KR20240012571A - optical laminate - Google Patents

Abstract

[Problem] In an optical laminate containing a polarizer in which iodine is adsorbed and oriented, an increase in the iodine concentration of the adhesive layer laminated on the optical laminate is suppressed.
[Solution] An optical laminate including a polarizing plate including a polarizer, and an optical function layer including at least one adhesive layer, wherein the polarizer is a polyvinyl alcohol-based resin film in which iodine is adsorbed and oriented, and the adhesive layer An optical laminate containing a total of 1 mass% to 10 mass% of low molecular weight components having a silver molecular weight of 500 or less is provided.

Description

optical laminate

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. In touch panel display devices mainly used in portable information terminals such as smart phones and tablets, a conductive layer for forming a touch sensor is sometimes provided on the image display element. When a polarizer is included in a touch panel display device, a laminate including a polarizer and a laminate having an adhesive layer may be bonded to a conductive layer with the adhesive layer in direct contact (for example, , Patent Document 1).

Japanese Patent Publication No. 2015-052765

In the laminate having an adhesive layer, iodine contained in the polarizer sometimes migrated to the adhesive layer, and the iodine concentration in the adhesive layer increased. Iodine migration is particularly likely to occur in a high temperature and high humidity 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 are likely to occur.

The purpose of the present invention is to suppress an increase in the iodine concentration of the pressure-sensitive adhesive layer laminated on the optical laminate in an optical laminate containing a polarizer in which iodine is adsorbed and oriented.

The present invention provides an optical laminate exemplified below.

[1] An optical laminate including a polarizing plate including a polarizer and an optical functional layer including at least one adhesive layer,

The polarizer is a polyvinyl alcohol-based resin film with iodine adsorbed and oriented,

An optical laminate, wherein the adhesive layer contains a total of 1 mass% or more and 10 mass% or less of low molecular weight components having a molecular weight of 500 or less.

[2] The optical functional layer includes a first retardation layer and a second retardation layer including a cured product of a polymerizable liquid crystal compound,

The optical laminate according to [1], wherein at least one layer of the 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 contains 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, [1 ] The optical laminate according to any one of [3] to [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 function layer side of the polarizer,

The optical laminate according to [5], wherein the protective film has a moisture permeability of 350 g/(m2·24 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 visibility-corrected 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 an adhesive layer laminated on a surface of the optical function layer opposite to the polarizing plate.

According to the present invention, even if it is an optical laminate containing a polarizer in which iodine is adsorbed and oriented, an increase in the iodine concentration of the pressure-sensitive adhesive layer laminated on the optical laminate can be suppressed.

1 is a cross-sectional view schematically showing an example of an optical laminate according to an embodiment of the present invention.
Figure 2 is a cross-sectional view schematically showing another example of an optical laminated body according to an embodiment of the present invention.
3 is a cross-sectional view schematically showing another example of an optical laminate according to an embodiment of the present invention.
4 is a cross-sectional view schematically showing another example of an optical laminate according to an 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 drawings below, the scale of each component is appropriately adjusted to make it easier to understand, 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 laminated body of this embodiment. The optical laminates 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. The polarizing plate 10 includes a polarizer 11. The polarizer 11 is a polyvinyl alcohol-based resin film in which iodine is adsorbed and oriented.

The polarizing plate 10 may be a single-protection type polarizing plate having a protective film 12 on one side of the polarizer 11, as shown in FIGS. 1 to 3 . At this time, the polarizer 11 is directly laminated on the optical function layer 20 through the bonding layer 24. The polarizing plate 10 may be a double-protection type polarizing plate having a protective film 12 and a protective film 13 on both sides of the polarizer 11, as shown in FIG. 4 .

The optical function layer 20 may include two retardation layers, that is, the first retardation layer 21 and the second retardation layer 22, as shown in FIGS. 1 to 4 . The first phase difference layer 21 and the second phase difference layer 22 may be laminated through the bonding layer 23. The polarizing plate 10 and the optical function layer 20 may be bonded together by the bonding layer 24. The optical function layer 20 includes at least one adhesive layer. Among the bonding layers 23 and 24, one may be an adhesive layer, the other may be an adhesive layer, or both may be an adhesive layer. The optical functional layer 20 may also include an adhesive layer in addition to this. In the optical function layer 20, preferably the first phase difference layer 21, the adhesive layer, and the second phase difference layer 22 are in contact with each other in this order.

In the optical laminated body 100 shown in FIG. 1 and the optical laminated body 400 shown in FIG. 4, the first phase difference layer 21 and the second phase difference layer 22 are a bonding layer 23 that is an adhesive layer. The first retardation layer 21 and the polarizing plate 10 are laminated through a bonding layer 24, which is an adhesive layer.

In the optical laminate 200 shown in FIG. 2, the first phase difference layer 21 and the second phase difference layer 22 are laminated through a bonding layer 23, which is an adhesive layer, and the first phase difference layer 21 and the polarizing plate 10 are laminated through a bonding layer 24, which is an adhesive layer.

In the optical laminate 300 shown in FIG. 3, the first phase difference layer 21 and the second phase difference layer 22 are laminated through a bonding layer 23 that is an adhesive layer.

