JP2014215472A - Adhesive for manufacturing polarizing plate and polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive for manufacturing a polarizing plate, which maintains high adhesiveness of a protective film and furthermore enables a polarizing plate having high weather resistance to be manufactured.SOLUTION: The adhesive for manufacturing a polarizing plate is composed of a radiation curable composition containing: a compound (A) having one or more alicyclic epoxy groups in a molecule and including an ester group; a compound (B) having one or more alicyclic epoxy groups in a molecule and not including an ester group; a hydroxyl group-containing compound (C) having three hydroxyl groups in a molecule; and a photoacid generator (E), the radiation curable composition further includes an oxetane compound (D) or none. In the radiation curable composition, [the sum of the total number of epoxy groups of (A) and (B) and the total number of oxetanyl groups of (D)]/[the total number of hydroxyl groups of (C)] is 6.0 or less, and [the total number of epoxy groups of (B)]/[the sum of the total number of epoxy groups of (A) and (B) and the total number of oxetanyl groups of (D)] is 0.4 or less.

Description

  The present invention relates to an adhesive for producing a polarizing plate and a polarizing plate. Moreover, the manufacturing method of a radiation-curable composition, the adhesive agent which consists of a radiation-curable composition, and a polarizing plate is also described.

  In recent years, liquid crystal display devices have been widely used as display devices for displaying characters, images, and the like. Such a liquid crystal display device usually includes a liquid crystal cell composed of two polarizing plates and a glass substrate, a transparent electrode, a color filter, a light distribution film, a liquid crystal, and the like disposed therebetween. In general, a polarizing plate used in a liquid crystal display device is obtained by bonding a protective film such as a triacetyl cellulose film on one or both surfaces of a polarizing film (polarizer) obtained by adsorbing iodine or the like on a stretched and oriented polyvinyl alcohol sheet. It is formed by bonding through an agent layer. In recent years, from the viewpoint of power saving, there has been a movement to convert the backlight of the liquid crystal display device into an LED. Due to the heat generated by the LED, the polarizing plate has weather resistance such as moisture resistance, thermal shock resistance, and high temperature resistance. It has been demanded. In particular, a polarizing plate using a triacetylcellulose-based film having a high moisture permeability as a protective film has not been sufficiently weather-resistant, and therefore is being replaced by a film having a low moisture permeability.

  On the other hand, what has various hardening systems is known as a composition suitable for the adhesive agent used for manufacture of a polarizing plate. Among them, it is known that a curing reaction proceeds by heating, ultraviolet irradiation, etc., and those capable of forming an adhesive layer or film having a high crosslinking density can exhibit good adhesive strength and coating film strength. . As resin compositions that can be cured by heating, ultraviolet irradiation, or the like, radically polymerizable and cationically polymerizable resins are known.

  The radical polymerization of the resin composition may stop before the curing has sufficiently progressed, or may cause curing shrinkage as the polymerization reaction proceeds. On the other hand, although cationic polymerization is insufficient in terms of adhesive strength, it has the advantage that it does not cause radical termination reaction or deactivation, and the degree of curing shrinkage is small.

  Therefore, as a material applicable to an optical member such as a polarizing plate in which slight distortion of the base material is a problem, an alicyclic epoxy compound as a cationic polymerizable compound, a compound having at least two hydroxyl groups in the molecule In addition, it is known that an adhesive composition containing a photoacid generator can be cured in a short time and is excellent in performance such as adhesive strength (for example, see Patent Document 1).

JP-A-10-330717

  However, the polarizing plate using the adhesive has a problem that the protective film is peeled off in a wet heat test, a temperature impact test, and a high temperature holding test. This was considered to be because the adhesive film was not sufficiently cured because the polarizing film absorbed the radiation. Therefore, a highly weather-resistant polarizing plate excellent in moisture and heat resistance, thermal shock resistance, and high-temperature holding resistance, and an adhesive for producing a polarizing plate capable of producing such a polarizing plate are required.

  Accordingly, an object of the present invention is to provide an adhesive for producing a polarizing plate that enables production of a polarizing plate having high weather resistance while maintaining high adhesion of the protective film, or to provide such a polarizing plate. There is to do.

  Therefore, as a result of intensive studies by the present inventors to solve the above problems, the total number of epoxy groups of a specific epoxy compound contained in the composition and the total number of hydroxyl groups of the trifunctional alcohol contained in the composition It was found that by keeping the ratio in a certain range, the protective film of the polarizing plate was not peeled off even after the wet heat test and the temperature shock test while maintaining the adhesiveness, and the reliability could be ensured. Furthermore, as the specific epoxy compound, a compound having two or more alicyclic epoxy groups in the molecule and an ester group, and one or more alicyclic epoxy groups in the molecule, and an ester group In addition to the wet heat test and the temperature impact test, the protective film of the polarizing plate does not peel off after the high temperature holding test while maintaining the adhesiveness, and the reliability can be ensured. As a result, the present invention has been completed.

