JP2011076058A - Polarizing plate and photosetting adhesive for forming polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate excellent in adhesiveness between a protective film and a polarizer and punching workability and excellent in water resistance as well. <P>SOLUTION: The polarizing plate is constituted so that both surfaces of a polyvinyl alcohol-based polarizer are each coated with a protective film via the following adhesive layer. The adhesive layer is formed by curing a photosetting adhesive containing 60 to 99.8 mass% of a radical polymerizable compound (a), 0.02 to 40 mass% of a cationic polymerizable compound (c) having a cationic polymerizable functional group but no (meth)acryloyl group, a photo-radical polymerization initiator (d), and a photo-cation polymerization initiator (e). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  Liquid crystal display devices are rapidly spreading in the market for watches, mobile phones, personal digital assistants (PDAs), notebook computers, personal computer monitors, DVD players, TVs, and the like. The liquid crystal display device visualizes the polarization state by switching of the liquid crystal, and a polarizer is used from the display principle. In particular, in applications such as TV, higher brightness, higher contrast, and wider viewing angle are required, and polarizing plates are also required to have higher transmittance, higher degree of polarization, and higher color reproducibility.

  A polarizer used in a liquid crystal display-related field or the like is usually manufactured by uniaxially stretching a material obtained by adsorbing iodine or a dye on polyvinyl alcohol (PVA). This polyvinyl alcohol-based polarizer shrinks due to heat and moisture, resulting in a decrease in polarization performance. Then, what stuck the protective film on the surface of the PVA type | system | group polarizer is used as a polarizing plate.

As an adhesive for sticking a protective film to a polarizer, an aqueous solution (PVA adhesive) of a polyvinyl alcohol resin has been widely used (see Patent Documents 1 and 2).
Patent Document 3 discloses a polarizing plate using a water-based urethane adhesive.

By the way, as represented by TV in particular, as the screen size of image display devices has been increasing in recent years, the demand for larger polarizing plates has increased, which has become an important issue.
However, in the polarizing plate using the water-based adhesive described above, the size of the polarizing plate changes due to the heat of the backlight, and the distortion caused by the change in size is localized in a part of the screen. When the image is to be displayed in black, there is a problem that so-called light omission (unevenness) that partly leaks light becomes noticeable.

For the reasons described above, it has been proposed to use a cationic polymerizable ultraviolet curable adhesive instead of the water-based adhesive (see Patent Document 4).
However, in the case of a cationic polymerizable UV curable adhesive, a dark reaction (post-polymerization) occurs after UV irradiation. Therefore, when a long cured product is formed into a take-up roll, there is a problem that curling tends to occur during storage. . In addition, the cationic polymerizable ultraviolet curable adhesive is susceptible to the influence of humidity during curing and has a problem that the cured state tends to vary. Therefore, in order to develop a uniform cured state, it is necessary to strictly control the moisture content of the PVA polarizer, not to mention the environmental humidity.
Radical polymerizable ultraviolet curable adhesives are excellent in that these problems are relatively small.

By the way, liquid crystal display devices are used in various environments as their applications expand, and high environmental resistance is required for polarizing plates constituting liquid crystal display devices.
For example, a liquid crystal display device for mobile use typified by a mobile phone is required to have high moisture and heat resistance.

As described above, the radical polymerizable ultraviolet curable adhesive is superior in various respects as compared with the cationic polymerizable curable adhesive.
However, when a radical polymerizable UV curable adhesive is used, if it is exposed to a humid heat environment for a long time, the polarization performance is likely to deteriorate, and color loss of a polarizer colored with iodine or dye occurs at the cut end. There is a problem that it is easy to do.
Moreover, under severer conditions (for example, immersed in hot water at 60 ° C.) than in a humid heat environment, color loss of the polarizer is remarkably generated.
That is, in the present situation where the usage environment of the polarizing plate is more severe, it is the actual situation that a polarizing plate having a heat and humidity resistance that exceeds the conventional polarizing plate is desired.

  Furthermore, an adhesive composition using a (meth) acrylic radical polymerizable compound and a cationic polymerizable compound has been proposed in order to easily bond a polarizing film polyvinyl alcohol film and a plastic film with sufficient strength. (Patent Document 5). However, this technique requires further improvement in punching workability.

Japanese Patent Laid-Open No. 09-258023 JP-A-2005-208456 JP 2004-37841 A JP 2008-233874 A JP 2008-260879 A

  An object of the present invention is to provide a polarizing plate having a polyvinyl alcohol-based polarizer and a protective film as constituent layers, excellent adhesion between the protective film and the polarizer and punching workability, and excellent water resistance.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned target can be achieved by the polarizing plate shown below, and have completed the present invention.
That is, the present invention includes a polyvinyl alcohol polarizer, an adhesive layer formed by curing a photocurable adhesive, and a protective film, and both surfaces of the polarizer are respectively covered with a protective film via the adhesive layer. A polarizing plate,
The photocurable adhesive includes a main agent composed of a radical polymerizable compound and a cationic polymerizable compound, a photo radical polymerization initiator, and a photo cationic polymerization initiator,
As the radical polymerizable compound, the radical polymerizable compound (a) that forms a homopolymer having a glass transition temperature of −80 ° C. to 0 ° C. is contained in the main agent in an amount of 60 to 99.8% by mass,
As the cationic polymerizable compound, containing 0.02 to 40% by mass of a cationic polymerizable compound (c) having no (meth) acryloyl group in the main agent,
The present invention relates to a polarizing plate comprising 1 to 10 parts by mass of the radical photopolymerization initiator and 0.5 to 5 parts by mass of the cationic photopolymerization initiator with respect to 100 parts by mass of the main agent.

