WO2016072358A1

WO2016072358A1 - Method for manufacturing optical film provided with protective film

Info

Publication number: WO2016072358A1
Application number: PCT/JP2015/080676
Authority: WO
Inventors: 宙孝石川; 泰礼加藤; 規光坂田
Original assignee: 住友化学株式会社
Priority date: 2014-11-04
Filing date: 2015-10-30
Publication date: 2016-05-12
Also published as: TW201632921A; CN107073921A; TWI666474B; KR20170078716A

Abstract

Provided is a method for manufacturing an optical film provided with a protective film, the method including a step for affixing a protective film to the surface of an optical film, wherein the peel force of the protective film from the optical film in both end sections in the width direction of the optical film provided with a protective film obtained by the step for affixing the protective film is increased relative to the peel force in the other portion of the optical film provided with a protective film. This manufacturing method preferably further includes a step for removing both end sections in the width direction after the step for affixing the protective film.

Description

Method for producing optical film with protective film

The present invention relates to a method for producing an optical film with a protective film formed by laminating a protective film on the surface of an optical film, and more particularly to a production method in which the optical film is a polarizing plate.

An optical film used for an image display device such as a liquid crystal display device may be a laminated film composed of a plurality of films. For example, a polarizing plate, which is a kind of optical film, is generally laminated with a protective film on one or both sides of a polarizer, which is an optical film, and further laminated with an optical film having an optical function other than the polarizer. It has the structure. The polarizing plate is usually laminated with another raw material film continuously unwound from the film roll to the raw material film that is continuously unwound from the film roll and conveyed. It is manufactured by a so-called roll-to-roll method in which a laminated film (polarizing plate) is wound into a roll.

In the method of manufacturing an optical film such as a roll-to-roll method, when winding an optical film such as a polarizing plate manufactured as a long product, in order to protect the optical film surface, In general, a protective film (also called a surface protective film) that can be peeled off on the film surface is similarly laminated by a roll-to-roll method, and wound up as an optical film with a protective film [for example, Japanese Patent Application Laid-Open No. 2008-2008]. -275722 (Patent Document 1), JP 2012-121269 (Patent Document 2)]. This protective film is a film for temporarily protecting the surface of an optical film product. For example, when assembling an image display device (more specifically, an optical film with a protective film is bonded to an image display element). And then removed).

JP 2008-275722 A JP 2012-121269 A

As described above, since the protective film is accompanied by a peeling process for peeling and removing the protective film from the optical film, antistatic performance is required to prevent the generation of static electricity at the time of peeling. Further, in order to enhance the antistatic performance and facilitate the peeling process, low adhesion to the optical film (low peeling force of the protective film to the optical film) is also required. However, the low adhesion of the protective film causes a new problem called “floating”. In this specification, “floating” means that when the optical film with a protective film is manufactured or when the manufactured optical film with a protective film is stored and transported as a take-up roll, the protective film is at the end in the width direction. This means that the protective film is partially peeled off and the protective film is lifted at that portion. When such “floating” occurs in an optical film with a protective film, for example, when the optical film with a protective film is passed through a nip roll in a later process, the air that has entered the “floating” portion is sandwiched between the nip rolls and compressed. The compressed air can cause quality defects such as streak marks on the optical film.

Therefore, the present invention suppresses the problem of “floating” of the protective film during the production of the optical film with the protective film (particularly when the optical film is a polarizing plate), while protecting the optical film in the protective film peeling process. An object of the present invention is to provide a method for producing an optical film with a protective film in which low adhesion of the film is realized and the protective film can be removed and removed relatively easily.

This invention provides the manufacturing method of the optical film with a protective film shown below.
[1] A method for producing an optical film with a protective film comprising a step of bonding a protective film to the surface of the optical film,
In the optical film with a protective film obtained by the step of bonding the protective film, the peeling force of the protective film with respect to the optical film at both ends in the width direction is higher than the other parts of the optical film with the protective film. Manufacturing method.

[2] The manufacturing method according to [1], further including a step of removing both end portions in the width direction after the step of bonding the protective film.

[3] The manufacturing method according to [1] or [2], wherein the peeling force is increased by further including a step of performing a corona treatment before the step of bonding the protective film.

[4] The manufacturing method according to [3], wherein the corona treatment is performed on the optical film.

[5] The manufacturing method according to any one of [1] to [4], wherein a peeling force of the protective film with respect to the optical film is 0.09 N / 25 mm or more at both ends in the width direction.

