JP7689846B2 - Optical laminate and display device - Google Patents

Description

The present invention relates to an optical laminate, a display device, and a method for manufacturing an optical laminate.

Liquid crystal display devices (LCDs) are widely used not only in LCD televisions, but also in personal computers, mobile devices such as mobile phones, and in-vehicle applications such as car navigation systems. Typically, LCD displays have a liquid crystal panel member in which polarizing plates are attached to both sides of a liquid crystal cell with an adhesive, and display is achieved by controlling the light from a backlight member with the liquid crystal panel member. In recent years, organic electroluminescence (EL) display devices have also come to be widely used in TVs, mobile devices such as mobile phones, and in-vehicle applications such as car navigation systems, just like LCD displays. In LCD displays and organic EL displays, retardation films are used to provide functions such as expanding the viewing angle and preventing reflection of external light.

As mentioned above, polarizing plates are increasingly being installed in vehicles as components of liquid crystal display devices and organic EL display devices. Polarizing plates used in in-vehicle image display devices are more often exposed to high-temperature environments than those used in other mobile applications such as televisions and mobile phones, and are therefore required to have minimal change in properties at high temperatures (high-temperature durability).

On the other hand, when used for car navigation systems and other applications, in-vehicle display devices need to have touch panel functionality. In recent years, the proportion of on-cell and in-cell touch panels has been increasing, and in these applications, the polarizing plate on the viewing side is positioned on the outermost side, so in addition to the durability mentioned above, anti-glare functionality is also required.

JP 2011-081219 A (Patent Document 1) discloses the use of an antiglare hard coat film in which a multi-layered antireflection layer formed by sputtering is laminated on an antiglare layer to prevent reflections of external light (Example 1, etc.).

Patent Document 2 describes a polarizing plate including a retardation film using a cyclic olefin resin for the purpose of expanding the viewing angle. In addition, Patent Document 3 describes a polarizing plate including a retardation film using a cyclic olefin resin as a λ/4 plate for the purpose of preventing reflection of external light.

It was found that such polarizing plates have good visibility after being laminated to a display device, and even though no cracks were observed after a heat durability test (105°C for 500 hours), cracks may occur in the retardation film if the plate is stored in an environment at a temperature of 23°C and a relative humidity of 55% for about a month.

JP 2011-081219 A Patent No. 5383594 JP 2014-194483 A

The object of the present invention is to solve the above problems and to provide an optical laminate that has good anti-glare function even when using an optical laminate containing a retardation film that adds functions to an image display device, and that does not develop cracks in the retardation film even when stored for one month in an environment at a temperature of 23°C and a relative humidity of 55% after a heat durability test.

The present invention provides the following optical laminate, display device, and method for producing the optical laminate.
[1] An optical laminate having a retardation film, a polarizing element, and an antireflection film in this order,
The retardation film has a tensile modulus of elasticity at 23° C. of 3000 MPa or less,
The polarizing element has a moisture content equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20% and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%,
The following requirement (i) and the following requirement (ii):
(i) The anti-reflection film has a moisture permeability of 300 g/ ^m2 ·day or less at a temperature of 40° C. and a relative humidity of 90%;
(ii) a protective film having a moisture permeability of 300 g/ ^m2 ·day or less at a temperature of 40° C. and a relative humidity of 90% is provided between the polarizing element and the antireflection film;
An optical laminate that satisfies at least one of the above.
[2] An optical laminate having a retardation film, a polarizing element, and an antireflection film in this order,
The retardation film has a tensile modulus of elasticity at 23° C. of 3000 MPa or less,
The optical laminate has a moisture content equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20% and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%,
The following requirement (i) and the following requirement (ii):
(i) The anti-reflection film has a moisture permeability of 300 g/ ^m2 ·day or less at a temperature of 40° C. and a relative humidity of 90%;
(ii) a protective film having a moisture permeability of 300 g/ ^m2 ·day or less at a temperature of 40° C. and a relative humidity of 90% is provided between the polarizing element and the antireflection film;
An optical laminate that satisfies at least one of the above.
[3] The optical laminate according to [1] or [2], further comprising a protective film between the polarizing element and the antireflection film.
[4] The polarizing plate according to any one of [1] to [3], wherein the retardation film is made of a cyclic olefin resin.
[5] The polarizing plate according to any one of [1] to [4], wherein the retardation film has an in-plane retardation value of 80 nm or more at a wavelength of 550 nm.
[6] The antireflection film includes a base film and an antireflection layer provided on a surface of the base film,
The optical laminate according to any one of [1] to [5], wherein the antireflection layer is made of a plurality of thin films having different refractive indices.
[7] The optical laminate according to [6], wherein the antireflection layer includes a thin film containing silicon dioxide (SiO ₂ ) as a main component.
[8] The optical laminate according to [6] or [7], wherein the antireflection layer includes a thin film containing niobium pentoxide (Nb ₂ O ₅ ) or titanium dioxide (TiO ₂ ) as a main component.
[9] The optical laminate according to any one of [6] to [8], wherein the antireflection layer has a thickness of 100 nm to 350 nm.
[10] The optical laminate according to any one of [6] to [9], wherein the antireflection film further has a hard coat layer provided between the base film and the antireflection layer.
[11] A display cell and the optical laminate according to any one of [1] to [10],
A display device, wherein the optical laminate is laminated on a viewing side surface of the display cell in an orientation in which the polarizing element and the anti-reflection film are disposed in this order from the display cell side.
[12] A method for producing the optical laminate according to [1],
A method for producing an optical laminate, comprising a moisture content adjusting step of adjusting the moisture content of the polarizing element so that it is equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or lower than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%.
[13] A method for producing the optical laminate according to [2],
A method for producing an optical laminate, comprising a moisture content adjusting step of adjusting the moisture content of the optical laminate to be equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or lower than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%.

The present invention provides an optical laminate that has good anti-glare function even when using an optical laminate containing a retardation film that adds functionality to an image display device, and that does not develop cracks in the retardation film even when stored for one month in an environment at a temperature of 23°C and a relative humidity of 55% after a heat durability test.

FIG. 2 is an example of a schematic cross-sectional view showing a layer structure of an optical laminate.

[Optical laminate]
The optical laminate according to the embodiment of the present invention has a retardation film, a polarizing element, and an anti-reflection film in this order. The anti-reflection film is disposed on the viewing side surface of the polarizing element. The retardation film is disposed on the surface opposite to the viewing side surface of the polarizing element. The optical laminate may have a protective film (hereinafter also referred to as "first protective film") laminated on the anti-reflection film side surface of the polarizing element, or may have a protective film (hereinafter also referred to as "second protective film") laminated on the surface opposite to the anti-reflection film side of the polarizing element. In this specification, the first protective film is a protective film laminated between the polarizing element and the anti-reflection film, and the second protective film is a protective film laminated between the polarizing element and the retardation film. In addition, in this specification, the polarizing plate refers to a laminate including a polarizing element and, in the case where the first protective film and/or the second protective film are bonded to the polarizing element, also including these.

Figure 1 is an example of a schematic cross-sectional view showing the layer structure of the optical laminate according to this embodiment. The optical laminate 100 includes a retardation film 30, a polarizing element 10, and an anti-reflection film 20, and further includes a first protective film 11 laminated on the surface of the polarizing element 10 on the anti-reflection film 20 side.

The optical laminate according to this embodiment has at least one of the following characteristics (a) and (b).
(a) The moisture content of the polarizing element is equal to or greater than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20% and is equal to or less than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%.
(b) The moisture content of the optical laminate is equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20% and is equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%.
Regarding (a) above, the moisture content of the polarizing element is preferably equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30% and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 45%. The moisture content of the polarizing element is more preferably equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30% and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 40%.
Regarding (b) above, the moisture content of the optical laminate is preferably equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30%, and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 45%. The moisture content of the optical laminate is more preferably equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30%, and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 40%.

