JP2016118776A - Polarizing plate with protection film and laminate including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate with a protection film which hardly causes deformation due to change in temperature and humidity; and to provide a laminate including the same.SOLUTION: There are provided a polarizing plate with a protection film that includes a polarizing plate including a polarizer, and a protection film laminated on one surface thereof, in which the protection film has moisture permeability at temperature of 40°C and relative humidity of 90% of 15 g/(m24 hr) or less; and a laminate including the same.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarizing plate with a protective film formed by laminating a protective film on the surface of a polarizing plate, and a laminate including the same.

  In recent years, mobile terminals such as smartphones are rapidly increasing in screen size and slimming in terms of design and portability. In order to realize long-time driving with a limited thickness, the polarizing plate used is also required to have high brightness and thin and light weight.

  Conventionally, a polarizing plate in which a protective film made of triacetyl cellulose is bonded to both surfaces of a polyvinyl alcohol polarizer with a polyvinyl alcohol adhesive has been generally used. However, from the viewpoints of thinning, durability, cost, productivity, etc., in recent years, in addition to triacetyl cellulose as a protective film, (meth) acrylic resins, chain polyolefin resins, cyclic polyolefin resins, etc. In addition, a thin protective film is used (see, for example, paragraph [0005] of Patent Document 1).

JP 2004-245925 A

  As described above, in recent years, there is a tendency to use a thin polarizing plate having no stiffness. However, such a polarizing plate is sensitive to changes in the environment in which it is placed, in particular, temperature changes and humidity changes, and tends to easily undergo deformation typified by curling (warping) with environmental changes. A polarizing plate with a protective film is generally marketed as a polarizing plate with a protective film to which a peelable protective film (also called a surface protective film) for protecting the surface is attached. The same tendency is applied to the plate.

  Then, an object of this invention is to provide the polarizing plate with a protective film which hardly produces the curl accompanying a temperature change and humidity change, and a laminated body containing the same.

The present invention provides the following polarizing plate with a protective film and an image display device.
[1] A polarizing plate including a polarizer and a protective film laminated on one surface thereof,
The protective film is a polarizing plate with a protective film, wherein the moisture permeability M at a temperature of 40 ° C. and a relative humidity of 90% is 15 g / (m ² · 24 hr) or less.

  [2] The polarizing plate with a protective film according to [1], wherein the polarizing plate has a thickness of 125 μm or less.

  [3] The polarizing plate with a protective film according to [1] or [2], wherein the other surface of the polarizing plate is configured by the surface of the first pressure-sensitive adhesive layer.

  [4] Any one of [1] to [3], wherein the protect film includes a second pressure-sensitive adhesive layer laminated on the one surface and a single-layer base film laminated thereon. A polarizing plate with a protective film according to claim 1.

  [5] Any of [1] to [4], wherein the polarizing plate further includes a protective film laminated on at least one surface of the polarizer via a cured product layer of an active energy ray-curable adhesive. A polarizing plate with a protective film as described in 1.

[6] The other surface of the polarizing plate is composed of the surface of the first pressure-sensitive adhesive layer,
The polarizing plate with a protective film according to any one of [1] to [5], further comprising a separate film laminated on the other surface of the polarizing plate.

[7] The polarizing plate further includes an optical film other than the polarizer,
The polarizing plate with a protective film according to any one of [1] to [6], wherein the protective film is laminated on a surface of the optical film.

  [8] The polarizing plate with a protective film according to [7], wherein the optical film is a brightness enhancement film.

  [9] The polarizing plate with a protective film according to any one of [1] to [8], wherein the polarizer has a thickness of 15 μm or less.

  [10] A laminate comprising an image display element and the polarizing plate with a protective film according to any one of [1] to [9] laminated thereon.

  ADVANTAGE OF THE INVENTION According to this invention, the polarizing plate with a protective film which hardly produces the curl accompanying a temperature change and humidity change, and a laminated body containing the same can be provided. This polarizing plate with a protective film and a laminate comprising the same can be suitably used for an image display device.

It is a schematic sectional drawing which shows typically an example of the layer structure of the polarizing plate with a protective film which concerns on this invention. It is a schematic sectional drawing which shows an example of the laminated constitution of the polarizing plate with a protective film which concerns on this invention. It is a schematic sectional drawing which shows another example of the layer structure of the polarizing plate with a protective film which concerns on this invention. It is a schematic sectional drawing which shows another example of the layer structure of the polarizing plate with a protective film which concerns on this invention.

<Polarizing plate with protective film>
(1) Configuration of Polarizing Plate with Protective Film FIG. 1 is a schematic cross-sectional view schematically showing an example of a layer configuration of a polarizing plate with a protective film according to the present invention. With reference to FIG. 1, an example of the polarizing plate with a protective film of this invention is demonstrated. The polarizing plate with a protective film of the present invention includes a polarizing plate 100 including a polarizer (not shown in FIG. 1), and a protective film 60 laminated on one surface thereof. The surface on the side of the protective film 60 in the polarizing plate 100 (the surface on which the protective film 60 is bonded) can be, for example, the surface of a protective film, another optical film, or a layer added on the film.

  The other surface of the polarizing plate 100, that is, the surface opposite to the surface on which the protective film 60 is laminated is not particularly limited, but is configured by the surface of the first pressure-sensitive adhesive layer 31, for example, as shown in FIG. May be. In this case, a peelable separate film 70 for temporarily protecting the surface may be laminated on the outer surface of the first pressure-sensitive adhesive layer 31 (the other surface of the polarizing plate 100).

  The protective film 60 includes a base film 61 and a second pressure-sensitive adhesive layer 62 laminated thereon, and is bonded and laminated to the polarizing plate 100 through the pressure-sensitive adhesive layer.

  In the present invention, the polarizing plate 100 is a polarizing element including at least a polarizer, and usually further includes a protective film bonded to one side or both sides thereof. In addition to the protective film, other optical films such as a film having an optical function different from that of the polarizer, and layers added on the film such as an optical layer may be included. Various optical films including a protective film can be bonded via an adhesive layer or a pressure-sensitive adhesive layer. In the case where one outermost layer of the polarizing plate 100 is the first pressure-sensitive adhesive layer 31 and the separate film 70 is laminated on the outer surface thereof, the separate film 70 is not included in the polarizing plate 100.

