CN117157372A

CN117157372A - Surface protection sheet

Info

Publication number: CN117157372A
Application number: CN202280024098.7A
Authority: CN
Inventors: 熊仓健太; 小坂尚史; 岛崎雄太; 本田哲士
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2021-03-25
Filing date: 2022-03-09
Publication date: 2023-12-01
Also published as: CN117062889A

Abstract

The application provides a surface protection sheet, which can maintain the adhesiveness required for protection even when used for a mode of processing a protection object in a liquid in a state of being attached to the protection object, and can realize the peeling of the protection object without damage or deformation during peeling. The surface protection sheet has an adhesive layer. The adhesive layer has a loss elastic modulus G' at 60 ℃ of 10kPa to 50 kPa. The surface protection sheet has a water peeling force FW1 of 1.0N/20mm or less after 30 minutes of warm water immersion.

Description

Surface protection sheet

Technical Field

The present application relates to a surface protection sheet.

The present application claims priority from japanese patent application No. 2021-52064 filed on 25 th 3 rd year 2021, japanese patent application No. 2021-151205 filed on 16 th 9 th year 2021, and japanese patent application No. 2021-151207 filed on 16 th 9 th year 2021, the entire contents of which are incorporated herein by reference.

Background

In processing or transporting various articles, a technique is known in which a protective sheet (adhesive sheet) is bonded to the surface of the article for the purpose of preventing damage (flaws, contamination, corrosion, etc.) to the surface. For example, in various treatments such as chemical treatment using a chemical solution (etching solution) for glass, semiconductor wafers, metal plates, and the like, or physical treatment such as cutting and polishing, a surface protection sheet is attached to a non-treated surface of an object to be protected, whereby the non-treated surface is protected. Patent document 1 is an example of a prior art document on a protective sheet for chemical treatment. Patent document 2 is a prior art document on a water-peelable pressure-sensitive adhesive sheet.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2015-193688

Patent document 2: japanese patent application laid-open No. 2020-23656

Disclosure of Invention

Problems to be solved by the invention

After the surface protection sheet has achieved the protection purpose, it is removed from the adherend (protection object) at an appropriate timing. Therefore, the surface protection sheet is required to have adhesion required for protecting the object to be protected during a protection period such as a chemical treatment and easy peelability at the time of peeling and removing from the object to be protected. If the peeling force against the object to be protected is large, for example, when the thickness of the object to be protected is small, the object to be protected may be broken or deformed due to the peeling force when the surface protection sheet is peeled off and removed from the object to be protected.

In recent years, electronic devices (for example, portable electronic devices) such as smart phones, tablet personal computers, and various wearable devices have been reduced in size and thickness, and along with these, semiconductor members and optical members such as glass used in these electronic devices have also been reduced in thickness. Therefore, the surface protection sheet for protecting the above member is required to have an easy peelability that does not cause breakage or deformation of the thin protection object when the surface protection sheet is peeled off and removed from the protection object.

For example, the glass panel used as the optical member may be thinned by a glass thinning process using a chemical solution such as hydrofluoric acid. In the above-described glass thinning treatment, the surface protection sheet may be used for protection of the non-treated surface of the glass. When the surface protection sheet used in this application is peeled off from the glass panel after the treatment, there are problems such as reduction in yield due to breakage of the thinned glass caused by an increase in peeling force during the treatment, peeling method, and the like. In particular, window glass and cover glass used for foldable displays and rollable displays are thinned to a thickness of about 100 μm or less in order to impart flexibility. Therefore, the risk of breakage upon peeling of the surface protective sheet is greater. If the peel strength of the surface protection sheet is set to a low level, the load applied to the adherend at the time of peeling is reduced, and the risk of breakage or deformation can be reduced, but the adhesion (adhesiveness) to the object to be protected is reduced, and in a serious case, the chemical liquid penetrates into the protection region, and in the protection period, warpage, peeling, and the like may occur from the adherend, and the protection purpose may not be achieved. It is more difficult to achieve both the adhesion required for protection and the easy peelability of an adherend from breakage for a brittle material such as thin glass having a thin thickness.

The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a surface protection sheet capable of maintaining adhesiveness required for protection even when used in a system for treating an object to be protected in a liquid in a state of being attached to the object to be protected, and capable of realizing peeling without breakage or deformation of the object to be protected at the time of peeling.

Means for solving the problems

According to the present specification, a surface protection sheet having an adhesive layer can be provided. In the surface protection sheet, the adhesive layer has a loss elastic modulus G' of 10kPa to 50kPa at 60 ℃. The surface protective sheet has a water peeling force (water peeling force after 30 minutes of warm water immersion) FW1 of 1.0N/20mm or less, and the water peeling force (water peeling force after 30 minutes of warm water immersion) is a water peeling force measured by bonding the adhesive surface of the surface protective sheet to the surface of an alkaline glass having a surface with a water contact angle of 20 degrees or less, immersing the surface of the surface protective sheet in warm water at 60 ℃ + -2 ℃ for 30 minutes, lifting the surface protective sheet from the warm water and wiping off adhering water, and then supplying 20 μL of distilled water between the alkaline glass and the adhesive surface to allow the distilled water to enter one end of the interface between the alkaline glass and the adhesive surface, and then measuring the surface protective sheet at a peeling angle of 180 degrees and a peeling speed of 300 mm/min at a temperature of 23 ℃.

The inventors of the present application have made studies and developments on an adhesive sheet (water-peelable adhesive sheet) which can be easily peeled off by an aqueous liquid such as water and which has improved water-resistant reliability at the time of bonding. According to the water-peelable pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet can be removed from the adherend without damaging the adherend or with little physical load by water peeling using an aqueous liquid such as water. In the technology disclosed herein, the water stripping described above is utilized. Specifically, since the water peeling force FW1 after 30 minutes of immersion in warm water is 1.0N/20mm or less, the surface protection sheet can be peeled off (water peeling) without breakage or deformation of the adherend (protection object) when peeled off after use in, for example, a chemical solution (typically in the form of an aqueous solution) or warm water. The surface-protecting sheet has water-peelability as described above, but on the other hand, the adhesive provided on the surface-protecting sheet has a 60 ℃ loss elastic modulus g″ in a range of 10kPa to 50kPa, and therefore, even when used in, for example, a chemical solution (typically in the form of an aqueous solution) or warm water, the adhesive agent maintains an adhesion state with an adherend under the action of the adhesive term (60 ℃ loss elastic modulus g″) of the adhesive agent, and does not exhibit a decrease in adhesion force due to water-peelability or a decrease in adhesion force is suppressed. Therefore, even when the surface protection sheet is treated in a liquid such as a chemical solution or warm water in a state of being attached to the protection object, the adhesion required for protection can be maintained. Such a surface protection sheet can be a surface protection sheet excellent in protection (for example, peeling from the edge portion does not occur in the above-described liquid treatment). According to the surface protection sheet, the adhesion required for protection can be provided, and even when the object to be protected is a brittle material having a thin thickness such as thin glass, peeling of the object to be protected (the object to be protected) from breakage can be achieved by peeling with water at the time of peeling.

In some preferred embodiments, the aforementioned adhesive layer comprises a water affinity agent. According to the adhesive layer containing the water affinity agent, an adhesive that suitably realizes both the adhesive force in a normal state (normal state) and the water peelability is easily obtained.

In some embodiments, the surface protective sheet is formed from the aforementioned adhesive layer and a substrate layer supporting the adhesive layer. With such a configuration, the surface protection sheet can have a protection function by the base layer on the back surface side and adhesion to the protection object by the adhesive layer.

In some preferred embodiments, the thickness (total thickness) of the surface-protecting sheet is 20 to 100 μm. The surface protection sheet having the above total thickness easily exerts a good protection function. For example, it is easy to obtain a protective property such as prevention of penetration of a chemical solution.

The surface-protecting sheet disclosed herein is suitable as a surface-protecting sheet used in a process of chemically and/or physically treating glass or semiconductor wafers in a liquid, for example. In the surface-protecting sheet disclosed here, in the above-mentioned application, the surface-protecting sheet can have adhesion required for protecting the object to be protected during the above-mentioned treatment, and can be peeled off smoothly from the glass or semiconductor wafer as the object to be protected (adherend) by water peeling during the peeling after the treatment. In the surface protection sheet having the above-mentioned water peeling force after the warm water immersion, even in the case where the object to be protected is a brittle material having a thin thickness such as thin glass, peeling of the object to be protected from breakage can be realized based on its water peeling property. For example, in the case where the processing step is a step of thinning the glass or the semiconductor wafer, the thickness of the protection object at the time of peeling is smaller than that at the time of attaching, and the risk of breakage is greater. By using the surface-protecting sheet disclosed herein in such applications, both the protective property by the adhesive force and the easy peelability (easy water peelability) without damaging the object to be protected can be achieved.

Drawings

Fig. 1 is a cross-sectional view schematically showing one embodiment of a surface protective sheet.

Fig. 2 is a cross-sectional view schematically showing another embodiment of the surface protective sheet.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described. It is to be noted that matters necessary for the practice of the present invention except the cases specifically mentioned in the present specification can be understood by those skilled in the art based on the teachings of the present invention and technical knowledge at the time of application described in the present specification. The present invention can be implemented based on the content disclosed in the present specification and technical common knowledge in the field. In the drawings below, members and portions that perform the same function are denoted by the same reference numerals, and overlapping description may be omitted or simplified. The embodiments described in the drawings are shown for clarity of illustration of the present invention, and do not necessarily represent the exact dimensions or scale-down of the actual article provided.

< construction example of surface protective sheet >

Fig. 1 shows a cross-sectional structure of a surface protection sheet according to one embodiment. As shown in fig. 1, the surface protection sheet 1 is in the form of a single-sided adhesive pressure-sensitive adhesive sheet having an adhesive surface 1A and an adhesive layer 20 provided on one side 10A of a sheet-like base material layer (support base material) 10. The surface protection sheet 1 is used to attach the surface 20A of the pressure-sensitive adhesive layer 20 as the adhesive surface 1A thereof to an adherend (protection object). The back surface 10B (the surface opposite to the one surface 10A) of the base material layer 10 is also the back surface 1B of the surface protection sheet 1, and forms the outer surface of the surface protection sheet 1. The surface protection sheet 1 before use (i.e., before attachment to an adherend) may be in the form of a release liner-equipped surface protection sheet 50 in which the adhesive surface 1A is protected by a release liner 30 that serves as a release surface on at least the pressure-sensitive adhesive layer 20 side. Alternatively, the surface protection sheet may be configured such that the other surface (back surface) 10B of the base material layer 10 is a release surface, and the surface protection sheet 1 is wound in a roll shape, whereby the pressure-sensitive adhesive layer 20 is brought into contact with the back surface and the surface (bonding surface 1A) thereof is protected.

In addition, as shown in fig. 2, the base material layer 10 of the surface protection sheet 2 may have a multilayer structure. In this embodiment, the surface protection sheet 2 has a structure in which an adhesive layer 20 is provided on one surface 10A of a sheet-like base material layer (support base material) 10, and the base material layer 10 has a laminated structure of a first layer 11 and a second layer 12. Specifically, the base material layer 10 includes a first layer 11 as a main layer of the base material layer 10, and a second layer 12 constituting one surface (back surface) 10B of the base material layer 10. In this embodiment, the second layer 12 is a layer containing an inorganic material. The adhesive layer 20 is adhered to the first layer 11 side surface 10A of the base material layer 10. The surface protection sheet 2 before use (i.e., before attachment to an adherend) may be in the form of a release liner-equipped surface protection sheet 50 in which the adhesive surface 2A is protected by a release liner 30 that serves as a release surface on at least the pressure-sensitive adhesive layer 20 side. Alternatively, the surface protection sheet may be formed such that the other surface (back surface) 10B of the base material layer 10 is a peeled surface, and the surface protection sheet 2 is wound in a roll shape, whereby the pressure-sensitive adhesive layer 20 is brought into contact with the back surface and the surface thereof is protected.

< Property of surface protective sheet >

(Water peeling force after 30 minutes of warm Water immersion FW 1)

One of the features of the surface-protecting sheet disclosed herein is that the water peeling force FW1 after 30 minutes of warm water immersion is 1.0N/20mm or less. As described above, the surface protection sheet having the water peeling force FW1 of 1.0N/20mm or less after 30 minutes of hot water immersion can be peeled off (water peeling) without breaking or deforming the object to be protected, for example, when the sheet is peeled off after use in a chemical solution (typically in the form of an aqueous solution) or in hot water. More specifically, for example, by supplying a small amount of aqueous liquid between the object to be protected and the pressure-sensitive adhesive layer and allowing the aqueous liquid to enter the interface between the object to be protected and the pressure-sensitive adhesive layer to create a peeling starting point, the peeling strength of the pressure-sensitive adhesive layer from the object to be protected can be significantly reduced. By utilizing this property, the surface protection sheet can be easily peeled from the object to be protected without damaging or deforming the object to be protected by water peeling using an aqueous liquid such as water. According to the surface protection sheet having such a characteristic (water peeling characteristic), even when the object to be protected is a brittle material having a thin thickness such as thin glass, peeling of the adherend can be achieved without breakage at the time of peeling, for example, after use in a chemical solution (typically in the form of an aqueous solution) or warm water.

The water separation force FW1 after the 30-minute warm water immersion is, for example, less than 1.0N/20mm, preferably not more than 0.9N/20mm or not more than 0.8N/20mm, and may be not more than 0.6N/20 mm. In some preferred embodiments, the water release force FW1 after the 30-minute warm water immersion is less than 0.5N/20mm, more preferably less than 0.4N/20mm, still more preferably about 0.3N/20mm or less, or may be 0.2N/20mm or less, or may be 0.15N/20mm or less, or may be 0.10N/20mm or less. The surface protection sheet exhibiting the water peeling force FW1 after the 30-minute warm water immersion exhibits good water peeling properties even after being used in a liquid treatment such as a chemical solution or warm water. The lower limit value of the water release force FW1 after the 30-minute warm water immersion is appropriately set so as to exhibit the desired water release property, and is not limited to a specific range. The lower limit value of the water peeling force FW1 after 30 minutes of warm water immersion may be 0.0N/20mm or 0.01N/20mm or more (for example, 0.05N/20mm or more).

The water peeling force FW1 after 30 minutes of immersion in warm water is a water peeling force [ N/20mm ] measured by adhering a surface protective sheet to an alkaline glass having a surface with a water contact angle of 20 degrees or less, immersing in warm water at 60+ -2 degrees for 30 minutes, lifting up and wiping off adhering water from the warm water, supplying 20. Mu.L of distilled water between the alkaline glass and the adhering surface, allowing the distilled water to enter one end of the interface between the alkaline glass and the adhering surface, and measuring the peeling force [ N/20mm ] under conditions of a temperature of 23 degrees, a peeling angle of 180 degrees, and a speed of 300 mm/min. More specifically, the water release force FW1 after 30 minutes of warm water immersion can be measured by the method described in examples described later.

(degree of decrease in Water Peel force FW1/F1 after 30 minutes of warm Water immersion)

The surface-protecting sheet disclosed herein preferably has a water release force FW1[ N/20mm ] after 30 minutes of warm water immersion of 50% or less of an adhesion force F1[ N/20mm ] after 30 minutes of warm water immersion. In other words, with the above surface protection sheet, the formula: the degree of decrease in water peel force [% ] after 30 minutes of warm water immersion represented by FW 1/F1X100 is preferably 50% or less. As described above, the surface protection sheet having the water peeling force FW1 reduced to 50% or less of the water peeling force F1 after 30 minutes of warm water immersion has an adhesive force equal to or higher than a predetermined value as described above even after use in, for example, a chemical solution (typically, in the form of an aqueous solution) or warm water in a state of being attached to the protection object, and can be peeled off (water peeling) without breakage or deformation of the protection object at the time of peeling. According to the surface protection sheet satisfying the above characteristics, it is possible to provide the adhesion required for protection, and it is possible to desirably realize peeling without breakage of the adherend at peeling even when the object to be protected is a brittle material having a thin thickness such as thin glass. In some embodiments, the degree of decrease in the water peel force after the 30-minute warm water immersion is preferably 30% or less, more preferably 20% or less, still more preferably 10% or less, and particularly preferably 5% or less (e.g., 3% or less). According to the surface protection sheet exhibiting such a degree of decrease in water peeling force after 30 minutes of warm water immersion, it is possible to obtain a surface protection sheet which can achieve both of adhesion reliability at the time of protection and easy peelability at the time of peeling. The lower limit of the degree of decrease in the water peeling force after the 30-minute warm water immersion is theoretically 0%, and may be about 1% or more (for example, 2% or more) in practical use.

(adhesive force F1 after 30 minutes of warm water immersion)

In the technology disclosed herein, the surface protection sheet is designed such that the adhesion force F1 after 30 minutes of warm water immersion is higher than the water peeling force FW1 after 30 minutes of warm water immersion. The adhesive force F1 after the 30-minute warm water immersion may be, for example, 0.5N/20mm or more, and is typically greater than 1.0N/20mm. The surface protection sheet satisfying the above characteristics can maintain the adhesion required for protection even when used in a system for treating an object to be protected in a liquid in a state of being attached to the object to be protected. For example, even when used in a chemical solution (typically in the form of an aqueous solution) or in warm water, the adhesive strength is not lowered or lowered due to the water peelability, and the adhesion state with an adherend can be maintained. Such a surface protection sheet can be a surface protection sheet excellent in protection (for example, peeling from the edge portion does not occur in the above-described liquid treatment). In some embodiments, the adhesive force F1 after 30 minutes of warm water immersion is preferably 1.5N/20mm or more, may be 2.0N/20mm or more, may be 2.5N/20mm or more, or may be 3.0N/20mm or more. There is a tendency to: the higher the adhesion force F1 after 30 minutes of warm water immersion, the easier the high protective function is maintained even when used in a mode of performing a liquid treatment such as a chemical solution or warm water. The upper limit of the adhesive force F1 after 30 minutes of warm water immersion can be set appropriately according to the required adhesive property, and thus is not limited to a specific range, and may be, for example, about 15N/20mm or less, about 10N/20mm or less, or about 5N/20mm or less.

The adhesion F1 after immersion in warm water for 30 minutes is an adhesion surface obtained by bonding a surface protection sheet to a surface of an alkaline glass having a surface with a water contact angle of 20 degrees or less, immersing in warm water at 60.+ -. 2 ℃ for 30 minutes, then lifting and wiping off the adhering water from the warm water, and then measuring the peel strength [ N/20mm ] under conditions of a temperature of 23 ℃ and a peel angle of 180 degrees and a speed of 300 mm/min. More specifically, the adhesive force F1 after 30 minutes of warm water immersion can be measured by the method described in examples described later.

(Normal adhesive force F0)

In some embodiments, the surface-protecting sheet preferably has a normal adhesion force F0 of 0.5N/20mm or more. The surface protection sheet having the normal adhesion force F0 of a predetermined value or more easily exhibits good adhesion to the protection object. In some preferred embodiments, the normal adhesion force F0 is 1.0N/20mm or more (e.g., greater than 1.0N/20 mm), more preferably 3.0N/20mm or more (e.g., greater than 3.0N/20 mm), or may be 5.0N/20mm or more (e.g., greater than 5.0N/20 mm), or may be 7.0N/20mm or more. The larger the normal adhesion force F0, the more easily a high adhesion reliability is obtained. According to the technology disclosed herein, even when the surface protection sheet is attached to the protection object with high adhesive force, the water peeling can be used at the time of peeling, and smooth peeling and removal of the surface protection sheet can be realized without damaging or deforming the protection object. Therefore, the adhesion force (normal adhesion force F0) can be set to a higher level than in the conventional surface protection sheet in which the adhesion force is limited and peelability is obtained. This means that even when used in a more severe environment, sufficient protection can be ensured due to high adhesion reliability, and is useful in practical use. The upper limit of the normal adhesion force F0 is not limited to a specific range, and may be, for example, about 20N/20mm or less, about 15N/20mm or less, about 10N/20mm or less, or about 6N/20mm or less, since it is appropriately set according to the required adhesion property.

The normal adhesion F0 is a peel strength [ N/20mm ] measured under conditions of a temperature of 23 ℃, a peel angle of 180 degrees, and a speed of 300 mm/min after the surface of the alkali glass having a surface with a water contact angle of 20 degrees or less is adhered to the surface of the alkali glass and kept at the temperature of 23 ℃ for 1 hour in an atmosphere of 50% RH. More specifically, the normal adhesion force F0 can be measured by the method described in examples described later.

(degree of decrease in Normal Water Peel force FW 0/F0)

In some embodiments, the surface protection sheet preferably has a normal water peel force FW0[ N/20mm ] of 50% or less of the normal adhesion force F0[ N/20mm ]. In other words, with the above surface protection sheet, the formula: the normal water peel force reduction degree [% ] represented by FW0/F0×100 is preferably 50% or less. The surface protection sheet satisfying such characteristics is favorably adhered to the adherend, and can be easily peeled from the object by performing water peeling using an aqueous liquid such as water at the time of peeling. According to such a surface protection sheet, adhesion required for protection can be exhibited, and peeling of an adherend can be achieved without breakage at the time of peeling. In some preferred embodiments, the normal water peel force reduction degree is 30% or less, more preferably 20% or less, still more preferably 10% or less, and may be 5% or less (for example, 3% or less). According to the surface protection sheet exhibiting such a degree of reduction in normal water peel force, it is possible to obtain a surface protection sheet which can achieve both adhesion reliability at the time of protection and easy peelability at the time of peeling. The lower limit of the normal water peel force decrease degree is theoretically 0%, and may be about 1% or more (for example, 2% or more) in practical use.

(Normal Water Peel force FW 0)

The normal water peel force FW0 is not particularly limited, and is, for example, 4N/20mm or less, 3.5N/20mm or less (for example, less than 3.0N/20 mm), and may be less than 1.5N/20mm, or about 1.0N/20mm or less. In the surface-protecting sheet satisfying the water peeling property, the adhesive layer can be easily peeled off by imparting an aqueous liquid such as water to the adhesion interface with the object to be protected and allowing the aqueous liquid to enter the interface. In some embodiments, normal water peel force FW0 may be 0.7N/20mm or less, 0.5N/20mm or less, or 0.3N/20mm or less (e.g., 0.1N/20mm or less). The lower limit value of the normal water peeling force FW0 is appropriately set so as to exhibit the desired water peelability, and is not limited to a specific range. The normal water peel force FW0 may have a lower limit of 0.0N/20mm or more (for example, 0.1N/20mm or more).

In addition, in some embodiments, the water release force FW1 of the surface protection sheet after the above 30-minute warm water immersion may be the same as the normal water release force FW0 or less than the normal water release force FW0. The surface protection sheet thus constituted did not undergo an increase in water peel force due to aging even after 30 minutes of immersion in warm water. Therefore, even when the surface protection sheet is exposed to a temperature higher than normal temperature (for example, about 40 ℃ or higher) during a liquid treatment such as a chemical liquid treatment or the like during the protection period, the adhesion between the surface protection sheet and the adherend is not increased or the increase in adhesion is suppressed, and when the surface protection sheet is peeled off, peeling of the adherend is easily achieved based on the desired water peelability. The water release force FW1 after 30 minutes of warm water immersion may be 70% or less, or 50% or less, or 30% or less, or 10% or less (e.g., 5% or less) of the normal water release force FW0. The water release force FW1 after 30 minutes of warm water immersion is not particularly limited, and may be 0% or more, or 1% or more of the normal water release force FW0.

