JP2023078679A - Method of manufacturing polarizing plate - Google Patents

Abstract

To provide a method of manufacturing a polarizing plate which is superior in permeability even when using a polarizer including a cured body of an aligned polymerizable liquid crystal compound and a dichroic pigment.SOLUTION: A method of manufacturing a polarizing plate comprises steps of: coating a surface of a first film 10 including an optical function layer with an active energy beam curing type adhesive; sticking the first film 10 including the optical function layer on a surface of a second film 20 including a polarizer with the applied active energy beam curing type adhesive so as to obtain a laminate 30; and starting irradiating the adhesive in the laminate 30 with an active energy beam in 2 to 8 seconds after the first film 10 and second film 20 are stuck together to cure the adhesive. The polarizer includes a cured body of an aligned polymerizable liquid crystal compound and a dichroic pigment.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a polarizing plate.

Conventionally, a method for manufacturing a polarizing plate, in which a stretched polyvinyl alcohol film (stretched PVA) film containing a polarizer and a film containing a retardation plate are laminated using an active energy ray-curable adhesive. It has been known.

JP 2014-48496 A

As the polarizer, it is conceivable to use a polarizer containing a cured product of an oriented polymerizable liquid crystal compound and a dichroic dye instead of stretched PVA.

However, the present inventors have found that when a film containing such a specific polarizer and a film containing an optical functional layer such as a retardation plate are adhered with an active energy ray-curable resin, the resulting polarizing plate It was found that the transmittance decreased.

The present invention has been made in view of the above problems, and even when using a cured product of an aligned polymerizable liquid crystal compound and a polarizer containing a dichroic dye, it is excellent in suppressing a decrease in transmittance. It aims at providing the manufacturing method of a polarizing plate.

A method for manufacturing a polarizing plate according to one aspect of the present invention includes a step of applying an active energy ray-curable adhesive to the surface of a first film including an optical function layer;
obtaining a laminate by bonding the first film containing the optical function layer to the surface of the second film containing the polarizer via the applied active energy ray-curable adhesive;
Within 2 to 8 seconds after laminating the first film and the second film, the active energy ray curing type is started by irradiating the adhesive in the laminate with an active energy ray. and obtaining a cured product layer of the adhesive. The polarizer contains a cured product of an oriented polymerizable liquid crystal compound and a dichroic dye.

In this method, the second film can include an overcoat layer and the polarizer in order from the surface of the side bonded to the first film.

The active energy ray-curable adhesive can contain a cationic polymerizable compound and a photocationic polymerization initiator.

The dose of the active energy ray (accumulated light dose in the UVA region (320-390 nm)) can be 150-800 mJ/cm ² .

The first film may include at least one retardation plate.

In the above method, the active energy ray includes ultraviolet rays of 320 nm, the transmittance of the first film at 320 nm is less than 10%, the transmittance of the second film at 320 nm is 10 to 99%, and The active energy ray can be irradiated from the second film toward the first film.

The thickness of the cured product layer of the active energy ray-curable adhesive can be 0.5 to 3 μm.

The above method includes the step of peeling off a release substrate provided on the surface of the first film before the step of applying an active energy ray-curable adhesive to the surface of the first film including the optical functional layer. The method of any one of claims 1-7, further comprising:

INDUSTRIAL APPLICABILITY According to the present invention, a method for producing a polarizing plate that is excellent in suppressing a decrease in transmittance even when a polarizer containing a cured product of an oriented polymerizable liquid crystal compound and a dichroic dye is used is provided. be.

FIG. 1 is a flowchart showing an example of the manufacturing method of this embodiment. FIG. 2 is a cross-sectional view showing an example of the first film 10. As shown in FIG. FIG. 3 is a cross-sectional view showing an example of the second film 20. As shown in FIG. FIG. 4 is a cross-sectional view showing an example of the laminate (polarizing plate) obtained by this embodiment.

An embodiment of the present invention will be described with reference to the drawings.

A method for manufacturing a polarizing plate according to an embodiment of the present invention includes the steps of: applying an active energy ray-curable adhesive to the surface of a first film including an optical function layer; a step of bonding the first film containing the optical function layer to the surface of the second film containing the polarizer to obtain a laminate; and bonding the first film and the second film together. a step of starting to irradiate the active energy ray-curable adhesive in the laminate with an active energy ray for 2 to 8 seconds to obtain a cured product layer of the active energy ray-curable adhesive; , provided.

One embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow diagram showing a manufacturing method according to one embodiment of the present invention. 2 is a cross-sectional view showing an example of the first film 10, FIG. 3 is a cross-sectional view showing an example of the second film 20, and FIG. 4 is a cross-sectional view showing an example of the obtained laminate (polarizing plate).

(First film)
The first film 10 includes an optical functional layer. An example of an optical functional layer is a retardation plate.
The first film 10 may be a single layer, or may be a laminate of multiple layers. For example, the first film 10 may have multiple retardation plates. Examples of retardation plates are λ/4 plates, λ/2 plates, positive C plates, and the like. The thickness of each retardation layer can be 0.1 to 10 μm.

The retardation plate may include a stretched film of a thermoplastic resin such as a cycloolefin polymer, or may include a cured film of an oriented polymerizable liquid crystal compound.

A polymerizable liquid crystal compound is a liquid crystal compound having a polymerizable functional group (preferably a photopolymerizable functional group). A photopolymerizable functional group is a group that can participate in a polymerization reaction by an active radical generated from a photopolymerization initiator, an acid, or the like. Photopolymerizable functional groups include vinyl group, vinyloxy group, 1-chlorovinyl group, isopropenyl group, 4-vinylphenyl group, acryloyloxy group, methacryloyloxy group, oxiranyl group and oxetanyl group.

The type of polymerizable liquid crystal compound is not particularly limited, and rod-like liquid crystal compounds, discotic liquid crystal compounds, and mixtures thereof can be used. The liquid crystallinity of the liquid crystal compound may be either thermotropic liquid crystal or lyotropic liquid crystal, but thermotropic liquid crystal is preferred in that it enables precise film thickness control. The phase-ordered structure of the thermotropic liquid crystal may be nematic liquid crystal or smectic liquid crystal. A photopolymerization initiator or the like can be appropriately used for the polymerization.

Each retardation plate may have a forward wavelength dispersion property in which the in-plane retardation decreases as the wavelength increases, or may have a reverse wavelength dispersion property in which the in-plane retardation increases as the wavelength increases. .

