WO2015068561A1 - Method for producing laminated optical film - Google Patents

Abstract

Provided is a method for producing a laminated optical film and containing: a pasting step for pasting together a first film and a second film with an adhesive layer therebetween formed a manner such that the post-curing thickness is no greater than 2.5 μm; and a curing step for curing the adhesive layer after pasting together the first film and second film. The first film and/or second film is an optical film, and in the pasting step, the viscosity of the adhesive layer when pasting together the first film and second film is no greater than 60 cP.

Description

Method for producing laminated optical film

The present invention relates to a method for producing a laminated optical film, and more particularly to a method for producing a laminated optical film including a step of laminating films via an adhesive layer.

Various laminated optical films are used in optical devices such as image display devices (liquid crystal display devices, organic EL display devices, etc.), one of which is a polarizing plate used in liquid crystal display devices and the like. It is. In the present specification, a laminated optical film refers to a laminate composed of a plurality of films, and at least one of the films constituting the laminate is an optical film. An optical film refers to a film used for optical applications such as being used as a member of an optical device.

A polarizing plate is usually manufactured by laminating a protective film on one or both sides of a polarizing film using an adhesive. For example, in JP 2010-230806 A (Patent Document 1), a polarizing film and a protective film are bonded via an adhesive layer made of an ultraviolet curable adhesive, and then the ultraviolet ray is irradiated to form an adhesive layer. A method for producing a polarizing plate to be cured is described.

JP 2010-230806 A

In recent years, there has been a demand for further reduction in the thickness of optical devices, and accordingly, there has been a demand for further reduction in thickness of laminated optical films such as polarizing plates incorporated therein. For this reason, when using an adhesive agent for film bonding for producing a laminated optical film, it is desirable to reduce the thickness of the adhesive layer made of the adhesive as much as possible.

However, it has been clarified by the present inventors that when the thickness of the adhesive layer is made smaller, small bubbles are generated in the entire adhesive layer. Even if these bubbles are very small, the light passing through the laminated optical film is scattered, which may have an unexpected influence on the optical function of the laminated optical film.

Therefore, an object of the present invention is to produce a laminated optical film capable of performing film bonding without causing bubbles in the adhesive layer even when the thickness of the adhesive layer interposed between the films is made smaller. It is to provide a method.

This invention provides the manufacturing method of the laminated optical film shown below.
[1] A laminating step of laminating the first film and the second film through an adhesive layer formed so that the thickness after curing is 2.5 μm or less, the first film, and the second A curing step of curing the adhesive layer after pasting the film,
At least one of the first film and the second film is an optical film,
The said bonding process WHEREIN: The manufacturing method of a laminated optical film whose viscosity of the said adhesive bond layer when bonding a said 1st film and a said 2nd film is 60 cP or less.

[2] The method for producing a laminated optical film according to [1], further including a heating step of heating the adhesive layer and adjusting the viscosity to 60 cP or less before the bonding step.

[3] The method for producing a laminated optical film according to [2], wherein, in the heating step, the adhesive layer is heated by infrared irradiation.

[4] The method for producing a laminated optical film according to [2] or [3], wherein in the heating step, the adhesive layer is heated to 40 ° C. or higher.

[5] The method for producing a laminated optical film according to any one of [1] to [4], wherein the adhesive constituting the adhesive layer is a solventless curable adhesive.

[6] The laminated optical film according to [1], wherein the adhesive layer has a viscosity adjusted to 60 cP or less by including a solvent when the first film and the second film are bonded together. Manufacturing method.

[7] The method for producing a laminated optical film according to any one of [1] to [6], wherein the adhesive constituting the adhesive layer is an active energy ray-curable adhesive.

[8] A method for producing a laminated optical film while continuously transporting the long first film and the long second film so that the longitudinal direction thereof is the transport direction,
An application step of continuously applying an adhesive to the bonding surface of the first film or the second film to form an adhesive layer;
The bonding step of passing the first film and the second film between a pair of bonding rolls so that their conveying directions are parallel; and
The method for producing a laminated optical film according to any one of [1] to [7], comprising:

[9] The lamination according to [8], wherein an angle formed between the pair of bonding rolls by the first film and the second film passed between the pair of bonding rolls is 60 ° or less. Manufacturing method of optical film.

[10] The method for producing a laminated optical film according to [8] or [9], wherein a conveyance speed of the first film and the second film passed between the pair of bonding rolls is 10 m / min or more. .

[11] The method for producing a laminated optical film according to any one of [8] to [10], wherein a width of the first film and the second film is 0.4 to 2 m.

[12] The method for producing a laminated optical film according to any one of [1] to [11], wherein the first film is a polarizing film and the second film is a protective film.

According to the method of the present invention, a laminated optical film can be produced without generating bubbles in the adhesive layer even when the thickness of the adhesive layer interposed between the films is extremely small, 2.5 μm or less. Can do.

It is a side view which shows typically an example of the manufacturing method of the laminated optical film which concerns on this invention, and a manufacturing apparatus used therewith. It is a side view which shows typically another example of the manufacturing method of the laminated optical film which concerns on this invention, and the manufacturing apparatus used for it.

The present invention relates to a method for producing a laminated optical film by laminating a first film and a second film using a curable adhesive. At least one of the first and second films is an optical film, and typically both are optical films. The laminated optical film obtained by the method of the present invention is an optical member used as a member of an optical device such as an image display device (liquid crystal display device or the like), for example, and one typical example is a polarizing plate.

The polarizing plate includes a polarizing film as a first film that is an optical film, and a protective film as a second film that is an optical film that is laminated and bonded to one surface of the polarizing film via an adhesive layer. At least. The polarizing plate may further include a protective film as a third film laminated and bonded to the other surface of the polarizing film via an adhesive layer.

Hereinafter, the method for producing a laminated optical film according to the present invention will be described in detail with reference to embodiments. In the following description, an embodiment in which the first film is a polarizing film, the second film is a protective film, and the manufactured laminated optical film is a polarizing plate will be described. Since the problem can be similarly applied to other laminated optical films that are bonded using an adhesive, the present invention can also be suitably applied to the production of other laminated optical films.

In one embodiment, the method for producing a laminated optical film according to the present invention includes the following steps:
An application step of applying an adhesive to the bonding surface of the first film or the second film to form an adhesive layer;
It can be a method including a bonding step of bonding the first film and the second film through the adhesive layer, and a curing step of curing the adhesive layer in this order. Hereinafter, each step will be described in detail with reference to FIG. FIG. 1 is a side view schematically showing an example of a method for producing a laminated optical film according to the present invention and a production apparatus used therefor. FIG. 1 shows an example of manufacturing a polarizing plate by bonding a protective film 20 (second film) to one surface of a polarizing film 10 (first film). In general, as shown in FIG. 1, a laminated optical film such as a polarizing plate is continuously produced as a long product by performing a process in each step while continuously unwinding and transporting a long film. Can be manufactured. However, the production method of the present invention is not limited to continuous production using such a long film, and may be a method using a single wafer film.

<Application process>
Referring to FIG. 1, in this step, first, a roll (rolled product) of a long polarizing film 10 and a roll of a long protective film 20 are prepared, and these are continuously used by using an unshown unwinding device. The film is conveyed while being unwound. Each film is conveyed so that the longitudinal direction thereof is the conveyance direction. A guide roll 60 for supporting the traveling film is appropriately provided in the film conveyance path. The arrow in FIG. 1 shows the conveyance direction of a film, or the rotation direction of various rolls.

