WO2018216598A1 - Polarizing film, polarizing film with adhesive layer, and image display device - Google Patents

Abstract

The present invention is a polarizing film which has a first resin film on one surface of a polarizer having a thickness of 10 μm or less, while having a second resin film on the other surface of the polarizer, and which is configured such that: the water vapor permeabilities of the first resin film and the second resin film are 100 g/(m2·day) or less; and at least the first resin film among the first resin film and the second resin film has a breaking stress of 13 N or more and an elongation at break of 2.5 mm or more in a direction orthogonal to the absorption axis of the polarizer. Since a polarizing film according to the present invention comprises resin films having low water vapor permeabilities on both surfaces of a polarizer having a thickness of 10 μm or less, deterioration of the polarizer due to humidification is suppressed (good reliability in terms of humidification) and occurrence of through cracks is able to be suppressed even in an environment under severe thermal shock.

Description

Polarizing film, polarizing film with adhesive layer, and image display device

The present invention relates to a polarizing film and a polarizing film with an adhesive layer having the polarizing film and an adhesive layer. Moreover, this invention relates to the image display apparatus containing the said polarizing film with an adhesive layer.

In various image display devices, a polarizing film is used for image display. For example, in a liquid crystal display device (LCD), it is indispensable to dispose polarizing films on both sides of a glass substrate on which a liquid crystal panel surface is formed because of its image forming method. Further, in the organic EL display device, a circularly polarizing film in which a polarizing film and a quarter wavelength plate are laminated is disposed on the viewing side of the organic light emitting layer in order to shield the specular reflection of external light on the metal electrode.

As the polarizing film, generally, a polyvinyl alcohol film and a polarizer made of a dichroic material such as iodine are bonded to one or both surfaces with a protective film bonded with a polyvinyl alcohol adhesive or the like. ing.

In a severe environment of thermal shock (for example, a heat shock test in which a temperature condition of −40 ° C. and 85 ° C. is repeated), the polarizing film spreads along the absorption axis direction of the polarizer due to a change in the contraction stress of the polarizer. There is a problem that cracks (through cracks) are likely to occur. Therefore, in order to suppress the shrinkage of the polarizer and reduce the influence of thermal shock, a polarizing film usually has a 40 to 80 μm triacetyl cellulose (TAC) film as a protective film on both sides of the polarizer. A combined laminate is used. However, even in the polarizing film protected on both sides, the change in the shrinkage stress of the polarizer is not negligible, and it is difficult to completely suppress the influence of the shrinkage. It was inevitable that the shrinkage occurred.

On the other hand, in recent years, image display devices such as liquid crystal display devices have become thinner, and accordingly, polarizers are also required to be thinner. If it is a thin polarizer with a thickness of 10 μm or less, the change in shrinkage stress is small, so that a through-crack is hardly generated. For example, a polarizing film is disclosed in which a protective film is bonded to one or both sides of a thin polarizer having a thickness of 10 μm or less, and generation of through cracks is suppressed (see, for example, Patent Documents 1 to 3). In particular, if the protective film is a double-sided protective polarizing film with both sides of a thin polarizer bonded, the protective film provided on both sides can suppress the amount of shrinkage of the polarizer during the heat shock test. Can be effectively suppressed.

Japanese Patent Laying-Open No. 2015-187727 Japanese Patent Laying-Open No. 2015-152911 JP 2013-072951 A

However, on the other hand, a thin polarizer having a thickness of 10 μm or less has a problem that the optical characteristics in a humidified environment are likely to deteriorate. Therefore, even if it is a double-sided protective polarizing film using the said thin polarizer described in patent documents 1 thru | or 3 etc., depending on the kind of protective film, a polarizer deteriorates with a water | moisture content in humidification environment, and a polarizing film The optical characteristics are significantly deteriorated.

Therefore, in order to suppress the deterioration of the polarizer due to such moisture, the moisture permeability is extremely low as a protective film to be bonded to both surfaces of the thin polarizer (specifically, 100 g / (m ² · day) or less). The use of a resin film is being studied. However, when such a resin film having extremely low moisture permeability is used as a protective film, the polarizer can be prevented from degrading in a humidified environment, but a thin polarizer having a thickness of 10 μm or less is used. And although the protective film was bonded together on both surfaces of the said thin polarizer, the new subject that a penetration crack generate | occur | produces in a polarizing film by the thermal shock test etc. was discovered.

The present invention is a polarizing film in which a resin film with low moisture permeability is laminated on both sides of a polarizer having a thickness of 10 μm or less, suppressing deterioration of the polarizer due to humidification (humidification reliability), and severe thermal shock It aims at providing the polarizing film which can suppress generation | occurrence | production of a penetration crack also under environment.

Moreover, this invention aims at providing the polarizing film with an adhesive layer which has the said polarizing film and an adhesive layer. Furthermore, an object of this invention is to provide the image display apparatus containing the said polarizing film or a polarizing film with an adhesive layer.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found the following polarizing film and completed the present invention.