The optical laminate satisfies at least one of the following requirement (i) and the following requirement (ii).
(i) The anti-reflection film has a moisture permeability of 300 g/m ² ·day or less at a temperature of 40° C. and a relative humidity of 90%.
(ii) Between the polarizing element and the antireflection film, there is a protective film having a moisture permeability of 300 g/m ² ·day or less at a temperature of 40° C. and a relative humidity of 90%.
Satisfying the above requirement (ii) is equivalent to satisfying the following requirement (iia).
(iia) A first protective film having a moisture permeability of 300 g/m ² ·day or less at a temperature of 40° C. and a relative humidity of 90% is laminated on the surface of the polarizing element on the antireflection film side.

In the optical laminate of this embodiment, the moisture content of the polarizing element is within the above range, and at least one of the above requirements (i) and (ii) is satisfied, so that no cracks (cracks) occur in the retardation film after a heat durability test (105°C for 500 hours), and furthermore, even when stored for about one month in an environment at a temperature of 23°C and a relative humidity of 55%, the occurrence of cracks in the retardation film can be suppressed. Although the detailed mechanism is unknown, it is believed that this is because the moisture permeability of the anti-reflection film and the first protective film is set within a predetermined range, which suppresses moisture transfer to the polarizing element and suppresses dimensional changes during storage, thereby suppressing the occurrence of cracks in the retardation film.

<Polarizing element>
The polarizing element may be a polarizing element formed by adsorbing and orienting a dichroic dye in a layer containing a polyvinyl alcohol (hereinafter also referred to as "PVA")-based resin (also referred to as a "PVA-based resin layer" in this specification). Examples of such polarizing elements include a polarizing element formed by using a PVA-based resin film, dyeing the PVA-based resin film with a dichroic dye, and uniaxially stretching the film, and a polarizing element formed by using a laminated film obtained by applying a coating liquid containing a PVA-based resin onto a base film, dyeing the PVA-based resin layer, which is a coating layer of the laminated film, with a dichroic dye, and uniaxially stretching the laminated film.

The polarizing element is made of a PVA-based resin obtained by saponifying a polyvinyl acetate-based resin. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate and other monomers that can be copolymerized with it. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

The degree of saponification of the PVA-based resin is preferably about 85 mol% or more, more preferably about 90 mol% or more, and even more preferably about 99 mol% to 100 mol%. The degree of polymerization of the PVA-based resin is 1000 to 10000, preferably 1500 to 5000. This PVA-based resin may be modified, for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc. modified with aldehydes.

The thickness of the polarizing element in this embodiment is preferably 5 to 50 μm, more preferably 5 to 30 μm, and even more preferably 8 to 25 μm. By making the thickness of the polarizing element 50 μm or less, it is possible to suppress the effect of polyenation of the PVA-based resin on the deterioration of optical properties in a high-temperature environment, and by making the thickness of the polarizing element 5 μm or more, it is easy to configure it to achieve the desired optical properties.

The luminosity-corrected single transmittance of the polarizing element is preferably 38.8% to 44.8%, more preferably 40.4% to 43.2%, and even more preferably 40.7% to 43.0%. If the luminosity-corrected single transmittance exceeds 44.8%, the optical properties may deteriorate significantly, such as turning red in a high-temperature environment, while if the luminosity-corrected single transmittance is less than 38.8%, polyenization may easily progress in a high-temperature environment, resulting in significant deterioration of the optical properties.

The luminosity-corrected single transmittance can be determined by measuring the luminosity-corrected Y value using a 2-degree visual field (C light source) as specified in JIS Z8701-1982. The luminosity-corrected single transmittance can be easily measured using, for example, a spectrophotometer (model number: V7100) manufactured by JASCO Corporation.

(Feature (a))
In the case of having the characteristic (a), the moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20% and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%. Preferably, the moisture content is equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30% and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 45%. More preferably, the moisture content is equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 42%, even more preferably, the equilibrium moisture content is equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 40%, and most preferably, the equilibrium moisture content is equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 38%. If the moisture content is lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20%, the handling property of the polarizing element is reduced and it becomes easy to crack. By being equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%, it is possible to provide an optical laminate having excellent wet heat durability and high temperature durability. It is presumed that if the moisture content of the polarizing element is high, the PVA-based resin contained in the polarizing element is easily polyenated. The moisture content of the polarizing element is the moisture content of the polarizing element in the optical laminate.

Methods for checking whether the moisture content of a polarizing element is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48% include storing the polarizing element for a certain period of time in an environment adjusted to the above temperature and relative humidity ranges and checking that there is no change in mass, or calculating in advance the equilibrium moisture content of the polarizing element in an environment adjusted to the above temperature and relative humidity ranges and comparing the moisture content of the polarizing element with the pre-calculated equilibrium moisture content. If there is no change in the mass of a polarizing element after storing it for a certain period of time, it can be considered that the moisture content has reached equilibrium in the storage environment.

Methods for producing a polarizing element having a moisture content equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48% are not particularly limited, but examples include a method in which the polarizing element is stored in an environment adjusted to the above temperature and relative humidity range for 10 minutes to 3 hours, or a method in which the polarizing element is heat-treated at 30°C to 90°C.

Another preferred method for producing a polarizing element having the above moisture content is to store a laminate in which a protective film is laminated on at least one side of a polarizing element, or a laminate constructed using a polarizing element, in an environment adjusted to the above temperature and relative humidity ranges for 10 minutes to 120 hours, or to heat treat the laminate at 30°C to 90°C. When producing an image display device, an image display panel in which an optical laminate is laminated on an image display cell can be stored in an environment adjusted to the above temperature and relative humidity ranges for 10 minutes to 3 hours, or to heat treat the image display panel at 30°C to 90°C.

The moisture content of the polarizing element is preferably adjusted to be within the above numerical range at the material stage used to construct the optical laminate, which is a polarizing element alone or a laminate of a polarizing element and a protective film. If the moisture content is adjusted after the optical laminate is constructed, curling may become too large, which may lead to problems when the optical laminate is attached to an image display cell. By constructing the optical laminate using a polarizing element that has been adjusted to have the above moisture content at the material stage before the optical laminate is constructed, an optical laminate including a polarizing element whose moisture content satisfies the above numerical range can be easily constructed. The moisture content of the polarizing element in the optical laminate may be adjusted to be within the above numerical range when the optical laminate is attached to the image display cell. In this case, the optical laminate is less likely to curl because it is attached to the image display cell.

(Feature (b))
In the case of having the characteristic (b), the moisture content of the optical laminate is equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20% and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%. Preferably, the moisture content is equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30% and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 45%. More preferably, the moisture content is equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 42%, even more preferably, the equilibrium moisture content is equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 40%, and most preferably, the equilibrium moisture content is equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 38%. If the moisture content of the optical laminate is lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20%, the optical laminate is less easy to handle and is more likely to crack. If the moisture content of the optical laminate is higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%, the transmittance of the polarizing element is more likely to decrease. It is presumed that if the moisture content of the optical laminate is high, the polyenation of the PVA-based resin is more likely to proceed.

Methods for checking whether the moisture content of the optical laminate is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48% include storing the optical laminate for a certain period of time in an environment adjusted to the above temperature and relative humidity ranges and checking that there is no change in mass, or calculating in advance the equilibrium moisture content of the optical laminate in an environment adjusted to the above temperature and relative humidity ranges and comparing the moisture content of the optical laminate with the pre-calculated equilibrium moisture content. If there is no change in mass after storing the optical laminate for a certain period of time, it can be considered that the moisture content has reached equilibrium in the storage environment.

Methods for producing an optical laminate having a moisture content equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48% are not particularly limited, but examples include a method in which the optical laminate is stored in an environment adjusted to the above temperature and relative humidity range for 10 minutes to 3 hours, or a method in which the optical laminate is heated at 30°C to 90°C.

