TWI793212B - Method for producing polarizing plate sheet with protective film - Google Patents

Abstract

Provided is a method for producing a polarizing plate sheet with protective film, containing a step of obtaining a polarizing plate with protective film by laminating a protective film containing a region satisfying the formula: TD elastic modulus-MD elastic modulus≧300 MPa on one side of a polarizing plate, and a step of cutting out a sheet of the polarizing plate with protective film from the aforesaid region. In the formula, the TD elastic modulus is the tensile elastic modulus in the TD direction at a temperature of 23℃ and a relative humidity of 55% RH, and MD elastic modulus is the tensile modulus in the MD direction at a temperature of 23℃ and a relative humidity of 55% RH.

Description

Manufacturing method of polarizing plate sheet with protective film

The present invention relates to a method for manufacturing a polarizer plate with a protective film. Furthermore, the present invention also relates to a polarizing plate sheet with a protective film, and a long polarizing plate with a protective film.

In recent years, image display devices such as liquid crystal display devices and organic EL display devices, such as portable terminals such as smart phones, are rapidly developing towards larger screens and simplification in terms of design and portability. In order to achieve long-term driving with a limited thickness, high brightness and thinner and lighter weight are also required for the polarizer used.

In the past, polarizers were generally used in which a polarizer made of polyvinyl alcohol-based resin was bonded with a protective film made of cellulose triacetate (TAC) through an adhesive. However, in recent years, from the viewpoints of thinning, durability, cost, productivity, etc., protective films made of resins other than TAC have also begun to be used [for example, Japanese Patent Laying-Open No. 2004-245925 (Patent Document 1 )].

Along with the demand for thinner polarizers, the thinner polarizers and protective films are progressing. The sheet-shaped body of the polarizing plate obtained by cutting out a thin and inelastic polarizing plate (especially a strip-shaped polarizing plate) is prone to arcuate reverse bending deformation. In this specification, this deformation is also called "curl (curl)".

Generally speaking, the polarizing plate circulating in the market is a polarizing plate with a protective film, and a peelable protective film (also called a surface protective film) is attached to the surface for protection. Regarding the polarizing plate with a protective film, if it is made into a sheet-like body when it becomes thinner, it tends to be easily curled.

There are two kinds of curls of polarizing plate sheet with protective film: "normal curl" and "reverse curl". In polarizing plate sheets with protective films including "laminates of polarizing plates and protective films", "normal curl" refers to curling that makes the surface on the polarizing plate side convex, and "reverse curl" refers to making the protective film The side surface exhibits a convex curl.

If the reverse curl occurs, when the polarizing plate side of the polarizing plate sheet with a protective film is bonded to image display elements such as liquid crystal cells and organic EL elements through an adhesive layer, it is easy to cause bonding errors, Or the bad situation that air bubbles are mixed in the interface between the adhesive layer and the image display element.

The polarizing plate with a protective film becomes a further multilayer structure by laminating one or more other optical functional layers on the polarizing plate side through an adhesive layer or an adhesive layer. At this time, when a layer is further added to the polarizing plate with a protective film, the above-mentioned multilayer structure is deformed in the reverse curl direction.

Therefore, it is preferable that the protective film-attached polarizing plate sheet has a sufficiently large positive curl in consideration of producing the above-mentioned multilayer structure. This is because when the said multilayer structure has a reverse curl, it is easy to cause the said trouble when it is bonded to an image display element.

On the other hand, when the protective film-attached polarizing plate is directly bonded to the image display device without making the above-mentioned multilayer structure, its large positive curl does not hinder its bonding to the image display device.

The object of the present invention is to provide a method capable of producing a "polarizer plate with a protective film" having a relatively large positive curl.

Another object of the present invention is to provide a "polarizer sheet with a protective film" that can have a large positive curl.

Still another object of the present invention is to provide a long polarizing plate with a protective film, which can provide a "polarizing plate with a protective film sheet" with a large positive curl.

The present invention provides a method of manufacturing a polarizing plate sheet with a protective film, a polarizing plate sheet with a protective film, and a long polarizing plate with a protective film as shown below.

[1] A method of manufacturing a polarizing plate sheet with a protective film, comprising the following steps: attaching a protective film comprising a region satisfying the following formula (I) to one side of a polarizing plate to obtain a polarizing plate with a The step of polarizing plate with protective film; and the step of cutting out the sheet-shaped body of polarizing plate with protective film from the aforementioned area; TD elastic modulus-MD elastic modulus≧300MPa (I)

In the formula, TD elastic modulus refers to the tensile elastic modulus in the TD direction at a temperature of 23°C and a relative humidity of 55%RH, and MD elastic modulus refers to the tensile elastic modulus at a temperature of 23°C and a relative humidity of 55%RH. Tensile modulus of elasticity in the MD direction.

[2] The manufacturing method according to [1], wherein the polarizing plate and the protective film are sandwiched between a pair of rollers and bonded together.

[3] The production method according to [2], wherein the polarizing plate is elongated, and the protective film is elongated.

[4] The production method according to [3], wherein the tension before lamination of the polarizing plate is 200 N/m or less, and the tension before lamination of the protective film is 300 N/m or more.

[5] The manufacturing method according to any one of [1] to [4], wherein the absorption axis of the polarizing plate is bonded to the MD direction of the protective film in parallel.

[6] The production 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 sheet with a protective film, comprising: a polarizing plate and a protective film laminated on one side thereof; wherein the aforementioned protective film satisfies the following formula (II), the first elastic modulus -The second elastic modulus≧300MPa (II)

In the formula, the first elastic modulus refers to the tensile elastic modulus in the 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 refers to the Tensile elastic modulus in the direction parallel to the absorption axis of the aforementioned polarizing plate at a temperature of 23°C and a relative humidity of 55%RH.

[8] The polarizing plate sheet with a protective film according to [7], wherein the amount of curling in a direction parallel to the absorption axis of the polarizing plate to make the surface on the side of the polarizing plate convex is: More than 40mm.

[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 strip-shaped polarizing plate with a protective film, comprising: a strip-shaped polarizing plate and a strip-shaped protective film laminated on one side of the polarizing plate; wherein, the aforementioned protective film includes the following formula: In the area of (III), the first modulus of elasticity - the second modulus of elasticity≧300MPa (III) In the formula, the first modulus of elasticity refers to the elastic modulus at the temperature of 23°C and the relative humidity of 55%RH. The tensile elastic modulus in the direction perpendicular to the absorption axis of the polarizing plate. The second elastic modulus refers to the tensile modulus of the absorption axis of the aforementioned strip-shaped polarizing plate at a temperature of 23°C and a relative humidity of 55%RH. Tensile modulus of elasticity in the parallel direction.

[11] The elongated polarizing plate with a protective film according to [10], wherein the region spans the entire width direction of the protective film.

According to the present invention, it is possible to provide a method capable of producing a "polarizer sheet with a protective film" having a large positive curl.

According to the present invention, it is possible to provide a "polarizer sheet with a protective film" that can have a large positive curl.

According to the present invention, a long polarizing plate with a protective film can be provided, which can provide a “polarizing plate with a protective film sheet” having a large positive curl.

1‧‧‧Protective film

2, 2a, 2b‧‧‧polarizer

3‧‧‧Polarizing plate with protective film

5‧‧‧Laminating roller

10‧‧‧Polarizer

20‧‧‧The first thermoplastic resin film

30‧‧‧The second thermoplastic resin film

40‧‧‧Substrate film

50‧‧‧adhesive layer

60‧‧‧Strip-shaped polarizing plate with protective film

61‧‧‧Absorption axis of polarizer

70‧‧‧MD crimp amount measurement sample

80‧‧‧The corner of the sample for measurement

Fig. 1 is a flow chart showing a method of manufacturing a polarizer plate with a protective film.

