JP7680258B2 - optical laminate - Google Patents

Description

The present invention relates to an optical laminate.

Polarizers are one of the optical components that make up display devices such as liquid crystal display devices and organic EL display devices, and are known to use polyvinyl alcohol-based resin films in which iodine is adsorbed and oriented (e.g., Patent Documents 1 to 3, etc.). In touch panel type display devices that are mainly used in portable information terminals such as smartphones and tablets, a conductive layer for forming a touch sensor may be provided on the image display element. When incorporating a polarizer into a touch panel type display device, a laminate with an adhesive layer, in which an adhesive layer is provided on a laminate including a polarizer, may be attached onto the conductive layer (e.g., Patent Document 2).

JP 2019-139007 A JP 2020-177570 A JP 2020-160138 A

In laminates with an adhesive layer, the iodine concentration in the adhesive layer can increase when placed in a high-temperature, high-humidity environment. When the conductive layer of a touch panel type display device is a metal layer, if the iodine concentration in the adhesive layer increases, problems such as corrosion of the metal layer are more likely to occur.

The present invention aims to suppress an increase in iodine concentration in the second adhesive layer under a high-temperature and high-humidity environment in an optical laminate including, in this order, a first adhesive layer, a first protective film, a polarizer, a first retardation layer, and a second adhesive layer.

The present invention provides the following optical laminate.
[1] An optical laminate including, in this order, a first pressure-sensitive adhesive layer, a first protective film, a polarizer, a first retardation layer, and a second pressure-sensitive adhesive layer,
the polarizer is a polyvinyl alcohol-based resin film in which iodine is adsorbed and oriented,
The first retardation layer includes a cured layer of a polymerizable liquid crystal compound,
The moisture permeability of the entire layer disposed between the polarizer and the first pressure-sensitive adhesive layer at a temperature of 40° C. and a relative humidity of 90% RH is defined as A1,
When the moisture permeability of the entire layer disposed between the polarizer and the second pressure-sensitive adhesive layer at a temperature of 40° C. and a relative humidity of 90% RH is A2, the relationship of the following formula (I) is satisfied:
A1>A2 (I)
and
The first pressure-sensitive adhesive layer comprises the following [a] and [b]:
[a] the first pressure-sensitive adhesive layer has a saturated moisture content of 0.5% or more at a temperature of 25° C. and a relative humidity of 80% RH;
[b] the first pressure-sensitive adhesive layer contains an ionic compound;
An optical laminate satisfying at least one of the above.
[2] The optical laminate according to [1], wherein the ratio (A1/A2) of the moisture permeability A1 to the moisture permeability A2 is 1.1 or more.
[3] The optical laminate according to [1] or [2], in which the first pressure-sensitive adhesive layer satisfies the condition [a].
[4] The optical laminate according to any one of [1] to [3], further comprising a surface functional layer between the first pressure-sensitive adhesive layer and the first protective film.
[5] The optical laminate according to any one of [1] to [4], further comprising a second protective film between the polarizer and the first retardation layer.
[6] The optical laminate according to [5], wherein the second protective film and the first retardation layer are laminated via a first bonding layer.
[7] Further, a second retardation layer is provided between the first retardation layer and the second pressure-sensitive adhesive layer,
The second retardation layer includes a cured layer of a polymerizable liquid crystal compound,
The optical laminate according to any one of [1] to [6], wherein the first retardation layer and the second retardation layer are laminated via a second bonding layer.
[8] The optical laminate according to any one of [1] to [7], further comprising a metal layer on the opposite side of the second pressure-sensitive adhesive layer to the first retardation layer.
[9] The optical laminate according to any one of [1] to [8], further comprising a front plate on the side of the first pressure-sensitive adhesive layer opposite to the polarizer side.

The optical laminate of the present invention includes a first pressure-sensitive adhesive layer, a first protective film, a polarizer, a first retardation layer, and a second pressure-sensitive adhesive layer in this order, and can suppress an increase in the iodine concentration in the second pressure-sensitive adhesive layer in a high-temperature, high-humidity environment.

FIG. 1 is a cross-sectional view illustrating an example of an optical laminate according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a schematic diagram of another example of an optical laminate according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a schematic diagram of yet another example of an optical laminate according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a schematic diagram of yet another example of an optical laminate according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the optical laminate will be described with reference to the drawings.
(optical laminate)
1 to 4 are schematic cross-sectional views showing an example of an optical laminate of the present embodiment. The optical laminates 1 to 4 of the present embodiment have a first pressure-sensitive adhesive layer 21, a first protective film 32, a polarizer 31, a first retardation layer 11, and a second pressure-sensitive adhesive layer 22 in this order. The polarizer 31 is a polyvinyl alcohol-based resin film in which iodine is adsorbed and aligned. The first retardation layer 11 includes a cured layer of a polymerizable liquid crystal compound.

The first pressure-sensitive adhesive layer 21 and the first protective film 32 are preferably in direct contact with each other. The optical laminates 1 to 4 may have a surface functional layer between the first pressure-sensitive adhesive layer 21 and the first protective film 32. The surface functional layer is preferably provided so as to be in direct contact with the first protective film 32. When the optical laminates 1 to 4 include a surface functional layer, the surface functional layer and the first pressure-sensitive adhesive layer 21 may be in direct contact with each other.

The first protective film 32 and the polarizer 31 may be laminated via the third bonding layer 25. When the optical laminates 1 to 4 include the third bonding layer 25, it is preferable that the first protective film 32 and the polarizer 31 are provided so as to be in direct contact with the third bonding layer 25. Alternatively, the first protective film 32 may be provided so as to be in direct contact with the polarizer 31.

As shown in Figs. 1 to 4, the optical laminates 1 to 4 may have a second protective film 33 between the polarizer 31 and the first retardation layer 11. The polarizer 31 and the second protective film 33 may be laminated via a fourth bonding layer 26. When the optical laminates 1 to 4 include the fourth bonding layer 26, it is preferable that the polarizer 31 and the second protective film 33 are provided so as to be in direct contact with the fourth bonding layer 26. Alternatively, the first protective film 32 may be provided so as to be in direct contact with the polarizer 31.

The second protective film 33 and the first retardation layer 11 may be laminated via the first bonding layer 23. When the optical laminates 1 to 4 include the first bonding layer 23, it is preferable that the second protective film 33 and the first retardation layer 11 are provided so as to be in direct contact with the first bonding layer 23. Alternatively, the first retardation layer 11 may be provided so as to be in direct contact with the second protective film 33.

Although the optical laminates 1 to 4 shown in Figures 1 to 4 have the fourth bonding layer 26 and the second protective film 33, the optical laminate may not have these. An optical laminate that does not have the fourth bonding layer 26 and the second protective film 33 may have the polarizer 31, the first bonding layer 23, the first retardation layer 11, and the second adhesive layer 22 laminated in this order on the second adhesive layer 22 side of the polarizer 31.

The first retardation layer 11 and the second adhesive layer 22 may be in direct contact as shown in FIG. 1 and FIG. 3. Alternatively, the optical laminate may have a second retardation layer 12 between the first retardation layer 11 and the second adhesive layer 22 as shown in FIG. 2 and FIG. 4. The second retardation layer 12 includes a cured layer of a polymerizable liquid crystal compound. When the optical laminate includes the second retardation layer 12, the first retardation layer 11 and the second retardation layer 12 may be laminated via the second bonding layer 24. When the optical laminates 2 and 4 include the second bonding layer 24, it is preferable that the first retardation layer 11 and the second retardation layer 12 are provided so as to be in direct contact with the second bonding layer 24.

