JP7796490B2 - Polarizing plate and laminate - Google Patents

Description

The present invention relates to a polarizing plate and also to a laminate comprising a polarizing plate.

Image display devices such as liquid crystal display devices and organic EL display devices are widely used in mobile applications such as personal computers and mobile phones, and in-vehicle applications such as car navigation systems. Image display devices used in these applications generally have a transparent member such as a glass plate or transparent resin plate placed on the surface to protect the display panel.

In addition, polarizing plates are commonly used in liquid crystal display panels and organic EL display panels, and in these cases, the transparent member and polarizing plate are laminated together via a pressure-sensitive adhesive layer or adhesive layer.

To improve the visibility and mechanical strength of image display devices, UV-curable acrylic resin compositions are sometimes used as adhesives for laminating transparent members and polarizing plates. However, UV-curable acrylic resin compositions can be inhibited from curing by oxygen in the air. Therefore, a UV-addition-curable silicone adhesive composition has been proposed that uses a hydrosilylation reaction with a UV-activated platinum catalyst to cure the resin composition (Patent Document 1).

Japanese Patent Application Laid-Open No. 2020-055945

UV-addition-curable silicone adhesive compositions have the property of gradually curing after being irradiated with UV light. This offers the advantage of allowing any order to be set for the adhesive composition application process, UV irradiation and composition curing process, and lamination of components, and is therefore becoming increasingly popular.

However, when manufacturing an image display panel by laminating a polarizing plate having a hard coat layer on its surface with a transparent member, the ultraviolet addition-curable silicone adhesive composition may not cure sufficiently.

The present invention aims to provide a polarizing plate that can sufficiently cure an ultraviolet-addition-curable silicone adhesive composition within a certain period of time, even when a polarizing plate having a hard coat layer on its surface and a transparent member are laminated together using an ultraviolet-addition-curable silicone adhesive composition.

The present invention provides the polarizing plate and laminate exemplified below.
[1] A polarizing plate comprising a polarizer and a hard coat layer, wherein the hard coat layer constitutes at least one outermost surface of the polarizing plate, and the hard coat layer has an absorbance of 4.5 or less at a wavelength of 300 nm.
[2] The hard coat layer is made of a cured layer of a photocurable resin composition,
The polarizing plate according to [1], wherein the photocurable resin composition contains a radical polymerization initiator as a photopolymerization initiator.
[3] The polarizing plate according to [1] or [2], wherein the cured layer of the photocurable resin composition contains a cured product of a (meth)acrylic resin.
[4] The polarizing plate according to [2], wherein the radical polymerization initiator is an α-hydroxyacetophenone-based photopolymerization initiator or an α-aminoacetophenone-based photopolymerization initiator.
[5] The polarizing plate according to any one of [1] to [4], wherein the hard coat layer has a thickness of 0.5 μm or more and 10 μm or less.
[6] The polarizing plate according to any one of [1] to [5],
a transparent member;
The hard coat layer and the transparent member are laminated via an ultraviolet addition curing silicone adhesive layer.
[7] The laminate according to [6], wherein the thickness of the ultraviolet addition-curable silicone adhesive layer is 10 μm or more and 1000 μm or less.
[8] The laminate according to [6] or [7], wherein the ultraviolet addition-curable silicone adhesive layer is a cured layer of an ultraviolet addition-curable silicone adhesive composition.
[9] The laminate according to any one of [6] to [8], wherein the transparent member is a glass plate, a transparent resin plate, or a touch panel.

The present invention provides a polarizing plate that can sufficiently cure the ultraviolet-addition-curable silicone adhesive composition within a certain period of time, even when a polarizing plate having a hard coat layer on its surface and a transparent member are laminated together using an ultraviolet-addition-curable silicone adhesive composition.

FIG. 2 is a schematic cross-sectional view showing an example of a layer structure of a polarizing plate. FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of the laminate. FIG. 2 is a conceptual diagram illustrating the curing time of an ultraviolet addition-curable silicone adhesive composition. FIG. 2 is a schematic cross-sectional view illustrating a method for measuring the cure time of an ultraviolet addition-curable silicone adhesive composition.

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments. In all of the drawings, the scale has been adjusted appropriately to make each component easier to understand, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component.

<Polarizing plate>
The polarizing plate of the present invention includes a polarizer and a hard coat layer, the hard coat layer constituting at least one outermost surface of the polarizing plate, and the hard coat layer has an absorbance of 4.5 or less at a wavelength of 300 nm. The polarizing plate of the present invention will be described below with reference to the drawings. Polarizing plate 10 shown in FIG. 1 includes a polarizer 11 and a hard coat layer 12. Polarizing plate 10 may further include layers other than the layers described above. Examples of such layers include a thermoplastic resin film, an attachment layer, an optically functional layer, and a protective film. Polarizing plate 10 shown in FIG. 1 further includes a thermoplastic resin film 13 between polarizer 11 and hard coat layer 12. The polarizing plate may be a linear polarizing plate or a circular polarizing plate in which a retardation layer (described below) is laminated on a linear polarizing plate.

[Polarizer]
A polarizer formed by adsorbing and aligning a dichroic dye in a layer containing a polyvinyl alcohol (hereinafter also referred to as "PVA")-based resin (also referred to as a "PVA-based resin layer" in this specification) can be used as the polarizer 11. Examples of such polarizers include a polarizer formed by using a PVA-based resin film, dyeing the PVA-based resin film with a dichroic dye, and uniaxially stretching the film, and a polarizer formed by using a laminated film obtained by applying a coating liquid containing a PVA-based resin onto a substrate film, dyeing the PVA-based resin layer, which is a coating layer of the laminated film, with a dichroic dye, and uniaxially stretching the laminated film.

The polarizer 11 is formed from a PVA-based resin obtained by saponifying a polyvinyl acetate-based resin. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate with other copolymerizable monomers. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

The degree of saponification of the PVA-based resin is preferably approximately 85 mol% or higher, more preferably approximately 90 mol% or higher, and even more preferably approximately 99 mol% to 100 mol%. The degree of polymerization of the PVA-based resin is 1,000 to 10,000, preferably 1,500 to 5,000. This PVA-based resin may be modified, such as polyvinyl formal, polyvinyl acetal, or polyvinyl butyral modified with aldehydes.

The thickness of the polarizer 11 is preferably 5 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, and even more preferably 8 μm or more and 30 μm or less. A thickness of 50 μm or less for the polarizer 11 can suppress the effect of polyenation of the PVA-based resin on degradation of optical properties in high-temperature environments, while a thickness of 5 μm or more for the polarizer 11 makes it easier to achieve the desired optical properties.

The moisture content of the polarizer 11 is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%. Preferably, it is equal to or greater than the equilibrium moisture content at a temperature of 30% and a relative humidity of 45% at a temperature of 20°C and a relative humidity of 45%. More preferably, it is equal to or less than the equilibrium moisture content at a temperature of 42% at a temperature of 20°C and a relative humidity of 40%. Most preferably, it is equal to or less than the equilibrium moisture content at a temperature of 38% at a temperature of 20°C and a relative humidity of 45%. If the moisture content is below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 40%, the polarizer 11 becomes less easy to handle and more likely to crack. By keeping the moisture content at or less than the equilibrium moisture content at a temperature of 48% at a temperature of 20°C and a relative humidity of 48%, a laminate with excellent high-temperature durability can be provided. The moisture content of the polarizer 11 is the moisture content of the polarizer in the polarizing plate.

