JP6291679B2 - Method for producing surface protective film for transparent conductive substrate, surface protective film for transparent conductive substrate, and laminate - Google Patents

Description

  The present invention relates to a method for producing a surface protective film for a transparent conductive substrate, a surface protective film for a transparent conductive substrate, and a laminate.

  Conventionally, transparent conductive substrates have been widely used as materials for products such as touch panels, liquid crystal display devices, organic electroluminescence (organic EL) devices, plasma display panels (PDP), and solar cells. As the transparent conductive substrate, one having a transparent conductive layer provided on one side of the substrate is generally used. In the transparent conductive substrate, a film such as polyester or glass is used as the material of the substrate. Moreover, ITO (Indium Tin Oxide) is usually used for the transparent conductive layer.

When manufacturing a product using a transparent conductive substrate, the step of crystallizing the conductive layer of the transparent conductive substrate, the step of correcting the distortion of the substrate, the step of patterning the conductive layer of the transparent conductive substrate, Any one or more processes involving heat treatment such as a process of forming an electrode on the conductive substrate is performed. By performing a process involving these heat treatments, there is a risk that foreign matter or dirt may adhere to the surface of the transparent conductive substrate. If foreign matter or dirt adheres to the surface of the transparent conductive substrate, the quality of the product may be adversely affected. For this reason, conventionally, a protective film is pasted on the surface of a transparent conductive substrate in the middle of manufacture to prevent foreign matter and dirt from adhering to the surface of the transparent conductive substrate.
As a protective film affixed on the surface of a transparent conductive substrate, there exists what used the base material which consists of a polyester film.

Conventionally, in the polyester film, various proposals have been made to prevent precipitation of oligomers from the polyester film to the surface.
For example, Patent Document 1 discloses a method for preventing oligomer precipitation on the film substrate surface by irradiating the film substrate with ultraviolet rays, modifying at least a part of the film substrate, and forming a film. Have been described.
Patent Document 2 proposes that a coating layer containing polyvinyl alcohol is provided on the surface of the polyester film as a coating layer for preventing precipitation of oligomers.

In addition, in a protective film that is attached to the surface of a transparent conductive substrate, if the peelability from the transparent conductive substrate is insufficient, a phenomenon called zipping that emits a buzzing sound at the time of peeling tends to occur. In the protective film in which zipping occurs at the time of peeling, the transparent conductive substrate is easily damaged at the time of peeling.
Patent Document 3 discloses a (meth) acrylic polymer having a glass transition temperature of −40 ° C. or lower and a (meth) acrylic having a glass transition temperature of 5 to 20 parts by weight of 80 ° C. or higher as a surface protective sheet that does not cause zipping. There has been proposed a surface protective sheet obtained by coating a pressure sensitive adhesive for a protective sheet containing a polymer and a crosslinking agent on a support.

International Publication No. 2010/061851 JP 2003-183429 A JP 2005-146151 A

  In the protective film to be attached to the surface of the transparent conductive substrate, in the case of using a polyester film as a base material, by performing heat treatment on the transparent conductive substrate to which the protective film is attached, an oligomer present in the base material is obtained. It may be deposited and transferred to the surface of the transparent conductive substrate to which the protective film is attached. The oligomer transferred to the surface of the transparent conductive substrate causes the surface of the transparent conductive substrate to become cloudy and decreases the transparency of the transparent conductive substrate. For this reason, it is required to prevent oligomer transfer from the base material of the protective film to the transparent conductive substrate.

However, the techniques described in Patent Document 1 and Patent Document 2 prevent oligomer precipitation from the polyester film to the surface, and it is necessary to form a member for preventing oligomer precipitation on the surface of the film. there were.
That is, in the technique described in Patent Document 1, it is necessary to irradiate the film substrate with ultraviolet rays and to prepare an ultraviolet irradiation device in order to provide a film for preventing the precipitation of oligomers. Further, the technique described in Patent Document 2 requires a step of providing a coating layer for preventing oligomer precipitation on the surface of the polyester film.
For this reason, when manufacturing the surface protection film for transparent conductive substrates using the technique of patent document 1 and patent document 2, the process of forming the member for preventing precipitation of an oligomer was required.

  Also, conventionally, a transparent conductive substrate that does not easily cause oligomer transfer from the base material of the protective film to the transparent conductive substrate without forming a member for preventing oligomer precipitation, and has excellent peelability and wettability. There was no method for producing a surface protective film for the use.

The present invention has been made in view of the above circumstances, and even when heat treatment is performed on a transparent conductive substrate to which a protective film is attached, oligomer transfer from the base material of the protective film hardly occurs to the transparent conductive substrate. Moreover, it is an object to provide a method for producing a surface protective film for a transparent conductive substrate excellent in peelability and wettability.
Moreover, this invention makes it a subject to provide the surface protection film for transparent conductive substrates manufactured using said manufacturing method.
Furthermore, this invention provides the laminated body which laminates | stacks said surface protective film for transparent conductive substrates on a transparent conductive substrate, and can manufacture a high quality transparent conductive substrate efficiently with a high yield. Let it be an issue.