As the protective film 60, a film having a moisture permeability M as a whole including the second pressure-sensitive adhesive layer 62 of 15 g / (m ² · 24 hr) or less under conditions of a temperature of 40 ° C. and a relative humidity of 90% is used. . The moisture permeability M is preferably 12 g / (m ² · 24 hr) or less. Thereby, the curl accompanying the temperature change and humidity change of the polarizing plate with a protective film can be effectively suppressed. Suppression of curling (warping) is 1) the polarizing plate is broken when stress is applied in the process, 2) foreign matter is mixed between the protective film and the polarizing plate due to deformation (distortion) due to curling, and 3) the polarizing plate. This is advantageous for suppressing problems such as causing a bonding error or causing air bubbles to be mixed into the bonding interface. The moisture permeability M is measured by a cup method defined in JIS Z 0208. The moisture permeability M is usually 0 g / (m ² · 24 hr) or more, and more typically exceeds 0 g / (m ² · 24 hr).

  The thickness T of the polarizing plate 100 is usually 200 μm or less, and is preferably 150 μm or less, more preferably 125 μm or less, and still more preferably 100 μm or less from the viewpoint of thinning. The smaller the thickness T, the easier it is to curl, but according to the present invention, curling can be effectively suppressed even in such a case. The thickness T is usually 50 μm or more.

The polarizing plate with a protective film has the following formula (1):
M ≦ T / 15 + 10 (1)
It is preferable to satisfy. As a result, it is possible to effectively suppress curling due to temperature change and humidity change according to the thickness T of the polarizing plate 100. In a preferred embodiment, the polarizing plate with a protective film satisfies M ≦ 15 and T ≦ 100, and satisfies the above formula (1).

Further, when the humidity expansion coefficient of the polarizing plate 100 is C ₁ and the humidity expansion coefficient of the protective film 60 is C ₂ , the absolute value of these differences is preferably 50 [ppm ·% RH ⁻¹ ] or less. 30 [ppm ·% RH ⁻¹ ] or less is more preferable. This makes it possible to more effectively suppress curling associated with the temperature change and humidity change of the polarizing plate with a protective film. The absolute value of the difference is 0 or more, and may be 10 [ppm ·% RH ⁻¹ ] or more. The humidity expansion coefficients C ₁ and C ₂ are measured according to the description in the example section described later.

  The polarizing plate with a protective film according to the present invention is usually a sheet of polarizing plate with a protective film. This single-wafer is obtained by laminating another raw material film continuously unwound from the film roll to the raw material film continuously unwound from the film roll and transported. It can be obtained by producing a long polarizing plate with a protective film by a so-called roll-to-roll method in which the laminated film is wound into a roll, and then cutting it.

  The shape of the single wafer is not particularly limited, but preferably has a square shape having a long side and a short side, and is typically a rectangle. Although the length of a long side and a short side is not specifically limited, Usually, the long side of a sheet body is 50 mm or more, and a short side is 30 mm or more. The curl is more likely to occur as the size of the sheet body increases. If the size (long side and / or short side) is too small, the curl problem itself is less likely to occur.

  Next, examples of the layer configuration of the polarizing plate 100 will be described with reference to FIGS. 2 to 4, but the layer configuration is not limited to these examples. For example, the other surface of the polarizing plate, that is, the surface opposite to the surface on which the protective film 60 is laminated, is not limited to the first pressure-sensitive adhesive layer 31, but is an optical film such as a protective film or a layer added on the film. You may be comprised by the surface of.

  The polarizing plate which the polarizing plate with a protective film shown by FIG. 2 has is the polarizer 10, the protective film 21 bonded on the one surface, the protective film 22 bonded on the other surface, and the protective film The first pressure-sensitive adhesive layer 31 is laminated on the outer surface of 22. The polarizing plate which the polarizing plate with a protective film shown by FIG. 3 has is the protective film 21 bonded on the polarizer 10, the one surface, the protective film 22 bonded on the other surface, and the protective film. 22 includes a first pressure-sensitive adhesive layer 31 laminated on the outer surface of 22 and a brightness enhancement film 50 that is an optical film laminated on the outer surface of the protective film 21 via a third pressure-sensitive adhesive layer 32. The polarizing plate of the polarizing plate with a protective film shown in FIG. 4 is omitted in FIG. 3 except that the protective film 21 is omitted and the third pressure-sensitive adhesive layer 32 is laminated directly on the surface of the polarizer 10. It has the same layer structure as the polarizing plate shown.

  Although illustration is abbreviate | omitted, bonding with the polarizer 10 and the protective films 21 and 22 can be performed using an adhesive agent.

(2) Polarizer The polarizer 10 has the property of absorbing linearly polarized light having a vibration surface parallel to the absorption axis and transmitting linearly polarized light having a vibration surface orthogonal to the absorption axis (parallel to the transmission axis). An absorptive polarizer, and a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film can be suitably used. The polarizer 10 is, for example, a step of uniaxially stretching a polyvinyl alcohol resin film; a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye; a dichroic dye being adsorbed It can be produced by a method comprising a step of treating a polyvinyl alcohol resin film with an aqueous boric acid solution; and a step of washing with water after the treatment with the boric acid aqueous solution.

  As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, (meth) acrylamides having ammonium groups, and the like.

  The saponification degree of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The average degree of polymerization of the polyvinyl alcohol resin is usually 1000 to 10000, preferably 1500 to 5000. The average degree of polymerization of the polyvinyl alcohol resin can be determined according to JIS K 6726.

  What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of the polarizer 10 (polarizing film). The method for forming the polyvinyl alcohol-based resin into a film is not particularly limited, and a known method is employed. The thickness of the polyvinyl alcohol-based raw film is not particularly limited, but in order to make the thickness of the polarizer 10 15 μm or less, it is preferable to use a film having a thickness of 5 to 35 μm. More preferably, it is 20 μm or less. If an attempt is made to stretch a polyvinyl alcohol-based raw film having a thickness of more than 35 μm to obtain a polarizer 10 having a thickness of 15 μm or less, it is necessary to increase the stretching ratio. Even when the thickness of the polarizer 10 is set to 15 μm or less, the temperature is high. Dimensional shrinkage under the environment increases. Moreover, when thickness is less than 5 micrometers, the handleability at the time of extending | stretching falls and it becomes easy to produce malfunctions, such as a cutting | disconnection at the time of polarizer manufacture.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, you may uniaxially stretch in these several steps.

  In uniaxial stretching, it may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a hot roll. Further, the uniaxial stretching may be dry stretching in which stretching is performed in the air, or may be wet stretching in which stretching is performed in a state where a polyvinyl alcohol-based resin film is swollen using a solvent or water. The draw ratio is usually 3 to 8 times.

  As a method for dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing the dichroic dye is employed. As the dichroic dye, iodine or a dichroic organic dye is used. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

As the dyeing treatment with iodine, a method of immersing a polyvinyl alcohol resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide is usually 0.5 to 20 parts by weight per 100 parts by weight of water. Moreover, the temperature of this aqueous solution is 20-40 degreeC normally. On the other hand, as a dyeing treatment with a dichroic organic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic organic dye is usually employed. The aqueous solution containing the dichroic organic dye may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The content of the dichroic organic dye in this aqueous solution is usually 1 × 10 ⁻⁴ to 10 parts by weight per 100 parts by weight of water. The temperature of this aqueous solution is usually 20 to 80 ° C.

