KR20190002337A - Polarizing plate with protective film - Google Patents

Abstract

The present invention provides a polarizing plate with a protective film which can appropriately peel off a protective film attached to a polarizing plate. The polarizing plate with a protective film (1) is comprised by laminating the protective film on at least one surface of a polarizing layer (20) so as to be peelable. A first peeling force which is a peeling force between the polarizing layer (20) and the protective film (10) is 0.29 N / 60 mm to 1 N / 60 mm. A second peeling force of a back surface which is an opposite side to a facing side to 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 surface and a tape when a peeling force measurement tape is bonded to the back surface.

Description

{POLARIZING PLATE WITH PROTECTIVE FILM}

The present 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. In the polarizing plate bonded to the display panel, a protective film for protecting the polarizing plate is usually bonded to a surface opposite to the side where the display panel is bonded to the polarizing plate. This protective film is peeled from the polarizing plate after assembling or inspecting the display panel (e.g., Patent Document 1, etc.).

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

An object of the present invention is to provide a polarizing plate with a protective film capable of suitably peeling a protective film pasted to a polarizing plate.

The present invention provides the following polarizing plate with a protective film.

[1] A polarizing plate with a protective film formed by laminating a protective film on at least one surface of a polarizing layer such that the protective film can be peeled off,

A first peeling force which is a peeling force between the polarizing layer and the protective film is 0.29 N / 60 mm or more and 1 N / 60 mm or less,

A second peeling force of the back surface which is a surface opposite to the side facing the polarizing layer of the protective film is 6 N / 25 mm or more,

And the second peeling force is a peeling force between the back surface and the tape when a peeling force measurement tape is bonded to the back surface.

[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 protective film has a base film and an adhesive layer provided on the base film and disposed on the polarizing layer side,

The polarizing plate with a protective film according to [1] or [2], wherein the loss coefficient tan? Of the pressure-sensitive adhesive layer is 0.2 or more.

[4] The polarizing element according to any one of [1] to [4], wherein the polarizing layer is a composite polarizing layer having a polarizing film and a resin layer provided on the polarizing film,

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

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

[6] The polarizing film is a polyvinyl alcohol-based resin layer in which a dichroic dye is adsorbed and oriented,

The resin layer is a brightness enhancement film according to [4] or [5].

In the polarizing plate with protective film of the present invention, the protective film attached to the polarizing plate can be suitably peeled off.

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

The polarizing plate with a protective film according to the present embodiment is a polarizing plate with a protective film formed by laminating a protective film on at least one surface of a polarizing layer so as to be peelable. The first peeling force, which is the peeling force between the polarizing layer and the protective film, 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 opposite to the polarizing layer of the protective film is 6 N / 25 mm or more. The second peeling force is a peeling force between the back surface and the tape when the peeling force measurement tape is bonded to the back surface.

The polarizing plate with protective film may have a pressure-sensitive adhesive layer on a surface (the other surface) opposite to the side of the polarizing layer opposite to the protective film, and may have a separator for releasably covering the pressure-sensitive adhesive layer.

The polarizing layer included in the polarizing plate with 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, a polarizing plate with a protective film is usually bonded to the display panel through an adhesive layer which is exposed by peeling a separator of a polarizing plate with a protective film. Thereafter, after assembling or inspecting the display panel, the protective film is peeled from the polarizing plate with protective film bonded to the display panel. The protective film may be peeled off 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.

Since the protective film is peeled off after assembling or inspecting the display panel as described above, an adhesion force is given between the protective film and the polarizing layer to such an extent as not to be easily peeled off during the assembling process of the display panel or during the inspection process . For this reason, when the protective film is peeled off using the peeling member, a problem of peeling failure such as peeling of the protective film may occur. Further, the peeling of the protective film using the peeling member can be carried out by a human hand or by a machine, but recently, automation by a machine has been proceeding. In the peeling by the human hand, the tensile direction and the tensile speed of the peeling member, the tensile force applied to the peeling member, and the like can be finely adjusted during the peeling process, so that it is easy to easily peel off the protective film. On the other hand, in the peeling by the machine, the pulling direction, the tensile speed of the peeling member, and the tensile force applied to the peeling member are limited, and thus the problem of peeling failure such as the peeling of the protective film tends to occur.