That is, the present invention
Compound (A) having at least one alicyclic epoxy group in the molecule and containing an ester group,
Compound (B) having at least one alicyclic epoxy group in the molecule and not containing an ester group,
A radiation curable composition comprising a hydroxyl group-containing compound (C) having three hydroxyl groups in the molecule, and a photoacid generator (E),
The radiation curable composition contains or does not contain an oxetane compound (D) having one or more oxetanyl groups in the molecule,
[The sum of the total number of epoxy groups of the compound (A) and the compound (B) in the composition and the total number of oxetanyl groups of the oxetane compound (D)] / [the total number of hydroxyl groups of the hydroxyl group-containing compound (C) in the composition] 6.0 or less,
[Total number of epoxy groups of compound (B) in composition] / [sum of total number of epoxy groups of compound (A) and compound (B) in composition and total number of oxetanyl groups of oxetane compound (D)] is 0. Provided is an adhesive for producing a polarizing plate, comprising a radiation curable composition of 4 or less.

（上記式（Ｉ）中、Ｘは、エステル基を含有する連結基を示す。） In the polarizing plate production adhesive,
The compound (A) is preferably a compound represented by the following formula (I).

(In the above formula (I), X represents a linking group containing an ester group.)

  Moreover, in the said adhesive agent for polarizing plate manufacture, it is preferable that a hydroxyl-containing compound (C) is a polyester triol.

The present invention also provides:
Provided is a polarizing plate obtained by adhering a protective film to at least one surface of a polarizing film using the polarizing plate-producing adhesive.

The polarizing plate is preferably a polarizing plate obtained by curing the polarizing plate-producing adhesive by radiation irradiation with an irradiation light amount of 300 mJ / cm ² or less.

  In the polarizing plate formed by adhering the protective film using the adhesive for producing the polarizing plate of the present invention, the polarizing plate is protected even after the wet heat test, the temperature impact test, and the high temperature holding test while maintaining the high adhesiveness of the protective film. The film does not peel off, ensuring reliability.

[1. Radiation curable composition]
The radiation curable composition is:
Compound (A) having at least one alicyclic epoxy group in the molecule and containing an ester group,
Compound (B) having at least one alicyclic epoxy group in the molecule and not containing an ester group,
A radiation curable composition comprising a hydroxyl group-containing compound (C) having three hydroxyl groups in the molecule, and a photoacid generator (E),
The radiation curable composition contains or does not contain an oxetane compound (D),
[The sum of the total number of epoxy groups of the compound (A) and the compound (B) in the composition and the total number of oxetanyl groups of the oxetane compound (D)] / [the total number of hydroxyl groups of the hydroxyl group-containing compound (C) in the composition] 6.0 or less,
[Total number of epoxy groups of compound (B) in composition] / [sum of total number of epoxy groups of compound (A) and compound (B) in composition and total number of oxetanyl groups of oxetane compound (D)] is 0. It is sufficient if it is made of a radiation curable composition having 4 or less, and is not particularly limited in other respects.

  In the radiation curable composition, [the sum of the total number of epoxy groups of the compound (A) and the compound (B) in the composition and the total number of oxetanyl groups of the oxetane compound (D)] / [hydroxyl group-containing compound in the composition ( Adhesiveness improves because the total number of hydroxyl groups in C) is 6.0 or less. The reason for the above effect is that when the ratio is 6.0 or less, the number of hydroxyl groups remaining in the radiation-cured product is large, and the hydrogen bonding effect at the interface between the adherend and the adhesive-cured product. May be expressed. In addition, the said mechanism is estimation and does not limit the scope of the invention. When the radiation curable composition does not contain the oxetane compound (D), the total number of oxetanyl groups of the oxetane compound (D) in the composition is naturally zero, and the same applies to the following.

  In the radiation curable composition, [the sum of the total number of epoxy groups of the compound (A) and the compound (B) in the composition and the total number of oxetanyl groups of the oxetane compound (D)] / [hydroxyl group-containing compound in the composition ( The total number of hydroxyl groups in C) is 6.0 or less. However, considering that the total number of hydroxyl groups in the hydroxyl group-containing compound (C) is too large, the weather resistance tends to be lowered. It is preferable that it is 2.0, it is more preferable that it is 2.0-4.0, and it is especially preferable that it is 2.6-3.2.

  In the radiation curable composition, [total number of epoxy groups of compound (B) in composition] / [total number of epoxy groups of compound (A) and compound (B) in composition and total oxetanyl of oxetane compound (D) Adhesiveness improves because the sum with a radix] is 0.4 or less. The reason for the above effects is that the balance between the softness provided by the compound (A) and the compound (D) and the hardness provided by the compound (B) is well taken, and the adhesive layer has both hardness and toughness. It is possible that In addition, the said mechanism is estimation and does not limit the scope of the invention.

  In the radiation curable composition, [total number of epoxy groups of compound (B) in composition] / [total number of epoxy groups of compound (A) and compound (B) in composition and total oxetanyl of oxetane compound (D) The sum of the number of radicals] is 0.4 or less, but considering that the high temperature retention tends to be lowered when the total number of epoxy groups in the compound (B) is too small, it is 0.1 to 0.4. Is more preferable, 0.15-0.4 is more preferable, and 0.2-0.4 is particularly preferable.

  The content of the compound (A) in the radiation curable composition is not particularly limited, but is 20 to 60% by weight, for example, with respect to the total amount of the radiation curable composition, from the viewpoints of radiation exposure and degree of curing. It is preferably 30 to 50% by weight, more preferably 35 to 45% by weight.

  The content of the compound (B) in the radiation curable composition is not particularly limited, but is, for example, 1 to 30% by weight with respect to the total amount of the radiation curable composition from the viewpoint of high temperature retention and adhesive strength. It is preferably 5 to 25% by weight, and more preferably 8 to 20% by weight.