  The inventors of the present invention have intensively studied to solve the above-mentioned problems, and an adhesive layer for attaching the protective film base material to the transparent conductive substrate is used to transfer the oligomer from the protective film base material to the transparent conductive substrate. It was considered to have a function to prevent Since the adhesive layer is an indispensable member in the surface protective film for transparent conductive substrates, it must be formed separately as a member for preventing oligomer precipitation between the base material of the protective film and the transparent conductive substrate. There is no.

As a method for preventing the oligomer from transferring from the base material to the transparent conductive substrate, it is conceivable to use a material having a high glass transition temperature as the material for the adhesive layer.
However, if the adhesive layer is formed of a material having a high glass transition temperature, the peelability from the transparent conductive substrate becomes insufficient. For this reason, zipping is likely to occur at the time of peeling, and the transparent conductive substrate is easily damaged, and the efficiency of the peeling work is low. Moreover, the adhesive layer having a high glass transition temperature has insufficient wettability with respect to the substrate of the transparent conductive substrate. For this reason, when a protective film and a transparent conductive substrate are affixed, there may be a phenomenon called air gap where air enters between the adhesive layer of the protective film and the transparent conductive substrate. When air gaps are generated, a heat treatment is performed on the transparent conductive substrate to which the protective film is attached, thereby forming a mark of the protective film on the transparent conductive substrate. The sticking marks deteriorate the quality of the transparent conductive substrate.

  Accordingly, the present inventors have repeatedly studied the relationship between the glass transition temperature of the adhesive layer and the peelability and wettability. As a result, it was found that in order to ensure the peelability and wettability of the adhesive layer, the glass transition temperature of the resin component forming the adhesive layer needs to be −30 ° C. or lower.

  Furthermore, the present inventors have formed a pressure-sensitive adhesive layer having a function of preventing a transition of an oligomer, which is composed of a resin component having a glass transition temperature of −30 ° C. or less, on a substrate made of a polyester film. Repeated examination. As a result, a pressure-sensitive adhesive composition containing a (meth) acrylic acid ester copolymer in which a polymer having a molecular weight of 100,000 or less and a large amount of unreacted monomer remains on the substrate is applied to remove the unreacted monomer. The inventors have found that an adhesive layer may be formed using a method of performing a heat treatment step, and have come up with the present invention.

The present invention employs the following configuration.
(1) On one surface of a substrate made of a polyester film, the polymer having a molecular weight of 100,000 or less is 5% by mass or less of the whole, and the unreacted monomer is 0.5 to 10% by mass with respect to the charged monomer. A coating step of applying a pressure-sensitive adhesive composition containing a (meth) acrylic acid ester copolymer having a glass transition temperature of −30 ° C. or lower and a crosslinking agent, and a heat treatment step of removing the unreacted monomer. The manufacturing method of the surface protection film for transparent conductive substrates characterized by these.

(2) The molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of the (meth) acrylic acid ester copolymer is 3.0 or less, for the transparent conductive substrate according to (1) A method for producing a surface protective film.
(3) The method for producing a surface protective film for a transparent conductive substrate according to (1) or (2), wherein the heat treatment step is performed at 80 to 150 ° C. for 30 seconds to 10 minutes.
(4) The transparent conductivity according to any one of (1) to (3), including a step of forming an oligomer precipitation preventing layer for preventing oligomer precipitation on the other surface of the substrate. A method for producing a surface protective film for a substrate.

(5) A surface protective film for a transparent conductive substrate, manufactured using the method for manufacturing a surface protective film for a transparent conductive substrate according to any one of (1) to (4).
(6) A laminate, wherein the surface protective film for a transparent conductive substrate according to (5) is laminated on a transparent conductive substrate.

According to the method for producing a surface protective film for a transparent conductive substrate of the present invention (hereinafter sometimes abbreviated as “protective film”), a protective film provided with an adhesive layer having a function of preventing oligomer transfer is obtained. It is done.
The protective film produced using the production method of the present invention is less susceptible to oligomer transfer from the protective film substrate to the transparent conductive substrate, even if the protective film is attached to the transparent conductive substrate with heat treatment. Moreover, it has excellent peelability and wettability.

  In the laminate of the present invention, the protective film produced using the production method of the present invention is laminated on the transparent conductive substrate. The transition of the oligomer from the base material to the transparent conductive substrate is difficult to occur, and the decrease in the transparency of the transparent conductive substrate due to the transition of the oligomer can be prevented. In addition, since the laminate of the present invention uses a protective film having excellent wettability, it is possible to prevent the occurrence of air scratches at the time of forming the laminate, and it is difficult to form marks due to air scratches after the protective film is peeled off. A high-quality transparent conductive substrate can be obtained. And since the laminated body of this invention uses the protective film excellent in peelability, it is hard to produce zipping at the time of peeling of a protective film, and can perform a peeling operation | work efficiently with a high yield.

FIG. 1 is a schematic cross-sectional view for explaining an example of the surface protective film for a transparent conductive substrate of the present invention. FIG. 2 is a schematic cross-sectional view for explaining an example of the laminate of the present invention.

  Hereinafter, the manufacturing method of the protective film of this invention, a protective film, and a laminated body are demonstrated in detail. In addition, the material, dimension, etc. which are illustrated in the following description are examples, and this invention is not limited to them. The present invention can be appropriately modified and implemented without changing the gist thereof.

