JP2022183013A - optical laminate - Google Patents

Abstract

To provide an optical laminate comprising a polarizer having iodine adsorbed and aligned thereon, which suppresses an increase in iodine concentration of an adhesive layer laminated thereon.SOLUTION: An optical laminate is provided, comprising a polarizing plate including a polarizer and an optical functional group including at least one adhesive layer, where the polarizer is a polyvinyl alcohol-based resin film having iodine adsorbed and aligned thereon and the adhesive layer contains 1-10 mass%, inclusive, of a low-molecular-weight component with molecular weights of 500 or less in total.SELECTED DRAWING: Figure 1

Description

The present invention relates to optical laminates.

A polarizer is one of the optical components that constitute a display device such as a liquid crystal display device or an organic EL display device, and it is known that a polyvinyl alcohol-based resin film in which iodine is adsorbed and oriented is used. 2. Description of the Related Art In a touch panel type display device mainly used in mobile information terminals such as smartphones and tablets, a conductive layer for forming a touch sensor may be provided on an image display element. When a polarizer is incorporated into a touch panel type display device, a laminate containing an adhesive layer provided with an adhesive layer on a laminate containing a polarizer is laminated on the conductive layer so that the adhesive layer is in direct contact. There is (for example, patent document 1).

JP 2015-052765 A

In the adhesive layer-attached laminate, iodine contained in the polarizer migrated to the adhesive layer, and the iodine concentration in the adhesive layer sometimes increased. Migration of iodine is particularly likely to occur in a hot and humid environment. When the conductive layer is a metal layer, if the iodine concentration in the adhesive layer in contact with the conductive layer increases, problems such as corrosion of the metal electrode tend to occur.

An object of the present invention is to suppress an increase in the iodine concentration of a pressure-sensitive adhesive layer laminated on an optical layered body including a polarizer in which iodine is adsorbed and oriented.

The present invention provides optical laminates exemplified below.
[1] An optical laminate comprising a polarizing plate containing a polarizer and an optical functional layer containing at least one adhesive layer,
The polarizer is a polyvinyl alcohol-based resin film in which iodine is adsorbed and oriented,
The optical laminate in which the adhesive layer contains a total of 1% by mass or more and 10% by mass or less of low-molecular-weight components having a molecular weight of 500 or less.
[2] The optical function layer includes a first retardation layer and a second retardation layer containing a cured product of a polymerizable liquid crystal compound,
The optical laminate according to [1], wherein at least one adhesive layer is laminated between the first retardation layer and the second retardation layer.
[3] The adhesive layer is a cured layer of an active energy ray-curable adhesive,
The optical laminate according to [1] or [2], wherein the low-molecular-weight component includes an unpolymerized monomer of the active energy ray-curable adhesive.
[4] The low molecular weight component contains at least one selected from the group consisting of a monomer having an epoxy group, a monomer having an oxetane ring, a monomer having an acryloyloxy group, and a monomer having a methacryloyloxy group. The optical laminate according to any one of [3].
[5] The optical laminate according to any one of [1] to [4], wherein the polarizing plate has a protective film on one or both sides of the polarizer.
[6] The polarizing plate has the protective film on the optical functional layer side of the polarizer,
The optical laminate according to [5], wherein the protective film has a moisture permeability of 350 g/(m ² ·24 hr) or more at a temperature of 40° C. and a relative humidity of 90% RH.
[7] The optical laminate according to any one of [1] to [6], wherein the luminosity correction single transmittance Ty of the polarizing plate at a wavelength of 550 nm is 43.5% or more.
[8] The optical laminate according to any one of [1] to [7], further comprising a pressure-sensitive adhesive layer laminated on the surface of the optical functional layer opposite to the polarizing plate.

According to the present invention, even in an optical layered body including a polarizer in which iodine is adsorbed and oriented, it is possible to suppress an increase in the iodine concentration of the adhesive layer laminated on the optical layered body.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically an example of the optical laminated body which concerns on embodiment of this invention. FIG. 3 is a cross-sectional view schematically showing another example of the optical layered body according to the embodiment of the present invention; FIG. 3 is a cross-sectional view schematically showing another example of the optical layered body according to the embodiment of the present invention; FIG. 3 is a cross-sectional view schematically showing another example of the optical layered body according to the embodiment of the present invention;

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In all the drawings below, the scale of each component is adjusted appropriately to facilitate understanding, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component.

<Optical laminate>
1 to 4 are schematic cross-sectional views schematically showing an example of the optical layered body of this embodiment. The optical layered bodies 100, 200, 300 and 400 of this embodiment have the polarizing plate 10 and the optical function layer 20 in this order. The polarizing plate 10 and the optical function layer 20 may be in direct contact with each other. Polarizing plate 10 includes a polarizer 11 . The polarizer 11 is a polyvinyl alcohol resin film in which iodine is adsorbed and oriented.

The polarizing plate 10 may be a single protective polarizing plate having a protective film 12 on one side of a polarizer 11, as shown in FIGS. At this time, the polarizer 11 is laminated directly on the optical function layer 20 via the bonding layer 24 . Polarizing plate 10 may be a dual protective polarizing plate having protective films 12 and 13 on both sides of polarizer 11, as shown in FIG.

The optical function layer 20 may include two retardation layers, a first retardation layer 21 and a second retardation layer 22, as shown in FIGS. 1-4. The first retardation layer 21 and the second retardation layer 22 may be laminated via the bonding layer 23 . The polarizing plate 10 and the optical function layer 20 may be bonded together by a bonding layer 24 . The optical function layer 20 includes at least one adhesive layer. One of the bonding layers 23 and 24 may be an adhesive layer, the other may be an adhesive layer, or both may be adhesive layers. The optical function layer 20 may also contain an adhesive layer. In the optical function layer 20, preferably the first retardation layer 20, the adhesive layer, and the second retardation layer 22 are in contact with each other in this order.

In the optical layered body 100 shown in FIG. 1 and the optical layered body 400 shown in FIG. 4, the first retardation layer 21 and the second retardation layer 22 are laminated via the bonding layer 23 which is an adhesive layer. The first retardation layer 21 and the polarizing plate 10 are laminated via a bonding layer 24 which is an adhesive layer. In the optical laminate 200 shown in FIG. 2, the first retardation layer 21 and the second retardation layer 22 are laminated via the bonding layer 23, which is an adhesive layer, and the first retardation layer 21 and the polarizing The plate 10 is laminated via a bonding layer 24 that is an adhesive layer. In the optical layered body 300 shown in FIG. 3, the first retardation layer 21 and the second retardation layer 22 are laminated via the bonding layer 24, which is an adhesive layer.

As shown in FIGS. 1 to 4, the optical function layer 20 may have an adhesive layer 30. FIG. The adhesive layer 30 may be laminated on the surface of the optical function layer 20 opposite to the polarizing plate 10 . The adhesive layer 30 may be laminated on the side of the second retardation layer 22 opposite to the polarizing plate 10 . The adhesive layer 30 may be provided in direct contact with the second retardation layer 22 .