  The content of the hydroxyl group-containing compound (C) in the radiation curable composition is not particularly limited, but from the viewpoint of adhesive strength and curability, for example, 10 to 50 weights with respect to the total amount of the radiation curable composition. %, Preferably 20 to 45% by weight, more preferably 35 to 40% by weight.

  The content of the hydroxyl group-containing compound (C) includes the epoxy group-containing compound [compound (A) and compound (B) in the radiation curable composition from the viewpoint of coating property and the like. It is not limited to a cyclic epoxy group], for example, 40 to 70 parts by weight and 51 to 70 parts by weight with respect to 100 parts by weight of the total amount of the photoacid generator (E) and other components described later. Is preferable, and it is more preferable that it is 61-70 weight part.

  Although content in particular of the oxetane compound (D) in the said radiation curable composition is not restrict | limited, From a storage stability and a sclerosing | hardenable viewpoint, it is 5-30 weight with respect to the total amount of the said radiation curable composition, for example. %, Preferably 5 to 20% by weight, more preferably 5 to 10% by weight.

  The content of the photoacid generator (E) in the radiation curable composition is not particularly limited, but is, for example, 0.1 to 10% by weight with respect to the total amount of the radiation curable composition. It is preferably 10% by weight, and more preferably 2 to 5% by weight. When the usage-amount of a photo-acid generator (E) is less than the said range, the problem of insufficient adhesive force by a curing failure and the fall of a weather resistance may arise. On the other hand, when the usage-amount of a photo-acid generator (E) exceeds the said range, since the density | concentration of the ionic substance after hardening is high, water resistance may deteriorate.

  The blending ratio of the compound (A) and the compound (B) in the radiation curable composition is not particularly limited, but is 95: 5 to 40:60 (weight ratio) from the viewpoint of high temperature retention and curability. : The latter), preferably 90:10 to 60:40 (the former: the latter), and particularly preferably 80:20 to 70:30 (the former: the latter).

  The mixing ratio of the total amount of the compound (A) and the compound (B) and the hydroxyl group-containing compound (C) in the radiation curable composition is not particularly limited, but is 30 by weight from the viewpoint of curability and the like. It is preferably 70-80: 20 (the former: the latter), more preferably 45: 55-70: 30 (the former: the latter), and 55: 45-60: 40 (the former: the latter). Is particularly preferred.

  The mixing ratio of the total amount of the compound (A) and the compound (B) and the oxetane compound (D) in the radiation curable composition is not particularly limited, but is 60:40 by weight from the viewpoint of acceleration of curing. ~ 95: 5 (the former: the latter) is preferable, 65:35 to 90:10 (the former: the latter) is more preferable, and 70:30 to 85:15 (the former: the latter) is preferable. Particularly preferred.

  The viscosity of the radiation curable composition is not particularly limited, but is preferably 40 to 800 mPa · s, and more preferably 40 to 500 mPa · s from the viewpoint of coating workability.

[1-1. Compound (A)]
The compound (A) is not particularly limited as long as it is a compound having one or more alicyclic epoxy groups in the molecule and containing an ester group. In the present specification, the alicyclic epoxy group means an epoxy group composed of two adjacent carbon atoms and oxygen atoms constituting the alicyclic ring. Moreover, as a compound (A), only 1 type may be used and 2 or more types may be mixed and used. The compound (A) is more preferably a compound having two or more (for example, 2 to 6) alicyclic epoxy groups in the molecule.

As the compound (A), a compound having a cyclohexene oxide group is preferable from the viewpoint of transparency and heat resistance, and a compound represented by the following formula (I) is particularly preferable. The cyclohexene ring of the cyclohexene oxide group may be a substituent such as a C _1-12 alkyl group (particularly a C _1-4 alkyl group), a C _2-12 alkenyl group (particularly a C _2-4 alkenyl group), etc. The substituents may be singular or plural, and when there are a plurality of substituents, these substituents may be the same or different.

  In the above formula (I), X represents a linking group containing an ester group. The ester group also includes a carbonate group (carbonate ester group). The linking group containing an ester group may not contain a chemical group other than an ester group. For example, in addition to an ester group, a divalent hydrocarbon group, a carbonyl group, an ether bond, an amide group, these May be a linking group including a group in which a plurality of are connected.

  As said bivalent hydrocarbon group, a C1-C18 linear or branched alkylene group, a bivalent alicyclic hydrocarbon group, etc. are mentioned. Examples of the linear or branched alkylene group having 1 to 18 carbon atoms include a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylene group, a propylene group, and a trimethylene group. Examples of the divalent alicyclic hydrocarbon group include 1,2-cyclopentylene group, 1,3-cyclopentylene group, cyclopentylidene group, 1,2-cyclohexylene group, 1,3-cyclopentylene group, And divalent cycloalkylene groups (including cycloalkylidene groups) such as cyclohexylene group, 1,4-cyclohexylene group and cyclohexylidene group.

  Typical examples of the alicyclic epoxy compound represented by the above formula (I) include compounds represented by the following formulas (I-1) to (I-10). In the following formulas (I-5) and (I-7), l and m each represent an integer of 1 to 30. R in the following formula (I-5) is an alkylene group having 1 to 8 carbon atoms, methylene group, ethylene group, propylene group, isopropylene group, butylene group, isobutylene group, s-butylene group, pentylene group, hexylene. And linear or branched alkylene groups such as a group, a heptylene group, and an octylene group. Among these, C1-C3 linear or branched alkylene groups, such as a methylene group, ethylene group, a propylene group, an isopropylene group, are preferable. N1 to n6 in the following formulas (I-9) and (I-10) each represent an integer of 1 to 30. Among them, the compound (I-1) (celloxide 2021P and the like) is used alone, or the compound (I-1) (celloxide 2021P and the like) and other alicyclic epoxy compounds represented by the formula (I) and It is preferable to use together.

