JP7542967B2 - Laminate - Google Patents

Description

The present invention relates to a laminate, and more specifically to a laminate in which a surface protection film is releasably laminated to one surface of a polarizing plate including a polarizer, and a release film is releasably laminated to the other surface via an adhesive layer.

2. Description of the Related Art Polarizing plates are widely used in image display devices such as liquid crystal displays and organic electroluminescence (EL) displays, and particularly in recent years in various mobile devices such as smartphones.
Conventionally, a polarizing plate including a polarizing plate, specifically, for example, a polarizing plate having a protective film laminated on one or both sides of a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film, has been used as the polarizing plate.

Such polarizing plates are generally distributed on the market as a laminate with a peelable surface protection film (also called a protect film) and a release film (also called a separate film) attached to the surface to prevent the surface from becoming dirty or scratched.

When attaching a polarizing plate to a display element such as a liquid crystal cell or an organic EL element, the release film attached to the surface is peeled off, and the polarizing plate is attached to the display element via the exposed adhesive layer. When peeling off the release film, as shown in Patent Document 1 [JP Patent Publication 6-48633], the surface protection film side of the laminate (a film in which a surface protection film is laminated on one side of a polarizing plate and a release film is laminated on the other side) is fixed to a holding table by a method such as suction or adsorption, and a release tape is attached to the release film. After that, the release tape is pulled to remove the release film from the polarizing plate surface. At this time, since the phenomenon in which the polarizing plate peels off from the surface protection film can be suppressed, it is preferable that the surface protection film has a relatively low rigidity, specifically, a rigidity K3, which is expressed as the product of the maximum force (F (N)) and the strain (S (mm)) measured by the measurement method shown below, is 1.00 N-mm or less.

However, with conventional laminates, when the release film is peeled off, the movement of the release film causes the fixed polarizing plate and surface protection film to float up from the support table, causing the polarizing plate and surface protection film to become unfixed, making it difficult to peel off the release film. In recent years, polarizing plates have become thinner, losing their stiffness and becoming relatively less rigid, making peeling defects even more likely to occur.

This problem can be solved by increasing the suction or adsorption force used to fix the laminate, or by decreasing the adhesive strength of the release film, but on the other hand, new problems arise. Namely, if the force acting on the laminate, such as the suction or adsorption force, becomes too strong, marks will remain on the polarizing plate, degrading its appearance. Furthermore, if the adhesive strength of the release film is reduced, a gap will form between the release film and the polarizing plate when the laminate is subjected to an impact during transportation, etc.

Japanese Patent Application Publication No. 6-48633

The object of the present invention is to provide a laminate that does not cause peeling problems of the release film.

[1] A surface protective film is peelably laminated on one surface of a polarizing plate,
a release film is releasably laminated on the other surface of the polarizing plate via an adhesive layer;
The polarizing plate includes a polarizer,
A laminate having a rigidity K3 of 1.00 N mm or less, the rigidity K3 being expressed as the product (F3 (N) x S3 (mm)) of the maximum force F3 (N) and the strain S3 (mm), when the maximum force (F (N)) measured by the following measurement method is F3 and the strain (S (mm)) is S3, wherein the rigidity K3 is expressed as the product (F3 (N) x S3 (mm)) of the maximum force F3 (N) and the strain S3 (mm),
A laminate in which, when a layer consisting of the polarizing plate and the surface protective film is used as a measurement film, the maximum force (F (N)) measured by the following measurement method is defined as F1 and the distortion (S (mm)) is defined as S1, and the rigidity K1 expressed as the product (F1 (N) x S1 (mm)) of the maximum force F1 (N) and the distortion S1 (mm) is 3.70 N-mm or more and 10.0 N-mm or less.

How to measure:
A measurement table having a circular through hole in the center when viewed from above, a diameter of the through hole on the top surface of 30 mm, and a shape of the through hole when viewed from the side composed of a columnar lower part and a hemispherical upper part,
A rectangular measurement film measuring 25 mm x 43 mm is placed on the
A needle having a spherical tip, a tip diameter of 1 mm, and a curvature radius of 0.5 mm was vertically lowered from above the measurement film at a speed of 1.0 cm/sec so that the needle passed through the center of the through-hole of the measurement table.
The maximum load required to maintain the bent state of the film after the tip of the needle comes into contact with the film to be measured is measured as the maximum force F (N), and the strain S (mm) of the film at that time is measured.

[2] The laminate described in [1], in which the stiffness K2 expressed as the product of the maximum force F2 (N) and the strain S2 (mm) measured by the measurement method using the polarizing plate as a measurement film, where F2 (N) is the maximum force measured by the measurement method and S2 is the strain (S (mm)), is 1.00 N-mm or less.

[3] The laminate according to claim 1 or 2, wherein the adhesion between the polarizing plate and the release film is 0.02 to 0.05 N/25 mm.

[4] A step of fixing the surface protective film in the laminate according to any one of [1] to [3] on a holding table with an adhesion force of 0.1 to 0.3 N/60 mm;
A method for producing a polarizing plate with a surface protective film, comprising the step of peeling off the release film from the laminate.

The present invention provides a laminate that does not cause peeling problems with the release film.

FIG. 2 is a schematic cross-sectional view showing an example of a layer structure of the laminate of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of a layer structure of the laminate of the present invention. FIG. 1 is a schematic diagram showing an apparatus for measuring the maximum force F and strain S of a film in a deflected state. 1 is a diagram for explaining the maximum force F and strain S when the film is bent. FIG. 11 is an image showing an example of a state in which a crease has occurred in a film.

<Laminate>
The laminate has a surface protective film laminated on one side of the polarizing plate, and a release film laminated on the other side of the polarizing plate. The polarizing plate has at least a polarizer. Hereinafter, an example of the layer structure of the laminate of the present invention will be described with reference to the drawings. The polarizing plate may have a protective film, a retardation layer, a brightness enhancement film, etc. in addition to the polarizer. The polarizing plate may also have a pressure-sensitive adhesive layer for bonding the polarizer, the retardation layer, the brightness enhancement film, etc. to each other.

Figure 1 is a schematic cross-sectional view showing an example of the laminate of the present invention. The laminate 100 shown in Figure 1 (a) is composed of a surface protection film 30 laminated on one side of a polarizing plate 10, and a release film 20 laminated on the other side of the polarizing plate 10. The surface protection film 30 is composed of a base film 31 and an adhesive layer 32 laminated thereon. The surface protection film 30 can be peeled off from the polarizing plate 10 in a state in which the base film 31 and the adhesive layer 32 are laminated. The polarizing plate 10 has a layer structure in which a protective film 12 is laminated on one side of a polarizer 11 via an adhesive layer (not shown), a brightness improvement film 14 is laminated on the other side via an adhesive layer 16, and an adhesive layer 15 is laminated on the protective film 12. The surface protection film 30 is laminated on the brightness improvement film 14. A release film 20 is laminated on the adhesive layer 15. This release film 20 can be peeled off from the polarizing plate 10 leaving the adhesive layer 15.

The laminate 101 shown in FIG. 1(b) is composed of a surface protection film 30 laminated on one side of the polarizing plate 10, and a release film 20 laminated on the other side of the polarizing plate 10. The surface protection film 30 is composed of a base film 31 and an adhesive layer 32 laminated thereon. The surface protection film 30 can be peeled off from the polarizing plate 10 with the base film 31 and the adhesive layer 32 laminated thereon. The polarizing plate 10 has a layer structure in which a protective film 12 is laminated on one side of the polarizer 11 via an adhesive layer (not shown), a protective film 13 is laminated on the other side via an adhesive layer (not shown), an adhesive layer 15 is laminated on the protective film 12, and a brightness enhancement film 14 is laminated on the protective film 13 via an adhesive layer 16. The surface protection film 30 is laminated on the brightness enhancement film 14. A release film 20 is laminated on the adhesive layer 15. This release film 20 can be peeled off from the polarizing plate 10 leaving the adhesive layer 15.

The laminate 102 shown in FIG. 2(a) is composed of a surface protection film 30 laminated on one side of the polarizing plate 10, and a release film 20 laminated on the other side of the polarizing plate 10. The surface protection film 30 is composed of a base film 31 and an adhesive layer 32 laminated thereon. The surface protection film 30 can be peeled off from the polarizing plate 10 with the base film 31 and the adhesive layer 32 laminated thereon. The polarizing plate 10 has a layer structure in which a protective film 12 is laminated on one side of the polarizer 11 via an adhesive layer (not shown), a protective film 13 is laminated on the other side via an adhesive layer (not shown), a retardation layer 17 is laminated on the protective film 12 via an adhesive layer or adhesive layer (not shown), and an adhesive layer 15 is laminated on the retardation layer 17. A release film 20 is laminated on this adhesive layer 15. This release film can be peeled off from the polarizing plate 10 leaving the adhesive layer 15.

