JP6811549B2 - Laminated film and image display device - Google Patents

Description

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

In various image display devices, a polarizing film is used for displaying an image. For example, in a liquid crystal display (LCD), it is indispensable to arrange polarizing films on both sides of a glass substrate forming a liquid crystal panel surface from the image forming method. As such a polarizing film, generally, a protective film is bonded to one side or both sides of a polyvinyl alcohol-based film and a polarizing element made of a dichroic material such as iodine with a polyvinyl alcohol-based adhesive or the like. It is used.

In recent years, there has been a strong demand for weight reduction and thinning in image display devices such as liquid crystal display devices, and it is possible to reduce the weight and weight of various optical members such as polarizing films used in image display devices. There is a demand, and various thin polarizing films have been studied.

However, the thin polarizing film has a problem that its durability under high temperature and high humidity is low, and warpage and cracks occur. As a thin polarizing plate that suppresses such warpage and has excellent durability under high temperature and high humidity, for example, a first adhesive layer, a transparent protective layer formed from a resin film having a specific moisture permeability, a specific A polarizing plate in which a second adhesive layer having a bulk water absorption rate and a polarizing film having a thickness of 10 μm or less are laminated in this order is known (see Patent Document 1).

Japanese Patent No. 5871408

The thinner the polarizer, the more easily it is affected by moisture in a humidified environment, and the moisture deteriorates the polarizer and the degree of polarization of the polarizer decreases. Therefore, a polarizing film using the polarizer was used. Display unevenness is easily visible in the image display device. As a method of suppressing such display unevenness, it is conceivable to use a protective film having low moisture permeability to suppress deterioration of the polarizer due to moisture.

In recent years, the quality of panels has been increasing in the movement to increase the resolution. Since the panel transmittance decreases due to high definition, the demand for increasing the brightness of the module as a whole is accelerating, and the polarizing plate is also required to improve the transmittance. In addition, there are demands for specializing in design aspects such as thinning the entire module and narrowing the frame, and there is a growing demand for lower shrinkage after reliability and thinner overall polarizing plates. We are trying to improve the above request with a thin polarizer. However, in a thin polarizing element having a thickness of 10 μm or less, when the single transmittance is set to 43% or more in order to improve white brightness, even if a low moisture permeability protective film is used, it is often displayed on an image display device after a humidification test. The unevenness was visually recognized, and it was not sufficient in terms of suppressing the unevenness.

In Patent Document 1, the present invention is not limited to the case where a thin polarizing element having an extremely high transmittance of 43% or more is used, and the problem of display unevenness that can occur only when such a thin polarizing element is used. Is not mentioned at all.

Therefore, in the present invention, there is provided a thin laminated film capable of improving the white brightness and suppressing the occurrence of display unevenness after the humidification test even when a polarizing element having a thickness of 10 μm or less is used. The purpose is.

As a result of diligent studies to solve the above problems, the present inventors have found the following laminated film and have completed the present invention.

That is, the present invention is a laminated film including an adhesive layer, a polarizing film, and a luminance improving film in this order.
The polarizing film is a polarizing film having a protective film on at least one side of a polarizing element containing a polyvinyl alcohol-based resin.
The thickness of the polarizer is 10 μm or less, and the single transmittance is 43.0% or more.
The brightness improving film has a degree of polarization of 90% or more.
The present invention relates to a laminated film characterized in that the thickness of the protective film is 25 μm or less and the moisture permeability is 200 g / (m ² · day) or less.

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

The creep value of the pressure-sensitive adhesive layer is 100 to 150 μm.
After the laminated film is left at 85 ° C. for 500 hours, the heat shrinkage rate of the polarizer in the absorption axis direction is preferably 0.5% or less.

The polarizer and the protective film are laminated via an adhesive layer.
The bulk water absorption of the adhesive layer is preferably 10% by weight or less.

The polarizing film is a polarizing film having a protective film on only one side of the polarizer.
It is preferable that the laminated film contains the pressure-sensitive adhesive layer, the protective film, the polarizer, and the brightness improving film in this order, or contains the pressure-sensitive adhesive layer, the polarizer, the protective film, and the brightness improving film in this order.

The present invention also relates to an image display device having the laminated film.

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. Further, since a brightness improving film having a degree of polarization of 90% or more is used, there is a problem when a polarizer having a thickness of 10 μm or less and a single transmittance of 43% or more is used (display unevenness after the humidification test). Can be suppressed. Specifically, since the brightness improving film converts the light from the backlight into polarized light, polarized light is incident on the lower plate polarizer. Therefore, even if the polarizer is deteriorated due to the humidified environment and the degree of polarization is lowered, the polarized light is incident, so that the influence of the deterioration of the degree of polarization of the polarizer on the visibility can be reduced.

By using the laminated film of the present invention as a polarizing plate on the backlight side of a liquid crystal display device, it is possible to provide a thin liquid crystal display device having high white brightness and high optical reliability.

It is sectional drawing which shows one Embodiment of the laminated film of this invention schematically. (A) It is sectional drawing which shows typically one Embodiment of the laminated film of this invention. (B) It is sectional drawing which shows typically one Embodiment of the laminated film of this invention.

1. 1. Laminated film The laminated film of the present invention includes an adhesive layer, a polarizing film, and a brightness improving film in this order.
The polarizing film is a polarizing film having a protective film on at least one side of a polarizing element containing a polyvinyl alcohol-based resin.
The thickness of the polarizer is 10 μm or less, and the single transmittance is 43.0% or more.
The degree of polarization of the brightness improving film is 90% or more , and the degree of polarization is 90% or more.
The protective film has a thickness of 25 μm or less and a moisture permeability of 200 g / (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. The dimensions of each configuration in FIGS. 1 and 2 show an example thereof, 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 improving film 3 in this order. As shown in FIG. 1, the polarizing film 2 may be a double protective polarizing film having protective films 2b and 2c on both sides of the polarizing element 2a, and as shown in FIG. 2, only one side of the polarizing element 2a. It may be a single protective polarizing film having a protective film 2b. When the polarizing film 2 is a single-sided protective polarizing film, as shown in FIG. 2A, the pressure-sensitive adhesive layer 4, the polarizer 2a, the protective film 2b, and the brightness improving film 3 may be provided in this order, and FIG. As shown in (b), the pressure-sensitive adhesive layer 4, the protective film 2b, the polarizer 2a, and the brightness improving film 3 may be provided in this order.