As shown in Figures 3 and 4, the optical laminate may have a metal layer 15 on the side of the second adhesive layer 22 opposite the first retardation layer 11. It is preferable that the metal layer 15 is provided so as to be in direct contact with the second adhesive layer 22.

As shown in Figures 3 and 4, the optical laminate may have a front plate 16 on the side of the first adhesive layer 21 opposite the first retardation layer 11. It is preferable that the front plate 16 is provided so as to be in direct contact with the first adhesive layer 21.

The optical laminates 1 to 4 satisfy the relationship of the following formula (I) and at least one of the following [a] and [b].
A1>A2 (I)
[In the formula (I),
A1 is the moisture permeability of the entire layer disposed between the polarizer 31 and the first pressure-sensitive adhesive layer 21 at a temperature of 40° C. and a relative humidity of 90% RH.
A2 is the moisture permeability of the entire layer disposed between the polarizer 31 and the second pressure-sensitive adhesive layer 22 at a temperature of 40° C. and a relative humidity of 90% RH.

[a] The first pressure-sensitive adhesive layer 21 has a saturated moisture content of 0.5% or more at a temperature of 25° C. and a relative humidity of 80% RH;
[b] The first pressure-sensitive adhesive layer 21 contains an ionic compound.

In this specification, the entire layer disposed between the polarizer 31 and the first adhesive layer 21 refers to all layers disposed between the polarizer 31 and the first adhesive layer 21, excluding the polarizer 31 and the first adhesive layer 21. In the optical laminates 1 to 4 shown in Figures 1 to 4, the entire layer disposed between the polarizer 31 and the first adhesive layer 21 is the laminated structure portion S1 of the first protective film 32 and the third bonding layer 25. When the optical laminate has the above-mentioned surface functional layer, the laminated structure portion S1 includes the surface functional layer, the first protective film 32, and the third bonding layer 25.

In this specification, the entire layer disposed between the polarizer 31 and the second adhesive layer 22 refers to all layers disposed between the polarizer 31 and the second adhesive layer 22, excluding the polarizer 31 and the second adhesive layer 22. In the optical laminates 1 and 3 shown in FIG. 1 and FIG. 3, the entire layer disposed between the polarizer 31 and the second adhesive layer 22 is the laminated structure portion S2 of the fourth adhesive layer 26, the second protective film 33, the first adhesive layer 23, and the first retardation layer 11. In the optical laminates 2 and 4 shown in FIG. 2 and FIG. 4, the entire layer disposed between the polarizer 31 and the second adhesive layer 22 is the laminated structure portion S2 of the fourth adhesive layer 26, the second protective film 33, the first adhesive layer 23, the first retardation layer 11, the second adhesive layer 24, and the second retardation layer 12.

By satisfying the relationship of the above formula (I), the optical laminates 1 to 4 can have different moisture permeabilities (moisture permeability A1) on the first adhesive layer 21 side of the polarizer 31 and moisture permeability (moisture permeability A2) on the second adhesive layer 22 side of the polarizer 31. This makes it easier to move moisture in the optical laminates 1 to 4 toward the first adhesive layer 21 side than toward the second adhesive layer 22 side in a high-temperature, high-humidity environment. In the optical laminates 1 to 4, iodine contained in the polarizer 31 also moves along with the movement of moisture, so that iodine also moves more easily toward the first adhesive layer 21 side than toward the second adhesive layer 22 side. Therefore, it is considered that the optical laminates 1 to 4 can suppress an increase in the iodine concentration of the second adhesive layer 22. The metal layers shown in FIG. 3 and FIG. 4 may be corroded by iodine. By suppressing the increase in iodine concentration in the second adhesive layer 22 as in optical laminates 1 to 4, when a metal layer 15 is provided on the second adhesive layer 22 (FIGS. 3 and 4), it is expected that corrosion of the metal layer 15 can be suppressed in a high-temperature, high-humidity environment.

The moisture permeability A1 is preferably more than 350 g/( ^m2 ·24hr), more preferably 450 g/( ^m2 ·24hr) or more, may be 500 g/( ^m2 ·24hr) or more, may be 1000 g/( ^m2 ·24hr) or more, or may be 2500 g/( ^m2 ·24hr) or more. From the viewpoint of suppressing the deterioration of the optical properties of the optical laminates 1 to 4 due to an increase in the amount of iodine migration in a high-temperature and high-humidity environment, the moisture permeability A1 is usually 5000 g/( ^m2 ·24hr) or less.

The moisture permeability A2 is preferably 2500 g/( ^m2 ·24hr) or less, more preferably 1000 g/( ^m2 ·24hr) or less, even more preferably 500 g/( ^m2 ·24hr) or less, may be 400 g/( ^m2 ·24hr) or less, and even more preferably 350 g/( ^m2 ·24hr) or less. The smaller the moisture permeability A2, the easier it is to suppress the migration of iodine to the second pressure-sensitive adhesive layer 22 side. From the viewpoint of suppressing the deterioration of the optical properties of the polarizer 31 in a high-temperature and high-humidity environment, the moisture permeability A2 is usually 1 g/( ^m2 ·24hr) or more.

The ratio of the moisture permeability A1 to the moisture permeability A2 (A1/A2) may be greater than 1, but is preferably 1.1 or greater, may be 1.5 or greater, may be 2.0 or greater, and is usually 10 or less. The moisture permeability A1 and the moisture permeability A2 can be measured for the laminated structure portions S1 and S2 by the method described in the examples below.

The moisture permeability A1 of the laminated structure portion S1 and the moisture permeability A2 of the laminated structure portion S2 can be adjusted by adjusting the moisture permeability of the layers included in the laminated structure portions S1 and S2. The moisture permeability A1 of the laminated structure portion S1 can be adjusted, for example, by adjusting the moisture permeability of the first protective film 32 and/or the third bonding layer 25. The moisture permeability A2 of the laminated structure portion S2 can be adjusted, for example, by adjusting the moisture permeability of at least one of the fourth bonding layer 26, the second protective film 33, the first bonding layer 23, the first retardation layer 11, the second bonding layer 24, and the second retardation layer 12. The moisture permeability of the layers can be adjusted, for example, by adjusting the materials constituting the layers, the thickness of the layers, etc.

When the polarizer 31 and the first protective film 32 are laminated via the third bonding layer 25, or when the polarizer 31 and the second protective film 33 are laminated via the fourth bonding layer 26, the third bonding layer 25 and the fourth bonding layer 26 may be formed of a thin adhesive layer (for example, an adhesive layer having a thickness of about 0.1 μm) formed using a water-based adhesive mainly composed of polyvinyl alcohol. In this case, the moisture permeability of the third bonding layer 25 and the fourth bonding layer 26 is very large, so that the influence on the values of the moisture permeability A1 and A2 of the laminated structure parts S1 and S2 is negligibly small. Therefore, it is considered that the moisture permeability A1 of the laminated structure part S1 is substantially the same as the moisture permeability of the entire layer excluding the third bonding layer 25 from the laminated structure part S1, and the moisture permeability A2 of the laminated structure part S2 is substantially the same as the moisture permeability of the entire layer excluding the fourth bonding layer 26 from the laminated structure part S2.

When the optical laminates 1 to 4 satisfy the above [a], moisture is more easily retained in the first pressure-sensitive adhesive layer 21. Therefore, in a high-temperature, high-humidity environment, moisture and iodine are more likely to move toward the first pressure-sensitive adhesive layer 21 side than toward the second pressure-sensitive adhesive layer 22 side, and an increase in the iodine concentration in the second pressure-sensitive adhesive layer 22 can be suppressed.

