WO2023145360A1

WO2023145360A1 - Surface protective sheet and treatment method

Info

Publication number: WO2023145360A1
Application number: PCT/JP2022/047932
Authority: WO
Inventors: 健太熊倉; 尚史小坂; 雄太島▲崎▼; 恵子椎葉
Original assignee: 日東電工株式会社
Priority date: 2022-01-28
Filing date: 2022-12-26
Publication date: 2023-08-03
Also published as: TW202339955A; JPWO2023145360A1; CN118475664A

Abstract

Provided is a peelable surface protective sheet which adheres well to an object to be treated when the object is treated, and allows for peeling without damaging or deforming an adherend when peeled off. Provided is a surface protective sheet comprising a substrate layer and an adhesive layer provided on one surface of the substrate layer. The surface protective sheet has a water peeling force FW0 of at most 50% of an adhesive force F0. In addition, the adhesive layer includes a base polymer and a tackifier. The content of the tackifier in the adhesive layer is more than 10 parts by weight with respect to 100 parts by weight of the base polymer.

Description

Surface protection sheet and treatment method

TECHNICAL FIELD The present invention relates to a surface protective sheet and a processing method.
This application claims priority based on Japanese Patent Application No. 2022-012359 filed on January 28, 2022, the entire contents of which are incorporated herein by reference.

BACKGROUND ART There is known a technique of adhering a protective sheet (adhesive sheet) to a surface of an article to protect the surface from damage (scratches, stains, corrosion, etc.) when processing or transporting the article. ing. For example, the surface protection sheet is the object of processing in various processes such as chemical processing of glass, semiconductor wafers, metal plates, etc. using chemical solutions (etching liquids) and physical processing such as cutting and polishing. By sticking to the non-treated surface of the article, the non-treated surface is protected. Japanese Patent Laid-Open No. 2002-100000 is cited as a prior art document relating to a protective sheet for chemical treatment. Patent Document 2 is a prior art document relating to a water-releasable pressure-sensitive adhesive sheet.

Japanese Patent Application Publication No. 2015-193688 Japanese Patent Application Publication No. 2020-23656

The surface protection sheet is removed from the adherend (object to be processed) at an appropriate timing after the protection purpose is achieved. Therefore, the surface protection sheet is required to have adhesiveness necessary for protecting the object to be treated during treatment such as chemical solution treatment, and easy peelability when peeling off the object to be treated. If the peeling force from the object to be treated is large, for example, when the object to be treated is thin, the object to be treated may be damaged due to the peeling force when the surface protective sheet is peeled off from the object to be treated. There is a risk of deformation.

In recent years, electronic devices such as smartphones, tablet computers, and various wearable devices (e.g., portable electronic devices) are becoming smaller and thinner, and along with this, the semiconductor materials and glass used in these electronic devices Optical members such as optical members also tend to be thinned. Therefore, the surface protective sheet used to protect the above-mentioned members also needs to have easy peelability so that the thin object to be processed is not damaged or deformed when the surface protective sheet is peeled off from the thin object to be processed.

For example, the glass panel used as the optical member can be thinned by a glass slimming process using a chemical solution such as hydrofluoric acid. In the glass slimming process, a surface protection sheet may be used to protect the non-processed surface of the glass. The surface protective sheet used for such applications may break the thinned glass when it is removed from the glass panel after the treatment due to the increase in peeling force and the peeling mode during the treatment. , there are problems such as a decrease in yield. 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 during peeling of the surface protective sheet is greater. If the peel strength of the surface protection sheet is set low, the load applied to the adherend during peeling can be reduced, and the risk of damage or deformation can be reduced. The chemical liquid may permeate into the protected area, or in severe cases, the adhesive may lift or peel off from the adherend during or after the treatment, and the protection purpose may not be achieved. It is more difficult to achieve both adhesiveness necessary for protection and easy peelability that does not damage the adherend for thin brittle materials such as thin glass.

The present invention was created in view of the above circumstances, and is a surface that can be peeled off, which adheres well to the object to be treated when the object is treated, and does not damage or deform the adherend when peeled. The purpose is to provide a protective sheet. Another related object is to provide a treatment method using the surface protective sheet.

According to this specification, a surface protection sheet is provided that includes a base layer and an adhesive layer provided on one side of the base layer. This surface protection sheet has a water peeling force FW0 of 50% or less of the adhesive force F0. Here, the water peeling force FW0 is measured by bonding the adhesive surface of the surface protective sheet to the surface of alkali glass having a water contact angle of 20 degrees or less, and exposing the surface to 1 in an environment of 23°C and 50% RH. After holding for a period of time, 20 μL of distilled water was supplied between the alkali glass and the adhesion surface, and the distilled water was allowed to enter one end of the interface between the alkali glass and the adhesion surface. It is a water peel force [N/20 mm] measured under conditions of a peel angle of 180 degrees and a speed of 300 mm/min. The adhesion force F0 was determined by bonding an adhesive surface of a surface protective sheet to an alkali glass surface having a water contact angle of 20 degrees or less, and holding the sheet in an environment of 23° C. and 50% RH for 1 hour. After that, the peel strength [N/20 mm] is measured under the conditions of a temperature of 23° C., a peel angle of 180 degrees, and a speed of 300 mm/min. Also, the pressure-sensitive adhesive layer contains a base polymer and a tackifier. The content of the tackifier in the adhesive layer is more than 10 parts by weight with respect to 100 parts by weight of the base polymer.

Since the surface protective sheet has a water peel strength reduction rate FW0/F0 of 50% or less, it adheres well to the adherend and can be peeled off using an aqueous liquid such as water (typically can be peeling in the presence of water), the peeling force can be reduced, and peeling can be performed without damaging or deforming the adherend. For example, even if the adherend is a thin and brittle material such as thin glass, the adherend can be peeled off and removed without being damaged. In addition, since the pressure-sensitive adhesive layer of the surface protection sheet contains more than 10 parts by weight of the tackifier with respect to 100 parts by weight of the base polymer, the above-mentioned peelability can be maintained even after immersion in warm water or water. It can have sufficient adhesion. Therefore, even when used in a mode in which the adherend contacts a liquid while attached to the adherend (for example, a mode in which the adherend is treated in a liquid), the surface protection sheet It is possible to maintain a state of close contact with the adherend, and for example, it is possible to make it more difficult for the edge to peel off during or after the treatment. Normally, a surface protection sheet is designed to limit adhesive force because it is assumed to be removed from an adherend. Unlike a protective sheet, a predetermined amount or more of a tackifier, which is an adhesive force-improving component, can be added to achieve both a high level of adhesion to adherends and peelability and removability.

In some preferred embodiments, the content of the tackifier in the pressure-sensitive adhesive layer is more than 10 parts by weight and less than 100 parts by weight with respect to 100 parts by weight of the base polymer. By setting the amount of the tackifier to be used in an appropriate range, the tackifier is well compatible with the adhesive, and the effects of addition of the tackifier (adhesive properties such as adhesive strength) are likely to be effectively exhibited.

In some preferred embodiments, the pressure-sensitive adhesive layer contains at least one selected from tackifier resins and acrylic oligomers as the tackifier. By using a component selected from tackifier resins and acrylic oligomers as a tackifier, the effects of the technology disclosed herein are preferably exhibited.

In some preferred embodiments, the pressure-sensitive adhesive layer contains, as the tackifier, at least one tackifier resin selected from rosin-based tackifier resins, rosin derivative tackifier resins and terpene phenol resins. By using the specific type of tackifying resin, the effect of the technique disclosed herein is preferably exhibited.

In some embodiments, the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as the base polymer. In embodiments using an acrylic pressure-sensitive adhesive layer, the effects of the technology disclosed herein can be preferably exhibited.

In some preferred embodiments, the pressure-sensitive adhesive layer contains a water affinity agent. According to the structure provided with the adhesive layer containing a water affinity agent, it is easy to obtain a degree of decrease in water peel strength of 50% or less, and it is easy to obtain a pressure sensitive adhesive that satisfactorily achieves both adhesive strength and water peelability.

In some aspects, the thickness of the pressure-sensitive adhesive layer is more than 10 µm and 100 µm or less. Since the surface protection sheet disclosed herein has water releasability, even if the pressure-sensitive adhesive layer is formed thicker within the above range to increase adhesive strength, it can be smoothly removed from the adherend using an aqueous liquid such as water. Can be peeled off. Therefore, by utilizing the thickness of the pressure-sensitive adhesive layer, it is possible to achieve both adhesive strength and peelability at a higher level.

Also provided herein is a method of processing. This treatment method comprises a step of attaching a surface protective sheet to the surface of an object to be treated having a surface with a water contact angle of 20 degrees or less; a step of performing a treatment, wherein the object to be treated contacts a liquid in the treatment; a step of peeling off the surface protection sheet from the treated object in the presence of water to remove it; including. Further, the surface protection sheet includes a substrate layer and an adhesive layer provided on one surface of the substrate layer, and has a water peeling force FW0 of 50% or less of the adhesive force F0. Here, the water peeling force FW0 is measured by bonding the adhesive surface of the surface protective sheet to the surface of alkali glass having a water contact angle of 20 degrees or less, and exposing the surface to 1 in an environment of 23°C and 50% RH. After holding for a period of time, 20 μL of distilled water was supplied between the alkali glass and the adhesion surface, and the distilled water was allowed to enter one end of the interface between the alkali glass and the adhesion surface. It is a water peel force [N/20 mm] measured under conditions of a peel angle of 180 degrees and a speed of 300 mm/min. The adhesive force F0 is measured after bonding the adhesive surface of the surface protective sheet to the surface of alkali glass having a water contact angle of 20 degrees or less and holding the adhesive surface in an environment of 23° C. and 50% RH for 1 hour. , the peel strength [N/20 mm] measured under the conditions of a temperature of 23° C., a peel angle of 180 degrees, and a speed of 300 mm/min. Further, the adhesive layer contains a base polymer and a tackifier. The content of the tackifier in the adhesive layer is more than 10 parts by weight with respect to 100 parts by weight of the base polymer.
In the above method, by using a surface protective sheet that satisfies the water peeling force reduction degree (FW0≦F0×0.5), when the object to be treated to which the surface protective sheet is attached is in contact with a liquid. In addition, the intended treatment can be carried out while protecting the portion to which the surface protection sheet is attached. In addition, since the surface protection sheet can be smoothly removed from the treated object by peeling it off in the presence of water after the completion of treatment, even if the treated object is a thin, brittle material such as thin glass, the surface protective sheet can be peeled off easily. Peeling removal is possible without damaging the object to be processed. Furthermore, since the pressure-sensitive adhesive layer of the surface protection sheet contains more than 10 parts by weight of the tackifier with respect to 100 parts by weight of the base polymer, it is possible to maintain the removability from the object to be treated and maintain the adhesiveness in hot water, water, etc. It can have sufficient adhesion even after being immersed. Therefore, when the object to be treated is treated in a liquid while being attached to the object to be treated, the surface protective sheet adheres well to the object to be treated and does not peel off at the edges during or after the treatment. protection can be achieved.

In some preferred embodiments, the liquid is an aqueous solution. The technique disclosed here can be suitably used for treatment using an aqueous solution.

From the above, according to this specification, there is provided a surface protective sheet for use in any of the treatment methods disclosed herein. Such a surface protection sheet has a degree of reduction in water peel strength of 50% or less, and uses an adhesive containing a predetermined amount or more of a tackifier, so that the adhesiveness and peelability to the object to be treated are maintained at a high level. compatible and particularly suitable for the processing methods disclosed herein.

In addition, the surface protection sheet disclosed herein is suitable as a surface protection sheet used in a process of chemically and/or physically treating glass or semiconductor wafers in liquid, for example. In the above applications, the surface protective sheet disclosed herein can have the adhesiveness necessary for protecting the object to be treated during the treatment, and when peeled off after the treatment, the object to be treated (attached) It can be smoothly removed from glass and semiconductor wafers, which are materials (body), by peeling in the presence of water. The surface protective sheet having the above-mentioned degree of reduction in water peeling force can be peeled off without damaging the object due to its water peeling property even when the object to be treated is a thin and brittle material such as thin glass. For example, in a mode in which the above-described processing step is a step of thinning glass or a semiconductor wafer, the thickness of the object to be processed during peeling is smaller than that during adhesion, and the risk of breakage is greater. By using the surface protection sheet disclosed herein for such applications, high adhesion due to the addition of a predetermined amount or more of a tackifier, and easy peelability (easy water peelability) that does not damage the object to be treated can be compatible.

1 is a cross-sectional view schematically showing one embodiment of a surface protective sheet; FIG. FIG. 3 is a cross-sectional view schematically showing another form example of the surface protection sheet.

A preferred embodiment of the present invention will be described below. Matters other than the matters specifically mentioned in the present specification and matters necessary for the implementation of the present invention are based on the teaching of the implementation of the invention described in the present specification and the common general knowledge at the time of filing. can be understood by those skilled in the art. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field. Further, in the drawings below, members and portions having the same function may be denoted by the same reference numerals, and redundant description may be omitted or simplified. Moreover, the embodiments described in the drawings are schematics for the purpose of clearly explaining the present invention, and do not necessarily accurately represent the size or scale of the products actually provided.

<Configuration 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 protective sheet 1 has an adhesive surface 1A, and a sheet-like base material layer (support base material) 10 is provided with an adhesive layer 20 on one surface 10A thereof. It is in the form of a flexible adhesive sheet. The surface protection sheet 1 is used by attaching the surface 20A of the pressure-sensitive adhesive layer 20, which is the adhesive surface 1A, to an adherend (object to be protected). The back surface 10B of the base material layer 10 (the surface opposite to the one surface 10A) is also the back surface 1B of the surface protective sheet 1 and constitutes the outer surface of the surface protective sheet 1 . The surface protection sheet 1 before use (that is, before being attached to an adherend) has a release liner-attached surface in which the adhesive surface 1A is protected by a release liner 30 whose release surface is at least the pressure-sensitive adhesive layer 20 side. It can be in the form of a protective sheet 50 . Alternatively, the other surface (back surface) 10B of the base material layer 10 serves as a release surface, and when the surface protection sheet 1 is wound into a roll, the pressure-sensitive adhesive layer 20 comes into contact with the back surface ( It may be a surface protective sheet in which the adhesive surface 1A) is protected.

Further, 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 configuration 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 is the first It has a laminated structure of a layer 11 and a second layer 12 . Specifically, the base material layer 10 includes a first layer 11 that is a main layer of the base material layer 10 and a second layer 12 that constitutes one surface (back surface) 10B of the base material layer 10 . In this embodiment, the second layer 12 is an inorganic material containing layer. The adhesive layer 20 adheres to the first layer 11 side surface 10A of the base material layer 10 . The surface protective sheet 2 before use (that is, before being attached to an adherend) has a release liner-attached surface in which the adhesive surface 2A is protected by a release liner 30 whose release surface is at least the pressure-sensitive adhesive layer 20 side. It can be in the form of a protective sheet 50 . Alternatively, the other surface (back surface) 10B of the base material layer 10 is a release surface, and when the surface protection sheet 2 is wound into a roll, the pressure-sensitive adhesive layer 20 contacts the back surface and the surface is It may be a surface protective sheet in a protected form.

<Characteristics of Surface Protection Sheet>
(Decrease in normal water peel strength FW0/F0)
The surface protective sheet disclosed herein has a water peeling force FW0 [N/20 mm] of 50% or less of the adhesive force F0 [N/20 mm]. In other words, the surface protective sheet has a water peeling force decrease [%] represented by the formula: FW0/F0×100; of 50% or less. A surface protective sheet that satisfies these properties can be easily removed from the adherend by performing peeling using an aqueous liquid such as water while adhering well to the adherend. Can be stripped. According to such a surface protective sheet, it is possible to exhibit adhesiveness necessary for protection and to peel off without damaging the adherend during peeling. The water peeling force FW0, the adhesive force F0, and the degree of water peeling force reduction are also referred to as normal water peeling force FW0, normal adhesive force F0, and degree of normal water peeling force reduction, respectively, for the purpose of distinguishing them from other characteristics. In some preferred embodiments, the normal water peel strength reduction is 30% or less, more preferably 20% or less, still more preferably 10% or less, and particularly preferably 5% or less, for example 3%. It may be less than or equal to 2% or less (for example, 1.5% or less). A surface protective sheet exhibiting such a degree of reduction in normal water peeling force can achieve a better balance between adhesion reliability during protection and easy peelability during peeling. Theoretically, the lower limit of the normal water peel strength reduction is 0%, and practically, it may be about 1% or more (for example, 2% or more).

Normal state adhesive strength F0 is measured after bonding the adhesive surface of the surface protective sheet to the surface of alkali glass having a surface with a water contact angle of 20 degrees or less, and holding it in an environment of 23 ° C. and 50% RH for 1 hour. , the peel strength [N/20 mm] measured under the conditions of a temperature of 23° C., a peel angle of 180 degrees, and a speed of 300 mm/min. More specifically, the normal adhesive strength F0 is measured by the method described in Examples below.

Normal water peeling force FW0 was determined by bonding the adhesive surface of the surface protective sheet to the surface of alkali glass having a surface with a water contact angle of 20 degrees or less, and holding it in an environment of 23 ° C. and 50% RH for 1 hour. After that, 20 μL of distilled water was supplied between the alkali glass and the adhesion surface, and the distilled water was allowed to enter one end of the interface between the alkali glass and the adhesion surface. water peeling force [N/20 mm] measured under conditions of 300 mm/min. The normal water peeling force FW0 is more specifically measured by the method described in Examples below.

