Optical laminate and display device

Abstract

[Problem] To provide an optical laminate including a polarizing element, suitable for a display device for automotive use, and having excellent moisture heat resistance and high temperature resistance. [Solution] An optical laminate having a polarizing element and an anti-reflective film, wherein the polarizing element has a moisture content greater than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20°C, and less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48°C, and furthermore, the following requirements (i) and (ii): (i) The above anti-reflective film has a moisture permeability of 20 g / ㎡·day or less at a temperature of 40℃ and a relative humidity of 90%. (ii) Between the polarizing element and the anti-reflective film, there is a protective film having a moisture permeability of 20 g / ㎡·day or less at a temperature of 40℃ and a relative humidity of 90%. An optical laminate satisfying at least one of the following.

Description

Technology Field

[0001] The present invention relates to an optical laminate, a display device, and a method for manufacturing an optical laminate. Background Technology

[0002] Liquid crystal display (LCD) devices are widely used not only in liquid crystal televisions but also in mobile devices such as personal computers and mobile phones, and in automotive applications such as car navigation systems. Typically, a liquid crystal display device has a liquid crystal panel member in which a polarizing plate containing a polarizing element is bonded to both sides of a liquid crystal display cell with an adhesive layer, and display is performed by controlling light from a backlight member to the liquid crystal panel member.

[0003] In addition, organic EL display devices are also being widely used recently in mobile devices such as televisions and mobile phones, and in automotive applications such as car navigation, just like liquid crystal display devices. In organic EL display devices, in order to suppress the external light from being reflected from the metal electrode (cathode) and appearing as a mirror, a circular polarizer (a laminate including a polarizing element and a λ / 4 plate, which may be simply referred to as a polarizer hereinafter) may be placed on the viewing side surface of the organic EL display cell.

[0004] As mentioned above, polarizers are increasingly being installed in vehicles as components of liquid crystal displays or organic EL displays. Compared to those used for other mobile applications such as televisions or mobile phones, polarizers used in automotive displays are frequently exposed to humid and hot environments or high-temperature environments, so they require durability against humid heat and high temperatures.

[0005] Meanwhile, when automotive display devices are used for applications such as car navigation, a touch panel function is required. Among touch panels, the proportion of on-cell and in-cell types has recently been increasing; since the polarizing plate on the viewing side is positioned at the outermost surface for these applications, an anti-reflection function is also required in addition to the aforementioned durability.

[0006] Japanese Patent Publication No. 2011-081219 (Patent Document 1) discloses the use of a glare-resistant hard coat film in which a multilayer anti-reflection layer formed by sputtering is laminated on a glare-resistant layer for the purpose of preventing external light from shining (Example 1, etc.). Prior art literature

[0007] [Patent Document 1] Japanese Patent Publication No. 2011-081219 The problem to be solved

[0008] The present invention provides an optical laminate comprising a polarizing element, which is suitable for a display device for automotive applications and has excellent moisture and heat resistance and high temperature resistance, a display device using the optical laminate, and a method for manufacturing the optical laminate. means of solving the problem

[0009] The present invention provides the following optical laminate, display device, and method for manufacturing an optical laminate.

[0010] [1] An optical laminate having a polarizing element and an anti-reflective film,

[0011] The above polarizing element has a moisture content that is greater than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%.

[0012] The following requirements (i) and (ii):

[0013] (i) The above anti-reflective film has a moisture permeability of 20 g / ㎡·day or less at a temperature of 40℃ and a relative humidity of 90%.

[0014] (ii) Between the polarizing element and the anti-reflective film, there is a protective film having a moisture permeability of 20 g / ㎡·day or less at a temperature of 40℃ and a relative humidity of 90%.

[0015] An optical laminate satisfying at least one of the following.

[0016] [2] An optical laminate having a polarizing element and an anti-reflective film,

[0017] The above optical laminate has a moisture content that is greater than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%.

[0018] The following requirements (i) and (ii):

[0019] (i) The above anti-reflective film has a moisture permeability of 20 g / ㎡·day or less at a temperature of 40℃ and a relative humidity of 90%.

[0020] (ii) Between the polarizing element and the anti-reflective film, there is a protective film having a moisture permeability of 20 g / ㎡·day or less at a temperature of 40℃ and a relative humidity of 90%.

[0021] An optical laminate satisfying at least one of the following.

[0022] [3] An optical laminate described in [1] or [2] having a protective film between the polarizing element and the anti-reflection film.

[0023] [4] The anti-reflection film comprises a base film and an anti-reflection layer formed on the surface of the base film, and

[0024] The above anti-reflection layer is composed of a plurality of thin films with different refractive indices, an optical laminate described in any 1 of [1] to [3].

[0025] [5] The above anti-reflection layer comprises a thin film having silicon dioxide (SiO2) as the main component, an optical laminate as described in [4].

[0026] [6] The above anti-reflection layer comprises a thin film having niobium pentoxide (Nb2O5) or titanium dioxide (TiO2) as the main component, an optical laminate as described in [4] or [5].

[0027] [7] The above anti-reflection layer is an optical laminate described in any one of [4] to [6], having a thickness of 100 nm to 350 nm.

[0028] [8] The above anti-reflection film is an optical laminate described in any one of [4] to [7], having a hard coat layer formed between the above-mentioned film and the above-mentioned anti-reflection layer.

[0029] [9] Having a display cell and an optical laminate described in any one of [1] to [8],

[0030] A display device in which the optical laminate is laminated on the visible side surface of the display cell in a direction arranged from the display cell side in the order of the polarizing element and the anti-reflection film.

[0031]

[10] As a method for manufacturing an optical laminate as described in [1],

[0032] A method for manufacturing an optical laminate having a moisture content adjustment process that adjusts the moisture content of the polarizing element to be greater than or equal to the equilibrium moisture content at a temperature of 20°C and relative humidity of 20%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and relative humidity of 48%.

[0033]

[11] As a method for manufacturing an optical laminate as described in [2],

[0034] A method for manufacturing an optical laminate having a moisture content adjustment process that adjusts the moisture content of the optical laminate to be greater than or equal to the equilibrium moisture content at a temperature of 20°C and relative humidity of 20%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and relative humidity of 48%. Effects of the invention

[0035] According to the present invention, an optical laminate comprising a polarizing element, which is suitable for a display device for automotive use and has excellent moisture heat durability and high temperature durability, a display device using said optical laminate, and a method for manufacturing said optical laminate can be provided. Brief explanation of the drawing

[0036] Figure 1 is an example of a schematic cross-sectional view illustrating the layer configuration of an optical laminate. Specific details for implementing the invention

[0037] [Optical Laminate]

[0038] An optical laminate according to an embodiment of the present invention comprises a polarizing element and an anti-reflective film. The anti-reflective film is disposed on the visible side surface of the polarizing element. The optical laminate may have a protective film laminated on the anti-reflective film side surface of the polarizing element (hereinafter also referred to as a "first protective film"), or a protective film laminated on the surface opposite to the anti-reflective film side of the polarizing element (hereinafter also referred to as a "second protective film"). In this specification, the first protective film is a protective film laminated between the polarizing element and the anti-reflective film. Furthermore, in this specification, a polarizing plate refers to a laminate that includes a polarizing element and, in the case of having a first protective film and / or a second protective film bonded to the polarizing element, also includes these.

[0039] FIG. 1 is an example of a schematic cross-sectional view illustrating the layer configuration of an optical laminate according to the present embodiment. The optical laminate (100) comprises a polarizing element (10) and an anti-reflection film (20), and further comprises a first protective film (11) laminated on the surface of the anti-reflection film (20) side of the polarizing element (10), and a second protective film (12) laminated on the surface opposite to the anti-reflection film (20) side of the polarizing element (10).

[0040] The optical laminate according to the present embodiment has at least one of the following features (a) and (b).

[0041] (a) The moisture content of the polarizing element is greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20%, and less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%.

[0042] (b) The moisture content of the optical laminate is greater than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%.

[0043] Regarding (a) above, the moisture content of the polarizing element is preferably greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and also less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45%. More preferably, the moisture content of the polarizing element is greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and also less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 40%.

[0044] Regarding (b) above, the moisture content of the optical laminate is preferably greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and also less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45%. More preferably, the moisture content of the optical laminate is greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and also less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 40%.

[0045] The optical laminate satisfies at least one of the following requirements (i) and (ii).

