weight average molecular weight (Mw _A ) of 800,000 or more and a glass transition temperature (Tg _A ) of −40 ° C. or less. Copolymer,
(B) A low molecular weight acrylic copolymer having a weight average molecular weight (Mw _B ) of less than 800,000 and a glass transition temperature (Tg _B ) of −40 ° C. or more, and (C) a crosslinked structure reacting with a carboxyl group A polyfunctional compound containing two or more functional groups capable of forming
In the comprising as essential components polarizing film for pressure-sensitive adhesive composition, a carboxyl group contained in the repeating units (a ₁₎ is present at the end of pendant side chains of the repeating units (a _1), and There is provided a pressure-sensitive adhesive composition, wherein the number of carbon atoms contained in the pendant side chain is 4 or more.

  The liquid crystal display device to which the polarizing film is attached using the pressure-sensitive adhesive composition for polarizing film of the present invention is a large-screen LCD, and can be polarized even if it is placed under severe transportation conditions due to export or the like. The film is not peeled off from the liquid crystal display device and bubbles are not generated in the pressure-sensitive adhesive layer, and the white spot phenomenon does not occur in the liquid crystal display device. The pressure-sensitive adhesive composition for polarizing film of the present invention is also excellent in reworkability when a polarizing film is stuck and recyclability when regenerating a liquid crystal cell from a used liquid crystal display panel.

The high molecular weight acrylic copolymer which is the component (A) of the present invention has a repeating unit derived from an acrylic ester and a methacrylic ester as a main component, for example, based on the high molecular weight acrylic copolymer (A). The total content is 50% by weight or more and contains a repeating unit (a ₁ ) containing a carboxyl group in the molecule. The carboxyl group contained in the repeating units (a _1), it was present at the end of pendant side chains of the repeating units (a _1), and the number of carbon atoms contained in the pendant side chain is 4 or more It is characterized by.

The pendant side chain of the repeating unit (a ₁ ) is preferably represented by the following general formula (1) or (2).

In the above general formula (1) or (2), X ¹ is an alkylene group having 2 to 6 carbon atoms, specifically ethylene group, 1,3-propylene group, 1,2-propylene group, 1,4-butylene. Group, 1,3-butylene group, 1,2-butylene group, 1,5-pentylene group, 1,4-pentylene group, 1,3-pentylene group, 2,5-pentylene group, 3,5-pentylene group 2-methyl-1,4-butylene group, 3-methyl-1,4-butylene group, 2-ethyl-1,3-propylene group, 1,6-hexylene group, 1,5-hexylene group, 2,6-hexylene group, 2-ethyl-1,4-butylene group and the like can be mentioned, and preferably a linear alkylene group having 5 carbon atoms, that is, 1,5-pentylene group. . X ² is an alkylene group having 2 to 4 carbon atoms, specifically ethylene group, 1,3-propylene group, 1,2-propylene group, 1,4-butylene group, 1,3-butylene group, 1,2 -Butylene group etc. can be mentioned, Preferably it is a C2-C2 alkylene group, ie, ethylene group. Y ¹ represents an ethylene group, a 1,2-phenylene group or a 1,2-cyclohexylene group. Further, n is a rational number of 1 to 10, and this is because the monomer that provides the repeating unit (a ₁ ) is usually supplied as a mixture, and thus the repeating (X ¹ —COO) in the monomer It is shown as the average number of repetitions. Preferably, n is a rational number of 1 to 2.

More preferably, the pendant side chain of the repeating unit (a ₁ ) is represented by the general formula (1).

Specifically, the high molecular weight acrylic copolymer (A) particularly preferably used in the present invention includes the following repeating units (a ₁ ) to (a ₃ ),

(A ₁ ) The following general formula (3) or (4),

0.1 to 10% by weight of a repeating unit containing a carboxyl group represented by

_{(A 2)} represented by the following general formula (5),

The repeating unit derived from an acrylate ester having a glass transition temperature (Tg) of not more than −50 ° C.

(A ₃ ) A copolymer can be constituted with the above repeating units (a ₁ ) and (a ₂ ), and 0 to 30% by weight of repeating units other than the repeating units (a ₁ ) and (a ₂ ),
It is preferable that it is comprised by these.

In the above general formulas (3) to (5), R ¹ is a hydrogen atom or a methyl group, R ² represents a linear or branched alkyl group having 4 to 10 carbon atoms, and specifically, for example, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, i-octyl group, 2-ethyl-hexyl group, n-nonyl group, i-nonyl group, n-decyl Groups, preferably n-butyl group, n-octyl group, i-octyl group, 2-ethyl-hexyl group, n-nonyl group, i-nonyl group, more preferably n-butyl. It is a group. X ¹ , X ² , Y ¹ and n are as defined in the general formulas (1) and (2). Furthermore the repeating units _(a 1) ~% by weight respectively of the configuration of _{(a 3)} is a representation of the sum of the repeating units _{(a 1) ~ (a 3} ) as 100% by weight.

  In the present invention, as a suitable monomer corresponding to the repeating unit represented by the general formula (3), for example, (meth) acrylic acid dimer (preferably having an average value of n of about 1.4), Examples thereof include ω-carboxy-polycaprolactone mono (meth) acrylate (preferably having an average value of n of about 2). As these monomers, for example, those commercially available under trade names such as “M-5600” and “M-5300” [above, manufactured by Toagosei Co., Ltd.] can be used.

  Suitable monomers corresponding to the repeating unit represented by the general formula (4) include, for example, monohydroxyethyl (meth) acrylate succinate, monohydroxyethyl (ta) acrylate fumarate, monohydroxy phthalate Examples thereof include ethyl (meth) acrylate and 1,2-dicarboxycyclohexane monohydroxyethyl (meth) acrylate. These monomers include, for example, “light ester HO-MS”, “light acrylate HOA-MS”, “light acrylate HOA-MPL”, “light acrylate HOA-HH” [manufactured by Kyoeisha Chemical Co., Ltd.] What is marketed by name can be used.

In the high molecular weight acrylic copolymer (A), the repeating unit (a ₁ ) containing a carboxyl group is more preferably a repeating unit represented by the general formula (3).

Configuration amount in the general formula (3) or the repeating unit represented by (4) of _{(a 1),} a high molecular weight acrylic copolymer (A) is the sum of the repeating units _(a 1) ~ _{(a 3)} Based on 100% by weight, the range is preferably 0.1 to 10% by weight as described above, more preferably 0.5 to 8% by weight, and particularly preferably 1 to 5% by weight. If the constituent amount of the repeating unit (a ₁ ) is not less than the lower limit value, it is preferable because the generation of bubbles due to insufficient cohesive force is suppressed, and if it is not more than the upper limit value, the cohesive force is excessive. This is preferable because inconveniences such as peeling and white spotting phenomenon hardly occur.

The repeating unit (a ₂ ) represented by the general formula (5) constitutes a main component of the high molecular weight acrylic copolymer (A), and a suitable acrylic corresponding to the repeating unit (a ₂ ). Specific examples of the acid ester include n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, i-octyl acrylate, n-nonyl acrylate, i-nonyl acrylate and the like. Among these, n-butyl acrylate, 2-ethylhexyl acrylate and i-octyl acrylate are preferable, and n-butyl acrylate is particularly preferable. These acrylic acid esters may be used alone or in combination of two or more.

  The “glass transition temperature (Tg) of the polymer consisting only of this repeating unit” mentioned herein includes L.P. E. The glass transition temperatures of the monomers described in Nielsen, translated by Nojiharu Onoki, “Mechanical properties of polymers”, pages 11 to 35, are applied.

The constituent amount of the repeating unit (a ₂ ) represented by the general formula (5) in the high molecular weight acrylic copolymer (A) is based on a total of 100% by weight of the repeating units (a ₁ ) to (a ₃ ). As described above, the range is preferably 60 to 99.9% by weight, more preferably 72 to 99.5% by weight, and particularly preferably 85 to 99% by weight. If the constituent amount of the repeating unit (a ₂ ) is not less than the lower limit value, it is preferable because the generation of bubbles due to insufficient cohesive force is suppressed, and if it is not more than the upper limit value, the cohesive force is excessive. This is preferable because inconveniences such as peeling and white spotting phenomenon hardly occur.

In the present invention, specific examples of the comonomer corresponding to the repeating unit (a ₃ ) that can be used as an optional component in the high molecular weight acrylic copolymer (A) include the repeating unit (a ₁ ). Acrylic esters other than the corresponding monomers, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, i-butyl acrylate, t-butyl acrylate, tridecyl acrylate, stearyl acrylate, oleyl acrylate and the like ( Preferably methyl acrylate); methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, n-octyl methacrylate. 2-ethylhexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, etc. (preferably methyl methacrylate); saturated fatty acid vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, “vinyl versatate” (trade name), etc .; aromatic And vinyl monomers such as styrene, α-methylstyrene, vinyl toluene and the like; and vinyl cyanide monomers such as acrylonitrile and methacrylonitrile.

