JP2021004299A - Protective sheet - Google Patents

Abstract

To provide a Low-E glass plate protective sheet capable of having a protective function of a Low-E glass plate being a protection object, and also capable of maintaining excellent detachability while preventing or suppressing contamination on a surface of the protection object even being adhered onto the protection object for a long period of time.SOLUTION: A protective sheet is a Low-E glass plate protective sheet including an adhesive layer 2. The adhesive layer contains a base polymer at a proportion of 95 wt.% or more. In the protective sheet, a chloride ion amount measured by hot water extraction is less than 300 μg per 1 g of the adhesive layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to a protective sheet.

There is known a technique for protecting the surface of various articles by adhering a protective sheet to the surface for the purpose of preventing damage (scratches, stains, corrosion, etc.) on the surface when processing or transporting the articles. The protection targets are diverse. For example, a protective sheet is also used for a glass plate with a Low-E (Low-Emissivity) layer (Low-E glass plate), which has become widespread in recent years. The Low-E glass plate is preferably used as a building material for window glass and the like because of the effect of improving the cooling and heating efficiency of the indoor space by the Low-E layer. In the manufacture of Low-E glass plates, the Low-E layer surface is usually exposed as it is until the Low-E glass plate and other glass plates are paired with the Low-E layer side surface facing inward. A protective sheet is attached to the surface. This protects the Low-E layer from damage, wear, deterioration, corrosion and the like. Prior art documents 1 and 2 which disclose the prior art relating to the manufacturing method of the glass unit include Patent Documents 1 and 2.

In the application of surface protection, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive; the same applies hereinafter) may be preferably used as a peelable adhesive means. Generally, the pressure-sensitive adhesive exhibits a state of a soft solid (viscoelastic body) in a temperature range near room temperature, and has a property of easily adhering to an adherend by pressure. A surface protective sheet using an adhesive typically has an adhesive layer on one side of a sheet-like base material made of a material such as a resin, and the adhesive layer is adhered to an adherend (protection object). By doing so, it is configured to achieve the protection purpose. Prior art documents that disclose an adhesive sheet that can be used as a surface protective sheet include Patent Documents 3 to 6. Patent Document 3 discloses a surface protective sheet that protects the surface of the metal plate during drawing, and Patent Document 4 discloses a surface protective sheet of an optical film such as a polarizing plate. Patent Document 5 relates to a surface protective sheet of a hydrophilic coated plate having a self-cleaning property. Patent Document 6 works on the ease of peeling and the reduction of stainability of the surface protective sheet for a metal plate on which a coating film is formed.

European Patent No. 2150669 International Publication No. 2016/139318 JP-A-2017-186517 Japanese Patent No. 5719194 JP 2012-131976 Japanese Patent No. 3571460

The Low-E glass plate is exposed to the external environment while being protected by a protective sheet, and operations such as processing and cleaning can be performed. The protective sheet has good adhesive strength to the Low-E glass plate, which is the object to be protected, so that it does not float or peel off, so that it adheres to the surface of the Low-E glass plate and is physically damaged or worn. In addition to protecting the Low-E glass plate from damage, it blocks the ingress of moisture and moisture to prevent deterioration and corrosion of the Low-E layer. Then, after the end of the protection period, the protective sheet needs to be removed from the object to be protected without any adhesive residue. However, the Low-E glass plate may have a long protection period with a protective sheet due to its transportation, storage, etc., and in such a usage mode, the adhesive strength increases due to temperature changes and the like, and the desired peeling occurs. There is a risk that the sex cannot be maintained. Although it is conceivable to add an adhesive force adjusting agent to suppress the increase in the adhesive force over time, the adhesive force adjusting agent may migrate to the surface of the adherend and contaminate the surface of the object to be protected.

The present invention was created in view of the above problems, can have a protective function of a Low-E glass plate which is a protected object, and can be attached to the protected object for a long period of time. It is an object of the present invention to provide a Low-E glass plate protective sheet capable of maintaining good peelability while preventing or suppressing contamination of the surface of a protected object even in such a case.

According to the present specification, a Low-E glass plate protective sheet is provided. This protective sheet includes an adhesive layer. The pressure-sensitive adhesive layer contains the base polymer in an amount of 95% by weight or more. With this configuration, the protective sheet can maintain good peelability while preventing or suppressing contamination of the surface of the protected object even when the protective sheet is attached to the protected object for a long period of time. This is based on the finding that when the amount of components other than the base polymer used in the Low-E glass plate protective pressure-sensitive adhesive increases, it tends to be difficult to obtain peelability over time. By composing most of the adhesive with a base polymer, the amount of additives that affect the peelability over time is limited, and the target Low-E glass is prevented or suppressed from being contaminated on the surface of the object to be protected. It can have a plate protection function.

The protective sheet according to some preferred embodiments has a chloride ion content measured by hot water extraction of less than 300 μg per gram of the pressure-sensitive adhesive layer. With such a configuration, corrosion and the like in the Low-E glass plate can be prevented for a long period of time without adding a corrosion preventive component such as a rust preventive or limiting the amount used thereof. In this regard, the present inventors have deteriorated or corroded the Low-E glass plate to be protected even though the protective sheet is sufficiently protected (hereinafter collectively referred to as "corrosion, etc."). As a result of examination, it was discovered that corrosion of the Low-E layer may occur due to the protective sheet itself. Then, by investigating that the cause of the corrosion etc. is the chloride ion contained in the adhesive of the protective sheet and limiting the amount of chloride ion of the adhesive, the corrosion etc. in the Low-E glass plate can be prolonged. We have reached a configuration that can be prevented over time.

In some preferred embodiments, the pressure-sensitive adhesive layer is formed from a water-dispersible pressure-sensitive adhesive composition. The water-dispersible pressure-sensitive adhesive composition is more desirable than the solvent-type pressure-sensitive adhesive composition in which the pressure-sensitive adhesive component is dissolved in an organic solvent from the viewpoint of environmental hygiene and the like. In such a configuration, the effect of the technique disclosed herein (combining protection performance such as corrosion prevention and peelability over time) can be preferably realized.

In some preferred embodiments, the content of the rust preventive in the pressure-sensitive adhesive layer is 3% by weight or less. The pressure-sensitive adhesive layer having the above structure does not contain a rust preventive agent or contains a rust preventive agent at a ratio of a predetermined value or less. A rust preventive is a preferable additive for Low-E glass plate applications from the viewpoint of corrosion prevention and the like, but as the amount used increases, it tends to be difficult to obtain peelability over time. By limiting the use of the rust preventive to a predetermined amount or less, it is possible to suppress an increase in the adhesive strength with time and preferably maintain good peelability. Also, in some embodiments, the pressure-sensitive adhesive layer comprises the rust preventive. As a result, the corrosion prevention property can be preferably exhibited. Preferable examples of the rust preventives that can be used include amine-based rust preventives. In the embodiment in which the amine-based rust preventive is used, by limiting the content to a predetermined amount or less, both corrosion prevention and aging peelability can be preferably achieved at the same time.

In some preferred embodiments, the base polymer is selected from acrylic and rubber polymers. Examples of the pressure-sensitive adhesive (layer) preferably used in the technique disclosed herein include an acrylic pressure-sensitive adhesive containing an acrylic-based polymer and a rubber-based pressure-sensitive adhesive containing a rubber-based polymer.

In some preferred embodiments, the base polymer is crosslinked by a crosslinker. By using a polymer cross-linked with a cross-linking agent as a base polymer, a protective sheet having good peelability can be preferably obtained. Preferable examples of the cross-linking agent include an oxazoline-based cross-linking agent. In the embodiment in which the oxazoline-based cross-linking agent is used, the effect of the technique disclosed herein (peeling property over time) can be preferably exhibited.

The protective sheet according to some aspects comprises a substrate layer. The base material layer supports the pressure-sensitive adhesive layer, and the protective sheet includes a base material layer and a pressure-sensitive adhesive layer provided on one surface of the base material layer. This configuration is suitable for protecting Low-E glass plates. The base material layer is more preferably made of a resin film. As such a base material layer, a base material layer made of a polyolefin-based resin film, a base material layer made of a polyester-based resin film, and a base material layer made of a vinyl chloride-based resin film can be preferably adopted.

The protective sheet disclosed herein preferably has a 180-degree peel strength of 3.3 N / 20 mm or less with respect to a Low-E glass plate after 1 week at 50 ° C. A protective sheet satisfying this characteristic can be satisfactorily peeled off from the adherend because the adhesive force with time is sufficiently suppressed even if the sticking period to the adherend is long.

It is sectional drawing which shows typically one form example of a protective sheet. It is a schematic diagram for demonstrating one Embodiment of the manufacturing method of a glass unit.

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in the present specification and necessary for the practice of the present invention are based on the teachings regarding the practice of the invention described in the present specification and the common general knowledge at the time of filing. Can be understood by those skilled in the art. The present invention can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the art.

As described above, the term "adhesive" as used herein refers to a material that exhibits a soft solid state (viscoelastic body) in a temperature range near room temperature and has the property of easily adhering to an adherend by pressure. .. The adhesive referred to here is generally a complex tensile modulus E ^* (1 Hz) as defined in "CA Dahlquist," Adhesion: Fundamentals and Practice ", McLaren & Sons, (1966) P. 143". <material having a property that meets the ¹⁰ 7 dyne / cm ² (typically, a material having the properties in 25 ° C.) may be.
Further, the concept of the protective sheet in the present specification may include what is called an adhesive sheet, an adhesive tape, an adhesive label, an adhesive film and the like. The protective sheet disclosed here may be in the form of a roll or in the form of a single leaf. Alternatively, the sheet may be further processed into various shapes.

<Structure of protective sheet>
The protective sheet disclosed herein typically has an adhesive layer on a substrate layer (supporting substrate). The cross-sectional structure of the protective sheet according to one embodiment is shown in FIG. The protective sheet 10 has a structure in which the pressure-sensitive adhesive layer 2 is provided on one surface 1A of the sheet-shaped base material layer 1, and the surface 2A of the pressure-sensitive adhesive layer 2 is attached to an adherend (protection object). Used with attachment. The back surface 1B of the base material layer 1 (the surface opposite to one surface 1A) is also the back surface of the protective sheet 10 and constitutes the outer surface of the protective sheet 10. In the protective sheet 10 before use (that is, before sticking to the adherend), the surface (adhesive surface, that is, the sticking surface to the adherend) 2A of the pressure-sensitive adhesive layer 2 is at least the peeling surface on the pressure-sensitive adhesive layer side. It can be in the form protected by a release liner (not shown). Alternatively, the other surface (back surface) 1B of the base material layer 1 is a peeling surface, and when the protective sheet 10 is wound in a roll shape, the adhesive layer 2 comes into contact with the back surface and its surface (adhesion). Surface) 2A may be a protective sheet 10 in a protected form.

As the release liner, a conventional release paper or the like can be used, and the release liner is not particularly limited. For example, a release liner having a release treatment layer on the surface of a liner base material such as a plastic film or paper, a release liner made of a low-adhesive material of a fluoropolymer (polytetrafluoroethylene or the like) or a polyolefin resin can be used. it can. The peeling treatment layer may be formed by surface-treating the liner base material with various peeling treatment agents such as silicone-based, long-chain alkyl-based, fluorine-based, and molybdenum sulfide.

The width of the protective sheet disclosed herein is not particularly limited. For example, by using a protective sheet having a width of about 1 m or more and further about 1.5 m or more, it is possible to efficiently protect a Low-E glass plate having a relatively large area. The width of the protective sheet according to some preferred embodiments is approximately 2 m or more. Such a wide protective sheet can achieve the protective function with one or a small number of low-E glass plates having a large area. In the above-mentioned low-E glass plate protection application, for example, a protective sheet having a width of about 2.5 m or more, more preferably about 2.6 m or more can be preferably used. The width of the protective sheet can be more than 2.6 m (eg, 3 m or more, and even about 3.3 m or more). The upper limit of the width of the protective sheet is not particularly limited, and from the viewpoint of productivity, handleability, etc., about 5 m or less is appropriate, for example, about 4 m or less.

The protective sheet disclosed here may be, for example, a sheet specified by having a long side and a short side on its plane (sheet surface). The long side is defined as the side longer than the short side, and the short side is defined as the side shorter than the long side. Further, for example, the short side can be a side substantially orthogonal to the long side. The length direction of the protective sheet is a direction along the long side, and the width direction is a direction orthogonal to the length direction. Therefore, in the present specification, "width" is defined as a length in a direction orthogonal to the length direction. Protective sheets referred to as elongated, strip-shaped, and rectangular-shaped are typical examples of the protective sheets disclosed herein. The long side is a line segment extending substantially linearly, while the short side is not limited to a straight line and may be a curved line, a polygonal line, or the like. For example, the length (distance in the length direction) of the long protective sheet is equal to or longer than the above width.

The thickness of the protective sheet disclosed herein is not particularly limited, and it is appropriate to set it to about 1000 μm or less (typically about 300 μm or less, for example, about 150 μm or less) from the viewpoint of handleability, lightness, and the like. .. In some embodiments, the thickness of the protective sheet can be preferably about 120 μm or less, more preferably about 100 μm or less, even more preferably about 75 μm or less, for example less than 60 μm. The thickness of the protective sheet can typically be greater than 20 μm, preferably greater than 30 μm, more preferably greater than 40 μm, for example greater than 45 μm.
In the present specification, the thickness of the protective sheet includes the thickness of the pressure-sensitive adhesive layer and the base material layer, but does not include the thickness of the release liner.

<Adhesive layer>
The pressure-sensitive adhesive layer disclosed herein is characterized by a proportion of 95% by weight or more of the base polymer. According to the technique disclosed herein, it is possible to exhibit a protective function capable of preventing deterioration and corrosion of the Low-E glass plate in a configuration containing the base polymer in a proportion of 95% by weight or more. Further, by setting the content ratio of the base polymer to 95% by weight or more, the amount of the additive that affects the peelability over time is limited, and the peelability is good even when it is attached to the object to be protected for a long period of time. Can be maintained. Further, by forming most of the pressure-sensitive adhesive with a base polymer, it is possible to limit the transfer of additives and the like to the surface of the adherend, and prevent or suppress contamination of the surface of the object to be protected. From the viewpoint of peelability over time, the content ratio of the base polymer in the pressure-sensitive adhesive layer is preferably about 96% by weight or more, more preferably about 97% by weight or more, and about 98% by weight or more (for example, about 99% by weight or more). It may be. The upper limit of the content ratio of the base polymer in the pressure-sensitive adhesive layer is 100% by weight, and may be 99.5% by weight or less in order to realize the desired properties (for example, corrosion resistance, adhesion, etc.), 98. It may be 5.5% by weight or less, or 97.5% by weight or less.

In the present specification, the base polymer of the pressure-sensitive adhesive layer refers to a polymer that forms a layer made of a pressure-sensitive adhesive and that functions as a pressure-sensitive adhesive component (also referred to as “sticky polymer”). The weight of the base polymer in the pressure-sensitive adhesive layer shall include the cross-linking agent bonded to the base polymer by a cross-linking reaction. Similarly, for a base polymer obtained by emulsion polymerization using a reactive surfactant, the reactive surfactant incorporated into the base polymer after the polymerization reaction shall be included in the weight of the base polymer.

The type of the base polymer is not particularly limited, and therefore, the type of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited. The pressure-sensitive adhesive layer is one or two selected from various polymers (adhesive polymers) such as acrylic-based, polyester-based, urethane-based, polyether-based, rubber-based, silicone-based, polyamide-based, and fluorine-based polymers. It may be a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing the above as a base polymer. The technique disclosed herein can be preferably implemented, for example, in the form of a protective sheet provided with an acrylic pressure-sensitive adhesive layer or a rubber-based pressure-sensitive adhesive layer.