[0046] (i) The anti-reflective film has a moisture permeability of 20 g / m²·day or less at a temperature of 40°C and a relative humidity of 90%.

[0047] (ii) Between the polarizing element and the anti-reflective film, there is a protective film having a moisture permeability of 20 g / m²·day or less at a temperature of 40°C and a relative humidity of 90%.

[0048] Satisfying the above requirement (ii) means the same as satisfying the following requirement (iia).

[0049] (iia) A first protective film laminated on the surface of the anti-reflection film side of the polarizing element, having a moisture permeability of 20 g / m²·day or less at a temperature of 40°C and a relative humidity of 90°C.

[0050] The optical laminate of the present embodiment can improve moist heat durability and high temperature durability by ensuring that the water content of the polarizing element is within the range described above and by satisfying at least one of the requirements (i) and (ii). As an optical laminate with excellent moist heat durability, an optical laminate can be provided that has a small change in polarization degree before and after being left in a moist heat environment. The moist heat environment is, for example, an environment with a temperature of 85°C and a relative humidity of 85%. The evaluation of moist heat durability can be performed according to the evaluation method described in the example. As an optical laminate with excellent high temperature durability, an optical laminate can be provided that has a small change in transmittance before and after being left in a high temperature environment. The high temperature environment is, for example, an environment with a temperature of 95°C. The evaluation of high temperature durability can be performed according to the evaluation method described in the example.

[0051] Polarizing element

[0052] A polarizing element may be used in which a dichroic pigment is adsorbed and oriented on a layer containing a polyvinyl alcohol (hereinafter also referred to as "PVA")-based resin (in this specification, also referred to as a "PVA-based resin layer"). Examples of such a polarizing element include one formed by using a PVA-based resin film, dyeing the PVA-based resin film with a dichroic pigment, and uniaxially stretching it, or one formed by using a laminated film obtained by applying a coating solution containing a PVA-based resin onto a base film, dyeing the PVA-based resin layer which is the coating layer of the laminated film with a dichroic pigment, and uniaxially stretching the laminated film.

[0053] The polarizing element is formed from a PVA-based resin obtained by saponifying a polyvinyl acetate-based resin. As for the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers copolymerizable thereto may be used. Examples of other copolymerizable monomers include, for instance, unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

[0054] 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. The PVA-based resin may be modified, and may be, for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc., modified with aldehydes.

[0055] The thickness of the polarizing element of the present embodiment is preferably 5 to 50 μm, more preferably 5 to 30 μm, and even more preferably 8 to 25 μm. By having a thickness of 50 μm or less, the effect of polyenification of the PVA-based resin on the degradation of optical properties under high-temperature environments can be suppressed, and by having a thickness of 5 μm or more, it becomes easier to achieve a configuration that achieves desired optical properties.

[0056] The luminous sensitivity correction 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 luminous sensitivity correction single transmittance exceeds 44.8%, the deterioration of optical properties, such as reddening under high temperature conditions, may increase, and if the luminous sensitivity correction single transmittance is less than 38.8%, polyenification may easily proceed under high temperature conditions, leading to greater deterioration of optical properties.

[0057] The luminous sensitivity correction single transmittance can be obtained by measuring the Y value after performing luminous sensitivity correction using a 2-degree field of view (C light source) as specified in JIS Z8701-1982. The luminous sensitivity correction single transmittance can be easily measured, for example, with a spectrophotometer manufactured by Nihon Bunko Co., Ltd. (model number: V7100).

[0058] (Features (a))

[0059] In the case of having feature (a), the moisture content of the polarizing element is greater than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%. Preferably, it is greater than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45%. More preferably, it is less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 42%, even more preferably, less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 40%, and most preferably, less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 38%. If the moisture content falls below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20%, the handling properties of the polarizing element are reduced, making it prone to breakage. By having an equilibrium moisture content at or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%, an optical laminate with excellent moisture-heat durability and high-temperature durability can be provided. It is presumed that if the water content of the polarizing element is high, the polyenification of the PVA-based resin included in the polarizing element becomes more likely to proceed. The above water content of the polarizing element refers to the water content of the polarizing element within the optical laminate.

[0060] As a method to determine whether the moisture content of a polarizing element is greater than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%, it can be considered that equilibrium with the environment has been reached if there is no change in mass for a certain period of time by storing it in an environment adjusted to the range of the temperature and relative humidity, or it can be confirmed by calculating the equilibrium moisture content of the polarizing element in advance in an environment adjusted to the range of the temperature and relative humidity, and comparing the moisture content of the polarizing element with the equilibrium moisture content calculated in advance.

[0061] A method for manufacturing a polarizing element having a moisture content greater than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%, is not particularly limited, but examples include storing the polarizing element for 10 minutes or more and 3 hours or less in an environment adjusted to the range of the above temperature and relative humidity, or heat treating at a temperature of 30°C or more and 90°C or less.

[0062] Other preferred methods for manufacturing a polarizing element with the above-mentioned moisture content include storing a laminate having a protective film laminated on at least one side of the polarizing element, or a laminate formed using the polarizing element, in an environment adjusted to the range of temperature and relative humidity for 10 minutes or more and 120 hours or less, or heat treating at 30°C or more and 90°C or less. In the production of an image display device, methods may also include storing an image display panel, in which an optical laminate is laminated to an image display cell, in an environment adjusted to the range of temperature and relative humidity for 10 minutes or more and 3 hours or heat treating at 30°C or more and 90°C or less.

[0063] It is preferable that the moisture content of the polarizing element be adjusted to the above numerical range during the material stage used to form an optical laminate, either as a polarizing element alone or as a laminate of a polarizing element and a protective film. If the moisture content is adjusted after the optical laminate is formed, the curl may become excessive, making it prone to problems during bonding to an image display cell. By forming an optical laminate using a polarizing element that has been adjusted to the above moisture content during the material stage prior to forming the optical laminate, an optical laminate equipped with a polarizing element whose moisture content satisfies the above numerical range can be easily formed. The moisture content of the polarizing element within the optical laminate may also be adjusted to the above numerical range while the optical laminate is bonded to an image display cell. In this case, since the optical laminate is bonded to the image display cell, curl is less likely to occur.

[0064] (Features (b))

[0065] In the case of having feature (b), the moisture content of the optical laminate is greater than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%. Preferably, it is greater than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 45%. More preferably, it is less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 42%, even more preferably, less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 40%, and most preferably, less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 38%. If the moisture content of the optical laminate falls below the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20%, the handling properties of the optical laminate are reduced, making it prone to breakage. If the moisture content of the optical laminate exceeds the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%, the transmittance of the polarizing element is prone to deterioration. It is presumed that if the water content of the optical laminate is high, the polyenification of the PVA-based resin proceeds more easily.

[0066] As a method to determine whether the moisture content of an optical laminate is within the range of an equilibrium moisture content of 20°C and 20% relative humidity, and an equilibrium moisture content of 48% relative humidity at a temperature of 20°C, if there is no change in mass for a certain period of time while stored in an environment adjusted to the range of the temperature and relative humidity, it can be considered that equilibrium with the environment has been reached, or the equilibrium moisture content of the optical laminate in the environment adjusted to the range of the temperature and relative humidity can be calculated in advance and verified by comparing the moisture content of the optical laminate with the pre-calculated equilibrium moisture content.

[0067] A method for manufacturing an optical laminate having a moisture content greater than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%, is not particularly limited, but examples include storing the optical laminate for 10 minutes or more and 3 hours or less in an environment adjusted to the range of the above temperature and relative humidity, or heat treating at a temperature of 30°C or more and 90°C or less.

[0068] In the production of an image display device, there is also a method of storing an image display panel, in which an optical laminate is laminated to an image display cell, for 10 minutes or more and 3 hours or heat treating it at a temperature of 30°C or higher and 90°C or lower.

[0069] (Method for manufacturing a polarizing element)

[0070] The method for manufacturing a polarizing element is not particularly limited, but a typical method is to produce it by extruding a polyvinyl alcohol-based resin film that has been wound in a roll shape and performing stretching, dyeing, crosslinking, etc. (hereinafter referred to as “Manufacturing Method 1”) or a method including a process of stretching a laminate obtained by applying a coating solution containing a polyvinyl alcohol-based resin onto a substrate film to form a polyvinyl alcohol-based resin layer as a coating layer (hereinafter referred to as “Manufacturing Method 2”).