1 to 4, the optical function layer 20 may have an adhesive layer 30. The adhesive layer 30 may be laminated on the surface of the optical function layer 20 on the opposite side to the polarizing plate 10. The adhesive layer 30 may be laminated on the side opposite to the polarizing plate 10 of the second retardation layer 22. The adhesive layer 30 may be provided in direct contact with the second phase difference 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 phase difference layer 21, a second phase difference 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. Includes. The optical laminate 400 includes a protective film 12, a polarizer 11, a protective film 13, a first retardation layer 21, an adhesive layer, a second retardation layer 22, and an adhesive layer 30. Include them in this order:

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

In a conventional optical laminate, when the adhesive layer is a cured layer of a photocurable adhesive, the adhesive is cured by applying sufficient light irradiation. Additionally, the amount of additives added to the adhesive was small. For this reason, the low molecular weight component contained in the adhesive layer after curing was usually less than 1% by mass. However, when the low molecular weight component was less than 1% by mass, migration of iodine from the polarizer containing iodine could not be suppressed, and the iodine concentration in the adhesive layer in contact with the metal layer laminated on the optical laminate was increasing. The present inventors have obtained the knowledge that an increase in the iodine concentration of the adhesive layer can be suppressed by providing a layer containing a low-molecular-weight component capable of capturing iodine between the polarizer containing iodine and the adhesive layer in contact with the metal layer. . This is thought to be because iodine is captured by low-molecular-weight components.

Examples of low-molecular-weight components capable of capturing iodine include molecules having an epoxy group, molecules having an oxetane ring, molecules having an acryloyloxy group, and molecules having a methacryloyloxy group; Molecules having amino group, amide group, acetyl group, carbamine skeleton, isocyanate skeleton, acrylate group, methacryl group, urea group, etc.; Molecules having a urethane skeleton, urethane acrylate skeleton, pyridine skeleton, piperidine skeleton, pyrrolidine skeleton, acridine skeleton, acridone skeleton, etc.; Molecules having cationic substituents; polar molecule; Cyclic molecules such as cyclodextrin and [n]-CPP; metal ions such as silver, copper, and zinc; Porous materials such as activated carbon and zeolite can be mentioned.

In the present invention, attention was paid to the adhesive layer as a layer containing a low-molecular component capable of capturing iodine. The adhesive layer is preferably a cured layer of an active energy ray-curable adhesive. The low molecular weight component contained in the adhesive layer may include unpolymerized monomers of the active energy ray-curable adhesive, a polymerization initiator, a decomposition product of the polymerization initiator, and other additives. These low-molecular-weight components contained in the adhesive layer can capture iodine. From the viewpoint of making it easy to control the compatibility of the adhesive and suppressing bleed-out in a high-humidity heat environment, it is preferable that the low-molecular-weight component capable of capturing iodine is an unpolymerized monomer of the adhesive. The unpolymerized monomer contained in the adhesive preferably includes 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. do. The content of unpolymerized monomer in the adhesive layer can be changed, for example, by adjusting the degree of curing of the adhesive. In the optical laminate, layers other than the adhesive layer, such as a polymerizable liquid crystal retardation layer, may contain a low-molecular-weight component.

The adhesive layer included in the optical function layer contains 1 mass% or more and 10 mass% or less of a low molecular weight component with a molecular weight of 500 or less, and may be 3 mass% or more, and may be 8 mass% or less. The higher the content of low-molecular-weight components, the more effective it is in capturing iodine. On the other hand, if the content of the low-molecular-weight component is too high, there is a risk that the effect of suppressing the migration of iodine may be reduced. Additionally, if the content of the low molecular weight component is too high, there is a risk that the optical function of the polarizing plate may deteriorate. When the optical function layer includes a plurality of adhesive layers, the above range is a ratio of the sum of the masses of the low molecular components contained in the plurality of adhesive layers to the sum of the masses of the plurality of adhesive layers.

The ratio (mass %) of the low-molecular component contained in the adhesive layer is obtained by (mass of the low-molecular component contained in the adhesive layer (W2))/(mass of the adhesive layer (W1)). The mass (W2) of the low molecular component contained in the adhesive layer is calculated as follows. First, the entire plurality of layers joined by the adhesive layer are freeze-pulverized, and the obtained powder is extracted into a solvent. By analyzing this using gas chromatography, the amount of low molecular weight components with a molecular weight of 500 or less can be determined. By using a device that connects a mass spectrometer (MS) to a gas chromatograph, the functional groups of low-molecular-weight components can be specified. By mass spectrometry, the component derived from the adhesive layer among the low molecular components can be identified, and the mass (W2) of the low molecular component contained in the adhesive layer can be calculated. 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 phase contrast layer, an adhesive layer, and a second phase contrast layer, but the adhesive layer for bonding to the metal layer is removed. It is desirable to conduct analysis. The mass (W1) of the adhesive layer can be calculated as (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 the first phase contrast layer and the second phase difference layer are bonded together 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 with 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 the low molecular weight component can be calculated using the following formula.

{Ratio of low molecular weight components contained in the adhesive layer (mass %)} = [Content of low molecular weight components derived from the adhesive layer in the test solution (mg/mL) × Test solution amount (mL)] / [Mass of the laminate (mg) × {Thickness of adhesive layer (㎛)/Thickness of laminate (㎛)}]×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 an image display device. 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 laminated body can be used in display devices such as smart phones and tablets, and can be particularly suitably used in touch panel display devices. 1 to 4, the metal layer 40 may be a metal wiring layer constituting a touch panel sensor.

Hereinafter, each member constituting the optical laminate will be described.

[Polarizer]

The polarizing plate includes a polarizer. The polarizing plate may have a protective film on one side or both sides of the polarizer. The polarizing plate may further include a base film, an alignment film, etc. When having a protective film on one side of a polarizer, the protective film may be laminated on the side opposite to the optical function layer of the polarizer. When the polarizer is directly laminated to the optical function layer through the adhesive layer, iodine is likely to migrate from the polarizer to the optical function layer. Even in an optical laminate having such a structure, migration of iodine can be suppressed when the optical function layer contains an adhesive layer containing many low molecular components.