The laminate 103 shown in FIG. 2(b) is composed of a surface protection film 30 laminated on one side of the polarizing plate 10, and a release film 20 laminated on the other side of the polarizing plate 10. The surface protection film 30 is composed of a base film 31 and an adhesive layer 32 laminated thereon. The surface protection film 30 can be peeled off from the polarizing plate 10 with the base film 31 and the adhesive layer 32 laminated thereon. The polarizing plate 10 has a layer structure in which a retardation layer 17 is laminated on one side of the polarizer 11 via an adhesive layer or adhesive layer (not shown), a protective film 13 is laminated on the other side via an adhesive layer (not shown), and an adhesive layer 15 is laminated on the retardation layer 17. A release film 20 is laminated on the adhesive layer 15. The release film 20 can be peeled off from the polarizing plate 10 leaving the adhesive layer 15.

In the laminates 100 to 103, the surface protection film 30 and the release film 20 are preferably members that constitute the outermost surface of the laminate. The laminates 100 to 103, the polarizing plate 10, the release film 20, and the surface protection film 30 may have layers other than those shown in the figure.

In the laminate of this embodiment, the layer consisting of the polarizing plate and the surface protective film has a maximum force F1 (N) and distortion S1 (mm) measured by the above measurement method, that is, the product of the maximum force F1 (N) and distortion S1 (mm) in the deflected state when the piercing tool is vertically lowered on the layer, is 3.70 N·mm or more. The product (K1) of the maximum force F1 (N) and distortion S1 (mm) in the deflected state is preferably 4.5 N·mm or more, more preferably 5.0 N·mm or more, and is usually 10.0 N·mm or less, and preferably 9.0 N·mm or less. In order to set the product (K1) of the force F1 (N) and distortion S1 (mm) in such a range, it is preferable to select and combine, for example, a surface protective film and a polarizing plate. If a surface protection film with a relatively large product (K3) of the maximum force F3 (N) and the strain S3 (mm), i.e., a surface protection film with high rigidity, is used as the surface protection film, the product (K1) of F1 (N) and S1 (mm) will be large. Examples of such surface protection films include a thick surface protection film and a surface protection film made of a hard resin. In addition, even if a polarizing plate with high rigidity is used, the product (K1) of F1 (N) and S1 (mm) will be large.

F1 (N) can be 1.0 N or more and 3.0 N or less, and may be 1.5 N or more and 3.0 N or less. S1 (mm) can be 1.5 mm or more and 5.0 mm or less, and may be 2.0 mm or more and 4.0 mm or less.

The product of the maximum force F1 (N) and the strain S1 (mm) in the bent state can be measured using, for example, a compression tester KES-G5 manufactured by Kato Tech Co., Ltd.
A specific description will be given with reference to FIG. 3, FIG. 4 and FIG.

Here, we explain how to measure the maximum force [F (N)] and [strain S (mm)] when the film to be measured (measurement film) is in a bent state. When the measurement film is a layer consisting of a polarizing plate and a surface protection film, F1 and S1 are measured. When the measurement film is a polarizing plate, F2 and S2 are measured. When the measurement film is a surface protection film, F3 and S3 are measured.

First, the measurement film 3 to be measured is placed on the measurement table 2. The measurement film 3 is a layer consisting of a polarizing plate and a surface protection film, or a polarizing plate alone, or a surface protection film alone. A fixing jig is not required on the measurement film 3. The table 2 has a circular gap (through hole) in the center when viewed from the top, and the diameter of the gap on the top surface (double arrow 44) is 30 mm. The shape of the gap when viewed from the side can be, for example, a shape consisting of a columnar lower part and a hemispherical upper part (bell-shaped), a pyramidal shape (cone-shaped, conical shape), or a shape that becomes thinner toward the tip (tapered shape). The size of the measurement film 3 to be measured is a rectangle of 25 mm (double arrow 43) x 43 mm (double arrow 42).

Next, the piercing jig 1 is lowered vertically from above the placed film 3. At this time, the piercing jig 1 is made to pass through the center of the circular gap. The piercing jig 1 is a needle with a spherical tip, a tip diameter of 1 mmφ, and a curvature of 0.5R (radius of curvature 0.5 mm). The speed at which the piercing jig 1 is lowered is 1.0 cm/sec.

After the tip of the piercing tool (needle) 1 comes into contact with the measurement film 3, the maximum load (N) and strain (mm) that maintains the bent state of the film 3 are measured. That is, as the piercing tool 1 is lowered onto the measurement film 3, wrinkles and folds occur in the measurement film 3 (for example, the folds shown in Figures 4(b) and 5), but in this embodiment, the load and strain (length of double arrow 40) just before that are measured. The bent state of the measurement film 3 refers to a state in which the film 3 is bowed (for example, an arc-shaped, elliptical arc-shaped, catenary-shaped, or other arc-shaped) when viewed from the side (Figure 4(a)).

In the laminate of this embodiment, when the piercing tool is vertically lowered on the polarizing plate alone, the product (K2) of the maximum force F2 (N) and the distortion S2 (mm) in the bent state may be 1.00 N·mm or less, or may be 0.70 N·mm or less. In this case, when the piercing tool is vertically lowered on the surface protection film alone, if the product (K3) of the maximum force F3 (N) and the distortion S3 (mm) in the bent state is 0.50 N·mm or more, it is preferable that the release film is less likely to have a peeling failure. If the product of the maximum force F2 (N) and the distortion S2 (mm) is 0.30 N·mm or less, it is also preferable that the product of the maximum force F3 (N) and the distortion S3 (mm) is 0.30 N·mm or more. When the product of the maximum force F2 (N) and the strain S2 (mm) is 0.20 N·mm or less, it is also preferable that the product of the maximum force F3 (N) and the strain S3 (mm) is 0.50 N·mm or more. Even when a polarizing plate with low rigidity is used, by selecting a surface protection film with high rigidity accordingly, it is possible to reduce peeling failure of the release film. By using such a combination, even when the laminate has a polarizing plate with low rigidity, peeling failure of the release film is unlikely to occur.

The laminate may be obtained by producing a long laminate using a roll-to-roll process while transporting each component that constitutes the laminate, and then cutting the laminate, or by preparing each component of a specific shape and stacking them in sequence.

The shape of the laminate is not particularly limited, but can be a rectangle, a polygon such as a triangle, a circle, an ellipse, or a combination thereof.

When the laminate has a rectangular shape with long and short sides, the length of the long sides is preferably 35 to 5 cm, more preferably 25 to 10 cm, and the length of the short sides is preferably 25 to 5 cm, more preferably 20 to 6 cm. By setting the size within these ranges, peelability can be further improved.

Each member of the laminate will be described below.
<Polarizing Plate>
When the piercing tool is vertically lowered onto the polarizing plate alone, the product (K2) of the maximum force F2 (N) and the strain S2 (mm) in the deflected state is usually 0.10 N·mm or more, preferably 0.15 N·mm or more, more preferably 0.20 N·mm or more, and even more preferably 0.30 N·mm or more. The product (K2) of the maximum force F2 (N) and the strain S2 (mm) may be 1.00 N·mm or less, or 0.70 N·mm or less. Even if the product K2 is 1.00 N·mm or less, the laminate of the present invention can peel off the release film without causing peeling failure. The product (K2) of the maximum force F2 (N) and the strain S2 (mm) can be obtained by the same method as the method of obtaining the product of the maximum force F1 (N) and the strain S1 (mm) described above.

F2 (N) can be 0.20 N or more and 1.0 N or less, and may be 0.3 N or more and 0.8 N or less. S2 (mm) can be 0.5 mm or more and 3.0 mm or less, and may be 1.0 mm or more and 2.0 mm or less.

When the polarizing plate is provided with a protective film on only one side of the polarizer, or when the polarizing plate is provided with a brightness enhancement film, the product (K2) of the maximum force F2 (N) and the strain S2 (mm) tends to be small. The stretching ratio and stretching temperature of the polarizer can also affect the magnitude of the product of the maximum force F2 (N) and the strain S2 (mm). For example, when the stretching ratio of the polarizer is increased, the product (K2) of the maximum force F2 (N) and the strain S2 (mm) tends to be small, and when the stretching ratio of the polarizer is decreased, the product (K2) tends to be large.

The polarizing plate 10 is a polarizing element that includes at least a polarizer, and typically further includes a thermoplastic resin film that is laminated to one or both sides of the polarizing plate. The thermoplastic resin film can be a protective film that protects the polarizer, another film having an optical function, or the like. The thermoplastic resin film may have a resin layer (e.g., at least one optical layer selected from a hard coat layer, an antistatic layer, an antiglare layer, a light diffusion layer, an antireflection layer, a low refractive index layer, an antifouling layer, etc.) laminated on its surface. The thermoplastic resin film can be laminated to the polarizer via an adhesive layer. The surface protection film 30 may be laminated on the surface of this resin layer.

The effect of the present invention is remarkable when the laminate further includes a brightness enhancement film and a retardation layer. A polarizing plate including a brightness enhancement film, etc., has low rigidity and is prone to peeling defects. According to the present invention, even when the laminate includes a brightness enhancement film, etc., the occurrence of peeling defects can be reduced.

The thickness (μm) of the polarizing plate is usually 150 μm or less, and the effect of the present invention is remarkable when the thickness is 75 μm or less, which has low rigidity, or even 70 μm or less. The thickness of the polarizing plate 10 is preferably 30 μm or more, and more preferably 50 μm or more.