[0071] Manufacturing method 1 can be manufactured by following the steps of: uniaxially stretching a polyvinyl alcohol-based resin film; dyeing the polyvinyl alcohol-based resin film with a dichroic pigment such as iodine to adsorb the dichroic pigment; treating the polyvinyl alcohol-based resin film with the adsorbed dichroic pigment with an aqueous boric acid solution; and washing with water after treatment with the aqueous boric acid solution.

[0072] The swelling process is a treatment process in which a polyvinyl alcohol-based resin film is immersed in a swelling bath. This process can remove dirt or blocking agents from the surface of the polyvinyl alcohol-based resin film and, in addition, can suppress dyeing non-uniformity by swelling the polyvinyl alcohol-based resin film. Typically, a medium with water as the main component, such as water, distilled water, or pure water, is used for the swelling bath. Surfactants, alcohols, etc., may be appropriately added to the swelling bath according to conventional methods.

[0073] 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. In addition, the immersion time in the swelling bath cannot be determined uniformly because the degree of swelling of the polyvinyl alcohol-based resin film is affected by the temperature of the swelling bath, but it 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 performed only once, or it may be performed multiple times if necessary.

[0074] The dyeing process is a treatment process in which a polyvinyl alcohol-based resin film is immersed in a dyeing bath (iodine solution), and dichroic substances such as iodine or dichroic dyes can be adsorbed and oriented onto the polyvinyl alcohol-based resin film. The iodine solution is typically preferably an aqueous iodine solution and contains iodine and an iodide as a dissolving agent. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. Among these, potassium iodide is suitable from the perspective of controlling the potassium content in the polarizing element.

[0075] In the dyeing bath, the concentration of iodine is preferably about 0.01 to 1 weight%, and more preferably about 0.02 to 0.5 weight%. In the dyeing bath, the concentration of iodide is preferably about 0.01 to 10 weight%, more preferably about 0.05 to 5 weight%, and even more preferably about 0.1 to 3 weight%.

[0076] The temperature of the dyeing bath is preferably about 10 to 50°C, more preferably about 15 to 45°C, and even more preferably about 18 to 30°C. In addition, the immersion time in the dyeing bath cannot be determined uniformly because the degree of dyeing of the polyvinyl alcohol-based resin film is affected by the temperature of the dyeing bath, but it is preferably about 10 to 300 seconds, and more preferably about 20 to 240 seconds. The dyeing process may be performed only once, or it may be performed multiple times if necessary.

[0077] The crosslinking process is a treatment process in which a polyvinyl alcohol-based resin film dyed in a dyeing process is immersed in a treatment bath (crosslinking bath) containing a boron compound, and the polyvinyl alcohol-based resin film is crosslinked by the boron compound, so that iodine molecules or dye molecules can be adsorbed onto the crosslinked structure. Examples of boron compounds include boric acid, borates, borax, etc. The crosslinking bath is generally an aqueous solution, but may also be a mixed solution of water and an organic solvent that is miscible with water, for example. In addition, the crosslinking bath preferably contains potassium iodide from the perspective of controlling the potassium content in the polarizing element.

[0078] In the crosslinking bath, the concentration of the boron compound is preferably about 1 to 15 weight%, more preferably about 1.5 to 10 weight%, and more preferably about 2 to 5 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 weight%, more preferably about 1.5 to 10 weight%, and more preferably about 2 to 5 weight%.

[0079] The temperature of the crosslinking bath is preferably around 20 to 70°C, and more preferably around 30 to 60°C. In addition, the immersion time in the crosslinking bath cannot be determined uniformly because the degree of crosslinking of the polyvinyl alcohol-based resin film is affected by the temperature of the crosslinking bath, but it is preferably around 5 to 300 seconds, and more preferably around 10 to 200 seconds. The crosslinking process may be performed only once, or it may be performed multiple times if necessary.

[0080] The stretching process is a treatment process for stretching a polyvinyl alcohol-based resin film in at least one direction to a predetermined ratio. Generally, the polyvinyl alcohol-based resin film is uniaxially stretched in the conveying direction (length direction). The stretching method is not particularly limited, and either the wet stretching method or the dry stretching method may be employed. The stretching process may be performed only once, or it may be performed multiple times if necessary. The stretching process may be performed at any stage in the manufacture of the polarizing element.

[0081] In the wet stretching method, the treatment bath (stretching bath) may typically use a solvent such as water or a mixed solution of water and an organic solvent that is miscible with water. From the perspective of controlling the potassium content in the polarizing element, it is preferable for the stretching bath to contain potassium iodide. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably about 1 to 15 weight%, more preferably about 2 to 10 weight%, and more preferably about 3 to 6 weight%. Additionally, the treatment bath (stretching bath) may contain a boron compound from the perspective of suppressing film breakage during stretching, and in this case, the concentration of the boron compound in the stretching bath is preferably about 1 to 15 weight%, more preferably about 1.5 to 10 weight%, and more preferably about 2 to 5 weight%.

[0082] 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. In addition, the immersion time in the stretching bath cannot be determined uniformly because the degree of stretching of the polyvinyl alcohol-based resin film is affected by the temperature of the stretching bath, but it is preferably about 10 to 800 seconds, and more preferably about 30 to 500 seconds. In addition, the stretching treatment in the wet stretching method may be carried out together with one or more treatment processes among the swelling process, dyeing process, crosslinking process, and washing process.

[0083] Examples of dry stretching methods include roll-to-roll stretching, heated roll stretching, and compression stretching. Additionally, the dry stretching method may be performed together with a drying process.

[0084] The total stretching ratio (cumulative stretching ratio) applied to the polyvinyl alcohol-based resin film can be appropriately set according to the purpose, but it is preferable that it be about 2 to 7 times, more preferable that it be about 3 to 6.8 times, and even more preferable that it be about 3.5 to 6.5 times.

[0085] The cleaning process is a treatment process in which a polyvinyl alcohol-based resin film is immersed in a cleaning bath, and foreign substances remaining on the surface of the polyvinyl alcohol-based resin film can be removed. Typically, a medium consisting mainly of water, such as water, distilled water, or pure water, is used for the cleaning bath. In addition, from the perspective of controlling the potassium content in the polarizing element, it is preferable to use potassium iodide in the cleaning bath, and in this case, the concentration of potassium iodide in the cleaning bath is preferably about 1 to 10 weight%, more preferably about 1.5 to 4 weight%, and even more preferably about 1.8 to 3.8 weight%.

[0086] 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. In addition, the immersion time in the cleaning bath cannot be determined uniformly because the degree of cleaning of the polyvinyl alcohol-based resin film is affected by the temperature of the cleaning bath, but it 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 performed only once, or it may be performed multiple times if necessary.

[0087] The drying process is a process of obtaining a polarizing element by drying a polyvinyl alcohol-based resin film cleaned in a cleaning process. Drying is performed by any suitable method, such as natural drying, air drying, or heat drying.

[0088] Manufacturing method 2 can be manufactured by following the steps of: applying a coating solution containing the polyvinyl alcohol-based resin onto a substrate film; uniaxially stretching the obtained laminated film; dyeing the polyvinyl alcohol-based resin layer of the uniaxially stretched laminated film with a dichroic pigment to adsorb the dichroic pigment and form a polarizing element; treating the film with the adsorbed dichroic pigment with an aqueous boric acid solution; and washing with water after 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 from the polarizing element.

[0089] Anti-reflective film

[0090] The anti-reflective film has an anti-reflective function that reduces the reflectance of light incident from the visible side surface of the optical laminate. The optical laminate has an anti-reflective film to prevent a decrease in contrast caused by reflection of external light. As an anti-reflective film, to satisfy the above requirement (i), an anti-reflective film having a moisture permeability of 20 g / m²·day or less, preferably 10 g / m²·day or less, at a temperature of 40°C and a relative humidity of 90% may be used. The moisture permeability of the anti-reflective film is a value measured according to the method described in the examples described later. By using such an anti-reflective film with low moisture permeability, moisture heat durability and high temperature durability can be improved. 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 base film, etc. The moisture permeability of the anti-reflective film at a temperature of 40°C and a relative humidity of 90% is typically 1 g / m²·day or more.

[0091] For example, an anti-reflective film may be used that has an anti-reflective layer on one side of a base film. The base film is not particularly limited, but a material equivalent to that used for the protective film described below may be used.

[0092] As for the anti-reflective film, a known anti-reflective film or a commercially available anti-reflective film may be used, and for example, the following are examples.