The conveyance path | route of the protective film 20 is arrange | positioned at the bonding surface side (upper side in FIG. 1) of the polarizing film to which the protective film 20 is bonded. Usually, the conveyance direction (film longitudinal direction) of the polarizing film 10 and the conveyance direction (film longitudinal direction) of the protective film 20 are parallel. In FIG. 1, although the example which bonds the protective film 20 to the one surface of the polarizing film 10 is shown, the protective film (3rd film) 21 is also bonded to the other surface of the polarizing film 10 like FIG. In this case, as shown in FIG. 2, a transport path for the protective film 21 (third film) is further provided below the polarizing film 10. When a film other than the second film is further bonded to the first film using a curable adhesive like the third film, such other film is preferably according to the method of the present invention. Although it is bonded, it is also possible to bond using a conventional method.

In this step, the adhesive coating device 30 is used to apply a curable adhesive to the bonding surface of the polarizing film 10 or the bonding surface of the protective film 20 to form an adhesive layer (not shown). In the example of FIG. 1, a curable adhesive is applied to the protective film 20 side. A means for applying the curable adhesive to the bonding surface is not particularly limited, and various application methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. When the protective film 21 (third film) is bonded to the other surface of the polarizing film 10, a curable adhesive for bonding the protective film 20 (second film), and the protective film 21 (third film). ) May be the same or different from the curable adhesive for bonding, but is preferably the same from the viewpoint of production efficiency.

The curable adhesive is applied so that the thickness of the polarizing plate, that is, the thickness after curing is 2.5 μm or less. The reason why the thickness of the adhesive layer is set to 2.5 μm or less in the present invention is that the problem of generation of bubbles occurs only when such a very thin adhesive layer is formed. Accordingly, the method of the present invention is a particularly effective means for reducing the thickness of the adhesive layer to 2.5 μm or less, and according to the present invention, the thickness of the adhesive layer is further 2.0 μm or less, and still more Even when the thickness is 1.5 μm or less, the generation of bubbles can be effectively prevented or suppressed. In addition, the thickness of an adhesive bond layer can be measured according to the method as described in the term of the Example mentioned later. The thickness of the adhesive layer after curing is usually 0.5 μm or more.

The environmental temperature at which the coating process is performed and the temperature of the curable adhesive when applied are not particularly limited. These temperatures can be, for example, about 10 to 35 ° C. (about 25 ° C. or the like).

Next, the polarizing film 10, the protective film 20, and the curable adhesive will be described.
(1) Polarizing film The polarizing film 10 as the first film can be obtained by adsorbing and orienting a dichroic dye to a polyvinyl alcohol resin, and the dichroic dye is applied to a uniaxially stretched polyvinyl alcohol resin film. Those having adsorbed and oriented are preferably used.

As the polyvinyl alcohol resin constituting the polarizing film 10, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids and acrylamides having ammonium groups.

The degree of saponification of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal and polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol resin is usually about 1000 to 10,000, and preferably about 1500 to 5,000.

A film obtained by forming such a polyvinyl alcohol resin is used as a raw film of the polarizing film 10. The method for forming the polyvinyl alcohol-based resin into a film is not particularly limited, and a known method is employed. The thickness of the polyvinyl alcohol-based raw film is, for example, about 10 to 150 μm.

The polarizing film is usually a step of uniaxially stretching the original film made of the polyvinyl alcohol resin, a step of dyeing the polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye, It is manufactured through a process of treating the adsorbed polyvinyl alcohol-based resin film with a boric acid aqueous solution and a step of washing with water after the treatment with the boric acid aqueous solution.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after the dyeing of the dichroic dye. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, you may uniaxially stretch in these several steps.

In the uniaxial stretching, rolls having different peripheral speeds may be uniaxially stretched or may be stretched uniaxially using a hot roll. Further, the uniaxial stretching may be dry stretching in which stretching is performed in the air, or may be wet stretching in which stretching is performed in a state where a solvent is used and a polyvinyl alcohol-based resin film is swollen. The draw ratio is usually about 3 to 8 times.

As a method for dyeing a polyvinyl alcohol resin film with a dichroic dye, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye is employed. Specifically, iodine or a dichroic dye is used as the dichroic dye. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C. Further, the immersion time (dyeing time) in this aqueous solution is usually about 20 to 1800 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution is usually about 1 × 10 ⁻⁴ to 10 parts by weight per 100 parts by weight of water, and preferably about 1 × 10 ⁻³ to 1 part by weight. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dichroic dye solution used for dyeing is usually about 20 to 80 ° C. The immersion time (dyeing time) in this aqueous solution is usually about 10 to 1800 seconds.

The boric acid treatment after dyeing with a dichroic dye can usually be performed by immersing the dyed polyvinyl alcohol resin film in a boric acid-containing aqueous solution.

The amount of boric acid in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight per 100 parts by weight of water, and preferably 5 to 12 parts by weight. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight and preferably about 5 to 12 parts by weight per 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C.

The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually about 5 to 40 ° C. The immersion time is usually about 1 to 120 seconds.

After the water washing, a drying process is performed to obtain the polarizing film 10. The thickness of the polarizing film 10 is usually about 1 to 80 μm, preferably about 5 to 40 μm. The drying process can be performed using a hot air dryer or a far infrared heater. The temperature for the drying treatment is usually about 30 to 100 ° C., preferably 50 to 80 ° C. The drying time is usually about 60 to 600 seconds, preferably 120 to 600 seconds.

The moisture content of the polarizing film 10 is reduced to a practical level by the drying treatment. The water content is usually 5 to 20% by weight, preferably 8 to 15% by weight. If the moisture content is less than 5% by weight, the flexibility of the polarizing film 10 is lost, and the polarizing film 10 may be damaged or broken after drying. Moreover, when a moisture content exceeds 20 weight%, the thermal stability of the polarizing film 10 may be inferior.

The film width of the long polarizing film 10 is not particularly limited, and can usually be about 0.2 to 2 m, but the inventors' study that the adhesive layer tends to contain bubbles as the film width increases. It has become clear. Therefore, the method of the present invention is particularly effective when the film width is large, for example, when the width of the first film is 0.4 to 2 m.

(2) Protective film The protective film 20 as the second film is laminated on the polarizing film 10 and plays at least the role of protecting the polarizing film 10. The protective film 20 is not particularly limited as long as it has translucency (preferably transparency), and can be a film made of a thermoplastic resin film or a glass material. Examples of the film made of a glass material include glass films described in JP 2012-247785 A, International Publication No. 12/090693, JP 08-283041 A, and the like.

Specific examples of the thermoplastic resin constituting the protective film 20 include, for example, polyolefin resins such as chain polyolefin resins (polypropylene resin films, polyethylene resin films, etc.) and cyclic polyolefin resins (norbornene resins); Polyester resin such as polyethylene terephthalate; (Meth) acrylic resin such as methyl methacrylate resin; Cellulose resin such as cellulose triacetate and cellulose diacetate; Polycarbonate resin; Polyvinyl alcohol resin; Polyvinyl acetate resin Polyarylate resin; Polystyrene resin; Polyether sulfone resin; Polysulfone resin; Polyamide resin; Polyimide resin; and mixtures or copolymers thereof. The protective film 20 may have a multilayer structure of resin layers made of a thermoplastic resin.

