Method for manufacturing an optical stack

Abstract

Provided is a method for manufacturing an optical laminate that enables efficient curl adjustment of the optical laminate. The present invention provides a method for manufacturing an optical laminate, which successively includes a step of humidifying a phase difference laminate including a moisture-absorbing film and a liquid crystal cured layer, and a step of obtaining a laminate in which the phase difference laminate is bonded to a polarizing plate having a polarizing film and a resin film laminated to at least one surface of the polarizing film via an adhesive layer.

Description

Technical Field

[0001] This invention relates to a method for manufacturing optical laminates. Background Technology

[0002] As polarizing plates used in image display devices such as liquid crystal displays and organic EL displays, polarizing plates have traditionally been made by bonding a protective film formed of triacetyl cellulose (TAC) to a polarizing film formed of polyvinyl alcohol resin using an adhesive. In recent years, from the viewpoints of thin film production, durability, cost, and productivity, protective films formed of resins other than TAC have also been used (for example, Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2004-245925 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] A phase retardation layer and an adhesive layer are sometimes stacked on one side of a polarizer. Optical laminates containing such polarizers are required to be thin, but thin optical laminates, especially monolithic optical laminates that can be obtained by cutting from long strip optical laminates, are prone to warping into an arc shape. In this specification, this deformation is also referred to as "curling".

[0008] To suppress curling, conventional methods involve humidifying a single sheet cut from an optical laminate sandwiched between a protective film and a separating film in a humidification chamber. Humidifying the polarizer allows for the adjustment of the optical laminate's curling. However, the protective and separating films are mostly made of low-permeability films, resulting in the problem of requiring a long time to humidify the polarizer.

[0009] The purpose of this invention is to provide a method for manufacturing an optical laminate that can efficiently adjust the curl of the optical laminate.

[0010] Methods for solving problems

[0011] The present invention provides a method for manufacturing an optical laminate as illustrated below.

[0012] [1] A method for manufacturing an optical laminate, comprising the following steps:

[0013] The process of humidifying a phase difference laminate containing a hygroscopic film and a liquid crystal curing layer, and

[0014] The process of obtaining a laminate formed by bonding the phase difference laminate to a polarizing plate having a polarizing film and a resin film laminated on at least one side of the polarizing film via an adhesive layer.

[0015] [2] According to the manufacturing method described in [1], the hygroscopic membrane comprises a cellulose resin.

[0016] [3] According to the manufacturing method described in [1] or [2], wherein,

[0017] In the aforementioned polarizing plate, the aforementioned resin film is laminated on one side of the aforementioned polarizing film.

[0018] In the process of obtaining the above-mentioned laminate, the phase difference laminate is laminated onto the other side of the polarization film.

[0019] [4] The manufacturing method according to any one of [1] to [3] includes a step of winding the laminate after the step of obtaining the laminate.

[0020] [5] The manufacturing method according to [4] further includes a step of peeling off the hygroscopic film after the above-mentioned winding step.

[0021] [6] The manufacturing method according to any one of [1] to [5], wherein, in the above-mentioned humidification step, humidification is performed until the moisture content of the above-mentioned hygroscopic membrane reaches the equilibrium moisture content in an environment with a temperature of 20°C or higher and 80°C or lower and a relative humidity of 45% or higher.

[0022] Invention Effects

[0023] According to the present invention, the curling of the optical laminate can be efficiently adjusted in the manufacturing method of the optical laminate. Attached Figure Description

[0024]

【 Figure 1 [Figure 1] is an example of a method for manufacturing an optical laminate according to the present invention.

[0025] [Explanation of Labels in the Attached Image]

[0026] 10 Protective film; 11 Polarizing plate; 12, 18 Adhesive layers; 13, 19 Separating film; 14, 16 Moisture-absorbing film; 15 Liquid crystal curing layer; 17 Phase difference laminate. Detailed Implementation

[0027] The method for manufacturing the optical laminate according to the present invention comprises, in sequence:

[0028] The process of humidifying a phase difference laminate containing a hygroscopic film and a liquid crystal curing layer, and

[0029] The process of obtaining a laminate formed by bonding the phase difference laminate to a polarizing plate having a polarizing film and a resin film laminated on at least one side of the polarizing film via an adhesive layer.

[0030] If the phase retardation laminate containing the hygroscopic film and the liquid crystal curing layer is pre-humidified and then bonded to the polarizing plate via the adhesive layer, the moisture in the hygroscopic film moves to the polarizing plate, enabling short-term humidification of the polarizing plate. The adhesive layer and the liquid crystal curing layer do not significantly impede the movement of moisture from the hygroscopic film to the polarizing plate. Conventionally, after stacking the protective film, the polarizing plate, the liquid crystal curing layer, and the separator film, the optical laminate is placed in a humidified environment for 3 to 7 days to humidify the polarizing plate. According to the method of the present invention, it is not necessary to humidify the optical laminate sandwiched between the protective film and the separator film for an extended period. For example, sufficient humidification of the polarizing plate can be achieved during the conventional storage period of several hours to several days from the time the liquid crystal curing layer is bonded to the polarizing plate until the separator film is bonded to the liquid crystal curing layer. Even if the hygroscopic film is peeled off during the bonding process of the release liner, the amount of humidification (moisture content of the polarizing plate) can be increased compared to humidifying the optical laminate sandwiched between the protective film and the release liner using conventional methods.

[0031] Humidification via a polarizing plate can regulate the curling of optical laminates. Even optical laminates with protective films are prone to curling if fabricated as single sheets. There are two types of curling in optical laminates: "positive curling" and "negative curling." For optical laminates, "positive curling" results in a concave surface on the protective film side, while "negative curling" results in a convex surface on the protective film side. If negative curling occurs, when bonding the single sheet of the optical laminate to image display elements such as liquid crystal cells and organic EL elements via its adhesive layer, it can easily lead to bonding errors or air bubbles entering the interface between the adhesive layer and the image display element.

[0032] Besides the aforementioned classifications of "positive curl" and "negative curl," the curling of optical laminates can also be categorized into "MD curl" and "TD curl." "MD curl" is caused by stress (contraction, expansion, etc.) in a direction parallel to the MD direction of the elongated optical laminate from which the monolithic sheet of the optical laminate is cut. "TD curl" is caused by stress (contraction, expansion, etc.) in a direction parallel to the TD direction of the elongated optical laminate from which the monolithic sheet of the optical laminate is cut. The MD direction refers to the mechanical flow direction of the film, i.e., the length direction of the film, while the TD direction refers to the direction orthogonal to the MD direction.

[0033] Polarizing films, especially those made by stretching polyvinyl alcohol-based resin films, possess hygroscopic and swelling properties, and are particularly prone to swelling in the TD direction. By humidifying the polarizing film, the TD curl of the optical laminate can be adjusted. Positive / negative curl can be adjusted by changing the position of the polarizing film within the optical laminate.