The method for manufacturing polarizer 11 is not particularly limited, but typical examples include a method in which a pre-wound polyvinyl alcohol-based resin film is fed out and stretched, dyed, crosslinked, etc. (hereinafter referred to as "Manufacturing Method 1"), and a method in which a coating liquid containing a polyvinyl alcohol-based resin is applied to a substrate film to form a polyvinyl alcohol-based resin layer as a coating layer, and the resulting laminate is stretched (hereinafter referred to as "Manufacturing Method 2").

Manufacturing method 1 can be achieved by uniaxially stretching a polyvinyl alcohol-based resin film, dyeing the polyvinyl alcohol-based resin film with a dichroic dye such as iodine to adsorb the dichroic dye, treating the polyvinyl alcohol-based resin film with the adsorbed dichroic dye in an aqueous boric acid solution, and rinsing the film with water after treatment with the aqueous boric acid solution.

The swelling process is a treatment step in which the polyvinyl alcohol-based resin film is immersed in a swelling bath. This process removes dirt and blocking agents from the surface of the polyvinyl alcohol-based resin film, and by swelling the polyvinyl alcohol-based resin film, it is possible to suppress uneven dyeing. The swelling bath typically uses a medium whose main component is water, distilled water, pure water, or other water. Surfactants, alcohol, etc. may also be added to the swelling bath as appropriate, according to conventional methods.

The temperature of the swelling bath is preferably about 10 to 60°C, more preferably about 15 to 45°C, and even more preferably about 18 to 30°C. The immersion time in the swelling bath cannot be determined in general because the degree of swelling of the polyvinyl alcohol resin film is affected by the temperature of the swelling bath, but is preferably about 5 to 300 seconds, more preferably about 10 to 200 seconds, and even more preferably about 20 to 100 seconds. The swelling process may be carried out once, or multiple times as necessary.

The dyeing process is a treatment process in which a polyvinyl alcohol-based resin film is immersed in a dye bath (iodine solution), allowing iodine or a dichroic substance such as a dichroic dye to be adsorbed and oriented in the polyvinyl alcohol-based resin film. The iodine solution is typically preferably an aqueous iodine solution, containing iodine and an iodide as a solubilizing agent. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Among these, potassium iodide is preferred from the perspective of controlling the potassium content in the polarizer.

The iodine concentration in the dye bath is preferably about 0.01 to 1% by mass, and more preferably about 0.02 to 0.5% by mass. The iodide concentration in the dye bath is preferably about 0.01 to 10% by mass, more preferably about 0.05 to 5% by mass, and even more preferably about 0.1 to 3% by mass.

The temperature of the dye bath is preferably about 10 to 50°C, more preferably about 15 to 45°C, and even more preferably about 18 to 30°C. The immersion time in the dye bath cannot be determined in general because the degree of dyeing of the polyvinyl alcohol resin film is affected by the temperature of the dye bath, but is preferably about 10 to 300 seconds, and more preferably about 20 to 240 seconds. The dyeing process may be carried out once, or multiple times as necessary.

The crosslinking process is a treatment step in which the polyvinyl alcohol-based resin film dyed in the dyeing process is immersed in a treatment bath (crosslinking bath) containing a boron compound. The boron compound crosslinks the polyvinyl alcohol-based resin film, allowing iodine molecules or dye molecules to be adsorbed to the crosslinked structure. Examples of boron compounds include boric acid, borate salts, and borax. The crosslinking bath is generally an aqueous solution, but it may also be, for example, a mixed solution of water and an organic solvent that is miscible with water. Furthermore, the crosslinking bath preferably contains potassium iodide in order to control the potassium content in the polarizer.

The concentration of the boron compound in the crosslinking bath is preferably approximately 1 to 15% by mass, more preferably approximately 1.5 to 10% by mass, and even more preferably approximately 2 to 5% by mass. Furthermore, when potassium iodide is used in the crosslinking bath, the concentration of potassium iodide in the crosslinking bath is preferably approximately 1 to 15% by mass, more preferably approximately 1.5 to 10% by mass, and even more preferably approximately 2 to 5% by mass.

The temperature of the crosslinking bath is preferably about 20 to 70°C, and more preferably about 30 to 60°C. The immersion time in the crosslinking bath cannot be determined in general because the degree of crosslinking of the polyvinyl alcohol resin film is affected by the temperature of the crosslinking bath, but is preferably about 5 to 300 seconds, and more preferably about 10 to 200 seconds. The crosslinking process may be carried out only once, or multiple times as necessary.

The stretching process is a processing step in which a polyvinyl alcohol-based resin film is stretched to a predetermined magnification in at least one direction. Generally, the polyvinyl alcohol-based resin film is stretched uniaxially in the conveying direction (longitudinal direction). There are no particular restrictions on the stretching method, and either wet stretching or dry stretching can be used. The stretching process may be carried out only once, or multiple times as necessary. The stretching process may be carried out at any stage in the production of a polarizer.

The treatment bath (stretching bath) used in the wet stretching method can typically be water or a solvent such as a mixture of water and a water-miscible organic solvent. The stretching bath preferably contains potassium iodide to control the potassium content in the polarizer. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably approximately 1 to 15% by mass, more preferably approximately 2 to 10% by mass, and even more preferably approximately 3 to 6% by mass. Furthermore, the treatment bath (stretching bath) can contain a boron compound to prevent film breakage during stretching. In this case, the concentration of the boron compound in the stretching bath is preferably approximately 1 to 15% by mass, more preferably approximately 1.5 to 10% by mass, and even more preferably approximately 2 to 5% by mass.

The temperature of the stretching bath is preferably about 25 to 80°C, more preferably about 40 to 75°C, and even more preferably about 50 to 70°C. The immersion time in the stretching bath cannot be determined in general because the degree of stretching of the polyvinyl alcohol resin film is affected by the temperature of the stretching bath, but is preferably about 10 to 800 seconds, and more preferably about 30 to 500 seconds. The stretching treatment in the wet stretching method may be carried out together with one or more of the following treatment processes: swelling, dyeing, crosslinking, and washing.

Dry stretching methods include, for example, inter-roll stretching, heated roll stretching, and compression stretching. Dry stretching may also be performed in conjunction with a drying process.

The total stretching ratio (cumulative stretching ratio) applied to the polyvinyl alcohol-based resin film can be set appropriately depending on the purpose, but is preferably approximately 2 to 7 times, more preferably approximately 3 to 6.8 times, and even more preferably approximately 3.5 to 6.5 times.

The cleaning process is a treatment step in which the polyvinyl alcohol-based resin film is immersed in a cleaning bath, which allows the removal of foreign matter remaining on the surface of the polyvinyl alcohol-based resin film. The cleaning bath typically uses a medium whose main component is water, such as distilled water or pure water. Furthermore, from the perspective of controlling the potassium content in the polarizer, it is preferable to use potassium iodide in the cleaning bath. In this case, the concentration of potassium iodide in the cleaning bath is preferably approximately 1 to 10% by mass, more preferably approximately 1.5 to 4% by mass, and even more preferably approximately 1.8 to 3.8% by mass.

The temperature of the cleaning bath is preferably about 5 to 50°C, more preferably about 10 to 40°C, and even more preferably about 15 to 30°C. The immersion time in the cleaning bath cannot be determined in general because the degree of cleaning of the polyvinyl alcohol resin film is affected by the temperature of the cleaning bath, but is preferably about 1 to 100 seconds, more preferably about 2 to 50 seconds, and even more preferably about 3 to 20 seconds. The cleaning process may be carried out once, or multiple times as necessary.

The drying step is a step in which the polyvinyl alcohol-based resin film washed in the washing step is dried to obtain a polarizer. Drying can be carried out by any appropriate method, such as natural drying, air drying, or heat drying.

