TW201906959A - Protective film polarizer - Google Patents

Abstract

The present invention provides a polarizing plate with protective film in which a protective film affixed to a polarizing plate can be approprintely peeled off. A polarizing plate with protective film 1 according to the present invention is formed by laminating a peelable protective film on at least one side of a polarizing layer 20. The first peeling force which is the peeling force between the polarizing layer 20 and the protective film 10 is 0.29 N/ 60 mm or more and 1 N/ 60 mm or less, and the second peeling force of the back surface, which is the surface opposite to the side facing the polarizing layer of the protective film 10, is 6 N/ 25 mm or more. The second peeling force is the peeling force between the back side and the tape when a tape for peeling force measurement is pasted on the back side.

Description

   Polarizer with protective film   

The invention relates to a polarizing plate with a protective film.

The polarizing plate is used by being bonded to a display panel such as a liquid crystal panel. A protective film for protecting a polarizing plate is generally attached to a polarizing plate attached to a display panel on a surface opposite to a side where the display panel is attached. After the display panel is assembled or inspected, the protective film is peeled from the polarizing plate (for example, Patent Document 1).

    [Prior technical literature]         [Patent Literature]    

[Patent Document 1] Japanese Patent Laid-Open No. 2014-59378

An object of the present invention is to provide a polarizing plate with a protective film, which can well peel off the protective film attached to the polarizing plate.

This invention provides the polarizing plate with a protective film shown below.

[1] A polarizing plate with a protective film is formed by a peelable protective film on at least one area of a polarizing layer, wherein the peeling force between the polarizing layer and the protective film, that is, the first peeling force is 0.29 N / 60mm or more and 1N / 60mm or less, the second peeling force of the surface of the protective film opposite to the side facing the polarizing layer, that is, the back is 6N / 25mm or greater, and the second peeling force is bonded to the back The peeling force between the said back surface and the said tape at the time of a peeling force measurement tape.

[2] The polarizing plate with a protective film according to [1], wherein the second peeling force is 15 N / 25 mm or less.

[3] The polarizing plate with a protective film according to [1] or [2], wherein the protective film has a base film and an adhesive layer provided on the base film and disposed on the polarizing layer side, and The loss coefficient tanδ of the adhesive layer is 0.2 or more.

[4] The polarizing plate with a protective film according to any one of [1] to [3], wherein the polarizing layer is a composite polarizing layer having a polarizing film and a resin layer provided on the polarizing film. A protective film is provided on the resin layer.

[5] The polarizing plate with a protective film according to the item [4], wherein the resin layer has a multilayer structure.

[6] The polarizing plate with a protective film according to [4] or [5], wherein the polarizing film is a polyvinyl alcohol-based resin layer that has adsorbed and oriented a dichroic dye, and the resin layer is brightened. membrane.

The polarizing plate with a protective film of the present invention can well peel off the protective film attached to the polarizing plate.

1‧‧‧ polarizer with protective film

10‧‧‧ protective film

11‧‧‧ substrate film

12‧‧‧ the first adhesive layer (adhesive layer)

20‧‧‧ polarizing layer

21‧‧‧ polarizing film

22‧‧‧resin layer

25‧‧‧ Laminating layer

30‧‧‧ separation layer

35‧‧‧ 2nd adhesive layer

FIG. 1 is a schematic cross-sectional view showing an example of a polarizing plate with a protective film of the present invention.

The polarizing plate with a protective film in this embodiment is a polarizing plate with a protective film formed by peeling a protective film on at least one area of the polarizing layer. The peeling force between the polarizing layer and the protective film is the first peeling force system. From 0.29N / 60mm to 1N / 60mm, the second peeling force of the surface of the protective film opposite to the side facing the polarizing layer, that is, the back surface, is 6N / 25mm or more. The second peeling force is a peeling force between the back surface and the tape when the back surface is bonded to the tape for peeling force measurement.

The polarizing plate with a protective film has an adhesive layer on the side (the other surface) of the polarizing layer opposite to the side facing the protective film, and may have a separation layer for peelably coating this adhesive layer.

The polarizing layer included in the polarizing plate with a protective film can be used by being bonded to a display panel such as a liquid crystal panel or an organic EL panel. When a polarizing layer is provided on a display panel, the polarizing plate with a protective film is generally bonded to the display panel through an adhesive layer exposed after the separation layer of the polarizing plate with a protective film is peeled off. Then, after the display panel is assembled or inspected, the protective film is peeled from the polarizing plate with a protective film attached to the display panel. The peeling of the protective film can be performed by attaching a peeling member such as a peeling tape to the back surface of the protective film and pulling the peeling member in a predetermined direction.