(Normal state adhesive strength F0)
In some aspects, the surface protective sheet preferably has a normal state adhesive strength F0 of 0.5 N/20 mm or more. A surface protection sheet having a normal state adhesive strength F0 of a predetermined value or more tends to exhibit good adhesiveness to an adherend. In some preferred embodiments, the normal adhesive force F0 is 1.0 N/20 mm or more, more preferably 3.0 N/20 mm or more (e.g., greater than 3.0 N/20 mm), even more preferably 5.0 N/20 mm or more. (for example, more than 5.0 N/20 mm), may be 7.0 N/20 mm or more, may be 7.5 N/20 mm or more, may be 8.0 N/20 mm or more, or may be 9.0 N/20 mm or more. , 10.0/20 mm or more. High adhesion reliability is likely to be obtained as the normal state adhesive strength F0 increases. According to the technology disclosed herein, even if the surface protection sheet is attached to the adherend with high adhesive strength, when peeled off, an aqueous liquid is used to form a smooth surface without damaging or deforming the adherend. The protective sheet can be peeled off. Therefore, it is possible to set the adhesive force (normal state adhesive force F0) higher than that of the conventional surface protection sheet that obtains releasability by limiting the adhesive force. This means that sufficient protection can be ensured based on high adhesion reliability even when used in a harsher environment, which is practically useful. Since the upper limit of the normal state adhesive strength F0 is appropriately set according to the required adhesiveness, it is not limited to a specific range, and may be, for example, about 20 N/20 mm or less, or about 15 N/20 mm or less. , approximately 10 N/20 mm or less.

(Normal water peeling force FW0)
The normal water peeling force FW0 is preferably designed to be lower than the normal adhesive force F0. The normal water peeling force FW0 is, for example, suitably less than 3 N/20 mm, may be less than 1.5 N/20 mm, and may be approximately 1.0 N/20 mm or less. The pressure-sensitive adhesive layer of the surface protection sheet that satisfies the above-mentioned water peeling property can be easily peeled off by applying an aqueous liquid such as water to the adhesive interface with the adherend and allowing it to enter the interface. In some preferred embodiments, the normal water peeling force FW0 may be 0.7 N/20 mm or less, 0.5 N/20 mm or less, or 0.3 N/20 mm or less (for example, 0.1 N/20 mm or less). It's okay. The lower limit of the normal water peeling force FW0 is appropriately set so as to exhibit the desired water peeling property, and is not limited to a specific range. The lower limit of the normal water peeling force FW0 may be 0.0 N/20 mm, or 0.01 N/20 mm or more (for example, 0.1 N/20 mm or more).

(Adhesive strength F1 after immersion in hot water for 30 minutes)
In some embodiments, the surface protective sheet preferably has an adhesive strength F1 of 0.5 N/20 mm or more after being immersed in warm water for 30 minutes. A surface protection sheet that satisfies the above properties can protect an adherend (also referred to as an object to be treated) even when used in a manner in which the adherend is treated in a liquid while attached to it. The required adhesion can be retained. For example, even if it is used in a chemical solution (typically in the form of an aqueous solution) or in hot water, it does not exhibit a decrease in adhesive strength based on water removability, or the decrease in adhesive strength is suppressed, and the state of adhesion to the adherend can be maintained. Such a surface protective sheet can have excellent protective properties such that it does not peel off from the edges during the submerged treatment, for example. In some aspects, the adhesive strength F1 after immersion in warm water for 30 minutes is preferably 1.0 N/20 mm or more, more preferably 1.5 N/20 mm or more, and still more preferably 2.0 N/20 mm or more, and 2.5 N /20 mm or more, or 3.0 N/20 mm or more (for example, 3.5 N/20 mm or more). In some preferred embodiments, the adhesive strength F1 after immersion in hot water for 30 minutes is 4.0 N/20 mm or more, may be 5.0 N/20 mm or more, or is 6.0 N/20 mm or more (for example, 7.5 N/ 20 mm or more). The greater the adhesive strength F1 after immersion in hot water for 30 minutes, the easier it is to maintain a high protective function even when used in a mode in which treatment in a liquid such as a chemical solution or hot water is performed. The upper limit of the adhesive strength F1 after immersion in warm water for 30 minutes is appropriately set according to the required adhesiveness, so it is not limited to a specific range. It may be 20 mm or less, or approximately 5 N/20 mm or less.

Adhesive strength F1 after immersion in hot water for 30 minutes is measured by bonding the adhesive surface of the surface protection sheet to the surface of alkali glass having a water contact angle of 20 degrees or less, and immersing in hot water at 60°C ± 2°C for 30 minutes. Then, the peel strength [N/20 mm] is measured under the conditions of a temperature of 23° C., a peel angle of 180 degrees, and a speed of 300 mm/min after pulling up from the warm water and wiping off adhering water. More specifically, the adhesive strength F1 after immersion in hot water for 30 minutes is measured by the method described in Examples below.

(Water peeling force FW1 after immersion in hot water for 30 minutes)
In some embodiments, the water peel strength FW1 of the surface protective sheet after immersion in warm water for 30 minutes is not particularly limited, and for example, it is preferably designed to be lower than the peel strength F1 after immersion in warm water for 30 minutes. The water peeling force FW1 after immersion in hot water for 30 minutes is, for example, less than 1.0 N/20 mm, may be less than 0.5 N/20 mm, is suitably less than 0.4 N/20 mm, and is approximately 0. .3 N/20 mm or less is preferable. In some preferred embodiments, the water peeling force FW1 after immersion in hot water for 30 minutes may be 0.2 N/20 mm or less, 0.15 N/20 mm or less, or 0.10 N/20 mm or less. The surface protective sheet exhibiting the water peeling force FW1 after being immersed in hot water for 30 minutes can exhibit good water peeling properties even after being used for treatment in a liquid such as a chemical solution or hot water. The lower limit of the water peeling force FW1 after immersion in warm water for 30 minutes is appropriately set so as to exhibit the desired water peeling property, and is not limited to a specific range. The lower limit of the water peeling force FW1 after immersion in warm water for 30 minutes may be 0.0 N/20 mm, or 0.01 N/20 mm or more (for example, 0.05 N/20 mm or more).

After immersion in hot water for 30 minutes, the water peeling force FW1 was measured by attaching the adhesive surface of the surface protection sheet to the surface of alkali glass having a water contact angle of 20 degrees or less, and soaking in hot water at 60 ° C. ± 2 ° C. for 30 minutes. After immersing and wiping off adhering water from the hot water, 20 μL of distilled water is supplied between the alkali glass and the adhesion surface, and the distilled water is applied to the interface between the alkali glass and the adhesion surface. It is the water peel force [N/20 mm] measured under the conditions of a temperature of 23° C., a peel angle of 180 degrees, and a speed of 300 mm/min after entering one end. More specifically, the water peeling force FW1 after immersion in hot water for 30 minutes is measured by the method described in Examples below.

(Decrease in water peel strength after immersion in warm water for 30 minutes FW1/F1)
In some embodiments, the surface protective sheet has a water peel strength FW1 [N/20 mm] after immersion in hot water for 30 minutes, which is 50% or less of the adhesive strength F1 [N/20 mm] after immersion in hot water for 30 minutes. preferable. In other words, it is preferable that the surface protective sheet has a water peeling force decrease [%] after immersion in warm water for 30 minutes, represented by the formula: FW1/F1×100, of 50% or less. In this way, the surface protection sheet having the water peel strength FW1 after immersion in warm water for 30 minutes and reduced to 50% or less of the adhesive strength F1 after immersion in warm water for 30 minutes is in a state of being attached to the adherend, and the predetermined value is obtained as described above. After immersion in hot water for 30 minutes as described above, the adherend can be peeled without being damaged or deformed while maintaining adhesive strength. More specifically, the surface protective sheet can be easily peeled off from the adherend by using an aqueous liquid such as water. For example, a small amount of aqueous liquid is supplied between the adherend and the pressure-sensitive adhesive layer, and the water-based liquid enters the interface between the adherend and the pressure-sensitive adhesive layer to trigger peeling. The peel strength of the pressure-sensitive adhesive layer from the adherend can be significantly reduced. Using this property, the surface protective sheet can be peeled off without damaging or deforming the adherend by peeling using an aqueous liquid such as water. According to such a surface protection sheet, it is possible to have the adhesiveness necessary for protection, and even if the adherend is a thin and brittle material such as thin glass, the adherend will not be damaged during peeling. can be realized. In some embodiments, the degree of water peel strength reduction after immersion in hot water for 30 minutes is preferably 30% or less, more preferably 20% or less, even more preferably 10% or less, and particularly preferably 5% or less (e.g., 3% below). According to such a surface protective sheet that exhibits a decrease in water peeling force after immersion in warm water for 30 minutes, it is possible to achieve a better balance between adhesion reliability during protection and easy peelability during peeling. In some preferred embodiments, the degree of decrease in water peel strength after immersion in warm water for 30 minutes is 2% or less, may be 1.5% or less, or may be 1.0% or less. The lower limit of the degree of decrease in water peeling force after immersion in warm water for 30 minutes is theoretically 0%, and practically may be about 1% or more (for example, 2% or more).

In some embodiments, the surface protective sheet preferably has a water peeling force FW1 after immersion in hot water for 30 minutes that is equal to or smaller than the normal water peeling force FW0 described later. The surface protection sheet thus constructed does not show an increase in water peeling force due to aging even after being immersed in hot water for 30 minutes. Therefore, even if the surface protection sheet is exposed to temperatures higher than room temperature (e.g., about 40° C. or higher) during the protection period, for example, in liquid treatment such as chemical treatment, the surface protection sheet maintains the adhesive strength to the adherend. does not increase, or the increase in adhesive strength is suppressed, and when the surface protective sheet is peeled off, it is easy to achieve peeling without damaging the adherend due to the expected water peelability. The water peel strength FW1 after immersion in hot water for 30 minutes may be 90% or less, 70% or less, 50% or less, 30% or less, or 10% or less of the normal water peel strength FW0. The water peeling force FW1 after immersion in hot water for 30 minutes is not particularly limited, but may be 0% or more, 1% or more (for example, 3% or more), or 10% or more of the normal water peeling force FW0. , 30% or more, 50% or more, or 70% or more.

(Adhesive strength F2 after immersion in warm water for 1 hour)
In some embodiments, the surface protective sheet preferably has an adhesive strength F2 of 0.5 N/20 mm or more after being immersed in hot water for 1 hour. A surface protective sheet that satisfies the above properties can improve the adhesiveness required for protection even when used in a manner in which the adherend is treated in a liquid while attached to the adherend. can hold well. For example, even if it is used in a chemical solution (typically in the form of an aqueous solution) or in hot water, it is less likely to cause a decrease in adhesive strength due to water removability. . In some preferred embodiments, the adhesive strength F2 after immersion in hot water for 1 hour is 1.0 N/20 mm or more, may be 1.5 N/20 mm or more, may be 2.0 N/20 mm or more, or may be 2.5 N/20 mm or more. It may be 20 mm or more (for example, 3.0 N/20 mm or more). The greater the adhesive strength F2 after immersion in hot water for 1 hour, the easier it is to maintain an excellent protective function even when used in a mode in which treatment in a liquid such as a chemical solution or hot water is performed. The upper limit of the adhesive force F2 after immersion in hot water for 1 hour is appropriately set according to the required adhesiveness, so it is not limited to a specific range, and may be, for example, about 15 N/20 mm or less, or about 10 N/ It may be 20 mm or less, or approximately 5 N/20 mm or less.

Adhesive force F2 after immersion in hot water for 1 hour is measured by bonding the adhesive surface of the surface protection sheet to the surface of alkali glass having a water contact angle of 20 degrees or less, and immersing in hot water at 60°C ± 2°C for 1 hour. Then, the peel strength [N/20 mm] is measured under the conditions of a temperature of 23° C., a peel angle of 180 degrees, and a speed of 300 mm/min after pulling up from the warm water and wiping off adhering water. More specifically, the adhesive strength F2 after immersion in hot water for 1 hour is measured by the method described in Examples below.

(Water peeling force FW2 after immersion in hot water for 1 hour)
In some embodiments, the water peeling force FW2 of the surface protective sheet after immersion in warm water for 1 hour is not particularly limited, and is, for example, less than 0.5 N/20 mm, suitably less than 0.4 N/20 mm, It is preferably about 0.3 N/20 mm or less. In some preferred embodiments, the water peeling force FW2 after immersion in warm water for 1 hour may be 0.2 N/20 mm or less, 0.15 N/20 mm or less, or 0.10 N/20 mm or less. The surface protection sheet exhibiting the water peeling force FW2 after being immersed in hot water for 1 hour can exhibit good water peeling properties even after being used for treatment in a liquid such as a chemical solution or hot water. The lower limit of the water peeling force FW2 after immersion in hot water for 1 hour is appropriately set so as to exhibit the desired water peeling property, and is not limited to a specific range. The lower limit of the water peeling force FW2 after immersion in warm water for 30 minutes may be 0.0 N/20 mm, or 0.01 N/20 mm or more (for example, 0.03 N/20 mm or more).

After immersion in hot water for 1 hour, the water peeling force FW2 was measured by attaching the adhesive surface of the surface protection sheet to the surface of alkali glass having a water contact angle of 20 degrees or less, and immersing it in hot water at 60 ° C. ± 2 ° C. for 1 hour. After immersing and wiping off adhering water from the hot water, 20 μL of distilled water is supplied between the alkali glass and the adhesion surface, and the distilled water is applied to the interface between the alkali glass and the adhesion surface. It is a water peeling force [N/20 mm] measured under the conditions of a temperature of 23° C., a peeling angle of 180 degrees, and a speed of 300 mm/min after entering one end. More specifically, the water peeling force FW2 after immersion in hot water for 1 hour is measured by the method described in Examples below.

(Decrease in water peel strength after immersion in warm water for 1 hour FW2/F2)
In some embodiments, the surface protective sheet has a water peel strength FW2 [N/20 mm] after being immersed in warm water for 1 hour, which is 50% or less of the adhesive strength F2 [N/20 mm] after being immersed in warm water for 1 hour. is preferred. In other words, it is preferable that the surface protective sheet has a water peeling force decrease [%] after immersion in hot water for 1 hour, represented by the formula: FW2/F2×100, of 50% or less. In this way, the surface protection sheet having the water peeling force FW2 after immersion in warm water for 1 hour and reduced to 50% or less of the adhesive force F2 after immersion in warm water for 1 hour is in a state of being attached to the adherend, and the predetermined value is obtained as described above. After immersion in hot water for 1 hour, the adherend can be peeled without damage or deformation during peeling while maintaining the adhesive strength. More specifically, the surface protective sheet can be peeled off without damaging or deforming the adherend by using an aqueous liquid such as water for the peeling. In some preferred embodiments, the degree of reduction in water peel strength after immersion in warm water for 1 hour is preferably 30% or less, more preferably 20% or less, and even more preferably 10% or less (eg, 1% or less). According to the surface protection sheet that shows the degree of decrease in water peeling force after immersion in hot water for 1 hour, the adhesion reliability during protection even when used under more severe conditions such as long-term submerged treatment. and easy peelability at the time of peeling can be compatible. The lower limit of the degree of decrease in water peeling force after immersion in hot water for 1 hour is theoretically 0%, and practically may be about 1% or more (for example, 2% or more).

In some embodiments, the surface protective sheet preferably has a water peeling force FW2 after being immersed in hot water for 1 hour that is equal to or smaller than the normal water peeling force FW0 described later. The surface protective sheet thus constructed does not show an increase in water peeling force due to aging even after being immersed in hot water for 1 hour. Therefore, even if it is exposed to temperatures higher than room temperature (for example, about 40° C. or higher) for a long time during the protection period, for example, in liquid treatment such as chemical treatment, the surface protection sheet does not affect the adherend. The adhesive strength does not increase or the increase in adhesive strength is suppressed, and when the surface protective sheet is peeled off, it is easy to achieve peeling without damaging the adherend due to the expected water peelability. The water peel strength FW2 after immersion in hot water for 1 hour may be 70% or less, 50% or less, 30% or less, or 10% or less of the normal water peel strength FW0. The water peeling force FW2 after immersion in hot water for 1 hour is not particularly limited, but may be 0% or more of the normal water peeling force FW0, or may be 1% or more.

(Underwater trigger peel force)
Although not particularly limited, in some embodiments, the surface protective sheet is measured under the conditions of a peel angle of 20 degrees and a tensile speed of 1000 mm / min in water at room temperature (23 to 25 ° C.). It is preferable that the peel force is 0.2 N/10 mm or more. A surface protection sheet satisfying this property tends to be excellent in the edge peeling prevention property. In processes such as transportation, external forces such as vibrations that can cause edge peeling of the surface protective sheet are considered to be high-speed peeling loads applied at a relatively shallow angle to the adherend. The surface protective sheet exhibiting a peel force of 0.2 N/10 mm or more under the conditions of a peel angle of 20 degrees and a peel speed of 1000 mm/min. Even when external force such as vibration is applied in the process of treating the adherend with the protective sheet attached to the adherend in a liquid such as a chemical solution or water, it is excellent against the external force. It is possible to exhibit the end peeling prevention property. From the viewpoint of improving the edge peeling prevention property, the above-mentioned peel force triggered in water is more preferably 0.3 N/10 mm or more, still more preferably 0.5 N/10 mm or more, and particularly preferably 0.6 N/10 mm or more (for example, 0.6 N/10 mm or more). 7 N/10 mm or more). The upper limit of the trigger peel force in water is not particularly limited, and is, for example, 3 N/10 mm or less, and may be 2 N/10 mm or less (eg, 1 N/10 mm or less). The underwater triggered peel force can be preferably realized mainly by setting the 25° C. bending rigidity value of the surface protective sheet within a predetermined range. In addition, the above water triggered peel strength can be improved also by the composition of the pressure-sensitive adhesive (for example, the use and amount of the tackifier, selection of the type, etc.). More specifically, the trigger peel force in water is measured by the method described in Examples below.