Fig. 2 is a schematic cross-sectional view showing an example of the layer configuration of a polarizing plate.

Fig. 3 is a schematic cross-sectional view showing another example of the layer configuration of a polarizing plate.

Fig. 4 is a side view showing an example of a bonding step S101 of bonding a polarizing plate and a protective film.

Fig. 5 is a schematic cross-sectional view showing an example of the configuration of a polarizer sheet with a protective film.

Fig. 6 is a schematic diagram illustrating a method of preparing a sample for measuring the amount of MD curl and a measurement point of the amount of MD curl.

Fig. 7 is a graph showing the relationship between "positions in the width direction of protective films 1 to 3 used respectively" and "difference in modulus of elasticity" in Experimental Examples 1 to 3.

Fig. 8 shows "the position in the width direction of the polarizing plate with protective film cut out from the strip-shaped polarizing plate with protective film" and "the cut out polarizing plate with protective film" in Experimental Examples 1 to 3. The graph of the relationship between the MD curl amount of the polarizing plate sheet of the film".

<Manufacturing method of polarizer sheet with protective film>

With reference to Fig. 1, the manufacturing method of the polarizing plate sheet with protective film of the present invention includes the following steps: a bonding step S101, which is to bond the protective film to one side of the polarizing plate to obtain a protective film. The polarizing plate of the film; and the cutting step S102 is cutting out the sheet-shaped body of the polarizing plate with the protective film.

Each step will be described in detail below.

In this specification, a "sheet" means a film of a small size cut out from a film of a large size (for example, a strip-shaped (belt-shaped) film).

(1) Bonding step S101

(1-1) Polarizing plate for lamination step S101

(1-1-1) Composition of polarizing plate

A polarizing plate is a polarizing element that includes at least a polarizer, and usually includes a thermoplastic resin film attached to one or both sides of the polarizer.

The thermoplastic resin film may be a protective film for protecting a polarizer, other optical films having different optical functions from the polarizer, or the like. Examples of other optical films include retardation films, brightness enhancement films, and the like.

The thermoplastic resin film may have a resin layer (for example, an optical layer) laminated on its surface. Examples of the resin layer include a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, an antifouling layer, and the like.

The thermoplastic resin film can be bonded to the polarizer via an adhesive layer or an adhesive layer.

The thickness of the polarizing plate is usually 150 μm or less, preferably 100 μm or less from the viewpoint of thinning the polarizing plate and making it easy to manufacture a polarizing plate plate with a protective film with a sufficiently large positive curl. 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 FIG. 2 and FIG. 3 , but the layer configuration is not limited to these examples.

The polarizer 2a shown in FIG. 2 includes: a polarizer 10; a first thermoplastic resin film 20 bonded to one side of the polarizer 10; a second thermoplastic resin film 30 bonded to the other side of the polarizer 10. 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 on only one side of the polarizing plate 10 is beneficial to thinning the polarizing plate.

Although illustration is omitted in FIGS. 2 and 3 , it is preferable to bond the polarizer 10 and the first and second thermoplastic resin films 20 and 30 using an adhesive.

The polarizing plate used in the bonding step S101 is preferably in the shape of a strip.

The length of the elongated polarizing plate used in the bonding step S101 is, for example, 100 to 20000 m, preferably 1000 to 10000 m. Moreover, the width of the elongated polarizing plate used in the bonding step S101 is, for example, 0.5 to 3 m, preferably 1 to 2.5 m.

(1-1-2) Polarizer

The polarizer 10 constituting the polarizer is an absorbing polarizer that absorbs linearly polarized light with a vibrating plane parallel to its absorption axis, and transmits and holds it perpendicular to the absorption axis (parallel to the transmission axis) The properties of linearly polarized light on the vibrating surface. An example of the polarizer 10 is a polarizer in which a dichroic dye is adsorbed and aligned on a polyvinyl alcohol-based resin film stretched along one axis. Such a polarizer 10 can be manufactured, for example, by a method including: a step of uniaxially stretching a polyvinyl alcohol-based resin film; a step of dichroic pigment; a step of treating the polyvinyl alcohol resin film adsorbed with dichroic pigment with a cross-linking solution such as boric acid aqueous solution; and a step of washing with water after being treated with the cross-linking solution.

As the polyvinyl alcohol-based resin, what saponified polyvinyl acetate-based resin can be used. As for the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other copolymerizable monomers can also be mentioned. wait. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides with ammonium groups.

In this specification, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid. The same applies to "(meth)acryl", "(meth)acrylate", and the like.

The saponification degree of polyvinyl alcohol-based resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin can be modified, for example, poly(vinyl formal) or poly(vinyl acetal) modified with aldehydes can be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually 1,000 to 10,000, preferably 1,500 to 5,000.

The degree of saponification and the average degree of polymerization of polyvinyl alcohol-based resins can be obtained in accordance with JIS K 6726.

A film obtained from such a polyvinyl alcohol-based resin is used as a raw material film of the polarizer 10 . The method of forming a polyvinyl alcohol-based resin into a film is not particularly limited, and a known method can be used. The thickness of the polyvinyl alcohol-based resin film is not particularly limited, for example, it is about 10 to 150 μm, preferably 50 μm or less, more preferably 35 μm or less.

Axial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing of the dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before or during crosslinking treatment. Also, one-axis stretching may be performed in these plural stages.

In the case of one-axis stretching, one-axis stretching can be performed between rollers with different peripheral speeds, or one-axis stretching can be performed using a hot roller. In addition, the uniaxial stretching may be dry stretching in which stretching is carried out in the atmosphere, or wet stretching in which the polyvinyl alcohol-based resin film is stretched in a swollen state using a solvent or water. The elongation ratio is usually 3 to 8 times.

A method of dyeing a polyvinyl alcohol-based resin film with a dichroic dye is, for example, a method of immersing the film in an aqueous solution containing a dichroic dye. Dichroic pigments can use iodine or Dichroic organic dyes. Moreover, it is preferable to implement the immersion process of water before a dyeing process about a polyvinyl-alcohol-type resin film.

The cross-linking treatment after dyeing with a dichroic dye generally employs a method of immersing the dyed polyvinyl alcohol-based resin film in an aqueous solution containing boric acid. When using iodine as a dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide.

The thickness of the polarizer 10 is generally about 2 to 40 μm. From the viewpoint of thinning the polarizing plate, the thickness of the polarizing plate 10 is preferably 20 μm or less, more preferably 15 μm or less, still more preferably 10 μm or less.

On the other hand, from the viewpoint of ease of manufacturing a polarizing plate with a protective film with a sufficiently large positive curl, the thickness of the polarizing plate 10 is preferably large, specifically, it is preferably 10 μm or more, and more preferably It is 15 μm or more, more preferably 20 μm or more.

(1-1-3) First and second thermoplastic resin films

The first and second thermoplastic resin films 20 and 30 are independently films made of light-transmitting thermoplastic resin (preferably optically transparent thermoplastic resin). The thermoplastic resins constituting the first and second thermoplastic resin films 20 and 30 may be polymers such as chain polyolefin resins (polypropylene resins, etc.), cyclic polyolefin resins (norbornene resins, etc.), etc. Olefin-based resins; cellulose-based resins such as cellulose triacetate and cellulose diacetate; polyester-based resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonate-based resins; (Meth)acrylic resins such as acrylic methyl resins; polystyrene resins; polyvinyl chloride resins; acrylonitrile/butadiene/styrene resins; acrylonitrile/styrene resins; polyvinyl acetate Resin; Polyvinylidene Chloride Resin; Polyamide Resin; Polyacetal Resin; Modified Polyphenylene Ether Resin; resin; polyether resin; polyaryl resin; polyamideimide resin; polyimide resin, etc.