That is, the present invention is a polarizing film having a first resin film on one surface of a polarizer having a thickness of 10 μm or less and a second resin film on the other surface,
The moisture permeability of the first resin film and the second resin film are both 100 g / (m ² · day) or less,
At least the first resin film of the first resin film and the second resin film has a breaking stress of 13 N or more and a breaking elongation of 2.5 mm or more in a direction perpendicular to the absorption axis of the polarizer. The present invention relates to a polarizing film.

In the polarizing film, the first resin film and the second resin film are preferably any resin film selected from a cycloolefin resin film and a (meth) acrylic resin film.

In the polarizing film, a stretched film of a cycloolefin-based resin film can be suitably used as the first resin film. Moreover, an acrylic resin film can be suitably used as the first resin film.

The present invention also relates to a polarizing film with a pressure-sensitive adhesive layer comprising the polarizing film and a pressure-sensitive adhesive layer.

In the polarizing film with the pressure-sensitive adhesive layer, it is preferable that the pressure-sensitive adhesive layer is used in a mode having the second resin film side of the polarizing film.

The present invention also relates to an image display device, wherein the polarizing film or the polarizing film with an adhesive layer is disposed in an image display cell.

In the image display device, the polarizing film or the polarizing film with an adhesive layer is preferably used in such a manner that the second resin film side is disposed on the image display cell side.

As described above, a polarizing film in which a resin film having low moisture permeability (specifically, 100 g / (m ² · day) or less) is laminated on both sides of a thin polarizer as a protective film suppresses deterioration of the polarizer due to humidification. Although it is possible (we can improve humidification reliability), it has been newly found that through cracks occur. As a cause of the occurrence of through cracks, it is considered that a resin film (protective film) having a low moisture permeability has a low breaking stress and a small elongation at break. If the breaking stress of the protective film is low in the direction perpendicular to the absorption axis of the polarizer, it is thought that the brittleness of the protective film is a trigger and penetration cracks are likely to occur in the polarizing film. Also, if the protective film has a small elongation at break in the direction perpendicular to the absorption axis of the polarizer, a penetration crack occurs when the polarizing film follows the expansion / contraction of the protective film or the expansion / contraction of the polarizer. It becomes easy to do. A combination of the low breaking stress of such a protective film and a small elongation at break is considered to cause a through crack.

In the present invention, as the first resin film of the polarizing film and at least the first resin film of the second resin film, the breaking stress is 13 N or more and the breaking elongation is 2.5 mm or more in at least one direction (in-plane). And the one direction of the resin film is arranged in a direction perpendicular to the absorption axis of the polarizer. In the present invention, the polarizing film having such a configuration can be used in a direction perpendicular to the absorption axis of the polarizer even under a severe environment of thermal shock (for example, a heat shock test in which temperature conditions of −40 ° C. and 85 ° C. are repeated). Since the amount of shrinkage of the polarizing film as a whole can be reduced, it is possible to suppress the occurrence of through cracks in the polarizing film even when protective films having low moisture permeability are laminated on both sides of the polarizer. That is, the polarizing film of the present invention can achieve both suppression of polarizer deterioration by humidification (improvement of humidification reliability) and suppression of occurrence of through cracks.

Moreover, the present invention can provide a polarizing film with an adhesive layer that achieves both improved humidification reliability and suppression of the occurrence of through cracks, and an image display device using the polarizing film with the adhesive layer.

It is sectional drawing which shows typically one Embodiment of the polarizing film of this invention. It is sectional drawing which shows typically one Embodiment of the polarizing film with an adhesive layer of this invention.

1. Polarizing Film The polarizing film of the present invention has a configuration of a first resin film on one surface of a polarizer having a thickness of 10 μm or less and a second resin film on the other surface. The moisture permeability of the first resin film and the second resin film are both 100 g / (m ² · day) or less.

The configuration of the polarizing film of the present invention will be described in detail with reference to FIG. In addition, the dimension of each structure in FIG. 1 shows the example, and this invention is not limited to this.

As shown in FIG. 1, the polarizing film F1 of the present invention has a first resin film b1 on one surface of a polarizer a, and a second resin film b2 on the other surface. The first resin film b1 and the second resin film b2 can be bonded to the polarizer a through an adhesive layer (not shown). Moreover, the polarizing film F1 of this invention can contain layers other than the said layer (for example, an easily adhesive layer, various functional layers, etc.).

Further, the first resin film b1 and the second resin film b2 satisfy the low moisture permeability, and at least the first resin film b1 satisfies the physical properties related to the breaking stress and breaking elongation. The polarizing film F1 of the present invention is preferably arranged so that the second resin film b2 side is the image display cell side from the viewpoint of suppressing the occurrence of through cracks.

Hereinafter, each component will be described.

(1) Polarizer In the present invention, a thin polarizer having a thickness of 10 μm or less is used. The thickness of the polarizer is preferably 8 μm or less, more preferably 7 μm or less, and further preferably 6 μm or less from the viewpoint of reducing the thickness and preventing the occurrence of through cracks. 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 thickness unevenness, excellent visibility, and less dimensional change, and therefore excellent durability against thermal shock.

A polarizer using a polyvinyl alcohol resin is used. Examples of polarizers include dichroic iodine and dichroic dyes on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. Examples thereof include polyene-based oriented films such as those obtained by adsorbing substances and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic substance such as iodine is preferable.