(20 degree trigger peel strength)
In some preferred embodiments, the surface protective sheet is formed by attaching an adhesive surface of the surface protective sheet to an alkali glass surface having a water contact angle of 20 degrees or less, and exposing the surface protective sheet to an environment of 23°C and 50% RH. After holding for 24 hours, 20 μL of distilled water was dropped between the alkali glass and the adhesive surface, and the trigger peel force measured under the conditions of 23° C., 20 degree peel angle and 1000 mm/min speed was 0.00. It is 5 N/10 mm or more. A surface protective sheet that satisfies the above characteristics is subject to external forces acting in the thickness direction of the surface protective sheet, such as vibration during transportation and physical loads during physical processing, which can cause peeling at the edges of the surface protective sheet. Even when a physical load (also referred to as a peeling load) is applied, peeling from the edge is unlikely to occur. Such edge delamination resistance can be exerted against the physical loads described above regardless of the presence or absence of water. From the viewpoint of improving the edge peeling prevention property, the trigger peel force is more preferably 0.6 N/10 mm or more, still more preferably 0.7 N/10 mm or more, and particularly preferably 0.8 N/10 mm or more (for example, 0.9 N /10 mm or more). The upper limit of the trigger peeling force is not particularly limited, and is, for example, 3 N/10 mm or less, and may be 2 N/10 mm or less (eg, 1 N/10 mm or less). The trigger release force can be achieved based on the adhesive composition (use of tackifier, selection of tackifier species, type and amount of hydrophilic agent, etc.). It can also be adjusted by setting the mechanical properties (for example, 25° C. bending rigidity value) of the surface protective sheet within a predetermined range. More specifically, the trigger peel strength is measured by the method described in Examples below.

(moisture permeability)
In some embodiments, the surface protective sheet preferably has a moisture permeability of 24 g/(m ² ·day) or less as measured by the cup method. With such a structure having a limited moisture permeability, even if the surface protection sheet comes into contact with an aqueous liquid, such as being put into a liquid while attached to an adherend, Aqueous liquid hardly permeates into the adhesion interface with the adherend, and the decrease in adhesive strength due to water releasability does not occur, or the decrease in adhesive strength is suppressed. As a result, the adhesive force to the adherend is maintained, and the surface protective sheet can maintain the state of close contact with the adherend. Such a surface protective sheet can be one that does not peel off from the edges during, for example, submerged treatment such as chemical treatment. In some preferred embodiments, the moisture permeability of the surface protective sheet is about 20 g/(m ² ·day) or less, more preferably about 16 g/(m ² ·day) or less, still more preferably about 12 g/( m ² ·day) or less, particularly preferably approximately 8 g/(m ² ·day) or less, may be approximately 5 g/(m ² ·day) or less, for example approximately 3 g/(m ² ·day) or less It's okay. Further, when the surface protective sheet is exposed to heat such as hot water, if the moisture permeability is excessively low, the water removability may not be effectively exhibited due to aging due to the heating. From such a viewpoint, in some embodiments, the moisture permeability of the surface protective sheet is suitably 1 g/(m ² ·day) or more, preferably about 3 g/(m ² ·day) or more. Yes, more preferably greater than 5 g/(m ² ·day), for example greater than 6 g/(m ² ·day).

More specifically, the moisture permeability of the surface protection sheet is, for example, 23 g/(m ² ·day) or more or less, 22 g/(m ² ·day) or more or less, or 21 g/(m ² ·day) or more. or less, 20 g/(m ² ·day) or more or less, 19 g/(m ² ·day) or more or less, 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 or less, 15 g/(m ² ·day) or more or less, 14 g/(m ² ·day) or more or less, 13 g/(m ² ·day) or more or 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) or more or less.

The above moisture permeability of the surface protective sheet can be obtained by selecting and using an appropriate non-moisture permeable or low moisture permeable material (typically the base material). More specifically, the moisture permeability of the surface protection sheet is measured by the method described in Examples below.

(25°C bending stiffness value)
In some embodiments, the surface protection sheet has a bending rigidity value D at 25°C (25°C bending rigidity value D) within the range of 1.0 × 10 ^-6 to 1.0 × 10 ^-2 Pa·m ³ Preferably. A surface protection sheet that satisfies this property is a process in which the adherend is treated in a liquid such as a chemical solution or water in a state where the surface protection sheet is attached to the adherend, and when an external force such as vibration is applied, However, peeling from the end portion is less likely to occur against the external force. Specifically, the surface protective sheet is given a certain range of rigidity (flexural rigidity at 25°C) to increase the stress (peel stress) against external forces such as vibrations that can cause peeling of the edge of the surface protective sheet in the above process. Thus, even when an external force such as vibration is applied during the above process, it is possible to prevent edge peeling and reduce the risk of edge peeling. By setting the 25° C. flexural rigidity value D to a predetermined value (for example, 10 ⁻² Pa·m ³ ) or less, the surface protective sheet has rigidity suitable for surface protection applications, and exhibits good peeling workability. Easy to handle. The surface followability of the adherend also tends to improve.

The 25° C. bending stiffness value D may be 5.0×10 ⁻⁶ Pa·m 3 or more, preferably 1.0×10 ⁻⁵ Pa·m ³ ^or more, from the viewpoint of edge peeling prevention. , more preferably 5.0×10 ⁻⁵ Pa·m ³ or more, still more preferably 1.0×10 ⁻⁴ Pa·m ³ or more, and may be 3.0×10 ⁻⁴ Pa·m ³ or more. The 25° C. flexural rigidity value D is preferably 5.0×10 ⁻³ Pa·m ³ or less, more preferably 1.0×10 ⁻ It is ³ Pa·m ³ or less, more preferably 5.0×10 ⁻⁴ Pa·m ³ or less, and may be 1.0×10 ⁻⁵ Pa·m ³ or less. A low 25° C. bending stiffness value D within a predetermined range is advantageous in terms of improving the surface followability of the adherend.

The 25° C. flexural rigidity value D [Pa·m ³ ] is obtained by setting the thickness of the base material layer to h [m] and the Poisson's ratio of the base material to ν, and the tensile modulus of elasticity of the surface protection sheet at a temperature of 25° C. (25 ℃ tensile modulus) is E [Pa], the formula:
D=Eh ³ /12(1−ν ² );
It is a value obtained by Since the bending rigidity value of the pressure-sensitive adhesive layer is much smaller than the bending rigidity value of the base material layer, the bending rigidity of the surface protection sheet may depend on the bending rigidity of the base material layer. Therefore, in the present specification, the flexural rigidity value D of the surface protective sheet refers to a value converted per cross-sectional area of the base layer constituting the surface protective sheet. The cross-sectional area of the substrate layer is calculated based on the thickness of the substrate layer. The thickness h of the base material layer is a value obtained by subtracting the thickness of the pressure-sensitive adhesive layer from the measured thickness of the surface protection sheet. The Poisson's ratio ν is a value (dimensionless number) determined by the material of the substrate layer, and when the material is a resin, 0.35 can usually be adopted as the value of ν.
The 25° C. flexural rigidity value D [Pa·m ³ ] is obtained by substituting the 25° C. tensile modulus E [Pa] and the substrate thickness h [m] obtained from the tensile test described in Examples below into the above formula. is obtained by The 25° C. bending rigidity value may be a 25° C. bending rigidity value in the longitudinal direction (MD: Machine Direction), or a 25° C. bending rigidity value in the width direction (TD: a direction orthogonal to the Transverse Direction MD), Therefore, it may be at least one of the 25 ° C. bending stiffness value of MD and the 25 ° C. bending stiffness value of TD, or any arbitrary regardless of whether it is MD or TD It may be a 25° bending stiffness value in one direction.
The 25° C. bending rigidity value D 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.

(25°C tensile modulus)
Although not particularly limited, in some aspects, the 25° C. tensile modulus of the surface protection sheet may be 100 MPa or more, or 500 MPa or more. In some preferred embodiments, the 25° C. tensile modulus is 1000 MPa or higher, more preferably 3000 MPa or higher, even more preferably 5000 MPa or higher, and may be 6000 MPa or higher. The higher the 25°C tensile modulus, the higher the 25°C bending stiffness value. The upper limit of the 25° C. tensile modulus is not particularly limited, and may be, for example, 30 GPa or less, 15 GPa or less, 10 GPa or less, 8000 MPa or less, 6000 MPa or less, or 4500 MPa or less. The lower the 25° C. tensile modulus, the lower the 25° C. bending stiffness value. In addition, the surface protective sheet having a tensile modulus of elasticity at 25°C within the above range tends to have good peeling workability, handleability and surface followability.

(Stress at 100% elongation at 25°C)
Although not particularly limited, in some embodiments, the stress at 100% elongation at 25° C. of the surface protective sheet may be 10 N/mm ² or more, preferably 30 N/mm ² or more. is 50 N/mm ² or more, more preferably 80 N/mm ² or more, and may be 120 N/mm ² or more. As the stress at 100% elongation increases, the surface protective sheet tends to have a predetermined rigidity or higher, and tends to be more likely to prevent edge peeling. The upper limit of the stress at 100% elongation is, for example, 300 N/mm ² or less, may be 200 N/mm ² or less, or may be 100 N/mm ² or less. A surface protective sheet having a stress at 100% elongation within the above range tends to exhibit good peeling workability, handleability and surface followability.

(25°C breaking stress)
Although not particularly limited, in some aspects, the breaking stress of the surface protective sheet at 25°C may be 10 N/mm ² or more, or 30 N/mm ² or more (for example, 50 N/mm ² or more). suitable, preferably 100 N/mm ² or more, more preferably 120 N/mm ² or more, and may be 150 N/mm ² or more. As the breaking stress increases, the surface protective sheet tends to have a predetermined rigidity or higher, and tends to be more likely to prevent peeling at the edges. The upper limit of the breaking stress is, for example, 500 N/mm ² or less, may be 300 N/mm ² or less, may be 200 N/mm ² or less, or may be 150 N/mm ² or less. A surface protective sheet having a breaking stress within the above range tends to exhibit good peeling workability, handleability, and surface followability.

(25°C breaking strain)
Although not particularly limited, in some aspects, the breaking strain of the surface protective sheet at 25°C may be 500% or less, suitably less than 300%, preferably 250% or less, It may be 200% or less. The smaller the breaking strain, the easier it is for the surface protective sheet to have a predetermined rigidity or more, and the easier it is for the end peeling prevention properties to be obtained. The lower limit of the breaking strain is, for example, 120% or more, may be 150% or more, or may be 200% or more. A surface protective sheet having a breaking strain within the above range tends to exhibit good peeling workability, handleability and surface followability.

The 25° C. tensile modulus is obtained from linear regression of a stress-strain curve obtained from a tensile test described in the Examples below. In addition, the stress at 100% elongation [N/mm ² ], breaking stress [N/mm ² ] and breaking strain [%] can also be measured by the tensile test described in Examples below. The mechanical property values (tensile modulus, stress at 100% elongation, breaking stress and breaking strain) of the pressure-sensitive adhesive layer are much smaller than those of the base material layer, and the above mechanical properties of the surface protective sheet are the same as those of the base layer. It can depend on the mechanical properties of the material layer. Therefore, in this specification, the tensile modulus, stress at 100% elongation and breaking stress of the surface protective sheet refer to values converted per cross-sectional area of the substrate layer constituting the surface protective sheet. The cross-sectional area of the substrate layer is calculated based on the thickness of the substrate layer. Let the thickness of a base material layer be the value which deducted the thickness of an adhesive layer from the measured value of the thickness of a surface protection sheet. The 25° C. tensile modulus may be the 25° C. tensile modulus in MD or the 25° C. tensile modulus in TD. It may be the 25° C. tensile modulus of at least one of the moduli, or the 25° C. tensile modulus in any one direction, whether MD or TD. Similarly, the stress at 100% elongation, stress at break and strain at break may each be a measured value of MD (stress at 100% elongation, stress at break or strain at break), or may be a measured value of TD. and thus may be a measurement in MD and/or a measurement in TD, or any one-way measurement, whether MD or TD. .

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

<Adhesive layer>
The surface protective sheet disclosed here typically comprises an adhesive layer. The adhesive layer includes, for example, acrylic adhesives, rubber adhesives (natural rubber, synthetic rubber, mixtures thereof, etc.), silicone adhesives, polyester adhesives, urethane adhesives, polyether It may be a pressure-sensitive adhesive layer containing one or more pressure-sensitive adhesives selected from various pressure-sensitive adhesives such as poly-based pressure-sensitive adhesives, polyamide-based pressure-sensitive adhesives, fluorine-based pressure-sensitive adhesives, and the like. The adhesive layer includes acrylic polymer, rubber polymer (natural rubber, synthetic rubber, mixture thereof, etc.), silicone polymer, polyester polymer, urethane polymer, polyether polymer, polyamide polymer, fluorine polymer. As a base polymer, one or more of various rubber-like polymers such as From the viewpoint of adhesive performance, cost, etc., a pressure-sensitive adhesive containing an acrylic polymer or a rubber-based polymer as a base polymer can be preferably employed. Among them, a pressure-sensitive adhesive having an acrylic polymer as a base polymer (acrylic pressure-sensitive adhesive) is preferable. The technique disclosed here is preferably implemented in a mode using an acrylic pressure-sensitive adhesive.

In this specification, the "base polymer" of the adhesive refers to the main component of the rubber-like polymer contained in the adhesive, and can also be used to mean the structural polymer that forms the adhesive. The term "rubber-like polymer" refers to a polymer that exhibits rubber elasticity in a temperature range around room temperature. In this specification, the term "main component" refers to a component contained in an amount exceeding 50% by weight unless otherwise specified.

As used herein, 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 one (meth)acryloyl group in one molecule. Moreover, in this specification, "(meth)acryloyl" is meant to comprehensively refer to acryloyl and methacryloyl. Similarly, "(meth)acrylate" is a generic term for acrylate and methacrylate, and "(meth)acrylic" is generic for acrylic and methacrylic. 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 water-dispersed or solvent-based pressure-sensitive adhesives. In this case, the "monomer component constituting the acrylic polymer" in this specification can be rephrased as "the monomer component constituting the acrylic polymer". In addition, in the present specification, the content of the additive component represented by the relative amount of the "monomer component constituting the polymer" or the "monomer component constituting the acrylic polymer" is relative to the "acrylic polymer". It can be rephrased as quantity.

(Acrylic adhesive)
From the viewpoint of weather resistance and the like, in some embodiments, an acrylic pressure-sensitive adhesive containing an acrylic polymer as a base polymer can be preferably used as a constituent material of the pressure-sensitive adhesive layer.

As the acrylic pressure-sensitive adhesive, for example, it is 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. A material containing an acrylic polymer is preferable. Hereinafter, a (meth)acrylic acid alkyl ester having an alkyl group having X or more and Y or less carbon atoms at the ester end may be referred to as "(meth)acrylic acid _CXY alkyl ester". The (meth)acrylic acid alkyl ester having a chain (linear or branched) alkyl group may be used alone or in combination of two or more.

In some embodiments, the proportion of the (meth)acrylic acid C _1-20 alkyl ester in the total monomer components may be, for example, 40% by weight or more, or even 45% by weight or more, because it facilitates balancing properties. It may be 50% by weight or more (for example, 55% by weight or more). For the same reason, the proportion of the (meth)acrylic acid C _1-20 alkyl ester in the monomer component may be, for example, 90% by weight or less, may be 70% by weight or less, or may be 65% by weight or less (for example, 55% by weight). below). In some other embodiments, the proportion of the (meth)acrylic acid C _1-20 alkyl ester in the total monomer components may be, for example, 70% by weight or more, and 80% by weight, because it facilitates balancing properties. or more, or 90% by weight or more. For the same reason, the proportion of the (meth)acrylic acid C _1-20 alkyl ester in the monomer component may be, for example, 99.9% by weight or less, 99.5% by weight or less, or 99% by weight or less. good.

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

Among these, it is preferable to use at least (meth)acrylic acid C _4-20 alkyl ester, and it is more preferable to use at least (meth)acrylic acid C _4-18 alkyl ester. For example, an acrylic pressure-sensitive adhesive containing one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) as the monomer component is preferred, and an acrylic pressure-sensitive adhesive containing at least BA is particularly preferred. Other examples of (meth)acrylic acid C _4-20 alkyl esters that can be preferably used include isononyl acrylate, n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate (2EHMA), isostearyl acrylate (iSTA ) and the like.