[6] The protective film includes a pressure-sensitive adhesive layer bonded to the surface and a base film that supports the pressure-sensitive adhesive layer. The manufacturing method according to [1] or [2], wherein the peeling force is increased by using a material that is higher than the portion.

[7] The production method according to any one of [1] to [6], wherein the optical film is a polarizing plate.

According to the present invention, while suppressing the problem of “lifting” of the protective film during the production of the optical film with the protective film or when storing and transporting the manufactured optical film with the protective film as a take-up roll, In the peeling step, the low adhesion of the protective film to the optical film is realized, and a method for producing an optical film with a protective film that can peel and remove the protective film relatively easily can be provided.

That is, according to the present invention, the adhesiveness between the optical film and the protective film is enhanced at both ends in the width direction. Therefore, when manufacturing an optical film with a protective film, specifically, when the protective film is bonded, after the bonding, The problem of “floating” of the protective film at the time of winding of the optical film with a film and at the time of storage / transportation in a roll state can be suppressed, and thereby the above-mentioned poor quality can also be suppressed. Moreover, if the both ends in the width direction are removed from the optical film with a protective film having improved adhesion at both ends in the width direction until the protection film is peeled off, the protection in the peeling step is performed. The film can be peeled and removed relatively easily. The present invention is particularly effective for a polarizing plate that is prone to quality defects due to “floating” of the protective film.

It is a schematic process drawing which shows the manufacturing method of the polarizing plate with a protective film which concerns on this invention. It is a schematic sectional drawing which shows an example of the laminated constitution of a polarizing plate. It is a schematic top view for demonstrating the evaluation method of a float.

Hereinafter, the present invention will be described in more detail with reference to the case where the optical film is a polarizing plate, but the present invention is not limited to this example, and the case where the optical film is a polarizing plate will be described as an example. The following description to be described can be applied to other optical films. The other optical film can be a single layer film or a multilayer film.

With reference to FIG. 1, the manufacturing method of the polarizing plate with a protective film which concerns on this invention includes the process of bonding the protective film 20 on the surface of the polarizing plate 10 [FIG. 1 (a) and (b)]. In the width direction both ends A of the polarizing plate 1 with a protective film obtained by the step of laminating the protective film 20, the peeling force of the protective film 20 with respect to the polarizing plate 10 is applied to other parts of the polarizing plate 1 with the protective film. It is characterized by being higher than that. By controlling the peeling force so as to increase the peeling force at both ends A in the width direction and bonding the polarizing plate 10 and the protective film 20, the above problem of “floating” and thus the above-mentioned quality defect can be effectively suppressed. can do. Such a feature is that it is not always necessary to increase the peeling force (adhesiveness) in the entire bonding interface between the polarizing plate 10 and the protective film 20 in order to suppress the “float”, and the peeling force at both ends A in the width direction. This is based on the idea that only improvement is necessary and the examination results that support this.

Moreover, according to the polarizing plate 1 with a protective film which raised the peeling force only about the width direction both ends A instead of the whole area | region of the said bonding interface in this way, it passes through the simple process of removing the width direction both ends A. Thus, a polarizing plate 1 ′ with a protective film comprising the polarizing plate 10 ′ and the protective film 20 ′ from which both end portions A in the width direction have been removed can be easily obtained [FIG. 1 (c)]. In this polarizing plate with a protective film 1 ′, the protective film 20 ′ is relatively removed in the peeling step of the protective film 20 ′ (for example, the peeling step after the polarizing plate with protective film 1 ′ is bonded to the image display element). Since it can peel and remove easily, while being able to improve the antistatic performance of polarizing plate 1 'with a protective film, the ease of implementation of the said peeling process can be improved. If the width direction both ends A which are peeled off and are removed are set outside the effective width range of the polarizing plate 1 with the protective film, the yield of the polarizing plate 1 'with the protective film may decrease. Absent.

Hereinafter, the manufacturing method of the polarizing plate with a protective film according to the present invention will be described in detail with reference to embodiments. A plurality of embodiments shown below differ in a specific method for increasing the peeling force at both ends A in the width direction of the polarizing plate 1 with a protective film.