The saturated moisture content of the first adhesive layer 21 is 0.5% or more, and may be 0.6% or more, or may be 0.7% or more. From the viewpoint of suppressing the increase in the amount of moisture movement and the increase in the amount of iodine movement in a high-temperature and high-humidity environment, which leads to a decrease in the optical properties of the optical laminates 1 to 4, it is preferable that the saturated moisture content of the first adhesive layer 21 is 3.0% or less.

The saturated moisture content of the first adhesive layer 21 can be adjusted, for example, by the composition of the resin contained in the adhesive composition used to form the first adhesive layer 21. For example, when the adhesive composition contains a (meth)acrylic resin, the saturated moisture content of the first adhesive layer 21 can be adjusted by adjusting the amount of a polar monomer (described later) contained in the monomer composition for obtaining the (meth)acrylic resin. The saturated moisture content of the first adhesive layer 21 can be measured by the method described in the examples below.

When the optical laminates 1 to 4 satisfy the above [b], iodine that has migrated into the first adhesive layer 21 in a high-temperature, high-humidity environment may react with the ionic compound contained in the first adhesive layer 21. When iodine is consumed by reaction with the ionic compound, the iodine concentration in the first adhesive layer 21 decreases, making it easier for iodine to migrate toward the first adhesive layer 21, and it is believed that an increase in the iodine concentration in the second adhesive layer 22 can be suppressed.

The first adhesive layer 21 may contain one or more ionic compounds. It is preferable that the ionic compound has antistatic properties.

The cationic component of the ionic compound contained in the first adhesive layer 21 may be an inorganic cation or an organic cation. Examples of organic cations include pyridinium cation, imidazolium cation, ammonium cation, sulfonium cation, phosphonium cation, piperidinium cation, pyrrolidinium cation, etc., and examples of inorganic cations include lithium ion, potassium ion, etc. Examples of inorganic cations include lithium ion, potassium ion, etc. It is preferable that the cationic component of the ionic compound is an organic cation.

The anion component of the ionic compound contained in the first pressure-sensitive adhesive layer 21 may be an inorganic anion or an organic anion. Since the ionic compound has excellent antistatic performance, the anion component of the ionic compound is preferably an anion component containing a fluorine atom. Examples of the anion component containing a fluorine atom include a hexafluorophosphate anion [(PF ₆ ⁻ )], a bis(trifluoromethanesulfonyl)imide anion [(CF ₃ SO ₂ ) ₂ N ⁻ ] anion, and a bis(fluorosulfonyl)imide anion [(FSO ₂ ) ₂ N ⁻ ] anion.

The content of the ionic compound in the first adhesive layer 21 is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, may be 1.0 parts by mass or more, or may be 5.0 parts by mass or more, and is usually 10 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic resin in the first adhesive layer 21.

From the viewpoint of suppressing an increase in the iodine concentration in the second adhesive layer 22 in a high-temperature and high-humidity environment, it is preferable that the optical laminates 1 to 4 satisfy the above [a], and may satisfy both the above [a] and the above [b].

The optical laminates 1 to 4 can form a circular polarizing plate and can be used as an anti-reflection film in an organic EL (electroluminescence) display device or the like. When the optical laminates 1 and 3 shown in Figs. 1 and 3 are circular polarizing plates, the first retardation layer 11 is preferably a λ/4 retardation layer. When the optical laminates 2 and 4 shown in Figs. 2 and 4 are circular polarizing plates, it is preferable that one of the first retardation layer 11 and the second retardation layer 12 is a λ/4 retardation layer, and the other is a λ/2 retardation layer or a positive C layer. The λ/4 retardation layer may have reverse wavelength dispersion.

The optical laminates 1 to 4 can be used in display devices such as smartphones and tablets, and are particularly suitable for use in touch panel type display devices. The metal layer 15 of the optical laminates 3 and 4 may be a metal wiring layer that constitutes a touch panel sensor of a touch panel. Examples of the display device include an organic EL display device and a liquid crystal display device. The display device may be a flexible display.

Hereinafter, each of the members constituting the optical laminates 1 to 4 will be described.
(Polarizer)
When unpolarized light is incident, the polarizer transmits linearly polarized light having a vibration plane perpendicular to the absorption axis. The polarizer is a polyvinyl alcohol-based resin film (hereinafter sometimes referred to as a "PVA-based film") in which iodine is adsorbed and oriented.

Examples of polarizers include PVA-based films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, which have been dyed with iodine and stretched. If necessary, the PVA-based film in which iodine has been adsorbed and oriented by the dyeing process may be treated with an aqueous boric acid solution, followed by a washing step in which the aqueous boric acid solution is washed off. Publicly known methods can be used for each step.

Polyvinyl alcohol resins (hereinafter sometimes referred to as "PVA resins") can be produced by saponifying polyvinyl acetate resins. Polyvinyl acetate resins can be polyvinyl acetate, which is a homopolymer of vinyl acetate, or they can be copolymers of vinyl acetate and other monomers that can be copolymerized with vinyl acetate. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides with ammonium groups.

The saponification degree of the PVA-based resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The PVA-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can be used. The average polymerization degree of the PVA-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000. The saponification degree and average polymerization degree of the PVA-based resin can be determined in accordance with JIS K 6726 (1994). If the average polymerization degree is less than 1,000, it is difficult to obtain favorable polarizing performance, and if it is more than 10,000, the film processability may be poor.

The manufacturing method of a polarizer including a PVA-based film may include the steps of preparing a substrate film, applying a solution of a resin such as a PVA-based resin onto the substrate film, and performing drying or the like to remove the solvent to form a resin layer on the substrate film. A primer layer may be formed in advance on the surface of the substrate film on which the resin layer is to be formed. As the substrate film, a resin film such as PET or a film using a thermoplastic resin that can be used for a protective layer described later can be used. As a material for the primer layer, a resin obtained by crosslinking a hydrophilic resin used in a polarizer can be mentioned.

Next, the amount of solvent such as water in the resin layer is adjusted as necessary, and then the base film and resin layer are uniaxially stretched, and then the resin layer is dyed with iodine to adsorb and align the iodine in the resin layer. Next, if necessary, the resin layer with iodine adsorbed and oriented is treated with an aqueous boric acid solution, followed by a washing step to wash off the aqueous boric acid solution. This produces a resin layer with iodine adsorbed and oriented, i.e., a polarizer film. Publicly known methods can be used for each step.

The amount of boric acid in the boric acid-containing aqueous solution used to treat the PVA-based film or resin layer with iodine adsorption and orientation is usually about 2 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. 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 about 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 about 60 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50°C or higher, preferably 50 to 85°C, and more preferably 60 to 80°C.

The uniaxial stretching of the PVA-based film, the substrate film, and the resin layer may be performed before dyeing, during dyeing, or during boric acid treatment after dyeing, and uniaxial stretching may be performed at each of these multiple stages. The PVA-based film, the substrate film, and the resin layer may be uniaxially stretched in the MD direction (film conveying direction). In this case, they may be uniaxially stretched between rolls with different peripheral speeds, or may be uniaxially stretched using a heated roll. The PVA-based film, the substrate film, and the resin layer may be uniaxially stretched in the TD direction (direction perpendicular to the film conveying direction). In this case, a so-called tenter method can be used. The above stretching 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 film or the resin layer is swollen with a solvent. In order to express the performance of the polarizer, the stretching ratio is 4 times or more, preferably 5 times or more, and particularly preferably 5.5 times or more. There is no particular upper limit to the stretch ratio, but it is preferably 8 times or less to prevent breakage, etc.

A polarizer produced by a manufacturing method using a substrate film can be obtained by laminating the first protective film or the second protective film and then peeling off the substrate film. This method makes it possible to further reduce the thickness of the polarizer.