The chain polyolefin resin includes not only homopolymers of chain olefins such as polyethylene resins and polypropylene resins, but also copolymers composed of two or more kinds of chain olefins. More specific examples include: polypropylene resins (polypropylene resins that are homopolymers of propylene, copolymers mainly composed of propylene), polyethylene resins (polyethylene resins that are homopolymers of ethylene, ethylene resins as the main copolymer).

Cyclic polyolefin resin is a general term for resins formed by polymerizing cyclic olefins as polymer units. Specific examples of cyclic polyolefin resins include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, and combinations of cyclic olefins and chain olefins such as ethylene or propylene. Copolymers (representatives are random copolymers), graft polymers modified with unsaturated carboxylic acids or their derivatives, and their hydrogenated products. Among them, a norbornene-based resin using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer as a cyclic olefin is suitable.

Cellulose-based resin refers to one or all of the hydrogen atoms in the hydroxyl groups of cellulose obtained from raw material cellulose such as cotton linter or wood pulp (wide-leaf pulp, softwood pulp) etc. Cellulose organic acid esters or cellulose mixed organic acid esters substituted with acyl, propionyl and/or butyryl groups. For example, those which consist of acetate, propionate, butyrate of cellulose, and these mixed esters etc. are mentioned. Among them, cellulose triacetate, cellulose diacetate, cellulose acetate propionate, and cellulose acetate butyrate are preferred.

Polyester-based resins are resins other than the above-mentioned cellulose-based resins having ester bonds, and generally include polycondensates of polycarboxylic acids or their derivatives and polyhydric alcohols. Polycarboxylic acid or its derivative Bivalent dicarboxylic acids or derivatives thereof that can be used by living organisms include, for example, terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalate. Dihydric diols can be used as the polyhydric alcohol, and examples thereof include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, and cyclohexanedimethanol. Examples of suitable polyester-based resins include polyethylene terephthalate.

Polycarbonate-based resins refer to engineering plastics containing "polymers formed by combining monomer units through carbonate groups", and are resins with high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate-based resin may be a resin called modified polycarbonate obtained by modifying the polymer backbone in such a way as to reduce the photoelastic coefficient, or a copolymerized polycarbonate with improved wavelength dependence.

A (meth)acrylic resin is a polymer containing a structural unit derived from a (meth)acrylic resin monomer. The polymer is typically a methacrylate-containing polymer. Preferably, it is a polymer containing a structural unit derived from methacrylate in a ratio of 50% by weight or more relative to all structural units. The (meth)acrylic resin may be a homopolymer of methacrylate, or may be a copolymer containing structural units derived from other polymerizable monomers. In this case, the ratio of the structural units derived from other polymerizable monomers is preferably 50% by weight or less with respect to all structural units.

The methacrylate constituting the (meth)acrylic resin is preferably an alkyl methacrylate. Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methyl Alkyl methacrylates with an alkyl carbon number of 1 to 8, such as tert-butyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, and 2-hydroxyethyl methacrylate. The number of carbon atoms in the alkyl group contained in the alkyl methacrylate is preferably 1-4. In (meth)acrylic resin, methacrylate may be used individually by 1 type, and may use 2 or more types together.

The other polymerizable monomers that can constitute the (meth)acrylic resin include, for example, acrylate and other compounds having a polymerizable carbon-carbon double bond in the molecule. Other polymerizable monomers may be used alone or in combination of two or more. The acrylate is preferably an alkyl acrylate. Examples of alkyl acrylate include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, acrylic acid Alkyl acrylates having 1 to 8 alkyl carbon atoms, such as cyclohexyl ester and 2-hydroxyethyl acrylate, etc. The carbon number of the alkyl group contained in the alkyl acrylate is preferably 1-4. In the (meth)acrylic resin, only one type of acrylate may be used alone, or two or more types may be used in combination.

Other compounds having polymerizable carbon-carbon double bonds in their molecules include, for example, vinyl compounds such as ethylene, propylene, and styrene, and vinyl cyanide compounds such as acrylonitrile. Other compounds having polymerizable carbon-carbon double bonds in their molecules may be used alone or in combination of two or more.

The first and second thermoplastic resin films 20 and 30 can be protective films laminated on one side of the polarizer 10 to protect the polarizer 10 . The first or second thermoplastic resin film 20, 30 may be a protective film having optical functions such as retardation film and brightness enhancement film.

For example, stretching (uniaxial stretching or biaxial stretching, etc.) a thermoplastic resin film made of the above materials, or forming a liquid crystal layer on the film, can produce a retardation film with an arbitrary retardation value. . The first and/or second thermoplastic resin films 20 and 30 may have a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer laminated on the surface.

The thickness of the first and second thermoplastic resin films 20 and 30 is usually 1 to 100 μm, but is preferably 5 to 60 μm, more preferably 5 to 50 μm from the viewpoint of strength and handleability.

From the viewpoint of easy manufacture of a polarizing plate with a protective film having a sufficiently large positive curl, it is preferable that the thicknesses of the first thermoplastic resin film 20 and the second thermoplastic resin film 30 be small, specifically, It is 40 μm or less, more preferably 30 μm or less.

As in the polarizing plate 2a shown in FIG. 2, when thermoplastic resin films are provided on both sides of the polarizing plate 10, the thermoplastic resin films may be composed of the same type of thermoplastic resin, or may be composed of different types of thermoplastic resin. Also, the thicknesses may be the same or different. Furthermore, they may have the same phase difference characteristics, or may have different phase difference characteristics. When the composition of the thermoplastic resin film bonded to both sides is different, the polarizer sheet with protective film is particularly prone to curling, which is particularly advantageous in the present invention.

(1-1-4) Adhesive

As described above, the first and second thermoplastic resin films 20 and 30 can be bonded to the polarizer 10 via an adhesive layer, for example. As the adhesive for forming the adhesive layer, water-based adhesives, active energy ray-curable adhesives, or thermosetting adhesives can be used, preferably water-based adhesives and active energy ray-curable adhesives.

Examples of the water-based adhesive include an adhesive composed of a polyvinyl alcohol-based resin aqueous solution, a water-based two-component urethane-based emulsion adhesive, and the like. Among them, a water-based adhesive composed of a polyvinyl alcohol-based resin aqueous solution is suitably used. As for the polyvinyl alcohol-based resin, in addition to the vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, it is also possible to use Polyvinyl alcohol-based copolymers obtained by saponification of copolymers made of other monomers, or those whose hydroxyl groups have been partially modified Modified polyvinyl alcohol polymers, etc. The water-based adhesive may include crosslinking agents such as aldehyde compounds (glyoxal, etc.), epoxy compounds, melamine compounds, methylol compounds, isocyanate compounds, amine compounds, and polyvalent metal salts.

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 laminating the polarizer 10 and the first and second thermoplastic resin films 20 and 30 . After the drying step, there may be an aging step such as aging at a temperature of 20 to 45°C.

The active energy ray-curable adhesive refers to an adhesive containing a curable compound that is cured by irradiation of active energy rays such as ultraviolet rays, visible light, electron rays, and X-rays, and is preferably an ultraviolet-curable adhesive.