The optical laminate 100 includes a protective film 12, a polarizer 11, a first retardation layer 21, an adhesive layer, a second retardation layer 22, and an adhesive layer 30 in this order. The optical laminate 200 includes a protective film 12, a polarizer 11, an adhesive layer, a first retardation layer 21, a second retardation layer 22, and an adhesive layer 30 in this order. The optical laminate 300 includes a protective film 12, a polarizer 11, an adhesive layer, a first retardation layer 21, an adhesive layer, a second retardation layer 22, and an adhesive layer 30 in this order. The optical laminate 400 includes a protective film 12, a polarizer 11, a protective film 13, a first retardation layer 22, an adhesive layer, a second retardation layer 22, and an adhesive layer 30 in this order.

As shown in FIGS. 1-4, the optical stacks 100, 200, 300 and 400 may be laminated with a metal layer 40. FIG. The metal layer 40 is preferably laminated on the side opposite to the polarizing plate 10 with the adhesive layer 30 interposed therebetween. The metal layer 40 may be provided in direct contact with the adhesive layer 30 .

In conventional optical laminates, when the adhesive layer is a cured layer of a photocurable adhesive, the adhesive is cured by irradiating sufficient light. Also, the amount of additive added to the adhesive was small. For this reason, the content of low-molecular-weight components in the cured adhesive layer was usually less than 1% by mass. However, if the low-molecular-weight component is less than 1% by mass, the transfer of iodine from the iodine-containing polarizer cannot be suppressed, and the iodine concentration in the pressure-sensitive adhesive layer in contact with the metal layer laminated on the optical layered body increases. was rising. The present inventors have found that by providing a layer containing a low-molecular-weight component capable of capturing iodine between the iodine-containing polarizer and the adhesive layer in contact with the metal layer, an increase in the iodine concentration of the adhesive layer can be suppressed. I got the knowledge that I can do it. It is believed that this is because iodine is captured by the low-molecular-weight component.

Low-molecular-weight components capable of capturing iodine include, for example, epoxy group-containing molecules, oxetane ring-containing molecules, acryloyloxy group-containing molecules, methacryloyloxy group-containing molecules; Molecules having skeleton, acrylate group, methacryl group, urea group, etc.; Molecules having urethane skeleton, urethane acrylate skeleton, pyridine skeleton, piperidine skeleton, pyrrolidine skeleton, acridine skeleton, acridone skeleton, etc.; molecules; polar molecules; cyclic molecules such as cyclodextrin and [n]-CPP; metal ions such as silver, copper and zinc; and porous materials such as activated carbon and zeolite.

In the present invention, attention was paid to an adhesive layer as a layer containing a low-molecular-weight component capable of trapping iodine. The adhesive layer is preferably a cured layer of an active energy ray-curable adhesive. The low-molecular-weight components contained in the adhesive layer may include unpolymerized monomers of the active energy ray-curable adhesive, polymerization initiators, decomposition products of polymerization initiators, and other additives. These low molecular weight components contained in the adhesive layer can trap iodine. The low-molecular-weight component capable of trapping iodine is preferably an unpolymerized monomer of the adhesive, from the viewpoint of facilitating control of the compatibility of the adhesive and suppressing bleed-out in a high-humidity-heat environment. The unpolymerized monomer contained in the adhesive preferably contains at least one selected from the group consisting of a monomer having an epoxy group, a monomer having an oxetane ring, a monomer having an acryloyloxy group, and a monomer having a methacryloyloxy group. The content of unpolymerized monomers in the adhesive layer can be varied, for example, by adjusting the degree of curing of the adhesive. In the optical layered body, a layer other than the adhesive layer, such as a polymerizable liquid crystal retardation layer, may contain a low-molecular-weight component.

The adhesive layer contained in the optical function layer contains 1% by mass or more and 10% by mass or less of a low molecular weight component having a molecular weight of 500 or less, and may be 3% by mass or more and may be 8% by mass or less. . The higher the content of the low-molecular-weight component, the more effectively iodine can be captured, which is preferable. On the other hand, if the content of the low-molecular-weight component is too high, the effect of suppressing iodine migration may decrease. Also, if the content of the low-molecular-weight component is too high, the optical functions of the polarizing plate may deteriorate. When the optical function layer includes a plurality of adhesive layers, the above range is the ratio of the total weight of the low-molecular-weight components contained in the plurality of adhesive layers to the total weight of the plurality of adhesive layers.

The proportion (% by mass) of the low-molecular-weight components contained in the adhesive layer is determined by (mass W2 of low-molecular-weight components contained in the adhesive layer)/(mass W1 of the adhesive layer). The mass W2 of the low-molecular-weight component contained in the adhesive layer is determined as follows. First, the entirety of a plurality of layers bonded by an adhesive layer is freeze-pulverized, and the resulting powder is extracted into a solvent. By analyzing this by gas chromatography, the amount of low molecular weight components having a molecular weight of 500 or less can be obtained. Functional groups of low-molecular-weight components can also be identified by using an apparatus in which a mass spectrometer (MS) is connected to gas chromatography. By mass spectrometry, it is possible to identify a component derived from the adhesive layer among the low-molecular-weight components, and to calculate the mass W2 of the low-molecular-weight component contained in the adhesive layer. The plurality of layers bonded by the adhesive layer may be the entire optical function layer, or may be a laminate including a polarizer, a first retardation layer, an adhesive layer and a second retardation layer. However, it is preferable to remove the adhesive layer for bonding to the metal layer before performing the analysis. The mass W1 of the adhesive layer can be calculated by (mass of the entire laminate subjected to gas chromatography) x {(thickness of the adhesive layer)/(thickness of the entire laminate layer subjected to gas chromatography)}.

For example, using a laminate in which a first retardation layer and a second retardation layer are bonded by an adhesive layer, the content of the low-molecular-weight component in the adhesive layer is calculated as follows. First, the laminate is freeze-pulverized, extracted into a solvent and filtered to obtain a test solution to be subjected to gas chromatography. Gas chromatography is performed to quantify the content of low-molecular-weight components from the peak area of the low-molecular-weight components. The content of low-molecular-weight components can be calculated by the following formula.
{Proportion of low-molecular-weight components contained in the adhesive layer (% by mass)} = [content of low-molecular-weight components derived from the adhesive layer in the test solution (mg/mL) x amount of test solution (mL)]/[laminate mass (mg) x {thickness of adhesive layer (μm)/thickness of laminate (μm)}] x 100

The optical laminate can constitute a circularly polarizing plate (including an elliptically polarizing plate). The optical laminate can be used as an antireflection film for image display devices. Examples of image display devices include organic electroluminescence (organic EL) display devices, inorganic electroluminescence (inorganic EL) display devices, liquid crystal display devices, and electroluminescence display devices. The display device may be a flexible display.

The optical layered body can be used for display devices such as smartphones and tablets, and can be particularly suitably used for touch panel type display devices. 1 to 4, the metal layer 40 may be a metal wiring layer that constitutes the touch panel sensor.

