CN102012535A - Polarizing plate and photocurable adhesive for forming polarizing plate - Google Patents

Abstract

The present invention provides a polarizing plate, which is a polarizing plate in which both sides of a polyvinyl alcohol-based polarizer are covered with a protective film via an adhesive layer, and the adhesive layer contains 60 to 99.8% by mass of Compound (a), 0.02-40% by mass of cationic polymerizable compound (c) having cationic polymerizable functional group and no (meth)acryloyl group, photoradical polymerization initiator (d) and photocationic polymerization initiator ( The photocurable adhesive of e) is cured.

Description

Polarizing plate and photocurable adhesive for polarizing plate formation

technical field

The present invention relates to a polarizing plate used in liquid crystal display devices and the like, and a photocurable adhesive for forming the polarizing plate.

Background technique

Liquid crystal display devices are rapidly flooding the market in watches, mobile phones, personal portable terminals (PDAs), notebooks, monitors for computers, DVD players, and TVs. A liquid crystal display device is a device that visualizes a state of polarization caused by switching of liquid crystals, and a polarizer can be used based on the display principle. In particular, high brightness, high contrast, and wide viewing angle are increasingly required in applications such as TVs, and high transmittance, high polarization, and high color reproducibility are also increasingly required for polarizers.

Polarizers used in fields related to liquid crystal displays and the like are generally manufactured by uniaxially stretching polyvinyl alcohol (PVA) in which iodine or a dye has been adsorbed. This polyvinyl alcohol-based polarizer shrinks due to heat or moisture, causing a decrease in polarizing performance. Here, what bonded the protective film to the surface of the PVA type polarizer was used as a polarizing plate.

As an adhesive for adhering a protective film to a polarizer, an aqueous solution of a polyvinyl alcohol-based resin (PVA-based adhesive) has conventionally been widely used (see Patent Documents 1 and 2).

In addition, Patent Document 3 discloses a polarizing plate using a water-based polyurethane adhesive.

However, in recent years, with the advancement of the screen size of image display devices typified by TVs in particular, there has been an increasing demand for larger size polarizing plates, which has become an important issue.

However, in the polarizing plate using the above-mentioned water-based adhesive, the size of the polarizing plate changes due to the heat of the backlight, and the deformation caused by the dimensional change locally exists in a part of the screen. When it should be displayed as black, there is a problem that part of light leaks, that is, light leakage (spots) becomes conspicuous.

From the above reasons, a technique of using a cationic polymerizable ultraviolet curable adhesive instead of a water-based adhesive has been proposed (see Patent Document 4).

However, cationic polymerizable UV-curable adhesives have a dark reaction (post-polymerization) after ultraviolet irradiation, so when winding a long cured product into a roll, curling tends to occur during storage. The problem. In addition, cationic polymerizable ultraviolet curable adhesives are easily affected by humidity during curing, and there is a problem that the curing state tends to be uneven. Here, in order to express a uniform cured state, not only the ambient humidity but also the moisture content of the PVA-based polarizer must be strictly controlled.

Radical polymerizable ultraviolet curable adhesives are excellent in that such problems are relatively few.

However, liquid crystal display devices are used in various environments along with the expansion of their applications, and high environmental resistance is required for polarizing plates constituting the liquid crystal display devices.

For example, liquid crystal display devices for mobile use represented by mobile phones are required to have high moisture and heat resistance durability.

As described above, radically polymerizable ultraviolet curable adhesives are superior to cationically polymerizable curable adhesives in various respects.

However, when using a radically polymerizable UV-curable adhesive, if it is exposed to a humid and hot environment for a long time, the polarizing performance is likely to be reduced, and the color of the polarizer colored with iodine or dye is likely to fall off at the cut end. The problem.

In addition, under conditions (for example, immersion in warm water at 60° C.) harsher than a hot and humid environment, color loss of the polarizer remarkably occurs.

That is, in today's environment in which polarizing plates are used more harshly, it is true that a polarizing plate having further improved moisture and heat resistance of conventional polarizing plates is desired.

Furthermore, in order to bond the polyvinyl alcohol-based film and the plastic film of the polarizing plate with a simple and sufficient strength, an adhesive composition using a (meth)acrylic radical polymerizable compound and a cationic polymerizable compound in combination has been proposed (patent Document 5). However, this technology requires further improvement in press workability.

Patent Document 1: Japanese Patent Application Laid-Open No. 09-258023

Patent Document 2: Japanese Unexamined Patent Publication No. 2005-208456

Patent Document 3: Japanese Patent Laid-Open No. 2004-37841

Patent Document 4: Japanese Patent Laid-Open No. 2008-233874

Patent Document 5: Japanese Patent Laid-Open No. 2008-260879

Contents of the invention

The object of the present invention is to provide a polarizing plate comprising a polyvinyl alcohol-based polarizer and a protective film, which is excellent in adhesion between the protective film and the polarizer and in press workability, and is excellent in water resistance. Also excellent.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention found that the object can be achieved by the polarizing plate shown below, and completed the present invention.