When producing an image display device, an image display panel in which the optical laminate is laminated on an image display cell may be stored in an environment adjusted to the above temperature and relative humidity range for 10 minutes to 3 hours or may be heat-treated at 30°C to 90°C.

(Method of manufacturing polarizing element)
The method for producing the polarizing element is not particularly limited, but typical methods include a method in which a polyvinyl alcohol-based resin film that has been previously wound into a roll is sent out and stretched, dyed, crosslinked, and the like to produce the polarizing element (hereinafter referred to as "production method 1"), and a method including a step of applying a coating liquid containing a polyvinyl alcohol-based resin onto a substrate film to form a polyvinyl alcohol-based resin layer as a coating layer, and stretching the resulting laminate (hereinafter referred to as "production method 2").

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

The swelling process is a treatment process in which the polyvinyl alcohol-based resin film is immersed in a swelling bath. This process can remove dirt and blocking agents from the surface of the polyvinyl alcohol-based resin film, and can also suppress uneven dyeing by swelling the polyvinyl alcohol-based resin film. The swelling bath usually uses a medium whose main component is water, distilled water, pure water, or other water. The swelling bath may contain surfactants, alcohol, and the like, as appropriate, according to conventional methods.

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

The dyeing process is a process in which the polyvinyl alcohol resin film is immersed in a dye bath (iodine solution), and dichroic substances such as iodine or dichroic dyes can be adsorbed and oriented in the polyvinyl alcohol resin film. The iodine solution is usually preferably an aqueous iodine solution, and contains iodine and an iodide as a dissolving aid. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Among these, potassium iodide is preferred from the viewpoint of controlling the potassium content in the polarizing element.

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

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

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

In the crosslinking bath, the concentration of the boron compound is preferably about 1 to 15% by weight, more preferably about 1.5 to 10% by weight, and even more preferably about 2 to 5% by weight. In addition, when potassium iodide is used in the crosslinking bath, the concentration of potassium iodide in the crosslinking bath is preferably about 1 to 15% by weight, more preferably about 1.5 to 10% by weight, and even more preferably about 2 to 5% by weight.

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

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

In the wet stretching method, the treatment bath (stretching bath) can usually use water or a solvent such as a mixed solution of water and an organic solvent miscible with water. The stretching bath preferably contains potassium iodide from the viewpoint of controlling the potassium content in the polarizing element. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably about 1 to 15% by weight, more preferably about 2 to 10% by weight, and more preferably about 3 to 6% by weight. In addition, the treatment bath (stretching bath) can contain a boron compound from the viewpoint of suppressing film breakage during stretching. In this case, the concentration of the boron compound in the stretching bath is preferably about 1 to 15% by weight, more preferably about 1.5 to 10% by weight, and more preferably about 2 to 5% by weight.

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

Examples of dry stretching methods include roll-to-roll stretching, heated roll stretching, and compression stretching. The dry stretching method may be carried out together with a drying process.

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

The cleaning process is a process in which the polyvinyl alcohol-based resin film is immersed in a cleaning bath, and foreign matter remaining on the surface of the polyvinyl alcohol-based resin film can be removed. The cleaning bath usually uses a medium whose main component is water, such as distilled water or pure water. In addition, from the viewpoint of controlling the potassium content in the polarizing element, it is preferable to use potassium iodide in the cleaning bath. In this case, the concentration of potassium iodide in the cleaning bath is preferably about 1 to 10% by weight, more preferably about 1.5 to 4% by weight, and even more preferably about 1.8 to 3.8% by weight.

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

The drying process is a process in which the polyvinyl alcohol-based resin film cleaned in the cleaning process is dried to obtain a polarizing element. The drying process can be carried out by any suitable method, such as natural drying, air drying, or heat drying.

The manufacturing method 2 can be produced through the steps of applying a coating liquid containing the polyvinyl alcohol resin onto a substrate film, uniaxially stretching the resulting laminated film, dyeing the polyvinyl alcohol resin layer of the uniaxially stretched laminated film with a dichroic dye to adsorb the dichroic dye to form a polarizing element, treating the film with the adsorbed dichroic dye with an aqueous boric acid solution, and washing with water after the treatment with the aqueous boric acid solution. The substrate film used to form the polarizing element may be used as a protective layer for the polarizing element. If necessary, the substrate film may be peeled off and removed from the polarizing element.

(Retardation film)
The retardation film used has a tensile modulus of elasticity of 3000 MPa or less at 23° C. Even with a retardation film having such a tensile modulus, cracks can be prevented according to the present invention. The lower limit of the tensile modulus of elasticity at 23° C. is not particularly limited, but can be, for example, 1000 MPa or more. For example, an olefin resin can be used as the material for such a retardation film. The olefin resin is a resin consisting of structural units derived from chain aliphatic olefins such as ethylene and propylene, or alicyclic olefins such as norbornene and its substitutes (hereinafter, these are also collectively referred to as norbornene monomers). The olefin resin may be a copolymer using two or more monomers.

Among them, olefin resins are preferably cyclic olefin resins, which are resins mainly containing structural units derived from alicyclic olefins. A typical example of an alicyclic olefin constituting a cyclic olefin resin is a norbornene monomer. Norbornene is a compound in which one carbon-carbon bond of norbornane becomes a double bond, and is named bicyclo[2,2,1]hept-2-ene according to the IUPAC nomenclature system. Examples of norbornene substitutions include 3-substitutions, 4-substitutions, and 4,5-disubstitutions, with the double bond positions of norbornene at the 1,2-positions, and further include dicyclopentadiene and dimethanooctahydronaphthalene.

The cyclic olefin resin may or may not have a norbornane ring in its constituent units. Norbornene monomers forming cyclic olefin resins that do not have a norbornane ring in their constituent units include, for example, those that become five-membered rings by ring opening, typically norbornene, dicyclopentadiene, 1- or 4-methylnorbornene, and 4-phenylnorbornene. When the cyclic olefin resin is a copolymer, the molecular arrangement is not particularly limited, and it may be a random copolymer, a block copolymer, or a graft copolymer.

More specific examples of cyclic olefin resins include ring-opening polymers of norbornene monomers, ring-opening copolymers of norbornene monomers and other monomers, polymer modifications obtained by adding maleic acid or cyclopentadiene to these, and polymers or copolymers obtained by hydrogenating these; addition polymers of norbornene monomers, and addition copolymers of norbornene monomers and other monomers. Examples of other monomers used in copolymerization include α-olefins, cycloalkenes, and non-conjugated dienes. The cyclic olefin resin may also be a copolymer using one or more of norbornene monomers and other alicyclic olefins.

Among the above specific examples, the cyclic olefin resin is preferably a resin obtained by hydrogenating a ring-opening polymer or ring-opening copolymer using a norbornene monomer. Such a cyclic olefin resin is made into a film-like material that has been subjected to a stretching process in advance, and a shrinkable film having a predetermined shrinkage rate is laminated to this and heat-shrunk, thereby providing a retardation film with high uniformity and a large retardation value.

Commercially available cyclic olefin resins using such norbornene monomers include "Zeonex" and "Zeonor" sold by Zeon Corporation, and "Arton" sold by JSR Corporation. Films and stretched films of these cyclic olefin resins are also available commercially, such as "Zeonor Film" from Optes Corporation, "Arton Film" from JSR Corporation, and "S-Cina" from Sekisui Chemical Co., Ltd.