[Protective film]
FIG. 1 is a schematic cross-sectional view for explaining an example of the protective film of the present invention. The protective film 10 shown in FIG. 1 is suitably used when a heat treatment is performed on a transparent conductive substrate on which the protective film 10 is attached. The protective film 10 includes a base material 2, an adhesive layer 1 formed on one surface 2a (upper surface in FIG. 1) of the base material 2, and the other surface 2b (lower surface in FIG. 1) of the base material 2. It has an oligomer precipitation preventing layer 3 formed thereon, and a release sheet 4 disposed on a surface 1a (upper surface in FIG. 1) on the side facing the transparent conductive substrate of the adhesive layer 1.

(Base material)
The base material 2 consists of a polyester film.
Examples of the polyester used for the substrate 2 include polyesters produced by polycondensation of dicarboxylic acid or its ester and glycol.
Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, 1,4-cyclohexyl dicarboxylic acid, and the like.
Examples of the glycol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol and the like.

  As a method for polycondensation of dicarboxylic acid or its ester and glycol, a conventionally known method can be used arbitrarily, and specifically, for example, the following method can be used. First, a bisglycol ester of an aromatic dicarboxylic acid or a low polymer thereof is produced by a method of transesterification between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol. Moreover, the bisglycol ester of aromatic dicarboxylic acid or its low polymer may be produced by a method in which an aromatic dicarboxylic acid and glycol are directly esterified. Thereafter, the bisglycol ester of aromatic dicarboxylic acid or a low polymer thereof is polycondensed by heating under reduced pressure.

  As the polyester used for the substrate 2, it is preferable to use a polyester having a low oligomer content. The oligomer here refers to a plurality of types of low-molecular compounds derived from polyester that are separated and precipitated from the polyester that is the material of the substrate 2 by heating the substrate 2. A polyester having a low oligomer content can be obtained, for example, by performing solid-state polymerization in which a polyester chip is kept at a temperature of 180 ° C. to 240 ° C. for 1 hour to 20 hours under reduced pressure or under the flow of an inert gas.

  As the polyester used for the substrate 2, polyethylene terephthalate, polyethylene-2,6-naphthalate, or poly-1,4-cyclohexanedimethylene terephthalate is preferably used, and polyethylene terephthalate is particularly preferably used.

  The polyester film used as the substrate 2 may contain an additive in addition to the polyester as necessary. For example, the polyester film used as the substrate 2 may contain particles for the purpose of improving the running property when producing the polyester film. As particles, inorganic particles such as calcium carbonate, kaolin, silica, aluminum oxide, titanium oxide, alumina, and barium sulfate, organic particles such as (meth) acrylic resin and / or guanamine resin, and catalyst residue are made into particles. Examples include precipitated particles. Moreover, the polyester film used for the base material 2 may contain various stabilizers, lubricants, antistatic agents and the like in addition to these particles.

  As a formation method of the polyester film used for the base material 2, the conventionally well-known film forming method can be used, and there is no restriction | limiting in particular. For example, the polyester film used for the base material 2 can be formed by the method shown below. First, a polyester chip is dissolved and stretched 2 to 6 times at 60 to 120 ° C. by a roll stretching method to obtain a uniaxially stretched polyester film. Subsequently, the uniaxially stretched polyester film is stretched 2 to 6 times at 80 to 130 ° C. in a direction perpendicular to the previous stretching direction in the tenter. Furthermore, heat treatment (heat setting) of the polyester film is performed at 150 to 250 ° C. for 1 to 600 seconds.

The polyester film used for the substrate 2 may be a single layer or a multilayer structure. In the case of a polyester film having a multilayer structure, the polyester as the material of each layer may be different from each other, or part or all may be the same.
The thickness of the substrate 2 is preferably 12 to 188 μm.

(Adhesive layer)
The adhesive layer 1 is disposed so as to face the transparent conductive substrate to which the protective film 10 is attached. The pressure-sensitive adhesive layer 1 is obtained by applying and cross-linking the pressure-sensitive adhesive composition on one surface 2a of the substrate 2 by a method described later.

  Although the thickness in particular of the adhesion layer 1 is not restrict | limited, It is preferable that it is 3-100 micrometers, and it is more preferable that it is 5-40 micrometers. When the thickness of the pressure-sensitive adhesive layer 1 is 3 μm or more, the adhesive force of the pressure-sensitive adhesive layer 1 and the function of preventing oligomer transfer can be sufficiently obtained. Moreover, it can prevent that the adhesive force of the adhesion layer 1 becomes high too much that the thickness of the adhesion layer 1 is 100 micrometers or less, and it becomes difficult to peel a protective film from the surface of an electroconductive conductive substrate.

(Oligomer precipitation prevention layer)
The oligomer precipitation preventing layer 3 prevents the oligomer from precipitating from the base material 2 on the other surface 2b of the base material 2, and is provided as necessary.
As the oligomer precipitation preventing layer 3, a conventionally known layer can be used. Examples of the oligomer precipitation preventing layer 3 include polyvinyl alcohol and epoxy resin. By providing the oligomer precipitation preventing layer 3 on the other surface 2b of the base material 2, when a plurality of laminates obtained by laminating the protective film 10 on the transparent conductive substrate are stacked, the oligomer deposition prevention of the protective film 10 is prevented. It is possible to prevent the oligomer from transferring from the base material 2 to the surface of the laminate in contact with the layer 3.