[0093] (a) An anti-reflective film using the principle of a so-called moth-eye structure, which includes an uneven pattern in which the period of the unevenness is controlled to be less than or equal to the wavelength of visible light (an anti-reflective film described in Japanese Patent Publication No. 2010-122599, Japanese Patent Publication No. 2001-517319, Japanese Patent Publication No. 2004-205990, Japanese Patent Publication No. 2004-287238, Japanese Patent Publication No. 2001-27505, Japanese Patent Publication No. 2002-286906, International Publication No. 2006 / 059686, etc.). As a commercially available product, for example, Mosmite (registered trademark, manufactured by Mitsubishi Chemical Co., Ltd.) may be used.

[0094] (b) an anti-reflective film comprising a fine uneven pattern that exhibits optical function (an anti-reflective film as described in Japanese Patent Publication No. 2004-59822, Japanese Patent Publication No. 5-46064, Japanese Patent Publication No. 6-85103, etc.).

[0095] (c) An anti-reflective film comprising an uneven pattern composed of countless fine unevennesses with a pitch less than or equal to the wavelength of light (an anti-reflective film as described in Japanese Patent Publication No. 2001-264520, Japanese Patent Publication No. 9-80205, etc.).

[0096] (d) an anti-reflective film having a single layer or multiple layers with adjusted refractive index (an anti-reflective film described in Japanese Patent Publication No. 2000-187102, Japanese Patent Publication No. 6-186401, Japanese Patent Publication No. 2004-345333, etc.). As commercial products, for example, MTAR and MTAGAR (manufactured by Mikan Co.) may be used.

[0097] The thickness of the anti-reflective film is, for example, 10 μm or more and 100 μm or less.

[0098] As an anti-reflective film, it is suitable to have a thin film with strictly controlled thickness and refractive index, or an anti-reflective layer formed by stacking two or more thin films. Furthermore, in this specification, a thin film refers to a film with a thickness of 1 μm or less. The anti-reflective layer may be configured to exhibit an anti-reflective function by canceling out the reversed phases of incident light and reflected light using the interference effect of light. The wavelength range of visible light exhibiting the anti-reflective function is, for example, 380 to 780 nm, and the wavelength range with particularly high visual sensitivity is in the range of 450 to 650 nm; it is preferable to design the anti-reflective layer to minimize the reflectance at the center wavelength of 550 nm. The thickness of the anti-reflective layer is preferably 100 nm to 350 nm, and more preferably 150 nm to 300 nm.

[0099] In designing an anti-reflection layer based on the interference effect of light, means to enhance the interference effect include, for example, increasing the difference in refractive index between the anti-reflection layer and the anti-glare hard coat layer described later. Generally, in a multilayer anti-reflection layer structured by stacking 2 to 15 thin films (thin films with strictly controlled thickness and refractive index), by forming multiple layers of components with different refractive indices to a predetermined thickness, the degree of freedom in the optical design of the anti-reflection layer is increased, the anti-reflection effect can be further enhanced, and the spectral reflection characteristics can be made uniform (flat) in the visible light region. Since thin films require high thickness precision, the formation of each layer is generally carried out using dry methods such as vacuum deposition, sputtering, or CVD. Sputtering is preferred in terms of keeping the water vapor transmission rate within a predetermined range. Furthermore, by using an anti-reflection film in which each layer is formed by sputtering, an optical laminate with high scratch resistance can be constructed.

[0100] As for the anti-reflection layer, it is preferable to use a structure in which a low-refractive-index layer and a high-refractive-index layer are alternately laminated. While it does not matter whether the high-refractive-index layers or the low-refractive-index layers have the same refractive index, it is desirable to use the same material and have the same refractive index from the perspective of suppressing material costs and film formation costs.

[0101] Materials constituting the low-refractive-index layer include silicon dioxide (SiO2), silicon oxynitride (SiON), gallium oxide (Ga2O3), aluminum oxide (Al2O3), lanthanum oxide (La2O3), lanthanum fluoride (LaF3), magnesium fluoride (MgF2), and aluminum sodium fluoride (Na3AlF6). Among these, silicon dioxide (SiO2) is the most desirable due to its low refractive index, lack of absorption in the visible light region, and high film strength.

[0102] Materials constituting the high-refractive-index layer include niobium pentoxide (Nb2O5), titanium dioxide (TiO2), zirconium dioxide (ZrO2), tantalum pentoxide (Ta2O5), silicon oxynitride (SiON), silicon nitride (Si3N4), and silicon niobium oxide (SiNbO). Among these, niobium pentoxide (Nb2O5) or titanium dioxide (TiO2) are more preferable due to their high refractive index and high film strength, and niobium pentoxide (Nb2O5) is the most preferable due to the absence of absorption in the visible light region.

[0103] The refractive index can be changed to some extent by controlling the compositional ratio of any compound to deviate from the stoichiometric ratio, or by controlling the film density during film formation. Furthermore, the materials constituting the low-reflectivity layer and the high-reflectivity layer are not limited to the above compounds, as long as they satisfy the aforementioned refractive index conditions. Additionally, unavoidable impurities may be included.

[0104] The anti-reflective film may include a hard coat layer between the substrate film and the anti-reflective layer. By forming the hard coat layer, mechanical properties such as hardness and elastic modulus of the anti-reflective layer can be improved. It is preferable that the hard coat layer 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.

[0105] Examples of curable resins include thermosetting resins, UV-curing resins, and electron beam-curing resins. Examples of types of curable resins include various resins such as 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 may be appropriately selected and used.

[0106] Among these, acrylic resins, acrylicurethane resins, and epoxy resins are preferred due to their high hardness, ability to be cured by UV light, and excellent productivity, and among these, acrylicurethane resins are preferred. UV-curable resins include UV-curable monomers, oligomers, polymers, etc. UV-curable resins that are preferably used include, for example, those having UV-polymerizable functional groups, and among these, those containing acrylic monomers or oligomers having two or more, particularly three to six, of the said functional groups as components.

[0107] In order to provide anti-glare and anti-glowing properties to the anti-reflective film, it is preferable that the hard coat layer formed on the surface of the substrate film has anti-glare properties. As an anti-glare hard coat layer, for example, fine particles are dispersed in the above-mentioned curable resin matrix. As for the fine particles dispersed in the resin matrix, transparent materials such as various metal oxide fine particles including silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide; glass fine particles; cross-linked or uncross-linked organic fine particles including various transparent polymers such as polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, melamine, and polycarbonate; and silicone fine particles may be used without particular limitation. One or more of these fine particles may be appropriately selected and used. Among these, fine particles with a refractive index higher than that of the matrix resin are preferred, and organic fine particles with a refractive index of 1.5 or higher, such as styrene beads (refractive index 1.59), are preferred. The average particle diameter of the fine particles is preferably 1 to 10 μm, more preferably 2 to 5 μm. The ratio of fine particles is not particularly limited, but 6 to 20 parts by weight per 100 parts by weight of the matrix resin is preferred.

[0108] A hard coat layer can be formed, for example, by applying a solution containing a curable resin onto a substrate film. It is preferable that the solution for forming the hard coat layer 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 aforementioned fine particles onto a transparent film in addition to the curable resin. The solution may contain additives such as a leveling agent, a thixotropic agent, or an antistatic agent. In forming the anti-glare hard coat layer, by including a thixotropic agent (such as silica or mica with a particle diameter of 0.1 μm or less) in the solution, a fine uneven structure formed by protruding particles can be easily formed on the surface of the hard coat layer.

[0109] The thickness of the hard coat layer is not particularly limited, but to achieve high hardness, it is preferable to have a thickness of 0.5 μm or more, and more preferable to have a thickness of 1 μm or more. Considering the ease of formation by coating, the thickness of the hard coat layer is preferably 15 μm or less, more preferable to have a thickness of 12 μm or less, and even more preferable to have a thickness of 10 μm or less. In addition, in order to maintain a high moisture permeability of the film substrate so as not to hinder the release of moisture from the polarizing element to the outside, it is also preferable that the thickness of the hard coat layer be within the above range.

[0110] The arithmetic mean roughness Ra of the surface on the side of the formation surface of the anti-reflection layer of the base film is preferably 1.5 nm or less, and more preferably 1.0 nm or less. The arithmetic mean roughness Ra may be 0.00 nm or more, or 0.05 nm or more. If a hard coat layer is formed on the base film, the arithmetic mean roughness of the hard coat layer becomes the arithmetic mean roughness of the surface on the side of the formation surface of the anti-reflection layer of the base film. The arithmetic mean roughness Ra is obtained from an observation image of the 1 μm direction using an atomic force microscope (AFM).