In addition, the retardation film used in the present invention may be a film made of a mixed resin containing two or more types of olefin resins, or a film made of a mixed resin of an olefin resin and another thermoplastic resin. For example, a mixed resin containing two or more types of olefin resins may be a mixture of a cyclic olefin resin and a chain aliphatic olefin resin as described above. When using a mixed resin of an olefin resin and another thermoplastic resin, the other thermoplastic resin is appropriately selected depending on the purpose. Specific examples include polyvinyl chloride resins, cellulose resins, polystyrene resins, acrylonitrile/butadiene/styrene copolymer resins, acrylonitrile/styrene copolymer resins, (meth)acrylic resins, polyvinyl acetate resins, polyvinylidene chloride resins, polyamide resins, polyacetal resins, polycarbonate resins, modified polyphenylene ether resins, polybutylene terephthalate resins, polyethylene terephthalate resins, polyphenylene sulfide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polyarylate resins, liquid crystal resins, polyamideimide resins, polyimide resins, and polytetrafluoroethylene resins. These thermoplastic resins can be used alone or in combination of two or more. The thermoplastic resins can also be used after any suitable polymer modification. Examples of polymer modification include copolymerization, crosslinking, molecular end modification, and stereoregularity impartation.

When a mixed resin of an olefin resin and another thermoplastic resin is used, the content of the other thermoplastic resin is usually about 50% by weight or less, and preferably about 40% by weight or less, based on the total resin. By keeping the content of the other thermoplastic resin within this range, it is possible to obtain a retardation film that has a small absolute value of the photoelastic coefficient, exhibits good wavelength dispersion characteristics, and is excellent in durability, mechanical strength, and transparency.

Such olefin resins can be formed into films by casting from a solution or melt extrusion. When forming a film from a mixture of two or more resins, the film formation method is not particularly limited, and examples of methods that can be used include a method in which a film is formed by casting a homogeneous solution obtained by stirring and mixing the resin components with a solvent in a specified ratio, and a method in which the resin components are melt mixed in a specified ratio and then melt extrusion is used to form a film.

The retardation film may contain other components such as residual solvents, stabilizers, plasticizers, antioxidants, antistatic agents, and ultraviolet absorbers as necessary, within the scope of the present invention. It may also contain a leveling agent to reduce surface roughness.

The retardation film used in the present invention is preferably applied to one having an in-plane retardation value of 80 nm or more at a wavelength of 550 nm. The in-plane retardation value at a wavelength of 550 nm may be, for example, 300 nm or less, or 200 nm or less. Even if it has such a high retardation value, the retardation film does not crack even if it is stored for one month in an environment at a temperature of 23°C and a relative humidity of 55% after a heat durability test. In general, the higher the retardation value, the more aligned the molecular orientation of the retardation film is, and the more likely it is that cracks will occur when subjected to external forces.

The above-mentioned retardation film can be obtained by known methods such as longitudinal uniaxial stretching, tenter transverse uniaxial stretching, simultaneous biaxial stretching, and sequential biaxial stretching. In addition to appropriately adjusting the stretching ratio and stretching speed so as to obtain the desired retardation value, various temperatures during stretching, such as the preheating temperature, stretching temperature, heat setting temperature, and cooling temperature, and their patterns can be appropriately selected.

The thickness of the retardation film is not particularly limited, but is preferably within the range of 15 to 80 μm, more preferably within the range of 18 to 45 μm, and most preferably within the range of 20 to 30 μm. If the thickness of the norbornene-based resin film is less than 15 μm, the film tends to be difficult to handle and to exhibit a predetermined retardation value, while if the thickness of the norbornene-based resin film exceeds 80 μm, the film may be poor in processability, the transparency may decrease, and the weight of the obtained polarizing plate may increase.

(Other functional layers)
The polarizing plate of the present invention may have other functional layers such as an antistatic layer or a second retardation layer. For example, when used in an IPS mode liquid crystal display device, a positive C plate may be used as the second retardation layer. The positive C plate may be laminated between the polarizing element and the retardation film, or may be laminated on the surface of the retardation film opposite to the polarizing element side.

<Anti-reflection film>
The anti-reflective film has an anti-reflective function of reducing the reflectance of light incident from the viewing side surface of the optical laminate. The optical laminate has an anti-reflective film to prevent contrast reduction due to reflection of external light. In order to satisfy the above requirement (i), an anti-reflective film having a moisture permeability of 300 g/m ² ·day or less, preferably 100 g/m ² ·day or less at a temperature of 40% and a relative humidity of 90% can be used as the anti-reflective film. The moisture permeability of the anti-reflective film is a value measured according to the method described in the examples below. By using such an anti-reflective film with low moisture permeability, it is possible to improve the durability against moist heat and high temperature. The moisture permeability of the anti-reflective film can be adjusted by the material and thickness of the anti-reflective layer, the material and thickness of the substrate film, etc. The moisture permeability of the anti-reflective film at a temperature of 40% and a relative humidity of 90% is usually 1 g/m ² ·day or more.

The anti-reflection film may be, for example, a film having an anti-reflection layer on one side of a substrate film. There are no particular limitations on the substrate film, but it may be made of the same material as that used for the protective film described below.

The anti-reflective film may be a known anti-reflective film or a commercially available anti-reflective film, for example, the following:

(a) An anti-reflection film using the principle of the so-called moth-eye structure, which is made of an uneven pattern in which the period of the unevenness is controlled to be equal to or less than the wavelength of visible light (anti-reflection films described in JP 2010-122599 A, JP 2001-517319 A, JP 2004-205990 A, JP 2004-287238 A, JP 2001-27505 A, JP 2002-286906 A, WO 2006/059686, etc.). As a commercially available product, for example, Mosmite (registered trademark, manufactured by Mitsubishi Chemical Corporation) can be used.
(b) Antireflection films consisting of fine concave-convex patterns that exhibit optical functions (antireflection films described in JP-A-2004-59822, JP-B-5-46064, JP-B-6-85103, etc.).
(c) An anti-reflection film having an uneven pattern composed of countless minute unevennesses with a pitch equal to or less than the wavelength of light (anti-reflection films described in JP-A-2001-264520, JP-A-9-80205, etc.).
(d) Antireflection films having a single layer or multiple layers with an adjusted refractive index (antireflection films described in JP-A-2000-187102, JP-A-6-186401, JP-A-2004-345333, etc.). Commercially available products include, for example, MTAR and MTAGAR (manufactured by Mitate Co., Ltd.).
The thickness of the anti-reflection film is, for example, not less than 10 μm and not more than 100 μm.

An anti-reflection film is preferably a thin film with a strictly controlled thickness and refractive index, or an anti-reflection layer consisting of two or more thin films stacked together. In this specification, a thin film refers to a film with a thickness of 1 μm or less. The anti-reflection layer can be configured to exhibit an anti-reflection function by canceling out the inverted phases of incident light and reflected light using the interference effect of light. The wavelength region of visible light that exhibits the anti-reflection function is, for example, 380 to 780 nm, and the wavelength region with particularly high visibility is the range of 450 to 650 nm. It is preferable to design the anti-reflection layer so that the reflectance at the center wavelength of 550 nm is minimized. The thickness of the anti-reflection layer is preferably 100 nm to 350 nm, and more preferably 150 nm to 300 nm.

In designing an anti-reflection layer based on the interference effect of light, a method for improving the interference effect is, for example, to increase the difference in refractive index between the anti-reflection layer and the anti-glare hard coat layer described later. In general, in a multi-layer anti-reflection layer having a structure in which 2 to 15 thin films (thin films with strictly controlled thickness and refractive index) are laminated, the degree of freedom in the optical design of the anti-reflection layer is increased by forming multiple layers of components with different refractive indexes to a predetermined thickness, and the anti-reflection effect can be improved and the spectral reflection characteristics can be made uniform (flat) in the visible light range. Since high thickness accuracy is required for thin films, each layer is generally formed by a dry method such as vacuum deposition, sputtering, or CVD. Since the moisture permeability is set within a predetermined range, it is preferable to use sputtering. In addition, by using an anti-reflection film in which each layer is formed by sputtering, an optical laminate with high scratch resistance can be constructed.

As the anti-reflection layer, a layer in which low refractive index layers and high refractive index layers are alternately laminated is preferably used. The high refractive index layers or the low refractive index layers do not have to have the same refractive index, but it is preferable from the viewpoint of reducing material costs and film formation costs to use the same material and have the same refractive index.