[0034] Specifically, regarding TD curl, when a measurement sample (monolith) is cut from a strip-shaped optical laminate according to the description in the later embodiments section, and the measurement sample is placed on a horizontal platform with its concave side facing up, its size can be measured as curl (absorption axis curl) where the two corners of the two diagonals of the measurement sample with the larger angle to the absorption axis direction of the polarizer of the measurement sample are raised. When the absorption axis direction of the polarizer in the strip-shaped polarizer with a protective film is parallel to the MD direction of the protective film, the MD curl can be measured as curl where the two corners of the two diagonals of the measurement sample with the larger angle to the MD direction of the strip-shaped optical laminate are raised.

[0035] <Optical laminate>

[0036] The optical laminate of the present invention comprises: a polarizing plate (linear polarizing plate), one or more liquid crystal curing layers, and an adhesive layer. Although optical laminates containing one or more liquid crystal curing layers are prone to curling, according to the present invention, the curling can be adjusted to a desired value in a short time, thus enabling efficient manufacturing of the optical laminate. The optical laminate sequentially comprises, for example, a protective film, a polarizing plate, an adhesive layer, a liquid crystal curing layer, and a hygroscopic film. Another example of an optical laminate sequentially comprises a protective film, a polarizing plate, an adhesive layer, a liquid crystal curing layer, an adhesive layer, and a release film.

[0037] Optical laminates can be strips or monoliths. In this specification, a "monolithic material" refers to a smaller film cut from a larger film (e.g., a strip-shaped film).

[0038] The length of the elongated optical laminate is, for example, 100m or more and 20,000m or less, preferably 1,000m or more and 10,000m or less. The width of the elongated optical laminate is, for example, 0.5m or more and 3m or less, preferably 1m or more and 2.5m or less.

[0039] There are no particular limitations on the size, shape, and cut angle of the optical laminate as a monolithic element. The monolithic element of the optical laminate is preferably square, more preferably a square shape having a long side and a short side. This square shape is preferably rectangular. When the monolithic element is rectangular, the length of the long side is, for example, 50 mm to 300 mm, preferably 70 mm to 150 mm. The length of the short side is, for example, 30 mm to 200 mm, preferably 40 mm to 100 mm.

[0040] While there are no particular restrictions, when the monolith is rectangular in shape, the absorption axis of the polarizer can be at a 45-degree angle relative to its long and short sides when observed from the protective film side. When the monolith is rectangular in shape, the absorption axis of the polarizer can be parallel to its long side or at a 90-degree angle when observed from the protective film side.

[0041] When a monolithic element of an optical laminate is bonded to an image display element such as a liquid crystal cell or an organic EL element via its adhesive layer, the monolithic element preferably does not have the anti-curl measured as described in the embodiments section below. More preferably, the positive curl is 20 mm or less, or it is a flat state without curl. Even more preferably, the positive curl is 10 mm or less, or it is a flat state without curl. Particularly preferably, the positive curl is 5 mm or less, or it is a flat state without curl. Regarding the optical laminate, it is preferable that the curl in the structure with or without a separator film is as described above, and more preferably that the curl in the structure without at least a separator film is as described above.

[0042] <The process of humidifying the phase difference laminate>

[0043] The following is for reference Figure 1 The manufacturing method of the optical laminate is described in detail. In this process, the moisture content of the phase retardation laminate 17 is increased by humidification. The phase retardation laminate 17 includes hygroscopic films 14 and 16 and a liquid crystal curing layer 15. The hygroscopic films 14 and 16, which readily absorb moisture from the air, can increase their moisture content in a short time.

[0044] Regarding humidification, it can be performed by placing the phase difference laminate 17 in an environment with regulated relative humidity, for example, by introducing the phase difference laminate 17 into a humidification chamber with regulated relative humidity. Alternatively, a long strip-shaped phase difference laminate 17 can be introduced into the humidification chamber and humidified while being conveyed along the guide rollers.

[0045] Regarding humidification, it can be carried out in an environment with a temperature above 20°C and below 80°C and a relative humidity of above 45%, preferably in an environment with a relative humidity of above 55%, and more preferably in an environment with a relative humidity of above 60%, thereby enabling efficient humidification of the phase difference laminate 17. The relative humidity is typically below 99%, preferably below 95%.

[0046] Regarding the humidification time, there is no particular limitation on the degree to which the hygroscopic membranes 14 and 16 contained in the phase difference laminate 17 are sufficiently humidified. For example, it can be 5 seconds or more and 120 minutes or less, preferably 3 minutes or more and 60 minutes or less, and more preferably 30 minutes or more and 60 minutes or less. The humidification time can be the residence time of the phase difference laminate 17 in the humidification chamber, or it can be the conveying time of the elongated phase difference laminate 17. In the humidification process, humidification can be carried out until the hygroscopic membranes 14 and 16 reach the equilibrium moisture content.

[0047] After the humidification process, the hygroscopic membranes 14 and 16 contained in the phase difference laminate 17 are preferably adjusted to a higher moisture content than the equilibrium moisture content under normal storage conditions (temperature around 23°C, relative humidity around 55%) after the manufacture of the laminate 103. For example, when the hygroscopic membranes 14 and 16 are triacetylcellulose membranes, the moisture content after the humidification process is preferably 1% by mass or more and 5% by mass or less, more preferably 2% by mass or more and 4.5% by mass or less, and may also be 2% by mass or more and 4% by mass or less. The moisture content is determined by the same method as the equilibrium moisture content, specifically according to the following formula:

[0048] Moisture content (mass%) = {(mass of phase difference laminate before drying - mass of phase difference laminate after drying) / mass of phase difference laminate before drying} × 100

[0049] To obtain this information. Drying refers to the process of drying the membrane at 105°C for 2 hours.

[0050] In the humidification process, the hygroscopic films 14 and 16 contained in the phase retardation laminate 17 are humidified to a higher moisture content than the equilibrium moisture content at 23°C and 55% relative humidity, thereby enabling efficient humidification of the polarizer 11 in subsequent processes. It is desirable that the humidified hygroscopic films 14 and 16 maintain or substantially maintain the moisture content after humidification until the polarizer 11 is bonded to the phase retardation laminate 17 in subsequent processes.

[0051] In the humidification process, for example, when the elongated phase difference laminate 17 of the membrane material is introduced into the humidification chamber and humidified while being conveyed along the guide rollers, the membrane release speed is gradually increased towards the set speed while confirming the membrane conveying stability. In this case, the residence time of the initially released membrane in the humidification chamber is relatively longer compared to the membrane after reaching the set speed, and the residence time in the humidification chamber becomes uneven in the MD direction of the membrane. Due to this unevenness, the moisture content of the humidified membrane is uneven in the MD direction, and as a result, curling may occur in the MD direction (there may be partially curled portions and non-curled portions in the MD direction).

[0052] In one embodiment of the present invention, during the humidification process of the phase difference laminate 17, the hygroscopic films 14 and 16 contained in the phase difference laminate 17 are humidified until an equilibrium moisture content is reached in the storage environment after the manufacture of the laminate 103, the environment in which the laminate is cut out (described later), etc. This suppresses uneven moisture content in the MD direction of the phase difference laminate 17, and consequently, also suppresses curling distribution in the MD direction. The phase difference laminate 17 is humidified until the moisture content of the hygroscopic films 14 and 16 reaches an equilibrium moisture content in an environment with a preferred temperature of 20°C or higher and 80°C or lower, a relative humidity of 45% or higher, more preferably 55% or higher, and even more preferably 60% or higher.