Thus, as a result of examining a method for satisfactorily peeling off a protective film even when the adhesive force between the protective film and the polarizing layer is high or when the protective film is peeled off by a machine, the present inventors have found that a good It has been found that it is not sufficient to make the adhesive force between the protective film and the peeling member larger than the adhesive force between the polarizing layer and the protective film in order to realize peeling. Further, as a result of further study on the conditions capable of satisfactorily peeling the protective film from the polarizing layer, it was found that by adjusting the second peeling force of the protective film to 6 N / 25 mm or more, the protective film can be satisfactorily peeled from the polarizing layer . Thus, even when the adhesive force between the protective film and the polarizing layer is high, or when the protective film is peeled off by the machine, the peeling failure such as the peeling of the protective film is reduced and the peeling of the protective film is suitably performed . In the case of the polarizing plate with a protective film having the second peeling force, peeling of the protective film can be easily achieved even if the peeling speed for peeling the protective film is low or high. Further, by adjusting the second peeling force of the protective film to 6 N / 25 mm or more, even if the peeling tape (peeling member), which has been used for peeling the protective film, is used, the peeling tape and the protective film The adhesion to the back surface can be improved, and the peelability of the protective film from the polarizing layer can be improved.

Hereinafter, preferred embodiments of the polarizing plate with protective film of the present invention will be described with reference to the drawings. 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 10 with a protective film can be laminated on one side of the polarizing layer 20. 1, the protective film 10 may have a base film 11 and a first adhesive layer (adhesive layer) 12. In this case, the first adhesive layer 12 may be polarized Layer 20 side. The second adhesive layer 35 may be provided on the other side of the polarizing layer 20 of the polarizing plate 1 with the protective film and the separator 30 for protecting the second adhesive layer 35 May be provided.

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 functional layer or a protective layer. When the polarizing layer 20 is a composite polarizing layer having the resin layer 22, the resin layer 22 is disposed between the polarizing film 21 and the protective film 10, for example, as shown in Fig. 1 The polarizing film 21, the resin layer 22, and the protective film 10 may be stacked in this order. The polarizing film 21 and the resin layer 22 can be laminated through a bonding layer 25 formed using an adhesive or a pressure-sensitive adhesive.

Although not shown, the resin layer may be disposed between the polarizing film 21 and the second adhesive layer 35. In this case, for example, the polarizing film 21, the resin layer, the second adhesive layer 35, and the separator 30 may be stacked in this order. The resin layer can be bonded to the polarizing film 21 through a bonding layer formed using an adhesive, a pressure-sensitive adhesive, or the like. Further, the polarizing layer 20 may include a resin layer on only one side of the polarizing film 21, or may include a resin layer on both sides thereof.

The protective film 10 is detachably provided to the polarizing layer 20. The first peeling force which is the peeling force between the protective film 10 and the polarizing layer 20 is usually 0.29 N / 60 mm or more, preferably 0.3 N / 60 mm or more, 0.4 N / 60 mm or more, Further, it is usually 1 N / 60 mm or less, preferably 0.9 N / 60 mm or less. When the protective film 10 has the first adhesive layer 12 on the base film 11, the first peeling force is such that the peeling force between the first adhesive layer 12 and the polarizing layer 20 becomes the first It becomes a peeling force. The magnitude of the first peeling force is determined by the adhesive strength of the first adhesive layer 12 used for bonding the protective film 10 and the polarizing layer 20 or the adhesive force of the first adhesive layer 12 facing the polarizing layer 20 of the protective film 10 And the surface characteristics such as surface roughness. The first peeling force between the protective film 10 and the polarizing layer 20 is a value measured according to a measuring method described in the following embodiments.