That is, the present invention relates to a polarizing plate comprising a polyvinyl alcohol-based polarizer, an adhesive layer obtained by curing a photocurable adhesive, and a protective film, and is formed by A polarizing plate formed by covering both sides of the polarizer with a protective film,

The photocurable adhesive contains a main agent consisting of a radically polymerizable compound and a cationic polymerizable compound, a photoradical polymerization initiator and a photocationic polymerization initiator,

As the radical polymerizable compound, the main ingredient contains 60 to 99.8% by mass of a radical polymerizable compound (a) capable of forming a homopolymer having a glass transition temperature of -80°C to 0°C,

As the cation polymerizable compound, 0.02 to 40% by mass of a cation polymerizable compound (c) not having a (meth)acryloyl group is contained in the main ingredient,

1 to 10 parts by mass of the photoradical polymerization initiator and 0.5 to 5 parts by mass of the photocationic polymerization initiator are contained with respect to 100 parts by mass of the main agent.

Furthermore, the present invention relates to a photocurable adhesive for polarizing plate formation, characterized in that it contains a main agent consisting of a radically polymerizable compound and a cationic polymerizable compound, a photoradical polymerization initiator, and a photocationic polymerization initiator,

As the radical polymerizable compound, the main ingredient contains 60 to 99.8% by mass of a radical polymerizable compound (a) capable of forming a homopolymer having a glass transition temperature of -80°C to 0°C,

As the cation polymerizable compound, 0.02 to 40% by mass of a cation polymerizable compound (c) not having a (meth)acryloyl group is contained in the main ingredient,

1 to 10 parts by mass of the photoradical polymerization initiator and 0.5 to 5 parts by mass of the photocationic polymerization initiator are contained with respect to 100 parts by mass of the main agent.

Description of drawings

FIG. 1 is a sectional view (schematic view) showing an example of a polarizing plate of the present invention.

FIG. 2 is a flowchart (schematic diagram) showing an example of a method of manufacturing a polarizing plate of the present invention.

Symbol Description

1.5 Protective film

2 1st adhesive layer

3 polyvinyl alcohol polarizer

4 Second adhesive layer

1' Laminate of protective film 1 and layer 2' composed of curable composition

Laminate of 5' protective film 5 and layer 4' composed of curable composition

6 active energy rays

Detailed ways

Hereinafter, preferred embodiments of the present invention will be described. According to the present invention, a polarizing plate comprising a polyvinyl alcohol-based polarizer and a protective film as constituent layers, and a polarizing plate excellent in adhesiveness, press workability, and water resistance can be provided.

Adhesive layer

Hereinafter, the adhesive layer (or adhesive layer) which comprises the polarizing plate of this invention is demonstrated.

The adhesive layer (symbols 2 and 4 in FIGS. 1 and 2 ) is a layer obtained by curing a photocurable adhesive.

The photocurable adhesive contains a main agent composed of a photocurable compound and a polymerization initiator. The main ingredient includes a radical polymerizable component (radical polymerizable compound) and a cationic polymerizable component (cationically polymerizable compound).

The radically polymerizable component is a radically polymerizable compound (a) capable of forming a homopolymer having a glass transition temperature of -80°C to 0°C (hereinafter also referred to as "radically polymerizable compound (a)" or " The low Tg radically polymerizable compound (a)") may further contain, as an essential component, a radically polymerizable compound (b) (hereinafter also referred to as "radical polymerizable compound (b)" or "high Tg radical polymerizable compound (b)"). That is, as a radically polymerizable component, a radically polymerizable compound (a) having a glass transition temperature of a homopolymer of -80°C to 0°C is contained, and optionally a compound (a) having a glass transition temperature of a homopolymer of 60°C to 250°C is contained. The radically polymerizable compound (b) at °C.

Among the low Tg radically polymerizable compounds (a), examples of monofunctional compounds include: 2-hydroxyethyl acrylate (Tg of homopolymer: -9°C, the same below), 2-hydroxypropyl acrylate Hydroxy-terminated alkyl (meth)acrylate represented by ester (-7°C) and 4-hydroxybutyl acrylate (-55°C);

With 2-methoxyethyl acrylate (-43°C), 3-methoxybutyl acrylate (-47°C), tridecyl acrylate (-65°C) and tridecyl methacrylate ( -37°C) represented terminal alkyl alkyl (meth)acrylate;

Diethylene glycol monoethyl ether acrylate (-54°C), ethoxydiethylene glycol acrylate (-51°C), methoxypolyethylene glycol (n=9) acrylate (-71°C) and Alkyl-terminated (poly)alkylene glycol-based (meth)acrylate represented by methoxytripropylene glycol acrylate (-75°C);

Phenoxyethyl acrylate (-15°C), trifluoroethyl acrylate (-10°C), ω-carboxy-polycaprolactone acrylate (-46°C), etc.

In addition, among the low Tg radically polymerizable compounds (a), examples of polyfunctional compounds include polyethylene glycol (400) diacrylate (-28° C.), polyethylene glycol (600) diacrylate ( -42°C), triethylene glycol dimethacrylate (-5°C), ethoxylated (9) trimethylolpropane triacrylate (-19°C), etc.

The photocurable adhesive in the present invention can be used in combination of these materials suitably.

The low Tg radically polymerizable compound (a) is preferably a monofunctional compound. Even if it is a low Tg radically polymerizable compound (a), if only a polyfunctional compound is used, it may not be preferable in terms of performance in a cutting test to be described later. Here, in order to obtain a compound having good performance in the cleavage test, when a polyfunctional compound is used together as the low Tg radically polymerizable compound (a), in the low Tg radically polymerizable compound (a) (100% by mass) It is controlled to be less than about 40% by mass, preferably less than about 10% by mass.

