TW201808637A - Laminate film and image display device - Google Patents

Abstract

To provide a thin laminate film capable of improving white luminance even when a polarizer having a thickness of 10 [mu]m or less is used and capable of suppressing occurrence of display unevenness after a humidification test. A laminate film is provided, which includes an adhesive layer, a polarizing film and a luminance improving film, in this order. The polarizing film has a protective film on at least one surface of a polarizer comprising a polyvinyl alcohol resin, in which the polarizer has a thickness of 10 [mu]m or less and shows 43.0% or more of transmittance as a single film. The luminance improving film has a polarization degree of 90% or more. The protective film has a thickness of 25 [mu]m or less and a moisture permeability of 200 g/(m2.day) or less.

Description

Laminated film and image display device

The invention relates to a laminated film and an image display device including the laminated film.

2. Description of the Related Art In various image display devices, a polarizing film is used for displaying an image. For example, a liquid crystal display device (LCD) must have polarizing films on both sides of a glass substrate forming the surface of a liquid crystal panel because of its image formation method. Such a polarizing film is generally used: on one or both sides of a polarizer made of a polyvinyl alcohol-based film and a dichroic material such as iodine, a polyvinyl alcohol-based adhesive is used for bonding Protective film.

In recent years, for image display devices such as liquid crystal display devices, the demand for weight reduction and thinning has increased. Various optical components such as polarizing films used in image display devices are also expected to be thinner and lighter. Currently, thin polarized light is being targeted. Various investigations have been made on films.

However, the thin polarizing film has low durability under high temperature and high humidity, and there is a problem that warping or cracking occurs. As for a thin polarizing plate capable of suppressing such warpage and having excellent durability under high temperature and high humidity, for example, a polarizing plate is sequentially laminated with a first adhesive layer, a specific moisture permeability, and a resin. A transparent protective layer formed of a thin film, a second adhesive layer having a specific overall water absorption, and a polarizing film having a thickness of 10 μm or less (see Patent Document 1). Prior technical literature

[Patent Document 1] Japanese Patent No. 5871408

SUMMARY OF THE INVENTION The problem to be solved by the invention is that the thinner the polarizer, the easier it is to be affected by moisture in a humidified environment. The polarizer deteriorates due to the moisture, and the polarization degree of the polarizer is reduced. The device becomes easy to recognize uneven display. As a method of suppressing such display unevenness, it is expected that a protective film with low moisture permeability is used to suppress deterioration of the polarizer due to moisture.

In recent years, in order to improve the resolution, the high-definition engraving of the panel is in progress. Since the transmittance of the panel will be reduced due to high definition, the need for brightness improvement is accelerating for the entire module, and the transmittance of polarizers is also being improved. In addition, the need for special emphasis on the design of the module as a whole, such as thinning and narrowing the frame, has also followed. After reliability, the demand for low shrinkage and overall thinning of the polarizing plate has also increased. Under these circumstances, with the foregoing requirements, attempts are being made to improve the use of thin polarizers. However, for thin polarizers with a thickness of 10 μm or less, when the unit transmittance is 43% or more in order to improve white brightness, even if a protective film with low moisture permeability is used, after a humidification test, the image display device is often seen It shows unevenness, and it is not sufficient from the viewpoint of suppressing unevenness.

The aforementioned Patent Document 1 is not limited to the case of using a highly polarized thin polarizer having a transmittance of 43% or more, and it does not say at all that the problem of display unevenness that may occur only when such a thin polarizer is used.

Therefore, an object of the present invention is to provide a thin laminated film which can improve white brightness even when a polarizer having a thickness of 10 μm or less is used, and can suppress display unevenness after a humidification test. Means to solve the problem

The inventors of the present invention have intensively studied in order to solve the aforementioned problems, and as a result, they have found that the following laminated film finally completes the present invention.

That is, the present invention relates to a laminated film, which is characterized by sequentially including an adhesive layer, a polarizing film, and a brightness enhancement film, and the polarizing film is at least one side of a polarizer containing a polyvinyl alcohol resin. A polarizing film with a protective film thereon; the thickness of the polarizer is 10 μm or less and the unit transmittance is 43.0% or more; the polarization degree of the brightness enhancing film is 90% or more; the thickness of the protective film is 25 μm or less and the humidity is 200g / (m ²・ day) or less.

The boric acid content of the aforementioned polarizer is preferably 18 to 24% by weight.

The latent value of the adhesive layer is preferably 100 to 150 μm, and after the laminated film is left at 85 ° C. for 500 hours, the heat shrinkage of the polarizer in the absorption axis direction is preferably 0.5% or less.

The polarizer and the protective film are preferably laminated through the adhesive layer, and the overall water absorption of the adhesive layer is preferably 10% by weight or less.

The polarizing film is preferably a polarizing film having a protective film on only one side of the polarizer, and the laminated film includes an adhesive layer, a protective film, a polarizer, and a brightness enhancement film in sequence, or an adhesive layer and polarizing film in this order. Parts, protective films and brightness enhancement films.

In addition, the present invention relates to an image display device including the aforementioned laminated film. Invention effect

Since the laminated film of the present invention uses a polarizer having a thickness of 10 μm or less and a single transmittance of 43% or more, white brightness can be improved. Furthermore, by using a brightness enhancement film having a polarization degree of 90% or more, it is possible to suppress a problem when using a polarizer having a thickness of 10 μm or less and a cell transmittance of 43% or more (display unevenness occurs after a humidification test). Specifically, since the brightening film converts the light from the backlight into polarized light, the polarizer of the lower plate will have polarized light incident. Therefore, even if the polarizer is degraded and the degree of polarization is reduced in a humidified environment, the influence of the deterioration of the polarization of the polarizer on the visibility can be reduced due to the incidence of polarized light.

By using the laminated film of the present invention as a backlight-side polarizing plate of a liquid crystal display device, a thin liquid crystal display device with high white brightness and high optical reliability can be provided.

Form for implementing the invention 1. Laminated film The laminated film of the present invention is characterized in that it includes an adhesive layer, a polarizing film, and a brightness enhancement film in this order, and the polarizing film is a polarizer containing a polyvinyl alcohol resin. A polarizing film having a protective film on at least one side; the thickness of the polarizer is 10 μm or less and the unit transmittance is 43.0% or more; the polarization degree of the brightness enhancing film is 90% or more; the thickness of the protective film is 25 μm or less and transparent The humidity is 200g / (m ² · day) or less.

The structure of the laminated film of the present invention will be described in detail with reference to FIGS. 1 and 2. In addition, the dimensions of each structure in FIGS. 1 and 2 are used to show one example, and the present invention is not limited thereto.

As shown in FIGS. 1 and 2, the laminated film 1 of the present invention has an adhesive layer 4, a polarizing film 2, and a brightness enhancement film 3 in this order. The polarizing film 2 shown in FIG. 1 may be a double-sided protective polarizing film having protective films 2b and 2c on both sides of the polarizer 2a, or as shown in FIG. 2, only on one side of the polarizer 2a. A single-sided protective polarizing film having a protective film 2b thereon. When the polarizing film 2 is a single-sided protective polarizing film, it may have an adhesive layer 4, a polarizer 2a, a protective film 2b, and a brightness enhancing film 3 in sequence as shown in FIG. 2 (a), or as shown in FIG. 2 (b). As shown, there are an adhesive layer 4, a protective film 2b, a polarizer 2a, and a brightness enhancement film 3 in this order.