The second peeling force, which is the peeling force between the back surface of the protective film 10 opposite to the side opposed to the polarizing layer 20 and the peeling force measurement tape bonded to the back surface, is 6 N / 25 mm or more , More preferably not less than 7 N / 25 mm, more preferably not less than 8 N / 25 mm, not more than 9 N / 25 mm, more preferably not more than 15 N / Or less.

The first 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 as the second peeling force is 6 N / 25 mm or more. , The protective film 10 can be satisfactorily peeled off regardless of the peeling speed of the protective film 10 and the protective film 10 can be satisfactorily peeled by a human hand or by a machine.

And the second peeling force is 15 N / 25 mm or less, when the polarizing plate 1 with the protective film positioned at the uppermost position of the stacked article in which a plurality of polarizing plates 1 with a protective film are stacked is pulled up, It is possible to suppress the occurrence of multiple receivings that are pulled up in a state in which a plurality of these are overlapped. In the multi-receiving, the film-like member constituting the lowermost layer of the polarizing plate 1 with the protective film located on the upper side of the laminate and the uppermost layer of the polarizing plate 1 with the protective film positioned immediately below the lowest film- The protective film 10 is likely to come into close contact. If the second peeling force of the protective film 10 exceeds 15 N / 25 mm, the back surface of the protective film 10 tends to be more likely to come into close contact with the film-like member such as the separator 30 And it is considered that the problem of the above-described multiple reception becomes easy to occur. The lowest layer of the polarizing plate with protective film 1 is the separator 30 when the polarizing plate 1 with protective film 1 has the separator 30 and the polarizing plate 1 with protective film is the second adhesive layer 35, (The side opposite to the side of the protective film 10) of the polarizing layer 20 when the polarizing layer 20 and the separator 30 are not provided.

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 peeling force measurement tape is bonded to the back surface of the protective film 10, Lt; / RTI > is the value measured according to the measuring method described in " The tape for peeling force measurement is, for example, a thermosetting rubber-based pressure-sensitive adhesive layer formed on a base sheet of a polyester film.

The peeling force measurement tapes are each subjected to the following peeling test three times or more and the value of each peeling force is in the range of 13 N / 25 mm ± 1 N / 25 mm.

≪ Peeling test of tape for peeling force measurement >

(Preparation of test piece)

The adhesive surface of the tape for peeling force measurement is attached to the center of a glass substrate (0.4 mm thick, manufactured by Corning). The tape for peeling force measurement used here has a width of 25 mm and is at least 5 mm in length as a portion to be pinched in the jig of the peeling apparatus (described later), and at the start of peeling test, At least 50 mm. The peeling force measurement tape is attached onto the glass substrate over a length of at least 50 mm from one end in the longitudinal direction of the peeling force measurement tape and is peeled from the other end in the longitudinal direction of the peeling force measurement tape The glass substrate is attached so that the length of 5 mm is on the glass substrate but not attached to the glass substrate. The glass substrate to which the tape for peeling force measurement was attached was pressed in an autoclave at a temperature of 50 DEG C and a pressure of 0.6 MPa for 20 minutes and then stored for 24 hours under an environment of a temperature of 23 DEG C and a relative humidity of 50% Test specimens shall be used.

(Peeling test)

The test piece thus obtained is set in a peeling apparatus (LH-020N, manufactured by Imadate Seisakusho Co., Ltd.). At this time, the glass substrate of the test piece is fixed to the peeling apparatus, and the other end in the longitudinal direction of the tape for peeling force measurement of the test piece not attached to the glass substrate is pinned by the jig of the peeling apparatus. Thereafter, the other end in the longitudinal direction of the tape for peeling force measurement of the glass substrate of the test piece and the test piece (the peeling test piece of the peeling device) was peeled off in the longitudinal direction at a peeling speed of 3 m / min and a peeling angle of 90 Jig) is relatively moved to start peeling of the peeling force measurement tape, and immediately after the peeling force measurement tape peels from the glass substrate, immediately before the peeling force measurement tape completely peels from the glass substrate Is taken as the peeling force of the tape for peeling force measurement.

