JP6470828B1 - Manufacturing method of polarizing plate with protective film - Google Patents

Abstract

A method of manufacturing a polarizing plate sheet with a protective film having a relatively large positive curl is provided.
A process of obtaining a polarizing plate with a protective film by bonding a protective film including a region satisfying the formula: TD elastic modulus−MD elastic modulus ≧ 300 MPa to one side of the polarizing plate; The manufacturing method of the polarizing plate sheet with a protective film including the process of cutting out a body from the said area | region is provided. In the formula, the TD elastic modulus is the tensile elastic modulus in the TD direction at a temperature of 23 ° C. and a relative humidity of 55% RH, and the MD elastic modulus is the tensile force in the MD direction at a temperature of 23 ° C. and a relative humidity of 55% RH. Elastic modulus.
[Selection] Figure 1

Description

  The present invention relates to a method for producing a polarizing plate sheet with a protective film. The present invention also relates to a polarizing plate with a protective film and a polarizing plate with a long protective film.

  In recent years, image display devices such as liquid crystal display devices and organic EL display devices, for example, mobile terminals such as smartphones, are rapidly increasing in 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 made by bonding a protective film made of triacetyl cellulose (TAC) with an adhesive to a polarizer made of polyvinyl alcohol resin is generally used. However, in recent years, a protective film made of a resin other than TAC has been used from the viewpoint of thinning, durability, cost, productivity, and the like (for example, Patent Document 1).

JP 2004-245925 A

With the demand for thinner polarizing plates, thinner polarizers and protective films have been developed. A sheet of a polarizing plate that can be obtained by cutting out from a thin polarizing plate, particularly a long polarizing plate, is likely to be deformed in a bow shape. In this specification, this deformation is also referred to as “curl”.
The polarizing plate is generally distributed on the market 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. In the polarizing plate with a protective film, when it is thinned, the tendency to be easily curled when the sheet is made is the same.

There are two types of curling of a polarizing plate with a protective film: “normal curl” and “reverse curl”. In a polarizing plate with a protective film comprising a laminate of a polarizing plate and a protective film, the “normal curl” is a curl having a convex surface on the polarizing plate side, and the “reverse curl” is on the protective film side. A curl with a convex surface.
When reverse curling occurs, a bonding error may occur when the polarizing plate side of the polarizing plate with a protective film is bonded to an image display element such as a liquid crystal cell or an organic EL element via an adhesive layer. It becomes easy to cause a problem that bubbles are mixed in the interface between the pressure-sensitive adhesive layer and the image display element.

The polarizing plate with a protective film may be formed into a further multilayer structure by laminating one or more other optical functional layers on the polarizing plate side via an adhesive layer or an adhesive layer. In this case, the addition of a further layer to the polarizing plate with a protective film works in the direction of reverse curling the multilayer structure.
Accordingly, when considering that the multilayer structure is used, it is desirable that the polarizing plate with a protective film has a sufficiently large positive curl. This is because when the multilayer structure has a reverse curl, the above-described problems are likely to occur when the multilayer structure is bonded to the image display element.
On the other hand, when the polarizing plate with a protective film is bonded to the image display element as it is without forming the multilayer structure, the large positive curl it has does not hinder the bonding to the image display element.

The objective of this invention is providing the method which can manufacture the polarizing plate sheet with a protective film which has a comparatively big positive curl.
Another object of the present invention is to provide a polarizing plate sheet with a protective film that can have a relatively large positive curl.
Still another object of the present invention is to provide a polarizing plate with a long protective film that can provide a polarizing plate with a protective film having a relatively large positive curl.

The present invention provides the following method for producing a polarizing plate with a protective film, a polarizing plate with a protective film, and a polarizing plate with a long protective film.
[1] A step of bonding a protective film including a region satisfying the following formula (I) to one side of a polarizing plate to obtain a polarizing plate with a protective film;
Cutting out the sheet of polarizing plate with protective film from the region;
Of manufacturing a polarizing plate sheet with a protective film.
TD elastic modulus−MD elastic modulus ≧ 300 MPa (I)
[In the formula, the TD elastic modulus is the tensile elastic modulus in the TD direction at a temperature of 23 ° C. and a relative humidity of 55% RH, and the MD elastic modulus is in the MD direction at a temperature of 23 ° C. and a relative humidity of 55% RH. Tensile modulus. ]
[2] The production method according to [1], wherein the polarizing plate and the protective film are sandwiched and bonded between a pair of rolls.
[3] The manufacturing method according to [2], wherein the polarizing plate has a long shape, and the protective film has a long shape.
[4] The pre-bonding tension of the polarizing plate is 200 N / m or less,
The production method according to [3], wherein a tension before bonding of the protective film is 300 N / m or more.
[5] The manufacturing method according to any one of [1] to [4], in which the absorption axis of the polarizing plate and the MD direction of the protect film are bonded in parallel.
[6] The manufacturing method according to any one of [1] to [5], wherein the polarizing plate has a thickness of 70 μm or less.
[7] A polarizing plate and a protective film laminated on one side thereof,
A polarizing plate sheet with a protective film, wherein the protective film satisfies the following formula (II).
First elastic modulus−second elastic modulus ≧ 300 MPa (II)
[In the formula, the first elastic modulus is the tensile elastic modulus in the direction orthogonal to the absorption axis of the polarizing plate at a temperature of 23 ° C. and a relative humidity of 55% RH, and the second elastic modulus is a temperature of 23 ° C., It is a tensile elastic modulus in a direction parallel to the absorption axis of the polarizing plate at a relative humidity of 55% RH. ]
[8] The polarizing plate sheet with a protective film according to [7], wherein a curl amount in a direction parallel to an absorption axis of the polarizing plate having a convex surface on the polarizing plate side is 40 mm or more.
[9] The polarizing plate sheet with a protective film according to [7] or [8], wherein the polarizing plate has a thickness of 70 μm or less.
[10] A long polarizing plate and a long protective film laminated on one side thereof,
A polarizing plate with a long protective film, wherein the protective film includes a region satisfying the following formula (III).
First elastic modulus−second elastic modulus ≧ 300 MPa (III)
[In the formula, the first elastic modulus is the tensile elastic modulus in the direction perpendicular to the absorption axis of the long polarizing plate at a temperature of 23 ° C. and a relative humidity of 55% RH, and the second elastic modulus is It is a tensile elastic modulus in a direction parallel to the absorption axis of the long polarizing plate at a temperature of 23 ° C. and a relative humidity of 55% RH. ]
[11] The polarizing plate with a long protective film according to [10], wherein the region extends over the entire width direction of the protective film.

It is possible to provide a method capable of producing a polarizing plate sheet with a protective film having a relatively large positive curl.
A polarizing plate sheet with a protective film that can have a relatively large positive curl can be provided.
A polarizing plate with a long protective film that can provide a polarizing plate with a protective film having a relatively large positive curl can be provided.