[1-2. Compound (B)]
The compound (B) may be a compound having one or more alicyclic epoxy groups in the molecule (for example, 1 to 6, preferably 1 to 3) and not containing an ester group, There is no particular limitation in other respects. Moreover, as a compound (B), only 1 type may be used and 2 or more types may be mixed and used.

The compound (B) is preferably a compound having a cyclohexene oxide group from the viewpoints of transparency and heat resistance. The cyclohexene ring of the cyclohexene oxide group includes a C _1-12 alkyl group such as a methyl group (particularly a C _1-4 alkyl group) and a C _2-12 alkenyl group such as a vinyl group (particularly a C _2-4 alkenyl group). Group), a C _1-12 alkyloxiranyl group such as an oxiranyl group and a methyloxiranyl group (particularly a _C1-4 alkyloxiranyl group), and a substituent such as a formyl group. It is not necessary, but it is preferable to have it. When it has a substituent, the substituent may be singular or plural, and when there are a plurality of substituents, these substituents may be the same or different. .

The compound (B) is particularly preferably a compound represented by the following formula (II) from the viewpoints of transparency and heat resistance.

In the above formula (II), Y represents a hydrogen atom or a substituent such as a C _1-12 alkyl group (particularly a C _1-4 alkyl group), and Z represents a C ₁ such as a hydrogen atom or a methyl group. _-12 alkyl group (particularly, C _1-4 alkyl group), C _2-12 alkenyl groups such as vinyl group (in particular, C _2-4 alkenyl group), oxiranyl group, C _1-12 such as methyl oxiranyl group A substituent such as an alkyloxiranyl group (particularly a _C1-4 alkyloxiranyl group) or a formyl group is shown. Moreover, it is preferable that the cyclohexene ring of the compound represented by the above formula (II) has no substituent other than Y or Z. Moreover, it is preferable that at least one of Y and Z is not a hydrogen atom.

  As a typical example of the compound (B), 1,2,8,9-diepoxylimonene represented by the following formula (II-1) [1,2-epoxy-4- (2-methyloxiranyl) ) -1-methylcyclohexane, trade name “Celoxide 3000”, manufactured by Daicel Corporation], 1,2-epoxy-4-vinylcyclohexane (4-vinylcyclohexene monoepoxide, product represented by the following formula (II-2) Name "Celoxide 2000", manufactured by Daicel Corporation).

[1-3. Hydroxyl-containing compound (C)]
The hydroxyl group-containing compound (C) is not particularly limited as long as it has three hydroxyl groups in the molecule. Specifically, for example, polyester triol, glycerin, trimethylol ethane, trimethylol propane, adamantane triol and the like can be mentioned, but not particularly limited, polyester triol containing an ester group is preferable from the viewpoint of compatibility with an epoxy compound, Polycaprolactone triol is particularly preferred.

  As a hydroxyl-containing compound (C), only 1 type may be used and 2 or more types may be mixed and used.

  The polycaprolactone triol is not particularly limited, but a compound represented by the following formula (III) is preferable.

In the above formula (III), a, b and c are all integers of 1 or more, and are each in the range of, for example, 1 to 30, preferably 1 to 10, and a + b + c is preferably in the range of 3 to 30. R ¹ is a trivalent hydrocarbon group, preferably a trivalent aliphatic hydrocarbon group, and R ¹ preferably has 3 to 20 carbon atoms, more preferably 3 to 15 carbon atoms, still more preferably A typical example of R ¹ within the range of 3 to 10 includes trivalent hydrocarbon groups represented by the following formulas (VI-1) to (VI-4).

  Examples of commercially available products of polycaprolactone triol include, for example, Plaxel 303, Plaxel 305, Plaxel 308, Plaxel 312, Plaxel L312AL, Plaxel 320, Plaxel 320ML, Plaxel L320AL, Plaxel L330AL; However, from the viewpoint of easy mixing and no risk of precipitation, polycaprolactone triol that is liquid at room temperature, such as Plaxel 305, is preferable.

[1-4. Oxetane compound (D)]
The radiation curable composition may or may not contain an oxetane compound (D). The oxetane compound (D) is not particularly limited as long as it has one or more (for example, 1 to 6, preferably 1 to 3) oxetanyl groups in the molecule.

  Examples of the oxetane compound (D) include 3,3-bis (vinyloxymethyl) oxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, and 3-ethyl. -3- (hydroxymethyl) oxetane, 3-ethyl-3-[(phenoxy) methyl] oxetane, 3-ethyl-3- (hexyloxymethyl) oxetane, 3-ethyl-3- (chloromethyl) oxetane, 3, 3-bis (chloromethyl) oxetane, 1,4-bis [(3-ethyl-3-oxetanylmethoxy) methyl] benzene, bis ([1-ethyl (3-oxetanyl)] methyl) ether, 4,4′- Bis [(3-ethyl-3-oxetanyl) methoxymethyl] bicyclohexyl, 1,4-bis [(3-ethyl- -Oxetanyl) methoxymethyl] cyclohexane, 1,4-bis ([(3-ethyl-3-oxetanyl) methoxy] methyl) benzene, 3-ethyl-3 ([(3-ethyloxetan-3-yl) methoxy] methyl ) Oxetane, xylylene bisoxetane and the like. In the present invention, for example, commercial products such as trade names “OXT221”, “OXT121” (manufactured by Toagosei Co., Ltd.), and trade names “OXBP” (manufactured by Ube Industries) can also be used.