Manufacturing method 2 can be achieved by applying a coating liquid containing the polyvinyl alcohol resin to a substrate film, uniaxially stretching the resulting laminate film, dyeing the polyvinyl alcohol resin layer of the uniaxially stretched laminate film with a dichroic dye to adsorb the dichroic dye and form a polarizer, treating the film with the adsorbed dichroic dye with an aqueous boric acid solution, and rinsing with water after the treatment with the aqueous boric acid solution. The substrate film used to form the polarizer may also be used as a protective layer for the polarizer. If necessary, the substrate film may be peeled off and removed from the polarizer.

[Hard coat layer]
The hard coat layer 12 can have the function of improving the scratch resistance of the polarizing plate 10. The hard coat layer 12 forms the outermost surface on at least one side of the polarizing plate 10. When the polarizing plate has two or more hard coat layers, the hard coat layers may be arranged so as to form the outermost surfaces on both sides of the polarizing plate 10.

The hard coat layer 12 has an absorbance of 4.5 or less at a wavelength of 300 nm. Research by the inventors has revealed that if the absorbance of the hard coat layer 12 at a wavelength of 300 nm is 4.5 or less, the UV-addition-curable silicone adhesive composition can be sufficiently cured, even when a polarizing plate and a transparent member are laminated together using the UV-addition-curable silicone adhesive composition. This is presumably because, as described below, when the type and content of the photopolymerization initiator in the hard coat layer-forming composition is adjusted so that the absorbance of the hard coat layer at a wavelength of 300 nm is 4.5 or less, the photopolymerization initiator in the hard coat layer is less likely to react with the vinyl groups in the UV-addition-curable silicone adhesive composition, making it easier to suppress curing inhibition.

The absorbance of the hard coat layer 12 at a wavelength of 300 nm is preferably 3.5 or less, more preferably 3.0 or less, even more preferably 2.5 or less, particularly preferably 2.0 or less, even more particularly preferably 1.5 or less, and even more particularly preferably 1.0 or less, from the viewpoint of facilitating a shortening of the curing time of the UV-curable silicone adhesive. The absorbance of the hard coat layer 12 at a wavelength of 300 nm is typically greater than 0, and may be, for example, 0.01 or greater, or 0.1 or greater.

Methods for setting the absorbance of the hard coat layer 12 to 4.5 or less include, for example, selecting the type of photopolymerization initiator used in the hard coat layer-forming composition, adjusting the content of the photopolymerization initiator in the hard coat layer-forming composition, adjusting the thickness of the hard coat layer, and combinations of these.

The hard coat layer 12 is preferably composed of a cured layer of a photocurable resin composition (hereinafter also referred to as a hard coat layer-forming composition). Examples of photocurable resins include active energy ray-curable resins. The hard coat layer-forming composition includes a photocurable resin. The hard coat layer-forming composition may be, for example, a radical-curable composition. In addition to the photocurable resin, the hard coat layer-forming composition may contain, for example, a polymerization initiator, additives, solvents, etc. Examples of additives include plasticizers, ultraviolet absorbers, infrared absorbers, colorants such as pigments and dyes, fluorescent brighteners, dispersants, heat stabilizers, light stabilizers, antistatic agents, antioxidants, lubricants, surfactants, etc.

Photocurable resins include various resins such as polyester resins, (meth)acrylic resins, urethane resins, (meth)acrylic urethane resins, amide resins, silicone resins, silicate resins, epoxy resins, melamine resins, and oxetane resins. These curable resins can be used singly or in combination. In this specification, "(meth)acrylic" refers to acrylic and/or methacrylic, and the "(meth)" in "(meth)acrylate," "(meth)acryloyl," etc., has the same meaning.

Among these, (meth)acrylic resins, (meth)acrylic urethane resins, and epoxy resins are preferred due to their high hardness, UV curability, and excellent productivity, with (meth)acrylic resins being particularly preferred. UV-curable resins include UV-curable monomers, oligomers, polymers, and the like. Preferred UV-curable resins include those containing UV-polymerizable functional groups, particularly those containing acrylic monomers or oligomers with two or more, particularly 3 to 6, functional groups. Examples of such compounds include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, EO-modified pentaerythritol tetra(meth)acrylate, PO-modified pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, and triethylene glycol di(meth)acrylate. Examples include trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, PO-modified trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and tricyclodecane dimethanol di(meth)acrylate.

Of these, pentaerythritol tetra(meth)acrylate, EO-modified pentaerythritol tetra(meth)acrylate, PO-modified pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, PO-modified trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and tricyclodecane dimethanol di(meth)acrylate are preferred.
These may be contained in combination of two or more kinds, and commercially available products containing two or more kinds may also be used.

Commercially available (meth)acrylic resins can be used, including NK Ester A-DCP, DCP, A-TMPT, TMPT, ATM-35E, and A-TMMT manufactured by Shin-Nakamura Chemical Co., Ltd.; Viscoat (registered trademark) #195, Viscoat (registered trademark) #300, and Viscoat (registered trademark) #360 manufactured by Osaka Organic Chemical Industry Ltd.; acrylate monomers IRR 214-K, PETIA, PETRA, TMPTA, TMPEOTA, EBECRYL 135, OTA 480, and EBERCRYL 40 manufactured by Daicel-Allnex Corporation; and Beamset 710 and Beamset 730 manufactured by Arakawa Chemical Industries, Ltd.

The (meth)acrylic resin preferably accounts for 10% by mass or more and 99% by mass or less of the solid content of the hard coat layer-forming composition, and more preferably 50% by mass or more and 99% by mass or less.

To provide the polarizing plate with anti-glare and anti-glare properties, the hard coat layer preferably has anti-glare properties. Examples of anti-glare hard coat layers include those in which fine particles are dispersed in a matrix resin made of the above-mentioned photocurable resin. The fine particles dispersed in the matrix resin can be any of a variety of transparent materials, including metal oxide fine particles such as silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide; glass fine particles; crosslinked or uncrosslinked organic fine particles made of various transparent polymers such as polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, melamine, and polycarbonate; and silicone fine particles. These fine particles can be used singly or in combination. Fine particles with a refractive index higher than that of the matrix resin are preferred, such as organic fine particles with a refractive index of 1.5 or higher, such as styrene beads (refractive index 1.59). The average particle diameter of the fine particles is preferably 1 to 10 μm, more preferably 2 to 5 μm. There are no particular restrictions on the proportion of fine particles, but a ratio of 6 to 20 parts by weight per 100 parts by weight of matrix resin is preferred.

When the hard coat layer-forming composition is a radical-curable composition, a radical polymerization initiator can be used as the photopolymerization initiator. Examples of radical polymerization initiators include α-hydroxyacetophenone-based photopolymerization initiators, α-aminoacetophenone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, and intramolecular hydrogen abstraction photopolymerization initiators. Among these, α-hydroxyacetophenone-based photopolymerization initiators and α-aminoacetophenone-based photopolymerization initiators are preferred from the perspective of easily shortening the curing time of UV-curable silicone adhesives. Commercially available photopolymerization initiators can be used.

Commercially available examples of α-hydroxyacetophenone-based photopolymerization initiators include Omnirad 2959, Omnirad 184, Omnirad 127D, and Omnirad 1173 (IGM Resins). Commercially available examples of α-aminoacetophenone-based photopolymerization initiators include Omnirad 907 and Omnirad 369E (IGM Resins).

The content of the photopolymerization initiator in the hard coat layer-forming composition may be, for example, 0.1 to 15 parts by mass per 100 parts by mass of the photocurable resin. From the viewpoint of facilitating a shortening of the curing time of the UV-curable silicone adhesive, the content is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, and even more preferably 3 to 6 parts by mass.