Furthermore, the present invention includes a main agent composed of a radical polymerizable compound and a cationic polymerizable compound, a radical photopolymerization initiator, and a cationic photopolymerization initiator,
As the radical polymerizable compound, the radical polymerizable compound (a) that forms a homopolymer having a glass transition temperature of −80 ° C. to 0 ° C. is contained in the main agent in an amount of 60 to 99.8% by mass,
As the cationic polymerizable compound, containing 0.02 to 40% by mass of a cationic polymerizable compound (c) having no (meth) acryloyl group in the main agent,
Forming a polarizing plate, comprising 1 to 10 parts by mass of the radical photopolymerization initiator and 0.5 to 5 parts by mass of the cationic photopolymerization initiator with respect to 100 parts by mass of the main agent. The present invention relates to a photocurable adhesive for use.

  ADVANTAGE OF THE INVENTION According to this invention, it is a polarizing plate which uses a polyvinyl alcohol-type polarizer and a protective film as a structural layer, Comprising: The polarizing plate which is excellent in adhesiveness, stamping workability, and water resistance can be provided.

It is sectional drawing (image) which shows an example of the polarizing plate of this invention. It is a flowchart (image) which shows an example of the manufacturing method of the polarizing plate of this invention.

Hereinafter, preferred embodiments of the present invention will be described.
[Adhesive layer]
Hereinafter, the adhesive layer (or adhesive layer) constituting the polarizing plate of the present invention will be described.
The adhesive layer (reference numerals 2 and 4 in FIGS. 1 and 2) is formed by curing a photocurable adhesive.
A photocurable adhesive contains the main ingredient which consists of a photocurable compound, and a polymerization initiator. The main agent contains a radical polymerizable component (radical polymerizable compound) and a cationic polymerizable component (cation polymerizable compound).
The radical polymerizable component is a radical polymerizable compound (a) capable of forming a homopolymer having a glass transition temperature of −80 ° C. to 0 ° C. (hereinafter referred to as “radical polymerizable compound (a)” or “low Tg radical polymerization”). Radical polymerizable compound (b) (hereinafter referred to as “radical polymerizable compound (hereinafter referred to as“ radical polymerizable compound (”)”), which can form a homopolymer having a glass transition temperature of 60 ° C. to 250 ° C. b) "or" high Tg radical polymerizable compound (b) "). That is, the radical polymerizable component (a) having a glass transition temperature of −80 ° C. to 0 ° C. as the radical polymerizable component and the glass transition temperature of the homo polymer being 60 ° C. to 250 ° C. Compound (b) is optionally included.

Among the low Tg radical polymerizable compounds (a), as monofunctional ones, for example,
2-hydroxyethyl acrylate (Tg of homopolymer: −9 ° C., the same applies hereinafter),
2-hydroxypropyl acrylate (−7 ° C.), and 4-hydroxybutyl acrylate (−55 ° C.),
A hydroxyl-terminated alkyl (meth) acrylate represented by
2-methoxyethyl acrylate (−43 ° C.),
3-methoxybutyl acrylate (−47 ° C.),
Tridecyl acrylate (−65 ° C.), and tridecyl methacrylate (−37 ° C.),
An alkyl-terminated alkyl (meth) acrylate represented by:
Diethylene glycol monoethyl ether acrylate (−54 ° C.),
Ethoxydiethylene glycol acrylate (−51 ° C.),
Methoxypolyethylene glycol (n = 9) acrylate (−71 ° C.), and methoxytripropylene glycol acrylate (−75 ° C.),
An alkyl group-terminated (poly) alkylene glycol-based (meth) acrylate represented by:
Phenoxyethyl acrylate (−15 ° C.),
Trifluoroethyl acrylate (−10 ° C.),
ω-carboxy-polycaprolactone acrylate (−46 ° C.), and the like.

In addition, among the low Tg radical polymerizable compound (a), as a polyfunctional one,
Polyethylene glycol (400) diacrylate (−28 ° C.),
Polyethylene glycol (600) diacrylate (−42 ° C.),
Triethylene glycol dimethacrylate (−5 ° C.),
Ethoxylated (9) trimethylolpropane triacrylate (-19 ° C), and the like.

The photocurable adhesive in the present invention can be used by appropriately combining these materials.
As the low Tg radical polymerizable compound (a), a monofunctional compound is preferable. Even if it is a low Tg radically polymerizable compound (a), it may be unpreferable from the point of the cutter test performance mentioned later to use only a polyfunctional thing. Therefore, in order to improve the cutter test performance, when a polyfunctional compound is used as the low Tg radical polymerizable compound (a), the low Tg radical polymerizable compound (a) (100% by mass and It is preferable to suppress the content to less than 40% by mass, preferably less than 10% by mass.