The thickness of the polarizer is preferably 1 μm or more, may be 2 μm or more, may be 5 μm or more, and is preferably 30 μm or less, more preferably 15 μm or less, may be 10 μm or less, or may be 8 μm or less. The smaller the thickness of the polarizer, the more easily iodine will seep out in a high temperature and high humidity environment. Therefore, when the polarizer has a small thickness, it is expected that by using optical laminates 1 to 4 of this embodiment, corrosion that occurs in the metal layer when the second pressure-sensitive adhesive layer is attached to the metal layer can be effectively suppressed.

(Polarizing plate)
The polarizer can be formed into a polarizing plate by laminating a first protective film and a second protective film on each side of the polarizer. The polarizing plate may have the first protective film but not the second protective film.

(First protective film, second protective film)
As the first protective film and the second protective film, for example, a film formed from a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture blocking property, isotropy, stretchability, etc. is used. Specific examples of the thermoplastic resin 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 polyamide; polyimide resins; polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; cyclic polyolefin resins having cyclo- and norbornene structures (also called norbornene-based resins); (meth)acrylic resins; polyarylate resins; polystyrene resins; polyvinyl alcohol resins, and mixtures thereof. The resin compositions of the first protective film and the second protective film may be the same or different. In this specification, "(meth)acrylic" means that it may be either acrylic or methacrylic. The "(meth)" in (meth)acrylate, etc. has the same meaning.

The first protective film may have a phase difference, and may have anti-reflection properties, anti-glare properties, hard coat properties, etc. (hereinafter, a protective film having such properties may be referred to as a "functional protective film"). When the first protective film is not a functional protective film, a surface functional layer such as an anti-reflection layer, an anti-glare layer, a hard coat layer, etc. may be provided on one side of the polarizing plate. The surface functional layer is preferably provided so as to be in direct contact with the first protective film. The surface functional layer is preferably provided on the side of the first protective film opposite the polarizer side. The second protective film may have a phase difference.

The first protective film and the second protective film are each independently preferably 3 μm or more, more preferably 5 μm or more, and preferably 50 μm or less, more preferably 30 μm or less.

(First retardation layer, second retardation layer)
The first retardation layer and the second retardation layer each include a cured layer formed by polymerizing and curing a polymerizable liquid crystal compound. The first retardation layer and the second retardation layer each may include an alignment layer having an alignment regulating force for aligning the polymerizable liquid crystal compound in a desired direction.

The polymerizable liquid crystal compound may be a rod-shaped polymerizable liquid crystal compound or a disk-shaped polymerizable liquid crystal compound. Either one of these may be used, or a mixture containing both may be used. When the rod-shaped polymerizable liquid crystal compound is aligned horizontally or vertically 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 aligned, the optical axis of the polymerizable liquid crystal compound is in a direction perpendicular to the disk surface of the polymerizable liquid crystal compound. As the rod-shaped polymerizable liquid crystal compound, for example, those described in JP-T-11-513019 (claim 1, etc.) can be suitably used. As the disk-shaped polymerizable liquid crystal compound, those described in JP-A-2007-108732 (paragraphs [0020] to [0067], etc.) and JP-A-2010-244038 (paragraphs [0013] to [0108], etc.) can be suitably used.

In order for the cured layer formed by polymerizing the polymerizable liquid crystal compound to exhibit an in-plane retardation, the polymerizable liquid crystal compound may be aligned in an appropriate direction. When the polymerizable liquid crystal compound is rod-shaped, the in-plane retardation is exhibited by aligning the optical axis of the polymerizable liquid crystal compound horizontally to the plane of the base layer, in which case the optical axis direction and the slow axis direction coincide. When the polymerizable liquid crystal compound is disc-shaped, the in-plane retardation is exhibited by aligning the optical axis of the polymerizable liquid crystal compound horizontally to the plane of the base layer, in which case the optical axis and the slow axis are perpendicular to each other. The alignment state of the polymerizable liquid crystal compound can be adjusted by the combination of the alignment layer and the polymerizable liquid crystal compound.

A polymerizable liquid crystal compound is a compound having at least one polymerizable group and liquid crystal properties. When two or more types of polymerizable liquid crystal compounds are used in combination, it is preferable that at least one type has two or more polymerizable groups in the molecule. The 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 or acid generated from a photopolymerization initiator described later. Examples of the polymerizable group include a vinyl group, a vinyloxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxiranyl group, an oxetanyl group, a styryl group, and an allyl group. Among them, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group, and an oxetanyl group are preferable, and an acryloyloxy group is more preferable. The liquid crystallinity of the polymerizable liquid crystal compound may be thermotropic or lyotropic liquid crystal, and when thermotropic liquid crystals are classified according to the degree of order, they may be nematic or smectic liquid crystals.

The thickness of the first retardation layer and the second retardation layer may be, independently of each other, 0.1 μm or more, 0.5 μm or more, 1 μm or more, or 2 μm or more, and is preferably 10 μm or less, and may be 8 μm or less, or 5 μm or less.

The cured layer of the polymerizable liquid crystal compound can be formed by applying a liquid crystal layer-forming composition containing the polymerizable liquid crystal compound onto a substrate layer, drying the composition, and polymerizing the polymerizable liquid crystal compound. The liquid crystal layer-forming composition may be applied onto an 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 aligned vertically relative to the substrate layer, a horizontal alignment layer in which the molecular axis of the polymerizable liquid crystal compound is aligned horizontally relative to the substrate layer, or an inclined alignment layer in which the molecular axis of the polymerizable liquid crystal compound is aligned at an angle relative to the substrate layer.

As the alignment layer, it is preferable that the layer has a solvent resistance that does not dissolve the liquid crystal layer-forming composition containing the polymerizable liquid crystal compound when applied, and has heat resistance against the heat treatment for removing the solvent and for orienting the polymerizable liquid crystal compound. Examples of the alignment layer include an alignment polymer layer formed from an alignment polymer, a photoalignment polymer layer formed from a photoalignment polymer, and a groove alignment layer having a concave-convex pattern or multiple grooves on the layer surface.

As the substrate 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 first protective film and the second protective film described above 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 handling, it is preferably 1 to 300 μm or less, more preferably 20 to 200 μm, and even more preferably 30 to 120 μm. The substrate layer may be incorporated into the optical laminate together with the cured layer of the polymerizable liquid crystal compound, or the substrate layer may be peeled off and only the cured layer of the polymerizable liquid crystal compound, or the cured layer and the alignment layer may be incorporated into the optical laminate. When the substrate layer is incorporated into the optical laminate together with the cured 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.

(First adhesive layer, second adhesive layer)
The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are pressure-sensitive adhesive layers formed using a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition or the reaction product of the pressure-sensitive adhesive composition itself exhibits adhesiveness by being attached to an adherend such as a metal layer, and is called a pressure-sensitive adhesive. In addition, the pressure-sensitive adhesive layer formed using the active energy ray-curable pressure-sensitive adhesive composition described later can adjust the degree of crosslinking or adhesive strength by irradiating with active energy rays.