The normal water peel force FW0 is a water peel force [ N/20mm ] measured by bonding a surface protective sheet to an alkaline glass having a surface with a water contact angle of 20 degrees or less, holding the surface protective sheet in an environment of 23 ℃ and 50% rh for 1 hour, then supplying 20 μl of distilled water between the alkaline glass and the bonding surface, allowing the distilled water to enter one end of the interface between the alkaline glass and the bonding surface, and then measuring the surface protective sheet at a peeling angle of 180 degrees and a peeling speed of 300 mm/min at a temperature of 23 ℃. More specifically, the normal water peel force FW0 can be measured by the method described in examples described later.

(initial Peel force in Water)

Although not particularly limited, in some embodiments, the initial peel force in water of the surface-protecting sheet is preferably 0.2N/10mm or more, measured at a peel angle of 20 degrees and a stretching speed of 1000 mm/min in water at room temperature (23 to 25 ℃). Surface protection sheets satisfying this characteristic tend to be excellent in edge peeling prevention. In a process such as conveyance, external forces such as vibration, which may cause peeling of the end portions of the surface protection sheet, are considered to be high-speed peeling loads applied at a small angle to the protection object. Since the surface protective sheet having an initial peel force in water of 0.2N/10mm or more, which is performed under conditions of a peel angle of 20 degrees and a peel speed of 1000 mm/min, has a stress of a predetermined value or more with respect to the peel load, even when an external force such as vibration is applied to a process of treating a protective object in a liquid such as a chemical or water in a state in which the surface protective sheet is attached to the protective object, excellent edge peeling prevention can be exhibited against the external force. The initial peel force in water is more preferably 0.3N/10mm or more, still more preferably 0.5N/10mm or more, particularly preferably 0.6N/10mm or more (e.g., 0.7N/10mm or more) from the viewpoint of improving the end peeling resistance. The upper limit of the initial peel force in water is not particularly limited, and may be, for example, 3N/10mm or less, or 2N/10mm or less (for example, 1N/10mm or less). The above-mentioned initial peel force in water can be desirably achieved mainly by setting the 25 ℃ bending stiffness value of the surface protective sheet to a prescribed range. More specifically, the initial peel force in water can be measured by the method described in examples described below.

(moisture permeability)

In some embodiments, the surface-protecting sheet preferably has a moisture permeability of 24 g/(m) as measured by cup method ² Day) below. By setting the moisture permeability to such a limit, even if the surface protection sheet is put into a liquid or the like in a state of adhering to an adherend and brought into contact with an aqueous liquid, the aqueous liquid is less likely to penetrate into the adhesive interface with the adherend, and the adhesive force due to the water peelability is not reduced or the adhesive force reduction is suppressed. As a result, the adhesion force with the adherend is maintained, and the surface protective sheet can maintain the adhesion state with the adherend. Such a surface protection sheet can be a surface protection sheet which does not peel off from the edge portion during a liquid treatment such as a chemical liquid treatment. In some preferred embodiments, the surface protective sheet has a moisture permeability of about 20 g/(m) ² Day) belowMore preferably about 16 g/(m) ² Day) or less, more preferably about 12 g/(m) ² Day) or less, particularly preferably about 8 g/(m) ² Day) or less, may be about 5 g/(m) ² Day) or less, for example, may be about 3 g/(m) ² Day) below. In addition, when the surface protection sheet is exposed to heat such as warm water, if the moisture permeability is too low, the water peelability may not be effectively exhibited due to aging caused by the heating. From such a viewpoint, in some embodiments, the surface-protecting sheet has a moisture permeability of 1 g/(m) ² Day) or more, preferably about 3 g/(m) ² Day) or more, more preferably greater than 5 g/(m) ² Day), for example, may be greater than 6 g/(m) ² Day).

More specifically, the moisture permeability of the surface-protecting sheet may be, for example, 23 g/(m) ² Day) or more, or less, 22 g/(m) ² Day) or more, or less, 21 g/(m) ² Day) or more, or less, 20 g/(m) ² Day) or more, or less, 19 g/(m) ² Day) above or below 18 g/(m) ² Day) or more, or less, 17 g/(m) ² Day) or more, or less, 16 g/(m) ² Day) or more and less, 15 g/(m) ² Day) above or below 14 g/(m) ² Day) above or below 13 g/(m) ² Day) or more and less, 12 g/(m) ² Day) or more, or less, 11 g/(m) ² Day) or more, or less, 10 g/(m) ² Day) or more, or less, 9 g/(m) ² Day) or more, or less, 8 g/(m) ² Day) or more, or less, 7 g/(m) ² Day) or more, or less, 6 g/(m) ² Day) or more, or less, 5 g/(m) ² Day) or more, or less, 4 g/(m) ² Day) or more, or less, 3 g/(m) ² Day) or more, or less, 2 g/(m) ² Day) or more or less, or 1 g/(m) ² Day) above or below.

The above moisture permeability of the surface protective sheet can be obtained by selecting and using an appropriate material (typically, a base material) which is non-moisture permeability and low in moisture permeability. More specifically, the moisture permeability of the surface-protecting sheet can be measured by the method described in examples described later.

(bending stiffness value at 25 ℃ C.)

In some embodiments, the surface protective sheet preferably has a bending stiffness value at 25 ℃ (25 ℃ bending stiffness value) of 1.0X10 ^-6 ～1.0×10 ^-2 Pa·m ³ Within a range of (2). In the surface protection sheet satisfying such characteristics, even when an external force such as vibration is applied to a process of treating a protection object in a liquid such as a chemical liquid or water in a state where the surface protection sheet is attached to the protection object, peeling from the end portion is less likely to occur due to the external force. Specifically, by providing the surface protection sheet with a predetermined range of stiffness (bending stiffness at 25 ℃), the stress (peeling stress) against external forces such as vibration, which may cause peeling of the end portions of the surface protection sheet in the above-described process, is increased, and even when external forces such as vibration are applied in the above-described process, the occurrence of peeling of the end portions can be prevented or the risk of occurrence of peeling of the end portions can be reduced. The bending stiffness value at 25℃is set to a predetermined value (for example, 10 ^-2 Pa·m ³ ) In the following, the surface protection sheet has rigidity suitable for the surface protection application, and good peeling workability and handling property are easily obtained. There is a tendency that the surface following property of the protection object is also improved.

From the viewpoint of the end peeling prevention, the bending rigidity value D at 25℃may be 5.0X10 ^-6 Pa·m ³ The above is preferably 1.0X10 ^-5 Pa·m ³ The above is more preferably 5.0X10 ^-5 Pa·m ³ The above is more preferably 1.0X10 ^- ⁴ Pa·m ³ Above, it may be 3.0X10 ^-4 Pa·m ³ The above. The bending stiffness value D at 25℃is preferably 5.0X10 from the viewpoints of prevention of peeling at the end, peeling workability, handling property and the like ^-3 Pa·m ³ Hereinafter, more preferably 1.0X10 ^-3 Pa·m ³ Hereinafter, it is more preferable that the ratio is 5.0X10 ^-4 Pa·m ³ Hereinafter, it may be 1.0X10 ^-5 Pa·m ³ The following is given. The 25 ℃ bend is considered to improve the surface following property of the object to be protectedIt is advantageous that the bending stiffness value D is low in a prescribed range.

The bending stiffness value D [ Pa.m ] at 25 DEG C ³ ]The thickness of the base material layer is set to be h m]And the Poisson's ratio of the base material is v, and the tensile elastic modulus of the surface protection sheet at 25 ℃ is E [ Pa ]]Is represented by the formula: d=eh ³ /12(1-ν ² ) The value obtained. It should be noted that the bending stiffness value of the adhesive layer is very small compared to the bending stiffness value of the base material layer, and thus the bending stiffness of the surface protection sheet may depend on the bending stiffness of the base material layer. Therefore, in the present specification, the bending stiffness value D of the surface protection sheet means a value obtained by converting the unit cross-sectional area of the base material layer constituting the surface protection sheet. The cross-sectional area of the substrate layer can be calculated based on the thickness of the substrate layer. The thickness h of the base material layer is obtained by subtracting the thickness of the adhesive layer from the measured value of the thickness of the surface protection sheet. The poisson's ratio v is a value (dimensionless number) determined by the material of the base material layer, and in the case where the material is a resin, generally, 0.35 can be used as the value of v.

The bending stiffness value D [ Pa.m ] at 25 DEG C ³ ]The tensile elastic modulus E [ Pa ] at 25℃obtained by the tensile test described in examples to be described later]Thickness of substrate h [ m ]]Substituting the obtained result into the above formula. The 25℃bending stiffness value may be a 25℃bending stiffness value in the longitudinal direction (MD: mach ine Direction), or may be a 25℃bending stiffness value in the width direction (TD: tran sverse Direction, direction orthogonal to the MD), and thus may be at least one of a 25℃bending stiffness value in the MD and a 25℃bending stiffness value in the TD, or may be a 25℃bending stiffness value in either one of the MD and the TD.

The 25 ℃ bending stiffness value of the surface protective sheet can be obtained mainly by selecting the material of the base material layer constituting the surface protective sheet and setting the thickness.

(tensile elastic modulus at 25 ℃ C.)

Although not particularly limited, in some embodiments, the surface protective sheet may have a tensile elastic modulus at 25℃of 100MPa or more, or 500MPa or more. In some preferred embodiments, the tensile elastic modulus at 25℃is 1000MPa or more, more preferably 3000MP a or more, still more preferably 5000MPa or more, and may be 6000MPa or more. The higher the tensile elastic modulus at 25 ℃, the higher the 25 ℃ bending stiffness value can be obtained. The upper limit of the tensile elastic modulus at 25℃is not particularly limited, and may be, for example, 30GPa or less, 15GPa or less, 10GPa or less, 8000MPa or less, 6000MPa or less, 4500MPa or less. The lower the tensile elastic modulus at 25 ℃, the lower the 25 ℃ bending stiffness value can be obtained. In addition, the surface protective sheet having a tensile elastic modulus at 25 ℃ in the above range tends to be excellent in peeling workability, handleability, and surface following property.

(stress at 100% elongation at 25 ℃ C.)

Although not particularly limited, in some embodiments, the surface protective sheet may have a stress of 10N/mm at 100% elongation at 25 DEG C ² Above, 30N/mm ² The above is suitable, preferably 50N/mm ² The above is more preferably 80N/mm ² Above, 120N/mm may also be used ² The above. The greater the stress at 100% elongation, the more likely the surface protective sheet has a rigidity equal to or higher than a predetermined value, and the more likely the end peeling prevention property tends to be obtained. The upper limit of the stress at 100% elongation is, for example, 300N/mm ² Hereinafter, the concentration may be 200N/mm ² Hereinafter, the concentration may be 100N/mm ² The following is given. The surface protective sheet having the above-described range of stress at 100% elongation tends to easily exhibit good peeling workability, handleability, and surface following property.

(stress at break at 25 ℃ C.)

Although not particularly limited, in some embodiments, the surface protective sheet may have a breaking stress of 10N/mm at 25 DEG C ² Above, 30N/mm ² Above (e.g. 50N/mm) ² Above), preferably 100N/mm ² The above is more preferably 120N/mm ² Above, 150N/mm may also be used ² The above. The greater the breaking stress, the more easily the surface protective sheet has rigidity equal to or higher than a predetermined value, and the end peeling prevention property is easily obtained Is a tendency of (a) to be formed. The upper limit of the breaking stress is, for example, 500N/mm ² Hereinafter, 300N/mm may be used ² Hereinafter, the concentration may be 200N/mm ² Hereinafter, 150N/mm may be used ² The following is given. The surface protective sheet having the fracture stress in the above range tends to easily exhibit good peeling workability, handleability, and surface following property.

(strain at break at 25 ℃ C.)

Although not particularly limited, in some embodiments, the surface protective sheet may have a fracture strain of 500% or less, preferably less than 300%, and more preferably 250% or less, and also 200% or less at 25 ℃. The smaller the fracture strain, the more easily the surface protective sheet has a rigidity equal to or higher than a predetermined value, and the end peeling prevention property tends to be easily obtained. The lower limit of the fracture strain is, for example, 120% or more, or 150% or more, or 200% or more. The surface protective sheet having the fracture strain in the above range tends to easily exhibit good peeling workability, handleability, and surface following property.

The tensile elastic modulus at 25℃can be obtained from linear regression of a stress-strain curve obtained by a tensile test described in examples below. In addition, the 100% elongation stress [ N/mm ] ² ]Stress at break [ N/mm ] ² ]Strain at break [%]The measurement can also be performed by a tensile test described in examples described below. The mechanical properties of the adhesive layer (tensile elastic modulus, stress at 100% elongation, breaking stress, and breaking strain) are very small compared to those of the base material layer, and the mechanical properties of the surface protective sheet may depend on the mechanical properties of the base material layer. Therefore, in the present specification, the tensile elastic modulus, the stress at 100% elongation, and the breaking stress of the surface protective sheet refer to values obtained by converting the values into the unit cross-sectional area of the base material layer constituting the surface protective sheet. The cross-sectional area of the substrate layer can be calculated based on the thickness of the substrate layer. The thickness of the base material layer is obtained by subtracting the thickness of the adhesive layer from the measured value of the thickness of the surface protection sheet. The above-mentioned tensile elastic modulus at 25℃may be the tensile elastic modulus at 25℃in MD or the tensile elastic modulus at 25℃in TDThe modulus of elasticity may be at least one of a 25℃tensile modulus of elasticity in MD and a 25℃tensile modulus of elasticity in TD, or may be a 25℃tensile modulus of elasticity in either direction of MD or TD. Similarly, the 100% elongation stress, the breaking stress, and the breaking strain may be measured in MD (100% elongation stress, breaking stress, or breaking strain), or may be measured in TD, and thus may be at least one of measured in MD and measured in TD, or may be measured in either MD or TD.

The mechanical properties (tensile elastic modulus at 25 ℃, stress at 25 ℃ and 100% elongation, breaking stress at 25 ℃ and breaking strain at 25 ℃) of the surface protective sheet can be mainly set and adjusted by selecting the material of the base material layer constituting the surface protective sheet.

< adhesive layer >

(loss elastic modulus G' at 60 ℃ C.)

One of the features of the surface protection sheet disclosed herein is that the surface protection sheet includes an adhesive layer, and the adhesive layer has a loss elastic modulus g″ at 60 ℃ (60 ℃ loss elastic modulus G ") in a range of 10kPa to 50 kPa. According to the surface protection sheet having the pressure-sensitive adhesive layer having the above-mentioned 60 ℃ loss elastic modulus g″, the water resistance is improved based on the viscosity term (60 ℃ loss elastic modulus g″) of the pressure-sensitive adhesive, and even when the pressure-sensitive adhesive is used in, for example, a chemical solution (typically, an aqueous solution) or warm water, the pressure-sensitive adhesive layer maintains a state of adhesion to an adherend, and does not exhibit or suppress a decrease in adhesion due to water peelability. Therefore, even when the object to be protected is treated in a liquid in a state in which the surface protection sheet is attached to the object to be protected, the adhesion required for protection can be maintained. In addition, it is considered that when a peeling load is applied to the surface protective sheet end portion by expansion and contraction of the base material layer in warm water, the peeling load can be converted into heat energy and reduced in the adhesive having a predetermined adhesive property at 60 ℃. Such a surface protection sheet can be a surface protection sheet excellent in protection (for example, peeling from the edge portion does not occur in the above-described liquid treatment).

In some preferred embodiments, the adhesive layer has a 60℃loss elastic modulus G″ of 12kPa or more, more preferably 15kPa or more, and may be 18kPa or more, 22kPa or more, and may be 25kPa or more, 28kPa or more, and may be 30kPa or more, or 32kPa or more, from the viewpoint of adhesion after the dipping with a chemical solution or warm water. As shown in the results of examples described below, the 60 ℃ loss elastic modulus g″ of the adhesive layer has a positive correlation with the adhesion force F1 after 30 minutes of warm water immersion, and therefore, by setting the 60 ℃ loss elastic modulus g″ to a high level, the adhesion force F1 after 30 minutes of warm water immersion can be maintained to a high level. In some embodiments, the upper limit of the 60℃loss elastic modulus G' may be 45kPa or less, 40kPa or less, or 35kPa or less. By limiting the 60 ℃ loss elastic modulus g″ of the adhesive layer to a predetermined value or less, an adhesive having good adhesive properties suitable for surface protection applications can be easily obtained. In another embodiment, the adhesive layer may have a 60℃loss elastic modulus G″ of 30kPa or less, 25kPa or less, or 20kPa or less.

More specifically, the adhesive layer may have a 60 ℃ loss elastic modulus g″ of 11kPa or more and less, 12kPa or more and less, 13kPa or more and less, 14kPa or more and less, 15kPa or more and less, 16kPa or more and less, 17kPa or more and less, 18kPa or more and less, 19kPa or more and less, 20kPa or more and less, 21kPa or more and less, 22kPa or more and less, 23kPa or more, 24kPa or less, 25kPa or more, 26kPa or more and less, 27kPa or more, 28kPa or more and less, 29kPa or more and less, 30kPa or more and less, 31kPa or more and less, 32kPa or more and less, 33kPa or less, 34kPa or more and less, 35kPa or less, 36kPa or more, 37kPa or less, 38kPa or less, 39kPa or more and less, 40kPa or more and 48kPa or less, and 45kPa or more and more, or more, and 45kPa or more and 45kPa or more and or more, and 45kPa or more.

The 60℃loss elastic modulus G' can be obtained mainly by adjusting the molecular weight and molecular weight distribution of the polymer contained in the adhesive, but can also be adjusted by the crosslinking density in the adhesive. The 60℃loss elastic modulus G' of the adhesive layer can be measured by the method described in examples described later.

(adhesive kind)

The pressure-sensitive adhesive layer may be, for example, a pressure-sensitive adhesive layer containing 1 or 2 or more types of pressure-sensitive adhesives selected from the group consisting of acrylic pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives (natural rubber-based, synthetic rubber-based, and mixtures thereof), silicone pressure-sensitive adhesives, polyester pressure-sensitive adhesives, urethane pressure-sensitive adhesives, polyether pressure-sensitive adhesives, polyamide pressure-sensitive adhesives, and fluorine pressure-sensitive adhesives. The acrylic adhesive herein refers to an adhesive containing an acrylic polymer as a main component. The same applies to rubber adhesives and other adhesives.

In the present specification, the term "acrylic polymer" refers to a polymer derived from a monomer component containing more than 50% by weight of an acrylic monomer. The acrylic monomer refers to a monomer having at least 1 (meth) acryloyl group in 1 molecule. In the present specification, "(meth) acryl" means an acryl group and a methacryl group. Similarly, "(meth) acrylate" refers to acrylate and methacrylate, respectively, "(meth) acrylic acid-" refers to acrylic acid-and methacrylic acid-, respectively. The acrylic polymer may be an acrylic polymer. The acrylic polymer may be, for example, an acrylic polymer contained as a base polymer (main constituent polymer) in a water-dispersible or solvent-based adhesive. In this case, the "monomer component constituting the acrylic polymer" in this specification may be modified to be "monomer component constituting the acrylic polymer". In the present specification, the content of the additive component expressed as a relative amount to the "monomer component constituting the polymer" and the "monomer component constituting the acrylic polymer" may be modified as a relative amount to the "acrylic polymer".

(acrylic adhesive)

From the viewpoint of weather resistance and the like, in some embodiments, an acrylic adhesive may be preferably used as a constituent material of the adhesive layer.

The acrylic adhesive is preferably an acrylic adhesive containing an acrylic polymer composed of a monomer component containing more than 35% by weight of a (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms at the ester end. Hereinafter, alkyl (meth) acrylate having an alkyl group having not less than X and not more than Y at the ester end is sometimes referred to as C (meth) acrylate _X-Y Alkyl esters). The alkyl (meth) acrylate having the above chain-like (used in the meaning of including straight chain and branched chain) alkyl groups may be used singly or in combination of 1 or more than 2.

In some embodiments, from the viewpoint of easy uniformity of characteristics, the (meth) acrylic acid C in the whole monomer component _1-20 The proportion of the alkyl ester may be, for example, 40% by weight or more, 45% by weight or more, or 50% by weight or more (for example, 55% by weight or more). For the same reason, C (meth) acrylic acid in the monomer component _1-20 The proportion of the alkyl ester may be, for example, 90% by weight or less, 70% by weight or less, or 65% by weight or less (for example, 55% by weight or less). In other embodiments, from the viewpoint of easy uniformity of characteristics, the (meth) acrylic acid C in the whole monomer component _1-20 The proportion of the alkyl ester may be, for example, 70% by weight or more, 80% by weight or more, or 90% by weight or more. For the same reason, C (meth) acrylic acid in the monomer component _1-20 The proportion of the alkyl ester may be, for example, 99.9% by weight or less, 99.5% by weight or less, or 99% by weight or less.

As (meth) acrylic acid C _1-20 Specific examples of the alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, nonadecyl (meth) acrylate, and eicosyl (meth) acrylate.

Among them, at least (meth) acrylic acid C is preferably used _4-20 Alkyl esters, more preferably at least C (meth) acrylic acid _4-18 Alkyl esters. For example, an acrylic adhesive containing one or both of n-Butyl Acrylate (BA) and 2-ethylhexyl acrylate (2 EHA) as the monomer component is preferable, and an acrylic adhesive containing at least BA as the monomer component is particularly preferable. (meth) acrylic acid C as can be preferably used _4-20 Other examples of alkyl esters include isononyl acrylate, n-Butyl Methacrylate (BMA), 2-ethylhexyl methacrylate (2 EHMA), and isostearyl acrylate (iST A).

In some embodiments, the monomer component constituting the acrylic polymer may contain (meth) acrylic acid C in a proportion of 40% by weight or more _4-18 Alkyl esters. In this way, the monomer component containing a large amount of the alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms at the ester end tends to form an acrylic polymer having high lipophilicity. Acrylic acid with high lipophilicityThe polymer is easy to form an adhesive layer which is not easy to reduce the adhesive force even immersed in water such as warm water. (meth) acrylic acid C _4-18 The proportion of the alkyl ester in the monomer component may be, for example, 60% by weight or more, or 70% by weight or more, or 75% by weight or more, or 80% by weight or more. The (meth) acrylic acid C may be contained in a proportion of at least any of the above lower limit values _6-18 Monomer components of alkyl esters.

In addition, from the viewpoint of improving the cohesiveness of the adhesive layer and preventing cohesive failure, C (meth) acrylic acid _4-18 The proportion of the alkyl ester in the monomer component is preferably 99.5% by weight or less, but may be 99% by weight or less, 98% by weight or less, or 97% by weight or less. From the viewpoint of improving the cohesiveness of the adhesive layer, in some embodiments, the (meth) acrylic acid C _4-18 The proportion of the alkyl ester in the monomer component is preferably 95% by weight or less, for example 90% by weight or less. In other embodiments, (meth) acrylic acid C _4-18 The proportion of the alkyl ester in the monomer component may be 85% by weight or less, or 75% by weight or less. The (meth) acrylic acid C may be contained in a proportion of not more than any of the above-mentioned upper limit values _6-18 Monomer components of alkyl esters.

In some embodiments, it is preferable to use a composition comprising (meth) acrylic acid C _1-4 An acrylic polymer comprising a monomer component in which the proportion of an alkyl ester (preferably BA) in the alkyl (meth) acrylate having a chain alkyl group is more than 50% by weight. According to the acrylic polymer, an adhesive having an adhesive force and an adhesive force suitable for surface protection is easily obtained. (meth) acrylic acid C _1-4 The alkyl esters may be used alone or in combination of 1 or more than 2. (meth) acrylic acid C in the alkyl (meth) acrylate having the above chain alkyl group _1-4 The proportion of the alkyl ester is preferably 70% by weight or more, more preferably 85% by weight or more, and for example, may be 90% by weight or more. (meth) acrylic acid C _1-4 The upper limit of the proportion of the alkyl ester in the alkyl (meth) acrylate having the chain alkyl group is 100 wt% or less may be 99 wt% or less, for example, may be less than 97 wt%.