In some aspects, the monomer component constituting the acrylic polymer may contain the (meth)acrylic acid C _4-18 alkyl ester in a proportion of 40% by weight or more. Thus, a monomer component containing a relatively large amount of (meth)acrylic acid alkyl ester having an alkyl group of 4 or more carbon atoms at the ester end tends to form a highly lipophilic acrylic polymer. A highly lipophilic acrylic polymer tends to form a pressure-sensitive adhesive layer whose adhesive strength does not easily decrease even when immersed in water such as warm water. The proportion of the (meth)acrylic acid C _4-18 alkyl ester in the monomer component may be, for example, 60% by weight or more, 70% by weight or more, 75% by weight or more, or 80% by weight or more. A monomer component containing a (meth)acrylic acid C _6-18 alkyl ester in a ratio equal to or higher than any of the above lower limits may be used.
In addition, from the viewpoint of increasing the cohesiveness of the pressure-sensitive adhesive layer and preventing cohesive failure, the proportion of the (meth)acrylic acid _C4-18 alkyl ester in the monomer component is preferably 99.5% by weight or less. Yes, it 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 pressure-sensitive adhesive layer, in some embodiments, the proportion of the (meth)acrylic acid _C4-18 alkyl ester in the monomer component is 95% by weight or less, for example, 90% by weight or less is suitable. is. In some other embodiments, the proportion of the (meth)acrylic acid C _4-18 alkyl ester in the monomer component may be 85% by weight or less, or 75% by weight or less. It may be a monomer component containing a (meth)acrylic acid C _6-18 alkyl ester in a proportion not higher than any of the above upper limits.

In some embodiments, monomer components in which the proportion of (meth)acrylic acid C _1-4 alkyl ester (preferably BA) in the (meth)acrylic acid alkyl ester having a chain alkyl group exceeds 50% by weight A formed acrylic polymer is preferably used. According to such an acrylic polymer, it is easy to obtain a pressure-sensitive adhesive having adhesive strength and cohesive strength suitable for surface protection applications. (Meth)acrylic acid C _1-4 alkyl esters may be used alone or in combination of two or more. The ratio of the (meth)acrylic acid C _1-4 alkyl ester in the (meth)acrylic acid alkyl ester having a chain alkyl group is preferably 70% by weight or more, more preferably 85% by weight or more, for example It may be 90% by weight or more. The upper limit of the ratio of the (meth)acrylic acid C _1-4 alkyl ester to the (meth)acrylic acid alkyl ester having a chain alkyl group is 100% by weight, and may be 99% by weight or less. It may be less than weight percent.

In some preferred embodiments, the proportion of the (meth)acrylic acid C _2-4 alkyl ester in the (meth)acrylic acid alkyl ester having a chain alkyl group is more than 50% by weight (for example, 70% by weight or more, or 85% by weight or more, or 90% by weight or more). Specific examples of (meth)acrylic acid C _2-4 alkyl esters include ethyl acrylate, propyl acrylate, isopropyl acrylate, BA, isobutyl acrylate, s-butyl acrylate and t-butyl acrylate. (Meth)acrylic acid C _2-4 alkyl esters may be used alone or in combination of two or more. By using an acrylic polymer having such a monomer composition, a surface protective sheet having good adhesion to an adherend can be easily realized. Among them, as a preferred embodiment, the ratio of BA in the (meth)acrylic acid alkyl ester having a chain alkyl group is more than 50% by weight (for example, 70% by weight or more, or 85% by weight or more, or 90% by weight or more ). The ratio of the (meth)acrylic acid C _2-4 alkyl ester to the (meth)acrylic acid alkyl ester having a chain alkyl group is 100% by weight, and may be 99% by weight or less, for example 97% by weight. may be less than

In some preferred embodiments, acrylic acid formed from monomer components in which the proportion of (meth)acrylic acid C _7-12 alkyl ester in the (meth)acrylic acid alkyl ester having a chain alkyl group exceeds 30% by weight A polymer is preferably used. According to such an acrylic polymer, it is easy to realize a surface protective sheet having good adhesion to an adherend. The (meth)acrylic acid C _7-12 alkyl ester is preferably a (meth)acrylic acid C _8-9 alkyl ester, more preferably an acrylic acid C _8-9 alkyl ester, and particularly preferably 2EHA. (Meth)acrylic acid C _7-12 alkyl esters may be used alone or in combination of two or more. The ratio of the (meth)acrylic acid _C7-12 alkyl ester (preferably 2EHA) in the (meth)acrylic acid alkyl ester having a chain alkyl group may be 40% by weight or more, and 50% by weight or more may be Suitable, preferably 70% by weight or more, may be 85% by weight or more, for example 90% by weight or more, or may be 95% by weight or more. The upper limit of the ratio of the (meth)acrylic acid C _7-12 alkyl ester to the (meth)acrylic acid alkyl ester having the chain alkyl group is 100% by weight, and may be 99% by weight or less, for example, 97% by weight. It may be less than weight percent.

In some preferred embodiments, the monomer component contains one or more methacrylic acid alkyl esters as (meth)acrylic acid alkyl esters. By using a methacrylic acid alkyl ester, an acrylic polymer suitable for surface protection can be preferably designed. As the methacrylic acid alkyl ester, methacrylic acid C _1-10 alkyl ester is preferable, and methacrylic acid C _1-4 (more preferably C _2-4 ) alkyl ester is more preferable. The methacrylic acid alkyl ester may preferably be used in combination with an acrylic acid alkyl ester. When a methacrylic acid alkyl ester and an acrylic acid alkyl ester are used in combination, the weight _CAM of one or more methacrylic acid alkyl esters (for example, methacrylic acid C _2-4 alkyl esters) and one or more of The ratio of acrylic acid alkyl ester to weight C _AA (C _AM :C _AA ) is not particularly limited, and in some embodiments is usually about 1:9 to 9:1, about 2:8 to 8: 2, preferably about 3:7 to 7:3, more preferably about 4:6 to 6:4. In some other embodiments, the weight of methacrylic acid alkyl ester (e.g., methacrylic acid _C1 alkyl ester, i.e., methyl methacrylate (MMA)) in the total amount of (meth)acrylic acid alkyl esters (C _AM +C _AA ) by weight _CAM is usually about 30% by weight or less, about 10% by weight or less, may be about 5% by weight or less, and more preferably about 3% by weight or less. On the other hand, the lower limit may be generally about 0.1% by weight or more, and may be about 0.5% by weight or more.

The monomer component that constitutes the acrylic polymer contains the (meth)acrylic acid alkyl ester and, if necessary, other monomers (copolymerizable monomers) that can be copolymerized with the (meth)acrylic acid alkyl ester. good too. As a copolymerizable monomer, a monomer having a polar group (for example, a carboxy group, a hydroxyl group, a nitrogen atom-containing ring, etc.) can be preferably used. A monomer having a polar group can be useful for introducing a cross-linking point into the acrylic polymer or increasing the cohesive strength of the pressure-sensitive adhesive. The copolymerizable monomers may be used singly or in combination of two or more.

Specific non-limiting examples of copolymerizable monomers include the following.
Carboxy 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.
Acid anhydride group-containing monomers: for example maleic anhydride, itaconic anhydride.
Hydroxyl group-containing monomers: for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, (meth)acrylic 4-hydroxybutyl acid, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxy hydroxyalkyl (meth)acrylates such as methylcyclohexyl)methyl (meth)acrylate;
Monomers containing sulfonic or phosphoric acid groups: for example, styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfo propyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, 2-hydroxyethyl acryloyl phosphate and the like.
Epoxy group-containing monomers: For example, epoxy group-containing acrylates such as glycidyl (meth)acrylate and 2-ethylglycidyl (meth)acrylate, allyl glycidyl ether, glycidyl ether (meth)acrylate, and the like.
Cyano group-containing monomers: for example acrylonitrile, methacrylonitrile and the like.
Isocyanate group-containing monomers: for example, 2-isocyanatoethyl (meth)acrylate and the like.
Amido group-containing monomers: for example, (meth)acrylamide; N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth) N,N-dialkyl(meth)acrylamides such as acrylamide, N,N-di(n-butyl)(meth)acrylamide, N,N-di(t-butyl)(meth)acrylamide; N-ethyl(meth) N-alkyl (meth)acrylamides such as acrylamide, N-isopropyl (meth)acrylamide, N-butyl (meth)acrylamide, Nn-butyl (meth)acrylamide; N-vinylcarboxylic acid amides such as N-vinylacetamide genus; monomers having a hydroxyl group and an amide group, such as 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) ( N-hydroxyalkyl (meth)acrylamides such as meth)acrylamide; monomers having an alkoxy group and an amide group, such as N-methoxymethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, N-butoxymethyl ( N-alkoxyalkyl(meth)acrylamides such as meth)acrylamide; N,N-dimethylaminopropyl(meth)acrylamide, N-(meth)acryloylmorpholine and the like.
Amino group-containing monomers: for example aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate.
Monomers with epoxy groups: eg glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, allyl glycidyl ether.
Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N- Vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3 -morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinyl thiazole, N-vinylisothiazole, N-vinylpyridazine and the like (for example, lactams such as N-vinyl-2-caprolactam);
Monomers having a succinimide skeleton: for example, N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, N-(meth)acryloyl-8-oxyhexamethylenesuccinimide and the like.
Maleimides: For example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide and the like.
Itaconimides: for example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-lauryl itaconimide and the like.
Aminoalkyl (meth)acrylates: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, t (meth)acrylate - butylaminoethyl.
Alkoxy group-containing monomers: for example, 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, (meth)acrylic acid Alkoxyalkyl (meth)acrylates such as butoxyethyl and ethoxypropyl (meth)acrylate; Alkoxyalkylene glycol (meth)acrylates such as methoxyethylene glycol (meth)acrylate and methoxypolypropylene glycol (meth)acrylate. kind.
Alkoxysilyl group-containing monomers: for example, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acrylic Roxypropylmethyldiethoxysilane.
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 compounds: for example, styrene, α-methylstyrene, vinyltoluene and the like.
Olefins: For example, ethylene, butadiene, isoprene, isobutylene and the like.
(Meth)acrylic acid esters having an alicyclic hydrocarbon group: for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, etc. .
(Meth)acrylic acid esters having an aromatic hydrocarbon group: for example, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate and the like.
In addition, heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride and fluorine atom-containing (meth)acrylates, and silicon atom-containing such as silicone (meth)acrylates (meth)acrylates, (meth)acrylic acid esters obtained from terpene compound derivative alcohols, and the like.

When using such a copolymerizable monomer, the amount used is not particularly limited, but it is appropriate to use 0.01% by weight or more of the total monomer components. From the viewpoint of better exhibiting the effect of using the copolymerizable monomer, 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 total monomer components. Moreover, from the viewpoint of easily balancing adhesive properties, the amount of the copolymerizable monomer to be used is suitably 50% by weight or less, preferably 40% by weight or less, of the total monomer components.

In some aspects, the monomer component that constitutes the acrylic polymer may include a nitrogen atom-containing monomer. By using a monomer having a nitrogen atom, the cohesive strength of the pressure-sensitive adhesive can be increased, and the adhesive strength can be preferably improved. A monomer having a nitrogen atom can be used alone or in combination of two or more. A suitable example of the nitrogen atom-containing monomer is a nitrogen atom-containing ring monomer. As the monomer having a nitrogen atom-containing ring, those exemplified above can be used. For example, general formula (1):

N-vinyl cyclic amides represented by can be used. Here, in general formula (1), R ¹ is a divalent organic group, specifically -(CH ₂ ) _n -. n is an integer from 2 to 7 (preferably 2, 3 or 4). Among them, N-vinyl-2-pyrrolidone can be preferably employed. Another suitable example of a monomer having a nitrogen atom is (meth)acrylamide.

The amount of the nitrogen atom-containing monomer (preferably a nitrogen atom-containing ring-containing monomer) is not particularly limited, and may be, for example, 1% by weight or more, or 3% by weight or more of the total monomer components. Furthermore, it can be 5% by weight or more, or 7% by weight or more. In some aspects, the amount of the nitrogen atom-containing monomer used may be 10% by weight or more, 12% by weight or more, or 15% by weight of the total monomer components, from the viewpoint of improving adhesive strength. or more, or 20% by weight or more. In addition, the amount of the monomer having a nitrogen atom used is, for example, 40% by weight or less of the entire monomer component, and may be 35% by weight or less, 30% by weight or less, or 25% by weight or less. good too. In some other embodiments, the amount of the nitrogen atom-containing monomer used may be, for example, 20% by weight or less, or 15% by weight or less, of the total monomer components. In some other embodiments, the amount of the nitrogen atom-containing monomer used may be, for example, 12% by weight or less, 8% by weight or less, or 4% by weight or less of the total monomer component.

In some embodiments, the monomer component includes a carboxy group-containing monomer. Suitable examples of carboxy group-containing monomers include acrylic acid (AA) and methacrylic acid (MAA). AA and MAA may be used in combination. When AA and MAA are used together, their weight ratio (AA/MAA) is not particularly limited, and can be in the range of about 0.1-10, for example. In some embodiments, the weight ratio (AA/MAA) may be, for example, approximately 0.3 or greater, or approximately 0.5 or greater. Also, 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, the surface of the adhesive layer can be quickly blended with an aqueous liquid such as water. This can help reduce the water release force. The amount of the carboxy group-containing monomer used may be, for example, 0.05% by weight or more, 0.1% by weight or more, 0.3% by weight or more, or 0.5% by weight or more of the total monomer components. 0.8% by weight or more, 1.2% by weight or more, or 1.5% by weight or more. By using a predetermined amount or more of the carboxy group-containing monomer, the cohesive force and crosslink density of the pressure-sensitive adhesive layer can be increased. The proportion of the carboxy 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, or 3.5% by weight or less. , 3.0% by weight or less, or 2.5% by weight or less. It is preferable that the amount of the carboxyl group-containing monomer is not too large, from the viewpoint of suppressing the diffusion of water into the bulk of the pressure-sensitive adhesive layer and suppressing the decrease in adhesive strength when the adhesive layer comes into contact with an aqueous liquid such as immersion in warm water. In addition, the fact that the amount of the carboxyl group-containing monomer used is not too large is also advantageous from the viewpoint of preventing the water used for measuring the water peeling force from being absorbed by the adhesive layer and the water being insufficient during peeling. . The technology disclosed herein can also be preferably practiced in a mode in which the monomer component does not substantially contain a carboxy group-containing monomer. From this point of view, the proportion of the carboxy group-containing monomer in the monomer component may be, for example, less than 1% by weight, less than 0.3% by weight, or less than 0.1% by weight.

In some embodiments, the monomer component may contain hydroxyl group-containing monomers. By using a hydroxyl group-containing monomer, it is possible to adjust the cohesive force and crosslink density of the pressure-sensitive adhesive and improve the adhesive force. As the hydroxyl group-containing monomer, those exemplified above can be used, and for example, 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) can be preferably used. A hydroxyl-containing monomer can be used individually by 1 type or in combination of 2 or more types.

The amount used when using a hydroxyl group-containing monomer 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 total monomer components. 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 total monomer components. There may be. In some other embodiments, the amount of the hydroxyl group-containing monomer used may be 15% by weight or more, 20% by weight or more, or 25% by weight or more of the total monomer components. Further, from the viewpoint of suppressing the water absorption of the pressure-sensitive adhesive layer, in some embodiments, the amount of the hydroxyl group-containing monomer used is, for example, 40% by weight or less of the total monomer components, and 30% by weight or less. 20% by weight or less, 15% by weight or less, 10% by weight or less, 5% by weight or less, or 3% by weight or less. The technology disclosed herein can also be practiced in a mode in which the hydroxyl group-containing monomer is not substantially used as the monomer component of the pressure-sensitive adhesive layer.

In some preferred embodiments, the monomer component of the acrylic polymer includes a monomer having a nitrogen atom (e.g., an amide group-containing monomer such as (meth)acrylamide, NVP, etc.) as a monomer having a polar group (polar group-containing monomer). (a monomer having a nitrogen atom-containing ring) and a hydroxyl group-containing monomer (eg, HEA, 4HBA) are used in combination. This can effectively improve the adhesive strength. In an embodiment in which a nitrogen atom-containing monomer and a hydroxyl group-containing monomer are used in combination, the weight ratio (A _N /A _OH ) of the amount of the nitrogen atom-containing monomer, A _N , and the amount of the hydroxyl group-containing monomer, A _OH , is not particularly limited, For example, it may be 0.1 or more, 0.5 or more, 0.8 or more, 1.0 or more, or 1.2 or more. Further, the weight ratio (A _N /A _OH ) may be, for example, 10 or less, 5 or less, 3 or less, or 1.5 or less.

In some embodiments, the monomer component can include an alkoxysilyl group-containing monomer. The alkoxysilyl group-containing monomer is typically an ethylenically unsaturated monomer having at least one (preferably two or more, for example two or three) alkoxysilyl groups in one molecule. Specific examples are described above. The alkoxysilyl group-containing monomers may be used singly or in combination of two or more. By using an alkoxysilyl group-containing monomer, a crosslinked structure can be introduced into the pressure-sensitive adhesive layer by condensation reaction of silanol groups (silanol condensation). In addition, the alkoxysilyl group-containing monomer can also be grasped as a silane coupling agent, which will be described later.

In an aspect in which the monomer component contains an alkoxysilyl group-containing monomer, the ratio of the alkoxysilyl group-containing monomer to the total monomer component may be, for example, 0.005% by weight or more, and may be 0.01% by weight or more. is appropriate. Further, 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 adhesion to the adherend. It's okay.