A cured layer of the hard coat-forming composition can be formed by applying the hard coat-forming composition to a polarizer or a thermoplastic resin film and curing it by light irradiation. The thermoplastic resin film with the hard coat layer 12 can be attached to the polarizer 11 via an attachment layer.

The thickness of the hard coat layer 12 may be, for example, 10 μm or less, and preferably 8 μm or less. The thickness of the hard coat layer is usually 0.5 μm or more.

[Thermoplastic resin film]
The thermoplastic resin film 13 can function as a protective film that protects the surface of the polarizer 11 and also as a substrate film that supports the hard coat layer. The thermoplastic resin film 13 can be laminated on the polarizer via only an attachment layer.

The thermoplastic resin film 13 is not particularly limited, but may be a film made of a translucent (preferably optically transparent) thermoplastic resin, for example, a polyolefin resin such as a linear polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a norbornene resin); a cellulose resin such as triacetyl cellulose or diacetyl cellulose; a polyester resin such as polyethylene terephthalate or polybutylene terephthalate; a polycarbonate resin; a (meth)acrylic resin such as a methyl methacrylate resin; a polystyrene resin; a polyvinyl chloride resin; an acrylonitrile-butadiene-styrene resin; an acrylonitrile-styrene resin; a polyvinyl acetate resin; a polyvinylidene chloride resin; a polyamide resin; a polyacetal resin; a modified polyphenylene ether resin; a polysulfone resin; a polyethersulfone resin; a polyarylate resin; a polyamideimide resin; a polyimide resin; a maleimide resin, etc. Among these, it is preferable to use a film containing at least one resin selected from the group consisting of cellulose-based resins, cyclic polyolefin-based resins, (meth)acrylic-based resins, polystyrene-based resins, and maleimide-based resins.

These resins can be used alone or in combination of two or more. These resins can also be used after any suitable polymer modification. Examples of such polymer modifications include copolymerization, crosslinking, molecular end modification, stereoregularity control, and blending, including reactions between different polymers.

Cellulose-based resins can be organic acid esters or mixed organic acid esters of cellulose in which some or all of the hydrogen atoms in the hydroxyl groups of cellulose have been substituted with acetyl groups, propionyl groups, and/or butyryl groups. Examples include cellulose acetate esters, propionate esters, butyrate esters, and mixed esters thereof. Among these, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate are preferred.

These resins may contain appropriate additives as long as they do not impair transparency. Examples of additives include antioxidants, UV absorbers, antistatic agents, lubricants, nucleating agents, anti-fogging agents, anti-blocking agents, retardation reducers, stabilizers, processing aids, plasticizers, impact resistance aids, matting agents, antibacterial agents, and anti-fungal agents. Multiple types of these additives may be used in combination.

The thickness of the thermoplastic resin film 13 is typically 1 μm or more and 100 μm or less, but from the standpoint of strength, handleability, etc., it is preferably 5 μm or more and 60 μm or less, more preferably 10 μm or more and 55 μm or less, and even more preferably 15 μm or more and 50 μm or less.

The thermoplastic resin film 13 may also have other optical functions and may be formed into a laminated structure with multiple layers stacked together. From the perspective of optical properties, a thin protective film is preferable; however, if it is too thin, the strength decreases and processability becomes poor. The appropriate film thickness is 5 μm or more and 100 μm or less, preferably 10 μm or more and 80 μm or less, and more preferably 15 μm or more and 70 μm or less.

When the polarizer 11 has a thermoplastic resin film on both sides, if it is bonded using a water-based adhesive such as a PVA adhesive, it is preferable that the protective film on at least one side be either a cellulose acylate film or a (meth)acrylic resin film, in terms of moisture permeability, with a cellulose acylate film being particularly preferred.

When the polarizer 11 has a thermoplastic resin film on both sides, the types of thermoplastic resin films may be the same or different. When the polarizer 11 has a thermoplastic resin film on both sides, the thermoplastic resin film with a hard coat layer can be arranged so that the hard coat layer forms the outermost surface on both sides of the polarizing plate 10. The thermoplastic resin film may have a surface treatment layer (coating layer) such as an antistatic layer on its outer surface (the surface opposite the polarizer 11). Note that the thickness of the thermoplastic resin film includes the thickness of the surface treatment layer.

The thermoplastic resin film 13 may have a retardation function for purposes such as viewing angle compensation. In this case, the film itself may have a retardation function, or may have a separate retardation layer, or a combination of both. The film with a retardation function may be attached to the polarizer 11 via a pressure-sensitive adhesive layer or adhesive layer via another thermoplastic resin film that is attached to the polarizer 11.

[Laminating layer]
In the polarizing plate 10, an attachment layer is used to attach each layer. Examples of the attachment layer include an adhesive layer or a pressure-sensitive adhesive layer. The polarizing plate 10 can also be made into a pressure-sensitive adhesive layer-attached polarizing plate by laminating a pressure-sensitive adhesive layer on the polarizing plate 10 in order to attach it to an image display cell described below.

(adhesive layer)
The adhesive layer can be used, for example, to bond the thermoplastic resin film 13 to the polarizer 11. Any appropriate adhesive can be used as the adhesive constituting the adhesive layer. The adhesive can be a water-based adhesive, a solvent-based adhesive, a photocurable adhesive, or the like, but a water-based adhesive is preferred.

The thickness of the adhesive when applied can be set to any appropriate value. For example, it can be set so that an adhesive layer with the desired thickness is obtained after curing or heating (drying). The thickness of the adhesive layer is preferably 0.01 μm or more and 7 μm or less, more preferably 0.01 μm or more and 5 μm or less, even more preferably 0.01 μm or more and 2 μm or less, and most preferably 0.01 μm or more and 1 μm or less.

(Water-based adhesive)
Any appropriate aqueous adhesive can be used as the aqueous adhesive. Among these, aqueous adhesives containing a PVA-based resin (PVA-based adhesive) are preferably used. The average polymerization degree of the PVA-based resin contained in the aqueous adhesive is preferably about 100 to 5500, more preferably 1000 to 4500, from the viewpoint of adhesiveness. The average saponification degree is preferably about 85 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, from the viewpoint of adhesiveness.

The PVA-based resin contained in the aqueous adhesive preferably contains an acetoacetyl group, because it has excellent adhesion between the PVA-based resin layer and the protective film and excellent durability. The acetoacetyl-group-containing PVA-based resin can be obtained, for example, by reacting a PVA-based resin with diketene using any method. The degree of acetoacetyl group modification of the acetoacetyl-group-containing PVA-based resin is typically 0.1 mol% or more, and preferably about 0.1 mol% to 20 mol%.
The resin concentration of the aqueous adhesive is preferably 0.1% by mass or more and 15% by mass or less, and more preferably 0.5% by mass or more and 10% by mass or less.

Water-based adhesives can also contain crosslinking agents. Known crosslinking agents can be used. Examples include water-soluble epoxy compounds, dialdehydes, and isocyanates.

When the PVA-based resin is an acetoacetyl group-containing PVA-based resin, the crosslinking agent is preferably one of glyoxal, glyoxylate, or methylolmelamine, more preferably glyoxal or glyoxylate, and particularly preferably glyoxal.

Water-based adhesives can also contain organic solvents. Alcohols are preferred as organic solvents because they are miscible with water, and among alcohols, methanol or ethanol are more preferred.

The methanol concentration in the water-based adhesive is preferably 10% by mass or more and 70% by mass or less, more preferably 15% by mass or more and 60% by mass or less, and even more preferably 20% by mass or more and 60% by mass or less. A methanol concentration of 10% by mass or more makes it easier to suppress polyenation in high-temperature environments. Furthermore, a methanol content of 70% by mass or less can suppress deterioration of color hue.