When the retardation plate includes an oriented cured film of a polymerizable liquid crystal compound, the retardation plate may have an alignment film adjacent to the cured film.

The alignment film is used to orient the polymerizable liquid crystal compound during the production of the cured product layer of the polymerizable liquid crystal compound. The alignment film is not particularly limited, and may be a rubbing film of a resin such as PVA, or a photo-alignment film obtained by polymerizing a photopolymerizable resin film with polarized light or the like. The thickness of the alignment film can be 0.01 to 5 μm.

Examples of polymerizable liquid crystal compounds, auxiliary components such as polymerization initiators that are blended as necessary in the cured product layer of the polymerizable liquid crystal compound, materials for the alignment film, and methods for producing these are known, for example, It is disclosed in JP-A-2017-167517.

When the first film has a plurality of optical functional layers (retardation plate, etc.), the first film can contain adhesive or adhesive layers between the plurality of optical functional layers to fix them. Examples of adhesives are acrylic adhesives. An example of the adhesive is an active energy ray curable adhesive such as UV. The thickness of the adhesive or adhesive layer can be 0.1-10 μm.

In addition to the optical function layer, the first film has other layers such as an adhesive layer, a release base material (such as PET), etc. on the surface opposite to the surface to which the active energy ray-curable adhesive is applied. other membranes.

A typical example of the first film 10 is shown in FIG. This first film 10 includes, in order from the side (lower side) to which the active energy ray-curable adhesive is applied in the process described later, the reverse wavelength dispersion type λ / 4 plate 12, the adhesive or adhesive layer 14, the positive C It has a plate 16 and a release substrate 18 .

A release base material may be provided in advance on the surface of the first film 10 to which the active energy ray-curable adhesive is applied before the step of applying the active energy ray-curable adhesive, which will be described later. For example, the surface of the reverse wavelength dispersion λ/4 plate 12 in FIG. 1 may be previously covered with the release base material 19 . In such a case, after peeling the release base material 19 from the laminate 10 ′ having the first film 10 and the release base material 19, the surface of the first film 10 (for example, the reverse wavelength dispersion type λ / 4 plate 12 ) can be coated with an active energy ray-curable adhesive. As a result, the finally obtained polarizing plate can be prevented from being scratched or remaining with foreign matter on the surface of the first film 10 on which the adhesive is applied. As shown in FIG. 1, the peeled release base material can be appropriately wound around a core to form a roll 9. As shown in FIG.

The first film 10 can be long (eg, 10 to 5000 m) and can be in the form of a roll 1 pre-wound on a core, as shown in FIG.

(Second film)
The second film 20 shown in FIG. 1 is a polarizing plate containing a polarizer. The polarizer contains a cured product of an oriented polymerizable liquid crystal compound and a dichroic dye, and the dichroic dye is dispersed and aligned in the cured product of the polymerizable liquid crystal compound.

As for the polymerizable liquid crystal compound, those described in the section of the retardation plate can be used. As the polymerizable liquid crystal compound used for the polarizer, a smectic liquid crystal compound is preferable to a nematic liquid crystal compound, and a high-order smectic liquid crystal compound is more preferable. Among them, high-order smectic liquid crystal compounds forming smectic B phase, smectic D phase, smectic E phase, smectic F phase, smectic G phase, smectic H phase, smectic I phase, smectic J phase, smectic K phase or smectic L phase. Higher order smectic liquid crystal compounds forming a smectic B phase, a smectic F phase or a smectic I phase are more preferred. A photopolymerization initiator or the like can be appropriately used for the polymerization.

A dichroic dye is a dye that has different absorbances in the long-axis direction and the short-axis direction of the molecule.

Dichroic dyes preferably have a maximum absorption wavelength (λ _MAX ) in the range of 300 to 700 nm. Such dichroic dyes include, for example, acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes and anthraquinone dyes, with azo dyes being preferred. The azo dyes include monoazo dyes, bisazo dyes, trisazo dyes, tetrakisazo dyes and stilbene azo dyes, preferably bisazo dyes and trisazo dyes. The dichroic dyes may be used alone or in combination, but it is preferable to combine three or more dichroic dyes, more preferably three or more azo dyes. By combining three or more types of dichroic dyes, particularly three or more types of azo dyes, it becomes easier to control the polarization characteristics over the entire visible light range. Further, when combining three or more types of dichroic dyes, the problem of the present invention is solved by using more dichroic dyes that exhibit absorption at the longest wavelength than the other two types of dichroic dyes. It is preferable as one means.

The thickness of the polarizer is usually 10 µm or less, preferably 0.5 µm or more and 8 µm or less, and more preferably 1 µm or more and 5 µm or less.

The second film 20 can have an alignment layer in contact with the polarizer. The alignment film is a layer for orienting the liquid crystalline compound of the polarizer when manufacturing the polarizer. The material of the alignment film is not particularly limited, and it may be a rubbing layer of a resin such as PVA, or a photo-alignment film obtained by aligning a polymer layer having a photo-orientation group by irradiating polarized light or the like. Although the thickness of the alignment film is not limited, the thickness of the alignment film is usually in the range of 10-10000 nm, preferably in the range of 10-1000 nm, more preferably in the range of 50-200 nm. There is no particular limitation on the lamination order of the alignment film and the polarizer.

A composition containing an alignment film, a polymerizable liquid crystal compound and a dichroic dye, and a method for producing a polarizer using this composition are disclosed in JP-A-2017-167517, JP-A-2013-37353, and JP-A-2013-37353. 2013-33249, JP-A-2017-83843, WO2020/122117, WO2020/179864, etc. can be exemplified.

The second film 20 may further comprise at least one protective film that protects the polarizer or the stack of polarizer and alignment film. For example, the second film 20 can comprise a pair of protective films sandwiching a polarizer or a stack of polarizer and alignment films.

The protective film is a layer that protects the polarizer, and can have functions such as suppressing diffusion of the dichroic dye in the polarizer to the outside and suppressing diffusion of oxygen or the like from the outside into the polarizer. The protective film can be a cured product of polyvinyl alcohol-based resin or a cured product of active energy ray-curable resin (the same ones as those exemplified for UV-curable adhesives can be used). The two protective films may be made of the same type of material, or may be made of different materials.

The thickness of each protective film is not particularly limited, but can be, for example, 0.1 to 5 μm.