A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol in an aqueous iodine solution and stretching it 3 to 7 times the original length. If necessary, it may contain boric acid, zinc sulfate, zinc chloride or the like, or may be immersed in an aqueous solution of potassium iodide or the like. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with stains and antiblocking agents by washing the polyvinyl alcohol film with water, the polyvinyl alcohol film is also swollen to prevent unevenness such as uneven coloring. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched even in an aqueous solution of boric acid or potassium iodide or in a water bath.

The polarizer preferably contains boric acid from the viewpoint of stretching stability and humidification reliability. The boric acid content contained in the polarizer is preferably 22% by weight or less, more preferably 20% by weight or less, based on the total amount of the polarizer, from the viewpoint of suppressing the occurrence of through cracks. From the viewpoint of stretching stability and humidification reliability, the boric acid content with respect to the total amount of the polarizer is preferably 10% by weight or more, and more preferably 12% by weight or more.

As a thin polarizer, typically,
Patent No. 4751486,
Japanese Patent No. 4751481,
Patent No. 4815544,
Patent No. 5048120,
International Publication No. 2014/077599 pamphlet,
International Publication No. 2014/077636 Pamphlet,
Or the thin polarizer obtained from the production method described therein.

Among the thin polarizers, among the production methods including the step of stretching in the state of a laminate and the step of dyeing, Patent 4951486 and Patent No. 4 can be used because they can be stretched at a high magnification and the polarization performance can be improved. Preferred are those obtained by a process comprising a step of stretching in an aqueous boric acid solution as described in US Pat. No. 4,751,481, and US Pat. No. 4,815,544, and particularly described in US Pat. Nos. 4,751,481, and 4,815,544. What is obtained by the manufacturing method including the process of extending | stretching in the air auxiliary before extending | stretching in a certain boric acid aqueous solution is preferable. These thin polarizers can be obtained by a production method including a step of stretching and dyeing a polyvinyl alcohol-based resin (hereinafter also referred to as PVA-based resin) layer and a stretching resin base material in a laminated state. With this production method, even if the PVA-based resin layer is thin, it can be stretched without problems such as breakage due to stretching by being supported by the stretching resin substrate.

(2) First resin film The first resin film satisfies a moisture permeability of 100 g / (m ² · day) or less. The moisture permeability is preferably 80 g / (m ² · day) or less, and more preferably 70 g / (m ² · day) or less. Further, the lower limit value of moisture permeability 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 first resin film is in the above range, deterioration of the polarizer due to moisture can be suppressed.

The first resin film has a breaking stress of 13 N or more and a breaking elongation of 2.5 mm or more in at least one direction. About breaking stress and breaking elongation, it can measure by the measuring method as described in an Example.

Further, the breaking stress of the first resin film is 13N or more in at least one direction (in a state where the first resin film is provided on the polarizing film, a direction perpendicular to the absorption axis of the polarizer), Is preferably 15N or more, more preferably 20N or more.

The breaking elongation of the first resin film is 2.5 mm at least in the same direction as the breaking stress (in the state where the first resin film is provided on the polarizing film, the direction perpendicular to the absorption axis of the polarizer). It is above, Furthermore, 10 mm or more is preferable, Furthermore, 20 mm or more is preferable.

The thickness of the first resin film is not particularly limited, but is 10 μm or more from the viewpoint of lowering moisture permeability to increase humidification reliability and further increasing fracture strength to further suppress penetration cracks. It is preferable that it is 12 μm or more. On the other hand, from the viewpoint of thinning, it is preferably 50 μm or less, preferably 40 μm or less, and more preferably 30 μm or less.

The polarizer and the first resin film are arranged so that the absorption axis of the polarizer and the direction satisfying the breaking stress and breaking elongation of the first resin film are orthogonal to each other. In the present invention, “orthogonal” means that the angle formed by the absorption axis of the polarizer and the direction satisfying the breaking stress and breaking elongation of the first resin film is in the range of 85 ° to 95 °. The angle is preferably 87 ° to 92 °, more preferably 89 ° to 91 °, and particularly preferably around 90 °.

As the material for forming the first resin film, a material having transparency and a moisture permeability of 100 g / (m ² · day) or less can be used. Specific examples of the material include a cycloolefin resin film and a (meth) acrylic resin film.

The cycloolefin-based resin forming the cycloolefin-based resin film is a general term for resins that are polymerized using cycloolefin as a polymerization unit. For example, JP-A-1-240517, JP-A-3-14882, Examples thereof include resins described in JP-A-3-122137. Specific examples include cycloolefin ring-opening (co) polymers, cycloolefin addition polymers, copolymers of cycloolefins with α-olefins such as ethylene and propylene (typically random copolymers), Examples thereof include graft polymers obtained by modifying these with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Specific examples of the cycloolefin include norbornene monomers.

Various products are commercially available as cycloolefin resins. Specific examples include trade names “ZEONEX” and “ZEONOR” manufactured by ZEON CORPORATION, trade names “ARTON” manufactured by JSR Corporation, “TOPASS” manufactured by TICONA, and products manufactured by Mitsui Chemicals, Inc. Product name “APEL” and the like.