In some preferred embodiments, (meth) acrylic acid C _2-4 The proportion of the alkyl ester in the alkyl (meth) acrylate having the chain alkyl group is more than 50% by weight (for example, 70% by weight or more, 85% by weight or more, or 90% by weight or more). As (meth) acrylic acid C _2-4 Specific examples of the alkyl ester include ethyl acrylate, propyl acrylate, isopropyl acrylate, BA, isobutyl acrylate, sec-butyl acrylate and tert-butyl acrylate. (meth) acrylic acid C _2-4 The alkyl esters may be used alone or in combination of 1 or more than 2. When an acrylic polymer having such a monomer composition is used, a surface-protecting sheet having excellent adhesion to an adherend can be easily obtained. Among them, a preferable embodiment is one in which the BA is contained in the alkyl (meth) acrylate having the chain alkyl group in an amount of more than 50% by weight (for example, 70% by weight or more, 85% by weight or more, or 90% by weight or more). (meth) acrylic acid C _2-4 The proportion of the alkyl ester in the alkyl (meth) acrylate having the chain alkyl group may be 100% by weight, 99% by weight or less, or less than 97% by weight, for example.

In other embodiments, a composition comprising (meth) acrylic acid C is preferably used _7-12 An acrylic polymer comprising a monomer component in which the proportion of the alkyl ester in the alkyl (meth) acrylate having the chain alkyl group is more than 50% by weight. According to the acrylic polymer, a surface protection sheet having excellent adhesion to an adherend can be easily obtained. As the (meth) acrylic acid C _7-12 Alkyl esters, preferably C (meth) acrylic acid _8-9 Alkyl esters, more preferably acrylic acid C _8-9 Alkyl esters, particularly preferably 2EHA. (meth) acrylic acid C _7-12 The alkyl esters may be used alone or in combination of 1 or more than 2. (meth) acrylic acid C in the alkyl (meth) acrylate having the above chain alkyl group _7-12 The proportion of the alkyl ester (preferably 2 EHA) is preferably 70 wt% or more, more preferably 85 wt% or more, for example, 90 wt% or more, or more95% by weight or more. (meth) acrylic acid C _7-12 The upper limit of the proportion of the alkyl ester to the alkyl (meth) acrylate having the chain alkyl group may be 100% by weight, 99% by weight or less, for example, less than 97% by weight.

The monomer component constituting the acrylic polymer may contain an alkyl (meth) acrylate, and if necessary, other monomers (copolymerizable monomers) copolymerizable with the alkyl (meth) acrylate. As the copolymerizable monomer, a monomer having a polar group (for example, a carboxyl group, a hydroxyl group, a nitrogen atom-containing ring, or the like) can be preferably used. The monomer having a polar group can contribute to introducing crosslinking points into the acrylic polymer or to improving the cohesive force of the adhesive. The copolymerizable monomer may be used singly or in combination of 1 or more than 2.

As non-limiting specific examples of the copolymerizable monomer, the following monomers may be mentioned.

Carboxyl group-containing monomers: for example, acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and the like.

Monomers containing anhydride groups: such as maleic anhydride, itaconic anhydride.

Hydroxyl group-containing monomers: for example, hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate.

Monomers containing sulfonic or phosphoric groups: for example, styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2- (meth) acrylamide-2-methylpropanesulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxy naphthalene sulfonic acid, 2-hydroxyethyl acryl phosphate, and the like.

Epoxy group-containing monomers: for example, epoxy group-containing acrylates such as glycidyl (meth) acrylate and 2-ethyl glycidyl (meth) acrylate, allyl glycidyl ether, and glycidyl (meth) acrylate.

Cyano-containing monomers: for example, acrylonitrile, methacrylonitrile, and the like.

Isocyanate group-containing monomer: for example, 2-isocyanatoethyl (meth) acrylate, and the like.

Amide group-containing monomers: for example, (meth) acrylamide; n, N-dialkyl (meth) acrylamides such as N, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-dipropyl (meth) acrylamide, N-diisopropyl (meth) acrylamide, N-di (N-butyl) (meth) acrylamide, N-di (t-butyl) (meth) acrylamide, and the like; n-alkyl (meth) acrylamides such as N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, and N-N-butyl (meth) acrylamide; n-vinylcarboxylic acid amides such as N-vinylacetamide; monomers having a hydroxyl group and an amide group, such as N-hydroxyalkyl (meth) acrylamides, e.g., N- (2-hydroxyethyl) (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide, N- (1-hydroxypropyl) (meth) acrylamide, N- (3-hydroxypropyl) (meth) acrylamide, N- (2-hydroxybutyl) (meth) acrylamide, N- (3-hydroxybutyl) (meth) acrylamide, N- (4-hydroxybutyl) (meth) acrylamide, and the like; monomers having an alkoxy group and an amide group, for example, N-alkoxyalkyl (meth) acrylamides such as N-methoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, and N-butoxymethyl (meth) acrylamide; and N, N-dimethylaminopropyl (meth) acrylamide, N- (meth) acryloylmorpholine, and the like.

Amino group-containing monomers: such as aminoethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate.

Monomers having epoxy groups: such as glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether.

Monomers having a ring containing a nitrogen atom: for example, lactams such as N-vinyl-2-pyrrolidone, N-methyl vinyl pyrrolidone, N-vinyl pyridine, N-vinyl piperidone, N-vinyl pyrimidine, N-vinyl piperazine, N-vinyl pyrazine, N-vinyl pyrrole, N-vinyl imidazole, N-vinyl oxazole, N- (meth) acryl-2-pyrrolidone, N- (meth) acryl piperidine, N- (meth) acryl pyrrolidine, N-vinyl morpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1, 3-oxazin-2-one, N-vinyl-3, 5-morpholinedione, N-vinyl pyrazole, N-vinyl isoxazole, N-vinyl thiazole, N-vinyl isothiazole, N-vinyl pyridazine, and the like.

Monomers having a succinimide skeleton: for example, N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-oxyhexamethylene succinimide, and the like.

Maleimide: for example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, etc.

Itaconimides: for example, N-methyl itaconimide, N-ethyl itaconimide, N-butyl itaconimide, N-octyl itaconimide, N-2-ethylhexyl itaconimide, N-cyclohexyl itaconimide, N-month Gui Jiyi itaconimide, and the like.

Aminoalkyl (meth) acrylates: for example, aminoethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, N-diethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate.

Alkoxy group-containing monomers: for example, alkoxyalkyl (meth) acrylates such as 2-methoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxypropyl (meth) acrylate, and the like; methoxy ethylene glycol (meth) acrylate, methoxy polypropylene glycol (meth) acrylate, and the like.

Alkoxysilyl group-containing monomer: such as 3- (meth) acryloxypropyl trimethoxysilane, 3- (meth) acryloxypropyl triethoxysilane, 3- (meth) acryloxypropyl methyldimethoxysilane, 3- (meth) acryloxypropyl methyldiethoxysilane.

Vinyl esters: for example, vinyl acetate, vinyl propionate, and the like.

Vinyl ethers: for example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.

Aromatic vinyl compound: for example, styrene, alpha-methylstyrene, vinyltoluene, and the like.

Olefins: for example, ethylene, butadiene, isoprene, isobutylene, and the like.

(meth) acrylic acid ester having alicyclic hydrocarbon group: for example, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, adamantyl (meth) acrylate, and the like.

(meth) acrylic acid esters having an aromatic hydrocarbon group: for example, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, and the like.

And heterocyclic (meth) acrylates such as tetrahydrofurfuryl (meth) acrylate, halogen atom-containing (meth) acrylates such as vinyl chloride and fluorine atom-containing (meth) acrylates, silicon atom-containing (meth) acrylates such as silicone (meth) acrylates, and (meth) acrylates obtained from terpene compound derivative alcohols.

When such a copolymerizable monomer is used, the amount is not particularly limited, and is suitably set to 0.01% by weight or more of the entire monomer component. The amount of the copolymerizable monomer used may be 0.1% by weight or more, or 0.5% by weight or more based on the entire monomer component, from the viewpoint of better effect of use of the copolymerizable monomer. In addition, the amount of the copolymerizable monomer used is suitably 50% by weight or less, preferably 40% by weight or less, based on the total monomer components, from the viewpoint of easy uniformity of adhesive properties.

In some embodiments, the monomer component comprising the acrylic polymer may comprise a monomer having a nitrogen atom. By using a monomer having a nitrogen atom, the cohesive force of the adhesive can be improved, and the adhesive strength can be desirably improved. The monomer having a nitrogen atom may be used alone or in combination of 1 or more than 2. As a preferable example of the monomer having a nitrogen atom, a monomer having a ring having a nitrogen atom may be mentioned. As the monomer having a nitrogen atom-containing ring, the monomers exemplified above and the like can be used, and for example, an N-vinyl cyclic amide represented by the general formula (1) can be used.

[ chemical formula 1]

Here, in the general formula (1), R ¹ Is a 2-valent organic group, in particular- (CH) ₂ ) n-. n is an integer of 2 to 7 (preferably 2, 3 or 4). Among them, N-vinyl-2-pyrrolidone (NVP) can be preferably used. As another preferable example of the monomer having a nitrogen atom, (meth) acrylamide is given.

The amount of the monomer having a nitrogen atom (preferably, the monomer having a ring having a nitrogen atom) used is not particularly limited, and may be, for example, 1% by weight or more, 3% by weight or more, and further may be set to 5% by weight or more or 7% by weight or more of the entire monomer component. In some embodiments, the amount of the monomer having a nitrogen atom used may be 10% by weight or more, or 12% by weight or more, or 15% by weight or more, or 20% by weight or more of the entire monomer component from the viewpoint of improving the adhesion. The amount of the monomer having a nitrogen atom to be used is suitably 40% by weight or less, for example, of the entire monomer component, and may be 35% by weight or less, 30% by weight or less, or 25% by weight or less. In another embodiment, the amount of the monomer having a nitrogen atom used may be, for example, 20% by weight or less, or 16% by weight or less of the entire monomer component. In another embodiment, the amount of the monomer having a nitrogen atom to be used may be, for example, 12% by weight or less, 8% by weight or less, or 4% by weight or less of the entire monomer component.

In some embodiments, the monomer component comprises a carboxyl-containing monomer. Preferable examples of the carboxyl group-containing monomer include Acrylic Acid (AA) and methacrylic acid (MAA). AA and MAA may also be used in combination. In the case of using AA and MAA in combination, the weight ratio (AA/MAA) is not particularly limited, and may be set to a range of about 0.1 to 10, for example. In some embodiments, the weight ratio (AA/MAA) may be, for example, about 0.3 or more, or about 0.5 or more. The weight ratio (AA/MAA) may be, for example, about 4 or less, or about 3 or less.

By using a carboxyl group-containing monomer, an aqueous liquid such as water can be quickly fused with the surface of the adhesive layer. This can contribute to a reduction in water peel force. The amount of the carboxyl group-containing monomer used may be, for example, 0.05% by weight or more, or 0.1% by weight or more, or 0.3% by weight or more, or 0.5% by weight or more, or 0.8% by weight or more of the entire monomer component. The proportion of the carboxyl group-containing monomer may be, for example, 15% by weight or less, 10% by weight or less, 5% by weight or less, 4.5% by weight or less, 3.5% by weight or less, 3.0% by weight or less, or 2.5% by weight or less. From the viewpoint of suppressing diffusion of water into the adhesive layer main body and suppressing reduction of adhesion force when in contact with an aqueous liquid, such as warm water impregnation, it is preferable that the amount of the carboxyl group-containing monomer used is not excessive. In addition, from the viewpoint of preventing the phenomenon that water used in the measurement of the water peeling force is absorbed by the adhesive layer and the water is insufficient in the middle of peeling, it is also advantageous that the amount of the carboxyl group-containing monomer used is excessive. The techniques disclosed herein may be preferably carried out such that the monomer component does not substantially contain a carboxyl group-containing monomer. From this viewpoint, the proportion of the carboxyl group-containing monomer may be, for example, less than 1% by weight, less than 0.3% by weight, or less than 0.1% by weight in the monomer component.

In some embodiments, the monomer component may comprise a hydroxyl-containing monomer. By using a hydroxyl group-containing monomer, the cohesive force and crosslinking density of the adhesive can be adjusted, and the adhesive strength can be improved. As the hydroxyl group-containing monomer, the above-exemplified monomers and the like can be used, and for example, 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4 HBA) can be preferably used. The hydroxyl group-containing monomers may be used alone or in combination of 1 or more than 2.

The amount of the hydroxyl group-containing monomer used is not particularly limited, and may be, for example, 0.01% by weight or more, 0.1% by weight or more, or 0.5% by weight or more of the entire monomer component. In some preferred embodiments, the amount of the hydroxyl group-containing monomer used is 1% by weight or more, more preferably 5% by weight or more, still more preferably 10% by weight or more, for example, 12% by weight or more of the entire monomer component. In other embodiments, the amount of the hydroxyl group-containing monomer used may be 15% by weight or more, or 20% by weight or more, or 25% by weight or more of the entire monomer component. In some embodiments, the amount of the hydroxyl group-containing monomer used is, for example, 40 wt% or less, or 30 wt% or less, or 20 wt% or less, or 15 wt% or less, 10 wt% or less, 5 wt% or less, or 3 wt% or less of the entire monomer component, from the viewpoint of suppressing the water absorption of the pressure-sensitive adhesive layer. The techniques disclosed herein may also be practiced without substantially using a hydroxyl group-containing monomer as the monomer component of the adhesive layer.

In some preferred embodiments, as the monomer component of the acrylic polymer, a monomer having a nitrogen atom (for example, an amide group-containing monomer such as (meth) acrylamide, a ring-containing monomer having a nitrogen atom such as NVP, or the like) is used in combination with a hydroxyl group-containing monomer (for example, HEA, 4 HBA) as the polar group-containing monomer. This effectively improves the adhesion. In the combination of a monomer having a nitrogen atom with a monomer having a hydroxyl groupIn the mode (a), the amount A of the monomer having a nitrogen atom _N Amount A with hydroxyl group-containing monomer _OH Weight ratio (A) _N /A _OH ) The content is not particularly limited, and may be, for example, 0.1 or more, 0.5 or more, 0.8 or more, 1.0 or more, or 1.2 or more. In addition, the weight ratio (A _N /A _OH ) For example, the content may be 10 or less, 5 or less, 3 or less, or 1.5 or less.

In some embodiments, the monomer component may comprise an alkoxysilyl-containing monomer. Typically, the alkoxysilyl group-containing monomer is an ethylenically unsaturated monomer having at least 1 (preferably 2 or more, for example 2 or 3) alkoxysilyl groups in one molecule, and specific examples thereof are as described above. The above alkoxysilyl group-containing monomers may be used singly or in combination of 1 or more than 2. By using an alkoxysilyl group-containing monomer, a crosslinked structure formed by a condensation reaction of silanol groups (silanol condensation) can be introduced into the adhesive layer. The alkoxysilyl group-containing monomer may be regarded as a silane coupling agent described later.

In the case where the monomer component contains an alkoxysilyl group-containing monomer, the proportion of the alkoxysilyl group-containing monomer in the entire monomer component may be, for example, 0.005% by weight or more, and preferably 0.01% by weight or more. The proportion of the alkoxysilyl group-containing monomer may be, for example, 0.5% by weight or less, 0.1% by weight or less, or 0.05% by weight or less from the viewpoint of improving the adhesion to an adherend.

In addition, the total proportion of the alkoxyalkyl (meth) acrylate and the alkoxypolyalkylene glycol (meth) acrylate is limited to less than 20% by weight from the viewpoint of suppressing gelation with respect to the monomer components of the acrylic polymer according to some preferred embodiments. The total proportion of the alkoxyalkyl (meth) acrylate and the alkoxypolyalkylene glycol (meth) acrylate is more preferably less than 10% by weight, still more preferably less than 3% by weight, and particularly preferably less than 1% by weight, and in some embodiments, the monomer component does not substantially contain the alkoxyalkyl (meth) acrylate and the alkoxypolyalkylene glycol (meth) acrylate (the content is 0 to 0.3% by weight).

Likewise, the monomer component of the acrylic polymer disclosed herein may be a monomer component containing an alkoxy group-containing monomer in a proportion of less than 20 wt%, or a monomer component not containing an alkoxy group-containing monomer. The amount of the alkoxy group-containing monomer in the monomer component is preferably less than 10% by weight, more preferably less than 3% by weight, still more preferably less than 1% by weight, and in a particularly preferred embodiment, the monomer component contains substantially no alkoxy group-containing monomer (the content is 0 to 0.3% by weight).

In addition, in some preferred embodiments, the proportion of the hydrophilic monomer is set to an appropriate range for the monomer component of the acrylic polymer. Thus, the water releasability can be preferably exhibited. Herein, the term "hydrophilic monomer" in the present specification means a monomer having a carboxyl group, a monomer having an acid anhydride group, a monomer having a hydroxyl group, a monomer having a nitrogen atom (typically, an amide group-containing monomer such as (meth) acrylamide, a ring-containing monomer having a nitrogen atom such as NVP), and a monomer having an alkoxy group (typically, an alkoxyalkyl (meth) acrylate and an alkoxy polyalkylene glycol (meth) acrylate). In this embodiment, the proportion of the hydrophilic monomer in the monomer component of the acrylic polymer is preferably 40% by weight or less (for example, 35% by weight or less), more preferably 32% by weight or less, and for example, 30% by weight or less, or 28% by weight or less. The proportion of the hydrophilic monomer in the monomer component of the acrylic polymer may be 1% by weight or more, or 10% by weight or more, or 20% by weight or more, although not particularly limited.

In some embodiments, the monomer component constituting the acrylic polymer may include a (meth) acrylate containing an alicyclic hydrocarbon group. This can improve the cohesive force of the adhesive and the adhesive strength. The alicyclic hydrocarbon group-containing (meth) acrylate may be used alone or in combination of 1 or more than 2. As the alicyclic hydrocarbon group-containing (meth) acrylate, the alicyclic hydrocarbon group-containing (meth) acrylate exemplified above can be used, and for example, cyclohexyl acrylate or isobornyl acrylate can be preferably used. The amount of the alicyclic hydrocarbon group-containing (meth) acrylate used is not particularly limited, and may be, for example, 1 wt% or more, 3 wt% or more, or 5 wt% or more of the entire monomer component. In some embodiments, the alicyclic hydrocarbon group-containing (meth) acrylate may be used in an amount of 10% by weight or more, or 15% by weight or more, based on the total monomer components. The upper limit of the amount of the alicyclic hydrocarbon group-containing (meth) acrylate to be used is suitably set to about 40% by weight or less, for example, 30% by weight or less, or 25% by weight or less (for example, 15% by weight or less, and further 10% by weight or less).

In some preferred embodiments, the acrylic polymer contains 0.05mol to 0.45mol of a monomer having a polar group (polar group-containing monomer) per 100g of the acrylic polymer as a monomer component. This improves the adhesion to polar adherends, and the adhesion after, for example, immersion in warm water can be maintained at a high level. It is considered that the interfacial adhesion is improved by introducing the polar group into the acrylic polymer based on hydrogen bonding to a polar adherend such as glass. As the polar group-containing monomer, 1 or 2 or more of the above-mentioned carboxyl group-containing monomer (typically AA, MAA, etc.), hydroxyl group-containing monomer (typically HEA, 4HBA, etc.), nitrogen atom-containing monomer (typically amide group-containing monomer such as (meth) acrylamide, etc., and nitrogen atom-containing ring-containing monomer such as NVP, etc.) can be used. The proportion of the polar group-containing monomer in the monomer component of the acrylic polymer is preferably 0.10mol or more, more preferably 0.15mol or more, still more preferably 0.20mol or more, for example, 0.24mol or more per 100g of the acrylic polymer, from the viewpoint of effectively functioning as the polar group-containing monomer. The upper limit of the proportion of the polar group-containing monomer in the monomer component of the acrylic polymer is preferably 0.40mol or less, more preferably 0.35mol or less, and for example, may be 0.30mol or less per 100g of the acrylic polymer.

The composition of the monomer component may be set so that the glass transition temperature (hereinafter also referred to as "glass transition temperature of polymer") obtained by Fox formula based on the composition of the monomer component becomes-75 ℃ or higher and-10 ℃ or lower. In some embodiments, the glass transition temperature (Tg) of the polymer (e.g., acrylic polymer, typically acrylic polymer) is suitably-15℃or lower, preferably-20℃or lower, more preferably-25℃or lower, even more preferably-30℃or lower, and may be-40℃or lower (e.g., -55℃or lower). When the Tg of the polymer is low, the adhesion between the pressure-sensitive adhesive layer and the base layer and the adhesion to the adherend tend to be substantially improved. According to this pressure-sensitive adhesive layer, penetration of water into the interface between the adherend and the pressure-sensitive adhesive layer is easily suppressed under conditions where peeling of the pressure-sensitive adhesive layer is not desired. This is advantageous from the viewpoint of suppressing the decrease in the adhesion when the aqueous liquid is contacted, such as by dipping in warm water. In addition, from the viewpoint of easy improvement of adhesion, the Tg of the polymer may be, for example, -70℃or higher, or-65℃or higher. In other embodiments, the Tg may be, for example, at least-60℃or at least-50℃or at least-45℃or at least-40 ℃.

Here, the Fox formula is a relational expression between Tg of the copolymer and glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each monomer constituting the copolymer, as shown below.

1/Tg＝∑(Wi/Tgi)

In the above Fox formula, tg represents the glass transition temperature (unit: K) of the copolymer, wi represents the weight fraction (copolymerization ratio based on weight) of the monomer i in the copolymer, and Tgi represents the glass transition temperature (unit: K) of the homopolymer of the monomer i.

The glass transition temperature of the homopolymer used for calculation of Tg was the value described in the known data. For example, the following values are used as the glass transition temperature of the monomers listed below as homopolymers of the monomers.

As for the glass transition temperatures of homopolymers of monomers other than those exemplified above, the values described in "Polymer Handbook" (third edition, john Wiley & Sons, inc., 1989) are used. In this document, the highest value is used when a plurality of values are described.

The following measurement method was used for the monomer having no glass transition temperature of the homopolymer described in the Polymer Handbook (see Japanese patent application laid-open No. 2007-51271). Specifically, 100 parts by weight of monomer, 0.2 parts by weight of azobisisobutyronitrile and 200 parts by weight of ethyl acetate as a polymerization solvent were charged into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet pipe and a reflux condenser, and stirred for 1 hour while flowing nitrogen. After oxygen in the polymerization system was removed as described above, the temperature was raised to 63℃and the reaction was carried out for 10 hours. Then, the mixture was cooled to room temperature to obtain a homopolymer solution having a solid content concentration of 33% by weight. Subsequently, the homopolymer solution was cast on a release liner, and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. The test specimen was punched into a disk shape having a diameter of 7.9mm, and clamped by parallel plates, and viscoelasticity was measured in a temperature range of-70 to 150 ℃ by a shear mode at a temperature rise rate of 5 ℃/min while a shear strain having a frequency of 1Hz was applied by a viscoelasticity tester (ARES, rheometrics Co.) to determine the peak top temperature of tan delta as Tg of the homopolymer.