Furthermore, when using the high Tg radical polymerizable compound (b) described later, the high Tg radical polymerizable compound (b) is also preferably monofunctional rather than polyfunctional. In other words, when a polyfunctional radical polymerizable compound is used as the radical polymerizable compound ((a) or (a) + (b)), the proportion thereof is less than about 40% by mass in the main agent (100% by mass), Preferably it is less than about 10% by mass.
Alternatively, the ratio of the monofunctional radical polymerizable compound (monofunctional radical polymerizable compound (a) or the sum of monofunctional radical polymerizable compounds (a) and (b)) in the radical polymerizable compound is 60 It is preferably at least mass%, more preferably at least 70 mass%, and even more preferably at least 90 mass%.

  The radical polymerizable compound (a) preferably has a homopolymer glass transition temperature of −60 ° C. to −20 ° C., more preferably a homopolymer glass transition temperature of −60 ° C. to −40 ° C.

  Among these low Tg radical polymerizable compounds (a), those having a hydroxyl group such as hydroxyalkyl (meth) acrylate are preferable from the viewpoint of improving the adhesion to a PVA polarizer, and 4-hydroxybutyl acrylate is particularly preferable. . In view of making it difficult to lower the Tg of the cured product, it is preferable not to use 2-hydroxyethyl acrylate or 2-hydroxypropyl acrylate even if it has a hydroxyl group. That is, it is preferable that the alkyl group of hydroxyalkyl (meth) acrylate has about 4 to 40 carbon atoms.

  In addition, it is preferable to further use ω-carboxy-polycaprolactone mono (meth) acrylate as the low Tg radical polymerizable compound (a) in terms of enhancing the cohesive force of the adhesive layer after curing and improving the adhesive force. . However, since ω-carboxy-polycaprolactone mono (meth) acrylate is not very curable, the type and amount of the radical polymerization initiator is appropriately selected, the lamp of the ultraviolet irradiation device is appropriately selected, the irradiation intensity is Curability can be supplemented by appropriately selecting curing conditions such as irradiation dose, or by appropriately selecting the type and thickness of the protective film. The polymerization degree (n) of caprolactone of ω-carboxy-polycaprolactone mono (meth) acrylate is not particularly limited, but it is preferably about n = 2 to 20.

For example, the radically polymerizable compound (a) that is 60 to 99.8% by mass with respect to 100% by mass of the main agent is 10 to 99.8% by mass of hydroxyalkyl (meth) acrylate such as 4-hydroxybutyl acrylate, It is preferable to combine ω-carboxy-polycaprolactone mono (meth) acrylate in each range of 0 to 50% by mass.
Moreover, when mix | blending omega-carboxy-polycaprolactone mono (meth) acrylate, 10-99.7 mass% of hydroxyalkyl (meth) acrylate and 0.01- of omega-carboxy-polycaprolactone mono (meth) acrylate are included. More preferably, it is used in the range of 50% by mass.

Examples of the optionally compounded high Tg radical polymerizable compound (b) include:
Dicyclopentanyl methacrylate (Tg of homopolymer: 180 ° C., the same shall apply hereinafter),
Trifluoroethyl methacrylate (81 ° C.),
t-butyl methacrylate (113 ° C.),
Ethyl methacrylate (65 ° C.),
Tetrahydrofurfuryl methacrylate (68 ° C.),
And isobornyl acrylate (85 ° C.) and acryloylmorpholine (106 ° C.). Of these, isobornyl acrylate and acryloylmorpholine are preferably used from the viewpoint of heat resistance.
The radical polymerizable compound (b) preferably has a homopolymer glass transition temperature of 60 ° C. to 200 ° C., and more preferably a homo polymer glass transition temperature of 80 ° C. to 150 ° C.
The photocurable adhesive in the present invention can be used by appropriately combining these materials.

In addition, Tg of each homopolymer which can be formed from the said low Tg radically polymerizable compound (a) and high Tg radically polymerizable compound (b) is a value calculated | required as follows.
An appropriate amount of each compound and initiator are put in a plastic container, irradiated with ultraviolet rays, and cured, 10 mg as a measurement sample, and 10 ° C./min or 20 using a differential scanning calorimeter (DSC) Measured at a rate of temperature rise of ° C / min.

The cationically polymerizable compound (c) having no (meth) acryloyl group (hereinafter also referred to as “cationic polymerizable compound (c)”) has a cationically polymerizable functional group and is a (meth) acryloyl group. Such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 2- (3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane- 1 such as meta-dioxane, bis (3,4-epoxycyclohexylmethyl) adipate, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, vinylcyclohexene monooxide 1,2-epoxy-4-vinylcyclohexane Compounds or oxetani having one or more alicyclic epoxy groups in the molecule And compounds having a ru group. The cationically polymerizable compound (c) plays a role of improving the water resistance of the cured adhesive layer.
Of the compounds having an alicyclic epoxy group, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate is preferably used from the viewpoint of reactivity.

In the present invention, the cationically polymerizable compound (c) is selected from those having no (meth) acryloyl group from the viewpoint of securing adhesive force and improving punchability. A cationically polymerizable compound having a (meth) acryloyl group can be used in combination with the above (c). In this case, the amount of the cationically polymerizable compound having a (meth) acryloyl group is 20 in 100% by mass of the main agent. It is necessary to suppress to less than about 10% by mass, preferably less than about 10% by mass.
Alternatively, the proportion of the cationic polymerizable compound (c) having no (meth) acryloyl group in the entire cationic polymerizable compound is preferably 50% by mass or more, and more preferably 75% by mass or more.