Examples of cured products of polyvinyl alcohol-based resins include cured products of polyvinyl alcohol-based resins and cross-linking agents, and cured products of polyvinyl alcohol-based resins having polymerizable functional groups.

Examples of polyvinyl alcohol-based resins include partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, and amino group-modified polyvinyl alcohol. It is a modified polyvinyl alcohol resin.

The degree of saponification of the polyvinyl alcohol resin is usually about 85 mol% or more and 100 mol% or less, preferably 90 mol% or more, may be 95 mol% or more, or may be 98 mol% or more. good.

The average degree of polymerization of the polyvinyl alcohol resin is usually 1000 or more and 5000 or less, preferably 1500 or more and 3000 or less, and may be 2000 or less or 1500 or less.

The content of the polyvinyl alcohol-based resin in the uncured product of the polyvinyl alcohol-based resin is preferably 85% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass, based on the mass of the solid content of the uncured product. % by mass or more, and may be 100% by mass.

Examples of cross-linking agents are amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, polyvalent metal salts. In particular, aldehyde compounds such as glyoxal, methylol compounds such as methylolmelamine, and water-soluble epoxy resins are suitable. The water-soluble epoxy resin is a polyamide epoxy resin obtained by reacting epichlorohydrin with polyamide polyamine which is a reaction product of polyalkylene polyamine such as diethylenetriamine and triethylenetetramine and dicarboxylic acid such as adipic acid. can be done.

When the polyvinyl alcohol-based resin has a polymerizable functional group, a cured product can be obtained by heating or the like without using a cross-linking agent. Examples of polymerizable functional groups are vinyl, vinyloxy, 1-chlorovinyl, isopropenyl, 4-vinylphenyl, acryloyloxy, methacryloyloxy, oxiranyl and oxetanyl groups.

The cured product of the polyvinyl alcohol resin can be obtained by dissolving the polyvinyl alcohol resin and, if necessary, additives and the like in a solvent, applying the solution on a substrate, and drying.

FIG. 3 is a cross-sectional view showing an example of the second film 20. As shown in FIG. The second film 20 in FIG. 3 includes an overcoat layer (first protective film) 32, a polarizer 36, an alignment film 34, and a hard It has a coat layer (second protective film) 38 .

The second film 20 can be provided with a release base material 40 on the surface opposite to the surface to which the active energy ray-curable adhesive described below is applied (lower surface in FIG. 3). An example of the release base material 40 is a PET film or the like, and the release base material 40 may be a single layer or multiple layers.

A release base material may be provided in advance on the surface of the second film 20 to which the active energy ray-curable adhesive is applied before the step of applying the active energy ray-curable adhesive, which will be described later. For example, the surface of the overcoat layer (first protective film) 32 in FIG. 3 may be previously covered with the release base material 39 . In such a case, after peeling the release base material 39 from the laminate 20' having the second film 20 and the release base material 39, the surface of the second film 20 (for example, an overcoat layer (first protective film)) 32) can be laminated with the first film 10 coated with an active energy ray-curable adhesive. As a result, it is possible to prevent the surface of the second film 20 on which the adhesive is applied from being scratched or leaving foreign matter in the finally obtained polarizing plate. As shown in FIG. 1, the peeled protective film can be appropriately wound around a core to form a roll 9. As shown in FIG.

(Coating process)
In the coating step, the surface of the first film 10 including the optical functional layer is coated with an active energy ray-curable adhesive.

(Active energy ray-curable adhesive)
Active energy ray-curable adhesives are resins that cure when exposed to active energy rays. The active energy rays may be, for example, ultraviolet rays, visible light, electron beams, or X-rays. The active energy ray-curable adhesive may be an ultraviolet curable resin. UV curable resins can be prepared as solventless adhesives.

The active energy ray-curable adhesive preferably contains a cationic polymerizable compound.

The cured product layer of the cationic polymerizable compound can suppress diffusion of the dichroic dye from the polarizer to the outside. In addition, when the optical function layer of the first film is a cured product of a polymerizable liquid crystal compound, this cured product layer further suppresses diffusion of unpolymerized monomers from the optical function layer to the polarizer. can. Moreover, this cured product layer is also excellent in water resistance.

Cationic polymerizable compounds include compounds (including oligomers) that undergo cationic polymerization reaction and are cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays, or by heating. Examples of such compounds are epoxy compounds, oxetane compounds, vinyl compounds. These polymerizable compounds may be used alone or in combination of two or more. The curable resin may contain a radically polymerizable compound as a polymerizable compound in addition to the cationic polymerizable compound. A radically polymerizable compound is a compound capable of initiating a polymerization reaction by radical species generated from a radical photopolymerization initiator upon irradiation with light, for example.

The content of the cationic polymerizable compound contained in the adhesive is preferably 80 parts by mass or more and 100 parts by mass or less, more preferably 90 parts by mass or more and 99.5 parts by mass or less with respect to the total mass of the adhesive of 100 parts by mass. and more preferably 95 parts by mass or more and 99 parts by mass or less. When the content of the cationic polymerizable compound is within this range, the water resistance is excellent, and the effect of preventing diffusion of the dichroic dye to the outside of the polarizer is also excellent.

It is preferable to include a polymerizable compound having a cyclic ether structure as the cationic polymerizable compound. Cyclic ether structures include an oxirane ring, an oxetane ring, a tetrahydrofuran ring, a tetrahydropyran ring, and the like. Among them, it preferably contains a polymerizable compound having a cyclic ether structure with 2 to 4 carbon atoms, and more preferably contains an oxetane compound.

The oxetane compound is a compound having one or more oxetanyl groups (oxetane ring) in the molecule, and may be an aliphatic compound, an alicyclic compound or an aromatic compound. Oxetane compounds having one oxetanyl group include, for example, 3-ethyl-3-hydroxymethyloxetane, 2-ethylhexyloxetane, 3-ethyl-3-(phenoxymethyl)oxetane, 3-(cyclohexyloxy)methyl-3-ethyl oxetane and the like. Oxetane compounds having two or more oxetanyl groups include, for example, 1,4-bis[{(3-ethyloxetan-3-yl)methoxy}methyl]benzene (also referred to as "xylylene bisoxetane"), bis(3-ethyl-3-oxetanylmethyl)ether and the like. These oxetane compounds may be used alone or in combination of two or more. The oxetane compound may be used as the main component of the cationically polymerizable compound, or may be used together with the epoxy compound.