Each member constituting the optical laminate will be described below.
[Polarizer]
A polarizing plate includes a polarizer. The polarizing plate may have a protective film on one or both sides of the polarizer. The polarizing plate may further contain a substrate film, an alignment film, and the like. When the polarizer has a protective film on one side, the protective film may be laminated on the opposite side of the polarizer to the optical functional layer. When the polarizer is laminated directly on the optical functional layer via an adhesive layer, iodine easily migrates from the polarizer to the optical functional layer. Even in the optical layered body having such a structure, migration of iodine can be suppressed when the optical functional layer contains an adhesive layer containing a large amount of low-molecular-weight components.

The visibility correction total light transmittance Ty of the polarizing plate is preferably 43.5% or more, more preferably 44.5% or more, and may be 45.5% or more. When the total light transmittance Ty is 43.5% or more, the iodine content of the polarizing plate tends to be small. The visibility-corrected total light transmittance Ty can be measured with a spectrophotometer (V-7100 manufactured by JASCO Corp.).

(Polarizer)
A polarizer has the property of transmitting linearly polarized light having a plane of vibration perpendicular to the absorption axis when unpolarized light is incident thereon. The polarizer is a polyvinyl alcohol resin film in which iodine is adsorbed and oriented.

The polarizer is, for example, a polyvinyl alcohol-based resin film (hereinafter sometimes referred to as "PVA-based film") such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, and an ethylene/vinyl acetate copolymer-based partially saponified film. , dyeing treatment with iodine, and film-forming treatment such as stretching treatment can be used. If necessary, the PVA-based film having iodine adsorbed and oriented by the dyeing treatment may be treated with an aqueous boric acid solution, followed by a washing step of washing off the aqueous boric acid solution. A known method can be adopted for each step. The film thickness of the raw polyvinyl alcohol-based resin film is, for example, 10 μm or more and 100 μm or less, preferably 10 μm or more and 60 μm or less, and may be 15 μm or more and 30 μm or less.

A polyvinyl alcohol-based resin (hereinafter sometimes referred to as "PVA-based resin") is obtained by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate-based resin may be polyvinyl acetate, which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and other monomers copolymerizable therewith. Other monomers copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acid-based compounds, olefin-based compounds, vinyl ether-based compounds, unsaturated sulfone-based compounds, and (meth)acrylamide-based compounds having an ammonium group. .

The saponification degree of the PVA-based resin is usually about 85 mol % or more and 100 mol % or less, preferably 98 mol % or more. The PVA-based resin may be modified, and aldehyde-modified polyvinyl formal, polyvinyl acetal, and the like can also be used. The average degree of polymerization of the polyvinyl alcohol resin is usually 1000 or more and 10000 or less, preferably 1500 or more and 5000 or less. The average degree of polymerization of the polyvinyl alcohol-based resin can be determined according to JIS K 6726 (1994). If the average degree of polymerization is less than 1,000, it is difficult to obtain desirable polarizing performance, and if it exceeds 10,000, film workability may be poor.

Another method for manufacturing a polarizer containing a PVA-based film is to first prepare a base film, apply a solution of a resin such as a PVA-based resin on the base film, and perform drying to remove the solvent, etc. It may include a step of forming a resin layer on the film. As the base film, a resin film such as PET, or a film using a thermoplastic resin that can be used as a protective film, which will be described later, can be used. A primer layer can be formed in advance on the surface of the substrate film on which the resin layer is to be formed. Examples of the material for the primer layer include resins obtained by cross-linking hydrophilic resins used in polarizers.

Next, the amount of solvent such as moisture in the resin layer is adjusted as necessary, and then the base film and the resin layer are uniaxially stretched. Subsequently, the resin layer is dyed with iodine to cause iodine to be adsorbed and oriented on the resin layer. If necessary, the resin layer in which iodine is adsorbed and oriented is treated with an aqueous boric acid solution, and a washing step is performed to wash off the aqueous boric acid solution. As a result, a polarizer, which is a resin layer in which iodine is adsorbed and oriented, is produced. A known method can be adopted for each step.

The amount of boric acid in the boric acid-containing aqueous solution for treating the PVA-based film or PVA-based resin layer in which iodine is adsorbed and oriented is usually about 2 parts by mass or more and 15 parts by mass or less, and 5 parts by mass per 100 parts by mass of water. More than 12 parts by mass or less is preferable. This boric acid-containing aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. The immersion time in the boric acid-containing aqueous solution is usually 60 seconds or more and 1200 seconds or less, preferably 150 seconds or more and 600 seconds or less, and more preferably 200 seconds or more and 400 seconds or less. The temperature of the boric acid-containing aqueous solution is usually 50°C or higher, preferably 50°C or higher and 85°C or lower, and more preferably 60°C or higher and 80°C or lower.

The uniaxial stretching of the base film and the PVA-based resin layer may be performed before dyeing, during dyeing, or during boric acid treatment after dyeing. Each may be uniaxially stretched. The base film and the PVA-based resin layer may be uniaxially stretched in the MD direction (film transport direction). It may be stretched to Moreover, the base film and the PVA-based resin layer may be uniaxially stretched in the TD direction (the direction perpendicular to the film transport direction), in which case a so-called tenter method can be used. The stretching of the base film and the PVA-based resin layer may be dry stretching performed in the air, or wet stretching performed after the PVA-based resin layer is swollen with a solvent. good too. In order to exhibit the performance of the polarizer, the draw ratio is 4 times or more, preferably 5 times or more, and particularly preferably 5.5 times or more. Although there is no particular upper limit for the draw ratio, it is preferably 8 times or less from the viewpoint of suppressing breakage and the like.

A polarizer produced by a manufacturing method using a base film may be used as a linear polarizer with the base film peeled off or together with the base film. After laminating the protective film on the polarizer, the base film may be peeled off. According to this method, the thickness of the polarizer can be reduced.

The thickness of the polarizer is preferably 1 μm or more, and may be 2 μm or more or 5 μm or more. The thickness of the polarizer is preferably 30 μm or less, and may be 15 μm or less, 10 μm or less, or 8 μm or less. The smaller the thickness of the polarizer, the easier it is for iodine to seep out under a high-temperature, high-humidity environment.

(Protective film)
As the protective film, it is preferable to use a film formed from a thermoplastic resin that is excellent in transparency, mechanical strength, thermal stability, water barrier properties, isotropy, stretchability, and the like. Specific examples of thermoplastic resins include cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyethersulfone resins; polysulfone resins; polycarbonate resins; polyamide resins such as nylon and aromatic polyamides; Resin; polyolefin resins such as polyethylene, polypropylene, ethylene/propylene copolymer; cyclic polyolefin resins having cyclo- and norbornene structures (also referred to as norbornene-based resins); (meth)acrylic resins; polyarylate resins; polystyrene resins; Resins, as well as mixtures thereof, may be mentioned. When the polarizer has protective films on both sides, the resin composition of both protective films may be the same or different. In this specification, "(meth)acrylic" means either acrylic or methacrylic. "(Meth)" such as (meth)acrylate has the same meaning.

The protective film may have retardation, and may have antireflection properties and antiglare properties. The protective film may have a hard coat layer formed on a thermoplastic resin film. The hard coat layer may be formed on one side of the thermoplastic resin film, or may be formed on both sides. By providing a hard coat layer, a protective film having improved hardness and scratch resistance can be obtained.