Here, the "acrylic pressure-sensitive adhesive layer" refers to a pressure-sensitive adhesive layer using an acrylic polymer as a base polymer. Similarly, the "rubber-based pressure-sensitive adhesive layer" refers to a pressure-sensitive adhesive layer using a rubber-based polymer as a base polymer. The "acrylic polymer" is a monomer having at least one (meth) acryloyl group in one molecule (hereinafter, this may be referred to as "acrylic monomer") as a main constituent monomer component (main of the monomer). It refers to a polymer as a component (that is, a component that accounts for 50% by weight or more of the total amount of monomers constituting an acrylic polymer). Further, in the present specification, the “(meth) acryloyl group” means to comprehensively refer to an acryloyl group and a methacryloyl group. Similarly, "(meth) acrylate" is meant to comprehensively refer to acrylate and methacrylate.

(Acrylic polymer)
The acrylic polymer contains, for example, an alkyl (meth) acrylate (hereinafter, also referred to as “monomer A”) and another monomer copolymerizable with the alkyl (meth) acrylate (hereinafter, also referred to as “monomer B”). A polymer of a monomer raw material that can further contain.) Is preferable. The acrylic polymer typically has a copolymer composition corresponding to the composition of the monomer component contained in the monomer raw material.

As the monomer A, an alkyl (meth) acrylate represented by the following general formula (1) can be preferably used.
CH ₂ = C (R ¹ ) COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. Further, R ² is an alkyl group having 1 to 20 carbon atoms. Hereinafter, such a range of the number of carbon atoms may be expressed as "C _1-20 ". From the viewpoint of polymerization reactivity and polymerization stability, the alkyl (meth) acrylate are preferable ^{R 2} is an alkyl group of _{C 1-16,} ^{R 2} is _{C 1-12} (typically _{C 1-10,} e.g. Alkyl (meth) acrylate, which is an alkyl group of C _1-8 ), is more preferable.

Examples of the alkyl (meth) acrylate in which R ² is a C _1-20 alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl (meth) acrylate. ) Acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2 -Ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (Meta) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecil (meth) ) Acrylate, Eikosyl (meth) acrylate and the like can be mentioned. Such alkyl (meth) acrylates can be used alone or in combination of two or more.

In the technique disclosed herein, the alkyl acrylate as the monomer A is about 50% by weight or more (more preferably about 75% by weight or more, still more preferably about 90% by weight or more, for example, about 95% by weight) in all the monomer components. It can be preferably carried out in a mode that occupies the above). As the alkyl acrylate, an alkyl acrylate in which R ² in the above formula (1) is an alkyl group of C _1-20 is preferable, and R ² is C _1-12 (more preferably C _1-10 , particularly preferably C). Alkyl acrylate, which is the alkyl group of _1-8 ), is more preferable. The technique disclosed herein is also preferably carried out in an embodiment in which the alkyl acrylate is an alkyl acrylate in which R ² in the above formula (1) is an alkyl group of C _2-8 (typically C _4-8 ). Can be done. Alkylate acrylates may be used alone or in combination of two or more. When two or more kinds of alkyl acrylates are used, R ² is C _4-20 (more preferably C _4-10 , still more preferably C _4-8 ) for reasons such as adjusting the Tg of the acrylic polymer to the optimum range. Alkyl acrylate A1 which is an alkyl group of C1 and alkyl acrylate A2 which is an alkyl group of C _1-3 (more preferably C _1-2 , for example C ₂ ) may be used in combination. In that case, the weight ratio (A1: A2) of the alkyl acrylate A1 and the alkyl acrylate A2 is not particularly limited, and is, for example, about 5:95 to 95: 5, and it is appropriate to set it to about 10:90 to 90:10. For example, it is about 15:85 to 85:15.

In some preferred embodiments, the monomer component comprises one or more alkyl methacrylates as the monomer A. By using an alkyl methacrylate, a base polymer capable of exhibiting desired adhesive properties can be preferably designed. As the alkyl methacrylate, alkyl methacrylate in which R ² in the above formula (1) is an alkyl group of C _1-10 is preferable, and R ² is C _1-4 (more preferably C ₁ or C _2-4 ). Alkyl methacrylate, which is an alkyl group, is more preferable. The alkyl methacrylate can preferably be used in combination with an alkyl acrylate. When used in combination with alkyl methacrylate and alkyl acrylate, and weight C _AM of one or more alkyl methacrylates (e.g. C _2-4 alkyl methacrylates), together with one or more of the weight C _AA alkyl acrylate the ratio _{(C AM:} C _AA) is not particularly limited, in some embodiments, about 1: 9 to 9: 1, about 2: 8 to 8: 2 and appropriate to, preferably about It is 3: 7 to 7: 3, more preferably about 4: 6 to 6: 4. In some other embodiments, the alkyl (meth) acrylate of the total amount _(C AM _{+ C AA)} accounted alkyl methacrylates (such as _{C 1} alkyl methacrylate, i.e. methyl methacrylate (MMA)) by weight _{C AM} of, approximately 30 wt% or less , About 20% by weight or less is suitable, preferably about 10% by weight or less, and more preferably about 7% by weight or less. On the other hand, the lower limit is preferably about 0.1% by weight or more, about 1% by weight or more, and preferably about 2% by weight or more (for example, about 3% by weight or more).
The technique disclosed herein can be carried out in a manner in which the monomer component does not substantially contain alkyl methacrylate as the monomer A, and in a mode in which alkyl methacrylate is used, for example, C _1-3 alkyl methacrylate (typically). It can be carried out in a manner that does not include MMA).

In other preferred embodiments, acrylic polymer, alkyl acrylate carbon atoms in the alkyl group 4-9 (hereinafter, also referred to as a monomer m _A.) Wherein the monomer material may contain other monomers as required It is a polymer. The acrylic polymer can be synthesized by polymerizing a monomer raw material having a corresponding composition (monomer composition) by a known method.

Non-limiting examples of monomers _{m A,} n- butyl acrylate (BA), ethylhexyl acrylate to n-, 2-ethylhexyl acrylate (2EHA), n- octyl acrylate, n- nonyl acrylate and isononyl acrylate (iNA) is Can be mentioned. In the alkyl radical - _{(CH 2) 3} - alkyl acrylates are preferred, including the structure, in the alkyl radical - _{(CH 2) 4} - alkyl acrylates containing structure is more preferable. Suitable examples of monomers _{m A,} 2EHA, include BA and iNA. Monomer m _A can be used alone or in combination of two or more.

The amount of monomer m _A is typically at least 40 wt% of the total monomer raw material used in the synthesis of the acrylic polymer. Comprise a monomer m _A in a proportion of more than 40 wt% in the monomer composition is advantageous in terms of flexibility and low-temperature characteristics improve pressure-sensitive adhesive layer containing an acrylic polymer. From this viewpoint, the ratio of the monomers _{m A} is preferably 45 wt% or more, may be 50 wt% or more (e.g., 50 wt.%). Further, by the ratio of monomer m _A in the monomer in the composition and 99.9 wt% or less, it becomes easy to impart moderate cohesiveness to the adhesive layer containing an acrylic polymer. From this viewpoint, the proportion of the monomers m _A is preferably 95 wt% or less, more preferably 90 wt% or less, may be 85 wt% or less. In some embodiments, it may be less than 80 wt% the proportion of the monomers m _A, may be less than 70 wt% (e.g. 65 wt% or less).

The acrylic polymer in the technique disclosed herein may have a monomer composition containing a carboxy group-containing monomer (hereinafter, also referred to as monomer MB) as the monomer _B. That is, a monomer m _B in the acrylic polymer may be copolymerized. Monomer m _B is or introducing a crosslinking site into the acrylic polymer may serve to or enhance the cohesive force of the pressure-sensitive adhesive layer containing an acrylic polymer. Monomer m _B may also serve to improve it in a non-sticky residue to enhance the adhesion between the adhesive layer and the substrate layer containing an acrylic polymer (anchor property). Examples of the carboxy group-containing monomer include ethylene such as acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, and 1- [2- (methacryloyloxy) ethyl] succinic acid. Sexually unsaturated monocarboxylic acids; ethylenically unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, and citraconic acid and their anhydrides (eg, maleic anhydride, itaconic anhydride); and the like. The carboxy group-containing monomer may be used alone or in combination of two or more.

When using a monomer m _B, the proportion of the monomers m _B is not particularly limited in the monomer in the composition. The proportion of the monomers m _B may be, for example, 0.05 wt% or more, is suitably at least 0.1 wt%, preferably at least 0.5 wt% from the viewpoint of polymerization stability and dispersion stability, More preferably, it is 1% by weight or more. Further, in view of suppressing excessive increase of the peel strength (adhesive strength), the proportion of the monomers m _B is approximately 20 wt% or less (preferably about 10 wt% or less, typically less about 7% by weight to) the appropriate It is more preferably about 5% by weight or less, and further preferably about 4% by weight or less (for example, 3% by weight or less). From the viewpoint of suppressing corrosion of the Low-E glass plate, which is the object to be protected, it is preferable that the amount of the carboxy group-containing monomer used is limited.

The acrylic polymer in the technique disclosed herein is a homopolymer having an alkyl group having 4 to 20 carbon atoms as monomer A for the purpose of adjusting the glass transition temperature (Tg) of the acrylic polymer. Tg of alkyl is -50 ° C. or higher (meth) acrylate (hereinafter, also referred to as a monomer m _C.) may be copolymerized. Here, a monomer belonging to the monomer m _A described above, are excluded from the category of monomers m _C. Monomer m _C can be used alone or in combination of two or more. The monomer m _C preferably has a homopolymer Tg in the range of −40 ° C. to + 60 ° C., more preferably in the range of −30 ° C. to + 40 ° C. (for example, −20 ° C. to + 30 ° C.). Non-limiting examples of monomer m _C that may be preferably used include n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate and lauryl acrylate.

When the monomer m _C is used, the ratio of the monomer m _C in the monomer composition is not particularly limited. The proportion of the monomer m _C can be, for example, 1% by weight or more, 5% by weight or more, 10% by weight or more, and further 15% by weight or more. In some embodiments, from the viewpoint of better effective of monomers m _C, the ratio of the monomers m _C in the monomer in the composition may be more than 20 wt%, it may be more than 25 wt%, 30 wt% or more It may be 35% by weight or more (for example, 40% by weight or more). The ratio of the monomers m _C in the monomer in the composition may be less than 60 wt%, from the viewpoints of flexibility and low-temperature characteristics improve, 55 wt% or less approximately (typically about 50% by weight or less, for example approximately It is appropriate to set it to 45% by weight or less). In some embodiments, the proportion of the monomer mM _C may be less than 30% by weight, less than 20% by weight, less than 10% by weight (eg, less than 5% by weight, even less than 1% by weight). ..

The acrylic polymer in the art disclosed herein, as required, monomers m _A, m _B, monomers other than m _C (monomers m _D) may be copolymerized as a monomer A. Monomers m _D, the monomer m _A copolymerizable with various monomers can be used singly or in combination of two or more.

Monomers _{m D,} for example, may be used alkyl (meth) acrylate represented by the above general formula (1) (monomer _{m D1)} (except for groups corresponding to the monomer _{m A} or monomer _{m C.)} .. Specific examples of the alkyl (meth) acrylate that can be used as the monomer m _D1 include methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth) acrylate. The monomer m _D1 can be used alone or in combination of two or more.

Examples of the compound that can be used as the monomer m _D may include the following functional group-containing monomer (monomer B). Such a functional group-containing monomer can be useful for introducing cross-linking points into the acrylic polymer and increasing the cohesive force of the acrylic polymer.
Hydroxy group-containing monomers: For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, Hydroxyalkyls such as 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl acrylate Meta) acrylates; unsaturated alcohols such as vinyl alcohol and allyl alcohol.
Amid group-containing monomers: For example, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N-butyl (meth) acrylamide. , N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, diacetone (meth) acrylamide.
Imid group-containing monomers: for example, N-isopropylmaleimide, N-cyclohexylmaleimide, itaconimide.
Amino group-containing monomers: for example, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, t-butylaminoethyl (meth) acrylate.
Monomers having an epoxy group: for example, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether.
Cyanide-containing monomers: for example, acrylonitrile, methacrylonitrile.
Keto group-containing monomers: for example, diacetone (meth) acrylamide, diacetone (meth) acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.
Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinyl Pyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholin, N-vinylcaprolactam, N- (meth) acryloylmorpholine, N- (meth) acryloylpyrrolidone.
Alkoxysilyl group-containing monomers: For example, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, 3- (meth) acryloxy. Propylmethyldiethoxysilane.

Other examples of compounds which can be used as monomers m _D, vinyl acetate, vinyl ester monomers of vinyl propionate and the like; styrene, substituted styrene (alpha-methylstyrene), aromatic vinyl compounds such as vinyl toluene; cyclohexyl ( Non-aromatic ring-containing (meth) acrylates such as meta) acrylate, t-butylcyclohexyl (meth) acrylate, cyclopentyldi (meth) acrylate, isobornyl (meth) acrylate; aryl (meth) acrylate (eg, phenyl (meth) acrylate). , Benzyl (meth) acrylate), aryloxyalkyl (meth) acrylate (eg, phenoxyethyl (meth) acrylate), arylalkyl (meth) acrylate (eg, benzyl (meth) acrylate) and other aromatic ring-containing (meth) acrylates. Olefin-based monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; isocyanate group-containing monomers such as 2- (meth) acryloxyethyl isocyanate; methoxyethyl (meth) acrylate, An alkoxy group-containing monomer such as ethoxyethyl (meth) acrylate; a vinyl ether-based monomer such as methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether; and the like can be mentioned.

As yet another example of compounds which can be used as monomers m _D, polyfunctional monomers. Specific examples of the polyfunctional monomer include 1,6-hexanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and dipentaerythritol hexa. Examples thereof include compounds having two or more (meth) acryloyl groups in one molecule, such as (meth) acrylate and methylenebisacrylamide. When such a polyfunctional monomer is used, the amount used is not particularly limited, but it is appropriate to use 2% by weight or less (more preferably 1% by weight or less) of all the monomer components.

The amount of the monomer m _D used is appropriately set so as not to exceed 40% by weight of the monomer composition, preferably not to exceed 20% by weight, and more preferably not to exceed 10% by weight. It is not necessary to use the monomer m _D. The art disclosed herein, in a manner the amount of monomer m _D is less than 0 wt% to 5 wt% of the monomer composition may be preferably performed. Here, when the amount of the monomer m _D used is 0% by weight of the monomer composition, it means that the monomer m _D is not used at least intentionally.

Although not particularly limited, the ratio of monomer A (alkyl (meth) acrylate) to all the monomer components can be, for example, about 50% by weight or more, and it is appropriate to make it about 60% by weight or more. , About 70% by weight or more is preferable, about 80% by weight or more is more preferable, and about 85% by weight or more is further preferable. By containing the monomer A in a predetermined amount or more, a protective sheet having desired adhesive properties can be preferably realized. The technique disclosed herein can be preferably carried out, for example, in a manner in which the proportion of monomer A in the total monomer components is approximately 90% by weight or more. In some embodiments, the proportion of monomer A may be approximately 95% by weight or more, or may be approximately 97% by weight or more. A pressure-sensitive adhesive composition using such an acrylic polymer as a base polymer can be advantageous from the viewpoint of weather resistance of the pressure-sensitive adhesive layer formed from the composition (and thus, the protective sheet having the pressure-sensitive adhesive layer). Further, in the embodiment in which the monomer A and the monomer B are used in combination, the ratio of the monomer A to the total monomer components can be, for example, 99.9% by weight or less from the viewpoint of appropriately exerting the effect of the monomer B. , 99.5% by weight or less is preferable, 99% by weight or less is more preferable, or about 97% by weight or less (for example, 95% by weight or less) may be used.