  As boric acid treatment after dyeing with a dichroic dye, a method of immersing a dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution is usually employed. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The amount of boric acid in the boric acid-containing aqueous solution is usually 2 to 15 parts by weight per 100 parts by weight of water. The amount of potassium iodide in this aqueous solution is usually 0.1 to 15 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution may be 50 ° C. or higher, for example, 50 to 85 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually 5 to 40 ° C.

  The polarizer 10 is obtained by performing a drying process after washing with water. The drying process can be performed using a hot air dryer or a far infrared heater. The thickness of the polarizer 10 is preferably 15 μm or less, and more preferably 10 μm or less. Setting the thickness of the polarizer 10 to 15 μm or less is advantageous in reducing the thickness of the polarizing plate 100 and, in turn, the image display device. The thickness of the polarizer 10 is usually 2 μm or more. According to the present invention, even when the thickness of the polarizer 10 is as thin as 15 μm or less, curling due to temperature change and humidity change of the protective film-attached polarizing plate can be suppressed.

  By the drying process, the moisture content of the polarizer 10 is reduced to a practical level. The moisture content is usually 5 to 20% by weight, and preferably 8 to 15% by weight. When the moisture content is less than 5% by weight, the flexibility of the polarizer 10 is lost, and the polarizer 10 may be damaged or broken after drying. Moreover, when the moisture content exceeds 20% by weight, the thermal stability of the polarizer 10 may be inferior.

(3) Protective film The protective films 21 and 22 that can be laminated on one side or both sides of the polarizer 10 are light-transmitting (preferably optically transparent) thermoplastic resins, for example, chain polyolefin resins. (Polypropylene resins, etc.), polyolefin resins such as cyclic polyolefin resins (norbornene resins, etc.); cellulose resins such as triacetyl cellulose and diacetyl cellulose; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; Polycarbonate resins; (meth) acrylic resins such as methyl methacrylate resins; polystyrene resins; polyvinyl chloride resins; acrylonitrile / butadiene / styrene resins; acrylonitrile / styrene resins; polyvinyl acetate resins; salt Polyvinyl resin; Polyamide resin; Polyacetal resin; Modified polyphenylene ether resin; Polysulfone resin; Polyether sulfone resin; Polyarylate resin; Polyamideimide resin; Polyimide resin it can. Among these, it is preferable to use a polyolefin resin or a cellulose resin. In this specification, “(meth) acrylic resin” represents at least one selected from the group consisting of acrylic resins and methacrylic resins. The same applies to other terms with “(meta)”.

  Examples of the chain polyolefin-based resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more chain olefins.

  Cyclic polyolefin resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit. Specific examples of cyclic polyolefin resins include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene (typically Are random copolymers), graft polymers obtained by modifying them with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among these, norbornene resins using norbornene monomers such as norbornene and polycyclic norbornene monomers as cyclic olefins are preferably used.

  Cellulosic resins are those in which some or all of the hydrogen atoms in the hydroxyl groups of cellulose obtained from raw material cellulose such as cotton linter and wood pulp (hardwood pulp, conifer pulp) are substituted with acetyl groups, propionyl groups and / or butyryl groups. Further, it refers to a cellulose organic acid ester or a cellulose mixed organic acid ester. For example, cellulose acetate, propionate, butyrate, and mixed esters thereof can be used. Among these, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate are preferable.

  The (meth) acrylic resin is a polymer containing a structural unit derived from a (meth) acrylic monomer. The polymer is typically a polymer containing a methacrylic acid ester. Preferably, it is a polymer in which the proportion of structural units derived from methacrylic acid esters is 50% by weight or more based on the total structural units. The (meth) acrylic resin may be a methacrylic acid ester homopolymer or a copolymer containing structural units derived from other polymerizable monomers. In this case, the proportion of structural units derived from other polymerizable monomers is preferably 50% or less with respect to the total structural units.

  The methacrylic acid ester that can constitute the (meth) acrylic resin is preferably an alkyl methacrylate. Examples of alkyl methacrylates include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate. And alkyl methacrylate having 1 to 8 carbon atoms in the alkyl group, such as 2-hydroxyethyl methacrylate. Carbon number of the alkyl group contained in the methacrylic acid alkyl ester is preferably 1 to 4. In the (meth) acrylic resin, methacrylic acid esters may be used alone or in combination of two or more.

  As said other polymerizable monomer which can comprise a (meth) acrylic-type resin, the compound which has a polymerizable carbon-carbon double bond in an acrylate ester and another molecule | numerator can be mentioned. Other polymerizable monomers may be used alone or in combination of two or more. As the acrylic acid ester, an acrylic acid alkyl ester is preferable. Examples of the alkyl acrylate ester include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, and cyclohexyl acrylate. And alkyl acrylates having 1 to 8 carbon atoms in the alkyl group such as 2-hydroxyethyl acrylate. Carbon number of the alkyl group contained in the acrylic acid alkyl ester is preferably 1 to 4. In the (meth) acrylic resin, acrylic acid esters may be used alone or in combination of two or more.

  Other compounds having a polymerizable carbon-carbon double bond in the molecule include vinyl compounds such as ethylene, propylene and styrene, and vinylcyan compounds such as acrylonitrile. Other compounds having a polymerizable carbon-carbon double bond in the molecule may be used alone or in combination of two or more.

It is also useful to control the retardation value of the protective films 21 and 22 to a value suitable for an image display device such as a liquid crystal display device. For example, in an in-plane switching (IPS) mode liquid crystal display device, it is preferable to use a film having a substantially zero retardation value as the protective film 22. The phase difference value of substantially zero means that the in-plane retardation value R ₀ at a wavelength of 590 nm is 10 nm or less, the absolute value of the thickness direction retardation value R _th at a wavelength of 590 nm is 10 nm or less, and a wavelength of 480 to 750 nm. It means that the absolute value of the thickness direction retardation value _Rth at 15 is 15 nm or less.

  Depending on the mode of the liquid crystal display device, the protective films 21 and 22 may be stretched and / or shrunk to give a suitable retardation value. For example, a retardation layer (or film) having a single layer or a multilayer structure can be used as the protective film 22 for the purpose of viewing angle compensation. In this case, the polarizing plate 100 can be an elliptically polarizing plate or a circularly polarizing plate including a laminated structure of the polarizer 10 and the retardation layer, or a polarizing plate having a viewing angle compensation function including the retardation layer. .