The second peeling force of the protective film 10 can be adjusted by the surface characteristics such as the material of the resin forming the protective film 10 and the surface roughness of the protective film 10. The surface roughness of the protective film 10 can be adjusted by, for example, surface activation treatment such as plasma treatment or corona treatment.

The case where the polarizing layer 20 has a multilayer structure including a plurality of layers as in the case where the polarizing layer 20 constituting the polarizing plate 1 with a protective film 1 is a composite polarizing layer including the resin layer 22, Similarly, when the resin layer 22 has a multilayer structure, peeling of the protective film 10 tends to become unstable. As described above, the second peeling force of the back surface of the protective film 10 is 6 N / 25 mm or more, so that even in the case of the polarizing plate 1 with a protective film whose polarizing layer 20 is a composite polarizing layer, 10 can be improved.

1, when the protective film 10 has 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, further preferably 1.0 or more, and usually 5 or less, and more preferably 3 or less. When the loss coefficient tan? Is not less than 0.2, the first adhesive layer 12 has high viscosity and low elasticity, so that the above-mentioned problem of peeling failure is liable to occur. Therefore, by setting the second peeling force to 6 N / 25 mm or more in the protective film-attached polarizing plate 1 having the loss coefficient tan? Of the first adhesive layer 12 of 0.26 or more, Can be improved. The loss coefficient tan? Can be calculated by the following equation.

tan? = {(second peeling force [N / 25 mm]) ^3.5 / (first peeling force [N / 60 mm]) ^1.5 }

Hereinafter, the respective members constituting the polarizing plate with protective film will be described.

(Protective film)

The protective film may be composed of a resin layer having self-adhesive property, or may be a laminate of a first adhesive layer (adhesive layer) on a base film and a base film. As the resin having self-adhesive property, a film made of a polypropylene resin, a polyethylene resin, a mixture thereof, a copolymer or the like can be given.

The base film can be obtained by using a thermoplastic resin having translucency (preferably optically transparent). Examples of the thermoplastic resin include polyolefin resins such as a chain polyolefin resin (polypropylene resin and the like) and a cyclic polyolefin resin (norbornene resin and the like); Cellulose ester-based resins such as triacetylcellulose and diacetylcellulose; Polyester-based resin; Polycarbonate resin; (Meth) acrylic resins; Polystyrene type resin; Or mixtures and copolymers thereof, and the like. In the present specification, "(meth) acryl" means at least one selected from acrylic and methacrylic.

The base film of the protective film having a self-adhesive property and the protective film having an adhesive layer may contain one or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent and an antioxidant . The thickness of the protective film having self-adhesive property and the thickness of the base film of the protective film having the adhesive layer are preferably 200 占 퐉 or less, more preferably 100 占 퐉 or less, further preferably 50 占 퐉 or less, Usually 5 mu m or more.

(First adhesive layer)

When the protective film is a structure provided with a first adhesive layer on the base film, the first adhesive layer may be formed of, for example, a (meth) acrylic resin, a styrene resin, a silicone resin, a polyester resin, a polyurethane resin, Resin or the like as a base polymer and a crosslinking agent such as an isocyanate compound, an epoxy compound or an aziridine compound is added to the base polymer. The pressure-sensitive 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 탆, more preferably 2 to 30 탆, and still more preferably 5 to 10 탆.

(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, and a monoaxially stretched polyvinyl alcohol-based resin layer in which a dichroic dye such as iodine or a dichroic dye is adsorbed and oriented can be used. Such a polarizing film can be produced, for example, by subjecting a polyvinyl alcohol-based resin film to uniaxial stretching, dyeing with a dichroic dye, boric acid treatment, and the like. The thickness of the polarizing film can be, for example, 40 m or less, preferably 30 m or less, more preferably 20 m or less, further preferably 10 m or less, and usually 2 m or more.