The cycloolefin-based resin film is preferably used as a stretched film because it is difficult to satisfy the breaking stress and breaking elongation in an unstretched state. The stretched film can satisfy the breaking stress and breaking elongation in the stretching direction. The extent of stretching in the stretched film is not particularly limited as long as it satisfies the breaking stress and breaking elongation. The stretched film can be used as a retardation film having desired optical properties. For example, it can be used as a retardation film having a function of imparting a desired retardation to a stretched film and converting linearly polarized light into circularly polarized light or elliptically polarized light.

Any appropriate stretching method and stretching conditions (for example, stretching temperature, stretching ratio, stretching direction) may be employed for the stretching. Specifically, various stretching methods such as free end stretching, fixed end stretching / free end contraction, and fixed end contraction can be used singly or simultaneously or sequentially. The stretching direction can also be performed in various directions and dimensions such as a horizontal direction, a vertical direction, a thickness direction, and a diagonal direction. The stretching temperature is preferably in the range of glass transition temperature (Tg) ± 20 ° C. of the resin film.

The stretched film can be produced, for example, by stretching a resin film by means such as uniaxial stretching or fixed-end uniaxial stretching, simultaneous biaxial stretching or oblique stretching. As a specific example of uniaxial stretching, there is a method of stretching in the longitudinal direction (longitudinal direction) while running the resin film in the longitudinal direction. Another specific example of the uniaxial stretching includes a method of stretching in the transverse direction using a tenter. The draw ratio is preferably adjusted in the range of usually 10% to 500%.

Any appropriate (meth) acrylic resin can be adopted as the (meth) acrylic resin forming the (meth) acrylic resin film. For example, poly (meth) acrylate such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester -(Meth) acrylic acid copolymer, (meth) acrylic acid methyl-styrene copolymer (MS resin, etc.), polymer having alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer) And methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, poly (meth) acrylate C _1-6 alkyl such as poly (meth) acrylate methyl is used. More preferred is a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

Specific examples of the (meth) acrylic resin include (meth) acrylic resins having a ring structure in the molecule described in, for example, Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and JP-A-2004-70296. Examples of the resin include high Tg (meth) acrylic resins obtained by intramolecular crosslinking or intramolecular cyclization reaction.

As the (meth) acrylic resin, a (meth) acrylic resin having a lactone ring structure is particularly preferable in that it has high heat resistance, high transparency, and high mechanical strength.

Examples of the (meth) acrylic resin having the lactone ring structure include JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005. Examples thereof include (meth) acrylic resins having a lactone ring structure described in JP-A-146084.

The (meth) acrylic resin having a lactone ring structure has a mass average molecular weight (sometimes referred to as a weight average molecular weight), preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000. Preferably it is 50,000 to 500,000.

The (meth) acrylic resin has a Tg (glass transition temperature) of preferably 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. It is because it can be excellent in durability. Although the upper limit of Tg of the said (meth) acrylic-type resin is not specifically limited, From viewpoints of a moldability etc., Preferably it is 170 degrees C or less.
The (meth) acrylic resin having a lactone ring structure has a Tg (glass transition temperature) of preferably 115 ° C. or higher, more preferably 125 ° C. or higher, still more preferably 130 ° C. or higher, particularly preferably 135 ° C., most preferably. Is 140 ° C. or higher. It is because it can be excellent in durability. The upper limit of Tg of the (meth) acrylic resin having the lactone ring structure is not particularly limited, but is preferably 170 ° C. or less from the viewpoint of moldability and the like.

Some (meth) acrylic resin films can satisfy the breaking stress and breaking elongation even when they are unstretched. An unstretched (meth) acrylic resin film that can satisfy the breaking stress and breaking elongation can be prepared from the (meth) acrylic resin. On the other hand, the (meth) acrylic resin film can also be used as a stretched film. The stretched film can be appropriately stretched similarly to the cycloolefin resin film so as to satisfy the breaking stress and breaking elongation in the stretching direction.

Arbitrary appropriate adhesive layers (not shown) are used for the polarizer and the first resin film. The adhesive layer is formed of an adhesive. The type of the adhesive is not particularly limited, and various types can be used. The adhesive layer is not particularly limited as long as it is optically transparent. As the adhesive, various forms such as water-based, solvent-based, hot-melt-based, and active energy ray-curable types are used, but humidification reliability is used. In view of the above, an active energy ray-curable adhesive is suitable.

The active energy ray curable adhesive is an adhesive that cures by an active energy ray such as an electron beam or ultraviolet rays (radical curable type, cationic curable type), for example, in an electron beam curable type or an ultraviolet curable type. Can be used. As the active energy ray curable adhesive, for example, a photo radical curable adhesive can be used. When the photo radical curable active energy ray curable adhesive is used as an ultraviolet curable adhesive, the adhesive contains a radical polymerizable compound and a photo polymerization initiator. The adhesive coating method is appropriately selected depending on the viscosity of the adhesive and the target thickness. Examples of coating methods include reverse coaters, gravure coaters (direct, reverse and offset), bar reverse coaters, roll coaters, die coaters, bar coaters, rod coaters and the like. In addition, for coating, a method such as a dapping method can be appropriately used.