In addition, the monomer component of the acrylic polymer according to some preferred embodiments has a total ratio of alkoxyalkyl (meth)acrylate and alkoxypolyalkyleneglycol (meth)acrylate limited to less than 20% by weight from the viewpoint of suppressing gelation. It is The total proportion of the alkoxyalkyl (meth)acrylate and 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. In an aspect, the monomer component is substantially free of alkoxyalkyl (meth)acrylates and alkoxypolyalkyleneglycol (meth)acrylates (content of 0 to 0.3% by weight).
Similarly, the monomer component of the acrylic polymers disclosed herein may or may not contain less than 20% by weight of alkoxy group-containing monomers. 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, and even more preferably less than 1% by weight. In a particularly preferred embodiment, the monomer component contains an alkoxy group. Substantially free of monomers (content 0-0.3% by weight).

In addition, in some preferred embodiments, the proportion of hydrophilic monomers in the monomer component of the acrylic polymer is set within an appropriate range. Thereby, water removability is preferably exhibited. Here, the "hydrophilic monomer" in the present specification includes a carboxy group-containing monomer, an acid anhydride group-containing monomer, a hydroxyl group-containing monomer, a monomer having a nitrogen atom (typically, an amide group-containing monomer such as (meth)acrylamide). monomers, nitrogen atom-containing ring-containing monomers such as N-vinyl-2-pyrrolidone) and alkoxy group-containing monomers (typically alkoxyalkyl (meth)acrylates and alkoxypolyalkyleneglycol (meth)acrylates) do. In this embodiment, the proportion of the hydrophilic monomer in the monomer component of the acrylic polymer is suitably 40% by weight or less (for example, 35% by weight or less), preferably 32% by weight or less, for example, 30% by weight. It may be less than or equal to 28% by weight or less. Although not particularly limited, the proportion of the hydrophilic monomer in the monomer component of the acrylic polymer may be 1% by weight or more, 10% by weight or more, or 20% by weight or more. There may be.

In some aspects, the monomer component that constitutes the acrylic polymer may contain an alicyclic hydrocarbon group-containing (meth)acrylate. Thereby, the cohesive force of the pressure-sensitive adhesive can be increased, and the adhesive force can be improved. The alicyclic hydrocarbon group-containing (meth)acrylates may be used singly or in combination of two or more. As the alicyclic hydrocarbon group-containing (meth)acrylate, those exemplified above can be used, and for example, cyclohexyl acrylate and isobornyl acrylate can be preferably employed. The amount of the alicyclic hydrocarbon group-containing (meth)acrylate used is not particularly limited, and can be, for example, 1% by weight or more, 3% by weight or more, or 5% by weight or more of the total monomer components. In some aspects, the amount of the alicyclic hydrocarbon group-containing (meth)acrylate used may be 10% by weight or more, or 15% by weight or more, of the total monomer components. The upper limit of the amount of the alicyclic hydrocarbon group-containing (meth)acrylate used is suitably about 40% by weight or less, and may be, for example, 30% by weight or less, or 25% by weight or less (e.g., 15% by weight). % or less, or even 10% by weight or less).

In some preferred embodiments, the acrylic polymer contains, as a monomer component, a monomer having a polar group (polar group-containing monomer) in an amount of 0.05 mol to 0.45 mol per 100 g of the acrylic polymer. As a result, the adhesiveness to polar adherends is improved, and, for example, the adhesiveness after immersion in hot water can be maintained at a high level. By introducing the above polar group into the acrylic polymer, it is believed that interfacial adhesive strength is improved based on hydrogen bonding with a polar adherend such as glass. Polar group-containing monomers include the above-mentioned carboxy group-containing monomers (typically AA, MAA, etc.), hydroxyl group-containing monomers (typically HEA, 4HBA, etc.), and monomers having a nitrogen atom (typically ( meth) Amide group-containing monomers such as acrylamide, and nitrogen atom-containing ring-containing monomers such as NVP) can be used alone or in combination of two or more. The ratio of the polar group-containing monomer in the monomer component of the acrylic polymer is preferably 0.10 mol or more per 100 g of the acrylic polymer from the viewpoint of effectively exhibiting the action of the polar group-containing monomer. It is preferably 0.15 mol or more, more preferably 0.20 mol or more, and may be, for example, 0.24 mol or more. The upper limit of the ratio of the polar group-containing monomer in the monomer component of the acrylic polymer is suitably 0.40 mol or less, preferably 0.35 mol or less per 100 g of the acrylic polymer. .30 mol or less.

The composition of the monomer component is such that the glass transition temperature (hereinafter also referred to as the "glass transition temperature of the polymer") determined by the Fox formula based on the composition of the monomer component is −75° C. or higher and −10° C. or lower. can be set to In some embodiments, the glass transition temperature (Tg) of the polymer (for example, an acrylic polymer, typically an acrylic polymer) is suitably −15° C. or less, and −20° C. or less. It is preferably -25°C or lower, more preferably -30°C or lower, and may be -40°C or lower (for example, -55°C or lower). When the Tg of the polymer is lowered, the adhesion of the pressure-sensitive adhesive layer to the substrate layer and the adhesion to the adherend generally tend to be improved. According to such an adhesive layer, it is easy to suppress the intrusion of water into the interface between the adherend and the adhesive layer when the adhesive layer is not intended to be peeled off. This can be advantageous from the viewpoint of suppressing a decrease in adhesive force when contacting with an aqueous liquid such as immersion in warm water. The Tg of the polymer may be, for example, −70° C. or higher, or −65° C. or higher, from the viewpoint of facilitating an increase in adhesive strength. In some other embodiments, the Tg may be, for example, −60° C. or higher, −50° C. or higher, −45° C. or higher, or −40° C. or higher.

Here, the Fox formula is a relational expression between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below. .
1/Tg=Σ(Wi/Tgi)
In the above Fox formula, Tg is the glass transition temperature of the copolymer (unit: K), Wi is the weight fraction of the monomer i in the copolymer (weight-based copolymerization ratio), and Tgi is the content of the monomer i. It represents the glass transition temperature (unit: K) of a homopolymer.

As the glass transition temperature of the homopolymer used for calculating the Tg, the value described in the known materials shall be used. For example, for the monomers listed below, the following values are used as the glass transition temperatures of the homopolymers of the monomers.
2-ethylhexyl acrylate -70°C
n-butyl acrylate -55°C
n-butyl methacrylate 20°C
Isostearyl acrylate -18°C
Methyl methacrylate 105°C
Methyl acrylate 8°C
Cyclohexyl acrylate 15°C
N-vinyl-2-pyrrolidone 54°C
2-hydroxyethyl acrylate -15°C
4-hydroxybutyl acrylate -40°C
Dicyclopentanyl methacrylate 175°C
Isobornyl acrylate 94°C
Acrylic acid 106°C
Methacrylic acid 228°C

For the glass transition temperatures of homopolymers of monomers other than those exemplified above, the numerical values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. When multiple types of values are described in this document, the highest value is adopted.

For monomers for which the glass transition temperature of the homopolymer is not described in the above Polymer Handbook, the value obtained by the following measurement method shall be used (see Japanese Patent Application Publication No. 2007-51271). Specifically, 100 parts by weight of a monomer, 0.2 parts by weight of azobisisobutyronitrile and 200 parts by weight of ethyl acetate as a polymerization solvent were added to a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser. It is put in and stirred for 1 hour while nitrogen gas is circulated. After removing oxygen in the polymerization system in this way, the temperature is raised to 63° C. and the reaction is carried out for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution having a solid concentration of 33% by weight. Next, this homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. This test sample was punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to shear strain at a frequency of 1 Hz using a viscoelasticity tester (ARES, manufactured by Rheometrics Co., Ltd.) while applying a temperature range of -70 to 150 ° C. , the viscoelasticity is measured in shear mode at a heating rate of 5° C./min, and the peak top temperature of tan δ is defined as the Tg of the homopolymer.

The polymer contained in the pressure-sensitive adhesive layer disclosed herein (for example, an acrylic polymer, typically an acrylic polymer) is not particularly limited, but has an SP value of 23.0 (MJ/m ³ ) is preferably ^1/2 or less. A pressure-sensitive adhesive containing a polymer having such an SP value preferably realizes a pressure-sensitive adhesive having sufficient adhesive strength and excellent water removability by including, for example, a hydrophilic agent described later. can be. The above SP value is more preferably 21.0 (MJ/m ³ ) ^1/2 or less (for example, 20.0 (MJ/m ³ ) ^1/2 or less). ^The ^lower limit of ^the SP value ^is not particularly limited. Yes, preferably 18.0 (MJ/m ³ ) ^1/2 or more.

The SP value of the above polymer is calculated by Fedors' calculation method ["Polymer Engineering and Science (POLYMER ENG. &SCI.)", Vol. 14, No. 2 (1974), pp. 148-154. ] i.e. the expression:
SP value δ=(ΣΔe/ΣΔv) ^1/2
(Wherein, Δe is the vaporization energy Δe of each atom or atomic group at 25° C., and Δv is the molar volume of each atom or atomic group at the same temperature.);
can be calculated according to A polymer having the above SP value can be obtained by appropriately determining the monomer composition based on the common technical knowledge of those skilled in the art.

The pressure-sensitive adhesive layer uses a pressure-sensitive adhesive composition containing the above monomer component in the form of a polymer, an unpolymerized product (that is, a form in which the polymerizable functional group is unreacted), or a mixture thereof. can be formed by The pressure-sensitive adhesive composition includes a water-dispersed pressure-sensitive adhesive composition in which the pressure-sensitive adhesive (adhesive component) is dispersed in water, a solvent-based pressure-sensitive adhesive composition in which the pressure-sensitive adhesive is contained in an organic solvent, and a An active energy ray-curable pressure-sensitive adhesive composition prepared to form a pressure-sensitive adhesive by curing with an active energy ray (e.g., a photocurable pressure-sensitive adhesive composition), applied in a heat-melted state, and cooled to near room temperature It may be in various forms such as a hot-melt adhesive composition forming an adhesive.

In the polymerization, a known or commonly used thermal polymerization initiator or photopolymerization initiator can be used depending on the polymerization method, polymerization mode, etc. Such polymerization initiators can be used singly or in combination of two or more.

Although the thermal polymerization initiator is not particularly limited, for example, an azo polymerization initiator, a peroxide initiator, a redox initiator obtained by combining a peroxide and a reducing agent, and a substituted ethane initiator. etc. can be used. More specifically, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(2-amidinopropane) dihydrochloride , 2,2′-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2′-azobis(N,N′-dimethyleneisobutyramidine), 2,2′ - azo initiators such as azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate; persulfates such as potassium persulfate, ammonium persulfate; benzoyl peroxide, t-butyl hydroperoxide , hydrogen peroxide; substituted ethane-based initiators, such as phenyl-substituted ethane; redox, such as persulfate in combination with sodium bisulfite, peroxide in combination with sodium ascorbate system initiator; and the like, but are not limited to these. Thermal polymerization can be preferably carried out at a temperature of, for example, about 20 to 100°C (typically 40 to 80°C).

The photopolymerization initiator is not particularly limited, but for example, ketal photopolymerization initiator, acetophenone photopolymerization initiator, benzoin ether photopolymerization initiator, acylphosphine oxide photopolymerization initiator, α- Ketol photoinitiators, aromatic sulfonyl chloride photoinitiators, photoactive oxime photoinitiators, benzoin photoinitiators, benzyl photoinitiators, benzophenone photoinitiators, thioxanthone photoinitiators A polymerization initiator or the like can be used.

The amount of such a thermal polymerization initiator or photopolymerization initiator to be used is not particularly limited and can be a normal amount to be used according to the polymerization method, polymerization mode, etc. 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 is used with respect to 100 parts by weight of the monomer to be polymerized. can be done.

For the above polymerization, various conventionally known chain transfer agents (which can also be understood as molecular weight modifiers or polymerization degree modifiers) can be used as needed. Mercaptans such as n-dodecylmercaptan, t-dodecylmercaptan and thioglycolic acid can be used as the chain transfer agent. Alternatively, a chain transfer agent containing no sulfur atom (non-sulfur chain transfer agent) may be used. Specific examples of non-sulfur chain transfer agents include anilines such as N,N-dimethylaniline and N,N-diethylaniline; terpenoids such as α-pinene and terpinolene; α-methylstyrene and α-methylstyrene dimer. styrenes such as dibenzylideneacetone, cinnamyl alcohol, compounds having a benzylidenyl group such as cinnamylaldehyde; hydroquinones such as hydroquinone and naphthohydroquinone; quinones such as benzoquinone and naphthoquinone; 2,3-dimethyl-2-butene , olefins such as 1,5-cyclooctadiene; alcohols such as phenol, benzyl alcohol and allyl alcohol; benzyl hydrogens such as diphenylbenzene and triphenylbenzene;
A chain transfer agent can be used individually by 1 type or in combination of 2 or more types. When a chain transfer agent is used, the amount used can be, for example, about 0.01 to 1 part by weight per 100 parts by weight of the monomer component. The technology disclosed herein can also be preferably practiced in a mode that does not use a chain transfer agent.

The molecular weight of the polymer obtained by appropriately adopting the various polymerization methods described above (for example, an acrylic polymer, typically an acrylic polymer) is not particularly limited, and can be set in an appropriate range according to the required performance. . The weight average molecular weight (Mw) of the polymer is suitably about 10×10 ⁴ or more, for example about 15×10 ⁴ or more. By using a polymer (for example, an acrylic polymer) having an Mw of a predetermined value or more, both cohesive strength and adhesive strength can be achieved in a well-balanced manner. In some aspects, the Mw may be 20×10 ⁴ or more, may be 30×10 ⁴ or more (for example, more than 30×10 ⁴ ), or may be about 40× It may be 10 ⁴ or more, approximately 50×10 ⁴ or more, for example, approximately 55×10 ⁴ or more. The upper limit of the Mw of the polymer is not particularly limited, and may be, for example, about 500×10 ⁴ or less (for example, about 150×10 ⁴ or less) or about 75×10 ⁴ or less. In some preferred embodiments, the Mw may be less than 50×10 ⁴ , less than 40×10 ⁴ , less than 35×10 ⁴ (eg, less than 30×10 ⁴ ). A polymer having such an Mw tends to facilitate adjustment of the 60° C. loss elastic modulus of the pressure-sensitive adhesive within a predetermined range. Here, Mw refers to a value converted to standard polystyrene obtained by gel permeation chromatography (GPC). As the GPC apparatus, for example, model name "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) may be used. The same applies to the examples described later.

A surface protection sheet according to some embodiments has an adhesive layer formed from a water-dispersed adhesive composition. A representative example of the water-dispersible pressure-sensitive adhesive composition is an emulsion-type pressure-sensitive adhesive composition. An emulsion-type pressure-sensitive adhesive composition typically contains a polymer of monomer components and additives that are used as necessary.

　The emulsion polymerization of the monomer component is usually 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. Emulsifiers can be used singly or in combination of two or more.

Non-limiting examples of anionic emulsifiers include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkylphenyl ether sulfate, polyoxyethylene Examples include sodium ethylene alkylphenyl ether sulfate and sodium polyoxyethylene alkyl sulfosuccinate. Non-limiting examples of nonionic emulsifiers include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene polyoxypropylene block polymers, and the like. An emulsifier having a reactive functional group (reactive emulsifier) may be used. Examples of reactive emulsifiers include radically polymerizable emulsifiers having a structure in which a radically polymerizable functional group such as a propenyl group or an allyl ether group is introduced into the anionic emulsifier or nonionic emulsifier described above.

The amount of the emulsifier used in the emulsion polymerization may be, for example, 0.2 parts by weight or more, 0.5 parts by weight or more, or 1.0 parts by weight or more with respect to 100 parts by weight of the monomer component. It may be 5 parts by weight or more. Further, from the viewpoint of suppressing a decrease in adhesive strength after immersion in hot water, etc., in some embodiments, the amount of emulsifier used is suitably 10 parts by weight or less with respect to 100 parts by weight of the monomer component, and 5 parts by weight. parts by weight or less, and may be 3 parts by weight or less. The emulsifier used for emulsion polymerization here can also function as a water affinity agent for the pressure-sensitive adhesive layer.

According to emulsion polymerization, a polymerization reaction liquid in the form of an emulsion in which a polymer of monomer components is dispersed in water is obtained. A water-dispersible pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer can be preferably produced using the above polymerization reaction solution.

In some embodiments, the surface protection sheet has an adhesive layer formed from a solvent-based adhesive composition. A solvent-based pressure-sensitive adhesive composition typically contains a solution polymer of monomer components and additives used as necessary. The effects of the technique disclosed herein can be effectively exhibited in a form provided with a solvent-based pressure-sensitive adhesive layer. The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons); esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; Halogenated alkanes such as dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; Any one solvent or a mixture of two or more solvents can be used. According to the solution polymerization, a polymerization reaction liquid is obtained in which a polymer of monomer components is dissolved in a polymerization solvent. A solvent-based pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer can be preferably produced using the above polymerization reaction solution.

In some other embodiments, the surface protective sheet has an adhesive layer formed from an active energy ray-curable adhesive composition. As used herein, the term "active energy ray" refers to an energy ray having energy capable of causing chemical reactions such as polymerization reaction, cross-linking reaction, and initiator decomposition. Examples of active energy rays here include light such as ultraviolet rays, visible rays, and infrared rays, and radiation such as α rays, β rays, γ rays, electron beams, neutron rays, and X rays. A suitable example of the active energy ray-curable pressure-sensitive adhesive composition is a photocurable pressure-sensitive adhesive composition. A photocurable pressure-sensitive adhesive composition has the advantage that even a thick pressure-sensitive adhesive layer can be easily formed. Among them, an ultraviolet curable pressure-sensitive adhesive composition is preferred. Moreover, the effect by the technique disclosed here can be effectively exhibited also with the form provided with a photocurable adhesive layer.