  Although the thickness of the protective films 21 and 22 is 1-100 micrometers normally, it is preferable that it is 5-60 micrometers from viewpoints, such as intensity | strength and a handleability, and it is more preferable that it is 5-50 micrometers. When the thickness is within this range, the polarizer 10 is mechanically protected, and the polarizer 10 does not contract even when exposed to a humid heat environment, and stable optical characteristics can be maintained. As the protective films 21 and 22 are made thinner, curling due to temperature change and humidity change is more likely to occur. However, according to the present invention, even if the thickness of the protective films 21 and 22 is as thin as 30 μm or less, the temperature changes and humidity changes. The accompanying curl can be suppressed.

  The polarizing plate 100 may have a configuration that does not include at least one of the protective films 21 and 22 from the viewpoint of thinning, but preferably includes a protective film on at least one surface of the polarizer 10. When the protective film is laminated only on one surface of the polarizer 10, curling due to temperature change and humidity change is likely to occur. However, according to the present invention, the temperature change and humidity change are also caused in such a case. The accompanying curl can be suppressed.

  When a protective film is laminated | stacked only on one side of the polarizer 10, the activity similar to the below-mentioned active energy ray hardening adhesive is provided on the surface on the opposite side to the surface where the protective film in the polarizer 10 is laminated | stacked. A protective layer formed from the energy ray curable resin composition can also be provided. By providing the protective layer, even when the protective film is provided only on one surface of the polarizer 10, curling due to temperature change and humidity change and deterioration of the polarizer 10 can be more effectively suppressed. it can.

  When a protective film is bonded to both surfaces of the polarizer 10, these protective films may be made of the same kind of thermoplastic resin or may be made of different types of thermoplastic resins. Moreover, the thickness may be the same or different. Furthermore, they may have the same phase difference characteristics or different phase difference characteristics.

  At least one of the protective films 21 and 22 has a hard coat layer, an antiglare layer, a light diffusing layer, a retardation layer (a quarter wavelength retardation) on the outer surface (the surface opposite to the polarizer 10). A retardation layer having a value), an antireflection layer, an antistatic layer, a surface treatment layer (coating layer) such as an antifouling layer, or an optical layer.

  If the structures of the protective films (resin type, thickness, presence / absence of surface treatment layer, etc.) laminated on both surfaces of the polarizer 10 are different from each other, curling due to temperature change and humidity change is likely to occur. In this case, curling associated with temperature change and humidity change can be suppressed.

  The protective films 21 and 22 can be bonded to the polarizer 10 through an adhesive layer, for example. As the adhesive forming the adhesive layer, a water-based adhesive, an active energy ray-curable adhesive, or a thermosetting adhesive can be used, and a water-based adhesive and an active energy ray-curable adhesive are preferable.

  Examples of the water-based adhesive include an adhesive made of a polyvinyl alcohol-based resin aqueous solution, an aqueous two-component urethane emulsion adhesive, and the like. Among these, a water-based adhesive composed of a polyvinyl alcohol-based resin aqueous solution is preferably used. Polyvinyl alcohol resins include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. A polyvinyl alcohol copolymer obtained by saponifying a polymer, or a modified polyvinyl alcohol polymer obtained by partially modifying the hydroxyl group thereof can be used. The water-based adhesive can contain a crosslinking agent such as an aldehyde compound (glyoxal, etc.), an epoxy compound, a melamine compound, a methylol compound, an isocyanate compound, an amine compound, and a polyvalent metal salt.

  When using a water-based adhesive, it is preferable to carry out a drying step for removing water contained in the water-based adhesive after the polarizer 10 and the protective films 21 and 22 are bonded together. After the drying process, for example, a curing process for curing at a temperature of 20 to 45 ° C. may be provided.

  The active energy ray-curable adhesive refers to an adhesive that cures by irradiating active energy rays such as ultraviolet rays and electron beams, for example, a curable composition containing a polymerizable compound and a photopolymerization initiator, Examples thereof include a curable composition containing a photoreactive resin, a curable composition containing a binder resin and a photoreactive crosslinking agent. An ultraviolet curable adhesive is preferable. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable (meth) acrylic monomers, and photocurable urethane monomers, and oligomers derived from the photopolymerizable monomers. it can. As a photoinitiator, what contains the substance which generate | occur | produces active species like a neutral radical, an anion radical, and a cation radical by irradiation of an active energy ray can be mentioned. As an active energy ray-curable adhesive containing a polymerizable compound and a photopolymerization initiator, a curable composition containing a photocurable epoxy monomer and a cationic photopolymerization initiator, a photocurable (meth) acrylic monomer, and light A curable composition containing a radical polymerization initiator or a mixture of these curable compositions can be preferably used.

As the photocurable epoxy monomer, an alicyclic epoxy compound is preferable. An alicyclic epoxy compound refers to a compound having one or more structures in the molecule forming an oxirane ring together with carbon atoms of the alicyclic ring. An alicyclic epoxy compound may be used individually by 1 type, and may use 2 or more types together. The “structure in which an oxirane ring is formed together with the carbon atom of the alicyclic ring” is a group in which one or a plurality of hydrogen atoms are removed from (CH ₂ ) _m in the structure shown below. In the following formula, m is an integer of 2 to 5.

Therefore, a compound in which a group in which one or a plurality of hydrogen atoms in (CH ₂ ) _m are removed is bonded to another chemical structure can be an alicyclic epoxy resin. One or more hydrogen atoms in (CH ₂ ) _m may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among alicyclic epoxy compounds, alicyclic epoxy compounds having an oxabicyclohexane ring (m = 4 in the above formula) and an oxabicycloheptane ring (m = 5 in the above formula) are excellent in adhesion. It is preferable at the point which shows property. Specific examples of the alicyclic epoxy compounds that are preferably used are shown below.

  When an active energy ray-curable adhesive is used, the polarizer 10 and the protective films 21 and 22 are bonded together, and then a drying process is performed as necessary, followed by irradiation with active energy rays to cure the active energy ray. A curing step for curing the adhesive is performed. Therefore, when an active energy ray-curable adhesive is used, the adhesive layer is the cured product layer. The light source of the active energy ray is not particularly limited, but ultraviolet light having a light emission distribution at a wavelength of 400 nm or less is preferable. A wave excitation mercury lamp, a metal halide lamp, etc. can be used.

  In laminating the polarizer 10 and the protective films 21 and 22, in order to improve the adhesion, at least one of these laminating surfaces can be subjected to saponification treatment, corona treatment, plasma treatment or the like. .

  When protective films are bonded to both surfaces of the polarizer 10, the adhesive for bonding these protective films may be the same type of adhesive or different types of adhesives. When different types of adhesives are used, curling due to temperature change and humidity change is likely to occur. However, according to the present invention, curling due to temperature change and humidity change can be suppressed even in such a case.