In the present invention, the polarizing film 2 may be either a double-protective polarizing film or a single-protective polarizing film, but it is preferably a single-protective polarizing film from the viewpoint of thinning. Further, from the viewpoint of suppressing deterioration of the polarizer, an embodiment having a protective film 2b on the backlight side (FIG. 2A) is preferable. Further, the laminated film 1 of the present invention may be in contact with each of the above layers, and has another layer (for example, a layer such as an adhesive layer, an adhesive layer, an easy adhesive layer) between the layers. May be good.

Hereinafter, each component will be described.

(1) Polarizing film (1-1) Polarizer The polarizing element used in the present invention contains a polyvinyl alcohol-based resin, has a thickness of 10 μm or less, and has a single transmittance of 43.0% or more. All you need is.

The simple substance transmittance of the polarizer is 43.0% or more. When the single transmittance of the polarizer is 43.0% or more, the white brightness can be improved, and the power consumption can be reduced by increasing the brightness of the white display state of the liquid crystal display device (LCD), which is preferable. The upper limit of the single transmittance is not particularly limited, but is preferably 44.5% or less from the viewpoint of suppressing a decrease in the degree of polarization.

The thickness of the polarizer may be 10 μm or less, but is preferably 8 μm or less, more preferably 7 μm or less, and further preferably 6 μm or less. On the other hand, the thickness of the polarizer is preferably 2 μm or more, more preferably 3 μm or more. Such a thin polarizing element has less uneven thickness, excellent visibility, and less dimensional change, so that it has excellent durability against thermal shock.

As the polarizer, one using a polyvinyl alcohol-based resin is used. As the polarizer, for example, a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, an ethylene-vinyl acetate copolymerization system partially saponified film, and a bicolor property of iodine or a bicolor dye are used. Examples thereof include a uniaxially stretched film by adsorbing a substance, a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol and a dehydrogenated product of polyvinyl chloride. Among these, a polarizer made of a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable.

A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol by immersing it in an aqueous solution of iodine and stretching it 3 to 7 times its original length. If necessary, boric acid, zinc sulfate, zinc chloride and the like may be contained, or the mixture may be immersed in an aqueous solution such as potassium iodide. Further, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. In addition to being able to clean the surface of the polyvinyl alcohol film and blocking inhibitors by washing the polyvinyl alcohol film with water, it also has the effect of preventing non-uniformity such as uneven dyeing by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, stretching while dyeing, or stretching and then dyeing with iodine. It can be stretched even in an aqueous solution such as boric acid or potassium iodide or in a water bath.

As a thin polarizer, typically
Japanese Patent No. 4751486,
Japanese Patent No. 4751481
Patent No. 4815544,
Japanese Patent No. 5048120,
International Publication No. 2014/07759 Pamphlet,
International Publication No. 2014/077636 Pamphlet,
Etc., or the thin polarizing element obtained from the manufacturing method described in these.

The thin polarizer is patented in Patent No. 4751486, in that it can be stretched at a high magnification and the polarization performance can be improved even in a manufacturing method including a step of stretching in a laminated state and a step of dyeing. Those obtained by a production method including a step of stretching in an aqueous boric acid solution as described in Japanese Patent No. 4751481 and Japanese Patent No. 4815544 are preferable, and particularly described in Japanese Patent No. 4751481 and Japanese Patent No. 4815544. It is preferably obtained by a production method including a step of auxiliary stretching in the air before stretching in a certain boric acid aqueous solution. These thin polarizers can be obtained by a manufacturing method including a step of stretching a polyvinyl alcohol-based resin (hereinafter, also referred to as PVA-based resin) layer and a resin base material for stretching in a laminated state and a step of dyeing. With this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without problems such as breakage due to stretching because it is supported by the stretching resin base material.

The boric acid content of the highly transmissive polarizer used in the present invention is not particularly limited, but is preferably 18 to 24% by weight, more preferably 18 to 23% by weight, based on the weight of the polarizer. It is preferably more than 18% by weight and more preferably 23% by weight or less. When 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 during the contraction and expansion of the polarizer in the humidification test can be released. This may not be possible and cracks may occur in the polarizer. In addition, since the internal stress of the polarizer tends to accumulate, the panel warp tends to deteriorate. Further, when the boric acid content is less than 18%, the bond between the polyvinyl alcohol molecular chains of the polarizer tends to be weakened, the degree of polarization after the humidification test is significantly decreased, and the durability of the polarizer is decreased. May be done. The boric acid content of the polarizer is the boric acid concentration of the boric acid aqueous solution used for the boric acid treatment (for example, insolubilization treatment, cross-linking treatment) at the time of producing the polarizer, and the case where the polarizer is produced by stretching in water. It can be adjusted by the boric acid concentration of the stretching bath (boric acid aqueous solution) and the like. The method for measuring the boric acid content can be measured by the method described in Examples.

(1-2) Protective film The material for forming the protective film used in the present invention may be any material that is transparent and has a moisture permeability of 200 g / (m ² · day) or less. , Not particularly limited.

Protective film moisture permeability for use in the present invention ^{is, 200g / (m 2 · day} ) or less, preferably from 150g ^/ (m 2 · day) or less, more preferably 130g ^/ (m 2 · day) or less, 120 g / ( m ² · day) or less is more preferable. The lower limit of the moisture permeation is not particularly limited, but ideally, it is preferable that water vapor is not permeated at all (that is, 0 g / (m ² · day)). When the moisture permeability of the protective film is within the above range, it is possible to prevent the polarizer from deteriorating due to moisture and deteriorating the degree of polarization. The method for measuring the moisture permeability can be measured by the method described in Examples.

As described above, the moisture permeability of the protective film may be 200 g / (m ² · day) or less, but if the single transmittance of the polarizer exceeds 43.9%, display unevenness may be visually recognized. Therefore, the moisture permeability of the protective film is preferably 50 g / (m ² · day) or less, more preferably 40 g / (m ² · day) or less, and 30 g / (m ² · day) or less. Is more preferable.

The thickness of the protective film is 25 μm or less, preferably 20 μm or less. The lower limit of the thickness of the protective film is not particularly limited, but is usually about 1 μm or more. When the thickness of the protective film is 25 μm or less, the polarizing film can be thinned, which is preferable.