[0053] (Moisture-absorbing membrane)

[0054] As for the hygroscopic membranes 14 and 16, there are no particular limitations as long as they are highly hygroscopic; for example, membranes containing cellulose-based resins can be cited. Cellulose-based resins refer to cellulose organic esters or mixed cellulose organic esters in which some or all of the hydrogen atoms in the hydroxyl groups of cellulose obtained from raw materials such as cotton lint and wood pulp (broadleaf wood pulp, coniferous wood pulp) are substituted with acetyl, propionyl, and / or butyryl groups. Examples of cellulose-based resins include resins containing cellulose acetate, propionate, butyrate, and mixtures thereof. As for the hygroscopic membranes 14 and 16, it is preferable that they contain triacetylcellulose, diacetylcellulose, cellulose acetate-propionate, or cellulose acetate-butyrate. The hygroscopic membranes 14 and 16 can be the same membrane or different membranes. The hygroscopic membranes 14 and 16 are preferably membranes formed from cellulose-based resins, and more preferably membranes containing triacetylcellulose.

[0055] The thickness of the hygroscopic membranes 14 and 16 is typically 5 μm or more and 100 μm or less. From the viewpoint of easily retaining moisture and humidifying the polarizer 11 more efficiently, a greater thickness of the hygroscopic membranes 14 and 16 is preferred.

[0056] The hygroscopic films 14 and 16 can be laminated after the liquid crystal curing layer 15 is formed, or they can be used as substrate films for forming the liquid crystal curing layer 15. The phase retardation laminate 17 may have the hygroscopic film 14 or 16 on one side of the liquid crystal curing layer 15, or it may have the hygroscopic film 14 or 16 on both sides of the liquid crystal curing layer 15. The hygroscopic films 14 and 16 are preferably films that can be peeled off from the liquid crystal curing layer 15.

[0057] (Liquid crystal curing layer)

[0058] The liquid crystal curable layer 15 is a phase retardation layer (liquid crystal curable phase retardation layer) composed of a cured liquid crystal compound. The optical laminate can be a circular polarizer (including an elliptical polarizer) having a linear polarizer and a phase retardation layer. As the liquid crystal compound, a polymerizable liquid crystal compound having polymerizable groups is preferred. The polymerization reaction of the polymerizable liquid crystal compound can be a thermal polymerization reaction using a thermal polymerization initiator, but is preferably a photopolymerization reaction using a photopolymerization initiator. The liquid crystal curable phase retardation layer can be formed using known liquid crystal compounds. The type of liquid crystal compound is not particularly limited, and rod-shaped liquid crystal compounds, disk-shaped liquid crystal compounds, and mixtures thereof can be used.

[0059] The orientation of the liquid crystal compound contained in the phase retardation layer can be adjusted by an orientation film formed between the substrate film and the coating layer, or by using polarization irradiation to make the polymeric liquid crystal compound photo-oriented, or to make the orientation of the polymeric liquid crystal compound manifest or enhanced.

[0060] The substrate film coated with the composition containing the liquid crystal compound can be the aforementioned hygroscopic film 14 or 16. The liquid crystal curing layer 15 can also be laminated onto the polarizing plate 11 in the form of an alignment film.

[0061] The liquid crystal curing layer 15, serving as the phase retardation layer, can be one layer or two or more layers. Each phase retardation layer can have a slow axis in the same direction or have slow axes in different directions. The phase retardation layer includes a λ / 4 layer, and may further include at least one of a λ / 2 layer and a positive C layer. When the phase retardation layer includes a λ / 2 layer, the λ / 2 layer and the λ / 4 layer are stacked sequentially from the linear polarizer side. When the phase retardation layer includes a positive C layer, the λ / 4 layer and the positive C layer can be stacked sequentially from the linear polarizer side, or the positive C layer and the λ / 4 layer can be stacked sequentially from the linear polarizer side. The thickness of the liquid crystal curing layer 15 is, for example, 0.1 μm or more and 10 μm or less, preferably 0.5 μm or more and 8 μm or less, and more preferably 0.5 μm or more and 4 μm or less. From the viewpoint of more efficiently humidifying the polarizer 11, the liquid crystal curing layer 15 is preferably thinner.

[0062] <Process for obtaining a laminated structure with a phase difference layer bonded to a polarizer>

[0063] In this process, the phase retardation laminate 17 is bonded to the polarizer 11 via the adhesive layer 12. When the polarizer 11 is covered with a protective film 10 (laminar 101), the adhesive layer 12 and the phase retardation laminate 17 are laminated onto the side of the polarizer 11 opposite to the side covered with the protective film 10.

[0064] The resulting laminate 103 is preferably elongated. The length of the elongated laminate 103 is, for example, 100m or more and 20,000m or less, preferably 1,000m or more and 10,000m or less. The width of the elongated laminate 103 is, for example, 0.5m or more and 3m or less, preferably 1m or more and 2.5m or less.

[0065] Regarding the bonding of the polarizing plate 11 and the phase difference laminate 17, for example, the long strip-shaped polarizing plate 11 is continuously conveyed, and the long strip-shaped phase difference laminate 17 is continuously conveyed, and the polarizing plate 11 and the phase difference laminate 17 are overlapped and passed through and sandwiched between a pair of bonding rollers, thereby enabling the production of a laminate 103 in which two films are bonded.

[0066] The adhesive layer 12 can be laminated onto the surface of the polarizer 11 before the phase retardation laminate 17 is laminated. Before laminating the polarizer 11 and the phase retardation laminate 17, at least one of the bonding surfaces can be subjected to surface activation treatments such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, or saponification treatment. A release film 13 (laminate 102) can be laminated on the adhesive layer 12 side of the polarizer 11. In this case, the release film 13 is typically peeled off and removed when the phase retardation laminate 17 is laminated.

[0067] When the phase retardation laminate 17 has hygroscopic films 14 and 16 on both sides of the liquid crystal curing layer 15, it is preferable to peel off the hygroscopic film 14 on one side and laminate it onto the polarizer 11 with the liquid crystal curing layer 15 side attached. When the phase retardation laminate 17 has a hygroscopic film 16 on one side of the liquid crystal curing layer 15 and a substrate layer on the other side, it is preferable to peel off the substrate layer and laminate the laminate containing the liquid crystal curing layer 15 and the hygroscopic film 16 onto the polarizer 11 with the liquid crystal curing layer 15 side attached.

[0068] When the polarizing plate 11 is a single-sided protective polarizing plate with a resin film laminated on one side of the polarizing film, in order to humidify the polarizing plate 11 more efficiently, it is preferable to laminate a phase difference laminate 17 on the other side of the polarizing film (the side without the resin film).

[0069] (Polarizing plate)

[0070] Polarizing plate 11 is a linear polarizing plate containing a polarizing film, on which a resin film is laminated on one or both sides. Polarizing plate 11 with a resin film on only one side of the polarizing film is advantageous for thin-film polarizing plate 11.