In the present invention, the aforementioned polarizing film 2 may be any one of a double-sided protective polarizing film and a single-sided protective polarizing film, but from the viewpoint of thinning, it is preferably a single-sided protective polarizing film. Furthermore, from the viewpoint of suppressing the deterioration of the polarizer, it is preferable that the protective film 2b is provided on the backlight side (the aforementioned FIG. 2 (a)). In addition, in the laminated film 1 of the present invention, the aforementioned layers may be in contact with each other, and other layers (such as an adhesive layer or an adhesive layer, an easy-adhesive layer, etc.) may be provided between the layers.

Each component will be described below.

(1) Polarizing film (1-1) Polarizer The polarizer used in the present invention may be any one that contains a polyvinyl alcohol resin, has a thickness of 10 μm or less, and has a monomer transmittance of 43.0% or more.

The single transmittance of the aforementioned polarizer is 43.0% or more. By making the polarizer's single transmittance more than 43.0%, the white brightness can be improved, and the power consumption caused by the brightness increase of the white display state of the liquid crystal display device (LCD) can be reduced, which is ideal. In addition, although the upper limit of the monomer transmittance is not particularly limited, it is preferably 44.5% or less from the viewpoint of suppressing a decrease in polarization.

The thickness of the polarizer need only be 10 μm or less, but for example, it is preferably 8 μm or less, more preferably 7 μm or less, and more preferably 6 μm or less. On the other hand, the thickness of the polarizer is preferably 2 μm or more, and more preferably 3 μm or more. Such a thin polarizer has less unevenness in thickness, has excellent visibility, and has less durability to thermal shock due to less dimensional change.

As the polarizer, a polyvinyl alcohol-based resin has been used. Examples of the polarizer include a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, and an ethylene-ethyl acetate copolymer-based partially saponified film, which can adsorb two colors of iodine or a dichroic dye. Sexual substances are uniaxially extended; polyene-based alignment films such as dehydrated polyvinyl alcohol or dehydrochlorinated polyvinyl chloride. Among these, a polarizer composed of a polyvinyl alcohol-based film and a dichroic substance such as iodine is particularly suitable.

For example, a polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially extending it can be produced by immersing polyvinyl alcohol in an aqueous solution of iodine to dye, and then extending the original length to 3 ~ 7 times. If necessary, it may contain boric acid, zinc sulfate, zinc chloride, or the like, and may be immersed in an aqueous solution such as potassium iodide. If necessary, the polyvinyl alcohol-based film is immersed in water and washed with water before dyeing. In addition to washing the polyvinyl alcohol-based film with water, the polyvinyl alcohol-based film can be cleaned of dirt and adhesion preventing agents, and the polyvinyl alcohol-based film swells, which also has the effect of preventing uneven dyeing. Stretching can be performed after iodine staining, or it can be extended while dyeing, or it can be stretched and then stained with iodine. It can also be extended in an aqueous solution such as boric acid or potassium iodide or in a water bath.

As for the thin polarizer, representative examples include thin polarizers described in the following documents or thin polarizers made by the manufacturing methods contained therein: Japanese Patent No. 4751486, Japanese Patent No. 4751481 No. 4, Japanese Patent No. 4815544, Japanese Patent No. 5048120, International Publication No. 2014/077599 and International Publication No. 2014/077636.

As for the aforementioned thin polarizer, in the manufacturing method including the step of stretching in the state of a laminated body and the dyeing step, from the viewpoint of being able to stretch at a high magnification and improving the polarization performance, a method including using an aqueous solution of boric acid is used. It is suitable to prepare the method by performing the extension step (as described in Japanese Patent No. 4751486, Japanese Patent No. 4751481 and Japanese Patent No. 4815544), and it is supplemented with a solution containing a boric acid solution before extension. The method of manufacturing the steps in the air (as described in Japanese Patent No. 4,751,481 and Japanese Patent No. 4815544) is particularly preferred. These thin polarizers can be obtained by a manufacturing method including the following steps: a step of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as a PVA-based resin) layer and a stretching resin substrate in a laminated state and a dyeing step. According to this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without causing unfavorable conditions such as breakage due to stretching because it is supported by the resin base material for stretching.

The boric acid content of the high-transmitting polarizer used in the present invention is not particularly limited, but for example, relative to the weight of the polarizer, 18 to 24% by weight is preferable, more preferably 18 to 23% by weight, and more than 18% by weight It is more preferably 23% by weight or less. Once the boric acid content exceeds 24% by weight, the bond between the polyvinyl alcohol molecular chains of the polarizer becomes too strong, and the stress generated when the polarizer shrinks and expands during the humidification test cannot be liberated, and sometimes the polarizer may occur. The condition of cracks. In addition, since the polarizer easily accumulates internal stress, it also tends to deteriorate panel warpage. In addition, when the boric acid content is less than 18%, the bond between the polyvinyl alcohol molecular chains of the polarizer tends to weaken, and there is a case where the degree of reduction in polarization degree increases after the humidification test or the durability of the polarizer decreases. In addition, the boric acid content of the aforementioned polarizer can be determined by the boric acid concentration of the boric acid aqueous solution used in the boric acid treatment (for example, insolubilization treatment and cross-linking treatment) when manufacturing the polarizer, and the boric acid concentration of the extension bath (boric acid aqueous solution) used to manufacture the polarizer by stretching in water And so on. The method for determining the boric acid content can be determined by the method described in the examples.

(1-2) Protective film As far as the material for forming the protective film used in the present invention, it is only required to be a material that has transparency and can allow the moisture permeability to be less than 200 g / (m ² · day), and is not particularly limited.

The moisture permeability of the protective film used in the present invention is 200 g / (m ² · day) or less, and preferably 150 g / (m ² · day) or less, more preferably 130 g / (m ² · day) or less, 120 g / (m ² · day) is better. In addition, although the lower limit value of the moisture permeability is not particularly limited, ideally, it is preferable that water vapor is not penetrated at all (that is, 0 g / (m ² · day)). If the moisture permeability of the protective film is within the aforementioned range, it is possible to prevent the polarizer from deteriorating the degree of polarization due to moisture deterioration. The aforementioned method for measuring the moisture permeability can be measured by the method described in the examples.

As mentioned above, although the moisture permeability of the protective film may be less than 200 g / (m ² · day), the uneven transmittance of the polarizer may be seen when the unit transmittance exceeds 43.9%. Therefore, the moisture permeability of the protective film It is preferably 50 g / (m ² · day) or less, more preferably 40 g / (m ² · day) or less, and more preferably 30 g / (m ² · day) or less.

The thickness of the protective film is 25 μm or less, and preferably 20 μm or less. In addition, although the lower limit of the thickness of the protective film is not particularly limited, it is usually about 1 μm or more. When the thickness of the protective film is 25 μm or less, the polarizing film can be made into a thin film, which is ideal.