As the adhesive composition, any adhesive having excellent optical transparency that has been known in the art can be used without any particular restrictions. For example, an adhesive composition containing a base polymer such as an acrylic, urethane, silicone, or polyvinyl ether can be used. The adhesive composition may be an active energy ray curable adhesive composition or a heat curable adhesive composition. Among these, an adhesive composition having an acrylic resin as a base polymer, which is excellent in transparency, adhesive strength, removability (reworkability), weather resistance, heat resistance, etc., is preferable. The adhesive layer is preferably composed 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 first adhesive layer and the second adhesive layer may be formed using an active energy ray curable adhesive composition. The active energy ray curable adhesive composition can be formed by blending an ultraviolet-curable compound such as a multifunctional acrylate with the above-mentioned adhesive composition, forming an adhesive layer, and then curing the adhesive layer by irradiating it with ultraviolet light, thereby forming a harder adhesive layer. The active energy ray curable adhesive composition has the property of being cured by irradiation with energy rays such as ultraviolet rays and electron beams. The active energy ray curable adhesive composition has adhesiveness even before irradiation with energy rays, so it is an adhesive that has the property of adhering to an adherend such as a metal layer and curing by irradiation with energy rays to adjust the adhesion.

An active energy ray-curable adhesive composition generally contains a (meth)acrylic adhesive composition and an energy ray-polymerizable compound as the main components. Usually, a crosslinking agent is further blended, and if necessary, a photopolymerization initiator, a photosensitizer, etc. can also be blended.

The adhesive composition for forming the first adhesive layer preferably contains a (meth)acrylic resin. The (meth)acrylic resin preferably contains a structural unit derived from a (meth)acrylic acid ester, and may contain a structural unit derived from a monomer having a polar functional group (hereinafter sometimes referred to as a "polar monomer"), and other structural units other than these structural units. Examples of the polar functional group include a free carboxyl group, a hydroxyl group, an amino group, and a heterocyclic group such as an epoxy group.

Examples of (meth)acrylic acid esters include linear (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-octyl (meth)acrylate, and lauryl (meth)acrylate; and branched (meth)acrylic acid alkyl esters such as isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isooctyl (meth)acrylate. The number of carbon atoms in the alkyl portion of the (meth)acrylic acid alkyl ester is preferably 1 to 8, and more preferably 1 to 6. Only one type of (meth)acrylic acid ester may be used alone, or two or more types may be used in combination.

Examples of polar monomers include monomers having a free carboxyl group, such as (meth)acrylic acid and β-carboxyethyl (meth)acrylate; monomers having a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-(2-hydroxyethoxy)ethyl (meth)acrylate, 2- or 3-chloro-2-hydroxypropyl (meth)acrylate, and diethylene glycol mono(meth)acrylate; (meth)acryloylmorpholine, vinyl caprolactam, etc. Examples of the polar monomer include monomers having a heterocyclic group such as methacrylate, N-vinyl-2-pyrrolidone, vinylpyridine, tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, glycidyl (meth)acrylate, and 2,5-dihydrofuran; and monomers having an amino group different from the heterocyclic ring such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylate. The polar monomer may be used alone or in combination of two or more kinds.

Monomers that can introduce other structural units into the (meth)acrylic resin (hereinafter sometimes referred to as "other monomers") include monomers other than (meth)acrylic acid esters that have one olefinic double bond and at least one aromatic ring in the molecule. Other monomers include (meth)acrylic acid compounds with aromatic rings. Examples of (meth)acrylic acid compounds with aromatic rings include (meth)acrylic acid esters with aryloxyalkyl groups, specifically 2-phenoxyethyl (meth)acrylate, 2-(2-phenoxyethoxy)ethyl (meth)acrylate, (meth)acrylic acid esters of ethylene oxide-modified nonylphenol, 2-(o-phenylphenoxy)ethyl (meth)acrylate, and the like. The phenoxyethyl group-containing (meth)acrylic acid esters may be used alone or in combination of two or more types. Among them, examples of phenoxyethyl group-containing (meth)acrylic acid esters include 2-phenoxyethyl (meth)acrylate, 2-(o-phenylphenoxy)ethyl (meth)acrylate, and 2-(2-phenoxyethoxy)ethyl (meth)acrylate.

Other monomers other than those mentioned above include structural units derived from (meth)acrylic acid esters having an alicyclic structure in the molecule, structural units derived from styrene-based monomers, structural units derived from vinyl-based monomers, structural units derived from monomers having multiple (meth)acryloyl groups in the molecule, structural units derived from (meth)acrylamide monomers, etc. One type of other monomer may be used alone, or two or more types may be used in combination.

The (meth)acrylic resin contains, based on the total solid content, structural units derived from the (meth)acrylic acid esters, preferably in a proportion of 60 to 99.9% by mass, more preferably 65 to 998% by mass, structural units derived from polar monomers, preferably in a proportion of 0.1 to 30% by mass, more preferably 0.4 to 20% by mass, and structural units derived from monomers having one olefinic double bond and at least one aromatic ring in the molecule, preferably in a proportion of 0 to 30% by mass, more preferably 6 to 20% by mass.

The adhesive composition for forming the second adhesive layer is not particularly limited, but may be, for example, the adhesive composition for forming the first adhesive layer.

The first adhesive layer may contain an ionic compound. It is preferable that the second adhesive layer does not contain an ionic compound.

From the viewpoint of bonding to the front panel, the thickness of the first adhesive layer is preferably 5 μm or more and 300 μm or less, and more preferably 50 μm or more and 250 μm or less.

The thickness of the second adhesive layer is preferably 5 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less, from the viewpoint of bonding to the metal layer.

(metal layer)
The metal layer can be used as a conductive layer for constituting a touch sensor of a touch panel. The metal layer is a layer formed of one or more metals. The metal layer may have a passivation film (oxide film) formed on its surface. The metal layer may have a single-layer structure or a multi-layer structure. 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), tungsten (W), platinum (Pt), iron (Fe), indium (In), tin (Sn), iridium (Ir), rhodium (Rh), neodymium (Nd), molybdenum (Mo), and alloys containing two or more of these metals. Of these, the metal layer is preferably mainly composed of aluminum or copper, and may contain titanium as an additive. Here, the main component refers to a metal that accounts for 50% or more by mass of the metals constituting the metal layer.

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

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

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, its line width is usually 10 μm or less, may be 5 μm or less, or may be 3 μm or less, and is usually 0.5 μm or more.

(Front plate)
The front plate is a plate-like body that can function as a layer for protecting the display element of the display device and the like and can transmit light. The material and thickness of the front plate are not limited as long as the front plate is a plate-like body that can transmit light. The front plate may be composed of only one layer, or may be composed of two or more layers. Examples of the front plate include a resin plate (e.g., a resin plate, a resin sheet, a resin film, etc.) and a glass plate (e.g., a glass plate, a glass film, etc.). The front plate can constitute the outermost surface of the display device. The front plate may also be a resin film, or a resin film with a hard coat layer in which a hard coat layer is provided on at least one surface of the resin film to further improve hardness. When a resin film with a hard coat layer is used, it is preferable that the hard coat layer is provided so as to be disposed on the outermost surface of the display device. The front plate may also have a blue light cut function, a viewing angle adjustment function, etc.

The resin film forming the front panel is not limited as long as it is a resin film that can transmit light. For example, films formed of polymers such as triacetyl cellulose, acetyl cellulose butyrate, ethylene-vinyl acetate copolymer, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, polyester, polystyrene, polyamide, polyetherimide, poly(meth)acrylic, polyimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polyethersulfone, polymethyl (meth)acrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyamideimide can be used. These polymers can be used alone or in combination of two or more.

When the front panel is a glass plate, the glass plate is preferably tempered glass for displays. By using a glass plate, a front panel having excellent mechanical strength and surface hardness can be formed.

The thickness of the front panel may be, for example, 10 μm or more and 300 μm or less, preferably 20 μm or more and 200 μm or less, and more preferably 30 μm or more and 100 μm or less.