<First Embodiment>
The manufacturing method of the polarizing plate with a protective film according to this embodiment includes the following steps:
The peeling force of the protective film 20 with respect to the polarizing plate 10 at both ends A in the width direction of the polarizing plate 1 with the protective film obtained by bonding the protective film 20 to the surface of the polarizing plate 10 is different from that of the polarizing plate 1 with the protective film. In order to make it high compared with a part, the process of performing the surface activation process on the bonding surface, and the process of bonding the protective film 20 on the said surface of the polarizing plate 10 are included in this order.

As described above, preferably, after the step of pasting the protect film 20,
The method further includes a step of removing both end portions A in the width direction. Hereinafter, each step will be described.

(1) Process for surface activation treatment [Polarizing plate]
The layer configuration of the polarizing plate 10 used in this step is not particularly limited as long as it includes a polarizer, but usually includes a polarizer and a protective film laminated and bonded onto at least one surface thereof. The protective film may be laminated and bonded on both surfaces of the polarizer. The protective film is usually laminated and bonded onto the polarizer via an adhesive layer.

The polarizing plate 10 can also have layers (or films) other than a polarizer and a protective film. For example, a polarizing plate is generally marketed as a polarizing plate with an adhesive layer in which an adhesive layer for bonding to an image display element (for example, a liquid crystal cell) or other optical member is previously laminated on the outer surface of the polarizing plate. Although many, the polarizing plate 10 used by this invention can also contain such an adhesive layer. When an adhesive layer is included, a separate film (separator) for protecting the surface (outer surface) is usually laminated on the outer surface of the adhesive layer.

The protective film of the polarizing plate 10 has a surface treatment layer such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer on the outer surface (the surface opposite to the polarizer). (Coating layer) may be provided. Furthermore, the polarizing plate 10 can include a layer or a film having an optical function other than the polarizer. One example is a retardation film.

An example of the layer structure of the polarizing plate 10 is shown in FIG. The polarizing plate 10 shown in FIG. 2 includes a polarizer 100; a first protective film 200 that is bonded to one surface of the polarizer 100; a second protective film 300 that is bonded to the other surface of the polarizer 100; A pressure-sensitive adhesive layer 400 laminated on the outer surface of the second protective film 300; and a separate film 500 laminated on the outer surface of the pressure-sensitive adhesive layer 400. In addition to the polarizer 100 and the protective film (the first protective film 200 and the second protective film 300), the layer structure including the pressure-sensitive adhesive layer 400 and the separate film 500 is one of the preferable layer structures of the polarizing plate 10 used in the present invention. One.

The polarizer 100 is an optical film having a property of absorbing linearly polarized light having a vibration surface parallel to the optical axis and transmitting linearly polarized light having a vibration surface orthogonal to the optical axis. For example, the polarizer 100 is uniaxially stretched and has two colors. It can be a polyvinyl alcohol-based resin film in which a functional dye is adsorbed and oriented. As the dichroic dye, iodine or a dichroic organic dye is used. The polyvinyl alcohol-based resin constituting the polarizer 100 includes polyvinyl alcohol, which is a saponified product of polyvinyl acetate, as well as co-polymerization of vinyl acetate and other monomers (for example, ethylene and unsaturated carboxylic acid) copolymerizable therewith. It may be a vinyl alcohol copolymer which is a saponified product. The thickness of the polarizer 100 is usually about 5 to 40 μm.

The polarizer 100 includes a step of uniaxially stretching a polyvinyl alcohol-based resin film, a step of dyeing the polyvinyl alcohol-based resin film with a dichroic dye and adsorbing the dichroic dye, and polyvinyl alcohol on which the dichroic dye is adsorbed. It can manufacture by the method of including the process of wash | cleaning a system resin film with the boric-acid aqueous solution, and the process of washing with water after the process by boric-acid aqueous solution. The dichroic dye can be dyed by immersing the film in an aqueous solution containing the dichroic dye, and the treatment with the boric acid aqueous solution can be performed by immersing the film in the boric acid aqueous solution.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after the dyeing of the dichroic dye. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, you may uniaxially stretch in these several steps.

The first and second

protective films

200 and 300 may be a thermoplastic resin film having translucency (preferably optically transparent). Specific examples of thermoplastic resins include polyolefin resins such as chain polyolefin resins (polypropylene resins, etc.) and cyclic polyolefin resins (norbornene resins, etc.); polyester resins (polyethylene terephthalate resins, etc.); ) Acrylic resin (methyl methacrylate resin, etc.); Cellulosic resin (cellulose acetate resin such as triacetyl cellulose and diacetyl cellulose); Polycarbonate resin; Polyvinyl alcohol resin; Polyvinyl acetate resin; Polyarylate Polystyrene resin; Polyether sulfone resin; Polysulfone resin; Polyamide resin; Polyimide resin; and mixtures and copolymers thereof. The thickness of the first and second

protective films

200 and 300 is, for example, about 5 to 200 μm, preferably 10 to 150 μm, more preferably 15 to 100 μm. In the present specification, “(meth) acryl” means at least one selected from acryl and methacryl.