(Peeling film)
The release sheet 4 protects the surface 1a (upper surface in FIG. 1) of the pressure-sensitive adhesive layer 1 on the side facing the transparent conductive substrate.
As the release sheet 4, for example, a plastic film or paper can be used.
When paper is used as the release sheet 4, for example, glassine paper, coated paper, cast coated paper or the like may be used, or a laminated paper obtained by laminating a thermoplastic resin such as polyethylene on a base material made of these papers. It may be used.

  When a plastic film is used as the release sheet 4, for example, a polyethylene film, a polypropylene film, a polyethylene terephthalate film, or the like is preferably used.

A release agent is preferably applied to the surface of the release sheet 4 in order to further improve the peelability of the release sheet 4 from the pressure-sensitive adhesive layer 1. Examples of the release agent include silicone, olefin resin, isoprene resin, butadiene resin, long chain alkyl resin, alkyd resin, and fluorine resin. Among the release agents, a polypropylene resin which is an olefin resin is preferably used. Olefin resins are preferred because there is little component transfer from the release agent to the adhesive layer 1 and the transparent conductive substrate is hardly contaminated by the release agent component.
In addition, the surface of the release sheet 4 may be subjected to release and antifouling treatment using silica powder or the like, or may be subjected to antistatic treatment or the like, if necessary.

  The thickness of the release sheet 4 is preferably 0.01 to 200 μm, and preferably 5 to 100 μm. When the thickness of the release sheet 4 is 0.01 μm or more, the effect of protecting the surface 1 a on the side facing the transparent conductive substrate of the adhesive layer 1 is high, and the release sheet 4 is formed of the adhesive layer 1. It becomes easy to peel off from the surface.

[Method for producing protective film]
Next, as an example of the method for producing the protective film of the present invention, the method for producing the protective film 10 shown in FIG. 1 will be described as an example. In order to manufacture the protective film 10 shown in FIG. 1, by performing an application step of applying the pressure-sensitive adhesive composition on one surface 2 a of the substrate 2 and a heat treatment step of removing unreacted monomers described later. The adhesive layer 1 is formed.

The pressure-sensitive adhesive composition used in this embodiment contains a (meth) acrylic acid ester copolymer and a crosslinking agent. In this specification, the “(meth) acrylic acid ester copolymer” means an acrylic acid ester copolymer and / or a methacrylic acid ester copolymer.
In addition to the (meth) acrylic acid ester copolymer and the crosslinking agent, the pressure-sensitive adhesive composition includes a tackifier, a plasticizer, a filler, an antioxidant, an ultraviolet absorber, a silane coupling agent, etc. May be included.

The (meth) acrylic acid ester copolymer contained in the pressure-sensitive adhesive composition is obtained by copolymerizing a main monomer having tackiness and a monomer having a crosslinkable functional group.
The weight average molecular weight Mw of the (meth) acrylic acid ester copolymer is preferably 300,000 to 2,500,000, and more preferably 300,000 to 1,000,000. The weight average molecular weight Mw is a value in terms of polystyrene measured by a gel permeation chromatography (GPC) method. When the weight average molecular weight Mw of the (meth) acrylic acid ester copolymer is in the range of 300,000 to 2,500,000, the pressure-sensitive adhesive layer 1 having good pressure-sensitive adhesive performance is obtained.

In the (meth) acrylic acid ester copolymer, the polymer having a molecular weight of 100,000 or less is 5% by mass or less of the whole, and the unreacted monomer is 0.5 to 10% by mass with respect to the charged monomer. Such a (meth) acrylic acid ester copolymer has a low content of oligomers having a weight average molecular weight Mw of about 1,000 to 30,000, as shown below.
Further, the molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of the (meth) acrylic acid ester copolymer is preferably 3.0 or less, more preferably in the range of 2.0 to 3.0. preferable. The number average molecular weight Mn is a value in terms of polystyrene measured by a gel permeation chromatography (GPC) method. When the molecular weight distribution is in the above range, a (meth) acrylic acid ester copolymer having a smaller oligomer content is obtained.

  Generally, when producing the (meth) acrylic acid ester copolymer which is a resin component of an adhesive composition, the two-stage polymerization method is used. In the two-stage polymerization method, first, a copolymerization monomer and a polymerization initiator are polymerized in the presence of a solvent until the charged monomer is consumed by about 90% by mass (first-stage polymerization). Thereafter, in order to reduce the remaining unreacted monomer as much as possible, a polymerization initiator is added to perform the second stage polymerization.

  According to the inventor's research, when a (meth) acrylic acid ester copolymer is produced using a two-stage polymerization method, unreacted monomers remaining in the first stage polymerization are polymerized in the second stage polymerization. Thus, many oligomers having a molecular weight of about 1,000 to 30,000 are generated. The pressure-sensitive adhesive layer obtained by cross-linking the (meth) acrylic acid ester copolymer containing these oligomers is inferior in the density of the cross-linked portion of these oligomers, and the oligomer migrating from the polyester substrate Easy to penetrate. For this reason, in order to obtain the adhesion layer 1 which is hard to permeate | transmit the oligomer contained in the base material which consists of polyester, the oligomer of molecular weight about 1,000-30,000 contained in a (meth) acrylic acid ester copolymer is used. Less is preferred.