(1) Polarizer The polarizer constituting the polarizing plate 10 is an absorption-type polarizer that has the property of absorbing linearly polarized light having a vibration plane parallel to its absorption axis and transmitting linearly polarized light having a vibration plane perpendicular to the absorption axis (parallel to the transmission axis), and a polarizer in which a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol-based resin film can be suitably used. The polarizer can be manufactured, for example, by a method including a step of uniaxially stretching a polyvinyl alcohol-based resin film; a step of dyeing the polyvinyl alcohol-based resin film with the dichroic dye to adsorb it; a step of treating the polyvinyl alcohol-based resin film with the adsorbed dichroic dye with a crosslinking liquid such as an aqueous boric acid solution; and a step of washing with water after the treatment with the crosslinking liquid.

As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate with other monomers that can be copolymerized with vinyl acetate. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group.

In this specification, "(meth)acrylic" means at least one selected from acrylic and methacrylic. The same applies to "(meth)acryloyl" and "(meth)acrylate", etc.

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

A film made from such a polyvinyl alcohol-based resin is used as the raw film for the polarizer. The method for making the polyvinyl alcohol-based resin film is not particularly limited, and any known method can be used. There are no particular limitations on the thickness of the polyvinyl alcohol-based raw film, but in order to make the thickness of the polarizer 15 μm or less, it is preferable to use one with a thickness of 5 to 35 μm. More preferably, it is 20 μm or less.

The uniaxial stretching of the polyvinyl alcohol resin film can be performed before, simultaneously with, or after dyeing with a dichroic dye. When the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before or during the crosslinking treatment. The uniaxial stretching may also be performed in multiple stages.

In uniaxial stretching, the film may be stretched uniaxially between rolls with different peripheral speeds, or may be stretched uniaxially using a heated roll. The uniaxial stretching may be dry stretching in which stretching is performed in the atmosphere, or wet stretching in which the polyvinyl alcohol resin film is stretched in a swollen state using a solvent or water. The stretching ratio is usually 3 to 8 times.

A method for dyeing a polyvinyl alcohol-based resin film with a dichroic dye is, for example, to immerse the film in an aqueous solution containing the dichroic dye. Iodine or a dichroic organic dye is used as the dichroic dye. It is preferable to immerse the polyvinyl alcohol-based resin film in water before the dyeing process.

The crosslinking treatment after dyeing with a dichroic dye usually involves immersing the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid. When iodine is used as the dichroic dye, the aqueous solution containing boric acid preferably contains potassium iodide.

The thickness of the polarizer is usually 30 μm or less, preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. In particular, making the polarizer thickness 15 μm or less is advantageous for making the laminate thinner. The thickness of the polarizer is usually 2 μm or more, and from the viewpoint of providing stiffness to the polarizing plate, it is preferably 3 μm or more.

As the polarizer, for example, as described in JP 2016-170368 A, a polarizer in which a dichroic dye is oriented in a cured film formed by polymerizing a liquid crystal compound may be used. As the dichroic dye, a dye having absorption in a wavelength range of 380 to 800 nm may be used, and it is preferable to use an organic dye. As the dichroic dye, for example, an azo compound may be used.
The liquid crystal compound is a liquid crystal compound that can be polymerized while remaining aligned, and can have a polymerizable group in the molecule.

(2) Protective Film The protective film that can be laminated on one or both sides of the polarizer can be a film made of a light-transmitting (preferably optically transparent) thermoplastic resin, for example, a polyolefin resin such as a chain polyolefin resin (e.g., polypropylene resin) or a cyclic polyolefin resin (e.g., norbornene resin); a cellulose resin such as triacetyl cellulose or diacetyl cellulose; a polyester resin such as polyethylene terephthalate or polybutylene terephthalate; a polycarbonate resin; a (meth)acrylic resin such as a methyl methacrylate resin; a polystyrene resin; a polyvinyl chloride resin; an acrylonitrile-butadiene-styrene resin; an acrylonitrile-styrene resin; a polyvinyl acetate resin; a polyvinylidene chloride resin; a polyamide resin; a polyacetal resin; a modified polyphenylene ether resin; a polysulfone resin; a polyethersulfone resin; a polyarylate resin; a polyamideimide resin; a polyimide resin, or the like.

Examples of linear polyolefin resins include linear olefin homopolymers such as polyethylene resins (polyethylene resins which are homopolymers of ethylene, and copolymers mainly composed of ethylene) and polypropylene resins (polypropylene resins which are homopolymers of propylene, and copolymers mainly composed of propylene), as well as copolymers made of two or more linear olefins.

Cyclic polyolefin resin is a general term for resins polymerized using cyclic olefins as polymerization units, and examples of such resins include those described in JP-A-1-240517, JP-A-3-14882, and JP-A-3-122137. Specific examples of cyclic polyolefin resins include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers (typically random copolymers) of cyclic olefins with linear olefins such as ethylene and propylene, and graft polymers modified with unsaturated carboxylic acids or their derivatives, as well as hydrogenated products thereof. Of these, norbornene resins using norbornene monomers such as norbornene or polycyclic norbornene monomers as the cyclic olefin are preferably used.

Polyester resins are resins having ester bonds, excluding the cellulose ester resins described below, and are generally made of a polycondensation product of a polycarboxylic acid or its derivative and a polyhydric alcohol. As the polycarboxylic acid or its derivative, a divalent dicarboxylic acid or its derivative can be used, such as terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a divalent diol can be used, such as ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol. A representative example of a polyester resin is polyethylene terephthalate, which is a polycondensation product of terephthalic acid and ethylene glycol.

The (meth)acrylic resin is a resin whose main constituent monomer is a compound having a (meth)acryloyl group. Specific examples of the (meth)acrylic resin include poly(meth)acrylic acid ester such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate-(meth)acrylic acid ester copolymer; methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymer; methyl (meth)acrylate-styrene copolymer (MS resin, etc.); and copolymers of methyl methacrylate and compounds having alicyclic hydrocarbon groups (e.g. methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth)acrylate copolymer, etc.). Preferably, a polymer whose main component is poly(meth)acrylic acid C _1-6 alkyl ester such as polymethyl (meth)acrylate is used, and more preferably, a methyl methacrylate resin whose main component is methyl methacrylate (50 to 100% by weight, preferably 70 to 100% by weight) is used.

Cellulose ester resins are esters of cellulose and fatty acids. Specific examples of cellulose ester resins include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Other examples include copolymers of these and those in which some of the hydroxyl groups have been modified with other substituents. Of these, cellulose triacetate (triacetyl cellulose) is particularly preferred.

Polycarbonate resins are engineering plastics made of polymers in which monomer units are bonded via carbonate groups.

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

For example, depending on the mode of the liquid crystal display device, the protective film may be stretched and/or shrunk to provide a suitable retardation value. For example, for the purpose of compensating for the viewing angle, a single-layer or multi-layer retardation layer (or film) may be used as the protective film. In this case, the polarizing plate 10 may be an elliptical or circular polarizing plate including a laminated structure of a polarizer and a retardation layer, or a polarizing plate including a retardation layer and having a viewing angle compensation function.

The thickness of the protective film is usually 1 to 100 μm, but from the viewpoint of strength, handling, etc., it is preferably 5 to 60 μm, more preferably 10 to 55 μm, and even more preferably 15 to 40 μm. If a protective film having a thickness within this range is used as a polarizing plate, it is easy to adjust the product (K2) of F2 (N) and S2 (mm) of the polarizing plate itself having this protective film, and furthermore, the product (K1) of F1 (N) and S1 (mm) of the layer consisting of this polarizing plate and the surface protective film. Specifically, if a thick protective film is used as the protective film within the above range, the product (K2) and the product (K1) tend to be large, and if the thickness is thin within the above range, the product (K2) and the product (K1) tend to be small and flat. In addition, if the thickness of the protective film is within this range, the polarizer is mechanically protected, and the polarizer does not shrink even when exposed to a moist and hot environment, and stable optical properties can be maintained.

In addition, by selecting a material that exhibits high rigidity as the material constituting the protective film, it is possible to adjust the product (K1) of F1 (N) and S1 (mm) and the product (K2) of F2 (N) and S2 (mm). When a material with high rigidity is used as the material constituting the protective film, the product (K1) of F1 (N) and S1 (mm) and the product (K2) of F2 (N) and S2 (mm) tend to be large. When a material with low rigidity is used as the material constituting the protective film, the product (K1) of F1 (N) and S1 (mm) and the product (K2) of F2 (N) and S2 (mm) tend to be small.

When protective films are attached to both sides of the polarizer, these protective films may be made of the same type of thermoplastic resin or different types of thermoplastic resin. They may also have the same thickness or different thicknesses. Furthermore, they may have the same retardation characteristics or different retardation characteristics.

As described above, at least one of the protective films may have a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, a light diffusion layer, an antireflection layer, a low refractive index layer, an antistatic layer, or an antifouling layer on its outer surface (the surface opposite the polarizer). The thickness of the protective film includes the thickness of the surface treatment layer.

From the viewpoint of suppressing the intrusion of air bubbles between the surface protection film and the polarizing plate, it is preferable that the surface of the polarizing plate 10 on the surface protection film 30 side (the surface to which the surface protection film 30 is attached, which may be a surface treatment layer) has a small arithmetic mean roughness Ra in accordance with JIS B 0601:2013. Specifically, the Ra of the above surface is preferably 0.3 μm or less, more preferably 0.2 μm or less, and even more preferably 0.15 μm or less. The Ra of the above surface is usually 0.001 μm or more, for example 0.005 μm or more.