As in the example shown in FIG. 2, when the first protective film 200 is provided on one surface of the polarizer 100 and the second protective film 300 is provided on the other surface, the first protective film 200 and the second protective film 200 are provided. The protective film 300 may be made of the same kind of thermoplastic resin or may be made of a different kind of thermoplastic resin.

The polarizer 100, the 1st protective film 200, and the 2nd protective film 300 can be bonded through an adhesive bond layer. As the adhesive forming the adhesive layer, a water-based adhesive, that is, an adhesive component dissolved or dispersed in water, or an active energy ray-curable adhesive can be used.

The adhesive component of the water-based adhesive can be, for example, a polyvinyl alcohol resin or a urethane resin. The active energy ray-curable adhesive can be, for example, a curable composition containing an active energy ray-curable compound such as an epoxy compound or a (meth) acrylic compound and a polymerization initiator. The active energy ray-curable adhesive can be a solventless adhesive, but can also contain an organic solvent. If a solventless type adhesive is used, a drying process for removing the solvent becomes unnecessary. When an active energy ray-curable adhesive is used, after bonding a protective film through an adhesive layer, the active energy rays such as visible light, ultraviolet rays, X-rays, electron beams, etc., preferably ultraviolet rays are irradiated and bonded. The agent layer is cured. Therefore, in this case, the adhesive layer in the polarizing plate 10 is made of a cured product of an active energy ray-curable adhesive.

As shown in FIG. 2, when the first protective film 200 is provided on one surface of the polarizer 100 and the second protective film 300 is provided on the other surface, the first protective film 200 is bonded. The first adhesive layer and the second adhesive layer that bonds the second protective film 300 may be formed from the same type of adhesive or from different types of adhesive, From the viewpoint of production efficiency, it is preferably formed from the same kind of adhesive.

The pressure-sensitive adhesive layer 400 can be used for bonding a polarizing plate with a protective film to an image display element (for example, a liquid crystal cell) or another optical member. Examples include (meth) acrylic adhesives, urethane adhesives, silicone adhesives, polyester adhesives, polyamide adhesives, polyether adhesives, fluorine adhesives, and rubber adhesives. Among these, a (meth) acrylic pressure-sensitive adhesive is preferably used from the viewpoints of transparency, adhesive strength, reliability, reworkability, and the like. The thickness of the pressure-sensitive adhesive layer 400 is usually 2 to 40 μm.

The separate film 500 is provided for the purpose of temporarily protecting the adhesive layer 400 when the polarizing plate with a protective film is stored, transported, or inspected. The separate film 500 that protects the pressure-sensitive adhesive layer 400 is peeled off and removed immediately before the polarizing plate with a protective film is bonded to, for example, an image display element or another optical member.

The separate film 500 is usually composed of a thermoplastic resin film having a release treatment on one side, and the release treatment surface is bonded to the pressure-sensitive adhesive layer 400. The thermoplastic resin constituting the separate film 500 can be, for example, a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, and the like.

The layer configuration of the polarizing plate 10 used in this step is not limited to the example shown in FIG. 2, and for example, the following layer configuration may be used.

a) A configuration in which the separate film 500 or the pressure-sensitive adhesive layer 400 and the separate film 500 are omitted,
b) A configuration in which any one of the first protective film 200 and the second protective film 300 is omitted,
c) a configuration using an optical compensation film such as a retardation film as the second protective film 300;
d) A configuration having an optical compensation film such as a retardation film in addition to the first protective film 200 and the second protective film 300.

An example of the above b) is a configuration in which the second protective film 300 is omitted, and a preferred specific example thereof is that the pressure-sensitive adhesive layer 400 is directly laminated on the surface of the polarizer 100 opposite to the first protective film 200. The first protective film 200 / the polarizer 100 / the pressure-sensitive adhesive layer 400 / the separate film 500 has a layer structure.