  This inventor repeated research in order to reduce the production amount of an oligomer in the manufacture process of a (meth) acrylic acid ester copolymer. As a result, in the first stage polymerization, the reaction should be stopped so that the remaining amount of unreacted monomer is 0.5 to 10% by mass with respect to the charged monomer, and then the second stage polymerization should not be performed. I found. The (meth) acrylic acid ester copolymer thus obtained has a polymer having a molecular weight of 100,000 or less and 5% by mass or less of the whole, and becomes a (meth) acrylic acid ester copolymer with a small amount of oligomers. . Furthermore, the present inventor has more oligomer content when the molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of the obtained (meth) acrylic acid ester copolymer is 3.0 or less. I found it to be less.

  Moreover, the unreacted monomer in the (meth) acrylic acid ester copolymer is 0.5% by mass or more with respect to the charged monomer. For this reason, a polymer having a molecular weight of 100,000 or less can be suppressed to 5% by mass or less of the whole. The unreacted monomer in the (meth) acrylic acid ester copolymer is 10% by mass or less based on the charged monomer. For this reason, molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) can be suppressed to 3.0 or less.

  The (meth) acrylic acid ester copolymer has a glass transition temperature of −30 ° C. or lower. For this reason, the adhesion layer 1 excellent in peelability and wettability is obtained. When the glass transition temperature exceeds −30 ° C., the peelability and wettability of the pressure-sensitive adhesive layer 1 become insufficient. The glass transition temperature of the (meth) acrylic acid ester copolymer is preferably −35 ° C. or lower in order to further improve the peelability and wettability of the adhesive layer 1.

  Examples of the main monomer having adhesiveness used in the (meth) acrylate ester copolymer include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylic acid. 2-ethylhexyl etc. can be illustrated and these can be used 1 type or in combination of 2 or more types.

  Examples of the monomer having a crosslinkable functional group include monomers having a carboxyl group, a hydroxyl group, an epoxy group, and an amino group. Examples of the monomer having a carboxyl group include acrylic acid, methacrylic acid, fumaric acid, maleic acid, and itaconic acid. Examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, N-methylol (meth) acrylamide and the like. Examples of the monomer having an epoxy group include glycidyl (meth) acrylate.

  Further, the (meth) acrylic acid ester copolymer may contain vinyl acetate, styrene or the like in order to increase the cohesive force.

  A conventionally well-known thing can be used as a polymerization initiator, It does not specifically limit. For example, an azo type and a peroxide type are mentioned. As the azo series, 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis-2-methylbutyronitrile (AMBN), 2,2′-azobis (2-methylpropionic acid) Examples thereof include dimethyl and 4,4′-azobis-4-cyanovaleric acid. Among these, AIBN is preferable because the decomposition gas of the initiator hardly remains.

  Examples of the crosslinking agent contained in the pressure-sensitive adhesive composition include an isocyanate crosslinking agent, an epoxy crosslinking agent, and a metal chelate crosslinking agent. Among these crosslinking agents, it is preferable to use an isocyanate-based crosslinking agent.

  Although the ratio of the crosslinking agent with respect to the (meth) acrylic acid ester copolymer in the pressure-sensitive adhesive composition is not particularly limited, the crosslinking agent is added to 100 parts by mass (solid content) of the (meth) acrylic acid ester copolymer. It is preferable to contain 0.1-10 mass parts in solid content.

  In this embodiment, such a pressure-sensitive adhesive composition is applied on one surface 2a of the substrate 2 (application process). As a method for applying the pressure-sensitive adhesive composition, conventionally known methods such as a gravure coating method, a roll coating method, a die coating method, and a blade coating method can be used, and there is no particular limitation.

Next, a heat treatment step for removing unreacted monomers is performed.
The heat treatment temperature in the heat treatment step is not particularly limited as long as unreacted monomers can be removed, and is preferably in the range of 80 to 150 ° C., for example. Moreover, the heat processing time should just be able to remove an unreacted monomer, for example, it is preferable that it is 30 second-10 minutes.
In this embodiment, after the heat treatment step, a crosslinking step is performed in which the pressure-sensitive adhesive composition is crosslinked at room temperature of about 20 ° C. for 3 to 7 days.
The adhesive layer 1 is obtained by the above process.

  Moreover, in this embodiment, the process of forming the oligomer precipitation prevention layer 3 on the other surface 2b of the base material 2 is included. The step of forming the oligomer precipitation preventing layer 3 may be performed before the above-described pressure-sensitive adhesive composition coating step, or may be performed after the pressure-sensitive adhesive composition coating step. As a method of forming the oligomer precipitation preventing layer 3, a conventionally known method can be used.

Moreover, in this embodiment, the process of laminating | stacking the peeling sheet 4 on the surface 1a (upper surface in FIG. 1) of the side facing the transparent conductive substrate of the adhesion layer 1 is included. The step of laminating the release sheet 4 can be performed by a conventionally known method.
Through the above steps, the protective film 10 shown in FIG. 1 is obtained.

"Laminate"
FIG. 2 is a schematic cross-sectional view for explaining an example of the laminate of the present invention. A laminated body 30 shown in FIG. 2 is obtained by arranging the protective film 10 shown in FIG. 1 on one side of the transparent conductive substrate 20.
The transparent conductive substrate 20 shown in FIG. 2 is used as a material for products such as a touch panel, a liquid crystal display device, an organic electroluminescence (organic EL) device, a plasma display panel (PDP), and a solar cell.