The thickness of the protective film is preferably 3 μm or more, and may be 5 μm or more. The thickness of the protective film is preferably 50 μm or less, and may be 40 μm or less or 30 μm or less.

When the protective film is provided on the optical functional layer side of the polarizer, the moisture permeability of the protective film at a temperature of 40° C. and a relative humidity of 90% RH is preferably 350 g/(m ² ·24 hr) or more, and preferably 500 g/(m ² · 24 hr) or more, 750 g/(m ² ·24 hr) or more, or 1000 g/(m ² ·24 hr) or more. The moisture permeability of the protective film at a temperature of 40° C. and a relative humidity of 90% RH is, for example, 2500 g/(m ² ·24 hr) or less. When the moisture permeability of the protective film is high, iodine tends to migrate from the polarizing plate to the optical functional layer side. However, migration of iodine can be suppressed when the optical function layer contains an adhesive layer containing a large amount of low-molecular-weight components.

The protective film may be laminated to the polarizer via an adhesive layer or adhesive layer. The protective film is preferably laminated to the polarizer with an adhesive layer formed by drying a water-based adhesive containing a polyvinyl alcohol-based resin.

A surface functional layer such as an antireflection layer, an antiglare layer, or a hard coat layer may be further provided on one side of the polarizing plate. The surface functional layer is preferably provided so as to be in direct contact with the protective film. The surface functional layer is preferably provided on the opposite side of the protective film from the polarizer side.

[Optical function layer]
The optical function layer includes at least one adhesive layer. The optical function layer may include a protective layer, a liquid crystal cured layer, a retardation layer, a bonding layer, and the like. The optical function layer includes, for example, one or more retardation layers. The optical function layer includes, for example, two layers of retardation layers, a first retardation layer and a second retardation layer, and the first retardation layer and the second retardation layer may be laminated via a bonding layer. . The first retardation layer and the polarizing plate may be laminated via a bonding layer. Each lamination layer may be independently a pressure-sensitive adhesive layer or an adhesive layer.

The optical function layer includes a λ/4 layer as the first retardation layer and the second retardation layer, and may further include at least one of a λ/2 layer and a positive C layer. When the retardation layer includes a λ/2 layer, the λ/4 layer and the λ/2 layer may be laminated in order from the polarizing plate side, or the λ/2 layer and the λ/4 layer may be laminated in order. When the retardation layer includes a positive C layer, the λ/4 layer and the positive C layer may be laminated in order from the polarizing plate side, or the positive C layer and the λ/4 layer may be laminated in order.

The optical function layer may further include an adhesive layer laminated on the surface opposite to the polarizing plate. This pressure-sensitive adhesive layer is used as a bonding layer when the optical laminate is laminated on the metal layer.

(adhesive layer)
The adhesive layer can be formed by curing the curable component in the adhesive composition. Examples of the adhesive composition for forming the adhesive layer include adhesives other than pressure-sensitive adhesives (adhesives), such as water-based adhesives and active energy ray-curable adhesives.

Examples of water-based adhesives include adhesives obtained by dissolving or dispersing a polyvinyl alcohol-based resin in water. The method of drying when a water-based adhesive is used is not particularly limited. For example, a method of drying using a hot air dryer or an infrared ray dryer can be employed.

Active energy ray-curable adhesives include, for example, solvent-free active energy ray-curable adhesives containing curable compounds that are cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. mentioned. Adhesion between layers can be improved by using a non-solvent active energy ray-curable adhesive.

The active energy ray-curable adhesive preferably contains either one or both of a cationically polymerizable curable compound and a radically polymerizable curable compound because it exhibits good adhesiveness. The active energy ray-curable adhesive can further contain a cationic polymerization initiator such as a photocationic polymerization initiator or a radical polymerization initiator for initiating the curing reaction of the curable compound.

Examples of cationic polymerizable curable compounds include alicyclic epoxy compounds having an epoxy group bonded to an alicyclic ring, and polyfunctional aliphatic epoxy compounds having two or more epoxy groups and no aromatic ring. , monofunctional epoxy groups having one epoxy group (excluding those contained in alicyclic epoxy compounds), polyfunctional aromatic epoxy compounds having two or more epoxy groups and aromatic rings, etc. compounds; oxetane compounds having one or more oxetane rings in the molecule; and combinations thereof.

Radically polymerizable curable compounds include, for example, (meth)acrylic compounds (compounds having one or more (meth)acryloyloxy groups in the molecule), and other radically polymerizable double bonds. or a combination thereof.

The active energy ray-curable adhesive can contain a sensitizer such as a photosensitizer as needed. By using a sensitizer, the reactivity is improved, and the mechanical strength and adhesive strength of the adhesive layer can be further improved. A known sensitizer can be appropriately applied. When a sensitizer is blended, the blending amount is preferably 0.1 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass as the total amount of the active energy ray-curable adhesive.

Active energy ray-curable adhesives may optionally contain ion trapping agents, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow control agents, plasticizers, antifoaming agents, and antistatic agents. Additives such as agents, leveling agents, solvents and the like can be included.

When an active energy ray-curable adhesive is used, an adhesive layer can be formed by irradiating an active energy ray such as ultraviolet rays, visible light, electron beams, and X-rays to cure the adhesive coating layer. can. As the active energy ray, ultraviolet rays are preferable, and as a light source in this case, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, etc. can be used. can.

The thickness of the adhesive layer is preferably 0.01 μm or more, more preferably 0.05 μm or more, still more preferably 0.1 μm or more. The thickness of the adhesive layer is preferably 10 µm or less, more preferably 5 µm or less, from the viewpoint of enhancing flexibility.

(Adhesive layer)
An adhesive layer is formed using an adhesive composition. A pressure-sensitive adhesive composition exhibits adhesiveness when it is attached to an adherend, and is called a pressure-sensitive adhesive. As the adhesive composition, conventionally known adhesives having excellent optical transparency can be used without particular limitation. The adhesive layer can be formed from an adhesive composition containing a (meth)acrylic resin, rubber resin, urethane resin, ester resin, silicone resin, or polyvinyl ether resin as a base polymer. Among them, a pressure-sensitive adhesive composition using a (meth)acrylic resin as a base polymer, which is excellent in transparency, weather resistance, heat resistance, etc., is preferable. The adhesive composition may be active energy ray-curable or heat-curable. The pressure-sensitive adhesive layer preferably comprises a reaction product of a pressure-sensitive adhesive composition containing a (meth)acrylic resin, a cross-linking agent and a silane compound, and may contain other components.

The (meth)acrylic resin used in the adhesive composition includes (meth)acrylates such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Polymers or copolymers containing one or more acrylic acid esters as monomers are preferably used. Preferably, the base polymer is copolymerized with a polar monomer. Polar monomers include (meth)acrylic acid compounds, 2-hydroxypropyl (meth)acrylate compounds, hydroxyethyl (meth)acrylate compounds, (meth)acrylamide compounds, and N,N-dimethylaminoethyl (meth)acrylate compounds. , glycidyl (meth)acrylate compounds, and other monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like.