The polymer (for example, acrylic polymer, typically acrylic polymer) contained in the adhesive layer disclosed herein is not particularly limited, and the SP value is preferably 23.0 (MJ/m ³ ) ^1/2 The following is given. For adhesives comprising polymers having such SP values, for example, byThe adhesive agent, which is described later, is desirably contained so as to have sufficient adhesive strength and excellent water peelability. The SP value is more preferably 21.0 (MJ/m) ³ ) ^1/2 The following (e.g., 20.0 (MJ/m) ³ ) ^1/2 The following are described below). The lower limit of the SP value is not particularly limited, and is, for example, about 10.0 (MJ/m ³ ) ^1/2 The above, in addition, is about 15.0 (MJ/m ³ ) ^1/2 The above is suitable, preferably 18.0 (MJ/m ³ ) ^1/2 The above.

The SP value of the POLYMER can be calculated according to Fedors calculation [ see "POLYMER ENG" & sci "& gt, 14 th, 2 nd (1974), 148 to 154 th, that is, the following formula.

SP value δ= (ΣΔe/ΣΔv) ^1/2

(wherein Δe is the evaporation energy Δe of each atom or group at 25 ℃, and Δv is the molar volume of each atom or group at the same temperature);

the polymer having the above SP value can be obtained by appropriately determining the monomer composition based on the technical common knowledge of the person skilled in the art.

The adhesive layer may be formed using an adhesive composition including the monomer components having the above-described composition in the form of a polymer, an unpolymerized form (i.e., a form in which the polymerizable functional groups are unreacted), or a form of a mixture thereof. The adhesive composition may be a water-dispersible adhesive composition in which an adhesive (adhesive component) is dispersed in water, a solvent-based adhesive composition in which an adhesive is contained in an organic solvent, an active energy ray-curable adhesive composition (for example, a photocurable adhesive composition) prepared by curing an adhesive with active energy rays such as ultraviolet rays or radioactive rays, and various forms such as a hot-melt adhesive composition which forms an adhesive when applied in a heated and melted state and cooled to around room temperature.

In the polymerization, a known or commonly used thermal polymerization initiator, photopolymerization initiator, or the like may be used depending on the polymerization method, polymerization system, or the like. Such polymerization initiators may be used singly or in combination of 2 or more kinds as appropriate.

The thermal polymerization initiator is not particularly limited, and for example, azo polymerization initiators, peroxide initiators, redox initiators composed of a combination of a peroxide and a reducing agent, substituted ethane initiators, and the like can be used. More specifically, examples thereof include azo initiators such as 2,2' -azobisisobutyronitrile, 2' -azobis (2-methylpropionamidine) disulfate, 2' -azobis (2-amidinopropane) dihydrochloride, 2' -azobis [2- (5-methyl-2-imidazolin-2-yl) propane ] dihydrochloride, 2' -azobis (N, N ' -dimethylene isobutyl amidine), 2' -azobis [ N- (2-carboxyethyl) -2-methylpropionamidine ] hydrate, and the like; persulfates such as potassium persulfate, ammonium persulfate, and the like; peroxide initiators such as benzoyl peroxide, t-butyl hydroperoxide and hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; redox initiators such as a combination of persulfate and sodium bisulfite, and a combination of peroxide and sodium ascorbate; and the like, but are not limited thereto. The thermal polymerization can be preferably performed at a temperature of, for example, about 20 to 100 ℃ (typically 40 to 80 ℃).

The photopolymerization initiator is not particularly limited, and for example, a ketal-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, a benzoin ether-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, an α -ketol-based photopolymerization initiator, an aromatic sulfonyl chloride-based photopolymerization initiator, a photoactive oxime-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzil-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, and the like can be used.

The amount of the thermal polymerization initiator or photopolymerization initiator used is not particularly limited, and may be set to a usual amount suitable for the polymerization method, polymerization system, and the like. For example, about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, for example about 0.01 to 1 part by weight) of a polymerization initiator may be used with respect to 100 parts by weight of the monomer to be polymerized.

In the above polymerization, various conventionally known chain transfer agents (which may also be referred to as molecular weight regulators or polymerization degree regulators) may be used as needed. As the chain transfer agent, thiols such as n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycollic acid and the like can be used. Alternatively, a chain transfer agent (non-sulfur chain transfer agent) containing no sulfur atom may be used. Specific examples of the non-sulfur chain transfer agent include anilines such as N, N-dimethylaniline and N, N-diethylaniline; terpenes such as alpha-pinene and terpinolene; styrenes such as alpha-methylstyrene, alpha-methylstyrene dimer, etc.; compounds having a benzylidene group such as dibenzylidene acetone, cinnamyl alcohol, and cinnamaldehyde; hydroquinones such as hydroquinone and dihydroxynaphthalene; quinone such as benzoquinone and naphthoquinone; olefins such as 2, 3-dimethyl-2-butene and 1, 5-cyclooctadiene; alcohols such as phenol, benzyl alcohol, and allyl alcohol; benzyl hydrogens such as diphenyl benzene and triphenyl benzene; etc.

The chain transfer agent may be used alone or in combination of 1 or more than 2. When the chain transfer agent is used, the amount thereof may be set to be, for example, about 0.01 to 1 part by weight based on 100 parts by weight of the monomer component. The techniques disclosed herein may also preferably be practiced without the use of chain transfer agents.

The molecular weight of the polymer (for example, an acrylic polymer, typically an acrylic polymer) obtained by the above-described various polymerization methods is not particularly limited, and may be set in an appropriate range according to the required properties and the like. The weight average molecular weight (Mw) of the polymer is about 10X 10 ⁴ The above is suitable, for example, about 15X 10 ⁴ The above. By using a polymer having a Mw of a predetermined value or more (for example, an acrylic polymer), both the cohesive force and the adhesive force can be achieved with good balance. In some embodiments, the Mw may be 20X 10 from the standpoint of obtaining good adhesion reliability ⁴ Above, 30×10 may be used ⁴ Above (e.g. greater than 30X 10) ⁴ ) May also be about 40X 10 ⁴ Above, may be about 50×10 ⁴ Above, for example, may be about 55×10 ⁴ The above. The upper limit of the Mw of the polymer is not particularly limited. For example, even if the above polymer as a whole has a high Mw, the 60 ℃ loss elastic modulus of the adhesive can be adjusted to be within a prescribed range by increasing the amount of the low molecular weight component. The Mw may be, for example, about 500X 10 ⁴ The following (e.g., about 150×10) ⁴ Hereinafter), the Mw may also be about 75X 10 ⁴ The following is given. In some preferred embodiments, the Mw may be less than 50X 10 ⁴ Can also be smaller than 40×10 ⁴ Can also be less than 35×10 ⁴ (e.g. less than 30X 10) ⁴ ). According to the polymer having the Mw, the loss elastic modulus at 60 ℃ of the adhesive tends to be easily adjusted to a predetermined range. Here, mw refers to a value converted to standard polystyrene by gel permeation chromatography (GP C). As a GPC apparatus, for example, model name "HLC-8320GPC" (column: TSKgelGMH-H (S), manufactured by TOSOH Co., ltd.) may be used. The same applies to the examples described below.

Some embodiments relate to a surface protection sheet having an adhesive layer formed from a water-dispersible adhesive composition. As a typical example of the water-dispersible adhesive composition, an emulsion-type adhesive composition is given. Typically, the emulsion adhesive composition contains a polymer of a monomer component and an additive used as needed.

Emulsion polymerization of the monomer components is generally carried out in the presence of an emulsifier. The emulsifier for emulsion polymerization is not particularly limited, and known anionic emulsifiers, nonionic emulsifiers, and the like can be used. The emulsifier may be used alone or in combination of 1 or more than 2.

Non-limiting examples of the anionic emulsifier include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkylphenyl ether sulfate, sodium polyoxyethylene alkylsulfonylsuccinate and the like. Non-limiting examples of the nonionic emulsifier include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene polyoxypropylene block polymer, and the like. Emulsifiers having reactive functional groups (reactive emulsifiers) may also be used. Examples of the reactive emulsifier include radical polymerizable emulsifiers having a structure in which a radical polymerizable functional group such as an acryl group or an allyl ether group is introduced into the above-mentioned anionic emulsifier or nonionic emulsifier.

The amount of the emulsifier used in the emulsion polymerization may be, for example, 0.2 parts by weight or more, or 0.5 parts by weight or more, or 1.0 parts by weight or more, or 1.5 parts by weight or more, based on 100 parts by weight of the monomer component. In some embodiments, the amount of the emulsifier used is suitably 10 parts by weight or less, preferably 5 parts by weight or less, or 3 parts by weight or less, based on 100 parts by weight of the monomer component, from the viewpoint of suppressing the decrease in adhesion after the warm water immersion. The emulsifier used for emulsion polymerization may also function as a water affinity agent for the adhesive layer.

According to the emulsion polymerization, a polymerization reaction liquid in the form of an emulsion in which a polymer of a monomer component is dispersed in water can be obtained. The water-dispersible adhesive composition for forming the adhesive layer can be preferably produced using the above-mentioned polymerization reaction liquid.

In some preferred embodiments, the surface protective sheet has an adhesive layer formed from a solvent-based adhesive composition. Typically, the solvent-based adhesive composition contains a solution polymer of a monomer component and additives used as needed. The effect of the technology disclosed herein can be effectively exerted in a form having a solvent-type adhesive layer. The solvent (polymerization solvent) used for the solution polymerization can be appropriately selected from conventionally known organic solvents. For example, an aromatic compound (typically, an aromatic hydrocarbon) selected from toluene and the like can be used; esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1, 2-dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as t-butyl methyl ether; any one of 1 solvent or a mixed solvent of 2 or more of ketones such as methyl ethyl ketone. According to the solution polymerization, a polymerization reaction solution in which a polymer of a monomer component is dissolved in a polymerization solvent can be obtained. The solvent type adhesive composition for forming the adhesive layer can be preferably produced using the above-mentioned polymerization reaction liquid.

In another preferred embodiment, the surface-protecting sheet has an adhesive layer formed from the active energy ray-curable adhesive composition. In the present specification, the term "active energy ray" refers to an energy ray having energy capable of causing chemical reactions such as polymerization reaction, crosslinking reaction, and decomposition of an initiator. Examples of the active energy ray include light such as ultraviolet rays, visible rays, and infrared rays, radiation such as α rays, β rays, γ rays, electron rays, neutron beams, and X rays. As a preferable example of the active energy ray-curable adhesive composition, a photocurable adhesive composition is given. The photocurable adhesive composition has an advantage that it can be easily formed even in a thick adhesive layer. Among them, ultraviolet curable adhesive compositions are preferred. In addition, the effects of the techniques disclosed herein can be effectively exhibited in a form having a photocurable adhesive layer.

Typically, the photocurable adhesive composition includes at least a part of the monomer components (which may be part of the kind of monomer or part of the amount of monomer) of the composition in the form of a polymer. The polymerization method for forming the above polymer is not particularly limited, and various polymerization methods known in the art can be suitably employed. For example, it may be suitably employed: thermal polymerization (typically, in the presence of a thermal polymerization initiator) such as solution polymerization, emulsion polymerization, and bulk polymerization; photopolymerization by irradiation with light such as ultraviolet light (typically, in the presence of a photopolymerization initiator); radiation polymerization by irradiation with radiation such as beta rays and gamma rays; etc. Among them, photopolymerization is preferable.

Some preferred embodiments relate to photocurable adhesive compositions comprising a partial polymer of a monomer component. Such a partial polymer is typically a mixture of a polymer derived from a monomer component and an unreacted monomer, preferably in the form of a slurry (a liquid having a viscosity). Hereinafter, the partial polymer having this property may be referred to as "monomer syrup" or simply "syrup". The polymerization method in polymerizing the monomer component parts is not particularly limited, and various polymerization methods as described above may be appropriately selected and used. From the viewpoint of efficiency and simplicity, photopolymerization is preferably used. According to photopolymerization, the polymerization conversion (monomer conversion) of the monomer component can be easily controlled by polymerization conditions such as the irradiation amount (light amount) of light.

The polymerization conversion of the monomer mixture in the partial polymer is not particularly limited. The polymerization conversion may be set to, for example, about 70% by weight or less, and preferably about 60% by weight or less. The polymerization conversion is suitably about 50% by weight or less, preferably about 40% by weight or less (e.g., about 35% by weight or less) from the viewpoint of ease of preparation, coatability, etc. of the adhesive composition comprising the partial polymer. The lower limit of the polymerization conversion is not particularly limited, and is typically about 1% by weight or more, and is suitably set to about 5% by weight or more.

The partially polymeric adhesive composition comprising the monomer component can be obtained, for example, by: the entire amount of the monomer mixture containing the monomer components used to prepare the adhesive composition is partially polymerized using a suitable polymerization process (e.g., photopolymerization). In addition, the adhesive composition including the partial polymer of the monomer component may be a partial polymer or a complete polymer of a monomer mixture including a part of the monomer components used to prepare the adhesive composition, and a mixture with the remaining monomer components or a partial polymer thereof. In the present specification, the term "complete polymer" means a polymer having a polymerization conversion of more than 95% by weight.

Other components (e.g., photopolymerization initiator, polyfunctional monomer, crosslinking agent, water affinity agent, etc.) used as needed may be blended into the adhesive composition containing the above partial polymer. The method of blending such other components is not particularly limited, and may be contained in the monomer mixture in advance, or may be added to the partial polymer.

(Water affinity agent)

The adhesive layer may contain a water affinity agent as desired. By incorporating a water affinity agent in the pressure-sensitive adhesive layer, the peeling force can be effectively reduced by using an aqueous liquid such as water. For this reason, although not particularly limited explanation, the following can be considered: the water affinity agent generally has hydrophilic regions and is therefore easily biased to the surface of the pressure-sensitive adhesive layer, and thus can exert an effect of efficiently improving the water affinity of the pressure-sensitive adhesive layer surface, and effectively reducing the peeling force when the pressure-sensitive adhesive layer is brought into contact with water. The water affinity agent may be used alone or in combination of 1 or more than 2.

In some embodiments, as the water affinity agent, at least 1 compound a selected from the group consisting of a surfactant and a compound having a polyoxyalkylene skeleton may be used. As the surfactant and the compound having a polyoxyalkylene skeleton, 1 or 2 or more kinds of known surfactants and compounds having a polyoxyalkylene skeleton can be used without particular limitation. Needless to say, a compound having a polyoxyalkylene skeleton is present in the above surfactant, and vice versa.

As the surfactant usable as the compound a, known nonionic surfactants, anionic surfactants, cationic surfactants, and the like can be used. Among them, nonionic surfactants are preferable. The surfactant may be used alone or in combination of 1 or more than 2.

Examples of the nonionic surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether and polyoxyethylene oleyl ether; polyoxyethylene alkylphenyl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether; sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, and sorbitan monooleate; polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan triisostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate and other polyoxyethylene sorbitan fatty acid esters; polyoxyethylene glyceryl ether fatty acid esters; polyoxyethylene-polyoxypropylene block copolymers; etc. These nonionic surfactants may be used singly or in combination of 1 or more than 2.

Examples of the anionic surfactant include alkylbenzenesulfonates such as nonylbenzenesulfonate and dodecylbenzenesulfonate (for example, sodium dodecylbenzenesulfonate); alkyl sulfates such as lauryl sulfate (e.g., sodium lauryl sulfate, ammonium lauryl sulfate) and stearyl sulfate; a fatty acid salt; polyoxyethylene alkyl ether sulfates such as polyoxyethylene stearyl ether sulfate and polyoxyethylene lauryl ether sulfate (for example, sodium polyoxyethylene alkyl ether sulfate), polyoxyethylene alkylphenyl ether sulfates such as polyoxyethylene lauryl phenyl ether sulfate (for example, ammonium polyoxyethylene alkylphenyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, etc.), and polyether sulfates such as polyoxyethylene styrenated phenyl ether sulfate; polyoxyethylene alkyl ether phosphates such as polyoxyethylene stearyl ether phosphate and polyoxyethylene lauryl ether phosphate; polyoxyethylene alkyl ether phosphate salts such as sodium salt and potassium salt of the polyoxyethylene alkyl ether phosphate; sulfosuccinates such as laurylsuccinate and polyoxyethylene laurylsuccinate (e.g., sodium polyoxyethylene alkyl sulfosuccinate); polyoxyethylene alkyl ether acetate; etc. When the anionic surfactant forms a salt, the salt may be, for example, a metal salt (preferably a monovalent metal salt), such as a sodium salt, a potassium salt, a calcium salt, or a magnesium salt, an ammonium salt, or an amine salt. The anionic surfactants may be used alone or in combination of 1 or more than 2.

In some embodiments, for example, it may be preferable to use an anionic surfactant having at least one of a-POH group, -COH group, and-SOH group. Among them, preferred is a surfactant having a-POH groupAnd (3) an agent. Such surfactants typically comprise a phosphate structure, for example a monoester of phosphoric acid (ROP (=o) (OH) ₂ The method comprises the steps of carrying out a first treatment on the surface of the Wherein R is a 1-valent organic group), a diester ((RO) ₂ P (=o) OH; wherein R is the same or different 1-valent organic groups), mixtures comprising both monoesters and diesters, and the like. As a preferable example of the surfactant having a-POH group, polyoxyethylene alkyl ether phosphate is given. The number of carbon atoms of the alkyl group in the polyoxyethylene alkyl ether phosphate may be, for example, 6 to 20, 8 to 20, 10 to 20, 12 to 20, or 14 to 20.

Examples of the cationic surfactant include polyetheramines such as polyoxyethylene lauryl amine and polyoxyethylene stearyl amine. The cationic surfactants may be used alone or in combination of 1 or more than 2.

As the compound having a polyoxyalkylene skeleton which can be used as the compound a, for example, a polyalkylene glycol such as polyethylene glycol (PEG) and polypropylene glycol (PPG) can be used; polyethers containing polyoxyethylene units, polyethers containing polyoxypropylene units, compounds containing oxyethylene units and oxypropylene units (the units may be arranged randomly or in blocks); their derivatives; etc. In addition, a compound having a polyoxyalkylene skeleton in the above surfactant may be used. They may be used alone or in combination of 1 or more than 2. Among them, a compound containing a polyoxyethylene skeleton (also referred to as a polyoxyethylene segment) is preferably used, and PEG is more preferred.

The molecular weight (formula weight) of the compound having a polyoxyalkylene skeleton (e.g., polyethylene glycol) is not particularly limited, and for example, less than 1000 is suitable, and is preferably about 600 or less (e.g., 500 or less) from the viewpoint of the productivity of the adhesive composition. The lower limit of the molecular weight of the compound having a polyoxyalkylene skeleton (for example, polyethylene glycol) is not particularly limited, and a compound having a polyoxyalkylene skeleton having a molecular weight of about 100 or more (for example, about 200 or more, further about 300 or more) is preferably used.

Other examples of the water affinity agent include water-soluble polymers such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylic acid. The water-soluble polymer may be used alone or in combination of 1 or more than 2. In the technology disclosed herein, as the water affinity agent, 1 or 2 or more of the compounds a may be used, 1 or 2 or more of the water-soluble polymers may be used, or a combination thereof may be used.

The HLB of the water affinity agent is not particularly limited, and is, for example, 3 or more, preferably about 6 or more, and may be 8 or more (for example, 9 or more). In some preferred embodiments, the HLB of the water affinity agent is greater than 10. Thus, there is a tendency that water peelability is desirably exhibited. The HLB is more preferably 11 or more, still more preferably 12 or more, and particularly preferably 13 or more (e.g., 14 or more). By including a water affinity agent (typically, a surfactant) having an HLB in the above range in the adhesive layer, water peelability can be more effectively exhibited. The upper limit of the HLB is 20 or less, for example, 18 or less, 16 or less, or 15 or less.

In the present specification, HLB is a hydrophilic-lipophilic balance (hydrophilic-Lipophile Balance) by Griffin, and is a value indicating the degree of affinity of a surfactant for water or oil, and the ratio of hydrophilicity to lipophilicity is represented by a value ranging from 0 to 20. HLB is defined as W.C.Griffin: soc.cosmetic Chemists,1,311 (1949); the "surfactant handbook", third edition, published by book of engineering, 11/25/1972, p 179-182, et cetera, are commonly written by the Min's, shibolan, min Chi Jisheng, and Chi Lin Zhengxiong of the high bridge. The water affinity agent having the above HLB may be selected based on the technical knowledge of a person skilled in the art, as required, with reference to the above-mentioned references and the like.

Such a water affinity agent is preferably contained in the adhesive layer in a free form. The water affinity agent is preferably used in a liquid state at ordinary temperature (about 25 ℃) from the viewpoint of the productivity of the adhesive composition.

Typically, the adhesive layer comprising the water affinity agent is formed from an adhesive composition comprising the water affinity agent. The adhesive composition may be any of the above-mentioned water-dispersible adhesive composition, solvent-based adhesive composition, active energy ray-curable adhesive composition, hot-melt adhesive composition, and the like. In some preferred embodiments, the adhesive layer including the water affinity agent may be an adhesive layer formed of a photocurable or solvent-based adhesive composition. In such an adhesive layer, the effect of adding the water affinity agent can be desirably exerted. The adhesive layer may also have photocurability.

The content of the water affinity agent in the pressure-sensitive adhesive layer is not particularly limited, and may be set so as to appropriately exert the effect of using the water affinity agent. In some embodiments, the content of the water affinity agent may be set to, for example, 0.001 parts by weight or more, preferably 0.01 parts by weight or more, or 0.03 parts by weight or more, or 0.07 parts by weight or more, or 0.1 parts by weight or more, based on 100 parts by weight of the monomer component constituting the polymer (for example, acrylic polymer) included in the pressure-sensitive adhesive layer. In some preferred embodiments, the content of the water affinity agent may be, for example, 0.2 parts by weight or more, or 0.5 parts by weight or more, or 1.0 parts by weight or more, or 1.5 parts by weight or more, based on 100 parts by weight of the monomer component, from the viewpoint of obtaining a higher effect. In some embodiments, the amount of the water affinity agent used may be, for example, 20 parts by weight or less, preferably 10 parts by weight or less, more preferably 5 parts by weight or less, or 3 parts by weight or less, based on 100 parts by weight of the monomer component, from the viewpoint of suppressing excessive diffusion of water into the adhesive layer main body. From the viewpoint of suppressing the decrease in the adhesion when the aqueous liquid is contacted, such as the immersion in warm water, the content of the water affinity agent is preferably not too large. For example, in some embodiments, the content of the water affinity agent may be less than 2 parts by weight, or less than 1 part by weight, or less than 0.7 part by weight, or less than 0.3 part by weight, or less than 0.2 part by weight, relative to 100 parts by weight of the monomer component. The water affinity agent having HL B of 10 or more tends to exhibit good water peelability with a small amount of use.

(crosslinking agent)

The adhesive composition disclosed herein may contain a crosslinking agent as needed mainly for the purpose of crosslinking in the adhesive layer or crosslinking of the adhesive layer and the adjacent surface thereof. Typically, the crosslinking agent is contained in the adhesive layer in a form after the crosslinking reaction. By using the crosslinking agent, the cohesive force of the adhesive layer can be appropriately adjusted.

The type of the crosslinking agent is not particularly limited, and may be selected from conventionally known crosslinking agents so that the crosslinking agent exhibits an appropriate crosslinking function in the adhesive layer, for example, depending on the composition of the adhesive composition. Examples of usable crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, melamine-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, hydrazine-based crosslinking agents, and amine-based crosslinking agents. They may be used alone or in combination of 1 or more than 2. In the water-dispersible adhesive composition, a crosslinking agent which can be dissolved or dispersed in water is preferably used.