The visibility corrected 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 polarizer tends to be low. The visibility-corrected total light transmittance (Ty) can be measured with a spectrophotometer (V-7100, manufactured by Nihon Bunko Co., Ltd.).

(polarizer)

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

The polarizer is, for example, a polyvinyl alcohol-based resin film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, and an ethylene-vinyl acetate copolymer-based partially saponified film (hereinafter sometimes referred to as a “PVA-based film”). A fabric film that has been subjected to film production processes such as dyeing with iodine and stretching can be used. If necessary, the PVA-based film in which iodine has been adsorbed and oriented by dyeing treatment may be treated with an aqueous boric acid solution, and then a washing step of washing off the aqueous boric acid solution may be performed. Known methods can be adopted for each process. The film thickness of the polyvinyl alcohol-based resin fabric 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.

Polyvinyl alcohol-based resin (hereinafter sometimes referred to as “PVA-based resin”) is obtained by saponifying polyvinyl acetate-based resin. The polyvinyl acetate-based resin may be a copolymer of vinyl acetate and other monomers copolymerizable with it, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate. Other monomers that can be copolymerized 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, and is preferably 98 mol% or more. PVA-based resin may be modified, and polyvinyl formal, polyvinyl acetal, etc. modified with aldehydes can also be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually 1,000 or more and 10,000 or less, and preferably 1,500 or more and 5,000 or less. The average degree of polymerization of polyvinyl alcohol-based resin can be determined based on JIS K 6726 (1994). If the average degree of polymerization is less than 1000, it is difficult to obtain desirable polarization performance, and if the average degree of polymerization is more than 10000, film processability may be poor.

Another method of manufacturing a polarizer containing a PVA-based film is to first prepare a base film, apply a solution of a resin such as PVA-based resin onto the base film, and dry to remove the solvent, etc. to form a water solution on the base film. It may also include a step of forming a stratum. As the base film, a resin film such as PET or a film using a thermoplastic resin that can be used for a protective film described later can be used. A primer layer can be formed in advance on the surface of the base film where the resin layer is formed. Examples of the material of the primer layer include a resin obtained by crosslinking a hydrophilic resin used in a polarizer.

Subsequently, the amount of solvent such as moisture in the resin layer is adjusted as needed, and then the base film and the resin layer are uniaxially stretched. Subsequently, the resin layer is dyed with iodine to adsorb and orient the iodine to the resin layer. If necessary, the resin layer in which the iodine is adsorbed and oriented is treated with an aqueous boric acid solution, and a washing step is performed to wash away the aqueous boric acid solution. Thereby, a polarizer which is a resin layer in which iodine is adsorbed and oriented is manufactured. Known methods can be adopted for each process.

The amount of boric acid in the boric acid-containing aqueous solution for treating the PVA-based film or PVA-based resin layer with iodine adsorption orientation is usually about 2 parts by mass to 15 parts by mass, and 5 parts by mass to 12 parts by mass per 100 parts by mass of water. 2 or less is preferable. This boric acid-containing aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the aqueous solution containing boric acid is usually in the range of 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.

Uniaxial stretching of the base film and PVA-based resin layer may be performed before dyeing, may be performed during dyeing, may be performed during boric acid treatment after dyeing, or uniaxial stretching may be performed in each of these plural steps. The base film and the PVA-based resin layer may be uniaxially stretched in the MD direction (film transport direction). In this case, they may be uniaxially stretched between rolls with different peripheral speeds, or they may be uniaxially stretched using hot rolls. Additionally, the base film and the PVA-based resin layer may be uniaxially stretched in the TD direction (direction perpendicular to the film transport direction), and in this case, the so-called tenter method can be used. In addition, the stretching of the base film and the PVA-based resin layer may be dry stretching in which stretching is performed in the air, or wet stretching in which stretching is performed in a state in which the PVA-based resin layer is swollen with a solvent. In order to express the performance of the polarizer, the draw ratio is preferably 4 times or more, preferably 5 times or more, and especially 5.5 times or more. There is no particular upper limit to the stretch ratio, but from the viewpoint of suppressing breakage, etc., 8 times or less is preferable.

The polarizer produced by a manufacturing method using a base film may be used as a linear polarizer by peeling the base film or together with the base film. After laminating the protective film on the polarizer, the base film may be peeled. According to this method, thinning of the polarizer becomes possible.

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 and high humidity environment.

(protective film)

As a protective film, it is preferable to use a film formed of a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, and extensibility. Specific examples of thermoplastic resins include cellulose resins such as triacetylcellulose; Polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyethersulfone resin; polysulfone resin; polycarbonate resin; Polyamide resins such as nylon and aromatic polyamide; polyimide resin; Polyolefin resins such as polyethylene, polypropylene, and ethylene/propylene copolymer; Cyclic polyolefin resins having cyclo-based and norbornene structures (also referred to as norbornene-based resins); (meth)acrylic resin; polyarylate resin; polystyrene resin; Polyvinyl alcohol resin, and mixtures thereof can be mentioned. When a polarizer has protective films on both sides, the resin composition of both protective films may be the same or different. In addition, in this specification, “(meth)acrylic” means either acrylic or methacrylic. “(meth)” in (meth)acrylate and the like also has the same meaning.