The cyclic polyolefin-based resin is a resin having a monomer unit composed of a cyclic olefin such as norbornene or a polycyclic norbornene-based monomer. For example, a hydrogenated product of a ring-opened polymer of the above cyclic olefin, two or more cyclic olefins. Hydrogenated product of ring-opening copolymer used, cyclic olefin and chain olefin (ethylene, propylene, etc.) and / or aromatic compound having vinyl group etc. (styrene, α-methylstyrene, nuclear alkyl substituted styrene, etc.), etc. And an addition polymer.

The (meth) acrylic resin constituting the (meth) acrylic resin film may be a resin mainly composed of a methacrylic resin (including 50% by weight or more), preferably a methacrylic resin. By using a (meth) acrylic resin film as a protective film, the wet heat resistance and mechanical strength of a polarizing plate and a liquid crystal panel obtained by bonding the polarizing plate to a liquid crystal cell can be further improved. In this specification, (meth) acryl refers to methacryl and / or acryl, (meth) acrylate refers to methacrylate and / or acrylate, and (meth) acrylic acid refers to methacrylic acid and / or acrylic acid. Say.

The methacrylic resin is a polymer mainly composed of methacrylic acid ester (including 50% by weight or more). The methacrylic resin may be a homopolymer of one kind of methacrylic acid ester or a copolymer of methacrylic acid ester with other methacrylic acid ester or acrylic acid ester. Examples of the methacrylic acid esters include alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate and the like. The alkyl group usually has about 1 to 4 carbon atoms. Further, the acrylate ester copolymerizable with the methacrylic acid ester is preferably an alkyl acrylate, and examples thereof include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and the like. The group usually has about 1 to 8 carbon atoms. In addition to these, the copolymer contains an aromatic vinyl compound such as styrene, a vinyl cyanide compound such as acrylonitrile, etc., which is a compound having at least one polymerizable carbon-carbon double bond in the molecule. Also good.

The (meth) acrylic resin film preferably contains acrylic rubber particles from the viewpoint of impact resistance and film-forming property of the film. The amount of the acrylic rubber particles that can be contained in the (meth) acrylic resin is preferably 5% by weight or more, more preferably 10% by weight or more with respect to 100% by weight of the (meth) acrylic resin. The upper limit of the amount of the acrylic rubber particles is not critical, but if the amount of the acrylic rubber particles is too large, the surface hardness of the film is lowered, and when the film is subjected to surface treatment, it is resistant to the organic solvent in the surface treatment agent. Solvent property decreases. Therefore, the amount of acrylic rubber particles that can be contained in the (meth) acrylic resin is preferably 80% by weight or less, and more preferably 60% by weight or less.

Acrylic rubber particles are particles having an elastic polymer mainly composed of an acrylate ester (including 50% by weight or more) as an essential component, and may be of a single layer structure consisting essentially only of this elastic polymer. Alternatively, a multilayer structure having this elastic polymer as one layer may be used. Specifically, as the elastic polymer, 50 to 99.9% by weight of an alkyl acrylate and 0 to 49.9% by weight of at least one other vinyl monomer copolymerizable therewith, A cross-linked elastic copolymer obtained by polymerization of a monomer comprising 0.1 to 10% by weight of a polymerizable cross-linkable monomer is preferably used.

Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and the like, and the alkyl group usually has about 1 to 8 carbon atoms. Examples of other vinyl monomers copolymerizable with the above alkyl acrylate include compounds having one polymerizable carbon-carbon double bond in the molecule, and more specifically, methacrylic monomers. Examples thereof include methacrylic acid esters such as methyl acid, aromatic vinyl compounds such as styrene, vinylcyan compounds such as acrylonitrile, and the like. Examples of the copolymerizable crosslinkable monomer include a crosslinkable compound having at least two polymerizable carbon-carbon double bonds in the molecule, and more specifically, ethylene glycol diester. (Meth) acrylates of polyhydric alcohols such as (meth) acrylate and butanediol di (meth) acrylate, alkenyl esters of (meth) acrylic acid such as allyl (meth) acrylate and methallyl (meth) acrylate, divinyl Examples include benzene.

The protective film 20 can contain various additives as required. Specific examples of additives include fluorescent brighteners, dispersants, surfactants, heat stabilizers, light stabilizers, ultraviolet absorbers, infrared absorbers, antistatic agents, antioxidants, lubricants, organic dyes, pigments And inorganic pigments.

The thickness of the protective film 20 is usually about 2 to 300 μm, preferably 10 μm or more, preferably 200 μm or less, more preferably 150 μm or less, and further preferably 100 μm or less. Although the film width in particular in the elongate protective film 20 is not restrict | limited, Usually, it is set as the same width as the polarizing film 10 bonded. Even when both the widths of the polarizing film 10 and the protective film 20 are as large as 0.4 to 2 m, according to the method of the present invention, the generation of bubbles can be effectively prevented or suppressed.

The protective film 20 may be a film obtained by subjecting the thermoplastic resin film to stretching. Arbitrary retardation value can be provided by extending | stretching. A protective film having a predetermined retardation characteristic is also referred to as an optical compensation film or a retardation film. Examples of the stretching treatment include uniaxial stretching and biaxial stretching. Examples of the stretching direction include a machine flow direction (MD) of an unstretched film, a direction perpendicular to the machine flow direction (TD), and a direction oblique to the machine flow direction (MD). Biaxial stretching may be simultaneous biaxial stretching in which stretching is performed simultaneously in two stretching directions, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching in another direction.

The protective film 20 has a surface treatment layer such as a hard coat layer, an antiglare layer, an antistatic layer, an antireflection layer, and an antifouling layer on the surface opposite to the bonding surface with the polarizing film 10. Also good.

Moreover, in order to improve the adhesiveness with the polarizing film 10, it is preferable to subject the bonding surface of the protective film 20 to a surface activation treatment prior to the application of the curable adhesive. Specific examples of the surface activation treatment include plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment (immersion in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide). You may perform a surface activation process on the bonding surface of the polarizing film 10 instead of the bonding surface of the protective film 20, or with the bonding surface of the protective film 20. FIG.

Referring to the protective film 21 as the third film bonded to the other surface of the polarizing film 10 shown in the example of FIG. The second film (protective film 20) and the third film (protective film 21) may be the same type of film or different types of films.

(3) Curable adhesive The curable adhesive used in the present invention is an adhesive that can be cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays, or by heat. Among them, as a curable adhesive, an active energy ray-curable adhesive can be preferably used because it is excellent in adhesiveness, transparency, mechanical strength, thermal stability, etc., and an epoxy compound that is cured by cationic polymerization is used. An active energy ray-curable adhesive as a curable component can be more preferably used. The epoxy compound here means a compound having an average of 1 or more, preferably 2 or more epoxy groups in the molecule. Epoxy compounds may be used alone or in combination of two or more.

From the viewpoint of weather resistance, refractive index, cationic polymerizability, etc., for example, an epoxy compound contained in a curable adhesive such as an active energy ray curable adhesive is an epoxy compound that does not contain an aromatic ring in the molecule. Preferably there is. Examples of such epoxy compounds include hydrogenated epoxy compounds (glycidyl ethers of polyols having an alicyclic ring), aliphatic epoxy compounds, alicyclic epoxy compounds, and the like.