Examples of the material for forming the protective film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, and acrylic polymers such as polymethyl methacrylate and lactone-modified acrylic polymers. Examples thereof include styrene-based polymers such as polystyrene and acrylonitrile-styrene copolymer (AS resin), and polycarbonate-based polymers. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, and sulfone polymers. , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, allylate polymer, polyoxymethylene polymer, epoxy polymer, or Blends of the polymers and the like are also mentioned as examples of polymers forming the protective film. The protective film can also be formed as a cured layer of a thermosetting type or ultraviolet curable type resin such as acrylic type, urethane type, acrylic urethane type, epoxy type and silicone type.

(1-3) Adhesive layer The polarizer and the protective film are usually in close contact with each other via an adhesive layer.

The bulk water absorption of the adhesive layer is preferably 10% by weight or less, more preferably 8% by weight or less, further preferably 5% by weight or less, and 0.05 to 2% by weight. It is particularly preferable to have. When the bulk water absorption rate is 10% by weight or less, a polarizing film having excellent durability under high temperature and high humidity can be obtained. More specifically, the infiltration of water into the polarizer when placed in a high temperature and high humidity environment can be suppressed, and the change in the transmittance of the polarizer and the decrease in the degree of polarization can be suppressed. On the other hand, by setting the bulk water absorption rate to 0.05% by weight or more, it is possible to form an adhesive layer capable of appropriately absorbing the water contained in the polarizing element when it comes into contact with the polarizing element, and the obtained polarized light can be obtained. Poor appearance of the film (repellent, air bubbles, etc.) can be suppressed. The bulk water absorption rate is measured according to the water absorption rate test method described in JIS K 7209. Specifically, a water absorption rate when immersed for 24 hours adhesive layer has been turned into hard pure water 23 ° C., it is obtained from the following equation.
Bulk water absorption (%) = [{(weight of the adhesive layer after immersion) - (weight of the adhesive layer before immersion)} / (weight of the adhesive layer before immersion)] × 100

Examples of the adhesive that can satisfy the bulk water absorption rate include curable adhesives such as radical polymerization curable adhesives and cationic polymerization curable adhesives.

(Radical polymerization curing type adhesive)
The radical polymerization curable adhesive contains a radical polymerizable compound as a curable compound. The radically polymerizable compound may be a compound that is cured by active energy rays or a compound that is cured by heat. Examples of the active energy ray include an electron beam, ultraviolet rays, visible light and the like.

Examples of the radically polymerizable compound include compounds having a radically polymerizable functional group having a carbon-carbon double bond such as a (meth) acryloyl group and a vinyl group. As the radically polymerizable compound, a polyfunctional radically polymerizable compound is preferably used. As the radically polymerizable compound, only one kind may be used alone, or two or more kinds may be used in combination. Further, the polyfunctional radical polymerizable compound and the monofunctional radical polymerizable compound may be used in combination.

As the polymerizable compound, it is preferable to use a compound having a high logP value (octanol / water partition coefficient), and as the radical polymerizable compound, it is preferable to select a compound having a high logP value. Here, the logP value is an index showing the lipophilicity of a substance, and means a logarithmic value of the partition coefficient of octanol / water. A high logP value means that it is lipophilic, that is, it has a low water absorption rate. The logP value can be measured (the flask dipping method described in JIS-Z-7260), and is calculated based on the structure of each compound which is a constituent component (curable component, etc.) of the curable adhesive. It can also be calculated (ChemDraw Ultra manufactured by Cambridge Soft).

The logP value of the radically polymerizable compound is preferably 2 or more, more preferably 3 or more, and particularly preferably 4 or more. Within such a range, deterioration of the polarizing element due to moisture can be prevented, and a polarizing film having excellent durability under high temperature and high humidity can be obtained.

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 (). Meta) 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 Propropylene oxide adduct Di (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate, neopentyl glycol di (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate, cyclic trimethyl propanformal (meth) Acrylate, dioxane glycol di (meth) acrylate, trimethylpropantri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) ) Acrylate, esterified product of (meth) acrylate such as EO-modified diglycerin tetra (meth) acrylate and polyhydric alcohol; 9,9-bis [4- (2- (meth) acryloyloxyethoxy) phenyl] fluorene; epoxy Examples thereof include (meth) acrylate; urethane (meth) acrylate; polyester (meth) acrylate and the like.

Among the polyfunctional radical polymerizable compounds, a polyfunctional radical polymerizable compound having a high logP value is preferable. Such compounds include, for example, tricyclodecane dimethanol (meth) acrylate les over preparative (logP = 3.05), isobornyl (meth) acrylate (logP = 3.27) alicyclic (meth) acrylates such as Long-chain aliphatic (meth) acrylates such as 1,9-nonanediol di (meth) acrylate (logP = 3.68) and 1,10-decanediol diacrylate (logP = 4.10); neo-hydroxypivalate Multi-branched (meth) acrylates such as pentylglycol (meth) acrylic acid adduct (logP = 3.35), 2-ethyl-2-butylpropanediol di (meth) acrylate (logP = 3.92); bisphenol Adi (Meta) acrylate (logP = 5.46), bisphenol A ethylene oxide 4 mol adduct di (meth) acrylate (logP = 5.15), bisphenol A propylene oxide 2 mol adduct di (meth) acrylate (logP = 6) .10), bisphenol Apropylene oxide 4 mol adduct di (meth) acrylate (logP = 6.43), 9,9-bis [4- (2- (meth) acryloyloxyethoxy) phenyl] fluorene (logP = 7) .48), (meth) acrylate containing an aromatic ring such as p-phenylphenol (meth) acrylate (logP = 3.98) and the like can be mentioned.

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

Examples of the monofunctional radically polymerizable compound include (meth) acrylamide derivatives having a (meth) acrylamide group. By using the (meth) acrylamide derivative, a pressure-sensitive adhesive layer having excellent adhesiveness can be formed with high productivity. Specific examples of (meth) acrylamide derivatives include N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and N. N-alkyl group-containing (meth) acrylamide derivatives such as -butyl (meth) acrylamide, N-hexyl (meth) acrylamide; N-methylol (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-methylol-N- N-hydroxyalkyl group-containing (meth) acrylamide derivatives such as propane (meth) acrylamide; N-aminoalkyl group-containing (meth) acrylamide derivatives such as aminomethyl (meth) acrylamide and aminoethyl (meth) acrylamide; N-methoxymethyl N-alkoxy group-containing (meth) acrylamide derivatives such as acrylamide and N-ethoxymethylacrylamide; N-mercaptoalkyl group-containing (meth) acrylamide derivatives such as mercaptomethyl (meth) acrylamide and mercaptoethyl (meth) acrylamide can be mentioned. .. Further, as a heterocyclic-containing (meth) acrylamide derivative in which the nitrogen atom of the (meth) acrylamide group forms a heterocycle, for example, N-acrylloyl morpholine, N-acryloyl piperidine, N-methacryloyl piperidine, N-acryloyl pyrrolidine and the like. May be used. Among these, N-hydroxyalkyl group-containing (meth) acrylamide derivatives are preferable, and N-hydroxyethyl (meth) acrylamide is more preferable.