Examples of the comonomer corresponding to the repeating unit (a ₃ ) include dimethyl malate, di-n-butyl maleate, di-2-ethylhexyl malate, di-n-octyl malate, dimethyl fumarate, and di -Diesters of maleic acid or fumaric acid such as -n-butyl fumarate, di-2-ethylhexyl fumarate and di-N-octyl fumarate can also be used.

Further, the comonomer corresponding to the repeating unit (a ₃ ) is a monomer having at least one functional group in addition to one radical polymerizable unsaturated group in the molecule, if necessary. And a monomer other than the monomer corresponding to the repeating unit (a ₁ ) {the monomer corresponding to the general formulas (3) and (4)} (hereinafter referred to as a functional comonomer). Can also be copolymerized.

  As such a functional comonomer, as a functional group, for example, a carboxyl group other than the general formulas (1) and (2), an amide group or a substituted amide group, an amino group or a substituted amino group, a hydroxyl group, Mention may be made of monomers having a lower alkoxyl group, an epoxy group, a mercapto group or a silicon-containing group, and monomers having two or more radically polymerizable unsaturated groups in the molecule can also be used.

  Specific examples of these functional comonomers include, for example, monomers containing carboxyl groups such as acrylic acid, methacrylic acid, itaconic acid, maleic anhydride or anhydride groups thereof; acrylamide, methacrylamide, diacetone acrylamide, Amide group or substituted amide group-containing monomer such as N-methylolacrylamide, N-methylolmethacrylamide, Nn-butoxymethylacrylamide, Ni-butoxymethylacrylamide, N, N-dimethylacrylamide, N-methylacrylamide An amino group such as aminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl methacrylate; Substituted amino group-containing monomer;

For example, hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, allyl alcohol, methallyl alcohol, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate For example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-n-butoxyethyl acrylate, 2-methoxyethoxyethyl acrylate, 2-ethoxyethoxyethyl acrylate, 2-n-butoxyethoxyethyl acrylate, 2-methoxyethyl Methacrylate, 2-ethoxyethyl methacrylate, 2-n-butoxyethyl methacrylate, 2-methoxyethoxyethyl methacrylate Acrylate, 2-ethoxyethoxy ethyl methacrylate, 2-n-butoxyethoxy ethyl methacrylate, methoxy polyethylene glycol monoacrylate, lower alkoxyl group-containing monomers such as methoxy polyethylene glycol monomethacrylate;

For example, epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate, glycidyl allyl ether, glycidyl methallyl ether; mercapto group-containing monomers such as allyl mercaptan;

For example, vinyltrichlorosilane, vinyltribromosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri-n-propoxysilane, vinyltri-i-propoxysilane, vinyltri-n-butoxysilane, vinyltris (2-methoxyethoxy) silane , Vinyltris (2-hydroxymethoxyethoxy) silane, vinyltriacetoxysilane, vinyldiethoxysilanol, vinylethoxysilanol, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, vinylmethyldiacetoxysilane, allyltrimethoxysilane, allyltri Ethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-methacryloxypropyltris (2-meth Monomers having silicon-containing groups such as (ciethoxy) silane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyldimethylethoxysilane, 3-acryloxypropyldimethylmethoxysilane, 2-acrylamidoethyltriethoxysilane; And the like.

The constitutional amount of the repeating unit (a ₃ ) derived from these comonomers in the high molecular weight acrylic copolymer (A) is based on a total of 100% by weight of the repeating units (a ₁ ) to (a ₃ ). As described above, the content is preferably in the range of 0 to 30% by weight, more preferably 0 to 20% by weight, and particularly preferably 0 to 10% by weight. If the constituent amount of the repeating unit (a ₂ ) is not less than the lower limit value, it is preferable because the generation of bubbles due to insufficient cohesive force is suppressed, and if it is not more than the upper limit value, the cohesive force is excessive. This is preferable because inconveniences such as peeling and white spotting phenomenon hardly occur.

The high molecular weight acrylic copolymer (A) used in the present invention is required to have a weight average molecular weight (Mw _A ) of 800,000 or more, preferably 900 to 2,500,000, more preferably 100 to 200. It is good that it is in a range of 105, particularly preferably 105 to 1.5 million. If the weight average molecular weight (Mw _A ) is too low as less than the lower limit value, bubbles may be generated due to insufficient cohesion, etc., which is not preferable. On the other hand, if it is below this upper limit, a copolymer solution having a desired solid content concentration is preferable because it can be produced relatively easily without becoming too high in viscosity.

The ratio Mw _A / Mn _A of the weight average molecular weight (Mw _A ) and the number average molecular weight (Mn _A ) of the high molecular weight acrylic copolymer (A) suitably used in the present invention is generally 20 or less, preferably It should be 15 or less, particularly preferably in the range of 3-10. If the value of Mw _A / Mn _A is less than or equal to the upper limit value, it is preferable because inconveniences such as generation of bubbles and a decrease in reworkability due to insufficient cohesive force are unlikely to occur.

  In addition, the weight average molecular weight (Mw) and number average molecular weight (Mn) of an acrylic copolymer are the values measured by the following method.

Method for measuring average molecular weight (Mw and Mn):
It measures according to following (1)-(3).
(1) An acrylic copolymer solution is applied to release paper and dried at 100 ° C. for 2 minutes to obtain a film-like acrylic copolymer.
(2) The film-like acrylic copolymer obtained in the above (1) is dissolved in tetrahydrofuran so that the solid content is 0.2% by weight.
(3) The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the acrylic copolymer are measured using gel permeation chromatography (GPC) under the following conditions.

(conditions)
GPC: HLC-8220 GPC [manufactured by Tosoh Corporation]
Column: 4 TSK-GEL GMHXL used Mobile phase solvent: Tetrahydrofuran Flow rate: 0.6 mL / min Column temperature: 40 ° C

The high molecular weight acrylic copolymer (A) used in the present invention is also required to have a glass transition temperature (Tg _A ) of −40 ° C. or lower, more preferably −45 ° C. or lower, still more preferably. It should be −50 ° C. or lower. If Tg _A exceeds this temperature and is too high, the adhesive strength to the support substrate becomes too high, so that the reworkability is lowered, which is not preferable.

  In addition, the glass transition temperature (Tg) of the acrylic copolymer in this specification means the molar average glass transition temperature calculated | required by the following calculations.

ここでＴｇ_１、Ｔｇ_２・・・・・・及びＴｇ_ｎは、成分１、成分２・・・・・・及び成分ｎそれぞれの単独重合体のガラス転移温度であり、絶対温度（゜Ｋ）に換算し計算する。ｍ_１、ｍ_２・・・・・・及びｍ_ｎはそれぞれの成分のモル分率である。 Calculation of glass transition temperature (Tg):

Here _{Tg 1,} Tg 2 ...... and Tg _n is the glass transition temperature of the component 1, component 2 ...... and component n respectively homopolymers, absolute temperature (° K) Convert to and calculate. m ₁ , m ₂ ... and _mn are the mole fractions of the respective components.

Further, the high molecular weight acrylic copolymer (A) used in the present invention has a solubility parameter (SP _A ) in the range of 8.7 to 9.3, more preferably 8.9 to 9.2. preferable. If SP _A is not more than the above upper limit value, the compatibility with the low molecular weight acrylic copolymer (B) described later is excellent, and problems such as peeling and white spotting due to excessive cohesion occur. It is preferable because it is difficult. On the other hand, if it is at least the lower limit value, the compatibility with the low molecular weight acrylic copolymer (B) is excellent, and problems such as the generation of bubbles due to insufficient cohesive force are less likely to occur.

  Here, the solubility parameter (SP value) is an index representing the tendency of solubility of a substance. The SP value is measured or calculated by various methods. Brandrup, E .; H. Immergut, and E.M. A. It is described in detail in Grulke, “Polymer Handbook, Fourth Edition” (1999).

The SP value of the polymer was calculated by the following SP value calculation formula based on the molecular attractive constant G of each monomer.
SP = dΣG / M
Here, d represents density (g / L), ΣG represents the sum of molecular attraction constants in the molecule, and M represents molecular weight (g / mol).
Regarding the SP value of the copolymer, the solubility parameter was obtained by adding each SP value of the constituent monomers to each of the constituent mole fractions.

  The pressure-sensitive adhesive composition for polarizing film of the present invention contains a low molecular weight acrylic copolymer (B) as an essential copolymer component together with the high molecular weight acrylic copolymer (A) described above. It will be.

The low molecular weight acrylic copolymer (B) has a lower molecular weight than the high molecular weight acrylic copolymer (A) (weight average molecular weight less than 800,000), and a glass transition temperature (Tg _B ) of −40 ° C. or higher. Although it will not specifically limit if it is an acrylic type copolymer of this, like this high molecular weight acrylic type copolymer (A), the repeating unit derived from an acrylic ester and a methacrylic ester is a main component amount, for example, It is preferable that the total content is 50% by weight or more based on the high molecular weight acrylic copolymer (A).