The protective film may have a phase difference and may have anti-reflection properties and anti-glare 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 with 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 having a protective film on the optical function 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/(m2·24 hr) or more, and 500 g/(m2 ·24 hr) or more, 750 g/(㎡·24 hr) or more, or 1000 g/(㎡·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/(m2·24 hr) or less. When the moisture permeability of the protective film is high, it becomes easy for iodine to migrate from the polarizing plate to the optical function layer side. However, when the optical function layer contains an adhesive layer containing many low molecular components, migration of iodine can be suppressed.

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

One side of the polarizing plate may further be provided with a surface functional layer such as an anti-reflection layer, an anti-glare layer, or a hard coat layer. It is preferable that the surface functional layer is provided so as to directly contact the protective film. The surface functional layer is preferably provided on the side opposite to the polarizer side of the protective film.

[Optical functional 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, etc. The optical functional layer includes, for example, one or two or more layers of retardation layers. The optical functional layer includes, for example, a two-layer retardation layer, a first retardation layer, and a second retardation layer, and the first retardation layer and the second retardation layer may be laminated through a bonding layer. The first retardation layer and the polarizing plate may be laminated through a bonding layer. The bonding layer may each independently be an adhesive layer or an adhesive layer.

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

The optical function layer may further include an adhesive layer laminated on the surface opposite to the polarizing plate. This 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. As an adhesive composition for forming an adhesive layer, adhesives other than pressure-sensitive adhesives (adhesives) include, for example, water-based adhesives and active energy ray-curable adhesives.

Examples of water-based adhesives include adhesives in which polyvinyl alcohol-based resin is dissolved or dispersed in water. There is no particular limitation on the drying method when using a water-based adhesive, but for example, a drying method using a hot air dryer or an infrared dryer can be adopted.

Examples of the active energy ray-curable adhesive include a non-solvent type active energy ray-curable adhesive containing a curable compound that hardens by irradiation of active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. By using a solvent-free active energy ray-curable adhesive, the adhesion between layers can be improved.

The active energy ray-curable adhesive preferably contains 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 may further include a cationic polymerization initiator such as a photocationic polymerization initiator or a radical polymerization initiator for initiating the curing reaction of the curable compound.

Cationic polymerizable curable compounds include, for example, alicyclic epoxy compounds having an epoxy group bonded to an alicyclic ring, polyfunctional aliphatic epoxy compounds having two or more epoxy groups and no aromatic ring, and monofunctional epoxy groups having one epoxy group (however, alicyclic (excluding those included in the formula epoxy compounds), epoxy-based compounds such as polyfunctional aromatic epoxy compounds having two or more epoxy groups and having an aromatic ring; Oxetane compounds having one or two or more oxetane rings in the molecule; A combination of these can be mentioned.

Examples of radically polymerizable curable compounds include (meth)acrylic compounds (compounds having one or two or more (meth)acryloyloxy groups in the molecule), other vinyl compounds having a radically polymerizable double bond, or these. A combination of .

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

The active energy ray-curable adhesive may, if necessary, contain additives such as ion trapping agents, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, antifoaming agents, antistatic agents, leveling agents, and solvents. You can.

When an active energy ray-curable adhesive is used, the adhesive layer can be formed by curing the applied layer of the adhesive by irradiating active energy rays such as ultraviolet rays, visible light, electron beams, or X-rays. As an 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.

The thickness of the adhesive layer is preferably 0.01 μm or more, more preferably 0.05 μm or more, and 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 increasing flexibility.

(Adhesive layer)

The adhesive layer is formed using an adhesive composition. The adhesive composition exhibits adhesiveness by adhering itself to an adherend, and is called a so-called pressure-sensitive adhesive. As the adhesive composition, conventionally known adhesives with excellent optical transparency can be used without particular restrictions. The adhesive layer can be formed from an adhesive composition containing (meth)acrylic resin, rubber-based resin, urethane-based resin, ester-based resin, silicone-based resin, and polyvinyl ether-based resin as the base polymer. Among them, an adhesive composition containing a (meth)acrylic resin excellent in transparency, weather resistance, heat resistance, etc. as a base polymer is suitable. The adhesive composition may be of an active energy ray curing type or a thermosetting type. The adhesive layer is preferably comprised of a reaction product of an adhesive composition containing a (meth)acrylic resin, a crosslinking agent, and a silane compound, and may contain other components.

The (meth)acrylic resin used in the adhesive composition is one of (meth)acrylic acid esters such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Polymers or copolymers containing two or more types of monomers are suitably used. It is preferable to copolymerize a polar monomer with the base polymer. As polar monomers, (meth)acrylic acid compounds, (meth)acrylic acid 2-hydroxypropyl compounds, (meth)acrylic acid hydroxyethyl compounds, (meth)acrylamide compounds, and N,N-dimethylaminoethyl (meth)acrylate compounds. , monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc., such as a glycidyl (meth)acrylate compound.

The pressure-sensitive adhesive composition may contain only the base polymer, but usually further contains a crosslinking agent. The crosslinking agent is a divalent or higher metal ion, such as a metal ion that forms a carboxylic acid metal salt between carboxyl groups, a polyamine compound that forms an amide bond between carboxyl groups, and a polyepoxy that forms an ester bond between carboxyl groups. Examples include polyisocyanate compounds that form amide bonds between compounds, polyols, and carboxyl groups. The crosslinking agent is preferably a polyisocyanate compound.