The surface of the first resin film to which the polarizer is not adhered may be subjected to a treatment for the purpose of hard coat layer, antireflection treatment, sticking prevention, diffusion or antiglare.

(3) 2nd resin film It has a 2nd resin film in the surface on the opposite side to the surface in which the 1st resin film of the said polarizer was formed. The moisture permeability is preferably 40 g / (m ² · day) or less, and more preferably 30 g / (m ² · day) or less. Further, the lower limit value of moisture permeability 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 first resin film is in the above range, deterioration of the polarizer due to moisture can be suppressed.

The thickness of the second resin film is not particularly limited, but is 10 μm or more from the viewpoint of lowering moisture permeability to increase humidification reliability and further increasing fracture strength to further suppress penetration cracks. It is preferable that it is 12 μm or more. On the other hand, from the viewpoint of thinning, it is preferably 30 μm or less, and more preferably 25 μm or less.

The material for forming the second resin film may be any material that can form a film having transparency and a moisture permeability of 100 g / (m ² · day) or less. Specifically, the material similar to the material of the said 1st resin film, for example, a cycloolefin type resin film, a (meth) acrylic-type resin film, etc. can be mentioned.

Examples of the cycloolefin resin film and the (meth) acrylic resin film include those mentioned for the first resin film. Moreover, although there is no restriction | limiting other than the said moisture permeability, you may use the said 2nd resin film which has the same breaking stress and breaking elongation as a 1st resin film. When using a stretched film as the second resin film, there is a risk of developing a phase difference when the film expands and contracts under a harsh environment, and unevenness such as corner unevenness may occur due to the phase difference expression. The second resin film is preferably an unstretched film, and more preferably an unstretched cycloolefin resin film.

The polarizer and the second resin film are usually in close contact via an adhesive. Examples of the adhesive include those listed for the first resin film.

The surface of the second resin film to which the polarizer is not adhered may be subjected to a treatment for the purpose of hard coat layer, antireflection treatment, sticking prevention, diffusion or antiglare.

Since the polarizing film of the present invention uses a polarizer having a thickness of 10 μm or less, the entire polarizing film can be thinned. The thickness of the polarizing film can be 100 μm or less.

2. The polarizing film with an adhesive layer The polarizing film with an adhesive layer of this invention has the said polarizing film and an adhesive layer. Although there is no restriction | limiting in particular in the arrangement | positioning location of an adhesive layer, In the image display apparatus, since it is preferable to arrange | position the 1st resin film side in the said polarizing film outside a polarizer, the said adhesive layer is It is preferable to have it on the second resin film side of the polarizing film. A polarizing film with an adhesive layer having an adhesive layer on the second resin film side is disposed in the image display cell via the adhesive layer to form an image display device.

The pressure-sensitive adhesive layer can be laminated on the side having no polarizer of the second resin film. Specifically, for example, as shown in FIG. 2, the polarizing film F2 with the pressure-sensitive adhesive layer of the present invention has a first resin film b1, a polarizer a, a second resin film b2, and a pressure-sensitive adhesive layer c in this order. Is.

The polarizing film with the pressure-sensitive adhesive layer of the present invention can form a pressure-sensitive adhesive layer by directly applying the pressure-sensitive adhesive composition to the polarizing film and removing the solvent and the like by heating and drying. Moreover, the adhesive layer formed in the support body etc. can be transcribe | transferred to the said polarizing film, and a polarizing film with an adhesive layer can also be formed.

The pressure-sensitive adhesive layer is not particularly limited, and a known layer can be used. As such an adhesive layer, specifically, for example, a (meth) acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based or rubber-based polymer is used as a base polymer. Can be appropriately selected and used. Among these, acrylic pressure-sensitive adhesives based on (meth) acrylic polymers are excellent in optical transparency, exhibiting moderate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, weather resistance and heat resistance. Etc. are preferable.

The (meth) acrylic polymer is not particularly limited, and 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 terminal of the ester group. Can be mentioned. Alkyl (meth) acrylate refers to alkyl acrylate and / or alkyl methacrylate, and (meth) in the present invention has the same meaning.

Examples of the alkyl (meth) acrylate include those having a linear or branched alkyl group having 4 to 24 carbon atoms, and having a linear or branched alkyl group having 4 to 9 carbon atoms. Alkyl (meth) acrylates are preferred because they are easy to 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 can contain a copolymerizable monomer other than the alkyl (meth) acrylate as a monofunctional monomer component. Examples of such copolymerizable monomers include cyclic nitrogen-containing monomers, hydroxyl group-containing monomers, carboxyl group-containing monomers, and monomers having a cyclic ether group.

In addition to the monofunctional monomer, the monomer component forming the (meth) acrylic polymer can contain a polyfunctional monomer as 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, such as dipentaerythritol hexa (meth) acrylate, 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.