Furthermore, when the high Tg radically polymerizable compound (b) mentioned later is used, this high Tg radically polymerizable compound (b) is not preferably polyfunctional, but monofunctional is preferable. In other words, when using a polyfunctional radically polymerizable compound as the radically polymerizable compound ((a) or (a)+(b)), it is preferable that the ratio thereof is less than 40% by mass in the main ingredient (100% by mass). about, more preferably less than about 10% by mass.

Alternatively, the ratio of the monofunctional radical polymerizable compound (monofunctional radical polymerizable compound (a), or the total of monofunctional radical polymerizable compounds (a) and (b)) in the radical polymerizable compound is preferably It is 60 mass % or more, More preferably, it is 70 mass % or more, More preferably, it is 90 mass % or more.

The radically polymerizable compound (a) is more preferably a compound having a glass transition temperature of a homopolymer of -60°C to -20°C, and still more preferably a compound having a glass transition temperature of a homopolymer of -60°C to -40°C.

Among these low Tg radically polymerizable compounds (a), compounds having a hydroxyl group such as hydroxyalkyl (meth)acrylate are preferable from the viewpoint of improving the adhesiveness with PVA-based polarizers, and among them, preferably 4-Hydroxybutyl acrylate. Since it is difficult to lower the Tg of the cured product, it is preferable not to use 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate even if it has a hydroxyl group. That is, the number of carbon atoms in the alkyl group of the hydroxyalkyl (meth)acrylate is preferably about 4 to 40.

In addition, it is preferable to further use ω-carboxy-polycaprolactone mono(meth)acrylate as the low Tg radical polymerizable compound (a ). However, since the curability of ω-carboxy-polycaprolactone mono(meth)acrylate is not very good, it can be achieved by either properly selecting the type or amount of the radical polymerization initiator, or suitably selecting the The curability is assisted by appropriately selecting curing conditions such as irradiation intensity and exposure amount, or appropriately selecting the type and thickness of the protective film. The degree of polymerization (n) of caprolactone of ω-carboxy-polycaprolactone mono(meth)acrylate is not particularly limited, but is preferably about n=2-20.

For example, 60 to 99.8% by mass of the radically polymerizable compound (a) is preferably 10 to 99.8% by mass of hydroxyalkyl (meth)acrylate such as 4-hydroxybutyl acrylate based on 100% by mass of the total main ingredient. , ω-carboxy-polycaprolactone mono(meth)acrylate is combined in each range of 0 to 50% by mass.

In addition, when mixing ω-carboxy-polycaprolactone mono(meth)acrylate, it is more preferable that 10 to 99.7% by mass of hydroxyalkyl (meth)acrylate, ω-carboxy-polycaprolactone mono(meth)acrylate base) acrylate is used in the range of 0.01 to 50% by mass.

Examples of the high Tg radically polymerizable compound (b) that can be mixed optionally include: dicyclopentenyl methacrylate (Tg of homopolymer: 180°C, same below), trifluoroethyl methacrylate (81 ℃), tert-butyl methacrylate (113 ℃), ethyl methacrylate (65 ℃), tetrahydrofurfuryl methacrylate (68 ℃), isobornyl acrylate (85 ℃) and acryloylmorpholine ( 106°C), etc. Among them, isobornyl acrylate and acryloylmorpholine are preferably used from the viewpoint of heat resistance.

The radically polymerizable compound (b) is more preferably a compound having a homopolymer glass transition temperature of 60°C to 200°C, and still more preferably a compound having a homopolymer glass transition temperature of 80°C to 150°C.

The photocurable adhesive of this invention can be used combining these materials suitably.

In addition, Tg of each homopolymer formed from the above-mentioned low Tg radically polymerizable compound (a) and high Tg radically polymerizable compound (b) is a value obtained by the following operation.

Put an appropriate amount of each compound and initiator in a plastic container, irradiate with ultraviolet rays, take 10 mg of the cured substance as a measurement sample, and use a differential scanning calorimeter (DSC) at 10°C/min or The measurement was carried out at a heating rate of 20°C/min.

The cationically polymerizable compound (c) not having a (meth)acryloyl group (hereinafter also referred to as "cationically polymerizable compound (c)") is a compound having a cationically polymerizable functional group and not having a (meth)acryloyl group, Examples include: 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4 -epoxy)cyclohexane-m-dioxane, bis(3,4-epoxycyclohexylmethyl)adipate, bis(3,4-epoxycyclohexylmethyl)adipate, bis(3,4-epoxycyclohexylmethyl) adipate, vinylcyclohexene monoxide, 1,2-epoxy-4-vinylcyclohexane and other compounds containing one or more alicyclic epoxy groups in one molecule or Compounds having an oxetanyl group. The cationically polymerizable compound (c) plays a role of improving the water resistance of the adhesive layer after curing.

Among compounds having an alicyclic epoxy group, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate is preferably used from the viewpoint of reactivity.

In the present invention, as the cationically polymerizable compound (c), a compound not having a (meth)acryloyl group is selected from the viewpoint of securing an adhesive force and having good press workability. Although a cation polymerizable compound having a (meth)acryloyl group can be used in combination with the above (c), the mixing amount of the cation polymerizable compound having a (meth)acryloyl group in this case is based on 100 mass of the main ingredient %, must be controlled to less than about 20% by mass, preferably less than about 10% by mass.

Alternatively, the proportion of the cationically polymerizable compound (c) having no (meth)acryloyl group in the entire cationically polymerizable compound is preferably 50% by mass or more, more preferably 75% by mass or more.