Examples of the material forming the protective film include: polyester polymers such as polyethylene terephthalate or polyethylene naphthalate; cellulose polymers such as diethyl cellulose or triethyl cellulose; poly Acrylic polymers such as methyl methacrylate and lactone-modified acrylic polymers; styrene polymers such as polystyrene or acrylonitrile-styrene copolymer (AS resin); and polycarbonate polymers Wait. In addition, polyethylene, polypropylene, ring systems and even drop Polyolefin polymers such as polyolefins and ethylene-propylene copolymers, vinyl chloride polymers, fluorene polymers such as nylon or aromatic polyamines, fluorene polymers, fluorene polymers , Polyether fluorene-based polymer, polyether ether ketone-based polymer, polyphenylene sulfide-based polymer, vinyl alcohol-based polymer, vinylidene chloride-based polymer, ethylene butyral polymer, aryl ester polymer Polyacetal-based polymers, epoxy-based polymers, or blends of the aforementioned polymers can also be exemplified as the polymers forming the aforementioned protective films. The protective film may be formed in the form of a hardened layer of a thermosetting or UV-curable resin such as acrylic, urethane, urethane, epoxy, or siloxane.

(1-3) Adhesive layer The polarizer and the protective film are usually adhered through the adhesive layer.

The overall water absorption of the adhesive layer is preferably 10% by weight or less, more preferably 8% by weight or less, more preferably 5% by weight or less, and most preferably 0.05 to 2% by weight. If the overall water absorption is 10% by weight or less, a polarizing film having excellent durability under high temperature and high humidity can be obtained. More specifically, when placed in a high-temperature and high-humidity environment, the intrusion of water into the polarizer is suppressed, and the change in transmittance and the reduction in polarization of the polarizer can be suppressed. On the other hand, by making the overall water absorption rate 0.05% by weight or more, an adhesive layer that can appropriately absorb the water content of the polarizer when in contact with the polarizer can be formed, and the appearance of the resulting polarizing film can be suppressed from being poor (shrinkage, bubbles, etc.) ). The overall water absorption can be measured in accordance with the water absorption test method described in JIS K 7209. Specifically, the water absorption rate after the hardened adhesive layer is immersed in pure water at 23 ° C. for 24 hours can be obtained by the following formula. Overall water absorption (%) = [((weight of the bonding layer after immersion)-(weight of the bonding layer before immersion)) / (weight of the bonding layer before immersion)] × 100

Examples of the adhesive that can satisfy the aforementioned overall water absorption include hardening adhesives such as radical polymerization hardening adhesives and cationic polymerization hardening adhesives.

(Radical Polymerization Hardening Adhesive) The radical polymerization hardening adhesive contains a radical polymerizable compound used as a curable compound. The radical polymerizable compound may be a compound hardened by active energy rays, or a compound hardened by heat. Examples of active energy rays include electron rays, ultraviolet rays, and visible rays.

Examples of the radically polymerizable compound include compounds having a radically polymerizable functional group having a carbon-carbon double bond, such as a (meth) acrylfluorenyl group and a vinyl group. As the radically polymerizable compound, a polyfunctional radically polymerizable compound can be used. The radical polymerizable compound may be used singly or in combination of two or more kinds. Moreover, you may use together a polyfunctional radical polymerizable compound and a fluorene functional radical polymerizable compound.

The polymerizable compound is preferably a compound having a higher logP value (octanol / water partition coefficient), and a compound having a higher logP value is also preferably selected for a radical polymerizable compound. Here, the logP value is an index representing the lipophilicity of a substance, and means the logarithm of the partition coefficient of octanol / water. A high logP value means lipophilicity, which means low water absorption. The logP value can be measured (flask shaking method described in JIS-Z-7260), and can also be calculated by calculation based on the structure of each compound of the hardening type adhesive constituent (hardening component, etc.) (ChemDraw Ultra manufactured by CambridgeSoft).

The logP value of the radical polymerizable compound is preferably 2 or more, more preferably 3 or more, and more preferably 4 or more. Within this range, it is possible to prevent the polarizer from deteriorating due to moisture and obtain a polarizing film having excellent durability under high temperature and high humidity.

Examples of the polyfunctional radical polymerizable compound include tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1, 9-nonanediol di (meth) acrylate, 1,10-decanediol diacrylate, 2-ethyl-2-butylpropanediol di (meth) acrylate, bisphenol A di (meth) Acrylate, bisphenol A ethylene oxide adduct di (meth) acrylate, bisphenol A propylene oxide adduct di (meth) acrylate, bisphenol A diepoxypropyl ether bis (methyl) Base) acrylate, neopentyl glycol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, cyclic trimethylolpropane formal (meth) acrylate, di Alkanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, neopentaerythritol tri (meth) acrylate, neopentaerythritol tetra (meth) acrylate, dixin Esters of (meth) acrylates and polyols, such as pentaerythritol penta (meth) acrylate, dinepentaerythritol hexa (meth) acrylate, EO modified diglycerol tetra (meth) acrylate, etc. Compounds; 9,9-bis [4- (2- (meth) propenyloxyethoxy) phenyl] fluorene; epoxy (meth) acrylates; carbamate (meth) acrylates ; Polyester (meth) acrylate and the like.

Among the aforementioned polyfunctional radical polymerizable compounds, a polyfunctional radical polymerizable compound having a higher logP value is still preferred. Examples of such compounds include: tricyclodecanedimethanol di (meth) acrylate (logP = 3.05), (meth) acrylic acid Ester (logP = 3.27) and other alicyclic (meth) acrylates; 1,9-nonanediol di (meth) acrylate (logP = 3.68), 1,10-decanediol diacrylate (logP = 4.10) ) Equal long-chain aliphatic (meth) acrylate; hydroxytrimethylacetic acid neopentyl glycol (meth) acrylic acid adduct (logP = 3.35), 2-ethyl-2-butylpropanediol bis (methyl) Group) multi-chain (meth) acrylates such as acrylate (logP = 3.92); and 4 mol addition of bisphenol A di (meth) acrylate (logP = 5.46) and bisphenol A ethylene oxide Di (meth) acrylate (logP = 5.15), bisphenol A propylene oxide 2 mol addition adduct Di (meth) acrylate (logP = 6.10), bisphenol A propylene oxide 4 mol addition Di (meth) acrylate (logP = 6.43), 9,9-bis [4- (2- (meth) acryloxyethoxy) phenyl] pyrene (logP = 7.48), p-phenylene Phenol (meth) acrylate (logP = 3.98) and other aromatic ring-containing (meth) acrylates.

When a polyfunctional radical polymerizable compound and a monofunctional radical polymerizable compound are used in combination, the polyfunctional radical polymerizable content ratio is preferably 20 to 97% by weight, and more preferably 50 to 30% by weight relative to the total amount of the radical polymerizable compound. 95% by weight, more preferably 75 to 92% by weight, and even more preferably 80 to 92% by weight. Within this range, a polarizing film having excellent durability under high temperature and high humidity can be obtained.