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

The polymerization initiator, chain transfer agent, emulsifier and the like used for radical polymerization are not particularly limited, and known ones commonly used in this 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 polymerization initiator, the amount of chain transfer agent used, and the reaction conditions, and the amount 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 4,000,000. By making the weight average molecular weight larger than 400,000, it is possible to satisfy the durability of the pressure-sensitive adhesive layer, or to suppress the occurrence of adhesive residue due to the reduced cohesive force of the pressure-sensitive adhesive layer. On the other hand, when the weight average molecular weight is larger than 4 million, the bonding property tends to be lowered. Furthermore, in the solution system, the viscosity becomes too high, and coating may be difficult. The weight average molecular weight is a value measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene. In addition, 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 can contain a crosslinking agent. Examples of crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, silicone crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, silane crosslinking agents, alkyletherified melamine crosslinking agents, metal chelate crosslinking agents, Examples of the crosslinking agent include oxides, and these can be used alone or in combination of two or more. As said crosslinking agent, an isocyanate type crosslinking agent and an epoxy-type crosslinking agent are used preferably.

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

In the pressure-sensitive adhesive composition used in the present invention, a (meth) acrylic oligomer can be contained in order to improve the adhesive force. Furthermore, 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.

Furthermore, the pressure-sensitive adhesive composition used in the present invention may contain other known additives, such as polyether compounds of polyalkylene glycols such as polypropylene glycol, powders of colorants and pigments, dyes, and the like. , Surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, UV absorbers, polymerization inhibitors, inorganic or organic fillers, It can be added as appropriate depending on the application in which metal powder, particles, foil, etc. are used. Moreover, you may employ | adopt the redox system which added a reducing agent within the controllable range.

The method for forming the pressure-sensitive adhesive layer can be performed by a known method.

Various methods are used as a method for applying the pressure-sensitive adhesive composition. Specifically, for example, by 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 thereof include an extrusion coating method.

The heating and drying temperature is preferably about 30 to 200 ° C, more preferably about 40 to 180 ° C, and further preferably about 80 to 150 ° C. By setting the heating temperature in the above range, an 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 further 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, for example, plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and nonwoven fabric, nets, foam sheets, metal foils, and laminates thereof. Although a thin leaf body etc. can be mentioned, a plastic film is used suitably from the point which is excellent in 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.

The thickness of the separator is usually about 5 to 200 μm, preferably about 5 to 100 μm. For the separator, silicone type, fluorine type, long chain alkyl type or fatty acid amide type release agent, release by silica powder, and antifouling treatment, coating type, kneading type, vapor deposition, as required An antistatic treatment such as a mold can also be performed. In particular, the release property from the pressure-sensitive adhesive layer can be further improved by appropriately performing a release treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment on the surface of the separator.

In addition, the sheet | seat which carried out the peeling process used in preparation of said polarizing film with an adhesive layer can be used as a separator of the polarizing film with an adhesive layer as it is, and can simplify in a process surface.

In the polarizing film with the pressure-sensitive adhesive layer, when forming the pressure-sensitive adhesive layer, an anchor layer is formed on the surface of the polarizing film (for example, the second resin film), or various types of easy adhesion such as corona treatment and plasma treatment are performed. After the treatment, the pressure-sensitive adhesive layer can be formed. Moreover, you may perform an easily bonding process on the surface of an adhesive layer.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is preferably 5 to 100 μm, for example, and preferably 10 to 50 μm.

3. Image Display Device The image display device of the present invention only needs to include the polarizing film of the present invention or the polarizing film with a pressure-sensitive adhesive layer, and other configurations may be the same as those of conventional image display devices. it can. The polarizing film or the polarizing film with an adhesive layer is applied to an image display cell. For example, when the image display device is a liquid crystal display device, the polarizing film or the polarizing film with an adhesive layer can be applied to either the viewing side or the backlight side of the image display cell (liquid crystal cell). When the image display device is an organic EL display device, the polarizing film or the polarizing film with an adhesive layer can be applied to the viewing side of the image display cell. It is preferable that the polarizing film or the polarizing film with the pressure-sensitive adhesive layer is disposed so that the second resin film side is the image display cell side. Since the image display device of the present invention includes the polarizing film or the polarizing film with the pressure-sensitive adhesive layer, it has high reliability.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. In addition, all the parts and% in each example are based on weight.

(Production of polarizer)
One side of an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) having a water absorption of 0.75% and Tg of 75 ° C. is subjected to corona treatment. Alcohol (degree of polymerization: 4200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization: 1200, degree of acetoacetyl modification: 4.6%, degree of saponification: 99.0 mol% or more, Japan An aqueous solution containing 9: 1 ratio of synthetic chemical industry (trade name “Gosefimer Z200”) is applied and dried at 25 ° C. to form a PVA resin layer having a thickness of 11 μm. Produced.
The obtained laminate was uniaxially stretched in the longitudinal direction (longitudinal direction) 2.0 times between rolls having different peripheral speeds in an oven at 120 ° C. (air-assisted stretching process).
Next, the laminate was immersed in an insolubilization bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Subsequently, it was immersed in a dyeing bath having a liquid temperature of 30 ° C. while adjusting the iodine concentration and the immersion time so that the polarizing plate had a predetermined transmittance. In this example, 0.2 parts by weight of iodine was blended with 100 parts by weight of water, and immersed in an aqueous iodine solution obtained by blending 1.0 part by weight of potassium iodide (dyeing treatment). .
Subsequently, it was immersed for 30 seconds in a crosslinking bath having a liquid temperature of 30 ° C. (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water). (Crosslinking treatment).
Thereafter, the laminated body was added to a boric acid aqueous solution having a liquid temperature of 70 ° C. (an aqueous solution obtained by adding 4.5 parts by weight of boric acid and 5 parts by weight of potassium iodide to 100 parts by weight of water). While being immersed, uniaxial stretching was performed in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds so that the total stretching ratio was 5.5 times (in-water stretching treatment).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 30 ° C. (cleaning treatment).
As a result, an optical film laminate including a polarizer having a thickness of 5 μm was obtained. The obtained polarizer had a boric acid content of 20% by weight.