Examples of materials constituting the low refractive index layer (or materials that are the main components of the low refractive index layer) include silicon dioxide (SiO ₂ ), silicon oxynitride (SiON), gallium oxide (Ga ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ), lanthanum fluoride (LaF ₃ ), magnesium fluoride (MgF ₂ ), sodium aluminum fluoride (Na ₃ AlF ₆ ), etc. Among these, silicon dioxide (SiO ₂ ) is the most preferable because of its low refractive index, lack of absorption in the visible light range, high film strength, etc.

Examples of materials constituting the high refractive index layer (or materials that are the main components of the high refractive index layer) include niobium pentoxide (Nb ₂ O ₅ ), titanium dioxide (TiO ₂ ), zirconium dioxide (ZrO ₂ ), tantalum pentoxide (Ta ₂ O ₅ ), silicon oxynitride (SiON), silicon nitride (Si ₃ N ₄ ), and niobium silicon oxide (SiNbO). Among these, niobium pentoxide (Nb ₂ O ₅ ) or titanium dioxide (TiO ₂ ) is more preferred due to its high refractive index and high film strength, and niobium pentoxide (Nb ₂ O ₅ ) is most preferred due to its lack of absorption in the visible light region.

The refractive index of any compound can be changed to some extent by controlling the composition ratio of the constituent elements so that it deviates from the stoichiometric composition ratio, or by controlling the film formation density. Note that the materials constituting the low reflectance layer and the high reflectance layer are not limited to the above compounds, as long as they satisfy the above-mentioned refractive index conditions. In addition, unavoidable impurities may be included.

The anti-reflection film may have a hard coat layer between the substrate film and the anti-reflection layer. The provision of the hard coat layer can improve the mechanical properties of the anti-reflection layer, such as hardness and elastic modulus. The hard coat layer preferably has high surface hardness and excellent scratch resistance. The hard coat layer can be formed, for example, by applying a solution containing a curable resin onto the substrate film.

Examples of curable resins include thermosetting resins, ultraviolet curing resins, and electron beam curing resins. Types of curable resins include polyester resins, acrylic resins, urethane resins, acrylic urethane resins, amide resins, silicone resins, silicate resins, epoxy resins, melamine resins, oxetane resins, and acrylic urethane resins. One or more of these curable resins can be appropriately selected and used.

Among these, acrylic resins, acrylic urethane resins, and epoxy resins are preferred because they have high hardness, can be cured with ultraviolet light, and have excellent productivity, and among these, acrylic urethane resins are preferred. UV-curable resins include UV-curable monomers, oligomers, polymers, and the like. Preferred UV-curable resins include those that have a UV-polymerizable functional group, and in particular those that contain an acrylic monomer or oligomer having two or more, particularly 3 to 6, functional groups as a component.

In order to provide the anti-reflective film with anti-glare and anti-glare properties, it is preferable that the hard coat layer provided on the surface of the substrate film has anti-glare properties. Examples of anti-glare hard coat layers include those in which fine particles are dispersed in the above-mentioned curable resin matrix. As fine particles to be dispersed in the resin matrix, there are no particular limitations on the types of fine particles that can be used, such as various metal oxide fine particles such as silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide, glass fine particles, crosslinked or uncrosslinked organic fine particles made of various transparent polymers such as polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, melamine, and polycarbonate, and silicone fine particles, which have transparency. These fine particles can be used by appropriately selecting one or more types. Among them, fine particles with a higher refractive index than the matrix resin are preferable, and for example, organic fine particles with a refractive index of 1.5 or more such as styrene beads (refractive index 1.59) are preferable. The average particle size of the fine particles is preferably 1 to 10 μm, more preferably 2 to 5 μm. There are no particular restrictions on the proportion of microparticles, but a ratio of 6 to 20 parts by weight per 100 parts by weight of matrix resin is preferred.

The hard coat layer can be formed, for example, by applying a solution containing a curable resin onto a substrate film. The solution for forming the hard coat layer preferably contains an ultraviolet polymerization initiator. To form an anti-glare hard coat layer containing fine particles, it is preferable to apply a solution containing the above-mentioned fine particles in addition to the curable resin onto a transparent film. The solution may contain additives such as a leveling agent, a thixotropic agent, and an antistatic agent. In forming the anti-glare hard coat layer, by adding a thixotropic agent (silica, mica, etc. with a particle diameter of 0.1 μm or less) to the solution, a fine uneven structure due to protruding particles can be easily formed on the surface of the hard coat layer.

The thickness of the hard coat layer is not particularly limited, but in order to achieve high hardness, it is preferably 0.5 μm or more, and more preferably 1 μm or more. In consideration of ease of formation by coating, the thickness of the hard coat layer is preferably 15 μm or less, more preferably 12 μm or less, and even more preferably 10 μm or less. In addition, in order to maintain high moisture permeability of the film substrate so as not to prevent the release of moisture from the polarizing element to the outside, it is preferable that the thickness of the hard coat layer is within the above range.

The arithmetic mean roughness Ra of the surface of the substrate film on the side on which the anti-reflection layer is formed is preferably 1.5 nm or less, more preferably 1.0 nm or less. The arithmetic mean roughness Ra may be 0.00 nm or more, or may be 0.05 nm or more. When a hard coat layer is formed on the substrate film, the arithmetic mean roughness of the hard coat layer is the arithmetic mean roughness of the surface of the substrate film on the side on which the anti-reflection layer is formed. The arithmetic mean roughness Ra is determined from an observation image of 1 μm square using an atomic force microscope (AFM).

As described above, by forming a hard coat layer by coating, the arithmetic mean roughness of the surface of the substrate film can be reduced. If the surface of the substrate film is smooth, the arithmetic mean roughness of the surface of the antireflection layer formed thereon will also be small, and the scratch resistance of the antireflection film will tend to improve.

<Protective film>
The protective film is not particularly limited, but is preferably made of a material excellent in transparency, mechanical strength, thermal stability, moisture shielding property, and phase difference value stability, etc. The material of the protective film is not particularly limited, but examples thereof include films made of methyl methacrylate resin, polyolefin resin, cyclic olefin resin, polyvinyl chloride resin, cellulose resin, styrene resin, acrylonitrile-butadiene-styrene resin, acrylonitrile-styrene resin, polyvinyl acetate resin, polyvinylidene chloride resin, polyamide resin, polyacetal resin, polycarbonate resin, modified polyphenylene ether resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polysulfone resin, polyethersulfone resin, polyarylate resin, polyamideimide resin, and polyimide resin.

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

The cellulose-based resin may be an organic acid ester or mixed organic acid ester of cellulose in which some or all of the hydrogen atoms in the hydroxyl groups of cellulose are replaced with acetyl groups, propionyl groups, and/or butyryl groups. Examples include cellulose acetate, propionate, butyrate, and mixed esters thereof. Among these, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate, and the like are preferred.

These resins may contain suitable additives as long as the transparency is not impaired. Examples of additives include antioxidants, UV absorbers, antistatic agents, lubricants, nucleating agents, antifogging agents, antiblocking agents, retardation reducing agents, stabilizers, processing aids, plasticizers, impact resistance aids, matting agents, antibacterial agents, and fungicides. A combination of these additives may be used.

The thickness of the protective film is usually 1 to 100 μm, but from the viewpoints of strength, ease of handling, etc., it is preferably 5 to 60 μm, more preferably 10 to 55 μm, and even more preferably 15 to 50 μm.

The protective film may also have other optical functions, and may be formed into a laminated structure in which multiple layers are laminated. From the viewpoint of optical properties, it is preferable that the thickness of the protective film is thin, but if it is too thin, the strength decreases and the processability becomes poor. The appropriate thickness is 5 to 100 μm, preferably 10 to 80 μm, and more preferably 15 to 70 μm.

In the case of a configuration in which protective films are provided on both sides of a polarizing element, when bonding is performed using a water-based adhesive such as a PVA adhesive, it is preferable that the protective film on at least one side is either a cellulose acylate film or a (meth)acrylic polymer film in terms of moisture permeability, and of these, a cellulose acylate film is preferred.