Typically, the photocurable pressure-sensitive adhesive composition contains at least part of the monomer components of the composition (may be part of the types of monomers or part of the amount). It is contained in the form of a polymer. The polymerization method for forming the polymer is not particularly limited, and conventionally known various polymerization methods can be appropriately employed. For example, thermal polymerization such as solution polymerization, emulsion polymerization, bulk polymerization (typically performed in the presence of a thermal polymerization initiator); photopolymerization performed by irradiating light such as ultraviolet rays (typically, conducted in the presence of a photopolymerization initiator); radiation polymerization conducted by irradiating radiation such as β-rays and γ-rays; Among them, photopolymerization is preferred.

A photocurable pressure-sensitive adhesive composition according to some embodiments contains a partial polymer of a monomer component. Such a partial polymer is typically a mixture of a polymer derived from the monomer component and an unreacted monomer, and preferably presents a syrup (viscous liquid). Hereinafter, the partial polymer having such properties is sometimes referred to as "monomer syrup" or simply "syrup". The polymerization method for partially polymerizing the monomer component is not particularly limited, and various polymerization methods as described above can be appropriately selected and used. A photopolymerization method can be preferably employed from the viewpoint of efficiency and convenience. According to photopolymerization, the polymerization conversion rate of the monomer component (monomer conversion) can be easily controlled by the polymerization conditions such as the irradiation amount of light (light amount).

The polymerization conversion rate of the monomer mixture in the partially polymerized product is not particularly limited. The polymerization conversion rate can be, for example, about 70% by weight or less, preferably about 60% by weight or less. From the viewpoint of ease of preparation and coating properties of the pressure-sensitive adhesive composition containing the partially polymerized product, the polymerization conversion rate is suitably about 50% by weight or less, and about 40% by weight or less (for example, about 35% by weight). below) is preferred. Although the lower limit of the polymerization conversion rate is not particularly limited, it is typically about 1% by weight or more, and about 5% by weight or more is suitable.

A pressure-sensitive adhesive composition containing a partially polymerized product of a monomer component can be obtained, for example, by partially polymerizing a monomer mixture containing all of the monomer components used in the preparation of the pressure-sensitive adhesive composition by an appropriate polymerization method (e.g., photopolymerization method). can be obtained by In addition, the pressure-sensitive adhesive composition containing a partial polymer of monomer components is a partial polymer or a complete polymer of a monomer mixture containing a part of the monomer components used in the preparation of the pressure-sensitive adhesive composition, and the remaining monomers. It may be a mixture with a component or a partial polymer thereof. In the present specification, the term "completely polymerized product" means that the polymerization conversion rate is over 95% by weight.

The pressure-sensitive adhesive composition containing the partial polymer is blended with a tackifier and optionally other components (e.g., photopolymerization initiator, polyfunctional monomer, cross-linking agent, hydrophilic agent, etc.). can be The method of blending such other components is not particularly limited. For example, they may be included in the above monomer mixture in advance or may be added to the above partial polymer.

(Tackifier)
The adhesive layer disclosed herein comprises greater than 10 parts by weight of tackifier to 100 parts by weight of base polymer. As a result, the adhesive strength is improved, and the adhesive strength F1 after immersion in warm water for 30 minutes can be improved, so that sufficient adhesive strength can be maintained even after being immersed in warm water or water. Therefore, even when used in a mode in which the adherend contacts a liquid while attached to the adherend (for example, a mode in which the adherend is treated in a liquid), the surface protection sheet It is possible to maintain a state of close contact with the adherend, and for example, it is possible to prevent peeling of the edges during and after the treatment. Further, according to the technology disclosed herein, even if the surface protective sheet is attached to the adherend with high adhesive strength, the adherend is damaged or damaged by peeling using an aqueous liquid such as water when peeling. The surface protective sheet can be removed without deformation. Therefore, it is possible to increase the adhesion reliability and the protective function by including a predetermined amount or more of a tackifier, which is an adhesive force-improving component, in the pressure-sensitive adhesive. By using the water-peeling technology disclosed herein, it is possible to add a tackifier that is an adhesive force-improving component to achieve both adhesion to an adherend and peelability at a high level.

The amount of the tackifier used may be about 11 parts by weight or more, or about 12 parts by weight, preferably about 10 parts by weight based on 100 parts by weight of the base polymer (for example, an acrylic polymer) contained in the adhesive layer. 15 parts by weight or more, more preferably 18 parts by weight or more, more preferably 20 parts by weight or more (for example, 22 parts by weight or more), may be 25 parts by weight or more, may be 28 parts by weight or more, or may be 32 parts by weight. or more, or 35 parts by weight or more. The amount of the tackifier used relative to 100 parts by weight of the base polymer is, for example, suitably less than 100 parts by weight, and may be approximately 80 parts by weight or less, may be 70 parts by weight or less, or may be 50 parts by weight. Part or less is acceptable. By limiting the amount of the tackifier to be used within an appropriate range, the tackifier is well compatible with the tackifier, and the effects of addition of the tackifier (adhesive properties such as adhesive strength) are likely to be exhibited effectively. In some preferred embodiments, the amount of tackifier used is less than 50 parts by weight, more preferably less than 40 parts by weight, more preferably 35 parts by weight or less, and most preferably 32 parts by weight, based on 100 parts by weight of the base polymer. parts or less, may be 30 parts by weight or less, or may be 25 parts by weight or less.

Although not particularly limited, as the tackifier, one with an acid value is preferably used. By using a tackifier having an acid value equal to or higher than a predetermined value, for example, the adhesion to polar adherends can be improved, and the adhesion after immersion in hot water can be maintained at a high level. The acid value of the tackifier is, for example, above 10 mgKOH/g, suitably above 15 mgKOH/g, preferably above 20 mgKOH/g, more preferably above 23 mgKOH/g. The upper limit of the acid value is usually, for example, 200 mgKOH/g or less, and from the viewpoint of water removability, it may be 100 mgKOH/g or less, 50 mgKOH/g or less, or 40 mgKOH/g or less. The acid value of the tackifier can be measured by the potentiometric titration method specified in JIS K 0070:1992.

As the tackifier, various components that can improve adhesive strength can be used without particular limitation. Preferred examples of tackifiers include tackifier resins and acrylic oligomers. A tackifier can be used individually by 1 type or in combination of 2 or more types.

(tackifying resin)
Examples of tackifying resins include rosin-based tackifying resins, rosin derivative tackifying resins, petroleum-based tackifying resins, terpene-based tackifying resins, terpene phenol resins, phenol-based tackifying resins, ketone-based tackifying resins, and the like. be done. These can be used individually by 1 type or in combination of 2 or more types.

Examples of the rosin-based tackifying resin include rosins such as gum rosin, wood rosin, tall oil rosin, stabilized rosin (e.g., stabilized rosin obtained by disproportionating or hydrogenating the above rosin), polymerized rosin (e.g., , a multimer of the above rosin, typically a dimer), modified rosin (e.g., unsaturated acid-modified rosin modified with an unsaturated acid such as maleic acid, fumaric acid, (meth)acrylic acid, etc.), etc. mentioned.
Examples of the rosin derivative tackifying resin include esterified rosin-based tackifying resins (for example, rosin esters such as stabilized rosin esters and polymerized rosin esters), phenol-modified rosin-based resins (phenol-modified rosin ) and esters thereof (phenol-modified rosin esters).
Examples of the petroleum-based tackifying resin include aliphatic petroleum resins, aromatic petroleum resins, copolymer petroleum resins, alicyclic petroleum resins, and hydrides thereof.
Examples of the terpene-based tackifying resin include α-pinene resin, β-pinene resin, aromatic modified terpene-based resin, and hydrogenated terpene-based resin.
The terpene phenol resin refers to a polymer containing a terpene residue and a phenol residue, and a copolymer of a terpene and a phenol compound (terpene-phenol copolymer resin) and a homopolymer or copolymer of a terpene. It is a concept that includes both phenol-modified coalescence (phenol-modified terpene resin). Terpene phenolic resins include hydrogenated terpene phenolic resins.
Examples of the phenol-based tackifying resin include alkylphenol resins obtained from alkylphenol and formaldehyde. Examples of alkylphenol resins include novolac and resole types.
Examples of the ketone-based tackifying resin include ketone-based resins obtained by condensation of ketones (e.g., aliphatic ketones such as methyl ethyl ketone, methyl isobutyl ketone, and acetophenone; alicyclic ketones, such as cyclohexanone and methylcyclohexanone) and formaldehyde. ; and the like.

In some embodiments, as the tackifying resin, one or more selected from rosin-based tackifying resins, rosin derivative tackifying resins and terpene phenol resins can be preferably used. In some preferred embodiments, a rosin derivative tackifying resin is used as the tackifying resin. Preferred examples of rosin derivative tackifying resins include rosin esters such as stabilized rosin esters and polymerized rosin esters.

In a water-dispersible pressure-sensitive adhesive composition, it is preferable to use a water-dispersible tackifying resin in which the tackifying resin as described above is dispersed in an aqueous solvent. For example, by mixing an aqueous dispersion of an acrylic polymer and an aqueous tackifying resin, a PSA composition containing these components in desired proportions can be easily prepared. In some aspects, as the water-dispersible tackifier resin, one that does not substantially contain at least an aromatic hydrocarbon-based solvent can be preferably used from the viewpoint of consideration for environmental hygiene. It is more preferable to use a water-dispersible tackifying resin that does not substantially contain aromatic hydrocarbon solvents and other organic solvents.

Examples of commercially available water-dispersible tackifying resins containing rosin esters include, for example, trade names "Super Ester E-720", "Super Ester E-730-55" and "Super Ester E-" manufactured by Arakawa Chemical Industries, Ltd. 865NT", "Super Ester NS" series, etc., and Harima Kasei's product names "Harrier SK-90D", "Harrier SK-70D", "Harrier SK-70E", "Neotor 115E", etc. be done. In addition, commercially available terpene phenol resins (which may be in the form of water-dispersed terpene phenol resins) include trade names "Tamanol E-100", "Tamanol E-200" and "Tamanol E" manufactured by Arakawa Chemical Industries. -200NT" and the like.

The softening point of the tackifying resin is not particularly limited. A tackifying resin having a softening point of 80° C. or higher can be preferably used from the viewpoint of suppressing a decrease in the cohesive strength of the pressure-sensitive adhesive layer. The softening point of the tackifying resin may be 90° C. or higher, 100° C. or higher, 110° C. or higher, or 120° C. or higher. Tackifying resins with a softening point of 130° C. or higher or 140° C. or higher may be used. In addition, from the viewpoint of adhesiveness to the substrate layer, adhesiveness to the adherend, etc., a tackifier resin having a softening point of 200° C. or lower or 180° C. or lower can be preferably used. As the softening point of the tackifying resin, a nominal value described in literature, catalogs, etc. can be adopted. If there is no nominal value, the softening point of the tackifier resin can be measured based on the softening point test method (ring and ball method) specified in JIS K5902 or JIS K2207.

(acrylic oligomer)
As the acrylic oligomer, one having a higher Tg than the Tg of the above acrylic polymer (for example, an acrylic polymer) can be preferably used. The Tg of the acrylic oligomer is not particularly limited, and may be, for example, about 20°C or higher and 300°C or lower. The Tg may be, for example, about 30° C. or higher, about 40° C. or higher, about 60° C. or higher, about 80° C. or higher, or about 100° C. or higher. As the Tg of the acrylic oligomer increases, the effect of improving the cohesive strength tends to generally increase. In addition, from the viewpoint of anchoring property to the base material layer, impact absorption property, etc., the Tg of the acrylic oligomer may be, for example, about 250° C. or less, may be about 200° C. or less, or about 180° C. or less or about 150° C. It can be below. Incidentally, the Tg of the acrylic oligomer is a value calculated based on the Fox's formula, like the Tg of the acrylic polymer described above.

The Mw of the acrylic oligomer is not particularly limited. Also, the Mw of the acrylic oligomer may be, for example, less than approximately 30,000, suitably less than approximately 10,000, less than approximately 7,000, or less than approximately 5,000. When Mw is within the above range, the effect of improving cohesiveness and adhesiveness of the pressure-sensitive adhesive layer tends to be favorably exhibited. The Mw of the acrylic oligomer can be measured by GPC and obtained as a value converted to standard polystyrene. Specifically, for example, it can be measured using HPLC8020 manufactured by Tosoh Corporation, using TSKgelGMH-H(20)×2 columns, and using tetrahydrofuran solvent at a flow rate of about 0.5 mL/min.

As the monomer component constituting the acrylic oligomer, various (meth)acrylic acid C _1-20 alkyl esters described above; various alicyclic hydrocarbon group-containing (meth)acrylates described above; Hydrogen group-containing (meth)acrylates; (meth)acrylates obtained from terpene compound derivative alcohols; and other (meth)acrylate monomers can be mentioned. These can be used individually by 1 type or in combination of 2 or more types.

Acrylic oligomers include alkyl (meth)acrylates having branched alkyl groups such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; alicyclic hydrocarbon group-containing (meth)acrylates and aromatic hydrocarbons From the viewpoint of improving adhesiveness, it is preferable to contain an acrylic monomer having a relatively bulky structure, represented by a group-containing (meth)acrylate, as a monomer unit. In addition, when ultraviolet rays are used in synthesizing an acrylic oligomer or in preparing a pressure-sensitive adhesive layer, a monomer having a saturated hydrocarbon group at the ester end is preferable because it is less likely to cause polymerization inhibition. Alkyl (meth)acrylates and saturated alicyclic hydrocarbon group-containing (meth)acrylates in which the group has a branched structure can be preferably used.

The ratio of the (meth)acrylate monomer to 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 (e.g., 80% by weight). or more, and further 90% by weight or more). In some preferred embodiments, the acrylic oligomer has a monomer composition consisting essentially of one or more (meth)acrylate monomers. When the monomer component contains an alicyclic hydrocarbon group-containing (meth)acrylate and a (meth)acrylic acid C _1-20 alkyl ester, their weight ratio is not particularly limited. In some embodiments, the weight ratio of alicyclic hydrocarbon group-containing (meth)acrylate/(meth)acrylic acid C _1-20 alkyl ester is, for example, 10/90 or more, 20/80 or more, or 30/70 or more. and can be 90/10 or less, 80/20 or less, or 70/30 or less.

As the constituent monomer components of the acrylic oligomer, in addition to the above (meth)acrylate monomers, functional group-containing monomers can be used as necessary. Functional group-containing monomers include monomers having a nitrogen atom-containing heterocyclic ring 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-diethyl(meth)acrylamide; carboxy group-containing monomers such as AA and MAA; hydroxyl group-containing monomers such as 2-hydroxyethyl(meth)acrylate; These functional group-containing monomers can be used singly or in combination of two or more. When a functional group-containing monomer is used, the ratio of the functional group-containing monomer to the total monomer components constituting the acrylic oligomer can be, for example, 1% by weight or more, 2% by weight or more, or 3% by weight or more, and For example, it can be 15% by weight or less, 10% by weight or less, or 7% by weight or less. The acrylic oligomer may be one in which no functional group-containing monomer is used.

Suitable acrylic oligomers include, for example, dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopentanyl acrylate (DCPA), In addition to homopolymers of 1-adamantyl methacrylate (ADMA) and 1-adamantyl acrylate (ADA), copolymers of DCPMA and methyl methacrylate (MMA), copolymers of DCPMA and IBXMA, copolymers of ADA and MMA copolymers of CHMA and isobutyl methacrylate (IBMA); copolymers of CHMA and IBXMA; copolymers of CHMA and acryloylmorpholine (ACMO); copolymers of CHMA and diethylacrylamide (DEAA); A copolymer of CHMA and AA can be mentioned.

An acrylic oligomer can be formed by polymerizing its constituent monomer components. The polymerization method and polymerization mode are not particularly limited, and conventionally known various polymerization methods (for example, solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be employed in an appropriate mode. The types of polymerization initiators (e.g., azo polymerization initiators) that can be used as necessary are generally as exemplified for the synthesis of the acrylic polymer, and the amount of the polymerization initiator and the optionally used chain transfer agent The amount of (for example, mercaptans) is appropriately set based on common technical knowledge so as to achieve a desired molecular weight, so detailed description is omitted.

(Water affinity agent)
If desired, the pressure-sensitive adhesive layer can contain a water affinity agent. By including a water-affinitive agent in the pressure-sensitive adhesive layer, it is possible to effectively reduce the peel strength using an aqueous liquid such as water. The reason for this is not particularly limited, but in general, the water affinity agent tends to be unevenly distributed on the surface of the pressure-sensitive adhesive layer by having a hydrophilic region, thereby efficiently increasing the water affinity of the pressure-sensitive adhesive layer surface. It is considered that the effect of increasing the peel force is exhibited, and the peel force is effectively reduced when the pressure-sensitive adhesive layer comes into contact with water. A water affinity agent can be used individually by 1 type or in combination of 2 or more types.

In some embodiments, at least one compound A selected from surfactants and compounds having a polyoxyalkylene skeleton can be used as the hydrophilic agent. As the surfactant and the compound having a polyoxyalkylene skeleton, one or more of known surfactants and compounds having a polyoxyalkylene skeleton can be used without particular limitation. Needless to say, among the surfactants described above, there are compounds having a polyoxyalkylene skeleton, and vice versa.