(light-curing adhesive)
Photocurable adhesives are adhesives that cure upon irradiation with light such as ultraviolet light, and examples thereof include adhesives containing a polymerizable compound and a photopolymerization initiator, adhesives containing a photoreactive resin, and adhesives containing a binder resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, as well as oligomers derived from these monomers. Examples of the photopolymerization initiator include compounds containing substances that generate active species such as neutral radicals, anion radicals, and cation radicals upon irradiation with ultraviolet light or the like.

(Adhesive layer)
The pressure-sensitive adhesive layer can be used, for example, to attach a retardation film, which will be described later. The pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition whose main component is a resin such as a (meth)acrylic resin, a rubber resin, a urethane resin, an ester resin, a silicone resin, or a polyvinyl ether resin. Among these, a pressure-sensitive adhesive composition whose base polymer is a (meth)acrylic resin, which is excellent in transparency, weather resistance, heat resistance, etc., is preferred. The pressure-sensitive adhesive composition may be a photocurable or thermosetting type. The thickness of the pressure-sensitive adhesive layer is usually 3 μm or more and 30 μm or less, and preferably 3 μm or more and 25 μm or less.

The (meth)acrylic resin (base polymer) used in the pressure-sensitive adhesive composition is preferably a polymer or copolymer containing one or more (meth)acrylic acid esters as monomers, such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. It is preferable to copolymerize a polar monomer into the base polymer. Examples of polar monomers include monomers having a carboxyl group, hydroxyl group, amide group, amino group, or epoxy group, such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

The pressure-sensitive adhesive composition may contain only the base polymer, but typically also contains a crosslinking agent. Examples of crosslinking agents include divalent or higher metal ions that form metal carboxylates with carboxyl groups; polyamine compounds that form amide bonds with carboxyl groups; polyepoxy compounds or polyols that form ester bonds with carboxyl groups; and polyisocyanate compounds that form amide bonds with carboxyl groups. Of these, polyisocyanate compounds are preferred.

The thickness of the adhesive layer is preferably 1 μm or more and 200 μm or less, more preferably 2 μm or more and 100 μm or less, even more preferably 2 μm or more and 80 μm or less, and particularly preferably 3 μm or more and 50 μm or less.

[Optical functional layer]
The optical functional layer can be, for example, a retardation layer. Examples of the retardation layer include a layer that imparts a λ/2 retardation, a layer that imparts a λ/4 retardation (positive A plate), and a positive C plate. The optical functional layer may include an alignment layer and a substrate, or may have two or more liquid crystal layers, alignment layers, and substrates. When the polarizing plate has a polarizing element and a film that imparts a λ/4 retardation, the polarizing plate can be a circular polarizing plate.
The thermoplastic resin film 13 can also serve as a retardation layer, or a retardation layer can be laminated separately from these films. In the latter case, the retardation layer can be laminated on the polarizing plate via a pressure-sensitive adhesive layer or an adhesive layer.

Examples of retardation layers include birefringent films made from stretched films of light-transmitting thermoplastic resins, and the above-mentioned liquid crystal layer formed on a substrate film. The substrate film is typically a film made from a thermoplastic resin, and one example of a thermoplastic resin is a cellulose ester resin such as triacetyl cellulose.

Examples of other optically functional layers include light collectors, brightness enhancement films, reflective layers (reflective films), semi-transmissive reflective layers (semi-transmissive reflective films), light diffusion layers (light diffusion films), anti-reflection films, etc.

[Protection film]
The polarizing plate 10 can be made into a polarizing plate with a protective film by laminating a protective film for protecting its surface (typically the surface of the polarizer, hard coat layer, or thermoplastic resin film). After the polarizing plate 10 is attached to, for example, an image display element or other optical member, the protective film is peeled off and removed together with its pressure-sensitive adhesive layer.

The protective film is composed of, for example, a substrate film and an adhesive layer laminated thereon. The adhesive layer is as described above.
The resin constituting the base film may be, for example, a thermoplastic resin such as a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate, or a polycarbonate-based resin. A polyester-based resin such as polyethylene terephthalate is preferred.

The thickness of the protective film is not particularly limited, but is preferably in the range of 20 μm or more and 200 μm or less. If the thickness of the substrate is 20 μm or more, it tends to provide strength to the polarizing plate 10.

[Method of manufacturing polarizing plate]
The manufacturing method of the polarizing plate 10 can be, for example, a method in which a hard coat layer 12 is formed on a thermoplastic resin film 13, and then the surface of the thermoplastic resin film 13 opposite to the hard coat layer 12 is bonded to a polarizer 11 via an adhesive layer to obtain a polarizing plate.

<Laminate>
The laminate of this embodiment includes the polarizing plate 10 and a transparent member, with the hard coat layer 12 and the transparent member laminated together via an ultraviolet addition-curable silicone adhesive layer. The laminate of the present invention will be described with reference to Fig. 2. The laminate 20 shown in Fig. 2 includes the polarizing plate 10, an ultraviolet addition-curable silicone adhesive layer 21, and a transparent member 22 laminated together.

[UV addition-curable silicone adhesive layer]
The ultraviolet addition curable silicone adhesive layer 21 can have the function of adhering the polarizing plate 10 and the transparent member 22. The ultraviolet addition curable silicone adhesive layer 21 may be light-transmitting, and is preferably optically transparent.

The thickness of the UV-addition-curable silicone adhesive layer 21 may be, for example, 10 μm or more and 1000 μm or less, preferably 15 μm or more and 800 μm or less, more preferably 20 μm or more and 700 μm or less, and even more preferably 25 μm or more and 600 μm or less.

The UV-addition-curable silicone adhesive layer 21 can be formed from a UV-addition-curable silicone adhesive composition. UV-addition-curable silicone adhesive compositions do not cure immediately after UV irradiation, but rather undergo a gradual curing reaction after UV irradiation. This tends to make it easier to bond or fix components together between UV irradiation and curing. The UV-addition-curable silicone adhesive composition may be translucent before curing, and from the standpoint of curability, it is preferably colorless and transparent before curing, and even more preferably colorless and transparent before and after curing.

The curing time of a UV-curable silicone adhesive composition may be, for example, 1 minute to 24 hours at an ambient temperature of 20°C to 80°C. In this specification, the curing time of a UV-curable silicone adhesive refers to the time from the start of dynamic viscoelasticity measurement until the storage shear modulus and loss shear modulus become equal when the UV-curable silicone adhesive is irradiated with UV light to initiate the curing reaction and then dynamic viscoelasticity measurement is performed while the adhesive is curing. To explain the curing time with reference to Figure 3, where G' represents the storage modulus and G" represents the loss modulus, the curing time is the time from the start of dynamic viscoelasticity measurement A to the point B (gel point) at which G' and G" become equal. The time from UV irradiation to the start of dynamic viscoelasticity measurement is typically 5 minutes.

The UV-addition-curable silicone adhesive composition may be, for example, a composition containing a silicone polymer having an alkenyl group, a silicone polymer having an H group, and a photoactivatable catalyst, and can be cured by UV irradiation through a hydrosilylation reaction between the silicone polymer having an alkenyl group and the silicone polymer having an H group.

Preferably, the alkenyl group has 2 to 10 carbon atoms, more preferably 2 to 6. Specific examples include vinyl, allyl, butenyl, pentenyl, and hexenyl groups, with vinyl being particularly preferred.

The silicone polymer having an alkenyl group may have, in addition to the alkenyl group, at least one of a monovalent saturated hydrocarbon group and an aryl group.