(Preparation of adhesive to be applied to transparent protective film)
An ultraviolet curable adhesive was prepared by mixing 40 parts by weight of N-hydroxyethylacrylamide (HEAA), 60 parts by weight of acryloylmorpholine (ACMO), and 3 parts by weight of a photoinitiator “IRGACURE 819” (manufactured by BASF).

(Resin film)
<Protective film 1>
Unstretched acrylic resin film having a thickness of 15 μm: 40 ° C., 92% R.D. H. Moisture permeability: 50 g / (m ² · day), breaking stress: 15 N, breaking elongation: 4 mm.
<Protective film 2>
Stretched cycloolefin resin film having a thickness of 17 μm (trade name: ZT12, manufactured by Zeon Corporation): 40 ° C., 92% R.D. H. Moisture permeability: 22 g / (m ² · day), breaking stress: 15 N, breaking elongation: 25 mm.
<Protective film 3>
Unstretched acrylic resin film (trade name: HX-40UC, manufactured by Toyo Kohan Co., Ltd.) having a thickness of 47 μm: 40 ° C., 92% R.D. H. Moisture permeability: 65 g / (m ² · day), breaking stress: 39 N, breaking elongation: 4 mm.
<Protective film 4>
13 μm thick cycloolefin resin film (trade name: ZF14, manufactured by Nippon Zeon Co., Ltd.): 40 ° C., 92% R.D. H. Permeability: 29 g / (m ² · day), breaking stress: 9 N, breaking elongation: 4 mm.
<Protective film 5>
27 μm thick cycloolefin resin film (trade name: ZF12, manufactured by Nippon Zeon Co., Ltd.): 40 ° C., 92% R.D. H. Moisture permeability: 23 g / (m ² · day), breaking stress: 13 N, breaking elongation: 2.2 mm.
<Protective film 6>
Triacetylcellulose film having a thickness of 32 μm (trade name: KC2UAHC, manufactured by Konica Minolta): 40 ° C., 92% R.D. H. Moisture permeability: 796 g / (m ² · day), breaking stress: 41 N, breaking elongation: 2.7 mm.
<Protective film 7>
25 μm thick triacetylcellulose film (trade name: KC2UA, manufactured by Konica Minolta): 40 ° C., 92% R.D. H. Moisture permeability: 1804 g / (m ² · day), breaking stress: 28 N, breaking elongation: 16 mm.

Example 1 (Production of polarizing film)
While applying the ultraviolet curable adhesive to the surface of the polarizer (thickness: 5 μm) of the optical film laminate so that the thickness of the adhesive layer after curing is 0.1 μm, the protective film 1 ( After laminating the first resin film), the adhesive was cured by irradiating ultraviolet rays as active energy rays. Ultraviolet irradiation is performed using a gallium-encapsulated metal halide lamp, an irradiation device: Fusion UV Systems, Inc. Light HAMMER 10, Inc., bulb: V bulb, peak illuminance: 1600 mW / cm ² , integrated irradiation amount 1000 / mJ / cm ² (wavelength 380 to 440 nm) ), And the illuminance of ultraviolet rays was measured using a Sola-Check system manufactured by Solatell. Next, the amorphous PET base material is peeled off, and the UV curable adhesive is applied to the peeled surface so that the thickness of the adhesive layer after curing is 0.1 μm, and corona treatment in advance. After bonding the protective film 4 (second resin film), ultraviolet rays were irradiated in the same manner as described above to cure the adhesive, and a polarizing film having protective films on both sides of the thin polarizer was produced. The protective film was bonded so that the direction in which the breaking stress and breaking elongation were measured was a direction (90 °) perpendicular to the absorption axis of the polarizer.

Examples 2 to 3, Comparative Examples 1 to 3
In Example 1, a polarizing film was obtained in the same manner as in Example 1 except that the protective film used for the first resin film and the second resin film was changed as shown in Table 1.

The following evaluation was performed about the polarizing film obtained by the Example and the comparative example. The results are shown in Table 1. In addition, it shows together about the measuring method of the water vapor transmission rate of the protective film used in each example, protective film breaking stress, and breaking elongation.

<Water vapor permeability of transparent protective film>
The moisture permeability was measured according to a moisture permeability test (cup method) of JIS Z0208. A sample cut to a diameter of 6 cm was set in a moisture permeable cup (opening diameter: diameter 6 cm) containing about 15 g of calcium chloride, and the temperature was 40 ° C. and the humidity was 92% R.D. H. The moisture permeability (g / (m ² · day)) was determined by measuring the weight increase of calcium chloride before and after being left for 24 hours.