When the above-mentioned functional group-containing monomer is copolymerized with the acrylic polymer, the ratio of the functional group-containing monomer to all the monomer components constituting the acrylic polymer is about 0.1% by weight or more (typically). Is preferably about 0.5% by weight or more, for example, about 1% by weight or more, and is preferably about 40% by weight or less (typically about 30% by weight or less, for example, about 20% by weight or less). Is preferable. For example, when a hydroxyl group-containing monomer is copolymerized with an acrylic monomer, the ratio of the hydroxyl group-containing monomer to all the monomer components is about 0.001% by weight or more (typically) from the viewpoint of obtaining a desired cohesive force. Is about 0.01% by weight or more, for example, about 0.1% by weight or more), preferably about 1% by weight or more, more preferably about 3% by weight or more, and about 10% by weight. It is appropriate to set it to% or less (typically about 7% by weight or less, for example, about 5% by weight or less).

(Rubber polymer)
In another preferred embodiment, the pressure-sensitive adhesive layer can be a rubber-based pressure-sensitive adhesive layer. Examples of the base polymers include natural rubber; styrene-butadiene rubber (SBR); polyisoprene; butene (referring to 1-butene and cis- or trans-2-butene) and / or 2-methylpropene (isoprene). Butene-based polymer containing the above as a main monomer; ABA type block copolymer rubber and its hydride, for example, styrene-butadiene-styrene block copolymer rubber (SBS), styrene-isoprene-styrene block copolymer rubber. (SIS), styrene-isoprene-styrene block copolymer rubber (SIBS), styrene-vinyl isoprene-styrene block copolymer rubber (SVIS), styrene-ethylene-butylene-styrene block co-weight, which is a hydride of SBS. Various rubber-based polymers such as coalesced rubber (SEBS) and styrene-ethylene-propylene-styrene block copolymer rubber (SEPS), which is a hydride of SIS, can be mentioned. These rubber-based polymers may be used alone or in combination of two or more.

(Tg of base polymer)
The Tg of the base polymer (acrylic polymer in the case of the acrylic pressure-sensitive adhesive layer) of the pressure-sensitive adhesive layer disclosed herein is not particularly limited. The Tg of the base polymer can be, for example, about 0 ° C. or lower. In some preferred embodiments, the Tg of the base polymer of the pressure-sensitive adhesive layer is approximately −5 ° C. or lower. According to the base polymer having such Tg, a pressure-sensitive adhesive layer having excellent adhesion to an adherend can be preferably formed. Better effects can be achieved according to aspects in which the Tg of the base polymer is approximately −15 ° C. or lower (more preferably approximately −20 ° C. or lower, eg, approximately −25 ° C. or lower). In another preferred embodiment, from the viewpoint of adhesiveness to the adherend, the Tg of the base polymer of the pressure-sensitive adhesive layer is about −35 ° C. or lower, more preferably about −40 ° C. or lower, still more preferably about −45 ° C. The following (for example, less than about -50 ° C, more about -52 ° C or less, or about -55 ° C or less). The Tg of the base polymer is preferably −70 ° C. or higher, preferably about −65 ° C. or higher, more preferably −60 ° C. or higher, and even more preferably −” from the viewpoint of adhesive cohesiveness and the like. It is 55 ° C. or higher (for example, about −50 ° C. or higher), and may be about −35 ° C. or higher. The Tg of the base polymer can be adjusted by appropriately changing the monomer composition (that is, the type and amount ratio of the monomers used in the synthesis of the polymer).

In the present specification, the Tg of a polymer is a Fox based on the Tg of a homopolymer of each monomer constituting the polymer and the weight fraction (copolymerization ratio based on the weight) of the monomer. The value obtained from the formula of. As shown below, the Fox formula is a relational formula between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer.
1 / Tg = Σ (Wi / Tgi)
In the above Fox formula, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction of the monomer i in the copolymer (copolymerization ratio based on the weight), and Tgi is the homopolymer of the monomer i. Represents the glass transition temperature (unit: K) of.

As the glass transition temperature of the homopolymer used for calculating Tg, the value described in the publicly known material shall be used. For example, for the monomers listed below, the following values are used as the glass transition temperature of the homopolymer of the monomer.
2-Ethylhexyl acrylate-70 ° C
n-hexyl acrylate-65 ° C
n-octyl acrylate-65 ° C
Isononyl acrylate -60 ° C
n-Nonyl acrylate -58 ° C
n-Butyl acrylate -55 ° C
Ethyl acrylate -20 ° C
Lauryl acrylate 0 ° C
2-Ethylhexyl methacrylate -10 ° C
Methyl acrylate 8 ℃
n-Butyl methacrylate 20 ° C.
Methyl methacrylate 105 ° C
Acrylic acid 106 ℃
Methacrylic acid 228 ° C
Vinyl acetate 32 ° C
Styrene 100 ° C

For Tg of homopolymers of monomers other than those exemplified above, the values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. The highest value is adopted for the monomers for which multiple types of values are described in this document. When the Tg of the homopolymer is not described in the Polymer Handbook, the value obtained by the measuring method described in JP-A-2007-51271 shall be used.

(Synthesis of base polymer)
The method for obtaining the base polymer (for example, an acrylic polymer) is not particularly limited. For example, known polymerization methods such as a solution polymerization method, an emulsion polymerization method, a massive polymerization method, and a suspension polymerization method can be appropriately adopted. Alternatively, photopolymerization performed by irradiating light such as UV (typically performed in the presence of a photopolymerization initiator), radiation polymerization performed by irradiating radiation such as β-rays and γ-rays, and the like. Active energy ray irradiation polymerization may be adopted. In some preferred embodiments, the base polymer (eg, acrylic polymer) is obtained by emulsion polymerization of the monomer raw material having the composition as described above. For example, as the monomer supply method in the emulsion polymerization method, a batch charging method, a continuous supply (dropping) method, a divided feeding (dropping) method, or the like in which all the monomer raw materials are supplied at once can be appropriately adopted. A part or all of the monomer components may be mixed with water and a surfactant in advance to emulsify, and the emulsified solution may be supplied to the polymerization vessel.

The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, and the like. The polymerization temperature is preferably about 20 ° C. or higher, preferably about 40 ° C. or higher, more preferably about 50 ° C. or higher, may be about 60 ° C. or higher, about 65 ° C. or higher, and further about 70 ° C. It may be above ° C. The polymerization temperature is preferably about 170 ° C. or lower (typically about 140 ° C. or lower), preferably about 95 ° C. or lower (for example, about 85 ° C. or lower). In emulsion polymerization, the polymerization temperature is preferably about 95 ° C. or lower (for example, about 85 ° C. or lower).

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons), acetic acid esters such as ethyl acetate, aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane are preferably used.

Examples of the polymerization initiator include, but are not limited to, an azo-based initiator, a peroxide-based initiator, and a redox-based initiator in which a peroxide and a reducing agent are combined. The polymerization initiator may be used alone or in combination of two or more.
Examples of azo-based initiators are 2,2'-azobisisobutyronitrile, 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropion amidine] hydrate, 2,2'. -Azobis (2-methylpropion amidine) disulfate, 2,2'-azobis (2-methylpropion amidine) dihydrochloride, 2,2'-azobis (2-methylpropion amidine) dihydrochloride, 2,2'- Examples thereof include azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis (N, N'-dimethyleneisobutyramidine) dihydrochloride.
Examples of peroxide-based initiators are persulfates such as potassium persulfate and ammonium persulfate; benzoyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, dilauroyl peroxide, di-n. -Octanoyl peroxide, di (4-methylbenzoyl) peroxide, t-butyl peroxybenzoate, t-butyl peroxysobutyrate, t-hexyl peroxypivalate, t-butyl peroxypivalate, di (2-ethylhexyl) peroxydi Carbon peroxide, di (4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxy2-ethylhexano Ate, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclododecane, 1,1-bis (t-hexylperoxy) cyclohexane, Examples include hydrogen peroxide.
Examples of redox-based initiators include a combination of peroxide and ascorbic acid (combination of hydrogen peroxide solution and ascorbic acid, etc.), a combination of peroxide and iron (II) salt (hydrogen peroxide solution). (Combination with iron (II) salt, etc.), combination of persulfate and sodium hydrogen peroxide, and the like.

The amount of the polymerization initiator used can be appropriately selected depending on the type of the initiator, the type of the monomer (composition of the monomer component), the polymerization conditions and the like. The amount of the polymerization initiator used is, for example, about 0.005 to 1 part by weight with respect to 100 parts by weight of the monomer raw material, and is appropriately in the range of about 0.001 to 0.5 parts by weight. The range is preferably in the range of 002 to 0.3 parts by weight, and more preferably in the range of 0.005 to 0.1 parts by weight.

For emulsion polymerization, various conventionally known chain transfer agents (which can also be grasped as a molecular weight adjuster or a degree of polymerization adjuster) can be used, if necessary. The chain transfer agent may be used alone or in combination of two or more. Examples of the chain transfer agent include mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, glycidyl mercaptan, 2-mercaptoethanol, mercaptoacetic acid, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. Can be preferably used. When a chain transfer agent is used, the amount used may be, for example, about 0.01 to 1 part by weight, and 0.02 to 0.1 parts by weight, based on 100 parts by weight of all the monomer components. Is preferable, and it is more preferably 0.03 to 0.07 parts by weight. The techniques disclosed herein may also be preferably practiced in aspects that do not use chain transfer agents.

The surfactant (emulsifier) used for emulsion polymerization is not particularly limited, and known anionic surfactants, nonionic surfactants and the like can be used. A surfactant having a radically polymerizable functional group may be used. Hereinafter, a surfactant having a radically polymerizable functional group is also referred to as a reactive (polymerizable) surfactant. On the other hand, a general surfactant having no radically polymerizable functional group may be referred to as a non-reactive (non-polymerizable) surfactant. The surfactant may be used alone or in combination of two or more.

Examples of non-reactive surfactants are sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkyl phenyl ether sulfate, polyoxy. Anionic emulsifiers such as sodium ethylenealkylphenyl ether sulfate and sodium polyoxyethylene alkyl sulfosuccinate; nonions such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene polyoxypropylene block polymer. System emulsifiers; and the like.

The reactive surfactant is not particularly limited as long as it has a radically polymerizable functional group. For example, it may be a reactive surfactant having a structure in which a radically polymerizable functional group is introduced into the anionic surfactant or nonionic surfactant as described above. Examples of the radically polymerizable functional group include a vinyl group, a propenyl group, an isopropenyl group, a vinyl ether group (vinyloxy group), an allyl ether group (allyloxy group) and the like. The concept of a propenyl group here includes a 1-propenyl group (CH _3- CH = CH-) and a 2-propenyl group (CH ₂ = CH-CH _2- ; sometimes referred to as an allyl group). included.

Examples of anionic reactive surfactants are polyoxyethylene (allyloxymethyl) alkyl ether sulfate (eg ammonium salt), polyoxyethylene nonylpropenylphenyl ether sulfate (eg ammonium salt), alkylallyl sulfosuccinic acid. Examples thereof include salts (for example, sodium salts), metharoxypolyoxypropylene sulfates (for example, sodium salts), polyoxyalkylene alkenyl ether sulfates (for example, ammonium salts in which the terminal of the alkenyl group is an isopropenyl group) and the like. When the anionic reactive surfactant forms a salt, the salt may be a metal salt such as a sodium salt or a non-metal salt such as an ammonium salt or an amine salt.
Examples of nonionic reactive surfactants include polyoxyethylene nonylpropenylphenyl ether and the like.

Although not particularly limited, in some embodiments, a reactive surfactant having an oxyethylene chain may be preferably used. Here, the oxyethylene chain refers to a repeating structure of oxyethylene units, that is, a structural portion represented by − (C ₂ H ₄ O) _n −. n indicates the number of repetitions in oxyethylene units. For example, a reactive surfactant having this repetition number n of about 5 to 30 (for example, 8 to 25) is preferable.

From the viewpoint of polymerization stability during emulsion polymerization and the like, a reactive surfactant having a propenyl group can be preferably adopted in some embodiments. Reactive surfactants having a propenyl group and an oxyethylene chain are particularly preferred.

From the viewpoint of emulsification performance and the like, an anionic reactive surfactant (for example, an anionic reactive surfactant having an oxyethylene chain) can be preferably adopted in some embodiments. When the anionic reactive surfactant forms a salt, the salt is preferably a non-metal salt, and more preferably an ammonium salt.
When a nonionic reactive surfactant is used, other surfactants such as anionic reactive surfactant, anionic non-reactive surfactant, nonionic non-reactive surfactant, etc. More favorable results can be achieved by using in combination with.

By emulsion-polymerizing the monomer raw material in the presence of a reactive surfactant having a radically polymerizable functional group, the reactive surfactant can react and be incorporated into a base polymer (for example, an acrylic polymer). The reactive surfactant incorporated into the base polymer is less likely to bleed out to the surface of the pressure-sensitive adhesive layer because its movement within the pressure-sensitive adhesive layer is restricted. Therefore, the use of the reactive surfactant can suppress the bleeding out of the low molecular weight compound to the surface of the pressure-sensitive adhesive layer. This is preferable from the viewpoint of low pollution. From the viewpoint of achieving better low pollution, a mode in which only a reactive surfactant is used as the surfactant during emulsion polymerization can be preferably adopted.

The amount of the surfactant used is preferably about 0.1 part by weight or more (for example, about 0.5 part by weight or more) with respect to 100 parts by weight of all the monomer components. Further, it is appropriate that the amount of the reactive surfactant used is about 10 parts by weight or less (for example, about 5 parts by weight or less) with respect to 100 parts by weight of all the monomer components, and it is about 4 parts by weight or less. May be good. The amount of the non-reactive surfactant used is about 5 parts by weight or less with respect to 100 parts by weight of all the monomer components, and about 4 parts by weight or less from the viewpoint of adhesive properties and low contamination of the surface of the adherend. It is suitable, preferably about 3 parts by weight or less (for example, about 2 parts by weight or less).

The pressure-sensitive adhesive layer of the protective sheet disclosed herein can be a pressure-sensitive adhesive layer formed from various forms of pressure-sensitive adhesive composition. Examples of the form of the pressure-sensitive adhesive composition include a composition in which a pressure-sensitive adhesive (adhesive component) is contained in an organic solvent (solvent-type pressure-sensitive adhesive composition), and a form in which at least a part of the pressure-sensitive adhesive is dispersed in an aqueous solvent. Composition (water-dispersed pressure-sensitive adhesive composition), composition prepared to be cured by active energy rays such as ultraviolet rays and radiation to form a pressure-sensitive adhesive (active energy ray-curable pressure-sensitive adhesive composition), heating. Examples thereof include a hot melt type pressure-sensitive adhesive composition which is coated in a molten state and forms a pressure-sensitive adhesive when cooled to around room temperature.
From the viewpoint of reducing the environmental load, a water-dispersible pressure-sensitive adhesive composition can be preferably adopted. As a preferred example of such a water-dispersible pressure-sensitive adhesive composition, a water-dispersion type pressure-sensitive adhesive composition containing an acrylic polymer as a base polymer (acrylic water-dispersion type pressure-sensitive adhesive composition, typically an acrylic emulsion-type pressure-sensitive adhesive). Composition). Further, from the viewpoint of adhesive properties, a solvent-based pressure-sensitive adhesive composition is preferable. A hot-melt adhesive composition that does not require the use of a solvent is advantageous in that it is easy to handle in a production process.

(Crosslinking agent)
In the techniques disclosed herein, the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer preferably contains a cross-linking agent. A pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing a base polymer and a cross-linking agent typically comprises a polymer having a structure cross-linked by the cross-linking agent (base polymer). According to such a pressure-sensitive adhesive layer, the surface hardness of the pressure-sensitive adhesive layer can be appropriately adjusted, and good peelability over time can be easily realized. The type of the cross-linking agent used is not particularly limited, and can be appropriately selected from conventionally known cross-linking agents.