[1-5. Photoacid generator (E)]
Although it does not restrict | limit especially as a photo-acid generator (E), The thing which generate | occur | produces an acid by ultraviolet irradiation and has an effect | action which starts cationic polymerization by the generated acid is preferable.

  Examples of the photoacid generator (E) include triarylsulfonium hexafluorophosphates (for example, p-phenylthiophenyldiphenylsulfonium hexafluorophosphate) and sulfonium salts such as triarylsulfonium hexafluoroantimonate (in particular, triaryls). Sulfonium salt); diaryliodonium hexafluorophosphate, diaryliodonium hexafluoroantimonate, bis (dodecylphenyl) iodonium tetrakis (pentafluorophenyl) borate, iodonium [4- (4-methylphenyl-2-methylpropyl) phenyl] hexafluoro Iodonium salts such as phosphate; phosphonium salts such as tetrafluorophosphonium hexafluorophosphate; N-hexylpi It can be mentioned pyridinium salts such as tetrafluoroborate or the like. These can be used alone or in combination of two or more.

  As a photo-acid generator (E), you may use commercial items, such as brand name "CPI-100P" and "CPI-101A" (above, San Apro company make), for example.

[1-6. Other ingredients]
In addition to the components (A) to (E), the radiation curable composition is preferably an organic solvent for adjusting the viscosity as required (an organic solvent capable of cationic curing). 3-butanediol, etc., all of which are manufactured by Daicel Corporation as specific examples of commercially available products), inorganic fillers for improving adhesive strength and screen printability (for example, Denki Kagaku Kogyo Co., Ltd.) Spherical silica manufactured by FB-5SDC, FB-3SDC, etc.) and silane coupling agents that improve adhesion strength (for example, Dynasylan AMEO, Dynasylan GLYMO, etc. manufactured by Evonik Degussa Japan), coating performance Leveling agents (for example, BYK-307, BYK-333, etc., manufactured by BYK Japan) and other additives may be contained within a range not impeding the effects of the present invention.

[2. adhesive]
The adhesive described in the present specification is not particularly limited as long as it is made of the radiation curable composition. The preferable aspect of the said adhesive agent can be considered similarly to the preferable aspect of the adhesive agent for polarizing plate manufacture of this invention mentioned later. As a preferable use of the adhesive, in addition to a polarizing plate production use, a backlight light guide plate use and a film coat use for a liquid crystal display can be considered.

[3. Adhesive for polarizing plate production]
The adhesive for producing a polarizing plate of the present invention is not particularly limited as long as it is composed of the radiation curable composition.

  As described in Japanese Patent Application Laid-Open No. 2008-257199 or Japanese Patent Application Laid-Open No. 2011-28234, there is an attempt to increase curability by adding a photosensitizer to an adhesive. However, although the photosensitizer increases curability, there is a risk of an increase in viscosity due to room lighting during work. Since the adhesive for producing a polarizing plate of the present invention increases the curability by blending the hydroxyl group-containing compound (C) having three hydroxyl groups in the molecule, there is little increase in viscosity due to room lighting during work, and From the viewpoint of being particularly useful for applications used in polarizing plates, it is preferable that no photosensitizer is contained.

  The adhesive for producing a polarizing plate of the present invention has an adhesive strength evaluated by a method described later of, for example, 2.0 N / 25 mm or more (for example, 2.0 to 4.0 N / 25 mm), preferably 2. It is 5N / 25mm or more (for example, 2.5-4.0N / 25mm), More preferably, it is 3.0N / 25mm or more (for example, 3.0-4.0N / 25mm).

  The polarizing plate production adhesive of the present invention has a degree of polarization of the polarizing plate after various weather resistance tests such as a wet heat test, a temperature impact test, and a high temperature holding test evaluated by the methods described later, for example, 80%. Or more (for example, 80 to 99%), preferably 85% or more (for example, 85 to 99%), and more preferably 90% or more (for example, 90 to 99%).

[4. Polarizing plate and manufacturing method of polarizing plate]
The polarizing plate of this invention should just be a polarizing plate which adhere | attaches a protective film on the at least one surface of a polarizing film using the said adhesive agent for polarizing plate manufacture, and is not restrict | limited in particular at another point.