Further, as the monofunctional radical polymerizable compound, a (meth) acrylic acid derivative having a (meth) acryloyloxy group; (meth) acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, croton. Carboxyl group-containing monomers such as acid and isocrotonic acid; lactam-based vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam and methylvinylpyrrolidone; vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole , Vinyl imidazole, vinyl oxazole, vinyl morpholin, and other vinyl-based monomers having a nitrogen-containing heterocycle may be used.

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

The radical polymerization curable adhesive may further contain other additives. When the radical polymerization curable adhesive contains a curable compound that is cured by active energy rays, the adhesive may further contain, for example, a photopolymerization initiator, a photoacid generator, a silane coupling agent, and the like. When the radical polymerization curable adhesive contains a curable compound that is cured by heat, the adhesive may further contain a thermal polymerization initiator, a silane coupling agent, and the like. In addition, examples of other additives include polymerization inhibitors, polymerization initiators, leveling agents, wettability improvers, surfactants, plasticizers, ultraviolet absorbers, inorganic fillers, pigments, dyes and the like. ..

(Cynic polymerization curable adhesive)
The cationically polymerizable curable adhesive contains a cationically polymerizable compound as a curable compound. Examples of the cationically polymerizable compound include compounds having an epoxy group and / or an oxetanyl group. As the compound having an epoxy group, a compound having at least two epoxy groups in the molecule is preferably used. Examples of the compound having an epoxy group include a compound having at least two epoxy groups and at least one aromatic ring (aromatic epoxy compound), and at least two epoxy groups in the molecule, of which at least. One is a compound (alicyclic epoxy compound) formed between two adjacent carbon atoms constituting an alicyclic ring.

The cationic polymerization curable adhesive preferably contains a photocationic polymerization initiator. The photocationic polymerization initiator generates a cationic species or Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates a polymerization reaction of an epoxy group or an oxetanyl group. In addition, the cationic polymerization curable adhesive may further contain the above-mentioned additive.

In the adhesive layer, the curable adhesive is applied on a polarizer or a protective film, then the polarizing film and the resin film (transparent protective layer) are bonded to each other, and then the curable adhesive is cured. Can be formed.

The polarizer and the protective film may be subjected to a surface modification treatment before applying the curable adhesive. Examples of the surface modification treatment include corona treatment, plasma treatment, and saponification treatment.

As the method for applying the curable adhesive, any appropriate method can be adopted depending on the viscosity of the adhesive and the desired thickness of the adhesive layer or the like. Examples of the coating method include coating with a reverse coater, a gravure coater (direct, reverse or offset), a bar reverse coater, a roll coater, a die coater, a bar coater, a rod coater, or the like. Moreover, you may adopt the coating by the dipping method.

Any suitable method can be adopted as the curing method of the curable adhesive. When the curable adhesive contains a curable compound that is cured by the active energy ray, the adhesive can be cured by irradiating the active energy ray from the polarizing film side or the transparent protective layer side. 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. Conditions such as the wavelength and irradiation amount of the active energy rays can be set to arbitrary appropriate conditions according to the type of curable compound used and the like. If the curable adhesive contains a curable compound that cures by heat, the adhesive can be cured by heating. The heating conditions can be set to any suitable conditions depending on the type of curable compound used and the like. For example, it can be cured by heating at a temperature of 60 to 200 ° C. for 30 seconds to 5 minutes.

Further, as the adhesive, a commonly used water-based adhesive 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 adhesives, water-based polyurethanes, and water-based polyesters.

The thickness of the adhesive layer is not particularly limited, but is preferably, for example, about 0.1 to 3 μm, and more preferably about 0.3 to 2 μm. When the thickness of the adhesive layer is within the above range, a polarizing plate having excellent adhesiveness and appearance can be obtained, which is preferable.

The surface of the protective film to which the polarizer is not adhered may be subjected to a hard coat layer, antireflection treatment, anti-sticking treatment, or treatment for the purpose of diffusion or anti-glare.

(2) Adhesive Layer The pressure-sensitive adhesive layer used in the present invention is not particularly limited, and a pressure-sensitive adhesive layer formed from a known pressure-sensitive adhesive composition can be used.

The creep value of the pressure-sensitive adhesive layer is preferably 100 to 150 μm, more preferably 120 to 140 μm. By creep value is in the range, after heating test can be suppressed shrinkage of the polarizing film, warpage due to stress release, preferred because it can suppress the crack. Here, the creep value refers to the amount of displacement (μm) of the adhesive layer after 1 hour obtained from a creep test in which the adhesive layer is fixed to a substrate with an adhesive area of 10 mm × 10 mm and a load of 500 g is applied. Say.

The pressure-sensitive adhesive layer is not particularly limited, and known ones can be used. Specific examples of such an adhesive layer include a (meth) acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluoropolymer, a rubber polymer, or the like as a base polymer. Can be appropriately selected and used. Among these, acrylic adhesives based on (meth) acrylic polymers have excellent optical transparency, exhibit appropriate wettability, cohesiveness, and adhesive properties, and have weather resistance and heat resistance. It is preferable because it is excellent in such factors.

The (meth) acrylic polymer is not particularly limited, but can be obtained by polymerizing a monomer component containing an alkyl (meth) acrylate having an alkyl group having 4 to 24 carbon atoms at the end of the ester group. Can be mentioned. The alkyl (meth) acrylate refers to an alkyl acrylate and / or an alkyl methacrylate, and has the same meaning as the (meth) of the present invention.

Examples of the alkyl (meth) acrylate include those having a linear or branched chain alkyl group having 4 to 24 carbon atoms, and having a linear or branched chain alkyl group having 4 to 9 carbon atoms. Alkyl (meth) acrylates are preferable because they can easily balance the adhesive properties. These alkyl (meth) acrylates can be used alone or in combination of two or more.