(1st lamination layer, 2nd lamination layer, 3rd lamination layer, 4th lamination layer)
The first attachment layer, the second attachment layer, the third attachment layer, and the fourth attachment layer (hereinafter, these may be collectively referred to as "attachment layers") are each independently a pressure-sensitive adhesive layer or an adhesive layer.

When the attachment layer is a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer can be formed using the pressure-sensitive adhesive composition described above for the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer.

When the lamination layer is an adhesive layer, the adhesive layer can be formed by curing a curable component in the adhesive composition. The adhesive composition for forming the adhesive layer is an adhesive other than a pressure-sensitive adhesive (adhesive), such as a water-based adhesive or an active energy ray-curable adhesive.

An example of a water-based adhesive is an adhesive in which a polyvinyl alcohol resin is dissolved or dispersed in water. There are no particular limitations 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 used.

Examples of active energy ray-curable adhesives include solvent-free active energy ray-curable adhesives that contain a curable compound that cures when exposed to active energy rays such as ultraviolet light, visible light, electron beams, and X-rays. By using a solvent-free active energy ray-curable adhesive, it is possible to improve the adhesion between layers.

The active energy ray curable adhesive preferably contains either one or both of a cationic polymerizable curable compound and a radically polymerizable curable compound, since these exhibit good adhesive properties. The active energy ray curable adhesive may further contain a cationic polymerization initiator, such as a photocationic polymerization initiator, for initiating the curing reaction of the curable compound, or a radical polymerization initiator.

Examples of cationic polymerizable curable compounds include epoxy-based compounds such as 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, monofunctional epoxy compounds having one epoxy group (excluding those included in alicyclic epoxy compounds), polyfunctional aromatic epoxy compounds having two or more epoxy groups and an aromatic ring; oxetane compounds having one or more oxetane rings in the molecule; and combinations of these.

Examples of radically polymerizable curable compounds include (meth)acrylic compounds (compounds having one or more (meth)acryloyloxy groups in the molecule), other vinyl compounds having radically polymerizable double bonds, or combinations of these.

The active energy ray curable adhesive may contain a sensitizer such as a photosensitizer assistant, if necessary. The use of a sensitizer improves reactivity, and the mechanical strength and adhesive strength of the adhesive layer can be further improved. Any known sensitizer may be used as appropriate. When a sensitizer is added, the amount of the sensitizer added is preferably in the range of 0.1 to 20 parts by mass per 100 parts by mass of the total amount of the active energy ray curable adhesive.

The active energy ray curable adhesive may contain additives such as ion trapping agents, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow control agents, plasticizers, defoamers, antistatic agents, leveling agents, and solvents, as necessary.

When an active energy ray curing adhesive is used, the adhesive layer can be formed by irradiating the adhesive coating layer with active energy rays such as ultraviolet rays, visible light, electron beams, or X-rays to cure the adhesive layer. As the active energy ray, ultraviolet rays are preferred, and in this case, the light source can be 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.

When the lamination layer is a pressure sensitive adhesive layer, the thickness is preferably 3 μm or more, may be 10 μm or more, may be 15 μm or more, and is preferably 30 μm or less, may be 25 μm or less, or may be 20 μm or less. When the lamination layer is an adhesive layer, the thickness is preferably 0.1 μm or more, may be 0.5 μm or more, and is preferably 10 μm or less, and may be 5 μm or less.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[Production Examples 1 and 2: Production of (meth)acrylic resins]
A monomer mixture containing the monomer composition shown in Table 1 (mass % when the total amount of monomers is 100 mass %) and diluted with ethyl acetate was charged into a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer, and a stirrer, and the air in the reaction vessel was replaced with nitrogen gas to make it oxygen-free, while raising the internal temperature to 55 ° C. Then, the entire amount of a solution in which azobisisobutyronitrile (polymerization initiator) was dissolved in ethyl acetate was added. After adding the polymerization initiator, the temperature was maintained for 1 hour, and then ethyl acetate was continuously added to the reaction vessel while maintaining the internal temperature at 54 to 56 ° C., and the addition of ethyl acetate was stopped when the concentration of the (meth)acrylic resin became 35 mass %, and the temperature was kept at this temperature until 12 hours had elapsed from the start of the addition of ethyl acetate. Finally, ethyl acetate was added to adjust the concentration of the (meth)acrylic resin to 20 mass %, and an ethyl acetate solution of the (meth)acrylic resin was prepared.

The weight average molecular weight (Mw) and number average molecular weight (Mn) of the obtained (meth)acrylic resin were measured by the following procedure. The weight average molecular weight (Mw) and number average molecular weight (Mn) were measured in standard polystyrene equivalents using a GPC apparatus with four "TSKgel XL" columns manufactured by Tosoh Corporation and one "Shodex GPC KF-802" column manufactured by Showa Denko K.K. and sold by Shoko Tsusho K.K., connected in series as columns for a total of five columns, tetrahydrofuran was used as the eluent, and the sample concentration was 5 mg/mL, the sample introduction amount was 100 μL, the temperature was 40°C, and the flow rate was 1 mL/min. The results of the weight average molecular weight (Mw) and Mw/Mn are shown in Table 1.

[Production Example 3: Production of (meth)acrylic resin]
A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen inlet tube was charged with 98.5 parts by mass of n-butyl acrylate, 1.0 parts by mass of acrylic acid, 0.5 parts by mass of 2-hydroxyethyl acrylate, 200 parts by mass of ethyl acetate and 0.08 parts by mass of 2,2'-azobisisobutyronitrile, and the air in the reaction vessel was replaced with nitrogen gas. The reaction solution was heated to 60°C while stirring under a nitrogen atmosphere, reacted for 6 hours, and then cooled to room temperature. The formation of a (meth)acrylic resin was confirmed in the obtained solution. In addition, the weight average molecular weight (Mw) and number average molecular weight (Mn) of a part of the obtained solution were measured by the above procedure. The results of the weight average molecular weight (Mw) and Mw/Mn are shown in Table 1.

The abbreviations in the "Monomer composition" column in Table 1 represent the following monomers.
BA: Butyl acrylate MA: Methyl acrylate PEA: 2-phenoxyethyl acrylate HEA: 2-hydroxyethyl acrylate AA: Acrylic acid

[Formulation Examples 1, 4 to 6: Preparation of Pressure-Sensitive Adhesive Compositions]
To 100 parts by mass of the solid content of the (meth)acrylic resin obtained in Production Example 1, 0.5 parts by mass of "Coronate L" (a solution of trimethylolpropane adduct of tolylene diisocyanate in ethyl acetate: solid content concentration 75% by mass) obtained from Tosoh Corporation as a crosslinking agent and 0.5 parts by mass of "KBM-403" (3-glycidoxypropyltrimethoxysilane) obtained from Shin-Etsu Chemical Co., Ltd. as a silane compound were added, and for Formulation Examples 4 to 6, N-octyl-4-methylpyridinium hexafluorophosphorus as an ionic compound was mixed in the amount shown in Table 2, and ethyl acetate was added so that the solid content concentration became 15% by mass to prepare a solution of the adhesive composition. The amount of the crosslinking agent (parts by mass) is calculated as the solid content.

Formulation Example 2: Preparation of Pressure Sensitive Adhesive Composition
To 100 parts by mass of the solid content of the (meth)acrylic resin obtained in Production Example 2, 0.2 parts by mass of "Coronate L" obtained from Tosoh Corporation (ethyl acetate solution of trimethylolpropane adduct of tolylene diisocyanate: solid content concentration 75% by mass) as a crosslinking agent and 0.5 parts by mass of "KBM-403" (3-glycidoxypropyltrimethoxysilane) obtained from Shin-Etsu Chemical Co., Ltd. as a silane compound were added, and ethyl acetate was further added so that the solid content concentration became 15% by mass to prepare a solution of the adhesive composition. The blending amount (parts by mass) of the crosslinking agent is the amount converted into solid content.