  As shown in FIG. 2, the transparent conductive substrate 20 includes a substrate 5 and a conductive layer 6 provided on one surface (the lower surface in FIG. 2) of the substrate 5. A protective film 10 shown in FIG. 1 is attached to the surface of the transparent conductive substrate 20 opposite to the conductive layer 6. Therefore, as shown in FIG. 2, the substrate 5 of the transparent conductive substrate 20 and the adhesive layer 1 of the protective film 10 are disposed opposite to each other and attached.

In the present embodiment, the substrate 5 has hard coat layers 12 and 13 provided on the upper and lower surfaces of the base 11 respectively.
The substrate 11 is made of a transparent material, and a film or glass can be used.
Examples of the material for the film used as the substrate 11 include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polymethyl methacrylate, styrene polymers such as polystyrene and acrylonitrile / styrene copolymer (AS resin), polycarbonate, polyethylene, and polypropylene. Examples thereof include polyolefins having a cyclo or norbornene structure and polyolefins such as ethylene / propylene copolymers, and these can be used alone or in combination of two or more.

  The hard coat layers 12 and 13 increase the surface hardness of the substrate 5 and prevent the substrate 5 from being scratched. The hard coat layers 12 and 13 are obtained, for example, by applying a hard coat agent to both the upper and lower surfaces of the substrate 11. As the hard coat agent, ultraviolet (UV) and / or electron beam curable paints, silicone hard coat agents, phosphazene resin hard coat agents and the like can be used. Among the above hard coat agents, it is preferable to use a UV curable paint from the viewpoint of easy formation of the hard coat layers 12 and 13. As the UV curable paint, those of vinyl polymerization type, polythiol / polyene type, epoxy type, amino alkyd type, etc. can be used.

  An antiglare layer may be provided on the upper surface and / or the lower surface of the substrate 5. The antiglare layer has functions such as preventing glare of the transparent conductive substrate 20 and preventing reflection. Examples of the antiglare layer include those using a difference in refractive index and those formed with a fine uneven shape on the surface.

  Although the thickness in particular of the board | substrate 5 is not restrict | limited, It is preferable that it is 10-1000 micrometers, and it is more preferable that it is 20-500 micrometers.

The conductive layer 6 is not particularly limited, but is a thin film of a metal oxide such as ITO (Indium Tin Oxide), tin / antimony, zinc or tin oxide, or a very thin film of a metal such as gold, silver, palladium or aluminum. It is preferable that it consists of.
The conductive layer 6 can be formed by, for example, a sputtering method on the substrate 5.
The thickness of the conductive layer 6 is not particularly limited, but is preferably 5 nm or more, and more preferably 10 to 200 nm.

  The protective film 10 of the laminate 30 of this embodiment is affixed to the substrate 5 of the transparent conductive substrate 20 before performing a heat treatment for crystallizing the conductive layer 6 of the transparent conductive substrate 20. . The conductive layer 6 may be formed before the protective film 10 is attached to the substrate 5 or may be formed after the protective film 10 is attached to the substrate 5.

Examples of the method for attaching the protective film 10 to the substrate 5 of the transparent conductive substrate 20 include the following methods.
First, the release sheet 4 (see FIG. 1) provided on the surface of the protective film 10 on the side facing the transparent conductive substrate 20 is peeled off. Next, the substrate 5 of the transparent conductive substrate 20 and the adhesive layer 1 of the protective film 10 are arranged to face each other, and the transparent conductive substrate 20 and the protective film 10 are bonded together to form a laminate 30. Thereafter, the laminate 30 is heated and / or pressurized as necessary.

In the present embodiment, heat treatment for crystallizing the conductive layer 6 of the transparent conductive substrate 20 is performed in the state of the laminated body 30. The heat treatment temperature and heat treatment time in this heat treatment can be determined according to the material and thickness of the conductive layer 6 and the substrate 5. For example, the heat treatment temperature is preferably 120 ° C to 150 ° C, and more preferably 140 ° C to 150 ° C. The heat treatment time is preferably 20 minutes to 90 minutes, and more preferably 30 minutes to 60 minutes.
In the present embodiment, the protective film 10 is peeled from the transparent conductive substrate 20 after the heat treatment for crystallizing the conductive layer 6.

  In the manufacturing method of the protective film 10 of the present embodiment, the polymer having a molecular weight of 100,000 or less is 5% by mass or less of the whole surface 2a of the substrate 2 made of a polyester film, and the unreacted monomer is used as the charged monomer. On the other hand, a pressure-sensitive adhesive composition containing a (meth) acrylic acid ester copolymer having a glass transition temperature of −30 ° C. or lower and a crosslinking agent is applied (application step). . In the next step, a heat treatment step for removing unreacted monomers is performed. Furthermore, it crosslinks by curing at room temperature. For this reason, the protective film 10 provided with the adhesion layer 1 which has a function which prevents transfer of an oligomer is obtained.