[0071] The thickness of the polarizer 11 is typically 5 μm or more and 150 μm or less. From the viewpoint of thin-film polarizer 11, it is preferably 80 μm or less, more preferably 70 μm or less, and even more preferably 60 μm or less, 50 μm or less, or 40 μm or less. The smaller the thickness of the polarizer 11, the easier it is for the optical laminate to curl. However, according to the present invention, even when the thickness of the polarizer 11 is small, the curling of the optical laminate can be efficiently adjusted. The thickness of the polarizer 11 can also be 20 μm or more, 25 μm or more, or 30 μm or more.

[0072] (Polarizing film)

[0073] A polarizing film has the property of absorbing linearly polarized light with a vibration plane parallel to the absorption axis and transmitting linearly polarized light with a vibration plane orthogonal to the absorption axis (parallel to the transmission axis). An example of a polarizing film is one obtained by adsorbing and orienting a dichroic dye onto a uniaxially stretched polyvinyl alcohol (PVA) resin film. Such a polarizing film can be manufactured, for example, by a method including: a step of uniaxially stretching the PVA resin film; a step of adsorbing the dichroic dye by dyeing the PVA resin film with the dichroic dye; a step of treating the PVA resin film adsorbed with the dichroic dye with a crosslinking solution such as an aqueous boric acid solution; and a step of washing with water after treatment with the crosslinking solution.

[0074] As a polyvinyl alcohol-based resin, a resin obtained by saponifying a polyvinyl acetate-based resin can be used. Besides polyvinyl acetate as a homopolymer of vinyl acetate, copolymers with other monomers capable of copolymerizing with vinyl acetate can also be cited as polyvinyl acetate-based resins. Examples of other monomers capable of copolymerizing with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides containing ammonium groups.

[0075] In this specification, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid. The same applies to "(meth)acryloyl", "(meth)acrylate", etc.

[0076] The degree of saponification of polyvinyl alcohol (PVA) resins is typically 85 mol% or more and 100 mol% or less, preferably 98 mol% or more. PVA resins can be modified; for example, aldehyde-modified PVA formal or PVA acetal can be used. The average degree of polymerization of PVA resins is typically 1000 or more and 10000 or less, preferably 1500 or more and 5000 or less. The degree of saponification and average degree of polymerization of PVA resins can be determined according to JIS K 6726.

[0077] The film obtained by forming a polyvinyl alcohol-based resin is used as the raw material film for polarizing films. The method for forming the polyvinyl alcohol-based resin film is not particularly limited, and known methods can be used. The thickness of the polyvinyl alcohol-based resin film is not particularly limited, but is, for example, about 10 μm or more and 150 μm or less, preferably 50 μm or less, and more preferably 35 μm or less.

[0078] Uniaxial stretching of polyvinyl alcohol (PVA) resin films can be performed before, during, or after dyeing with dichroic pigments. When uniaxial stretching is performed after dyeing, it can be done before or during crosslinking treatment. Alternatively, uniaxial stretching can be performed at multiple stages.

[0079] When performing uniaxial stretching, stretching can be carried out uniaxially between rollers with different circumferential speeds, or it can be done using hot rollers. Furthermore, uniaxial stretching can be dry stretching performed in the atmosphere, or wet stretching performed while the polyvinyl alcohol-based resin film is swollen using solvents or water. The stretching ratio is typically 3 to 8 times.

[0080] One method for dyeing polyvinyl alcohol (PVA) resin films with dichroic dyes is to immerse the film in an aqueous solution containing the dichroic dye. Iodine or dichroic organic dyes can be used as the dichroic dye. It should be noted that it is preferable to pre-immerse the PVA resin film in water before the dyeing process.

[0081] As a cross-linking treatment following dyeing with dichroic pigments, a common method is to immerse the dyed polyvinyl alcohol-based resin film in an aqueous solution containing boric acid. When iodine is used as the dichroic pigment, it is preferable that the aqueous solution containing boric acid contains potassium iodide.

[0082] Cross-linked polyvinyl alcohol (PVA) resin membranes are typically washed with water. This washing process can be performed, for example, by immersing the cross-linked PVA resin membrane in water. The water temperature during washing is usually above 1°C and below 40°C.

[0083] The polarizing film is obtained by drying after washing with water. The drying process can be carried out by using a hot air dryer, by contacting the film with a hot roller, or by using a far-infrared heater. The drying temperature is usually above 30°C and below 100°C, preferably above 50°C and below 90°C.

[0084] Through drying, the moisture content of the polarizing film is reduced to a practical level. Its moisture content is typically 5% by mass or more and 20% by mass or less, preferably 8% by mass or more and 15% by mass or less. If the moisture content is less than 5% by mass, the polarizing film may lose its flexibility, be damaged after drying, or break. If the moisture content exceeds 20% by mass, the polarizing film may have poor thermal stability. The moisture content mentioned here is determined by the drying gravimetric method, as described above.

[0085] The thickness of the polarizing film is typically between 2 μm and 40 μm. From the viewpoint of thinning the polarizing plate 11, the thickness of the polarizing film is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. The thicker the polarizing film, the easier it is for the optical laminate to curl up. However, according to the present invention, even if the thickness of the polarizing film is, for example, 10 μm or more, more preferably 15 μm or more, and particularly 20 μm or more, the curling up of the optical laminate can be efficiently controlled.

[0086] (Resin film)

[0087] The resin film is a film made of a light-transmitting thermoplastic resin, preferably an optically transparent thermoplastic resin. Examples of resin films include cyclic polyolefin resin films; cellulose resin films formed from resins such as triacetylcellulose and diacetylcellulose; polyester resin films formed from resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polycarbonate resin films; (meth)acrylic resin films; and polypropylene resin films, etc., which are known in the art. The resin film is preferably a cellulose resin film, and more preferably a resin film containing triacetylcellulose.

[0088] From the viewpoint of thinning optical laminates, the thickness of the resin film is typically 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, further preferably 40 μm or less, and even more preferably 30 μm or less. The thickness of the resin film is typically 5 μm or more, preferably 10 μm or more. The smaller the thickness of the resin film, the easier it is for the optical laminate to curl; however, according to the present invention, even if the thickness of the resin film is as thin as, for example, 40 μm or less, and further, 30 μm or less, curling can be efficiently controlled.

[0089] Resin films can serve as protective films for polarizing films. They can also possess optical functions such as phase retardation films and brightness enhancement films. For example, phase retardation films with arbitrary phase difference values ​​can be produced by stretching (uniaxial or biaxial stretching, etc.) a thermoplastic resin film formed from the aforementioned materials. Resin films can have surface treatment layers (coatings) on their surface, such as hard coatings, anti-glare layers, anti-reflective layers, antistatic layers, and antifouling layers.

[0090] The resin film can be bonded to the polarizing film via an adhesive layer or a bonding agent layer. Preferably, the resin film is bonded to the polarizing film via an adhesive layer. As the adhesive forming the adhesive layer, a water-based adhesive, an active energy radiation-cured adhesive, or a thermosetting adhesive can be used, preferably a water-based adhesive or an active energy radiation-cured adhesive.