(4) Other optical films The polarizing plate 100 can contain other optical films other than the polarizer 10 and the protective films 21 and 22, The representative examples are the brightness enhancement film 50 and retardation film. When the polarizing plate 100 includes another optical film, the protect film 60 may be laminated on the surface of the optical film.

  The brightness enhancement film 50 is also referred to as a reflective polarizing film, and a polarization conversion element having a function of separating outgoing light from a light source (backlight) into transmitted polarized light and reflected polarized light or scattered polarized light is used. By arranging the brightness enhancement film 50 on the polarizer 10, the emission efficiency of linearly polarized light emitted from the polarizer 10 can be improved by using retroreflected light that is reflected polarized light or scattered polarized light. The brightness enhancement film 50 can be laminated on the polarizer 10 via the pressure-sensitive adhesive layer (third pressure-sensitive adhesive layer 32). Another film such as a protective film may be interposed between the polarizer 10 and the brightness enhancement film 50.

  The brightness enhancement film 50 can be, for example, an anisotropic reflective polarizer. An example of the anisotropic reflective polarizer is an anisotropic multiple thin film that transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction, and a specific example thereof is “DBEF” manufactured by 3M. (See JP-A-4-268505). Another example of the anisotropic reflective polarizer is a composite of a cholesteric liquid crystal layer and a λ / 4 plate, and a specific example thereof is “PCF” manufactured by Nitto Denko (see JP-A-11-231130). ). Yet another example of an anisotropic reflective polarizer is a reflective grid polarizer, a specific example of which is a metal grid reflective polarizer that emits reflected polarized light even in the visible light region by finely processing the metal (US Patent). No. 6288840, etc.), and a film obtained by adding metal fine particles to a polymer matrix and stretching (see JP-A-8-184701, etc.).

  A surface activation treatment may be performed in advance on the bonding surface of the brightness enhancement film 50 with the third pressure-sensitive adhesive layer 32. Thereby, it can be set as the polarizing plate 100 excellent in wet heat durability which does not produce peeling easily between the 3rd adhesive layer 32 and the brightness improvement film 50 in a wet heat environment. As the surface activation treatment, dry treatment such as corona treatment, plasma treatment, discharge treatment (glow discharge treatment, etc.), flame treatment, ozone treatment, UV ozone treatment, ionizing active ray treatment (ultraviolet treatment, electron beam treatment, etc.) And wet treatment such as ultrasonic treatment using a solvent such as water and acetone, alkali treatment, and anchor coat treatment. These processes may be performed alone or in combination of two or more. Among these, corona treatment and plasma treatment are preferable for continuously treating a roll-shaped film.

  On the outer surface of the brightness enhancement film 50, a hard coat layer, an antiglare layer, a light diffusion layer, a retardation layer (such as a retardation layer having a retardation value of ¼ wavelength), an antireflection layer, an antistatic layer, and an antifouling layer A surface treatment layer (coating layer) such as a layer or an optical layer may be provided. By forming such a layer, the adhesion to the backlight tape and the uniformity of the display image can be improved. Although the thickness of the brightness enhancement film 50 is usually 10 to 100 μm, it is preferably 10 to 50 μm, more preferably 10 to 30 μm, from the viewpoint of thinning the polarizing plate 100.

(5) Adhesive layer (pressure-sensitive adhesive layer)
The 1st adhesive layer 31 can be used in order to bond a polarizing plate with a protective film to an image display element (for example, liquid crystal cell) or another optical member. The third pressure-sensitive adhesive layer 32 is used for bonding optical films constituting the polarizing plate 100 (for example, another optical film such as the brightness enhancement film 50 and the polarizer 10 or the protective film 21). The first pressure-sensitive adhesive layer 31 and the third pressure-sensitive adhesive layer 32 are pressure-sensitive adhesive compositions mainly composed of a resin such as (meth) acrylic, rubber-based, urethane-based, ester-based, silicone-based, or polyvinylether-based. Can be configured. Especially, the adhesive composition which uses (meth) acrylic resin excellent in transparency, weather resistance, heat resistance, etc. as a base polymer is suitable. The pressure-sensitive adhesive composition may be an active energy ray curable type or a thermosetting type.

  Examples of the (meth) acrylic resin (base polymer) used in the pressure-sensitive adhesive composition include butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and (meth) acrylic acid 2- A polymer or copolymer having one or more (meth) acrylic acid esters such as ethylhexyl as a monomer is preferably used. The base polymer is preferably copolymerized with a polar monomer. Examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, glycidyl ( Mention may be made of monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like, such as (meth) acrylate.

  The pressure-sensitive adhesive composition may contain only the above base polymer, but usually further contains a crosslinking agent. As a crosslinking agent, a metal ion having a valence of 2 or more, which forms a carboxylic acid metal salt with a carboxyl group; a polyamine compound, which forms an amide bond with a carboxyl group; Examples thereof include epoxy compounds and polyols that form ester bonds with carboxyl groups; polyisocyanate compounds that form amide bonds with carboxyl groups. Of these, polyisocyanate compounds are preferred.

  The active energy ray-curable pressure-sensitive adhesive composition has a property of being cured by irradiation with active energy rays such as ultraviolet rays and electron beams, and has an adhesive property even before irradiation with active energy rays. It is a pressure-sensitive adhesive composition having such a property that it can be adhered to an adherend such as the like and can be cured by irradiation with active energy rays to adjust the adhesion. The active energy ray-curable pressure-sensitive adhesive composition is preferably ultraviolet curable. The active energy ray-curable pressure-sensitive adhesive composition further contains an active energy ray-polymerizable compound in addition to the base polymer and the crosslinking agent. Further, if necessary, a photopolymerization initiator, a photosensitizer and the like may be contained.

  Adhesive composition consists of fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than base polymers, tackifiers, fillers (metal powder and other inorganic powders) Etc.), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, antifoaming agents, corrosion inhibitors, photopolymerization initiators and the like.

  The 1st adhesive layer 31 and the 3rd adhesive layer 32 can be formed by apply | coating the organic solvent dilution liquid of the said adhesive composition on a base material, and making it dry. The substrate can be a polarizer 10, protective films 21, 22, other optical films such as a brightness enhancement film 50, a separate film (for example, a separate film 70), and the like. When the active energy ray-curable pressure-sensitive adhesive composition is used, a cured product having a desired degree of curing can be obtained by irradiating the formed pressure-sensitive adhesive layer with active energy rays.