The polyvinyl alcohol-based resin used for the polyvinyl alcohol-based resin layer may be one obtained by saponifying a polyvinyl acetate-based resin. The degree of saponification of the polyvinyl alcohol-based resin can be usually from 80.0 to 100.0 mol%, preferably from 90.0 to 99.5 mol%, and more preferably from 94.0 to 99.0 mol%. The saponification degree can be obtained according to JIS K6726-1994. The polyvinyl alcohol resin may be a modified polyvinyl alcohol partially modified.

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

(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 functional layer and a protective layer. The resin layer may have a single layer structure or a multilayer structure of two or more layers, and in the case of a multilayer structure, the layers may be bonded together with an adhesive or with an adhesive.

Examples of the optical function layer include a retardation film, a brightness enhancement film, a film having an antiglare function, a film having a surface antireflection function, a reflective film, a transflective film having a reflection function and a transmissive function, . For example, when the polarizing film is a polyvinyl alcohol-based resin layer in which a dichroic dye is adsorbed and oriented, the optical function layer can be a brightness enhancement film. The optical function layer may have a single-layer structure or a multilayer structure of two or more layers.

The protective layer is not particularly limited as long as it is provided for the purpose of protecting the polarizing film or the optical functional layer. For example, the protective film having the self-tackiness or the thermoplastic resin same as the base film of the protective film having the adhesive layer A formed film may be used. The protective layer may be, for example, a surface treatment layer (coating layer) such as a hard coat layer, an antifouling layer, and an antistatic layer. The protective layer may have a single-layer structure or a multi-layer structure of two or more layers.

(Second adhesive layer)

As the second adhesive layer, the same adhesive composition as the first adhesive layer can be used. The pressure-sensitive adhesive composition comprising the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may be the same or different from each other. The thickness of the second adhesive layer is preferably from 2 to 45 탆, more preferably from 2 to 30 탆, and further preferably from 5 to 10 탆. The thickness of the second adhesive layer may be the same as or different from the thickness of the first adhesive layer.

(Separator)

As the separator, a film subjected to a releasing treatment such as a silicone treatment can be used. Examples of the separator include films made of various resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, and polyarylate.

(Bonding layer)

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

As the water-based adhesive composition, an adhesive composition using a polyvinyl alcohol-based resin or a urethane resin as a main component may be mentioned. Examples of the active energy ray curable adhesive composition include an adhesive composition that can be cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. Specifically, an adhesive composition comprising a cationic polymerizable epoxy compound as a curable component and an adhesive composition containing a radically polymerizable (meth) acrylic compound as a curable component can be given.

(Production method of polarizing plate with protective film)

The polarizing plate 1 with a protective film is manufactured by preparing a polarizing film 21 and laminating a resin layer or the like as required to obtain a polarizing layer 20. For example, as shown in Fig. 1, the polarizing film 21 and the resin layer 22 may be laminated through the bonding layer 25 to obtain the polarizing layer 20. The resin layer 22 may be laminated on the bonding layer 25 after the bonding layer 25 is formed on the polarizing film 21 and the bonding layer 25 And the resin layer 22 may be laminated such that the side of the bonding layer 25 faces the polarizing film 21. [

Subsequently, the protective film 10 is laminated on the resin layer 22 laminated on the polarizing film 21. At this time, 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 side of the polarizing layer 20. Thereafter, the second adhesive layer 35 may be formed on the surface of the polarizing layer 20 opposite to the side where the protective film 10 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 separator 30 and the second adhesive layer 35 and the polarizing layer 20 The second adhesive layer 35 may be laminated together with the separator 30. In this case,

Example

Hereinafter, the present invention is described in more detail based on examples and comparative examples, but the present invention is not limited to these examples.

[Measurement of first peel force]

The first peeling force between the protective film and the polarizing layer was measured as follows. A protective film-attached polarizing plate was prepared in which the absorption axis of the polarizing layer of the polarizing plate with the protective film was oriented in the longitudinal direction and cut into a length of 60 mm or more and a width of 60 mm in a direction orthogonal to the longitudinal direction. The first peeling force measurement tape has a width of 25 mm and is at least 10 mm in length as a portion to be pinched in the jig of the peeling apparatus (described later), and at the start of measurement of the first peeling force, And the length of the portion where the polarizing plate is bonded to the protective film has a total length of 5 to 10 mm.