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

In addition to the monofunctional monomer, the monomer component forming the (meth) acrylic polymer may contain a polyfunctional monomer, if necessary, in order to adjust the cohesive force of the pressure-sensitive adhesive. .. The polyfunctional monomer is a monomer having at least two polymerizable functional groups having an unsaturated double bond such as a (meth) acryloyl group or a vinyl group, and is, for example, dipentaerythritol hexa (meth) acrylate, 1 , 6-Hexanediol di (meth) acrylate, and trimerol propantri (meth) acrylate. The polyfunctional monomer may be used alone or in combination of two or more.

For the production of such (meth) acrylic polymers, known production methods such as solution polymerization, radiation polymerization such as ultraviolet polymerization, bulk polymerization, and various radical polymerizations such as emulsion polymerization can be appropriately selected. Further, the obtained (meth) acrylic polymer may be any of a random copolymer, a block copolymer, a graft copolymer and the like.

The polymerization initiator, chain transfer agent, emulsifier and the like used for radical polymerization are not particularly limited, and known ones usually used in this field can be appropriately selected and used. Further, the weight average molecular weight of the (meth) acrylic polymer can be controlled by the amount of the polymerization initiator and the chain transfer agent used, and the reaction conditions, and the amount of the (meth) acrylic polymer used is appropriately adjusted according to these types.

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 larger than 400,000, the durability of the pressure-sensitive adhesive layer can be satisfied, and the cohesive force of the pressure-sensitive adhesive layer can be suppressed to suppress the formation of adhesive residue. On the other hand, when the weight average molecular weight is larger than 4 million, the adhesiveness tends to decrease. Further, the pressure-sensitive adhesive may become too viscous in a solution system, making coating difficult. The weight average molecular weight was measured by GPC (Gerupami et Shon chromatography) refers to a value calculated in terms of polystyrene. It is difficult to measure the molecular weight of the (meth) acrylic polymer obtained by radiation polymerization.

The pressure-sensitive adhesive composition used in the present invention may contain a cross-linking agent. Examples of the cross-linking agent include isocyanate-based cross-linking agent, epoxy-based cross-linking agent, silicone-based cross-linking agent, oxazoline-based cross-linking agent, aziridine-based cross-linking agent, silane-based cross-linking agent, alkyl etherified melamine-based cross-linking agent, metal chelate-based cross-linking agent, and excess Examples thereof include cross-linking agents such as oxides, and these can be used alone or in combination of two or more. As the cross-linking agent, an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent are preferably used.

The cross-linking agent may be used alone or in combination of two or more, but the content as a whole is based on 100 parts by weight of the (meth) acrylic polymer. The cross-linking agent is preferably contained in the range of 0.01 to 10 parts by weight.

The pressure-sensitive adhesive composition used in the present invention may contain a (meth) acrylic oligomer in order to improve the adhesive strength. Further, the pressure-sensitive adhesive composition used in the present invention may contain a silane coupling agent in order to increase the water resistance at the interface when applied to a hydrophilic adherend such as glass of the pressure-sensitive adhesive layer.

Further, the pressure-sensitive adhesive composition used in the present invention may contain other known additives, for example, a polyether compound of a polyalkylene glycol such as polypropylene glycol, a powder such as a colorant and a pigment, and a dye. , Surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, antioxidants, light stabilizers, UV absorbers, polymerization inhibitors, inorganic or organic fillers, It can be appropriately added depending on the application in which the metal powder, particles, foil, etc. are used. Further, a redox system to which a reducing agent is added may be adopted within a controllable range.

The method for forming the pressure-sensitive adhesive layer can be carried out by a known method and is not particularly limited. For example, the pressure-sensitive adhesive composition is directly formed on a film (polarizer, protective film) for forming the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer can be formed by applying and removing the solvent or the like by heating and drying. Further, the pressure-sensitive adhesive layer formed on the support or the like can be transferred onto the film (polarizer, protective film).

Various methods are used as the method for applying the pressure-sensitive adhesive composition. Specifically, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coater, etc. Examples include a method such as an extrusion coating method.

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

As the support, for example, a peeled sheet (separator) can be used. A silicone release liner is preferably used as the release-treated sheet.

Examples of the constituent material of the separator include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester film, porous materials such as paper, cloth, and non-woven fabric, nets, foam sheets, metal foils, and laminates thereof. A thin leaf body or the like can be mentioned, but a plastic film is preferably used because of its excellent surface smoothness.

Examples of the plastic film include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, and ethylene. -Vinyl acetate copolymer film and the like can be mentioned.

The thickness of the separator is usually about 5 to 200 μm, preferably about 5 to 100 μm. If necessary, the separator may be released from a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based mold release agent, silica powder, or the like, as well as antifouling treatment, coating type, kneading type, or vapor deposition. Antistatic treatment such as mold can also be performed. In particular, the peelability from the pressure-sensitive adhesive layer can be further enhanced by appropriately performing a peeling treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment on the surface of the separator.

The peeled sheet used in producing the laminated film can be used as it is as a separator for the laminated film, and the process can be simplified.

Further, in the laminated film, when forming the pressure-sensitive adhesive layer, an anchor layer is formed on the surface of the film (polarizer, protective film) forming the pressure-sensitive adhesive layer, and various types of easy adhesion such as corona treatment and plasma treatment are performed. The pressure-sensitive adhesive layer can be formed after the treatment. Further, the surface of the pressure-sensitive adhesive layer may be subjected to an easy-adhesion treatment.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is preferably, for example, 10 to 30 μm, and preferably 15 to 25 μm.

(3) Luminance Improvement Film The luminance improvement film used in the present invention has a degree of polarization of 90% or more, preferably 95% or more. In the present invention, since the brightness improving film having a degree of polarization of 90% or more is used, uneven visibility can be reduced. Since the brightness improving film converts the light from the backlight into polarized light, polarized light is incident on the polarizing film. That is, even if the degree of polarization of the polarizing film deteriorates due to a high temperature and high humidity environment, the polarized light is incident through the brightness improving film having a high degree of polarization, so that the influence of the deterioration of the degree of polarization of the polarizing film is small and the display unevenness is displayed. Can be suppressed.