  The thickness of the first pressure-sensitive adhesive layer 31 and the third pressure-sensitive adhesive layer 32 is usually 1 to 40 μm, but suppresses the dimensional change of the polarizing plate 100 while maintaining the viewpoint of thinning the polarizing plate 100 and good workability. In view of the above, it is preferably 3 to 25 μm (for example, 3 to 20 μm, more preferably 3 to 15 μm).

  It is preferable that the 3rd adhesive layer 32 shows the storage elastic modulus of 0.15-1 MPa in the temperature range of 23-80 degreeC. Thereby, the dimensional change which is easy to generate | occur | produce with the shrinkage | contraction of the polarizer 10 in a humid heat environment can be suppressed, and durability of the polarizing plate 100 can be improved. Further, even when the image display device on which the polarizing plate 100 is mounted is placed in a humid heat environment, the movement of the polarizing plate 100 is suppressed, so that the reliability of the image display device can be improved.

  “Showing a storage elastic modulus of 0.15 to 1 MPa in a temperature range of 23 to 80 ° C.” means that the storage elastic modulus is a value within the above range at any temperature within this range. Since the storage elastic modulus usually decreases gradually as the temperature rises, if both the storage elastic modulus at 23 ° C. and 80 ° C. are within the above range, the storage elastic modulus within the above range is exhibited at the temperature in this range. Can be seen. The storage elastic modulus of the third pressure-sensitive adhesive layer 32 can be measured using a commercially available viscoelasticity measuring device, for example, a viscoelasticity measuring device “DYNAMIC ANALYZER RDA II” manufactured by REOMETRIC.

  As a method for adjusting the storage elastic modulus to the above range, an oligomer, specifically, a urethane (meth) acrylate oligomer is further added to a pressure-sensitive adhesive composition containing a base polymer or a crosslinking agent. An active energy ray-curable pressure-sensitive adhesive composition (preferably an ultraviolet curable pressure-sensitive adhesive composition) can be mentioned. More preferably, the adhesive layer is appropriately cured by irradiating active energy rays.

  The storage elastic modulus of the 1st adhesive layer 31 may be the same as that of the 3rd adhesive layer 32, and may differ.

(6) Separate film The separate film 70 is a film that is temporarily attached to protect the surface of the first pressure-sensitive adhesive layer 31 until it is bonded to an image display element (for example, a liquid crystal cell) or another optical member. The separate film 70 is usually composed of a thermoplastic resin film that has been subjected to a release treatment on one side, and the release treatment surface is bonded to the first pressure-sensitive adhesive layer 31. The thermoplastic resin constituting the separate film 70 can be, for example, a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, and the like. In order to protect the surface of the third pressure-sensitive adhesive layer 32 until an optical film such as the brightness enhancement film 50 is bonded, a separate film similar to the above can be bonded. The thickness of the separate film 70 is, for example, 10 to 50 μm.

(7) Protective film The protective film 60 is comprised by the base film 61 and the 2nd adhesive layer 62 laminated | stacked on it. The protective film 60 is a film for protecting the surface of the polarizing plate 100. Usually, for example, after the polarizing plate with a protective film is bonded to an image display element or another optical member, the second adhesive layer that the protective film 60 has is attached. 62 is peeled off.

As described above, the protective film 60 as a whole including the second pressure-sensitive adhesive layer 62 has a moisture permeability of 15 g / (m ² · 24 hr) or less under the conditions of a temperature of 40 ° C. and a relative humidity of 90%, It is preferably 12 g / (m ² · 24 hr) or less. As a method for adjusting the moisture permeability of the protective film 60 within the above range, a material having a low moisture permeability may be used as a constituent material of the base film 61. Examples of the low moisture permeable material are low moisture permeable resins, preferably thermoplastic resins. Specifically, polyolefin resins such as polyethylene resins and polypropylene resins; cyclic polyolefin resins; polyethylene terephthalate and polyethylene naphthalates. Examples thereof include polyester resins such as phthalates; polycarbonate resins; (meth) acrylic resins.

  The base film 61 may have a single layer structure or a multilayer structure. For example, even when a resin film having a relatively high moisture permeability is used, the moisture permeability of the protective film 60 can be adjusted within the above range by laminating a low moisture permeability film or layer thereon. The base film 61 preferably has a single-layer structure from the viewpoints of manufacturability and manufacturing cost.

  Further, the moisture permeability of the protective film 60 may be adjusted within the above range by increasing the thickness of the base film 61. The thickness of the base film 61 can be 20 to 190 μm (for example, 30 to 140 μm), and the thickness of the protect film 60 can be 60 to 200 μm (for example, 70 to 150 μm). When the thickness of the protective film 60 exceeds 200 μm, it is disadvantageous in terms of cost, roll transportability, and reworkability of the protective film 60.

  Regarding the configuration of the second pressure-sensitive adhesive layer 62, the description of the first pressure-sensitive adhesive layer 31 and the third pressure-sensitive adhesive layer 32 is basically cited, but the thickness of the second pressure-sensitive adhesive layer 62 is increased. Alternatively, the moisture permeability of the protective film 60 can be adjusted within the above range by adding a hygroscopic substance (hygroscopic particles or the like) to the second pressure-sensitive adhesive layer 62. The moisture permeability of the protective film 60 may be adjusted within the above range by combining a plurality of methods described above.

The present invention is particularly advantageous when the polarizing plate 100 included in the polarizing plate with a protective film has a configuration that easily causes curling due to temperature change and humidity change, including a case where the polarizing plate 100 has an asymmetric layer configuration with respect to the polarizer 10. It is. An example of a configuration that easily causes curling due to temperature change and humidity change is as follows.
(A) A configuration in which the polarizer 10 and / or the protective films 21 and 22 are thin,
(B) a configuration in which the adhesive layer interposed between the polarizer 10 and the protective film is a cured product layer of an active energy ray-curable adhesive;
(C) Configuration in which a protective film is bonded only to one side of the polarizer 10,
(D) A configuration in which a protective film is bonded to one surface of the polarizer 10 and an optical film (such as a brightness enhancement film) other than the protective film is bonded to the other surface,
(E) Configurations of the protective films (resin type, thickness, presence / absence of surface treatment layer, etc.) bonded to both surfaces of the polarizer 10 are different from each other,
(F) a configuration in which adhesive layers for bonding protective films to both surfaces of the polarizer 10 are formed of different types of adhesives;
(G) The structure by which the protective film is bonded on both surfaces of the polarizer 10, and the other optical film is bonded on one protective film,
(H) In addition, with the polarizer 10 as a reference, the total number of films and layers on one side is different from the total number of films and layers on the other side.