The protective film can be attached to the polarizer, for example, via an adhesive layer. The adhesive that forms the adhesive layer can be a water-based adhesive, an active energy ray-curable adhesive, or a heat-curable adhesive, and is preferably a water-based adhesive or an active energy ray-curable adhesive.

Examples of water-based adhesives include adhesives made of an aqueous solution of polyvinyl alcohol-based resins, and water-based two-liquid urethane-based emulsion adhesives. Of these, water-based adhesives made of an aqueous solution of polyvinyl alcohol-based resins are preferably used. Examples of polyvinyl alcohol-based resins that can be used include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, polyvinyl alcohol copolymers obtained by saponifying a copolymer of vinyl acetate and other monomers that can be copolymerized with it, and modified polyvinyl alcohol polymers in which the hydroxyl groups of these copolymers are partially modified. Water-based adhesives can contain crosslinking agents such as aldehyde compounds (such as glyoxal), 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 process to remove water contained in the water-based adhesive after laminating the polarizer and the protective film. After the drying process, a curing process may be carried out, for example, at a temperature of 20 to 45°C.

The above-mentioned active energy ray curable adhesive is an adhesive containing a curable compound that cures when irradiated with active energy rays such as ultraviolet light, visible light, electron beams, and X-rays, and is preferably an ultraviolet ray curable adhesive.

The curable compound may 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), an oxetane compound (a compound having one or more oxetane rings in the molecule), or a combination thereof. Examples of the radical polymerizable curable compound include a (meth)acrylic compound (a compound having one or more (meth)acryloyloxy groups in the molecule), other vinyl compounds having a radical polymerizable double bond, or a combination thereof. A cationic polymerizable curable compound and a radical polymerizable curable compound may be used in combination. The active energy ray curable adhesive usually further contains a cationic polymerization initiator and/or a radical polymerization initiator for initiating the curing reaction of the curable compound.

When laminating the polarizer and the protective film, at least one of the lamination surfaces may be subjected to a surface activation treatment in order to enhance adhesion. Examples of surface activation treatments include dry treatments such as corona treatment, plasma treatment, discharge treatment (glow discharge treatment, etc.), flame treatment, ozone treatment, UV ozone treatment, and ionizing active ray treatment (ultraviolet ray treatment, electron beam treatment, etc.); and wet treatments such as ultrasonic treatment using a solvent such as water or acetone, saponification treatment, and anchor coat treatment. These surface activation treatments may be performed alone or in combination of two or more.

When protective films are attached to both sides of a polarizer, the adhesive used to attach these protective films may be the same type of adhesive or different types of adhesive.

(3) Other Films The polarizing plate 10 may include other films other than the polarizer and the protective film, typical examples of which are a brightness enhancement film and a retardation layer. When the polarizing plate 10 includes other films, the surface protective film 30 may be laminated on the surface of the other films or on the surface of a surface treatment layer laminated on the other films.

The brightness enhancement film is also called a reflective polarizer, and a polarization conversion element having a function of separating light emitted from a light source (backlight) into transmitted polarized light and reflected polarized light or scattered polarized light is used. By disposing the brightness enhancement film on the polarizer, the output efficiency of the linearly polarized light output from the polarizer can be improved by utilizing the retroreflected light, which is reflected polarized light or scattered polarized light. The brightness enhancement film can be laminated on the polarizer via an adhesive layer.
Another film, such as a protective film, may be interposed between the polarizer and the brightness enhancing film.

The brightness enhancement film can be, for example, an anisotropic reflective polarizer. One example of an anisotropic reflective polarizer is an anisotropic multi-layer thin film that transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction, a specific example of which is "APF" manufactured by 3M. Another example of an anisotropic reflective polarizer is a composite of a cholesteric liquid crystal layer and a λ/4 plate, a specific example of which is "PCF" manufactured by Nitto Denko Corporation. Yet another example of an anisotropic reflective polarizer is a reflective grid polarizer, a specific example of which is a metal grid reflective polarizer that is microfabricated on metal to emit reflective polarized light even in the visible light region, and a film that is stretched by adding metal fine particles to a polymer matrix.

As described above, the outer surface of the brightness enhancement film may be provided with a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, a light diffusion layer, a retardation layer (e.g., a retardation layer having a retardation value of 1/4 wavelength), an antireflection layer, a low refractive index layer, an antistatic layer, or an antifouling layer. The formation of such layers can improve adhesion to the backlight tape and the uniformity of the displayed image. The thickness of the brightness enhancement film 50 is usually 10 to 100 μm, but is preferably 10 to 50 μm, and more preferably 10 to 30 μm.

Examples of retardation layers include a quarter-wave (λ/4) plate, a half-wave (λ/2) plate, and a positive C plate. The λ/4 plate is a layer whose in-plane retardation value Re(550) at a wavelength of 550 [nm] satisfies the relationship 100 nm≦Re(550)≦200 nm. The λ/4 plate may exhibit reverse wavelength dispersion that satisfies Re(450)<Re(550)<Re(650). The λ/2 plate is a layer whose Re(550) satisfies 210 nm≦Re(550)≦300 nm. The positive C plate satisfies the relationship Nz>Nx≧Ny, and it is preferable that the retardation value Rth(λ) in the thickness direction at a wavelength λ [nm] satisfies the relationship -300 nm≦Rth(550)≦-20 nm.

The retardation layer can be formed, for example, from the resins exemplified as the materials for the protective film, and among these, cyclic olefin resins and styrene resins are preferred. The retardation layer may be formed from a single layer or multiple layers. A retardation layer having multiple layers may include, for example, a resin film (substrate film) exemplified as the material for the protective film, and a layer in which a liquid crystal compound is polymerized and cured, or a layer in which multiple (e.g., two) layers in which a liquid crystal compound is cured. The layer having a retardation can be a resin film and/or a layer in which a liquid crystal compound is cured. The resin film can also serve as the protective film.

The retardation layer may consist of one type of retardation layer, or may consist of multiple types of retardation layers. When the retardation layer consists of multiple retardation layers, a combination of a quarter-wave plate and a half-wave plate, or a combination of a quarter-wave plate and a positive C plate is preferred.

The retardation layer preferably includes a layer in which the liquid crystal compound is hardened, and when the retardation layer is composed of a plurality of layers, each of the retardation layers may include a layer in which the liquid crystal compound is hardened. Although the type of liquid crystal compound is not particularly limited, it can be classified into a rod-shaped type (rod-shaped liquid crystal compound) and a disk-shaped type (disk-shaped liquid crystal compound, discotic liquid crystal compound) based on its shape. Furthermore, there are low molecular type and polymer type. Note that a polymer generally refers to a polymer with a degree of polymerization of 100 or more (Polymer Physics, Phase Transition Dynamics, Masao Doi, page 2, Iwanami Shoten, 1992). In this embodiment, any liquid crystal compound can be used. Furthermore, two or more rod-shaped liquid crystal compounds, two or more disk-shaped liquid crystal compounds, or a mixture of a rod-shaped liquid crystal compound and a disk-shaped liquid crystal compound may be used.

As the rod-shaped liquid crystal compound, for example, those described in claim 1 of JP-T-11-513019 or paragraphs [0026] to [0098] of JP-A-2005-289980 can be preferably used. As the discotic liquid crystal compound, for example, those described in paragraphs [0020] to [0067] of JP-A-2007-108732 or paragraphs [0013] to [0108] of JP-A-2010-244038 can be preferably used.

It is more preferable to form the retardation layer using a liquid crystal compound having a polymerizable group (a rod-shaped liquid crystal compound or a discotic liquid crystal compound). This makes it possible to reduce temperature and humidity changes in the optical properties.

The liquid crystal compound may be a mixture of two or more kinds. In that case, it is preferable that at least one of them has two or more polymerizable groups. In other words, it is preferable that the retardation layer is a layer formed by fixing a rod-shaped liquid crystal compound having a polymerizable group or a discotic liquid crystal compound having a polymerizable group by polymerization. In this case, it is no longer necessary for the liquid crystal to show liquid crystallinity after it has become a layer.

The type of polymerizable group contained in the rod-shaped liquid crystal compound or discotic liquid crystal compound is not particularly limited, and is preferably a functional group capable of an addition polymerization reaction, such as a polymerizable ethylenically unsaturated group or a ring-polymerizable group. More specifically, examples of such a functional group include a (meth)acryloyl group, a vinyl group, a styryl group, and an allyl group. Among these, a (meth)acryloyl group is preferable. The (meth)acryloyl group is a concept that includes both a methacryloyl group and an acryloyl group.

The method for forming the retardation layer is not particularly limited, and known methods can be used. For example, a composition for forming an optically anisotropic layer (hereinafter simply referred to as "composition") containing a liquid crystal compound having a polymerizable group is applied to a specific substrate (including a temporary substrate) to form a coating film, and the resulting coating film is subjected to a curing treatment (irradiation with ultraviolet rays (light irradiation treatment) or heat treatment) to produce a retardation layer. The produced retardation layer can be transferred onto a polarizer or a protective film, for example.