The first protective film and the second protective film may be the same or different. The first protective film and the second protective film may have a surface treatment layer (coating layer) such as an antistatic layer on their outer surfaces (the surfaces opposite the polarizing element). The thickness of the first protective film and the second protective film includes the thickness of the surface treatment layer.

In order to satisfy the above requirement (ii), a protective film having a moisture permeability of 300 g/ ^m2 ·day or less at a temperature of 40° C. and a relative humidity of 90% can be used as the first protective film. The moisture permeability of the protective film can be adjusted by the material, thickness, etc. As a protective film having a moisture permeability of 300 g/ ^m2 ·day or less at a temperature of 40° C. and a relative humidity of 90%, a cyclic olefin resin film, a film laminated with a water vapor barrier layer by a dry method, etc. are preferably used.

On the other hand, when the anti-reflection film satisfies the above requirement (i) and has a moisture permeability of 100 g/ ^m2 ·day or less at a temperature of 40°C and a relative humidity of 90%, it is preferable that the second protective film has a moisture permeability of 200 g/ ^m2 ·day or more at a temperature of 40°C and a relative humidity of 90%.
In producing an optical laminate, as described below, the second protective film may be laminated to the polarizing element 10 using a laminating agent (adhesive or pressure sensitive adhesive) such as a water-based adhesive, and then a laminating layer may be formed by a drying process, and then the first protective film may be laminated. In this case, by setting the moisture permeability of the protective film laminated on the retardation film side of the polarizing element to the above range, moisture contained in the laminating agent can be easily removed by the drying process.

At least one of the protective films may have a retardation function for the purpose of compensating for viewing angle, etc. In that case, the film itself may have a retardation function, may have a separate retardation layer, or may have a combination of both.
The film having a retardation function may be attached to the polarizing element via a pressure-sensitive adhesive layer or an adhesive layer via another protective film that is attached to the polarizing element.

<Laminating layer>
In the optical laminate, a bonding layer is used to bond the layers together. Examples of the bonding layer include an adhesive layer and a pressure-sensitive adhesive layer.

(adhesive layer)
The adhesive layer can be used, for example, to attach a protective film to a polarizing element. Any appropriate adhesive can be used as the adhesive constituting the adhesive layer. The adhesive can be a water-based adhesive, a solvent-based adhesive, an active energy ray curing adhesive, or the like, but a water-based adhesive is preferred.

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

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

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

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

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

The water-based adhesive may also contain an organic solvent. The organic solvent is preferably an alcohol because it is miscible with water, and among alcohols, methanol or ethanol is more preferable. Some urea compounds have low solubility in water, but some have sufficient solubility in alcohol. In that case, one preferred embodiment is to dissolve the urea compound in alcohol to prepare an alcohol solution of the urea compound, and then add the alcohol solution of the urea compound to the aqueous PVA solution to prepare the adhesive.

The methanol concentration of the water-based adhesive is preferably 10% by mass or more and 70% by mass or less, more preferably 15% by mass or more and 60% by mass or less, and even more preferably 20% by mass or more and 60% by mass or less. By having a methanol concentration of 10% by mass or more, it becomes easier to suppress polyenation in a high-temperature environment. In addition, by having a methanol content of 70% by mass or less, deterioration of the hue can be suppressed.

(Active energy ray curing adhesive)
The active energy ray curable adhesive is an adhesive that is cured by irradiation with active energy rays such as ultraviolet rays, and examples thereof include an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, and an adhesive containing a binder resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, and oligomers derived from these monomers. Examples of the photopolymerization initiator include a compound containing a substance that generates active species such as neutral radicals, anion radicals, and cation radicals when irradiated with active energy rays such as ultraviolet rays.

(Adhesive Layer)
The pressure-sensitive adhesive layer can be used, for example, to attach an anti-reflection film to the first protective film.

The adhesive layer can be composed of an adhesive composition mainly composed of a resin such as a (meth)acrylic resin, a rubber resin, a urethane resin, an ester resin, a silicone resin, or a polyvinyl ether resin. Among them, an adhesive composition having a (meth)acrylic resin as a base polymer, which has excellent transparency, weather resistance, heat resistance, etc., is preferable. The adhesive composition may be of an active energy ray curing type or a heat curing type. The thickness of the adhesive layer is usually 3 to 30 μm, and preferably 3 to 25 μm.

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

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

The storage modulus of the adhesive layer is preferably 0.001 to 0.350 MPa, more preferably 0.001 to 0.200 MPa, even more preferably 0.001 to 0.180 MPa, and particularly preferably 0.010 to 0.170 MPa, at a frequency of 1 Hz and a temperature of 23°C. The storage modulus of the adhesive layer can be measured according to the method described in the Examples below.

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

As described above, in the present invention, by using an antireflection film in which each layer is formed by sputtering, an optical laminate having high scratch resistance can be formed.
In this case, by controlling the storage modulus and thickness of the adhesive layer used to attach the antireflection film to the first protective film within the following ranges, an optical laminate having high indentation hardness, represented by pencil hardness, and an antireflection layer that is less likely to crack can be formed, which is particularly preferred.

In particular, the storage modulus of the pressure-sensitive adhesive layer for bonding the first protective film and the anti-reflection film is preferably 0.050 to 0.170 MPa, more preferably 0.080 to 0.170 MPa, even more preferably 0.100 to 0.170 MPa, and particularly preferably 0.120 to 0.160 MPa.

The thickness of the adhesive layer is preferably 3 to 30 μm, more preferably 3 to 20 μm, even more preferably 3 to 10 μm, and particularly preferably 3 to 8 μm.

[Method of manufacturing optical laminate]
The method for producing an optical laminate of this embodiment includes a moisture content adjusting step. In the moisture content adjusting step, when an optical laminate having the characteristic (a) is produced, the moisture content of the polarizing element is adjusted so that the moisture content of the polarizing element is equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20%, and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%. The moisture content adjusting method of the polarizing element is as described above. In the moisture content adjusting step, when an optical laminate having the characteristic (b) is produced, the moisture content of the optical laminate is adjusted so that the moisture content of the optical laminate is equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20%, and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%. The moisture content adjusting method of the optical laminate is as described above.

As a step other than the moisture content adjustment step, a lamination step of laminating each layer may be included, such as a step of laminating a polarizing element and a protective film to obtain a polarizing plate, a step of laminating a polarizing plate and an anti-reflection film, a step of laminating a polarizing plate and a retardation film, etc. The order of the moisture content adjustment step and each lamination step is not limited, and the moisture content adjustment step and the lamination step may be performed in parallel.

[Display device]
The optical laminate can be used in various display devices such as liquid crystal display devices and organic EL display devices. A display device using the optical laminate of this embodiment can be excellent in wet heat durability and high temperature durability. Since the display device using the optical laminate of this embodiment has excellent wet heat durability and high temperature durability, it can be suitably used as a display device for vehicle mounting.

The display device has a display cell and an optical laminate laminated on the viewing side surface of the display cell, and the optical laminate is laminated on the viewing side surface of the display cell in an orientation in which the retardation film, the polarizing element, and the anti-reflection film are arranged in this order from the display cell side. The display cell and the optical laminate are laminated, for example, using the above-mentioned adhesive layer.

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

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

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, parts and percentages indicating the content or amount used are based on mass unless otherwise specified. In the following examples, the physical properties were measured by the following methods.

[Measurement method]
(1) Method for Measuring Film Thickness Measurement was performed using a digital micrometer MH-15M manufactured by Nikon Corporation.

(2) Moisture Permeability of Antireflection Film In accordance with JIS K 7129:2008, Appendix B, the moisture permeability of the antireflection film was measured in an atmosphere having a temperature of 40° C. and a relative humidity of 90%.