It is a flowchart which shows the manufacturing method of a polarizing plate sheet with a protective film. It is a schematic sectional drawing which shows an example of the laminated constitution of a polarizing plate. It is a schematic sectional drawing which shows another example of the laminated constitution of a polarizing plate. It is a side view which shows an example of bonding process S101 which bonds a polarizing plate and a protective film. It is a schematic sectional drawing which shows an example of the laminated constitution of a polarizing plate sheet with a protective film. It is the schematic explaining the preparation method of the sample for a measurement of MD curl amount, and the measurement point of MD curl amount. It is a graph which shows the relationship between the width direction position of the protect films 1-3 used in Experimental Examples 1-3, respectively, and an elasticity modulus difference. The relationship between the width direction position which cuts out the polarizing plate sheet with a protective film from the long polarizing plate with a protective film of Experimental Examples 1-3, and the MD curl amount of the cut polarizing plate with a protective film is shown. It is a graph.

<Production method of polarizing plate with protective film>
With reference to FIG. 1, the manufacturing method of the polarizing plate sheet with a protective film according to the present invention includes the following steps:
A protective film is bonded to one side of the polarizing plate to obtain a polarizing plate with a protective film, and a cutting step S102 for cutting out the sheet of the polarizing plate with protective film.
including. Hereinafter, each step will be described in detail.
In the present specification, the “sheet body” refers to a film having a smaller size cut out from a film having a larger size (for example, a long (band-shaped) film).

(1) Pasting step S101
(1-1) Polarizing plate provided for bonding step S101 (1-1-1) Configuration of polarizing plate The polarizing plate is a polarizing element including at least a polarizer, and is usually bonded to one side or both sides thereof. A thermoplastic resin film.
The thermoplastic resin film can be a protective film for protecting the polarizer, another optical film having an optical function different from that of the polarizer, or the like. Examples of other optical films are a retardation film and a brightness enhancement film.
The thermoplastic resin film may include a resin layer (for example, an optical layer) laminated on the surface thereof. Examples of the resin layer are a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer.
A thermoplastic resin film can be bonded to a polarizer via an adhesive layer or an adhesive layer.

The thickness of the polarizing plate is usually 150 μm or less, and is preferably 100 μm or less, more preferably from the viewpoint of thinning the polarizing plate and facilitating production of a polarizing plate with a protective film having a sufficiently large positive curl. Is 80 μm or less, more preferably 70 μm or less.
The thickness of the polarizing plate is usually 20 μm or more or 30 μm or more.

Examples of the layer configuration of the polarizing plate will be described with reference to FIGS. 2 and 3, but the layer configuration is not limited to these examples.
A polarizing plate 2 a shown in FIG. 2 includes a polarizer 10; a first thermoplastic resin film 20 bonded to one surface of the polarizer 10; a second thermoplastic film bonded to the other surface of the polarizer 10. A resin film 30 is provided. The first and second thermoplastic resin films 20 and 30 are, for example, protective films.

  As in the polarizing plate 2b shown in FIG. 3, one of the first and second thermoplastic resin films 20 and 30 may be omitted. In the polarizing plate 2b, the second thermoplastic resin film 30 is omitted. Such a polarizing plate having a thermoplastic resin film only on one surface of the polarizer 10 is advantageous for thinning the polarizing plate.

  Although illustration is abbreviate | omitted in FIG.2 and FIG.3, bonding with the polarizer 10 and the 1st and 2nd thermoplastic resin films 20 and 30 can be preferably performed using an adhesive agent.

It is preferable that the polarizing plate used for bonding process S101 is elongate.
The length of the elongate polarizing plate used for bonding process S101 is 100-20000 m, for example, Preferably it is 1000-10000 m. Moreover, the width | variety of the elongate polarizing plate provided to bonding process S101 is 0.5-3 m, for example, Preferably it is 1-2.5 m.

(1-1-2) Polarizer The polarizer 10 constituting the polarizing plate absorbs linearly polarized light having a vibration plane parallel to the absorption axis, and has a vibration plane orthogonal to the absorption axis (parallel to the transmission axis). It is an absorptive polarizer having the property of transmitting linearly polarized light. An example of the polarizer 10 is a polarizer in which a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol resin film. Such a 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; It can be produced by a method comprising a step of treating the adsorbed polyvinyl alcohol-based resin film with a crosslinking solution such as an aqueous boric acid solution; and a step of washing with water after the treatment with the crosslinking 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.

  In the present specification, “(meth) acryl” means at least one selected from acryl and methacryl. The same applies to “(meth) acryloyl”, “(meth) acrylate”, 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 saponification degree and average polymerization degree of the polyvinyl alcohol-based resin can be determined according to JIS K 6726.

  A film made of such a polyvinyl alcohol resin is used as a raw film of the polarizer 10. The method for forming the polyvinyl alcohol-based resin into a film is not particularly limited, and a known method is employed. Although the thickness in particular of a polyvinyl alcohol-type resin film is not restrict | limited, For example, it is about 10-150 micrometers, Preferably it is 50 micrometers or less, More preferably, it is 35 micrometers or less.

  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 or during the crosslinking 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 crosslinking treatment after dyeing with a dichroic dye, a method of immersing a dyed polyvinyl alcohol 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 thickness of the polarizer 10 is usually about 2 to 40 μm. From the viewpoint of thinning the polarizing plate, the thickness of the polarizer 10 is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less.
On the other hand, from the viewpoint of facilitating the production of a polarizing plate with a protective film having a sufficiently large positive curl, the thickness of the polarizer 10 is preferably large, specifically, preferably 10 μm or more, more preferably 15 μm. More preferably, it is 20 μm or more.

(1-1-3) First and second thermoplastic resin films The first and second thermoplastic resin films 20 and 30 are each independently a light-transmitting thermoplastic resin, preferably optically transparent. It is a film comprised of a new thermoplastic resin. The thermoplastic resin constituting the first and second thermoplastic resin films 20 and 30 is, for example, a polyolefin resin such as a chain polyolefin resin (polypropylene resin or the like) or a cyclic polyolefin resin (norbornene resin or the like). A cellulose resin such as triacetyl cellulose and diacetyl cellulose; a polyester resin such as polyethylene terephthalate and polybutylene terephthalate; a polycarbonate resin; a (meth) acrylic resin such as a methyl methacrylate resin; a polystyrene resin; Polyvinyl chloride resin; Acrylonitrile butadiene styrene resin; Acrylonitrile styrene resin; Polyvinyl acetate resin; Polyvinylidene chloride resin; Polyamide resin; Polyacetal resin; Modified polyphenylene Ether-based resins; polysulfone resins; poly (ether sulfone) resins; polyarylate resin; polyamideimide resin; may be a polyimide resin or the like.

  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. More specific examples include polypropylene resins (polypropylene resins that are homopolymers of propylene and copolymers mainly composed of propylene), polyethylene resins (polyethylene resins that are homopolymers of ethylene and ethylene mainly) A copolymer).