Examples of the monofunctional radical polymerizable compound include a (meth) acrylamido derivative having a (meth) acrylamido group. When a (meth) acrylamide derivative is used, an adhesive layer with excellent adhesiveness can be formed with high productivity. Specific examples of the (meth) acrylamide derivative include N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, and N, N-diethyl N-alkyl-containing compounds such as (meth) acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, N-hexyl (meth) acrylamide (Meth) acrylamide derivatives; N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-hydroxymethyl-N-propane (meth) acryl N-hydroxyalkyl-containing (meth) acrylamide derivatives such as amidine; N-aminoalkyl-containing alkyl groups such as aminomethyl (meth) acrylamide, aminoethyl (meth) acrylamide (Meth) acrylamide derivatives; N-alkoxyl-containing (meth) acrylamide derivatives such as N-methoxymethacrylamine and N-ethoxymethacrylamine And N-mercaptoalkyl-containing (meth) acrylamide derivatives such as mercaptomethyl (meth) acrylamide and mercaptoethyl (meth) acrylamide, and the like. In addition, as the heterocyclic-containing (meth) acrylamide derivative in which the nitrogen atom in the (meth) acrylamino group forms a heterocyclic ring, for example, an N-acrylfluorenyl group can also be used. Phenyl, N-propenylpiperidine, N-methacrylopropylpiperidine, N-propenylpyridine, and the like. Among them, a (meth) acrylamide derivative containing an N-hydroxyalkyl group is preferable, and N-hydroxyethyl (meth) acrylamide is more preferable.

In addition, as for the aforementioned monofunctional radical polymerizable compound, (meth) acrylic acid derivatives having (meth) acryloxy groups; (meth) acrylic acid, carboxyethyl acrylate, and carboxypentyl acrylate Esters, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and other carboxyl-containing monomers; N-vinylpyrrolidone, N-vinyl-ε-caprolactam, Limonamine vinyl monomers such as methyl vinyl pyrrolidone; vinyl pyridine, vinyl piperidone, vinyl pyrimidine, vinyl piperidine Vinylpyridine , Vinylpyrrole, vinylimidazole, vinyl Azole, vinyl Vinyl-based monomers having a nitrogen-containing heterocyclic ring such as phthaloline and the like.

When a polyfunctional radical polymerizable compound and a monofunctional radical polymerizable compound are used in combination, the content ratio of the monofunctional radical polymerizable polymer is preferably 3 to 80% by weight, and more preferably 5 to 30% by weight relative to the total amount of the radical polymerizable compound. 50% by weight, more preferably 8 to 25% by weight, and even more preferably 8 to 20% by weight. Within this range, a polarizing film having excellent durability under high temperature and high humidity can be obtained.

The said radical polymerization hardening type adhesive agent may further contain another additive. When the radical polymerization hardening type adhesive contains a hardening compound that can be hardened by active energy rays, the adhesive may further contain, for example, a photopolymerization initiator, a photoacid generator, and a silane coupling agent. In addition, when the radical polymerization hardening type adhesive contains a hardening compound that can be hardened by heat, the adhesive may further include a thermal polymerization initiator, a silane coupling agent, and the like. In addition, other additives include, for example, a polymerization inhibitor, a polymerization initiator, a leveling agent, a wettability improver, a surfactant, a plasticizer, an ultraviolet absorber, an inorganic filler, a pigment, and a dye.

(Cation polymerization hardening type adhesive agent) The said cation polymerization hardening type adhesive agent contains a cationically polymerizable compound as a hardening compound. Examples of the cationically polymerizable compound include compounds having an epoxy group and / or an oxo group. The compound having an epoxy group is preferably a compound having at least two epoxy groups in the molecule. Examples of the compound having an epoxy group include a compound (aromatic epoxy compound) having at least two epoxy groups and at least one aromatic ring, at least two epoxy groups in the molecule, and at least one of which A compound (alicyclic epoxy compound) and the like between two adjacent carbon atoms constituting an alicyclic ring.

The aforementioned cationic polymerization hardening type adhesive preferably contains a photocationic polymerization initiator. The photo-cationic polymerization initiator will generate cationic species or Lewis acid and initiate the polymerization reaction of epoxy group or oxo group due to the irradiation of active energy rays such as visible light, ultraviolet rays, X-rays, and electron rays. The cation polymerization hardening type adhesive may further contain the aforementioned additives.

The said adhesive layer can be formed by coating the said hardening type adhesive agent on a polarizer or a protective film, bonding a polarizing film and the said resin film (transparent protective layer), and hardening this hardening type adhesive agent.

The polarizer and the protective film may be subjected to a surface modification treatment before the hardening-type adhesive is applied. Examples of the surface modification treatment include a treatment using a corona treatment, a plasma treatment, and a saponification treatment.

The coating method of the aforementioned hardening type adhesive may adopt any appropriate method depending on the viscosity of the adhesive and the thickness of the required adhesive layer. The coating method may be, for example, coating using a reverse coater, gravure coating (direct, reverse or flat plate), reverse bar coater, roll coater, die coater, bar coater, rod coater, etc. . In addition, coating by a dipping method may be used.

The hardening method of the hardening type | mold adhesive can use arbitrary appropriate methods. When the hardening type adhesive contains a hardening compound which can be hardened by active energy rays, the active energy rays can be irradiated from the polarizing film side or the transparent protective layer side to harden the adhesive. From the viewpoint of preventing deterioration of the polarizing film, it is preferable to irradiate the active energy rays from the transparent protective layer side. The conditions such as the wavelength of the active energy ray and the amount of irradiation can be set to any appropriate conditions depending on the type of the hardening compound used. When the hardening type adhesive contains a hardening compound that can be hardened by heat, the adhesive can be hardened by heating. The heating conditions can be set to any appropriate conditions depending on the type of the hardening compound used and the like. For example, it can be hardened by heating at a temperature of 60 to 200 ° C for 30 seconds to 5 minutes.

In addition, as the adhesive, a water-based adhesive generally used can also be used. Examples of the water-based adhesive include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex-based, water-based polyurethanes, and water-based polyesters.

The thickness of the aforementioned adhesive layer is not particularly limited. For example, it is preferably about 0.1 to 3 μm, and more preferably about 0.3 to 2 μm. If the thickness of the adhesive layer falls within the foregoing range, a polarizing plate having excellent adhesion and appearance is highly desirable.

The surface of the protective film that is not attached to the polarizer may also be treated with a hard coating or anti-reflection treatment to prevent adhesion, diffusion, and even anti-glare.

(2) Adhesive layer The adhesive layer used in the present invention is not particularly limited, and an adhesive layer formed of a conventional adhesive composition can be used.

The latent value of the aforementioned adhesive layer is preferably 100 to 150 μm, and more preferably 120 to 140 μm. The creep value falling within the aforementioned range can suppress the shrinkage of the polarizing film after the heating test, and can suppress the warpage and cracks caused by stress liberation, which is ideal. Here, the so-called creep value refers to the shift amount (μm) of the adhesive layer after one hour obtained from a creep test in which the adhesive layer was fixed to the substrate with an area of 10 mm × 10 mm and a load of 500 g was applied.

The adhesive layer is not particularly limited, and conventional materials can be used. Specifically, such an adhesive layer can be appropriately selected and used, for example, from a (meth) acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based or A polymer such as a rubber-based polymer is a base polymer. Among the overdue, acrylic adhesives based on (meth) acrylic polymers have excellent optical transparency and show moderate wettability, cohesiveness, and adhesion characteristics, and weather resistance and heat resistance. And so excellent and ideal.

Although the said (meth) acrylic-type polymer is not specifically limited, For example, the thing obtained by superposing | polymerizing the monomer component containing the (meth) acrylic-acid alkyl group which has a C4-C24 alkyl group in the terminal of an ester group is mentioned. In addition, alkyl (meth) acrylate is called alkyl acrylate and / or alkyl methacrylate, and has the same meaning as (meth) in the present invention.