The pressure-sensitive adhesive composition may contain only the above base polymer, but usually further contains a cross-linking agent. As a cross-linking agent, a metal ion having a valence of 2 or more and forming a carboxylic acid metal salt with a carboxyl group, a polyamine compound forming an amide bond with a carboxyl group, and a carboxyl group Examples include polyepoxy compounds or polyols that form ester bonds with and polyisocyanate compounds that form amide bonds with carboxyl groups. The cross-linking agent is preferably a polyisocyanate compound.

The active energy ray-curable pressure-sensitive adhesive composition has the property of being cured by being irradiated with an active energy ray such as an ultraviolet ray or an electron beam. It has the property that it can be adhered to an adherend and can be cured by irradiation with active energy rays to adjust the adhesion force. The active energy ray-curable pressure-sensitive adhesive composition is preferably UV-curable. The pressure-sensitive adhesive composition may further contain an active energy ray-polymerizable compound in addition to the base polymer and the cross-linking agent. If necessary, a photopolymerization initiator, a photosensitizer, etc. may be contained.

Examples of active energy ray-polymerizable compounds include (meth)acrylate monomers having at least one (meth)acryloyloxy group in the molecule; Examples thereof include (meth)acrylic compounds such as (meth)acryloyloxy group-containing compounds such as (meth)acrylate oligomers having one (meth)acryloyloxy group. The adhesive composition can contain 0.1 parts by mass or more of the active energy ray-polymerizable compound with respect to 100 parts by mass of the solid content of the adhesive composition, and 10 parts by mass or less, 5 parts by mass or less, or 2 parts by mass. can be included below.

Examples of photopolymerization initiators include benzophenone, benzyldimethylketal, 1-hydroxycyclohexylphenylketone and the like. A photoinitiator can contain 1 type(s) or 2 or more types. When the adhesive composition contains a photopolymerization initiator, the total content thereof may be, for example, 0.01 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the solid content of the adhesive composition.

The adhesive composition contains fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than base polymers, tackifiers, fillers (metal powders and other inorganic powders). etc.), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, antifoaming agents, corrosion inhibitors, photopolymerization initiators, and other additives.

The pressure-sensitive adhesive layer can be formed by applying an organic solvent-diluted solution of the above pressure-sensitive adhesive composition onto a substrate and drying it. The pressure-sensitive adhesive layer can also be formed using a pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition. When an active energy ray-curable pressure-sensitive adhesive composition is used, a pressure-sensitive adhesive layer having a desired degree of curing can be obtained by irradiating the formed pressure-sensitive adhesive layer with an active energy ray.

Although the thickness of the pressure-sensitive adhesive layer is not particularly limited, it is preferably 1 μm or more and 100 μm or less, more preferably 3 μm or more and 50 μm or less, and may be 20 μm or more.

(retardation layer)
The retardation layer contains a cured product of a polymerizable liquid crystal compound. The retardation layer may include an alignment layer having an alignment control force for aligning the polymerizable liquid crystal compound in a desired direction. The retardation layer may include an overcoat layer that protects its surface, a substrate layer that supports the retardation layer, and the like.

The polymerizable liquid crystal compound includes a rod-like polymerizable liquid crystal compound and a disk-like polymerizable liquid crystal compound, and one of them may be used, or a mixture containing both of them may be used. When the rod-shaped polymerizable liquid crystal compound is aligned horizontally or vertically with respect to the substrate layer, the optical axis of the polymerizable liquid crystal compound coincides with the long axis direction of the polymerizable liquid crystal compound. When the discotic polymerizable liquid crystal compound is oriented, the optical axis of the polymerizable liquid crystal compound exists in a direction orthogonal to the discotic surface of the polymerizable liquid crystal compound. As the rod-like polymerizable liquid crystal compound, for example, those described in JP-A-11-513019 (claim 1 etc.) can be preferably used. As the discotic polymerizable liquid crystal compound, JP-A-2007-108732 (paragraphs [0020] to [0067], etc.), JP-A-2010-244038 (paragraphs [0013] to [0108], etc.) described in can be preferably used.

In order for a cured product layer formed by polymerizing a polymerizable liquid crystal compound to exhibit an in-plane retardation, the polymerizable liquid crystal compound may be oriented in a suitable direction. When the polymerizable liquid crystal compound is rod-shaped, an in-plane retardation is expressed by aligning the optical axis of the polymerizable liquid crystal compound horizontally with respect to the plane of the substrate layer. match the direction. When the polymerizable liquid crystal compound has a discotic shape, an in-plane retardation is expressed by aligning the optical axis of the polymerizable liquid crystal compound horizontally with respect to the plane of the substrate layer, and in this case, the optical axis and the slow axis are orthogonal to The alignment state of the polymerizable liquid crystal compound can be adjusted by combining the alignment layer and the polymerizable liquid crystal compound.

A polymerizable liquid crystal compound is a compound having at least one polymerizable group and having liquid crystallinity. When two or more polymerizable liquid crystal compounds are used in combination, at least one preferably has two or more polymerizable groups in the molecule. A polymerizable group means a group that participates in a polymerization reaction, and is preferably a photopolymerizable group. Here, the photopolymerizable group means a group that can participate in a polymerization reaction by an active radical generated from a photopolymerization initiator described below, an acid, or the like. Examples of the polymerizable group include vinyl group, vinyloxy group, 1-chlorovinyl group, isopropenyl group, 4-vinylphenyl group, acryloyloxy group, methacryloyloxy group, oxiranyl group, oxetanyl group, styryl group and allyl group. be done. Among them, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group and an oxetanyl group are preferred, and an acryloyloxy group is more preferred. The liquid crystallinity of the polymerizable liquid crystal compound may be either thermotropic liquid crystal or lyotropic liquid crystal, and thermotropic liquid crystal may be classified into nematic liquid crystal or smectic liquid crystal according to the degree of order.

The thickness of the retardation layer may be 0.1 μm or more, 0.5 μm or more, 1 μm or more, 2 μm or more, or 10 μm or less. is preferable, and may be 8 μm or less, or may be 5 μm or less.

The cured product layer of the polymerizable liquid crystal compound can be formed by applying a liquid crystal layer-forming composition containing a polymerizable liquid crystal compound on the substrate layer, drying the composition, and polymerizing the polymerizable liquid crystal compound. The composition for forming a liquid crystal layer may be applied onto the alignment layer formed on the substrate layer.

The alignment layer may be a vertical alignment layer in which the molecular axis of the polymerizable liquid crystal compound is vertically aligned with respect to the base layer, or a horizontal alignment layer in which the molecular axis of the polymerizable liquid crystal compound is horizontally aligned with respect to the base layer. or a tilted alignment layer in which the molecular axis of the polymerizable liquid crystal compound is tilted with respect to the substrate layer.

The alignment layer has a solvent resistance that does not dissolve when a composition for forming a liquid crystal layer containing a polymerizable liquid crystal compound is applied, etc., and has heat resistance to heat treatment for removing the solvent and aligning the polymerizable liquid crystal compound. things are preferred. Examples of the alignment layer include an alignment polymer layer formed of an alignment polymer, a photo-alignment polymer layer formed of a photo-alignment polymer, and a groove alignment layer having an uneven pattern or a plurality of grooves on the layer surface. can be done.