The active energy ray-curable adhesive composition has the property of curing upon exposure to active energy rays such as ultraviolet rays or electron beams, has adhesiveness even before irradiation of active energy rays, and can be adhered to an adherend such as a film, and can be irradiated with active energy rays. It has the property of being able to adjust the adhesion by hardening. The active energy ray-curable adhesive composition is preferably of an ultraviolet ray-curable type. The adhesive composition may further contain an active energy ray polymerizable compound in addition to the base polymer and crosslinking 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; (meth)acrylic compounds, such as (meth)acryloyloxy group-containing compounds, such as (meth)acrylate oligomers, which are obtained by reacting two or more types of functional group-containing compounds and have at least two (meth)acryloyloxy groups in the molecule. can be mentioned. The adhesive composition may contain an active energy ray polymerizable compound in an amount of 0.1 parts by mass or more, 10 parts by mass or less, 5 parts by mass or less, or 2 parts by mass or less, based on 100 parts by mass of the solid content of the adhesive composition.

Examples of photopolymerization initiators include benzophenone, benzyldimethylketal, and 1-hydroxycyclohexylphenylketone. The photopolymerization initiator may contain one type or two or more types. When the adhesive composition contains a photopolymerization initiator, the total content may be, for example, 0.01 part by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of solid content of the adhesive composition.

The adhesive composition includes fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, tackifiers, fillers (metal powders and other inorganic powders, etc.), antioxidants, and ultraviolet rays. It may contain additives such as absorbents, dyes, pigments, colorants, defoaming agents, corrosion inhibitors, and photopolymerization initiators.

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

The thickness of the adhesive layer is not particularly limited, but for example, 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.

(Phase difference layer)

The retardation layer contains a cured product of a polymerizable liquid crystal compound. The retardation layer may include an alignment layer having an orientation regulating force that orients the polymerizable liquid crystal compound in a desired direction. The retardation layer may include an overcoat layer that protects the surface, a base material layer that supports the retardation layer, etc.

Examples of the polymerizable liquid crystal compound include a rod-shaped polymerizable liquid crystal compound and a disc-shaped polymerizable liquid crystal compound. Either one of these may be used, or a mixture containing both of these may be used. When the rod-shaped polymerizable liquid crystal compound is horizontally or vertically aligned with respect to the base layer, the optical axis of the polymerizable liquid crystal compound coincides with the long axis direction of the polymerizable liquid crystal compound. When the disk-shaped polymerizable liquid crystal compound is oriented, the optical axis of the polymerizable liquid crystal compound exists in a direction perpendicular to the disk surface of the polymerizable liquid crystal compound. As a rod-shaped polymerizable liquid crystal compound, for example, those described in Japanese Patent Publication No. Hei 11-513019 (Claim 1, etc.) can be suitably used. Disk-shaped polymerizable liquid crystal compounds are described in Japanese Patent Application Laid-Open No. 2007-108732 (paragraphs [0020] to [0067], etc.) and Japanese Patent Application Laid-Open No. 2010-244038 (paragraphs [0013] to [0108], etc.). Those described can be suitably used.

In order for the cured material layer formed by polymerizing the polymerizable liquid crystal compound to exhibit an in-plane retardation, the polymerizable liquid crystal compound may be oriented in an appropriate direction. When the polymerizable liquid crystal compound is rod-shaped, an in-plane retardation occurs by aligning the optical axis of the polymerizable liquid crystal compound horizontally with respect to the plane of the base layer, and in this case, the optical axis direction and the slow axis direction coincide. When the polymerizable liquid crystal compound is disk-shaped, an in-plane retardation occurs by aligning the optical axis of the polymerizable liquid crystal compound horizontally with respect to the plane of the base layer, and in this case, the optical axis and the slow axis are orthogonal. 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 that has at least one polymerizable group and has liquid crystallinity. When using two or more types of polymerizable liquid crystal compounds together, it is preferable that at least one type has two or more polymerizable groups in the molecule. A polymerizable group means a group involved in a polymerization reaction, and it is preferable that it is a photopolymerizable group. Here, the photopolymerizable group refers to a group that can participate in the polymerization reaction by active radicals or acids generated from a photopolymerization initiator described later. As polymerizable groups, 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. etc. can be mentioned. Among them, acryloyloxy group, methacryloyloxy group, vinyloxy group, oxiranyl group and oxetanyl group are preferable, and acryloyloxy group is more preferable. The liquid crystallinity of the polymerizable liquid crystal compound may be either thermotropic liquid crystal or lyotropic liquid crystal. If thermotropic liquid crystals are classified by degree of order, they may be nematic liquid crystal or smectic liquid crystal.

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, and preferably 10 μm or less, 8 μm or less, or 5 μm or less. .

The cured layer of the polymerizable liquid crystal compound can be formed by applying a composition for forming a liquid crystal layer containing the polymerizable liquid crystal compound on a base layer, drying the composition, and polymerizing the polymerizable liquid crystal compound. The composition for forming a liquid crystal layer may be applied on the alignment layer formed on the base 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 may be 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 the molecules of the polymerizable liquid crystal compound may be horizontally aligned with respect to the base layer. It may be an inclined orientation layer whose axis is obliquely oriented with respect to the base layer.

The alignment layer preferably has solvent resistance that does not dissolve by coating of a composition for forming a liquid crystal layer containing a polymerizable liquid crystal compound, and has heat resistance to heat treatment for removing the solvent or aligning the polymerizable liquid crystal compound. . Examples of the orientation layer include an orientation polymer layer formed of an orientation polymer, a photo-orientation polymer layer formed of a photo-orientation polymer, and a groove orientation layer having a concavo-convex pattern or a plurality of grooves (grooves) on the layer surface.