[0091] Examples of water-based adhesives include adhesives formed from aqueous solutions of polyvinyl alcohol (PVA) resins and water-based two-component urethane emulsion adhesives. Among these, water-based adhesives formed from aqueous solutions of PVA resins are particularly suitable. As for PVA resins, in addition to polyvinyl alcohol homopolymers obtained by saponifying polyvinyl acetate homopolymers, PVA copolymers obtained by saponifying copolymers of vinyl acetate with other monomers that can copolymerize with it, or modified PVA polymers obtained by partially modifying their hydroxyl groups, are also suitable. Water-based adhesives may contain crosslinking agents such as aldehyde compounds (glyoxal, etc.), epoxy compounds, melamine compounds, hydroxymethyl compounds, isocyanate compounds, amine compounds, and polyvalent metal salts.

[0092] When using water-based adhesives, it is preferable to perform a drying process to remove water contained in the water-based adhesive after bonding the polarizing film to the resin film. Alternatively, a curing process can be performed after the drying process, for example, at a temperature of 20°C or higher and 45°C or lower.

[0093] So-called active energy ray curing adhesives are adhesives containing curing compounds that are cured by irradiation with active energy rays such as ultraviolet light, visible light, electron beams, and X-rays, with ultraviolet curing adhesives being preferred.

[0094] The curable compound can be a cationicly polymerizable curable compound or a free radical polymerizable curable compound. Examples of cationicly polymerizable curable compounds include epoxy compounds (compounds having one or more epoxy groups in the molecule), oxetane compounds (compounds having one or more oxetane rings in the molecule), or combinations thereof. Examples of free radical polymerizable curable compounds include (meth)acrylic acid compounds (compounds having one or more (meth)acryloyloxy groups in the molecule), other vinyl compounds having free radical polymerizable double bonds, or combinations thereof. Cationicly polymerizable curable compounds and free radical polymerizable curable compounds can be used in combination. Active energy radiation-curable adhesives typically also contain cationic polymerization initiators and / or free radical polymerization initiators for initiating the curing reaction of the curable compound.

[0095] When bonding polarizing films and resin films, surface activation treatment can be applied to the bonding surfaces of at least one of them to improve adhesion. Examples of surface activation treatments include dry treatments such as corona treatment, plasma treatment, discharge treatment (glow discharge treatment, etc.), flame treatment, ozone treatment, UV ozone treatment, and ionizing active ray treatment (ultraviolet treatment, electron beam treatment, etc.); and wet treatments such as ultrasonic treatment, saponification treatment, and anchoring coating treatment using solvents such as water and acetone. These surface activation treatments can be performed individually or in combination.

[0096] When resin films are bonded to both sides of a polarizing film, the adhesive used to bond these resin films can be the same type of adhesive or different types of adhesive.

[0097] (Adhesive layer)

[0098] The adhesive layer 12 bonds the polarizer 11 to the phase retardation laminate 17. The adhesive layer 12 can be composed of an adhesive composition with (meth)acrylic resin, rubber resin, urethane resin, ester resin, silicone resin, or polyvinyl ether resin as the main component. Among these, an adhesive composition using (meth)acrylic resin as the base polymer, which exhibits excellent transparency, weather resistance, and heat resistance, is suitable. The adhesive composition can be either an active energy radiation-cured type or a thermosetting type.

[0099] As the (meth)acrylic resin (base polymer) used in the adhesive composition, polymers or copolymers using one or more (meth)acrylates such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate as monomers can be suitably used. For the base polymer, copolymerization of polar monomers is preferred. Examples of polar monomers include (meth)acrylate compounds, 2-hydroxypropyl (meth)acrylate compounds, hydroxyethyl (meth)acrylate compounds, (meth)acrylamide compounds, N,N-dimethylaminoethyl (meth)acrylate compounds, and glycidyl (meth)acrylate compounds, which have carboxyl, hydroxyl, amide, amino, or epoxy groups.

[0100] The adhesive composition may contain only the aforementioned base polymer, but typically also contains a crosslinking agent. Examples of crosslinking agents include divalent or higher metal ions that form carboxylic acid metal salts with carboxyl groups; polyamine compounds that form amide bonds with carboxyl groups; polyepoxide compounds or polyols that form ester bonds with carboxyl groups; and polyisocyanate compounds that form amide bonds with carboxyl groups. Among these, polyisocyanate compounds are preferred.

[0101] The active energy radiation-curing adhesive composition possesses the property of curing upon irradiation with active energy radiation such as ultraviolet light or electron beams. It also exhibits adhesiveness even before irradiation, enabling it to adhere tightly to substrates such as films, and the ability to adjust the adhesion strength through curing upon irradiation with active energy radiation. The active energy radiation-curing adhesive composition is preferably ultraviolet-curing. In addition to the base polymer and crosslinking agent, the active energy radiation-curing adhesive composition contains an active energy radiation polymerizable compound. Depending on the requirements, it may also contain photopolymerization initiators, photosensitizers, etc.

[0102] The adhesive composition may contain additives such as microparticles, beads (resin beads, glass beads, etc.) for imparting light scattering properties, glass fibers, resins other than the base polymer, antistatic agents, tackifiers, fillers (metal powders, other inorganic powders, etc.), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, defoamers, and corrosion inhibitors.

[0103] The adhesive layer 12 can be formed by dissolving or dispersing the adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare an adhesive liquid, applying it to the polarizing plate 11, and drying it. The adhesive layer 12 can be pre-formed as a sheet on a release film 13 that has undergone a demolding treatment, and then transferred to the target surface of the polarizing plate 11. In the case of using an active energy ray-curable adhesive composition, a cured product with the desired degree of curing can be produced by irradiating the formed adhesive layer 12 with active energy rays.

[0104] The thickness of the adhesive layer 12 is typically 1 μm or more and 40 μm or less, but from the viewpoint of thinning optical laminates, it is preferably 2 μm or more and 30 μm or less.

[0105] (Separating membrane)

[0106] The release film 13 is a film temporarily attached to protect the surface of an image display element or other optical component before the adhesive layer 12 is bonded to it. The release film 13 is typically made of a thermoplastic resin film that has undergone a release treatment on one side using a silicone-based, fluorine-based, or similar release agent, and the release-treated side is bonded to the adhesive layer 12.

[0107] The thermoplastic resin constituting the separator 13 may be, for example, a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, or a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate. The thickness of the separator 13 is, for example, 10 μm or more and 50 μm or less.

[0108] (Protective film)

[0109] A protective film 10 may be laminated onto the polarizer 11. The protective film 10 is a peelable film used to protect the surface of the polarizer 11. Optical laminates commonly available on the market are mostly equipped with a protective film 10. The protective film 10 is adhered to the surface of the polarizer 11 on the side opposite to the side where the liquid crystal curing layer 15 and the adhesive layer 12 are laminated. The protective film 10 is, for example, formed from an adhesive layer and a substrate film laminated via the adhesive layer. The protective film 10 is typically peeled off along with the adhesive layer, for example, after the optical laminate is laminated to an image display element, etc.