As the substrate layer, a film made of a resin material can be used. For example, a film made of the resin material described as the thermoplastic resin used for forming the above-described protective film can be used. The thickness of the substrate layer is not particularly limited, but in general, from the viewpoint of workability such as strength and handleability, it is preferably 1 μm or more and 300 μm or less, more preferably 20 μm or more and 200 μm or less, and 30 μm or more and 120 μm or less. It is even more preferable to have The substrate layer may be incorporated in the optical laminate together with the cured layer of the polymerizable liquid crystal compound, and the substrate layer is peeled off to obtain only the cured layer of the polymerizable liquid crystal compound, or the cured layer and the cured layer of the polymerizable liquid crystal compound. Alignment layers may be incorporated into the optical stack. When the substrate layer is incorporated into the optical layered body together with the cured product layer of the polymerizable liquid crystal compound, the thickness of the substrate layer may be less than 30 μm, for example, 25 μm or less.

[Metal layer]
A metal layer can be used as a conductive layer for forming a touch sensor of a touch panel. A metal layer is a layer formed of one or more metals. The metal layer may have a passive film (oxide film) formed on its surface. The metal layer may have a single layer structure or a multilayer structure. Note that the passivation film is not counted as one layer.

Metals constituting the metal layer include aluminum (Al), copper (Cu), gold (Au), silver (Ag), titanium (Ti), palladium (Pd), chromium (Cr), nickel (Ni), and tungsten. (W), platinum (Pt), iron (Fe), indium (In), tin (Sn), iridium (Ir), rhodium (Rh), neodymium (Nd), molybdenum (Mo), or these metals alloys containing more than one species. Among these, the metal layer preferably contains aluminum or copper as a main component, and may contain titanium as an additive. Here, the main component refers to a metal that accounts for 50% by mass or more of the metal that constitutes the metal layer.

The metal layer can be formed on, for example, a light-transmitting substrate, and may be a continuous film formed over the entire surface of the light-transmitting substrate, or a metal wiring formed on the surface of the light-transmitting substrate. It can be layers. The metal wiring layer may be a metal mesh. The light-transmitting base material may be any material as long as it has light-transmitting properties.

The method for forming the metal layer is not particularly limited. and the like.

The thickness of the metal layer is usually 0.01 μm or more, and may be 0.05 μm or more. It is more preferably 0.8 μm or less.

When the metal layer is a metal wiring layer, the line width is usually 10 μm or less, may be 5 μm or less, may be 3 μm or less, and is usually 0.5 μm or more.

<Method for manufacturing optical laminate>
One embodiment of the method for producing an optical laminate includes a step of laminating layers using an active energy ray-curable adhesive. For example, a first retardation layer including a cured layer of a polymerizable liquid crystal compound and a polymerizable liquid crystal compound A step of laminating the second retardation layer containing the cured layer of with an active energy ray-curable adhesive, or the first retardation layer and the polarizing plate containing the cured layer of the polymerizable liquid crystal compound are cured with an active energy ray. It includes a step of laminating with a mold adhesive. In this step, the curing degree of the adhesive is adjusted so that the active energy ray-curable adhesive is not completely cured and unpolymerized monomers remain in the adhesive layer. The degree of curing of the adhesive can be adjusted by controlling the irradiation amount of the active energy ray, the amount of transmission of the active energy ray, and the like.

For example, the amount of active energy ray irradiation for curing the adhesive can be reduced to such an extent that the adhesive is not completely cured. The dose of active energy rays (UVB) may be 90% or less or 80% or less of the dose when the adhesive is completely cured. The active energy ray dose may be, for example, 550 mJ/cm ² or less, 450 mJ/cm ² or less, 400 mJ/cm ² or less, 350 mJ/cm ² or less, or 300 mJ/cm ² or less. The dose of active energy rays is usually 200 mJ/cm ² or more.

The transmission amount of active energy rays (UVB) can be adjusted, for example, by adding an ultraviolet absorber. The ultraviolet absorber may be contained in any layer from the adhesive layer to the surface layer on the active energy ray irradiation side, and may be contained in the substrate layer or the pressure-sensitive adhesive layer. Although the ultraviolet absorber is not particularly limited, for example, an oxybenzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a salicylic acid ester ultraviolet absorber, a benzophenone ultraviolet absorber, a cyanoacrylate ultraviolet absorber, and a triazine ultraviolet absorber. Organic UV absorbers such as titanium oxide, zinc oxide, indium oxide, tin oxide, talc, kaolin, calcium carbonate, titanium oxide composite oxide, zinc oxide composite oxide, ITO (tin-doped indium oxide), ATO Inorganic UV absorbers such as (antimony-doped tin oxide) can be mentioned.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[Calculation of ratio of low-molecular-weight components]
Using a laminate having a configuration of first substrate layer / first retardation layer / adhesive layer (ultraviolet curable adhesive layer) / second retardation layer / second substrate layer, The ratio of low-molecular-weight components was calculated. First, the first substrate layer and the second substrate layer were peeled off from the laminate. A laminate of the first retardation layer/adhesive layer/second retardation layer was freeze-pulverized, dissolved in a solvent (acetonitrile) and then filtered to obtain a test solution.

The resulting test solution was subjected to gas chromatography to quantify low-molecular-weight components from the peak areas of components having a molecular weight of 500 or less. According to mass spectrometry, approximately 40% of the components having a molecular weight of 500 or less were unpolymerized monomers (epoxy group-containing monomers) of the UV-curable adhesive. The measurement conditions were as follows.
Apparatus: Agilent 6850 GC (Agilent Technologies, Inc.)
Carrier gas: Helium Flow rate: 1.0 mL/min. (constant flow)
Column: DB-5 0.25 mmΦ×30 m, 0.25 μm (Agilent Technologies, Inc.)
Oven: 50°C (5min.Hold) -10°C/min. -320°C (8 min. Hold)
Injection volume: 1.0 μL
Inlet temperature: 250°C
Injection mode: splitless (split vent purge flow rate: 50 mL/min., 1 min. gas saver: 15 mL/min., 2 min.)
Detection: FID (250°C, H2: 40 mL/min., Air: 400 mL/min. Makeup: He, 45 mL/min.)

The proportion of low-molecular-weight components was calculated according to the following formula.
{Content of low-molecular-weight components in adhesive (%)} = {Content of low-molecular-weight components derived from adhesive layer in test solution (mg/mL)} ÷ {powder amount when preparing test solution (mg)} × {Amount of solvent used when preparing the test solution (mL)} ÷ {Thickness of the adhesive layer (μm)} × {Thickness of the entire laminate after removing the first base layer and the second base layer by peeling (μm )}×100

[Measurement of iodine content in adhesive layer]
The optical laminate was cut into a size of 25 mm×50 mm, and after the protective film was peeled off, the polarizing plate side was attached to non-alkali glass using an adhesive. The optical laminate was stored in an oven at a temperature of 85° C. and a relative humidity of 85% RH for 240 hours. The release film on the side of the second retardation layer was peeled off, and the adhesive on the adhesive layer was scraped off. The amount of iodine [ppm] contained in the scraped adhesive was measured by oxidation combustion ion chromatography performed under the following conditions.