As the surfactant that can be used as compound A, known nonionic surfactants, anionic surfactants, cationic surfactants, etc. can be used. Among them, nonionic surfactants are preferred. Surfactant can be used individually by 1 type or in combination of 2 or more types.

Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether; Polyoxyethylene alkylphenyl ethers such as oxyethylene nonylphenyl ether; Sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate and sorbitan monooleate; Polyoxyethylene sorbitan monolaurate, polyoxyethylene Polyoxyethylene sorbitan such as sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan triisostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate fatty acid ester; polyoxyethylene glyceryl ether fatty acid ester; polyoxyethylene-polyoxypropylene block copolymer; These nonionic surfactants can be used singly or in combination of two or more.

Examples of anionic surfactants include alkylbenzene sulfonates such as nonylbenzene sulfonate, dodecylbenzene sulfonate (e.g. sodium dodecylbenzene sulfonate); lauryl sulfates (e.g. sodium lauryl sulfate, ammonium lauryl sulfate); Alkyl sulfates such as octadecyl sulfate; fatty acid salts; polyoxyethylene alkyl ether sulfates such as polyoxyethylene octadecyl ether sulfate and polyoxyethylene lauryl ether sulfate (e.g., sodium polyoxyethylene alkyl ether sulfate); Polyoxyethylene alkylphenyl ether sulfates such as ethylene lauryl phenyl ether sulfate (e.g., ammonium polyoxyethylene alkylphenyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, etc.), polyoxyethylene styrenated phenyl ether sulfates, etc. Polyether sulfate; polyoxyethylene alkyl ether phosphate such as polyoxyethylene stearyl ether phosphate and polyoxyethylene lauryl ether phosphate; sodium salt, potassium salt, etc. of the above polyoxyethylene alkyl ether phosphate sulfosuccinates such as lauryl sulfosuccinate, polyoxyethylene lauryl sulfosuccinate (e.g., sodium polyoxyethylene alkyl sulfosuccinate); polyoxyethylene alkyl ether acetate; is mentioned. When the anionic surfactant forms a salt, the salt is, for example, a metal salt (preferably a monovalent metal salt) such as sodium salt, potassium salt, calcium salt, magnesium salt, ammonium salt, amine salt, etc. can be Anionic surfactant can be used individually by 1 type or in combination of 2 or more types.

In some embodiments, for example, anionic surfactants having at least one of -POH, -COH and -SOH groups can be preferably used. Among them, surfactants having a —POH group are preferred. Such surfactants typically contain a phosphate ester structure, e.g. monoesters of phosphoric acid (ROP(=O)(OH) ₂ ; where R is a monovalent organic group), diesters ((RO) ₂ P(=O)OH; where R are the same or different monovalent organic groups), mixtures including both monoesters and diesters, and the like. Preferable examples of surfactants having a —POH group include polyoxyethylene alkyl ether phosphates. The number of carbon atoms of the alkyl group in the polyoxyethylene alkyl ether phosphate may be, for example, 6-20, 8-20, 10-20, 12-20, or 14-20.

Examples of cationic surfactants include polyetheramines such as polyoxyethylene laurylamine and polyoxyethylene stearylamine. A cationic surfactant can be used individually by 1 type or in combination of 2 or more types.

Examples of compounds having a polyoxyalkylene skeleton that can be used as compound A include polyalkylene glycols such as polyethylene glycol (PEG) and polypropylene glycol (PPG); polyethers containing polyoxyethylene units, and polyoxypropylene units. Polyethers, compounds containing oxyethylene units and oxypropylene units (the arrangement of these units may be random or block-like); derivatives thereof; and the like can be used. Compounds having a polyoxyalkylene skeleton among the surfactants described above can also be used. These can be used individually by 1 type or in combination of 2 or more types. Among them, it is preferable to use a compound containing a polyoxyethylene skeleton (also referred to as a polyoxyethylene segment), and PEG is more preferable.

The molecular weight (chemical formula weight) of the compound having a polyoxyalkylene skeleton (e.g., polyethylene glycol) is not particularly limited, and is suitably, for example, less than 1,000. 500 or less). The lower limit of the molecular weight of the compound having a polyoxyalkylene skeleton (eg, polyethylene glycol) is not particularly limited, and compounds having a molecular weight of about 100 or more (eg, about 200 or more, further about 300 or more) are preferably used.

Other examples of hydrophilic agents include water-soluble polymers such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylic acid. A water-soluble polymer can be used individually by 1 type or in combination of 2 or more types. In the technology disclosed herein, as the water affinity agent, one or two or more of the compounds A may be used, one or two or more of the water-soluble polymers may be used, and these may be used in combination. may

The HLB of the hydrophilic agent is not particularly limited, and is, for example, 3 or more, suitably about 6 or more, and may be 8 or more (eg, 9 or more). In some preferred embodiments, the HLB of the hydrophilic agent is 10 or greater. As a result, there is a tendency for the water removability to be favorably expressed. The HLB is more preferably 11 or more, still more preferably 12 or more, and particularly preferably 13 or more (for example, 14 or more). By including a water affinity agent (typically a surfactant) having an HLB within the above range in the pressure-sensitive adhesive layer, the water removability can be more effectively exhibited. The upper limit of HLB is 20 or less, and may be, for example, 18 or less, 16 or less, or 15 or less.

In addition, HLB in the present specification is Hydrophile-Lipophile Balance by Griffin, which is a value representing the degree of affinity of a surfactant to water or oil, and the ratio of hydrophilicity to lipophilicity is between 0 and 20. is expressed as a numerical value. The definition of HLB is given by W. C. Griffin: J. Soc. Cosmetic Chemists, 1,311 (1949), Kotami Takahashi, Yoshiro Namba, Motoo Koike, Masao Kobayashi, "Surfactant Handbook", 3rd edition, Kogakutoshosha Publishing, November 25, 1972, p.179- 182 and the like. The hydrophilic agent having the above HLB can be selected based on the common general technical knowledge of those skilled in the art, for example, by referring to the above references as necessary.

Such a water affinity agent is preferably contained in the adhesive layer in a free form. As the water affinity agent, one that is liquid at room temperature (about 25° C.) is preferably used from the standpoint of preparation of the pressure-sensitive adhesive composition.

A pressure-sensitive adhesive layer containing a water affinity agent is typically formed from a pressure-sensitive adhesive composition containing a water affinity agent. The pressure-sensitive adhesive composition may be any of the water-dispersed pressure-sensitive adhesive composition, the solvent-based pressure-sensitive adhesive composition, the active energy ray-curable pressure-sensitive adhesive composition, the hot-melt pressure-sensitive adhesive composition, and the like. In some preferred embodiments, the pressure-sensitive adhesive layer containing a water-affinitive agent can be a pressure-sensitive adhesive layer formed from a water-dispersed or solvent-based pressure-sensitive adhesive composition. In such a pressure-sensitive adhesive layer, the effect of addition of the water affinity agent can be preferably exhibited. The adhesive layer may have photocurability.

The content of the hydrophilic agent in the pressure-sensitive adhesive layer is not particularly limited, and can be set so that the effect of using the hydrophilic agent is appropriately exhibited. In some aspects, the content of the water affinity agent can be, for example, 0.001 parts by weight or more per 100 parts by weight of the base polymer (for example, an acrylic polymer) contained in the pressure-sensitive adhesive layer, and 0.01 parts by weight or more. Part by weight or more is suitable, and it may be 0.03 part by weight or more, 0.07 part by weight or more, or 0.1 part by weight or more. In some preferred embodiments, the content of the hydrophilic agent may be, for example, 0.2 parts by weight or more, and 0.3 parts by weight or more from the viewpoint of obtaining a higher effect, with respect to 100 parts by weight of the base polymer. It may be 0.4 parts by weight or more, 0.5 parts by weight or more, 1.0 parts by weight or more, or 1.5 parts by weight or more. Further, from the viewpoint of suppressing excessive diffusion of water into the bulk of the pressure-sensitive adhesive layer, in some embodiments, the amount of the water affinity agent used is, for example, 20 parts by weight or less with respect to 100 parts by weight of the base polymer. It is suitable to be 10 parts by weight or less, preferably 5 parts by weight or less, and may be 3 parts by weight or less. It is preferable that the content of the water-affinity agent is not too high from the viewpoint of suppressing a decrease in adhesive strength when the adhesive is brought into contact with an aqueous liquid such as immersion in warm water. For example, in some embodiments, the content of the hydrophilic agent relative to 100 parts by weight of the base polymer may be less than 2 parts by weight, less than 1 part by weight, less than 0.7 parts by weight, or 0.3 parts by weight. It may be less than 0.2 parts by weight. Hydrophilic agents with an HLB of 10 or more tend to exhibit good water removability even when used in small amounts.

In the technique disclosed herein, the use of a tackifier can improve the adhesive strength after immersion in hot water, so the amount of water-philic agent that can cause a decrease in adhesive strength when in contact with an aqueous liquid such as immersion in warm water is reduced. There is no need to limit it, and it is also possible to increase the amount of the hydrophilic agent. By using a tackifier and a water-affinitive agent, it is possible to achieve a high level of both adhesion to adherends and peelability. In an embodiment using a tackifier and a water affinity agent, the ratio (C _A /C _B ) of the water affinity agent amount (C _A ) to the tackifier amount (C _B ) contained in the pressure-sensitive adhesive layer on a weight basis. is not particularly limited, but is, for example, 0.0001 or more, suitably 0.001 or more, preferably 0.01 or more, more preferably 0.02 or more, and still more preferably 0 on a weight basis. 0.03 or more, may be 0.05 or more, or may be 0.1 or more. By increasing the amount of the water affinity agent used relative to the amount of the tackifier used, the adhesiveness based on the use of the tackifier is kept within a predetermined range, while suppressing the water peeling force to a low level. Peeling removability can be maintained or improved. The upper limit of the ratio (C _A /C _B ) is not particularly limited, and is suitably 1 or less, preferably 0.5 or less, more preferably 0.3 or less, even if it is less than 0.15. Well, even less than 0.1. By limiting the amount of the hydrophilic agent to be used with respect to the amount of the tackifier, it is possible to maintain or improve the adhesive strength after immersion in hot water while maintaining water releasability.

(crosslinking agent)
The pressure-sensitive adhesive composition disclosed herein may optionally contain a cross-linking agent mainly for the purpose of cross-linking within the pressure-sensitive adhesive layer or cross-linking between the pressure-sensitive adhesive layer and its adjacent surface. The cross-linking agent is typically contained in the pressure-sensitive adhesive layer in a form after the cross-linking reaction. The cohesive strength of the pressure-sensitive adhesive layer can be appropriately adjusted by using the cross-linking agent.

The type of the cross-linking agent is not particularly limited, and is selected from conventionally known cross-linking agents so that the cross-linking agent exhibits an appropriate cross-linking function in the pressure-sensitive adhesive layer according to, for example, the composition of the pressure-sensitive adhesive composition. be able to. Examples of cross-linking agents that can be used include isocyanate cross-linking agents, epoxy cross-linking agents, oxazoline cross-linking agents, aziridine cross-linking agents, carbodiimide cross-linking agents, melamine cross-linking agents, urea cross-linking agents, metal alkoxide cross-linking agents, metal Examples include chelate-based cross-linking agents, metal salt-based cross-linking agents, hydrazine-based cross-linking agents, amine-based cross-linking agents, and the like. These can be used individually by 1 type or in combination of 2 or more types. In a water-dispersible pressure-sensitive adhesive composition, it is preferable to use a water-soluble or dispersible cross-linking agent.

As the isocyanate-based cross-linking agent, a bifunctional or higher polyfunctional isocyanate compound can be used. For example, aromatic isocyanates such as tolylene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris(p-isocyanatophenyl) thiophosphate, diphenylmethane diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate isocyanate; and the like. Commercially available products include trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate L"), trimethylolpropane/hexamethylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name " Coronate HL"), isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX"), trimethylolpropane/xylylene diisocyanate adduct (manufactured by Mitsui Chemicals, trade name "Takenate D-110N"), etc. can be exemplified by isocyanate adducts of In a water-dispersible pressure-sensitive adhesive composition, it is preferable to use an isocyanate-based cross-linking agent that is soluble or dispersible in water. For example, a water-soluble, water-dispersible or self-emulsifying isocyanate cross-linking agent can be preferably employed. A so-called blocked isocyanate-type isocyanate-based cross-linking agent in which the isocyanate group is blocked can be preferably used.

As the epoxy-based cross-linking agent, those having two or more epoxy groups in one molecule can be used without particular limitation. An epoxy-based cross-linking agent having 3 to 5 epoxy groups in one molecule is preferred. Specific examples of epoxy-based cross-linking agents include N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and 1,6-hexane. Diol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether and the like. Commercially available epoxy-based cross-linking agents include products manufactured by Mitsubishi Gas Chemical Co., Ltd. under the trade names of "TETRAD-X" and "TETRAD-C", DIC under the trade name of "Epiclon CR-5L", and products manufactured by Nagase ChemteX Corporation. name "Denacol EX-512", product name "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd., and the like.

As the oxazoline-based cross-linking agent, those having one or more oxazoline groups in one molecule can be used without particular limitation. In a water-dispersed pressure-sensitive adhesive composition, it is preferable to use an oxazoline-based cross-linking agent that is soluble or dispersible in water.
The oxazoline group may be any of 2-oxazoline group, 3-oxazoline group and 4-oxazoline group. Generally, an oxazoline-based cross-linking agent having a 2-oxazoline group can be preferably used. For example, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4- Water-soluble copolymers or water-dispersible copolymers obtained by copolymerizing addition-polymerizable oxazolines such as methyl-2-oxazoline and 2-isopropenyl-5-ethyl-2-oxazoline with other monomers , can be used as an oxazoline-based cross-linking agent.
Examples of commercially available products of oxazoline-based cross-linking agents include the trade name "Epocross WS" series and "Epocross K" series manufactured by Nippon Shokubai Co., Ltd., and the like.

Examples of aziridine cross-linking agents include trimethylolpropane tris [3-(1-aziridinyl) propionate], trimethylol propane tris [3-(1-(2-methyl) aziridinyl propionate)] and the like. be done.
A low-molecular-weight compound or a high-molecular-weight compound having two or more carbodiimide groups can be used as the carbodiimide-based cross-linking agent.

In some embodiments, peroxides may be used as cross-linking agents. Peroxides include di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butyl peroxyneodecanoate. , t-hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutyl peroxyisobutyrate, di benzoyl peroxide and the like. Among these, di(4-t-butylcyclohexyl)peroxydicarbonate, dilauroyl peroxide, dibenzoyl peroxide and the like are mentioned as peroxides having particularly excellent cross-linking reaction efficiency. In addition, when a peroxide is used as the polymerization initiator, it is also possible to use the remaining peroxide that has not been used in the polymerization reaction for the cross-linking reaction. In that case, the residual amount of the peroxide is quantified, and if the ratio of the peroxide is less than the predetermined amount, the peroxide may be added as necessary so that the predetermined amount is obtained. Peroxide can be quantified by the method described in Japanese Patent No. 4971517.

The amount used when using a cross-linking agent (the total amount when using two or more cross-linking agents) is not particularly limited. From the viewpoint of realizing a pressure-sensitive adhesive that exhibits adhesive properties such as adhesive strength and cohesive strength in a well-balanced manner, the amount of the cross-linking agent used is based on 100 parts by weight of the base polymer (for example, an acrylic polymer) contained in the pressure-sensitive adhesive composition. For example, it is about 10 parts by weight or less, and is suitably about 5 parts by weight or less, may be 3 parts by weight or less, may be 2 parts by weight or less, may be 1 part by weight or less, or may be 1 weight part. It may be less than part. In some embodiments, the amount of the cross-linking agent (e.g., isocyanate-based cross-linking agent) used relative to 100 parts by weight of the base polymer may be, for example, 0.50 parts by weight or less, or 0.40 parts by weight or less. 0.30 parts by weight or less, or 0.20 parts by weight or less. The lower limit of the amount of the cross-linking agent to be used is not particularly limited, and the amount may be more than 0 parts by weight with respect to 100 parts by weight of the base polymer. In some embodiments, the amount of the cross-linking agent used can be, for example, 0.001 parts by weight or more, may be 0.01 parts by weight or more, or 0.05 parts by weight, relative to 100 parts by weight of the base polymer. parts or more, or 0.10 parts by weight or more. In some other embodiments, the amount of the cross-linking agent used may be, for example, 0.5 parts by weight or more, 1 part by weight or more, or 1.5 parts by weight with respect to 100 parts by weight of the base polymer. It can be more than that.

Alternatively, it may be a pressure-sensitive adhesive composition that does not contain a cross-linking agent as described above. When using a photocurable pressure-sensitive adhesive composition as the pressure-sensitive adhesive composition disclosed herein, the pressure-sensitive adhesive composition may be substantially free of a cross-linking agent such as an isocyanate-based cross-linking agent. Here, the pressure-sensitive adhesive composition substantially does not contain a cross-linking agent (typically an isocyanate-based cross-linking agent) means that the amount of the cross-linking agent is 0.05 with respect to 100 parts by weight of the base polymer or the monomer component of the base polymer. Less than parts by weight (for example, less than 0.01 parts by weight).