The monovalent saturated hydrocarbon group preferably has 1 to 12 carbon atoms, more preferably 1 to 6. Specific examples include unsubstituted or substituted monovalent saturated hydrocarbon groups, which may be linear, branched, or cyclic, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, and n-heptyl; cycloalkyl groups such as cyclohexyl; and halogenated alkyl groups such as chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl. Of these, methyl is preferred from the standpoint of heat resistance.

Aryl groups preferably have 6 to 20 carbon atoms, more preferably 6 to 10. Specific examples include phenyl, naphthyl, tolyl, xylyl, mesityl, and halogen-substituted aryl groups such as chlorophenyl, with phenyl being preferred.

The H group may be a silicon-bonded hydrogen atom [H group in a hydrosilyl group (Si-H group)]. The silicone polymer having the H group may have a substituted or unsubstituted monovalent hydrocarbon group excluding aliphatic unsaturated hydrocarbon groups. The substituted or unsubstituted monovalent hydrocarbon group excluding aliphatic unsaturated hydrocarbon groups may have, for example, 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms. The monovalent hydrocarbon group may be linear, branched, or cyclic. Specific examples include saturated aliphatic monovalent hydrocarbon groups such as linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, and n-hexyl, and cycloalkyl groups such as cyclohexyl; aryl groups such as phenyl and tolyl; aromatic or aromatic-group-containing monovalent hydrocarbon groups such as aralkyl groups such as benzyl and phenylethyl; halogen-substituted monovalent hydrocarbon groups such as 3,3,3-trifluoropropyl, and cyano-substituted monovalent hydrocarbon groups such as cyanoethyl. Of these, methyl is preferred.

The silicone polymer containing H groups is preferably blended in an amount such that the molar ratio of hydrosilyl groups to alkenyl groups (hydrosilyl groups/alkenyl groups) is 0.5 to 2, and particularly 1 to 1.2. Within this range, the composition tends to have excellent curability and the resulting cured product tends to have excellent hardness.

Examples of photoactivated catalysts include platinum group metal catalysts (hereinafter, for simplicity, simply referred to as platinum group metal catalysts) that are activated by light with a wavelength of 200 to 500 nm. Platinum group metal catalysts are inactive in the dark, but upon irradiation with light with a wavelength of 200 to 500 nm, they are transformed into active platinum group metal catalysts at room temperature, promoting the hydrosilylation reaction between alkenyl groups in silicone polymers that contain alkenyl groups and silicon-bonded hydrogen atoms in silicone polymers that contain H groups.

Specific examples of platinum group metal catalysts include (η5-cyclopentadienyl)trialiphatic platinum compounds and their derivatives. Of these, cyclopentadienyltrimethylplatinum, methylcyclopentadienyltrimethylplatinum, and their derivatives in which the cyclopentadienyl group has been modified are preferred. Bis(β-diketonato)platinum compounds can also be used, with bis(acetylacetonato)platinum compounds and their derivatives in which the acetylacetonato group has been modified being preferred.

The amount of platinum group metal catalyst in a UV-addition-curable silicone adhesive composition is not limited, as long as it is an amount that promotes the curing (hydrosilylation reaction) of the composition. The amount of platinum group metal atoms in the composition, calculated by mass, relative to the total mass of the silicone polymer having alkenyl groups and the silicone polymer having H groups may be, for example, 0.01 ppm or more and 500 ppm or less, preferably 0.05 to 100 ppm, and more preferably 0.01 to 50 ppm.

The UV-addition-curable silicone adhesive composition may further contain adhesive aids, reaction control agents, thixotropy control agents such as fumed silica; reinforcing agents such as crystalline silica; antioxidants; light stabilizers; heat resistance improvers such as metal oxides and metal hydroxides; colorants such as titanium oxide; thermal conductivity-imparting fillers such as alumina and crystalline silica; viscosity adjusters such as non-reactive silicone oils that do not have reactive functional groups; conductivity-imparting agents such as metal powders of silver, gold, etc.; pigments, dyes, etc. for coloring.

Examples of adhesion promoters include organic compounds containing at least one functional group selected from the group consisting of (meth)acrylic, carbonyl, epoxy, alkoxysilyl, and amide groups per molecule. Specific examples of adhesion promoters containing alkoxysilyl groups include γ-(glycidoxypropyl)trimethoxysilane (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.), γ-(methacryloxypropyl)trimethoxysilane (trade name: KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.), and hydrolysis condensates thereof. Specific examples of compounds containing at least one of the above functional groups and an organosiloxane skeleton include those represented by the following structural formula:

(In the formula, Me means a methyl group.)

Furthermore, specific examples of adhesion promoters that do not contain an organosiloxane skeleton include allyl glycidyl ether, vinylcyclohexene monoxide, 2-allylmalonate diethyl, allyl benzoate, diallyl phthalate, pyromellitic acid tetraallyl ester, and triallyl isocyanurate.

Specific examples of reaction inhibitors include 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclohexanol, ethynylmethyldecylcarbinol, 3-methyl-3-trimethylsiloxy-1-butyne, 3-methyl-3-trimethylsiloxy-1-pentyne, 3,5-dimethyl-3-trimethylsiloxy-1-hexyne, 1-ethynyl-1-trimethylsiloxycyclohexane, bis(2,2-dimethyl-3-butynoxy)dimethylsilane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, and 1,3,3-tetramethyl-1,3-divinyldisiloxane, with 1-ethynylcyclohexanol, ethynylmethyldecylcarbinol, and 3-methyl-1 -butyn-3-ol, etc.

Examples of UV-curable silicone adhesive compositions that can be used include those described in JP-A-2020-055945 and JP-A-2020-117654. Alternatively, commercially available UV-curable silicone adhesive compositions can be used. Examples of commercially available UV-curable silicone adhesive compositions include KER-4550, KER-4410, KER-4510, KER-4690-A/B, and KER-4691-A/B (manufactured by Shin-Etsu Chemical Co., Ltd.).
[Transparent material]
Examples of the transparent member 22 include a front panel (window layer) and a touch panel. A front panel having appropriate mechanical strength and thickness is used. Examples of such front panels include transparent resin plates such as polyimide resin, acrylic resin, and polycarbonate resin, and glass plates. A functional layer such as an anti-reflection layer may be laminated on the viewing side of the front panel. Furthermore, when the front panel is a transparent resin plate, a hard coat layer may be laminated to increase physical strength, or a low-moisture permeability layer may be laminated to reduce moisture permeability.
As the touch panel, various types of touch panels such as resistive, capacitive, optical, and ultrasonic touch panels, as well as glass or transparent resin plates equipped with touch sensor functions, are used. When a capacitive touch panel is used as the transparent member, it is preferable to provide a front panel made of glass or transparent resin plate on the viewing side further than the touch panel.

[Method of manufacturing laminate]
The method for producing the laminate includes a coating step, an ultraviolet irradiation step, a curing step, and a laminating step, and for each step, the following methods can be used, for example.

(A) Coating Step In the coating step, the ultraviolet addition-curable silicone adhesive composition can be coated onto one of the substrates. The coating method is not particularly limited, and examples include coating using slit coating, the DAM-Fill method, the fishbone method, and the like. The DAM-Fill method can be a method in which a dam material is provided around the periphery of the image display panel to prevent the ultraviolet addition-curable silicone adhesive composition from spreading before curing, a transparent member is placed on the dam material, and the ultraviolet addition-curable silicone adhesive composition is then injected. After the ultraviolet addition-curable silicone adhesive composition is injected, alignment and degassing are performed as necessary, and then ultraviolet light is irradiated to cause curing.