<Measurement of breaking stress>
After cutting each protective film to 100 mm x 100 mm, using an autograph (product name: AG-IS, manufactured by Shimadzu Corporation) as a tensile tester, the test sample is pulled at a speed of 300 mm / min, between chucks A tensile test was performed at a distance of 100 mm and at room temperature (23 ° C.) to obtain a stress-strain curve. The stress when the protective film broke was obtained and used as the breaking stress. Note that the breaking stress was measured in a direction perpendicular to the absorption axis of the polarizer.

<Measurement of elongation at break>
Each protective film was measured using a tensile tester in an environment of 23 ° C. and 50% RH. Set the chuck so that the initial length of measurement (initial chuck interval) is 10 mm, perform a tensile test under the condition of a tensile speed of 50 mm / min, and measure the elongation at break [elongation at break (elongation at break)]. did. The elongation at break (elongation at break) represents the elongation when the test piece breaks in a tensile test and is calculated by the following equation.
“Elongation at break (Elongation at break)” = “Length of test piece at break (chuck interval at break)” − “Initial length (10 mm)”

<Measurement of change in polarization degree (ΔP) of polarizing film>
The polarizing films obtained in Examples and Comparative Examples were subjected to 85 ° C./85% R.D. H. For 500 hours. The polarization degree of the polarizing film before and after the addition was measured using a spectrophotometer with an integrating sphere (V7100 manufactured by JASCO Corporation), and the amount of change ΔP in the polarization degree was determined by the following equation.
Change amount of polarization degree ΔP (%) = (Polarization degree before injection (%)) − (Polarization degree after introduction (%))
The degree of polarization P is the transmittance when two identical polarizing films are overlapped so that their transmission axes are parallel (parallel transmittance: Tp), and they are overlapped so that their transmission axes are orthogonal to each other. It is calculated | required by applying the transmittance | permeability (orthogonal transmittance | permeability: Tc) at the time of combining to the following formula | equation.
Polarization degree P (%) = {(Tp−Tc) / (Tp + Tc)} ^1/2 × 100
Each transmittance is represented by a Y value obtained by correcting visibility with a two-degree field of view (C light source) of JIS Z8701, with 100% of the completely polarized light obtained through the Granteller prism polarizer.

<Confirmation of penetration crack: heat shock test>
A polarizing film with a pressure-sensitive adhesive layer was prepared by providing an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm on the second resin film side of the polarizing films obtained in Examples and Comparative Examples. The polarizing film with an adhesive layer was cut into 50 mm × 150 mm (absorption axis direction was 50 mm), and bonded to 0.5 mm-thick alkali-free glass to prepare a sample. When the sample is subjected to a heat shock of −40 to 85 ° C. in an environment of × 500 times for 30 minutes each and then taken out and visually, at least one penetration crack is generated in the polarizing film. “Yes” was given, and “None” was given when no occurrence occurred.

The 85 ° C. and 85% R.V. H. The absolute value of the degree of polarization change (ΔP) after standing in the environment for 500 hours is preferably less than 0.1%, more preferably 0.05% or less, and 0.03% or less. Is more preferable. In the polarizing film of the present invention, since the first resin film satisfies a breaking stress of 13 N or more and a breaking elongation of 2.5 mm or more, the heat shock (for example, a heat shock test in which temperature conditions of −40 ° C. and 85 ° C. are repeated) is severe. Even in difficult environments, the shrinkage force of the polarizing film as a whole becomes extremely small, and furthermore, the use of a low moisture permeation protective film suppresses deterioration of the polarizer due to water, resulting in exposure to harsh environments. However, the change in the degree of polarization is small and the optical characteristics are excellent.

F1 Polarizing film F2 Polarizing film with adhesive layer a Polarizer b1 First resin film b2 Second resin film c Adhesive layer

Claims (8)

1. A polarizing film having a first resin film on one surface of a polarizer having a thickness of 10 μm or less and a second resin film on the other surface,
   The moisture permeability of the first resin film and the second resin film are both 100 g / (m ² · day) or less,
   At least the first resin film of the first resin film and the second resin film has a breaking stress of 13 N or more and a breaking elongation of 2.5 mm or more in a direction perpendicular to the absorption axis of the polarizer. Polarizing film.
2. The polarizing film according to claim 1, wherein the first resin film and the second resin film are both resin films selected from cycloolefin resin films and acrylic resin films.
3. The polarizing film according to claim 1 or 2, wherein the first resin film is a stretched film of a cycloolefin resin film.
4. The polarizing film according to claim 1 or 2, wherein the first resin film is an acrylic resin film.
5. A polarizing film with an adhesive layer, comprising the polarizing film according to any one of claims 1 to 4 and an adhesive layer.
6. 6. The polarizing film with a pressure-sensitive adhesive layer according to claim 5, wherein the pressure-sensitive adhesive layer is provided on the second resin film side of the polarizing film.
7. An image display device, wherein the polarizing film according to any one of claims 1 to 4 or the polarizing film with an adhesive layer according to claim 5 or 6 is disposed in an image display cell.
8. The image display device according to claim 7, wherein the polarizing film or the polarizing film with an adhesive layer is disposed so that the second resin film side is the image display cell side.

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