The hydrogenated epoxy compound is obtained by causing epichlorohydrin to react with an alicyclic polyol obtained by hydrogenating an aromatic ring of an aromatic polyol. Examples of the aromatic polyol include bisphenol type compounds such as bisphenol A, bispheel F, and bisphenol S; novolak type resins such as phenol novolac resin, cresol novolac resin, hydroxybenzaldehyde phenol novolak resin; tetrahydroxydiphenylmethane, tetra Examples thereof include polyfunctional compounds such as hydroxybenzophenone and polyvinylphenol. Among the hydrogenated epoxy compounds, hydrogenated bisphenol A diglycidyl ether is preferable.

Examples of the aliphatic epoxy compounds include polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof. More specifically, 1,4-butanediol diglycidyl ether; 1,6-hexanediol diglycidyl ether; glycerin triglycidyl ether; trimethylolpropane triglycidyl ether; polyethylene glycol diglycidyl ether; propylene Diglycidyl ether of glycol; Polyglycidyl of polyether polyol obtained by adding one or more alkylene oxides (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol or glycerin Examples include ether.

The alicyclic epoxy compound is an epoxy compound having one or more epoxy groups bonded to the alicyclic ring in the molecule. The “epoxy group bonded to an alicyclic ring” means a bridged oxygen atom —O— in the structure represented by the following formula. In the following formula, m is an integer of 2 to 5.

A compound in which a group in which one or more hydrogen atoms in (CH ₂ ) _m in the above formula are removed is bonded to another chemical structure can be an alicyclic epoxy compound. One or more hydrogen atoms in (CH ₂ ) _m may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among the alicyclic epoxy compounds, an epoxy compound having an oxabicyclohexane ring (m = 3 in the above formula) or an oxabicycloheptane ring (m = 4 in the above formula) It is preferably used because it provides good adhesion with the protective film 20. Specific examples of alicyclic epoxy compounds that are preferably used are shown below, but are not limited to these compounds.

(A) Epoxycyclohexylmethyl epoxycyclohexanecarboxylates represented by the following formula (I):

In the formula (I), R ¹ and R ² each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.

(B) Epoxycyclohexanecarboxylates of alkanediol represented by the following formula (II):

In formula (II), R ³ and R ⁴ each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms, and n represents an integer of 2 to 20.

(C) Epoxycyclohexyl methyl esters of dicarboxylic acid represented by the following formula (III):

In formula (III), R ⁵ and R ⁶ each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms, and p represents an integer of 2 to 20.

(D) Epoxycyclohexyl methyl ethers of polyethylene glycol represented by the following formula (IV):

In formula (IV), R ⁷ and R ⁸ independently of each other represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms, and q represents an integer of 2 to 10.

(E) Epoxycyclohexyl methyl ethers of alkanediol represented by the following formula (V):

In the formula (V), R ⁹ and R ¹⁰ independently of each other represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms, and r represents an integer of 2 to 20.

(F) Diepoxy trispiro compound represented by the following formula (VI):

In the formula (VI), R ¹¹ and R ¹² each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.

(G) Diepoxy monospiro compound represented by the following formula (VII):

In formula (VII), R ¹³ and R ¹⁴ each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.

(H) Vinylcyclohexene diepoxides represented by the following formula (VIII):

In the formula (VIII), R ¹⁵ represents a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.
(I) Epoxycyclopentyl ethers represented by the following formula (IX):

In the formula (IX), R ¹⁶ and R ¹⁷ each independently represent a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.

(J) Diepoxytricyclodecanes represented by the following formula (X):

In the formula (X), R ¹⁸ represents a hydrogen atom or a linear alkyl group having 1 to 5 carbon atoms.
Among the alicyclic epoxy compounds exemplified above, the following alicyclic epoxy compounds are commercially available or similar to them, and are more preferably used because they are relatively easy to obtain. .

(A) Esterified product of 7-oxabicyclo [4.1.0] heptane-3-carboxylic acid and (7-oxa-bicyclo [4.1.0] hept-3-yl) methanol [formula (I) In which R ¹ = R ² = H],
(B) 4-methyl-7-oxabicyclo [4.1.0] heptane-3-carboxylic acid and (4-methyl-7-oxa-bicyclo [4.1.0] hept-3-yl) methanol Ester compound of [In the formula (I), R ¹ = 4-CH ₃ , R ² = 4-CH ₃ compound],
(C) Esterified product of 7-oxabicyclo [4.1.0] heptane-3-carboxylic acid and 1,2-ethanediol [in the formula (II), R ³ = R ⁴ = H, n = 2 Compound],
(D) (7-oxabicyclo [4.1.0] hept-3-yl) methanol and adipic acid ester compound [compound of formula (III) wherein R ⁵ = R ⁶ = H, p = 4] ,
(E) (4-Methyl-7-oxabicyclo [4.1.0] hept-3-yl) esterified product of methanol and adipic acid [in the formula (III), R ⁵ = 4-CH ₃ , R ⁶ = 4-CH ₃ , p = 4 compound]
(F) Etherified product of (7-oxabicyclo [4.1.0] hept-3-yl) methanol and 1,2-ethanediol [in the formula (V), R ⁹ = R ¹⁰ = H, r = Compound of 2].

The epoxy equivalent of the epoxy compound is usually in the range of 30 to 3000 g / equivalent, preferably 50 to 1500 g / equivalent. When the epoxy equivalent is less than 30 g / equivalent, the flexibility of the adhesive layer after curing may be reduced or the adhesive strength may be reduced. On the other hand, when it exceeds 3000 g / equivalent, compatibility with other components contained in the adhesive may be lowered.

The curable adhesive containing the epoxy compound as a curable component preferably contains a cationic polymerization initiator, and when an active energy ray-curable adhesive is used, it preferably contains a photocationic polymerization initiator. Cationic polymerization initiators generate cationic species or Lewis acids by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, electron beams, or heat, and initiate an epoxy group polymerization reaction. The polymerization initiator generates a cationic species or a Lewis acid by irradiation with an active energy ray, and initiates an epoxy group polymerization reaction.

The method of curing the adhesive by irradiation with active energy rays using a cationic photopolymerization initiator enables curing at room temperature, reducing the need to consider the heat resistance of the polarizing film 10 or distortion due to expansion, and the film This is advantageous in that the gap can be well bonded. In addition, since the photocationic polymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with an epoxy compound.

Examples of the photocationic polymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-allene complexes.

Examples of the aromatic diazonium salt include benzenediazonium hexafluoroantimonate, benzenediazonium hexafluorophosphate, benzenediazonium hexafluoroborate, and the like.

Examples of the aromatic iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di (4-nonylphenyl) iodonium hexafluorophosphate, and the like.

Examples of the aromatic sulfonium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, 4,4′-bis (diphenylsulfonio) diphenyl sulfide bis ( Hexafluorophosphate), 4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide, bis (hexafluoroantimonate), 4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio ] Diphenyl sulfide bis (hexafluorophosphate), 7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate, 7- [Di (p-toluyl) sulfonio] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate, 4-phenylcarbonyl-4′-diphenylsulfonio-diphenyl sulfide, hexafluorophosphate, 4- (p-tert-butylphenylcarbonyl) ) -4'-diphenylsulfonio-diphenyl sulfide, hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenyl sulfide, tetrakis (pentafluorophenyl) borate, etc. Can be mentioned.

Examples of the iron-allene complex include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, xylene-cyclopentadienyl iron (II). -Tris (trifluoromethylsulfonyl) methanide and the like.