As a method for producing a polarizing plate by adhering a protective film to at least one surface of the polarizing film using the adhesive for producing a polarizing plate, for example, between the polarizing film and the protective film by a conventionally known method After applying a polarizing plate manufacturing adhesive to the film and pressure-bonding the protective film coated with the polarizing plate manufacturing adhesive with a roller or the like and the polarizing film, i-line (365 nm), h-line (405 nm), g -A polarizing plate is obtained by irradiating light (radiation) containing a line (436 nm) etc. by illumination intensity 10-1200 mW / cm < ² > and irradiation light quantity 20-2500 mJ / cm < ² >, and hardening a photocurable adhesive composition. be able to. From the viewpoint of suppressing deterioration of the protective film and the polarizing film due to radiation such as ultraviolet rays and from the viewpoint of productivity, the irradiation light amount is preferably ^{20 to} 600 mJ / cm ² , more preferably ²⁰ to 300 mJ / cm ² . In particular, when the irradiation light quantity is 300 mJ / cm ² or less, there is a great advantage that the deterioration of the protective film and the polarizing film due to the radiation is dramatically reduced. Moreover, after applying the adhesive for polarizing plate manufacture with a bar coater, a roll coater, a gravure roll, etc. and sticking a protective film on at least one surface of a polarizing film, i-line, h-line, g-line, etc. It is also possible to obtain a polarizing plate by irradiating a radiation containing the same as in the above case to cure the photocurable adhesive composition. A polarizing plate can also be obtained by applying an adhesive for producing a polarizing plate between the protective film and the polarizing film (upper and lower layers) and irradiating and adhering radiation from one side in the same manner as described above. When viewed from the side irradiated with radiation, light in the ultraviolet region reaches only about one third on the lower surface of the polarizing film. Therefore, it is curable by adding a hydroxyl group-containing compound (C) having three hydroxyl groups in the molecule. The adhesive for producing a polarizing plate of the present invention, which is improved, is particularly useful.

[4-1. Polarizing film]
The polarizing film is not particularly limited, and specific examples include a polyvinyl alcohol polarizing film produced by adsorbing a dichroic dye on a polyvinyl alcohol resin film and uniaxially stretching the dichroic dye.

  The polyvinyl alcohol resin used for the polarizing film is usually obtained by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, and the like. The saponification degree of the polyvinyl alcohol-based resin is not particularly limited, but is preferably about 85 to 100 mol%. The polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol resin is not particularly limited, but is preferably about 1,000 to 10,000.

  However, the polyvinyl alcohol resin is not limited to those obtained by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, and a small amount of unsaturated carboxylic acid (including salts, esters, amides, nitriles, etc.) , Modified polyvinyl alcohols containing components copolymerizable with vinyl acetate, such as olefins having 2 to 30 carbon atoms (including ethylene, propylene, n-butene, isobutene, etc.), vinyl ethers, unsaturated sulfonates, etc. Resin or the like may be used.

  The weight average molecular weight of the polyvinyl alcohol-based resin is not particularly limited, but is preferably 60000 to 300000.

  What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizing film. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method.

  The method for producing the polarizing film is not particularly limited. For example, a step of dyeing a polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye, a polyvinyl alcohol type on which the dichroic dye is adsorbed It is manufactured by a manufacturing method including a step of treating a resin film with a boric acid aqueous solution, a step of uniaxially stretching a polyvinyl alcohol-based resin film, and the like. The step of dyeing a polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye, and the step of treating the polyvinyl alcohol resin film adsorbed with the dichroic dye with an aqueous boric acid solution are simultaneously performed. You can go.

  Uniaxial stretching may be performed before dyeing with a dichroic dye, may be performed simultaneously with dyeing, or may be performed after dyeing. In uniaxial stretching, it may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a hot roll. Further, it may be dry stretching such as stretching in the air, or may be wet stretching in which stretching is performed in a state swollen with a solvent. The draw ratio is preferably about 1.5 to 10 times.

  For example, the polyvinyl alcohol resin film is dyed with a dichroic dye by immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. Although it does not restrict | limit especially as a dichroic pigment | dye, For example, an iodine, a dichroic organic dye, etc. are used.

  The dyeing method when iodine is used as the dichroic dye is not particularly limited. For example, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is employed. The content of iodine in this aqueous solution is preferably about 0.01 to 0.5 parts by weight with respect to 100 parts by weight of water, and the content of potassium iodide is preferably about 100 parts by weight of water. About 0.5 to 10 parts by weight. The immersion time (dyeing time) in this aqueous solution is preferably about 30 to 300 seconds.

  The boric acid treatment after dyeing with a dichroic dye is performed by immersing the polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution. The boric acid content in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight with respect to 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The content of potassium iodide in the boric acid-containing aqueous solution is usually about 1 to 20 parts by weight with respect to 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually about 10 to 1200 seconds.

  As described above, it is possible to produce a polarizing film in which a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol-based resin film. The thickness of the polarizing film can be about 10 to 40 μm.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[1. Preparation of radiation curable composition]
Components (A) to (E) were added to a container equipped with a stirrer at the blending ratio shown in Table 1, and stirred for 4 hours to mix uniformly. Stirring was stopped and the mixture was allowed to stand for 24 hours to obtain a radiation curable composition used in Examples 1 to 4. Similarly, the radiation curable composition used for Comparative Examples 1-5 was obtained. In addition, the compound name of each component in Table 1 is as follows.
(A) component:
Celoxide 2021P: 3,4-epoxycyclohexylmethyl (3,4-epoxy) cyclohexanecarboxylate (manufactured by Daicel Corporation, epoxy equivalent = 126)
(B) component:
Celoxide 3000: 1,2,8,9-diepoxy limonene (manufactured by Daicel Corporation, epoxy equivalent = 84)
Celoxide 2000: 1,2-epoxy-4-vinylcyclohexane (manufactured by Daicel Corporation, epoxy equivalent = 62)
(C) component:
PLACCEL 305: polycaprolactone triol, molecular weight 550
(Daicel Corporation, hydroxyl equivalent = 183)
Component (C ′) (hydroxyl group-containing compound having two hydroxyl groups in the molecule):
PLACCEL 205: polycaprolactone diol, molecular weight 530
(Daicel Corporation, hydroxyl equivalent = 265)
PLACCEL CD205PL: polycarbonate diol, molecular weight 500
(Daicel Corporation, hydroxyl equivalent = 250)
(D) component:
OXT-221: Aron Oxetane 221
(Toa Gosei Co., Ltd., oxetanyl equivalent = 107)
(E) component:
CPI-100P: Diphenyl [4- (phenylthio) phenyl] sulfonium hexafluorophosphate (manufactured by San Apro Co., Ltd.)