The composition can be applied by known methods, such as wire bar coating, extrusion coating, direct gravure coating, reverse gravure coating, and die coating.

The composition may contain components other than the liquid crystal compound described above. For example, the composition may contain a polymerization initiator. The polymerization initiator used may be, for example, a thermal polymerization initiator or a photopolymerization initiator, depending on the type of polymerization reaction. For example, photopolymerization initiators include α-carbonyl compounds, acyloin ethers, α-hydrocarbon-substituted aromatic acyloin compounds, polynuclear quinone compounds, and combinations of triaryl imidazole dimers and p-aminophenyl ketones. The amount of polymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the total solid content of the composition.

The composition may also contain a polymerizable monomer from the viewpoint of the uniformity and strength of the coating film. Examples of the polymerizable monomer include radically polymerizable or cationic polymerizable compounds. Among them, polyfunctional radically polymerizable monomers are preferred.

The polymerizable monomer is preferably one that is copolymerizable with the above-mentioned liquid crystal compound containing a polymerizable group. Specific examples of the polymerizable monomer include those described in paragraphs [0018] to [0020] of JP-A No. 2002-296423. The amount of the polymerizable monomer used is preferably 1 to 50% by mass, and more preferably 2 to 30% by mass, based on the total mass of the liquid crystal compound.

The composition may also contain a surfactant from the viewpoint of the uniformity and strength of the coating film. Examples of surfactants include conventionally known compounds. Among them, fluorine-based compounds are particularly preferred.

The composition may contain a solvent, and an organic solvent is preferably used. Examples of the organic solvent include amides (e.g., N,N-dimethylformamide), sulfoxides (e.g., dimethyl sulfoxide), heterocyclic compounds (e.g., pyridine), hydrocarbons (e.g., benzene, hexane), alkyl halides (e.g., chloroform, dichloromethane), esters (e.g., methyl acetate, ethyl acetate, butyl acetate), ketones (e.g., acetone, methyl ethyl ketone), and ethers (e.g., tetrahydrofuran, 1,2-dimethoxyethane).
Among these, alkyl halides and ketones are preferred. Two or more kinds of organic solvents may be used in combination.

The composition may also contain various alignment agents, such as vertical alignment promoters, such as a polarizer interface side vertical alignment agent and an air interface side vertical alignment agent, and horizontal alignment promoters, such as a polarizer interface side horizontal alignment agent and an air interface side horizontal alignment agent. Furthermore, the composition may contain, in addition to the above components, an adhesion improver, a plasticizer, a polymer, etc.

The retardation layer may include an alignment film that has the function of determining the alignment direction of the liquid crystal compound. The alignment film generally contains a polymer as the main component. Polymer materials for the alignment film are described in many documents, and many commercial products are available. Among them, it is preferable to use polyvinyl alcohol, polyimide, or derivatives thereof as the polymer material, and it is particularly preferable to use modified or unmodified polyvinyl alcohol.

The alignment film is usually subjected to a known alignment treatment. For example, rubbing treatment or photo-alignment treatment using polarized light is included. From the viewpoint of the surface roughness of the alignment film, photo-alignment treatment is preferred.

The thickness of the layer in which the liquid crystal compound is cured is not particularly limited, but is preferably 0.5 to 10 μm, and more preferably 1.0 to 5 μm. The thickness of the alignment film is not particularly limited, but is often 20 μm or less, and is preferably 0.01 to 10 μm, more preferably 0.01 to 5 μm, and even more preferably 0.01 to 1 μm.

(4) Adhesive Layer The polarizing plate 10 preferably has an adhesive layer 15 on its outermost surface. This adhesive layer can be used to attach the polarizing plate 10 to a display element (e.g., a liquid crystal cell, an organic EL element) or other optical member, and is an adhesive layer that is exposed by peeling off the release film 20. The adhesive layer can also be used to laminate a polarizer, a protective film, a brightness improvement film, and a retardation layer. In FIG. 1, the adhesive layer 16 corresponds to this. The adhesive layer can be composed of an adhesive composition mainly composed of a resin such as a (meth)acrylic, rubber, urethane, ester, silicone, or polyvinyl ether resin. Among them, an adhesive composition having a (meth)acrylic resin as a base polymer, which is excellent in transparency, weather resistance, heat resistance, etc., is preferable. The adhesive composition may be an active energy ray curable type or a heat curable type.

As the (meth)acrylic resin (base polymer) used in the adhesive composition, for example, a polymer or copolymer containing one or more (meth)acrylic acid esters as monomers, such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, is preferably used. It is preferable to copolymerize a polar monomer into the base polymer. Examples of polar monomers include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc., such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

The adhesive composition may contain only the base polymer, but usually further contains a crosslinking agent. Examples of crosslinking agents include divalent or higher metal ions that form metal carboxylates with carboxyl groups; polyamine compounds that form amide bonds with carboxyl groups; polyepoxy compounds or polyols that form ester bonds with carboxyl groups; and polyisocyanate compounds that form amide bonds with carboxyl groups. Of these, polyisocyanate compounds are preferred.

An active energy ray curable adhesive composition is an adhesive composition that has the property of being cured when exposed to active energy rays such as ultraviolet rays or electron beams, that has adhesiveness even before exposure to active energy rays and can be adhered to an adherend such as a film, and that has the property of being cured by exposure to active energy rays and capable of adjusting the adhesive strength. The active energy ray curable adhesive composition is preferably an ultraviolet ray curable type. The active energy ray curable adhesive composition further contains an active energy ray polymerizable compound in addition to a base polymer and a crosslinking agent. If necessary, a photopolymerization initiator, a photosensitizer, etc. may also be contained.

The adhesive composition may contain additives such as fine particles for imparting light scattering properties, beads (e.g., resin beads, glass beads), glass fibers, resins other than the base polymer, antistatic agents, tackifiers, fillers (e.g., metal powders and other inorganic powders), antioxidants, UV absorbers, dyes, pigments, colorants, defoamers, corrosion inhibitors, and photopolymerization initiators.

The adhesive layer can be formed by applying an organic solvent dilution of the adhesive composition onto a substrate and drying it. The substrate can be a polarizer, a protective film, another optical film such as a brightness enhancing film, a release film (e.g., release film 20), etc. When an active energy ray curable adhesive composition is used, the formed adhesive layer can be irradiated with active energy rays to form a cured product having the desired degree of cure.

The thickness of the adhesive layer 15 is usually 1 to 40 μm, but from the viewpoint of making the laminate thin and suppressing dimensional changes in the polarizing plate 10 while maintaining good processability, it is preferably 3 to 25 μm (for example, 3 to 20 μm, or even 3 to 15 μm). The thickness of the adhesive layer 16 is usually 1 to 20 μm, but preferably 3 to 10 μm.

The adhesive layer 15 on which the release film 20 is laminated can have an adhesion to the release film of 0.20 N/25 mm or less, preferably 0.10 N/25 mm or less, more preferably 0.05 N/25 mm or less, and may be 0.04 or less. By having such an adhesion, the polarizing plate does not float when the release film is peeled off, and the peelability is further improved. In addition, the adhesion is 0.02 N/25 mm or more. By having such an adhesion, it is easy to prevent a gap from occurring between the release film and the adhesive layer even if an impact is applied to the laminate during transportation, etc. In this specification, the adhesion of the adhesive layer to the release film is a value measured by the method described in the examples below.

<Surface protection film>
The surface protective film 30 can include a base film 31 and a pressure-sensitive adhesive layer 32 laminated thereon. The surface protective film 30 is a film for protecting the surface of the polarizing plate 10, and is usually peeled off and removed together with the pressure-sensitive adhesive layer thereof after the laminate is attached to, for example, a display element or other optical members.

When the piercing tool is lowered vertically onto the surface protection film alone, the product (K3) of the maximum force F3 (N) and the distortion S3 (mm) in the deflected state is preferably 0.15 N·mm or more, more preferably 0.25 N·mm or more, and even more preferably 0.40 N·mm or more. The product (K3) of the maximum force F3 (N) and the distortion S3 (mm) is 1.00 N·mm or less, and may be 0.90 N·mm or less, 0.80 N·mm or less, 0.70 N·mm or less, or 0.60 N·mm or less. The product (K3) of the maximum force F3 (N) and the distortion S3 (mm) can be calculated using the same method as the above-mentioned method for calculating the product of the maximum force F1 (N) and the distortion S1 (mm).

F3 (N) can be 0.20 N or more and 1.0 N or less, and may be 0.3 N or more and 0.6 N or less. S3 (mm) can be 0.3 mm or more and 3.0 mm or less, and may be 0.5 mm or more and 2.0 mm or less.

Surface protection films are generally stiffer than brightness-enhancing films, which is important for improving the releasability of the release film. In this specification, the thickness of the surface protection film is the sum of the thickness of the base film and the thickness of the adhesive layer laminated thereon, and is preferably 30 μm or more, more preferably 50 μm or more. On the other hand, if the thickness of the surface protection film is too large, peeling is likely to occur between the surface protection film and the polarizing plate when the release film is peeled off, so the thickness of the surface protection film is preferably 100 μm or less, more preferably 70 μm or less. However, even if the thickness is the same, the product of the maximum force F3 (N) and the strain S3 (mm) may differ depending on the material, manufacturing method, etc.