The oxetane compound preferably includes an oxetane compound having two or more oxetanyl groups in the molecule. By including such an oxetane compound, it is possible to obtain a dense cured product with a high cross-linking density, effectively suppress the diffusion of the dichroic dye from the polarizer, and cause changes in optical performance over time. A difficult polarizing plate can be obtained.

The content of the oxetane compound may be, for example, 10 parts by mass or more, preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and still more preferably 45 parts by mass with respect to 100 parts by mass of the total amount of the cationic polymerizable compounds. parts or more, particularly preferably 50 parts by mass or more. When the content of the oxetane compound is at least the above lower limit value, the second cured product layer is more excellent in heat resistance and heat and humidity resistance, so that the water resistance, heat resistance and heat and humidity resistance of the polarizing plate can be effectively improved. can. This makes it possible to obtain a polarizing plate whose optical performance is less likely to change over time. The content of the oxetane compound is preferably 90 parts by mass or less, more preferably 85 parts by mass or less, and even more preferably 80 parts by mass or less with respect to 100 parts by mass of the total amount of the cationic polymerizable compounds. In addition, the content of the oxetane compound may be a combination of the above lower limit and upper limit, and is preferably 30 parts by mass or more and 90 parts by mass or less, more preferably 100 parts by mass of the total amount of the cationic polymerizable compound. is 40 parts by mass or more and 85 parts by mass or less. The content of the oxetane compound is, for example, 25 parts by mass or more, preferably 35 parts by mass or more, more preferably 40 parts by mass or more, and for example 100 parts by mass or less, relative to 100 parts by mass of the total amount of the adhesive. preferably 90 parts by mass or less, more preferably 85 parts by mass or less.

The adhesive preferably contains an epoxy compound as a polymerizable compound in addition to the oxetane compound. An epoxy compound is a compound having one or more, preferably two or more epoxy groups in the molecule. This adhesive preferably contains 10 parts by mass or more and 2000 parts by mass or less, more preferably 30 parts by mass or more and 1000 parts by mass or less, still more preferably 30 parts by mass or more and 500 parts by mass of an oxetane compound with respect to 100 parts by mass of an epoxy compound. Including part.

Epoxy compounds may be used alone or in combination of two or more. Examples of epoxy compounds include alicyclic epoxy compounds, aromatic epoxy compounds, hydrogenated epoxy compounds, and aliphatic epoxy compounds. Among them, the epoxy compound preferably contains an alicyclic epoxy compound or an aliphatic epoxy compound, and more preferably contains an alicyclic epoxy compound, from the viewpoint of weather resistance, curing speed and adhesiveness.

The alicyclic epoxy compound is a compound having one or more epoxy groups bonded to an alicyclic ring in the molecule, and preferably has two or more epoxy groups bonded to the alicyclic ring in the molecule. The “epoxy group bonded to an alicyclic ring” means a bridging oxygen atom —O— in the structure represented by formula (II) below. In the following formula (I), m is an integer of 2-5.

A compound in which one or more hydrogen atoms in (CH ₂ ) _m in the above formula (II) are removed and the group is bonded to another chemical structure can be an alicyclic epoxy compound. One or more hydrogen atoms in (CH ₂ ) _m may optionally be substituted with a linear alkyl group such as methyl or ethyl.

From the viewpoint of increasing the glass transition temperature of the cured product, an epoxycyclopentane structure [m = 3 in the above formula (II)] or an epoxycyclohexane structure [m = 4 in the above formula (II)]. A cyclic epoxy compound is preferred, and an alicyclic diepoxy compound represented by the following formula (IIA) is more preferred. A cured product layer of a cationic polymerizable compound containing an alicyclic diepoxy compound represented by the following formula (IIA) has a high glass transition temperature and can suppress diffusion of a dye at high temperatures.

式（ＩＩＡ）中、Ｒ^１及びＲ^２は各々独立に水素原子又は炭素数１～６のアルキル基を表し、アルキル基の炭素数が３以上である場合は脂環式構造を有していてもよい。炭素数１～６のアルキル基は直鎖又は分枝アルキル基であってよく、脂環式構造を有するアルキル基としては、シクロプロピル基、シクロブチル基、シクロペンチル基等が挙げられる。

In formula (IIA), R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and when the alkyl group has 3 or more carbon atoms, it has an alicyclic structure. good too. Alkyl groups having 1 to 6 carbon atoms may be linear or branched alkyl groups, and alkyl groups having an alicyclic structure include cyclopropyl, cyclobutyl and cyclopentyl groups.

In formula (IIA), X represents an oxygen atom, an alkanediyl group having 1 to 6 carbon atoms, or a group represented by any one of the following formulas (IIa) to (IId). Examples of the alkanediyl group having 1 to 6 carbon atoms include methylene group, ethylene group, propane-1,2-diyl group and the like.

When X in formula (IIA) is a group represented by any one of formulas (IIa) to (IId), Y ¹ to Y ⁴ in each formula are each independently an alkanediyl group having 1 to 20 carbon atoms. and when the alkanediyl group has 3 or more carbon atoms, it may have an alicyclic structure. a and b each independently represents an integer of 0 to 20;

Examples of alicyclic epoxy compounds include the following A to M compounds. Chemical formulas A to M shown in the following paragraphs correspond to compounds A to M, respectively.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,
B: 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,
C: ethylene bis(3,4-epoxycyclohexanecarboxylate),
D: bis (3,4-epoxycyclohexylmethyl) adipate,
E: bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate,
F: diethylene glycol bis(3,4-epoxycyclohexylmethyl ether), G: ethylene glycol bis(3,4-epoxycyclohexylmethyl ether),
H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispiro[5.2.2.5.2.2]henicosane,
I: 3-(3,4-epoxycyclohexyl)-8,9-epoxy-1,5-dioxaspiro[5.5]undecane,
J: 4-vinylcyclohexene dioxide,
K: limonene oxide,
L: bis(2,3-epoxycyclopentyl) ether,
M: dicyclopentadiene dioxide.

The alicyclic epoxy compound is preferably 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate because of its easy availability. Also, from the viewpoint of being able to effectively suppress dye diffusion, a 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol is preferred. An alicyclic epoxy compound may be used singly or in combination of multiple different alicyclic epoxy compounds.