The polarizing layer side of the polarizing plate with the protective film cut out from above was fixed to a glass substrate (0.4 mm thick, manufactured by Corning) through a pressure-sensitive adhesive, pressurized in an autoclave at a temperature of 50 캜 and a pressure of 0.6 MPa for 20 minutes, 23 캜 and 50% relative humidity for 24 hours. Subsequently, the first peeling force measurement tape was fixed to one end side of the end portion of the polarizing plate with the protective film fixed on the glass substrate and extending in the width direction (the side perpendicular to the absorption axis). At this time, in the portion where the first peeling force measurement tape overlaps with the one end side of the protective film, the middle point in the width direction of the first peeling force measurement tape and the middle point of the one end side of the protective film are matched In addition, the first peeling force measurement tape is bonded to the protective film in a length of 5 to 10 mm in the longitudinal direction at the one end side, and the remainder of the first peeling force measurement tape is punched in the longitudinal direction on the protective film So as to form a test piece for first peeling force measurement.

The obtained first peel strength measurement test piece was set in a peeling apparatus (LH-020N, manufactured by Imadate Seisakusho Co., Ltd.), and the remainder of the first peeling force measurement tape (the protruding portion on the protective film) The device was pinched by the jig. Subsequently, the test piece for the first peeling force measurement and the remainder of the first peeling force measurement tape (the jig of the peeling device) were peeled off in the longitudinal direction at a peeling speed of 3 m / min and a peeling angle of 90 [ ) Was relatively moved, and the peeling of the protective film from the polarizing layer of the test piece for the first peeling force measurement was started. Thereafter, the peeling force between the time when the protective film is peeled to the position of the end portion in the longitudinal direction of the first peeling force measurement tape bonded on the protective film, and the time when the protective film is completely peeled from the polarizing layer, 1 peel strength. When the protective film can not be peeled from the polarizing layer at the time of starting peeling of the protective film from the test piece for first peeling force measurement, it is preferable that, at the side of the one end side to which the first peeling force measurement tape is bonded, A protective film was slightly peeled off from the layer to form a peeling instrument, and the first peeling force was measured.

(Characteristics of tape for first peeling force measurement)

The first peeling force measurement tape has the values of the peeling forces obtained in the peeling test carried out three times or more in the following procedure using the following test pieces in the range of 13 N / 25 mm ± 1 N / 25 mm .

(Test piece)

The adhesive surface of the tape for measuring the first peeling force was attached to the center of a glass substrate (0.4 mm thick, manufactured by Corning). At this time, as the peeling force measurement tape, a tape having a width of 25 mm and having a length of at least 5 mm as a length of a portion to be pinched in a jig of a peeling apparatus (described later), and a length Of at least 50 mm. The first peeling force measurement tape is stuck on a glass substrate over a length of at least 50 mm from one end in the longitudinal direction of the first peeling force measurement tape, Was attached to the glass substrate so that a length of at least 5 mm from the other end of the glass substrate was not attached to the glass substrate. The glass substrate with the tape for peeling force measurement thus attached was pressed in an autoclave at a temperature of 50 DEG C and a pressure of 0.6 MPa for 20 minutes and then stored in an environment of a temperature of 23 DEG C and a relative humidity of 50% Respectively.

(Peeling test)

The test piece obtained as described above was set in a peeling apparatus (LH-020N, manufactured by Imadate Seisakusho Co., Ltd.). At this time, the glass substrate of the test piece was fixed to the peeling apparatus, and the other end in the longitudinal direction of the tape for peeling force measurement of the test piece not attached to the glass substrate was pinned by the jig of the peeling apparatus. Thereafter, the first peel strength measuring tape of the test piece was peeled off in the longitudinal direction at a peeling speed of 3 m / min and a peeling angle of 90, (The portion pinched with the jig of the peeling apparatus) is relatively moved to start the peeling of the first peeling force measurement tape, and immediately after peeling off the first peeling force measurement tape from the glass substrate, the first peeling force measurement The peeling force from the time when the tape was completely peeled off from the glass substrate was taken as the peeling force of the first peeling force measurement tape.