The substrate film is preferably a thermoplastic resin film. Examples of the thermoplastic resin constituting the thermoplastic resin film include polyolefin resins such as polyethylene resins and polypropylene resins; cyclic polyolefin resins; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polycarbonate resins; (meth)acrylic resins, etc. The substrate film may have a single layer structure or a multilayer structure.

The thickness of the substrate film can be 20 to 150 μm (e.g., 30 to 80 μm, preferably 30 to 60 μm). The configuration of the adhesive layer is basically the same as that described above for the adhesive layer of the polarizing plate.

In particular, the pressure-sensitive adhesive layer preferably has a storage modulus of 0.15 MPa or less at 80°C, more preferably 0.14 MPa or less, and even more preferably 0.10 MPa or less. Typically, the storage modulus of the pressure-sensitive adhesive layer at 80°C is 0.01 MPa or more. In this specification, the storage modulus of the pressure-sensitive adhesive layer can be measured using a commercially available viscoelasticity measuring device, for example, the viscoelasticity measuring device "DYNAMIC ANALYZER RDA II" manufactured by REOMETRIC.

The surface protection film 30 may contain an antistatic agent. The antistatic agent may be contained in the adhesive layer, for example. Instead of or in addition to containing an antistatic agent in the adhesive layer, an antistatic layer containing an antistatic agent may be provided on the surface of the base film opposite to the surface on which the adhesive layer is laminated.

The antistatic agent may be an ionic compound, which is a compound having an inorganic or organic cation and an inorganic or organic anion.
Two or more ionic compounds may be used.

<Release film>
The release film 20 is a film that is temporarily attached to protect the surface of the adhesive layer until it is attached to a display element (e.g., a liquid crystal cell, an organic EL element) or other optical member. The release film 20 can adjust the adhesion to the adhesive layer 15 by performing a release treatment on one side of the release film 20 using a silicone-based, fluorine-based or other release agent. The release film 20 is made of a release-treated thermoplastic resin film, and the adhesive layer can be attached to the release-treated surface.

The thermoplastic resin constituting the release film 20 can be, for example, a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, or a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate. The thickness of the release film 20 is, for example, 10 to 50 μm.

The laminates 100 to 103 can be attached to a display element (e.g., a liquid crystal cell, an organic EL element) by peeling off the release film 20. Furthermore, the laminates can be incorporated into a display device (e.g., a liquid crystal display device, an organic EL display device) by peeling off the surface protection film 30. When constructing a display device, the laminate 10 according to the present invention may be used for a polarizing plate arranged on the viewing side, may be used for a polarizing plate arranged on the backlight side, or may be used for polarizing plates on both the viewing side and the backlight side.

For example, the release film can be peeled off from the laminate as follows. The surface of the laminate on the surface protective film side is fixed to a holding stand, and a release tape is attached onto the release film. The method of fixing the laminate is not particularly limited, and the laminate may be fixed by suction force from the surface protective film side, or may be fixed by adhesive force. From the viewpoint of not leaving a mark on the polarizing plate, the adhesion force between the fixed surface protective film and the holding stand is preferably 0.1 to 0.3 N/60 mm, and more preferably 0.15 to 0.2 N/60 mm. The laminate of the present invention exhibits good releasability even when fixed with such a small pressure.
The position where the release tape is attached is not particularly limited, and when the laminate is rectangular, it can be attached to any of the four corners (diagonal parts) or the center of any of the four sides. The release tape may be attached to one place on the release film, or to multiple places. The release tape is then raised to peel off the release film. The peeling angle can be 90 to 180°, and the peeling speed can be 0.1 to 10 m/min.

The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

(1) Method of measuring stiffness (F x S) Using a compression tester KES-G5 manufactured by Kato Tech Co., Ltd., the maximum force F (N) and strain S (mm) when each film was bent were measured, and the product of the two was calculated. A specific description will be given with reference to Figs. 3 and 4. The size of the measurement film 3 was a rectangle with a short side of 25 mm (double arrow 43) x a long side of 43 mm (double arrow 42). For the piercing jig 1, a needle with a spherical tip, a tip diameter of 1 mmφ, and a curvature of 0.5R was used. As shown in Fig. 3, the film 3 to be measured was placed on the table 2, and the piercing jig 1 was lowered vertically onto the film 3. The table 2 on which the film 3 was placed had a circular hole extending from the upper surface to the lower surface, with the upper hole diameter (double arrow 44) being 30 mm, and the lower hole diameter (double arrow 41) being 10 mm. The load on the piercing jig 1 was 1 kg, and the descending speed of the piercing jig was 1.0 cm/sec. After the piercing jig 1 came into contact with the film 3 to be measured, the maximum load (N) and distortion (the length of the double-headed arrow 40 in FIG. 4( a)) (mm) of the film in a warped state (the state immediately before wrinkles or folds were generated) were measured.

(2) Method for Measuring Film Thickness Measurement was performed using a digital micrometer MH-15M manufactured by Nikon Corporation.

(3) Method for Measuring Adhesion Strength The adhesion strength between the release film and the pressure-sensitive adhesive layer of the polarizing plate was measured using an Autograph (registered trademark) AGS-X, which is a bench-top precision universal testing machine manufactured by Shimadzu Corporation.

(4) Evaluation method of peelability of release film The laminate produced in each example was fixed to a glass plate (holding table) so that the surface protective film was on the lower side. An adhesive sheet was used for fixing, and the force (adhesion) of fixing was 0.1 to 0.3 N/60 mm. A release tape was attached to one of the four corners of the release film so that the long side direction of the release tape was parallel to the long side direction of the laminate. The release tape used was No. 315, a polyester adhesive tape manufactured by Nitto Denko Corporation, with a width of 12 mm and a length of the attached part of 10 mm. One end of the release tape was gripped with a chuck, and the release film was peeled off. The peeling speed was 3 m/min, and the peeling angle was 180°. At this time, if the layer consisting of the polarizing plate and the surface protective film floated off the glass to which the laminate was fixed, it was judged as poor peeling (NG), and if the release film could be peeled off without floating off, it was judged as good peeling (OK).

[Example 1]
The laminate was prepared as follows.
A polarizer (thickness 5 μm) in which iodine was adsorbed and oriented in a polyvinyl alcohol resin was produced. A cyclic olefin resin (COP) film (manufactured by Zeon Corporation, thickness 30 μm) on which a hard coat layer was formed was attached to one surface of the polarizer via a UV-curable adhesive, and a retardation layer (thickness 20 μm) made of a cyclic olefin resin was attached to the other surface of the polarizer via the same adhesive.
Next, a retardation layer (thickness 5 μm) including a layer in which a polymerizable liquid crystal compound was cured was formed on the cyclic olefin resin film. An acrylic adhesive layer (thickness 20 μm) was formed on a release film (thickness 38 μm) made of a polyester resin film, and this acrylic adhesive layer was laminated on the retardation layer. A surface protection film (thickness 65 μm in total of the substrate film and the acrylic adhesive layer) made of a substrate film (thickness 50 μm) and an acrylic adhesive layer (thickness 15 μm) made of a polyester resin was prepared, and this acrylic adhesive layer was laminated on the cyclic olefin resin film on which the hard coat layer was formed to obtain a film.

The obtained film was cut into a rectangle with a long side of 26.6 cm and a short side of 20.0 cm to obtain a laminate. The laminate had a layer structure of release film/adhesive layer/retardation layer (layer of hardened liquid crystal compound)/retardation layer (COP film)/polarizer/COP film with hard coat layer formed/surface protection film. The thickness of the polarizing plate in this laminate [adhesive layer/retardation layer (layer of hardened liquid crystal compound)/retardation layer (COP film)/polarizer/COP film with hard coat layer formed] was 80 μm, the thickness of the release film was 38 μm, and the thickness of the surface protection film was 65 μm.

In addition, the release film (38 μm) was peeled off from the film obtained above, leaving the adhesive layer, to obtain a layer consisting of a polarizing plate and a surface protection film. This layer was cut into a rectangle of 25 mm x 43 mm to obtain measurement film 3, and the maximum force (F) in the deflected state was measured using the above measurement method, which was designated as F1, and the distortion (S) was measured and designated as S1.
From the film obtained above, the release film (thickness 38 μm) was peeled off leaving the adhesive layer, and the surface protective film (thickness 65 μm) was further peeled off to obtain a polarizing plate (thickness 80 μm). This polarizing plate was cut into a rectangle of 25 mm x 43 mm to be used as a measurement film 3, and the maximum force (F) in the warped state was measured by the above measurement method to be F2, and the maximum strain (S) in the warped state was measured to be S2. The surface protective film used above was cut into a rectangle of 25 mm x 43 mm to be used as a measurement film, and the maximum force (F) in the warped state was measured by the above measurement method to be F3, and the strain (S) in the warped state was measured to be S3. As a result, F1 = 2.69 N, S1 = 3.4 mm, F2 = 0.52 N, S2 = 1.1 mm, F3 = 0.46 N, and S3 = 1.6 mm.

The adhesion strength between the adhesive layer and the release film was 0.04 N/25 mm, and no peeling was observed between the adhesive layer and the release film due to transportation or other reasons.