Specific examples of the cross-linking agent include oxazoline-based cross-linking agent, aziridine-based cross-linking agent, isocyanate-based cross-linking agent, epoxy-based cross-linking agent, melamine-based cross-linking agent, peroxide-based cross-linking agent, urea-based cross-linking agent, and metal alkoxide-based cross-linking agent. , Metal chelate-based cross-linking agent, metal salt-based cross-linking agent, carbodiimide-based cross-linking agent, hydrazine-based cross-linking agent, amine-based cross-linking agent, silane coupling agent and the like. These can be used alone or in combination of two or more. For example, it is preferable to use one or more selected from the group consisting of an oxazoline-based cross-linking agent, an aziridine-based cross-linking agent, an isocyanate-based cross-linking agent, and an epoxy-based cross-linking agent. Of these, oxazoline-based cross-linking agents, isocyanate-based cross-linking agents, and epoxy-based cross-linking agents are more preferable. In the embodiment using the water-dispersible pressure-sensitive adhesive composition, a water-soluble or dispersible cross-linking agent is preferable, and a water-soluble (that is, water-soluble) cross-linking agent is particularly preferable.

As the oxazoline-based cross-linking agent, those having one or more oxazoline groups in one molecule can be used without particular limitation. In the water-dispersible pressure-sensitive adhesive composition, it is preferable to use an oxazoline-based cross-linking agent that can be dissolved or dispersed in water.
The oxazoline group may be any of a 2-oxazoline group, a 3-oxazoline group, and a 4-oxazoline group. A oxazoline-based cross-linking agent having a 2-oxazoline group can be preferably used. For example, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4- A water-soluble copolymer or an aqueous-dispersed copolymer obtained by copolymerizing an addition-polymerizable oxazoline such as methyl-2-oxazoline or 2-isopropenyl-5-ethyl-2-oxazoline with another monomer. , Can be used as an oxazoline-based cross-linking agent.
Commercially available oxazoline-based cross-linking agents include, for example, the trade names "Epocross WS-500", "Epocross WS-700", "Epocross K-2010E", "Epocross K-2020E", and "Epocross K-" manufactured by Nippon Shokubai. 2030E ”and the like.

Examples of the aziridine-based cross-linking agent include trimethylolpropane tris [3- (1-aziridinyl) propionate], trimethylolpropane tris [3- (1- (2-methyl) aziridinyl propionate)], and the like. Be done. Examples of commercially available aziridine-based cross-linking agents include trade names “Chemitite PZ-33” and “Chemitite DZ-22E” manufactured by Nippon Shokubai Co., Ltd.

As an example of the isocyanate-based cross-linking agent, a polyfunctional isocyanate compound having two or more functions can be used. For example, aromatic isocyanates such as tolylene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris (p-isocyanatophenyl) thiophosphate, diphenylmethane diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate. Isocyanate; etc. Commercially available products include trimethylolpropane / tolylene diisocyanate adduct (manufactured by Toso, trade name "Coronate L") and trimethylolpropane / hexamethylene diisocyanate adduct (manufactured by Toso, trade name "Coronate L"). Examples of isocyanate adducts such as "Coronate HL") and isocyanurates of hexamethylene diisocyanate (manufactured by Toso Co., Ltd., trade name "Coronate HX") can be exemplified. In the water-dispersible pressure-sensitive adhesive composition, it is preferable to use an isocyanate-based cross-linking agent that can be dissolved or dispersed in water. For example, a water-soluble, water-dispersible or self-emulsifying isocyanate-based cross-linking agent can be preferably adopted. A so-called blocked isocyanate type isocyanate-based cross-linking agent in which the isocyanate group is blocked can be preferably used.

As the epoxy-based cross-linking agent, one having two or more epoxy groups in one molecule can be used without particular limitation. An epoxy-based cross-linking agent having 3 to 5 epoxy groups in one molecule is preferable. In the water-dispersible pressure-sensitive adhesive composition, it is preferable to use an epoxy-based cross-linking agent that can be dissolved or dispersed in water.
Specific examples of the epoxy-based cross-linking agent include N, N, N', N'-tetraglycidyl-m-xylene diamine, 1,3-bis (N, N-diglycidyl aminomethyl) cyclohexane, and 1,6-hexane. Examples thereof include diol diglycidyl ether, polyethylene glycol diglycidyl ether, and polyglycerol polyglycidyl ether.
Commercially available epoxy-based cross-linking agents include Mitsubishi Gas Chemical Company's product names "TETRAD-X" and "TETRAD-C", DIC's product name "Epicron CR-5L", and Nagase ChemteX's products. Examples thereof include the name "Denacol EX-512" and the product name "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd.

As the carbodiimide-based cross-linking agent, a low molecular weight compound or a high molecular weight compound having two or more carbodiimide groups can be used. In the water-dispersible pressure-sensitive adhesive composition, it is preferable to use a carbodiimide-based cross-linking agent that can be dissolved or dispersed in water. Examples of commercially available carbodiimide-based cross-linking agents include the carbodilite V series (aqueous solution type) such as "carbodilite V-02", "carbodilite V-02-L2", and "carbodilite V-04" manufactured by Nisshinbo. Examples thereof include a carbodilite series such as a carbodilite E series (water-dispersed type) such as "carbodilite E-01", "carbodilite E-02", and "carbodilite E-04".

The content of the cross-linking agent (total amount of the cross-linking agent) in the pressure-sensitive adhesive composition disclosed herein is not particularly limited, and suitable properties can be obtained after cross-linking in consideration of the composition and molecular weight of the base polymer. Can be set. Although not particularly limited, the amount of the cross-linking agent used with respect to 100 parts by weight of the base polymer (typically an acrylic polymer) is about 0.01 parts by weight or more, and about 0.1 parts by weight or more. It is preferably about 1 part by weight or more (for example, about 2 parts by weight or more). From the viewpoint of adhesiveness and the like, the amount of the cross-linking agent used may be about 15 parts by weight or less (preferably about 10 parts by weight or less, for example, about 5 parts by weight or less) with respect to 100 parts by weight of the base polymer. It is suitable, and from the viewpoint of enhancing the adhesion to the adherend, it is preferably about 4 parts by weight or less, more preferably less than 3.5 parts by weight, and further preferably less than 3 parts by weight.

(Phosphate ester)
The pressure-sensitive adhesive composition (and thus the pressure-sensitive adhesive layer) disclosed herein may contain a phosphate ester. Examples of the phosphoric acid ester include alkyl phosphoric acid esters such as lauryl phosphate and lauryl phosphate, phosphoric acid esters having an oxyethylene chain, and salts thereof. The salt may be, for example, a sodium salt, a potassium salt, a barium salt, a triethanolamine salt or the like of the phosphoric acid ester. Hereinafter, unless otherwise specified, "phosphate ester" is used in the sense of including a salt. Of these, it is more preferable to use a phosphoric acid ester having an oxyethylene chain. A phosphoric acid ester having an oxyethylene chain mainly suppresses an increase in adhesive strength with time (that is, improves the stability of adhesive strength), and water or acid between the adhesive layer and the surface of the adherend. , It is possible to prevent the ingress of corrosion-inducing components such as alkali. Here, the oxyethylene chain includes a chain-like structural portion containing at least one ethylene oxide (EO) unit and further containing another oxyalkylene unit (for example, an oxyalkylene unit having about 3 to 6 carbon atoms). Say. A preferred example of a phosphoric acid ester having an oxyethylene chain is a phosphoric acid ester having an oxyethylene chain composed of EO units or a repetition thereof. For example, a phosphoric acid ester represented by the following general formula (a) or a salt thereof can be preferably adopted.

R ¹ in the above general formula (a) is −OH or − (OCH ₂ CH ₂ ) _n OR ³ , and R ² represents − (OCH ₂ CH ₂ ) _m OR ⁴ . n and m represent the number of moles of EO added. The EO addition mole number n is an integer of 1 to 30, typically an integer of about 1 to 20, preferably an integer of about 1 to 10, and may be an integer of, for example, about 1 to 8. The number of moles of EO added n is preferably an integer of about 1 to 6, and more preferably an integer of about 1 to 4 (for example, 2 to 4). In the general formula (a), the EO addition mole number m can typically be substantially the same as the EO addition mole number n. n and m may be the same or different. The above R ³ and R ⁴ are monovalent organic groups (typically hydrocarbon groups), and are, for example, independently selected from an alkyl group, a cycloalkyl group, an aryl group, an alkylaryl group and an arylalkyl group, respectively. Can be the basis for being. R ³ and R ⁴ are preferably linear or branched alkyl groups, aryl groups or alkylaryl groups. R ³ and R ⁴ are independently organic groups having 1 to 30 carbon atoms, and may be organic groups having 6 or more carbon atoms (preferably 8 or more, for example, 11 or more). In some preferred embodiments, R ³ and R ⁴ can be organic groups having 20 or less carbon atoms, preferably 18 or less, for example 15 or less. The salt of the phosphoric acid ester represented by the general formula (a) can be, for example, a sodium salt, a potassium salt, a barium salt, a triethanolamine salt or the like of these phosphoric acid esters. The phosphoric acid ester may be used alone or in combination of two or more.

Examples of the phosphoric acid ester include polyoxyethylene alkyl phosphoric acid esters such as polyoxyethylene tridecyl ether phosphoric acid, polyoxyethylene lauryl ether phosphoric acid, and polyoxyethylene octadecyl ether phosphoric acid; polyoxyethylene nonylphenyl ether phosphoric acid. , Polyoxyethylene alkylaryl phosphate, such as polyoxyethylene octylphenyl ether phosphoric acid, polyoxyethylene dinonylphenyl ether phosphoric acid, polyoxyethylene dioctylphenyl ether phosphoric acid, and the like. In some embodiments, phosphate esters having a molecular weight of 150-5000 can be preferably used.

The amount of the phosphoric acid ester used can be, for example, about 0.05 parts by weight or more, preferably about 0.1 parts by weight or more, based on 100 parts by weight of the base polymer (for example, an acrylic polymer). It is more preferable that the amount is about 0.3 parts by weight or more (for example, about 0.5 parts by weight or more). From the viewpoint of low contamination of the surface of the adherend, the amount of the phosphoric acid ester used is approximately 5 parts by weight or less (for example, 3 parts by weight or less) with respect to 100 parts by weight of the base polymer (for example, acrylic polymer). This is appropriate, preferably about 2 parts by weight or less, more preferably about 1 part by weight or less (for example, 0.1 part by weight or less). The technique disclosed herein can be preferably carried out in a manner in which the pressure-sensitive adhesive layer is substantially free of phosphate ester. According to the pressure-sensitive adhesive layer which does not contain phosphoric acid ester or has a content thereof of a predetermined amount or less, contamination of the surface of the adherend can be highly suppressed.

(anti-rust)
The pressure-sensitive adhesive layer disclosed herein may or may not contain a rust inhibitor. The pressure-sensitive adhesive layer according to some preferred embodiments may contain a rust inhibitor. The rust preventive is not particularly limited, and an appropriate species is selected from the rust preventive action on the adherend. Examples of the rust preventive agent include amine compounds (for example, organic acid amine salts, inorganic acid amine salts, triethanolamine, fatty acid amine compounds, alicyclic amines (specifically, polyoxyalkylene-containing alicyclic amines). ), Azol compounds (triazole compounds, etc.), nitrites, ammonium benzoate, ammonium phthalate, ammonium stearate, ammonium palmitate, ammonium oleate, ammonium carbonate, dicyclohexylamine benzoate, urea, urotropin, thio Examples thereof include urea, phenyl carbamate, cyclohexylammonium-N-cyclohexylcarbamate (CHC) and the like. These rust preventives may be used alone or in combination of two or more. Of these, amine compounds and azole compounds are preferable. It is desirable to select the rust preventive agent type in consideration of the influence on the adhesive properties (for example, the possibility of inhibiting the cross-linking reaction).

The content of the rust preventive (for example, an amine compound (amine rust preventive) or an azole compound (azole rust preventive)) is not particularly limited, and for example, 0.01% by weight or more (for example) in the pressure-sensitive adhesive layer ( Typically, it can be 0.05% by weight or more). From the viewpoint of obtaining a better corrosion prevention effect, the above content may be 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more, or 1% by weight or more. It may be 1.5% by weight or more, or 2% by weight or more (for example, 2.5% by weight or more). On the other hand, the content of the rust preventive is preferably less than 5% by weight in the pressure-sensitive adhesive layer, and in some preferred embodiments, the content of the rust preventive in the pressure-sensitive adhesive layer is 3% by weight or less. is there. By limiting the amount of the rust preventive to be used to a predetermined amount or less, it is possible to suppress an increase in the adhesive strength with time and preferably maintain good peelability. The content of the rust preventive in the pressure-sensitive adhesive layer is more preferably about 2% by weight or less, and may be about 1.5% by weight or less (for example, about 1.0% by weight or less). The techniques disclosed herein can also be preferably implemented in aspects that substantially do not use rust inhibitors. Adhesive layers that do not contain or have a limited content of rust inhibitors can result in highly suppressed contamination of the adherend surface. Further, in the embodiment in which the base polymer crosslinked with a cross-linking agent (for example, an oxazoline-based cross-linking agent) is used, a rust preventive agent (for example, an amine-based rust preventive agent) that may inhibit the cross-linking reaction of the cross-linking agent is contained. The limited amount is particularly significant from the viewpoint of exfoliation over time.

(Other ingredients, etc.)
The pressure-sensitive adhesive layer may contain a known pressure-sensitive adhesive such as a rosin-based pressure-sensitive adhesive, a terpene-based pressure-sensitive adhesive, and a hydrocarbon-based pressure-sensitive adhesive, if necessary. From the viewpoint of avoiding excessively high peel strength, the amount of the tackifier used is preferably about 5 parts by weight or less, and more preferably about 1 part by weight or less with respect to 100 parts by weight of the base polymer. .. Since the protective sheet disclosed herein can effectively control the adhesive force through the composition of the base polymer, Tg, the gel fraction of the pressure-sensitive adhesive, and the like, it can be preferably implemented even in an embodiment in which a pressure-sensitive adhesive is not used.

The pressure-sensitive adhesive layer may be used as a viscosity modifier (thickening agent, etc.), a cross-linking aid, a plasticizer, a softener, a filler, an antistatic agent, an antioxidant, an ultraviolet absorber, an antioxidant, etc. It may contain various optional additives that are common in the field of adhesives, such as light stabilizers and antifoaming agents. In addition, the pressure-sensitive adhesive composition according to some aspects has a content of a plasticizer such as a fatty acid ester limited to less than 5 parts by weight (for example, less than 1 part by weight) with respect to 100 parts by weight of the base polymer. possible. Typically, the pressure-sensitive adhesive composition may be substantially free of plasticizer. Further, the technique disclosed herein can be preferably carried out in a manner in which an antistatic agent (which may be a conductive agent) such as an ionic compound (for example, an ionic liquid or an alkali metal salt) is substantially not contained. Regarding other matters relating to the above-mentioned various optional additives, various additives and various methods known in the past can be appropriately adopted based on common general technical knowledge, and the present invention is not particularly characterized. Therefore, detailed description thereof will be omitted. To do.

In the technique disclosed herein, in the embodiment in which the aqueous dispersion type pressure-sensitive adhesive composition is used for forming the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition is, for example, an acrylic polymer obtained by emulsion polymerization using a surfactant. It can be prepared by mixing the aqueous dispersion of No. 1 with other components (for example, a cross-linking agent) used as needed. The aqueous dispersion may contain an aqueous liquid described below. For example, it is possible to use a polymerization reaction solution obtained by emulsion polymerization, or a polymerization reaction solution that has been subjected to treatments such as pH adjustment (for example, neutralization), adjustment of non-volatile content, and adjustment of viscosity, if necessary. it can. Usually, the dispersion stability of the emulsion can be improved by adding a neutralizing agent such as aqueous ammonia to the polymerization reaction solution to adjust the pH to an appropriate range (for example, in the range of about pH 6 to 9).