[Measurement of Second Peel Force]

The second peeling force between the protective film and the peeling force measurement tape was measured in the following manner. A protective film-attached polarizing plate was prepared in which the absorption axis of the polarizing layer of the protective film-attached polarizing plate was cut in the longitudinal direction at a length of 60 mm or more and a width of 60 mm in a direction orthogonal to the longitudinal direction. The tape for measuring the second peeling force had a width of 25 mm and had a length of at least 5 mm as a length of a portion to be attached to the jig of the peeling apparatus (described later), and at the start of measurement of the second peeling force, And a length of at least 50 mm as a length of a bonding portion of the polarizing plate and the protective film. The second peeling force measurement tape has a peeling force equal to the peeling force described in the section of the characteristic of the first peeling force measurement tape.

The polarizing layer of the polarizing plate with the protective film cut out from above was fixed to a glass substrate (0.4 mm thick, manufactured by Corning) with a pressure-sensitive adhesive and pressurized in an autoclave at a temperature of 50 캜 and a pressure of 0.6 MPa for 20 minutes, 23 캜 and 50% relative humidity for 24 hours. Subsequently, the protective film was bonded onto the protective film over the length of at least 50 mm from one end in the longitudinal direction of the second peeling force measurement tape, at the center of the protective film of the polarizing plate with the protective film fixed on the glass substrate, A test piece for measurement of the second peeling force was used in which the protective tape had a length of at least 5 mm from the other end in the longitudinal direction of the measurement tape but not bonded to the protective film.

The obtained second peel strength test piece was set on a peeling device (LH-020N, manufactured by Imadate Seisakusho Co., Ltd.) and bonded to the protective film in the second peel strength measuring tape of the second peel strength measuring test piece And the other end in the longitudinal direction was pinched by the jig of the peeling apparatus. Thereafter, the second peeling force measurement test piece and the second peeling force measurement tape length were measured so that the second peeling force measurement tape was peeled in the longitudinal direction at a peeling speed of 3 m / min and a peeling angle of 90 [ (The portion pinched with the jig of the peeling apparatus) is relatively moved to start peeling off the second peeling force measurement tape, and immediately after peeling off the second peeling force measurement tape from the protective film, The peeling force from the time when the tape for peeling force measurement was completely peeled off from the protective film was measured as the second peeling force.

[Calculation of loss coefficient tan?] [

The loss factor tan? Was calculated by the following formula.

tan? = {(second peeling force [N / 25 mm]) ^3.5 / (first peeling force [N / 60 mm]) ^1.5 }

[Peelability test]

The polarizing plate with the protective film obtained in each of the Examples and Comparative Examples was fixed to a glass substrate (0.4 mm thick, manufactured by Corning) with a pressure-sensitive adhesive and pressurized in an autoclave at a temperature of 50 캜 and a pressure of 0.6 MPa for 20 minutes, , And then stored at an ambient temperature of 23 DEG C and a relative humidity of 50% for 24 hours. Subsequently, on one end side of the polarizing plate with the protective film fixed on the glass substrate and extending in the width direction of the protective film (side perpendicular to the absorption axis), a peeling tape (the first peeling force measurement tape A tape having the peeling force equal to the peeling force described in the section of the characteristics of the tape. At this time, in the portion where the peeling tape overlaps with the one end side of the protective film, the middle point in the width direction of the peeling tape and the middle point of the one end side of the protective film are made to coincide with each other, The test pieces were bonded to a protective film in a length of 5 to 10 mm in the longitudinal direction on one end side and fixed so that the remainder of the peeling tape protruded in the longitudinal direction on the protective film.