The main component of the photocurable adhesive contains the radical polymerizable compound (a) in the range of 60 to 99.8% by mass and the cationic polymerizable compound (c) in the range of 0.02 to 40% by mass. a): 60 to 99% by mass, cation polymerizable compound (c): preferably 1 to 40% by mass, radical polymerizable compound (a): 90 to 99% by mass, cation polymerizable compound (c): More preferably, it is 1-10 mass%.
When the amount of the low Tg radical polymerizable compound (a) is less than 60% by mass, the formed adhesive layer becomes too hard, and the adhesive strength cannot be ensured, and the punching processability is deteriorated.
On the other hand, when the amount of the low Tg radical polymerizable compound (a) is more than 99.8% by mass, that is, when the cationic polymerizable compound (c) is hardly contained, the water resistance of the formed adhesive layer is deteriorated, and the polarization When the plate is immersed in warm water, the color of the PVA polarizer is lost.

The high Tg radical polymerizable compound (b) contributes to improvement in adhesive strength when an acetylcellulose-based resin film such as triacetylcellulose is used as the protective film.
When the high Tg radical polymerizable compound (b) is used, the low Tg radical polymerizable compound (a): 60 to 75% by mass, the high Tg radical polymerizable compound (b): 0.01 to 39.98% by mass. Cationic polymerizable compound (c): 0.02 to 24.99% by mass is preferable, low Tg radical polymerizable compound (a): 60 to 70% by mass, high Tg radical polymerizable compound (b): It is more preferable that they are 10-35 mass%, cationically polymerizable compound (c): 5-20 mass%.

Alternatively, the photocurable adhesive in a preferred embodiment is a monofunctional radically polymerizable compound (a) that forms a homopolymer having a glass transition temperature of −80 ° C. to 0 ° C. as the main agent: 60 to 99.8 mass %When,
Monofunctional radically polymerizable compound (b) that forms a homopolymer having a glass transition temperature of 60 ° C to 250 ° C: 0 to 39.98% by mass;
Cationic polymerizable compound having a cationic polymerizable functional group and not having a (meth) acryloyl group (c): 0.02 to 40% by mass (provided that the total of the above (a) to (c) is 100% by mass) And)
As a polymerization initiator, radical photopolymerization initiator (d): 1 to 10 parts by mass (based on a total of 100 parts by mass of the above (a) to (c)),
Photocationic polymerization initiator (e): 0.5-5 mass parts (with respect to the total 100 mass parts of said (a)-(c)).
More preferably, the low Tg radical polymerizable compound (a): 60 to 99% by mass, the high Tg radical polymerizable compound (b): 0 to 39% by mass, and the cationic polymerizable compound (c): 1 to 40% by mass. including.

In addition to the low Tg radical polymerizable compound (a) and the high Tg radical polymerizable compound (b), another radical polymerizable compound may be added to the photocurable adhesive in the present invention. Examples of other radical polymerizable compounds include urethane acrylate, epoxy acrylate, polyester acrylate, and polyether acrylate. However, as described above, the radically polymerizable compound is preferably used in a limited blending range.
Moreover, you may add an additive suitably to the photocurable adhesive agent in this invention as needed. As the additive, a silane coupling agent is preferable in that the adhesive force with the protective film can be increased and shrinkage of the polarizing plate can be suppressed. As the silane coupling agent, those having an acryloyl group are preferable.

The photocurable adhesive in the present invention contains a photoradical polymerization initiator (d).
The radical photopolymerization initiator (d) is not particularly limited. (Merck), Ezacure KIP150, TZT (Nihon Shibel Hegner), Kayacure BMS, Kayacure DMBI, (Nippon Kayaku).
Among these, it is preferable to use DAROCUR-TPO that is photobleached in terms of enhancing the transparency of the adhesive layer after photocuring.
The blending ratio of the radical photopolymerization initiator (d) is 1 to 10 parts by mass with respect to a total of 100 parts by mass of the radical polymerizable compounds (a) and (b) and the cationic polymerizable compound (c). It is preferable that it is 1-5 mass parts.

The photocurable adhesive in the present invention contains a photocationic polymerization initiator (e).
Examples of the cationic photopolymerization initiator (e) include sulfonium salts such as UVACURE 1590 (manufactured by Daicel Cytec) and CPI-110P (manufactured by San Apro), IRGACURE 250 (manufactured by Ciba Specialty Chemicals), and WPI-113 (Wako Pure Chemical). And iodonium salts such as Rp-2074 (manufactured by Rhodia Japan).
The blending ratio of the photo cationic polymerization initiator (e) is 0.5 to 10 parts by mass with respect to 100 parts by mass in total of the radical polymerizable compounds (a) and (b) and the cationic polymerizable compound (c). Yes, it is preferably 0.5 to 5 parts by mass.

  In addition to the above-mentioned main agent and polymerization initiator, the photocurable adhesive is known in various manners such as a polymerization inhibitor, a polymerization initiation assistant, an ultraviolet absorber, a plasticizer, a colorant, an antioxidant, an antifoaming agent, and a plasticizer. These additives can be included as needed within a range not inhibiting the effects of the present invention.