Although not particularly limited, the nonvolatile content (NV) of the pressure-sensitive adhesive composition is, for example, about 20% by weight or more (typically about 30% by weight or more, preferably about 30% by weight or more) from the viewpoint of drying efficiency and the like. It can be about 40% by weight or more), and can be about 75% by weight or less (typically about 70% by weight or less, preferably about 60% by weight or less) from the viewpoint of coatability and the like. ..

(Amount of chloride ion)
In the pressure-sensitive adhesive layer disclosed herein, the amount of chloride ions measured by hot water extraction is not particularly limited. In some embodiments, the amount of chloride ions per gram of pressure-sensitive adhesive (layer) can be less than 300 μg. According to the pressure-sensitive adhesive layer in which the amount of chloride ions is limited, in the Low-E glass plate to be protected without adding a corrosion inhibitor such as a rust inhibitor or while limiting the amount used thereof. There is a tendency to prevent corrosion and the like. The amount of chloride ion per 1 g of the pressure-sensitive adhesive (layer) is appropriately about 250 μg or less, and can be about 200 μg or less (for example, about 150 μg or less). By limiting the amount of chloride ions of the adhesive that comes into contact with the Low-E glass plate, it is possible to obtain a configuration that makes it easy to prevent corrosion and the like in the Low-E glass plate for a long period of time. In some embodiments, the amount of chloride ions per gram of pressure-sensitive adhesive (layer) may be approximately 100 μg or less, 95 μg or less, 90 μg or less, 85 μg or less, 75 μg or less. (Approximately 70 μg or less) may be used. The lower limit of the amount of chloride ions per 1 g of the pressure-sensitive adhesive (layer) is ideally 0 μg, but from the viewpoint of production efficiency, practically permissible level, etc., it may be about 1 μg or more, and is about 10 μg. It may be more than or equal to, and may be about 50 μg or more. In some other aspects, the amount of chloride ions per gram of the pressure-sensitive adhesive (layer) may be approximately 70 μg or more, or approximately 100 μg or more (for example, approximately 120 μg or more). According to the technique disclosed herein, by adding a limited amount of a rust preventive to the pressure-sensitive adhesive layer containing the above-mentioned concentration of chloride ions, good corrosion prevention is performed without impairing the peelability over time. Sex can be realized.

The amount of chloride ions per 1 g of the pressure-sensitive adhesive (layer) is measured by the method described in Examples described later. Alternatively, the amount of chloride ions in the protective sheet and the base material layer constituting the protective sheet is measured by hot water extraction, and the amount of chloride ions from the pressure-sensitive adhesive layer is calculated from the difference in the amount of chloride ions between the two. The obtained value may be obtained by converting it into a value per unit pressure-sensitive adhesive (layer).

(Gel fraction)
The weight fraction (gel fraction) of the ethyl acetate insoluble component of the pressure-sensitive adhesive layer disclosed herein is not particularly limited, and may be, for example, about 40% or more. In some embodiments, the gel fraction of the pressure-sensitive adhesive layer is preferably about 50% or more, preferably about 60% or more, and more preferably about 70% or more (for example, about 80% or more). The gel fraction of the pressure-sensitive adhesive layer may be, for example, about 90% or more (for example, about 95% or more). As the gel fraction increases, the cohesiveness of the pressure-sensitive adhesive tends to improve, and the adhesive strength over time tends to be suppressed. The upper limit of the gel fraction is 100% in principle. In some embodiments, the gel fraction can be, for example, approximately 98% or less, and may be approximately 92% or less (eg, approximately 85% or less). The gel fraction is, for example, the composition and content ratio of the base polymer, the polymerization method and polymerization conditions of the base polymer, the molecular weight of the base polymer, the presence or absence of the use of the cross-linking agent and the selection of the type and the amount used, the type and amount of the additive, etc. Can be adjusted by. The gel fraction is measured by the method described in Examples below.

(Swelling degree)
The degree of swelling of the pressure-sensitive adhesive layer disclosed herein is not particularly limited, and may be approximately 30 times or less. From the viewpoint of peelability over time, the degree of swelling is preferably about 25 times or less, preferably about 22 times or less, more preferably about 20 times or less, for example, even if it is about 18 times or less. Good. The lower limit of the degree of swelling is 1 in principle, and can be about 3 times or more, for example, about 5 times or more. The degree of swelling is adjusted by, for example, the composition and content ratio of the base polymer, the polymerization method and polymerization conditions of the base polymer, the molecular weight of the base polymer, the type (distance between functional groups) and the amount of the cross-linking agent used, the type and amount of the additive, and the like. can do. The degree of swelling is measured by the method described in Examples described later.

(Adhesive layer thickness)
The thickness of the pressure-sensitive adhesive layer constituting the protective sheet disclosed herein is not particularly limited. From the viewpoint of preventing adhesive residue on the adherend, the thickness of the pressure-sensitive adhesive layer is preferably about 50 μm or less, about 30 μm or less, preferably about 15 μm or less, and more preferably about 8 μm or less (for example, less than 6 μm). preferable. In some embodiments, the thickness of the pressure-sensitive adhesive layer is preferably about 5 μm or less, may be about 4 μm or less, and may be, for example, 3 μm or less from the viewpoint of peelability and the like. From the viewpoint of adhesiveness, the thickness of the pressure-sensitive adhesive layer is preferably about 0.5 μm or more, preferably about 1 μm or more, and more preferably more than 2 μm. The thickness of the pressure-sensitive adhesive layer may be more than 3 μm, for example, more than 4 μm.

<Base layer>
The protective sheet disclosed herein may include a substrate layer. As the base material layer, a resin film, a rubber sheet, a foam sheet, a composite thereof, or the like can be used. Examples of the rubber sheet include a natural rubber sheet, a butyl rubber sheet and the like. Examples of the foam sheet include a foamed polyurethane sheet, a foamed chloroprene rubber sheet, and the like.

The technique disclosed herein can be preferably applied to a protective sheet having a resin film as a base material layer. The "resin film" referred to here is typically a film formed by molding a resin composition mainly containing a resin component as shown below into a film shape, and is distinguished from so-called non-woven fabrics and woven fabrics. (That is, the concept excluding non-woven fabrics and woven fabrics). A substantially non-foamed resin film is preferred. Here, the non-foaming resin film refers to a resin film that has not been intentionally treated to form a foam, and specifically, the foaming ratio is less than about 1.1 times (for example, 1.05 times). Less than, typically less than 1.01 times) resin film.

Examples of resin components constituting the resin film include polyolefin-based resins (polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, etc.) and polyvinyl chloride-based resins (typically, soft poly). Vinyl chloride resin), polyvinyl acetate resin, polyurethane resin (ether polyurethane, ester polyurethane, carbonate polyurethane, etc.), urethane (meth) acrylate resin, thermoplastic elastomer (olefin elastomer, styrene elastomer, etc.) Acrylic elastomer, etc.), polyester resin (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, etc.), polycarbonate resin, polyamide resin, polyimide resin, fluorine resin, cellophane resin, etc. Examples include resin. These resin components may be used alone or in combination of two or more. Preferable examples of the resin film include a polyolefin resin film, a polyester resin film, and a vinyl chloride resin film.

Although not particularly limited, one or two selected from the group consisting of polyolefin resins, polyvinyl chloride resins, polyurethane resins, thermoplastic elastomers and polyester resins in the protective sheets according to some aspects. A base material layer containing a resin component of more than one species as a main component (typically, a base material layer containing such a resin component in a proportion of more than 50% by weight) can be preferably adopted. In some other aspects, a base material layer including a polyolefin-based resin layer, a polyester-based resin layer, or a polyvinyl chloride-based resin layer can be preferably used in consideration of performance, handleability, cost, and the like. Among the above resin materials, polyolefin-based resins, polyurethane-based resins and olefin-based elastomers are preferable from the viewpoint of thermal stability and lightness, and polyolefin-based resins and olefin-based elastomers are particularly preferable from the viewpoint of handleability and the like.

The protective sheet disclosed herein is preferably carried out in a mode including a base material layer containing a polyolefin-based resin as a main component (containing in a proportion exceeding 50% by weight), that is, a mode in which a polyolefin-based resin film is used as the base material layer. obtain. For example, a polyolefin-based resin film in which 50% by weight or more of the entire base material layer is a polyethylene (PE) resin or a polypropylene (PP) resin can be preferably adopted. In other words, in the polyolefin resin film, the total amount of the PE resin and the PP resin may occupy 50% by weight or more of the entire base material layer. The polyolefin-based resin film may be a blend of a PE resin and a PP resin.

The PP resin may contain various polymers (propylene-based polymers) containing propylene as a constituent monomer as a main component. It may be a PP resin substantially composed of one kind or two or more kinds of propylene-based polymers. The concept of a propylene-based polymer referred to here includes, in addition to homopolypropylene, a random copolymer (random polypropylene) of propylene and another monomer and a block copolymer (block polypropylene). The concept of the propylene-based polymer referred to here includes, for example, the following.
Propylene homopolymer (homopolypropylene). For example, isotactic polypropylene.
A random copolymer (random polypropylene) of propylene and another α-olefin (typically one or more selected from ethylene and α-olefins having 4 to 10 carbon atoms). Preferably, random polypropylene having propylene as a main monomer (main constituent monomer, that is, a component accounting for 50% by weight or more of the total monomer).
A copolymer (block polypropylene) obtained by block-copolymerizing propylene with another α-olefin (typically, one or more selected from ethylene and an α-olefin having 4 to 10 carbon atoms). Preferably, block polypropylene containing propylene as a main monomer (main constituent monomer, that is, a component accounting for 50% by weight or more of the total monomer).

The PE resin may contain various polymers (ethylene-based polymers) containing ethylene as a constituent monomer as a main component. It may be a PE resin substantially composed of one kind or two or more kinds of ethylene-based polymers. The ethylene-based polymer may be a homopolymer of ethylene, and is obtained by copolymerizing ethylene as a main monomer with another α-olefin as a submonomer (random copolymerization, block copolymerization, etc.). May be good. Preferable examples of the α-olefin include 3 to 10 carbon atoms such as propylene, 1-butene (which may be branched 1-butene), 1-hexene, 4-methyl-1-pentene, 1-octene and the like. Α-olefins of. For example, a PE resin containing an ethylene polymer in which α-olefin as the submonomer is copolymerized in a proportion of about 10% by weight or less (typically about 5% by weight or less) can be preferably adopted.

The PE resin also contains a PE resin containing a copolymer of ethylene and a monomer having another functional group in addition to the polymerizable functional group (functional group-containing monomer), and the functional group-containing monomer is copolymerized with an ethylene-based polymer. It may be a PE resin or the like. Examples of the copolymer of ethylene and the functional group-containing monomer include ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), and ethylene-acrylic. Methyl acrylate copolymer (EMA), ethyl ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA), ethylene- (meth) acrylic acid (ie, acrylic acid and / or methacrylic acid). ) Examples thereof include those in which the copolymer is crosslinked with metal ions.

The density of the PE resin is not particularly limited. The concept of PE resin as used herein includes any of high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE). In some embodiments, the density of the PE resin can be, for example, about 0.90 to 0.94 g / cm ³ . Preferred PE resins include LDPE and LLDPE. The PE resin may contain one or more LDPEs and one or two or more LLDPEs. The blend ratio of each LDPE or LLDPE and the blend ratio of LDPE and LLDPE are not particularly limited, and can be appropriately set so as to be a PE resin exhibiting desired characteristics. The base material layer of the protective sheet disclosed herein contains an LLDPE film containing LLDPE in an amount of more than 50% by weight (preferably about 75% by weight or more, for example, about 90% by weight or more) or more than 50% by weight (preferably about 90% by weight or more). A polyethylene-based resin film such as an LDPE film containing a proportion of about 75% by weight or more, for example, about 90% by weight or more) can be preferably adopted. A laminated resin film containing such a polyethylene-based resin film as a component may be used.

The resin film (for example, a polyolefin-based resin film) used as the base material layer of the protective sheet disclosed herein may contain an appropriate component that is permitted to be contained in the base material layer, if necessary. For example, fillers, colorants (pigments such as inorganic pigments, dyes), antioxidants, light stabilizers (meaning to include radical scavengers, ultraviolet absorbers, etc.), antioxidants, plasticizers, slips. Additives such as agents and anti-blocking agents can be appropriately added. The blending amount of each additive can be, for example, about the same as the usual blending amount in the field of the resin film used as the base material layer of the protective sheet.

The base material layer may have a single-layer structure, or may have a multi-layer structure of two layers, three layers or more. In the case of a multilayer structure, it is preferable that at least one layer (preferably all layers) is any of the above-mentioned resin films. For example, a base material layer having a thickness of 75% or more (more preferably 90% or more) composed of a single layer or a multilayer (typically a single layer) polyolefin resin film is preferable. The entire base material layer may be a base material layer made of a single layer or a multi-layer polyolefin resin film. From the viewpoint of economy, a base material layer made of a resin film having a single layer structure (for example, LLDPE film, LDPE film, etc.) can be preferably adopted.

The method for producing the base material layer may appropriately adopt a conventionally known method, and is not particularly limited. For example, when a resin film is used as the base material layer, a resin film produced by appropriately adopting a conventionally known general film molding method such as inflation molding, extrusion molding, T die casting molding, or calendar roll molding is used. Can be used.

In a configuration in which at least one surface of the base material layer (the surface on the adhesive layer side) is the surface of the resin film, the surface of the resin film is subjected to corona discharge treatment, plasma treatment, ozone exposure, flame exposure, and ultraviolet irradiation treatment. , Acid treatment, alkali treatment, application of undercoating agent, and other conventionally known surface treatments may be applied. Such a surface treatment may be a treatment for improving the adhesion between the base material layer and the pressure-sensitive adhesive layer, in other words, the anchoring property of the pressure-sensitive adhesive layer on the base material layer. In the embodiment in which the polyolefin-based resin film is used as the base material layer, it is particularly meaningful to perform the above surface treatment.

The thickness of the base material layer constituting the protective sheet disclosed herein is not particularly limited. The thickness of the base material layer can be, for example, about 800 μm or less (typically about 250 μm or less). In some embodiments, the thickness of the substrate layer (typically a non-foamed resin film) is preferably about 150 μm or less, more preferably about 100 μm or less, even more preferably less than 65 μm, for example less than 55 μm. obtain. When the thickness of the base material layer is reduced, the protective sheet tends to follow the shape of the adherend and the floating and peeling tends to be suppressed. Further, from the viewpoint of protection of the adherend, handleability, etc., the thickness of the base material layer is typically about 10 μm or more, preferably about 25 μm or more, more preferably more than 30 μm, still more preferably more than 40 μm, for example. It can be greater than 45 μm.