The content of the alicyclic epoxy compound is preferably 1 part by mass or more and 80 parts by mass or less, more preferably 3 parts by mass or more and 70 parts by mass or less, still more preferably 3 parts by mass, with respect to the total amount of 100 parts by mass of all the polymerizable compounds. It is more than 60 parts by mass and less than 60 parts by mass. When the content of the alicyclic epoxy compound is within this range, curing by irradiation with active energy rays such as ultraviolet rays proceeds rapidly, and a cured product layer having excellent heat and humidity resistance and sufficient hardness is formed. can do.

The aliphatic epoxy compound is a compound having at least one epoxy ring bonded to an aliphatic carbon atom in the molecule, and preferably has two or more epoxy rings in the molecule. The aliphatic epoxy compound has, for example, at least one oxirane ring (three-membered cyclic ether) bonded to an aliphatic carbon atom in the molecule, preferably two or more. Examples of aliphatic epoxy compounds include monofunctional epoxy compounds such as butyl glycidyl ether and 2-ethylhexyl glycidyl ether; 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and neopentyl glycol diglycidyl Bifunctional epoxy compounds such as ethers; Trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether and other trifunctional or higher epoxy compounds; and an epoxy compound having one epoxy group and an oxirane ring bonded to an aliphatic carbon atom.

From the viewpoint of being able to obtain an adhesive that has a low viscosity and is easy to apply, a bifunctional epoxy compound ( Also referred to as "aliphatic diepoxy compound".) is preferred.

〔式（ＩＩＩ）中、Ｚは炭素数１～９のアルキレン基、炭素数３もしくは４のアルキリデン基、２価の脂環式炭化水素基、又は式－Ｃ_ｍＨ_２ｍ－Ｚ^１－Ｃ_ｎＨ_２ｎ－で示される２価の基を表す。－Ｚ^１－は、－Ｏ－、－ＣＯ－Ｏ－、－Ｏ－ＣＯ－、－ＳＯ_２－、－ＳＯ－又はＣＯ－を表し、ｍ及びｎは各々独立に１以上の整数を表す。ただし、ｍ及びｎの合計は９以下である。

[In the formula (III), Z is an alkylene group having 1 to 9 carbon atoms, an alkylidene group having 3 or 4 carbon atoms, a divalent alicyclic hydrocarbon group, or the formula -C _m H _2m -Z ¹ -C _n Represents a divalent group represented by H _2n -. -Z ¹ - represents -O-, -CO-O-, -O-CO-, -SO ₂ -, -SO- or CO-, and m and n each independently represent an integer of 1 or more. However, the sum of m and n is 9 or less.

The divalent alicyclic hydrocarbon group may be, for example, a divalent alicyclic hydrocarbon group having 4 to 8 carbon atoms, such as a divalent residue represented by the following formula (IIIA). .

Specific examples of the compound represented by formula (III) include diglycidyl ethers of alkanediols; diglycidyl ethers of oligoalkylene glycols having a repeating number of up to about 4; and diglycidyl ethers of alicyclic diols.

Diols (glycols) capable of forming the aliphatic diepoxy compound represented by formula (III) include ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl- 2-ethyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl -1,5-pentanediol, 2-methyl-2,4-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5- alkanediols such as heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol and 1,9-nonanediol; oligoalkylene glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol and dipropylene glycol; ; Cyclohexanediol, cyclohexanedimethanol, and other cycloaliphatic diols.

From the viewpoint of obtaining an adhesive with low viscosity and easy to apply, the aliphatic epoxy compound should contain 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and neopentyl glycol diglycidyl ether. is preferred. 1,6-Hexanediol diglycidyl ether and pentaerythritol polyglycidyl ether are preferable in terms of maintaining optical performance. As the aliphatic epoxy compound, one kind of aliphatic epoxy compound may be used alone, or a plurality of different kinds may be used in combination.

When the adhesive contains an aliphatic epoxy compound, the content of the aliphatic epoxy compound is, for example, 1 part by mass or more and 90 parts by mass or less with respect to 100 parts by mass of the total amount of all polymerizable compounds contained in the adhesive. It is preferably 1 part by mass or more and 40 parts by mass or less, more preferably 3 parts by mass or more and 30 parts by mass or less, still more preferably 5 parts by mass or more and 20 parts by mass or less, and particularly preferably 7 parts by mass or more and 15 parts by mass or less. . When the content of the aliphatic epoxy compound is within this range, a cationically polymerizable composition having a low viscosity and being easy to apply can be obtained.

An aromatic epoxy compound is a compound having an aromatic ring and an epoxy group in its molecule. Specific examples thereof include bisphenol-type epoxy compounds such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diglycidyl ether of bisphenol S, or oligomers thereof; phenol novolak epoxy resin, cresol novolac epoxy resin, hydroxybenzaldehyde phenol novolak novolac epoxy resins such as epoxy resins; polyfunctional epoxies such as glycidyl ether of 2,2′,4,4′-tetrahydroxydiphenylmethane and glycidyl ether of 2,2′,4,4′-tetrahydroxybenzophenone Compound; including polyfunctional epoxy resins such as epoxidized polyvinyl phenol.

From the viewpoint of reducing the viscosity of adhesives, aromatic epoxy compounds include glycidyl ethers of phenols, glycidyl ethers of aromatic compounds having two or more alcoholic hydroxyl groups, glycidyl ethers of polyhydric phenols, and benzoic acids. It preferably contains at least one selected from the group consisting of glycidyl esters, glycidyl esters of polybasic acids, styrene oxide, and epoxidized divinylbenzene. As the aromatic epoxy compound, one having an epoxy equivalent of 80 to 500 is preferable because it improves the curability of the cationic polymerizable composition. As the aromatic epoxy compound, one type of aromatic epoxy compound may be used alone, or a plurality of different types may be used in combination.

Commercially available aromatic epoxy compounds can be used, for example, Denacol EX-121, Denacol EX-141, Denacol EX-142, Denacol EX-145, Denacol EX-146, Denacol EX-147, Denacol EX-201. , Denacol EX-203, Denacol EX-711, Denacol EX-721, On-coat EX-1020, On-coat EX-1030, On-coat EX-1040, On-coat EX-1050, On-coat EX-1051, On-coat EX- 1010, Oncoat EX-1011, Oncoat 1012 (manufactured by Nagase ChemteX Co., Ltd.); HP4032, HP4032D, HP4700 (manufactured by DIC Corporation); ESN-475V (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.); Epicoat YX8800, jER828EL (manufactured by Mitsubishi Chemical Corporation); Epiclon N-665, Epiclon HP-7200 (manufactured by DIC); EOCN-1020, EOCN-102S, EOCN-103S, EOCN-104S, XD-1000, NC-3000, EPPN-501H, EPPN- 501HY, EPPN-502H, NC-7000L (manufactured by Nippon Kayaku Co., Ltd.); 4000, ADEKA RESIN EP-4005, ADEKA RESIN EP-4100, ADEKA RESIN EP-4901 (manufactured by ADEKA); TECHMORE VG-3101L, EPOX-MKR710, EPOX-MKR151 (manufactured by Printec).