<Laminated body, liquid crystal panel and image display device>
The polarizing plate with a protective film according to the present invention can be suitably applied to a laminate including an image display element and a polarizing plate with a protective film laminated thereon. In this laminate, the polarizing plate with a protective film is an image display element through an adhesive layer (for example, the first adhesive layer 31) (after having a separate film such as the separate film 70 peeled off). Can be pasted on top. After the polarizing plate with a protective film is bonded to the image display element, the protective film 60 is peeled and removed at a desired timing. The laminate can be a liquid crystal panel including an image display element and a polarizing plate laminated on one side or both sides thereof, or a production intermediate thereof. The protective film 60 is used to display an image after a laminated body is constructed, a liquid crystal panel in which the protective film 60 is bonded, or a liquid crystal panel in which the protective film 60 is bonded. It is peeled off after building the device. Usually, in the final product as an image display device, the protective film 60 is peeled off.

  The image display device may be any device such as a liquid crystal display device or an organic EL display device, but is preferably a liquid crystal display device. The liquid crystal display device includes a liquid crystal panel including a liquid crystal cell as an image display element, and a backlight. In constructing a liquid crystal display device, the polarizing plate with a protective film according to the present invention may be used for a polarizing plate disposed on the viewing side, or may be used for a polarizing plate disposed on the backlight side. The polarizing plate with a protective film according to the present invention is preferably used at least as a polarizing plate on the backlight side.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the following examples, the moisture permeability of the film, the humidity expansion coefficient, the thickness, the in-plane retardation value R ₀ and the thickness direction retardation value R _th , the storage elastic modulus of the adhesive layer, and the curl amount of the polarizing plate with a protective film are Measured according to the following method.

(1) Moisture permeability The moisture permeability [g / (m ² · 24 hr)] of the protective film at a temperature of 40 ° C. and a relative humidity of 90% was measured by a cup method defined in JIS Z 0208.

(2) Humidity Expansion Coefficient The humidity expansion coefficient [ppm ·% RH ⁻¹ ] of the polarizing plate and the protective film was measured according to the following method. The film sample was cut into 100 mm × 100 mm, and the length in the film transport direction at 23 ° C. and 50% RH and at 23 ° C. and 90% RH was measured.
Humidity expansion coefficient = (L90−L50) / (L50 × ΔH)
Then, the humidity expansion coefficient [ppm ·% RH ⁻¹ ] was measured. Here, L50 is the length (mm) in the film conveyance direction at 23 ° C. and 50% RH, L90 is the length (mm) in the film conveyance direction at 23 ° C. and 90% RH, and ΔH is 40 (= 90-50)% RH.

(3) Thickness Measured using a digital micrometer “MH-15M” manufactured by Nikon Corporation.

(4) In-plane retardation value _Re and thickness direction retardation value _Rth
Using “KOBRA-ADH” manufactured by Oji Scientific Instruments, which is a phase difference meter based on the parallel Nicol rotation method, measurement was performed at 23 ° C. with light having a wavelength of 590 nm, 483 nm, or 755 nm.

(5) Storage elastic modulus The storage elastic modulus G 'of the pressure-sensitive adhesive layer was measured according to the following (I) to (III).
(I) Two samples of 25 ± 1 mg are taken out from the pressure-sensitive adhesive layer, and each is formed into a substantially ball shape. (II) The obtained approximately ball-shaped sample is attached to the upper and lower surfaces of the I-shaped jig, and the upper and lower surfaces are sandwiched between the L-shaped jig. The configuration of the measurement sample is L-shaped jig / adhesive / I-shaped jig / adhesive / L-shaped jig.
(III) The storage elastic modulus G ′ of the thus prepared sample was measured using a dynamic viscoelasticity measuring device “DVA-220” manufactured by IT Measurement Control Co., Ltd. at a temperature of 23 ° C. or 80 ° C., a frequency of 1 Hz, Measure under conditions of initial strain of 1N.

(6) Curling amount A sheet of 221 mm × 139 mm size was cut out from the polarizing plate with a protective film, and the separate film attached to the first pressure-sensitive adhesive layer of this sheet was peeled off, and 225 mm × 145 mm, thickness 0 Bonding to 4 mm non-alkali glass gave a measurement sample. The measurement sample was allowed to stand in an 80 ° C. and 90% RH environment for 5 hours, and then returned to room temperature (23 ° C. and 50% RH). Thereafter, the measurement sample was placed on a measurement table of a two-dimensional measuring instrument “NEXIV VMR-1207” manufactured by Nikon Corporation with the polarizing plate side facing up. Subsequently, the surface of the center part of the polarizing plate was focused, and the focal point was focused on the four corners of the polarizing plate, and the distance of the height difference from the reference focal point was measured. The average distance at the four corners was taken as the curl amount.

(Production of polarizer)
A 20 μm-thick polyvinyl alcohol film (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) is about 5 times longitudinally uniaxially stretched by dry stretching and further kept in a pure water at 60 ° C. while maintaining tension. After being immersed for 1 minute, it was immersed for 60 seconds in a 28 ° C. aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100. Then, it was immersed for 300 seconds in 72 degreeC aqueous solution whose weight ratio of potassium iodide / boric acid / water is 8.5 / 8.5 / 100. Subsequently, after washing with pure water at 26 ° C. for 20 seconds, drying treatment was performed at 65 ° C. to obtain a 7 μm thick polarizer in which iodine was adsorbed and oriented on the polyvinyl alcohol film.

(Preparation of protective film)
Three types of protective films:
Protect film A: composed of a 75 μm thick base film made of polyethylene terephthalate and a 13 μm thick acrylic second pressure-sensitive adhesive layer (moisture permeability 8 g / (m ² · 24 hr), humidity expansion coefficient 6. 4 ppm ·% RH ⁻¹ , total thickness 88 μm),
Protect film B: composed of a 75 μm-thick base film made of polyethylene terephthalate and a 18 μm thick acrylic second pressure-sensitive adhesive layer (moisture permeability 10 g / (m ² · 24 hr), humidity expansion coefficient 6. 8ppm ・% RH ⁻¹ , total thickness 93μm)
Protect film C: composed of a 38 μm thick base film made of polyethylene terephthalate and a 20 μm thick acrylic second pressure-sensitive adhesive layer (moisture permeability 17 g / (m ² · 24 hr), humidity expansion coefficient 6. 4ppm ・% RH ⁻¹ , total thickness 58μm)
Prepared.

(Preparation of first protective film)
A film obtained by laminating an acrylic hard coat layer having a thickness of 7 μm on a triacetylcellulose film (thickness 25 μm, trade name “KC2UA”) manufactured by Konica Minolta Co., Ltd. was prepared.

(Preparation of second protective film)
Cyclic polyolefin resin film (thickness 13 μm, in-plane retardation value R _e = 0.8 nm at wavelength 590 nm, thickness direction retardation value R _th = 3.4 nm at wavelength 590 nm, manufactured by Nippon Zeon Co., Ltd., wavelength 483 nm Thickness direction retardation value R _th = 3.5 nm and thickness direction retardation value R _th = 2.8 nm at a wavelength of 755 nm were prepared.