The curable compound may be a cation polymerizable curable compound or a radical polymerizable curable compound. Cationic polymerizable curable compounds include, for example, epoxy-based compounds (compounds having one or more epoxy groups in the molecule), oxetane-based compounds (compounds having one or two epoxy groups in the molecule). The compound of the above oxetane ring), or a combination thereof. Radical polymerizable curable compounds include, for example, (meth)acrylic resin compounds (compounds having one or more (meth)acryloxy groups in the molecule), which have radical polymerizability Other vinyl compounds with double bonds, or combinations thereof. A cation 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 starting the curing reaction of the curable compound.

When bonding the polarizer 10 and the first and second thermoplastic resin films 20 and 30 , surface activation treatment may be performed on the bonding surface of at least one of them in order to improve adhesiveness. Surface activation treatment can enumerate such as: corona treatment, plasma treatment, discharge treatment (glow discharge treatment etc.), flame treatment, ozone treatment, UV ozone treatment, ionizing active line treatment (ultraviolet treatment, electron beam treatment, etc.) wet treatment. These surface-activating treatments may be performed independently, or may combine 2 or more types.

When bonding thermoplastic resin films on both sides of the polarizer 10 , the adhesives used to bond the thermoplastic resin films may be the same type of adhesive or different types of adhesives.

(1-2) Protective film for lamination step S101

(1-2-1) Composition of protective film

A protective film is a film used to protect the surface of a polarizing plate. Usually, for example, after attaching a polarizing plate sheet with a protective film to an image display element, etc., if there is an adhesive layer, the adhesive layer is peeled off one by one. Therefore, the protective film 1 is bonded to the above-mentioned surface of the polarizing plate 2 in a peelable manner.

The protective film can be composed of, for example, a base film and an adhesive layer laminated thereon.

The base film can be made of thermoplastic resins (such as polyolefin resins such as polyethylene resins, polypropylene resins, and cyclic polyolefin resins; polyester resins such as polyethylene terephthalate and polyethylene naphthalate). resin; polycarbonate resin; (meth)acrylic resin, etc.). The base film may have a single-layer structure or a multi-layer structure.

The adhesive layer can be composed of (meth)acrylic resin adhesive, epoxy adhesive, urethane adhesive, silicone adhesive, and the like.

In addition, the protective film may be a self-adhesive resin film such as polypropylene resin or polyethylene resin. At this time, the protective film does not have an adhesive layer.

The thickness of the protective film may be, for example, 5 to 150 μm, preferably 10 to 100 μm, more preferably 20 to 75 μm, even more preferably 25 to 70 μm (for example, 60 μm or less, preferably 55 μm or less). When the thickness of the protective film is less than 5 μm, the protection of the polarizing plate becomes insufficient, and it is also disadvantageous in terms of handleability. When the thickness of the protective film exceeds 150 μm, it is disadvantageous in terms of thinning the polarizing plate sheet with the protective film and reworkability of the protective film.

The protective film used in the bonding step S101 is preferably in the shape of a strip.

The length of the elongated protective film used in the bonding step S101 is, for example, 100 to 20000 m, preferably 1000 to 10000 m. Moreover, the width of the elongated protective film used in the bonding step S101 is, for example, 0.5 to 3 m, preferably 1 to 2.5 m.

(1-2-2) Elastic modulus of protective film

The protective film used in the bonding step S101 includes a region satisfying the following formula (I): TD elastic modulus-MD elastic modulus≧300MPa (I)

In formula (I), TD elastic modulus refers to the tensile elastic modulus (MPa) in the TD direction at a temperature of 23°C and a relative humidity of 55%RH. Tensile elastic modulus (MPa) in the MD direction at a humidity of 55%RH.

The MD direction refers to the mechanical flow direction of the film, that is, the longitudinal direction of the film; the TD direction refers to the direction perpendicular to the MD direction.

By attaching the protective film including the above-mentioned area to the polarizing plate and cutting out the sheet-shaped body from the area in the cutting step S102, that is, by making the cut-out sheet-shaped body have the protective film satisfying the formula (I) film, a polarizer plate with a protective film and a sufficiently large positive curl can be obtained.

The above-mentioned "cutting out the sheet-shaped body from this region" means that the entire protective film of the cut-out sheet-shaped body is included in this region.

Here, the curl of the polarizing plate sheet with a protective film can be classified into two types of "MD curl" and "TD curl" in addition to the above-mentioned "normal curl" and "reverse curl". . "MD curl" refers to the stress (shrinkage force) parallel to the MD direction of the "strip-shaped polarizing plate with protective film" to be cut out of the "polarizing plate with protective film". , expansion force, etc.) produced by the curl.

Regarding MD curl, specifically, according to the description in the items of the examples described later, a measurement sample (sheet) is cut out from a long polarizing plate with a protective film, and the measurement sample has a concave surface. When it is placed on a horizontal platform facing upwards, it is possible to measure the "diagonal that has the smallest angle with the MD direction of the long polarizing plate with a protective film among the two diagonals" of the measurement sample. The size that the upper two corners curl up. In a long polarizing plate with a protective film, when the direction of the absorption axis of the polarizing plate is parallel to the MD direction of the protective film, in terms of MD curl, the "two diagonals" of the measurement sample can be measured The angle between the polarizer and the absorption axis direction of the polarizing plate of the sample for measurement is a curl with two corners on the small diagonal line facing upwards (curl in the absorption axis direction).

"TD Curl" refers to the stress (shrinkage force) in the direction parallel to the TD direction of the "strip-shaped polarizing plate with protective film" to be cut out of the "polarizing plate with protective film". , expansion force, etc.) produced by the curl.

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

The "satisfying formula (I)" in the above "the protective film provided in the laminating step S101 includes a region satisfying the formula (I)" and "the cut sheet has a protective film satisfying the formula (I)" refers to the And the whole of this protective film all satisfies formula (I), that is, no matter take measurement at any position of this protective film Using the sample, the TD elastic modulus and MD elastic modulus measured according to the description of the items of the examples described later all satisfy the formula (I).

According to the review of the present inventors, it can be seen that if the plural points are measured on the left side of the formula (I) along the TD direction of the generally available protective film, the value on the left side of the system will vary greatly with the batch number of the product, etc. By. On the other hand, it can also be seen that if multiple points are measured on the left side of the formula (I) along the MD direction of a commonly available protective film, the value on the left side will not vary greatly within the same roll.

It can be said that the protective film that satisfies the formula (I) across the TD direction as a whole usually satisfies the formula (I) across the entire protective film (that is, no matter taking the sample for measurement from any position of the protective film). .

From the viewpoint of improving the productivity of polarizing plate sheets with a protective film, the above-mentioned region of the protective film preferably has as large an occupied area as possible, and it is more preferable that the region is expanded and used for the bonding step S101 At least the entirety of the protective film in the TD direction (width direction), and more preferably the entirety of the protective film.

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

The protective film used in the bonding step S101 can be used to measure the left side of the formula (I) for the obtained protective film and include the region satisfying the formula (I).

(1-3) Bonding of polarizing plate and protective film

Referring to FIG. 4 , bonding of the polarizing plate 2 and the protective film 1 can be performed using, for example, a pair of rollers (bonding rollers) 5 and 5 . From the viewpoint of production efficiency, this method is particularly advantageous when the polarizing plate 2 and the protective film 1 are formed into long strips.

Specifically, when the long polarizing plate 2 is continuously conveyed, the long protective film 1 is also continuously conveyed at the same time, and the protective film 1 is overlapped on one side of the polarizing plate 2, and a pair of stickers are sandwiched between them. Between the closing rollers 5 and 5, a polarizing plate 3 with a protective film attached to two films can be produced.