More preferably, the low molecular weight acrylic copolymer (B) used in the present invention contains the following monomers (b ₁ ) to (b ₃ ),
(B ₁ ) The following general formula (6),
H ₂ C = CHCOOR ²
(6)
[Wherein R ² represents a linear or branched alkyl group having 4 to 10 carbon atoms]
A monomer having a relatively small copolymerizability with the acrylic ester (b ₂ ) and the monomer (b ₁ ), wherein the homopolymer has a glass transition temperature (Tg) of −50 ° C. or lower. A monomer having a copolymerization ratio [1 / γ _{(b2 / b1)} ] of less than 0.5 with the monomer (b ₁ ), and (b ₃ ) the monomer (b ₁ ) A copolymer having a relatively high copolymerizability, preferably a monomer having a copolymerizability ratio [1 / γ _{(b3 / b1)} ] of 0.5 or more, and having a glass transition temperature (Tg) _B ) is in the range of -40 to 0 ° C.

In the previous development research, the present inventors have made the glass transition temperature (Tg _B ) of the component (B) slightly higher than before, for example, −30 to − It is better to use a material such as 5 ° C; in order to obtain a copolymer having such a glass transition temperature (Tg _B ) range, for example, butyl acrylate (BA) or the like and methyl methacrylate (MMA) or the like are used together. Upon polymerization, due to the poor copolymerization between BA and MMA, a hard copolymer with a large amount of MMA is produced first, and the remaining BA-based, extremely soft, lower molecular weight copolymer. I knew that coalescence was likely to occur. In such a pressure-sensitive adhesive composition for polarizing film, which is combined with such a low molecular weight acrylic copolymer, this extremely soft and low molecular weight copolymer tends to bleed and contaminate the adherend.

  Therefore, the present inventors have used MMA, butyl methacrylate (as monomers for imparting hardness to monomers that form extremely flexible polymers such as BA, etc., in the formation of low molecular weight acrylic copolymers. BMA), ethyl methacrylate (EMA), and other monomers that have low copolymerizability with BA and the like, and the remaining BA is polymerized in a form close to a single, resulting in a very soft, lower molecular weight copolymer. It was found that the above problems can be greatly improved by using a monomer having good copolymerizability with BA or the like, for example, methyl acrylate (MA).

The glass transition temperature (Tg _B ) of the low molecular weight acrylic copolymer which is the component (B) of the present invention needs to be −40 ° C. or higher, −40 to 0 ° C., and further −30 to −5. It is preferable that it is the range of -25 degreeC, especially -25--10 degreeC. If Tg _B is too low, less than the lower limit temperature, bubbles associated with insufficient cohesive force are likely to be generated, and the recyclability tends to be reduced, which is not preferable. On the other hand, if it is below this upper limit temperature, since it is hard to produce malfunctions, such as generation | occurrence | production of peeling accompanying the fall of the wettability of the pressure sensitive adhesive with respect to glass, it is preferable.

The monomer (b ₁ ) which is an essential monomer constituting the low molecular weight acrylic copolymer (B) is represented by the general formula (6), specifically, the high molecular weight Although what is used as a monomer corresponding to the repeating unit (a ₂ ) in the acrylic copolymer (A) can be used, it is dissolved in the high molecular weight acrylic copolymer (A) as described later. The use of butyl acrylate (BA) is particularly preferred from the standpoint of easily reducing the difference in property parameters (ΔSP = SP _B −SP _A ).

The amount of the monomer _{(b 1),} the said monomer _{(b 1)} which type of own and, on the type of the later-described monomer _{(b 2)} and _{(b 3),} the glass transition temperature range In general, based on 100% by weight of the total of the monomers (b ₁ ) to (b ₃ ) constituting the low molecular weight acrylic copolymer (B). In general, it should be in the range of 10 to 90% by weight, preferably 20 to 85% by weight, more preferably 25 to 75% by weight, particularly preferably 30 to 65% by weight.

The monomer (b ₂ ) is a monomer having a relatively low copolymerizability with the monomer (b ₁ ), and preferably has a copolymerizability ratio [1 / γ _{(b2 / b1)} ] of 0. It is a monomer of less than 5. The copolymerization ratio here is the reciprocal (1 / γ) of the reactivity ratio γ in the Lewis-Mayo formula of the monomer copolymerization theory.

In general, the reactivity ratio of the monomer A to the monomer B is determined by the growth reaction rate constant k _{pAA in} which the monomers A are chain-bonded, and the growth reaction rate in which the monomer A and the monomer B are chain-bonded. It is expressed as a value (k _pAA / k _pAB ) divided by a constant k _pAB . Therefore, the monomer _{(b 1)} and the copolymerization ratios of [1 _/ γ _(b2 / _b1)] is the monomer of less than 0.5 _{(b 2)} is
[1 / γ _{(b2 / b1)} ] = [kp _{(b1) (b2)} / kp _{(b2) (b2)} ] <0.5
It is a monomer that satisfies

  For details on the Lewis-Mayo formula, refer to, for example, Shinzo Omi, “Operation design of radical polymerization reaction” (published by IPC Co., Ltd.), page 73 and after.

When said monomer _{(b 1)} is BA, copolymerizable ratio of the monomer _{(b 1)} [1 _/ γ _(b2 / _b1)] is the monomer of less than 0.5 _{(b 2} ), For example, methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate; For example, hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, i-butyl. Functionality such as methacrylate, t-butyl methacrylate It is preferable to use a methacrylic acid ester having no group.

When the monomer (b ₁ ) is other than BA, the copolymerization ratio [1 / γ _{(b2 / b1)} ] of the desired monomer with the monomer (b ₁ ) is, for example, The copolymerization ratio [1 / γ _{(b2 / b1)} ] is less than 0.5 among these monomers since it can be obtained by calculation according to the method detailed in “Polymer Handbook 4th Edition” of These monomers may be appropriately selected and used as the monomer (b ₂ ).

The amount of the monomer (b ₂ ) used is appropriately selected depending on the type of the monomer (b ₂ ) and the type of the monomer (b ₁ ) and the monomer (b ₃ ) described later. In general, it is generally 5 to 85% by weight based on the total 100% by weight of the monomers (b ₁ ) to (b ₃ ) constituting the low molecular weight acrylic copolymer (B), preferably It should be 10 to 75% by weight, more preferably 15 to 65% by weight, particularly preferably 20 to 55% by weight. If the amount used is greater than or equal to the lower limit, bubbles associated with insufficient cohesive force are unlikely to occur and recyclability is unlikely to decrease. On the other hand, if the amount is less than or equal to the upper limit, the pressure sensitive adhesive for glass is preferred. It is preferable because peeling due to a decrease in wettability hardly occurs.

Another essential monomer (b ₃ ) constituting the low molecular weight acrylic copolymer (B) in the present invention is a monomer having a relatively large copolymerizability with the monomer (b ₁ ), Preferably, the monomer having a copolymerizability ratio [1 / γ _{(b3 / b1)} ] of 0.5 or more,
[1 / γ _{(b3 / b1)} ] = [kp _{(b1) (b3)} / kp _{(b3) (b3)} ] ≧ 0.5
It is a monomer that satisfies

When said monomer _{(b 1)} is BA, copolymerizable ratio of the monomer _{(b 1)} [1 _/ γ _(b3 / _b1)] is 0.5 or more monomers _{(b 3} ), For example, acrylic esters such as methyl acrylate and ethyl acrylate; saturated fatty acid vinyl esters such as vinyl formate, vinyl acetate and vinyl propionate; and amide group-containing monomers such as acrylamide. It is preferable to use acrylic acid esters having no functional group such as methyl acrylate and ethyl acrylate.

When the monomer (b ₁ ) is other than BA, the copolymerization ratio [1 / γ _{(b3 / b1)} ] of the desired monomer with the monomer (b ₁ ) is the same as described above. Among these monomers, a monomer having a copolymerizability ratio [1 / γ _{(b3 / b1)} ] of 0.5 or more is designated as the monomer (b ₃ ). What is necessary is just to select and use suitably.

The amount of the monomer (b ₃ ) used is appropriately selected depending on the type of the monomer (b ₃ ) and the type of the monomer (b ₁ ) and the monomer (b ₂ ) described later. In general, it is generally 5 to 85% by weight based on the total 100% by weight of the monomers (b ₁ ) to (b ₃ ) constituting the low molecular weight acrylic copolymer (B), preferably 5 to 70% by weight, more preferably 10 to 60% by weight, and particularly preferably 15 to 50% by weight. If the amount used is greater than or equal to the lower limit, bubbles associated with insufficient cohesive force are unlikely to occur and recyclability is unlikely to decrease. On the other hand, if the amount is less than or equal to the upper limit, the pressure sensitive adhesive for glass is preferred. It is preferable because peeling due to a decrease in wettability hardly occurs.

The low molecular weight acrylic copolymer (B) is a reactive functional group capable of forming a crosslinked structure by reacting with a functional group of the polyfunctional compound (C) described later in the molecule, if necessary, for example, contain reactive functional groups of the monomer (b ₂₎ a carboxyl group-containing monomer and a hydroxyl group-containing monomer in, such as from the monomer (b ₃₎ in the amide group-containing monomer can do.