<Characteristics of protective sheet>
(Amount of chloride ion)
The protective sheet disclosed herein is not particularly limited, but the amount of chloride ions measured by hot water extraction is less than 30 μg per 1 g of the protective sheet (for example, about 25 μg or less, and further about 20 μg or less). Is appropriate. According to the protective sheet in which the amount of chloride ions is limited in this way, corrosion in the Low-E glass plate to be protected without adding a corrosion inhibitor such as a rust inhibitor or while limiting the amount used thereof. It is easy to obtain a configuration that prevents such problems over a long period of time. The amount of chloride ion per 1 g of the protective sheet is preferably less than 15 μg, more preferably less than 12 μg, still more preferably less than 10 μg. In some preferred embodiments, the amount of chloride ions measured by hot water extraction is less than 8.9 μg per gram of protective sheet (eg, approximately 8.5 μg or less). In some embodiments, the amount of chloride ions per gram of protective sheet is preferably less than 8.0 μg, more preferably less than 7.0 μg, even more preferably less than 6.5 μg, particularly preferably less than 6.0 μg (eg 5). (Less than 5.5 μg). The lower limit of the amount of chloride ions per 1 g of the protective sheet is ideally 0 μg, but from the viewpoint of production efficiency, practical allowable level, etc., it may be about 1 μg or more, and is about 3 μg or more. It may be about 5 μg or more. In some other embodiments, the amount of chloride ions per gram of protective sheet may be approximately 8 μg or greater, or may be approximately 12 μg or greater. According to the technique disclosed herein, by using a limited amount of rust preventive for a protective sheet containing the above-mentioned concentration of chloride ions, good corrosion prevention property can be obtained without impairing the peelability over time. It can be realized. The amount of chloride ion per 1 g of the protective sheet is measured by the method described in Examples described later.

(Initial adhesive strength to glass)
The protective sheet disclosed here has an initial peel strength (initial adhesive strength against glass) measured at a tensile speed of 0.3 m / min and a peel angle of 180 degrees 30 minutes after being attached to a Low-E glass plate. It is appropriate that it is about 0.01 N / 20 mm or more. In some embodiments, the initial peel strength may be approximately 0.05 N / 20 mm or greater (eg, approximately 0.1 N / 20 mm or greater). In some preferred embodiments, the initial peel strength is approximately 0.5 N / 20 mm or higher (eg, approximately 1 N / 20 mm or higher) and may be approximately 1.5 N / 20 mm or higher. The protective sheet exhibiting the above initial peel strength adheres well to the adherend within a relatively short time after being attached to the adherend, and is good because it is less likely to come off from the adherend. Can demonstrate excellent protection performance. The upper limit of the initial peel strength is not particularly limited, and from the viewpoint of light peelability, about 5 N / 20 mm or less is suitable, preferably about 3.3 N / 20 mm or less, and more preferably about 2.5 N / 20 mm or less ( For example, it is about 2N / 20mm or less). The initial peel strength is measured by the method described in Examples described later.

(Adhesion to glass over time)
The protective sheet disclosed herein is attached to a Low-E glass plate and stored at 50 ° C. for 7 days, and then has a tensile speed of 0.3 m / min and a peel strength over time measured at a peeling angle of 180 degrees (against glass). Adhesive strength over time) is preferably about 3.3 N / 20 mm or less. A protective sheet satisfying this characteristic can sufficiently suppress the adhesive force with time even if the sticking period to the adherend is relatively long, and can maintain the light peelability from the adherend. Therefore, the removal workability from the adherend is excellent. According to the protective sheet having a peel strength over time of about 3.0 N / 20 mm or less (more preferably about 2.7 N / 20 mm or less, still more preferably about 2.4 N / 20 mm or less, for example, about 2.1 N / 20 mm or less). , Better peeling workability (peeling property over time) can be realized. Further, from the viewpoint of suppressing peeling during the protection period of the adherend (for example, during processing of the adherend to which the protective sheet is attached), the peel strength with time is about 0.05 N / 20 mm or more. It is appropriate, preferably about 0.1 N / 20 mm or more, and more preferably about 0.3 N / 20 mm or more. The peel strength with time may be about 1 N / 20 mm or more (for example, about 1.5 N / 20 mm or more). The peel strength with time is measured by the method described in Examples described later.

(Peeling strength ratio)
Although not particularly limited, the protective sheet disclosed herein has a ratio of the time-dependent peel strength P ₂ [N / 20 mm] to the initial peel strength P ₁ [N / 20 mm] (that is, the P ₂ / P ₁ ratio). It can be 5 times or less. A small P ₂ / P ₁ ratio means that the peel strength does not increase with time. This makes it possible to achieve both initial adhesiveness and light peelability during peeling work. From this point of view, the P ₂ / P ₁ ratio may be preferably 4 or less, more preferably 3 or less, still more preferably 2 or less, for example 1.8 or less, 1.5 or less, and further 1.3. It may be as follows. Further, the P ₂ / P ₁ ratio is typically 0.8 or more, and can be, for example, 1 or more.

(VOC emission amount)
From the viewpoint of environmental hygiene, the protective sheet disclosed herein includes the protective sheet (including a base material layer and an adhesive layer, but does not include a release liner) when the protective sheet is heated at 80 ° C. for 30 minutes. The total amount of volatile organic compounds (VOCs) emitted from 1 g (hereinafter, also simply referred to as VOC emission amount) is 1000 μg (hereinafter, this may be referred to as “μg / g”). ) The following is preferable. The VOC emission amount is more preferably 500 μg / g or less (for example, 300 μg / g or less, typically 100 μg / g or less). The amount of VOC emitted is measured by the following method.

[VOC measurement test]
The protective sheet is cut to a predetermined size (here, a size of about 5 cm ² in area), the release liner is peeled off, and the sample piece is used. The sample piece is placed in a 20 mL vial and sealed. Next, the vial is heated at 80 ° C. for 30 minutes, and 1.0 mL (sample gas) of the heated gas is injected into a gas chromatograph (GC) measuring device using a headspace autosampler (HSS). Based on the obtained gas chromatogram, the amount of gas generated from the sample piece is determined as an n-decane equivalent amount. From the obtained values, the VOC emission amount (μg / g) per 1 g of the protective sheet (excluding the release liner) is determined. The n-decane conversion amount is obtained by regarding the detection intensity of the generated gas obtained by GC Mass as the detection intensity of n-decane and applying a calibration curve of n-decane prepared in advance. The settings for HSS and GC are as follows.
HSS: Model "7694" manufactured by Agilent Technologies
Heating time: 30 minutes Pressurization time: 0.12 minutes Loop filling time: 0.12 minutes Loop equilibrium time: 0.05 minutes Injection time: 3 minutes Sample loop temperature: 160 ° C
Transfer line temperature: 200 ° C
GC device: Model "6890" manufactured by Agilent Technologies
Column: J & W Capillary Column manufactured by GL Sciences, Ltd. Product name "DB-ffAP" (inner diameter 0.533 mm x length 30 m, film thickness 1.0 μm)
Column temperature: 250 ° C (heats from 40 ° C to 90 ° C at 10 ° C / min, then rises to 250 ° C at 20 ° C / min and holds for 5 minutes)
Column pressure: 24.3 kPa (constant flow mode)
Carrier gas: Helium (5.0 mL / min)
Injection: split (split ratio 12: 1)
Injection port temperature: 250 ° C
Detector: FID
Detector temperature: 250 ° C

The protective sheet disclosed here has anti-corrosion properties evaluated as no discoloration in a Low-E glass plate corrosion evaluation test (40 ° C. 92% RH × 7 days) carried out by the method described in Examples described later. Can have. A protective sheet that satisfies this characteristic can exhibit excellent corrosion resistance in Low-E glass plate protection applications.

<Preparation method of adhesive composition>
The method for preparing the pressure-sensitive adhesive composition disclosed herein is not particularly limited, and a conventionally known or commonly used method for preparing a pressure-sensitive adhesive composition can be appropriately adopted. The method for preparing the pressure-sensitive adhesive composition according to some aspects, though not particularly limited, is, for example, (a) the electric conductivity is less than 300 μS / cm; and (b) the chloride ion amount is 35 μg / cm. It is preferable to use an aqueous liquid that satisfies at least one of less than mL; According to this method, a pressure-sensitive adhesive composition capable of preventing corrosion in the Low-E layer can be obtained. Such pressure-sensitive adhesive compositions are particularly preferably used for protective applications of Low-E glass plates.

(Preparation of aqueous liquid)
The method for preparing the pressure-sensitive adhesive composition according to some aspects may include the step of preparing the above-mentioned aqueous liquid. The aqueous liquid satisfying the above (a) and / or (b) is desired from among surface water, raw water containing groundwater (which may be well water), tap water, and treated water subjected to known water treatment. It can be obtained by selecting an aqueous liquid satisfying the electric conductivity and / or the amount of chloride ion of the above by, if necessary, analysis or the like.

In some preferred embodiments, the aqueous liquid is obtained by subjecting an aqueous liquid (untreated aqueous liquid) such as raw water to a known treatment such as filtration, membrane separation, ion exchange, distillation, physical adsorption, electrolysis and the like. Be done. Of these, treatment by membrane separation using a reverse osmosis membrane, nanofiltration membrane, ultrafiltration membrane, microfiltration membrane or the like is more preferable, and a reverse osmosis membrane is particularly preferable. When ion exchange is adopted as the water treatment method, any of cation exchange (using cation exchange resin), anion exchange (using anion exchange resin), and a mixture of these can be used, but corrosion, etc. From the viewpoint of removing anions (typically chloride ions), which are considered to be the main cause of the above, when ion exchange water is used, it is preferable to adopt anion exchange. In this embodiment, the untreated aqueous liquid used in the treatment step has an electric conductivity of 300 μS / cm or more and a chloride ion amount of 35 μg / mL or more. The processing device is not particularly limited, and a known or conventional processing device can be used. The treatment conditions may be appropriately set according to the untreated water, the equipment, and the required water quality, and are not limited to specific conditions.

(Preparation of adhesive composition)
Then, using the aqueous liquid prepared as described above, a polymer-containing liquid containing a polymer (base polymer) as an adhesive component is obtained. That is, the method disclosed herein may include the step of obtaining a polymer-containing liquid containing the above-mentioned aqueous liquid and polymer. The usage pattern of the aqueous liquid is not particularly limited as long as it is used for preparing the pressure-sensitive adhesive composition, and the timing of use is not particularly limited. The aqueous liquid is also referred to as water for preparing the pressure-sensitive adhesive composition. Examples of the usage form of the preparation water include use as polymerization water in polymer polymerization and post-polymerization water added after polymerization (post-addition water). The obtained polymer-containing liquid may be used as it is as a pressure-sensitive adhesive composition, or a polymer-containing liquid mixed with additional components may be used as a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition obtained by using the aqueous liquid may be in the form of an aqueous dispersion type pressure-sensitive adhesive composition in which at least a part (typically all) of the polymer is dispersed in the water-based liquid. The details of the polymer (typically the base polymer) used in the pressure-sensitive adhesive composition, the details of the pressure-sensitive adhesive composition, and other matters related to the preparation of the pressure-sensitive adhesive composition are as described above. Is omitted.

In some preferred embodiments, the aqueous liquid is used as polymerization water in emulsion polymerization. That is, the method for preparing a pressure-sensitive adhesive composition disclosed herein may include a step of performing emulsion polymerization in the presence of the above-mentioned aqueous liquid to obtain a polymer. Since the details of the polymer obtained by emulsion polymerization are as described above, redundant description will be omitted.

(Characteristics of aqueous liquid)
In some embodiments, the electrical conductivity of the aqueous liquid used in the preparation of the pressure-sensitive adhesive composition is not particularly limited. Chloride ions in the aqueous liquid are preferably limited to less than a predetermined amount, in which case the electrical conductivity of the aqueous liquid does not have to be less than 300 μS / cm. On the other hand, since the electric conductivity correlates with the amount of ions in the aqueous liquid, the electric conductivity of the aqueous liquid in some other embodiments is preferably 300 μS / cm from the viewpoint of limiting the amount of ions causing corrosion and the like. Less than, more preferably less than 200 μS / cm, even more preferably less than 100 μS / cm, particularly preferably less than 50 μS / cm (eg less than 30 μS / cm, even less than 15 μS / cm). Such an aqueous liquid can be used as having a property of preventing corrosion or the like without quantifying the amount of chloride ions considered to be the main cause of corrosion or the like.

The lower limit of the electrical conductivity of the aqueous liquid used may be the theoretical lower limit (around 0.05 μS / cm at room temperature), but in consideration of production efficiency, a practically acceptable level, etc., it is approximately 1 μS / cm or more. It may be about 5 μS / cm or more, it may be about 10 μS / cm or more, and it may be about 50 μS / cm or more (for example, about 100 μS / cm or more, and further about 200 μS / cm or more). There may be.

The electrical conductivity of an aqueous liquid is measured at room temperature (23 ° C.) using a commercially available electrical conductivity meter. Specifically, the measurement can be performed using a portable electric conductivity meter "ES-71" manufactured by HORIBA, Ltd. or an equivalent product thereof.

In some embodiments, the aqueous liquid used to prepare the pressure-sensitive adhesive composition preferably has a limited amount of chloride ions. Specifically, when the electric conductivity of the aqueous liquid is 300 μS / cm or more, the chloride ion amount is preferably less than 35 μg / mL. Thereby, the effect of preventing corrosion and the like can be realized. Although not particularly limited, the amount of chloride ion in the aqueous liquid is preferably less than 35 μg / mL even when its electric conductivity is less than 300 μS / cm. In that case, the aqueous liquid used in the preparation of the pressure-sensitive adhesive compositions disclosed herein contains less than 35 μg / mL chloride ions regardless of their electrical conductivity.

In some embodiments, the amount of chloride ion in the aqueous liquid is preferably less than 35 μg / mL (eg, less than 30 μg / mL), preferably less than 25 μg / mL, more preferably less than 20 μg / mL, and further. It is preferably less than 15 μg / mL, particularly preferably less than 10 μg / mL, most preferably less than 5 μg / mL, and may be less than 3 μg / mL (eg, less than 1 μg / mL). The lower limit of the chloride ion amount of the aqueous liquid is ideally 0 μg / mL, but it may be about 1 μg / mL or more in consideration of production efficiency, a practically acceptable level, etc., and is about 3 μg. It may be / mL or more.

In some preferred embodiments, the aqueous liquid has a ratio (A _Cl / C) of chloride ion amount A _Cl [μg / mL] to electrical conductivity C [μS / cm] of approximately 1/5 or less. When the above ratio (A _Cl / C) is not more than a predetermined value, it means that the amount of chloride ions is relatively low among all the ions. By setting the above ratio (A _Cl / C) to about 1/5 or less, it is possible to preferably achieve both corrosion prevention and productivity. The above ratio (A _Cl / C) is more preferably about 1/8 or less, may be about 1/10 or less, or may be about 1/15 or less. The lower limit of the ratio (A _Cl / C) is not particularly limited and may be about 1/30 or more (for example, about 1/20 or more).

It is desirable that the aqueous liquid used in the preparation of the pressure-sensitive adhesive composition according to some aspects has a limited amount of sulfate ions from the viewpoint of preventing corrosion and the like. The amount of sulfate ion in the aqueous liquid is about 50 μg / mL or less, and it is appropriate that it is about 35 μg / mL or less (for example, about 25 μg / mL or less), preferably about 15 μg / mL or less, more preferably about 5 μg. It is less than / mL, more preferably about 2 μg / mL or less (for example, about 1 μg / mL or less). The lower limit of the amount of sulfate ion in the aqueous liquid is ideally 0 μg / mL, but it may be about 10 μg / mL or more in consideration of production efficiency, a practically acceptable level, etc., and is about 20 μg. It may be / mL or more.

It is desirable that the aqueous liquid used in the preparation of the pressure-sensitive adhesive composition according to some aspects has a limited amount of nitrate ions from the viewpoint of preventing corrosion and the like. The amount of nitrate ion in the aqueous liquid is about 30 μg / mL or less, and it is appropriate that it is about 20 μg / mL or less (for example, about 10 μg / mL or less), preferably about 7 μg / mL or less, more preferably about 5 μg. It is less than / mL, more preferably about 2 μg / mL or less (for example, about 1 μg / mL or less). The lower limit of the amount of nitrate ion in the aqueous liquid is ideally 0 μg / mL, but it may be about 1 μg / mL or more in consideration of production efficiency, a practically acceptable level, etc., and is about 3 μg. It may be / mL or more, and may be approximately 5 μg / mL or more (for example, 10 μg / mL or more).