The MD direction (conveyance direction) of the polarizing plate 2 and the MD direction (conveyance direction) of the protective film 1 are normally parallel. The so-called parallel means that the angle between the MD direction of the polarizing plate 2 and the MD direction of the protective film 1 is 0°±5°, preferably 0°±2°.

From the viewpoint of increasing the MD positive curl of the obtained polarizing plate sheet with protective film, it is preferable to bond the two films so that the absorption axis of the polarizing plate 2 and the MD direction of the protective film 1 become parallel. . The so-called parallel means that the angle formed by the absorption axis of the polarizer 2 and the MD direction of the protective film 1 is 0°±5°, preferably 0°±2°.

By passing the laminated body of the polarizing plate 2 and the protective film 1 between the pair of bonding rollers 5, 5, the laminated body is pressed from the top and bottom, so that the two films are adhered to each other.

The polarizer 2 has a transparent (clear) hard coat (hard coat with a smooth surface) on its outermost surface. The adhesive force is easy to improve, and there is a tendency to easily obtain a polarizing plate sheet with a protective film having a sufficiently large MD positive curl. Therefore, the polarizing plate 2 preferably has a transparent hard coat (hard coat with a smooth surface) on its outermost surface.

When the protective film 1 is composed of a base film and an adhesive layer laminated thereon, if the protective film 1 is overlapped on one side of the polarizing plate 2 and passed between a pair of bonding rollers 5, 5, Then, the adhesive layer of the protective film 1 overlaps with the aforementioned single surface of the polarizing plate 2 . Before laminating the protective film 1 and the polarizer 2, plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, Surface activation treatment such as saponification treatment.

In the step of bonding by a pair of bonding rollers 5 and 5, the pressure (clamping pressure) applied to the laminate of the protective film 1 and the polarizing plate 2 is, for example, 0.01 to 0.5 MPa, and may be 0.05 to 0.3 MPa. As the bonding rollers 5 and 5 , conventionally known ones such as those made of metal (containing alloys such as SUS) or rubber can be used on the surface.

In the step of laminating the polarizing plate 2 and the protective film 1, it is preferable to apply tension to the polarizing plate 2 and the protective film 1 while laminating, and it is more preferable to make the tension of the polarizing plate 2 higher than that of the protective film 1 before lamination. Low tension before fit. Such tension control is beneficial to increase the MD positive curl of the obtained polarizer plate with protective film. Tension before bonding refers to the tension applied in the MD direction of the film before bonding the two films (the laminate of the two films passes through a pair of bonding rollers 5, 5), and can be measured according to the description of the items in the examples described later.

From the standpoint of increasing the MD positive curl of the obtained polarizing plate sheet with protective film, the tension of the polarizing plate 2 in the MD direction before bonding is preferably 250 N/m or less, more preferably 200 N/m. below m.

From the same viewpoint, the tension before bonding in the MD direction of the protective film 1 is preferably 260 N/m or more, more preferably 300 N/m or more.

(2) Cut out step S102

This step is the step of cutting out the region satisfying the formula (I) in the polarizing plate with protective film 3 obtained in laminating step S101 to obtain the polarizing plate sheet with protective film.

Cutting out (cutting) can be performed using a conventionally known cutting means such as a cutting knife.

As mentioned above, "the sheet-shaped body is cut out from a region" means that the entire protective film of the cut-out sheet-shaped body is included in the region.

The size, shape and cutting angle of the cut out polarizer with protective film are not particularly limited.

The polarizing plate sheet with the protective film is preferably a square shape, more preferably a square shape with a long side and a short side. The square shape is preferably a rectangle.

When the shape of the polarizing plate with 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, preferably 40 mm to 100 mm.

Generally speaking, when the size of the polarizing plate sheet-shaped body with a protective film becomes larger, it tends to be difficult to generate MD positive curl. Therefore, when the size of the polarizing plate 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 sufficient MD positive curl amount.

Although there is no particular limitation, if the shape of the polarizing plate sheet with a protective film is a rectangle, when the polarizing plate sheet with a protective film is viewed from the protective film side, it can be compared with its long side and short side. The polarizing plate with protective film sheet was cut out from the polarizing plate with protective film 3 so that the absorption axis direction of the polarizing plate (MD direction of the polarizing plate) was at an angle of 45 degrees.

Alternatively, if the shape of the polarizing plate sheet with protective film is rectangular, when viewing the polarizing plate sheet with protective film from the side of the protective film, the absorption of the polarizing plate can be reduced relative to its long side. The axial direction (the MD direction of the polarizing plate) is parallel or at an angle of 90 degrees, and the protective film-attached polarizing plate sheet is cut out from the protective film-attached polarizing plate 3 .

<Polarizer sheet with protective film>

The polarizing plate sheet with protective film of the present invention comprises a polarizing plate and a protective film laminated on one side thereof, and the protective film satisfies the following formula (II): The first modulus of elasticity - the second modulus of elasticity≧300MPa (II).

In formula (II), the first elastic modulus refers to the tensile elastic modulus (MPa) in the 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 The modulus refers to the tensile elastic modulus (MPa) in the direction parallel to the absorption axis of the polarizing plate at a temperature of 23°C and a relative humidity of 55%RH.

By having the protective film satisfying the formula (II), the polarizing plate sheet with the protective film can have a sufficiently large MD positive curl.

If a polarizing plate sheet with a protective film having a sufficiently large MD positive curl is used, even if the above-mentioned multilayer structure is formed by laminating one or more other optical functional layers on the polarizing plate side, the It can maintain the state without reverse curl (flat state) or the state with normal curl, so when the polarizing plate sheet or multilayer structure with protective film is attached to the image display element through the adhesive layer, It can suppress the generation of lamination error, or can suppress the bad situation of air bubbles mixed in the interface between the adhesive layer and the image display element.

The polarizing plate sheet with a protective film of the present invention can be produced by the above-mentioned method for producing a polarizing plate sheet with a protective film.

The so-called direction perpendicular to the absorption axis of the polarizing plate refers to the direction between the protective film and the polarizing plate when the polarizing plate sheet with a protective film is manufactured by the above-mentioned method of manufacturing a polarizing plate sheet with a protective film. The TD direction is synonymous.

The so-called "satisfaction of formula (II)" means that the span and the entirety of the protective film satisfy the formula (II), that is, no matter from any position of the protective film, the sample for measurement is taken according to the records of the items in the following examples. Both the first elastic modulus and the second elastic modulus satisfy the formula (II).

The reason is the same as that described in the item <Method of Manufacturing a Polarizing Plate with Protective Film>. In the polarizing plate with a protective film, the absorption axis of the polarizing plate is perpendicular to the span. The protective film that satisfies the formula (II) in the direction of the entire protective film is usually said to span the entire protective film (that is, no matter where the sample for measurement is taken from any position of the protective film) and it satisfies the formula (II).

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

The size and shape of the polarizing plate sheet with protective film are not particularly limited, and the specific size and shape refer to the record in the item "Manufacturing method of polarizing plate sheet with protective film". When the size of the polarizing plate plate with a protective film is large, it may be preferable to make the left side of the formula (II) larger in order to provide a sufficient amount of positive curl in MD.

Polarizing plate flakes with protective film (the polarizing plate flakes with protective film obtained according to the manufacturing method of polarizing plate flakes with protective film of the present invention are also the same) preferably show MD positive Curl, more preferably, can show MD positive curl even when the above-mentioned multilayer structure is produced, or show a lithographic state without curl, and the MD positive curl amount measured according to the description of the items in the examples described later is 40 mm or more. The amount of MD positive curl may be 45 mm or more. The MD positive curl amount is preferably at most 100 mm.