The main ingredient of the photocurable adhesive contains 60 to 99.8% by mass of the radically polymerizable compound (a), 0.02 to 40% by mass of the cationic polymerizable compound (c), preferably 60% by mass of the radically polymerizable compound (a). ~99% by mass, 1-40% by mass of the cationically polymerizable compound (c), more preferably 90-99% by mass of the radically polymerizable compound (a), and 1-10% by mass of the cationically polymerizable compound (c).

If the low Tg radically polymerizable compound (a) is less than 60% by mass, the formed adhesive layer becomes too hard, and not only the adhesive force cannot be ensured, but also the press workability is deteriorated.

On the other hand, if the low Tg radically polymerizable compound (a) is more than 99.8% by mass, that is, if the cationic polymerizable compound (c) is hardly contained, the water resistance of the formed adhesive layer will deteriorate. Soak the polarizer in warm water, and the color of the PVA polarizer will come off.

When a cellulose acetate-based resin film such as cellulose triacetate is used as a protective film, the high Tg radically polymerizable compound (b) contributes to the improvement of the adhesive force.

When using a high Tg radically polymerizable compound (b), it is preferable that the low Tg radically polymerizable compound (a) is 60 to 75% by mass, the high Tg radically polymerizable compound (b) is 0.01 to 39.98% by mass, and the cationically polymerizable 0.02 to 24.99% by mass of the active compound (c), more preferably 60 to 70% by mass of the low Tg radically polymerizable compound (a), 10 to 35% by mass of the high Tg radically polymerizable compound (b), and cationically polymerized The neutral compound (c) is 5 to 20% by mass.

Or, the photocurable adhesive in a preferred embodiment is the adhesive of following characteristics:

Monofunctional radically polymerizable compound (a) that can form a homopolymer with a glass transition temperature of -80°C to 0°C as the main ingredient: 60 to 99.8% by mass, and can form a glass transition temperature of 60°C to 250°C Homopolymer monofunctional radically polymerizable compound (b): 0 to 39.98% by mass, and cationically polymerizable compound (c) having a cationically polymerizable functional group and not having a (meth)acryloyl group: 0.02 to 40% by mass (wherein, the total of the above (a) to (c) is 100% by mass);

And as a polymerization initiator, photoradical polymerization initiator (d): 1-10 mass parts (total 100 mass parts with respect to said (a)-(c)), and photocationic polymerization initiator (e): 0.5- 5 parts by mass (100 parts by mass in total with respect to the above (a) to (c)).

More preferably, it contains 60-99 mass % of low Tg radical polymerizable compound (a), 0-39 mass % of high Tg radical polymerizable compound (b), and 1-40 mass % of cation polymerizable compound (c).

In addition to the low Tg radical polymerizable compound (a) and the high Tg radical polymerizable compound (b), other radical polymerizable compounds may be further added to the photocurable adhesive agent of this invention. Examples of other radically polymerizable compounds include urethane acrylate, epoxy acrylate, polyester acrylate, and polyether acrylate. However, as mentioned above, the radically polymerizable compound is preferably used within the limited mixing range.

Moreover, in the photocurable adhesive agent of this invention, you may add an appropriate additive as needed. A silane coupling agent is preferable as an additive because it can increase the adhesive force with a protective film and can suppress shrinkage of a polarizing plate. It is preferable to have an acryloyl group as a silane coupling agent.

The photocurable adhesive agent of this invention contains a photoradical polymerization initiator (d).

There is no particular limitation on the photoradical polymerization initiator (d), for example, IRGACURE-184, 907, 651, 1700, 1800, 819, 369, 261, DAROCUR-TPO (DAROCUR-TPO ) (manufactured by Ciba Chemical Co., Ltd.), Dejian-1173 (DAROCUR-1173) (manufactured by Merck, Esacure-KIP 150, TZT (manufactured by SiberHegner, Japan), Kayacure BMS, Kayacure DMBI (manufactured by Nippon Kayaku Co., Ltd.) and the like.

Among them, it is preferable to use photobleached DAROCUR-TPO from the viewpoint of improving the transparency of the adhesive layer after photocuring.

The mixing ratio of the photoradical polymerization initiator (d) is 1 to 10 parts by mass, preferably It is 1-5 mass parts.

The photocurable adhesive agent of this invention contains a photocationic polymerization initiator (e).

Examples of the photocationic polymerization initiator (e) include sulfonium salts such as UVACURE 1590 (manufactured by Daicel-Cytec), CPI-110P (manufactured by San-Apro), or IRGACURE 250 (manufactured by Ciba Specialty Chemicals), WPI-113 (manufactured by Wako Pure Chemical Industries, Ltd.), Rp-2074 (manufactured by Rhodia Japan Co., Ltd.), and the like.

The mixing ratio of the photocationic polymerization initiator (e) is 0.5 to 10 parts by mass, preferably 0.5 to 5 parts by mass.

The photocurable adhesive may contain, as necessary, a polymerization inhibitor, a polymerization initiation adjuvant, an ultraviolet absorber, a Various known additives such as plasticizers, colorants, antioxidants, defoamers, and plasticizers.

Polarizer

The polyvinyl alcohol-based polarizer (in FIGS. 1 and 2 , reference numeral 3 ) used in the polarizing plate of the present invention will be described.