[2. Manufacture or preparation of adhesive substrate]
[PVA film (polarizing film)]
A dyeing solution was prepared by dissolving 20 parts by weight of boric acid, 0.2 parts by weight of iodine, and 0.5 parts by weight of potassium iodide in 480 parts by weight of water. After immersing a PVA (polyvinyl alcohol) film (Vinylon film # 40, manufactured by Aicello) for 30 seconds in this dyeing solution, the film was stretched twice in one direction and dried to obtain a PVA film having a thickness of 30 μm. Produced.

[Protective film]
A PMMA (polymethyl methacrylate) film was used as the protective film. The protective film was subjected to corona discharge treatment on the film surface with a discharge amount of 320 W · min / m ² using a corona surface treatment device (“Corona Surface Modification Evaluation Device (TEC-4AX)” manufactured by Kasuga Electric Co., Ltd.). Bonding was performed within 1 hour after the surface treatment.

[3. Production of polarizing plate]
[Examples 1 to 4, Comparative Examples 1 to 5]
The obtained radiation curable composition was coated on a PMMA film (protective film) using a wire bar coater # 3, and a PVA film was applied thereon using a metal roller so that bubbles and other defects would not enter. Pasted. Next, the radiation curable composition is coated on the PMMA film (protective film) using a wire bar coater # 3, and is pasted on the bonded PVA film so that bubbles and other defects do not enter. Combined. On a glass plate, a four-way despite bonded taped, high pressure mercury lamp (UVC-02516S1AA02: manufactured by Ushio Inc., illuminance 120 mW / cm ^2, irradiation amount 199mJ / cm ²⁾ was irradiated with light.

[4. Evaluation]
The viscosity of the obtained radiation curable composition and the peel strength (adhesiveness) of the polarizing plate were evaluated by the following methods. The results are shown in Table 1. In the obtained radiation curable composition, [the sum of the total number of epoxy groups of the compounds (A) and (B) in the composition and the total number of oxetanyl groups of the oxetane compound (D)] / [in the composition Total number of hydroxyl groups of the hydroxyl group-containing compound (C)], and [Total number of epoxy groups of the compound (B) in the composition] / [Total number of epoxy groups of the compound (A) and compound (B) in the composition and the oxetane compound ( The sum of D) with the total number of oxetanyl groups] is also shown in Table 1. In the case of Comparative Examples 2 and 3, [the sum of the total number of epoxy groups of the compound (A) and the compound (B) in the composition and the total number of oxetanyl groups of the oxetane compound (D)] / [hydroxyl group content in the composition] The value of the total number of hydroxyl groups of the compound (C ′) is shown in parentheses [].

(Peeling strength of polarizing plate)
The peel strength of the produced polarizing plate was measured according to “JIS K6854-4 Adhesive—Peel Adhesion Strength Test Method Part 4: Floating Roller Method”. The produced polarizing plate was fixed on a metal plate (made of stainless steel, dimensions: length 200 mm, width 25 mm, thickness 1.5 mm) with a double-sided adhesive tape (ST-416P, manufactured by Sumitomo 3M). In the polarizing plate, the end in the longitudinal direction was peeled between the PVA film and the protective film using a cutter knife. According to JIS method, when a sample is attached to a floating roller, the edge of the peeled film sample is fixed to a gripping tool of a tensile tester, and the gripping tool is raised at a speed of 300 mm / min by the tensile tester, and the film peels off. The average peel force (N / 25 mm) was measured.
The adhesive force between PMMA and PVA on the side opposite to the UV irradiation surface was measured. ○ represents an adhesive force of 2.5 N / 25 mm or more, Δ represents an adhesive force of 2 to 2.5 / 25 mm, and × represents an adhesive force of less than 2 N / 25 mm.

(Evaluation of heat and humidity resistance, thermal shock resistance, and high temperature resistance)
As shown below, wet weather test, temperature impact test, or high temperature holding test various weather resistance tests, by visually observing the polarizing plate before and after the test, respectively, wet and heat resistance of the polarizing plate, thermal shock resistance, and The high temperature resistance was evaluated. As evaluation criteria for resistance to moist heat, thermal shock resistance, and high temperature retention, the polarizing plate appearance after various tests was determined by measuring the degree of polarization of the polarizing plate after various weather resistance tests as follows. The results are shown in Table 1.

(Measurement of degree of polarization)
Using an elliptical polarization measuring device (KOBRA-WPR, manufactured by Oji Scientific Instruments), the degree of polarization of the polarizing plate after various weather resistance tests was measured. Table 1 shows the degree of polarization at a wavelength of 748 nm. In addition, when the degree of polarization is less than 80%, color loss of the polarizing plate can be visually observed, but when it is 85% or more, no change is visually observed. In this study, the difference in the degree of polarization was small before and after the test at other wavelengths (446, 498, 548, and 630 nm).