Although there is no particular limitation, if the shape of the polarizing plate sheet with a protective film is rectangular, when viewing the polarizing plate sheet with a protective film from the side of the protective film, the long and short sides of the The direction of the absorption axis of the polarizing plate forms an angle of 45 degrees.

Alternatively, if the shape of the polarizing plate sheet with protective film is rectangular, when viewing the polarizing plate sheet with protective film from the side of the protective film, the direction of the absorption axis of the polarizing plate can be adjusted relative to its long side. Become parallel or become an angle of 90 degrees.

An example of the layer configuration of the polarizer sheet with a protective film is shown in FIG. 5 . As shown in FIG. 5, when the protective film 1 is composed of the base film 40 and the adhesive layer 50 laminated thereon, the adhesive layer 50 of the protective film 1 is the same as the above-mentioned unit of the polarizing plate 2. overlap in a way that faces meet.

For a more specific description of the polarizing plate 2 and the protective film 1 , refer to the description in the item <Method for Manufacturing Polarizing Plate Sheet with Protective Film>.

<Strip-shaped polarizing plate with protective film>

The strip-shaped polarizing plate with a protective film of the present invention includes a "strip-shaped polarizing plate" and "a strip-shaped protective film laminated on one side thereof", and the protective film includes the following formula (III) The area: The first modulus of elasticity - the second modulus of elasticity≧300MPa (III).

In the formula (III), the first elastic modulus refers to the tensile elastic modulus (MPa) in the direction perpendicular to the absorption axis of the elongated polarizing plate at a temperature of 23°C and a relative humidity of 55%RH , The second elastic modulus refers to the tensile elastic modulus (MPa) in the direction parallel to the absorption axis of the strip-shaped polarizing plate at a temperature of 23°C and a relative humidity of 55%RH.

If the "strip-shaped polarizing plate with a protective film" including the above region is used, by cutting out the sheet from this region, the cut sheet has a protective film satisfying the formula (III), so Polarizer sheets with protective films can be produced with sufficiently large positive curls.

The above-mentioned "cutting out the sheet-shaped body from the region" means that the entire protective film of the cut-out sheet-shaped body is included in the region.

The elongated polarizing plate with protective film of the present invention can be manufactured by carrying out the bonding step S101 of the above-mentioned manufacturing method of polarizing plate sheet with protective film.

The so-called direction perpendicular to the absorption axis of the polarizing plate is used to manufacture a strip-shaped polarizing plate with a protective film by performing the bonding step S101 of the above-mentioned method of manufacturing a polarizing plate with a protective film. , is synonymous with the TD direction of the protective film and polarizer.

The so-called "satisfaction of formula (III)" means that the span and the entirety of the protective film satisfy formula (III), that is, no matter where the protective film is taken from any position of the sample for measurement, it is measured according to the records of the items in the following examples Both the first elastic modulus and the second elastic modulus satisfy the formula (III).

For the same reason as that described in the item <Method of Manufacturing Polarizing Plate Sheet with Protective Film>, in a long polarizing plate with protective film, absorption across and from the polarizing plate A protective film that satisfies Formula (III) with its axes in the direction perpendicular to the entirety can generally be said to satisfy Formula (III) across the entire protective film (that is, no matter where the sample for measurement is taken from any position of the protective film).

From the viewpoint of increasing the productivity of polarizing plate sheets with a protective film, it is preferable that the above-mentioned region of the protective film has as large an occupied area as possible, and it is more preferable that the region be expanded and used in the bonding step. In S101, at least the entirety of the protective film in the width direction is more preferably extended to the entirety of the protective film.

From the point of view of increasing the MD positive curl of the "polarizing plate plate with protective film" cut out from "strip-shaped polarizing plate with protective film", the left side of formula (III) is more It is preferably at least 400 MPa, more preferably at least 500 MPa. The left side of formula (III) is usually 2000MPa or less, typically 1500MPa or less.

The size, shape and cut-out angle of the polarizer sheet with protective film are not particularly limited, and the specific size, shape and cut-out angle refer to the item <Method of Manufacturing Polarizer Sheet with Protective Film> record. When the size of the "polarizing plate sheet with protective film" cut out from the "strip-shaped polarizing plate with protective film" is large, in order to give sufficient amount of positive curl to MD, sometimes formula (III ) is preferably larger on the left side.

The length of the strip-shaped polarizing plate with a protective film is, for example, 100 to 20000 m, preferably 1000 to 10000 m. Furthermore, the width of the elongated polarizing plate with a protective film is, for example, 0.5 to 3 m, preferably 1 to 2.5 m.

For a more specific description of the layer composition of the "strip-shaped polarizing plate with a protective film", the polarizing plate constituting the "strip-shaped polarizing plate with a protective film", and the protective film, please refer to <with protection The description of the items of "Method for manufacturing polarizing plate sheet with protective film" and <Polarizing plate sheet with protective film>.

<Multilayer Construct>

On the polarizing plate side surface of "polarizing plate with protective film" or "strip-shaped polarizing plate with protective film", one or more other layers can be further laminated through an adhesive layer or an adhesive layer Optical functional layer or separation film (peeling film), etc.

The optical functional layer may be a retardation layer or the like, and the optical functional layer may be laminated on the polarizing plate side through an adhesive layer or an adhesive layer.

[Example]

Hereinafter, although experimental examples are given and the present invention is more specifically described, the present invention is not limited to these examples.

In the following experimental examples, the thickness of the polarizing plate and the film, the elastic modulus difference of the protective film, the tension before lamination of the polarizing plate and the protective film in the MD direction, and the thickness of the polarizing plate sheet with the protective film The amount of MD curl is measured in the following manner.

(1) Thickness of polarizer and film

Measurement was performed using a digital micrometer "MH-15M" manufactured by Nikon Co., Ltd.

(2) The elastic modulus difference of the protective film

Use a supercutter to cut out rectangular pieces with a long side of 100 mm x a short side of 25 mm from the strip-shaped polarizing plate with a protective film. Regarding the cutting out, the long side of the small piece is parallel to the MD direction of the strip-shaped polarizing plate with a protective film, and the short side of the small piece is aligned with the TD of the strip-shaped polarizing plate with a protective film. directions in a parallel fashion. This small piece was peeled from the polarizing plate, and the obtained small piece of the protective film alone was used as a sample for measurement of MD elastic modulus.

And similarly, a rectangular piece with a long side of 100 mm x a short side of 25 mm was cut out from the long polarizing plate with a protective film using a super cutter. However, for this cutting, the long side of the small piece is parallel to the TD direction of the long polarizer with a protective film, and the short side of the small piece is aligned with the long polarizer with a protective film. The MD direction is carried out in a parallel manner. This small piece was peeled from the polarizing plate, and the obtained small piece of the protective film alone was used as a sample for measurement of TD elastic modulus.

Next, use the upper and lower grips of the tensile testing machine [Autograph AG-Xplus testing machine manufactured by Shimadzu Corporation] so that the distance between the grips is 5 cm. Clamp the two ends of the above-mentioned measurement sample in the longitudinal direction, and stretch the measurement sample in the longitudinal direction of the measurement sample at a tensile speed of 1mm/min in an environment of 23°C and a relative humidity of 55%. From the slope of the straight line between 3 and 6 MPa in the obtained stress-strain curve, the tensile elastic modulus [MPa] at 23°C and 55% relative humidity was calculated. At this time, only the thickness value of the biaxially stretched polyethylene terephthalate (base film) was used as the thickness for calculating the stress.

The tensile modulus calculated from the measurement sample for which the MD elastic modulus was measured is the MD elastic modulus, and the tensile elastic modulus calculated from the measurement sample for which the TD elastic modulus was measured is the TD elastic modulus.