Polyvinyl alcohol, ethylene-vinyl alcohol copolymer, etc. are mentioned as a polyvinyl-alcohol-type resin which forms a polarizer, ie, becomes a polarizer base material, However, Ethylene-vinyl alcohol copolymer is preferable from a water resistance point. Examples of polyvinyl alcohol include partially saponified polyvinyl alcohol in which several tens of acetic acid groups remain, fully saponified polyvinyl alcohol in which no acetic acid group remains, or modified polyvinyl alcohol in which hydroxyl groups are modified, but are not particularly limited. in these alcohols. A polyvinyl alcohol-type resin may be used individually by 1 type, and may use 2 or more types together.

Specific examples of the polyvinyl alcohol include RS Polymer RS-110 (saponification degree = 99%, polymerization degree = 1,000) manufactured by Kuraray Co., Ltd., Kuraray POVAL LM-20SO (saponification degree = 1,000) manufactured by the same company. =40%, degree of polymerization=2,000), Gohsenol NM-14 (degree of saponification=99%, degree of polymerization=1,400) manufactured by Nippon Synthetic Chemical Industry Co., Ltd., etc. Polyvinyl alcohol can be obtained, for example, by saponifying polymers of fatty acid vinyl esters such as vinyl acetate, vinyl propionate, and vinyl pivalate using an alkali catalyst or the like.

The above-mentioned ethylene-vinyl alcohol copolymer is a saponified product of ethylene and vinyl acetate copolymer, that is, obtained by saponifying an ethylene-vinyl acetate random copolymer. It includes saponified products with only a few mol% of acetic acid groups remaining, and completely saponified products without remaining acetic acid groups, and is not particularly limited.

The polarizer can be obtained by thinning the above-mentioned polyvinyl alcohol-based resin by methods such as casting molding, and adsorbing and aligning iodine or a dichroic dye (dichroic dye) according to a known method. The polarizer may also be cross-linked or stretched with boric acid or the like. Stretching may be performed at any stage before dyeing, simultaneously with dyeing, or after dyeing. The shape of the polarizer is not particularly limited, and examples thereof include films. In addition, in this specification, the term "film" includes not only thin objects (less than 1 mm in thickness) but also thick sheets (for example, 1 to 5 mm in thickness). The thickness of the polarizer is not particularly limited, but is preferably about 10 to 40 μm, for example.

protective film

The protective film (in FIGS. 1 and 2, reference numerals 1 and 5) used for the polarizing plate of the present invention will be described.

The protective film is not particularly limited. Specifically, a cellulose acetate-based resin film such as triacetyl cellulose (TAC), which is most widely used as a protective film for polarizing plates at present, can be used, or a moisture permeability lower than triacetyl cellulose can be used. transparent resin film.

As a material constituting the protective film having a moisture permeability lower than that of cellulose triacetate, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, and isotropy can be used. Specific examples of such thermoplastic resins include cycloolefin resins and acrylic resins.

Cycloolefin-based resins are a general term for resins polymerized with cyclic olefins as polymerized units. Specific examples include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and α-olefins such as ethylene and propylene (represented by random copolymers) ), and graft polymers modifying these with unsaturated carboxylic acids or derivatives thereof, and hydrogenated products of these, etc., preferably norbornene-based resins. The norbornene-based resin film can be obtained by known methods described in JP-A-2005-164632 , JP-A-2006-201736 , JP-A-2008-233279 and the like.

Various cycloolefin-based resins are available on the market. Specific examples include the product name "ZEONOR" manufactured by ZEON Co., Ltd., the product name "ARTON" manufactured by JSR Corporation, the product name "TOPAS" manufactured by TICONA Corporation, and the product manufactured by Mitsui Chemicals Co., Ltd. Trade name "Apel".

Acrylic resins include polymethyl methacrylate, and are resins (=copolymers) mainly composed of (meth)acrylates of alkyl esters such as methyl methacrylate and butyl methacrylate. Depending on the situation, it is blended with other resins to form a thin film. The acrylic film can be obtained by a known method described in JP-A-2002-361712 or the like.

As an acrylic film, there are various products on the market. As a specific example, the product name "Acryplen" manufactured by Mitsubishi Rayon Corporation, and the product name "Sunduren" manufactured by Kaneka Corporation are mentioned.

In the protective film used in the polarizing plate of the present invention, both surfaces of 1 and 5 may have the same composition or different compositions. For example, there is no problem even if a cycloolefin-based resin film is used in 1 and an acrylic resin film is used in 5.

The thickness of the protective film can be appropriately determined, but it is generally about 1 to 500 μm from the viewpoint of workability such as strength and handleability, and thin layer properties. Especially preferably, it is 1-300 micrometers, More preferably, it is 5-200 micrometers. The thicknesses of the protective films 1 and 5 may be the same or different.

In addition, when protective films are provided on both sides of the polarizer, protective films made of the same polymer material may be used on the inner and outer sides, or protective films made of different polymer materials may be used. For example, even when acrylic films are used on both sides of the polarizer, the types of acrylic polymers may be different from each other, and the additives to be mixed may also be different from each other, without any limitation.

The polarizing plate of the present invention can be obtained by performing the following operations.

That is, it is preferably manufactured by the following method: on the surface of the first protective film 1 side, the first photocurable adhesive is coated to form the first curable adhesive layer 2',

On the surface of the 2nd protective film 5 side, coat the 2nd photocurable adhesive agent, form the 2nd curable adhesive agent layer 4 ',

Then, on each face of the polyvinyl alcohol-based polarizer 3, simultaneously/or sequentially overlap the first curable adhesive layer 2' and the second curable adhesive layer 4',

Active energy rays are irradiated from the second protective film 5 side to cure the first curable adhesive layer 2' and the second curable adhesive layer 4'.