As the isocyanate-based crosslinking agent, a polyfunctional isocyanate compound having 2 or more functions can be used. Examples thereof include aromatic isocyanates such as toluene diisocyanate, xylylene diisocyanate, polymethylene polyphenyl diisocyanate, tris (p-isocyanatophenyl) thiophosphate and diphenylmethane diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate; etc. Examples of the commercial products include an isocyanate adduct such as trimethylolpropane/toluene diisocyanate trimer adduct (trade name "Coronate L" manufactured by TOSOH Co., ltd.), trimethylolpropane/hexamethylene diisocyanate trimer adduct (trade name "Coronate HL" manufactured by TOSOH Co., ltd.), isocyanurate of hexamethylene diisocyanate (trade name "Coronate HX" manufactured by TOSOH Co., ltd.), and trimethylolpropane/xylylene diisocyanate adduct (trade name "Takenate D-110N" manufactured by Sanjing chemical Co., ltd.). In the water-dispersible adhesive composition, an isocyanate-based crosslinking agent which can be dissolved or dispersed in water is preferably used. For example, a water-soluble, water-dispersible or self-emulsifiable isocyanate-based crosslinking agent can be preferably used. An isocyanate-based crosslinking agent in which isocyanate groups are blocked, so-called blocked isocyanate-based crosslinking agent, can be preferably used.

As the epoxy-based crosslinking agent, a crosslinking agent having 2 or more epoxy groups in 1 molecule can be used without particular limitation. Preferably an epoxy-based crosslinking agent having 3 to 5 epoxy groups in 1 molecule. Specific examples of the epoxy-based crosslinking agent include N, N' -tetraglycidyl m-xylylenediamine, 1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane, 1, 6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycidyl ether, and the like. Examples of the commercial products of the epoxy-based crosslinking agent include trade names "TETRAD-X", "TETRAD-C", trade name "EPICLON CR-5L", trade name "Denacol EX-512", trade name "TEPIC-G", and the like.

As the oxazoline-based crosslinking agent, a crosslinking agent having 1 or more oxazoline groups in 1 molecule may be used without particular limitation.

Examples of the aziridine-based crosslinking agent include trimethylolpropane tris [3- (1-aziridinyl) propionate ], trimethylolpropane tris [3- (1- (2-methyl) aziridinylpropionate) ] and the like.

As the carbodiimide-based crosslinking agent, a low molecular compound or a high molecular compound having 2 or more carbodiimide groups can be used.

In some embodiments, peroxides may also be used as crosslinking agents. Examples of the peroxide include bis (2-ethylhexyl) peroxydicarbonate, bis (4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butyldicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1, 3-tetramethylbutyl peroxyisobutyrate, and dibenzoyl peroxide. Among them, as peroxides having particularly excellent crosslinking reaction efficiency, bis (4-t-butylcyclohexyl) peroxydicarbonate, dilauroyl peroxide, dibenzoyl peroxide and the like can be mentioned. In the case where a peroxide is used as the polymerization initiator, a peroxide which is not used in the polymerization reaction and remains may be used in the crosslinking reaction. In this case, the remaining amount of the peroxide is quantified, and if the ratio of the peroxide does not satisfy the predetermined amount, the peroxide may be added as needed so as to be a predetermined amount. The peroxide can be quantified by the method described in Japanese patent No. 4971517.

The amount of the crosslinking agent used (in the case of using 2 or more crosslinking agents, the total amount of these) is not particularly limited. The amount of the crosslinking agent to be used is suitably set to about 5 parts by weight or less, or may be set to 3 parts by weight or less, or may be set to 2 parts by weight or less, or may be set to 1 part by weight or less, or may be set to less than 1 part by weight, based on 100 parts by weight of the monomer component (for example, the monomer component of the acrylic polymer) contained in the adhesive composition, from the viewpoint of achieving an adhesive exhibiting adhesive properties such as adhesive force, cohesive force, and the like with good balance. In some embodiments, the amount of the crosslinking agent (for example, isocyanate-based crosslinking agent) used may be, for example, 0.50 parts by weight or less, or 0.40 parts by weight or less, or 0.30 parts by weight or less, or 0.20 parts by weight or less, based on 100 parts by weight of the monomer component. The lower limit of the amount of the crosslinking agent to be used is not particularly limited, and may be more than 0 parts by weight based on 100 parts by weight of the monomer component. In some embodiments, the amount of the crosslinking agent used may be, for example, 0.001 parts by weight or more, or 0.01 parts by weight or more, or 0.05 parts by weight or more, or 0.10 parts by weight or more, based on 100 parts by weight of the monomer component.

Alternatively, the adhesive composition may be one that does not contain the crosslinking agent as described above. When a photocurable adhesive composition is used as the adhesive composition disclosed herein, the adhesive composition may be an adhesive composition containing substantially no crosslinking agent such as an isocyanate-based crosslinking agent. The term "substantially no crosslinking agent (typically, isocyanate-based crosslinking agent") in the adhesive composition "means that the amount of the crosslinking agent is less than 0.05 parts by weight (for example, less than 0.01 parts by weight) based on 100 parts by weight of the monomer component.

In order to allow the crosslinking reaction to proceed more efficiently, a crosslinking catalyst may be used. Examples of the crosslinking catalyst include metal-based crosslinking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, iron acetylacetonate, butyltin oxide, and dioctyltin dilaurate. Among them, tin-based crosslinking catalysts such as dioctyltin dilaurate are preferable. The amount of the crosslinking catalyst used is not particularly limited. The amount of the crosslinking catalyst used may be, for example, about 0.0001 parts by weight or more, about 0.001 parts by weight or more, about 0.005 parts by weight or more, or about 1 part by weight or less, about 0.1 parts by weight or less, or about 0.05 parts by weight or less, based on 100 parts by weight of the monomer components (for example, the monomer components of the acrylic polymer) contained in the adhesive composition.

In the adhesive composition for forming the adhesive layer, a compound generating keto-enol tautomerism may be contained as a crosslinking retarder as desired. For example, in an adhesive composition containing an isocyanate-based crosslinking agent or an adhesive composition usable in combination with an isocyanate-based crosslinking agent, a compound that causes keto-enol tautomerism can be preferably used. This can exert the effect of prolonging the pot life of the adhesive composition.

As compounds that produce keto-enol tautomerism, various β -dicarbonyl compounds can be used. Specific examples thereof include beta-diketones such as acetylacetone and 2, 4-hexanedione; acetoacetates such as methyl acetoacetate and ethyl acetoacetate; propionyl acetate esters such as ethyl propionylacetate; isobutyryl acetates such as isobutyryl ethyl acetate; malonates such as methyl malonate and ethyl malonate; etc. Among them, acetylacetone and acetoacetates are preferable. The compounds that produce keto-enol tautomerism may be used alone or in combination of 1 or more than 2.

The amount of the compound that causes keto-enol tautomerism may be, for example, 0.1 to 20 parts by weight, preferably 0.5 to 15 parts by weight, for example, 1 to 10 parts by weight, or 1 to 5 parts by weight, based on 100 parts by weight of the monomer component (for example, the monomer component of the acrylic polymer) contained in the adhesive composition.

(multifunctional monomer)

In the adhesive composition (and thus the adhesive layer), a polyfunctional monomer may be used as needed. The multifunctional monomer can contribute to the adjustment of the aggregation force and the like. The polyfunctional monomer may be a crosslinked structure having a suitable flexibility by reacting the ethylenically unsaturated group with light (for example, ultraviolet rays) irradiation or the like after the adhesion to the adherend at the time of forming the pressure-sensitive adhesive layer. Thus, in this specification, a "multifunctional monomer" may be modified as a crosslinking agent. For example, in the adhesive layer formed of the photocurable adhesive composition, a polyfunctional monomer may be preferably used. As the polyfunctional monomer, a compound having 2 or more ethylenically unsaturated groups can be used. The polyfunctional monomer may be used alone or in combination of 1 or more than 2.

Examples of the ethylenically unsaturated group included in the polyfunctional monomer include, but are not limited to, acryl, methacryl, vinyl, and allyl groups. From the standpoint of photoreactivity, preferable ethylenically unsaturated groups include acryl and methacryl. Among them, acryl is preferable.

The polyfunctional monomer is preferably a compound having 2 to 10 ethylenically unsaturated groups in the molecule, more preferably a compound having 2 to 8 ethylenically unsaturated groups in the molecule, and still more preferably a compound having 2 to 6 ethylenically unsaturated groups in the molecule. In some embodiments, as the polyfunctional monomer, a compound having 4 or less (specifically, 2 to 4, for example, 2 or 3, preferably 2) ethylenically unsaturated groups in the molecule may be used. By using such a polyfunctional monomer in which the number of ethylenically unsaturated groups is limited, an adhesive layer achieving both elongation and strength is easily obtained.

Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ethylene glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 12-dodecanediol di (meth) acrylate, trimethylol propane tri (meth) acrylate, tetramethylol methane tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butanediol (meth) acrylate, hexanediol di (meth) acrylate, and the like. Among them, trimethylolpropane tri (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, dipentaerythritol hexa (meth) acrylate are preferable, and 1, 6-hexanediol diacrylate is more preferable.

The amount of the polyfunctional monomer to be used varies depending on the molecular weight, the number of functional groups, and the like, and is suitably set to a range of about 0.01 to 3.0 parts by weight based on 100 parts by weight of the monomer component (typically, the acrylic polymer or the monomer component of the polymer) forming the polymer included in the pressure-sensitive adhesive layer. In some embodiments, the amount of the polyfunctional monomer used may be, for example, 0.02 parts by weight or more, or 0.1 parts by weight or more, or 0.5 parts by weight or more, or 1.0 parts by weight or more, or 2.0 parts by weight or more, based on 100 parts by weight of the monomer component. By increasing the amount of the polyfunctional monomer used, a higher cohesive force tends to be obtained. On the other hand, from the viewpoint of avoiding the decrease in the adhesion between the pressure-sensitive adhesive layer and the adjacent layer due to the excessive increase in the cohesive force, the amount of the polyfunctional monomer used may be, for example, 10 parts by weight or less, 5.0 parts by weight or less, or 3.0 parts by weight or less, based on 100 parts by weight of the monomer component. In some embodiments, the amount of the polyfunctional monomer used is, for example, 1.0 part by weight or less, preferably 0.5 parts by weight or less, more preferably 0.3 parts by weight or less, and may be 0.2 parts by weight or less, based on 100 parts by weight of the monomer component.

(acrylic oligomer)

The pressure-sensitive adhesive layer disclosed herein may contain an acrylic oligomer from the viewpoints of improving the cohesive force, improving the adhesion to the substrate layer, improving the adhesion to an adherend, and the like. According to the technology disclosed herein, even if the surface protection sheet is attached to the protection object with high adhesive force, the surface protection sheet can be peeled off and removed by water peeling without damaging or deforming the protection object at the time of peeling. Therefore, the adhesive agent can contain an adhesion-improving component such as an acrylic oligomer, thereby improving adhesion reliability and protecting function. The adhesive layer containing the acrylic oligomer may be formed using an adhesive composition containing the acrylic oligomer. As the acrylic oligomer, an acrylic oligomer having a Tg higher than that of the acrylic polymer (for example, acrylic polymer) can be preferably used.

The Tg of the acrylic oligomer is not particularly limited, and may be, for example, about 20 ℃ to 300 ℃. The Tg may be, for example, about 30℃or higher, about 40℃or higher, about 60℃or higher, or about 80℃or higher or about 100℃or higher. When Tg of the acrylic oligomer is high, the effect of improving the cohesion tends to be substantially improved. In addition, from the viewpoints of anchoring property to a base material layer, impact absorbability, and the like, the Tg of the acrylic oligomer may be, for example, about 250 ℃ or less, about 200 ℃ or less, or about 180 ℃ or less, or about 150 ℃ or less. The Tg of the acrylic oligomer is a value calculated based on Fox expression, similarly to the Tg of the acrylic polymer.

The Mw of the acrylic oligomer is not particularly limited, and may be, for example, about 1000 or more, suitably about 1500 or more, or may be about 2000 or more, or may be about 3000 or more. The Mw of the acrylic oligomer may be, for example, less than about 30000, suitably less than about 10000, more suitably less than about 7000, or more suitably less than about 5000. If the Mw is within the above range, the effect of improving the cohesiveness and adhesiveness of the pressure-sensitive adhesive layer can be easily and suitably exerted. The Mw of the acrylic oligomer can be measured by GPC and obtained as a value in terms of standard polystyrene. Specifically, for example, two TSKgelGMH-H (20) columns may be used in HPLC8020 manufactured by TOSOH corporation, and the measurement may be performed in tetrahydrofuran solvent at a flow rate of about 0.5 mL/min.

The monomer components constituting the acrylic oligomer include the following (meth) acrylate monomers: various (meth) acrylic acids C as described above _1-20 Alkyl esters; the above-mentioned various alicyclic hydrocarbon group-containing (meth) acrylates; the above-mentioned various aromatic hydrocarbon group-containing (meth) acrylates; (meth) acrylic esters derived from terpene compound derivative alcohols; etc. They may be used alone or in combination of 1 or more than 2.

From the viewpoint of improving the adhesion, the acrylic oligomer preferably contains an alkyl (meth) acrylate having a branched structure in an alkyl group such as isobutyl (meth) acrylate or t-butyl (meth) acrylate; an alicyclic hydrocarbon group-containing (meth) acrylate, an aromatic hydrocarbon group-containing (meth) acrylate, and the like, as a monomer unit. In addition, in the case of ultraviolet rays used in the synthesis of the acrylic oligomer or in the production of the pressure-sensitive adhesive layer, a monomer having a saturated hydrocarbon group at the ester end is preferable in terms of being less likely to cause polymerization inhibition, and for example, an alkyl (meth) acrylate having a branched alkyl group or a (meth) acrylate containing a saturated alicyclic hydrocarbon group can be preferably used.

The proportion of the (meth) acrylic acid ester monomer in the total monomer components constituting the acrylic oligomer is typically more than 50% by weight, preferably 60% by weight or more, more preferably 70% by weight or more (for example, 80% by weightMore than 90 wt.%). In some preferred embodiments, the acrylic oligomer has a monomer composition that comprises substantially only 1 or more than 2 (meth) acrylate monomers. In the case where the monomer component contains an alicyclic hydrocarbon group-containing (meth) acrylate and a C1-20 alkyl (meth) acrylate, the weight ratio thereof is not particularly limited. In some embodiments, the alicyclic hydrocarbon group-containing (meth) acrylate/(meth) acrylic acid C _1-20 The weight ratio of the alkyl ester may be set to, for example, 10/90 or more, 20/80 or more, or 30/70 or more, and may be set to 90/10 or less, 80/20 or less, or 70/30 or less.

As the constituent monomer component of the acrylic oligomer, a functional group-containing monomer may be used as required in addition to the above-mentioned (meth) acrylate monomer. Examples of the functional group-containing monomer include monomers having a nitrogen atom-containing heterocycle such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; amino group-containing monomers such as N, N-dimethylaminoethyl (meth) acrylate; amide group-containing monomers such as N, N-diethyl (meth) acrylamide; AA. Carboxyl group-containing monomers such as MAA; hydroxy-containing monomers such as 2-hydroxyethyl (meth) acrylate. These functional group-containing monomers may be used singly or in combination of 1 or more than 2. When the functional group-containing monomer is used, the proportion of the functional group-containing monomer in the entire monomer components constituting the acrylic oligomer may be, for example, 1 wt% or more, 2 wt% or more, or 3 wt% or more, or may be, for example, 15 wt% or less, 10 wt% or less, or 7 wt% or less. The acrylic oligomer may be an acrylic oligomer in which a functional group-containing monomer is not used.

Examples of the preferable acrylic oligomer include homopolymers of dicyclopentanyl methacrylate (dcdma), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopentanyl acrylate (dcpa), 1-adamantyl methacrylate (ADMA), 1-adamantyl acrylate (ADA), and copolymers of dcdma and MMA, copolymers of dcdma and IBXMA, copolymers of ADA and Methyl Methacrylate (MMA), copolymers of CH MA and isobutyl methacrylate (IBMA), copolymers of CHMA and IBXMA, copolymers of CHMA and Acryloylmorpholine (ACMO), copolymers of CHMA and Diethylacrylamide (DEAA), and copolymers of CHMA and AA.

The acrylic oligomer can be formed by polymerizing its constituent monomer components. The polymerization method and the polymerization method are not particularly limited, and various polymerization methods (for example, solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) known in the past may be employed in an appropriate manner. The type of the polymerization initiator (for example, azo-based polymerization initiator) that can be used as needed is generally as exemplified for the synthesis of the acrylic polymer, and the amount of the polymerization initiator and the amount of the chain transfer agent (for example, a thiol) that is optionally used are appropriately set based on technical common knowledge so as to have a desired molecular weight, and therefore, detailed description thereof is omitted.

When the acrylic oligomer is contained in the pressure-sensitive adhesive layer or the pressure-sensitive adhesive composition, the content thereof may be set to, for example, 0.01 parts by weight or more, or 0.05 parts by weight or more, or 0.1 parts by weight or more, or 0.2 parts by weight or more, based on 100 parts by weight of the monomer component of the polymer (typically, acrylic polymer) contained in the pressure-sensitive adhesive layer, from the viewpoint of obtaining a higher effect. In view of compatibility with the polymer (typically, an acrylic polymer), the content of the acrylic oligomer is suitably set to less than 50 parts by weight, preferably less than 30 parts by weight, more preferably 25 parts by weight or less, for example, 10 parts by weight or less, or 5 parts by weight or less, or 1 part by weight or less, based on 100 parts by weight of the monomer component.

(tackifying resin)

The pressure-sensitive adhesive layer may contain a tackifying resin. According to the technology disclosed herein, even if the surface protection sheet is attached to the protection object with high adhesive force, the surface protection sheet can be peeled off and removed by water peeling without damaging or deforming the protection object at the time of peeling. Therefore, the adhesive agent can contain an adhesion-improving component such as an adhesion-improving resin to improve adhesion reliability and improve a protective function. Examples of the tackifying resin include rosin-based tackifying resins, rosin derivative tackifying resins, petroleum-based tackifying resins, terpene-based tackifying resins, phenol-based tackifying resins, and ketone-based tackifying resins. They may be used alone or in combination of 1 or more than 2.

Examples of the rosin-based tackifying resin include rosin such as gum rosin, wood rosin, and tall oil rosin, stabilized rosin (e.g., stabilized rosin obtained by disproportionation or hydrogenation treatment of the rosin), polymerized rosin (e.g., a polymer of the rosin, typically a dimer), modified rosin (e.g., unsaturated acid-modified rosin modified with an unsaturated acid such as maleic acid, fumaric acid, or (meth) acrylic acid), and the like.

Examples of the rosin-derivative tackifying resin include an esterified product of the rosin-based tackifying resin (for example, a rosin ester such as a stabilized rosin ester or a polymerized rosin ester), a phenol modified product of the rosin-based resin (phenol-modified rosin), and an esterified product thereof (phenol-modified rosin ester).

Examples of the petroleum-based tackifying resin include aliphatic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, alicyclic petroleum resins, and hydrides thereof.

Examples of the terpene-based tackifying resin include α -pinene resins, β -pinene resins, aromatic modified terpene-based resins, terpene phenol resins, and the like.

Examples of the ketone-based tackifying resin include ketone-based resins obtained by condensing ketones (for example, aliphatic ketones such as methyl ethyl ketone, methyl isobutyl ketone, and acetophenone; alicyclic ketones such as cyclohexanone and methylcyclohexanone) with formaldehyde; etc.

In some embodiments, 1 or 2 or more kinds of tackifying resins selected from rosin-based tackifying resins, rosin derivative tackifying resins, and terpene phenol resins can be preferably used. Among them, the rosin derivative tackifying resin is preferable, and preferable examples thereof include rosin esters such as stabilized rosin esters and polymerized rosin esters.

In the water-dispersible adhesive composition, the above-described water-dispersible tackifying resin in the form of being dispersed in an aqueous solvent is preferably used. For example, an adhesive composition containing these components in a desired ratio can be easily prepared by mixing an aqueous dispersion of an acrylic polymer with a water-dispersible tackifying resin. In some embodiments, as the water-dispersible tackifying resin, a water-dispersible tackifying resin that is at least substantially free of an aromatic hydrocarbon solvent may be preferably used from the viewpoint of environmental sanitation and the like. More preferably, a water-dispersible tackifying resin substantially free of aromatic hydrocarbon solvents and other organic solvents is used.

Examples of the commercial products of the water-dispersible tackifying resins containing rosin ESTERs include "SUPER ESTER E-720", "SUPER ESTER E-730-55", "SUPER ESTER E-865NT", etc. manufactured by the Deskaching chemical industry Co., ltd., and "HARIESTER SK-90D", "HA RIESTER SK-70D", "HARIESTER SK-70E", "NEOTALL 115E", etc. manufactured by HARIM A CHEMICALS, INC.. Further, as commercial products of terpene phenol resins (which may be in the form of water-dispersible terpene phenol resins), trade names "TAMANOL E-100", "TAMANOL E-200NT" and the like manufactured by the Kingchuan chemical industry Co.

The softening point of the tackifying resin is not particularly limited. From the viewpoint of suppressing the decrease in the cohesive force of the adhesive layer, a tackifying resin having a softening point of 80 ℃ or higher can be preferably used. The softening point of the tackifying resin may be 90℃or higher, or 100℃or higher, or 110℃or higher, or 120℃or higher. The tackifying resin having a softening point of 130 ℃ or more or 140 ℃ or more may be used. In addition, from the viewpoints of adhesion to a base material layer, adhesion to an adherend, and the like, an adhesion-imparting resin having a softening point of 200 ℃ or less or 180 ℃ or less can be preferably used. The softening point of the tackifying resin may be a nominal value described in a document, a catalogue, or the like. When the nominal value is not found, the softening point of the tackifying resin can be measured based on the softening point test method (the ring-and-ball method) specified in JIS K5902 or JIS K2207.

The amount of the tackifying resin used is suitably 1 part by weight or more, but may be 5 parts by weight or more, or 10 parts by weight or more, based on 100 parts by weight of the monomer component constituting the polymer contained in the pressure-sensitive adhesive layer, from the viewpoint of suitably exhibiting the effect of use. In addition, from the viewpoint of achieving both adhesion to the substrate layer and the adherend and cohesiveness with good balance, the amount of the tackifying resin used may be, for example, 70 parts by weight or less, 50 parts by weight or less, 40 parts by weight or less, 30 parts by weight or less, or 20 parts by weight or less, based on 100 parts by weight of the monomer component. Alternatively, the adhesive layer may be an adhesive layer substantially containing no tackifying resin.

(silane coupling agent)

In some embodiments, the adhesive layer may contain a silane coupling agent. According to the adhesive layer containing the silane coupling agent, a surface protection sheet having high adhesion can be suitably realized. The silane coupling agent may be used alone or in combination of 1 or more than 2.