As described above, since the protective film is peeled off after the display panel is assembled or inspected, there is a bonding force between the protective film and the polarizing layer that imparts a degree of difficulty in peeling the display panel during the assembly step or the inspection step. . Therefore, when peeling a protective film using the said peeling member, there exists a possibility that a peeling defect, such as failure to peel a protective film, may arise. At the same time, although the above-mentioned peeling of the protective film using the peeling member can be performed manually or mechanically, in recent years, it has been automated by machinery. In the manual peeling, since the stretching direction or speed of the peeling member, the tensile force applied to the peeling member, and the like can be fine-tuned in the peeling step, the protective film is easily peeled off easily. On the other hand, in the mechanical peeling, the stretching direction or speed of the peeling member, and the tensile force applied to the peeling member are limited, so that problems such as poor peeling of the protective film cannot be peeled off easily.

Therefore, the present inventors have found that when the adhesion between the protective film and the polarizing layer is high and how to peel the protective film mechanically, the protective film can be peeled off. It is not sufficient to make only the adhesive force between the protective film and the peeling member greater than the adhesive force between the polarizing layer and the protective film. In addition, the conditions under which the protective film can be well peeled from the polarizing layer were also examined. As a result, it was found that the protective film can be well peeled from the polarizing layer by adjusting the second peeling force of the protective film to 6 N / 25 mm or more. Therefore, even in the case where the adhesion between the protective film and the polarizing layer is high, or when the protective film is peeled mechanically, it is possible to reduce peeling defects such as the protective film being unable to peel, and to peel the protective film well. . As long as it is a polarizing plate with a protective film having the above-mentioned second peeling force, it is easy to achieve good peeling of the protective film regardless of whether the peeling speed of the peeling protective film is low or high. In addition, by adjusting the second peeling force of the protective film to 6N / 25mm or more, even if a peeling tape (peeling member) that has been used for peeling of the protective film has been used, the peeling tape and the protective film can be improved. Adhesion between the back surfaces can improve the peelability of the protective film from the polarizing layer.

Hereinafter, preferred embodiments of the polarizing plate with a protective film of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of a polarizing plate with a protective film.

As shown in FIG. 1, the protective film-attached polarizing plate 1 may have a protective film 10 laminated on one side of the polarizing layer 20. As shown in FIG. 1, the protective film 10 may be a substrate film 11 and a first adhesive layer (adhesive layer) 12. In this case, the first adhesive layer 12 is disposed on the polarizing layer 20 side. A second adhesive layer 35 may be provided on the other side of the polarizing layer 20 of the polarizing plate 1 with a protective film, and a separation layer 30 may be provided to protect the second adhesive layer 35.

The polarizing layer 20 may be a composite polarizing layer including at least a polarizing film 21 and a resin layer 22 laminated on the polarizing film 21. The resin layer 22 is not particularly limited as long as it is a layer containing a resin as described later, and may be, for example, an optical function layer or a protective layer. When the polarizing layer 20 is a composite polarizing layer having a resin layer 22, as shown in FIG. 1, the resin layer 22 is disposed between the polarizing film 21 and the protective film 10. The polarizing layer 20 can be formed by the polarizing film 21, the resin layer 22, and the protective film 10. Sequentially laminated structure. The polarizing film 21 and the resin layer 22 are laminated through a bonding layer 25 formed by using an adhesive or an adhesive.

Although not shown in the figure, the resin layer may be disposed between the polarizing film 21 and the second adhesive layer 35. In this case, a structure in which the polarizing film 21, the resin layer, the second adhesive layer 35, and the separation layer 30 are laminated can be formed, for example. The resin layer can be bonded to the polarizing film 21 through a bonding layer formed using an adhesive, an adhesive, or the like. Meanwhile, the polarizing layer 20 may include a resin layer only on one side of the polarizing film 21, or may include a resin layer on both sides.

The protective film 10 is provided so as to be peelable from the polarizing layer 20. The peeling force between the protective film 10 and the polarizing layer 20, that is, the first peeling force, is usually 0.29N / 60mm or more, preferably 0.3N / 60mm or more, and may be 0.4N / 60mm or more. 1N / 60mm or less, and preferably 0.9N / 60mm or less. When the protective film 10 has the first adhesive layer 12 on the base film 11, the first peeling force is the peeling force between the first adhesive layer 12 and the polarizing layer 20 as the first peeling force. The magnitude of the first peeling force depends on the adhesive force of the first adhesive layer 12 for bonding the protective film 10 to the polarizing layer 20 and the material or surface roughness of the surface of the protective film 10 facing the polarizing layer 20 Surface properties such as degree. The first peeling force between the protective film 10 and the polarizing layer 20 is a value measured in accordance with a measuring method described in Examples described later.