The curable adhesive layers 2' and 4' and the protective films 1 and 5 may be the same as or different from each other. That is, the curable adhesive layer 2' and the curable adhesive layer 4' (in other words, the first photocurable adhesive and the second photocurable adhesive) may have the same composition or different compositions. . The thicknesses of the formed adhesive layers 2 and 4 may be the same as or different from each other, and are not particularly limited, but are generally preferably 0.1 μm to 50 μm, and more preferably 0.5 μm to 20 μm.

Hereinafter, each step will be described based on FIG. 2 .

Process (a)

The step (a) is a step of applying a photocurable adhesive for forming an adhesive layer on each of the protective films 1 and 5 as shown in FIG. , and laminated bodies 1' and 5' having curable adhesive layers 2' and 4' were obtained.

It does not specifically limit as a coating method of a photocurable adhesive, For example, a die coating method, the roll coating method, the gravure coating method, the spin coating method etc. are mentioned.

process (b)

The step (b) is a step in which, as shown in FIG. 2( b ), the laminated body 1 ′ having the protective film 1 and the curable adhesive layer 2 ′ is superimposed on the polyvinyl alcohol-based polarizer 3 , respectively. On one surface (the upper surface in the figure), the laminated body 5' having the protective film 5 and the curable adhesive layer 4' is superimposed on the other surface (the lower surface in the figure) of the polyvinyl alcohol-based polarizer 3.

process (c)

Step (c) is the following step: as shown in FIG. 2(c), by irradiating active energy rays 6, the curable adhesive sandwiched between the protective films 1, 5 and the polyvinyl alcohol-based polarizer 3 Layers 2 ′, 4 ′ are cured to form adhesive layers 2 , 4 .

In the figure, although the situation of irradiating the active energy ray 6 from the protective film 5 side is shown, the active energy ray 6 may also be irradiated from the protective film 1 side, or the active energy ray may be irradiated from both sides at the same time or sequentially from both sides. Ray 6.

The irradiation amount of active energy rays is not particularly limited, but it is preferable to expose with light having a wavelength of 200 to 450 nm and an illuminance of 1 to 500 mW/cm ² so that the irradiation amount is 10 to 5000 mJ/cm ² . When the irradiation amount is less than 10 mJ/cm ² , the curing of the ultraviolet curable composition cannot be accelerated, and the desired performance may not be exhibited. When the irradiation amount exceeds 5000 mJ/cm ² , the irradiation time becomes very long, and there is a problem in productivity. Examples of the type of active energy rays to be irradiated include visible light, ultraviolet rays, infrared rays, X-rays, α-rays, β-rays, and γ-rays, among which ultraviolet rays are particularly preferred. As a light irradiation device, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, an excimer lamp, and the like are preferably used.

After the active energy ray 6 is irradiated, aging may be performed at room temperature for about one week.

Through the step (c), the curable adhesive layers 2 ′, 4 ′ are cured to become the adhesive layers 2 , 4 , and the polarizer 3 and the protective films 1 and 5 are bonded via the adhesive layers 2 , 4 . The formed polarizing plate (refer to FIG. 1, (d) in FIG. 2).

In addition, the polarizing plate of the present invention can also be produced by the following method: on one surface of the polyvinyl alcohol-based polarizer 3, a photocurable adhesive is coated to form the first curable adhesive layer 2' Cover the surface of the formed first curable adhesive layer 2' with the first protective film 1, and then apply a photocurable adhesive on the other surface of the polyvinyl alcohol-based polarizer 3, Form the second curable adhesive layer 4', cover the surface of the formed second curable adhesive layer 4' with the second protective film 5, and then irradiate active energy rays from the second protective film 5 side, The first curable adhesive layer 2' and the second curable adhesive layer 4' are cured.

The polarizing plate is a plate including a polarizer, an adhesive layer, and a protective film as essential components as described above, but may also include other arbitrary structures. For example, a reflection layer, an antireflection layer, a hard coat layer, an antifouling layer, an antifogging layer, an antisticking layer, etc. may be contained at an arbitrary position as needed.

Example

Production example of (polyvinyl alcohol-based polarizer)

20 parts by mass of boric acid, 0.2 parts by mass of iodine, and 0.5 parts by mass of potassium iodide were dissolved in 480 parts by mass of water to prepare a dyeing solution. After immersing a PVA film (vinylon film #40, manufactured by Aicello) in this dyeing solution for 30 seconds, the film was stretched twice in one direction and dried to obtain a PVA polarizer with a film thickness of 30 μm.

Example 1

The UV absorber-containing acrylic film manufactured by Mitsubishi Rayon Co., Ltd.: HBD-002 (50 μm) was used as the protective film 1, and the UV absorber-free cycloolefin film ZEONOR film "ZF-14" manufactured by Nippon Zeon Co., Ltd. was used. ” (100 μm) as the protective film 5, and corona treatment was performed on the respective surfaces with a discharge amount of 300 W·min/m ² . Within 1 hour after the surface treatment, use the ring bar coater #3 to coat the photopolymerizable composition shown in Table 1 on the protective films 1 and 5, respectively, to form curable adhesive layers 2', 4', The above-mentioned PVA polarizer is sandwiched between the curable adhesive layers 2' and 4' to obtain a protective film 1/curable adhesive layer 2'/PVA-based polarizer 3/curable adhesive. A laminate composed of layer 4'/protective film 5.