[0110] The substrate film of the protective film 10 can be made of thermoplastic resin, such as polyethylene resin, polypropylene resin, cyclic polyolefin resin, and other polyolefin resins; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polycarbonate resins; (meth)acrylic resins, etc. The substrate film can be a single-layer structure or a multi-layer structure. The adhesive layer of the protective film 10 can be made of (meth)acrylic adhesives, epoxy adhesives, urethane adhesives, silicone adhesives, etc. The protective film 10 can be a self-adhesive resin film such as polypropylene resin and polyethylene resin. In this case, the protective film 10 does not have an adhesive layer.

[0111] The thickness of the protective film 10 can be, for example, 5 μm or more and 150 μm or less, preferably 10 μm or more and 100 μm or less, more preferably 20 μm or more and 75 μm or less, and even more preferably 25 μm or more and 70 μm or less (e.g., 60 μm or less, and further 55 μm or less). When the thickness of the protective film 10 is less than 5 μm, the protection of the polarizer 11 may become insufficient, and it is also disadvantageous in terms of operability. If the thickness of the protective film 10 exceeds 150 μm, it is disadvantageous in terms of thinning of the optical laminate and reprocessability of the protective film 10.

[0112] <Process of winding laminate>

[0113] When the stack 103 of the polarizer 11 and the phase retardation stack 17 is elongated, the stack 103 can be sequentially wound onto a winding roller, or the process of stacking the separator 19 or peeling off the hygroscopic film 16 can be performed without winding. Typically, when manufacturing an elongated optical stack, the elongated material is wound in each stacking process. Until the wound stack 103 is used in the next process, the moisture in the phase retardation stack 17 is sufficiently moved to the polarizer 11. For example, when the stack 103, which sequentially includes the protective film 10, the polarizer 11, the adhesive layer 12, the liquid crystal curing layer 15, and the hygroscopic film 16, is wound into a roll, the hygroscopic film 16 has a reduced surface area exposed to air, thus allowing for faster movement of moisture to the polarizer 11.

[0114] After obtaining the laminate 103 of polarizer 11 and phase difference laminate 17, it is preferable to wind the laminate 103 without performing a process of drying the laminate 103.

[0115] <Process for peeling off the moisture-absorbing film>

[0116] After the phase retardation laminate 17 is stacked on the polarizer 11, it is preferable to leave the liquid crystal curing layer 15 while peeling and removing the hygroscopic film 16 from the laminate 103. The hygroscopic film 16 can be peeled off directly after the phase retardation laminate 17 is stacked on the polarizer 11, or it can be temporarily wound on a roller (as described in the winding process) and peeled off while being wound up in a subsequent process.

[0117] The optical laminate after the hygroscopic film 16 has been removed can be further bonded with a release film 19 (laminate 104) via an adhesive layer 18. The release film 19 and the adhesive layer 18 can be the release film 13 and the adhesive layer 12 described above, respectively.

[0118] <Process of cutting out the laminated body>

[0119] When the laminate obtained by the above method is elongated, it is preferable to cut out a single piece from the elongated laminate. Cutting (cutting) can be performed using conventionally known cutting methods such as cutting tools. Regarding the size, shape, and cutting angle of the single piece, please refer to the description in the above-mentioned <Optical Laminates>.

[0120] For the freshly cut single sheet, the amount of anti-curl is 10 mm or less, more preferably 5 mm or less, or it is in a flat state without curling, or in a forward curling state. By adjusting in this way, the final curling adjustment process described later is unnecessary, or the time required for the final curling adjustment process can be shortened.

[0121] <Final adjustment of the curling process>

[0122] If the monolith obtained by the above method undergoes anti-curling, it is appropriate to adjust it by humidification. Humidification can be performed by placing the monolith in an environment with regulated relative humidity, such as storing the monolith in a humidified room with regulated relative humidity.

[0123]

Example

[0124] The present invention will be described in more detail below with examples, but the invention is not limited thereto. In the examples, “%” and “parts” refer to mass percentage and mass parts unless otherwise specified.

[0125] [Method for determining curl]

[0126] A rhomboid-shaped cut-out sheet with a long side of 155 mm and a short side of 78 mm is cut from the laminate 104, with its diagonals parallel to the MD and TD directions, respectively. The sheet from which the release liner 19 is peeled off is used as a test sheet. After thoroughly eliminating static electricity from the test sheet, it is placed on a reference surface (horizontal platform) with the concave side facing upwards. The height of each of the four corners of the test sheet from the reference surface is measured. If the corner of the test sheet floats when the test sheet is placed on the reference surface with the protective film side facing upwards, this curl is defined as positive curl, and the height of the corner from the reference surface is represented by a positive value. On the other hand, if the corner of the test sheet floats when the test sheet is placed on the reference surface with the protective film side facing downwards, this curl is defined as negative curl, and the height of the corner from the reference surface is represented by a negative value.

[0127] The measured MD curl value is obtained by averaging the heights of the two corners on the diagonal parallel to the MD direction from the reference plane. The measured TD curl value is obtained by averaging the heights of the two corners on the diagonal parallel to the TD direction from the reference plane. If the MD curl value and TD curl value are positive or 0, it indicates that anti-curling is suppressed. When the value is negative, the larger the absolute value, the more developed the anti-curling is.

[0128] [Method for determining the moisture content of optical laminates]

[0129] A rhomboid-shaped cutout with a long side of 155 mm and a short side of 78 mm was cut from the laminate 104, with its diagonals parallel to the MD and TD directions, respectively. The sheet from which the release film 19 was peeled off was used as a test sheet. The test sheet was dried at 105°C for 2 hours, and the mass after drying was compared with the mass before drying to determine the moisture content of the optical laminate.

[0130] Moisture content (mass%) = {(mass of optical laminate before drying - mass of optical laminate after drying) / mass of optical laminate before drying} × 100

[0131] [Preparation of the adhesive layer]

[0132] The adhesive layer was manufactured using the following method. In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen inlet tube, 97.0 parts of n-butyl acrylate, 1.0 part of acrylic acid, 0.5 parts of 2-hydroxyethyl acrylate, 200 parts of ethyl acetate, and 0.08 parts of 2,2'-azobisisobutyronitrile were added. The air in the reaction vessel was replaced with nitrogen. The reaction solution was heated to 60°C while stirring and reacted for 6 hours, then cooled to room temperature. The weight-average molecular weight of a portion of the resulting solution was determined, confirming the yield of a (meth)acrylate polymer with a molecular weight of 1.8 million.

[0133] 100 parts of the obtained (meth)acrylate polymer (solid content conversion value; the same below), 0.30 parts of trimethylolpropane-modified toluene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate L") as an isocyanate-based crosslinking agent, and 0.30 parts of 3-epoxypropoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry Co., Ltd., trade name "KBM403") as a silane coupling agent were mixed and stirred thoroughly. The mixture was then diluted with ethyl acetate to obtain a coating solution of the adhesive composition.