[0111] As mentioned above, forming a hard coat layer by application can reduce the arithmetic mean roughness of the surface of the substrate film. If the surface of the substrate film is smooth, the arithmetic mean roughness of the surface of the anti-reflective layer formed thereon is also reduced, and the scratch resistance of the anti-reflective film tends to improve.

[0112] Protective Film

[0113] As for the protective film, although not particularly limited, it is desirable to include a material having excellent transparency, mechanical strength, thermal stability, moisture barrier properties, and stability of phase difference values. As for the material of the protective film, although not particularly limited, examples include films comprising 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.

[0114] These resins can be used alone or in combination of two or more types. Additionally, these resins may be used after performing any suitable polymer modification. Examples of such polymer modifications include copolymerization, crosslinking, molecular end modification, stereoregularity control, and mixing, including cases involving reactions between heterogeneous polymers.

[0115] Cellulose-based resins may be organic acid esters or mixed organic acid esters of cellulose in which some or all of the hydrogen atoms in the hydroxyl groups of cellulose are substituted with acetyl groups, propionyl groups, and / or butyryl groups. Examples include acetic acid esters, propionic acid esters, butyric acid esters, and mixed esters thereof. Among these, triacetylcellulose, diacetylcellulose, cellulose acetate propionate, cellulose acetate butyrate, etc. are preferred.

[0116] These resins may be formulated with appropriate additives to the extent that transparency is not impaired. Examples of additives include antioxidants, ultraviolet absorbers, antistatic agents, lubricants, nucleating agents, antifogging agents, anti-blocking agents, phase difference reducing agents, stabilizers, processing aids, plasticizers, impact resistance aids, gloss removers, antibacterial agents, antifungal agents, etc. Multiple types of these additives may be used in combination.

[0117] The thickness of the protective film is typically 1 to 100 μm, but from the perspective of strength or handling, it is preferable to have a thickness of 5 to 60 μm, more preferable to have a thickness of 10 to 55 μm, and even more preferable to have a thickness of 15 to 50 μm.

[0118] The protective film may simultaneously have other optical functions and may be formed as a laminated structure in which multiple layers are stacked. From the perspective of optical properties, it is desirable for the film thickness of the protective film to be thin, but if it is excessively thin, the strength is reduced and processability becomes inferior. An appropriate film thickness is 5 to 100 μm, preferably 10 to 80 μm, and more preferably 15 to 70 μm.

[0119] The protective film may be a film such as a cellulose acylate-based film, a film containing a polycarbonate resin, a film containing a cycloolefin resin such as norbornene, a (meth)acrylic polymer film, or a polyester resin-based film such as polyethylene terephthalate. In the case of a configuration having protective films on both sides of a polarizing element, when bonding using a water-based adhesive such as PVA adhesive, it is preferable that at least one of the protective films be either a cellulose acylate-based film or a (meth)acrylic polymer film in terms of moisture permeability, and among these, a cellulose acylate film is preferred.

[0120] 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 to the polarizing element). Additionally, the thickness of the first protective film and the second protective film includes the thickness of the surface treatment layer.

[0121] As a first protective film, in order to satisfy the above requirement (ii), a protective film having a moisture permeability of 20 g / m²·day or less at a temperature of 40°C and a relative humidity of 90% may be used. The moisture permeability of the protective film can be adjusted by the material, thickness, etc. As a protective film having a moisture permeability of 20 g / m²·day or less at a temperature of 40°C and a relative humidity of 90%, a cyclic olefin resin film, a film having a water vapor barrier layer laminated in a dry manner, etc. are preferably used.

[0122] At least one of the protective films may be equipped with a phase difference function for purposes such as viewing angle compensation. In this case, the film itself may have a phase difference function, may have a separate phase difference layer, or may be a combination of both.

[0123] In addition, the film having a phase difference function may be configured to be bonded through an adhesive layer or an adhesive layer via another protective film bonded to the polarizing element.

[0124] <Joining layer>

[0125] In an optical laminate, a bonding layer is used to bond each layer. Examples of bonding layers include an adhesive layer or a pressure-sensitive adhesive layer.

[0126] (Adhesive layer)

[0127] The adhesive layer can be used, for example, for bonding a protective film to a polarizing element. Any suitable adhesive may be used as the adhesive constituting the adhesive layer. The adhesive may be a water-based adhesive, a solvent-based adhesive, an active energy beam curing adhesive, etc., but a water-based adhesive is preferred.

[0128] 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 a desired thickness is obtained after curing or after 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.

[0129] (Water-based adhesive)

[0130] As a water-based adhesive, any suitable water-based adhesive may be used. Among these, a water-based adhesive (PVA-based adhesive) containing a PVA-based resin is preferably used. The average degree of polymerization of the PVA-based resin included in the water-based adhesive is preferably 100 to 5500, more preferably 1000 to 4500, in terms of adhesion. The average degree of saponification is preferably 85 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, in terms of adhesion.

[0131] As for the PVA-based resin included in the above-mentioned water-based adhesive, it is preferable that it contains acetoacetyl groups, because the adhesion between the PVA-based resin layer and the protective film is excellent and the durability is excellent. The acetoacetyl group-containing PVA-based resin is obtained, for example, by reacting a PVA-based resin with diketene by any method. The degree of acetoacetyl group modification of the acetoacetyl group-containing PVA-based resin is typically 0.1 mol% or more, and preferably about 0.1 mol% to 20 mol%.

[0132] The resin concentration of the above-mentioned water-based adhesive is preferably 0.1 mass% to 15 mass%, and more preferably 0.5 mass% to 10 mass%.

[0133] Water-based adhesives may also contain a crosslinking agent. Known crosslinking agents may be used. Examples include water-soluble epoxy compounds, dialdehydes, isocyanates, etc.

[0134] In the case where the PVA-based resin is an acetoacetyl group-containing PVA-based resin, it is preferable that the crosslinking agent be one of glyoxal, glyoxylate, or methylolmelamine, and it is preferable that it be one of glyoxal or glyoxylate, and it is particularly preferable that it be glyoxal.

[0135] Water-based adhesives may contain organic solvents. Alcohols are preferred as organic solvents due to their miscibility with water, and among alcohols, methanol or ethanol is more preferable. Some urea-based compounds have low solubility in water but sufficient solubility in alcohol. In such cases, one preferred embodiment is to prepare an adhesive by dissolving the urea-based compound in alcohol to prepare an alcoholic solution of the urea-based compound, and then adding the alcoholic solution of the urea-based compound to an aqueous PVA solution.

[0136] The concentration of methanol in the water-based adhesive is preferably 10 mass% or more and 70 mass% or less, more preferably 15 mass% or more and 60 mass% or less, and even more preferably 20 mass% or more and 60 mass% or less. By having a methanol concentration of 10 mass% or more, it becomes easier to suppress polyenification under high-temperature environments. In addition, by having a methanol content of 70 mass% or less, color deterioration can be suppressed.

[0137] (Active energy beam curing adhesive)

[0138] Active energy beam curing adhesives are adhesives that cure by irradiating active energy beams, such as ultraviolet rays. Examples include adhesives containing a polymerizable compound and a photopolymerization initiator, adhesives containing a photoreactive resin, and adhesives containing a binder resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, 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, anionic radicals, and cationic radicals, when irradiated with active energy beams, such as ultraviolet rays.

[0139] (Adhesive layer)

[0140] The adhesive layer can be used, for example, for bonding an anti-reflective film to a first protective film.

[0141] The adhesive layer may be composed of an adhesive composition having a resin as the main component, such as (meth)acrylic resin, rubber resin, urethane resin, ester resin, silicone resin, or polyvinyl ether resin. Among these, an adhesive composition having (meth)acrylic resin as the base polymer, which has excellent transparency, weather resistance, and heat resistance, is suitable. The adhesive composition may be an active energy beam curing type or a thermosetting type. The thickness of the adhesive layer is typically 3 to 30 μm, and preferably 3 to 25 μm.