The periphery of the laminated body was fixed with cellophane tape so that the protective film 1 was in contact with the tin plate and fixed on the tin plate.

A polarizing plate was produced by irradiating ultraviolet rays with a maximum illuminance of 500 mW/cm ² and an integrated light intensity of 800 mJ/cm ² from the protective film 5 side with a UV irradiation device (manufactured by Toshiba Corporation, high-pressure mercury lamp). The thickness of each formed adhesive layer is 3-4 micrometers.

Embodiment 2～8, comparative example 1～7

Except having changed the photocurable polymer composition as shown in Table 1 and Table 2, it carried out similarly to Example 1, produced the polarizing plate, and evaluated the performance by the method mentioned later.

Examples 9 and 10

In addition to replacing the protective film 1 in Example 9 with a cellulose triacetate film containing an ultraviolet absorber manufactured by Fujifilm Co., Ltd.: trade name "FujiTac" (80 μm), the protective film 1 in Example 10 A polarizing plate was obtained in the same manner as in Example 3 except that the cycloolefin film ZEONOR film "ZF-14" (100 μm) containing no ultraviolet absorber manufactured by Nippon Zeon Co., Ltd. was used, and the same evaluation was performed.

Example 11

In addition to replacing the protective film 1 with a cellulose triacetate film containing an ultraviolet absorber manufactured by Fujifilm Co., Ltd.: trade name "FujiTac" (80 μm), and replacing the protective film 5 with a cellulose triacetate that does not contain an ultraviolet absorber Plain film: Except for the brand name "TACPHAN N882GL" (80 μm), a polarizing plate was obtained in the same manner as in Example 3, and the same evaluation was performed.

Example 12

Protective films 1 and 5 were used in the same manner as in Example 11, using a photocurable adhesive containing a high Tg radically polymerizable compound (b) shown in Table 1, and a polarizing plate was obtained in the same manner as in Example 3, and the same procedure was carried out. evaluation of.

Example 13

Except that the protective films 1 and 5 were changed to ZEONOR film ZEONOR film "ZF-14" (100 μm), which does not contain ultraviolet absorbers, manufactured by Zeon Corporation, the same photocurable adhesive was used as in Example 12, A polarizing plate was obtained, and the same evaluation was performed.

Examples 14 and 15

Protective films 1 and 5 were used in the same manner as in Example 13, using a photocurable adhesive containing a polyfunctional acrylate (b) or a cationic polymerizable compound (x) having an acryloyl group shown in Table 1, and compared with Example 1. 13 A polarizing plate was obtained in the same manner, and the same evaluation was performed.

Comparative Examples 8-11

Protective film 1, 5 is the cycloolefin film ZEONOR film "ZF-14" (100 μ. M) that does not contain ultraviolet absorber made by Zeon Co., Ltd. of Japan, and uses the photocurable adhesive agent described in Table 2 to obtain a polarizing plate. Do the same evaluation.

Adhesive force (peel strength)

The resulting polarizing plate was cut into a size of 25 mm×150 mm using a cutting machine to prepare a sample. The sample was stuck on the metal plate with double-sided adhesive tape (DF8712S manufactured by Toyo Ink Manufacturing Co., Ltd.). A peeling start was provided between the protective film of the sample (polarizing plate) and the polarizer, and the adhesive force was measured at a peeling speed of 300 mm/min in an environment of 23° C. and 50% RH. The adhesive strength in the table was evaluated according to the following criteria.

2.5(N/25mm) or more◎

Above 1.5(N/25mm)～less than 2.5(N/25mm)○

Above 1.0(N/25mm)～less than 1.5(N/25mm)△

Less than 1.0(N/25mm)×

Cutting Test (Adhesion Test)

A knife of a cutting machine was put between the protective film of the obtained polarizing plate and the polarizer, and the way of entering the knife when the knife was advanced was evaluated according to the following criteria.

The knife of the cutting machine is not easy to enter between the membranes◎

When the knife of the cutting machine is advanced, the knife stops when it enters 4~5mm between the films○

The knife of the cutting machine enters the membrane smoothly×

Stamping workability

The prepared polarizing plate was punched from the protective film 1 side using a 100 mm×100 mm knife made by Dumbbell Corporation.

The peeling state around the punched polarizing plate was observed visually.

With respect to the area of the polarizing plate (100cm ² ), the ratio (%) of the peeled area is less than 1% is ◎, 1% to less than 2% is ○, 2% to less than 3% is △, and the peeled area If it is 3% or more, it is marked as x.

Warm water immersion test (water resistance)

The obtained polarizing plate was cut into a size of 25mm×50mm using a cutting machine, and as a sample, it was immersed in constant temperature water (60°C) for 24 hours and 72 hours respectively, and the color of the sample (polarizing plate) was visually observed for color loss. degree.

The ratio (%) of the color loss area to the area of the polarizing plate was less than 10%, ⊚, 10% to less than 30%, and 30% or more.

Table 1 and Table 2 show the evaluation results. Details on the compounds used and the protective film are given below in Table 1.

As shown in Table 1, any of the examples can form a polarizer excellent in adhesiveness, press workability, and water resistance.