The second peeling force between the surface of the protective film 10 opposite to the side facing the polarizing layer 20, that is, the back surface, and the peeling force measuring tape attached to the back surface, that is, the second peeling force is 6N / 25mm or more, and It is preferably 7N / 25mm or more, and more preferably 8N / 25mm or more, and may be 9N / 25mm or more. At the same time, it is usually preferably 15N / 25mm or less, and more preferably 13N / 25mm or less.

Since the second peeling force is 6N / 25mm or more, the first peeling force between the polarizing layer 20 and the protective film 10 is 0.29N / 60mm or more and 1N / 60mm or less with the protective film and the protective film 10 The peeling speed is good regardless of the peeling speed, and at the same time, the protective film 10 can be peeled well even manually or mechanically.

Since the second peeling force is 15N / 25mm or less, when the polarizing plate 1 with a protective film is placed on the top of a laminate formed by laminating a plurality of polarizing plates 1 with a protective film, it can be suppressed to In the state where a plurality of polarizing plates 1 with a protective film are overlapped, multiple grips are pulled up. The film-like member of the lowermost layer of the polarizing plate 1 with protection located above the laminate, and the film of the uppermost layer of the polarizing plate 1 with the protective film 10 located directly below the film-like member of the lowermost layer. When it is easy to close, such multiple grasps are liable to occur. When the second peeling force of the protective film 10 exceeds 15 N / 25 mm, when the back surface of the protective film 10 comes into contact with a film-like member such as the separation layer 30, adhesion tends to occur, so it is considered that the multiple gripping problem described above is likely to occur. . In addition, regarding the lowermost layer of the polarizing plate 1 with a protective film, the polarizing plate 1 with a protective film has a separating layer 30 when the polarizing plate 1 with a protective film has it, and the polarizing plate 1 with a protective film does not have the second adhesive layer 35 and the separating layer. At 30 o'clock, it is the outermost layer (the side opposite to the protective film 10 side) of the polarizing layer 20.

The second peeling force of the protective film 10 is the peeling force between the back surface of the protective film 10 and the tape when the tape for measuring the peeling force is attached to the back surface of the protective film 10, and it is measured according to the measurement method described in the examples described later. value. The tape for measuring the peeling force is, for example, one in which a thermosetting rubber-based adhesive layer is formed on a base sheet of a polyester film.

The value of the respective peeling force obtained by performing the peeling test shown below three or more times for the peeling force measuring tape system is in the range of 13 N / 25 mm ± 1 N / 25 mm.

<Peel test of tape for measuring peel force>

(Preparation of test piece)

The center of a glass substrate (0.4 mm in thickness, manufactured by Corning) was adhered to the adhesive surface of the peeling force measurement tape. The peeling force measurement tape used at this time has a width of 25 mm, has a length of at least 5 mm to be clamped in a jig portion of a peeling device (to be described later), and has a length of at least a sticking portion to be adhered to a glass substrate at the time of starting a peeling test. 50mm total length. At the same time, the peeling force measuring tape is adhered to the glass substrate in a state where it is pasted on the glass substrate by a length of at least 50 mm from one end in the longitudinal direction of the peeling force measuring tape, and is separated from the longitudinal direction of the measuring tape. A length of at least 5 mm from one end is located on the glass substrate but is not attached to the glass substrate. The glass substrate to which the tape for measuring peeling force was affixed was pressed in an autoclave at a temperature of 50 ° C and a pressure of 0.6 MPa for 20 minutes, and then stored in an environment of a temperature of 23 ° C and a relative humidity of 50% for 24 hours to prepare Test strip.

(Peel test)

The test piece obtained in the above was attached to a peeling device (LH-020N, Imada Manufacturing Co., Ltd.). At this time, the glass substrate of the test piece was fixed in a peeling device, and the peeling force measuring tape of the test piece was clamped with the jig of the peeling device and not adhered to the other end of the glass substrate in the longitudinal direction. Then, at the peeling speed of 3 m / min and the peeling angle of 90 °, the other end of the longitudinal direction of the peeling force measuring tape of the glass substrate of the test piece and the peeling force measuring tape of the test piece was peeled in the longitudinal direction ( The part clamped by the jig of the peeling device) is relatively moved, and the peeling of the peeling force measuring tape is started. The peeling force measuring tape is just peeled from the glass substrate, and it is peeled just before the peeling force measuring tape is completely peeled from the glass substrate. The peeling force was set to the peeling force of the peeling force measuring tape.