  The low molecular weight acrylic copolymer (B) used in the present invention needs to have a weight average molecular weight (Mw) measured in accordance with the above-mentioned “Method for measuring weight average molecular weight” of less than 800,000. The range is preferably 3 to 400,000, more preferably 5 to 200,000, still more preferably 60 to 180,000, and particularly preferably 7 to 150,000. If the weight average molecular weight (Mw) exceeds the upper limit and is too high, disadvantages such as white spots are likely to occur. On the other hand, if it is more than the lower limit, it is preferable because inconveniences such as generation of bubbles due to insufficient cohesive force and a decrease in recyclability hardly occur.

Further, the low molecular weight acrylic copolymer (B) used in the present invention preferably has a solubility parameter (SP _B ) in the range of 8.7 to 9.3, preferably in the range of 8.9 to 9.2. More preferably. If SP _B is less than or equal to the upper limit, the compatibility with the high molecular weight acrylic copolymer (A) is excellent, and problems such as the occurrence of peeling due to a decrease in the wettability of the pressure sensitive adhesive to glass occur. It is preferable because it is less likely to occur, and if it is not less than the lower limit, it is excellent in compatibility with the high molecular weight acrylic copolymer (A), and problems such as bubble generation due to insufficient cohesive force are unlikely to occur.

Also the solubility parameter of the low molecular weight acrylic copolymer _(B) (SP B), the difference between the solubility parameter of the high molecular weight acrylic copolymer _{(A) (SP A) ΔSP} (= SP B -SP _A ) is preferably 0.5 or less, more preferably 0.3 or less. If the difference ΔSP in the solubility parameter is not more than the upper limit, it is preferable because the compatibility between the high molecular weight acrylic copolymer (A) and the low molecular weight acrylic copolymer (B) is extremely excellent.

  In the pressure-sensitive adhesive composition for polarizing film of the present invention, the low molecular weight acrylic copolymer (B) described above is 5 to 100 parts by weight of the high molecular weight acrylic copolymer (A). It is preferable to contain 100 parts by weight, preferably 7 to 70 parts by weight, and more preferably 15 to 50 parts by weight. If the amount of the component (B) used is not less than the lower limit value, it is preferable because the occurrence of white spot phenomenon can be sufficiently prevented. On the other hand, if it is not more than the upper limit value, the effect of preventing the generation of bubbles is excellent. In addition, it is preferable because the problem of deterioration of reworkability or the like hardly occurs.

  The high molecular weight acrylic copolymer (A) and the low molecular weight acrylic copolymer (B) used in the present invention are not particularly limited to the polymerization method, and include solution polymerization, emulsion polymerization, suspension polymerization, and the like. In the production of the pressure-sensitive adhesive composition for a polarizing film of the present invention using a mixture of copolymers obtained by polymerization, the treatment process is relatively simple and in a short time. It is preferable to polymerize by solution polymerization.

  In solution polymerization, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as needed are generally charged in a polymerization tank, and stirred in a nitrogen stream or at the reflux temperature of the organic solvent. The reaction is performed by heating for several hours. In this case, at least a part of the organic solvent, the monomer, the polymerization initiator and / or the chain transfer agent may be sequentially added.

  Examples of the organic solvent for polymerization include aromatics such as benzene, toluene, ethylbenzene, N-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha. Hydrocarbons; for example, aliphatic or alicyclic hydrocarbons such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, turpentine oil; , Ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, methyl benzoate and the like; for example, acetone, methyl ethyl ketone, methyl-i- Keto such as butyl ketone, isophorone, cyclohexanone, methylcyclohexanone Kind;

For example, glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether; for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, i -Alcohols such as propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol and t-butyl alcohol; These organic solvents can be used alone or in admixture of two or more.

  Among these organic solvents for polymerization, when polymerizing the high molecular weight acrylic copolymer (A), it is preferable to use an organic solvent that hardly causes chain transfer during the polymerization reaction, for example, esters and ketones, In particular, from the viewpoint of the solubility of the high molecular weight acrylic copolymer (A) and the ease of the polymerization reaction, use of ethyl acetate, methyl ethyl ketone, acetone or the like is preferable. Moreover, when manufacturing a low molecular weight acrylic copolymer (B), it is preferable to use the organic solvent which produces a chain transfer easily, for example, alcohols and aromatic hydrocarbons. In particular, toluene, isopropyl alcohol, and the like are preferable in view of the ease of the polymerization reaction.

  As said polymerization initiator, it is possible to use the organic peroxide, an azo compound, etc. which can be used by normal solution polymerization.

  Examples of such organic peroxides include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, di-2- Ethylhexylperoxydicarbonate, t-butylperoxybivalate, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-amylperoxycyclohexyl) ) Propane, 2,2-bis (4,4-di-t-octylperoxycyclohexyl) propane, 2,2-bis (4,4-di-α-cumylperoxycyclohexyl) propane, 2,2-bis ( 4,4-di-t-butylperoxycyclohexyl) butane, , 2-bis (4,4-di-t-octylperoxycyclohexyl) butane, and examples of the azo compound include 2,2′-azobis-i-butylnitrile and 2,2′-azobis-2. , 4-dimethylvaleronitrile, 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, and the like.

  Among these organic peroxides, in the polymerization of the high molecular weight acrylic copolymer (A), it is preferable to use a polymerization initiator that does not cause a graft reaction during the polymerization reaction, and particularly preferably an azobis type. The amount used is usually 0.01 to 2 parts by weight, preferably 0.1 to 1.0 parts by weight, based on 100 parts by weight of the total amount of monomers. In the case of producing the low molecular weight acrylic copolymer (B), although it varies depending on the reaction temperature, a polymerization initiator having a low 10-hour half-life temperature is preferred, for example, a 10-hour half-life temperature is 80 ° C. or less, A polymerization initiator at 70 ° C. or lower is more preferable. The amount used is usually 0.1 to 5 parts by weight, preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the total amount of monomers.

  Further, in the production of the high molecular weight acrylic copolymer (A) used in the present invention, it is normal not to use a chain transfer agent. However, as long as the object and effect of the present invention are not impaired, as necessary. Can be used. On the other hand, when producing a low molecular weight acrylic copolymer (B), polymerization is often carried out in the presence of a chain transfer agent.

  Examples of such chain transfer agents include cyanoacetic acid; alkyl esters having 1 to 8 carbon atoms of cyanoacetic acid; bromoacetic acid; alkyl esters having 1 to 8 carbon atoms of bromoacetic acid; anthracene, phenanthrene, fluorene, 9 -Aromatic compounds such as phenylfluorene; aromatic nitro compounds such as p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, p-nitrotoluene; benzoquinone, 2, 3, 5, Benzoquinone derivatives such as 6-tetramethyl-p-benzoquinone; borane derivatives such as tributylborane;

Halogenated hydrocarbons such as carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, 3-chloro-1-propene; Aldehydes such as chloral and furaldehyde: alkyl mercaptans having 1 to 18 carbon atoms; aromatic mercaptans such as thiophenol and toluene mercaptan; mercaptoacetic acids and alkyl esters having 1 to 10 carbon atoms of mercaptoacetic acid; 12 hydroxyalkyl mercaptans; terpenes such as binene and terpinolene;

When producing the high molecular weight acrylic copolymer (A) used in the present invention, it is preferable not to use a chain transfer agent, and when producing the low molecular weight acrylic copolymer (B). Of the above chain transfer agents, preferably 0.005 to 3 parts by weight of mercaptans and halogenated hydrocarbons are used with respect to 100 parts by weight of the total of monomers (b ₁ ) to (b ₃ ). it can.

  The polymerization temperature is generally in the range of about 30 to 180 ° C., preferably 50 to 150 ° C. When the high molecular weight acrylic copolymer (A) is produced, it is preferably 50 to 90 ° C., more preferably Is 50 to 80 ° C., and in the case of producing the low molecular weight acrylic copolymer (B), it is preferably 70 to 110 ° C., more preferably 80 to 100 ° C.

  When an unreacted monomer is contained in a polymer obtained by a solution polymerization method or the like, it can be purified by a reprecipitation method using methanol or the like in order to remove the monomer.

  The pressure-sensitive adhesive composition for polarizing film of the present invention comprises, as essential components, the high molecular weight acrylic copolymer (A) and the low molecular weight acrylic copolymer (B). A) It comprises a polyfunctional compound (C) containing two or more functional groups capable of reacting with a carboxyl group present in it to form a crosslinked structure.

  The polyfunctional compound (C) is not particularly limited as long as it reacts with the high molecular weight acrylic copolymer (A) to form a cross-linked structure. Polyisocyanate compound, polyepoxy compound , Polyaziridine compounds, melamine formaldehyde condensates, metal salts, metal chelate compounds and the like. Of these polyfunctional compounds, polyisocyanate compounds, polyaziridine compounds and / or polyepoxy compounds from the viewpoints of adhesion to the polarizing film and stability after blending with the acrylic copolymer (A) The use of polyisocyanate compounds is particularly preferred. These polyfunctional compounds (C) can be used alone or in combination of two or more.