Formulation Example 3: Preparation of Pressure Sensitive Adhesive Composition
A solution of a pressure-sensitive adhesive composition was prepared in the same manner as in Formulation Example 2, except that the amount of the crosslinking agent was changed to 1.0 part by mass.

Formulation Example 7: Preparation of Pressure Sensitive Adhesive Composition
100 parts by mass (solid content equivalent; the same applies hereinafter) of the (meth)acrylic resin obtained in Production Example 3, 0.30 parts by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Tosoh Corporation, product name "Coronate L") as an isocyanate-based crosslinking agent, and 0.30 parts by mass of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM403") as a silane coupling agent were mixed, thoroughly stirred, and diluted with ethyl acetate to obtain a coating solution of a pressure-sensitive adhesive composition.

[Preparation of Pressure-Sensitive Adhesive Sheets (1) to (6)]
The adhesive compositions prepared in Formulation Examples 1 to 6 were applied to the release-treated surface of a separate film made of a release-treated polyethylene terephthalate film ("PLR-382190" available from Lintec Corporation) using an applicator so that the thickness after drying would be 25 μm, and an adhesive layer was prepared by drying for 1 minute at a temperature of 100° C. The release-treated surface of a separate film made of a release-treated polyethylene terephthalate film ("PLR-251130" available from Lintec Corporation) was attached to the surface of the obtained adhesive layer opposite to the separate film side, to prepare adhesive sheets (1) to (6).

[Preparation of Pressure-Sensitive Adhesive Sheet (7)]
The adhesive composition prepared in Formulation Example 7 was applied to the release-treated surface of a separate film ("SP-PLR382190" available from Lintec Corporation) using an applicator so that the thickness after drying would be 25 μm, and an adhesive layer was prepared by drying for 1 minute at a temperature of 100° C. The release-treated surface of another separate film ("SP-PLR381031" available from Lintec Corporation) was bonded to the surface of the obtained adhesive layer opposite to the separate film side, to prepare an adhesive sheet (7).

Example 1
(Preparation of Polarizer)
A 30 μm thick polyvinyl alcohol-based resin film (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) was uniaxially stretched longitudinally by about 5 times by dry stretching, and then, while maintaining the tension, was immersed in pure water at a temperature of 60 ° C. for 1 minute, and then, was immersed in an aqueous solution at a temperature of 28 ° C. in which the mass ratio of iodine/potassium iodide/water was 0.05/5/100 for 60 seconds. Then, it was immersed in an aqueous solution at a temperature of 72 ° C. in which the mass ratio of potassium iodide/boric acid/water was 8.5/8.5/100 for 300 seconds. It was subsequently washed with pure water at a temperature of 26 ° C. for 20 seconds, and then, was dried at a temperature of 65 ° C. to obtain a polarizer having a thickness of 12 μm in which iodine was adsorbed and aligned in the polyvinyl alcohol-based resin film.

(Preparation of Water-Based Adhesive)
A polyvinyl alcohol aqueous 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. A water-soluble polyamide epoxy resin ("Sumirez Resin 650 (30)" manufactured by Taoka Chemical Co., Ltd., solid content concentration 30% by mass) was mixed with the obtained aqueous solution in a ratio of 1.5 parts by mass per 100 parts by mass of water to obtain a water-based adhesive.

(Preparation of Polarizing Plate)
The aqueous adhesive obtained above was applied to one surface of the polarizer obtained above, and a triacetyl cellulose film (hereinafter, sometimes referred to as a "TAC film") having a hard coat layer (hereinafter, sometimes referred to as an "HC layer") was laminated thereon. A TAC film was laminated on the other surface of the polarizer using the aqueous adhesive obtained above, and dried at a temperature of 80°C for 5 minutes to obtain a polarizing plate having protective films on both surfaces of the polarizer. The layer structure of the polarizing plate was HC layer (surface functional layer)/TAC film (first protective film)/aqueous adhesive layer (third bonding layer)/polarizer/aqueous adhesive layer (fourth bonding layer)/TAC film (second protective film). A protective film having an adhesive layer on a substrate 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 a "polarizing plate with PF").

(Preparation of λ/2 Retardation Layer)
A composition for forming an alignment layer was applied onto a substrate layer formed of a transparent resin and dried to perform a λ/2 alignment treatment. Next, a composition for forming a liquid crystal layer containing a discotic polymerizable liquid crystal compound was applied onto the alignment layer, and the alignment of the polymerizable liquid crystal compound was fixed by heating and UV irradiation, thereby forming a first cured material layer (λ/2 retardation layer) having a thickness of 2 μm on the alignment layer of the substrate layer.

(Preparation of λ/4 Retardation Layer)
A liquid crystal layer-forming composition containing a rod-shaped nematic polymerizable liquid crystal compound was applied to a rubbed alignment layer on a substrate layer formed of a transparent resin, and solidified while maintaining the refractive index anisotropy, thereby forming a second cured material layer (λ/4 retardation layer) having a thickness of 1 μm on the alignment layer of the substrate layer.

(Preparation of Retardation Layer with Base Layer)
The surface of the first cured material layer on the substrate layer and the surface of the second cured material layer on the substrate layer were each subjected to a corona treatment. The corona-treated surfaces of the first cured material layer and the second cured material layer were bonded together using an active energy ray curable adhesive so that the angle between the slow axes of the first cured material layer and the second cured material layer was 60°. Thereafter, an ultraviolet ray irradiation device (manufactured by Fusion UV Systems Co., Ltd.) was used from the second cured material layer side to irradiate ultraviolet rays with an integrated light amount of 400 mJ/cm ² (UV-B) to cure the active energy ray curable adhesive and form an adhesive layer. The bonding was performed using a laminator, and the active energy ray curable adhesive was applied so that the thickness of the adhesive layer after curing was 3 μm. As a result, a retardation layer with a substrate layer was obtained in which the substrate layer/alignment layer/first cured material layer (first retardation layer)/adhesive layer (second bonding layer)/second cured material layer (second retardation layer)/alignment layer/substrate layer were laminated in this order. In the retardation layer with the base layer, the total thickness of the first cured product layer, the adhesive layer, and the second cured product layer was 6 μm.

(Preparation of optical laminate)
The first cured material layer exposed by peeling off the base material layer and the alignment layer on the first cured material layer side of the retardation layer with the base material layer obtained above was laminated to the polarizing plate side of the polarizing plate with the PF obtained above using an acrylic adhesive layer (first lamination layer, storage modulus: 125,500 Pa) having a thickness of 5 μm. The lamination of the first cured material layer and the polarizing plate was performed so that the angle between the slow axis of the first cured material layer and the transmission axis of the polarizer was 15°. Next, a 15 μm thick adhesive layer (second adhesive layer, storage modulus: 25,500 Pa) and a separate film were laminated in this order on the second cured material layer exposed by peeling off the base material layer and the alignment layer on the second cured material layer side to obtain a laminate (1). The storage modulus of the first lamination layer and the second adhesive layer was measured by the following procedure.