The second peeling force of the protective film 10 can be adjusted according to the surface characteristics such as the resin material of the protective film 10 or the surface roughness of the protective film 10. The surface roughness of the protective film 10 can be adjusted by a surface activation treatment such as a plasma treatment or a corona treatment.

For example, when the polarizing layer 20 forming the polarizing plate 1 with a protective film is a composite polarizing layer containing a resin layer 22, the general polarizing layer 20 has a multilayer structure having several layers, or the general resin layer 22 has a multilayer structure as described later. The peeling of the protective film 10 tends to be unstable. By setting the second peeling force of the back surface of the protective film 10 to 6N / 25 mm or more as described above, even in the polarizing plate 1 with a protective film of the polarizing layer 20 being a composite polarizing layer, the peeling characteristics of the protective film 10 can be effectively improved.

As shown in FIG. 1, when the protective film 10 includes the base film 11 and the first adhesive layer 12, the first adhesive layer 12 preferably has a loss coefficient tan of 0.2 or more, more preferably 0.5 or more, and 1.0 or more. More preferably, it is usually 5 or less, and more preferably 3 or less. When the loss coefficient tan is 0.2 or more, since the viscosity of the first adhesive layer 12 becomes higher and the elasticity becomes lower, the problem of the above-mentioned peeling failure is likely to occur. Therefore, in the polarizing plate 1 with a protective film having a loss coefficient tan of the first adhesive layer 12 of 0.26 or more, by setting the second peeling force to 6N / 25 mm or more, the peeling characteristics of the protective film 10 can be effectively improved. The loss coefficient tan δ can be calculated from the following formula.

tanδ = {(second peeling force [N / 25mm]) ^3.5 / (first peeling force [N / 60mm]) ^1.5 } × 0.0001

Hereinafter, each member of the polarizing plate as a protective film is demonstrated.

(Protective film)

The protective film may be composed of a resin layer having self-adhesiveness, or may be a substrate film and a first adhesive layer (adhesive layer) laminated on the substrate film. Examples of the resin having self-adhesive properties include films made of polypropylene resins, polyethylene resins, or mixtures thereof, copolymers, and the like.

The base film can be obtained by using a thermoplastic resin having translucency (preferably optically transparent). Examples of the thermoplastic resins include polyolefin resins such as chain polyolefin resins (polypropylene resins, etc.) and cyclic polyolefin resins (norbornene resins, etc.); such as triethylfluorene cellulose, Cellulose ester resin of diacetyl cellulose; polyester resin; polycarbonate resin; (meth) acrylic resin; polystyrene resin; or mixtures of these, copolymers, etc. Of the film. The "(meth) acrylic acid" in this specification means at least one selected from acrylic acid and methacrylic acid.

The base film with a self-adhesive protective film and a protective film with an adhesive layer may contain one or more kinds of lubricants, plasticizers, dispersants, heat stabilizers, ultraviolet absorbers, infrared absorbers, Antistatic agent, antioxidant additive. The thickness of the protective film with self-adhesiveness and the thickness of the base film of the protective film with an adhesive layer are preferably 200 μm or less, more preferably 100 μm or less, and 50 μm or less. At the same time, strength and use From the viewpoint of sex, it is usually 5 μm or more.

(1st adhesive layer)

When the protective film has a structure in which the first adhesive layer is provided on the base film, the first adhesive layer system may be, for example, a (meth) acrylic resin, a styrene resin, a silicone resin, a polyester resin, or a polyurethane. Based resins, polyether based resins, etc. are used as the base polymer, and the base polymer is formed by adding an adhesive composition such as an isocyanate compound, an epoxy compound, or an aziridine compound as a crosslinking agent. The adhesive composition may contain a crosslinking catalyst, a weathering stabilizer, a tackifier, a plasticizer, a softener, a dye, a pigment, and the like. The thickness of the first adhesive layer is preferably 2 to 45 μm, more preferably 2 to 30 μm, and even more preferably 5 to 10 μm.

(Polarizing film)

The polarizing film is an optical member having a function of emitting polarized light to incident light such as natural light. The polarizing film is preferably a linear polarizer. A uniaxially-stretched polyvinyl alcohol-based resin layer can be used to adsorb dichroic dyes such as directional iodine and dichroic dye. Such a polarizing film can be produced, for example, by applying uniaxial stretching, dyeing of a dichroic dye, or boric acid treatment to a polyvinyl alcohol-based resin film. The thickness of the polarizing film may be, for example, 40 μm or less, preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less, and usually 2 μm or more.