Examples of the silane coupling agent include silicon compounds having an epoxy structure such as 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl methyl dimethoxy silane, and 2- (3, 4-epoxycyclohexyl) ethyl trimethoxysilane; amino group-containing silicon compounds such as 3-aminopropyl trimethoxysilane, N- (2-aminoethyl) 3-aminopropyl trimethoxysilane and N- (2-aminoethyl) 3-aminopropyl methyl dimethoxysilane; 3-chloropropyl trimethoxysilane; silane coupling agents containing a (meth) acrylic group, such as acetoacetyl-containing trimethoxysilane, 3-acryloxypropyl trimethoxysilane, and 3-methacryloxypropyl triethoxysilane; and silane coupling agents containing an isocyanate group such as 3-isocyanatopropyl triethoxysilane. Among them, preferable examples include 3-glycidoxypropyl trimethoxysilane and acetoacetyl-containing trimethoxysilane.

The amount of the silane coupling agent to be used is not particularly limited, and may be set so that a desired effect of use can be obtained. In some embodiments, the amount of the silane coupling agent used may be, for example, 0.001 parts by weight or more, or 0.005 parts by weight or more, or 0.01 parts by weight or more, or 0.015 parts by weight or more, based on 100 parts by weight of the monomer components constituting the polymer contained in the pressure-sensitive adhesive layer, from the viewpoint of obtaining a higher effect. In some embodiments, the amount of the silane coupling agent used may be 3 parts by weight or less, 1 part by weight or less, or 0.5 part by weight or less, based on 100 parts by weight of the monomer component constituting the pressure-sensitive adhesive layer, from the viewpoint of improving the adhesion. In addition, the techniques disclosed herein may be practiced using an adhesive composition that does not substantially contain a silane coupling agent. By limiting the use of the silane coupling agent or not using the silane coupling agent, the increase of adhesive force with time can be suppressed, and good water releasability can be easily obtained.

In the case where the monomer component includes an alkoxysilyl group-containing monomer, the alkoxysilyl group-containing monomer may be used as part or all of the silane coupling agent included in the pressure-sensitive adhesive layer.

(photopolymerization initiator)

The pressure-sensitive adhesive composition and the photocurable pressure-sensitive adhesive layer disclosed herein may contain a photopolymerization initiator (also referred to as a photoreaction catalyst) as needed for the purpose of imparting photocurability and the like. As the photopolymerization initiator, as in the photopolymerization initiator exemplified as a photopolymerization initiator usable for synthesizing an acrylic polymer, a ketal-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, a benzoin ether-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, an α -ketol-based photopolymerization initiator, an aromatic sulfonyl chloride-based photopolymerization initiator, a photoactive oxime-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzil-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, and the like can be used. The photopolymerization initiator may be used alone or in combination of 2 or more kinds as appropriate.

The content of the photopolymerization initiator in the pressure-sensitive adhesive layer is not particularly limited, and may be set so as to suitably exhibit a desired effect. In some embodiments, the content of the photopolymerization initiator may be set to, for example, about 0.005 parts by weight or more, preferably 0.01 parts by weight or more, and may be set to 0.05 parts by weight or more, may be set to 0.10 parts by weight or more, may be set to 0.15 parts by weight or more, or may be set to 0.20 parts by weight or more, based on 100 parts by weight of the monomer component of the polymer (typically, the acrylic polymer) included in the pressure-sensitive adhesive layer. By increasing the content of the photopolymerization initiator, the photocurability of the adhesive layer is improved. The content of the photopolymerization initiator is preferably 5 parts by weight or less, more preferably 2 parts by weight or less, and may be 1 part by weight or less, 0.7 part by weight or less, or 0.5 part by weight or less, based on 100 parts by weight of the monomer component. From the viewpoint of improving the storage stability (for example, stability against photodegradation) of the surface-protecting sheet, it is advantageous that the content of the photopolymerization initiator is not excessive.

Typically, the adhesive layer including the photopolymerization initiator may be formed using an adhesive composition (e.g., a solvent-type adhesive composition) including the photopolymerization initiator. The adhesive composition including the photopolymerization initiator may be prepared, for example, by mixing other components used in the composition with the photopolymerization initiator. In addition, in the case of preparing the adhesive composition using a polymer (typically, an acrylic polymer) synthesized (photopolymerized) in the presence of a photopolymerization initiator, a residue (unreacted product) of the photopolymerization initiator used in synthesizing the above polymer may be used as a part or all of the photopolymerization initiator contained in the adhesive layer. The same applies to the case of using an acrylic oligomer synthesized in the presence of a photopolymerization initiator as an acrylic oligomer used as needed. From the viewpoint of ease of manufacturing management, the adhesive layer disclosed herein can be preferably formed using an adhesive composition prepared by newly adding the above-described amount of photopolymerization initiator to other constituent components.

(other Components)

The adhesive composition used for forming the adhesive layer may be an adhesive composition containing an acid or a base (ammonia or the like) used for the purpose of pH adjustment or the like as needed. Examples of other optional components that may be contained in the composition include viscosity modifiers (e.g., thickeners), leveling agents, plasticizers, fillers, colorants such as pigments and dyes, stabilizers, preservatives, and various additives that are generally used in the field of adhesive compositions such as anti-aging agents. As for such various additives, conventionally known additives can be used by a conventional method, and since the present invention is not particularly characterized, detailed description thereof is omitted. Although not particularly limited, the technology disclosed herein may be preferably implemented so as to include an adhesive layer containing the polymer (for example, an acrylic polymer) as a main component. In some preferred embodiments, the polymer (e.g., acrylic polymer) may be present in the adhesive layer in an amount of about 85 wt% or more (e.g., 85 to 100 wt%), or 90 wt% or more, or 95 wt% or more.

(formation of adhesive layer)

The adhesive layer may be a cured layer of the adhesive composition. That is, the adhesive layer can be formed by applying (e.g., coating) the adhesive composition to an appropriate surface and then suitably performing a curing treatment. In the case of performing 2 or more curing treatments (drying, crosslinking, polymerization, etc.), they may be performed simultaneously or in multiple stages. In the adhesive composition using a partial polymer (acrylic polymer syrup) of a monomer component, the final copolymerization reaction is typically performed as the above-mentioned curing treatment. That is, a portion of the polymer is subjected to further copolymerization to form a complete polymer. For example, in the case of a photocurable adhesive composition, light irradiation is performed. If necessary, a curing treatment such as crosslinking and drying may be performed. For example, in the case where drying with the photocurable adhesive composition is required, the photocuring may be performed after the drying. In the adhesive composition using the complete polymer, typically, the curing treatment is performed by drying (heat drying) or crosslinking, if necessary. The adhesive layer having a multilayer structure of two or more layers can be produced by bonding the adhesive layers formed in advance. Alternatively, the adhesive composition may be applied to the first adhesive layer formed in advance, and the second adhesive layer may be formed by curing the adhesive composition.

The application of the adhesive composition can be performed using a conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a blade coater, or a spray coater. For example, as a method for providing the pressure-sensitive adhesive layer on the base material layer, a direct method of forming the pressure-sensitive adhesive layer by directly applying the pressure-sensitive adhesive composition to the base material layer, or a transfer method of transferring the pressure-sensitive adhesive layer formed on the release surface to the base material layer may be used.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and may be, for example, about 3 μm to 1000 μm. In some embodiments, the thickness of the pressure-sensitive adhesive layer is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, from the viewpoint of improving the water-resistant reliability by bringing the pressure-sensitive adhesive layer into close contact with the substrate layer and the adherend. In some embodiments, the thickness of the pressure-sensitive adhesive layer may be 500 μm or less, 300 μm or less, 200 μm or less, or 150 μm or less, for example, from the viewpoint of preventing the occurrence of slip residue due to cohesive failure of the pressure-sensitive adhesive layer. In some preferred embodiments, the thickness of the pressure-sensitive adhesive layer is 100 μm or less, more preferably 60 μm or less, still more preferably 50 μm or less, for example, 40 μm or less, or 30 μm or less. Since the thickness of the adhesive layer is limited, penetration of water from the end of the adhesive layer is limited, and a decrease in adhesive strength in a state immersed in an aqueous liquid or warm water can be suppressed. The pressure-sensitive adhesive layer may have a single-layer structure or a multilayer structure of two or more layers.

< substrate layer >

The surface protection sheet disclosed herein may comprise a substrate layer. Non-limiting examples of the material of the base material layer include various resin films such as polyolefin films, polyester films, and polyvinyl chloride films; a foam sheet formed of a foam such as polyurethane foam, polyethylene foam, polychloroprene foam, or the like; fabrics and nonwoven fabrics formed by various fibrous substances (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, semisynthetic fibers such as acetate) alone or in a blended manner; paper such as japanese paper, high-quality paper, kraft paper, crepe paper, etc.; metal foils such as aluminum foil, copper foil, and stainless steel (SUS); and the like, an appropriate material may be selected from 1 of them, or a layered body composed of a combination of 2 or more of them, to be used as the base material layer. Examples of the substrate layer of the composite structure include a laminated substrate (multilayer substrate) having a structure in which a metal foil and the resin film are laminated, a resin sheet reinforced with inorganic fibers such as glass cloth, and the like.

As a material of the base material layer, various films (hereinafter also referred to as base material films) can be preferably used. The substrate film may be a porous film such as a foam film or a nonwoven fabric sheet, or may have a structure in which a porous layer is laminated with a non-porous layer. In some embodiments, as the base film, a film containing a (self-supporting or independent) resin film capable of maintaining its shape independently as a base film may be preferably used. The term "resin film" as used herein refers to a non-porous structure, and typically refers to a resin film that contains substantially no bubbles (no pores). Therefore, the resin film is a concept distinguished from the foam film and the nonwoven fabric. The resin film may have a single-layer structure or a multilayer structure (for example, a three-layer structure) of two or more layers.

As a resin material constituting the resin film, for example, polyester such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and the like can be used; polyolefins such as Polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers; polycycloolefins derived from monomers having an aliphatic ring structure such as a norbornene structure; polyamide (PA) such as nylon 6, nylon 66, and partially aromatic polyamide; polyimide (PI) such as transparent polyimide (CPI), polyamide imide (PAI); polyetheretherketone (PEEK); polyethersulfone (PES); polyphenylene Sulfide (PPS); polycarbonate (PC); polyurethane (PU); ethylene vinyl acetate copolymer (EVA); polyvinyl alcohol (PVA); a polystyrene; an ABS resin; polyvinyl chloride; polyvinylidene chloride; fluororesins such as Polytetrafluoroethylene (PTFE); acrylic resins such as polymethyl methacrylate; cellulose polymers such as diacetylcellulose, triacetylcellulose (TAC); a vinyl butyral polymer; an aryl ester polymer; polyoxymethylene polymer; and epoxy polymers. The substrate layer disclosed herein may be a substrate layer whose surface is composed of the above-described resin material. The resin film that can be used as the base layer may be selected from a resin film formed using a resin material containing 1 kind of the above resin alone, and a resin film formed using a resin material obtained by blending 2 or more kinds of the above resins, and an appropriate material may be used. The resin film may be a composite resin film obtained by laminating a resin layer containing 1 or 2 or more kinds of resin materials and a resin layer containing 1 or 2 or more kinds of resin materials which are the same as or different from the resin layer. The resin film may be unstretched or stretched (for example, uniaxially stretched or biaxially stretched).

In some preferred embodiments, a polyolefin resin film is used as the base material layer. By using the polyolefin resin film, a surface-protecting sheet exhibiting suitable characteristics at a suitable thickness can be desirably obtained. Here, the polyolefin resin means a resin containing polyolefin in a proportion of more than 50% by weight. As the polyolefin resin, 1 kind of polyolefin may be used alone, or 2 or more kinds of polyolefin may be used in combination. The polyolefin may be, for example, a homopolymer of an α -olefin, a copolymer of 2 or more α -olefins, a copolymer of 1 or 2 or more α -olefins and other vinyl monomers, or the like. Specific examples thereof include ethylene-propylene copolymers such as PE, PP, poly-1-butene, poly-4-methyl-1-pentene, and ethylene-propylene rubber (EPR), ethylene-propylene-butene copolymers, ethylene-vinyl alcohol copolymers, and ethylene-ethyl acrylate copolymers. Any of Low Density (LD) polyolefin and High Density (HD) polyolefin may be used. Examples of the polyolefin resin film include an unstretched polypropylene (CPP) film, a biaxially oriented polypropylene (OPP) film, a low density polyethylene (LDP E) film, a Linear Low Density Polyethylene (LLDPE) film, a Medium Density Polyethylene (MDPE) film, a High Density Polyethylene (HDPE) film, a Polyethylene (PE) film obtained by blending 2 or more Polyethylenes (PE), a PP/PE blend film obtained by blending polypropylene (PP) and Polyethylene (PE), and the like. Among them, an OPP film is preferable from the viewpoint of moisture permeability.

Other preferable examples of the resin material constituting the resin film include polyvinylidene chloride resin, PPS resin, urethane resin, EVA resin, and fluorine resin such as PTFE. Here, the polyvinylidene chloride resin means a resin containing polyvinylidene chloride in an amount of more than 50% by weight. Similarly, PPS resin means a resin containing PPS in a proportion of more than 50% by weight. The same applies to polyurethane resin, EVA resin, and fluororesin. The polyolefin resins (PE, PP), polyvinylidene chloride resin, PPs resin, polyurethane resin, EVA resin, and fluororesin exemplified above may be used in combination with other materials, or may be used alone and as a base material layer.

The resin film may contain known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slip agents, and antiblocking agents, if necessary. The blending amount of the additive is not particularly limited and may be appropriately set according to the application and the like.

The method for producing the resin film is not particularly limited. For example, conventionally known general resin film molding methods such as extrusion molding, inflation molding, T-die casting molding, calender roll molding and the like can be suitably employed.

The base material layer may be substantially composed of such a resin film. Alternatively, the base material layer may include an auxiliary layer in addition to the resin film. Examples of the auxiliary layer include an optical property adjusting layer (e.g., a coloring layer or an antireflection layer), a printed layer for imparting a desired appearance, a laminate layer, an antistatic layer, an undercoat layer, and a surface treatment layer such as a release layer.

In other embodiments, the substrate layer has a layer containing an inorganic material (layer containing an inorganic material). The effects resulting from the techniques disclosed herein can also be achieved by employing a substrate layer comprising a layer comprising an inorganic material. By disposing the layer containing an inorganic material, barrier properties (moisture permeability preventing properties) tend to be improved. In some embodiments, the substrate layer having the inorganic material-containing layer includes a substrate main layer including the resin film or the like, and has a structure including the inorganic material-containing layer provided on at least one surface of the substrate main layer. In other embodiments, the substrate layer may be a substrate layer substantially composed of a layer containing an inorganic material.

As the inorganic material used for the layer containing an inorganic material, a material capable of forming a hydrophilic surface can be used from various metal materials including simple substances of transition metal elements and metalloid elements, alloys, inorganic compounds such as inorganic oxides, and the like. The inorganic material may be used alone or in combination of 1 or more than 2. Preferable examples of the inorganic material include oxides (inorganic oxides, typically metal oxides) such as titanium oxide, zinc oxide, magnesium oxide, aluminum oxide, silicon oxide, cerium oxide, chromium oxide, zirconium oxide, manganese oxide, zinc oxide, iron oxide, tin oxide, and niobium oxide. Among them, an inorganic oxide such as silicon oxide can be used as a preferable inorganic material. Further, as other preferable examples of the inorganic material, metal foils (metal materials) such as aluminum foil, copper foil, stainless steel (SUS) and the like can be given. The layer containing an inorganic material may contain various organic materials (including organic polymer compounds that can be used as a coating agent or a binder) in addition to the inorganic materials described above.

The amount of the inorganic material (for example, an inorganic oxide such as silicon oxide) in the inorganic material-containing layer may be set to an appropriate amount that can obtain a target hydrophilic surface, and is not limited to a specific range. For example, the content ratio of the inorganic material in the inorganic material-containing layer may be set to about 30 wt% or more, and may be appropriately set to about 50 wt% or more (for example, more than 50 wt%), or may be set to about 70 wt% or more. In some preferred embodiments, the inorganic material is contained in the inorganic material-containing layer in a proportion of about 90 to 100% by weight (for example, about 95% by weight or more).

The method for forming the layer containing an inorganic material is not particularly limited, and the layer can be formed by an appropriate method according to a desired thickness or the like. For example, an inorganic material formed in a layered state by a known film formation method such as a vacuum deposition method, a sputtering method, or a plating method can be used. When an inorganic compound is used as the inorganic material, various vapor deposition methods can be used, and for example, a physical vapor deposition method (PVD) such as a vacuum vapor deposition method, a sputtering method, or an ion plating method, a chemical vapor deposition method (CVD) such as an atomic layer deposition layer, or the like can be used. The formation of the coating layer containing an inorganic polymer such as polysiloxane may be performed as follows: the coating agent that can obtain a surface exhibiting a desired water contact angle is appropriately selected from known coating agents and used by a conventional method.

The thickness of the layer containing an inorganic material is not particularly limited. In the embodiment in which the base material layer has a base material main layer and an inorganic material-containing layer, the thickness of the inorganic material-containing layer is preferably about 5 μm or less (for example, less than 5000 nm) or about 2 μm or less (for example, less than 2000 nm) from the viewpoint of not impairing the function of the base material layer main body (main layer of the base material layer). In some embodiments, the thickness of the inorganic material-containing layer is less than 1000nm, more preferably less than 500nm, even more preferably less than 100nm, and particularly preferably less than 50nm, and may be less than about 30nm, less than about 20nm, or less than about 15nm (e.g., less than 10 nm). By forming such a layer containing an inorganic material with a small thickness, desired characteristics such as barrier properties (moisture permeability preventing properties) can be imparted to the base material layer without impairing the function of the base material layer (main layer of the base material layer). From the viewpoints of light weight and optical characteristics, it is also advantageous to form a layer containing an inorganic material to be thin. The thickness of the layer containing an inorganic material is preferably 1nm or more (for example, 3nm or more), and may be about 5nm or more, or may be about 10nm or more (for example, 15nm or more) from the viewpoint of reducing the moisture permeability.

In the embodiment in which the base material layer includes the base material main layer and the inorganic material-containing layer, the thickness of the base material main layer (in the case where the base material layer includes a plurality of layers other than the inorganic material-containing layer, the total thickness of the layers other than the inorganic material-containing layer) is preferably 50% or more, more preferably 70% or more, still more preferably 90% or more, and may be 97% or more (for example, 99% or more).

The base material layer may have a single-layer structure or a multilayer structure having two or more layers. As the substrate layer having a single-layer structure, a substrate layer formed of a resin film can be mentioned. The base layer made of the resin film is suitable for a surface protection sheet for chemical treatment such as etching liquid. There is a tendency that softness and flexibility are also excellent. Examples of the base material layer having a multilayer structure include a structure formed of a resin film having a multilayer structure, a structure having a base material main layer and a layer containing an inorganic material.

In some embodiments, the substrate layer (substrate film used as the substrate layer) preferably has a moisture permeability of 24 g/(m) as measured by cup method ² Day) below. By setting the configuration having such a limited moisture permeability, even when the adhesive is used in contact with an aqueous liquid such as a chemical treatment or a warm water immersion, the penetration of the aqueous liquid into the adhesive layer is moderately prevented by the presence of the low moisture permeability base material layer, and the adhesive strength due to the water peelability is not reduced or the adhesive strength is suppressed. As a result, the adhesion force with the adherend is maintained, and the surface protective sheet can maintain the adhesion state with the adherend. In some preferred embodiments, the substrate layer has a moisture permeability of about 18 g/(m) ² Day) or less, more preferably about 14 g/(m) ² Day) or less, more preferably about 10 g/(m) ² Day) or less, particularly preferably about 8 g/(m) ² Day) or less, may be about 5 g/(m) ² Day) or less (e.g., about 3 g/(m) ² Day) the following). In addition, when the surface protection sheet is exposed to heat such as warm water, if the moisture permeability is too low, the water peelability may not be effectively exhibited due to aging caused by heat. From such a point of view, in some embodiments, the substrate layer has a moisture permeability of 1 g/(m) ² Day) or more, preferably about 3 g/(m) ² Day) or more, for example, may be greater than 5 g/(m) ² Day).

More specifically, the moisture permeability of the base material layer may be, for example, 23 g/(m) ² Day) or more, or less, 22 g/(m) ² Day) or more, or less, 21 g/(m) ² Day) or more, or less, 20 g/(m) ² Day) or more, or less, 19 g/(m) ² Day) above or below 18 g/(m) ² Day) or more, or less, 17 g/(m) ² Day) or more, or less, 16 g/(m) ² Day) or more and less, 15 g/(m) ² Day) above or below 14 g/(m) ² Day) above or below 13 g/(m) ² Day) or more and less, 12 g/(m) ² Day) or more, or less, 11 g/(m) ² Day) or more, or less, 10 g/(m) ² Day) or more, or less, 9 g/(m) ² Day) or more, or less, 8 g/(m) ² Day) or more, or less, 7 g/(m) ² Day) or more, or less, 6 g/(m) ² Day) or more, or less, 5 g/(m) ² Day) or more, or less, 4 g/(m) ² Day) or more, or less, 3 g/(m) ² Day) or more, or less, 2 g/(m) ² Day) or more or less, or 1 g/(m) ² Day) above or below.

The above moisture permeability of the base material layer can be obtained by selecting and using an appropriate base material which is non-moisture permeable and low in moisture permeability. More specifically, the moisture permeability of the substrate layer can be measured by the method described in examples described below.

The 25 ℃ bending stiffness value of the base material layer (base material film used as the base material layer) may be set to the same range as the range of 25 ℃ bending stiffness value that can be used for the surface protection sheet described above, and thus overlapping description is omitted. Similarly, the ranges of the tensile elastic modulus at 25 ℃, the stress at 25 ℃ at 100% elongation, the stress at 25 ℃ at break, and the strain at 25 ℃ at break that can be used for the base material layer may be set to the same ranges as the ranges of the tensile elastic modulus at 25 ℃, the stress at 25 ℃ at 100% elongation, the stress at break at 25 ℃, and the strain at break at 25 ℃ of the surface protection sheet, respectively, and thus overlapping description is omitted. The substrate layer was measured by the same method as the substrate layer (substrate film used as the substrate layer) in terms of the 25℃bending rigidity value, the 25℃tensile elastic modulus, the 25℃100% elongation stress, the 25℃breaking stress and the 25℃breaking strain, respectively, except that the substrate layer was used as the test piece. The thickness and cross-sectional area of the base material layer can be used as the thickness and cross-sectional area of the test piece for calculating the bending stiffness value at 25 ℃, tensile elastic modulus at 25 ℃, stress at 25 ℃ 100% elongation and breaking stress at 25 ℃. The substrate layer may have a 25 ℃ bending stiffness value of MD, a 25 ℃ bending stiffness value of TD, or a 25 ℃ bending stiffness value of TD, similar to the 25 ℃ bending stiffness value of the surface protection sheet, and thus may have at least one 25 ℃ bending stiffness value of MD and TD, or may have a 25 ℃ bending stiffness value in either direction of MD or TD. Similarly, the substrate layer may have a tensile elastic modulus at 25 ℃ of MD, or may have a tensile elastic modulus at 25 ℃ of TD, and thus may have at least one tensile elastic modulus at 25 ℃ of either the tensile elastic modulus at 25 ℃ of MD or the tensile elastic modulus at 25 ℃ of TD, or may have a tensile elastic modulus at 25 ℃ in either direction of MD or TD. Similarly, the stress at 100% elongation, the stress at break, and the strain at break of the base material layer may be measured in MD (stress at 100% elongation, stress at break, or strain at break), or may be measured in TD, and thus may be at least one of measured in MD and measured in TD, or may be measured in either direction of MD or TD.