(Preparation of first adhesive layer)
A commercially available pressure-sensitive adhesive layer with a separate film having a 20 μm-thick acrylic pressure-sensitive adhesive layer provided on a release-treated surface of a separate film made of polyethylene terephthalate with a thickness of 38 μm that has been subjected to a mold release treatment is a first with a separate film. Prepared as an adhesive layer. The storage elastic modulus of this pressure-sensitive adhesive layer was 0.05 MPa at 23 ° C. and 0.04 MPa at 80 ° C.

(Preparation of aqueous adhesive)
3 parts by weight of carboxyl group-modified polyvinyl alcohol [“KL-318” manufactured by Kuraray Co., Ltd.] was dissolved in 100 parts by weight of water to prepare an aqueous polyvinyl alcohol solution. To the obtained aqueous solution, 1.5 parts by weight of water-soluble polyamide epoxy resin (“Smile Resin 650 (30) manufactured by Taoka Chemical Industry Co., Ltd., solid content concentration: 30% by weight)” per 100 parts by weight of water. The aqueous adhesive was obtained by mixing at a ratio of

<Example 1>
A polarizing plate with a protective film having the same layer structure as that shown in FIG. First, the first protective film 21 is bonded to one side of the polarizer 10 using the aqueous adhesive so that the hard coat layer is on the side far from the polarizer 10, and the aqueous system is also applied to the opposite surface. The 2nd protective film 22 was bonded using the adhesive agent. Thereafter, it was dried at 80 ° C. for 5 minutes and then cured at 40 ° C. for 168 hours. The resulting polarizing plate had a humidity expansion coefficient of 28 ppm ·% RH ⁻¹ .

  Next, the first pressure-sensitive adhesive layer 31 (having a separate film on the outer surface) was bonded to the surface of the second protective film 22 opposite to the polarizer 10 side. Furthermore, said protective film A was bonded through the 2nd adhesive layer to the outer surface of the hard-coat layer of the 1st protective film 21, and the polarizing plate with a protective film was obtained. About the obtained polarizing plate with a protective film, the curl amount was measured according to said method. The results are shown in Table 1.

<Example 2>
A polarizing plate with a protective film and its sheet were prepared in the same manner as in Example 1 except that the protective film B was used instead of the protective film A, and the curl amount was measured. The results are shown in Table 1.

<Comparative Example 1>
A polarizing plate with a protective film and its sheet were prepared in the same manner as in Example 1 except that the protective film C was used instead of the protective film A, and the curl amount was measured. The results are shown in Table 1.

(Preparation of first protective film (B))
Triacetylcellulose film (thickness 25 μm, trade name “KC2TW”, in-plane retardation value R _e = 1.2 nm at a wavelength of 590 nm, thickness direction retardation value R _th = 1 at a wavelength of 590 nm, manufactured by Konica Minolta Co., Ltd. .3 nm).

(Preparation of third adhesive layer)
Separation treatment surface of a separate film composed of a polyethylene terephthalate film having a thickness of 38 μm obtained by subjecting an organic solvent solution obtained by adding a urethane acrylate oligomer and an isocyanate crosslinking agent to a copolymer of butyl acrylate and acrylic acid. In addition, a third pressure-sensitive adhesive layer with a separate film was prepared by coating with a die coater such that the thickness after drying was 5 μm and drying. The storage elastic modulus of the third pressure-sensitive adhesive layer was 0.40 MPa at 23 ° C. and 0.18 MPa at 80 ° C.

<Example 3>
First, the first protective film (B) is bonded as the first protective film 21 to the one surface of the polarizer 10 using the aqueous adhesive, and the third pressure-sensitive adhesive layer (outer surface) is bonded to the opposite surface. (Having a separate film). Next, after separating and removing the separate film of the third pressure-sensitive adhesive layer, a 26 μm thick brightness enhancement film (“Advanced Polarized Film, Version 3” manufactured by 3M) was formed on the surface of the third pressure-sensitive adhesive layer exposed by peeling. Was pasted. The resulting polarizing plate had a humidity expansion coefficient of 9.3 ppm ·% RH ⁻¹ .

  Furthermore, the said protective film A was bonded through the 2nd adhesive layer on the outer surface of the brightness enhancement film, and the polarizing plate with a protective film was obtained. About the obtained polarizing plate with a protective film, the curl amount was measured according to said method. The results are shown in Table 1.

<Comparative Example 2>
A polarizing plate with a protective film and its sheet were prepared in the same manner as in Example 3 except that the protective film C was used instead of the protective film A, and the curl amount was measured. The results are shown in Table 1.

  DESCRIPTION OF SYMBOLS 10 Polarizer, 21, 22 Protective film, 31 1st adhesive layer, 32 3rd adhesive layer, 50 Brightness improvement film, 60 Protective film, 61 Base film, 62 2nd adhesive layer, 70 Separate film, 100 Polarizing plate.

Claims (10)

A polarizing plate including a polarizer and a protective film laminated on one surface thereof,
The protective film is a polarizing plate with a protective film, wherein the moisture permeability at a temperature of 40 ° C. and a relative humidity of 90% is 15 g / (m ² · 24 hr) or less.   The polarizing plate with a protective film according to claim 1, wherein the polarizing plate has a thickness of 125 μm or less.   The other surface of the said polarizing plate is a polarizing plate with a protective film of Claim 1 or 2 comprised by the surface of the 1st adhesive layer.   The said protective film is comprised by the 2nd adhesive layer laminated | stacked on said one surface, and the single-layer base film laminated | stacked on it, The any one of Claims 1-3. Polarizing plate with protective film.   The said polarizing plate further contains the protective film laminated | stacked through the hardened | cured material layer of an active energy ray hardening adhesive agent on the at least one surface of the said polarizer, The any one of Claims 1-4. Polarizing plate with protective film. The other surface of the polarizing plate is composed of the surface of the first pressure-sensitive adhesive layer,
The polarizing plate with a protective film according to claim 1, further comprising a separate film laminated on the other surface of the polarizing plate. The polarizing plate further includes an optical film other than the polarizer,
The polarizing plate with a protective film according to any one of claims 1 to 6, wherein the protective film is laminated on a surface of the optical film.   The polarizing plate with a protective film according to claim 7, wherein the optical film is a brightness enhancement film.   The polarizing plate with a protective film according to claim 1, wherein the polarizer has a thickness of 15 μm or less.   The laminated body containing an image display element and the polarizing plate with a protective film of any one of Claims 1-9 laminated | stacked on it.

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