  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 polyester-based resin is a resin other than the cellulose-based resin having an ester bond, and is generally made of a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a divalent diol can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol. Examples of suitable polyester-based resins include polyethylene terephthalate.

  The polycarbonate-based resin is an engineering plastic made of a polymer in which monomer units are bonded via a carbonate group, and is a resin having high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate-based resin may be a resin called a modified polycarbonate in which the polymer skeleton is modified in order to lower the photoelastic coefficient, a copolymerized polycarbonate with improved wavelength dependency, or the like.

  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% by weight or less based on 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.

The 1st and 2nd thermoplastic resin films 20 and 30 can be protective films for protecting the polarizer 10 laminated and bonded to one surface of the polarizer 10. The 1st or 2nd thermoplastic resin films 20 and 30 can also be a protective film which has optical functions like a phase difference film and a brightness enhancement film.
For example, a retardation provided with an arbitrary retardation value by stretching (such as uniaxial stretching or biaxial stretching) a thermoplastic resin film made of the above materials or forming a liquid crystal layer or the like on the film. It can be a film. The first and / or second thermoplastic resin films 20 and 30 are laminated on the surface thereof, such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer (coating). Layer).

Although the thickness of the 1st and 2nd thermoplastic resin films 20 and 30 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.
From the viewpoint of facilitating production of a polarizing plate with a protective film having a sufficiently large positive curl, the thickness of the first thermoplastic resin film 20 or the second thermoplastic resin film 30 is preferably small, specifically , Preferably 40 μm or less, more preferably 30 μm or less.

  In the case where a thermoplastic resin film is provided on both surfaces of the polarizer 10 as in the polarizing plate 2a shown in FIG. 2, these thermoplastic resin films may be composed of the same kind of thermoplastic resin, or different types. The thermoplastic resin may be used. Moreover, the thickness may be the same or different. Furthermore, they may have the same phase difference characteristics or different phase difference characteristics. When the structures of the thermoplastic resin films to be bonded on both sides are different, curling is particularly likely to occur in the polarizing plate with a protective film, and the present invention is particularly advantageous in such a case.

(1-1-4) Adhesive As mentioned above, the 1st, 2nd thermoplastic resin films 20 and 30 can be bonded to the polarizer 10 through an adhesive bond 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-system adhesive, after bonding the polarizer 10 and the 1st, 2nd thermoplastic resin films 20 and 30, the drying process for removing the water contained in a water-system adhesive is implemented. It is preferable. 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 is an adhesive containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays, preferably an ultraviolet curable adhesive. is there.

  The curable compound can be a cationic polymerizable curable compound or a radical polymerizable curable compound. Examples of the cationic polymerizable curable compound include an epoxy compound (a compound having one or more epoxy groups in the molecule) and an oxetane compound (one or two or more oxetane rings in the molecule). Or a combination thereof. Examples of the radical polymerizable curable compound include (meth) acrylic compounds (compounds having one or more (meth) acryloyloxy groups in the molecule) and radical polymerizable double bonds. Other vinyl compounds or combinations thereof can be mentioned. A cationic polymerizable curable compound and a radical polymerizable curable compound may be used in combination. The active energy ray-curable adhesive usually further includes a cationic polymerization initiator and / or a radical polymerization initiator for initiating a curing reaction of the curable compound.

  In laminating the polarizer 10 and the first and second thermoplastic resin films 20 and 30, at least one of these laminating surfaces may be subjected to a surface activation treatment in order to enhance adhesiveness. Good. 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, saponification treatment, and anchor coat treatment. These surface activation treatments may be performed alone or in combination of two or more.

  When a thermoplastic resin film is bonded to both surfaces of the polarizer 10, the adhesive for bonding these thermoplastic resin films may be the same type of adhesive or a different type of adhesive. May be.

(1-2) Protective film used for bonding step S101 (1-2-1) Structure of protect film The protect film is a film for protecting the surface of the polarizing plate, and usually, for example, an image display element or the like. After the polarizing plate with a protective film is bonded to the substrate, the adhesive layer is peeled and removed together with the adhesive layer. Therefore, the protect film 1 is detachably bonded to the surface of the polarizing plate 2.

The protective film can be composed of, for example, a base film and an adhesive layer laminated thereon.
The base film is a thermoplastic resin, for example, a polyolefin resin such as a polyethylene resin, a polypropylene resin, or a cyclic polyolefin resin; a polyester resin such as polyethylene terephthalate or polyethylene naphthalate; a polycarbonate resin; a (meth) acrylic resin It can be made of resin or the like. The base film may have a single layer structure or a multilayer structure.
The pressure-sensitive adhesive layer can be composed of (meth) acrylic pressure-sensitive adhesive, epoxy-based pressure-sensitive adhesive, urethane-based pressure-sensitive adhesive, silicone-based pressure-sensitive adhesive, and the like.
Further, the protective film may be a resin film having self-adhesive properties such as a polypropylene resin and a polyethylene resin. In this case, the protective film does not have an adhesive layer.

  The thickness of the protective film can be, for example, 5 to 150 μm, preferably 10 to 100 μm, more preferably 20 to 75 μm, and further preferably 25 to 70 μm (for example, 60 μm or less, further 55 μm or less). is there. When the thickness of the protective film is less than 5 μm, the polarizing plate may not be sufficiently protected, and it is disadvantageous in terms of handleability. When the thickness of the protective film exceeds 150 μm, it is disadvantageous in terms of reducing the thickness of the polarizing plate with the protective film and the reworkability of the protective film.

It is preferable that the protective film provided to bonding process S101 is elongate.
The length of the elongate protective film used for bonding process S101 is 100-20000m, for example, Preferably it is 1000-10000m. Moreover, the width | variety of the elongate protective film provided to bonding process S101 is 0.5-3m, for example, Preferably it is 1-2.5m.

(1-2-2) Elastic modulus of the protective film The protective film used in the bonding step S101 is represented by the following formula (I):
TD elastic modulus−MD elastic modulus ≧ 300 MPa (I)
The area that satisfies is included.
In formula (I), the TD elastic modulus is the tensile elastic modulus (MPa) in the TD direction at a temperature of 23 ° C. and a relative humidity of 55% RH, and the MD elastic modulus is a temperature of 23 ° C. and a relative humidity of 55% RH. It is the tensile elasticity modulus (MPa) in MD direction in.
The MD direction means the machine flow direction of the film, that is, the longitudinal direction of the film, and the TD direction means a direction orthogonal to the MD direction.

By sticking the protective film including the region to the polarizing plate, and cutting out the sheet from the region in the cutting step S102, that is, the cut sheet including a protective film satisfying the formula (I) A polarizing plate sheet with a protective film having a sufficiently large positive curl can be obtained.
The above-mentioned “cut out a sheet from the area” means that the entire protective film of the cut sheet is included in the area.