[Polarizer]
A polyvinyl alcohol polarizer (reference numeral 3 in FIGS. 1 and 2) used in the polarizing plate of the present invention will be described.
Examples of the polyvinyl alcohol-based resin that forms the polarizer, that is, the base material of the polarizer, include polyvinyl alcohol and ethylene / vinyl alcohol copolymer. From the viewpoint of water resistance, the ethylene / vinyl alcohol copolymer is used. Is preferred. Examples of polyvinyl alcohol include partially saponified polyvinyl alcohol in which several tens of percent of acetate groups remain, fully saponified polyvinyl alcohol in which acetate groups do not remain, and modified polyvinyl alcohol in which hydroxyl groups have been modified. Is not to be done. A polyvinyl alcohol-type resin can be used individually by 1 type, or can also use 2 or more types together.

  Specific examples of the polyvinyl alcohol include RS-110 (degree of saponification = 99%, degree of polymerization = 1,000) manufactured by Kuraray Co., Ltd., and Kuraray Poval LM-20SO (degree of saponification) manufactured by the same company. = 40%, polymerization degree = 2,000), Gohsenol NM-14 manufactured by Nippon Synthetic Chemical Industry Co., Ltd. (degree of saponification = 99%, polymerization degree = 1.400), and the like. Polyvinyl alcohol is obtained, for example, by saponifying a polymer of a fatty acid vinyl ester such as vinyl acetate, vinyl propionate or vinyl pivalate using an alkali catalyst or the like.

  The ethylene-vinyl alcohol copolymer is obtained by saponifying a copolymer of ethylene and vinyl acetate, that is, an ethylene-vinyl acetate random copolymer, and has an acetate group of several tens mol%. The remaining saponified product is not particularly limited, and includes a partially saponified product in which only a few mol% of acetic acid groups remain or no acetic acid group remains.

  The polarizer can be obtained by forming a film of the above-described polyvinyl alcohol resin by a casting molding method or the like according to a known method, and adsorbing and orienting iodine or a dichroic dye (dichroic dye). The polarizer may be cross-linked or stretched with boric acid or the like. When stretching is performed, the shape of the polarizer 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 a film. In this specification, the term “film” includes not only a sheet having a small thickness (thickness of less than 1 mm) but also a thick sheet (for example, having a thickness of 1 to 5 mm). Although the thickness of a polarizer is not specifically limited, For example, about 10-40 micrometers is preferable.

[Protective film]
The protective film (reference numerals 1 and 5 in FIGS. 1 and 2) used for the polarizing plate of the present invention will be described.
The protective film is not particularly limited. Specifically, the moisture permeability is lower than that of an acetylcellulose-based resin film such as triacetylcellulose (TAC) that is currently most widely used as a protective film for polarizing plates, or triacetylcellulose. A transparent resin film can be used.
As a material constituting the protective film having a moisture permeability lower than that of triacetyl cellulose, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is used. Specific examples of such thermoplastic resins include cycloolefin resins and acrylic resins.

  The cycloolefin-based resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), And a graft polymer obtained by modifying these with an unsaturated carboxylic acid or a derivative thereof, a hydride thereof, or the like, and a norbornene-based resin is preferable. The norbornene resin film can be obtained by a known method described in JP-A No. 2005-164632, JP-A No. 2006-201736, JP-A No. 2008-233279, and the like.

  Various products are commercially available as cycloolefin resins. Specific examples include the product name “ZEONOR” manufactured by ZEON CORPORATION, the product name “ARTON” manufactured by JSR Corporation, the product name “TOPAS” manufactured by TICONA, and the product name “APEL” manufactured by Mitsui Chemicals, Inc. Can be mentioned.

The acrylic resin is a resin (= copolymer) mainly composed of (meth) acrylate of alkyl esters such as methyl methacrylate and butyl methacrylate as well as polymethyl methacrylate. In some cases, it is blended with another resin to form a film.
The acrylic film can be obtained by a known method described in JP-A No. 2002-361712.
Various products are commercially available for the acrylic film. Specific examples include the product name “Acryprene” manufactured by Mitsubishi Rayon Co., Ltd. and the product name “Sanduren” manufactured by Kaneka Corporation.

  The protective film used for the polarizing plate of the present invention may be the same or different on both sides of (1) and (5). For example, a cycloolefin resin film can be used for (1) and an acrylic resin film can be used for (5).

Although the thickness of a protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable. The thicknesses of the protective films (1) and (5) may be the same or different.
In addition, when providing a protective film in the both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used. For example, even when an acrylic film is used on both surfaces of a polarizer, the types of acrylic polymers may be different from each other, and additives to be blended may be different from each other, and there is no limitation.

The polarizing plate of the present invention can be obtained as follows.
That is, a first photocurable adhesive is applied to one surface of the first protective film (1) to form a first curable adhesive layer (2 ′),
A second photocurable adhesive is applied to one surface of the second protective film (5) to form a second curable adhesive layer (4 ′),
Next, the first curable adhesive layer (2 ′) and the second curable adhesive layer (4 ′) are simultaneously and / or sequentially overlapped on each surface of the polyvinyl alcohol polarizer (3),
It is produced by irradiating active energy rays from the second protective film (5) side and curing the first curable adhesive layer (2 ′) and the second curable adhesive layer (4 ′). It is preferable.