[0134] On the release surface (peel surface) of the first release film (manufactured by LINTEC Corporation: SP-PLR382190), which becomes the release layer, an adhesive composition coating solution is applied using an applicator to achieve a dried thickness of 25 μm. The coating is then dried at 100°C for 1 minute to form an adhesive layer. On the opposite side of the adhesive layer from the side where the first release film was applied, a second release film (manufactured by LINTEC Corporation: SP-PLR381031) is applied, resulting in an adhesive layer with release films on both sides.

[0135] [Preparation of polarizing plate (101) with protective film]

[0136] A 20 μm thick polyvinyl alcohol (PVA) film (average degree of polymerization approximately 2400, saponification degree ≥ 99.9 mol%) was uniaxially stretched to approximately 5 times its original thickness using a dry stretching method. While kept taut, the film was immersed in pure water at 60°C for 1 minute, followed by immersion in an aqueous solution of iodine / potassium iodide / water at a mass ratio of 0.05 / 5 / 100 at 28°C for 60 seconds. Subsequently, it was immersed in an aqueous solution of potassium iodide / boric acid / water at a mass ratio of 8.5 / 8.5 / 100 at 72°C for 300 seconds. After washing with pure water at 26°C for 20 seconds, the film was dried at 65°C to obtain a 7 μm thick polarized film obtained by adsorbing and orienting iodine onto the PVA film.

[0137] An epoxy adhesive was applied to one side of the polarizing film, and a transparent norbornene resin film with a thickness of 13 μm was laminated as a protective layer. The epoxy adhesive was prepared by dissolving 3 parts of carboxyl-modified polyvinyl alcohol (Kuraray Co., Ltd., trade name "KL-318") in 100 parts of water, and adding 1.5 parts of a polyamide epoxy additive (Taoka Chemical Industry Co., Ltd., trade name "Sumirez Resin 650(30)", an aqueous solution with a solid content of 30%) as a water-soluble epoxy resin to the aqueous solution. By operating in this way, a polarizing plate with a resin film laminated on one side of the polarizing film was obtained.

[0138] A protective film, obtained by forming a 15 μm acrylic adhesive layer on a 38 μm thick polyethylene terephthalate (PET) film, is laminated onto the surface of the resin film opposite to the polarizing film to obtain a 73 μm thick polarizing plate 101 with a protective film.

[0139] [Preparation of phase difference stack]

[0140] (Manufacturing of the first liquid crystal curing layer)

[0141] A 50 μm thick cyclic olefin polymer (COP) film was treated once using a corona treatment apparatus (AGF-B10, manufactured by Kasuga Electric Co., Ltd.) at an output power of 0.3 kW and a processing speed of 3 m / min. The following orientation layer forming composition (1) was applied to the corona-treated surface using a bar coater, dried at 80°C for 1 minute, and then irradiated with a polarized UV irradiation apparatus (SPOT CURE SP-7, manufactured by USHIO Electric Co., Ltd.) at 100 mJ / cm². 2 The cumulative light intensity was used to perform polarized UV exposure to obtain an alignment layer. The thickness of the obtained alignment layer was measured using a laser microscope (LEXT, manufactured by Olympus Corporation), and the result was 100 nm.

[0142] Next, the following liquid crystal layer forming composition (A-1) was coated onto the alignment layer using a rod coater. After drying at 120°C for 1 minute, the mixture was irradiated with ultraviolet light (under a nitrogen atmosphere, wavelength: 365nm, cumulative light intensity at wavelength 365nm: 1000mJ / cm²) using a high-pressure mercury lamp (UNICURE VB-15201BY-A, manufactured by USHIO Electric Co., Ltd.). 2 A first liquid crystal curing layer, serving as a phase retardation layer, is formed, resulting in a first liquid crystal curing layer with a substrate layer. The thickness of the first liquid crystal curing layer is 2 μm.

[0143] (Preparation of composition (1) for orientation layer formation)

[0144] An orientation material is mixed in the following solvent and stirred at 80°C for 1 hour to obtain a composition (1) for forming an orientation layer.

[0145] • Orientation materials (5 copies):

[0146] [Chemical Formula 1]

[0147]

[0148] Solvent (95 parts): Cyclopentanone

[0149] (Preparation of composition (A-1) for forming liquid crystal layer)

[0150] A polymerizable liquid crystal compound and a polymerization initiator were mixed in the following solvent and stirred at 80°C for 1 hour to obtain a liquid crystal layer forming composition (A-1). The polymerizable liquid crystal compound A1 and polymerizable liquid crystal compound A2 were synthesized by the method described in Japanese Patent Application Publication No. 2010-31223.

[0151] • Polymerizable liquid crystal compound A1 (80 parts):

[0152] [Chemical Formula 2]

[0153]

[0154] • Polymerizable liquid crystal compound A2 (20 parts):

[0155]

Chemical Formula 3

[0156]

[0157] • Polymerization initiator (6 parts):

[0158] 2-Dimethylamino-2-benzyl-1-(4-morpholinophenyl)butane-1-one (Ciba Specialty Chemicals, “Irgacure 369”)

[0159] Solvent (400 parts): Cyclopentanone

[0160] (Manufacturing of the second liquid crystal curing layer)

[0161] A corona treatment apparatus (AGF-B10, manufactured by Kasuga Electric Co., Ltd.) was used to treat a hygroscopic membrane, specifically an 80 μm thick triacetyl cellulose (TAC) membrane, as the substrate, at an output power of 0.3 kW and a processing speed of 3 m / min. The following orientation layer forming composition (2) was applied to the corona-treated surface using a bar coater and dried at 90°C for 1 minute to obtain an orientation layer. The thickness of the obtained orientation layer was measured using a laser microscope (LEXT, manufactured by Olympus Corporation), and the result was 34 nm.

[0162] Next, the following liquid crystal layer forming composition (B-1) was coated onto the alignment layer using a rod coater. After drying at 90°C for 1 minute, the mixture was irradiated with ultraviolet light (under a nitrogen atmosphere, wavelength: 365nm, cumulative light intensity at wavelength 365nm: 1000mJ / cm²) using a high-pressure mercury lamp (UNICUREVB-15201BY-A, manufactured by USHIO Electric Co., Ltd.). 2 A second liquid crystal curing layer, serving as a phase retardation layer, is formed, resulting in a second liquid crystal curing layer with a hygroscopic film. The thickness of the second liquid crystal curing layer is 1 μm.

[0163] (Preparation of composition (2) for orientation layer formation)

[0164] A composition (2) for forming an orientation layer was obtained by adding 2-butoxyethanol to Sunever SE-610 (manufactured by Nissan Chemical Industries, Ltd.), which is an orientation polymer. Regarding the obtained orientation layer forming composition (2), the solid content relative to the total amount of the composition is 1%, and the solvent content relative to the total amount of the composition is 99%. The solid content of Sunever SE-610 is calculated based on the concentration stated in the product specification sheet.

[0165] (Preparation of composition (B-1) for liquid crystal layer formation)

[0166] A polymerizable liquid crystal compound, a polymerization initiator, and a reaction additive are mixed in the following solvent, stirred at 80°C for 1 hour, and then cooled to room temperature to obtain a liquid crystal layer forming composition (B-1).