A preferred specific example of c) is a layer structure of first protective film 200 / polarizer 100 / retardation film (second protective film 300) / adhesive layer 400 / separate film 500. A preferred specific example of the above d) has a layer structure of first protective film 200 / polarizer 100 / second protective film 300 / retardation film / adhesive layer 400 / separate film 500. In this case, the 2nd protective film 300 and retardation film can be bonded through an adhesive layer, for example.

The retardation film is an optical film having optical anisotropy such as uniaxial or biaxial, and can be, for example, a stretched film of a thermoplastic resin. The thermoplastic resin may be those exemplified above for the first and second

protective films

200 and 300, and may be polyvinylidene fluoride / polymethyl methacrylate copolymer, liquid crystal polyester, acetyl cellulose, ethylene-vinyl acetate. A saponified copolymer, polyvinyl chloride, or the like can also be used. The draw ratio is usually about 1.01 to 6 times.

[Protect film]
The protective film 20 that is bonded to the polarizing plate 10 is a film that is temporarily bonded to protect the surface of the polarizing plate. Usually, for example, a polarizing plate with a protective film on an image display element or other optical member. Is peeled off together with the adhesive layer it has.

The protective film 20 can include a base film made of a thermoplastic resin and an adhesive layer provided on one side thereof. The thermoplastic resin constituting the base film can be, for example, a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, and the like. Regarding the pressure-sensitive adhesive layer that the protective film 20 has, the description of the pressure-sensitive adhesive layer 400 described above is cited. The protective film 20 is bonded to the surface of the polarizing plate 10 through the adhesive layer.

[Surface activation treatment]
The surface activation treatment performed before the step of bonding the protective film 20 to the surface of the polarizing plate 10 includes corona treatment, plasma treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment (for example, sodium hydroxide or Immersion treatment in an alkaline aqueous solution such as potassium hydroxide). Among these, corona treatment and plasma treatment are preferably used because it can be carried out relatively easily and has an excellent effect of increasing the peel strength (adhesiveness) of the protective film 20 to the polarizing plate 10. Preferably used. For example, when the corona treatment is performed, the peeling force tends to increase as the corona discharge amount increases. The amount of corona discharge is usually 10 W · min / m ² or more, and is preferably 15 W · min / m ² or more in order to increase the peeling force and effectively suppress the occurrence of “floating”. Further, the upper limit of the corona discharge amount is usually 80 W · min / m ² or less.

The surface activation treatment is performed only on the bonding surface portion that is included in both end portions A in the width direction of the polarizing plate 1 with a protective film obtained by bonding the protective film 20 to the polarizing plate 10. Thereby, the polarizing plate 1 with a protective film whose peeling force of the both ends A of the width direction was raised compared with the other part of the polarizing plate 1 with a protective film can be obtained. Thus, although the peeling force in the width direction both ends A is made higher than the other part of the polarizing plate 1 with the protective film, the other part is a part that is not subjected to the surface activation treatment. In other words, it can be said that the peeling force at both end portions A is higher than that in the case where the surface activation treatment is not performed (part).

In addition, the protective film 20 comprised by the base film and the adhesive layer provided in the single side | surface WHEREIN: In one Embodiment, the width | variety of an adhesive layer is smaller than the width | variety of a base film, and an adhesive layer is in both ends. Some have a base film portion that is not formed. In the case where such a protective film 20 is used, the width direction both ends A of the protective film-attached polarizing plate 1 refer to both end portions where the base film and the polarizing plate are bonded via an adhesive layer, The base film part in which the said adhesive layer is not formed is not included. The base film portion is not bonded to the polarizing plate, and is a portion that cannot cause the problem of “floating” in the first place.

The surface activation treatment is preferably performed at least on the bonding surface portion on the polarizing plate 10 side to be included in both ends A in the width direction. For example, in the case of using corona treatment, surprisingly, no increase in peeling force is recognized even if corona treatment is performed on the bonding surface portion on the side of the protective film 20 that will be included in both ends A in the width direction. The trend is clear. Therefore, it is preferable that the bonding surface part to which a corona treatment is given contains the bonding surface part by the side of the polarizing plate 10 which will be contained at the width direction both ends A at least.

The width of both ends A in the width direction where the surface activation treatment is performed is not particularly limited as long as sufficient adhesion to suppress “floating” is obtained, and is, for example, 1 mm or more per one end, preferably It is 5 mm or more. The upper limit of the width is not particularly limited, and may depend on, for example, 25 mm or less, preferably 15 mm or less per one end, although it depends on the width of the polarizing plate 1 with a protective film.