In each of the following experimental examples, since the absorption axis (MD direction) of the polarizer is parallel to the MD direction of the protective film, two films are bonded to produce a polarizing plate with a protective film, so the above formula ( The TD elastic modulus in I) is synonymous with the first elastic modulus in the above-mentioned formula (II) and formula (III), and the MD elastic modulus in the above-mentioned formula (I) is the same as the above-mentioned formula (II) and formula The second modulus of elasticity in (III) is synonymous.

Hereinafter, the TD elastic modulus (first elastic modulus) is simply called "TD elastic modulus", and the MD elastic modulus (second elastic modulus) is simply called "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) are simply called "elastic modulus difference".

(3) Tension before bonding of polarizing plate and protective film in MD direction

The film tension of the polarizing plate and protective film traveling between the “pair of bonding rollers for bonding the polarizing plate and the protective film” and the “pair of nip rollers on the upstream side and closest to the bonding roller” [N/m], Measured using a tension detection roller installed between the "laminating roller" and "the pair of nip rollers closest to the laminating roller" as the pre-laminating tension in the MD direction.

(4) MD curl of polarizer sheet with protective film

As shown in FIG. 6, in the obtained elongated polarizing plate 60 with a protective film, when viewed from the protective film side, the absorption axis 61 of the polarizing plate is 45 degrees with respect to the long side and the short side. In the method, a rectangular (long side 140 mm×short side 70 mm) small piece (sheet) was cut out using a super cutter, and this was used as a sample 70 for measuring the amount of MD curl. Cutting out of the measurement sample 70 was carried out in an environment of 23° C. and a relative humidity of 55% immediately after bonding the polarizing plate and the protective film.

The measurement sample 70 is placed on the reference plane (horizontal table) so that the concave side faces upward. In this state, each of the two corners 80 of the measurement sample 70 on "the diagonal with the smaller angle with the absorption axis direction of the polarizing plate of the measurement sample 70 among the two diagonals" is measured from As for the height calculated from the reference plane, the average value of the heights of the two corners 80 was calculated as the MD curl amount [mm].

The state where the protective film side is concave is the state with normal curl, and the state where the polarizer side is concave is the state with reverse curl. In Experimental Examples 1 to 3 described below, any of the samples for measurement (polarizing plate sheet with a protective film) had positive curl.

<Experimental Examples 1 to 3>

(A) Production of polarizers

A long polyvinyl alcohol film [average degree of polymerization: about 2400, degree of saponification: more than 99.9 mol%, thickness: 30 μm] is stretched to about 4 times in one axis by dry type while being continuously conveyed, and further maintained in tension In the state, after immersing in pure water at 40°C for 1 minute, immerse in an aqueous solution with a weight ratio of iodine/potassium iodide/water of 0.1/5/100 at 28°C for 60 seconds. 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. Then, After washing with pure water at 5°C for 5 seconds, dry at 70°C for 180 seconds to obtain a strip-shaped polarizer with iodine adsorbed and aligned on a polyvinyl alcohol film stretched in one axis. The thickness of the polarizer is 13 μm.

(B) Production of polarizing plate

The strip-shaped polarizer obtained in the above (A) was continuously conveyed, and at the same time, the strip-shaped first thermoplastic resin film [manufactured by Nippon Paper Co., Ltd. as a transparent hard coat product name "COP25ST-HC", A film with a transparent hard coat layer formed on a cyclic polyolefin resin film, thickness: 29 μm] and a long strip-shaped second thermoplastic resin film [manufactured by Fujifilm Co., Ltd. as triacetate cellulose (TAC) film The brand name "ZRG20SL", thickness: 20μm] is continuously conveyed, while injecting a water-based adhesive between the polarizer and the first thermoplastic resin film and between the polarizer and the second thermoplastic resin film, while passing through a pair of bonding rollers In between, a laminate film composed of the first thermoplastic resin film/water-based adhesive layer/polarizer/water-based adhesive layer/second thermoplastic resin film was obtained.

Next, the obtained laminated film was transported, and heat-treated at 80°C for 300 seconds by passing through a hot air dryer to dry the water-based adhesive layer to obtain a long polarizing plate.

The above-mentioned water-based adhesive used the following aqueous solution: a concentration of 3 obtained by dissolving polyvinyl alcohol powder [trade name "GOHSEFIMER" manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average degree of polymerization: 1100] in hot water at 95°C. % by weight of polyvinyl alcohol aqueous solution, mixing a crosslinking agent [sodium glyoxylate manufactured by Nippon Synthetic Chemical Industry Co., Ltd.] at a ratio of 1 part by weight to 10 parts by weight of polyvinyl alcohol powder of aqueous solution. The thickness of the obtained polarizing plate was 62 μm.

(C) Manufacture of strip-shaped polarizing plate with protective film

The strip-shaped polarizing plate obtained in the above (B) is continuously conveyed, and at the same time, the strip-shaped protective film [on biaxially stretched polyethylene terephthalate (thickness: 38 μm) (Meth) acrylic resin adhesive layer (thickness: 15 μm) laminated with a product name "AY-4212" manufactured by Fujimori Industry Co., Ltd.] is continuously conveyed, and by overlapping and passing through a pair of bonding rollers In between, the laminate of the protective film and the polarizing plate is pressed from top to bottom to continuously manufacture elongated polarizing plates with a protective film.

The protective film is bonded to the first thermoplastic resin film (transparent hard coat) surface of the polarizing plate through the adhesive layer.

In addition, the pressure (nip pressure) applied to the laminate of the protective film and the polarizing plate by the bonding roller 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 methods of the strip-shaped polarizing plates with protective films in Experimental Examples 1 to 3 are the same except that the protective films used are different (the products are the same, but the batch numbers are different). Hereinafter, the protective films used in Experimental Examples 1 to 3 are referred to as protective films 1 to 3, respectively.

For the obtained elongated polarizing plate with a protective film, the TD elastic modulus, the MD elastic modulus, and the difference in elastic modulus were calculated according to the above-mentioned method.

The protective films 1 to 3 each have a width (length in the TD direction) of 1300 mm. When measuring the elastic modulus of each protective film, it is in a certain arbitrary position in the MD direction, along the width direction, counting from one end of the width direction to 100mm, 280mm, 470mm, 650mm, 830mm, 1020mm and 1200mm, a total of 7 The measurement samples were cut out at the positions of the points, and the TD elastic modulus, the MD elastic modulus, and the elastic modulus difference were determined for each of the seven measurement samples. These results are shown in the column "1" of Table 1. Counting from one of the above arbitrary MD direction positions and along Seven measurement samples were cut out at a distance of 20 mm in the MD direction in the same manner as above, and the TD elastic modulus, MD elastic modulus, and elastic modulus difference were determined for each of the seven measurement samples. These results are shown in the "2" column of Table 1. Calculated from one of the above-mentioned arbitrary positions in the MD direction and at a position 50 mm apart along the MD direction, cut out seven measurement samples in the same manner as above, and obtain the TD elastic modulus for each of the seven measurement samples. number, MD elastic modulus, and elastic modulus difference. These results are shown in column "3" of Table 1.

7 shows a graph showing the relationship between the "position in the width direction" and the "difference in modulus of elasticity (modulus of elasticity described in column "1" of Table 1)" of the protective films 1 to 3.

Regarding the position where the sample for measurement is cut out, for example, "cut out the sample for measurement 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" and "measurement Cut out the sample for measurement in such a way that the central position in the width direction of the sample is consistent. The same applies to other positions counted from one end in the width direction.