[Example 2]
The laminate was prepared as follows.
A polarizer (thickness 8 μm) in which iodine was adsorbed and aligned in a polyvinyl alcohol resin was produced. A cyclic olefin resin film (manufactured by Zeon Corporation, thickness 30 μm) on which a hard coat layer was formed was attached to one surface of this polarizer via a water-based adhesive. A surface protection film (manufactured by Fujimori Kogyo Co., Ltd., product name FS-PF) consisting of a base film (thickness 38 μm) made of a polyester resin and an acrylic adhesive layer (thickness 17 μm) was prepared, and this acrylic adhesive layer was laminated on the cyclic olefin resin film on which the hard coat layer was formed.

The following laminated film was attached to the other surface of the polarizer via a UV-curable adhesive. This laminated film has a structure in which a retardation layer (thickness 1 μm, thickness direction retardation value Rth(590) = -110 to -150 nm) made of a cured polymerizable liquid crystal compound is laminated on a retardation layer (manufactured by Zeon Corporation, thickness 20 μm, in-plane retardation value Re(590) = 120 to 150 nm) made of a cyclic olefin resin film. The laminated film was attached so that the surface to be attached to the polarizer was the COP film surface of the laminated film.

An acrylic adhesive layer (Lintec Corporation, thickness 13 μm, #KC1) was formed on a release film (thickness 38 μm) made of a polyester resin film, and this acrylic adhesive layer was laminated on the retardation layer.

The obtained film was cut into a rectangle with a long side of 26.6 cm and a short side of 20.0 cm to obtain a laminate. The laminate had a layer structure of release film/adhesive layer/retardation layer (layer of hardened liquid crystal compound)/retardation layer (COP film)/polarizer/COP film with hard coat layer formed/surface protection film. The polarizing plate had a thickness of 72 μm, the release film had a thickness of 38 μm, and the surface protection film had a thickness of 55 μm.

Furthermore, F1 = 2.23 N, S1 = 2.6 mm, F2 = 0.56 N, S2 = 1.5 mm, F3 = 0.30 N, and S3 = 0.7 mm.

The adhesion strength between the adhesive layer and the release film was 0.02 N/25 mm, and no peeling was observed between the adhesive layer and the release film due to transportation, etc.

[Example 3]
The laminate was prepared as follows.
A polarizer (thickness 8 μm) in which iodine was adsorbed and aligned in a polyvinyl alcohol resin was produced. A cyclic olefin resin film (manufactured by Zeon Corporation, thickness 30 μm) on which a hard coat layer was formed was attached to one surface of this polarizer via a water-based adhesive. A surface protection film (manufactured by Fujimori Kogyo Co., Ltd., product name FS-PF) consisting of a base film (thickness 38 μm) made of a polyester resin and an acrylic adhesive layer (thickness 17 μm) was prepared, and this acrylic adhesive layer was laminated on the cyclic olefin resin film on which the hard coat layer was formed.

The following laminated film was attached to the other surface of the polarizer via an ultraviolet-curable adhesive.
This laminated film has a structure in which a retardation layer (thickness 1 μm, thickness direction retardation value Rth (590) = -110 to -150 nm) made of a cured polymerizable liquid crystal compound is laminated on a retardation layer (manufactured by Nippon Zeon Co., Ltd., thickness 22 μm, in-plane retardation value Re (590) = 120 to 150 nm) made of a cyclic olefin resin film. The laminated film was laminated so that the surface to be bonded to the polarizer was the COP film surface of the laminated film. An acrylic adhesive layer (manufactured by Lintec Corporation, thickness 13 μm, #KC1) was formed on a release film (thickness 38 μm) made of a polyester resin film with a smaller amount of silicone than that in Example 2, and this acrylic adhesive layer was laminated on the retardation layer.

The obtained film was cut into a rectangle with a long side of 26.6 cm and a short side of 20.0 cm to obtain a laminate. The laminate had a layer structure of release film/adhesive layer/retardation layer (layer of hardened liquid crystal compound)/retardation layer (COP film)/polarizer/COP film with hard coat layer formed/surface protection film. The polarizing plate had a thickness of 74 μm, the release film had a thickness of 38 μm, and the surface protection film had a thickness of 55 μm.

Furthermore, F1 = 2.15 N, S1 = 3.4 mm, F2 = 0.61 N, S2 = 1.6 mm, F3 = 0.30 N, and S3 = 0.7 mm.

The adhesion strength between the adhesive layer and the release film was 0.04 N/25 mm, and no peeling was observed between the adhesive layer and the release film due to transportation or other reasons.

[Example 4]
The laminate was prepared as follows.
A polarizer (thickness 8 μm) in which iodine was adsorbed and aligned in a polyvinyl alcohol resin was prepared. A brightness-enhancing film (manufactured by 3M, APF-V3, thickness 30 μm) was attached to one surface of the polarizer via an adhesive layer (thickness 5 μm), and a cyclic olefin resin film (manufactured by Nippon Zeon Co., Ltd., thickness 13 μm) was attached to the other surface of the polarizer via an ultraviolet-curable adhesive. An acrylic adhesive layer (Lintec Corporation, thickness 13 μm, #KC1) was formed on a release film (thickness 38 μm) made of a polyester resin film, and this acrylic adhesive layer was laminated on the cyclic olefin resin film. A surface protection film (manufactured by San-A Chemical Co., Ltd., product name OF-PF) made of a base film (thickness 38 μm) made of a polyester resin and an acrylic adhesive layer (thickness 15 μm) was prepared, and this acrylic adhesive layer was laminated on the brightness-enhancing film.

The obtained film was cut into a rectangle with a long side of 26.6 cm and a short side of 20.0 cm to obtain a laminate. The laminate had a layer structure of release film/adhesive layer/COP film/polarizer/adhesive layer/brightness enhancing film/surface protection film. The polarizing plate had a thickness of 69 μm, the release film had a thickness of 38 μm, and the surface protection film had a thickness of 53 μm.

Furthermore, F1 = 1.62 N, S1 = 3.5 mm, F2 = 0.61 N, S2 = 1.6 mm, F3 = 0.21 N, and S3 = 0.7 mm.

The adhesion strength between the adhesive layer and the release film was 0.02 N/25 mm, and no peeling was observed between the adhesive layer and the release film due to transportation, etc.

[Example 5]
The laminate was prepared as follows.
A polarizer (thickness 8 μm) in which iodine was adsorbed and aligned in a polyvinyl alcohol resin was prepared. A brightness enhancement film (manufactured by 3M, APF-V4, thickness 20 μm) was attached to one surface of the polarizer via an adhesive layer (thickness 15 μm), and a cyclic olefin resin film (manufactured by Nippon Zeon Co., Ltd., thickness 13 μm) was attached to the other surface of the polarizer via an ultraviolet-curable adhesive. An acrylic adhesive layer (Lintec Corporation, thickness 13 μm, #KC1) was formed on a release film (thickness 38 μm) made of a polyester resin film, and this acrylic adhesive layer was laminated on the cyclic olefin resin film. A surface protection film (manufactured by Fujimori Kogyo Co., Ltd., product name FY-PF) made of a base film (thickness 50 μm) made of a polyester resin and an acrylic adhesive layer (thickness 15 μm) was prepared, and this acrylic adhesive layer was laminated on the brightness enhancement film.

The obtained film was cut into a rectangle with a long side of 26.6 cm and a short side of 20.0 cm to obtain a laminate. The laminate had a layer structure of release film/adhesive layer/COP film/polarizer/adhesive layer/brightness enhancing film/surface protection film. The polarizing plate had a thickness of 69 μm, the release film had a thickness of 38 μm, and the surface protection film had a thickness of 65 μm.

Furthermore, F1 = 1.62 N, S1 = 2.4 mm, F2 = 0.25 N, S2 = 0.7 mm, F3 = 0.42 N, and S3 = 1.3 mm.

The adhesion strength between the adhesive layer and the release film was 0.02 N/25 mm, and no peeling was observed between the adhesive layer and the release film due to transportation, etc.

[Comparative Example 1]
The laminate was prepared as follows.
A polarizer (thickness 8 μm) in which iodine was adsorbed and aligned in a polyvinyl alcohol-based resin was produced. In producing the polarizer, the stretching ratio was set higher than that of the polarizer of Example 5. A brightness enhancing film (manufactured by 3M, APF-V4, thickness 20 μm) was attached to one surface of the polarizer via a pressure-sensitive adhesive layer (thickness 15 μm), and a cyclic olefin-based resin film (manufactured by Nippon Zeon Co., Ltd., thickness 13 μm) was attached to the other surface of the polarizer via a UV-curable adhesive. An acrylic pressure-sensitive adhesive layer (Lintec Corporation, thickness 13 μm, #KC1) was formed on a release film (thickness 38 μm) made of a polyester-based resin film, and the acrylic pressure-sensitive adhesive layer was laminated on the cyclic olefin-based resin film. A surface protection film (manufactured by Fujimori Kogyo Co., Ltd., product name AY-XA35) consisting of a base film (thickness 38 μm) made of a polyester resin and an acrylic adhesive layer (thickness 15 μm) was prepared, and this acrylic adhesive layer was laminated on the brightness enhancement film.