  Examples of the polyisocyanate compound include aromatic polyisocyanates such as xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate; for example, hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenation of the aromatic polyisocyanate compound. Polyisocyanate compounds derived from various polyisocyanates such as aliphatic or alicyclic polyisocyanates such as products; dimers or trimers of these polyisocyanates, or adducts of these polyisocyanates and polyols such as trimethylolpropane Can be mentioned.

  Among these polyisocyanate compounds, hexamethylene diisocyanate or xylylene dimer or trimer, or adducts of hexamethylene diisocyanate or xylylene diisocyanate and a polyol such as trimethylolpropane, etc. Polyisocyanate compounds derived from isocyanate are preferred.

  These polyisocyanate compounds include, for example, “Coronate HX”, “Coronate HL-S”, “Coronate 2234” (manufactured by Nippon Polyurethane Co., Ltd.), “Desmodur N3400” (manufactured by Sumitomo Bayer Urethane Co., Ltd.), “Duranate E-405-80T”, “Duranate TSE-100” (manufactured by Asahi Kasei Chemicals Corporation), “Takenate D-110N”, “Takenate D-120N”, “Takenate M-631N” [above, Mitsui Those commercially available under trade names such as “Takeda Chemical Co., Ltd.” can be suitably used.

  As the polyaziridine compound, a reaction product of a polyisocyanate compound and ethyleneimine can be used, and as the polyisocyanate compound, those exemplified above can be used. Also known is a compound obtained by adding ethyleneimine to a polyvalent ester of a polyol such as trimethylolpropane or pentaerythritol and an α, β-unsaturated carboxylic acid such as (meth) acrylic acid. Can be used as the active compound (C).

  Examples of such polyaziridine compounds include N, N′-hexamethylenebis (1-aziridinecarboxamide), methylenebis [N- (1-aziridinylcarbonyl) -4-aniline], tetramethylolmethanetris ( β-aziridinylpropionate), trimethylolpropane tris (β-aziridinylpropionate) and the like. Among these, for example, “TAZO”, “TAZM” [above, Mutual Pharmaceutical Co., Ltd. Made by a trade name such as “Chemite PZ-33” (manufactured by Nippon Shokubai Co., Ltd.) can be suitably used.

  Examples of the polyepoxy compound include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl. Ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcin diglycidyl ether, 2,2 -Dibromoneopentyl glycol diglycy Ether, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris (glycidyl) isocyanurate, tris (glycidoxyethyl) isocyanurate, 1 , 3-bis (N, N-glycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine and the like.

  Of these polyepoxy compounds, polyepoxy compounds containing three or more epoxy groups are preferable, and tris (glycidyl) isocyanurate, tris (glycidoxyethyl) isocyanurate, and 1,3-bis (N, N-glycidyl) are particularly preferable. More preferred is the use of a polyepoxy compound such as aminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N-glycidylaminomethyl) cyclohexane, The use of N, N, N ′, N′-tetraglycidyl-m-xylylenediamine is particularly preferred.

  As these polyepoxy compounds, for example, those commercially available under trade names such as “TETRAD-C”, “TETRAD-X” [manufactured by Mitsubishi Gas Chemical Co., Ltd.] can be suitably used.

  The amount of these polyfunctional compounds (C) used is usually 0.001 to 10 parts by weight, preferably 0.005 to 5 parts by weight, based on 100 parts by weight of the high molecular weight acrylic copolymer (A). Range. If the amount of the polyfunctional compound (C) used is too small and less than the lower limit value, bubbles due to insufficient cohesive force are likely to occur, and the adherend surface contamination is reduced. If the amount is too much, it is not preferable because peeling or white spot phenomenon easily occurs due to excessive cohesion.

  In particular, when a polyisocyanate compound is used as the polyfunctional compound (C), the amount used is based on the total carboxyl groups contained in the high molecular weight acrylic copolymer (A) and the low molecular weight acrylic copolymer (B). The isocyanate group of the polyisocyanate compound is preferably 0.01 to 1 equivalent, more preferably 0.02 to 0.8 equivalent, and particularly preferably 0.05 to 0.6 equivalent to 1 equivalent thereof. .

  In addition, the polyfunctional compound (C) can be used in combination of two or more as described above, and the polyisocyanate compound and the polyaziridine compound or the polyisocyanate compound and the polyepoxy compound are preferably combined. In that case, the polyisocyanate compound, the polyaziridine compound, and the polyepoxy compound can be appropriately selected within the above-mentioned usage amount ranges, but preferably, the polyisocyanate compound: polyaziridine compound are all in an active ingredient weight ratio. = 1 to 500: 1, particularly 10 to 300: 1, or polyisocyanate compound: polyepoxy compound = 1 to 300: 1, particularly 10 to 100: 1.

  The pressure-sensitive adhesive composition for polarizing film of the present invention comprises a high molecular weight acrylic copolymer (A), a low molecular weight acrylic copolymer (B) and the high molecular weight acrylic copolymer (A It is preferable to contain a silane compound (D) together with a polyfunctional compound (C) containing two or more functional groups capable of forming a cross-linked structure by reacting with (A).

  Examples of such a silane compound (D) include mercapto group-containing silane compounds such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, and γ-mercaptopropyldimethoxymethylsilane; Cycloaliphatic epoxy group-containing silane compounds such as 4-epoxycyclohexyl) ethyltrimethoxysilane and β- (3,4-epoxycyclohexyl) ethyltriethoxysilane; for example, methyltri (glycidyl) silane, γ-glycidoxypropylmethyl Epoxy group-containing silane compounds such as dimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane; for example, 3-triethoxysilylpropyl succinic acid (anhydride), 3-trimethoxysilyl The Such as lopyruccinic acid (anhydride), 3-methyldimethoxysilylpropyl succinic acid (anhydride), methyldiethoxysilylpropyl succinic acid (anhydride), 1-carboxy-3-triethoxysilylpropyl succinic acid (anhydride), etc. Carboxyl group-containing silane compounds;

For example, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltri Amino group-containing silane compounds such as ethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane; for example, hydroxyl such as γ-hydroxypropyltrimethoxysilane Group-containing silane compounds; for example, amide group-containing silane compounds such as γ-amidopropyltrimethoxysilane; for example, isocyanate group-containing silane compounds such as γ-isocyanatopropyltrimethoxysilane; Containing silane compound And use of an epoxy group-containing silane compound is preferable.

  The amount of the silane compound (D) used is preferably 0.01 to 5 parts by weight, more preferably 0.01 to 2 parts by weight, based on 100 parts by weight of the high molecular weight acrylic copolymer (A). Preferably it is 0.01-1.5 weight part, Most preferably, it is 0.02-1 weight part, Most preferably, it is 0.03-0.5 weight part. If the amount used is greater than or equal to the lower limit value, it is preferable because inconveniences such as peeling are unlikely to occur. On the other hand, if it is not more than the upper limit value, inconveniences such as peeling are less likely to occur.

  The pressure-sensitive adhesive composition for polarizing film of the present invention includes the above-described high molecular weight acrylic copolymer (A), low molecular weight acrylic copolymer (B), multifunctional compound (C), and silane cup. In addition to the ring agent (D), if necessary, a compound usually blended in a pressure-sensitive adhesive composition for polarizing film, such as a weather resistance stabilizer, tackifier, plasticizer, softener, dye, pigment Inorganic fillers and the like can be appropriately blended.

  The pressure-sensitive adhesive composition for polarizing film of the present invention comprises the high molecular weight acrylic copolymer (A) and, if necessary, the low molecular weight acrylic copolymer (B), and the polyfunctional compound ( It is preferable that the gel content after the formation of a crosslinked structure with C) is 20 to 80% by weight, particularly 30 to 70% by weight. If the gel content is equal to or higher than the lower limit value, it is preferable because inconveniences such as generation of bubbles can be suppressed, and if the gel content is equal to or lower than the upper limit value, problems such as peeling and white spots are hardly generated. The gel content is measured by the following method.

Measurement of gel content of pressure sensitive adhesive composition:
It measures according to following (1)-(7).
(1) A solution of a pressure-sensitive adhesive composition was applied onto release paper surface-treated with a silicone release agent so that the coating amount after drying was 25 g / m ^2, and hot air was applied at 100 ° C. for 90 seconds. Dry with a circulation dryer to form a film-like pressure-sensitive adhesive layer.
(2) The pressure-sensitive adhesive layer is cured at 23 ° C. and a humidity of 65% RH for 10 days.
(3) About 0.25 g of the film-like pressure-sensitive adhesive layer is applied to a precisely weighed 250 mesh wire net (100 mm × 100 mm), and wrapped so that the gel content does not leak. Thereafter, the weight is accurately measured with a precision balance to prepare a sample.
(4) Immerse the wire mesh in an ethyl acetate solution for 3 days.
(5) After immersion, the wire mesh is taken out, washed with a small amount of ethyl acetate, and dried at 120 ° C. for 24 hours. Thereafter, the weight is accurately measured with a precision balance.
(6) The gel content is calculated by the following formula.
Gel content (% by weight) = (C−A) / (B−A) × 100
However, A is the weight (g) of a wire mesh, B is the weight (resin weight) (g) of the wire mesh to which the resin is applied, and C is the weight of the wire mesh (gel resin weight) (g) after immersion.