<Sample combustion>
Apparatus: AQF-2100H manufactured by Mitsubishi Chemical Analytech Co., Ltd.
Combustion conditions: The combustion temperature was 1100° C., and the gas flow rates were argon flow rate of 200 mL/min, oxygen flow rate of 400 mL/min, and humidified air flow rate of 100 mL/min.
<Ion Chromatograph>
Apparatus: Integrion manufactured by Thermo Fisher Scientific
Column: IonPac AS19 manufactured by Thermo Fisher Scientific
Measurement conditions: the eluent was a KOH aqueous solution gradient, the flow rate was 1.0 mL/min, the injection volume was 100 μL, the measurement mode was a suppressor type, and the detector was an electrical conductivity detector.

[Measurement of storage modulus]
The pressure-sensitive adhesive layers were stacked to a thickness of 150 μm and bonded to a glass plate. For this sample for storage modulus measurement, a rheometer ("MCR-301" manufactured by Anton Parr) was used to measure the storage modulus under the conditions of a temperature of 25°C, a relative humidity of 50%, a stress of 1%, and a frequency of 1 Hz. gone.

[Thickness measurement]
The thickness of the layer was measured using a contact-type film thickness measuring device ("MS-5C" manufactured by Nikon Corporation). The thicknesses of the adhesive layer, the polarizer layer, and the alignment film were measured using a laser microscope ("OLS3000" manufactured by Olympus Corporation).

[Measurement of Visibility Correction Total Light Transmittance Ty and Visibility Correction Polarization Degree Py]
The total light transmittance Ty and the degree of polarization Py at a wavelength of 380 nm to 780 nm were measured using a spectrophotometer with an integrating sphere ["V7100" manufactured by JASCO Corporation, 2-degree field of view; C light source].

[Measurement of moisture permeability]
Using a constant temperature and humidity chamber, the water vapor transmission rate was measured by the moisture permeability test method (cup method, according to JIS Z 0208) under the measurement conditions of temperature of 40° C., relative humidity of 90% RH, and measurement time of 24 hours. The measured water vapor transmission rate was defined as the water vapor transmission rate at a temperature of 40°C and a relative humidity of 90% RH.

[Preparation of polarizing plate]
A polyvinyl alcohol-based resin film with a thickness of 30 μm (average degree of polymerization: about 2400, degree of saponification: 99.9 mol% or more) is longitudinally uniaxially stretched by about 5 times by dry stretching, and then is placed in pure water at a temperature of 60°C while maintaining the tension. After being immersed for 1 minute, it was immersed for 60 seconds in an aqueous solution having a mass ratio of iodine/potassium iodide/water of 0.05/5/100 at a temperature of 28°C. After that, it was immersed in an aqueous solution having a mass ratio of potassium iodide/boric acid/water of 8.5/8.5/100 at a temperature of 72°C. Subsequently, after washing with pure water at a temperature of 26°C for 20 seconds, a drying treatment was performed at a temperature of 65°C. A polarizer having a thickness of 12 μm was obtained, in which iodine was adsorbed and oriented on the polyvinyl alcohol-based resin film.

An aqueous polyvinyl alcohol solution was prepared by dissolving 3 parts by mass of carboxyl group-modified polyvinyl alcohol (“KL-318” manufactured by Kuraray Co., Ltd.) in 100 parts by mass of water. Water-soluble polyamide epoxy resin ["Sumireze Resin 650 (30)" manufactured by Taoka Chemical Co., Ltd., solid content concentration 30% by mass] was added to the resulting aqueous solution, and 1.5 parts by mass per 100 parts by mass of water. The proportions were mixed to obtain a water-based adhesive.

A triacetyl cellulose film (hereinafter sometimes referred to as "TAC film") having a hard coat layer (hereinafter sometimes referred to as "HC layer") coated with a water-based adhesive on one surface of a polarizer. ) was laminated. On the other side, the water-based adhesive was applied and a TAC film was laminated. By drying at a temperature of 80° C. for 5 minutes, a polarizing plate 1 having protective films on both sides of the polarizer was obtained. The moisture permeability of the TAC film with the HC layer was 450 g/(m ² ·24 hr), and the moisture permeability of the TAC film was 1200 g/(m ² ·24 hr). A protective film having an adhesive layer on a base film was laminated on the HC layer of the polarizing plate to obtain a polarizing plate with a protective film (hereinafter sometimes referred to as "polarizing plate with PF").

In the manufacturing process of the polarizer, the concentration of the aqueous solution containing iodine and the immersion time in the aqueous solution were adjusted to obtain polarizing plates 2 to 4 having different optical properties. Polarizing plates 3 and 4 used TAC films on both sides as protective films. Table 1 shows the total light transmittance Ty and the degree of polarization Py measured using a polarizing plate having protective films on both sides of the polarizer.

A 5 μm-thick acrylic pressure-sensitive adhesive layer (storage elastic modulus: 125000 Pa) was prepared, both sides of which were attached to release films. One side of the pressure-sensitive adhesive layer with a release film, from which one of the release films was peeled, was bonded to the opposite side (TAC film side) of the polarizing plate with PF from the PF. Subsequently, the other release film of the pressure-sensitive adhesive layer was peeled off to obtain a polarizing plate with the pressure-sensitive adhesive layer. The polarizing plate with an adhesive layer had a protective film/polarizing plate (protective film/polarizer/protective film)/adhesive layer in this order.

[Preparation of Retardation Layer]
(First retardation layer)
A composition for forming a liquid crystal layer containing a rod-shaped nematic polymerizable liquid crystal compound was applied onto a substrate layer formed of a transparent resin to prepare a first retardation layer with a first substrate layer. The first retardation layer had a quarter-wave retardation characteristic (a retardation value of 142 nm at a wavelength of 550 nm). The thickness of the first retardation layer was 1 μm.

(Second retardation layer)
A second retardation layer with a second substrate layer was produced by the following method. First, 10.0 parts by weight of polyethylene glycol di(meth)acrylate, 10.0 parts by weight of trimethylolpropane triacrylate, 10.0 parts by weight of 1,6-hexanediol di(meth)acrylate, and a photopolymerization initiator 1.50 parts by mass of Irgacure 907 was dissolved in 70.0 parts by mass of methyl ethyl ketone as a solvent to prepare a composition for forming an alignment layer. Subsequently, 20.0 parts by mass of a photopolymerizable nematic liquid crystal compound and 1.0 parts by mass of Irgacure 907 as a photopolymerization initiator are dissolved in 80.0 parts by mass of propylene glycol monomethyl ether acetate as a solvent, A composition for forming a liquid crystal layer was prepared.

One side of the substrate layer was subjected to corona treatment, and the alignment layer-forming composition prepared above was applied to the corona-treated side with a bar coater. After heat-treating the coating layer at a temperature of 80° C. for 60 seconds, it was irradiated with ultraviolet rays to polymerize and cure the alignment layer-forming composition to form an alignment layer having a thickness of 1.8 μm on the substrate layer. . The composition for forming a liquid crystal layer prepared above was applied onto the alignment layer. After heat-treating the coating layer at a temperature of 80° C. for 60 seconds, it was irradiated with ultraviolet rays to polymerize and cure the composition for forming a liquid crystal layer, thereby forming a cured liquid crystal layer having a thickness of 0.7 μm on the alignment layer. . As described above, a second retardation layer with a second substrate layer was obtained. The retardation value Rth of the second retardation layer was -75 nm.