Examples of the brightness improving film include a reflective polarizing plate. The reflective polarizing plate is a linearly polarized light separation type polarizing plate. Typical examples are a grid type polarizing plate, a multilayer thin film laminated polarizing plate made of two or more materials having different refractive indexes, a vapor-deposited multilayer thin film having different refractive indexes, and a birefringent layer multilayer thin film made of two or more kinds of materials having different refractive indexes. Laminates, stretched two or more resin laminates using two or more resins with different refractive indexes, and polarizing plates that separate linearly polarized light by reflecting / transmitting in orthogonal axial directions (linear polarization separation) Type reflective polarizing plate). Among these, a linearly polarized light separation type reflective polarizing plate is preferably used. As such a reflective polarizing plate, for example, those commercially available under the trade names "APF-V3" (polarization degree: 95%) and "APF-V4" (polarization degree: 92%) manufactured by 3M are used. You can also.

The brightness improving film can be laminated on the polarizer or the protective film via an adhesive layer or an adhesive layer. The adhesive layer or the adhesive layer is not particularly limited, and any known adhesive layer can be used. In addition, the adhesive layer or the adhesive layer described in the present specification can be used.

The laminated film of the present invention can be suitably used in an image display device, and in particular, can be suitably used as a backlight-side polarizing film in a liquid crystal display device. In that case, it can be attached to the liquid crystal cell via the pressure-sensitive 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, preferably 0.4% or less. Is more preferable. Since the laminated film of the present invention has the heat shrinkage rate, it is possible to suppress warpage and crack generation of the panel, and it is possible to cope with a narrow frame of the panel, which is preferable.

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

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

Since the image display device of the present invention includes the laminated film, it has high reliability.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. In addition, each part and% in each example is based on weight.

Production Example 1 (Production of a polarizer (1) having a thickness of 5 μm)
A stretched laminate in which a 9 μm-thick PVA layer was formed on an amorphous PET substrate was subjected to aerial auxiliary stretching at a stretching temperature of 130 ° C., and then the stretched laminate was subjected to iodine / potassium iodide (weight). A colored laminate is formed by immersing the colored laminate in an aqueous solution having a ratio of 0.5 / 8) and a concentration of 0.3%, and the colored laminate is further stretched in boric acid water at a stretching temperature of 65 ° C. to achieve a total draw ratio of 5.94 times. An optical film laminate containing a 5 μm-thick PVA layer stretched integrally with the amorphous PET substrate was produced. The PVA molecules in the PVA layer formed on the amorphous PET substrate by such two-step stretching are highly oriented, and the iodine adsorbed by staining is highly oriented in one direction as a polyiodine ion complex. An optical film laminate containing a PVA layer (polarizer) (1) having a thickness of 5 μm, which constitutes the high-performance polarizing film, was produced. The transmittance of the PVA layer of the obtained optical film laminate was 43.3%, and the boric acid content was 23% by weight.

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

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

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

Production Example 5 (Production of a polarizer (5) having a thickness of 7 μm)
A 20 μm-thick polyvinyl alcohol film having an average degree of polymerization of 2400 and a saponification degree of 99.9 mol% was immersed in warm water at 30 ° C. for 60 seconds to swell. Then, the film was dyed by immersing it in an aqueous solution having a concentration of iodine / potassium iodide (weight ratio = 0.5 / 8) at a concentration of 0.3% and stretching it up to 3.5 times. Then, stretching was carried out in a boric acid ester aqueous solution at 65 ° C. so that the total stretching ratio was 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 transmittance of the obtained polarizer was 43.3%, and the boric acid content was 23% by weight.

Production Example 6 (Production of a polarizer (6) having a thickness of 12 μm)
A polyvinyl alcohol film having an average degree of polymerization of 2400 and a saponification degree of 99.9 mol% and a thickness of 30 μm was immersed in warm water at 30 ° C. for 60 seconds to swell. Then, the film was dyed by immersing it in an aqueous solution having a concentration of iodine / potassium iodide (weight ratio = 0.5 / 8) at a concentration of 0.3% and stretching it up to 3.5 times. Then, stretching was carried out in a boric acid ester aqueous solution at 65 ° C. so that the total stretching ratio was 6 times. 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 transmittance of the obtained polarizer was 43.5%, and the boric acid content was 23% by weight.

Production Example 7 (Preparation of curable adhesive)
Hydroxyethylacrylamide (HEAA, logP = -0.56, homopolymer Tg = 123 ° C., manufactured by Kojinsha), 10 parts by weight, tetrahydrofurfuryl (meth) acrylate (FA-THFM, logP = 1.13, homopolymer) Tg = 45 ° C, Hitachi Chemical Co., Ltd., 10 parts by weight, tricyclodecanedimethanol diacrylate (trade name: light acrylate DCP-A, logP = 3.05, homopolymer Tg = 134 ° C, Kyoeisha Chemical Co., Ltd. (Manufactured by Co., Ltd.) 80 parts by weight, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one (trade name: IRGACURE907, logP = 2.09, manufactured by BASF) 3 parts by weight , Diethylthioxanthone (trade name: KAYACURE DETX-S, logP = 5.12, manufactured by Nippon Kayaku Co., Ltd.) 3 parts by weight are mixed, stirred at 50 ° C. for 1 hour, and cured by active energy rays. Obtained adhesive.

Production Example 8 (Preparation of acrylic protective film)
A methacrylic resin pellet having a glutarimide ring unit was dried at 100.5 kPa at 100 ° C. for 12 hours and extruded from a T die at a die temperature of 270 ° C. using a single-screw extruder to form a film. Further, the film is stretched in the transport direction in an atmosphere 10 ° C. higher than the Tg of the resin, and then stretched in the direction orthogonal to the film transport direction in an atmosphere 7 ° C. higher than the Tg of the resin to form the acrylic resin. A protective film composed was obtained. The moisture permeability of the obtained film was 150 g / (m ² · day), and the thickness was 20 μm.