The photocationic polymerization initiator may be used alone or in combination of two or more. Among these, aromatic sulfonium salts are preferably used because they have ultraviolet absorption characteristics even in a wavelength region of 300 nm or more, and thus can provide a cured product having excellent curability and good mechanical strength and adhesive strength.

The compounding amount of the photocationic polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 part by weight or more, and preferably 15 parts by weight or less with respect to 100 parts by weight of the epoxy compound. When the blending amount of the cationic photopolymerization initiator is less than 0.5 parts by weight with respect to 100 parts by weight of the epoxy compound, curing becomes insufficient and mechanical strength or adhesive strength tends to decrease. Moreover, when the compounding quantity of a photocationic polymerization initiator exceeds 20 weight part with respect to 100 weight part of epoxy-type compounds, the ionic substance in hardened | cured material will increase, and the hygroscopic property of hardened | cured material will become high, and polarization | polarized-light. The durability of the plate may be reduced.

When using a photocationic polymerization initiator, the active energy ray-curable adhesive can further contain a photosensitizer, if necessary. By using a photosensitizer, the reactivity of cationic polymerization is improved, and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreductive dyes.

More specific examples of photosensitizers include, for example, benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, α, α-dimethoxy-α-phenylacetophenone; benzophenone, 2,4-dichlorobenzophenone, o Benzophenone derivatives such as methyl benzoylbenzoate, 4,4′-bis (dimethylamino) benzophenone, 4,4′-bis (diethylamino) benzophenone; thioxanthone derivatives such as 2-chlorothioxanthone, 2-isopropylthioxanthone; 2 -Anthraquinone derivatives such as chloroanthraquinone and 2-methylanthraquinone; Acridone derivatives such as N-methylacridone and N-butylacridone; Others, α, α-diethoxyacetophenone, benzyl, fluo Examples include renon, xanthone, uranyl compounds, and halogen compounds. A photosensitizer may be used individually by 1 type and may use 2 or more types together. The photosensitizer is preferably contained within a range of 0.1 to 20 parts by weight in 100 parts by weight of the curable adhesive.

The curable adhesive may further contain a compound that promotes cationic polymerization, such as oxetanes and polyols.

Oxetanes are compounds having a 4-membered ring ether in the molecule. Specific examples of oxetanes include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 3-ethyl-3- (phenoxymethyl) oxetane, [(3-ethyl-3-oxetanyl) methyl] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, phenol novolak oxetane. Oxetanes are usually contained in the curable adhesive in a proportion of 5 to 95% by weight, preferably 30 to 70% by weight.

As the polyols, those having no acidic group other than phenolic hydroxyl groups are preferable. For example, polyol compounds having no functional groups other than hydroxyl groups, polyester polyol compounds, polycaprolactone polyol compounds, polyol compounds having phenolic hydroxyl groups, polycarbonates A polyol etc. can be mentioned. The molecular weight of the polyols is usually 48 or more, preferably 62 or more, more preferably 100 or more, and preferably 1000 or less. The polyols are contained in the curable adhesive in a proportion of usually 50% by weight or less, preferably 30% by weight or less.

Also, the curable adhesive may contain a radically polymerizable (meth) acrylic compound together with a cationically polymerizable curable component such as the above epoxy compound. By using a (meth) acrylic compound in combination, the effect of increasing the hardness and mechanical strength of the adhesive layer can be expected, and furthermore, adjustment of the viscosity and curing rate of the curable resin composition can be performed more easily. Will be able to.

The (meth) acrylic compound is obtained by reacting at least one (meth) acrylate monomer having at least one (meth) acryloyloxy group in the molecule or two or more functional group-containing compounds. Examples include (meth) acryloyloxy group-containing compounds such as (meth) acrylate oligomers having one (meth) acryloyloxy group. Only one (meth) acrylic compound may be used alone, or two or more may be used in combination. When two or more types are used in combination, two or more (meth) acrylate monomers may be used, two or more (meth) acrylate oligomers may be used, and, of course, one or more (meth) acrylate monomers. And one or more (meth) acrylate oligomers may be used in combination.

As the (meth) acrylate monomer, a monofunctional (meth) acrylate monomer having one (meth) acryloyloxy group in the molecule and a bifunctional (meth) acrylate having two (meth) acryloyloxy groups in the molecule Examples of the monomer include polyfunctional (meth) acrylate monomers having 3 or more (meth) acryloyloxy groups in the molecule.

Specific examples of monofunctional (meth) acrylate monomers include tetrahydrofurfuryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2- or 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, dicyclopentenyl (meth) acrylate, benzyl (Meth) acrylate, isobornyl (meth) acrylate, phenoxyethyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate , Including ethyl carbitol (meth) acrylate, trimethylolpropane mono (meth) acrylate, pentaerythritol mono (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate.

As the monofunctional (meth) acrylate monomer, a carboxyl group-containing (meth) acrylate monomer may be used. Specific examples of the monofunctional (meth) acrylate monomer containing a carboxyl group include 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, carboxyethyl (meth) acrylate, 2- ( (Meth) acryloyloxyethyl succinic acid, N- (meth) acryloyloxy-N ′, N′-dicarboxymethyl-p-phenylenediamine, 4- (meth) acryloyloxyethyl trimellitic acid.

Specific examples of the bifunctional (meth) acrylate monomer include alkylene glycol di (meth) acrylates, polyoxyalkylene glycol di (meth) acrylates, halogen-substituted alkylene glycol di (meth) acrylates, aliphatic polyol di (meta) ) Diacrylates of di (meth) acrylates of acrylates, hydrogenated dicyclopentadiene or tricyclodecane dialkanol, di (meth) acrylates of dioxane glycol or dioxane dialkanol, di (meth) acrylate adducts of bisphenol A or bisphenol F Meth) acrylates, bisphenol A or bisphenol F epoxy di (meth) acrylates.

More specific examples of the bifunctional (meth) acrylate monomer include ethylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1 , 6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol di (meth) acrylate, ditri Methylolpropane di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polyester Lenglycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, silicone di (meth) acrylate, di (meth) acrylate of hydroxypivalic acid neopentyl glycol ester, 2,2 -Bis [4- (meth) acryloyloxyethoxyethoxyphenyl] propane, 2,2-bis [4- (meth) acryloyloxyethoxyethoxycyclohexyl] propane, hydrogenated dicyclopentadienyl di (meth) acrylate, tricyclo Decanedimethanol di (meth) acrylate, 1,3-dioxane-2,5-diyldi (meth) acrylate (also known as dioxane glycol di (meth) acrylate), hydroxypivalaldehyde and trimethylo Di (meth) acrylate, tris (hydroxyethyl) of acetal compound [chemical name: 2- (2-hydroxy-1,1-dimethylethyl) -5-ethyl-5-hydroxymethyl-1,3-dioxane] with propane ) Isocyanurate di (meth) acrylate and the like.

The trifunctional or higher polyfunctional (meth) acrylate monomers include glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol. Of tri- or higher functional aliphatic polyols such as tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc. Poly (meth) acrylate is a typical one. Besides, poly (meth) acrylate of tri- or higher functional halogen-substituted polyol, alkyleneoxy of glycerin Adduct tri (meth) acrylate, trimethylolpropane alkylene oxide adduct tri (meth) acrylate, 1,1,1-tris [(meth) acryloyloxyethoxyethoxy] propane, tris (hydroxyethyl) isocyanurate tri Examples include (meth) acrylates.