In the aqueous liquid used for preparing the pressure-sensitive adhesive composition according to some aspects, it is appropriate that the total amount of nitrate ion, sulfate ion and chloride ion is about 80 μg / mL or less. By limiting the total amount of a plurality of types of ions that can cause such corrosion, corrosion and the like can be prevented more reliably. The total amount of the above three types of ions is preferably less than 50 μg / mL, more preferably less than 30 μg / mL, still more preferably less than 15 μg / mL, and about 10 μg / mL or less (for example, about 5 μg / mL or less). You may. The lower limit of the total amount of the three types of ions in the aqueous liquid is ideally 0 μg / mL, but it may be about 1 μg / mL or more from the viewpoint of production efficiency, a practically acceptable level, and the like. , It may be about 5 μg / mL or more, and may be about 10 μg / mL or more (for example, 30 μg / mL or more).

From the viewpoint of preventing corrosion and the like, in the technique disclosed herein, it is preferable to limit the amount of anions (typically chloride ions) among the ions contained in the aqueous liquid. On the other hand, the amount of cations in the aqueous liquid is not particularly limited. In some embodiments, the amount of cations in the aqueous liquid can be in the range of less than 300 μS / cm of electrical conductivity. For example, the amount of calcium ions and magnesium ions removed by a general water softening treatment is not particularly limited, and the amount of calcium ions and magnesium ions in the aqueous liquid used in the preparation of the pressure-sensitive adhesive composition is 1 μg / mL. It may be more than or equal to, about 10 μg / mL or more, and may be 20 μg / mL or more.

The chloride ion amount, sulfate ion amount, nitrate ion amount, calcium ion amount, and magnesium ion amount of the aqueous liquid are determined by an ion chromatograph method using each commercially available ion standard solution (for example, available from Wako Pure Chemical Industries, Ltd.). Can be measured. Specifically, it is measured by the following method.

[Measurement of ion amount of aqueous liquid]
The ion chromatography measurement conditions are as follows.
(Measurement condition)
Anion analysis:
Equipment: "ICS-3000" manufactured by Thermo Fisher Scientific
Separation column: Dionex IonPac AS18-fast (4 mm x 250 mm)
Guard column: Dionex IonPac AG18-fast (4 mm x 50 mm)
Removal system: Dionex AERS-500 (external mode)
Detector: Electrical conductivity detector Eluent: KOH aqueous solution (using eluent generator cartridge)
Eluent flow rate: 1.0 mL / min
Sample injection volume: 250 μL
Cationic analysis:
Equipment: "DX-320" manufactured by Thermo Fisher Scientific
Separation column: Dionex Ion Pac CS16 (5 mm x 250 mm)
Guard column: Dionex Ion Pac CG16 (5 mm x 50 mm)
Removal system: Dionex CSRS-500 (recycle mode)
Detector: Electrical conductivity detector Eluent: Methanesulfonic acid aqueous solution Eluent flow rate: 1.0 mL / min
Sample injection volume: 25 μL

Incidentally, it means a liquid composed mainly of water (H 2 _O) with an aqueous liquid as disclosed herein, in a ratio lower than water may contain organic solvents such as alcohol. Typically, a liquid having a water content of more than 50% by volume is used as the aqueous liquid. The proportion of water in the aqueous liquid is, for example, about 90% by volume or more, and about 99% by volume or more (for example, 99.9% by volume or more) is appropriate.

<Manufacturing method of protective sheet>
The techniques disclosed herein include methods of manufacturing protective sheets. The method for producing the protective sheet may be a method including a step of obtaining a pressure-sensitive adhesive composition by the above-mentioned preparation method and a step of forming a pressure-sensitive adhesive layer from the obtained pressure-sensitive adhesive composition. A protective sheet having such an adhesive layer can prevent corrosion and the like derived from the adhesive, and is therefore particularly preferably used for protection of Low-E glass plates. In the configuration in which the protective sheet includes the base material layer and the pressure-sensitive adhesive layer, the method for producing the protective sheet may include a step of providing the pressure-sensitive adhesive layer on one surface of the base material layer.

The pressure-sensitive adhesive layer can be formed according to a known method for forming a pressure-sensitive adhesive layer on a pressure-sensitive adhesive sheet. For example, a method (direct method) of forming a pressure-sensitive adhesive layer by directly applying (typically coating) the pressure-sensitive adhesive composition to a base material and drying it can be preferably adopted. Further, a method (transfer method) in which a pressure-sensitive adhesive composition is applied to a peelable surface (peeling surface) and dried to form a pressure-sensitive adhesive layer on the surface, and the pressure-sensitive adhesive layer is transferred to a substrate (transfer method). May be adopted. As the peeling surface, the surface of the peeling liner, the back surface of the peeling-treated base material, or the like can be used. The pressure-sensitive adhesive layer is typically formed continuously, but may be formed in a regular or random pattern such as a dot shape or a striped shape depending on the purpose and application.

The pressure-sensitive adhesive composition is applied by using a known or conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a comma coater, a dip roll coater, a die coater, a bar coater, a knife coater, and a spray coater. Can be done. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation, a curtain coating method, or the like. From the viewpoint of promoting the cross-linking reaction and improving the production efficiency, it is preferable to dry the pressure-sensitive adhesive composition under heating. The drying temperature can be, for example, about 40 ° C. to 150 ° C., preferably about 50 ° C. to 130 ° C. (for example, 60 ° C. to 100 ° C.). After the pressure-sensitive adhesive composition is dried, further aging may be performed for the purpose of adjusting the component transfer in the pressure-sensitive adhesive layer, advancing the cross-linking reaction, alleviating the strain that may exist in the base material or the pressure-sensitive adhesive layer, and the like. Good.

<Manufacturing method of glass unit>
The method for manufacturing the glass unit disclosed herein includes a step (A) of preparing a Low-E glass plate including a glass substrate and a Low-E layer laminated on the glass substrate; a Low-E glass plate. Step (B) of attaching a protective sheet to the surface of the Low-E layer; at least one selected from the group consisting of transportation, storage, processing, cleaning and handling of the Low-E glass plate to which the protective sheet is attached. Including an arbitrary step (C) of carrying out the above; a step of removing the protective sheet from the Low-E glass plate (D); and a step of assembling the glass unit using the Low-E glass plate (E); obtain. In this method, the protective sheet (also referred to as a surface protective sheet) disclosed here is used. Hereinafter, description will be made with reference to FIG.

First, in the step (A), as shown in FIG. 2, a Low-E glass plate 100 including a glass substrate 110 and a Low-E layer 120 laminated on the glass substrate 110 is prepared (S10). The Low-E glass plate 100 is prepared by forming a Low-E layer 120 on one surface of the glass substrate 110. The Low-E layer includes a metal layer, an oxide layer such as a metal oxide layer, and a nitride layer such as a silicon nitride layer, and usually has a multilayer structure, and is a known or commonly used method such as sputtering. Is formed by. Examples of the material constituting each layer of the Low-E layer include TiO ₂ , ZrO ₂ , Si _{X NY} , ZnO _X , Ag, NiCrO _X , SnO _{2, and the} like. As the infrared reflecting layer, an Ag layer is preferably used. In Low-E layer according to some embodiments, Ag layer is typically sandwiched ZnO _X layer. The material of the outermost surface of the Low-E layer (the surface to which the protective sheet is attached) is an oxide such as TiO ₂ layer, ZrO ₂ layer, ZnO _X layer, NiCrO _X layer, SnO ₂ layer, Si _{X NY} layer, etc. It is often a nitride of, and is usually not a metal such as Ag. The Low-E layer may have a multilayer structure of 5 layers or more, for example, 10 layers or more, and further 15 layers or more, depending on the purpose and required characteristics. The thickness of each layer is not particularly limited, and is usually 0 to 1000 Å, about 10 to 700 Å is suitable, for example, about 30 to 300 Å. The thickness (total thickness) of the Low-E layer can be about 10 nm to 1000 nm (for example, about 50 to 500 nm). The size of the glass substrate is not particularly limited, and the length of one side (width) is, for example, about 1 m or more, about 2 m or more, and recently, those exceeding 2.6 m, and further about 3 m or more (for example, about 3.3 m). The one with a large area (above) is used. The Low-E glass plate may be a commercially available product or a modified product thereof, or may be produced by a known or conventional method.

In the step (B), as shown in FIG. 2, the protective sheet 200 is attached to the surface of the Low-E layer 120 formed on the glass substrate 110 (S20). The protective sheet 200 is typically detachably attached to the surface. Here, "sticking so that it can be peeled off" means sticking that is intended or planned to be peeled off, and in many cases, the surface of the adherend after peeling off the protective sheet (adhesive sheet) is before sticking. It is a paste that can basically maintain the same state. From the viewpoint of protection, the size of the protective sheet 200 is preferably about the same as the surface of the Low-E layer 120. Two or more protective sheets may be partially overlapped on the surface to be protected to cover the surface. By covering the surface of the Low-E layer 120 with the protective sheet 200, corrosion of the Low-E layer 120 and the like can be prevented or suppressed.

After step (B), step (C) optionally includes at least one step selected from the group consisting of transport, storage, processing, cleaning and handling of the Low-E glass plate to which the protective sheet is attached. It can be carried out (S30). The processing can be cutting of a Low-E glass plate to which a protective sheet is attached, edge seams, or the like. The cutting means and the size after cutting are appropriately set according to the purpose and are not particularly limited. The protective sheet may remain attached to the surface of the Low-E layer even after the Low-E glass plate is cut. The cut Low-E glass plate is typically washed with water or the like. In the washing step, in addition to water, optionally a detergent (including a surfactant) may be used. During the above transportation, storage, processing such as cutting, washing such as washing with water, and various handling, as shown in FIG. 2, the Low-E layer 120 is damaged or worn due to the presence of the protective sheet 200 on it. Protected from deterioration, corrosion, etc.

Next, in the step (D), the protective sheet 200 is removed from the Low-E glass plate 100 (S40). After achieving the protective purpose, the protective sheet 200 is removed from the Low-E glass plate 100 which is an adherend. The Low-E glass plate 100 from which the protective sheet 200 has been removed is usually heat-treated in a heating furnace and tempered. Then, as shown in FIG. 2, a glass unit 300 is manufactured using the Low-E glass plate 100 (S50). The glass unit 300 is typically a heat-shielding or heat-insulating glass unit, and a pair of glass plates having at least one of them being a Low-E glass plate 100 is prepared, and a Low-E layer of the Low-E glass plate 100 is prepared. 120 It can be made by making a pair of glasses with the surface facing inward. Reference numerals 320 and 340 in the drawing represent other glass plates and spacers constituting the glass unit 300, respectively. The spacer 340 is arranged between the Low-E glass plate 100 and another glass plate 320 to create a space between the glass plates 100 and 320. In addition, in the method disclosed herein, a known or commonly used powder or liquid coating may be used in combination with the protective sheet.

<Protection method>
The protection method disclosed herein is a protection method using the protective sheet (also referred to as a surface protection sheet) disclosed here, and typically protects a part or all of the surface of the Low-E glass plate. How to do it. The protection method disclosed herein is characterized by including a step of sticking a protective sheet on the surface of a Low-E glass plate (sticking step).

Further, the protection method disclosed herein may further include a step (removal step) of removing the protective sheet from the Low-E glass plate. Further, between the sticking step and the removing step, at least one step selected from the group consisting of transportation, storage, processing, cleaning and handling may be optionally included for the article to which the protective sheet is stuck.

Preferable examples of the protection method disclosed herein are as described in the above-mentioned manufacturing method of the glass unit, and the sticking step and the removing step in the protection method are described in the steps (B) and (D) in the above manufacturing method. Corresponds to each. Other matters concerning the protection method are not particularly limited, but detailed description thereof will be omitted here because they can be understood by those skilled in the art in consideration of the above-mentioned description of the manufacturing method of the glass unit.

<Use>
The protective sheet disclosed here is suitable for a protective sheet for a glass plate used as a building material such as a window glass. The glass plate to be attached typically includes a glass substrate and a coating layer laminated on the glass substrate, and the coating layer may include a metal layer. More specifically, the glass plate is a glass plate having a Low-E layer on one surface. The Low-E layer usually includes a metal layer such as silver. In the production of the above glass plate, the Low-E layer forming surface may be exposed until the two glass plates including the Low-E glass plate are paired with the Low-E layer side surface facing inward. .. The protective sheet disclosed herein is preferably used for the purpose of preventing the Low-E layer forming surface from being damaged, worn, deteriorated, corroded or the like. That is, the protective sheet can be used as a Low-E layer forming surface protective sheet. Low-E glass plates are widely used as building materials such as window glass because they have higher heat insulation and heat insulation properties than conventional glass plates and can improve the cooling and heating efficiency of indoor spaces. The techniques disclosed herein can indirectly contribute to energy conservation and reduction of greenhouse gas emissions by being used in the production of such materials.

Further, the protective sheet disclosed herein is preferably used for a large-area adherend surface where the peel strength tends to be limited from the viewpoint of removal workability. The protective sheet disclosed herein is an adherend surface having a width of about 1 m or more, for example, about 1.5 m or more, and further about 2 m or more (typically about 3 m or more, further about 3.3 m or more). It is preferably used in a manner of covering the whole. The length of the surface of the adherend is equal to or greater than the above width. In some preferred embodiments, it is preferably used in an embodiment covering the entire surface of one of the above-mentioned large-area flat plates (preferably flat plates having a smooth surface). In particular, the area of glass plates for building materials such as window glass is increasing from the viewpoint of efficiency in production and transportation. The entire surface of a glass plate having such a large area (eg, a surface width of more than 2.6 m, typically a surface width of about 3 m or more, and even about 3.3 m or more) (typically. It is preferably used in a manner of covering the entire Low-E layer forming surface of the Low-E glass plate). According to a preferred embodiment of the technique disclosed herein, it is possible to maintain good peelability over time while exhibiting protective performance against an adherend having a large area as described above.

Further, since the protective sheet disclosed herein may have suppressed adhesive strength over time, for example, the sticking period to the adherend (which may also be the protection period of the adherend) is relatively long (which may also be the protection period of the adherend). Good removal workability can be exhibited even after typically (typically 2 weeks or more, for example, 4 weeks or more). Therefore, for example, it is suitably used even in a usage mode in which the period from attachment to the adherend (specifically, Low-E glass plate) to removal from the adherend can be 2 weeks or more (for example, 4 weeks or more). Can be done.

Matters disclosed by this specification include:
(1) A method for manufacturing a glass unit.
A step (A) of preparing a Low-E glass plate including a glass substrate and a Low-E layer laminated on the glass substrate;
In the step (B) of attaching a protective sheet to the surface of the Low-E layer of the Low-E glass plate;
With any step (C) of performing at least one selected from the group consisting of transport, storage, processing, cleaning and handling on the Low-E glass plate to which the protective sheet is attached;
In the step (D) of removing the protective sheet from the Low-E glass plate;
With the step (E) of assembling the glass unit using the Low-E glass plate;
Including
Here, the protective sheet is provided with an adhesive layer.
The method, wherein the pressure-sensitive adhesive layer contains a base polymer in a proportion of 95% by weight or more.
(2) The method according to (1) above, wherein the Low-E glass plate has a width of 1 m or more.
(3) The method according to (1) above, wherein the Low-E glass plate has a width of 2 m or more.
(4) The method according to (1) above, wherein the Low-E glass plate has a width of more than 2.6 m.
(5) The method according to (1) above, wherein the Low-E glass plate has a width of 3 m or more.
(6) The method according to any one of (1) to (5) above, wherein the Low-E layer includes a metal layer.
(7) The method according to any one of (1) to (5) above, wherein the Low-E layer contains a silver layer.
(8) The method according to any one of (1) to (7) above, wherein the thickness of the Low-E layer is 1000 nm or less.
(9) The method according to any one of (1) to (8) above, wherein the step (B) includes a step of covering the entire surface of one of the Low-E glass plates with at least one protective sheet. ..
(10) The step (C) is an indispensable step, and in the step (C), the Low-E glass plate is washed with water, any of the above (1) to (9). The method described in Crab.