The thickness of the base material layer is not particularly limited, and may be selected according to the purpose of protection, the mode of use, and the like. The thickness of the base material layer may be, for example, about 1000 μm or less, or about 300 μm or less, and is preferably about 100 μm or less (typically, less than 75 μm), more preferably about 50 μm or less, or 40 μm or less, or 30 μm or less from the viewpoint of weight reduction and thickness reduction. When the thickness of the base material layer is reduced, flexibility of the surface protection sheet and the following property of the adherend to the surface shape tend to be improved. Further, since the thickness of the base material layer is limited, deformation (expansion and contraction) of the base material layer due to heating is suppressed, and therefore, for example, even when the base material layer is used in a heated state such as hot water immersion, the adhesion state to the adherend tends to be easily maintained. In addition, from the viewpoint of handleability, workability, and the like, the thickness of the base material layer may be, for example, 2 μm or more, or may be more than 5 μm. In some embodiments, the thickness of the substrate layer is suitably about 10 μm or more, preferably about 15 μm or more, more preferably about 20 μm or more, and also about 30 μm or more. The greater the thickness of the base material layer, the more the protective properties of the adherend against penetration of chemical solutions and the like tend to be improved.

The surface of the base material layer on the adhesive layer side may be subjected to conventionally known surface treatments such as corona treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of primer (primer), as necessary. Such a surface treatment may be a treatment for improving the adhesion between the substrate layer and the adhesive layer, in other words, the anchoring property of the adhesive layer to the substrate layer. The primer composition is not particularly limited, and may be appropriately selected from known primer compositions. The thickness of the undercoat layer is not particularly limited, and is, for example, about 0.01 μm to 1 μm, preferably about 0.1 μm to 1 μm. The surface of the base material main layer (typically, the surface on the layer side containing an inorganic material) may be subjected to various surface treatments such as the above-described surface treatments and antistatic treatments.

The surface of the substrate layer on the side opposite to the pressure-sensitive adhesive layer side (hereinafter also referred to as the back surface) may be subjected to a conventionally known surface treatment such as a peeling treatment or an antistatic treatment, if necessary. For example, by surface-treating the back surface of the base material layer with a release treatment agent, the unwinding force of the surface protection sheet wound in a roll form can be reduced. As the release treatment agent, silicone release treatment agents, long-chain alkyl release treatment agents, olefin release treatment agents, fluorine release treatment agents, fatty acid amide release treatment agents, molybdenum sulfide, silica powder, and the like can be used.

< total thickness >

The thickness of the surface protective sheet (including the pressure-sensitive adhesive layer and the base layer, but not including the release liner) disclosed herein is not particularly limited, and may be set to 3 μm or more, or may be set to 5 μm or more, or 10 μm or more is suitable, and from the viewpoint of adhesion to an adherend such as step-following property, it is preferably 20 μm or more, more preferably 30 μm or more, still more preferably 40 μm or more, or may be set to 45 μm or more. The greater the thickness of the surface protection sheet, the more the protection of the adherend against penetration of chemical liquid or the like tends to be improved. The upper limit of the thickness of the surface protection sheet is, for example, 5mm or less, or 3mm or less, or 1mm or less. In some embodiments, the thickness of the surface-protecting sheet is suitably 300 μm or less (for example, 200 μm or less), preferably 100 μm or less, more preferably 75 μm or less, still more preferably 65 μm or less, and for example, 55 μm or less. Since the thickness of the surface protection sheet is limited to a predetermined value or less, deformation (expansion and shrinkage) of the surface protection sheet due to heating is suppressed, and the adhesion state to the adherend tends to be easily maintained. In view of reduction in thickness, miniaturization, weight saving, and resource saving, it is also advantageous to reduce the thickness of the adhesive sheet.

< Release liner >

The release liner used in the surface protective sheet disclosed herein is not particularly limited, and for example, may be used: a release liner having a release-treated surface of a liner substrate such as a resin film or paper, a release liner made of a low-adhesion material such as a fluorine-based polymer (polytetrafluoroethylene or the like) or a polyolefin-based resin (polyethylene, polypropylene or the like), or the like. For the release treatment, for example, a silicone-based release treatment agent, a long-chain alkyl-based release treatment agent, and the like can be used. In some modes, it may be preferable to use a release-treated resin film as a release liner.

< peeling method >

According to the present specification, a method of peeling a surface protection sheet attached to an adherend (protection object) can be provided. The peeling method includes a water peeling step of peeling the surface protective sheet from the adherend while allowing the aqueous liquid to enter into the interface to follow the movement of the peeling front in a state where the aqueous liquid is present at the interface between the adherend and the surface protective sheet at the peeling front of the surface protective sheet from the adherend. According to the water peeling step, the surface protection sheet can be peeled from the adherend effectively using the aqueous liquid.

As the aqueous liquid, a liquid containing a small amount of an additive as needed in water or a mixed solvent containing water as a main component can be used. As the solvent other than water constituting the above mixed solvent, a lower alcohol (e.g., ethanol) or a lower ketone (e.g., acetone) which can be uniformly mixed with water can be used. As the above-mentioned additives, known surfactants and the like can be used. From the viewpoint of avoiding contamination of the adherend, in some embodiments, it may be preferable to use an aqueous liquid substantially containing no additive. From the viewpoint of environmental sanitation, it is particularly preferable to use water as the aqueous liquid. The water is not particularly limited, and, for example, distilled water, ion-exchanged water, tap water, or the like may be used in view of purity, availability, or the like as required by the application.

In some embodiments, the above-described peeling method may be preferably performed in the following manner: in the same manner as in the measurement of the normal water peeling force FW0, for example, an aqueous liquid is supplied to the adherend in the vicinity of the outer edge of the surface protection sheet attached to the adherend, and the aqueous liquid is allowed to enter the interface between the surface protection sheet and the adherend from the outer edge of the surface protection sheet, and then peeling of the surface protection sheet is performed without supplying new water (i.e., using only the aqueous liquid supplied to the adherend before peeling starts). If water entering the interface between the surface protection sheet and the adherend following the movement of the peeling front is exhausted in the middle of the water peeling step, water may be intermittently or continuously added after the water peeling step is started. For example, in the case where the adherend has water absorption, in the case where the aqueous liquid easily remains on the surface or the adhesive surface of the adherend after peeling, or the like, a system in which water is added after the water peeling step is started may be preferably employed.

The amount of the aqueous liquid to be supplied before the start of peeling is not particularly limited as long as the aqueous liquid can be introduced from the outside of the adhering range of the surface protection sheet to the interface between the surface protection sheet and the adherend. The amount of the aqueous liquid may be, for example, 5. Mu.L or more, and usually 10. Mu.L or more is preferable, or 20. Mu.L or more. The upper limit of the amount of the aqueous liquid is not particularly limited. In some embodiments, the amount of the aqueous liquid may be, for example, 10mL or less, or 5mL or less, or 1mL or less, or 0.5mL or less, or 0.1mL or less, or 0.05mL or less from the viewpoint of improving workability. By reducing the amount of the aqueous liquid, the operation of removing the aqueous liquid by drying, wiping, or the like after peeling the surface protective sheet can be omitted or simplified.

The operation of allowing the aqueous liquid to enter the interface between the surface protective sheet and the adherend from the outer edge of the surface protective sheet at the start of peeling may be performed, for example, in the following manner: inserting the front end of a cutter, a needle or other tool into the interface at the outer edge of the surface protection sheet; the outer edge of the surface protection sheet is grasped by a hook, a claw or the like and lifted; a strong adhesive tape, a suction cup, or the like is attached to the back surface near the outer edge of the surface protection sheet, and one end of the surface protection sheet is lifted; etc. By forcibly introducing the aqueous liquid into the interface from the outer edge of the surface-protecting sheet in this manner, a state in which the aqueous liquid is present at the interface between the adherend and the surface-protecting sheet can be efficiently formed. In addition, it can be suitably and simultaneously realized that: good water peelability after the operation of forcedly allowing the aqueous liquid to enter the interface to form the peeling starting point is performed; and high water-resistant reliability when this operation is not performed.

< use >

The surface-protecting sheet disclosed herein can be used as a surface-protecting sheet for various purposes. For example, the surface protective sheet disclosed herein may be applied to a non-treated surface of the object to be protected, for example, in various treatments such as chemical treatment using a liquid medicine for glass, semiconductor wafers, metal plates, etc., or physical treatment such as cutting or polishing.

The kind of the object to be protected is not particularly limited. The surface protective sheet disclosed herein can be used for the protection of various components, materials. The surface protection sheet disclosed herein is suitable for protecting glass materials such as alkali glass and semiconductor wafers, because peeling by water peeling can be performed without breakage or deformation of an adherend during peeling. These materials are generally limited in thickness, and are brittle materials (also referred to as hard brittle materials) that are prone to cracking, chipping, cracking, and the like due to external forces during handling and peeling. By applying the peeling by water peeling to such an adherend, the breakage of the adherend at the time of peeling can be suitably prevented. The glass material to be the protection target may be a glass plate having a surface provided with a transparent conductive film (for example, an ITO (indium tin oxide) film) or an FPC locally, such as those used in tablet personal computers, mobile phones, organic LEDs (light emitting diodes), and the like. Further, as a preferable example of the object to be protected, a glass plate such as window glass and cover glass used for a foldable display and a rollable display can be given. These glass plates are formed with a thin thickness (for example, a thickness of 100 μm or less), and the risk of breakage is greater, but according to the technology disclosed herein, even in the case where the object to be protected is a brittle material with a thin thickness as described above, breakage of the object to be protected can be prevented at the time of peeling.

The water contact angle of the surface of the object to be protected to which the surface protection sheet is attached is not particularly limited. In some embodiments, the surface of the protection object may be a surface exhibiting hydrophilicity to such an extent that the water contact angle is, for example, 60 degrees or less, preferably 50 degrees or less. In some preferred embodiments, the water contact angle of the surface may be, for example, 45 degrees or less, 40 degrees or less, 35 degrees or less, or 30 degrees or less. When the water contact angle is reduced, water tends to spread out easily along the surface of the adherend, and desired water peelability tends to be easily obtained. The surface-protecting sheet disclosed herein can be preferably used for protecting a member having a surface formed of a material (e.g., glass such as an alkali glass plate or alkali-free glass) having a water contact angle of 20 degrees or less (e.g., 15 degrees or less, and further 10 degrees or less). The lower limit of the water contact angle on the surface of the protection object is in principle 0 degrees. In some embodiments, the water contact angle of the surface of the protection object may be greater than 0 degrees, or may be 1 degree or more, or may be 3 degrees or more, or may be 5 degrees or more. In other embodiments, the water contact angle of the surface of the object may be greater than 30 degrees, or greater than 50 degrees, or greater than 60 degrees (e.g., 70 degrees or greater). The surface protection sheets disclosed herein can be used with a variety of materials having different water contact angles. The water contact angle of the surface of the object to be protected can be measured by the same method as the contact angle measurement method described in examples described later.

The thickness of the object to be protected (e.g., glass plate, semiconductor wafer) is not particularly limited, and may be, for example, about 1mm or less, or about 500 μm or less or about 300 μm or less. The effect (prevention of breakage during peeling) by the technique disclosed herein can be more effectively exhibited for a thin protection object, and therefore, the thickness may be, for example, about 150 μm or less or about 100 μm or less. The lower limit of the thickness is, for example, about 10 μm or more (for example, 30 μm or more).

In some preferred embodiments, the protective sheet is suitable as a surface protective sheet used in a step of chemically and/or physically treating an object to be protected such as glass or a semiconductor wafer in a liquid. In the surface-protecting sheet disclosed here, in the above-mentioned application, the surface-protecting sheet can have adhesiveness required for protection of the object to be protected during the above-mentioned treatment, and can be peeled off smoothly from the object to be protected (adherend) by water peeling during peeling after the treatment. The chemical treatment includes treatment with a chemical solution containing an acid or an alkali, such as an etching solution including an aqueous hydrofluoric acid solution. For example, the surface protective sheet disclosed herein can be preferably used in an etching treatment in which glass is dissolved with a chemical solution (etching solution) in order to adjust the thickness of glass, remove burrs and microcracks formed on cut end surfaces of glass, an antiglare treatment, an etching treatment in which a metal surface is partially corroded with a chemical solution (etching solution), a plating treatment in which a connection terminal portion of a circuit board (a printed board, a flexible printed board (FPC), etc.) is partially plated with a chemical solution (plating solution), and the like. Among them, the present invention is particularly preferably applied to an application of etching treatment using an acidic chemical solution such as a hydrofluoric acid solution. The physical treatment includes polishing and cutting the surface of the object to be protected.

The surface protection sheet disclosed herein may be preferably used for glass thinning treatment. For example, a glass plate used as an optical member can be thinned by a glass thinning treatment using a chemical solution such as an aqueous hydrofluoric acid solution. In this glass thinning treatment, the surface protective sheet can be used for protection of the non-treated side of the glass. In the glass-thinning treatment, the glass plate may be thinned to about 150 μm or less (for example, about 100 μm or less), for example, although not particularly limited. The thickness of the glass sheet before the glass reduction treatment may be, for example, about 0.15mm to 5mm, and may be about 300 μm or more (for example, about 500 μm to 1000 μm). Such thinned glass is susceptible to breakage by external force at peeling, however, by using the surface protection sheet disclosed herein, the problem of breakage of the glass at peeling of the surface protection sheet can be eliminated or the risk thereof can be greatly reduced.

In addition, the surface protective sheet is also preferably used for manufacturing semiconductors. The semiconductor wafer may be, for example, a silicon wafer, a silicon carbide (SiC) wafer, a nitride semiconductor wafer (silicon nitride (SiN), gallium nitride (GaN), or the like), a compound semiconductor wafer such as a gallium arsenide wafer, or the like. In the above-described production of a semiconductor, the surface protective sheet disclosed herein can be preferably used in a semiconductor wafer processing (typically, a silicon wafer processing) step such as a step of thinning a semiconductor wafer (more specifically, a back grinding step of grinding the back surface of a semiconductor wafer) and a step of cutting the semiconductor wafer (for example, a dicing step). In the back grinding step, the semiconductor wafer may be thinned to about 150 μm or less (for example, about 100 μm or less), for example. The thickness of the semiconductor wafer before back grinding may be about 300 μm or more (for example, about 500 μm to 1000 μm). The use of a surface protective sheet that can maintain good properties (adhesion and water peelability) against such heating is particularly interesting because the semiconductor manufacturing process may be exposed to temperatures higher than the room temperature region (e.g., 40 to 90 ℃, preferably 40 to 60 ℃). The surface protection sheet used for this purpose may be simply referred to as a back surface polishing sheet or a dicing sheet.

In some embodiments, the surface-protecting sheet used in the various surface-protecting applications described above may be used in the following manner: in a state where one surface protection sheet is attached to one surface of one or a plurality of objects to be treated, the plurality of objects to be treated are continuously or individually transported into water such as a liquid medicine tank or a cleaning tank by using a transport means such as a roller, and target treatment is performed. In the process (including mounting and installation in a device) during and after the conveyance, external forces such as impact, vibration and deformation may be inevitably or unintentionally applied to the object to be protected. For example, as a conveying means used in the chemical liquid treatment or the cleaning treatment, a plurality of rollers arranged at predetermined intervals may be used, but in the conveyance by the rollers, a peeling load with a small peeling angle is easily applied without interruption due to a difference in height between the rollers, vibration, or the like. The surface protection sheet disclosed herein is excellent in the prevention of end peeling against external forces such as the vibration described above, and therefore has the following advantages: even when the protective material is used in a process including a step of treating the protective material in a liquid in a state of being attached to the protective material as described above, peeling from the edge portion is less likely to occur due to external forces such as vibration in the process.

The protection object may be a member constituting a device (optical device) such as a liquid crystal display device, an organic EL (electroluminescence) display device, a PDP (plasma display panel), a display device (image display device) such as an electronic paper, an input device such as a touch panel, or a portable electronic device such as a foldable display or a rollable display, for example.

Examples of the portable electronic devices include, for example, mobile phones, smartphones, tablet personal computers, notebook computers, various wearable devices (for example, wrist-worn type worn on the wrist like a wristwatch, component type worn on a part of the body using a jig, a band, or the like, eye-worn type including glasses type (monocular type, binocular type, also including head-worn type), clothing type mounted on a shirt, sock, hat, or the like, ear-worn type mounted on the ear like an earphone, or the like), digital cameras, digital video cameras, audio devices (portable music players, digital recording pens, or the like), calculators (desktop electronic calculators, or the like), portable game devices, electronic dictionaries, electronic notebooks, electronic books, in-vehicle information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, and the like. In the present specification, "portable" means not sufficient to be carried but means to have a level of portability that can be carried by an individual (a standard adult) relatively easily.

(protection method)

From the foregoing, according to the present specification, a surface protection method using the surface protection sheet disclosed herein can be provided. The surface protection method comprises the following steps: a step of attaching a surface protection sheet to at least a part of the protection object (protection object surface, protection object part); a step of subjecting the object to be protected to which the surface-protecting sheet is attached to a treatment (for example, a physical treatment such as a chemical treatment, a warm water immersion treatment, a water immersion treatment, cutting, or polishing); and a step of peeling the surface protection sheet from the protection object after the treatment. Here, the step of peeling the surface protection sheet from the protection object preferably includes the water peeling step described above. Details of the surface protective sheet, the water peeling step, the protective object, the treatment (glass thinning treatment, semiconductor wafer thinning treatment, etc.), and other matters (applications, etc.) are as described above, and thus overlapping descriptions are omitted. Typical examples of the object to be protected include a glass plate, a semiconductor wafer, and the like, which are subjected to a treatment such as glass thinning. Therefore, according to the present specification, a glass thinning method and a semiconductor manufacturing method including the above steps can be provided.

Examples

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

< evaluation method >

[ Normal adhesion force F0]

The surface protection sheet to be measured was cut into a size of 20mm in width and 100mm in length to prepare a test piece. The release liner covering the adhesive surface (adhesive layer surface) was peeled off from the test piece at 23 ℃ under 50% rh, and the exposed adhesive surface was pressed against an alkali glass plate (the surface of an alkali glass having a surface with a water contact angle of 20 degrees or less) as an adherend by one round trip of a 2kg rubber roller. The sample for evaluation obtained as described above was subjected to autoclave treatment (50 ℃,0.5mpa,15 minutes). After the sample for evaluation taken out of the autoclave was kept at 23℃under 50% RH for 1 hour, it was subjected to the same conditions according to JIS Z0237: 10.4.1 method 1 of 2009: the peel strength of the test piece from the adherend was measured using a tensile tester under conditions of a tensile speed of 300 mm/min and a peel angle of 180 degrees for 180 ° peel adhesion of the test piece (among them, the peel strength was measured before the migration to the following water peel force measurement, i.e., before distilled water was supplied to the peeling interface). The measurement was performed 3 times, and the average value thereof was regarded as normal adhesion F0[ N/20mm ]. The normal adhesion force F0 was measured such that the test piece attached to the adherend was peeled off from the bottom upward. As the adherend, an alkali glass plate (product name "Micro Slide Glass S200423", manufactured by Song Nitro industries Co., ltd.) was used. As the tensile tester, a universal tensile compression tester (apparatus name "tensile compression tester, TCM-1kNB", manufactured by Minebea corporation) or a product equivalent thereto may be used.

In the measurement, an appropriate lining material may be attached to the surface opposite to the surface protective sheet (the surface opposite to the adhesive surface) as needed to reinforce the test piece. As the lining material, for example, a polyethylene terephthalate (PET) film having a thickness of about 25 μm can be used.

[ Normal Water Peel force FW0]

In the measurement of the normal adhesion force F0, in the measurement of the peel strength of the test piece from the adherend, 20 μl of distilled water was supplied to the portion (peeling front) of the test piece from which the separation of the adherend was started, and the peel strength after the supply of distilled water was measured. The measurement was performed separately (i.e., 3 times) at the time of measurement of each normal adhesion F0, and the average value thereof was taken as normal water peel force FW0[ N/20mm ].

The conditions for measuring the peel strength after distilled water supply were in accordance with JIS Z0237: 10.4.1 method 1 of 2009: 180 ° peel adhesion to test panels. Specifically, the conditions of a tensile speed of 300 mm/min and a peeling angle of 180 degrees were set at a test temperature of 23℃using a tensile tester.

The normal water peel force FW0 may be measured continuously for each test piece, or the normal adhesion force F0 and the normal water peel force FW0 may be measured using different test pieces. For example, in the case where it is difficult to prepare a test piece of a length sufficient for continuous measurement, a method of measuring using different test pieces may be adopted. The measurement of the normal adhesion force F0 is similar to that of the adherend, the tensile tester, and other matters.

[ adhesion force F1 after 30 minutes of warm water immersion ]

The adhesion force F1 after 30 minutes of warm water immersion was measured by the same method as the normal adhesion force F0 except that the sample for evaluation (the alkaline glass plate to which the test piece (surface protection sheet) was attached) was immersed in warm water at 60±2 ℃ for 30 minutes, and then the adhesion water was pulled up from the warm water and wiped off, and then the peel strength was measured.

Specifically, as in the measurement of the normal adhesion force F0, the surface protection sheet to be measured was cut into a size of 20mm in width and 100mm in length to prepare a test piece. The release liner covering the adhesive surface (pressure-sensitive adhesive layer surface) was peeled off from the test piece at 23℃under 50% RH, and a 2kg rubber roller was reciprocated once to press the exposed adhesive surface against an alkali glass plate as an adherend. The sample for evaluation obtained as described above was subjected to autoclave treatment (50 ℃,0.5mpa,15 minutes). The sample for evaluation taken out of the autoclave was immersed in a water bath containing warm water at a set temperature of 60.+ -. 2 ℃ for 30 minutes. As the warm water, ion-exchanged water or distilled water is used. In warm water, the sample for evaluation was kept horizontal with the adhesive layer side facing upward. The distance (immersion depth) from the upper surface of the sample for evaluation to the water surface is set to 10mm or more (for example, about 10mm to 100 mm). Then, the sample for evaluation was lifted from the hot water, and the water adhering to the sample for evaluation was gently wiped off, and then, the sample was subjected to a treatment in an atmosphere of 23℃and 50% RH according to JIS Z0237: 10.4.1 method 1 of 2009: the peel strength of the test piece from the adherend was measured using a tensile tester under conditions of a tensile speed of 300 mm/min and a peel angle of 180 degrees for 180 ° peel adhesion of the test piece (among them, the peel strength was measured before the migration to the following water peel force measurement, i.e., before distilled water was supplied to the peeling interface). The measurement was performed 3 times, and the average value thereof was taken as F1[ N/20mm ] which was an adhesive force after 30 minutes of warm water immersion. The time from the lifting of the sample for evaluation from the warm water to the measurement of the peel strength was set to 10 minutes or less. The measurement of the normal adhesion force F0 is similar to that of the adherend, the tensile tester, and other matters.

[ Water Peel force FW1 after 30 minutes of warm Water immersion ]

The water release force FW1 after 30 minutes of warm water immersion was measured by the same method as the normal water release force FW0 except that the sample for evaluation (the alkaline glass plate to which the test piece (surface protection sheet) was attached) was immersed in warm water at 60±2 ℃ for 30 minutes, and then the adhering water was lifted from the warm water and wiped off.

Specifically, in the measurement of the adhesion force F1 after the 30-minute warm water immersion, in the measurement of the peel strength of the test piece from the adherend after the 30-minute warm water immersion, 20 μl of distilled water was supplied to the portion (peeling front) where the separation of the test piece from the adherend was started, and the peel strength after the supply of distilled water was measured. The measurement of the adhesion F1 after 30 minutes of warm water immersion was performed separately (i.e., 3 times), and the average value was taken as FW1[ N/20mm ] after 30 minutes of warm water immersion.