Even if the adhesive layer 1 of the protective film 10 of the present embodiment is made of a resin component having a low glass transition temperature of −30 ° C. or lower, the reason why the function of preventing oligomer transition is obtained is as follows. It is.
In the manufacturing method of the present embodiment, since the unreacted monomer is removed in the heat treatment step, a crosslinked portion of the unreacted monomer that easily allows the oligomer to pass through is not formed in the adhesive layer 1. For this reason, even if it consists of a resin component with a low glass transition temperature of −30 ° C. or lower, it is estimated that the entire adhesive layer 1 is difficult to transmit the oligomer.
On the other hand, for example, when the above pressure-sensitive adhesive composition is cross-linked under the condition that the unreacted monomer remains without performing the heat treatment step, the dense oligomer formed by cross-linking the polymer having a molecular weight exceeding 100,000 is permeated. A difficult part and a part that easily allows the oligomer formed by crosslinking the unreacted monomer to pass through are formed in the adhesive layer.

The protective film 10 manufactured using the manufacturing method of the present embodiment is transparent from the base material 2 by the adhesive layer 1 even if the transparent conductive substrate 20 (laminated body 30) to which the protective film 10 is attached is heat-treated. The transfer of the oligomer to the conductive substrate 20 is prevented. And the protective film 10 manufactured using the manufacturing method of this embodiment becomes the thing excellent in peelability and wettability.
Moreover, according to the manufacturing method of the protective film 10 of this embodiment, precipitation of an oligomer can be prevented, without forming the member for preventing precipitation of an oligomer between the base material 2 and the transparent conductive substrate 20. FIG. The protective film 10 can be manufactured.

  In the laminate 30 of the present embodiment, since the protective film 10 manufactured using the manufacturing method of the present embodiment is laminated on the transparent conductive substrate 20, the transparent conductive substrate 20 is heat-treated. However, it is difficult for the oligomer to transfer from the base material 2 of the protective film 10 to the transparent conductive substrate 20, and a decrease in the transparency of the transparent conductive substrate 20 due to the transfer of the oligomer can be prevented. Moreover, since the laminated body 30 of this embodiment uses the protective film 10 having excellent wettability, it is possible to prevent the occurrence of air galling during the formation of the laminated body 30, and adhesion due to air galling after the protective film 10 is peeled off. Traces are hardly formed, and a high-quality transparent conductive substrate 20 is obtained. And since the laminated body 30 of this embodiment uses the protective film 10 excellent in peelability, it is hard to produce zipping at the time of peeling of the protective film 10, and can perform peeling work efficiently with a high yield.

In addition, this invention is not limited to embodiment mentioned above.
For example, in the manufacturing method of the protective film of this invention, it is not necessary to provide an oligomer precipitation prevention layer. Moreover, you may perform the bonding process which bonds the protective film of this invention and a transparent conductive substrate to make a laminated body in any step at the time of manufacturing a product using a transparent conductive substrate. Moreover, you may perform the peeling process which peels a protective film from a laminated body in any step after a bonding process.

"(Meth) acrylic acid ester copolymer"
Using a reactor equipped with a stirrer, reflux condenser, dropping funnel, nitrogen gas inlet tube and thermometer, the charged monomers shown in Table 1 and the polymerization initiator were used in the proportions shown in Table 1, and toluene was used as the solvent. And solution polymerization was performed under a nitrogen gas atmosphere to obtain (meth) acrylic acid ester copolymers of Example 1, Example 2, Comparative Example 1, and Comparative Example 2.

  About the (meth) acrylic acid ester copolymer of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 thus obtained, the solid content, the weight average molecular weight Mw, the molecular weight distribution (weight average molecular weight Mw / Number average molecular weight Mn), ratio of the polymer having a molecular weight of 100,000 or less to the whole polymer “100,000 or less” (mass%), ratio of unreacted monomer to charged monomer “unreacted monomer” (mass%), glass transition temperature Tg (° C.) was examined by the following method. The results are shown in Table 1.

[Molecular weight]
The weight average molecular weight Mw of the (meth) acrylic acid ester copolymers of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 using values in terms of polystyrene measured by gel permeation chromatography (GPC) method. The number average molecular weight Mn and the content of components having a molecular weight of 100,000 or less were determined by the following methods.
GPC device: HLC-8020 (manufactured by Tosoh Corporation)
Column: TSKgel guardcolumn H _XL- H (manufactured by Tosoh Corporation)
TSKgel GMH _XL (Tosoh Corporation)
TSKgel GMH _XL (Tosoh Corporation)
TSKgel G2000H _XL (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Solvent: Tetrahydrofuran flow rate: 1 ml / min Molecular weight standard substance: Polystyrene detector: Differential refractive index detector Then, using the results obtained by the above method, molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) and molecular weight The ratio of “100,000 or less polymer” (% by mass) to the total of 100 or less of the polymer was calculated.

[Ratio of unreacted monomer to charged monomer]
The mass of unreacted monomer remaining in the (meth) acrylic acid ester copolymer was quantified and calculated using a gas chromatographic method.
[Tg (glass transition temperature)]
The glass transition temperature of the (meth) acrylic acid ester copolymer was measured using DSC (differential scanning calorimeter).