(3) Measurement of Thickness of Each Layer of the Antireflection Layer The thickness was measured using a reflection spectroscopic film thickness meter FE3000 manufactured by Otsuka Electronics Co., Ltd.

(4) Tensile modulus at 23°C (measured in accordance with JIS K 7161)
A test piece having a width of 15 mm and a length of 150 mm was cut out from the film parallel to the slow axis and the fast axis. Then, the test piece was clamped at both ends in the long side direction with the upper and lower grips of a tensile tester [AUTOGRAPH (registered trademark) AG-1S tester manufactured by Shimadzu Corporation] so that the distance between the grips was 100 mm, and pulled at a pulling speed of 50 mm/min in an environment of 23°C, and a stress-strain curve was created, and the tensile modulus in the direction parallel to the slow axis and the fast axis at 23°C was calculated. Among the tensile moduli in the direction parallel to the slow axis and the fast axis thus calculated, the larger value was taken as the tensile modulus at 23°C in the present invention.

(5) Storage Modulus The storage modulus G' of the pressure-sensitive adhesive layer was measured according to the following (I) to (III).
(I) Two samples of 25±1 mg each were taken out of the adhesive layer, and each was molded into an approximately ball-like shape. (II) The obtained approximately ball-like samples were attached to the top and bottom surfaces of an I-shaped jig, and both the top and bottom surfaces were sandwiched between L-shaped jigs. The measurement sample was structured as follows: L-shaped jig/adhesive layer/I-shaped jig/adhesive layer/L-shaped jig. (III) The storage modulus G' of the sample thus prepared was measured using a dynamic viscoelasticity measuring device "DVA-220" manufactured by IT Measurement and Control Co., Ltd. under the conditions of a temperature of 23°C, a frequency of 1 Hz, and an initial strain of 1 N.

(A) Preparation of Polarizing Element A 75 μm thick polyvinyl alcohol film made of polyvinyl alcohol with an average degree of polymerization of about 2,400 and a degree of saponification of 99.9 mol% or more was prepared. This polyvinyl alcohol film was uniaxially stretched by about 5 times in a dry state, and further immersed in pure water at 60° C. for 1 minute while maintaining a tension state. Then, the polyvinyl alcohol film was immersed in an aqueous solution of iodine/potassium iodide/water with a weight ratio of 0.05/5/100 at 28° C. for 60 seconds. Then, the polyvinyl alcohol film was immersed in an aqueous solution of potassium iodide/boric acid/water with a weight ratio of 8.5/8.5/100 at 72° C. for 300 seconds. The polyvinyl alcohol film was subsequently washed with pure water at 26° C. for 20 seconds, and then dried at 65° C. In this way, a polarizing element with a thickness of 28 μm in which iodine was adsorbed and aligned in the polyvinyl alcohol was obtained.

(B) Preparation of Adhesive 50 g of a modified PVA-based resin containing an acetoacetyl group (GOSENEX Z-410, manufactured by Mitsubishi Chemical Corporation) was dissolved in 950 g of pure water, heated at 90° C. for 2 hours, and then cooled to room temperature to obtain a PVA solution.

The PVA solution, maleic acid, glyoxal, and pure water were mixed together to prepare a PVA-based adhesive with the following concentrations for each compound:

PVA concentration 3.0% by weight
Maleic acid 0.01% by weight
Glyoxal 0.15% by weight

(C) Saponification of cellulose acylate film A commercially available cellulose acylate film TD40 (manufactured by Fujifilm Corporation: film thickness 40 μm) was immersed in a 1.5 mol/L NaOH aqueous solution (saponification solution) kept at 55° C. for 2 minutes, and then washed with water. Thereafter, the film was immersed in a 0.05 mol/L sulfuric acid aqueous solution at 25° C. for 30 seconds, and then passed through a water washing bath under running water for 30 seconds to neutralize the film. Then, the film was drained three times with an air knife to remove water, and then was allowed to stay in a drying zone at 70° C. for 15 seconds to dry, and a saponified film was produced.
The saponified film had a moisture permeability of 850 g/m ² ·day at a temperature of 40° C. and a relative humidity of 90%.

(D) Preparation of a laminate of a retardation film and a retardation layer It was prepared according to [0106] to [0109] of International Publication No. 2018/207798. An unstretched cycloolefin polymer film (manufactured by JSR Corporation, trade name Arton Film) was uniaxially stretched to prepare a cycloolefin polymer film (tensile modulus at 23 ° C. = 2742 MPa, in-plane retardation value Re = 110 nm at a wavelength of 550 nm, retardation value Rth = 55 nm in the thickness direction at a wavelength of 550 nm, film thickness 24 μm). A composition containing a rod-shaped liquid crystal compound was applied onto this cycloolefin polymer film (retardation film), and a retardation layer which is a positive C layer (in-plane retardation value Re = 0 nm at a wavelength of 550 nm, retardation value Rth = -100 nm in the thickness direction at a wavelength of 550 nm) was formed.

(E) Preparation of Optical Laminate (Preparation of Polarizing Plate 1)
The laminate of the retardation film and the retardation layer prepared above, the polarizing element, and the saponified cellulose acylate film (first protective film) are laminated together using a PVA-based adhesive so that the absorption axis of the polarizing element and the slow axis of the retardation film are parallel to each other. At this time, the laminate of the retardation film and the retardation layer (positive C layer) is laminated so that the retardation layer (positive C layer) side is on the polarizing element side. The adhesiveness between the retardation film and the polarizing element and the adhesive strength between the cellulose acylate film and the polarizing element are sufficient for practical use.

(Measurement of Equilibrium Moisture Content)
The polarizing plate 1 obtained above was stored for 72 hours at a temperature of 20° C. and a relative humidity of 30%, 35%, 40%, 45%, or 50%, and the moisture content was measured using the Karl Fischer method after storage for 66, 69, and 72 hours. The moisture content did not change after storage for 66, 69, and 72 hours under any humidity condition. Therefore, the moisture content of the polarizing plate 1 can be considered to be the same as the equilibrium moisture content of the storage environment. When the moisture content of the polarizing plate reaches equilibrium at a certain storage temperature, the moisture content of the polarizing element in the polarizing plate can also be considered to have reached equilibrium at that storage temperature. In addition, when the moisture content of the polarizing element in the polarizing plate reaches equilibrium in a certain storage environment, the moisture content of the polarizing plate can also be considered to have reached equilibrium in that storage environment.

The moisture content of the polarizing plate 1 obtained above immediately after drying was measured by the Karl Fischer method and compared with the above equilibrium moisture content. The moisture content of polarizing plate 1 was equivalent to the moisture content at a temperature of 20°C and a relative humidity of 40%. Polarizing plate 1 was further stored for 72 hours under conditions of a temperature of 20°C and a relative humidity of 40%.

(F) Preparation of Anti-Reflection Film (Preparation of Anti-Glare Hard Coat Film)
A solution of 40% by weight of solid content obtained by mixing 50 parts by weight of ultraviolet-curing urethane acrylate monomer (refractive index 1.51), 50 parts by weight of ultraviolet-curing acrylate monomer (refractive index 1.51), 14 parts by weight of methyl methacrylate-styrene copolymer beads (refractive index 1.55) having an average particle size of 3.5 μm, 5 parts by weight of benzophenone-based photopolymerization initiator, and toluene was applied onto a 40 μm-thick triacetyl cellulose film (refractive index 1.49) and dried at 120° C. for 5 minutes. Then, a curing treatment was performed by ultraviolet irradiation to form an anti-glare hard coat layer having a thickness of about 4 μm and an uneven structure on the surface, and an anti-glare hard coat film was produced. The arithmetic mean roughness Ra of this anti-glare hard coat layer was 0.43 nm.