As the base layer, a film formed of a resin material can be used, for example, a film using the resin material described as the thermoplastic resin used to form the above-described protective film. The thickness of the base material layer is not particularly limited, but generally, 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 more desirable. The base material layer may be included in the optical laminate together with the cured product layer of the polymerizable liquid crystal compound, and the base layer may be peeled off to provide only the cured product layer of the polymerizable liquid crystal compound, or the cured product layer and the alignment layer may be separated into the optical laminate. It may be included in the laminate. When the base layer is included in the optical laminate together with the cured product layer of the polymerizable liquid crystal compound, the thickness of the base layer may be less than 30 μm, for example, 25 μm or less.

[Metal layer]

The metal layer can be used as a conductive layer for constructing a touch sensor of a touch panel. A metal layer is a layer formed of one or more types of metal. 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 multi-layer structure. In addition, 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 two or more of these metals. alloys containing Among these, the metal layer preferably has aluminum or copper as its main component, and may contain titanium as an additive. Here, the main component refers to a metal that accounts for 50 mass% or more of the metals constituting the metal layer.

The metal layer can be formed, for example, on a translucent substrate. It may be a continuous film formed over the entire surface of the translucent substrate, or may be a metal wiring layer formed on the surface of the translucent substrate. The metal wiring layer may be a metal mesh. The light-transmitting substrate may be any material that has light-transmitting properties, and examples include films, glass films, and glass substrates using the resin materials described as thermoplastic resins above.

The method of forming the metal layer is not particularly limited, and may be formed on the surface of the light-transmitting substrate by, for example, the chemical vapor growth method, physical vapor growth method, inkjet printing method, gravure printing method, electrolytic plating, electroless plating, etc. described above.

The thickness of the metal layer is usually 0.01 μm or more, and may be 0.05 μm or more, and from the viewpoint of thinning, it is preferably 3 μm or less, more preferably 1 μm or less, and even 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 form of the method for manufacturing an optical laminate includes a step of bonding the layers using an active energy ray-curable adhesive, for example, curing the first retardation layer including a cured layer of the polymerizable liquid crystal compound and the polymerizable liquid crystal compound. A process of bonding a second retardation layer including a layer with an active energy ray-curable adhesive, or a step of bonding a first retardation layer including a cured layer of a polymerizable liquid crystal compound and a polarizing plate with an active energy ray-curable adhesive. Includes. In this step, the degree of curing of the adhesive is adjusted so that the active energy ray-curable adhesive does not completely cure and unpolymerized monomers remain in the adhesive layer. The degree of curing of the adhesive can be adjusted by controlling the irradiation amount of active energy rays, the amount of penetration of active energy rays, etc.

For example, the amount of active energy ray irradiation for curing the adhesive can be reduced to a level where the adhesive does not completely cure. The irradiation amount of active energy rays (UVB) may be 90% or less or 80% or less of the irradiation amount when the adhesive is completely cured. The active energy ray irradiation amount may be, for example, 550 mJ/cm2 or less, 450 mJ/cm2 or less, 400 mJ/cm2 or less, 350 mJ/cm2 or less, or 300 mJ/cm2 or less. The irradiation amount of active energy rays is usually 200 mJ/cm2 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 base material layer or the adhesive layer. There is no particular limitation on the ultraviolet absorber, but for example, organic UV absorbers such as oxybenzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, salicylic acid ester ultraviolet absorbers, benzophenone ultraviolet absorbers, cyanoacrylate ultraviolet absorbers, and triazine ultraviolet absorbers. absorbent; Inorganic ultraviolet rays such as titanium oxide, zinc oxide, indium oxide, tin oxide, talc, kaolin, calcium carbonate, titanium oxide-based complex oxide, zinc oxide-based complex oxide, ITO (tin-doped indium oxide), and ATO (antimony-doped tin oxide). An absorbent may be mentioned.

Example

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[Calculation of the ratio of low molecular weight components]

Using a laminate having the structure of first base material layer/first retardation layer/adhesive layer (ultraviolet curable adhesive layer)/second retardation layer/second base material layer, the ratio of low molecular weight components contained in the adhesive layer was calculated. . First, the first base material layer and the second base material layer were peeled and removed from this laminate. The laminate of the first phase contrast layer/adhesive layer/second phase contrast layer was freeze-pulverized, dissolved in a solvent (acetonitrile), and then filtered to obtain a test solution.

The obtained test solution was subjected to gas chromatography, and low-molecular-weight components were quantified from the peak area of components with a molecular weight of 500 or less. According to mass spectrometry, about 40% of the components with a molecular weight of 500 or less were unpolymerized monomers (monomers having an epoxy group) of the ultraviolet curable adhesive. The measurement conditions were as follows.

Equipment: Agilent 6850 GC (Agilent Technology Co., Ltd.)

Carrier gas: helium

Flow rate: 1.0 mL/min. (constant flow)

Column: DB-5 0.25 ㎜Φ×30 m, 0.25 ㎛ (Agilent Technology Co., Ltd.)

Oven: 50℃(5 min. Hold)-10℃/min.-320℃(8 min. Hold)

Injection volume: 1.0 μL

Inlet temperature: 250℃

Injection Mode: Splitless (Split Vent Purge Flow: 50 mL/min., 1 min. Gas Saver: 15 mL/min., 2 min.)

Detection: FID (250℃, H2: 40 mL/min., Air: 400 mL/min. make-up: He, 45 mL/min.)

According to the formula below, the ratio of low molecular weight components was calculated.