  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) have the same composition. It may be a different composition. The thicknesses of the adhesive layers (2) and (4) to be formed may be the same or different from each other, and are not particularly limited, but are generally preferably 0.1 μm to 50 μm, more preferably 0.5 μm. ˜20 μm.

Hereafter, it demonstrates for every process based on FIG.
[Step (a)]
In step (a), as shown in FIG. 2 (a), a photocurable adhesive for forming an adhesive layer is applied to one side of each of the protective films (1) and (5), and if necessary, And drying, etc. to obtain laminates (1 ′) and (5 ′) having curable adhesive layers (2 ′) and (4 ′).
The method for applying the photocurable adhesive is not particularly limited, and examples thereof include a die coating method, a roll coating method, a gravure coating method, and a spin coating method.

[Step (b)]
In step (b), as shown in FIG. 2 (b), the protective film (1) and the curable adhesive layer (2) are formed on one surface (upper surface in the figure) of the polyvinyl alcohol polarizer (3). A laminate (1 ') comprising:
A step of superimposing a laminate (5 ′) comprising a protective film (5) and a curable adhesive layer (4 ′) on the other surface (lower surface in the figure) of the polyvinyl alcohol polarizer (3). It is.

[Step (c)]
In the step (c), as shown in FIG. 2 (c), the active energy rays (6) are irradiated to the protective films (1) and (5) and the polyvinyl alcohol polarizer (3). This is a step of curing the sandwiched curable adhesive layers (2 ′) and (4 ′) to form adhesive layers (2) and (4).
Although the figure shows the case where the active energy ray (6) is irradiated from the protective film (5) side, the active energy ray (6) may be irradiated from the protective film (1) side or simultaneously from both sides. Alternatively, the active energy rays (6) may be irradiated sequentially from both sides.

The dose of the active energy ray is not particularly limited, wavelength 200 to 450 nm, the light intensity 1 to 500 mW / cm ^2, irradiation amount by irradiation so that 10~5000mJ / cm ² exposure It is preferable to do. If the amount of irradiation is less than 10 mJ / cm ^2, not promote curing of the ultraviolet curable composition, it wants performance may not be exhibited, if the amount of irradiation is higher than 5000 mJ / cm ² is very long irradiation time There is a problem in productivity. Examples of the active energy rays to be irradiated include visible light, ultraviolet rays, infrared rays, X rays, α rays, β rays, γ rays, and the like, and ultraviolet rays are particularly preferable. As the light irradiation device, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, an excimer lamp, or the like is preferably used.
After irradiation with the active energy ray (6), it can be aged at room temperature for about one week.
Through the step (c), the curable adhesive layers (2 ′) and (4 ′) are cured to form adhesive layers (2) and (4), and the polarizer (3) and the protective film (1). And (5) are bonded through the adhesive layers (2) and (4) to complete a polarizing plate (see (d) in FIGS. 1 and 2).

  The polarizing plate of the present invention is formed by applying a photocurable adhesive to one surface of the polyvinyl alcohol polarizer (3) to form a first curable adhesive layer (2 ′). Cover the surface of the first curable adhesive layer (2 ′) thus formed with the first protective film (1), and then apply a photocurable adhesive to the other surface of the polyvinyl alcohol polarizer (3). Forming a second curable adhesive layer (4 ′), covering the surface of the formed second curable adhesive layer (4 ′) with a second protective film (5), and It is produced by irradiating active energy rays from the second protective film (5) side and curing the first curable adhesive layer (2 ′) and the second curable adhesive layer (4 ′). You can also.

  As described above, the polarizing plate includes the polarizer, the adhesive layer, and the protective film as essential components, but may include other optional components. For example, a reflection layer, an antireflection layer, a hard coat layer, an antifouling layer, an antifogging layer, an antisticking layer, and the like can be included at an arbitrary position as required.

Production Example of [Polyvinyl Alcohol Polarizer] A staining solution was prepared by dissolving 20 parts by mass of boric acid, 0.2 parts by mass of iodine, and 0.5 parts by mass of potassium iodide in 480 parts by mass of water. A PVA film (Vinylon film # 40, manufactured by Aicello) was immersed in this dyeing solution for 30 seconds, and then the film was stretched twice in one direction and dried to obtain a PVA polarizer having a thickness of 30 μm.

[Example 1]
The protective film (1) is an acrylic film containing an ultraviolet absorber manufactured by Mitsubishi Rayon Co., Ltd .: HBD-002 (50 μm), and the protective film (5) does not contain an ultraviolet absorber manufactured by Nippon Zeon. A cycloolefin film and ZEONOR film “ZF-14” (100 μm) were used, and each surface was subjected to corona treatment with a discharge amount of 300 W · min / m ² . Within 1 hour after the surface treatment, each of the protective films (1) and (5) was coated with the photopolymerization composition shown in Table 1 using a wire bar coater # 3, and a curable adhesive layer (2 ′ ), (4 ′), the PVA polarizer is sandwiched between the curable adhesive layers (2 ′) and (4 ′), and the protective film (1) / curable adhesive layer (2 A laminate comprising ') / PVA polarizer (3) / curable adhesive layer (4') / protective film (5) was obtained.
Four sides of this laminate were fixed with cellophane tape so that the protective film (1) was in contact with the tin plate, and was fixed to the tin plate.
A polarizing plate was produced by irradiating ultraviolet rays having a maximum illuminance of 500 mW / cm ² and an integrated light amount of 800 mJ / cm ² from the protective film (5) side with a UV irradiation apparatus (high pressure mercury lamp manufactured by Toshiba Corporation). The thickness of each formed adhesive layer was 3 to 4 μm.