(Preparation of Antireflection Film 1)
According to the embodiment of JP 2019-035969 A, the above-mentioned antiglare hard-coated film was introduced into a roll-to-toll sputtering film-forming apparatus, and the antiglare hard-coated layer-forming surface was bombarded (plasma treatment with Ar gas) while the film was running. Then, a 5 nm SiOx layer (x<2) was formed as an adhesion improving layer, and a 20 nm Nb ₂ O ₅ layer, a 35 nm SiO ₂ layer, a 35 nm Nb ₂ O ₅ layer, and a 100 nm SiO ₂ layer were sequentially formed thereon to form a 4-layer antireflection layer having a thickness of 190 nm. A fluorine-based resin was formed as an antifouling layer on the antireflection layer to a thickness of 5 nm to produce an antireflection film 1. The moisture permeability of the antireflection film 1 at a temperature of 40 ° C. and a relative humidity of 90% was 5 g / m ² · day.

(Preparation of Anti-Reflection Films 2 and 3)
The film formation conditions were changed with reference to the examples in JP 2017-227898 A, and antireflection films 2 and 3, which have different moisture permeabilities from antireflection film 1, were produced. The moisture permeabilities of antireflection films 2 and 3 at a temperature of 40° C. and a relative humidity of 90% were 10 g/ ^m2 ·day and 60 g/ ^m2 ·day, respectively.

(Preparation of Antireflection Film 4)
Antireflection film 4 was produced in the same manner as antireflection film 1, except that the antireflection layer was formed by a coating type rather than a sputtering type and that the layer structure of the antireflection layer was as follows. Antireflection film 4 had a moisture permeability of 300 g/ ^m2 ·day at a temperature of 40° C. and a relative humidity of 90%.

The antireflection layer was formed with the following three-layer structure by referring to paragraph [0105] of JP-A-2004-126220.
1st layer: Medium refractive index layer (refractive index: 1.63, film thickness: 67 nm)
2nd layer: High refractive index layer (refractive index: 1.90, film thickness: 107 nm)
3rd layer: low refractive index layer (refractive index: 1.43, film thickness: 86 nm)

(G) Preparation of Adhesive Layers Adhesive layer A: A commercially available sheet-like acrylic adhesive layer with a 38 μm PET film with a release agent attached to both sides. The adhesive layer had a thickness of 5 μm and a storage modulus of 0.14 MPa.
Adhesive layer B: a commercially available sheet-like acrylic adhesive layer having a 38 μm PET film with a release agent on both sides. The adhesive layer had a thickness of 25 μm and a storage modulus of 0.06 MPa.

[Example 1]
An adhesive layer A was attached to the surface of the antireflection film 1 prepared above, on which no antireflection layer was laminated. When these materials were attached to each other, a corona treatment was performed on the surface to be attached of each material.

Anti-reflection film 1 was laminated on the surface of the cellulose acylate film (first protective film) of polarizing plate 1 prepared above via adhesive layer A, and adhesive layer B was laminated on the surface of the retardation film to prepare the optical laminate of Example 1. When these materials were laminated together, corona treatment was performed on the lamination surface of each material. The obtained optical laminate had a layer structure of "anti-reflection film 1/adhesive layer A/polarizing plate 1/adhesive layer B/PET with release agent."

The moisture content of the obtained optical laminate was adjusted by storing it for 72 hours under the same conditions as the polarizing plate used to construct it, so that the moisture content of the optical laminate was equivalent to that of the polarizing plate used to construct it. By storing the optical laminate for 72 hours, it can be considered that it has reached equilibrium in that storage environment, and the moisture content of the polarizing plate and polarizing element in the optical laminate can also be considered to have reached equilibrium in that storage environment. Furthermore, when the moisture content of the polarizing plate or polarizing element in the optical laminate reaches equilibrium in a certain storage environment, the moisture content of the optical laminate can also be considered to have reached equilibrium in that storage environment. Therefore, the moisture content of the optical laminate is the equilibrium moisture content at a temperature of 20°C and a relative humidity of 40%.

[Examples 2 to 4]
The optical laminates of Examples 2 to 4 were produced in the same manner as in Example 1, except that in the production of the optical laminate of Example 1, the antireflection films were changed to 2 to 4. Thereafter, the moisture content of the optical laminate was adjusted to be equivalent to that of the polarizing plate used by storing it for an additional 72 hours under the same conditions as those for storing the polarizing plate for 72 hours.

[Comparative Example 1]
The pressure-sensitive adhesive layer B was attached to the retardation film surface of the polarizing plate 1 to prepare an optical laminate of Comparative Example 1. When these materials were attached to each other, a corona treatment was performed on the attachment surface of each material. The obtained optical laminate had a layer structure of "polarizing plate 1/pressure-sensitive adhesive layer B/PET with release agent".

[evaluation]
(Reflection)
The obtained optical laminate was cut to a size of 200 mm × 200 mm, and was attached to an alkali-free glass having a thickness of 0.7 mm and a size of 300 mm × 300 mm via the pressure-sensitive adhesive layer B. The pressure-sensitive adhesive layer B was laminated on the polarizing plate 1, and the plate was cut to a size of 200 mm × 200 mm, and the polarizing plate 1 was attached to the side of the alkali-free glass to which the optical laminate was not attached via the pressure-sensitive adhesive layer B so that the absorption axes of the polarizing plates were in a crossed Nicol state, thereby preparing an evaluation sample.

The evaluation sample prepared above was placed on an observation table with the anti-reflection film facing the viewing side, and was irradiated obliquely with a tabletop fluorescent lamp. The reflection in the mirror surface direction relative to the irradiation direction was evaluated according to the following criteria. The evaluation results are shown in Table 1.
A: There is no fluorescent light reflection at all.
B: The fluorescent light reflection is barely visible.
C: Fluorescent light reflections are slightly visible.
D: Fluorescent light reflections are clearly visible.

(Crack evaluation)
The evaluation sample prepared above was stored in a heating environment at a temperature of 105 ° C for 500 hours, and then cooled to 23 ° C (normal temperature). After that, it was stored in an environment at a temperature of 23 ° C and a relative humidity of 55% for 30 days (1 month), and the retardation film was visually observed to confirm whether cracks occurred. Furthermore, the retardation film was visually observed in the same manner every 30 days for a total of 360 days to confirm the presence or absence of cracks. The results are shown in Table 1.

10 Polarizing element, 11 First protective film, 20 Anti-reflection film, 30 Retardation film, 100 Optical laminate.

Claims (2)

A method for producing an optical laminate having a retardation film, a polarizing element, and an antireflection film in this order, comprising:
The retardation film has a tensile modulus of elasticity at 23° C. of 3000 MPa or less,
The retardation film has a thickness of 18 to 45 μm,
The polarizing element has a moisture content equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20% and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%,
The following requirement (i) and the following requirement (ii):
(i) The anti-reflection film has a moisture permeability of 10 g/ ^m2 ·day or less at a temperature of 40° C. and a relative humidity of 90%;
(ii) a protective film having a moisture permeability of 300 g/ ^m2 ·day or less at a temperature of 40° C. and a relative humidity of 90% is provided between the polarizing element and the antireflection film;
At least one of the following is satisfied :
A method for producing an optical laminate, comprising a moisture content adjusting step of adjusting the moisture content of the polarizing element so that it is equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or lower than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48% . A method for producing an optical laminate having a retardation film, a polarizing element, and an antireflection film in this order, comprising:
The retardation film has a tensile modulus of elasticity at 23° C. of 3000 MPa or less,
The retardation film has a thickness of 18 to 45 μm,
The optical laminate has a moisture content equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20% and equal to or lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%,
The following requirement (i) and the following requirement (ii):
(i) The anti-reflection film has a moisture permeability of 10 g/ ^m2 ·day or less at a temperature of 40° C. and a relative humidity of 90%;
(ii) a protective film having a moisture permeability of 300 g/ ^m2 ·day or less at a temperature of 40° C. and a relative humidity of 90% is provided between the polarizing element and the antireflection film;
At least one of the following is satisfied :
A method for producing an optical laminate, comprising a moisture content adjusting step of adjusting the moisture content of the optical laminate to be equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or lower than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%.

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