"Adhesive composition"
The xylylene diisocyanate-based (XDI-based) cross-linking agent [Mitsui Chemical Co., Ltd.] was used for 100 parts by mass of the (meth) acrylic acid ester copolymer of Example 1, Example 2, Comparative Example 1, and Comparative Example 2. , Trade name “Takenate D-110N” (solid content 75% by mass)], 5.0 parts by mass of toluene, 30.0 parts by mass of toluene and 1.0 part by mass of ethyl acetate as a solvent, Example 1 and Example 2 The pressure-sensitive adhesive compositions of Comparative Example 1 and Comparative Example 2 were prepared.

"Protective film"
The pressure-sensitive adhesive compositions of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were placed on one side of a 125 μm-thick polyethylene terephthalate (PET) film [trade name “Lumirror T60” manufactured by Toray Industries, Inc.] An application step for applying the coating amount after drying to 10 g / m ² and a heat treatment step for 1 minute at 120 ° C. for removing unreacted monomers in the pressure-sensitive adhesive composition were performed. And after heat processing for 1 minute at 120 degreeC, the peeling sheet [The product name "40RL-01Z" made by Oji Paper Co., Ltd.] which has a silicone type release agent layer on an adhesive composition is laminated, and about 20 degreeC The pressure-sensitive adhesive composition was crosslinked at room temperature for 5 days to obtain protective films of Example 1, Example 2, Comparative Example 1, and Comparative Example 2.

  Thereafter, the obtained protective films of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were evaluated for wettability, peelability, and oligomer contamination by the following methods.

[Wettability]
A substrate 5 having hard coat layers 12 and 13 made of dipentaerythritol hexaacrylate on both upper and lower surfaces of a base 11 made of polyethylene terephthalate (PET) film was prepared. Thereafter, a conductive layer 6 made of ITO was formed on one surface of the substrate 5 to obtain a transparent conductive substrate 20 shown in FIG. Next, a protective film was attached to the surface of the transparent conductive substrate 20 opposite to the conductive layer 6. Then, the case where the protective film was easily wet and spread easily by visual observation and air gaps were hardly generated was evaluated as ◯, and the case where it was difficult to wet and spread was evaluated as x.

[Peelability]
A protective film was affixed to the surface of the transparent conductive substrate 20 opposite to the conductive layer 6 used for wettability evaluation and heated at 150 ° C. for 3 hours. Thereafter, the protective film was peeled off from the transparent conductive substrate 20 at a speed of 10 m / min, and the case where there was no zipping was evaluated as ◯, and the case where there was zipping was evaluated as x.

[Oligomer contamination]
After peeling off the protective film in the peelability evaluation, the surface of the transparent conductive substrate 20 opposite to the conductive layer 6 was observed at a magnification of 450 times using a digital microscope. As a result, the case where the transition of the oligomer was not confirmed on the surface of the transparent conductive substrate 20 opposite to the conductive layer 6 was evaluated as ◯, and the case where it was confirmed was evaluated as ×.

As shown in Table 1, the protective films of Example 1 and Example 2 were all good in terms of wettability, peelability, and oligomer contamination.
On the other hand, the protective film of Comparative Example 1 is produced in the (meth) acrylate copolymer because there are few unreacted monomers in the (meth) acrylate copolymer and many polymers having a molecular weight of 100,000 or less. It is estimated that there were many oligomers. As a result, the function of preventing the oligomer transfer from the base material to the transparent conductive substrate by the adhesive layer of the protective film is insufficient, and it is estimated that the evaluation of the oligomer contamination property of the protective film is x.
Further, the protective film of Comparative Example 2 has a small amount of unreacted monomer in the (meth) acrylic acid ester copolymer and a large amount of polymer having a molecular weight of 100,000 or less, but has a high glass transition temperature. The evaluation of the oligomer contamination property was ○. However, since the protective film of Comparative Example 2 had a high glass transition temperature, the evaluation of wettability and peelability was x.

  1: adhesive layer, 2: base material, 3: oligomer precipitation preventing layer, 4: release sheet, 5: substrate, 6: conductive layer, 10: protective film (surface protective film for transparent conductive substrate), 20: transparent conductive Substrate, 30: laminate.

Claims (6)

On one surface of a substrate made of a polyester film, the polymer having a molecular weight of 100,000 or less is 5% by mass or less of the whole, the unreacted monomer is 0.5 to 10% by mass with respect to the charged monomer, and the glass transition A coating step of applying a pressure-sensitive adhesive composition containing a (meth) acrylic acid ester copolymer and a crosslinking agent having a temperature of −30 ° C. or less;
And a heat treatment step for removing the unreacted monomer. A method for producing a surface protective film for a transparent conductive substrate.   The surface protective film for transparent conductive substrates according to claim 1, wherein the molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of the (meth) acrylic acid ester copolymer is 3.0 or less. Manufacturing method.   The said heat processing process is performed for 30 second-10 minutes at 80-150 degreeC, The manufacturing method of the surface protection film for transparent conductive substrates of Claim 1 or Claim 2 characterized by the above-mentioned.   The transparent conductive substrate according to any one of claims 1 to 3, further comprising a step of forming an oligomer precipitation preventing layer for preventing oligomer precipitation on the other surface of the base material. Method for manufacturing a surface protective film.   It manufactured using the manufacturing method of the surface protection film for transparent conductive substrates as described in any one of Claims 1-4, The surface protection film for transparent conductive substrates characterized by the above-mentioned.   A laminate comprising the transparent conductive substrate surface protective film according to claim 5 laminated on the transparent conductive substrate.

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