The peeling force at both ends A in the width direction is preferably 0.09 N / 25 mm or more, and more preferably 0.1 N / 25 mm or more in order to effectively suppress “floating”. When the peeling force is less than 0.09 N / 25 mm, the adhesion at the width direction both ends A is insufficient, and there is a possibility that “floating” cannot be effectively suppressed. Moreover, the peeling force in the width direction both ends A is usually 0.20 N / 25 mm or less. If the peeling force exceeds 0.20 N / 25 mm, the peeling process cannot be easily performed, and production efficiency may be reduced. The measuring method of peeling force follows description of the term of the Example mentioned later.

The surface activation treatment can be continuously performed on the raw material film (the polarizing plate 10 and / or the protective film 20) that is continuously conveyed. More specifically, for example, in the case of corona treatment, a corona discharge device is installed on the transport path of the long polarizing plate 10 that is continuously transported, at both ends in the width direction of the polarizing plate 10. The corona treatment can be continuously performed on both ends in the width direction of the polarizing plate 10 passing through the corona discharge device while the polarizing plate 10 is continuously conveyed.

Generally, the polarizing plate with a protective film obtained as a long product has both ends in the width direction in order to adjust the length in the width direction to a desired value, or to remove a part that is difficult to use as a product in terms of quality and appearance. The slit is removed, and more typically, the sheet is cut to adjust to a desired value not only in the width direction but also in the longitudinal direction to form a single wafer, and is bonded to an image display element or the like. Thus, the long polarizing plate with a protective film usually has an effective width (width actually used as a product), and both ends in the width direction outside the effective width range are removed. It is preferable that the width direction both ends A where the peeling force is increased are provided in both width direction ends outside the effective width range. Thereby, when implementing the process of removing the width direction both ends A, even if the said process is implemented, the fall of the yield of polarizing plate 1 'with a protective film can be prevented.

(2) The process of bonding the protective film 20 Bonding of the protective film 20 to the polarizing plate 10 can be performed by a conventionally well-known method. For example, on the surface of the long polarizing plate 10 that is continuously conveyed (for example, the surface on the side subjected to the corona treatment if the polarizing plate has been subjected to corona treatment at both ends in the width direction). It is possible to continuously bond the protective film 20 by disposing the long protective film 20 that is continuously transported and passing the laminate through a bonding roll and pressurizing it from above and below. By this step, the polarizing plate 1 with a protective film shown in FIG. 1B is obtained. The obtained polarizing plate 1 with a long protective film may be wound up in a roll shape.

According to the method of the present invention for increasing the peel strength at both ends A in the width direction, the protective film 1 is protected at the time of manufacturing the polarizing plate 1 with a protective film, specifically at the time of bonding the protective film 20 to the polarizing plate 10, after bonding. The problem of “floating” of the protective film 20 at the time of winding the polarizing plate with film 1 and at the time of storage and transportation in a roll state can be effectively suppressed.

(3) Step of removing both ends A in the width direction In this step, the slits are removed from both ends A in the width direction of the polarizing plate 1 with a protective film having an increased peeling force, so that the protective film 20 ′ is peeled off relatively easily. A polarizing plate 1 ′ with a protective film that can be removed can be obtained [FIG. 1 (c)]. Conventionally known cutting (cutting) means such as a shear cutter can be used for the slit. As described above, both end portions in the width direction of the polarizing plate 1 with a protective film are removed and also cut in the longitudinal direction to obtain a polarizing plate 1 ′ with a protective film that is a sheet having a desired size. Good.

The slit width at the time of slit removal at both ends in the width direction of the polarizing plate 1 with a protective film is not particularly limited as long as the portion where the slit is removed includes the entire width direction both ends A with enhanced peeling force. Usually, by removing this slit, a polarizing plate 1 ′ with a protective film having an effective width is produced.

Second Embodiment
The manufacturing method of the polarizing plate with a protective film according to this embodiment includes the following steps:
The step of preparing the protective film 20 in which the adhesive strength of the portion constituting the width direction both ends A in the pressure-sensitive adhesive layer is enhanced as compared with other portions, and the step of bonding the protective film 20 to the surface of the polarizing plate 10 Are included in this order.