The amount of UV-curable silicone adhesive composition applied to the substrate can be such that, after curing, the thickness of the UV-curable silicone adhesive layer will be, for example, 10 μm or more and 1000 μm or less.

Before applying the UV-addition-curable silicone adhesive composition, the bonding surface may be activated by a well-known pretreatment process such as primer treatment, plasma treatment, or excimer light treatment.

(B) Ultraviolet Irradiation Step In the ultraviolet irradiation step, the ultraviolet addition-curable silicone adhesive composition can be irradiated with ultraviolet light. Examples of ultraviolet irradiation methods include using a 365 nm UV-LED lamp, metal halide lamp, or the like as a ultraviolet light source to irradiate an appropriate amount of ultraviolet light.

For ultraviolet irradiation, light having a wavelength of preferably 200 to 500 nm, more preferably 200 to 380 nm is used. In this case, from the viewpoint of curing speed and prevention of discoloration, the irradiation temperature is preferably 20 to 80°C, the irradiation intensity is preferably 30 to 2000 mW/ ^cm² , and the irradiation dose is preferably 150 to 10000 mJ/ ^cm² .

(C) Curing Step In the curing step, the UV-irradiated UV-addition-curable silicone adhesive composition can be cured. Examples of curing methods include leaving the UV-irradiated UV-addition-curable silicone adhesive composition to stand in a predetermined environment to cure it, thereby forming a UV-addition-curable silicone adhesive layer. The curing temperature for the UV-addition-curable silicone adhesive composition is not particularly limited, but it is preferable to cure it in an air atmosphere at 20 to 80°C for 1 minute to 1 day.

(D) Laminating Step In the laminating step, another substrate is laminated on top of the UV-addition-curable silicone adhesive composition or UV-addition-curable silicone adhesive layer to form a laminate in which the two substrates are bonded together via the adhesive composition or UV-addition-curable silicone adhesive layer. Examples of laminating methods include placing the UV-addition-curable silicone adhesive layer-substrate laminate, which has been converted from a liquid to a semi-solid state through the coating, UV-irradiation, and curing steps, or the adhesive composition after the coating step, or the UV-addition-curable silicone adhesive composition-substrate laminate after the coating and UV-irradiation steps, in a vacuum or atmospheric pressure laminating device, and laminating the other substrate on top of the UV-addition-curable silicone adhesive composition or UV-addition-curable silicone adhesive layer to bond them together, and in the case of a UV-addition-curable silicone adhesive composition, carrying out the remaining steps to cure it and form a laminate.

Because UV-addition-curable silicone adhesive compositions are not inhibited by oxygen and the curing time after UV irradiation can be changed by adjusting the adhesive composition design and heating temperature, the procedures for the application, UV-irradiation, curing, and lamination processes can be freely selected and modified to suit the structure of the device being manufactured, such as a flat display or curved display.

A method for manufacturing a laminate will be described below using a specific example of a method for manufacturing a laminate comprising the polarizing plate and front panel described above. First, an ultraviolet addition-curable silicone adhesive composition is applied to the hard coat layer of the polarizing plate. Then, using a UV-LED lamp with a maximum intensity at a wavelength of approximately 365 nm, the ultraviolet addition-curable silicone adhesive composition is irradiated with ultraviolet light at 20 to 80° ^C (e.g., 23°C) for 1 second to ¹ hour (e.g., 30 seconds) at an irradiation intensity of 30 to 2,000 mW/ ^cm2 (e.g., 100 mW/ ^cm2 ) and a dose of 150 to 10,000 mJ/cm2 (e.g., 3,000 mJ/cm2), using 365 nm light as an index. The ultraviolet addition-curable silicone adhesive composition is then cured by leaving it to stand for 1 minute to 1 day (e.g., 30 minutes) in an environment of 20 to 80°C (e.g., 23°C), thereby forming a ultraviolet addition-curable silicone adhesive layer. Thereafter, a front panel is laminated on the UV-addition-curable silicone adhesive layer using a vacuum lamination device, thereby obtaining a laminate in which the polarizing plate and the front panel are laminated via the UV-addition-curable silicone adhesive layer. Alternatively, after the UV irradiation step, a vacuum lamination device may be used to first laminate the front panel on the UV-addition-curable silicone adhesive composition, thereby laminating the polarizing plate and the front panel via the UV-addition-curable silicone adhesive composition, followed by allowing the UV-addition-curable silicone adhesive composition to cure in an environment of 20 to 100°C (e.g., 60°C) for 1 minute to 1 day (e.g., 30 minutes). When the front panel is transparent, vacuum lamination may be performed after the coating step, followed by UV irradiation through the front panel to cure the composition. Alternatively, a UV-addition-curable silicone adhesive composition that has been previously UV-irradiated may be applied to an image display panel, followed by vacuum lamination with a cover panel, and then cured.

[Uses of the laminate]
The laminate 20 is used in various image display devices such as liquid crystal display devices and organic EL display devices. An example of an image display device is one having an image display cell, a pressure-sensitive adhesive layer laminated on the viewing-side surface of the image display cell, and a polarizing plate laminated on the viewing-side surface of the pressure-sensitive adhesive layer. Such an image display device may further include an ultraviolet-addition-curable silicone adhesive layer laminated on the viewing-side surface of the polarizing plate, and a transparent member laminated on the surface of the ultraviolet-addition-curable silicone adhesive layer. In particular, the laminate of the present invention is suitable for use in an image display device having an interlayer-filled structure in which a transparent member is disposed on the viewing side of the image display device, the polarizing plate and the image display cell are bonded together by a pressure-sensitive adhesive layer, and the polarizing plate and the transparent member are bonded together by a UV-addition-curable silicone adhesive layer. The member used to bond the polarizing plate and the image display cell is not limited to a pressure-sensitive adhesive layer, but may also be an adhesive layer.

[Image display cell]
Examples of image display cells include liquid crystal cells and organic EL cells. The liquid crystal cell may be a reflective liquid crystal cell that utilizes external light, a transmissive liquid crystal cell that utilizes light from a light source such as a backlight, or a semi-transmissive semi-reflective liquid crystal cell that utilizes both external light and light from the light source. When the liquid crystal cell utilizes light from a light source, the image display device (liquid crystal display device) has a polarizing plate disposed on the opposite side of the image display cell (liquid crystal cell) from the viewing side, and further has a light source disposed thereon. The polarizing plate on the light source side and the liquid crystal cell are preferably bonded together via an appropriate adhesive layer. The liquid crystal cell may be driven in any type, such as VA mode, IPS mode, TN mode, STN mode, or bend orientation (π type).

A suitable organic EL cell is one in which a light-emitting body (organic electroluminescence light-emitting body) is formed by sequentially laminating a transparent electrode, an organic light-emitting layer, and a metal electrode on a transparent substrate. The organic light-emitting layer is a laminate of various organic thin films, and various layer configurations can be used, such as a laminate of a hole-injection layer made of a triphenylamine derivative or the like and a light-emitting layer made of a fluorescent organic solid such as anthracene, a laminate of such a light-emitting layer and an electron-injection layer made of a perylene derivative or the like, or a laminate of a hole-injection layer, a light-emitting layer, and an electron-injection layer.

[Laminating the image display cell and polarizing plate]
A pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) is preferably used to bond the image display cell to the polarizing plate. Among these, a method of bonding the above-mentioned pressure-sensitive adhesive layer-attached polarizing plate to the image display cell is preferred from the viewpoint of workability, etc. A pressure-sensitive adhesive layer can also be formed by applying a diluted solution of the pressure-sensitive adhesive composition in an organic solvent onto the image display cell, and then the image display cell can be bonded to the polarizing plate.