(11) A step of attaching a protective sheet to the surface of a Low-E glass plate including a glass substrate and a Low-E layer laminated on the glass substrate (pasting step);
Here, the protective sheet is provided with an adhesive layer.
A method for protecting a Low-E glass plate, wherein the pressure-sensitive adhesive layer contains a base polymer in an amount of 95% by weight or more.
(12) Further including a step (removal step) of removing the protective sheet from the Low-E glass plate.
The attachment step and the removal step optionally include at least one step selected from the group consisting of transport, storage, processing, cleaning and handling of the Low-E glass plate to which the protective sheet is attached. The method according to (11) above.
(13) The Low-E glass plate has a width of 1 m or more and has a width of 1 m or more.
The method according to (11) or (12) above, wherein the pasting step includes a step of covering the entire surface of one of the Low-E glass plates with at least one protective sheet.

(14) The method according to any one of (1) to (13) above, wherein the amount of chloride ions measured by hot water extraction is less than 300 μg per 1 g of the pressure-sensitive adhesive layer.
(15) The method according to any one of (1) to (14) above, wherein the pressure-sensitive adhesive layer is formed from a water-dispersible pressure-sensitive adhesive composition.
(16) The method according to any one of (1) to (15) above, wherein the content of the rust preventive agent in the pressure-sensitive adhesive layer is 3% by weight or less.
(17) The method according to (16) above, wherein the rust preventive is an amine-based rust preventive.
(18) The method according to any one of (1) to (17) above, wherein the base polymer is selected from an acrylic polymer and a rubber polymer.
(19) The method according to any one of (1) to (18) above, wherein the base polymer is crosslinked by a cross-linking agent.
(20) The method according to (19) above, wherein the cross-linking agent is an oxazoline-based cross-linking agent.

(21) It has an adhesive layer and
The pressure-sensitive adhesive layer is a protective sheet containing a base polymer in an amount of 95% by weight or more.
(22) The protective sheet according to (21) above, wherein the amount of chloride ions measured by hot water extraction is less than 300 μg per 1 g of the pressure-sensitive adhesive layer.
(23) The protective sheet according to (21) or (22) above, wherein the pressure-sensitive adhesive layer is formed from a water-dispersible pressure-sensitive adhesive composition.
(24) The protective sheet according to any one of (21) to (23) above, wherein the content of the rust preventive agent in the pressure-sensitive adhesive layer is 3% by weight or less.
(25) The protective sheet according to (24) above, wherein the rust preventive is an amine-based rust preventive.
(26) The protective sheet according to any one of (21) to (25) above, wherein the base polymer is selected from an acrylic polymer and a rubber polymer.
(27) The protective sheet according to any one of (21) to (26) above, wherein the base polymer is crosslinked by a cross-linking agent.
(28) The protective sheet according to (27) above, wherein the cross-linking agent is an oxazoline-based cross-linking agent.
(29) The protective sheet according to any one of (21) to (28) above, which comprises a base material layer that supports the pressure-sensitive adhesive layer.
(30) The protective sheet according to any one of (21) to (29) above, wherein the 180 degree peel strength with respect to the Low-E glass plate after 1 week at 50 ° C. is 3.3 N / 20 mm or less.
(31) The protective sheet according to any one of (21) to (30) above, wherein the protective sheet is a Low-E glass plate protective sheet.

Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to those shown in the examples. In the following description, "part" and "%" are based on weight unless otherwise specified.

<Evaluation method>
[Measurement of gel fraction and swelling degree]
Approximately 0.1 g of adhesive layer sample (weight W ₁ ) is wrapped in a porous polytetrafluoroethylene film (weight W ₂ ) having an average pore size of 0.2 μm in a purse-like shape, and the mouth is tied with octopus thread (weight W ₃ ). .. As the porous polytetrafluoroethylene film, the trade name "Nitoflon (registered trademark) NTF1122" (manufactured by Nitto Denko KK, average pore diameter 0.2 μm, porosity 75%, thickness 85 μm) or an equivalent product thereof is used. After immersing this package in 50 mL of ethyl acetate and holding it at room temperature (typically 23 ° C.) for 7 days, the package is taken out, the ethyl acetate adhering to the outer surface is wiped off, and the weight of the package (W ₄ ). To measure. The parcel is then dried at 130 ° C. for 2 hours and the weight of the parcel (W ₅ ) is measured. By substituting each value into the following formula, the gel fraction and swelling degree of the pressure-sensitive adhesive layer can be calculated.
Gel fraction (%) = [(W _5- W _2- W ₃ ) / W ₁ ] x 100
Swelling degree (times) = (W _4- W _2- W ₃ ) / (W _5- W _2- W ₃ )

[Initial peel strength]
A protective sheet to be measured is cut into strips having a width of 20 mm and a length of 100 mm to prepare a test piece. Under a standard environment of 23 ° C. and 50% RH, this test piece is pressure-bonded to a Low-E glass plate as an adherend by reciprocating a 2 kg rubber roller twice. After holding this sample in the standard environment for 30 minutes, the initial peel strength (paired) under the standard environment under the conditions of a tensile speed of 0.3 m / min and a peel angle of 180 degrees using a universal tensile tester. Glass initial adhesive strength) [N / 20 mm] is measured. As the Low-E glass plate, a product number "RSFL6AS" (100 mm x 100 mm) manufactured by Nippon Sheet Glass Co., Ltd. is used. As the adherend, a Low-glass plate can be used without particular limitation, and an equivalent product of the above product or another commercially available Low-E glass plate may be used.

[Peeling strength over time]
A protective sheet to be measured is cut into strips having a width of 20 mm and a length of 100 mm to prepare a test piece. Under a standard environment of 23 ° C. and 50% RH, this test piece is pressure-bonded to a Low-E glass plate as an adherend by reciprocating a 2 kg rubber roller twice. This sample was stored in an environment of 50 ° C. for 7 days, then kept in a standard environment of 23 ° C. and 50% RH for 1 hour, and then in the standard environment using a universal tensile tester, the tensile speed was 0. The peel strength with time (adhesion to glass with time) [N / 20 mm] is measured under the conditions of 3 m / min and a peeling angle of 180 degrees. The Low-E glass plate used as the adherend is the same as in the case of the above initial peel strength measurement.

[Amount of chloride ions in adhesive (layer)]
Thoroughly wash the protective sheet to be measured with pure water, cut it into a sheet area of 200 cm and ² sizes, and collect only the adhesive. The collected adhesive is placed in a polypropylene (PP) container and weighed. 25 mL of pure water is added to a PP container, and warm extraction is performed at 120 ° C. for 1 hour using a dryer. With respect to the obtained extract, the amount of chloride ions in the extract was quantified using a commercially available chloride ion standard solution (obtained from Wako Pure Chemical Industries, Ltd.) by an ion chromatograph method, and the pressure-sensitive adhesive used for the extraction. The amount of chloride ion per 1 g is determined. The ion chromatography measurement conditions are as follows.
(Measurement condition)
Anion analysis:
Equipment: "ICS-3000" manufactured by Thermo Fisher Scientific
Separation column: Dionex IonPac AS18-fast (4 mm x 250 mm)
Guard column: Dionex IonPac AG18-fast (4 mm x 50 mm)
Removal system: Dionex AERS-500 (external mode)
Detector: Electrical conductivity detector Eluent: KOH aqueous solution (using eluent generator cartridge)
Eluent flow rate: 1.0 mL / min
Sample injection volume: 250 μL
Cationic analysis:
Equipment: "DX-320" manufactured by Thermo Fisher Scientific
Separation column: Dionex Ion Pac CS16 (5 mm x 250 mm)
Guard column: Dionex Ion Pac CG16 (5 mm x 50 mm)
Removal system: Dionex CSRS-500 (recycle mode)
Detector: Electrical conductivity detector Eluent: Methanesulfonic acid aqueous solution Eluent flow rate: 1.0 mL / min
Sample injection volume: 25 μL

[Amount of chloride ions in protective sheet]
The protective sheet to be measured is thoroughly washed with pure water, cut into a sheet area of 50 cm and ² sizes, placed in a polypropylene (PP) container, and weighed. 25 mL of pure water is added to a PP container, and warm extraction is performed at 120 ° C. for 1 hour using a dryer. For the obtained extract, the amount of chloride ion in the extract was quantified using a commercially available chloride ion standard solution (obtained from Wako Pure Chemical Industries, Ltd.) by ion chromatography, and the protective sheet used for extraction. The amount of chloride ion per 1 g is determined. The ion chromatography measurement conditions are the same as the measurement conditions for the chloride ion amount of the pressure-sensitive adhesive.

[Removability of protective sheet]
If the peel strength over time exceeds 3.3 N / 20 mm, good peelability tends not to be obtained. Therefore, based on this finding, when the peel strength over time is 3.3 N / 20 mm or less, it is marked with “◯”. The evaluation is made, and when the peel strength with time exceeds 3.3 N / 20 mm, it is evaluated as “x”.

[Low-E glass corrosion evaluation]
A test piece is prepared by cutting the protective sheet into strips having a width of 20 mm and a length of 100 mm. Under a standard environment of 23 ° C. and 50% RH, this test piece is pressure-bonded to the surface of the Low-E layer of a Low-E glass plate as an adherend by reciprocating a 2 kg rubber roller twice. As the Low-E glass plate, a product number "RSFL6AS" (100 mm x 100 mm) manufactured by Nippon Sheet Glass Co., Ltd. is used. After storing this sample in an environment of 40 ° C. and 92% RH for 7 days, the protective sheet is peeled off, and the state of the glass plate surface in the area protected by the protective sheet is visually observed. If no discoloration is observed, it is judged as "◎", if a slight discoloration is observed but at a level that is not practically problematic, it is judged as "○", and if discoloration is observed, it is judged as "x". Is determined. As the adherend, a Low-glass plate can be used without particular limitation, and an equivalent product of the above product or another commercially available Low-E glass plate may be used.

<Example 1>
Monomer raw material consisting of 58 parts of 2-ethylhexyl acrylate, 40 parts of n-butyl methacrylate and 2 parts of acrylic acid, reactive surfactant (trade name "Aqualon KH-1025" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., number of moles added by EO) A monomer raw material is obtained by mixing 3 parts of 30 or less polyoxyethylene-1- (allyloxymethyl) alkyl ether ammonium sulfate) and 150 parts of water for polymerization and emulsifying with an emulsifier (homomixer) while introducing nitrogen gas. Emulsion solution was prepared.
The emulsion was placed in a reaction vessel equipped with a thermometer, a nitrogen gas introduction pipe, a cooler and a stirrer, and heated to a liquid temperature of 50 ° C. while stirring under a nitrogen stream. To this, 0.03 part of 2,2'-azobis (2-methylpropion amidine) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., trade name "V-50") was added as a polymerization initiator, and the liquid temperature was around 50 ° C. The polymerization reaction was carried out for 5 hours. Ammonia water was added to the obtained polymerization reaction solution to adjust the pH to about 8. In this way, an aqueous dispersion of an acrylic polymer was prepared.
In this aqueous dispersion, 2 parts of an oxazoline-based cross-linking agent (trade name "Epocross WS-500" manufactured by Nippon Catalyst Co., Ltd.) and a rust preventive agent A (trade name) are added to 100 parts of the non-volatile content contained in the aqueous dispersion. "Lamiproof C-2", manufactured by Daiichi Kogyo Seiyaku Co., Ltd., 0.5 part of a polyoxyethylene-containing alicyclic amine) was mixed to prepare a pressure-sensitive adhesive composition according to this example.
This pressure-sensitive adhesive composition was applied to the corona-treated surface (first surface) of a polyethylene film having a thickness of 55 μm, which had been subjected to corona discharge treatment on one side, with a bar coater so that the thickness after drying was 6 μm. This was dried at 70 ° C. for 2 minutes and then aged at 50 ° C. for 1 day to prepare a single-sided adhesive pressure-sensitive adhesive sheet having an acrylic pressure-sensitive adhesive layer on one side of a base material layer made of a polyethylene film. The adhesive sheet thus obtained was used as a protective sheet according to this example.

<Examples 2-5>
A protective sheet according to each example was obtained in the same manner as in Example 1 except that the amount of the rust inhibitor A was shown in Table 1.

<Examples 6 to 7>
The rust preventive agent A is a rust preventive agent B (trade name "Killeslite W-16B", manufactured by Kirest Co., Ltd., containing an organic acid salt and a rust preventive component for iron) or a rust preventive agent C (trade name "thiolite C-560R13", A protective sheet according to each example was obtained in the same manner as in Example 2 except that the triethanolamine concentration was changed to 50 to 60%, manufactured by Chiyoda Chemical Co., Ltd.

Outline of the protective sheet of each example, gel fraction [%], swelling degree [times], initial peel strength [N / 20 mm], peel strength over time [N / 20 mm], chloride per 1 g of adhesive by hot water extraction. Table 1 shows the amount of substance ions [μg / adhesive 1 g], the amount of chloride ions per 1 g of protective sheet extracted by hot water extraction [μg / protective sheet 1 g], the peelability of the protective sheet, and the results of Low-E glass corrosion evaluation. Shown.

As shown in Table 1, all of the protective sheets according to Examples 1 to 7 had an adhesive strength equal to or higher than a predetermined value both at the initial stage and with time, and the Low-E glass corrosion evaluation was at a passing level. -E It is considered that it exhibits good protection performance against glass plates. Further, the protective sheets according to Examples 1 to 3 and Examples 6 to 7 having an adhesive layer containing a base polymer in an amount of 95% by weight or more have limited adhesive strength both in the initial stage and with time, and have good peelability. Indicated. In these cases, no contamination of the surface of the Low-E glass, which is the object to be protected, was observed. On the other hand, in Examples 4 to 5 in which the content of the base polymer was less than 95% by weight, the protective sheet peelability evaluation result was poor. From these results, according to the protective sheet provided with the adhesive layer containing the base polymer in a proportion of 95% by weight or more, it is possible to have a protective function against the Low-E glass plate, and the protected object can be protected for a long period of time. It can be seen that good peelability can be maintained even when pasted.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above.

1: Base material layer 1A: One surface 1B: The other surface 2: Adhesive layer 2A: Adhesive surface 10: Protective sheet 100: Low-E glass plate 110: Glass substrate 120: Low-E layer 200: Protective sheet 300 : Glass unit 320: Other glass plate 340: Spacer

Claims (10)

Low-E glass plate protective sheet
With an adhesive layer,
The pressure-sensitive adhesive layer is a protective sheet containing a base polymer in an amount of 95% by weight or more. The protective sheet according to claim 1, wherein the amount of chloride ions measured by hot water extraction is less than 300 μg per 1 g of the pressure-sensitive adhesive layer. The protective sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive layer is formed of a water-dispersible pressure-sensitive adhesive composition. The protective sheet according to any one of claims 1 to 3, wherein the content of the rust preventive agent in the pressure-sensitive adhesive layer is 3% by weight or less. The protective sheet according to claim 4, wherein the rust preventive is an amine-based rust preventive. The protective sheet according to any one of claims 1 to 5, wherein the base polymer is selected from an acrylic polymer and a rubber polymer. The protective sheet according to any one of claims 1 to 6, wherein the base polymer is crosslinked by a cross-linking agent. The protective sheet according to claim 7, wherein the cross-linking agent is an oxazoline-based cross-linking agent. The protective sheet according to any one of claims 1 to 8, further comprising a base material layer that supports the pressure-sensitive adhesive layer. The protective sheet according to any one of claims 1 to 9, wherein the 180 degree peel strength with respect to the Low-E glass plate after 1 week at 50 ° C. is 3.3 N / 20 mm or less.

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