The obtained test piece for peelability test was set on a peeling apparatus (LH-020N, manufactured by Imadate Seisakusho Co., Ltd.), and the remaining portion of the peeling tape (the portion protruding from the protective film) was pinned by the jig of the peeling apparatus. Thereafter, the test piece for peelability test in the longitudinal direction and the remainder of the peeling force measurement tape (the portion pinched by the jig of the peeling device) were relatively moved at a peeling speed of 3 m / min and a peeling angle of 90 degrees. As a result of the peelability test, it was evaluated that the peelability was evaluated to be good, peeling of the protective film was possible, peeling of the peelable tape from the protective film, or peeling of the protective film was impossible.

[Example 1]

(Production of polarizing plate with protective film)

The polyvinyl alcohol film was uniaxially stretched and stained with iodine to obtain a polarizing film having a thickness of 8 占 퐉. On one side of the resulting polarizing film, a cyclic olefin based resin film having a thickness of 13 占 퐉 was laminated via an adhesive made of an active energy ray curable resin. Subsequently, a brightness enhancement film having a multilayer structure was laminated on the other side of the polarizing film through a pressure-sensitive adhesive. Thereafter, the protective film having the first adhesive layer was laminated so that the first adhesive layer was disposed on the side of the brightness enhancement film. Further, 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 above-mentioned cyclic olefin based resin film, and the absorption axis of the polarizing layer was set in the longitudinal direction. The length along the width direction perpendicular to the longitudinal direction was 60 mm, the length along the longitudinal direction Was 60 mm or more to obtain a polarizing plate with a protective film. The obtained polarizing layer of the polarizing plate with a protective film is a layer structure of a brightness enhancing film / adhesive layer / polarizing film / adhesive layer / cycloolefin resin film.

Table 1 shows the measurement results of the first peeling force, the second peeling force and the loss coefficient tan? Of the protective film, polarizing layer and first adhesive layer used for the obtained polarizing plate with protective film. Table 1 shows the results of peelability test using a polarizing plate with protective film.

[Examples 2 to 7 and 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 a polarizing plate with a protective film was prepared in the same manner as in Example 1 except that the peeling property test was carried out at the peeling rate shown in Table 1 . The protective film was adjusted to the first peeling force and the second peeling force shown in Table 1 by subjecting the back surface and the first adhesive layer to corona treatment.

Table 1 shows the measurement results of the first peeling force, the second peeling force and the loss coefficient tan? Of the protective film, polarizing layer and first adhesive layer used for the obtained polarizing plate with protective film. Table 1 shows the results of peelability test using a polarizing plate with protective film.

From the results shown in Table 1, it can be seen that good peelability of the protective film can be obtained by setting the second peeling force to 6 N / 25 mm or more. From the results of Examples 1 to 7, it can be seen that by setting the second peeling force to 6 N / 25 mm or more, good peeling property of the protective film can be obtained even in the peeling condition where the peeling speed is high and strict.

1: Polarizing plate with protective film
10: Protective film
11: base film
12: First adhesive layer (adhesive layer)
20: polarizing layer
21: polarizing film
22: Resin layer
25: bonding layer
30: Separator
35: Second adhesive layer

Claims (6)

A polarizing plate with a protective film formed by laminating a protective film on at least one side of a polarizing layer so as to be peelable,
A first peeling force which is a peeling force between the polarizing layer and the protective film is 0.29 N / 60 mm or more and 1 N / 60 mm or less,
A second peeling force of the back surface which is a surface opposite to the side facing the polarizing layer of the protective film is 6 N / 25 mm or more,
And the second peeling force is a peeling force between the back surface and the tape when a peeling force measurement tape is bonded to the back surface. The polarizing plate with a protective film according to claim 1, wherein the second peeling force is 15 N / 25 mm or less. The polarizing plate according to claim 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 tan? Of the pressure-sensitive adhesive layer is 0.2 or more. The polarizing plate 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,
Wherein the protective film is provided on the resin layer. The polarizing plate with a protective film according to claim 4, wherein the resin layer has a multilayer structure. The polarizing film according to claim 4 or 5, wherein the polarizing film is a polyvinyl alcohol-based resin layer in which a dichroic dye is adsorbed and oriented,
Wherein the resin layer is a brightness enhancement film.

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