When the adhesive contains an aromatic epoxy compound, the adhesive becomes a hydrophobic resin, and the resulting cured product layer also becomes hydrophobic. Therefore, it is possible to prevent moisture from entering from the outside under high temperature and high humidity conditions, and to effectively suppress movement of the dichroic dye contained in the polarizer.

The content of the aromatic epoxy compound is preferably 1 part by mass or more and 70 parts by mass or less, more preferably 5 parts by mass or more and 60 parts by mass, relative to 100 parts by mass of the total amount of the polymerizable compounds contained in the adhesive. or less, more preferably 7 parts by mass or more and 55 parts by mass or less, and particularly preferably 10 parts by mass or more and 50 parts by mass or less. When the content of the aromatic epoxy compound is within this range, the hydrophobicity of the cured product layer can be improved, and diffusion of the dichroic dye out of the polarizer can be more effectively suppressed under high temperature and high humidity conditions. can.

The hydrogenated epoxy compound is a glycidyl ether of a polyol having an alicyclic ring, and is a nuclear hydrogenated polyol obtained by selectively hydrogenating the aromatic ring of an aromatic polyol under pressure in the presence of a catalyst. It can be a glycidyl-etherified hydroxy compound. Specific examples of aromatic polyols include bisphenol type compounds such as bisphenol A, bisphenol F and bisphenol S; novolac type resins such as phenol novolak resin, cresol novolak resin and hydroxybenzaldehyde phenol novolak resin; tetrahydroxydiphenylmethane and tetrahydroxybenzophenone. , Polyvinylphenol and other polyfunctional compounds. A glycidyl ether can be obtained by reacting epichlorohydrin with an alicyclic polyol obtained by subjecting an aromatic ring of an aromatic polyol to a hydrogenation reaction. Preferred among the hydrogenated epoxy compounds are hydrogenated diglycidyl ethers of bisphenol A.

The adhesive may further contain other curable compounds than those mentioned above. Specific examples of other curable compounds are cationically polymerizable compounds other than those mentioned above, such as lactone compounds, cyclic acetal compounds, cyclic thioether compounds, and spiro-orthoester compounds.

(Photo cationic polymerization initiator)
When the adhesive contains a cationic polymerizable compound, the adhesive preferably further contains a cationic photopolymerization initiator for initiating polymerization by irradiation with active energy rays.

A photocationic polymerization initiator generates cationic species or a Lewis acid upon irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, or electron beams, and initiates the polymerization reaction of a cationic polymerizable compound. Since the photocationic polymerization initiator acts catalytically with light, it is excellent in storage stability and workability even when mixed with a polymerizable compound. Examples of compounds that generate cationic species or Lewis acids upon irradiation with active energy rays include onium salts such as aromatic iodonium salts and aromatic sulfonium salts, aromatic diazonium salts, and iron-arene complexes.

An aromatic iodonium salt is a compound having a diaryliodonium cation, typically a diphenyliodonium cation.
An aromatic sulfonium salt is a compound having a triarylsulfonium cation, and typical cations include triphenylsulfonium cation, 4,4′-bis(diphenylsulfonio)diphenylsulfide cation, and the like. An aromatic diazonium salt is a compound having a diazonium cation, typically a benzenediazonium cation. The iron-arene complex is typically a cyclopentadienyl iron(II) arene cation complex.

The above cation forms a photocationic polymerization initiator in combination with an anion (anion). Examples of anions constituting the photocationic polymerization initiator include a special phosphorus-based anion [(Rf) _n PF _6-n ] ⁻ , hexafluorophosphate anion PF ₆ ⁻ , hexafluoroantimonate anion SbF ₆ ⁻ , and pentafluorohydroxyantimonate. Examples include the anion SbF ₅ (OH) ⁻ , the hexafluoroarsenate anion AsF ₆ ⁻ , the tetrafluoroborate anion BF ₄ ⁻ , the tetrakis(pentafluorophenyl)borate anion B(C ₆ F ₅ ) ₄ ⁻ and the like. Among them, from the viewpoint of the curability of the polymerizable compound and the safety of the resulting cured product layer, the photocationic polymerization initiator is a special phosphorus-based anion [(Rf) _n PF _6-n ] ⁻ or a hexafluorophosphate anion PF ₆ ⁻ is preferred.

A photocation polymerization initiator may be used individually by 1 type, or may be used in combination of multiple different types. Among them, aromatic sulfonium salts are preferable because they have ultraviolet absorption properties even in a wavelength region around 300 nm, and thus are excellent in curability and can provide a cured product having good mechanical strength and adhesive strength.

The content of the polymerization initiator in the adhesive is usually 0.5 parts by mass or more and 10 parts by mass or less, preferably 6 parts by mass or less, more preferably 3 parts by mass or less, relative to 100 parts by mass of the polymerizable compound. is. When the content of the polymerization initiator is within this range, the polymerizable compound can be sufficiently cured, and high mechanical strength and adhesive strength can be imparted to the cured product layer composed of the obtained cured product. .

The adhesive can contain additives commonly used in curable compositions, if desired. Such additives include, for example, ion trapping agents, antioxidants, chain transfer agents, polymerization accelerators (such as polyols), sensitizers, sensitizing aids, light stabilizers, tackifiers, thermoplastic resins, Fillers, flow modifiers, plasticizers, antifoaming agents, leveling agents, silane coupling agents, dyes, antistatic agents, ultraviolet absorbers and the like.

Examples of sensitizers include photosensitizers. A photosensitizer is a compound that exhibits a maximum absorption at a wavelength longer than the maximum absorption wavelength exhibited by a photocationic polymerization initiator and accelerates the polymerization initiation reaction by the photocationic polymerization initiator. A photosensitizer is a compound that further promotes the action of a photosensitizer. By blending a photosensitizer and a photosensitizing aid, it is possible to form a cured layer having desired performance even when the polarizing plate contains a film with low UV transmittance.