Example 1
The curable pressure-sensitive adhesive produced in Production Example 7 was applied to the surface of the polarizing film of the optical film laminate obtained in Production Example 1, and a corona-treated 20 μm-thick acrylic film was attached. Then, the acrylic film side was heated to 50 ° C. using an IR heater, the acrylic film side was irradiated with visible light to cure the curable adhesive, and then hot air dried at 70 ° C. for 3 minutes. A laminate composed of an amorphous PET base material / polarizer / adhesive layer (thickness: 1 μm) / acrylic film was obtained. The amorphous PET base material is peeled off from the obtained laminate, and a brightness improving film (trade name: APF-V4, degree of polarization:) is placed on the acrylic film surface via an acrylic adhesive layer having a thickness of 5 μm. 92%, made of 3M) were pasted together. A 20 μm-thick pressure-sensitive adhesive layer (trade name: No. 58, manufactured by Nitto Denko KK) was bonded to the polarizer surface of the obtained laminate to obtain a laminated film. The structure of this laminated film (adhesive layer / polarizer / protective film / brightness improving film) is referred to as structure A.

Example 2
The curable pressure-sensitive adhesive produced in Production Example 7 was applied to the surface of the polarizing film of the optical film laminate obtained in Production Example 1, and a corona-treated 20 μm-thick acrylic film was attached. Then, the acrylic film side was heated to 50 ° C. using an IR heater, the acrylic film side was irradiated with visible light to cure the curable adhesive, and then hot air dried at 70 ° C. for 3 minutes. A laminate composed of an amorphous PET base material / polarizer / adhesive layer (thickness: 1 μm) / acrylic film was obtained. A brightness-improving film (trade name: APF-V4, degree of polarization: 92%, manufactured by 3M) was attached to the polarizer surface of the obtained laminate via an acrylic adhesive layer having a thickness of 5 μm. The amorphous PET base material was peeled off from the obtained laminate, and a 20 μm-thick adhesive layer (trade name: No. 58, manufactured by Nitto Denko KK) was laminated on the acrylic film surface. I got a film. The structure of this laminated film (adhesive layer / protective film / polarizer / brightness improving film) is referred to as structure B.

Example 3
The curable pressure-sensitive adhesive produced in Production Example 7 was applied to one side of the polarizing element (5) obtained in Production Example 5, and a corona-treated acrylic film having a thickness of 20 μm was attached. Then, the acrylic film side was heated to 50 ° C. using an IR heater, the acrylic film side was irradiated with visible light to cure the curable adhesive, and then hot air dried at 70 ° C. for 3 minutes. A laminate composed of a polarizer / an adhesive layer (thickness: 1 μm) / an acrylic film was obtained. A brightness improving film (trade name: APF-V4, degree of polarization: 92%, manufactured by 3M) was attached to the acrylic film surface of the obtained laminate via an acrylic adhesive layer having a thickness of 5 μm. A 20 μm-thick pressure-sensitive adhesive layer (trade name: No. 58, manufactured by Nitto Denko KK) was bonded to the polarizer surface of the obtained laminate to obtain a laminated film.

Example 4
A laminated film was obtained in the same manner as in Example 1 except that the optical film laminate obtained in Production Example 2 was used and a corona-treated 13 μm-thick COP film was used.

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

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

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

The following measurements were carried out on the laminated films obtained in Examples and Comparative Examples.

<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).

<Single transmittance of polarizer>
The single transmittance T of the PVA layer (polarizer) used in Examples and Comparative Examples was measured using an ultraviolet-visible spectrophotometer (V7100, manufactured by JASCO Corporation). These transmittances are Y values measured by the JIS Z8701 double field of view (C light source) and corrected for luminosity factor.

<Boric acid content of polarizer>
The PVA layer (polarizer) used in Examples and Comparative Examples was dried by heating (120 ° C. for 2 hours) and then pulverized to obtain an evaluation sample having a weight of 1 g. All 1 g of the evaluation sample was dissolved in 500 mL of water at 95 ° C. To the obtained aqueous solution, 10 g of mannitol and 2 mL of a bromothymol blue solution (BTB solution) were added to prepare a sample solution. 0.1 mol / L sodium hydroxide was added dropwise to this sample solution until the neutralization point was reached, and the boric acid content (% by weight) was calculated from the added amount based on the following formula.

<Humidity permeability of protective film>
The moisture permeability of the protective film was measured according to the moisture permeability test (cup method) of JIS Z0208. A sample cut to a diameter of 60 mm is set in a moisture-permeable cup containing about 15 g of calcium chloride, placed in a 90% thermostat at 40 ° C., and the weight increase of calcium chloride before and after being left for 24 hours is measured to make it transparent. Humidity (g / m ² · day) was determined.

<Creep test>
The pressure-sensitive adhesive used in Examples and Comparative Examples was used to form a pressure-sensitive adhesive layer having a thickness of 25 μm. The obtained adhesive layer having a thickness of 25 μm was cut into a width of 10 mm × 30 mm and used as a sample. The upper part of this sample, 10 mm × 10 mm, was attached to a bake plate, autoclaved at 50 ° C. and 50 atm for 15 minutes, and then left at room temperature (23 ° C.) for 1 hour. Then, a load of 500 g was applied to the sample (load of tensile shear stress in the drooping direction), and the amount of displacement (μm) of the sample after 1 hour was measured.

<Bulk water absorption of adhesive layer>
The curable adhesive used in Examples and Comparative Examples was cured under the same conditions as in Examples to prepare a cured product (weight: M ¹ g) having a thickness of 100 μm. The evaluated cured product was immersed in pure water at 23 ° C. for 24 hours, then taken out and the water on the surface was wiped off, and then the weight (M ² g) of the evaluated cured product after immersion was measured. The bulk water absorption rate was calculated from the weight M ¹ g of the evaluated cured product before immersion and the weight M ² g of the evaluated cured product after immersion by the following formula.

<Polarization of brightness improving film>
The single transmittance T, the parallel transmittance Tp, and the orthogonal transmittance Tc of the luminance improving film were measured using an ultraviolet-visible spectrophotometer (V7100 manufactured by JASCO Corporation). These transmittances are Y values measured by the JIS Z8701 double field of view (C light source) and corrected for luminosity factor. The degree of polarization P of the brightness-improving film was determined by the following equation using the above transmittance.
Polarization degree P (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100

<Heat shrinkage rate>
The laminated films obtained in Examples and Comparative Examples are cut into a size of 100 mm × 100 mm so that the stretching direction of the polarizing element is 0 °, and are attached on a glass plate having a thickness of 1 mm via an adhesive layer. Together, they were used as measurement samples, and the four corners of the polarizing film were marked. The length L ₀ between the marks at the four corners of the polarizing film was measured with an image measuring machine (Quick Vision) manufactured by Mitutoyo Co., Ltd. The measured sample was placed in a heating oven at 85 ° C. for 500 hours, and then the length L ₅₀₀ between the marks at the four corners of the polarizing film was measured again. The dimensional change rate was calculated by the following formula.
Dimensional change rate (%) = {(L _500- L ₀ ) / L ₀ } x 100

<Glue dents>
In the visual inspection of the laminated films obtained in Examples and Comparative Examples, the occurrence of glue dents was visually confirmed. The number of glue dents generated per 1 m ² was counted.