Both Example 3 and Example 6 used a photocurable adhesive that did not contain a high Tg radically polymerizable compound (b) and contained a low Tg radically polymerizable compound (a) of 90% by mass. The low Tg radically polymerizable compound (a) in Example 3, which used ω-carboxy-polycaprolactone acrylate in addition to 4-hydroxybutyl acrylate, had higher cohesive force than Example 6 and was excellent in adhesive force.

In addition, Example 12 is the case of using a photocurable adhesive containing a high Tg radically polymerizable compound (b). Compared with Example 11 that does not contain a high Tg radically polymerizable compound (b), the Since the protective film is excellent in adhesiveness to a cellulose triacetate film, it is excellent in adhesive force and water resistance.

Furthermore, compared with Example 12, Example 13 is the case where the cycloolefin film with low moisture permeability was used for the protective film, and it is excellent in water resistance.

On the other hand, in Comparative Example 1 using a photocurable adhesive not containing the cationically polymerizable compound (c), water resistance was not good even for 24 hours.

In addition, in any of Comparative Examples 2 to 5 and 10 in which the content of the low-Tg radically polymerizable compound (a) is small, the adhesive force may be reduced because the cured adhesive layer becomes too hard, and the punching Processability is also not good.

Furthermore, in Comparative Examples 6 and 7, the content of the low Tg radically polymerizable compound (a) was small, and a trifunctional radically polymerizable compound was used instead of a monofunctional high Tg radically polymerizable compound (b), and a compound having When a compound of a cationically polymerizable functional group and a (meth)acryloyl group is used instead of the cationically polymerizable compound (c), the adhesive force is extremely small.

Although the content of the low Tg radically polymerizable compound (a) in Comparative Examples 8 and 9 was sufficient, a compound having a cationically polymerizable functional group and a (meth)acryloyl group was used instead of the cationically polymerizable compound (c) In this case, the adhesive force is very small.

In addition, Comparative Examples 4 to 9 were excellent in water resistance although the adhesive force was extremely low, and one of the reasons for this is considered to be that the adhesiveness shown by the cutter test was good.

Claims (11)

1. A polarizing plate, characterized in that it contains a polyvinyl alcohol-based polarizer, an adhesive layer formed by curing a photocurable adhesive, and a protective film, and the two sides of the polarizer are separated by A polarizing plate formed by covering the adhesive layer with a protective film, The photocurable adhesive contains a main agent consisting of a radically polymerizable compound and a cationic polymerizable compound, a photoradical polymerization initiator and a photocationic polymerization initiator, As the radical polymerizable compound, the main ingredient contains 60 to 99.8% by mass of a radical polymerizable compound (a) capable of forming a homopolymer having a glass transition temperature of -80°C to 0°C, As the cation polymerizable compound, 0.02 to 40% by mass of a cation polymerizable compound (c) not having a (meth)acryloyl group is contained in the main ingredient, 1 to 10 parts by mass of the photoradical polymerization initiator and 0.5 to 5 parts by mass of the photocationic polymerization initiator are contained with respect to 100 parts by mass of the main agent. 2. The polarizing plate according to claim 1, wherein the radical polymerizable compound (a) is monofunctional. 3. The polarizing plate according to claim 1, wherein the photocurable adhesive contains a compound having an alicyclic epoxy group as the cationically polymerizable compound (c). 4. The polarizing plate according to claim 2, wherein the photocurable adhesive contains 4-hydroxybutyl acrylate as the radical polymerizable compound (a). 5. The polarizing plate according to claim 4, wherein the photocurable adhesive further contains ω-carboxy-polycaprolactone mono(meth)acrylate as the radical polymerizable compound (a) . 6. The polarizing plate according to claim 4 or 5, wherein the main ingredient contains 10 to 99.8% by mass of 4-hydroxybutyl acrylate, ω-carboxy-polycaprolactone mono(meth)acrylic acid 0-50% by mass of ester is used as the radical polymerizable compound (a). 7 . The polarizing plate according to claim 1 , wherein the photocurable adhesive further contains a radically polymerizable compound (b) capable of forming a homopolymer having a glass transition temperature of 60° C. to 250° C. 7 . 8 . The polarizing plate according to claim 1 , wherein the ratio of the cation polymerizable compound (c) in the cation polymerizable compound is 75% by mass or more. 9. A photocurable adhesive for polarizing plate formation, characterized in that it contains a main agent consisting of a radically polymerizable compound and a cationic polymerizable compound, a photoradical polymerization initiator and a photocationic polymerization initiator, As the radical polymerizable compound, the main ingredient contains 60 to 99.8% by mass of a radical polymerizable compound (a) capable of forming a homopolymer having a glass transition temperature of -80°C to 0°C, As the cation polymerizable compound, 0.02 to 40% by mass of a cation polymerizable compound (c) not having a (meth)acryloyl group is contained in the main ingredient, 1 to 10 parts by mass of the photoradical polymerization initiator and 0.5 to 5 parts by mass of the photocationic polymerization initiator are contained with respect to 100 parts by mass of the main agent. 10 . The photocurable adhesive for forming a polarizing plate according to claim 9 , wherein the radical polymerizable compound (a) is monofunctional. 11 . 11. The photocurable adhesive for forming a polarizing plate according to claim 10, comprising 10 to 99.8% by mass of 4-hydroxybutyl acrylate, ω-carboxy-polycaprolactone mono(meth)acrylate 0 to 50% by mass as the radical polymerizable compound (a).

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