[Examples 2 to 8, Comparative Examples 1 to 7]
A polarizing plate was produced in the same manner as in Example 1 except that the photocurable polymer composition was changed as shown in Tables 1 and 2, and its performance was evaluated according to the method described later.

[Examples 9 and 10]
In Example 9, the protective film (1) is an ultraviolet absorber-containing triacetylcellulose-based film manufactured by Fuji Film Co., Ltd .: trade name “Fujitac” (80 μm), and in Example 10, the protective film (1) is ZEON A polarizing plate was obtained and evaluated in the same manner as in Example 3 except that it was replaced with a cycloolefin film and a ZEONOR film “ZF-14” (100 μm) which did not contain an ultraviolet absorber manufactured by the company.

[Example 11]
The protective film (1) is replaced with an ultraviolet absorbent-containing triacetyl cellulose film manufactured by Fuji Film Co., Ltd .: trade name “Fujitac” (80 μm), and the protective film (5) is a triacetyl cellulose containing no ultraviolet absorbent. System film: A polarizing plate was obtained and evaluated in the same manner as in Example 3 except that the product name was changed to “TACPHAN N882GL” (80 μm).

[Example 12]
The protective films (1) and (5) were prepared in the same manner as in Example 11, and as shown in Table 1, a photocurable adhesive containing a high Tg radical polymerizable compound (b) was used. Plates were obtained and evaluated similarly.

[Example 13]
Photocurable adhesion similar to Example 12 except that the protective films (1) and (5) were changed to a cycloolefin film and ZEONOR film “ZF-14” (100 μm) which do not contain an ultraviolet absorber manufactured by Nippon Zeon. A polarizing plate was obtained using an agent and evaluated in the same manner.

[Examples 14 and 15]
The protective films (1) and (5) were used in the same manner as in Example 13, and a photocurable adhesive containing a polyfunctional acrylate (b) or a cationically polymerizable compound (x) having an acryloyl group as shown in Table 1 was used. A polarizing plate was obtained in the same manner as in Example 13 and evaluated in the same manner.

[Comparative Examples 8 to 11]
Protective films (1) and (5) were made into a cycloolefin film and ZEONOR film “ZF-14” (100 μm) containing no UV absorber made by Nippon Zeon Co., Ltd., and the photocurable adhesives listed in Table 2 were used. A polarizing plate was obtained and evaluated in the same manner.

<Adhesive strength (peel strength)>
The obtained polarizing plate was cut into a size of 25 mm × 150 mm using a cutter to obtain a sample. The sample was affixed on the metal plate with a double-sided adhesive tape (DF8712S manufactured by Toyo Ink Manufacturing Co., Ltd.). The sample (polarizing plate) was previously provided with a peeling peel between the protective film and the polarizer, and the adhesive force was measured at a peel rate 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 ... ◎
1.5 (N / 25mm) or more to less than 2.5 (N / 25mm)
1.0 (N / 25mm) or more to less than 1.5 (N / 25mm) ・ ・ ・ △
Less than 1.0 (N / 25mm) ... ×

<Cutter test (adhesion test)>
The blade of a cutter was put between the protective film and the polarizer of the obtained polarizing plate, and how the blade entered when the blade was pushed forward was evaluated according to the following criteria.
The cutter blade does not easily fit between the films ... ◎
When the blade of the cutter is pushed forward, it stops when the blade enters 4-5 mm between the films ...
The blade of the cutter fits between the films without difficulty ... ×

<Punching workability>
The produced polarizing plate was punched out from the protective film (1) side using a 100 mm × 100 mm blade manufactured by Dumbbell.
The state of peeling around the punched polarizing plate was visually observed.
The ratio (%) of the peeled area with respect to the area (100 cm ² ) of the polarizing plate is 0 to less than 1% ◎, less than 1 to 2% ○, less than 2 to 3% Δ, Those having a peeled area of 3% or more were evaluated as x.

<Hot water immersion test (water resistance)>
The obtained polarizing plate was cut into a size of 25 mm × 50 mm with a cutter to obtain a sample, which was immersed in constant temperature water (60 ° C.) for 24 hours and 72 hours, respectively, and then a sample (polarizing plate) The degree of color loss was visually observed.
When the ratio (%) of the lost color area to the polarizing plate area was 0 to less than 10%, ◎, 10 to less than 30% were evaluated as ◯, and 30% or more were evaluated as ×.
The evaluation results are shown in Tables 1 and 2. Details of the compounds and protective films used are listed below Table 1.

As shown in Table 1, in any of the examples, a polarizer excellent in adhesiveness, punching workability, and water resistance could be formed.
Example 3 and Example 6 are both cases where a high-Tg radical polymerizable compound (b) is not used and a photo-curing adhesive having a low Tg radical polymerizable compound (a) content of 90% by mass is used. In Example 3, in which ω-carboxy-polycaprolactone acrylate is used in combination with 4-hydroxybutyl acrylate in addition to 4-hydroxybutyl acrylate as the low Tg radical polymerizable compound (a), the cohesive force is higher than that in Example 6, and the adhesive strength is high. Is excellent.