The polyvinyl alcohol-based resin used in the polyvinyl alcohol-based resin layer can be saponified using a polyvinyl acetate-based resin. The saponification degree of the polyvinyl alcohol-based resin is usually in the range of 80.0 to 100.0 mol%, preferably in the range of 90.0 to 99.5 mol%, and more preferably in the range of 94.0 to 99.0 mol%. The degree of saponification can be obtained in accordance with JIS K6726-1994. The polyvinyl alcohol-based resin may be a partially modified modified polyvinyl alcohol.

Examples of the polyvinyl acetate-based resin include copolymers of vinyl acetate and other monomers copolymerizable with the polyvinyl acetate, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate. Other monomers copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, (meth) acrylamidoamines having an ammonium group, and the like.

(Resin layer)

The resin layer is not particularly limited as long as it is a layer containing a resin, and examples thereof include an optical function layer and a protective layer. The resin layer may have a single-layer structure or a multilayer structure with two or more layers. In the case of a multilayer structure, each layer may be bonded with an adhesive or an adhesive.

The optical function layer system includes, for example, a retardation film, a brightness enhancement film, a glare function film, a film having a surface antireflection function, a reflection film, a transflective reflection film having both a reflection function and a transmission function, and a light diffusion film. For example, when the polarizing film is a polyvinyl alcohol-based resin layer that adsorbs and orients a dichroic dye, the optical function layer can be used as a brightness enhancement film. The optical function layer may have a single-layer structure or a multilayer structure with two or more layers.

The protective layer may be provided as long as it is provided for the purpose of protecting the polarizing film or optical function layer, and is not particularly limited. For example, the protective layer may be the above-mentioned protective film with self-adhesiveness, or a base using a protective film with an adhesive layer. Film made of the same thermoplastic resin. The protective layer may be a surface treatment layer (paint layer) such as a hard coat layer, an antifouling layer, or an antistatic layer. The protective layer may have a single-layer structure or a multilayer structure with two or more layers.

(2nd adhesive layer)

As the second adhesive layer, the same one as the adhesive composition forming the first adhesive layer can be used. The adhesive composition forming the first adhesive layer and the second adhesive layer may be the same as each other or different from each other. Meanwhile, the thickness of the second adhesive layer is preferably 2 to 45 μm, more preferably 2 to 30 μm, and even more preferably 5 to 10 μm. The thickness of the second adhesive layer may be the same as or different from the thickness of the first adhesive layer.

(Separation layer)

The separation layer can be a film that has been subjected to a release treatment such as polysiloxane treatment. Examples include various materials such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, and polyarylate Film made of resin.

(Lamination layer)

The bonding layer may be an adhesive layer formed using an adhesive composition, or may be an adhesive layer formed using an adhesive composition. Examples of the adhesive composition are the same as those used in the first adhesive layer and the second adhesive layer. Examples of the adhesive composition include an aqueous adhesive composition and an active energy ray-curable adhesive composition.

Examples of the aqueous adhesive composition include an adhesive composition using a polyvinyl alcohol resin or an amine ester resin as a main component. Meanwhile, examples of the active energy ray-curable adhesive composition include adhesive compositions that can be cured by irradiating active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. Specific examples include an adhesive composition containing a cationically polymerizable epoxy compound as a curable component, and an adhesive composition containing a radical polymerizable (meth) acrylic compound as a curable component.

(Manufacturing method of polarizing plate with protective film)

The polarizing plate 1 with a protective film is made of a polarizing film 21, and a polarizing layer 20 is obtained by laminating a resin layer or the like as necessary. For example, as shown in FIG. 1, the polarizing film 20 and the resin layer 22 can be laminated through the bonding layer 25 to obtain a polarizing layer 20. At this time, after the bonding layer 25 is formed on the polarizing film 21, the resin layer 22 may be laminated on the bonding layer 25, or the bonding layer 25 may be formed on the resin layer 22 to thereby bond the layer 25 and the polarizing film 21 Laminate the resin layer 22 face to face.