[0142] As a (meth)acrylic resin (base polymer) used in an adhesive composition, a polymer or copolymer having one or more types of (meth)acrylic acid esters, such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, as monomers is suitably used. It is preferable to copolymerize a polar monomer into the base polymer. Examples of polar monomers include monomers having carboxyl groups, hydroxyl groups, amide groups, amino groups, epoxy groups, etc., such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

[0143] The adhesive composition may comprise only the base polymer, but typically further comprises a crosslinking agent. Examples of crosslinking agents include a metal ion of divalent or higher that forms a metal carboxylate salt with a carboxyl group; a polyamine compound that forms an amide bond with a carboxyl group; a polyepoxy compound or a polyol that forms an ester bond with a carboxyl group; and a polyisocyanate compound that forms an amide bond with a carboxyl group. Among these, a polyisocyanate compound is preferred.

[0144] The storage modulus of the adhesive layer is preferably 0.001 to 0.350 MPa at a frequency of 1 Hz and a temperature of 23°C, 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.

[0145] 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.

[0146] In the present invention, as described above, by using an anti-reflection film in which each layer is formed by sputtering, an optical laminate with high scratch resistance can be constructed.

[0147] In this case, by controlling the storage modulus of the adhesive layer used for bonding the anti-reflective film to the first protective film and the thickness of the adhesive layer to the following ranges, it is possible to form an optical laminate with a high indentation hardness, represented by pencil hardness, and an anti-reflective layer that is resistant to breakage, which is particularly desirable.

[0148] Specifically, when measured according to the method described in the examples described below, the storage modulus of the adhesive layer 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.

[0149] 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.

[0150] [Method for manufacturing an optical laminate]

[0151] The method for manufacturing an optical laminate according to the present embodiment comprises a moisture content adjustment process and an anti-reflective film lamination process. In the moisture content adjustment process, when manufacturing an optical laminate having feature (a), the moisture content of the polarizing element is adjusted so that the moisture content of the polarizing element is equal to or greater than the equilibrium moisture content at a temperature of 20°C and relative humidity of 30%, and equal to or less than the equilibrium moisture content at a temperature of 20°C and relative humidity of 48%. The method for adjusting the moisture content of the polarizing element is as described above. In the moisture content adjustment process, when manufacturing an optical laminate having feature (b), the moisture content of the optical laminate is adjusted so that the moisture content of the optical laminate is equal to or greater than the equilibrium moisture content at a temperature of 20°C and relative humidity of 30%, and equal to or less than the equilibrium moisture content at a temperature of 20°C and relative humidity of 48%. The method for adjusting the moisture content of the optical laminate is as described above. The anti-reflective film lamination process laminates a polarizing element and an anti-reflective film. The order of the moisture content adjustment process and the anti-reflective film lamination process is not limited, and the moisture content adjustment process and the anti-reflective film lamination process may be performed in parallel. The method for manufacturing an optical laminate of the present embodiment may further include a protective film lamination process for laminating a polarizing element and a protective film.

[0152] [Display device]

[0153] The above-described optical laminate can be used in various display devices, such as liquid crystal display devices or organic EL display devices. A display device using the optical laminate of the present embodiment can be made to have excellent moisture heat durability and high temperature durability. Since the display device using the optical laminate of the present embodiment has excellent moisture heat durability and high temperature durability, it can be suitably used as a display device for automotive applications.

[0154] As a display device, it comprises a display cell and an optical laminate laminated on the visible side surface of the display cell, wherein the optical laminate laminate is laminated on the visible side surface of the display cell in a direction arranged from the display cell side in the order of a polarizing element and an anti-reflective film. For example, the aforementioned adhesive layer is used for laminating the display cell and the optical laminate laminate.

[0155] <Display Cell>

[0156] Examples of display cells include liquid crystal cells or organic EL cells. As for the liquid crystal cell, any of the following may be used: a reflective liquid crystal cell that utilizes external light, a transmissive liquid crystal cell that utilizes light from a light source such as a backlight, or a transflective / semi-reflective liquid crystal cell that utilizes both light from the outside and light from a light source. When the liquid crystal cell utilizes light from a light source, the display device (liquid crystal display device) has a polarizing plate placed on the side opposite to the viewing side of the display cell (liquid crystal cell), and a light source is also placed thereon. It is preferable that the polarizing plate on the light source side and the liquid crystal cell are bonded through a suitable adhesive layer. As for the driving method of the liquid crystal cell, any type such as VA mode, IPS mode, TN mode, STN mode, or bend orientation (π-type) may be used.

[0157] As an organic EL cell, a light-emitting body (organic electroluminescent light-emitting body) formed by sequentially stacking a transparent electrode, an organic light-emitting layer, and a metal electrode on a transparent substrate is suitably used. The organic light-emitting layer is a stack of various organic thin films, and various layer configurations may be employed, such as a stack of a hole injection layer containing a triphenylamine derivative, etc., and a light-emitting layer containing a fluorescent organic solid such as anthracene, a stack of these light-emitting layers and an electron injection layer containing a perylene derivative, etc., or a stack of a hole injection layer, a light-emitting layer, and an electron injection layer.

[0158] [Example]

[0159] The present invention will be explained more specifically below by presenting examples, but the present invention is not limited by these examples. In the examples, parts and % indicating content or usage amount are based on mass unless otherwise specified. Furthermore, the measurement of each physical property in the following examples was performed by the following method.

[0160] [measurement method]

[0161] (1) Method for measuring film thickness

[0162] It was measured using the MH-15M, a digital micrometer manufactured by Nikon Co., Ltd.

[0163] (2) Moisture permeability of anti-reflective film

[0164] In accordance with Annex B of JISK7129:2008, the water vapor permeability of the anti-reflective film was measured in an atmosphere at a temperature of 40°C and a relative humidity of 90%.

[0165] (3) Measure the thickness of each layer of the anti-reflection layer

[0166] It was measured using the FE3000 reflectance spectroscopic film thickness meter manufactured by Otsuka Denshi Co., Ltd.

[0167] (4) Storage modulus

[0168] The storage modulus G' of the adhesive layer was measured according to (I) to (III) below.

[0169] (I) Two samples of 25±1 mg each are taken from the adhesive layer and each is molded into a roughly bead shape.

[0170] (II) Attach the obtained approximately bead-shaped sample to the upper and lower surfaces of the I-type jig, and insert both the upper and lower surfaces between the L-type jigs. The composition of the measurement sample is L-type jig / adhesive layer / I-type jig / adhesive layer / L-type jig.

[0171] (III) The storage modulus G' of the sample prepared in this way was measured using the dynamic viscoelasticity measuring device “DVA-220” manufactured by IT Keisoku Seikyo Co., Ltd. under conditions of a temperature of 23°C, a frequency of 1 Hz, and an initial deformation of 1 N.

[0172] (A) Fabrication of a polarizing element

[0173] A polyvinyl alcohol film with a thickness of 75 μm containing polyvinyl alcohol with an average degree of polymerization of approximately 2,400 and a degree of saponification of 99.9 mol% or more was uniaxially stretched by approximately 5 times in a dry manner. While maintaining the tension state, it was immersed in pure water at 60°C for 1 minute, and then immersed in an aqueous solution with a weight ratio of iodine / potassium iodide / water of 0.05 / 5 / 100 at 28°C for 60 seconds. Subsequently, it was immersed in an aqueous solution with a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72°C for 300 seconds. Afterward, it was washed with pure water at 26°C for 20 seconds and dried at 65°C to obtain a polarizing element with a thickness of 28 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol.

[0174] (B) Preparation of adhesive

[0175] 50 g of modified PVA resin containing acetoacetyl groups (manufactured by Mitsubishi Chemical Corporation: Gosenex Z-410) was dissolved in 950 g of pure water, heated at 90°C for 2 hours, and then cooled to room temperature to obtain PVA solution A.

[0176] PVA-based adhesive 1 was prepared by mixing the above PVA solution A, maleic acid, glyoxal, and pure water so that each compound had the following concentrations.

[0177] PVA concentration 3.0 wt%

[0178] Maleic acid 0.01 wt%

[0179] Glyoxal 0.15 wt%

[0180] (C) Saponification of cellulose acylate film

[0181] A commercially available cellulose acylate film TD40 (manufactured by Fuji Film Co., Ltd.: film thickness 40 μm) was immersed for 2 minutes in a 1.5 mol / L NaOH aqueous solution (saponification solution) maintained at 55°C, and then the film was washed with water. After that, it was immersed for 30 seconds in a 0.05 mol / L sulfuric acid aqueous solution at 25°C, and then passed through a washing bath under flowing water for 30 seconds to neutralize the film. Then, after removing moisture by repeating the water removal process with an air knife three times, the film was dried by staying in a drying zone at 70°C for 15 seconds to produce a saponified film.