<Uneven>
A polarizing plate using the laminated films obtained in Examples and Comparative Examples on one side of a non-alkali glass having a thickness of 0.3 mm and a PVA film having a thickness of 12 μm on the other side (trade name: GRT1794KUHC3, transmittance: 43. 0%, manufactured by Nitto Denko KK, was bonded together so that the absorption axes of the respective polarizers were orthogonal to each other. H. It was put into a 90% environment for 500 hours. After taking out, in-plane streak-like unevenness on the backlight brightness (7000 cd / cm ² or 10000 cd / cm ² ) was visually confirmed in a dark room.
⊚: No streak-like unevenness even when a backlight of 10000 cd / cm ² is used.
〇: No streak-like unevenness when using a 7000 cd / cm ² backlight.
Δ: There is some streak-like unevenness when a backlight of 7000 cd / cm ² is used.
X: There is streak-like unevenness on the entire surface when a backlight of 7000 cd / cm ² is used.

<Crack>
The obtained laminated film was cut out to a size of 100 mm × 100 mm to prepare a sample. The obtained sample was attached to a glass plate, and a heat cycle test (-40 ° C to 85 ° C / 30 minutes) was performed for 200 cycles, and the presence or absence of cracks was visually confirmed.
〇: No cracks occurred.
×: There is a crack.

<White brightness>
After peeling off the polarizing plate on the TFT side of the iPad (registered trademark) Air (manufactured by Apple) panel and pasting the polarizing plates of Examples and Comparative Examples, the brightness in the white display state is SR-UL1 (TOPCON CORPORATION). The measurement was performed in a dark room using.

<Warp>
A polarizing plate using the laminated films obtained in Examples and Comparative Examples on one side of a non-alkali glass having a thickness of 0.3 mm and a PVA film having a thickness of 12 μm on the other side (trade name: GRT1794KUHC3, Nitto Denko KK). Was put together so that the absorption axes of the respective polarizers were orthogonal to each other, and the mixture was put into an environment of 85 ° C. for 500 hours. After taking out, the amount of warpage was measured using QVA606-PRO-AE10 (manufactured by Mitutoyo Co., Ltd.).
〇: No warpage occurred, or warpage to the extent that it did not cause a problem occurred.
X: Significant warpage occurred.

In Table 1, each abbreviation is as follows.
(Structure of laminated film)
Composition A: Adhesive layer / Polarizer / Protective film / Brightness improving film Composition B: Adhesive layer / Protective film / Polarizer / Brightness improving film (polarizer)
Polarizers (1) to (6): Polarizers (1) to (6) obtained in Production Examples 1 to 6.
(Brightness improvement film)
APF-V4: Brand name of brightness improving film, degree of polarization: 92%, made by 3M APF-V3: Product name of brightness improving film, degree of polarization: 95%, made by 3M DBEF-QV2: Product name of brightness improving film, polarized light Degree: 88%, 3M AF-film: Brand name of brightness improvement film, Polarization degree: 62%, Made by Extend (protective film)
Acrylic: Acrylic protective film obtained in Production Example 8, moisture permeability: 150 g / (m ² · day), thickness: 20 μm
COP: Cycloolefin protective film, moisture permeability: 30 g / (m ² · day), thickness: 13 μm, trade name: ZF14-013, TAC protective film made by Nippon Zeon, moisture permeability: 800 g / (m ² · day) , Thickness: 25 μm, Product name: TJ25UL, Made by Fuji Film (Adhesive layer)
No. 58: Product name, creep value: 120 μm, manufactured by Nitto Denko KK

1 Laminated film 2 Polarizing film 2a Polarizer 2b Protective film 2c Protective film 3 Brightness improving film 4 Adhesive layer

Claims (4)

A laminated film containing an adhesive layer, a polarizing film, and a brightness improving film in this order.
The polarizing film is a polarizing film having a protective film on only one side of a polarizing element containing a polyvinyl alcohol-based resin.
The laminated film includes the pressure-sensitive adhesive layer, the protective film, the polarizer, and the brightness improving film in this order.
The thickness of the polarizer is 10 μm or less, and the single transmittance is 43.0% or more.
The degree of polarization of the brightness improving film is 90% or more, and the degree of polarization is 90% or more.
Creep value of the pressure-sensitive adhesive layer (The creep value is the amount of displacement of the pressure-sensitive adhesive layer after 1 hour obtained from a creep test in which the pressure-sensitive adhesive layer is fixed to a substrate with an adhesive area of 10 mm × 10 mm and a load of 500 g is applied. μm) is 100 to 150 μm,
After the laminated film is left at 85 ° C. for 500 hours, the heat shrinkage rate of the polarizer in the absorption axis direction is 0.5% or less.
A laminated film having a thickness of 25 μm or less and a moisture permeability of 200 g / (m ² · day) or less measured by the following method.
<Humidity permeability of protective film>
The moisture permeability of the protective film is measured according to the moisture permeability test (cup method) of JIS Z0208. A sample cut to a diameter of 60 mm is set in a moisture permeable cup containing 15 g of calcium chloride, placed in a 90% thermostat at 40 ° C., and the weight increase of calcium chloride before and after being left for 24 hours is measured to measure the moisture permeability. (G / m ² · day) is calculated. The laminated film according to claim 1, wherein the boric acid content of the polarizer is 18 to 24% by weight. The polarizer and the protective film are laminated via an adhesive layer.
The bulk water absorption rate of the adhesive layer obtained from the following formula (the bulk water absorption rate is the water absorption rate when the cured adhesive layer is immersed in pure water at 23 ° C. for 24 hours) is 10% by weight or less. The laminated film according to claim 1 or 2 , wherein the laminated film is characterized by the above.
Bulk water absorption (%) = [{(Weight of adhesive layer after immersion)-(Weight of adhesive layer before immersion)} / (Weight of adhesive layer before immersion)] × 100 An image display device comprising the laminated film according to any one of claims 1 to 3 .

Images