Next, a protective film 10 is laminated on the resin layer 22 laminated on the polarizing film 21. In this case, when the protective film 10 has the first adhesive layer 12 on the base film 11, the first adhesive layer 12 is disposed on the polarizing layer 20 side. Then, the second adhesive layer 35 may be formed on a surface opposite to the side of the protective film 10 on which the polarizing layer 20 is laminated. The second adhesive layer 35 may be formed on the polarizing layer 20 or the second adhesive layer 35 may be formed on the separation layer 30 so that the second adhesive layer 35 and the polarizing layer 20 face each other such that the second adhesive layer 35 and the separating layer 30 face each other. Laminate together.

    [Example]    

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the scope of these examples.

[Measurement of first peeling force]

The first peeling force between the protective film and the polarizing layer was measured as follows. A polarizing plate with a protective film was prepared by taking the absorption axis of the polarizing layer of the polarizing plate with a protective film as the longitudinal direction, and cutting a polarizing plate with a protective film having a length of 60 mm and a width of 60 mm perpendicular to the longitudinal direction. In addition, the first peeling force measurement tape has a width of 25 mm, has a length of at least 10 mm having a portion sandwiched by a jig of a peeling device (described later), and is attached to a protective film at the beginning of the measurement of the first peeling force. The length of the bonding part of the protective film of the polarizing plate is a total length of 5 to 10 mm.

The polarizing layer side of the polarizing plate with a protective film cut out of the above was fixed on a glass substrate (0.4 mm thick, manufactured by Corning) through an adhesive, and then pressed in an autoclave at a temperature of 50 ° C and a pressure of 0.6 MPa. After 20 minutes, it was stored in an environment with a temperature of 23 ° C and a relative humidity of 50% for 24 hours. Next, a first peeling force measuring tape was fixed to one end of the protective film-attached polarizing plate with the protective film fixed to the glass substrate and extending in the width direction (the side perpendicular to the absorption axis). At this time, in a portion where the first peeling force measurement tape and the one end edge of the protective film overlap, the midpoint in the width direction of the first peeling force measurement tape and the middle point of the one end edge of the protective film coincide, At the same time, the first peeling force measurement tape is attached to the protective film in a length range from 5 to 10 mm in the length direction from the one end side, and the remaining part of the first peeling force measurement tape is extended from the protective film in the longitudinal direction. It protruded and was fixed, and the test piece for 1st peeling force measurement was produced.

The obtained test piece for measuring the first peeling force was mounted on a peeling device (LH-020N, Imada Manufacturing Co., Ltd.), and the remainder of the first tape for measuring the peeling force was clamped by a jig of the peeling device (from the protective film). On the top). Next, at the peeling speed of 3 m / min and the peeling angle of 90 °, the remaining part of the first peeling force test strip and the first peeling force measuring tape was peeled (using a peeling device) to peel the protective film in the longitudinal direction. The part clamped by the jig) was relatively moved, and the protective film was peeled from the polarizing layer of the test piece for measuring the first peeling force. Then, measure the peeling force from the peeling of the protective film to the end position in the longitudinal direction of the first peeling force measuring tape attached to the protective film, and immediately before the protective film is completely peeled from the polarizing plate. As the first peeling force. When the protective film is peeled from the test piece for the first peeling force measurement, when the protective film cannot be peeled from the polarizing layer, polarized light is emitted from the one end of the side to which the first peeling force measuring tape is attached. A small amount of the protective film was peeled from the layer to form a starting point for peeling, and the first peeling force was measured.

(Characteristics of the first tape for measuring peeling force)

The first tape for measuring the peeling force is a range in which the value of the respective peeling force obtained by performing the peeling test three or more times in the following procedure using the following test piece is 13N / 25mm ± 1N / 25mm.

(Test piece)

The center of a glass substrate (0.4 mm thick, manufactured by Corning) was adhered to the adhesive surface of the first peeling force measurement tape. At this time, the tape for measuring the peeling force is at least 5 mm with a width of 25 mm and a portion sandwiched by a jig having a peeling device (described later), and a length of at least 50 mm of an adhesive portion to be adhered to the glass substrate at the start of the peeling test. Total length. Moreover, the 1st peeling force measurement tape was stuck on the glass substrate so that it might stick to a board | substrate at least 50 mm from one end of the longitudinal direction of the 1st peeling force measurement tape, and from the longitudinal direction of the peeling force measurement tape. The other end has a length of at least 5 mm, and although it is located on the glass substrate, it is not attached to the glass substrate. The glass substrate to which the tape for measuring peeling force was adhered as described above was placed in an autoclave, pressurized at a temperature of 50 ° C and a pressure of 0.6 MPa for 20 minutes, and then stored in an environment of a temperature of 23 ° C and a relative humidity of 50% for 24 hours. To make a test piece.