  The wet heat test was performed under the conditions of a temperature of 60 ° C., a relative humidity of 90%, and 500 hours, and the polarization degree of the polarizing plate after the test was evaluated (wavelength 748 nm). The results are shown in Table 1. A indicates 90% or more, ○ indicates 85% or more and less than 90%, Δ indicates 80% or more and less than 85%, and X indicates less than 80%.

  The temperature impact test was performed under the conditions of a temperature of −40 ° C. to 80 ° C., 1 cycle 30 minutes, 100 cycles, and the polarization degree of the polarizing plate after the test was evaluated (wavelength 748 nm). The results are shown in Table 1. A indicates 90% or more, ○ indicates 85% or more and less than 90%, Δ indicates 80% or more and less than 85%, and X indicates less than 80%.

  A high temperature holding test was conducted under the conditions of a temperature of 80 ° C. for 100 hours, and the polarization degree of the polarizing plate after the test was evaluated (wavelength 748 nm). The results are shown in Table 1. A indicates 90% or more, ○ indicates 85% or more and less than 90%, Δ indicates 80% or more and less than 85%, and X indicates less than 80%.

<About Table 1>
[The sum of the total number of epoxy groups of the compound (A) and the compound (B) in the composition and the total number of oxetanyl groups of the oxetane compound (D)] / [the total number of hydroxyl groups of the hydroxyl group-containing compound (C) in the composition] 6.0 or less, and [total number of epoxy groups of compound (B) in composition] / [total number of epoxy groups of compound (A) and compound (B) in composition and total oxetanyl of oxetane compound (D) Examples 1 to 4 having a sum of the number of bases of 0.4 or less had an adhesive strength of 2.5 N / 25 mm or more, and the results of various weather resistance tests were good.

  In Comparative Example 1 in which the alicyclic epoxy compound only contains the ester group 2021P, the adhesive force, the wet heat test, and the temperature impact test result were good, but the high temperature holding test result was not preferable. The reason for the above results is that, in the examples, the amount of the compound (A) such as Celoxide 2021P is less than that of Comparative Example 1, and hydrolysis of the ester moiety is suppressed, resulting in improved optical properties. Conceivable. In addition, the said mechanism is estimation and does not limit the scope of the invention.

  Comparative Examples 2 and 3 using the compound (C ′) having only two hydroxyl groups in the molecule instead of the hydroxyl group-containing compound (C) having three hydroxyl groups in the molecule did not have good adhesion and weather resistance. .

  Increase the amount of compound (B) added, [total number of epoxy groups of compound (B) in composition] / [total number of epoxy groups of compound (A) and compound (B) in composition and oxetane compound (D) In Comparative Example 4 in which the sum of the total number of oxetanyl groups] exceeds 0.4, the initial adhesive force is less than 2 N / 25 mm (1.5 N / 25 mm), and the result is not suitable as an adhesive for producing a polarizing plate. It became.

  Moreover, the addition amount of compound (C) is reduced, and [the sum of the total number of epoxy groups of compound (A) and compound (B) in the composition and the total number of oxetanyl groups of oxetane compound (D)] / [in the composition Comparative Example 5 in which the total number of hydroxyl groups of the hydroxyl group-containing compound (C)] was a value exceeding 6.0 is: adhesion, appearance of polarizing plate after wet heat test, appearance of polarizing plate after temperature shock test, high temperature holding test As a result, it was inferior in any of the appearances of the polarizing plate later.

  According to the adhesive for producing a polarizing plate of the present invention, for a polarizing plate formed by adhering a protective film using the same, while maintaining high adhesiveness of the protective film, a wet heat test, a temperature impact test, and a high temperature holding test. Since the protective film of the polarizing plate does not peel off even after various weather resistance tests and the reliability can be secured, it is particularly useful as a material applicable to an optical member such as a polarizing plate.

Claims (5)

Compound (A) having at least one alicyclic epoxy group in the molecule and containing an ester group,
Compound (B) having at least one alicyclic epoxy group in the molecule and not containing an ester group,
A radiation curable composition comprising a hydroxyl group-containing compound (C) having three hydroxyl groups in the molecule, and a photoacid generator (E),
The radiation curable composition contains or does not contain an oxetane compound (D) having one or more oxetanyl groups in the molecule,
[The sum of the total number of epoxy groups of the compound (A) and the compound (B) in the composition and the total number of oxetanyl groups of the oxetane compound (D)] / [the total number of hydroxyl groups of the hydroxyl group-containing compound (C) in the composition] 6.0 or less,
[Total number of epoxy groups of compound (B) in composition] / [sum of total number of epoxy groups of compound (A) and compound (B) in composition and total number of oxetanyl groups of oxetane compound (D)] is 0. An adhesive for producing a polarizing plate, comprising a radiation curable composition having 4 or less. The adhesive for polarizing plate manufacture of Claim 1 whose compound (A) is a compound represented by following formula (I).

(In the above formula (I), X represents a linking group containing an ester group.)   The adhesive for polarizing plate manufacture according to claim 1 or 2, wherein the hydroxyl group-containing compound (C) is polyester triol.   The polarizing plate formed by adhere | attaching a protective film on the at least one surface of a polarizing film using the adhesive agent for polarizing plate manufacture of any one of Claims 1-3. The polarizing plate according to claim 4, wherein the adhesive for producing a polarizing plate is cured by radiation irradiation with an irradiation light amount of 300 mJ / cm ² or less.