  Next, the polarizing film in the present invention will be described.

  In the polarizing film of the present invention, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition for polarizing film of the present invention described above is formed on at least one surface of the polarizing base film. Except that the pressure-sensitive adhesive layer for adhering the film to the surface of the support substrate of the liquid crystal cell is formed of the pressure-sensitive adhesive composition of the present invention described above, it is configured in the same manner as a conventional polarizing film. It is what. That is, for example, as shown in FIG. 1, the polarizing film 1 in the present invention includes a polarizing base film 2 composed of a polarizer 2A and protective layers 2B and 2C laminated on both sides of the polarizer 2A, and the protective layer 2C. The pressure-sensitive adhesive layer 3 is formed on the surface, and the release paper 4 is affixed via the pressure-sensitive adhesive layer 3.

  The pressure-sensitive adhesive layer 3 preferably has a dry thickness of 10 to 50 μm, particularly 15 to 30 μm.

  Moreover, in the polarizing film in this invention shown in FIG. 1, although the pressure sensitive adhesive layer 3 and the release paper 4 were provided only in the protective layer 2C side, pressure sensitive adhesion was carried out to both the protective layer 2B side and the protective layer 2C side. You may provide the agent layer 3 and the release paper 4, respectively. Further, the protective layers 2B and 2C may or may not be provided, and instead of the protective layer or together with the protective layer, a layer having other functions such as a reflective layer and an antiglare layer may be provided.

  EXAMPLES Examples and comparative examples will be described below to specifically describe the effects of the present invention, but the present invention is not limited to these examples. In addition, preparation of a test piece and various test methods and evaluation methods used in Examples and Comparative Examples are as follows.

(1) Production of test polarizing film A pressure-sensitive adhesive composition was applied on a release paper surface-treated with a silicone-based release agent so that the coating amount after drying was 25 g / m ² . After drying with a hot air circulation dryer at 100 ° C. for 90 seconds to form a pressure-sensitive adhesive layer, a polarizing base film [cellulose triacetate (on both sides of a polarizer mainly composed of polyvinyl alcohol (PVA) film) (TAC) film laminated; about 190 μm] is bonded to the pressure-sensitive adhesive layer surface, pressed through a pressure nip roll, and then cured at 23 ° C. and 65% RH for 10 days to obtain a polarizing film. .

(2) Initial adhesion measurement and evaluation of adherend surface contamination (reworkability evaluation)
After cutting the polarizing film prepared in the previous section (1) into 25 mm × 150 mm, this polarizing film piece is pressure-bonded to a non-alkali glass plate “# 1737” manufactured by Corning, Inc. using a table laminating machine. Test sample. The sample was autoclaved (50 ° C., 5 kg / cm ²
20 minutes) and left for 24 hours under the conditions of 23 ° C. and 65% RH (conditioning treatment), and then the adhesive force at 180 ° peeling (peeling speed: 300 mm / min) is measured.

Moreover, the state of the glass plate surface after peeling is observed visually and evaluated according to the following criteria.
(Evaluation criteria)
A: Appearance abnormality such as spider cannot be confirmed.
○: A thin spider can be confirmed at the peeling start portion.
Δ: A thin spider can be confirmed on the entire surface.
X: A dark spider can be confirmed on the entire surface.

  Among the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive composition for polarizing films, those having such a high adhesive force that they cannot be peeled off from the liquid crystal cell (glass cell) are in terms of reworkability. It is not preferable. The adhesion measured by the above method is 12 N / in. Hereinafter, in particular, 10 N / in. The following are excellent in reworkability, and the adhesive strength is 12 N / in. If it exceeds, there is a problem with reworkability. In addition, there is a problem in reworkability when adhesive residue or spider is generated on the glass surface after peeling.

(3) Adhesive strength measurement after heat treatment and evaluation of adherend surface contamination (recyclability evaluation)
A test sample prepared and autoclaved in the same manner as in the previous section (2) was allowed to stand at 23 ° C. and 65% RH for 1 hour, and then heat-treated at 70 ° C. for 3 hours. After conditioning treatment in the same manner as in item (1), the adhesive strength at 180 ° peeling (peeling speed: 300 mm / min) is measured.

Moreover, the state of the glass plate surface after peeling is observed visually and evaluated according to the following criteria.
(Evaluation criteria)
A: Appearance abnormality such as spider cannot be confirmed.
○: A thin spider can be confirmed at the peeling start portion.
Δ: A thin spider can be confirmed on the entire surface.
X: A dark spider can be confirmed on the entire surface.

  Among the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive composition for polarizing films, those having such a high adhesive force that they cannot be peeled off from the liquid crystal cell (glass cell) are recyclable. It is not preferable. The adhesion measured by the above method is 15 N / in. Hereinafter, in particular, 10 N / in. The following are excellent in recyclability, and the adhesive strength is 15 N / in. If it exceeds 1, there is a problem with recyclability. Also, there is a problem in recyclability when adhesive residue is left on the glass surface after peeling.

(4) Evaluation of durability A test sample was prepared in the same manner as in the previous item (2) except that a 70 mm × 140 mm (long side) polarizing film piece cut so that the long side was 45 ° with respect to the absorption axis was used. After conditioning the same as in the previous item (2), it is left under the following temperature and humidity conditions, and the state of generation and peeling of bubbles is evaluated by visual observation. The evaluation criteria are as follows.

a) Heat resistance test 80 ° C., dry, 1000 hours (80 ° C., dry evaluation criteria)
A: Generation of bubbles is not recognized.
A: Generation of bubbles having a diameter of less than 100 μm is slightly observed.
Δ: Many bubbles with a diameter of 100 to 200 μm are observed.
X: Many bubbles with a diameter of 200 μm or more are observed.

b) Moisture and heat resistance test 60 ° C., 90% RH, 1000 hours (evaluation criteria of 65 ° C., 95% RH)
A: There is no peeling.
○: Peeling within 500 μm.
Δ: Peeling less than 2 mm.
X: Peeling of 2 mm or more.

c) Heat shock test −20 ° C./60° C., holding time 0.5 hour repeatedly 100 cycles A : No peeling.
○: Peeling within 500 μm.
Δ: Peeling less than 2 mm.
X: Peeling of 2 mm or more.

(5) In the same manner as in the item (4) before the evaluation test of the white spot phenomenon , a polarizing film is pasted on both surfaces of a 0.7 mm Corning non-alkali glass plate “# 1737” so that the polarization axes thereof are orthogonal to each other. The prepared test sample is prepared and subjected to a conditioning treatment in the same manner as in the previous section (4), and then left to stand at 80 ° C. under dry conditions for 1000 hours. After leaving, use a uniform light source and visually check for white spots.
A: No white spots are observed.
○: Almost no white spots are observed.
Δ: White spots are slightly noticeable.
X: White spots are large.

Production of high molecular weight acrylic copolymer (A) Production Example 1
In a reactor equipped with a thermometer, a stirrer, a nitrogen introducing tube and a reflux condenser, 98.5 parts by weight of n-butyl acrylate (BA), ω-carboxypolycaprolactone monoacrylate [“M-5300” (trade name) The pendant side chain is a monomer of the general formula (1), X ¹ is 1,5-pentylene, n≈2, molecular weight of about 300; manufactured by Toagosei Co., Ltd.] 1.5 parts by weight, ethyl acetate (EAc) 100 parts by weight and 0.2 parts by weight of azobisisobutyronitrile (AIBN) were added, and after the air in the reaction vessel was replaced with nitrogen gas, the content temperature of the reaction vessel was adjusted in a nitrogen atmosphere with stirring. The temperature was raised to 65 ° C. and reacted for 6 hours, and further heated to 70 ° C. and reacted for 2 hours. Thereafter, a solution in which 0.4 part by weight of AIBN was dissolved in 20 parts by weight of EAc was added dropwise over 1 hour, and the mixture was further reacted for 2 hours. After completion of the reaction, the reaction mixture was diluted with toluene to obtain a high molecular weight acrylic copolymer solution having a solid content of about 20.1% by weight and a viscosity of about 6750 mPa · s.

The obtained high molecular weight acrylic copolymer has a glass transition point (Tg _A ) of about −56.8 ° C., a solubility parameter (SP _A ) of about 9.0, a weight average molecular weight (Mw _A ) of about 1.2 million, and a weight. The ratio of the average molecular weight (Mn _A ) to the number average molecular weight (Mw _A / Mn _A ) was about 6.7.

Production Examples 2-3
In Production Example 1, the initial reaction temperature was changed from 65 ° C. to 70 ° C., and the amount of the initial AIBN was increased as appropriate. Obtained. Table 1 shows the solid content and viscosity of the obtained acrylic copolymer solution, and the values of Tg _A , SP _A , Mw _A and Mw _A / Mn _A of the copolymer.