Here, the curl of the polarizing plate with the protective film can be classified into two types of “MD curl” and “TD curl” separately from the above-mentioned “normal curl” and “reverse curl”. . “MD curl” refers to curl caused by stress (contraction force, expansion force, etc.) in a direction parallel to the MD direction of a long polarizing plate with a protective film from which a polarizing plate with a protective film is cut out. It is.
Specifically, the MD curl cuts out a measurement sample (single sheet) from a polarizing plate with a long protective film according to the description in the example section described later, and places the measurement sample on the concave side up. Of the two diagonal lines of the measurement sample, the two corners on the diagonal line with the smaller angle from the MD direction of the long polarizing plate with protective film are lifted when placed on a horizontal table. The size of the curl can be measured. When the absorption axis direction of the polarizing plate and the MD direction of the protective film are parallel to each other in the long polarizing plate with a protective film, the MD curl is one of the two diagonal lines of the measuring sample. It can be measured as a curl (curl in the absorption axis direction) in which two corners on a diagonal line with a smaller angle with the absorption axis direction are lifted.
“TD curl” refers to curl caused by stress (contraction force, expansion force, etc.) in a direction parallel to the TD direction of a long polarizing plate with a protective film from which a polarizing plate with a protective film is cut out. It is.

  The present invention focuses on MD curl. The “positive curl” in the “polarizing sheet with protective film having a sufficiently large positive curl” that can be produced according to the present invention refers to a positive curl that is an MD curl. Hereinafter, this curl is also referred to as “MD regular curl”.

  “Formula (I)” in the above “including a region in which the protective film used in the bonding step S101 satisfies the formula (I)” and “the cut sheet includes a protective film satisfying the formula (I)” “Fill” means that the TD elastic modulus and the MD elastic modulus measured according to the description in the section of the examples described later are taken throughout the protective film, that is, at any position of the protective film. It means satisfying the formula (I).

According to the inventor's study, when the left side of the formula (I) is measured at a plurality of points along the TD direction of a generally available protective film, the numerical value on the left side varies relatively depending on the product lot and the like. It became clear that there was something that happened. On the other hand, when the left side of the formula (I) was measured at a plurality of points along the MD direction of a generally available protective film, it was also found that there was no relatively large variation in the value on the left side in the same roll.
Therefore, the protective film satisfying the formula (I) over the entire TD direction usually satisfies the formula (I) over the entire protective film (that is, no matter where the sample for measurement is taken from the protective film). It can be said.

  The above-mentioned region of the protective film preferably has as large an occupied area as possible from the viewpoint of increasing the yield of the polarizing plate with protective film, and the region of the protective film to be subjected to the bonding step S101. It is more preferable that it extends over at least the entire TD direction (width direction), and it is even more preferable that it extends over the entire protective film.

  From the viewpoint of increasing the MD positive curl of the obtained polarizing plate with a protective film, the left side of the formula (I) is preferably 400 MPa or more, and more preferably 500 MPa or more. The left side of the formula (I) is usually 2000 MPa or less, and typically 1500 MPa or less.

  What is necessary is just to use what contains the area | region which satisfy | fills Formula (I) as a protective film provided to bonding process S101, measuring the left side of Formula (I) about the obtained protective film.

(1-3) Bonding of Polarizing Plate and Protective Film Referring to FIG. 4, bonding of polarizing plate 2 and protective film 1 is performed using, for example, a pair of rolls (bonding rolls) 5 and 5. be able to. This method is particularly advantageous when the polarizing plate 2 and the protective film 1 are long in terms of production efficiency.

Specifically, the long polarizing plate 2 is continuously conveyed, the long protective film 1 is continuously conveyed, the protective film 1 is overlapped on one side of the polarizing plate 2 and a pair of bonding rolls. By passing between 5 and 5, it can manufacture the polarizing plate 3 with a protective film by which both films were bonded.
The MD direction (conveying direction) of the polarizing plate 2 and the MD direction (conveying direction) of the protect film 1 are usually parallel. Parallel means that the angle formed between the MD direction of the polarizing plate 2 and the MD direction of the protect film 1 is 0 degree ± 5 degrees, and preferably 0 degree ± 2 degrees.
From the viewpoint of increasing the MD positive curl of the obtained polarizing plate with a protective film, it is preferable to bond both films so that the absorption axis of the polarizing plate 2 and the MD direction of the protective film 1 are parallel. Parallel means that the angle formed by the absorption axis of the polarizing plate 2 and the MD direction of the protect film 1 is 0 ° ± 5 °, preferably 0 ° ± 2 °.
Since the laminated body is pressed from above and below by passing the laminated body of the polarizing plate 2 and the protective film 1 between the pair of bonding rolls 5 and 5, both films are brought into close contact with each other.
When the polarizing plate 2 has a clear hard coat layer (a hard coat layer having a smooth surface) on the outermost surface, and the protective film 1 is bonded to the clear hard coat layer, the polarizing plate 2 and the protective film It is easy to increase the adhesive force between the protective film 1 and the polarizing plate sheet with a protective film tends to be easily obtained. Therefore, the polarizing plate 2 preferably has a clear hard coat layer (a hard coat layer having a smooth surface) on the outermost surface.

  When the protective film 1 is composed of a base film and a pressure-sensitive adhesive layer laminated thereon, the protective film 1 is stacked on one side of the polarizing plate 2 and passed between the pair of bonding rolls 5 and 5. The pressure-sensitive adhesive layer of the protective film 1 is overlaid so as to be in contact with the one side of the polarizing plate 2. Prior to lamination of the protective film 1 and the polarizing plate 2, at least one of the bonding surfaces of the protective film 1 and the polarizing plate 2 is subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, frame (flame) treatment, and saponification treatment. Such surface activation treatment may be performed.

  In the step of bonding with the pair of bonding rolls 5 and 5, the pressure (nip pressure) applied to the laminate of the protective film 1 and the polarizing plate 2 is, for example, 0.01 to 0.5 MPa, 0.05 It may be -0.3 MPa. As the bonding rolls 5 and 5, conventionally known ones such as those having a metal surface (including an alloy such as SUS) or rubber can be used.

  In the step of bonding the polarizing plate 2 and the protective film 1, it is preferable to perform bonding while applying tension to the polarizing plate 2 and the protective film 1, and the tension before bonding of the polarizing plate 2 is that of the protective film 1. It is more preferable that it is smaller than the tension before bonding. Such tension control is advantageous in increasing the MD positive curl of the obtained polarizing plate with a protective film. The tension before pasting means the tension applied in the MD direction of the film before the both films are pasted (the laminate of both films passes through the pair of pasting rolls 5 and 5), and the terms of the examples described later. Can be measured according to the description.

From the viewpoint of increasing MD positive curl of the obtained polarizing plate with a protective film, the pre-bonding tension in the MD direction of the polarizing plate 2 is preferably 250 N / m or less, and 200 N / m or less. Is more preferable.
From the same viewpoint, the tension before bonding in the MD direction of the protective film 1 is preferably 260 N / m or more, and more preferably 300 N / m or more.