(UV curable adhesive)
A UV-curable adhesive was prepared by mixing cationic curable components shown below.
3′,4′-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate (trade name: CEL2021P, manufactured by Daicel Corporation): 70 parts by mass Neopentyl glycol diglycidyl ether (trade name: EX-211, Nagase ChemteX Corporation) Company): 20 parts by weight 2-ethylhexyl glycidyl ether (trade name: EX-121, manufactured by Nagase ChemteX Corporation): 10 parts by weight Cationic polymerization initiator (trade name: CPI-100_50% solution, manufactured by San-Apro Co., Ltd.) : 4.5 parts by mass (substantial solid content: 2.25 parts by mass)
1,4-diethoxynaphthalene: 2.0 parts by mass

(Lamination of retardation layer)
The retardation layer side of the first retardation layer with the first substrate layer and the retardation layer side of the second retardation layer with the second substrate layer were each subjected to corona treatment. The prepared ultraviolet curable adhesive was applied to one corona-treated surface, and the first retardation layer with the first base layer and the second retardation layer with the second base layer were bonded together. An adhesive layer was formed by irradiating ultraviolet rays from the second base material layer side to cure the ultraviolet curable adhesive. As for ultraviolet rays, UVB with a wavelength of 315 nm to 280 nm was irradiated at 420 mJ/cm ² . The maximum transmittance in the UVB region of the second substrate layer was 36%. A laminate 1 in which a first substrate layer / first retardation layer (liquid crystal cured layer) / adhesive layer / second retardation layer (liquid crystal cured layer / alignment layer) / second substrate layer is laminated in this order Got. The thickness of the UV curable adhesive layer after curing was 1.5 μm.

Except for adding an ultraviolet absorber to the second base material layer to reduce the UVB transmittance to 12% and changing the UVB irradiation dose between 510 mJ/cm ² and 210 mJ/cm ² . Laminates 2 to 6 were produced in the same manner as for Laminate 1. Table 2 shows the results of calculating the ratio of the low-molecular-weight components contained in the adhesive layer for the laminates 1 to 6. The ratio of low-molecular-weight components increased as the UVB transmittance decreased and the UVB irradiation amount decreased.

As shown in Tables 3 to 6, laminates 1 to 6 and pressure-sensitive adhesive layer-attached polarizing plates 1 to 4 were combined and laminated to prepare optical laminates. At this time, the first substrate layer was peeled off from the laminate, and the first retardation layer and the adhesive layer of the adhesive layer-attached polarizing plate were laminated. Furthermore, one of the 15 μm-thick pressure-sensitive adhesive layers (storage elastic modulus: 25500 Pa) with both sides attached to the release film is peeled off, and the second substrate layer is peeled off. Laminated on the second retardation layer. did. Thus, an optical laminate was obtained in which the protective film/polarizing plate/adhesive layer/first retardation layer/adhesive layer/second retardation layer/adhesive layer/release film were laminated.

The protective film and the release film on the second retardation layer side were peeled off from the optical layered body. The optical layered body was attached to non-alkali glass via the pressure-sensitive adhesive layer on the second retardation layer side. A high-humidity heat test was performed by storing this laminate at a temperature of 60° C. and a relative humidity of 95% RH for 250 hours. The total light transmittance Ty and the degree of polarization Py before and after the high-humidity heat test were measured, and the rate of change in the degree of polarization (ΔPy)={(Py after test)−(Py before test)} was calculated.

Also, the iodine concentration was measured using the optical layered body. The protective film was peeled off from the optical layered body and attached to non-alkali glass. This laminate was subjected to a high humidity heat test (85° C. temperature, 85% RH relative humidity). The iodine concentration after the high-humidity heat test in the pressure-sensitive adhesive layer laminated on the second retardation layer was measured, and the reduction amount and reduction rate when compared with the optical laminate in which the laminate 1 was laminated were calculated. The amount of decrease is calculated by {(concentration of iodine contained in the pressure-sensitive adhesive layer of the optical laminate on which the laminate 1 is laminated)−(concentration of iodine contained in the pressure-sensitive adhesive layer of each optical laminate)}. The reduction rate (%) is {(concentration of iodine contained in the adhesive layer of the optical laminate on which the laminate 1 is laminated)-(concentration of iodine contained in the adhesive layer of each optical laminate)}/(laminate 1 is calculated as the iodine concentration contained in the pressure-sensitive adhesive layer of the laminated optical laminate).

When the proportion of the low-molecular-weight component contained in the adhesive layer is 1 to 10% by mass, the reduction rate of the iodine concentration in the adhesive layer is 25% or more, and the migration of iodine from the polarizer to the adhesive layer is suppressed. It was found that When the proportion of the low-molecular weight component contained in the adhesive layer is 3 to 8% by mass, the rate of decrease in the iodine concentration in the adhesive layer is 30% or more, and the migration of iodine from the polarizer to the adhesive layer is more likely. had been suppressed.

100,200,300,400 optical laminate 10 polarizing plate 11 polarizer 12,13 protective film 20 optical function layer 21 first retardation layer 22 second retardation layer 23,24 bonding layer , 30 adhesive layer, 40 metal layer.

Claims (8)

An optical laminate comprising a polarizing plate containing a polarizer and an optical functional layer containing at least one adhesive layer,
The polarizer is a polyvinyl alcohol-based resin film in which iodine is adsorbed and oriented,
The optical laminate in which the adhesive layer contains a total of 1% by mass or more and 10% by mass or less of low-molecular-weight components having a molecular weight of 500 or less. The optical function layer includes a first retardation layer and a second retardation layer containing a cured polymerizable liquid crystal compound,
2. The optical laminate according to claim 1, wherein at least one adhesive layer is laminated between the first retardation layer and the second retardation layer. The adhesive layer is a cured layer of an active energy ray-curable adhesive,
3. The optical layered product according to claim 1, wherein the low-molecular-weight component contains an unpolymerized monomer of the active energy ray-curable adhesive. 4. Any one of claims 1 to 3, wherein the low molecular weight component contains at least one selected from the group consisting of a monomer having an epoxy group, a monomer having an oxetane ring, a monomer having an acryloyloxy group, and a monomer having a methacryloyloxy group. 1. The optical layered body according to 1 or 2 above. The optical laminate according to any one of claims 1 to 4, wherein the polarizing plate has a protective film on one side or both sides of the polarizer. The polarizing plate has the protective film on the optical functional layer side of the polarizer,
6. The optical laminate according to claim 5, wherein the protective film has a moisture permeability of 350 g/(m ^<2> .24 hr) or more at a temperature of 40[deg.] C. and a relative humidity of 90% RH. The optical laminate according to any one of claims 1 to 6, wherein the luminosity correction single transmittance Ty of the polarizing plate at a wavelength of 550 nm is 43.5% or more. The optical laminate according to any one of claims 1 to 7, further comprising an adhesive layer laminated on the surface of the optical function layer opposite to the polarizing plate.

Images