The present invention will be specifically explained below based on examples. The materials, reagents, amounts and proportions of substances, procedures, etc. shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the present invention is not limited to the following examples. Unless otherwise specified, "%" and "parts" in the examples are % by mass and parts by mass.

[Measurement of cure time of UV addition-curable silicone adhesive composition]
The procedure for measuring the cure time of an ultraviolet addition-curable silicone adhesive composition will be described with reference to Figure 4. The polarizing plates obtained in the Examples and Comparative Examples were molded to a diameter of 11 mm, and 50 μL of an ultraviolet addition-curable silicone adhesive composition ("KER-4550" manufactured by Shin-Etsu Chemical Co., Ltd.; indicated as "adhesive" in the figure) was dropped onto the hard coat layer. The ultraviolet addition-curable silicone adhesive composition was then irradiated with ultraviolet light from a 365 nm UV-LED at a light intensity of 3,000 mJ/ ^cm2 to produce a polarizing plate sample [Figure 4(a)].
Thereafter, disk-shaped jigs 1 to 3 with protrusions each having a diameter of 11 mm were prepared for setting polarizing plate samples in a dynamic viscoelasticity measuring device (DMA/SDTA861 manufactured by METTLER TOLEDO). The polarizing plate samples were fixed to the protrusions (not shown) of jigs 1 and 3, respectively, so that the polarizing plate sides of the polarizing plate samples faced jigs 1 and 3, and jigs 2 was sandwiched between jigs 1 and 3 so that the adhesive layer sides of the polarizing plate samples fixed between jigs 1 and 3 were in contact with jigs 2. The jig spacing adjustment screws (not shown) provided on jigs 1 and 3 were adjusted to adjust the thickness of the adhesive layer to 500 μm [ FIG. 4( b)].
Jig 1, polarizing plate sample, jig 2, polarizing plate sample, and jig 3 were stacked in this order and set in a dynamic viscoelasticity measuring device, and the cure time of the UV-addition-curable silicone adhesive composition was measured under the following measurement conditions. Note that the time from UV irradiation to setting the polarizing plate and starting to measure the cure time was 5 minutes in all Examples and Comparative Examples. This time is not included in the cure times in Table 2.
Frequency: 1 Hz
Distortion: 4%
Temperature: 80℃

[Measurement of absorbance of hard coat layer]
The absorbance at wavelengths of 300 nm and 365 nm was measured using a spectrophotometer U-2500PC manufactured by Hitachi, Ltd. The absorbance of the hard coat layer was calculated using the following formula:
Absorbance of hard coat layer = (absorbance of hard coat film) - (absorbance of transparent film substrate)
was calculated using

[Preparation of hard coat layer-forming composition]
The components shown in Table 1 were mixed and stirred in the proportions shown in Table 1 to obtain compositions HC-1 to HC-4 for forming a hard coat layer.

Unit: parts by weight Photocurable resin: Beamset 710 (pentaerythritol polyacrylate), manufactured by Arakawa Chemical Industries, Ltd. Photopolymerization initiator A: Omnirad 2959, manufactured by IGM Resins Photopolymerization initiator B: Omnirad 369E, manufactured by IGM Resins Photopolymerization initiator C: Omnirad 907, manufactured by IGM Resins Solvent: methyl ethyl ketone

[Preparation of Hard Coat Film 11]
Composition HC-1 for forming a hard coat layer was applied to a transparent film substrate (triacetyl cellulose-based resin film, thickness 40 μm) by bar coating so that the film thickness after drying would be approximately 6 μm. The coating film was dried in an oven at 60°C for 150 seconds. The coating film was irradiated with ultraviolet light at an illuminance of 400 mW/cm ² and a light quantity of 300 mJ/cm ² using an electrodeless lamp H bulb manufactured by Fusion Corporation to form a hard coat layer, thereby obtaining hard coat film 11. The absorbance of the hard coat layer of hard coat film 11 was measured.

[Preparation of Hard Coat Films 12 to 14]
Hard coat films 12 to 14 were produced in the same manner as in the production of hard coat film 11, except that hard coat layer-forming composition HC-1 was changed to hard coat layer-forming compositions HC-2 to HC-4. The absorbance of the hard coat layer of each of the obtained hard coat films was measured.

Example 1
[Film saponification treatment]
The hard coat film 11 and the transparent film substrate were immersed in a 1.5 mol/L NaOH aqueous solution (saponification solution) maintained at 55°C for 2 minutes, and then washed with water. The film was then immersed in a 0.05 mol/L sulfuric acid aqueous solution at 25°C for 30 seconds, and then passed through a water washing bath under running water for 30 seconds to neutralize the film. The film was then drained three times with an air knife, and then allowed to dry in a drying zone at 70°C for 15 seconds, whereupon it was subjected to a saponification treatment.

[Preparation of Polarizing Plate]
A saponified hard coat film 11 and a saponified transparent film substrate were laminated on both sides of the iodine-PVA polarizer via a PVA adhesive. The surface of the saponified hard coat film 11 on which the hard coat layer was not formed was the surface to be attached to the iodine-PVA polarizer. Heat drying was performed to obtain the polarizing plate of Example 1. The results are shown in Table 2.

<Examples 2 and 3 and Comparative Example 1>
A polarizing plate was produced in the same manner as in Example 1, except that the hard coat film shown in Table 1 was used instead of Hard Coat Film 11 in Example 1. The results are shown in Table 2.

The results in Table 2 show that in the polarizing plates of Examples 1 to 3, in which the hard coat layer had an absorbance of 4.5 or less at a wavelength of 300 nm, the UV-addition-curable silicone adhesive composition was able to cure in a relatively short time. In contrast, in the polarizing plate of Comparative Example 1, in which the hard coat layer had an absorbance of more than 4.5 at a wavelength of 300 nm, the UV-addition-curable silicone adhesive composition was unable to cure within 60 minutes. It can be seen that the present invention provides a polarizing plate in which the UV-addition-curable silicone adhesive composition can be sufficiently cured within a certain period of time.

10 Polarizing plate, 11 Polarizer, 12 Hard coat layer, 13 Thermoplastic resin film, 20 Laminate, 21 UV addition-curable silicone adhesive layer, 22 Transparent member, A Starting point of dynamic viscoelasticity measurement, B Point at which G' and G'' become equal.

Claims (6)

A laminate including a polarizing plate and a transparent member,
the polarizing plate includes a polarizer and a hard coat layer,
the hard coat layer constitutes at least one outermost surface of the polarizing plate, and the hard coat layer has an absorbance of 2.0 or less at a wavelength of 300 nm;
the hard coat layer is a cured layer of a photocurable resin composition,
the photocurable resin composition contains a radical polymerization initiator as a photopolymerization initiator,
the radical polymerization initiator is an α-hydroxyacetophenone-based photopolymerization initiator or an α-aminoacetophenone-based photopolymerization initiator,
The hard coat layer and the transparent member are laminated via an ultraviolet addition curing silicone adhesive layer . The laminate according to claim 1 , wherein the cured layer of the photocurable resin composition comprises a cured product of a (meth)acrylic resin . The laminate according to claim 1 or 2, wherein the hard coat layer has a thickness of 0.5 μm or more and 10 μm or less . 4. The laminate according to claim 1, wherein the ultraviolet addition curable silicone adhesive layer has a thickness of 10 μm or more and 1000 μm or less. 5. The laminate according to claim 1 , wherein the ultraviolet addition-curable silicone adhesive layer is a cured layer of an ultraviolet addition-curable silicone adhesive composition. The laminate according to any one of claims 1 to 5 , wherein the transparent member is a glass plate, a transparent resin plate, or a touch panel.