Production Examples 4-5
A solution of a high molecular weight acrylic copolymer was prepared in the same manner as in Production Example 1 except that the amount of the carboxyl group-containing monomer “M-5300” used in Production Example 1 was changed and the amount of BA used was changed accordingly. Respectively. Table 1 shows the solid content and viscosity of the obtained acrylic copolymer solution, and the values of Tg _A , SP _A , Mw _A and Mw _A / Mn _A of the copolymer.

Production Examples 6-8
In Production Example 1, instead of using 1.5 parts by weight of “M-5300” as the carboxyl group-containing monomer, “M-5600” [(trade name); the pendant side chain is a single monomer of the general formula (1) Body, X ¹ is 1,5-pentylene, n≈1.4; manufactured by Toagosei Co., Ltd.] 1.5 parts by weight, monohydroxyethyl acrylate succinate ["light acrylate HOA-MS" (trade name); pendant The side chain is a monomer of the general formula (2), X ² and Y ¹ are both ethylene; made by Kyoeisha Chemical Co., Ltd.] (HOA) 1.5 parts by weight or acrylic acid (AA) 1 part by weight, Accordingly, solutions of high molecular weight acrylic copolymers were obtained in the same manner as in Production Example 1 except that the amount of BA was adjusted as necessary. Table 1 shows the solid content and viscosity of the obtained acrylic copolymer solution, and the values of Tg _A , SP _A , Mw _A and Mw _A / Mn _A of the copolymer.

Production Examples 9-12
In Production Example 1, instead of using 98.5 parts by weight of BA and 1.5 parts by weight of “M-5300” as monomers, the same procedure as in Production Example 1 was conducted except that the monomers shown in Table 1 were used. , Solutions of high molecular weight acrylic copolymers having different Tg _A were obtained. Table 1 shows the solid content and viscosity of the obtained acrylic copolymer solution, and the values of Tg _A , SP _A , Mw _A and Mw _A / Mn _A of the copolymer.

In addition, the symbol of the monomer in Table 1 is as follows.
EHA: 2-ethylhexyl acrylate BA: butyl acrylate EA: ethyl acrylate MA: methyl acrylate MMA: methyl methacrylate M-5300: ω-carboxypolycaprolactone monoacrylate (n≈2), molecular weight about 300
M-5600: ω-carboxypolycaprolactone monoacrylate (n≈1.4), molecular weight about 232
HOA: succinic acid monohydroxyethyl acrylate, molecular weight 216
AA: Acrylic acid

Production of low molecular weight acrylic copolymer (B) Production Example 21
36 parts by weight of BA, methyl acrylate [MA; copolymerization ratio to BA (1 / γ _{MA / BA} ) = 0.338], 20 parts by weight, n-butyl methacrylate [nBMA; copolymerization ratio to BA (1 / γ _{nBMA / BA} ) = 0.395] 44 parts by weight, 350 parts by weight of toluene and 0.5 parts by weight of AIBN were placed in a reaction vessel, and the air in the reaction vessel was replaced with nitrogen gas. The reaction vessel was heated to 90 ° C. and reacted for 6 hours. Thereafter, a solution in which 1.0 part by weight of AIBN was dissolved in 30 parts by weight of EAc was added dropwise over 1 hour, and the mixture was further reacted for 2 hours. After the reaction, it was diluted with toluene to obtain a solution of a low molecular weight acrylic copolymer having a solid content of about 20.0% by weight and a viscosity of about 20 mPa · s.

The resulting low molecular weight acrylic copolymer has a glass transition point (Tg _B ) of about −15 ° C., a solubility parameter (SP _B ) of about 9.08, and a weight average molecular weight (Mw _B ) of about 100,000. It was.

Production Examples 22-24
In Production Example 21, a low molecular weight acrylic was added in the same manner as in Production Example 21 except that the amount of initial AIBN was increased as appropriate in Production Example 22 and the amount of initial toluene was reduced as appropriate in Production Examples 23 and 24. A solution of a copolymer was obtained. Table 2 shows the solid content and viscosity of the resulting acrylic copolymer solution, and the Tg _B , SP _B and Mw _B values of the copolymer.

Production Examples 25-29
In Production Example 21, instead of using 36 parts by weight of BA, 20 parts by weight of MA and 44 parts by weight of nBMA as monomers, Tg _B was used in the same manner as in Production Example 11 except that the monomers shown in Table 2 were used. Of different low molecular weight acrylic copolymers were obtained. Table 2 shows the solid content and viscosity of the resulting acrylic copolymer solution, and the Tg _B , SP _B and Mw _B values of the copolymer.

In addition, the symbol of the monomer in Table 2 is as follows.
BA: Butyl acrylate MMA: Methyl methacrylate [(1 / γ _{MMA / BA} ) = 0.407]
EMA: ethyl methacrylate [(1 / γ _{EMA / BA} ) = 0.445]
nBMA: n-butyl methacrylate [(1 / _{γnBMA / BA} ) = 0.395]
iBMA: i-butyl methacrylate [(1 / γ _{iBMA / BA} ) = 0.396]
MA: Methyl acrylate [(1 / γ _{MA / BA} ) = 0.338]
EA: ethyl acrylate [(1 / γ _{EA / BA} ) = 0.786]

Preparation of pressure-sensitive adhesive composition for polarizing film Example 1
As component (A), 500 parts by weight of the high molecular weight acrylic copolymer solution obtained in Production Example 1 (about 100 parts by weight as the high molecular weight acrylic copolymer) is used, and as Component (B), Production Example These were mixed using 200 parts by weight of the low molecular weight acrylic copolymer solution obtained in 21 (about 40 parts by weight as a low molecular weight acrylic copolymer), and the isocyanate compound “Duranate” was added as a polyfunctional compound to this mixture. E-405-80T "(trade name) [manufactured by Asahi Kasei Chemicals Co., Ltd.] 1.2 parts by weight (active ingredient: about 0.96 parts by weight; isocyanate group: about 2.03 × 10 ⁻³ equivalents-equivalent ratio to carboxyl groups 0.406) (E-405) and γ-mercaptopropyltrimethoxysilane “Silaace S810” (trade name) [Chisso] as a silane coupling agent Co., Ltd.] (S810) 1.75 parts by weight [about 1.25 parts by weight with respect to a total of 100 parts by weight of component (A) and component (B)] was added and stirred well to obtain a solid content of about 20 A solution of a pressure sensitive adhesive composition for a polarizing film having a viscosity of 1 wt% and a viscosity of about 5200 mPa · s was obtained.

  Using the obtained pressure-sensitive adhesive composition solution for polarizing film, a polarizing film for test was prepared according to the above, and the above-mentioned various physical property tests were performed on this polarizing film. Table 3 shows the blended composition of the obtained pressure-sensitive adhesive composition for polarizing film, its characteristic values, that is, the viscosity and solid content of the solution of the composition, and the gel content of the obtained pressure-sensitive adhesive layer and the polarizing film. Table 4 shows the results of various physical property tests.

Examples 2-9 and Comparative Examples 1-3
In Example 1, instead of using the low molecular weight acrylic copolymer solution obtained in Production Example 1 as the component (A), the high molecular weight acrylic copolymer solution obtained in Production Examples 2 to 12 was used. Obtained a solution of a pressure-sensitive adhesive composition for a polarizing film in the same manner as in Example 1. Using these pressure-sensitive adhesive composition solutions, test polarizing films were prepared in the same manner as in Example 1, and the various physical properties tests described above were performed on the polarizing films.

  Table 3 shows the composition and characteristic values of the obtained pressure-sensitive adhesive composition for polarizing film, and Table 4 shows the gel content of the pressure-sensitive adhesive layer and the results of various physical properties tests of the polarizing film.

Examples 10 to 16 and Comparative Example 4
In Example 1, instead of using the low molecular weight acrylic copolymer solution obtained in Production Example 21 as the component (B), the low molecular weight acrylic copolymer solution obtained in Production Examples 22 to 29 was used. Obtained a solution of a pressure-sensitive adhesive composition for a polarizing film in the same manner as in Example 1. Using these pressure-sensitive adhesive composition solutions, test polarizing films were prepared in the same manner as in Example 1, and the various physical properties tests described above were performed on the polarizing films.

  Table 3 shows the composition and characteristic values of the obtained pressure-sensitive adhesive composition for polarizing film, and Table 4 shows the gel content of the pressure-sensitive adhesive layer and the results of various physical properties tests of the polarizing film.

Examples 17 to 19 and Comparative Example 5
In Example 1, the amount of the component (B) used is changed or not used, and the silane coupling agent (D) is 1.75 with respect to 100 parts by weight of the total amount of the component (A) and the component (B). A solution of a pressure-sensitive adhesive composition for a polarizing film was obtained in the same manner as in Example 1 except that the amount was adjusted so as to be parts by weight. Using these pressure-sensitive adhesive composition solutions, test polarizing films were prepared in the same manner as in Example 1, and the various physical properties tests described above were performed on the polarizing films.