As shown in Table 1 and Figure 7, it can be seen that the strip-shaped protective films 1 and 2 include the span and the whole (that is, the span and the TD direction as a whole (the direction perpendicular to the absorption axis of the strip-shaped polarizing plate) ), and across the entirety of the MD direction (the absorption axis direction of the elongated polarizing plate)) and satisfy the regions of formulas (I) and (III), and this region spans across the entirety of the width direction of the protective film.

In contrast, although the elongated protective film 3 includes the entirety of the TD direction (direction perpendicular to the absorption axis of the elongated polarizing plate) and the entire MD direction (absorption axis of the elongated polarizing plate) Axial direction) and satisfy the area of formula (I) and (III), but this area does not span the entire width direction of protective film. That is, in the elongated protective film 3 , only the region from one end in the width direction to about 700 mm from the one end satisfies the formulas (I) and (III).

Moreover, as mentioned above, the protective film which satisfies formula (I) and (III) at a certain arbitrary MD direction position also satisfies formula (I) and (III) at another MD direction position normally.

(D) Fabrication of polarizer sheet with protective film

As shown in Fig. 6, in the elongated polarizing plate with a protective film obtained from the above (C), the absorption axis of the polarizing plate is 45° relative to the long side and short side when viewed from the side of the protective film. In the way of precision, use a super cutting machine to cut out rectangular (long side 140mm x short side 70mm) small pieces (sheets) to obtain polarizer sheets with protective films.

About the obtained polarizing plate sheet-like body with a protective film, the amount of MD curl was measured according to the method mentioned above.

The strip-shaped polarizing plates with protective films of Experimental Examples 1 to 3 each had a width (length in the TD direction) of 1330 mm. When measuring the MD curl amount of the polarizing plate sheet with protective film obtained from each elongated polarizing plate with protective film, it is at a certain arbitrary position in the MD direction, along the width direction, from One end of the width direction is calculated as 100mm, 280mm, 470mm, Cut out polarizing plate sheets with protective films at 650mm, 830mm, 1020mm and 1200mm in total at 7 points, and measure the MD curl of these 7 sheets of sheets. Seven sheets of the sheet-like system were cut out from the vicinity of the cut-out 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. In addition, "the position in the width direction of the polarizing plate plate with protective film cut out from the long polarizing plate with protective film" and "the position of the cut-out polarizing film with protective film" in Experimental Examples 1 to 3 are shown. The graph of the relationship between the MD curl amount of the polarizing plate sheet is shown in Fig. 7.

Regarding the position of cutting out the polarizing plate sheet with protective film, for example, “cut out the polarizing plate sheet with protective film at a position 100 mm from one end in the width direction” means that “ Cut out the polarizing plate sheet with protective film so that the position 100 mm from one end in the width direction” coincides with the “center position in the width direction of the polarizing plate sheet with protective film”. The same applies to other positions counted from one end in the width direction.

The polarizing plate sheets with protective films cut out from the long polarizing plates with protective films of Experimental Examples 1 to 3 all had positive curls. Accordingly, the measured amount of MD curl is the amount of MD positive curl.

Seven sheets of polarizing plate sheets with a protective film cut out from the strip-shaped polarizing plate with a protective film in Experimental Example 1 using the protective film 1, and from Experimental Example 2 using the protective film 2 Among the 7 sheets of polarizing plate with protective film cut out from the strip-shaped polarizing plate with protective film, the protective film laminated on the polarizing plate satisfies formula (II).

Among the 7 sheets of polarizing plate with protective film cut out from the strip-shaped polarizing plate with protective film of Experimental Example 3 using protective film 3, in the strip-shaped polarizing plate with protective film The protection film laminated on the polarizing plate in the sheets cut out at the positions of 100mm, 280mm, 470mm and 650mm from one end of the polarizing plate in the width direction of the film satisfies the formula (II), but at 830mm, 1020mm and 1200mm The sheet cut out of the position is not satisfactory.

As shown in Table 2 and Figure 8, the polarizing plate sheet system with a protective film satisfying the formula (II) exhibits a MD positive curl of 40 mm or more. On the other hand, the MD positive curl amount of the polarizing plate plate with protective film not satisfying formula (II) is less than 40 mm.

S101, S102‧‧‧steps

Claims (11)

A method of manufacturing a polarizing plate sheet with a protective film, comprising the following steps: attaching a protective film containing a region satisfying the following formula (I) to one side of a polarizing plate to obtain a polarizing plate with a protective film The step of polarizing plate; and the step of cutting out the sheet-shaped body of polarizing plate with protective film from the aforementioned area; Resin film, 908MPa≧TD elastic modulus-MD elastic modulus≧338MPa (I) In the formula, TD elastic modulus refers to the tensile elastic modulus in the TD direction at a temperature of 23°C and a relative humidity of 55%RH , MD elastic modulus refers to the tensile elastic modulus in the MD direction at a temperature of 23°C and a relative humidity of 55%RH. The manufacturing method according to claim 1, wherein the polarizing plate and the protective film are sandwiched between a pair of rollers and bonded together. The manufacturing method according to claim 2, wherein the polarizing plate is in the shape of a strip, and the protective film is in the shape of a strip. The manufacturing method according to claim 3, wherein the tension before lamination of the polarizing plate is 200 N/m or less, and the tension before lamination of the protective film is 300 N/m or more. The manufacturing method according to any one of claims 1 to 4, wherein the absorption axis of the polarizing plate and the MD direction of the protective film are bonded in parallel. The manufacturing method according to any one of claims 1 to 4, wherein the thickness of the polarizing plate is 70 μm or less. A polarizing plate sheet with a protective film, comprising: a polarizing plate, and a protective film laminated on one side of the polarizing plate; wherein, the aforementioned protective film is attached to the surface of the polarizing plate in a peelable manner, and the aforementioned protective film It has a polyester resin film, and the aforementioned protective film satisfies the following formula (II), 908MPa≧1st elastic modulus-second elastic modulus≧338MPa (II) In the formula, the first elastic modulus refers to the temperature at 23 The tensile modulus of elasticity in the direction perpendicular to the absorption axis of the aforementioned polarizing plate at a temperature of 23°C and a relative humidity of 55%RH. The tensile elastic modulus in the direction parallel to the absorption axis of the polarizing plate. The sheet-shaped polarizing plate with a protective film as described in item 7 of the scope of the patent application, wherein the amount of curling in a direction parallel to the absorption axis of the polarizing plate to make the surface on the side of the polarizing plate convex is: More than 40mm. The sheet-shaped polarizing plate with a protective film according to claim 7 or 8, wherein the thickness of the polarizing plate is 70 μm or less. A strip-shaped polarizing plate with a protective film, comprising: a strip-shaped polarizing plate, and a strip-shaped protective film laminated on one side of the polarizing plate; wherein, the aforementioned protective film is bonded in a peelable manner To the surface of the polarizing plate, the protective film has a polyester resin film, and the protective film includes a region satisfying the following formula (III), 908MPa≧1st modulus of elasticity - 2nd modulus of elasticity≧338MPa (III) In the formula, the first modulus of elasticity refers to the difference between the above-mentioned strip-shaped polarizing plate at a temperature of 23°C and a relative humidity of 55%RH The tensile elastic modulus in the direction perpendicular to the absorption axis, the second elastic modulus refers to the tensile elastic modulus in the direction parallel to the absorption axis of the aforementioned strip-shaped polarizing plate at a temperature of 23°C and a relative humidity of 55%RH Tensile modulus of elasticity. The elongated polarizing plate with a protective film as described in claim 10, wherein the aforementioned region spans the entire width direction of the aforementioned protective film.

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