{Content of low-molecular components in the adhesive (%)}={Content of low-molecular components derived from the adhesive layer in the test solution (mg/mL)}÷{Amount of powder when preparing the test solution (mg)}×{When preparing the test solution Amount of solvent used (mL)}÷{Film thickness of adhesive layer (㎛)}

[Measurement of the amount of iodine contained in the adhesive layer]

The optical laminate was cut into a size of 25 mm x 50 mm, the protective film was peeled off, and the polarizing plate side was bonded to alkali-free 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 second retardation layer side was peeled off, and the adhesive of 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>

Device: AQF-2100H manufactured by Mitsubishi Kagaku Analytech Co., Ltd.

Combustion conditions: The combustion temperature was 1100°C, and the gas flow rate was 200 mL/min for argon, 400 mL/min for oxygen, and 100 mL/min for humidified air.

<Ion Chromatograph>

Device: 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 adhesive layer was stacked to a thickness of 150 μm and bonded to a glass plate. For this sample for storage elastic modulus measurement, the storage elastic modulus was measured using a rheometer (“MCR-301” manufactured by Anton MPr) under the conditions of a temperature of 25°C, relative humidity of 50%, stress of 1%, and frequency of 1 Hz. was carried out.

[Measurement of thickness]

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, polarizer layer, and alignment film were measured using a laser microscope (“OLS3000” manufactured by Olympus Corporation).

[Measurement of visibility-corrected total light transmittance (Ty) and visibility-corrected polarization (Py)]

The total light transmittance (Ty) and polarization (Py) from wavelength 380 nm to wavelength 780 nm were measured using a spectrophotometer with an integrating sphere [“V7100” manufactured by Nippon Bunko Co., Ltd., 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 measurement conditions of a temperature of 40°C, a relative humidity of 90% RH, and a measurement time of 24 hours. The measured water vapor transmission rate was taken as the water vapor transmission rate at a temperature of 40°C and a relative humidity of 90% RH.

[Production of polarizer]

A 30 ㎛ thick polyvinyl alcohol-based resin film (average degree of polymerization of approximately 2400, degree of saponification of 99.9 mol% or more) was vertically uniaxially stretched approximately 5 times by dry stretching and placed in pure water at a temperature of 60°C for 1 minute while maintaining tension. After immersion, it was immersed in an aqueous solution at a temperature of 28°C with a mass ratio of iodine/potassium iodide/water of 0.05/5/100 for 60 seconds. After that, it was immersed in an aqueous solution at a temperature of 72°C with a mass ratio of potassium iodide/boric acid/water of 8.5/8.5/100. Subsequently, it was washed with pure water at a temperature of 26°C for 20 seconds, and then dried at a temperature of 65°C. A polarizer with a thickness of 12 μm in which iodine was oriented by adsorption on a polyvinyl alcohol-based resin film was obtained.

With respect to 100 parts by mass of water, 3 parts by mass of carboxyl group-modified polyvinyl alcohol (“KL-318” manufactured by Kuraray Corporation) was dissolved to prepare an aqueous polyvinyl alcohol solution. A water-soluble polyamide epoxy resin [“Sumirez Resin 650 (30)” manufactured by Taoka Chemical Industries, Ltd., solid content concentration 30% by mass] was mixed with the obtained aqueous solution at a ratio of 1.5 parts by mass based on 100 parts by mass of water. Thus, a water-based adhesive was obtained.

A water-based adhesive is applied to one side of the polarizer, and a triacetylcellulose film (hereinafter sometimes referred to as “TAC film”) has a hard coat layer (hereinafter sometimes referred to as “HC layer”). was laminated. The water-based adhesive was applied to the other side and a TAC film was laminated. By drying at a temperature of 80°C for 5 minutes, polarizing plate 1 having a protective film on both surfaces of the polarizer was obtained. The moisture permeability of the TAC film with the HC layer was 450 g/(m2·24 hr), and the moisture permeability of the TAC film was 1200 g/(m2·24 hr). On the HC layer of the polarizing plate, a protection film having an adhesive layer on a base film was laminated to obtain a polarizing plate having a protection film (hereinafter sometimes referred to as “polarizing plate having 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 with different optical properties. Polarizing plates 3 and 4 used TAC films on both sides as protective films. The total light transmittance (Ty) and polarization degree (Py) measured using a polarizing plate having a protective film on both sides of the polarizer are shown in Table 1.

A 5 μm thick acrylic adhesive layer (storage modulus: 125000 Pa) was prepared, with both sides bonded to a release film. The side from which one release film of the adhesive layer with the release film was peeled was bonded to the side opposite to PF (TAC film side) of the polarizing plate with PF. Subsequently, the release film on the other side of the adhesive layer was peeled, and a polarizing plate with an adhesive layer was obtained. The polarizing plate with an adhesive layer had protection film/polarizing plate (protective film/polarizer/protective film)/adhesive layer in this order.

[Production of phase difference layer]

(First phase difference layer)

A composition for forming a liquid crystal layer containing a rod-shaped nematic polymerizable liquid crystal compound was applied onto a base layer formed of a transparent resin, and a first retardation layer having a first base layer was produced. The first phase difference layer had 1/4 wavelength phase difference characteristics (a phase difference value of 142 nm at a wavelength of 550 nm). The thickness of the first phase contrast layer was 1 μm.

(second phase difference layer)

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

Corona treatment was performed on one side of the base material layer, and the composition for forming an orientation layer prepared above was applied to the corona-treated side using a bar coater. After heat treatment was performed on the application layer at a temperature of 80°C for 60 seconds, ultraviolet rays were irradiated to polymerize and cure the composition for forming an orientation layer, thereby forming an orientation layer with a thickness of 1.8 μm on the base layer. On the alignment layer, the composition for forming a liquid crystal layer prepared above was applied. After heat treatment was performed on the applied layer at a temperature of 80°C for 60 seconds, ultraviolet rays were irradiated to polymerize and cure the composition for forming a liquid crystal layer, thereby forming a liquid crystal cured layer with a thickness of 0.7 μm on the alignment layer. As a result of the above, the second phase difference layer having the second base material layer was obtained. The phase difference value of the second phase difference layer was Rth=-75 nm.