On the other hand, (meth) acrylate oligomers include urethane (meth) acrylate oligomers, polyester (meth) acrylate oligomers, and epoxy (meth) acrylate oligomers.

The urethane (meth) acrylate oligomer is a compound having a urethane bond (—NHCOO—) and at least two (meth) acryloyloxy groups in the molecule. Specifically, a urethanization reaction product of a hydroxyl group-containing (meth) acrylate monomer and a polyisocyanate each having at least one (meth) acryloyloxy group and at least one hydroxyl group in the molecule, and a polyol Urethane reaction product of terminal isocyanate group-containing urethane compound obtained by reaction with isocyanate and (meth) acrylate monomer each having at least one (meth) acryloyloxy group and at least one hydroxyl group in the molecule, etc. It can be.

Examples of the hydroxyl group-containing (meth) acrylate monomer used in the urethanization reaction include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 2-hydroxy-3- Examples include phenoxypropyl (meth) acrylate, glycerin di (meth) acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol tri (meth) acrylate, and dipentaerythritol penta (meth) acrylate.

The polyisocyanate used for the urethanization reaction with a hydroxyl group-containing (meth) acrylate monomer includes hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, and aromatic diamethylenes among these diisocyanates. Diisocyanates obtained by hydrogenating isocyanates (for example, hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, etc.), di- or tri-isocyanates such as triphenylmethane triisocyanate, dibenzylbenzene triisocyanate, and the above And polyisocyanates obtained by increasing the amount of the diisocyanate.

In addition, as polyols used to obtain terminal isocyanate group-containing urethane compounds by reaction with polyisocyanates, polyester polyols, polyether polyols, etc. may be used in addition to aromatic, aliphatic or alicyclic polyols. Can do. Aliphatic and alicyclic polyols include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylolethane, trimethylolpropane, ditriol. Examples include methylolpropane, pentaerythritol, dipentaerythritol, dimethylolheptane, dimethylolpropionic acid, dimethylolbutanoic acid, glycerin, and hydrogenated bisphenol A.

The polyester polyol is obtained by a dehydration condensation reaction between the above polyols and a polybasic carboxylic acid or an anhydride thereof. The polybasic carboxylic acid or its anhydride includes (anhydrous) succinic acid, adipic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid, (anhydrous) Examples include phthalic acid, isophthalic acid, terephthalic acid, hexahydro (anhydride) phthalic acid and the like.

The polyether polyol may be a polyoxyalkylene-modified polyol obtained by a reaction of the above-described polyols or dihydroxybenzenes with an alkylene oxide, in addition to the polyalkylene glycol.

The polyester (meth) acrylate oligomer is a compound having an ester bond and at least two (meth) acryloyloxy groups in the molecule. Specifically, it can be obtained by dehydration condensation reaction of (meth) acrylic acid, polybasic carboxylic acid or anhydride thereof, and polyol. The polybasic carboxylic acid or its anhydride used in the dehydration condensation reaction includes (anhydrous) succinic acid, adipic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, (anhydrous) trimellitic acid, (anhydrous) pyrone Examples include merit acid, hexahydro (anhydride) phthalic acid, (anhydrous) phthalic acid, isophthalic acid, terephthalic acid and the like. Examples of the polyol used for the dehydration condensation reaction include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylolethane, trimethylolpropane, Examples include ditrimethylolpropane, pentaerythritol, dipentaerythritol, dimethylolheptane, dimethylolpropionic acid, dimethylolbutanoic acid, glycerin, and hydrogenated bisphenol A.

The epoxy (meth) acrylate oligomer can be obtained by an addition reaction of polyglycidyl ether and (meth) acrylic acid, and has at least two (meth) acryloyloxy groups in the molecule. Examples of the polyglycidyl ether used in the addition reaction include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A diglycidyl ether, and the like.

When a (meth) acrylic compound is added to the curable adhesive, the amount is preferably 20% by weight or less, more preferably 10% by weight or less, based on the amount of the entire curable component. When the compounding amount of the (meth) acrylic compound is increased, the adhesion between the polarizing film 10 and the protective film 20 tends to decrease.

When the curable adhesive contains a radical polymerizable curable component such as a (meth) acrylic compound, it is preferable to blend a radical polymerization initiator, and when an active energy ray curable adhesive is used, It is preferable to mix a radical photopolymerization initiator.

Specific examples of the photo radical polymerization initiator include acetophenone, 3-methylacetophenone, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1- [ Acetophenone-based initiators such as 4- (methylthio) phenyl-2-morpholinopropan-1-one and 2-hydroxy-2-methyl-1-phenylpropan-1-one; benzophenone, 4-chlorobenzophenone, 4,4 Benzophenone initiators such as' -diaminobenzophenone; benzoin ether initiators such as benzoin propyl ether and benzoin ethyl ether; thioxanthone initiators such as 4-isopropylthioxanthone; xanthone, fluorenone, camphorquinone, benz Aldehyde, including the anthraquinone.

The compounding amount of the photo radical polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 to 6 parts by weight with respect to 100 parts by weight of the (meth) acrylic compound. When the amount of the radical photopolymerization initiator is less than 0.5 parts by weight, the effect of using the (meth) acrylic compound tends to be hardly recognized. Moreover, when the quantity of radical photopolymerization initiator exceeds 20 weight part, durability of the polarizing plate obtained may fall.

Curable adhesives are ion trapping agents, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, antifoaming agents, antistatic agents, leveling as required. An additive such as an agent can be contained. Examples of the ion trapping agent include powdery bismuth-based, antimony-based, magnesium-based, aluminum-based, calcium-based, titanium-based, and mixed inorganic compounds. The antioxidant is a hindered phenol-based antioxidant. Etc.

As described above, the curable adhesive containing an epoxy compound as at least a part of the curable component can be used as a solvent-free curable adhesive substantially free of a solvent. It can also be diluted with a solvent. Specific examples of the solvent include aliphatic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; alcohols such as methanol, ethanol, propanol, isopropanol and n-butanol; acetone Ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; esters such as methyl acetate, ethyl acetate and butyl acetate; cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve; halogenation such as methylene chloride and chloroform Includes hydrocarbons.

<Bonding process>
In this step, the polarizing film 10 and the protective film 20 are bonded through the adhesive layer formed in the coating step. As shown in FIG. 1, the bonding of the film is a pair of bonding rolls in which the polarizing film 10 and the protective film 20 that are continuously conveyed are overlapped so that their longitudinal directions (conveying directions) are parallel. By passing between 40 and 40, it can carry out by pressing the film laminated | stacked with the bonding rolls 40 and 40 from the upper and lower sides. The pressure applied to the film by the bonding rolls 40, 40 is, for example, about 0.5 to 4 MPa.

At this time, in the present invention, the adhesive layer when the polarizing film 10 and the protective film 20 are bonded (when passed between the bonding rolls 40 and 40) (that is, the curable adhesive constituting the same). ) To be 60 cP or less. By setting the viscosity of the adhesive layer at the time of film bonding to 60 cP or less, a polarizing plate having no bubbles in the adhesive layer or significantly suppressing bubbles is obtained without impairing the adhesiveness between the films. Can do. The viscosity value here is a value measured according to the method described in the Examples section described later. In order to more effectively prevent the generation of bubbles, the viscosity of the adhesive layer is preferably 50 cP or less, and more preferably 40 cP or less.

On the other hand, if the viscosity of the adhesive layer is too low, the applied curable adhesive tends to protrude from the film during bonding. Therefore, the viscosity of the adhesive layer at the time of film bonding is preferably 10 cP or more, and more preferably 20 cP or more.