(2) Cutting process S102
This process is a process of cutting out from the said area | region which satisfy | fills Formula (I) in the polarizing plate 3 with a protective film obtained by bonding process S101, and obtaining a polarizing plate sheet with a protective film.
Cutting (cutting) can be performed using a conventionally known cutting means such as a cutting cutter.
As described above, “cutting out a sheet from an area” means that the entire protective film of the cut sheet is included in the area.

The size, shape, and cut-out angle of the cut-out polarizing plate with a protective film are not particularly limited.
The polarizing plate sheet with a protective film preferably has a rectangular shape, more preferably a rectangular shape having a long side and a short side. This square shape is preferably rectangular.
When the shape of the polarizing plate with a protective film is rectangular, the length of the long side is, for example, 50 mm to 300 mm, preferably 70 mm to 150 mm. The length of the short side is, for example, 30 mm to 200 mm, and preferably 40 mm to 100 mm.
In general, when the size of a polarizing plate with a protective film is increased, MD normal curls tend not to occur easily. Therefore, when the size of the polarizing plate with a protective film is large, it may be preferable to make the left side of the formula (I) larger in order to provide a sufficient MD positive curl amount.

Although not particularly limited, when the shape of the polarizing plate with a protective film is rectangular, when the polarizing plate with a protective film is viewed from the protective film side, the long side and the short side are not Thus, the polarizing plate with the protective film can be cut out from the polarizing plate 3 with the protective film so that the absorption axis direction of the polarizing plate (MD direction of the polarizing plate) forms an angle of 45 degrees.
Alternatively, when the shape of the polarizing plate with a protective film is rectangular, when the polarizing plate with a protective film is viewed from the protective film side, the absorption axis direction of the polarizing plate (polarizing plate with respect to the long side) The polarizing plate with a protective film may be cut out from the polarizing plate 3 with a protective film so that the (MD direction) is parallel or at an angle of 90 degrees.

<Polarized sheet with protective film>
The polarizing plate sheet with a protective film according to the present invention includes a polarizing plate and a protective film laminated on one surface thereof, and the protective film has the following formula (II):
First elastic modulus−second elastic modulus ≧ 300 MPa (II)
Meet.
In the formula (II), the first elastic modulus is a tensile elastic modulus (MPa) in a direction perpendicular to the absorption axis of the polarizing plate at a temperature of 23 ° C. and a relative humidity of 55% RH, and the second elastic modulus is It is the tensile elastic modulus (MPa) in a direction parallel to the absorption axis of the polarizing plate at a temperature of 23 ° C. and a relative humidity of 55% RH.

By providing the protective film satisfying the formula (II), the polarizing plate sheet with the protective film can have a sufficiently large MD positive curl.
According to the polarizing plate sheet with a protective film having a sufficiently large MD positive curl, even when the above multilayer structure is formed by laminating one or more other optical functional layers on the polarizing plate side. Because it can maintain a state without a reverse curl (flat state) or a state with a normal curl, a polarizing plate with a protective film or a multilayer structure is bonded to an image display element via an adhesive layer. In doing so, it is possible to suppress problems such as causing a bonding mistake or mixing bubbles in the interface between the pressure-sensitive adhesive layer and the image display element.

The polarizing plate sheet with a protective film according to the present invention can be manufactured by the above-described method for manufacturing a polarizing plate sheet with a protective film.
The direction perpendicular to the absorption axis of the polarizing plate is synonymous with the TD direction of the protective film and the polarizing plate when the polarizing plate with the protective film is produced by the above-described method for producing a polarizing plate with the protective film. It is.

“Satisfying the formula (II)” means that the first measurement is performed in accordance with the description in the section of the embodiment below, regardless of the position of the measurement film taken throughout the protection film. It means that the elastic modulus and the second elastic modulus satisfy the formula (II).
For the same reason as described in the section <Production method of polarizing plate with protective film>, the formula (II) is expressed over the entire direction perpendicular to the absorption axis of the polarizing plate in the polarizing plate with protective film. It can be said that the protective film to be filled usually satisfies the formula (II) throughout the entire protective film (that is, no matter where the sample for measurement is taken).

  From the viewpoint of increasing the MD positive curl of the polarizing plate with protective film, the left side of the formula (II) is preferably 400 MPa or more, and more preferably 500 MPa or more. The left side of the formula (II) is usually 2000 MPa or less, and typically 1500 MPa or less.

  The size and shape of the polarizing plate with protective film are not particularly limited, and the specific size and shape are described in the section <Method for producing polarizing plate with protective film>. When the size of the polarizing plate with a protective film is large, it may be preferable to make the left side of the formula (II) larger in order to give a sufficient MD positive curl amount.

  It is preferable that the polarizing plate sheet with a protective film (the same applies to the polarizing plate sheet with a protective film obtained by the method for producing a polarizing plate with a protective film according to the present invention) preferably exhibits MD positive curl. The MD positive curl amount measured in accordance with the description in the example section described later is 40 mm or more so that the multilayer structure can still show MD positive curl or a flat state without curl. It is more preferable. The MD positive curl amount may be 45 mm or more. The MD positive curl amount is preferably 100 mm or less.

Although not particularly limited, when the shape of the polarizing plate with a protective film is rectangular, when the polarizing plate with a protective film is viewed from the protective film side, the long side and the short side are not Then, the absorption axis direction of the polarizing plate may form an angle of 45 degrees.
Alternatively, when the shape of the polarizing plate with a protective film is rectangular, when the polarizing plate with a protective film is viewed from the protective film side, the absorption axis direction of the polarizing plate is parallel to the long side. There may be an angle of 90 degrees.

An example of the layer structure of the polarizing plate with protective film is shown in FIG. As shown in FIG. 5, when the protect film 1 is composed of the base film 40 and the pressure-sensitive adhesive layer 50 laminated thereon, the pressure-sensitive adhesive layer 50 included in the protect film 1 is the one side of the polarizing plate 2. It is piled up so that it may touch.
For more specific explanation of the polarizing plate 2 and the protective film 1, the description in the section <Method for producing polarizing plate with protective film> is cited.

<Long polarizing plate with protective film>
The polarizing plate with a long protective film according to the present invention includes a long polarizing plate and a long protective film laminated on one side, and the protective film has the following formula (III):
First elastic modulus−second elastic modulus ≧ 300 MPa (III)
The area that satisfies is included.
In the formula (III), the first elastic modulus is the tensile elastic modulus (MPa) in the direction orthogonal to the absorption axis of the long polarizing plate at a temperature of 23 ° C. and a relative humidity of 55% RH, and the second elasticity The modulus is a tensile elastic modulus (MPa) in a direction parallel to the absorption axis of the long polarizing plate at a temperature of 23 ° C. and a relative humidity of 55% RH.

According to the polarizing plate with a long protective film including the above region, the cut sheet is provided with a protective film satisfying the formula (III) by cutting the sheet from the region, so that the positive curl is sufficient. A large polarizing plate with a protective film can be obtained.
The above-mentioned “cut out a sheet from the area” means that the entire protective film of the cut sheet is included in the area.