Examples of the (meth) acrylic acid alkyl ester include a linear or branched chain alkyl group having 4 to 24 carbon atoms, and a linear or branched chain alkyl group having 4 to 9 alkyl groups (methyl) The alkyl acrylate is preferable from the viewpoint of easily achieving a balance in adhesive properties. These alkyl (meth) acrylates may be used individually by 1 type, and may be used in combination of 2 or more type.

The monomer component forming the (meth) acrylic polymer may contain a comonomer other than the aforementioned (meth) acrylic acid alkyl ester as a monofunctional monomer component. Examples of such a comonomer include a cyclic nitrogen-containing monomer, a hydroxyl-containing monomer, a carboxyl-containing monomer, and a monomer having a cyclic ether group.

In addition to the monomer component forming the (meth) acrylic polymer, in addition to the monofunctional monomer described above, in order to adjust the cohesive force of the adhesive, a polyfunctional monomer may be contained as necessary. The polyfunctional monomer is a monomer having at least two polymerizable functional groups having an unsaturated double bond such as a (meth) acrylfluorenyl group or a vinyl group, and examples thereof include dipentaerythritol hexa (meth) acrylic acid. Ester, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types.

For the production of such (meth) acrylic polymers, conventional production methods such as various types of radical polymerization such as solution polymerization and ultraviolet polymerization, block polymerization, and emulsion polymerization can be appropriately selected. The obtained (meth) acrylic polymer may be any of a random copolymer, a block copolymer, and a graft copolymer.

Polymerization initiators, chain transfer agents, emulsifiers, and the like used for radical polymerization are not particularly limited, and conventional substances commonly used in the technical field can be appropriately selected and used. In addition, the weight average molecular weight of the (meth) acrylic polymer can be controlled by the amount of the polymerization initiator, the chain transfer agent used, and the reaction conditions, and the amount used can be appropriately adjusted depending on the types thereof.

The weight average molecular weight of the (meth) acrylic polymer used in the present invention is preferably 400,000 to 4 million. By making the weight average molecular weight greater than 400,000, the durability of the adhesive layer can be satisfied, the cohesive force of the adhesive layer can be reduced, and the occurrence of residual glue can be suppressed. On the other hand, when the weight average molecular weight is more than 4 million, the adhesiveness tends to decrease. What's more, the viscosity of the adhesive in the solution system becomes too high, and sometimes it is difficult to apply. The weight average molecular weight refers to a value measured by GPC (gel permeation chromatography) and calculated using polystyrene conversion. In addition, it is difficult to measure the molecular weight of the (meth) acrylic polymer obtained by radiation polymerization.

The adhesive composition used in the present invention may contain a crosslinking agent. Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, polysiloxane-based crosslinking agents, Crosslinking agents such as oxazoline crosslinkers, acrylpropane crosslinkers, silane crosslinkers, alkyl etherified melamine crosslinkers, metal chelate crosslinkers, peroxides, etc. They can be used alone or in combination of two or more. As the crosslinking agent, an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent can be applied.

The aforementioned cross-linking agents may be used singly or as a mixture of two or more, but the content of the whole is preferably 0.01 to 10 parts by weight based on 100 parts by weight of the (meth) acrylic polymer. Range of shares.

The adhesive composition used in the present invention may contain a (meth) acrylic oligomer in order to improve adhesion. Furthermore, when the adhesive composition used in the present invention is applied to a hydrophilic adherend such as glass when the adhesive layer is used, a silane coupling agent may be contained in order to improve interfacial water resistance.

Furthermore, the adhesive composition used in the present invention may contain other conventional additives, for example, polyether compounds such as polypropylene glycol, polyether compounds such as polypropylene glycol, colorants, pigments, and other powders and dyes may be appropriately added depending on the application. , Surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, inorganic or organic fillers, metals Powder, granular / foil. In addition, within the controllable range, redox systems with reducing agents can also be used.

The formation method of the adhesive layer can be performed by a conventional method. Although not particularly limited, for example, the adhesive composition can be directly coated on the film (polarizing member, protective film) forming the adhesive layer, and borrowed. The solvent is removed by heating and drying to form an adhesive layer. In addition, an adhesive layer formed on a support or the like may be transferred onto the aforementioned film (polarizer, protective film).

Various methods can be used for the application method of an adhesive composition. Specifically, for example, a roll coating method, a contact roll coating method, a gravure coating method, a reverse coating method, a roll brush method, a spray coating method, a dip roll coating method, a bar coating method, a knife coating method, and an air knife coating method may be mentioned. , Curtain coating method, tape edge coating method and extrusion coating method using a die coater.

The aforementioned heating and drying temperature is preferably about 30 ° C to 200 ° C, more preferably about 40 ° C to 180 ° C, and more preferably about 80 ° C to 150 ° C. By setting the heating temperature within the aforementioned range, an adhesive layer having excellent adhesive properties can be obtained. The appropriate drying time can be adopted as the drying time. The aforementioned drying time is preferably about 5 seconds to 20 minutes, more preferably about 30 seconds to 10 minutes, and more preferably 1 minute to 8 minutes.

As the support, for example, a peeled sheet (spacer) can be used. Silicone release liners are suitable for the peeled sheet.

Examples of the constituent materials of the separator include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and non-woven cloth, nets, foamed sheets, metal foils, and the like. Laminates are suitable thin materials and the like, but from the viewpoint of excellent surface smoothness, plastic films are suitable for use.

Examples of the plastic film include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, and polyethylene terephthalate. Films, polybutylene phthalate films, polyurethane films, and ethylene-vinyl acetate copolymer films.

The thickness of the foregoing separator is usually 5 to 200 μm, and preferably about 5 to 100 μm. The separator may be subjected to mold release, antifouling treatment, coating type, or kneading type using a polysiloxane-based, fluorine-based, long-chain alkyl-based or fatty acid ammonium-based release agent, silicon dioxide powder, etc. as necessary. , Anti-static treatment such as evaporation type. In particular, the surface of the separator may be appropriately subjected to a peeling treatment such as a polysiloxane treatment, a long-chain alkyl treatment, or a fluorine treatment, thereby further improving the peelability of the adhesive layer.

In addition, the peeled-off sheet used in making the aforementioned laminated film can be directly used as a separator of the laminated film and the steps can be simplified.

In addition, in the case of the aforementioned laminated film, when forming the adhesive layer, various types of anchor layers can be formed on the surface of the film (polarizer, protective film) on which the adhesive layer is to be formed, or various corona treatments, plasma treatments, and the like can be performed. It is easy to form an adhesive layer after subsequent treatment. In addition, the surface of the adhesive layer can also be subjected to easy adhesion treatment.

The thickness of the adhesive layer is not particularly limited. For example, it is preferably 10 to 30 μm, and more preferably 15 to 25 μm.

(3) Brightening film The polarization degree of the brightening film used in the present invention is 90% or more, and more preferably 95% or more. Because the brightness enhancement film with a polarization degree of 90% or more is used in the present invention, uneven visibility can be reduced. Since the brightening film converts the light from the backlight into polarized light, the polarizing film will have polarized light incident. That is, even if the polarization degree of the polarizing film is deteriorated due to a high-temperature and high-humidity environment, since polarized light is incident through the brightness enhancing film having a high polarization degree, the polarization degree deterioration of the polarizing film has a small influence, and the occurrence of display unevenness can be suppressed.