[0182] (D) Fabrication of optical laminates

[0183] (Fabrication of Polarizer 1)

[0184] On both sides of the previously obtained polarizing element, the saponified cellulose acylate film prepared above was bonded using a PVA-based adhesive 1, adjusted so that the thickness of the adhesive layer after drying was 100 nm on both sides, and then dried at 80°C for 5 minutes to obtain a polarizing plate 1.

[0185] (Measurement of equilibrium moisture content)

[0186] The polarizer 1 obtained above was stored for 72 hours at a temperature of 20°C and relative humidity of 30%, 35%, 40%, 45%, or 50%, and the moisture content was measured using the Karl Fischer method at 66, 69, and 72 hours of storage. Under any humidity condition, the value of the moisture content did not change at 66, 69, and 72 hours of storage. Therefore, it can be assumed that the moisture content of polarizer 1 is equal to the equilibrium moisture content of the storage environment. When the moisture content of the polarizer reaches equilibrium at a certain storage temperature, it can be assumed that the moisture content of the polarizing element within the polarizer has also reached equilibrium at that storage temperature. Furthermore, when the moisture content of the polarizing element within the polarizer reaches equilibrium in a certain storage environment, it can be assumed that the moisture content of the polarizer has also reached equilibrium in that storage environment.

[0187] The moisture content of polarizer 1 obtained above immediately after drying was measured by the Karl Fischer method and compared with the equilibrium moisture content described above. It was equivalent to the moisture content at a temperature of 20°C and a relative humidity of 30%. Polarizer 1 was stored for 72 hours under conditions of a temperature of 20°C and a relative humidity of 30% so that it would be equivalent to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%.

[0188] (Fabrication of polarizing plates 2–5)

[0189] For each polarizer 1, the drying temperature or time was changed so that the moisture content became equivalent to the equilibrium moisture content listed in Table 1, and then stored for 72 hours under conditions of a temperature of 20°C and relative humidity of 35%, 40%, 45%, or 50%.

[0190] (E) Production of anti-reflective film

[0191] (Production of Banghyeonseong hard coat film)

[0192] A solution having a solid content of 40 wt%, comprising 50 parts by weight of a UV-curable urethane acrylate-based monomer (refractive index 1.51), 50 parts by weight of a UV-curable acrylate-based monomer (refractive index 1.51), 14 parts by weight of methyl methacrylate-styrene copolymer beads (refractive index 1.55) with an average particle diameter of 3.5 μm, 5 parts by weight of a benzophenone-based photopolymerization initiator, and toluene, was applied onto a triacetylcellulose film (refractive index 1.49) with a thickness of 40 μm and dried at 120°C for 5 minutes. Subsequently, a curing treatment was performed by UV irradiation to form a non-glossy hard coat layer with a thickness of approximately 4 μm having an uneven surface structure, thereby producing a non-glossy hard coat film. The arithmetic mean roughness Ra of this non-glossy hard coat layer was 0.43 nm.

[0193] (Production of Clear Hard Coat Film)

[0194] A solution with a solid content of 40 wt%, comprising 50 parts by weight of a UV-curable urethane acrylate-based monomer (refractive index 1.51), 50 parts by weight of a UV-curable acrylate-based monomer (refractive index 1.51), 5 parts by weight of a benzophenone-based photopolymerization initiator, and toluene, was applied onto a triacetylcellulose film (refractive index 1.49) with a thickness of 40 μm and dried at 120°C for 5 minutes. Subsequently, a curing treatment was performed by UV irradiation to form a clear hard coat layer with a flat surface and a thickness of approximately 4 μm, thereby producing a clear hard coat film. The arithmetic mean roughness Ra of this clear hard coat layer was 0.03 nm.

[0195] (Production of Anti-reflective Film 1)

[0196] Based on an embodiment of Japanese Patent Publication No. 2019-035969, the aforementioned anti-fouling hard coat film is introduced into a roll-to-roll sputter deposition apparatus, and while driving the film, bombardment treatment (plasma treatment with Ar gas) is performed on the surface forming the anti-fouling hard coat layer, and then 5 nm of SiO₂ is used as an adhesion enhancing layer.x A layer (x<2) was deposited, and on top of it, a 20 nm Nb2O5 layer, a 35 nm SiO2 layer, a 35 nm Nb2O5 layer, and a 100 nm SiO2 layer were deposited in sequence to form a 4-layer anti-reflective layer with a thickness of 190 nm. On the anti-reflective layer, a fluorine-based resin was formed as an antifouling layer to a thickness of 5 nm to produce an anti-reflective film 1. The water vapor transmission rate of anti-reflective film 1 at a temperature of 40°C and a relative humidity of 90% was 5 g / m²·day.

[0197] (Production of Anti-reflective Films 2 and 3)

[0198] By changing the film-making conditions with reference to the example of Japanese Patent Publication No. 2017-227898, anti-reflective films 2 and 3, which have different moisture permeability from anti-reflective film 1, were produced. The moisture permeability of anti-reflective films 2 and 3 at a temperature of 40°C and a relative humidity of 90% was 10 g / m²·day and 60 g / m²·day, respectively.

[0199] (Production of Anti-reflective Film 4)

[0200] Anti-reflective film 4 was produced in the same manner as anti-reflective film 1, except that a clear hard coat film was used instead of an anti-reflective hard coat film. The moisture permeability of anti-reflective film 4 at a temperature of 40°C and a relative humidity of 90% was 5 g / ㎡·day.

[0201] (Production of Anti-reflective Film 5)

[0202] Anti-reflective film 5 was produced in the same manner as anti-reflective film 1, except that the anti-reflective layer was changed from a sputtering method to a coating type and the layer composition of the anti-reflective layer was as follows. The moisture permeability of anti-reflective film 5 at a temperature of 40°C and a relative humidity of 90% was 300 g / ㎡·day.

[0203] The anti-reflection layer was made into a three-layer anti-reflection layer as described below, with reference to paragraph

[0105] of Japanese Patent Publication No. 2004-126220.

[0204] 1st medium refractive index layer (refractive index: 1.63, film thickness: 67 nm)

[0205] 2nd high-refractive-index layer (refractive index: 1.90, film thickness: 107 nm)

[0206] 3rd low-refractive-index layer (refractive index: 1.43, film thickness: 86 nm)

[0207] (F) Preparation of the adhesive layer

[0208] Adhesive layer A: A commercially available sheet-type acrylic adhesive layer with release agent-attached 38 μm PET attached to both sides. The thickness of the adhesive layer is 5 μm, and the storage modulus is 0.14 MPa.

[0209] Adhesive layer B: A commercially available sheet-type acrylic adhesive layer with release agent-attached 38 μm PET attached to both sides. The thickness of the adhesive layer is 25 μm, and the storage modulus is 0.06 MPa.

[0210] [Example 1]

[0211] Adhesive layer A was bonded to the surface of the anti-reflective film 1 prepared above that is not laminated with the anti-reflective layer. In addition, corona treatment was performed on the bonding surface of each material when bonding these materials.

[0212] An anti-reflective film 1 was laminated on one side of the polarizer 1 produced above through an adhesive layer A, and an adhesive layer B was laminated on the other side to produce the optical laminate of Example 1. In addition, corona treatment was performed on the bonding surfaces of each material when bonding these materials. The obtained optical laminate had a layer composition of “anti-reflective film 1 / adhesive layer A / polarizer 1 / adhesive layer B / release agent attached PET”.

[0213] For the obtained optical laminate, the moisture content of the optical laminate was adjusted by storing it for 72 hours under the same conditions as storing the polarizer for 72 hours, so that it becomes equivalent to the moisture content of the polarizer 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 polarizer and polarizing element in the optical laminate can likewise be considered to have reached equilibrium in that storage environment. Furthermore, when the moisture content of the polarizer or polarizing element in the optical laminate reaches equilibrium in a certain storage environment, the moisture content of the optical laminate can likewise be considered to have reached equilibrium in that storage environment.