That is, in the first embodiment, the surface activation treatment is performed in order to increase the peeling force at both end portions A in the width direction of the polarizing plate 1 with a protective film, whereas the present embodiment has both ends in the width direction. In order to increase the peeling force in the part A, the protective film 20 in which the adhesive force of the pressure-sensitive adhesive layer in the part corresponding to the width direction both ends A is used is used. Those skilled in the art can obtain a polarizing plate 1 with a protective film in which only the peeling force at both ends A in the width direction is increased by this method, and that the same effects as the first embodiment can be obtained. Can be easily understood.

About the process of bonding the protective film 20, and the process of removing the width direction both ends A preferably implemented following this, it is the same as that of the said 1st Embodiment, and the description in the said 1st Embodiment is referred. .

The protective film 20 used in the present embodiment can include a base film made of a thermoplastic resin and an adhesive layer provided on one surface thereof, as in the first embodiment. The pressure-sensitive adhesive layer of the protective film 20 used in the present embodiment can be formed by coating different pressure-sensitive adhesive compositions having different adhesive forces. Specifically, both end portions in the width direction of the polarizing plate 1 with protective film A pressure-sensitive adhesive layer X made of a pressure-sensitive adhesive composition provided in a part corresponding to A and a pressure-sensitive adhesive layer Y made of a pressure-sensitive adhesive composition provided in another part. Can do.

As a method for increasing the adhesive strength of the pressure-sensitive adhesive composition, for example, a method for increasing the molecular weight of the resin component in the pressure-sensitive adhesive composition (for example, a (meth) acrylic polymer for a (meth) acrylic pressure-sensitive adhesive) or pressure-sensitive adhesive Examples include a method of adding a tackifying resin to the agent composition.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following examples, the peeling force of the protective film with respect to the polarizing plate in the polarizing plate with the protective film was in accordance with the following measuring method.

(Protective film peeling force)
A test piece having a size of 25 mm × 150 mm was cut out from the end in the width direction including the corona-treated bonding interface in the obtained long polarizing plate with a protective film. Under the present circumstances, the test piece was cut out so that the short side direction might become parallel to the longitudinal direction of the elongate polarizing plate with a protective film. Next, the separate film was peeled from the test piece, and bonded to a glass substrate using the adhesive layer that the test piece had. Next, while fixing the polarizing plate side of the test piece, the protective film was removed from the polarizing plate using an AGS-D type tester manufactured by Shimadzu Corporation under the conditions of a peeling angle of 180 ° and a peeling speed of 300 mm / min. It peeled and the peeling force (unit: N / 25mm) was measured.

<Example 1>
[1] Production of Polarizing Plate and Surface Activation Treatment Continuous production of a long polarizing plate 10 having a layer structure shown in FIG. 2 is carried by continuously unwinding a long raw material film from a film roll. Manufactured. The polarizing plate 10 is composed of a first protective film 200 (TAC film) having a thickness of 60 μm / a polarizer 100 having a thickness of 25 μm (a uniaxially stretched polyvinyl alcohol film in which iodine is adsorbed and oriented) / a second protective film 300 having a thickness of 50 μm. (Retardation film made of cyclic polyolefin resin) / 20 [mu] m thick adhesive layer 400 ((meth) acrylic adhesive layer) / 38 [mu] m separate film 500 (polyethylene terephthalate film subjected to release treatment on one side) It is. Both the first protective film 200 and the second protective film 300 are an active energy ray-curable adhesive (an ultraviolet curable adhesive containing a curable compound that is a cationic polymerizable epoxy compound and a photocationic polymerization initiator). It is bonded to the polarizer 100 through an adhesive layer made of a cured product of “KR-70T” manufactured by ADEKA Corporation. The width of the polarizing plate 10 is 1330 mm. The effective width of the polarizing plate 10 is 1250 mm. Therefore, the end width outside the effective width range is 40 mm per one end.

While continuously transporting the polarizing plate 10 obtained above, corona treatment was performed on both ends in the width direction of the outer surface of the first protective film 200 using two corona discharge devices. The width of the end portion in the width direction subjected to the corona treatment ranges from the effective width of the polarizing plate 10 to about 15 mm to the outside of the effective width for each of both ends (the outer side is the adhesive layer of the protective film 20 outside this). It is a region where the pressure-sensitive adhesive layer is not bonded, and the corona discharge amount is 73 W · min / m ² .