The photosensitizer is preferably a compound that exhibits maximum absorption for light with a wavelength longer than 380 nm, for example. Examples of such photosensitizers include anthracene compounds described below.

9,10-dimethoxyanthracene,
9,10-diethoxyanthracene,
9,10-dipropoxyanthracene,
9,10-diisopropoxyanthracene,
9,10-dibutoxyanthracene,
9,10-dipentyloxyanthracene,
9,10-dihexyloxyanthracene,
9,10-bis(2-methoxyethoxy)anthracene,
9,10-bis(2-ethoxyethoxy)anthracene,
9,10-bis(2-butoxyethoxy)anthracene,
9,10-bis(3-butoxypropoxy)anthracene,
2-methyl- or 2-ethyl-9,10-dimethoxyanthracene,
2-methyl- or 2-ethyl-9,10-diethoxyanthracene,
2-methyl- or 2-ethyl-9,10-dipropoxyanthracene,
2-methyl- or 2-ethyl-9,10-diisopropoxyanthracene,
2-methyl- or 2-ethyl-9,10-dibutoxyanthracene,
2-methyl- or 2-ethyl-9,10-dipentyloxyanthracene,
2-methyl- or 2-ethyl-9,10-dihexyloxyanthracene.

The leveling agent is an additive that has the function of adjusting the fluidity of the curable composition and making the coating film obtained by coating the composition more flat. Examples include acrylate-based and perfluoroalkyl-based leveling agents. A commercially available product may be used as the leveling agent.

The content of the leveling agent is preferably 0.01 parts by mass or more and 5 parts by mass or less, more preferably 0.05 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the polymerizable compound.
When the content of the leveling agent is within this range, the second cured layer tends to be smoother.

As shown in FIG. 1 , the active energy ray-curable adhesive as described above is applied to the surface of the first film 10 . Specifically, the first film 10 is pulled out from the roll 1, and the coating device 3 continuously coats the surface of the first film 10 guided by the guide roll 2A with the active energy ray-curable adhesive. Examples of the coating device 3 are doctor blades, wire bars, die coaters, comma coaters and gravure coaters.

The thickness of the cured product layer after curing is preferably 0.1 to 5 μm, more preferably 0.5 to 3 μm, and it is suitable to adjust the coating amount of the adhesive so as to achieve such a thickness. . When the thickness of the cured product layer is within this range, the function of preventing diffusion of the dichroic dye from the polarizer can be further exhibited, and the thickness of the polarizing plate can be reduced.

(Lamination process)
The first film 10 coated with the adhesive is guided between the pair of bonding rolls 5 via the guide roll 2B. Moreover, the 2nd film 20 pulled out from the roll 4 is guided between a pair of bonding rolls 5 via the guide roll 2C.

By being pressed from both surfaces of the pair of bonding rolls 5, the first film 10 and the second film 20 are bonded via the active energy ray-curable adhesive, and the first film 10 is cured with the active energy ray. A laminate 30 is formed having the mold adhesive layer and the second film 20 in that order.

Specifically, the lower surface of the first film 10 in FIG. 2 and the upper surface of the second film 20 in FIGS. 3(a) and 3(b) are pasted together with an active energy ray-curable adhesive layer. In this state, the active energy ray-curable adhesive is uncured.

(Curing process)
During 2 to 8 seconds after bonding the first film 10 and the second film by the bonding roll 5, the active energy ray-curable adhesive layer in the laminate 30 is irradiated with an active energy ray. to start. Irradiation is preferably started within 2 to 4.5 seconds after lamination. Irradiation is started within 2 to 8 seconds after lamination, and it is not necessary to complete curing within 2 to 8 seconds after lamination. Therefore, the irradiation with active energy rays may be continued even after 8 seconds from bonding.

In FIG. 1, when bonding two films by a pair of bonding rolls 5, the bonding start position is the position L0 where the two films pass the line connecting the axes 5C between the pair of rolls. Moreover, the position (center position of irradiation) where the active energy ray is irradiated from the active energy ray source 6 with respect to the laminated body 30 conveyed after bonding is set to L1. Furthermore, let W be the distance along the film transport direction between the position L0 and the position L1.

In such a configuration, the time T from the bonding of the two films to the start of the irradiation of the active energy ray is V [m/s] for the transport speed of the film, and the position L0 and the position L1 W/V [s] based on the distance W [m] between Therefore, when the distance W is fixed, by changing the conveying speed V, it is possible to adjust W/V, that is, the time T from lamination to the start of irradiation. It is also possible to change the distance W to adjust W/V.

Another active energy ray source can be provided behind the active energy ray source 6 in FIG. 1, and additional irradiation can be performed, for example, after 8 seconds from lamination to increase the degree of curing.

The transport speed of the laminate 30 on the bonding roll in the bonding process can be 1 to 50 m/min.

The amount of active energy ray irradiation from the active energy ray source 6 (integrated light amount in the UVA region (320 to 390 nm)) can be 150 to 800 mJ/cm ² , preferably 350 to 600 mJ/cm ² . .

The active energy rays may be irradiated from the first film 10 side, from the second film 20 side, or from both sides.

When the first film is a member having UV absorption ability, the transmittance of the first film 10 in the ultraviolet region is low. For example, when the transmittance at 320 nm of the first film 10 is less than 10% and the transmittance at 320 nm of the second film 20 is 10 to 99%, from the second film 20 toward the first film 10 Irradiation with active energy rays is preferred.

In addition, in the mode of irradiating the active energy ray toward between the pair of bonding rolls 5 from which the bonded laminate 30 is paid out, the adhesive in the laminate is irradiated within 2 seconds after bonding. is excluded from the embodiments of the present invention.

FIG. 4 shows an example of a laminate (polarizing plate) when the first film 10 of FIG. 2 and the second film of FIG. 3 are bonded together. The first film 10 and the second film are bonded with a cured product layer 50 of an active energy ray-curable adhesive.

(Mechanism of action)
When the irradiation of the active energy ray to the laminate 30 is started in less than 2 seconds after bonding the first film 10 and the second film 20, deformation of the film caused when pressed by the bonding roll 5 occurs. , may cause the laminate 30 to curl.