[0167] • Polymerizable liquid crystal compound LC242 (manufactured by BASF) (19.2%):

[0168] [Chemical Formula 4]

[0169]

[0170] • Polymerization initiator (0.5%):

[0171] Irgacure (registered trademark) 907 (made by BASF JAPAN)

[0172] • Reaction additive (1.1%):

[0173] Laromer (registered trademark) LR-9000 (manufactured by BASF JAPAN)

[0174] Solvent (79.1%): Propylene glycol 1-monomethyl ether 2-acetic acid ester

[0175] (Preparation of adhesive composition)

[0176] The cationic curable components a1 to a3 shown below are mixed with a cationic polymerization initiator. After further mixing the cationic polymerization initiator and sensitizer shown below, degassing is performed to prepare a photocurable adhesive composition. It should be noted that the following formulation amounts are based on the amount of solid components.

[0177] • Cationic curing component a1 (70 parts):

[0178] 3',4'-Epoxycyclohexanecarboxylic acid 3',4'-Epoxycyclohexylmethyl ester (trade name: CEL2021P, manufactured by Daicel Co., Ltd.)

[0179] • Cationic curing component a2 (20 parts):

[0180] Neopentyl glycol diglycidyl ether (trade name: EX-211, manufactured by Nagase ChemteX Co., Ltd.)

[0181] • Cationic curing component a3 (10 parts):

[0182] 2-Ethylhexyl glycidyl ether (trade name: EX-121, manufactured by Nagase ChemteX Co., Ltd.)

[0183] • Cationic polymerization initiator (2.25 parts):

[0184] Trade name: CPI-100 (manufactured by San-Apro Co., Ltd.) 50% propylene carbonate solution

[0185] • Sensitizer (2 parts):

[0186] 1,4-Diethoxynaphthalene

[0187] (Fabrication of phase difference stacks)

[0188] A corona treatment (800 W, 10 m / min) was applied to the surface of the second liquid crystal curing layer with the hygroscopic film. An adhesive composition was then applied to the corona-treated surface using a coating machine, resulting in an adhesive layer thickness of 1 μm. Next, a corona treatment was applied to the surface of the first liquid crystal curing layer with the substrate layer under the same conditions, and the adhesive composition coating layer formed on the second liquid crystal curing layer with the hygroscopic film was bonded to it. The adhesive composition was cured by irradiating the second liquid crystal curing layer side with ultraviolet light using an ultraviolet irradiation device, resulting in a phase difference laminate 17 with a hygroscopic film 16 laminated on one side. The irradiation conditions were set to an irradiation intensity of 390 mW / cm² in the UVA region. 2 The cumulative light intensity is 420 mJ / cm². 2 The irradiation intensity in the UVB region is 400 mW / cm². 2 The cumulative light intensity is 400 mJ / cm². 2 .

[0189] [Example 1]

[0190] An optical laminate is obtained using the phase difference laminate 17 prepared above, the polarizer 101 with a protective film, and the adhesive layer with a double-sided isolation film. Specifically, it is performed as follows.

[0191] A corona treatment (800W, 10m / min) is applied to the side of the polarizer 101 opposite to the side of the protective film 10. Additionally, the second release film is peeled off from the adhesive layer with the double-sided release film prepared above. The corona-treated side of the polarizer 11 is then bonded to the peeled side of the second release film in the adhesive layer to obtain a polarizer 102 with the first release film 13.

[0192] After placing the phase retardation laminate 17 in an environment of 23°C and 55% humidity for 40 minutes, the exposed surface (the surface on the side of the first liquid crystal curing layer) after peeling off the COP film from the phase retardation laminate 17 is bonded to the adhesive layer 12 exposed after peeling off the first release film 13 from the polarizer 102 with the first release film 13, resulting in a laminate 103 in which the polarizer 11 and the liquid crystal curing layer 15 are laminated via the adhesive layer 12. Subsequently, the laminate 103 is wrapped in an aluminum moisture-proof bag and stored in an environment of 23°C and 55% humidity for 24 hours.

[0193] After 24 hours, the surface exposed by peeling off the TAC film (hygroscopic film 16) from the laminate 103 (the surface on the side of the second liquid crystal curing layer of the liquid crystal curing layer 15) is bonded to the adhesive layer exposed by peeling off the second release film from the adhesive layer with double-sided release films, resulting in a laminate 104 having an adhesive layer 18 and a first release film 19. The laminate 104 is cut into rectangular single sheets of a specified size to obtain an optical laminate A. The curl of the obtained optical laminate A is measured, and the TD curl value of the optical laminate A is calculated. In addition, the moisture content of the optical laminate A is measured by the dry weight method. The results are shown in Table 1.

[0194] [Example 2]

[0195] Except for placing the phase difference laminate 17 in an environment of 23 degrees Celsius and 55% humidity for 5 minutes, the optical laminate B was obtained using the same method as in Example 1. The curl of the obtained optical laminate B was measured, and the TD curl value of the optical laminate B was calculated. Furthermore, the moisture content of the optical laminate B was measured by the dry weight method. The results are shown in Table 1.

[0196] [Comparative Example 1]

[0197] Without humidifying the phase difference laminate 17, optical laminate C was obtained using the same method as in Example 1. The obtained optical laminate C was subjected to curl measurement, and the TD curl value of optical laminate C was calculated. Furthermore, the moisture content of optical laminate C was determined by the dry weight method. The results are shown in Table 1.

[0198] Table 1

[0199]

[0200] Table 1 shows that the moisture content of optical laminates A and B obtained from Examples 1 and 2 is higher than that of optical laminate C obtained from Comparative Example 1. Since moisture is efficiently transferred from the hygroscopic film to the polarizing plate, the polarizing plate is adequately humidified, and as a result, anti-curling can be presumed to be suppressed.

Claims

1. A method for manufacturing an optical laminate, comprising the following steps: The process of humidifying a phase difference laminate containing a hygroscopic film and a liquid crystal curing layer, and The process of obtaining a laminate formed by bonding the phase difference laminate to a polarizing plate having a polarizing film and a resin film laminated on at least one side of the polarizing film via an adhesive layer. The manufacturing method further includes a step of peeling off the hygroscopic film.

2. The manufacturing method according to claim 1, wherein, The hygroscopic membrane comprises a cellulose-based resin.

3. The manufacturing method according to claim 1 or 2, wherein, In the polarizing plate, the resin film is laminated on one side of the polarizing film. In the process of obtaining the laminate, the phase difference laminate is laminated to the other side of the polarization film.

4. The manufacturing method according to claim 1 or 2, comprising a step of winding the laminate after the step of obtaining the laminate.

5. The manufacturing method according to claim 4, wherein, The process of peeling off the hygroscopic film is performed after the winding process.

6. The manufacturing method according to claim 1 or 2, wherein, In the humidification process, humidification continues until the moisture content of the hygroscopic membrane reaches the equilibrium moisture content under conditions of a temperature above 20°C and below 80°C and a relative humidity above 45%.

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