  Table 3 shows the composition and characteristic values of the obtained pressure-sensitive adhesive composition for polarizing film, and Table 4 shows the gel content of the pressure-sensitive adhesive layer and the results of various physical properties tests of the polarizing film.

Examples 20-23
In Example 1, 0.96 parts by weight of polyisocyanate compound “Duranate E-405-80T” as an active ingredient is used as the polyfunctional compound (C), and 0.5% of “Silaace S810” is used as the silane coupling agent (C). Instead of using parts by weight [0.4 parts by weight relative to 100 parts by weight of component (A) and component (B)], as shown in Table 3, the type and / or amount of polyfunctional compound (B) And / or in the same manner as in Example 1 except that the type and / or amount of the silane coupling agent (D) is changed or is not used, respectively. Obtained. Using these pressure-sensitive adhesive composition solutions, test polarizing films were prepared in the same manner as in Example 1, and the various physical properties tests described above were performed on the polarizing films.

  Table 3 shows the composition and characteristic values of the obtained pressure-sensitive adhesive composition for polarizing film, and Table 4 shows the gel content of the pressure-sensitive adhesive layer and the results of various physical properties tests of the polarizing film.

In addition, the symbol of the polyfunctional compound (C) and silane coupling agent (D) in Table 3 is as follows.
E-405: “Duranate E-405-80T” modified hexamethylene diisocyanate, approximately 80% by weight of active ingredient, 7.1% by weight of NCO, manufactured by Asahi Kasei Chemicals Corporation D-120N: “Takenate D-120N Hydrogenated xylylene diisocyanate / trimethylolpropane adduct, active ingredient: about 75% by weight, NCO content: 11.0% by weight, manufactured by Mitsui Takeda Chemical Co., Ltd. TAZM: “TAZM” trimethylolpropane-Tris (β-azi Lysinylpropionate), active ingredient about 100% by weight, manufactured by Mutual Yakuhin Co., Ltd. TET-C: “TETRAD-C” 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, active ingredient about 100 % By weight, manufactured by Mitsubishi Gas Chemical Co., Ltd. S810: “Syra Ace S810” γ-mercaptopropyltrime Kishishiran, manufactured by Chisso Corporation S510: "Sila S510" γ- glycidoxypropyltrimethoxysilane, manufactured by Chisso Corporation

FIG. 1 is a cross-sectional view showing an example of the polarizing film of the present invention having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for polarizing film of the present invention. FIG. 2 is a schematic view of an apparatus used in an evaluation test of a white spot phenomenon of a pressure-sensitive adhesive composition. FIG. 3 is a schematic view of a sample prepared in an evaluation test of the white spot phenomenon of the pressure-sensitive adhesive composition.

Explanation of symbols

1: Polarizing film 2: Polarizing base film 2A
: Polarizers 2B and 2C: Protective layer 3: Pressure sensitive adhesive layer 4: Release paper 5: Simple photometric device 6: Light source 7: Diffuser 8: Luminance meter 9: Glass plate 10: Test sample 11: Light shielding plate

Claims (21)

The following (A) to (C):
(A) High molecular weight acrylic containing a repeating unit (a ₁ ) containing a carboxyl group in the molecule, having a weight average molecular weight (Mw _A ) of 800,000 or more and a glass transition temperature (Tg _A ) of −40 ° C. or less. Copolymer,
(B) A low molecular weight acrylic copolymer having a weight average molecular weight (Mw _B ) of less than 800,000 and a glass transition temperature (Tg _B ) of −40 ° C. or more, and (C) a crosslinked structure reacting with a carboxyl group A polyfunctional compound containing two or more functional groups capable of forming
In the comprising as essential components polarizing film for pressure-sensitive adhesive composition, a carboxyl group contained in the repeating units (a ₁₎ is present at the end of pendant side chains of the repeating units (a _1), and The pressure-sensitive adhesive composition, wherein the number of carbon atoms contained in the pendant side chain is 4 or more. The high molecular weight acrylic copolymer (A) and the low molecular weight acrylic copolymer (B) have a total of 50 repeating units derived from an acrylic ester and a methacrylic ester, respectively, based on the acrylic copolymer. The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition is contained by weight% or more. The pressure-sensitive adhesive composition according to claim 1, wherein the pendant side chain of the repeating unit (a ₁ ) is represented by the following general formula (1) or (2).

[Wherein, X ¹ represents an alkylene group having 2 to 6 carbon atoms, X ² represents an alkylene group having 2 to 4 carbon atoms, Y ¹ represents an ethylene group, a 1,2-phenylene group or a 1,2-cyclohexylene group. , N is a rational number from 1 to 10] In the general formula (1), pressure sensitive adhesive composition of claim 3 X ¹ is a straight-chain alkylene group having 5 carbon atoms. In the general formula (2), pressure sensitive adhesive composition of claim 3 X ² is an alkylene group having 2 carbon atoms. The content of the repeating unit (a ₁ ) in the high molecular weight acrylic copolymer (A) is 0 based on the total 100% by weight of all the repeating units constituting the high molecular weight acrylic copolymer (A). The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition is in the range of 1 to 10% by weight. The high molecular weight acrylic copolymer (A) has the following repeating units (a ₁ ) to (a ₃ ),
(A ₁ ) The following general formula (3) or (4),

[Wherein R ¹ is a hydrogen atom or a methyl group, and X ¹ , X ² , Y ¹ and n are as defined in the general formulas (1) and (2)]
0.1 to 10% by weight of a repeating unit containing a carboxyl group represented by
_{(A 2)} represented by the following general formula (5),

[Wherein R ² represents a linear or branched alkyl group having 4 to 10 carbon atoms]
The repeating unit derived from an acrylate ester having a glass transition temperature (Tg) of not more than −50 ° C.
(A ₃ ) A copolymer can be formed with the above repeating units (a ₁ ) and (a ₂ ), and 0 to 30% by weight of repeating units other than the repeating units (a ₁ ) and (a ₂ ),
[However, the total of repeating units (a ₁ ) to (a ₃ ) is 100% by weight]
The pressure-sensitive adhesive composition according to claim 1, comprising: The pressure-sensitive adhesive composition according to claim 1 or 7, wherein the solubility parameter (SP _A ) of the acrylic copolymer (A) is in the range of 8.7 to 9.3. The pressure sensitive adhesive composition according to claim 1, wherein the glass transition point of the low molecular weight acrylic copolymer (B) is in the range of -40 to 0 ° C. The pressure-sensitive adhesive composition according to claim 1, wherein the weight average molecular weight of the low molecular weight acrylic copolymer (B) is in the range of 3 to 400,000. The pressure-sensitive adhesive composition according to claim 9 or 10, wherein the solubility parameter (SP _B ) of the low molecular weight acrylic copolymer (B) is in the range of 8.7 to 9.3. The difference in solubility parameter (ΔSP = SP _B -SP _A ) between the low molecular weight acrylic copolymer (B) and the high molecular weight acrylic copolymer ( _A ) is 0.5 or less. Pressure sensitive adhesive composition. The low molecular weight acrylic copolymer (B) contains the following monomers (b ₁ ) to (b ₃ ),
(B ₁ ) The following general formula (6),
H ₂ C = CHCOOR ²
(6)
[Wherein R ² is as defined in the general formula (5)]
An acrylic ester whose homopolymer has a glass transition temperature (Tg) of −50 ° C. or lower,
(B ₂ ) a monomer having a relatively low copolymerizability with the monomer (b ₁ ), and (b ₃ ) a monomer having a relatively high copolymerizability with the monomer (b ₁ ). ,
The pressure-sensitive adhesive composition according to claim 9, which is an acrylic copolymer obtained by copolymerizing The pressure-sensitive adhesive according to claim 1, wherein the content of the low molecular weight acrylic copolymer (B) is in the range of 10 to 100 parts by weight based on 100 parts by weight of the high molecular weight acrylic copolymer (A). Composition. The pressure-sensitive adhesive composition according to claim 1, wherein the polyfunctional compound (C) is selected from the group consisting of a polyisocyanate compound, a polyaziridine compound, and a polyepoxy compound. The pressure-sensitive adhesive composition according to claim 1, wherein the polyfunctional compound (C) is a polyisocyanate compound. The amount of the polyisocyanate compound used is, based on the total carboxyl groups contained in the high molecular weight acrylic copolymer (A) and the low molecular weight acrylic copolymer (B), 0. The pressure-sensitive adhesive composition according to claim 16, which is in the range of 01 to 1 equivalent. The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition further contains a silane compound (D). The pressure-sensitive adhesive composition according to claim 14, wherein the silane compound (D) is a mercapto group-containing silane compound or an epoxy group-containing silane compound. The content of the silane compound (D) is in the range of 0.01 to 5 parts by weight based on a total of 100 parts by weight of the high molecular weight acrylic copolymer (A) and the low molecular weight acrylic copolymer (B). The pressure-sensitive adhesive composition according to claim 18 or 19. The gel content of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition after the formation of the crosslinked structure is in the range of 30 to 80% by weight based on the weight of the pressure-sensitive adhesive layer. Item 2. The pressure-sensitive adhesive composition according to Item 1.

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