The aforementioned brightness enhancement film may be, for example, a reflective polarizer. The reflective polarizer is a linearly polarized light-separating polarizer. Typical examples include wire-grid polarizers, multilayer thin-film laminated polarizers with two or more materials with mutually different refractive indices, vapor-deposited multilayer films with different refractive indexes, or two or more materials with different refractive indexes. Refractive layer multilayer film laminate, two or more resin laminate extensions using two or more resins with refractive index differences, polarizing plates that separate and reflect linearly polarized light in the direction of the orthogonal axis (linearly polarized separation type reflection) Polarizer). Among these, a linearly polarized light separation type reflective polarizer is particularly suitable. For example, the reflective polarizing plate of this type may be a commercially available product manufactured under the trade name "APF-V3" (polarization: 95%) and "APF-V4" (polarization: 92%) made in 3M.

The brightness enhancement film can be laminated on a polarizer or a protective film through an adhesive layer or an adhesive layer. The adhesive layer or the adhesive layer is not particularly limited, and any conventional one can be used. Moreover, you may use the adhesive layer or the adhesive layer as described in this specification.

The laminated film of the present invention is applicable to an image display device, and is particularly applicable to a backlight-side polarizing film of a liquid crystal display device. At this time, the liquid crystal cell can be attached through the adhesive layer.

After the laminated film of the present invention is left in an environment of 85 ° C. for 500 hours, the heat shrinkage rate in the absorption axis direction of the polarizer is preferably 0.5% or less, and preferably 0.4% or less. The laminated film of the present invention has the aforementioned heat shrinkage ratio to suppress the occurrence of warpage and cracks in the panel, and is also ideal for narrowing the panel frame.

2. Image display device The image display device of the present invention is characterized by having the aforementioned laminated film. The laminated film of the present invention can be suitably used as a backlight-side polarizing film of a liquid crystal display cell.

The image display device of the present invention only needs to include the laminated film of the present invention, and other structures may be the same as those of the conventional image display device.

The image display device of the present invention is highly reliable because it includes the aforementioned laminated film. Examples

Hereinafter, the present invention is specifically described by the embodiments, but the present invention is not limited by these embodiments. In addition, parts and% in each case are a basis of weight.

Manufacturing Example 1 (manufactured a polarizer (1) with a thickness of 5 μm) An air-assisted stretching at a stretching temperature of 130 ° C. was used to form a laminated body with a 9 μm-thick PVA layer formed on an amorphous PET substrate, and then an extended laminated body was formed. After immersing in an aqueous solution of 0.3% iodine / potassium iodide (weight ratio = 0.5 / 8) to produce a colored laminate, it is further extended with boric acid water at an extension temperature of 65 ° C to make the colored laminate at a total extension ratio of 5.94. An optical film laminate including a 5 μm-thick PVA layer extending integrally with the amorphous PET substrate was produced. An optical film laminate including a PVA layer (polarizer) (1) with a thickness of 5 μm, which constitutes a high-performance polarizing film, was generated. The PVA molecules of the PVA layer formed on the amorphous PET substrate in the high-performance polarizing film will be generated. Therefore, the two segments of the species extend to form a high-order alignment, and the iodine adsorbed by the dyeing will be oriented in a high-order direction in the form of a polyiodide ion complex. The PVA layer transmittance of the obtained optical film laminate was 43.3%, and the boric acid content was 23% by weight.

Manufacturing Example 2 (manufacturing a polarizer (2) with a thickness of 5 μm) A PVA layer (polarizer) containing a 5 μm thickness was produced in the same manner as in Manufacturing Example 1 except that the concentration of iodine / potassium iodide (weight ratio = 0.5 / 8) was changed to 0.2%. ) (2) The optical film laminate. The PVA layer transmittance of the obtained optical film laminate was 44.0%, and the boric acid content was 23% by weight.

Manufacturing Example 3 (manufactured polarizer (3) with a thickness of 5 μm) A PVA layer (polarizer) containing a thickness of 5 μm was produced in the same manner as in Manufacturing Example 1 except that the concentration of iodine / potassium iodide (weight ratio = 0.5 / 8) was changed to 0.23%. ) (3) The optical film laminate. The PVA layer transmittance of the obtained optical film laminate was 43.7%, and the boric acid content was 23% by weight.

Manufacturing Example 4 (manufacturing a polarizer (4) with a thickness of 5 μm) A PVA layer (polarizer) containing a 5 μm thickness was produced in the same manner as in Manufacturing Example 1, except that the concentration of iodine / potassium iodide (weight ratio = 0.5 / 8) was changed to 0.23%. ) (4) The optical film laminate. The PVA layer transmittance of the obtained optical film laminate was 42.8%, and the boric acid content was 23% by weight.

Production Example 5 (manufactured polarizer (5) with a thickness of 7 μm) A 20 μm thick polyvinyl alcohol film having an average degree of polymerization of 2400 and a degree of saponification of 99.9 mol% was immersed in warm water at 30 ° C. for 60 seconds to swell. Next, the film was dipped in an aqueous solution containing 0.3% of iodine / potassium iodide (weight ratio = 0.5 / 8) and stretched to 3.5 times while dyeing the film. Then, it extended | stretched in the boric acid ester aqueous solution of 65 degreeC so that the total extension ratio might become 6 times. After stretching, it was dried in an oven at 40 ° C. for 3 minutes to obtain a polarizer (5) having a thickness of 7 μm. The obtained polarizer had a transmittance of 43.3% and a boric acid content of 23% by weight.

Production Example 6 (manufactured polarizer (6) with a thickness of 12 μm) A 30 μm thick polyvinyl alcohol film having an average degree of polymerization of 2400 and a degree of saponification of 99.9 mol% was immersed in warm water at 30 ° C. for 60 seconds to swell. Next, the film was dyed while being immersed in an aqueous solution having a concentration of 0.3% of iodine / potassium iodide (weight ratio = 0.5 / 8) and extending to 3.5 times. Thereafter, stretching was performed at a total stretching ratio of 6 times in a 65 ° C borate aqueous solution. After stretching, it was dried in an oven at 40 ° C. for 3 minutes to obtain a polarizer (6) having a thickness of 12 μm. The obtained polarizer had a transmittance of 43.5% and a boric acid content of 23% by weight.

Production Example 7 (Preparation of hardening type adhesive agent) 10 parts by weight of hydroxyethylpropenamide (HEAA, logP = -0.56, homopolymer Tg = 123 ° C, manufactured by Hingrensha), (meth) acrylic acid tetrahydrofurfur Ester (FA-THFM, logP = 1.13, homopolymer Tg = 45 ° C, Hitachi Chemical Co., Ltd.) 10 parts by weight, tricyclodecane dimethanol diacrylate (trade name: Light acrylate DCP-A, logP = 3.05, homopolymer Tg = 134 ° C, 80 parts by weight of Kyoeisha Chemical Co., Ltd., 2-methyl-1- (4-methylthienyl) -2-morpholinopropane-1-one ( Trade name: IRGACURE907, logP = 2.09, manufactured by BASF) 3 parts by weight, diethylthiaxanthone (trade name: KAYACURE DETX-S, logP = 5.12, manufactured by Nippon Kayaku Co., Ltd.) 3 parts by weight It was stirred at 50 ° C. for 1 hour to obtain a hardening type adhesive which can be hardened by active energy rays.