(UV curable adhesive)

The cationic curing components shown below were mixed to prepare an ultraviolet curing adhesive.

3',4'-Epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (Product name: CEL2021P, manufactured by Daicel Corporation): 70 parts by mass

Neopentyl glycol diglycidyl ether (Product name: EX-211, manufactured by Nagase Chemtex Co., Ltd.): 20 parts by mass

2-Ethylhexylglycidyl ether (Product name: EX-121, manufactured by Nagase Chemtex Co., Ltd.): 10 parts by mass

Cationic polymerization initiator (Product name: CPI-100_50% solution, manufactured by San-Apro Co., Ltd.): 4.5 parts by mass (actual solid content 2.25 parts by mass)

1,4-diethoxynaphthalene: 2.0 parts by mass

(Stacking of phase contrast layers)

Corona treatment was performed on the retardation layer side of the first retardation layer having the first base material layer and the retardation layer side of the second retardation layer having the second base material layer, respectively. The prepared ultraviolet curable adhesive was applied to one corona-treated surface, and the first retardation layer having the first base material layer and the second retardation layer having the second base material layer were bonded together. The ultraviolet curable adhesive was cured by irradiating ultraviolet rays from the second base layer side to form an adhesive layer. UVB with a wavelength of 315 nm to 280 nm was irradiated at 420 mJ/cm2. The maximum transmittance in the UVB region of the second base layer was 36%. Laminate 1 was obtained in which the first base material layer/first phase difference layer (liquid crystal cured layer)/adhesive layer/second phase difference layer (liquid crystal hardened layer/orientation layer)/second base material layer were laminated in this order. The thickness of the ultraviolet curing adhesive layer after curing was 1.5 μm.

Laminated in the same manner as laminate 1, except that an ultraviolet absorber was added to the second base layer to reduce the UVB transmittance to 12%, and the UVB irradiation amount was changed between 510 mJ/cm2 and 210 mJ/cm2. Sieves 2 to 6 were produced. For laminates 1 to 6, the results of calculating the ratio of low-molecular-weight components contained in the adhesive layer are shown in Table 2. As the UVB transmittance became smaller and the UVB irradiation amount decreased, the proportion of low-molecular-weight components increased.

As shown in Tables 3 to 6, the laminates 1 to 6 and the polarizing plates 1 to 4 with an adhesive layer were combined and laminated to produce an optical laminate. At this time, the first base material layer was peeled from the laminate, and the first retardation layer and the adhesive layer of the polarizing plate having the adhesive layer were laminated. Additionally, the release film on one side of the 15 μm thick adhesive layer (storage modulus: 25,500 Pa) adhered to the release film on both sides was peeled, and the second base material layer was laminated on the peeled second retardation layer. In this way, an optical laminate was obtained in which the protection film/polarizing plate/adhesive layer/first retardation layer/adhesive layer/second retardation layer/adhesive layer/release film were laminated.

From the optical laminate, the protection film and the release film on the second phase difference layer side were peeled. The optical laminated body was bonded to alkali-free glass through the adhesive layer on the second retardation layer side. A high-humidity heat test was performed in which this laminate was stored for 250 hours at a temperature of 60°C and a relative humidity of 95% RH. The total light transmittance (Ty) and polarization degree (Py) before and after the high-humidity heat test were measured, and the rate of change in polarization degree (ΔPy) = {(Py after test) - (Py before test)} was calculated.

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

It was found that when the ratio of the low molecular weight component contained in the adhesive layer was 1 to 10% by mass, the rate of decrease in the iodine concentration of the adhesive layer was 25% or more, and the migration of iodine from the polarizer to the adhesive layer was suppressed. When the ratio of the low molecular weight component contained in the adhesive layer was 3 to 8% by mass, the rate of decrease in the iodine concentration of the adhesive layer was 30% or more, and the migration of iodine from the polarizer to the adhesive layer was further suppressed.

100, 200, 300, 400 optical laminate, 10 polarizer, 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 including a polarizing plate including a polarizer, and an optical function layer including at least one adhesive layer,
The polarizer is a polyvinyl alcohol-based resin film with iodine adsorbed and oriented,
An optical laminate, wherein the adhesive layer contains a total of 1% by mass to 10% by mass of low molecular weight components with a molecular weight of 500 or less. The method of claim 1, wherein the optical function layer includes a first retardation layer and a second retardation layer including a cured product of a polymerizable liquid crystal compound,
An optical laminate wherein at least one layer of the adhesive layer is laminated between the first retardation layer and the second retardation layer. The method of claim 1 or 2, wherein the adhesive layer is a cured layer of an active energy ray-curable adhesive,
An optical laminate wherein the low-molecular-weight component includes an unpolymerized monomer of the active energy ray-curable adhesive. The group according to any one of claims 1 to 3, wherein the low molecular weight component is 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. An optical laminate comprising at least one selected from. 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 method of claim 5, wherein the polarizing plate has the protective film on the optical function layer side of the polarizer,
An optical laminate in which the protective film has a moisture permeability of 350 g/(m2·24 hr) or more at a temperature of 40°C and a relative humidity of 90% RH. The optical laminate according to any one of claims 1 to 6, wherein the visibility corrected 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 a surface of the optical function layer opposite to the polarizing plate.