The polarizing plate with a long protective film according to the present invention can be manufactured by performing the bonding step S101 of the manufacturing method of the polarizing plate with a protective film described above.
The direction perpendicular to the absorption axis of the polarizing plate is protected when the polarizing plate with a long protective film is manufactured by performing the bonding step S101 of the manufacturing method of the polarizing plate with protective film described above. It is synonymous with the TD direction of a film and a polarizing plate.

“Satisfying the formula (III)” means that the first measurement is performed in accordance with the description in the section of the embodiment described later, regardless of where the measurement sample is taken over the entire protection film, that is, at any position of the protection film. It means that the elastic modulus and the second elastic modulus satisfy the formula (III).
For the same reason as described in the section <Method for producing polarizing plate with protective film>, in formula (III) over the entire direction perpendicular to the absorption axis of the polarizing plate in the polarizing plate with a long protective film. It can be said that the protective film to be filled usually satisfies the formula (III) throughout the protective film (that is, no matter where the sample for measurement is taken).

  The above-mentioned region of the protective film preferably has as large an occupied area as possible from the viewpoint of increasing the yield of the polarizing plate with protective film, and the region of the protective film to be subjected to the bonding step S101. It is more preferable that it extends over at least the entire width direction, and it is even more preferable that it extends over the entire protective film.

  From the viewpoint of increasing the MD positive curl of the polarizing plate with the protective film obtained by cutting out from the long polarizing plate with the protective film, the left side of the formula (III) is preferably 400 MPa or more, and 500 MPa or more. More preferably. The left side of the formula (III) is usually 2000 MPa or less, and typically 1500 MPa or less.

  The size, shape and cutting angle of the polarizing plate with protective film are not particularly limited, and the specific size, shape and cutting angle are described in the section <Method for producing polarizing plate with protective film>. Is quoted. When the size of the polarizing plate with a protective film obtained by cutting out from the long polarizing plate with a protective film is large, the left side of the formula (III) is made larger in order to give a sufficient MD positive curl amount. It may be preferable to do so.

  The length of the polarizing plate with a long protective film is, for example, 100 to 20000 m, preferably 1000 to 10,000 m. Moreover, the width | variety of a polarizing plate with a elongate protective film is 0.5-3 m, for example, Preferably it is 1-2.5 m.

  For a more specific description of the layer structure of the polarizing plate with the long protective film, the polarizing plate constituting the polarizing plate with the long protective film, and the protective film, <Method for producing polarizing plate with protective film> And the description in the section <Polarized sheet with protective film>.

<Multilayer structure>
On the polarizing plate side of the polarizing plate with a protective film or the polarizing plate with a long protective film, another one or more optical function layers, separate films (peeling films), etc. are further provided via an adhesive layer or an adhesive layer. You may laminate.
The optical functional layer may be a retardation layer or the like, and the optical functional layer can be laminated on the surface on the polarizing plate side via an adhesive layer or an adhesive layer.

  Hereinafter, although an example of an experiment is shown and the present invention is explained still more concretely, the present invention is not limited by these examples.

  In the following experimental examples, the thickness of the polarizing plate and the film, the difference in elastic modulus of the protective film, the tension before bonding in the MD direction of the polarizing plate and the protective film, and the MD curl amount of the polarizing plate with the protective film are as follows. Measured according to

(1) Thickness of polarizing plate and film The thickness was measured using a digital micrometer “MH-15M” manufactured by Nikon Corporation.

(2) Elastic modulus difference of protective film A rectangular piece having a long side of 100 mm and a short side of 25 mm was cut out from the polarizing plate with a long protective film using a super cutter. Cutting was performed so that the long side of the small piece was parallel to the MD direction of the polarizing plate with the long protective film, and the short side of the small piece was parallel to the TD direction of the polarizing plate with the long protective film. The polarizing plate was peeled off from this small piece, and the obtained small piece of the protective film was used as a sample for measuring MD elastic modulus.
Similarly, a rectangular piece having a long side of 100 mm and a short side of 25 mm was cut out from the long polarizing plate with a protective film using a super cutter. However, the cutting was performed so that the long side of the small piece was parallel to the TD direction of the polarizing plate with the long protective film, and the short side of the small piece was parallel to the MD direction of the polarizing plate with the long protective film. . The polarizing plate was peeled from this small piece, and the obtained small piece of the protective film alone was used as a sample for measuring the TD elastic modulus.

Next, the upper and lower grips of a tensile tester [manufactured by Shimadzu Corp. Autograph AG-Xplus tester] are sandwiched at both ends in the long side direction of the measurement sample so that the distance between the grips is 5 cm. From the slope of the straight line between 3 and 6 MPa in the obtained stress-strain curve, the measurement sample was pulled in the length direction of the measurement sample at a tensile speed of 1 mm / min in an environment with a relative humidity of 55%. The tensile elastic modulus [MPa] at a humidity of 55% was calculated. At this time, as the thickness for calculating the stress, only the thickness value of the biaxially stretched polyethylene terephthalate (base film) was used.
The tensile elastic modulus calculated from the measurement of the sample for measuring the MD elastic modulus is the MD elastic modulus, and the tensile elastic modulus calculated from the measurement of the sample for measuring the TD elastic modulus is the TD elastic modulus.

In each of the following experimental examples, a polarizing plate with a protective film is manufactured by pasting both films so that the absorption axis (MD direction) of the polarizing plate is parallel to the MD direction of the protective film. The TD elastic modulus in the formula (I) is synonymous with the first elastic modulus in the above formulas (II) and (III), and the MD elastic modulus in the above formula (I) is the above formula (II) and the formula (III ) Is synonymous with the second elastic modulus in FIG.
Hereinafter, the TD elastic modulus (first elastic modulus) is simply referred to as “TD elastic modulus”, and the MD elastic modulus (second elastic modulus) is simply referred to as “MD elastic modulus”.

From the obtained TD elastic modulus and MD elastic modulus, TD elastic modulus-MD elastic modulus (first elastic modulus-second elastic modulus) was calculated.
Hereinafter, TD elastic modulus−MD elastic modulus (first elastic modulus−second elastic modulus) is simply referred to as “elastic modulus difference”.

(3) Pre-bonding tension in the MD direction of the polarizing plate and the protective film A pair of bonding rolls for bonding the polarizing plate and the protective film, and a pair of nip rolls that are upstream and closest to the bonding roll Measuring the film tension [N / m] of the polarizing plate and the protective film traveling between the bonding roll and a pair of nip rolls closest to the bonding roll, It was set as the tension before pasting in the MD direction.