Production Example 8 (Preparation of acrylic protective film) A methacrylic resin pellet having a glutarimide ring unit was dried at 100.5 kPa and 100 ° C for 12 hours, and was removed from the uniaxial extruder at a mold temperature of 270 ° C. The T-die is extruded to form a film. The film is further extended in a gas environment 10 ° C higher than the resin's Tg in the gas transport direction, and then extended in a direction orthogonal to the film transportation direction in a gaseous environment higher than the resin's Tg by 7 ° C. It is a protective film made of resin. The obtained film had a moisture permeability of 150 g / (m ² · day) and a thickness of 20 μm.

Example 1 The hardening adhesive prepared in Example 7 was coated on the surface of the polarizing film of the optical film laminate obtained in Manufacturing Example 1, and an acrylic film having a thickness of 20 μm after corona treatment was applied. Then, the acrylic film side was heated to 50 ° C using an IR heater, and the acrylic film side was irradiated with visible light to harden the hardening type adhesive, followed by hot air drying at 70 ° C for 3 minutes to obtain an amorphous PET-based Laminated body made of a material / polarizer / adhesive layer (thickness: 1 μm) / acrylic film. The amorphous PET substrate was peeled from the obtained laminate, and a brightness enhancement film (trade name: APF-V4, polarization degree: 92%, 3M) was bonded to the acrylic surface through an acrylic adhesive layer having a thickness of 5 μm. A 20 μm-thick adhesive layer (trade name: No. 58, manufactured by Nitto Denko Corporation) was laminated on the polarizer surface of the obtained laminated body to obtain a laminated film. This laminated film structure (adhesive layer / polarizer / protective film / brightening film) is referred to as structure A.

Example 2 The surface of the polarizing film of the optical film laminate obtained in Manufacturing Example 1 was coated with the hardening adhesive prepared in Manufacturing Example 7 and an acrylic film having a thickness of 20 μm which was subjected to corona treatment was bonded. Then, the acrylic film side was heated to 50 ° C using an IR heater, and the acrylic film side was irradiated with visible light to harden the hardening type adhesive, followed by hot air drying at 70 ° C for 3 minutes to obtain an amorphous PET-based Laminated body made of a material / polarizer / adhesive layer (thickness: 1 μm) / acrylic film. A brightening film (trade name: APF-V4, polarization degree: 92%, manufactured by 3M) was bonded to the polarizer surface of the obtained laminated body through an acrylic adhesive layer having a thickness of 5 μm. An amorphous PET substrate was peeled from the obtained laminated body, and an adhesive layer (trade name: No. 58, manufactured by Nitto Denko Corporation) was bonded to an acrylic film surface to obtain a laminated film. This laminated film structure (adhesive layer / protective film / polarizer / brightening film) is referred to as a structure B.

Example 3 On one side of the polarizer (5) obtained in Manufacturing Example 5, the hardening type adhesive prepared in Manufacturing Example 7 was applied, and an acrylic film having a thickness of 20 μm subjected to corona treatment was bonded. Then, the acrylic film side was heated to 50 ° C using an IR heater, and the acrylic film side was irradiated with visible light to harden the hardening type adhesive, followed by hot air drying at 70 ° C for 3 minutes to obtain a polarizer / adhesive. Layer (thickness: 1 μm) / acrylic film. A brightening film (trade name: APF-V4, polarization degree: 92%, manufactured by 3M) was bonded to the acrylic film surface of the obtained laminate through an acrylic adhesive layer having a thickness of 5 μm. A 20 μm-thick adhesive layer (trade name: No. 58, manufactured by Nitto Denko Corporation) was laminated on the polarizer surface of the obtained laminated body to obtain a laminated film.

Example 4 A laminated film was prepared in the same manner as in Example 1 except that the optical film laminated body obtained in Production Example 2 was used, except that a COP film having a thickness of 13 μm was subjected to corona treatment.

Example 5 A laminated film was produced in the same manner as in Example 1 except that the optical film laminated body obtained in Production Example 3 was used.

Example 6 A laminated film was produced in the same manner as in Example 1 except that APF-V3 was used as the brightness enhancement film.

Comparative Examples 1 to 4 A laminated film was formed in the same manner as in Example 1 except that the polarizer, the protective film, the adhesive layer, and the brightness enhancement film were changed to those listed in Table 1.

The laminated films obtained in Examples and Comparative Examples were measured as follows.

<Measurement of Polarizer Thickness> The thickness of the PVA layer (polarizer) used in Examples and Comparative Examples was measured using a digital micrometer (KC-351C, manufactured by Anritsu Corporation).

<Single Transmittance of Polarizer> The ultraviolet transmittance spectrophotometer (V7100, manufactured by JASCO Corporation) was used to measure the single transmittance T of the PVA layer (polarizer) used in Examples and Comparative Examples. These transmittances are Y values obtained by color correction after measurement at a 2-degree viewing angle (C light source) in JIS Z8701.

<Boric acid content of polarizer> The PVA layer (polarizer) used in Examples and Comparative Examples was dried by heating (120 ° C, 2 hours), and then pulverized to obtain a sample for evaluation weighing 1 g. 1 g of the evaluation sample was completely dissolved in 500 mL of water at 95 ° C. To the obtained aqueous solution, 10 g of mannitol and 2 mL of bromovanillol blue solution (BTB solution) were added to prepare a sample solution. In this sample solution, 0.1 mol / L sodium hydroxide was titrated to meet the neutralization point, and then the boric acid content (% by weight) was calculated from the titration according to the following formula. [Mathematical formula 1]

<Moisture permeability of the protective film> The moisture permeability of the protective film is measured in accordance with the moisture permeability test (moisture permeability cup method) in accordance with JIS Z0208. The sample cut into a diameter of 60mm was installed in a moisture-permeable cup filled with about 15g of calcium chloride, put into a thermostat at 40 ° C and 90%, and the weight of calcium chloride was measured before and after 24 hours to determine the moisture permeability. (g / m ²・ day).

<Creep Test> Using the adhesives used in Examples and Comparative Examples, an adhesive layer having a thickness of 25 μm was formed. Let the obtained adhesive layer having a thickness of 25 μm be cut into a 10 mm wide × 30 mm thing as a sample. 10 mm × 10 mm of the upper part of the sample was affixed to a baking plate, followed by heat-pressing treatment at 50 ° C. and 50 atm for 15 minutes, and then left at room temperature (23 ° C.) for 1 hour. After that, a load of 500 g (tensile shear stress with the load in a downward direction) was loaded on the sample, and the sample shift amount (μm) after 1 hour was measured.