[2] Bonding of protective film to polarizing plate Continuously unwinds and transports a long protective film 20 (consisting of a (meth) acrylic adhesive layer and a polyethylene terephthalate film, thickness 53 μm) from the film roll. However, it arrange | positions on the outer surface of the 1st protective film 200 in the polarizing plate 10 after the corona treatment obtained by said [1], it passes through a bonding roll, the protection film 20 is bonded, and elongate protection A polarizing plate with a film was continuously produced.

<Examples 2 to 3>
A polarizing plate with a protective film was obtained in the same manner as in Example 1 except that the corona discharge amount was as shown in Table 1.

<Comparative Example 1>
A polarizing plate with a protective film was obtained in the same manner as in Example 1 except that the corona treatment was performed on both ends in the width direction of the protective film 20 instead of the polarizing plate 10. In Table 1, “Pf” means a protective film.

<Comparative example 2>
A polarizing plate with a protective film was obtained in the same manner as in Example 1 except that the corona treatment was not performed.

For the polarizing plate with a protective film obtained in Examples and Comparative Examples, the peeling force of the protective film was measured according to the above method. The results are shown in Table 1. Moreover, about the polarizing plate with a protective film obtained by the Example and the comparative example, the presence or absence of the float and the magnitude | size when it had the float were evaluated in accordance with the following procedure. The results are also shown in Table 1.

(Evaluation of floating)
With reference to FIG. 3, a test piece having a size of 700 mm × 1330 mm was cut out from the obtained polarizing plate with a protective film. Under the present circumstances, the test piece was cut out so that the short side direction might become parallel to the longitudinal direction of the elongate polarizing plate with a protective film. The long side direction (1330 mm) of the test piece is parallel to the width direction of the polarizing plate 10 and is the same width as the width of the polarizing plate 10. Note that “one end face of the polarizing plate with a protective film” described in FIG. 3 refers to the end face of the pressure-sensitive adhesive layer that the protective film 20 has. The obtained test piece is visually checked for the presence or absence of lift, and for those having a lift, the size of the test piece is defined as the distance from the inner end of the float to the effective end, and the “floating penetration L” is used as an index. As evaluated. It is evaluated that the smaller the L, the larger the float.

In Examples 1 to 3, no floating was observed in either the long polarizing plate with a protective film before cutting out the test piece or the test piece. On the other hand, in Comparative Examples 1 and 2, at both ends of the long polarizing plate with a protective film before cutting out the test piece, floating was recognized substantially uniformly in the longitudinal direction, and even in the above test piece cut out at an arbitrary position. About 20 floats were recognized in both Comparative Examples 1 and 2. The floating penetration L shown in Table 1 is the maximum value for these approximately 20 floats.

As described above, the polarizing film with a protective film has been described as an example of the optical film with a protective film. However, the optical film other than the polarizing plate is protected when wound up and stored and transported in a roll state. It can be expected that the problem of “floating” of the film can be suppressed and thereby the above-mentioned quality defect can be suppressed. Examples of the other optical film include films having optical functions such as a retardation film, a brightness enhancement film, an antiglare film, a light diffusion film, and a polarizer in addition to the protective film.

1, 1 'polarizing plate with protective film, 10, 10' polarizing plate, 20, 20 'protective film, 100 polarizer, 200 first protective film, 300 second protective film, 400 adhesive layer, 500 separate film, A Both ends of the polarizing plate with protective film in the width direction.

Claims

A method for producing an optical film with a protective film comprising a step of bonding a protective film to the surface of the optical film,
In the optical film with a protective film obtained by the step of bonding the protective film, the peeling force of the protective film with respect to the optical film at both ends in the width direction is higher than the other parts of the optical film with the protective film. Manufacturing method.
The manufacturing method of Claim 1 which further includes the process of removing the said width direction both ends after the process of bonding the said protective film.
The manufacturing method according to claim 1 or 2, wherein the peeling force is increased by further including a step of performing a corona treatment before the step of bonding the protective film.
The manufacturing method according to claim 3, wherein the corona treatment is performed on the optical film.
The manufacturing method according to any one of claims 1 to 4, wherein a peeling force of the protective film with respect to the optical film is 0.09 N / 25 mm or more at both ends in the width direction.
As the protective film, including a pressure-sensitive adhesive layer bonded to the surface and a base film supporting the pressure-sensitive adhesive layer, the adhesive force of the portion constituting the widthwise both ends of the pressure-sensitive adhesive layer is compared to other portions. The manufacturing method according to claim 1, wherein the peeling force is increased by using a material that has been increased.
The production method according to any one of claims 1 to 6, wherein the optical film is a polarizing plate.