(Peel test)

The test piece obtained in the above was attached to a peeling device (LH-020N, Imada Manufacturing Co., Ltd.). At this time, the glass substrate of the test piece was fixed to a peeling device, and the other end of the longitudinal direction of the peeling force measuring tape of the test piece that was not adhered to the glass substrate was clamped with a jig of the peeling device. Then, the glass substrate of the test piece and the first peeling force measuring tape of the test piece were peeled in a longitudinal direction at a peeling speed of 3 m / min and a peeling angle of 90 °. The other end (the part held by the jig of the peeling device) is relatively moved, and the peeling of the first test piece for peeling force measurement is started. The first test piece for peeling force measurement is just peeled from the glass substrate to the first The peeling force immediately before the peeling force measurement tape is completely peeled from the glass substrate is referred to as the peeling force of the first peeling force measurement tape.

[Measurement of the second peeling force]

The second peeling force of the protective film and the tape for measuring peeling force was measured as follows. The absorption axis of the polarizing layer of the polarizing plate with a protective film is taken as a length direction, and a polarizing plate with a protective film having a length of 60 mm or more and a width of 60 mm perpendicular to the longitudinal direction is cut to prepare a polarizing plate with a protective film. In addition, the second peeling force measurement tape has a width of 25 mm and has a length of at least 5 mm of a portion to be mounted on a jig of a peeling device (described later), and the second peeling force measurement is performed with a protective film. The length of the bonded portion of the protective film of the polarizer is at least 50mm in total. The second peeling force measurement tape has the same peeling force as that described in the characteristic item of the first peeling force measurement tape.

The polarizing layer of the polarizing plate with a protective film cut out was fixed on a glass substrate (0.4 mm thick, manufactured by Corning) with an adhesive, and the autoclave was pressed at a temperature of 50 ° C. and a pressure of 0.6 MPa for 20 minutes, and then at a temperature of Store at 23 ° C and 50% relative humidity for 24 hours. Next, the protective film is attached to the center of the protective film of the polarizing plate with a protective film fixed on the glass substrate, and is attached to the protective film by a length of at least 50 mm from one end in the longitudinal direction of the second peeling force measuring tape. A length of at least 5 mm from the other end in the longitudinal direction of the peeling force measurement tape is located on the protective film but is not attached to the protective film, and a test piece for the second peeling force measurement is set in this state.

The obtained test piece for measuring the second peeling force was set in a peeling device (LH-020N, Imada Manufacturing Co., Ltd.), and the second tape for measuring the peeling force of the second test piece for measuring the peeling force was clamped by the jig of the peeling device. Is not bonded to the other end in the longitudinal direction on the protective film. Then, at a peeling speed of 3 m / min and a peeling angle of 90 °, the second peeling force measurement test piece and the second peeling force measurement tape were separated from each other in the longitudinal direction of the second peeling force measurement tape. One end (the part held by the jig of the peeling device) is relatively moved, and the peeling of the second peeling force measuring tape is started. The second peeling force measuring tape has just been peeled from the protective film, and the second peeling force measuring tape is coming soon. The peeling force before complete peeling from the protective film was set as the second peeling force.

[Calculation of loss coefficient tanδ]

The loss loss tanδ is calculated by the following formula.

tanδ = {(second peeling force [N / 25mm]) ^3.5 / (first peeling force [N / 60mm]) ^1.5 } × 0.0001

[Peelability test]

The polarizing plate with a protective film obtained in each example and each comparative example was fixed to a glass substrate (0.4 mm thick, manufactured by Corning) with an adhesive, and then pressed in an autoclave at a temperature of 50 ° C. and a pressure of 0.6 MPa for 20 minutes. Then, store it in an environment with a temperature of 23 ° C and a relative humidity of 50% for 24 hours. Next, a peeling tape (having the first peeling from the first peeling film) is fixed to one of the end edges (edges perpendicular to the absorption axis) of the protective film of the polarizing plate with a protective film fixed to the glass substrate and extending in the width direction. A tape with the same peeling force as described in the characteristics of the tape for force measurement). At this time, in the portion where the peeling tape overlaps the one end side of the protective film, the midpoint in the width direction of the peeling tape matches the middle point of the one end side of the protective film, and the peeling tape is fixed at a position from the above. One end edge was bonded to the protective film in a length range of 5 to 10 mm in the longitudinal direction, and the remaining portion of the release tape protruded from the protective film in the longitudinal direction to prepare a test piece for peelability test.