<The overall water absorption of the adhesive layer> The hardening type adhesives used in the examples and comparative examples were cured under the same conditions as in the examples to produce a cured product for evaluation (weight: M ¹ g) having a thickness of 100 μm. The hardened material for evaluation was immersed in pure water at 23 ° C. for 24 hours, and then the surface moisture was taken out and wiped off, and then the weight (M ² g) of the hardened material for evaluation after immersion was measured. The overall water absorption was calculated from the weight M ¹ g of the hardened material for evaluation before immersion and the weight M ^{2 of the} hardened material for evaluation after immersion by the following formula. [Mathematical formula 2]

<Polarity of Brightening Film> The ultraviolet transmittance spectrophotometer (V7100, manufactured by JASCO Corporation) was used to measure the single transmittance T, parallel transmittance Tp, and orthogonal transmittance Tc of the brightening film. These transmittances are Y values obtained by color correction after measurement at a 2-degree viewing angle (C light source) in JIS Z8701. Using the above transmittance, the polarization degree P of the brightness enhancement film was determined by the following formula. Polarization P (%) = {(Tp-Tc) / (Tp ＋ Tc)} ^1/2 × 100

<Heating shrinkage rate> The laminated films obtained in the examples and comparative examples were cut to a size of 100 mm × 100 mm so that the direction of extension of the polarizer was 0 °, and were bonded to a glass plate having a thickness of 1 mm through an adhesive layer. Measure the sample, and mark the four corners of the polarizing film. The length L0 between the four corners of the polarizing film was measured with a Quick Vision machine made by Mitutoyo. The measured sample was put into a heating oven at 85 ° C for 500 hours, and the length L500 between the four corners of the polarizing film was measured immediately. The dimensional change rate is calculated by the following formula. Dimensional change rate (%) = ((L ₅₀₀ -L ₀ ) / L ₀ ) × 100

<Streak marks> In the appearance inspection of the laminated films obtained in the examples and comparative examples, occurrence of streak marks was confirmed visually. Count the number of paste marks per 1 m ² .

<Unevenness> The laminated films obtained in the Examples and Comparative Examples were laminated on one side of an alkali-free glass having a thickness of 0.3 mm, and a polarizing plate (trade name: GRT1794KUHC3) using a PVA film having a thickness of 12 μm was laminated on the other side. 43.0%, manufactured by Nitto Denko Corporation, so that the absorption axis of each polarizer is orthogonal, and it is put into the environment at 60 ° C and RH90% for 500 hours. After removing the backlight brightness in the darkroom (7000cd / cm ² or 10000cd / cm ²⁾ in stripes on the uneven surface within the visual confirmation. ：: When using a backlight of 10000 cd / cm ² , there is no unevenness in stripes. 〇: No unevenness in stripes when using a backlight of 7000 cd / cm ² . △: When using a backlight of 7000 cd / cm ² , there are some uneven bars. ×: When using a backlight of 7000 cd / cm ² , unevenness was observed in all areas.

<Crack> The obtained laminated film was cut to a size of 100 mm × 100 mm and a sample was produced. The obtained sample was bonded to a glass plate, and subjected to a 200-cycle thermal cycle test (-40 ° C to 85 ° C / 30 minutes), and the presence or absence of cracks was confirmed by visual inspection. 〇: No cracks occurred. ×: Cracks occurred.

<White brightness> After peeling off the TFT-side polarizer of the iPad (registered trademark) Air (manufactured by Apple) panel, and attaching the polarizers of Examples and Comparative Examples, whiteness was measured in a dark room using SR-UL1 (TOPCON CORPORATION). Brightness when displaying status.

<Warpage> The laminated films obtained in the examples and comparative examples were laminated on one side of an alkali-free glass having a thickness of 0.3 mm, and a polarizing plate (trade name: GRT1794KUHC3, Nitto) was laminated on the other side using a PVA film having a thickness of 12 μm. (Made by an electrician) so that the absorption axes of the polarizers are orthogonal to each other, and they are put in an environment of 85 ° C for 500 hours. After taking out, the amount of warpage was measured using QVA606-PRO-AE10 (made by Mitutoyo). ○: No warpage occurred or warpage that did not cause a problem. ×: Significant warpage occurred.

[Table 1]

In Table 1, the abbreviations are as follows. (Structure of laminated film) Structure A: Adhesive layer / polarizer / protective film / brightening film structure B: Adhesive layer / protective film / polarizer / brightening film (polarizer) Polarizer (1) ~ (6 ): Polarizers (1) to (6) obtained in Manufacturing Examples 1 to 6 (Brightening film) APF-V4: Trade name of the brightening film, polarization degree: 92%, 3M APF-V3: Product of brightening film Name, Polarization: 95%, DBEF-QV2 made by 3M: Product name of brightening film, Polarization: 88%, AF-film made by 3M: Product name of brightening film, Polarization: 62%, Extend (Protection Film) Acrylic: Acrylic protective film obtained in Production Example 8, moisture permeability: 150 g / (m ² · day), thickness: 20 μm COP: cycloolefin-based protective film, moisture permeability: 30 g / (m ² · day), thickness : 13 μm, trade name: ZF14-013, TAC-based protective film made by Zeon Corporation, moisture permeability: 800 g / (m ²・ day), thickness: 25 μm, trade name: TJ25UL, made by Fuji Film (adhesive layer) No. 58 : Product name, latent value: 120 μm, manufactured by Nitto Denko Corporation

1‧‧‧ laminated film
2‧‧‧ polarizing film
2a‧‧‧Polarizer
2b‧‧‧protective film
2c‧‧‧protective film
3‧‧‧brightening film
4‧‧‧ Adhesive layer

FIG. 1 is a cross-sectional view schematically showing an embodiment of a laminated film of the present invention. Fig. 2 (a) is a cross-sectional view schematically showing an embodiment of the laminated film of the present invention. Fig. 2 (b) is a cross-sectional view schematically showing an embodiment of the laminated film of the present invention.

1‧‧‧ laminated film

2‧‧‧ polarizing film

2a‧‧‧Polarizer

2b‧‧‧protective film

2c‧‧‧protective film

3‧‧‧brightening film

4‧‧‧ Adhesive layer

Claims (6)

A laminated film, characterized in that it comprises an adhesive layer, a polarizing film, and a brightness enhancement film in this order, and the polarizing film is a polarizing film having a protective film on at least one side of a polarizer containing a polyvinyl alcohol resin. ; The thickness of the polarizer is 10 μm or less, and the unit transmittance is 43.0% or more; the polarization degree of the brightness enhancement film is 90% or more; the thickness of the protective film is 25 μm or less, and the humidity is 200 g / (m ²・ Day) or less. For example, the laminated film of claim 1, wherein the boric acid content of the aforementioned polarizer is 18 to 24% by weight. For example, the laminated film of claim 1 or 2, wherein the latent value of the adhesive layer is 100 to 150 μm, and after the laminated film is left at 85 ° C. for 500 hours, the heat shrinkage of the polarizer in the direction of the absorption axis is obtained. 0.5% or less. The laminated film according to any one of claims 1 to 3, wherein the polarizer and the protective film are laminated through the adhesive layer, and the entire water absorption of the adhesive layer is 10% by weight or less. The laminated film according to any one of claims 1 to 4, wherein the aforementioned polarizing film is a polarizing film having a protective film only on one side of the polarizer, and the aforementioned laminated film sequentially includes an adhesive layer, a protective film, and a polarizer And brightening film, or sequentially including an adhesive layer, a polarizer, a protective film, and a brightening film. An image display device, comprising: a laminated film according to any one of claims 1 to 5.