The measurement of the water release force FW1 after 30 minutes of hot water immersion may be performed continuously for each test piece, and the measurement of the water release force FW1 after 30 minutes of hot water immersion may be performed for each test piece, or the measurement of the water release force FW1 after 30 minutes of hot water immersion and the measurement of the water release force FW1 after 30 minutes of hot water immersion may be performed for each test piece. The measurement of the normal adhesion force F0 is similar to that of the adherend, the tensile tester, and other matters.

In the above measurement (measurement of F0, FW0, F1, and FW 1), an adherend having a contact angle of the adhesion test piece with distilled water of 20 degrees or less (for example, 5 degrees to 10 degrees) was used as the adherend. Specifically, as the adherend, an alkali glass plate produced by the float method, in which the contact angle of the adhesion test piece against distilled water is 20 degrees or less (for example, 5 degrees to 10 degrees), can be used. As such an adherend, the above-mentioned alkali glass plate manufactured by songbaoning industrial company may be used, but not limited thereto, and a product equivalent to the alkali glass plate manufactured by songbaoning industrial company or other alkali glass plate may be used.

The contact angle of the alkali glass plate was measured by the following method. Specifically, the measurement was performed by the droplet method using a contact angle meter (trade name "DMo-501", manufactured by Kyowa interface science Co., ltd., control box "DMC-2", control and analysis software "FAMAS (version 5.0.30)") under an atmosphere of 23℃and 50% RH. The amount of distilled water added was set to 2. Mu.L, and the contact angle (N5) was calculated by the Θ/2 method from the image after 5 seconds of addition.

The inventors of the present application confirmed that: the adhesion and water peel strength after the immersion in warm water show a certain high correlation with the adhesion and water peel strength after the immersion in hydrofluoric acid aqueous solution, respectively. Based on this knowledge, the adhesion and water release force after the warm water immersion were used as an evaluation index for the suitability of the surface protection sheet for treatment in a liquid containing a chemical solution immersion.

[ loss elastic modulus G' at 60 ]

The loss elastic modulus G' [ Pa ] of the adhesive layer at 60 ℃ was determined by dynamic viscoelasticity measurement. Specifically, a plurality of adhesive layers to be measured were laminated to prepare an adhesive layer having a thickness of about 2 mm. The adhesive layer was punched into a disk-like shape having a diameter of 7.9mm by sandwiching it between parallel plates, and the resultant was fixed, and dynamic viscoelasticity was measured by a viscoelasticity tester (for example, ARES or a product equivalent thereto, manufactured by TA Instruments Co., ltd.) under the following conditions to obtain the loss elastic modulus G' [ Pa ] at 60 ℃.

Measurement mode: shear mode

Temperature range: -70-150 DEG C

Temperature increase rate: 5 ℃/min

Measurement frequency: 1Hz

The pressure-sensitive adhesive layer to be measured can be formed by applying the corresponding pressure-sensitive adhesive composition in a layered form and drying or curing the composition.

[ moisture permeability ]

The moisture permeability of the substrate (layer) and the surface protective sheet was measured in accordance with the moisture permeability test (cup method) of JIS Z0208. The method for measuring the moisture permeability of the substrate is as follows. That is, the base material according to each example was cut into a circular shape of 7cm Φ, and this was used as a sample for evaluation. Then, a predetermined amount of calcium chloride was charged into a test cup (aluminum, moisture permeable cup defined in JIS Z0208), and the cup mouth was sealed with the above-mentioned sample for evaluation. Specifically, the sample for evaluation was placed on the test cup so as to cover the mouth of the test cup, and the sample was placed on the test cup so as to be in contact with the edge (inner diameter 6cm, outer shape 9cm, edge width 1.5cm circular) of the test cup was placed on the test cup with the same shape of the annular gasket and the cover, and the test cup was fixed with a special screw. Next, the cup covered with the sample to be evaluated was stored at 40℃for 24 hours under 92% RH, and the change in total weight before and after storage (specifically, the change in weight based on the water absorption capacity of calcium chloride) was measured to determine the moisture permeability [ g/(m) ² Tian (heaven)]. The moisture permeability of the surface protection sheet was measured by the same method as that of the substrate except that the surface protection sheet was disposed with the cup side as the adhesive surface instead of the substrate, and the cup mouth was sealed and the measurement was performed.

[ tensile test ]

The surface protection sheet was cut into a rectangle having a width of 10mm to prepare a test piece. The test piece was stretched under the following conditions in accordance with JIS K7161, whereby a stress-strain curve was obtained.

(stretching conditions)

Measuring temperature: 25 DEG C

Stretching speed: 300 mm/min

Distance between chucks: 50mm

As the tensile tester, a universal tensile compression tester (apparatus name "tensile compression tester, TCM-1kNB", manufactured by Minebea corporation) or a product equivalent thereto may be used.

The tensile elastic modulus [ Pa ] at 25℃was determined from linear regression of the stress-strain curve. The tensile elastic modulus at 25℃is obtained by converting the value obtained by subtracting the thickness of the adhesive layer from the measured value of the thickness of the surface protective sheet or the value obtained by measuring the thickness of the base material layer itself into the value of the unit cross-sectional area of the base material layer.

In addition, 100% elongation stress [ N/mm ] at 25℃was measured by the tensile test ² ]Stress at break [ N/mm ] ² ]Strain at break [%]。

The 100% elongation stress is a load [ N ] measured when the test piece is elongated by 100% in the tensile test]Divided by the cross-sectional area of the substrate layer of the test piece [ mm ] ² ]To obtainIs a value of (2). The breaking stress is a load [ N ] at which the test piece in the tensile test is broken]Divided by the cross-sectional area of the substrate layer of the test piece [ mm ] ² ]The value obtained is the strain at break [%]Elongation at break of the test piece [%]。

The measured values (tensile elastic modulus, stress at 100% elongation, stress at break, and strain at break) in this example are measured values of MD obtained by matching the MD of the surface protection sheet (more specifically, the base material layer) with the stretching direction of the above-described stretching test, but the above-described stretching test may be performed on the TD of the surface protection sheet by changing the method of cutting the test piece, in addition to the MD of the surface protection sheet, and thus the above-described stretching test may be performed on the TD of the surface protection sheet to obtain measured values of TD. Alternatively, the above tensile test may be performed in either the MD or TD to obtain a measured value.

[ bending stiffness value at 25 ]

Bending stiffness value D [ Pa.m ] of surface protection sheet at 25 DEG C ³ ]The following equation is used to determine the value.

D＝Eh ³ /12(1-ν ² )；

In the above formula, E is the tensile elastic modulus [ Pa ] at 25 ℃ of the surface protection sheet, and h is the thickness [ m ] of the substrate layer. V is poisson's ratio, where v=0.35.

In this example, the 25℃bending stiffness value is the 25℃bending stiffness value of MD, but by changing the method of cutting the test piece as described above, not only the 25℃bending stiffness value of MD but also the 25℃bending stiffness value of TD can be obtained, or alternatively, the 25℃bending stiffness value in either direction of MD or TD can be obtained.

[ initial Peel force in Water ]

The surface protection sheet to be measured was cut into a size of 10mm in width and 100mm in length to prepare a test piece. The release liner covering the adhesive surface (adhesive layer surface) was peeled off from the test piece at 23 ℃ under 50% rh, and the exposed adhesive surface was pressed against an alkali glass plate (the surface of an alkali glass having a surface with a water contact angle of 20 degrees or less) as an adherend by one round trip of a 2kg rubber roller. At this time, one end of the test piece in the longitudinal direction is attached so as to protrude from the adherend. The sample for evaluation obtained as described above was subjected to autoclave treatment (50 ℃,0.5 mpa, 15 minutes). The sample for evaluation taken out of the autoclave was kept at 23℃and 50% RH for 1 hour, and then immersed in water at room temperature (23℃to 25 ℃). As the water, ion-exchanged water or distilled water is used. In water, the sample for evaluation was kept horizontal with the surface to which the test piece was attached facing upward. The distance (immersion depth) from the upper surface of the sample for evaluation to the water surface is set to 10mm or more (for example, about 10mm to 100 mm). As described above, in the state where the sample for evaluation was placed in water, a peel test was performed at a tensile speed of 1000 mm/min and a peel angle of 20 degrees from one end (the end protruding from the adherend) of the test piece in the longitudinal direction using a tensile tester in an environment of 23 ℃ and 50% rh within 1 minute from the start of immersion in water, and the maximum stress applied at the initial stage of peeling was recorded. The measurement was performed 3 times, and the average value of the maximum stress was used as the initial peel force [ N/10mm ] in water.

When the initial peeling force in water is 0.2N/10mm or more, it is determined that the end peeling prevention property against external forces such as vibration during the conveying process is excellent. In a process such as conveyance, an external force such as vibration, which may cause peeling of an end portion of the surface protection sheet, is considered to be a high-speed peeling load applied at a small angle to the protection object. The surface protection sheet, which exhibits an initial peel force in water of 0.2N/10mm or more under conditions of a peel angle of 20 degrees and a peel speed of 1000 mm/min, was judged to have excellent edge peeling prevention properties against external forces such as vibration, as a result of a large stress until peeling due to the peel load.

In the above test, an alkali glass plate (product name "Micro Slide Glass S200423", manufactured by Song Nitro industries Co., ltd.) was used as the adherend. As the tensile tester, a universal tensile compression tester (apparatus name "tensile compression tester, TCM-1kNB", manufactured by Minebea corporation) or a product equivalent thereto was used.

In the measurement, an appropriate lining material may be attached to the surface opposite to the surface protective sheet (the surface opposite to the adhesive surface) as needed to reinforce the test piece. As the lining material, for example, a PET film having a thickness of about 25 μm can be used.

< preparation of adhesive >

(adhesive S1)

A reaction vessel equipped with a condenser, nitrogen inlet, thermometer and stirrer was charged with 60 parts of N-Butyl Acrylate (BA), 6 parts of cyclohexyl acrylate (CHA), 18 parts of N-vinyl-2-pyrrolidone (NVP), 15 parts of 4-hydroxybutyl acrylate (4 HBA) and 1 part of isostearyl acrylate (iSTA), 0.125 part of alpha-thioglycerol as a chain transfer agent, and 0.2 part of ethyl acetate as a polymerization solvent as a thermal polymerization initiator, and solution polymerization was carried out under a nitrogen atmosphere to obtain a solution containing an acrylic polymer having Mw of 20 ten thousand.

To the solution obtained above, 0.05 part (based on the solid content) of an isocyanate-based crosslinking agent (trimethylolpropane/xylylene diisocyanate adduct, trade name: takenate D-110N, solid content concentration 75%) of dioctyltin dilaurate (trade name: EMBILIZER OL-1, manufactured by Tokyo Fine Chemical) as a crosslinking accelerator, 3 parts of acetylacetone as a crosslinking retarder, and 0.1 part of a nonionic surfactant (polyoxyethylene sorbitan monolaurate, HLB16.7, trade name: RHODOL TW-L120, manufactured by Kabushiki Kaisha) as a water affinity agent were added to 100 parts of the monomer component used for the preparation of the solution, and the mixture was uniformly mixed to prepare a solvent-based adhesive composition S1.

A release film (manufactured by mitsubishi resin Co., ltd., MRF#38) having a surface of the polyester film as a release surface and a release film (manufactured by mitsubishi resin Co., ltd., MRE#38) having a surface of the polyester film as a release surface and a thickness of 38 μm were prepared. The solvent type adhesive composition S1 prepared above was applied to the release surface of one release film (MRF#38), and dried at 60℃for 3 minutes, followed by 120℃for 3 minutes, to form an adhesive layer having a thickness of 25. Mu.m. The release surface of the other release film (MRE#38) was bonded to the pressure-sensitive adhesive layer for protection. An adhesive layer S1 having a surface protected by 2 sheets of release film was obtained as described above. The 60℃loss elastic modulus G' of the adhesive layer S1 was 32.5kPa.

(adhesive S2)

A reaction vessel equipped with a condenser, nitrogen inlet, thermometer and stirrer was charged with 72 parts of 2-ethylhexyl acrylate (2 EHA), 14 parts of NVP, 13 parts of 2-hydroxyethyl acrylate (HEA) and 1 part of Methyl Methacrylate (MMA), 0.12 part of α -thioglycerol as a chain transfer agent, and 0.2 part of ethyl acetate as a polymerization solvent as a thermal polymerization initiator, and then solution polymerization was carried out under a nitrogen atmosphere to obtain a solution containing an acrylic polymer having an Mw of 30 ten thousand.

To the solution obtained above, 0.75 parts (based on solid content) of the isocyanate-based crosslinking agent, 0.01 parts of the crosslinking accelerator, 3 parts of the crosslinking retarder, and 0.1 parts of the nonionic surfactant as a water affinity agent were added and uniformly mixed with respect to 100 parts of the monomer component used in the preparation of the solution, to prepare a solvent-based adhesive composition S2.

Except that the solvent type adhesive composition S2 was used, an adhesive layer S2 having a thickness of 25 μm was obtained by the same method as the formation of the adhesive layer S1, the surface of which was protected by 2 sheets of release film. The adhesive layer S2 had a loss elastic modulus G' of 15.6kPa at 60 ℃.

(adhesive S3)

A reaction vessel equipped with a condenser, nitrogen inlet, thermometer and stirrer was charged with 97 parts of BA, 3 parts of Acrylic Acid (AA) and 0.2 part of AIBN as a thermal polymerization initiator as monomer components, and the solution was polymerized under a nitrogen atmosphere to obtain a solution containing 100 ten thousand of acrylic polymer.

To the solution obtained above, 0.3 part (based on solid content) of an epoxy-based crosslinking agent (1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane, trade name: TETRAD-C, manufactured by Mitsubishi gas chemical corporation), 1 part (based on solid content) of an isocyanate-based crosslinking agent (75% ethyl acetate solution of trimethylolpropane/toluene diisocyanate 3 polymer adduct, manufactured by TOSOH corporation, trade name: coronate L), and 0.1 part (based on solid content) of a nonionic surfactant (polyoxyethylene alkyl ether, HLB12.5, trade name: naroaction ID-60, manufactured by Sanyo chemical industry Co., ltd.) as a water affinity agent were added to 100 parts of the monomer component used in the preparation of the solution, and the mixture was uniformly mixed to prepare a solvent-based adhesive composition S3.

Except that the solvent-based adhesive composition S3 was used, an adhesive layer S3 having a thickness of 25 μm was obtained by the same method as the production of the adhesive layer S1, the surface of which was protected by 2 release films. The adhesive layer S3 had a loss elastic modulus G' of 5.7kPa at 60 ℃.

(adhesive U1)

100 parts of a monomer mixture containing BA, CHA, 4HBA in a weight ratio of 67/14/19 were mixed with a trade name as a photopolymerization initiator: 0.09 part of Irgacure 651 (Ciba Specialty Chemicals Inc.. Manufactured by Ind.) and trade name: 0.09 part of Irgacure 184 (manufactured by Ciba Specialty Chemicals Inc.) was put into a four-necked flask together, and the mixture was photopolymerized by irradiation with ultraviolet rays under a nitrogen atmosphere until the viscosity (BH viscometer, no.5 rotor, 10rpm, measurement temperature: 30 ℃ C.) became about 15 Pa.s, whereby a monomer slurry of a partial polymer comprising the above-mentioned monomer mixture was prepared. To 100 parts of the monomer slurry were added 5 parts of NVP, 9 parts of HEA and 8 parts of 4HBA, 0.15 part of dipentaerythritol hexaacrylate (DPHA) as a polyfunctional monomer, and 0.3 part of a nonionic surfactant (polyoxyethylene sorbitan monolaurate, HLB16.7, trade name: RHEODOL TW-L120, manufactured by Kabushiki Kaisha) as a water affinity agent, followed by mixing uniformly to prepare an ultraviolet-curable adhesive composition U1.

The adhesive composition U1 obtained above was applied to a release film R1 (manufactured by Mitsu bishi Materials, mrf#38) having a thickness of 38 μm, which was a release surface, on one surface of the polyester film, and an adhesive layer U1 having a thickness of 25 μm was obtained by blocking air from a release film R2 (manufactured by Mitsubishi Materials, mre#38) having a thickness of 38 μm, which was a release surface, on one surface of the polyester film, and curing the film by irradiation with ultraviolet rays. The loss elastic modulus G' at 60 ℃ of the adhesive layer U1 was 19.7kPa.

(adhesive E1)

An aqueous emulsion (monomer emulsion) of a monomer mixture was prepared by mixing and emulsifying 85 parts of 2EHA, 13 parts of Methyl Acrylate (MA), 1.2 parts of AA, 0.75 part of methacrylic acid (MAA), 0.01 part of 3-glycidoxypropyl trimethoxysilane (KBM-403, manufactured by Xinyue chemical industry Co., ltd.), 0.05 part of t-dodecyl mercaptan as a chain transfer agent, and 1.9 parts of an emulsifier (LATEMUL E-118B, manufactured by Kagaku corporation) in 100 parts of ion-exchanged water.

The monomer emulsion was placed in a reaction vessel equipped with a condenser, a nitrogen inlet, a thermometer and a stirrer, and stirred at room temperature for 1 hour or more while introducing nitrogen gas. Next, the system was warmed to 60℃and 0.1 part of 2,2' -azobis [ N- (2-carboxyethyl) -2-methylpropionamidine ] hydrate (manufactured by Wako pure chemical industries, ltd., VA-057) was charged as a polymerization initiator, followed by reaction at 60℃for 6 hours to obtain an aqueous dispersion of an acrylic polymer. After cooling the system to room temperature, 10 parts by weight of a tackifying resin emulsion (aqueous dispersion of polymerized rosin ESTER having a softening point of 160 ℃ C. Manufactured by Deskland chemical Co., ltd.) was added to 100 parts by weight of the solid content of the aqueous dispersion of the acrylic polymer. Further, 10% aqueous ammonia as a pH adjuster and polyacrylic acid (an aqueous solution having a nonvolatile content of 36%) as a thickener were used, the pH was adjusted to about 7.5, and the viscosity was adjusted to about 9pa·s, thereby preparing an emulsion adhesive composition E1.

A release film (manufactured by mitsubishi resin Co., ltd., MRF#38) having a surface of the polyester film as a release surface and a release film (manufactured by mitsubishi resin Co., ltd., MRE#38) having a surface of the polyester film as a release surface and a thickness of 38 μm were prepared. The adhesive composition E1 was applied to the release surface of one release film (MRF#38), and dried at 120℃for 3 minutes to form an adhesive layer E1 having a thickness of 25. Mu.m. The release surface of the other release film (MRE#38) was bonded to the pressure-sensitive adhesive layer for protection. An adhesive layer E1 having a surface protected by 2 sheets of release film was obtained as described above. The adhesive layer E1 had a loss elastic modulus G' of 12.3kPa at 60 ℃.

Example 1 ]

As a base material layer, a stretched polypropylene (OPP) film (product name "Toray fan #25A-KW37", manufactured by Toray Co., ltd., biaxially stretched PP film having a moisture permeability of 6.4 g/(m) was prepared to have a thickness of 25. Mu.m ² Day). The release liner covering one surface of the release liner-equipped adhesive layer S1 obtained in the above was peeled off, and a 2kg rubber roll was reciprocated twice to press the exposed surface (adhesive surface) against the surface of the OPP film. As described above, a surface protective sheet (a single-sided adhesive sheet with a base layer) in which the adhesive surface is protected with a release liner was obtained. The surface-protecting sheet of this example has a bending stiffness value of 9.3X10 at 25 ℃ ^-6 Pa·m ³ Tensile elastic modulus at 25℃of 6.3X10 ⁹ Pa, stress at 25℃100% elongation of 85N/mm ² Breaking stress at 25 ℃ of 146N/mm ² The strain at break at 25℃was 239%.

< examples 2 to 4 and comparative example 1>

A surface protection sheet according to each example was obtained in the same manner as in example 1, except that the adhesive layer S2 (example 2), the adhesive layer U1 (example 3), the adhesive layer E1 (example 4), or the adhesive layer S3 (comparative example 1) was used instead of the adhesive layer S1.

The moisture permeability of the surface protective sheet according to each example was ±1.5 g/(m) of the moisture permeability of the base material (layer) used in each example ² Day).

< evaluation of Performance >

For the surface-protecting sheets according to each example, the normal adhesion F0[ N/20mm ], the normal water release FW0[ N/20mm ], the adhesion F1[ N/20mm ] after 30 minutes of warm water immersion and the water release FW1[ N/20mm ] after 30 minutes of warm water immersion were measured. The results are shown in Table 1. Table 1 also shows an outline of each example.

TABLE 1

As shown in Table 1, the surface protection sheets according to examples 1 to 4, in which an adhesive having a 60℃loss elastic modulus in the range of 10 to 50kPa was used, had an adhesive force of 1.4N/20mm or more even after 30 minutes of warm water immersion, and the water peeling force was reduced to 1.0N/20mm or less. From the results of examples 1 to 4, it was confirmed that the loss elastic modulus at 60℃of the adhesive and the adhesion after 30 minutes of warm water immersion had a positive correlation. In comparative example 1, in which an adhesive having a 60℃loss elastic modulus of less than 10kPa was used, the adhesion to the adherend was lost during the warm water immersion.

From the above results, it was found that, according to the surface protection sheet having the loss elastic modulus g″ at 60 ℃ of the pressure-sensitive adhesive layer of 10kPa to 50kPa, and the water peeling force FW1 after 30 minutes of hot water immersion of 1.0N/20mm or less, even when used in a system for treating the protection object in a liquid in a state of being attached to the protection object, it is possible to maintain the adhesion required for protection and realize peeling without breakage or deformation of the adhesion object at peeling.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the claims. The technology described in the claims includes examples in which various modifications and changes are made to the specific examples described above.

Description of the reference numerals

1. 2 surface protective sheet

1A, 2A bonding surface

1B, 2B back side

10 substrate layer

10A side

10B another side

11 first layer

12 second layer (layer containing inorganic material)

20 adhesive layer

20A bonding surface

30 Release liner

50 surface protective sheet with release liner

Claims

1. A surface protection sheet, which is a surface protection sheet having an adhesive layer,

the adhesive layer has a loss elastic modulus G' at 60 ℃ of 10kPa to 50kPa,

The surface protection sheet has a water peeling force FW1 of 1.0N/20mm or less (water peeling force after 30 minutes of warm water immersion), wherein the water peeling force FW1 is a water peeling force measured by bonding an adhesive surface of the surface protection sheet to a surface of an alkaline glass having a surface with a water contact angle of 20 degrees or less, immersing the surface of the alkaline glass in warm water at 60 ℃ + -2 ℃ for 30 minutes, lifting and wiping off adhering water from the warm water, and then supplying 20 mu L of distilled water between the alkaline glass and the adhesive surface to allow the distilled water to enter one end of an interface between the alkaline glass and the adhesive surface, and measuring the water peeling force under conditions of a temperature of 23 ℃, a peeling angle of 180 degrees, and a peeling speed of 300 mm/min.

2. The surface-protecting sheet of claim 1, wherein the adhesive layer comprises a water affinity agent.

3. The surface-protecting sheet according to claim 1 or 2, which is formed of the adhesive layer and a base material layer supporting the adhesive layer.

4. The surface-protecting sheet according to any one of claims 1 to 3, which has a thickness of 20 to 100 μm.

5. The surface-protecting sheet according to any one of claims 1 to 4, which is used in a step of chemically and/or physically thinning a glass or a semiconductor wafer in a liquid.