As a method of adjusting the viscosity of the adhesive layer to 60 cP or less,
1) A method in which a solvent is added to a curable adhesive having a viscosity exceeding 60 cP and diluted, and this is applied to the bonding surface of the polarizing film 10 or the protective film 20,
2) The method etc. which provide the heating process which heats an adhesive bond layer before film pasting (before passing between the bonding rolls 40 and 40) can be mentioned. Among these, the method 2) is preferable in that the viscosity can be lowered without using a separate solvent.

In the method 1), a curable adhesive such as the above-mentioned active energy ray-curable adhesive is mixed with a solvent, the diluted curable adhesive is applied in an application step, and then the solvent is volatilized. The pasting step is carried out while paying attention so that the viscosity of the adhesive layer at the time of film pasting does not exceed 60 cP. As the solvent, for example, those described above can be used. The amount of the solvent used is not particularly limited as long as the viscosity of the adhesive layer at the time of film bonding is 60 cP or less.

The heating means of the adhesive layer in the method 2) is not particularly limited, and may be heated by infrared irradiation, for example, or may be heated using a hot air heater or an oven. According to these means, it becomes easy to continuously heat the entire adhesive layer of the continuously conveyed film. Among these, heating by infrared irradiation is advantageous in that heating in a shorter time is possible and the adhesive layer can be continuously heated to a desired level even when the film conveyance speed is increased. Infrared rays may be irradiated from the adhesive layer side, or from the back side (the side having no adhesive layer) of the film on which the adhesive layer is formed, but preferably from the adhesive layer side. To do. In the example of FIG. 1, using the infrared irradiation device 70, the adhesive layer is heated by irradiating infrared rays from the side of the adhesive layer formed on the protective film 20. In the method 2), an adhesive having a property of lowering viscosity when heated is used. For example, the above-mentioned active energy ray-curable adhesive that can be used as a solventless adhesive can be suitably used. .

The infrared irradiation device 70 can irradiate infrared rays that can be absorbed by the curable adhesive. The above-mentioned active energy ray-curable adhesive containing an epoxy compound or an epoxy compound and a (meth) acrylic compound as a curable component generally absorbs infrared rays having a wavelength of about 6 to 12 μm. Therefore, as the infrared irradiation device 70, for example, a “far-infrared plate heater” manufactured by Yoko Electric Co., Ltd., which can emit infrared rays having a wavelength of 6 to 12 μm can be used.

The heating temperature of the adhesive layer is not particularly limited as long as the viscosity is 60 cP or less and can function as an adhesive even at the heating temperature, and is, for example, 40 ° C. or more, although it depends on the composition of the curable adhesive used. , More typically 50 ° C. or higher. The heating temperature is preferably 70 ° C. or lower, more preferably 65 ° C. or lower. If the heating temperature is too high, the adhesive layer or film may be thermally deteriorated.

With reference to FIG. 1, angle (theta) (both films are bonded) between polarizing film 10 and protective film 20 which are passed between a pair of bonding rolls 40 and 40 and a pair of bonding rolls 40 and 40 is made. The angle when viewed from the film width direction, sometimes formed by both films, is not particularly limited, and can be, for example, 60 ° or less. However, the smaller the angle θ, the more bubbles are likely to be generated in the adhesive layer. According to the present invention, even when the angle θ is 40 ° or less, it is possible to obtain a polarizing plate in which no bubbles are present in the adhesive layer or in which bubbles are significantly suppressed. The angle θ is usually 20 ° or more.

The passing speed (conveying speed) of the polarizing film 10 and the protective film 20 when passing between the pair of bonding rolls 40, 40 is not particularly limited and can be, for example, 10 m / min or more, but the passing speed is large. The more air bubbles are likely to be generated in the adhesive layer. According to the present invention, even when the passing speed is 20 m / min or more, it is possible to obtain a polarizing plate in which there are no bubbles in the adhesive layer or in which the bubbles are significantly suppressed. The passing speed is usually 40 m / min or less.

<Curing process>
This step is a step of curing the adhesive layer of the laminate of the polarizing film 10 and the protective film 20 bonded through the adhesive layer. When the adhesive layer is made of an active energy ray-curable adhesive, as shown in FIG. 1, an active energy ray irradiation device 80 is used to apply active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams. The adhesive layer can be cured by irradiation. When the laminate is composed of the polarizing film 10 and the protective film 20 and does not include the third film (the protective film laminated on the other surface of the polarizing film 10), the active energy ray is irradiated from the protective film 20 side. Alternatively, irradiation may be performed from the polarizing film 10 side, but irradiation is preferably performed from the protective film 20 side as shown in FIG.

The active energy ray can be visible light, ultraviolet ray, X-ray, electron beam, etc., but it is easy to handle, easy to prepare an active energy ray-curable adhesive and its stability, and its curing performance. From this viewpoint, ultraviolet rays are preferably used. The light source of the active energy ray is not particularly limited, but has a light emission distribution at a wavelength of 400 nm or less. Etc. can be preferably used.

The light irradiation intensity to the adhesive layer made of an ultraviolet curable adhesive is determined for each composition of the adhesive and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is not limited. It is preferably 0.1 to 100 mW / cm ² . When the light irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when the light irradiation intensity is 100 mW / cm ² or less, adhesion is caused by heat radiated from the light source and heat generated when the adhesive is cured There is little risk of yellowing of the agent and deterioration of the polarizing film. The light irradiation time to the adhesive layer is also controlled for each composition of the adhesive and is not particularly limited. However, the integrated light amount expressed as the product of the light irradiation intensity and the irradiation time is 10 to 5000 mJ / It is preferably set to be m ² . By integrated light quantity is 10 mJ / m ² or more to generate a sufficient amount of the active species derived from the polymerization initiator can proceed more reliably the curing reaction, also, that at 5000 mJ / m ² or less, Irradiation time does not become too long, and good productivity can be maintained.

It is also possible to install a plurality of active energy ray irradiation devices 80 and irradiate the active energy rays in a plurality of times.

When curing the adhesive layer by irradiating active energy rays, irradiating the active energy rays in a state where the laminate is in close contact with the convex curved surface can suppress wrinkles and curls that may occur in the resulting polarizing plate. Is advantageous. As the convex curved surface, an outer peripheral surface of a roll such as a guide roll or a cooling roll can be suitably used. In particular, when the active energy rays are irradiated in a state of being wound around the outer peripheral surface of the appropriately cooled cooling roll 50 as in the examples of FIGS. 1 and 2, the effect of suppressing wrinkles and curls is great. The temperature of the cooling roll is, for example, 10 to 30 ° C., preferably 15 to 25 ° C.

The polarizing plate obtained as described above is usually wound up sequentially by a winding device (not shown) to form a film roll.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the following examples, the thickness of the adhesive layer after curing and the viscosity of the adhesive layer at the time of film bonding were measured according to the following method.

(Thickness of the adhesive layer after curing)
Using a spectral interference film thickness meter manufactured by Keyence Corporation, the thickness of the adhesive layer after curing was measured at any five points, and the average value thereof was taken as the thickness of the adhesive layer.

(Viscosity of the adhesive layer at the time of film bonding)
Take UV curable adhesive in a sample cup and adjust its temperature to the same temperature as when the film was bonded, then use “E-type viscometer” manufactured by Toki Sangyo Co., Ltd. The measured value was taken as the viscosity of the adhesive layer during film bonding.