The obtained test piece for measuring peelability was mounted on a peeling device (LH-020N, Imada Manufacturing Co., Ltd.), and the remainder of the above-mentioned peeling tape (the portion protruding from the protective film) was clamped by a jig of the peeling device. Then, at the peeling speed of 3 m / min and the peeling angle of 90 °, the remaining portion of the test piece for peelability measurement and the above-mentioned peel force measurement tape (the portion sandwiched by the jig of the peeling device) was relatively moved in the longitudinal direction. As a result of the peelability test, those who peeled the protective film were evaluated as having good peelability, and those who could not peel the protective tape from the protective film or could not peel the protective film were evaluated as having poor peelability.

[Example 1]

(Production of polarizing plate with protective film)

A polyvinyl alcohol-based film was uniaxially stretched and dyed with iodine to obtain a polarizing film having a thickness of 8 μm. A cyclic olefin resin film having a thickness of 13 μm was laminated on one surface of the obtained polarizing film with an adhesive made of an active energy ray-curable resin interposed therebetween. Next, on the other side of the polarizing film, a brightness enhancement film having a multilayer structure is laminated via an adhesive. Then, the protective film having the first adhesive layer is laminated so that the first adhesive layer is disposed on the brightness enhancement film side. In addition, the protective film was subjected to a corona treatment on its back surface to adjust the second peeling force shown in Table 1.

Next, a second adhesive layer was formed on the cyclic olefin-based resin film, and the absorption axis of the polarizing layer was taken as the length direction. The length was cut to 60 mm along the width direction perpendicular to the length direction, and The length was 60 mm, and a polarizing plate with a protective film was obtained. The polarizing layer of the obtained protective film-attached polarizing plate was a layer structure of a brightness enhancement film / adhesive layer / polarizing film / adhesive layer / cyclic olefin resin film.

The protective film, the polarizing layer, and the first adhesive layer used in the obtained polarizing plate with a protective film were measured for the first peeling force, the second peeling force, and the loss coefficient tan, and the results are shown in Table 1. Meanwhile, a peeling test was performed using a polarizing plate with a protective film, and the results are shown in Table 1.

[Examples 2 to 7, Comparative Examples 1 to 6]

A polarizing plate with a protective film having a first peeling force and a second peeling force shown in Table 1 was used, and the peeling test was performed at the peeling speed shown in Table 1. The rest of the operation was performed in the same manner as in Example 1 to obtain protection with protection. Film of polarizing plate. In addition, the protective film was subjected to corona treatment on the back surface and the first adhesive layer to adjust the first peeling force and the second peeling force shown in Table 1.

The protective film, polarizing layer, and first adhesive layer used in the obtained protective film-attached polarizing plate were measured for a first peeling force, a second peeling force, and a loss coefficient tan δ, and the results are shown in Table 1. Moreover, the peeling test was performed using the polarizing plate with a protective film, and the result is shown in Table 1.

From the results shown in Table 1, it was found that by setting the second peeling force to be 6 N / 25 mm or more, good peelability of the protective film can be obtained. From the results of Examples 1 to 7, it can be seen that by setting the second peeling force to be 6 N / 25 mm or more, good peelability of the protective film can be obtained even under severe peeling conditions where the peeling speed is large.

Claims (6)

    A polarizing plate with a protective film is formed by laminating a peelable protective film on at least one side of a polarizing layer. The first peeling force between the polarizing layer and the protective film is 0.29N / 60mm. Above 1N / 60mm, the second peeling force of the surface of the protective film opposite to the side facing the polarizing layer, that is, the back surface is 6N / 25mm or more, and the second peeling force is determined by bonding the peeling force on the back surface. Peeling force between the back surface and the tape when the tape is used.         The polarizing plate with a protective film according to item 1 of the scope of patent application, wherein the second peeling force is 15N / 25mm or less.         The polarizing plate with a protective film according to item 1 or 2 of the scope of the patent application, wherein the protective film has a base film and an adhesive layer provided on the base film and disposed on the polarizing layer side. The loss coefficient tan δ is 0.2 or more.         The polarizing plate with a protective film according to any one of claims 1 to 3, wherein the polarizing layer is a composite polarizing layer having a polarizing film and a resin layer provided on the polarizing film, and the protective film is It is provided on the said resin layer.         The polarizing plate with a protective film according to item 4 of the scope of patent application, wherein the resin layer has a multilayer structure.         The polarizing plate with a protective film according to item 4 or 5 of the scope of the patent application, wherein the polarizing film is a polyvinyl alcohol-based resin layer that has adsorbed and oriented a dichroic dye, and the resin layer is a brightness enhancing film.