The obtained film was cut into a rectangle with a long side of 26.6 cm and a short side of 20.0 cm to obtain a laminate. The laminate had a layer structure of release film/adhesive layer/cyclic olefin resin film/polarizer/adhesive layer/brightness enhancement film/surface protection film. The polarizing plate had a thickness of 69 μm, the release film had a thickness of 38 μm, and the surface protection film had a thickness of 53 μm.

Furthermore, F1 = 1.09 N, S1 = 2.1 mm, F2 = 0.24 N, S2 = 0.6 mm, F3 = 0.22 N, and S3 = 0.5 mm.

The adhesion strength between the adhesive layer and the release film was 0.02 N/25 mm, and no peeling was observed between the adhesive layer and the release film due to transportation, etc.

[Comparative Example 2]
The laminate was prepared as follows.
A polarizer (thickness 8 μm) in which iodine was adsorbed and aligned in a polyvinyl alcohol resin was prepared. A brightness enhancement film (manufactured by 3M, APF-V4, thickness 20 μm) was attached to one surface of the polarizer via an adhesive layer (thickness 15 μm), and a cyclic olefin resin film (manufactured by Nippon Zeon Co., Ltd., thickness 13 μm) was attached to the other surface of the polarizer via an adhesive. An acrylic adhesive layer (manufactured by Lintec Corporation, thickness 13 μm, #KC1) was formed on a release film (thickness 38 μm) made of a polyester resin film, and this acrylic adhesive layer was laminated on the cyclic olefin resin film. A surface protection film (manufactured by Fujimori Kogyo Co., Ltd., product name AY-XA35) made of a base film (thickness 38 μm) made of a polyester resin and an acrylic adhesive layer (thickness 15 μm) was prepared, and this acrylic adhesive layer was laminated on the brightness enhancement film.

The obtained film was cut into a rectangle with a long side of 26.6 cm and a short side of 20.0 cm to obtain a laminate. The laminate had a layer structure of release film/adhesive layer/cyclic olefin resin film/polarizer/adhesive layer/brightness enhancement film/surface protection film. The polarizing plate had a thickness of 69 μm, the release film had a thickness of 38 μm, and the surface protection film had a thickness of 53 μm.

Furthermore, F1 = 1.21 N, S1 = 1.8 mm, F2 = 0.25 N, S2 = 0.7 mm, F3 = 0.25 N, and S3 = 0.5 mm.

The adhesion strength between the adhesive layer and the release film was 0.02 N/25 mm, and no peeling was observed between the adhesive layer and the release film due to transportation, etc.

[Comparative Example 3]
The laminate was prepared as follows.
A polarizer (thickness 5 μm) in which iodine was adsorbed and aligned in a polyvinyl alcohol resin was prepared. A brightness enhancement film (3M, APF-V4, thickness 20 μm) was attached to one surface of the polarizer via a pressure-sensitive adhesive layer (thickness 5 μm), and a protective film (thickness 20 μm) made of an acrylic resin was attached to the other surface of the polarizer via an adhesive. An acrylic pressure-sensitive adhesive layer (thickness 21 μm) was formed on a release film (thickness 38 μm) made of a polyester resin film, and this acrylic pressure-sensitive adhesive layer was laminated on the protective film made of the acrylic resin. A surface protective film made of a base film (thickness 40 μm) made of a polyester resin and an acrylic pressure-sensitive adhesive layer (thickness 16 μm) was prepared, and this acrylic pressure-sensitive adhesive layer was laminated on the brightness enhancement film.

The obtained film was cut into a rectangle with a long side of 26.6 cm and a short side of 20.0 cm to obtain a laminate. The laminate had a layer structure of release film/adhesive layer/optical protective film/polarizer/adhesive layer/brightness enhancing film/surface protective film. The polarizing plate had a thickness of 71 μm, the release film had a thickness of 38 μm, and the surface protective film had a thickness of 56 μm.

Furthermore, F1 = 1.55 N, S1 = 2.3 mm, F2 = 0.24 N, S2 = 1.3 mm, F3 = 0.21 N, and S3 = 1.1 mm.

The adhesion strength between the adhesive layer and the release film was 0.04 N/25 mm, and no peeling was observed between the adhesive layer and the release film due to transportation or other reasons.

The laminates produced in the above Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated for peelability.
The results are shown in Table 1. As shown in Table 1, the release film could be easily peeled off in the laminates of Examples 1 to 5. Furthermore, in all of the examples, no peeling problems occurred between the polarizing plate and the surface protective film.

[Table 1]
──────────────────────────────
Experimental example Adhesion K1 K2 K3 Peelability
[N/25mm] [N・mm] [N・mm] [N・mm] Rating
──────────────────────────────
Example 1 0.04 9.1 0.56 0.75 OK
Example 2 0.02 5.7 0.83 0.20 OK
Example 3 0.04 7.3 0.99 0.20 OK
Example 4 0.02 5.6 0.77 0.14 OK
Example 5 0.02 3.8 0.18 0.53 OK
──────────────────────────────
Comparative example 1 0.02 2.3 0.14 0.10 NG
Comparative example 2 0.02 2.2 0.18 0.11 NG
Comparative example 3 0.04 3.6 0.31 0.23 NG
──────────────────────────────

The present invention is useful because it can provide a laminate that does not cause peeling problems with the release film, even in the case of a polarizing plate with low rigidity.

REFERENCE SIGNS LIST 1 piercing jig 2 unit 3 film to be measured 10 polarizing plate 11 polarizer 12, 13 protective film 14 brightness enhancing film 15 adhesive layer 16 adhesive layer 17 retardation layer 20 release film 30 surface protective film 31 substrate film 32 adhesive layer 40, 41, 42, 43, 44 double arrows 100, 101, 102, 103 laminate

Claims (6)

A surface protection film including a base film and a pressure-sensitive adhesive layer laminated thereon is releasably laminated on one surface of the polarizing plate,
A release film made of a release-treated thermoplastic resin film is releasably laminated on the other surface of the polarizing plate via a pressure-sensitive adhesive layer having a thickness of 3 to 25 μm,
the polarizing plate has a layer structure including a polarizer, a protective film laminated on one surface of the polarizer via an adhesive layer, and a brightness enhancing film laminated on the other surface of the polarizer via a pressure-sensitive adhesive layer,
The surface protection film is used as a measurement film, and the maximum force (F(N)) measured by the following measurement method is F3, and the strain (S(mm)) is S3. When this maximum force (F(N)) is F3, and the strain (S(mm)) is S3, the stiffness K3 expressed as the product of the maximum force F3(N) and the strain S3(mm) (F3(N)×S3(mm)) is 0.1
A laminate having a strength of 4 N mm or more and 0.75 N mm or less,
a layer consisting of the polarizing plate and the surface protective film is used as a measurement film, and when the maximum force (F(N)) measured by the following measurement method is defined as F1 and the distortion (S(mm)) is defined as S1, a rigidity K1 expressed as the product (F1(N)×S1(mm)) of the maximum force F1(N) and the distortion S1(mm) is 3.8 N mm or more and 5.6 N mm or less,
The polarizing plate is used as a measurement film, and the maximum force (F(N)) measured by the measurement method is F2(N), and the distortion (S(mm)) is S2.
The stiffness K2 expressed as a product of (mm) is 0.18 N mm or more and 0.77 N mm or less,
the substrate film is made of a polyolefin resin, a cyclic polyolefin resin, a polyester resin , a polycarbonate resin, or a (meth)acrylic resin, and has a thickness of 30 to 80 μm;
The release film is made of a polyethylene resin, a polypropylene resin, or a polyester resin and has a thickness of 10 to 50 μm;
The adhesion strength between the polarizing plate and the release film is 0.02 to 0.05 N/25 mm, which is smaller than the adhesion strength between the polarizing plate and the surface protective film.
How to measure:
It has a circular through hole in the center when viewed from the top, and the diameter of the through hole on the top surface is 30 mm,
A measurement table in which the shape of the through hole when viewed from the side is composed of a columnar lower part and a hemispherical upper part,
A rectangular measurement film measuring 25 mm x 43 mm is placed on the
From above the measurement film, the tip is spherical, the tip diameter is 1 mmφ, and the radius of curvature is 0.
The needle, which is 1.5 mm in diameter, is inserted 1.0 cm so that the needle passes through the center of the through hole of the measurement table.
/sec vertical descent,
The maximum load required to maintain the bent state of the film after the tip of the needle comes into contact with the film to be measured is measured as the maximum force F (N), and the strain S (mm) of the film at that time is measured. 2. The laminate according to claim 1, wherein the brightness enhancement film is an anisotropic multi-layer thin film that transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction. The laminate according to claim 1 or claim 2, wherein the stiffness K3 is 0.20 N·mm or less. 4. The laminate according to claim 1, wherein the thermoplastic resin film is a film made of a polyester resin. 5. The laminate according to claim 1 , wherein the polarizer is a polyvinyl alcohol-based resin film having a dichroic dye adsorbed and oriented therein. A step of fixing the surface protective film of the laminate according to any one of claims 1 to 5 on a holding table with an adhesion force of 0.1 to 0.3 N/60 mm;
A method for producing a polarizing plate with a surface protective film, comprising the step of peeling off the release film from the laminate.

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