<Production example>
(A) Preparation of Polarizing Film After immersing roll-shaped polyvinyl alcohol film (thickness 75 μm, average polymerization degree of about 2400, saponification degree 99.9 mol% or more) in pure water at 30 ° C. Then, it was immersed at 30 ° C. in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.02 / 2/100. Then, it was immersed at 56.5 ° C. in an aqueous solution having a potassium iodide / boric acid / water weight ratio of 12/5/100. Subsequently, the film was washed with pure water at 8 ° C., dried at 65 ° C., and wound to obtain a film roll of a polarizing film (thickness: about 30 μm, width: 1300 mm) in which iodine was adsorbed and oriented on polyvinyl alcohol. Stretching was mainly performed in the iodine staining and boric acid treatment steps, and the total stretching ratio was 5.3 times.

(B) Preparation of protective film made of (meth) acrylic resin As a (meth) acrylic resin, a copolymer of methyl methacrylate / methyl acrylate (weight ratio 96/4) was prepared. As the acrylic rubber particles, the innermost layer is a hard polymer obtained by copolymerizing a small amount of allyl methacrylate with methyl methacrylate, the intermediate layer is mainly composed of butyl acrylate, and styrene and a small amount of methacrylic acid. It is a soft elastic body copolymerized with allyl, and the outermost layer is a three-layered elastic particle made of a hard polymer obtained by copolymerizing methyl methacrylate with a small amount of ethyl acrylate. Acrylic elastic polymer particles having an average particle diameter of about 250 nm when not present were prepared.

The pellets in which the above acrylic resin and acrylic rubber particles were blended at a weight ratio of 70/30 were put into a 65 mmφ single screw extruder and extruded from a T-shaped die having a set temperature of 275 ° C. The both sides of the extruded film-like molten resin are cooled by being sandwiched between two polishing rolls having a mirror surface set at 45 ° C., and are a long (meth) acrylic resin film having a thickness of 80 μm and a width of 1300 mm (protection) Film) was obtained as a film roll.

<Example 1>
A polarizing plate was manufactured by the following procedure using the same polarizing plate manufacturing apparatus as in FIG. Each of the polarizing film 10 and the protective film 20 was continuously unwound from the film roll of the polarizing film and the protective film obtained above, and these films were conveyed so that their longitudinal directions were in the conveying direction (conveying speed). : 30 m / min). An ultraviolet curable adhesive A containing an epoxy compound as a curable component was applied to the bonding surface of the protective film 20 using an adhesive coating device 30 (gravure coater).

Next, immediately before the bonding rolls 40, 40, an adhesive layer formed on the protective film 20 using a “far infrared plate heater” (infrared wavelength: 7 μm) manufactured by Yako Electric Co., Ltd. as the infrared irradiation device 70. Then, after irradiating infrared rays from the adhesive layer side and heating the adhesive layer to 60 ° C., the polarizing film 10 and the protective film 20 are overlapped so that their longitudinal directions (conveying directions) are parallel to each other. The film was bonded by pressing between the bonding rolls 40, 40. The angle θ in FIG. 1 is 45 °. The passing speed of the polarizing film 10 and the protective film 20 when passing between the bonding rolls 40 and 40 was 30 m / min. The viscosity of the adhesive layer at the time of film bonding is 30 cP.

Subsequently, the laminate obtained by film bonding is transported and wound around the outer peripheral surface of the cooling roll 50 set at 20 ° C., and there is a D bulb manufactured by Fusion UV Systems as an active energy ray irradiation device 80. Was used to cure the adhesive layer by irradiating ultraviolet rays with an integrated light quantity of 1500 mJ / cm ² . Finally, the obtained polarizing plate was wound up to obtain a film roll of the polarizing plate. The thickness of the adhesive layer after curing was 1.5 μm.

A rectangular sample was cut out from the obtained polarizing plate and observed from the surface using a reflection microscope (100 times) to confirm the presence or absence of bubbles in the cured adhesive layer. The results are shown in Table 1.

<Example 2>
Except that the ultraviolet curable adhesive B having an epoxy compound as a curable component was used instead of the ultraviolet curable adhesive A, and that the thickness of the adhesive layer after curing was as shown in Table 1. A polarizing plate was produced in the same manner as in Example 1, and the presence or absence of bubbles was confirmed in the same manner as in Example 1. The results are shown in Table 1.

<Comparative Example 1, Reference Example 1>
A polarizing plate was produced in the same manner as in Example 1 except that the thickness of the adhesive layer after curing, the temperature and viscosity of the adhesive layer at the time of film bonding were as shown in Table 1, and Example 1 In the same manner as above, the presence or absence of bubbles was confirmed. The results are shown in Table 1. In the polarizing plate of Comparative Example 1, many bubbles having a diameter of about 10 μm were confirmed in the cured adhesive layer.

10 polarizing film, 20, 21 protective film, 30 adhesive coating device, 40 bonding roll, 50 cooling roll, 60 guide roll, 70 infrared irradiation device, 80 active energy ray irradiation device.

Claims (12)

1. A laminating step of laminating the first film and the second film via an adhesive layer formed so that the thickness after curing is 2.5 μm or less, and the first film and the second film A curing step of curing the adhesive layer after pasting,
   At least one of the first film and the second film is an optical film,
   The said bonding process WHEREIN: The manufacturing method of a laminated optical film whose viscosity of the said adhesive bond layer when bonding a said 1st film and a said 2nd film is 60 cP or less.
2. The manufacturing method of the laminated | multilayer optical film of Claim 1 which further includes the heating process which heats the said adhesive bond layer and adjusts the viscosity to 60 cP or less before the said bonding process.
3. The method for producing a laminated optical film according to claim 2, wherein in the heating step, the adhesive layer is heated by infrared irradiation.
4. The method for producing a laminated optical film according to claim 2 or 3, wherein in the heating step, the adhesive layer is heated to 40 ° C or higher.
5. The method for producing a laminated optical film according to any one of claims 1 to 4, wherein the adhesive constituting the adhesive layer is a solventless curable adhesive.
6. The method for producing a laminated optical film according to claim 1, wherein the adhesive layer has a viscosity adjusted to 60 cP or less by containing a solvent when the first film and the second film are bonded together. .
7. The method for producing a laminated optical film according to any one of claims 1 to 6, wherein the adhesive constituting the adhesive layer is an active energy ray-curable adhesive.
8. A method for producing a laminated optical film while continuously conveying the long first film and the long second film so that the longitudinal direction thereof is the conveying direction,
   An application step of continuously applying an adhesive to the bonding surface of the first film or the second film to form an adhesive layer;
   The bonding step of passing the first film and the second film between a pair of bonding rolls so that their conveying directions are parallel; and
   The method for producing a laminated optical film according to any one of claims 1 to 7, comprising:
9. The laminated optical film according to claim 8, wherein an angle formed between the pair of bonding rolls by the first film and the second film passed between the pair of bonding rolls is 60 ° or less. Production method.
10. The method for producing a laminated optical film according to claim 8 or 9, wherein a conveyance speed of the first film and the second film passed between the pair of bonding rolls is 10 m / min or more.
11. The method for producing a laminated optical film according to any one of claims 8 to 10, wherein a width of the first film and the second film is 0.4 to 2 m.
12. The method for producing a laminated optical film according to any one of claims 1 to 11, wherein the first film is a polarizing film and the second film is a protective film.

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