[Storage Modulus of First Adhesive Layer and Second Pressure-Sensitive Adhesive Layer]
The pressure-sensitive adhesive layers constituting the first bonding layer and the second pressure-sensitive adhesive layer were laminated in a thickness of 0.2 mm. The laminated pressure-sensitive adhesive layers were punched out to form a cylindrical body with a diameter of 8 mm, which was used as a sample for measuring the storage modulus. The storage modulus [Pa] of the measurement sample was measured by a torsional shear method using a viscoelasticity measuring device (Physica, MCR300) under the following conditions in accordance with JIS K7244-6.
<Measurement conditions>
・Normal Force FN: 1N
Distortion γ: 1%
Frequency: 1Hz
・Temperature: 25℃

The adhesive layers of the adhesive sheet (1) prepared above were laminated in order so that the thickness after lamination was 100 μm, to obtain a laminated adhesive layer, which was used as the first adhesive layer. The protective film was peeled off from the obtained laminate (1), and the first adhesive layer was laminated on the exposed polarizing plate to obtain an optical laminate (1). The layer structure of the optical laminate (1) was a separate film/laminated adhesive layer (first adhesive layer)/HC layer (surface functional layer)/TAC film (first protective film)/water-based adhesive layer (third bonding layer)/polarizer/water-based adhesive layer (fourth bonding layer)/TAC film (second protective film)/acrylic adhesive layer (first bonding layer)/first cured material layer (first retardation layer)/adhesive layer (second bonding layer)/second cured material layer (second retardation layer)/adhesive layer (second adhesive layer)/separate film.

[Examples 2 to 6, Comparative Example 1]
A laminated adhesive layer was obtained by using the adhesive sheets (2) to (7) instead of the adhesive sheet (1), and optical laminates (2) to (7) were obtained in the same manner as in Example 1, except that this laminated adhesive layer was used.

[Measurement of Moisture Permeability]
The moisture permeability A1 of the laminated structure portion S1 (HC layer/TAC film/aqueous adhesive layer) between the polarizer and the first pressure-sensitive adhesive layer of each of the optical laminates (1) to (7), and the moisture permeability A2 of the laminated structure portion S2 (aqueous adhesive layer/TAC film/acrylic pressure-sensitive adhesive layer/first cured product layer/adhesive layer/second cured product layer) between the polarizer and the second pressure-sensitive adhesive layer were determined by the following procedure.

First, evaluation samples having the same layer structure as the laminated structure parts S1 and S2 of the optical laminates (1) to (7) were prepared. The water vapor transmission rate of the prepared evaluation samples was measured using a thermo-hygrostat under the measurement conditions of a temperature of 40°C, a relative humidity of 90% RH, and a measurement time of 24 hours by a moisture transmission test method (cup method, conforming to JIS Z 0208). The measured moisture vapor transmission rates of the laminated structure parts S1 and S2 were designated as moisture transmission rates A1 and A2 at a temperature of 40°C and a relative humidity of 90% RH, respectively.

The moisture permeability A1 of the laminated structure portion S1 was 450 g/( ^m2 ·24 hr), the moisture permeability A2 of the laminated structure portion S2 was 210 g/( ^m2 ·24 hr), and the ratio of the moisture permeability A1 to the moisture permeability A2 (A1/A2) was 2.1.

[Measurement of saturated moisture content of adhesive layer]
Each of the pressure-sensitive adhesive layers (thickness: 25 μm) of the pressure-sensitive adhesive sheets (1) to (7) prepared above was stored under the following storage condition (1), and then stored under the following storage condition (2). The mass of the pressure-sensitive adhesive layer after each storage condition was measured using a moisture adsorption/desorption measuring device IGA Sorp (manufactured by Hiden Isochema), and the saturated moisture content of the pressure-sensitive adhesive layer at a temperature of 25° C. and a relative humidity of 80% RH was calculated according to the following formula. The results are shown in Table 3.
Storage conditions (1): Temperature 25°C, dry atmosphere, storage time 24 hours
Storage conditions (2): Temperature 25°C, relative humidity 80% RH, storage time 15 hours
Saturated moisture content [%] = [(mass after storage condition (2)) - (mass after storage condition (1))]
/ (Mass after storage condition (1))

[Measurement of iodine content in second pressure-sensitive adhesive layer]
The optical laminates (1) to (7) obtained in the examples and comparative examples were cut to a size of 25 mm x 50 mm, the separation film on the first adhesive layer side was peeled off, and the exposed first adhesive layer was attached to alkali-free glass to prepare a test piece. The test piece was stored in an oven at a temperature of 85°C and a relative humidity of 85% RH for 240 hours, after which the separation film on the second adhesive layer side was peeled off, and the adhesive of the second 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. The results are shown in Table 3.
<Sample Combustion>
・Apparatus: Mitsubishi Chemical Analytech Co., Ltd. AQF-2100H
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: Integration manufactured by Thermo Fisher Scientific
Column: Thermo Fisher Scientific IonPac AS19
Measurement conditions: the eluent was a KOH aqueous solution gradient, the flow rate was 1.0 mL/min, the injection amount was 100 μL, the measurement mode was suppressor type, and the detector was an electrical conductivity detector.

1 to 4 optical laminate, 11 first retardation layer, 12 second retardation layer, 15 metal layer, 16 front plate, 21 first adhesive layer, 22 second adhesive layer, 23 first bonding layer, 24 second bonding layer, 25 third bonding layer, 26 fourth bonding layer, 31 polarizer, 32 first protective film, 33 second protective film, S1, S2 Laminated structure part.

Claims (9)

An optical laminate including a first pressure-sensitive adhesive layer, a first protective film, a polarizer, a second protective film, a first retardation layer, a second retardation layer, and a second pressure-sensitive adhesive layer in this order, and the first retardation layer and the second retardation layer are laminated via a second attachment layer,
the polarizer is a polyvinyl alcohol-based resin film in which iodine is adsorbed and oriented,
The first retardation layer includes a cured layer of a polymerizable liquid crystal compound,
The second retardation layer includes a cured layer of a polymerizable liquid crystal compound,
the second protective film is a film formed from a cellulose resin,
The moisture permeability of the entire layer disposed between the polarizer and the first pressure-sensitive adhesive layer at a temperature of 40° C. and a relative humidity of 90% RH is defined as A1,
When the moisture permeability of the entire layer disposed between the polarizer and the second pressure-sensitive adhesive layer at a temperature of 40° C. and a relative humidity of 90% RH is A2, the relationship of the following formula (I) is satisfied:
A1>A2 (I)
and
The first pressure-sensitive adhesive layer comprises the following [a ′ ] and [b]:
[a ' ] the first pressure-sensitive adhesive layer has a saturated moisture content of 2.1 % or more at a temperature of 25°C and a relative humidity of 80% RH ; and
the first pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic resin,
The (meth)acrylic resin contains a structural unit derived from a monomer having a free carboxyl group and a monomer having a hydroxyl group.
[b] the first pressure-sensitive adhesive layer contains an ionic compound;
An optical laminate satisfying at least one of the above. The optical laminate according to claim 1, wherein the ratio (A1/A2) of the moisture permeability A1 to the moisture permeability A2 is 1.1 or more. The optical laminate according to claim 1 , wherein the first pressure-sensitive adhesive layer satisfies the condition [a ′ ]. The optical laminate according to any one of claims 1 to 3, further comprising a surface functional layer between the first pressure-sensitive adhesive layer and the first protective film. The optical laminate according to claim 4, wherein the surface functional layer is a hard coat layer. The optical laminate according to any one of claims 1 to 5, wherein the second protective film and the first retardation layer are laminated via a first bonding layer. The optical laminate according to any one of claims 1 to 6, wherein the first pressure-sensitive adhesive layer satisfies [b]. The optical laminate according to any one of claims 1 to 7, further comprising a metal layer on the side of the second pressure-sensitive adhesive layer opposite to the first retardation layer side. The optical laminate according to any one of claims 1 to 8, further comprising a front plate on the side of the first adhesive layer opposite the polarizer side.

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