[0214] [Examples 2–6 and Comparative Examples 1–3]

[0215] Optical laminates of Examples 2 to 6 and Comparative Examples 1 to 3 were prepared in the same manner as Example 1, except that the polarizing plate and anti-reflective film listed in Table 1 were used as the polarizing plate and anti-reflective film for the optical laminate of Example 1, and then the moisture content of the optical laminate was adjusted by storing it for 72 hours under the same conditions as the polarizing plate was stored for 72 hours so as to be equivalent to the moisture content of the polarizing plate used.

[0216] [evaluation]

[0217] (See-through)

[0218] The obtained optical laminate was cut to a size of 200 mm × 200 mm and bonded to alkali-free glass with a thickness of 0.7 mm and a size of 300 mm × 300 mm through adhesive layer B. An adhesive layer B was laminated onto polarizer 1, cut to a size of 200 mm × 200 mm, and polarizer 1 was bonded to the side of the alkali-free glass optical laminate that was not bonded through adhesive layer B such that the absorption axes of the polarizers were cross-Nicols with each other, thereby producing an evaluation sample.

[0219] The evaluation sample prepared above was placed on an observation stand with the anti-reflective film facing the visible side, and a tabletop fluorescent light was shone obliquely on it. With respect to the direction of illumination, the reflection in the mirror direction was evaluated according to the following criteria. The evaluation results are shown in Table 1.

[0220] A: The reflection of the fluorescent light is not visible at all.

[0221] B: The reflection of the fluorescent light is barely visible.

[0222] C: A slight reflection of the fluorescent light is visible.

[0223] D: The reflection of the fluorescent light is clearly visible.

[0224] (Abrasion resistance)

[0225] Steel wool (Nippon Steel Wool Bonster #0000) was fixed to a scratch tester, and a load of 2000 g was applied to perform 10 reciprocating scratch tests. After the test, the appearance of the surface of the anti-reflective film was visually inspected. Those with no defects were designated as "A," and those with defects were designated as "D." The evaluation results are shown in Table 1.

[0226] (Moisture and heat endurance test)

[0227] The optical laminates fabricated above were each cut to a size of 35 mm × 35 mm, the release film was peeled off, and the samples were bonded to a glass plate measuring 50 mm × 50 mm with a thickness of 1 mm to produce evaluation samples. These evaluation samples were subjected to autoclave treatment for 1 hour at a temperature of 50°C and a pressure of 5 kgf / ㎠ (490.3 kPa), and then left for 24 hours in an environment with a temperature of 23°C and a relative humidity of 55%. Afterward, the degree of polarization was measured (initial value), and after storing for 500 hours under conditions of a temperature of 85°C and a relative humidity of 85%, the degree of polarization was measured again. The degree of polarization was calculated using a V7100 manufactured by Nihon Bunko Co., Ltd., by measuring the transmittance (Tp) when the two fabricated polarizers were superimposed with their absorption axes parallel and the transmittance (Tc') when they were superimposed with their absorption axes orthogonally, and the degree of polarization (P) was calculated from the following formula.

[0228] Polarization degree P=((Tp-Tc') / (Tp+Tc')) 0.5 ×100[%]

[0229] In addition, the amount of change in polarization degree was calculated from the following equation.

[0230] Change in polarization degree ΔP = (Polarization degree (initial value)) - (Polarization degree after storage)

[0231] Based on the results of the change in polarization degree above, an evaluation was performed according to the following criteria. The evaluation results are shown in Table 1.

[0232] A: Change in polarization degree ΔP is 0.01% or less,

[0233] B: Change in polarization degree ΔP is greater than 0.01% and less than or equal to 0.02%,

[0234] C: Change in polarization degree ΔP is greater than 0.02% and less than or equal to 0.05%,

[0235] D: The change in polarization degree ΔP is greater than 0.05%.

[0236] (High temperature endurance test)

[0237] Evaluation samples were prepared by cutting the optical laminates of Examples 1 to 6 and Comparative Examples 1 to 3 prepared above into sizes of 50 mm × 100 mm, peeling off the release film, and bonding the surface of adhesive layer B to alkali-free glass [product name "EAGLE XG", manufactured by Corning, Inc.]. These evaluation samples were subjected to autoclave treatment for 1 hour at a temperature of 50°C and a pressure of 5 kgf / ㎠ (490.3 kPa), followed by leaving them for 24 hours in an environment with a temperature of 23°C and a relative humidity of 55%. Subsequently, the transmittance was measured (initial value), stored in a heated environment at a temperature of 95°C, and the transmittance was measured at 240-hour intervals from 240 to 960 hours. Evaluation was performed based on the following criteria, using the time at which the decrease in transmittance relative to the initial value reached 5% or more. The obtained results are shown in Table 1.

[0238] A: Decrease in transmittance after 960 hours is less than 5%,

[0239] B: A decrease in transmittance of 5% or more after 720 hours or 960 hours,

[0240] C: Decrease in transmittance of 5% or more after 480 hours,

[0241] D: Decrease in transmittance of 5% or more after 240 hours.

[0242]

Claims

Claim 1 An optical laminate having a polarizing plate and an anti-reflective film, wherein the polarizing plate comprises a polarizing element; a protective film laminated on the surface of the polarizing element; and an adhesive layer bonding the anti-reflective film to the protective film, wherein the polarizing element has a moisture content that is greater than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 38%, and satisfies the following requirements (i): (i) the anti-reflective film has a moisture permeability of 20 g / m²·day or less at a temperature of 40°C and a relative humidity of 90%, and wherein the polarizing element is a polyvinyl alcohol in which a dichroic pigment is adsorbed and oriented, and the anti-reflective film comprises a base film and an anti-reflective layer formed on the surface of the base film, wherein the anti-reflective layer comprises an Nb2O5 layer and a SiO2 layer, and the adhesive layer has a storage modulus of 0.050 to 0.170 MPa and a thickness of 3 to 30 μm. Claim 2 An optical laminate having a polarizing plate and an anti-reflective film, wherein the polarizing plate comprises a polarizing element; a protective film laminated on the surface of the polarizing element; and an adhesive layer bonding the anti-reflective film to the protective film, wherein the optical laminate satisfies the following requirements (i): (i) the anti-reflective film has a moisture permeability of 20 g / m²·day or less at a temperature of 20°C and a relative humidity of 30%, and an equilibrium moisture content of 38% at a temperature of 20°C and a relative humidity of 38%, and the polarizing element is a polyvinyl alcohol in which a dichroic pigment is adsorbed and oriented, and the anti-reflective film comprises a base film and an anti-reflective layer formed on the surface of the base film, wherein the anti-reflective layer comprises an Nb2O5 layer and a SiO2 layer, and the adhesive layer has a storage modulus of 0.050 to 0.170 MPa and a thickness of 3 to 30 μm. Claim 3 An optical laminate having a protective film between the polarizing element and the anti-reflection film in claim 1 or 2. Claim 4 In claim 1 or 2, the anti-reflection layer is an optical laminate composed of a plurality of thin films with different refractive indices. Claim 5 delete Claim 6 delete Claim 7 In claim 4, the anti-reflection layer is an optical laminate having a thickness of 100 nm to 350 nm. Claim 8 In paragraph 4, the anti-reflection film is an optical laminate having a hard coat layer formed between the base film and the anti-reflection layer. Claim 9 A display device having a display cell and an optical laminate described in claim 1 or 2, wherein the optical laminate is laminated on the visible side surface of the display cell in a direction arranged from the display cell side in the order of the polarizing element and the anti-reflection film. Claim 10 A method for manufacturing an optical laminate according to claim 1, comprising a moisture content adjustment process for adjusting the moisture content of the polarizing element to be greater than or equal to the equilibrium moisture content at a temperature of 20°C and relative humidity of 30% and less than or equal to the equilibrium moisture content at a temperature of 20°C and relative humidity of 38%, wherein the moisture content adjustment process comprises a method of storing a polarizing plate for 10 minutes or more and 120 hours or less in an environment adjusted to a temperature of 20°C and a relative humidity of 30% to 38%, or a method of heat treatment at a temperature of 30°C or more and 90°C or less. Claim 11 A method for manufacturing an optical laminate as described in paragraph 2, comprising a moisture content adjustment process for adjusting the moisture content of the optical laminate to be greater than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30%, and less than or equal to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 38%, wherein the moisture content adjustment process comprises a method of storing the optical laminate for 10 minutes or more and 120 hours or less in an environment adjusted to a temperature of 20°C and a relative humidity of 30% to 38%, or a method of heat treatment at a temperature of 30°C or more and 90°C or less.

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