(4) MD Curling Amount of Polarizing Sheet with Protective Film As shown in FIG. 6, the absorption axis 61 of the polarizing plate when viewed from the protective film side from the obtained polarizing plate 60 with a protective film. Cut out a small piece (single piece) of a rectangle (long side 140 mm × short side 70 mm) with a super cutter so that the angle is 45 degrees with respect to the long side and the short side, and measure this MD curl amount Sample 70 was obtained. The sample 70 for measurement was cut out in an environment of 23 ° C. and 55% relative humidity immediately after the polarizing plate and the protective film were bonded.
The measurement sample 70 was placed on a reference surface (horizontal platform) with the concave side facing up. In this state, of the two diagonal lines of the measurement sample 70, the height from the reference plane is measured for each of the two corners 80 on the diagonal line having the smaller angle with the absorption axis direction of the polarizing plate of the measurement sample 70. Then, the MD curl amount [mm] was obtained as an average of the heights of the two corners 80.
A state where the protective film side is concave is a state having a normal curl, and a state where the polarizing plate side is concave is a state having a reverse curl. In the following Experimental Examples 1 to 3, any measurement sample (a polarizing plate with a protective film) had a positive curl.

<Experimental Examples 1-3>
(A) Production of polarizer About 4 times by dry method while continuously transporting a long polyvinyl alcohol film [average polymerization degree: about 2400, saponification degree: 99.9 mol% or more, thickness: 30 μm] The film was uniaxially stretched and immersed in pure water at 40 ° C. for 1 minute while maintaining the tension state, and then in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.1 / 5/100 at 28 ° C. for 60 seconds. Soaked. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 10.5 / 7.5 / 100 at 68 ° C. for 300 seconds. Subsequently, it was washed with pure water at 5 ° C. for 5 seconds and then dried at 70 ° C. for 180 seconds to obtain a long polarizer in which iodine was adsorbed and oriented on a uniaxially stretched polyvinyl alcohol film. The thickness of the polarizer was 13 μm.

(B) Production of Polarizing Plate While continuously transporting the long polarizer obtained in (A) above, the long first thermoplastic resin film [Clear Hard Coat manufactured by Nippon Paper Industries Co., Ltd.] Trade name “COP25ST-HC”, a film in which a clear hard coat layer is formed on a cyclic polyolefin resin film, thickness: 29 μm, and a long second thermoplastic resin film [Fuji Film Co., Ltd.] Product name “ZRG20SL”, thickness: 20 μm], which is a triacetylcellulose (TAC) film made by the production method, between the polarizer and the first thermoplastic resin film, and between the polarizer and the second thermoplastic resin. The first thermoplastic resin film / water-based adhesive layer / polarizer / water-based adhesive layer / second heat can be passed through a pair of laminating rolls while injecting the water-based adhesive between the films. To obtain a laminated film composed of a sexual resin film.
Subsequently, the obtained laminated film was transported, passed through a hot air dryer, and subjected to a heat treatment at 80 ° C. for 300 seconds to dry the aqueous adhesive layer to obtain a long polarizing plate.
In the above water-based adhesive, a concentration of 3 obtained by dissolving polyvinyl alcohol powder (trade name “GOHSPEIMER” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree: 1100) in hot water at 95 ° C. An aqueous solution in which a crosslinking agent (sodium glyoxylate manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was mixed with a 10% by weight polyvinyl alcohol powder in a proportion of 1 part by weight with respect to 10 parts by weight of polyvinyl alcohol powder was used. The obtained polarizing plate had a thickness of 62 μm.

(C) Production of polarizing plate with long protective film A long protective film [biaxially separated from the separate polarizing film while continuously conveying the long polarizing plate obtained in (B) above. A product name “AY-4212” manufactured by Fujimori Kogyo Co., Ltd., in which a (meth) acrylic pressure-sensitive adhesive layer (thickness: 15 μm) is laminated on stretched polyethylene terephthalate (thickness: 38 μm), is continuously conveyed. And the laminated body of a protective film and a polarizing plate was pressed from the upper and lower sides by putting these together and passing between a pair of bonding rolls, and the polarizing plate with a elongate protective film was manufactured continuously.
The protective film was bonded to the surface of the first thermoplastic resin film (clear hard coat film) of the polarizing plate through the adhesive layer.
In addition, the pressure (nip pressure) given to the laminated body of the protective film and the polarizing plate by the bonding roll was 0.1 MPa. At this time, the tension before bonding in the MD direction of the polarizing plate was 151 N / m, and the tension before bonding in the MD direction of the protective film was 327 N / m.

  The manufacturing method of the polarizing plate with a long protective film of Experimental Examples 1 to 3 is the same except that the protective film used is different (the product is the same, but the lot is different). Hereinafter, the protect films used in Experimental Examples 1 to 3 are also referred to as protect films 1 to 3, respectively.

From the obtained polarizing plate with a long protective film, the TD elastic modulus, MD elastic modulus, and elastic modulus difference were determined according to the above-described method.
Each of the protective films 1 to 3 has a width of 1300 mm (length in the TD direction). In measuring the elastic modulus of each protective film, a total of 7 positions of 100 mm, 280 mm, 470 mm, 650 mm, 830 mm, 1020 mm, and 1200 mm from one end in the width direction along one width in one arbitrary MD position. The measurement sample was cut out, and the TD elastic modulus, MD elastic modulus, and elastic modulus difference were determined for each of these seven measurement samples. These results are shown in the column “1” in Table 1. Seven measurement samples were cut out in the same manner as described above at a position 20 mm away from one arbitrary MD direction position along the MD direction, and TD elastic modulus and MD elasticity were measured for each of these seven measurement samples. The difference in modulus and elastic modulus was determined. These results are shown in the column “2” in Table 1. Seven measurement samples are cut out in the same manner as described above at a position 50 mm away from one arbitrary MD direction position along the MD direction, and the TD elastic modulus and MD elasticity of each of these seven measurement samples are cut out. The difference in modulus and elastic modulus was determined. These results are shown in the column “3” in Table 1.
Moreover, the graph which shows the relationship between the width direction position of the protective films 1-3 and an elastic modulus difference (elastic modulus described in the column of "1" of Table 1) is shown in FIG.
Regarding the position for cutting out the measurement sample, for example, “cutting out the measurement sample at a position 100 mm from one end in the width direction” means that the position 100 mm from one end in the width direction matches the center position in the width direction of the measurement sample. This means that a sample for measurement is cut out. The same applies to the positions from one end in the other width direction.

As shown in Table 1 and FIG. 7, the long protective films 1 and 2 cover the entire TD direction (the direction perpendicular to the absorption axis of the long polarizing plate) and the entire MD direction ( It can be seen that it includes a region satisfying the formulas (I) and (III) over the absorption axis direction of the long polarizing plate, and this region extends over the entire width direction of the protective film.
On the other hand, the long protective film 3 covers the entire TD direction (the direction orthogonal to the absorption axis of the long polarizing plate) and the entire MD direction (the absorption axis direction of the long polarizing plate). Includes a region satisfying the formulas (I) and (III), but this region does not cover the entire width direction of the protective film. That is, the long protective film 3 satisfies the formulas (I) and (III) only in the region from one end in the width direction to about 700 mm from the one end.
As described above, a protective film that satisfies the formulas (I) and (III) at one arbitrary position in the MD direction normally satisfies the formulas (I) and (III) also at other MD direction positions.