In addition, if irradiation with active energy rays is started after more than 8 seconds have passed since lamination, the transmittance of the laminate is lowered. Although the details of this reason are not clear, the uncured active energy ray-curable adhesive and the second film having a polarizer containing a cured product of an oriented polymerizable liquid crystal compound and a dichroic dye are in contact for a long time. Then, it is considered that the dichroic dye diffuses from the polarizer into the adhesive layer due to the influence of the polymerizable compound (monomer) or the like in the active energy ray-curable adhesive.

The present invention is not limited to the above embodiments, and various modifications are possible. For example, the lamination structure of the first film and the second film can take various forms other than those shown in the drawings, and the apparatus used for lamination is not limited to that shown in FIG. It can also be applied to double film lamination and curing.

In the apparatus shown in FIG. 1, the first film 10 and the second film 20 were laminated with an active energy ray-curable adhesive and cured by irradiating the active energy ray.
Layer structure of the first film (FIG. 2): reverse wavelength dispersion type λ/4 plate 12/adhesive layer 14/positive C plate 16/release substrate 18 in order from the adhesive coated side
Layer structure of the second film (Fig. 3): Overcoat layer 32/polarizer 36/alignment film 34/hard coat layer 38/release substrate 40 in order from the adhesive contact side
The first film had a transmittance of 0% for ultraviolet rays with a wavelength of 320 nm, and the second film had a transmittance of 15.4% for ultraviolet rays with a wavelength of 320 nm.

［二色性色素］

〔他の成分〕
重合開始剤；
２－ジメチルアミノ－２－ベンジル－１－（４－モルホリノフェニル）ブタン－１－オン
（イルガキュア３６９；ＢＡＳＦジャパン（株）製） ６部
レベリング剤；
ポリアクリレート化合物（ＢＹＫ－３６１Ｎ；ＢＹＫ－Ｃｈｅｍｉｅ社製）
１．２部
溶剤；o-キシレン ２５０部 The polarizer was a cured product of a composition containing a dichroic dye and a polymerizable liquid crystal compound shown below. The manufacturing method of the polarizer and the material and manufacturing method of the alignment film were the same as in Example 1 of JP-A-2020-003824.
[Polymerizable liquid crystal compound]

[Dichroic dye]

[Other ingredients]
polymerization initiator;
2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butan-1-one (Irgacure 369; manufactured by BASF Japan Ltd.) 6 parts leveling agent;
Polyacrylate compound (BYK-361N; manufactured by BYK-Chemie)
1.2 parts Solvent; o-xylene 250 parts

A cured product of a polyvinyl alcohol-based resin was used as the overcoat layer, and a cured product of an active energy ray-curable resin was used as the hard coat layer.

Active Energy Ray Curable Adhesive Cationic curable components 1 to 4 shown below and a cationic polymerization initiator were mixed. The obtained mixture was further mixed with a cationic polymerization initiator and a sensitizer shown below. The resulting solution was degassed to obtain an adhesive. In addition, the following compounding quantity is based on solid content.
- Cationic curable component 1 (7 parts): 3',4'-epoxycyclohexylmethyl 3',4'-epoxycyclohexane carboxylate (manufactured by Daicel Corporation, CEL2021P)
· Cationic curable component 2 (40 parts): fluorene type epoxy resin (Osaka Gas Chemicals Co., Ltd., OGSOLEG-200)
- Cationic curable component 3 (33 parts): neopentyl glycol diglycidyl ether (EX-211L manufactured by Nagase ChemteX Corporation)
· Cationic curable component 4 (20 parts): 3-ethyl-3 {[(3-ethyloxetan-3-yl) methoxy] methyl} oxetane (Toagosei Co., Ltd., OXT-221)
- Cationic polymerization initiator (2.25 parts (solid content)): trade name: 50% propylene carbonate solution of CPI-100 (manufactured by San-Apro Co., Ltd.) - Sensitizer (2 parts): 1,4-diethoxynaphthalene

Lamination conditions Adhesive film thickness: 1.3 μm
UV illuminance @UVA (320-390 nm): 400 mJ/cm ²
Distance W from bonding position to UV irradiation position: 1.5 m
In Examples 1 to 5 and Comparative Examples 1 and 2, by changing the transport speed V of the film, the time T from lamination to the start of UV irradiation was changed.

(evaluation)
Transmittance measurement device: UV-visible spectrophotometer "UV-2450" (manufactured by Shimadzu Corporation)
The transmittance at 520 nm of the laminate obtained by bonding was measured.

According to Examples, it was confirmed that a polarizing plate with high transmittance can be obtained.

10... First film, 12... λ/4 plate (optical function layer, retardation plate), 16... Positive C plate (optical function layer, retardation plate), 19... Release substrate, 20... Second film, 30 ... Laminate, 32 ... Overcoat layer, 36 ... Polarizer, 50 ... Cured material layer.

Claims (8)

A step of applying an active energy ray-curable adhesive to the surface of the first film including the optical function layer;
obtaining a laminate by bonding the first film containing the optical function layer to the surface of the second film containing the polarizer via the applied active energy ray-curable adhesive;
Within 2 to 8 seconds after laminating the first film and the second film, the active energy ray curing type is started by irradiating the adhesive in the laminate with an active energy ray. A step of obtaining a cured product layer of the adhesive,
A method for producing a polarizing plate, wherein the polarizer includes a cured product of an oriented polymerizable liquid crystal compound and a dichroic dye. 2. The method according to claim 1, wherein the second film includes an overcoat layer and the polarizer in order from the surface to which the first film is attached. The method according to claim 1 or 2, wherein the active energy ray-curable adhesive contains a cationic polymerizable compound and a photocationic polymerization initiator. 4. The method according to any one of claims 1 to 3, wherein the irradiation dose of the active energy ray is 150 to 800 mJ/cm ² . The method of any one of claims 1-4, wherein the first film comprises at least one retarder. The active energy ray contains ultraviolet rays of 320 nm, the transmittance of the first film to ultraviolet rays of 320 nm is less than 10%, the transmittance of ultraviolet rays of 320 nm of the second film is 10 to 99%, The method according to any one of claims 1 to 5, wherein the active energy ray is irradiated from the second film toward the first film. The method according to any one of claims 1 to 6, wherein the thickness of the cured product layer of the active energy ray-curable adhesive is 0.5 to 3 µm. Further comprising a step of peeling off a release substrate provided on the surface of the first film before the step of applying an active energy ray-curable adhesive to the surface of the first film including the optical function layer. Item 8. The method according to any one of Items 1 to 7.

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