  Moreover, Example 12 is a case where the photocurable adhesive agent containing a high Tg radically polymerizable compound (b) is used, and compared with Example 11 which does not contain a high Tg radically polymerizable compound (b). Since it is excellent in the adhesiveness with respect to the triacetylcellulose-type film of a film, it is excellent in the point of adhesive force and water resistance.

  Furthermore, Example 13 is a case where a cycloolefin film having low moisture permeability is used for the protective film as compared with Example 12, and is more excellent in terms of water resistance.

On the other hand, Comparative Example 1 using a photocurable adhesive that does not contain the cationically polymerizable compound (c) has poor water resistance even for 24 hours.
In Comparative Examples 2 to 5 and 10 having a low content of the low Tg radical polymerizable compound (a), the cured adhesive layer is too hard, or the adhesive force is small and the punching processability is not good.

  Further, Comparative Examples 6 and 7 have a low content of the low Tg radical polymerizable compound (a), and instead of the monofunctional high Tg radical polymerizable compound (b), a trifunctional radical polymerizable compound and a cationic polymerizable compound are used. In this case, a compound having a cationic polymerizable functional group and a (meth) acryloyl group was used instead of the compound (c), and the adhesive force was extremely small.

In Comparative Examples 8 and 9, although the content of the low Tg radical polymerizable compound (a) is sufficient, a compound having a cationic polymerizable functional group and a (meth) acryloyl group is used instead of the cationic polymerizable compound (c). In this case, the adhesive strength was extremely small.
In Comparative Examples 4 to 9, although the adhesive force was very small, the water resistance was considered to be one of the reasons that the adhesiveness by the cutter test was good.

DESCRIPTION OF SYMBOLS 1,5 Protective film 2 1st adhesive bond layer 3 Polyvinyl alcohol-type polarizer 4 2nd adhesive bond layer 1 'Laminated body of protective film (1) and layer (2') which consists of curable composition 5 ' Laminated body of protective film (5) and layer (4 ') comprising curable composition 6 Active energy rays

Claims (11)

A polarizing plate comprising a polyvinyl alcohol polarizer, an adhesive layer obtained by curing a photocurable adhesive, and a protective film, wherein both sides of the polarizer are respectively covered with a protective film via the adhesive layer There,
The photocurable adhesive includes a main agent composed of a radical polymerizable compound and a cationic polymerizable compound, a photo radical polymerization initiator, and a photo cationic polymerization initiator,
As the radical polymerizable compound, the radical polymerizable compound (a) that forms a homopolymer having a glass transition temperature of −80 ° C. to 0 ° C. is contained in the main agent in an amount of 60 to 99.8% by mass,
As the cationic polymerizable compound, containing 0.02 to 40% by mass of a cationic polymerizable compound (c) having no (meth) acryloyl group in the main agent,
1 to 10 parts by mass of the radical photopolymerization initiator and 100 to 5 parts by mass of the cationic photopolymerization initiator, respectively, with respect to 100 parts by mass of the main agent.
A polarizing plate characterized by that.   The polarizing plate according to claim 1, wherein the radical polymerizable compound (a) is monofunctional.   The polarizing plate according to claim 1 or 2, wherein the photocurable adhesive contains a compound having an alicyclic epoxy group as the cationic polymerizable compound (c).   The polarizing plate according to claim 2, wherein the photocurable adhesive contains 4-hydroxybutyl acrylate as the radical polymerizable compound (a).   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).   As the radical polymerizable compound (a), the main agent contains 4-hydroxybutyl acrylate: 10 to 99.8% by mass and ω-carboxy-polycaprolactone mono (meth) acrylate: 0 to 50% by mass. The polarizing plate according to claim 4 or 5.   The polarizing plate of any one of Claims 1-6 in which the said photocurable adhesive agent further contains the radically polymerizable compound (b) which forms the homopolymer whose glass transition temperature is 60 to 250 degreeC.   The polarizing plate of any one of Claims 1-7 whose ratio of the said cation polymerizable compound (c) in the said cation polymerizable compound is 75 mass% or more. A main agent composed of a radical polymerizable compound and a cationic polymerizable compound, a photo radical polymerization initiator, and a photo cationic polymerization initiator,
As the radical polymerizable compound, the radical polymerizable compound (a) that forms a homopolymer having a glass transition temperature of −80 ° C. to 0 ° C. is contained in the main agent in an amount of 60 to 99.8% by mass,
As the cationic polymerizable compound, containing 0.02 to 40% by mass of a cationic polymerizable compound (c) having no (meth) acryloyl group in the main agent,
Forming a polarizing plate, comprising 1 to 10 parts by mass of the radical photopolymerization initiator and 0.5 to 5 parts by mass of the cationic photopolymerization initiator with respect to 100 parts by mass of the main agent. Photo-curable adhesive.   The photocurable adhesive for polarizing plate formation according to claim 9, wherein the radical polymerizable compound (a) is monofunctional.   The said radically polymerizable compound (a) contains 4-hydroxybutyl acrylate: 10-99.8 mass%, and (omega) -carboxy-polycaprolactone mono (meth) acrylate: 0-50 mass%. Photocurable adhesive for polarizing plate formation.

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