(D) Production of polarizing plate with protective film As shown in FIG. 6, the polarizing plate absorbs when viewed from the protective film side from the polarizing plate with the long protective film obtained in (C) above. Cut out a small piece (sheet body) of a rectangle (long side 140 mm × short side 70 mm) with a super cutter so that the axis is 45 degrees with respect to the long side and the short side, and a polarizing plate with a protective film Got the body.

About the obtained polarizing plate sheet with a protective film, the MD curl amount was measured according to the method described above.
Each of the polarizing plates with a long protective film of Experimental Examples 1 to 3 has a width of 1330 mm (length in the TD direction). In measuring the MD curl amount of a polarizing plate with a protective film obtained from each long polarizing plate with a protective film, from one end in the width direction along the width direction at one arbitrary MD position. A polarizing plate with a protective film was cut out at a total of seven positions of 100 mm, 280 mm, 470 mm, 650 mm, 830 mm, 1020 mm and 1200 mm, and the MD curl amount was measured for each of these seven sheets. Seven sheets were cut from the vicinity of the cutting position of the measurement sample for measuring the elastic modulus difference of the protective film described in the column “1” of Table 1. The results are shown in Table 2. Moreover, the relationship between the width direction position which cuts out the polarizing plate sheet with a protective film from the long polarizing plate with a protective film of Experimental Examples 1-3, and the MD curl amount of the cut polarizing plate with a protective film cut out The graph which shows is shown in FIG.
Regarding the position for cutting out the polarizing plate sheet with a protective film, for example, “cutting out a polarizing plate sheet with a protective film at a position 100 mm from one end in the width direction” means that the position with a protective film is 100 mm from the one end in the width direction. This means that the polarizing plate sheet with a protective film is cut out so that the center position in the width direction of the polarizing plate sheet matches. The same applies to the positions from one end in the other width direction.
All of the polarizing plates with a protective film cut out from the long polarizing plates with a protective film in Experimental Examples 1 to 3 had a positive curl. Therefore, the measured MD curl amount is the amount of MD positive curl.

7 sheets of polarizing plates with a protective film cut out from the polarizing plate with a long protective film of Experimental Example 1 using the protective film 1 and the long protective film of Experimental Example 2 using the protective film 2 In the seven sheets of the polarizing plate with a protective film cut out from the polarizing plate with the protective film, the protective film laminated on the polarizing plate satisfies the formula (II).
Of the seven polarizing plates with protective film cut out from the polarizing plate with long protective film of Experimental Example 3 using the protective film 3, from one end in the width direction of the polarizing plate with long protective film Sheets cut at positions of 100 mm, 280 mm, 470 mm and 650 mm satisfy the formula (II) with respect to the protective film laminated on the polarizing plate, but the sheets cut at positions of 830 mm, 1020 mm and 1200 mm The body does not meet this.

  As shown in Table 2 and FIG. 8, the polarizing plate with a protective film satisfying the formula (II) exhibited an MD positive curl amount of 40 mm or more. On the other hand, in the polarizing plate sheet with a protective film that does not satisfy the formula (II), the MD curl amount was less than 40 mm.

  DESCRIPTION OF SYMBOLS 1 Protective film, 2, 2a, 2b Polarizing plate, 3 Polarizing plate with protective film, 5 Bonding roll, 10 Polarizer, 20 1st thermoplastic resin film, 30 2nd thermoplastic resin film, 40 Base film, 50 Adhesive layer, 60 polarizing plate with long protective film, 61 absorption axis of polarizing plate, sample for measuring 70 MD curl amount, corner of 80 measuring sample.

Claims (11)

Bonding a protective film including a region satisfying the following formula (I) to one surface of a polarizing plate to obtain a polarizing plate with a protective film;
Cutting out the sheet of polarizing plate with protective film from the region;
Of manufacturing a polarizing plate sheet with a protective film.
908 MPa ≧ TD elastic modulus−MD elastic modulus ≧ 338 MPa (I)
[In the formula, the TD elastic modulus is the tensile elastic modulus in the TD direction at a temperature of 23 ° C. and a relative humidity of 55% RH, and the MD elastic modulus is in the MD direction at a temperature of 23 ° C. and a relative humidity of 55% RH. Tensile modulus. ]   The manufacturing method according to claim 1, wherein the polarizing plate and the protective film are sandwiched and bonded between a pair of rolls.   The manufacturing method according to claim 2, wherein the polarizing plate has a long shape, and the protective film has a long shape. The pre-bonding tension of the polarizing plate is 200 N / m or less,
The manufacturing method of Claim 3 whose tension before pasting of the said protective film is 300 N / m or more.   The manufacturing method of any one of Claims 1-4 bonded so that the absorption axis of the said polarizing plate and MD direction of the said protective film may become parallel.   The manufacturing method according to claim 1, wherein the polarizing plate has a thickness of 70 μm or less. Including a polarizing plate and a protective film laminated on one side thereof,
A polarizing plate sheet with a protective film, wherein the protective film satisfies the following formula (II).
908 MPa ≧ first elastic modulus−second elastic modulus ≧ 338 MPa (II)
[In the formula, the first elastic modulus is the tensile elastic modulus in the direction orthogonal to the absorption axis of the polarizing plate at a temperature of 23 ° C. and a relative humidity of 55% RH, and the second elastic modulus is a temperature of 23 ° C., It is a tensile elastic modulus in a direction parallel to the absorption axis of the polarizing plate at a relative humidity of 55% RH. ] The curl amount in a direction parallel to the absorption axis of the polarizing plate having a convex surface on the polarizing plate side is 40 mm or more,
The curl amount is determined by placing a rectangular measurement sample with an absorption axis of the polarizing plate having an angle of 45 degrees with respect to the long side and the short side on the reference plane, and the angle between the measurement sample and the absorption axis direction of the polarizing plate. The polarizing plate sheet with a protective film according to claim 7, which is obtained as an average of the heights of the two corners when the height from the reference plane is measured for each of the two corners on the diagonal line having a smaller diameter. body.   The polarizing plate sheet with a protective film according to claim 7 or 8, wherein the polarizing plate has a thickness of 70 µm or less. Including a long polarizing plate and a long protective film laminated on one side thereof,
A polarizing plate with a long protective film, wherein the protective film includes a region satisfying the following formula (III).
908 MPa ≧ first elastic modulus−second elastic modulus ≧ 338 MPa (III)
[In the formula, the first elastic modulus is the tensile elastic modulus in the direction perpendicular to the absorption axis of the long polarizing plate at a temperature of 23 ° C. and a relative humidity of 55% RH, and the second elastic modulus is It is a tensile elastic modulus in a direction parallel to the absorption axis of the long polarizing plate at a temperature of 23 ° C. and a relative humidity of 55% RH. ]   The polarizing plate with a long protective film according to claim 10, wherein the region extends over the entire width direction of the protective film.