A cross-linking catalyst may be used to promote the cross-linking reaction more effectively. Examples of cross-linking catalysts include metallic cross-linking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, Nasem ferric, butyltin oxide, and dioctyltin dilaurate. Of these, tin-based cross-linking catalysts such as dioctyltin dilaurate are preferred. The amount of cross-linking catalyst used is not particularly limited. The amount of the cross-linking catalyst to be used is, for example, about 0.0001 parts by weight or more, about 0.001 parts by weight or more, about 0.001 part by weight or more, relative to 100 parts by weight of the base polymer (for example, an acrylic polymer) contained in the pressure-sensitive adhesive composition. 005 weight parts or more, or about 1 weight part or less, about 0.1 weight part or less, about 0.05 weight part or less, or the like.

The pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer may optionally contain a compound that causes keto-enol tautomerism as a cross-linking retarder. For example, a compound that produces keto-enol tautomerism can be preferably used in a pressure-sensitive adhesive composition containing an isocyanate-based cross-linking agent or a pressure-sensitive adhesive composition that can be used by blending an isocyanate-based cross-linking agent. Thereby, the effect of extending the pot life of the pressure-sensitive adhesive composition can be exhibited.
Various β-dicarbonyl compounds can be used as compounds that cause keto-enol tautomerism. Specific examples include β-diketones such as acetylacetone and 2,4-hexanedione; acetoacetates such as methyl acetoacetate and ethyl acetoacetate; propionyl acetates such as ethyl propionylacetate; and isobutyryl such as ethyl isobutyrylacetate. acetic acid esters; malonic acid esters such as methyl malonate and ethyl malonate; and the like. Among the preferred compounds are acetylacetone and acetoacetates. The compounds that cause keto-enol tautomerism can be used singly or in combination of two or more.
The amount of the compound that causes keto-enol tautomerism is, for example, 0.1 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the base polymer (eg, acrylic polymer) contained in the pressure-sensitive adhesive composition. 0.5 to 15 parts by weight, for example, 1 to 10 parts by weight, or 1 to 5 parts by weight.

(Polyfunctional monomer)
A multifunctional monomer may be used in the adhesive composition (and thus in the adhesive layer) as necessary. Polyfunctional monomers can serve purposes such as adjusting cohesion. The polyfunctional monomer forms a crosslinked structure with appropriate flexibility by reacting the ethylenically unsaturated groups when forming the pressure-sensitive adhesive layer or by irradiating light (e.g., ultraviolet rays) after application to the adherend. obtain. Therefore, in the present specification, the term "polyfunctional monomer" can be rephrased as a cross-linking agent. For example, a polyfunctional monomer can be preferably used in a pressure-sensitive adhesive layer formed from a photocurable pressure-sensitive adhesive composition. Compounds having two or more ethylenically unsaturated groups can be used as polyfunctional monomers. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types.

Examples of ethylenically unsaturated groups possessed by polyfunctional monomers include, but are not limited to, acryloyl groups, methacryloyl groups, vinyl groups and allyl groups. Preferred ethylenically unsaturated groups from the viewpoint of photoreactivity include acryloyl groups and methacryloyl groups. Among them, an acryloyl group is preferred.

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 2 to Compounds with 6 ethylenically unsaturated groups are more preferred. In some embodiments, a compound having 4 or less (specifically 2 to 4, for example 2 or 3, preferably 2) ethylenically unsaturated groups in the molecule is used as the polyfunctional monomer. can be used. By using such a polyfunctional monomer having a limited number of ethylenically unsaturated groups, it is easy to obtain a pressure-sensitive adhesive layer having both extensibility and strength.

Examples of polyfunctional monomers 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, penta Erythritol 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, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl(meth)acrylate, vinyl(meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl diol (Meth)acrylate, hexyl diol di(meth)acrylate and the like. Among them, trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate are preferable, and 1,6-hexanediol diacrylate is more preferable.

The amount of the polyfunctional monomer used varies depending on its molecular weight, the number of functional groups, etc. ) It is appropriate to make the range of about 0.01 to 3.0 parts by weight per 100 parts by weight. In some embodiments, the amount of the polyfunctional monomer used relative to 100 parts by weight of the monomer component may be, for example, 0.02 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, It may be 1.0 parts by weight or more, or 2.0 parts by weight or more. Higher cohesive strength tends to be obtained by increasing the amount of polyfunctional monomer used. On the other hand, from the viewpoint of avoiding deterioration of adhesion between the pressure-sensitive adhesive layer and the adjacent layer due to excessive cohesive strength improvement, the amount of the polyfunctional monomer used relative to 100 parts by weight of the monomer component is, for example, 10 parts by weight or less. 5.0 parts by weight or less, or 3.0 parts by weight or less. In some aspects, the amount of the polyfunctional monomer to be used is, for example, 1.0 parts by weight or less, preferably 0.5 parts by weight or less, more preferably 0.5 parts by weight or less, based on 100 parts by weight of the monomer component. It is 3 parts by weight or less, and may be 0.2 parts by weight or less.

(Silane coupling agent)
In some embodiments, the adhesive layer can contain a silane coupling agent. A pressure-sensitive adhesive layer containing a silane coupling agent can suitably provide a surface protective sheet with high adhesiveness. A silane coupling agent can be used individually by 1 type or in combination of 2 or more types.

Silane coupling agents include silicon compounds having an epoxy structure such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)3-aminopropyltrimethoxysilane, N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane; 3-chloro Propyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as acetoacetyl group-containing trimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane; 3-isocyanatopropyltriethoxysilane and isocyanate group-containing silane coupling agents such as Among them, preferred examples include 3-glycidoxypropyltrimethoxysilane and acetoacetyl group-containing trimethoxysilane.

The amount of the silane coupling agent used can be set so as to obtain the desired effect of use, and is not particularly limited. In some aspects, the amount of the silane coupling agent used may be, for example, 0.001 parts by weight or more with respect to 100 parts by weight of the monomer component constituting the polymer contained in the pressure-sensitive adhesive layer, resulting in a higher effect. from the viewpoint of obtaining , it may be 0.005 parts by weight or more, 0.01 parts by weight or more, or 0.015 parts by weight or more. Further, from the viewpoint of improving adhesion, in some embodiments, the amount of the silane coupling agent used may be, for example, 3 parts by weight or less with respect to 100 parts by weight of the monomer component constituting the pressure-sensitive adhesive layer. It may be less than or equal to 0.5 parts by weight. Moreover, the technology disclosed herein can be implemented in a mode using a PSA composition that does not substantially contain a silane coupling agent. By limiting the use of a silane coupling agent or not using a silane coupling agent, it is possible to suppress an increase in adhesive strength over time and to easily obtain good water removability.

In addition, in a mode in which the monomer component contains an alkoxysilyl group-containing monomer, the alkoxysilyl group-containing monomer may be used as part or all of the silane coupling agent contained in the pressure-sensitive adhesive layer.

(Photoinitiator)
The adhesive composition and the photocurable adhesive layer disclosed herein may optionally contain a photopolymerization initiator (also referred to as a photoreaction catalyst) for the purpose of imparting photocurability. can. As the photopolymerization initiator, similar to the photopolymerization initiators exemplified as those that can be used for synthesizing an acrylic polymer, a ketal photopolymerization initiator, an acetophenone photopolymerization initiator, a benzoin ether photopolymerization initiator, Acylphosphine oxide photoinitiators, α-ketol photoinitiators, aromatic sulfonyl chloride photoinitiators, photoactive oxime photoinitiators, benzoin photoinitiators, benzyl photoinitiators , a benzophenone-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, and the like can be used. A photoinitiator can be used individually by 1 type or in combination of 2 or more types as appropriate.

The content of the photopolymerization initiator in the adhesive layer is not particularly limited, and can be set so that the desired effect is appropriately exhibited. In some embodiments, the content of the photopolymerization initiator is, for example, about 0.005 parts by weight with respect to 100 parts by weight of the monomer component of the polymer (typically an acrylic polymer) contained in the pressure-sensitive adhesive layer. It is suitable to be 0.01 parts by weight or more, preferably 0.05 parts by weight or more, may be 0.10 parts by weight or more, or 0.15 parts by weight or more. may be 0.20 parts by weight or more. By increasing the content of the photopolymerization initiator, the photocurability of the pressure-sensitive adhesive layer is improved. Also, the content of the photopolymerization initiator with respect to 100 parts by weight of the monomer component is suitably 5 parts by weight or less, preferably 2 parts by weight or less, and may be 1 part by weight or less. It may be 7 parts by weight or less, or may be 0.5 parts by weight or less. It is advantageous from the viewpoint of improving the storage stability (for example, stability against photodegradation) of the surface protective sheet that the content of the photopolymerization initiator is not too high.

A pressure-sensitive adhesive layer containing a photopolymerization initiator can typically be formed using a pressure-sensitive adhesive composition (for example, a solvent-based pressure-sensitive adhesive composition) containing the photopolymerization initiator. A pressure-sensitive adhesive composition containing a photopolymerization initiator can be prepared, for example, by mixing other components used in the composition with the photopolymerization initiator. Further, when preparing a pressure-sensitive adhesive composition using a polymer (typically an acrylic polymer) synthesized (photopolymerized) in the presence of a photopolymerization initiator, when synthesizing the polymer You may utilize the residue (unreacted material) of the photoinitiator used for as a part or all of the photoinitiator contained in an adhesive layer. The same applies to the case of using an acrylic oligomer synthesized in the presence of a photopolymerization initiator as necessary. From the viewpoint of ease of production management, the adhesive layer disclosed herein is preferably formed using an adhesive composition prepared by newly adding the photopolymerization initiator in the amount described above to other constituent components. can be

(other ingredients)
The pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer may optionally contain an acid or base (aqueous ammonia or the like) used for purposes such as pH adjustment. 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 anti-aging agents. Examples include various additives commonly used in the field of pressure-sensitive adhesive compositions, such as As for such various additives, conventionally known ones can be used in a conventional manner, and since they do not particularly characterize the present invention, detailed description thereof will be omitted. In addition, although not particularly limited, the technology disclosed herein can be preferably implemented in a mode including a pressure-sensitive adhesive layer containing the polymer (for example, an acrylic polymer) as a main component.

(Formation of adhesive layer)
The adhesive layer may be a cured layer of an adhesive composition. That is, the pressure-sensitive adhesive layer can be formed by applying (for example, applying) the pressure-sensitive adhesive composition to a suitable surface and then appropriately performing a curing treatment. When two or more curing treatments (drying, cross-linking, polymerization, etc.) are carried out, these can be carried out simultaneously or in multiple stages. A pressure-sensitive adhesive composition using a partially polymerized monomer component (acrylic polymer syrup) typically undergoes a final copolymerization reaction as the curing treatment. That is, the partial polymer is subjected to a further copolymerization reaction to form a complete polymer. For example, in the case of a photocurable pressure-sensitive adhesive composition, light irradiation is carried out. Curing treatments such as cross-linking and drying may be performed as necessary. For example, when the photocurable pressure-sensitive adhesive composition needs to be dried, photocuring may be performed after drying. A pressure-sensitive adhesive composition using a completely polymerized product is typically subjected to drying (drying by heating), cross-linking, or the like as necessary as the curing treatment. A pressure-sensitive adhesive layer having a multi-layer structure of two or more layers can be produced by laminating pre-formed pressure-sensitive adhesive layers. Alternatively, the pressure-sensitive adhesive composition may be applied onto a previously formed first pressure-sensitive adhesive layer, and the pressure-sensitive adhesive composition may be cured to form the second pressure-sensitive adhesive layer.

Application of the adhesive composition can be carried out 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 knife coater, and a spray coater. For example, as a method of providing an adhesive layer on a substrate layer, a direct method of directly applying an adhesive composition to the substrate layer to form an adhesive layer may be used. A transfer method for transferring the agent layer to the substrate layer may be used.

The thickness of the adhesive layer is not particularly limited, and can be, for example, about 3 μm to 1000 μm. From the viewpoint of enhancing water resistance reliability by adhering the pressure-sensitive adhesive layer to the substrate layer or the adherend, in some embodiments, the thickness of the pressure-sensitive adhesive layer is preferably 5 μm or more (for example, more than 5 μm), more preferably It is 10 μm or more (for example, more than 10 μm), more preferably 15 μm or more, and particularly preferably 20 μm or more. The surface protective sheet disclosed herein has water-releasing properties and can be smoothly peeled off and removed from the adherend using an aqueous liquid. (which can be expressed as adhesion after hot water immersion) can be increased to retain or improve protection. Further, from the viewpoint of preventing the occurrence of adhesive residue due to cohesive failure of the adhesive layer, in some embodiments, the thickness of the adhesive layer may be, for example, 500 μm or less, 300 μm or less, or 200 μm or less. , 150 μm or less. In some preferred embodiments, the thickness of the pressure-sensitive adhesive layer is 100 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, for example 40 μm or less, or 30 μm or less. By restricting the thickness of the adhesive layer, water intrusion from the edges of the adhesive layer is restricted, and a decrease in adhesive strength in a state of being immersed in an aqueous liquid or warm water can be suppressed. In addition, the pressure-sensitive adhesive layer may have a single layer structure, or may have a multilayer structure of two or more layers.

In some embodiments, the loss elastic modulus G″ at 60°C (60°C loss elastic modulus G″) of the pressure-sensitive adhesive layer is preferably in the range of 10 kPa or more and 50 kPa or less. According to the surface protection sheet provided with the adhesive layer having a 60° C. loss elastic modulus G″ in the above range, the viscosity term (60° C. loss elastic modulus G″) of the adhesive improves hot water resistance, Even when used (typically in the form of an aqueous solution) or in warm water, it is easy to maintain a state of close contact with the adherend, and the decrease in adhesive strength due to water peelability does not occur or the decrease in adhesive strength is easily suppressed. Therefore, even when the surface protective sheet is attached to an adherend and the adherend is treated in a liquid, the adhesion required for protection can be preferably maintained. In hot water, a peeling load is applied to the edge of the surface protective sheet due to the expansion and contraction of the base material layer, but in the case of an adhesive having a predetermined viscosity term at 60°C, the peeling load is converted into thermal energy. Since it can be reduced, it is conceivable that a stable adhesion state is likely to be maintained. Such a surface protective sheet can have excellent protective properties such that it does not peel off from the edges during the submerged treatment, for example.

In some preferred embodiments, the 60° C. loss elastic modulus G″ of the pressure-sensitive adhesive layer is 12 kPa or more, more preferably 15 kPa or more, or 18 kPa or more, from the viewpoint of adhesion after immersion in a chemical solution or hot water. may be 22 kPa or more, 25 kPa or more, 28 kPa or more, 30 kPa or more, or 32 kPa or more. F1 can be kept high. In some embodiments, the upper limit of the 60° C. loss elastic modulus G″ may be 45 kPa or less, 40 kPa or less, or 35 kPa or less. By limiting to the following, it is easy to obtain a pressure-sensitive adhesive having good adhesive properties suitable for surface protection applications. In some other aspects, the 60° C. loss elastic modulus G″ of the adhesive layer may be 30 kPa or less, 25 kPa or less, or 20 kPa or less.

More specifically, the 60° C. loss elastic modulus G″ of the adhesive layer is 11 kPa or less or less, 12 kPa or more or less, 13 kPa or more or less, 14 kPa or more or less, 15 kPa or more or less, 16 kPa or more or less, 17 kPa or more or less, 18 kPa or less or less, 19 kPa or more or less, 20 kPa or more or less, 21 kPa or more or less, 22 kPa or more or less, 23 kPa or more or less, 24 kPa or more or less, 25 kPa or more or less, 26 kPa or more or less, 27 kPa or more or less, 28 kPa or less or less, 29 kPa or more or less, 30 kPa or more or less, 31 kPa or more or less, 32 kPa or more or less, 33 kPa or more or less, 34 kPa or more or less, 35 kPa or more or less, 36 kPa or more or less, 37 kPa or more or less, 38 kPa or less or less, 39 kPa or more or less, 40 kPa or more or less, 41 kPa or more or less, 42 kPa or more or less, 43 kPa or more or less, 44 kPa or more or less, 45 kPa or more or less, 46 kPa or more or less, It may be 47 kPa or more or less, 48 kPa or more or less, or 49 kPa or more or less.

The 60° C. loss elastic modulus G″ can be obtained mainly by adjusting the molecular weight and molecular weight distribution of the polymer contained in the adhesive, and can also be adjusted by adjusting the crosslink density in the adhesive. The 60° C. loss elastic modulus G″ of the pressure-sensitive adhesive layer is measured by the method described in Examples below.

(repulsion resistance)
Although it is not particularly limited, the adhesive (layer) has a peel distance of 3.0 mm after one hour from pressure bonding to the adherend in a repulsion resistance test carried out by the method described in Examples below. Adhesives with a thickness of 0 mm or less are preferably used. The pressure-sensitive adhesive (layer) having such repulsion resistance is less likely to be peeled off from the adherend at the edges against a physical load (peeling load) in the thickness direction of the surface protection sheet having the pressure-sensitive adhesive (layer). , can exhibit excellent edge peeling prevention properties. The peel distance (one hour after crimping) in the repulsion resistance test is preferably 1.0 mm or less, more preferably 0.5 mm or less, still more preferably 0.3 mm or less, and particularly preferably 0.2 mm or less. , most preferably 0.0 mm. The anti-repulsion property can be realized based on the adhesive composition (use of tackifier, selection of tackifier type, type and amount of hydrophilic agent, etc.).

<Base material layer>
Non-limiting examples of materials for the substrate layer include various resin films such as polyolefin films, polyester films, and polyvinyl chloride films; foam sheets made of foams such as polyurethane foam, polyethylene foam, and polychloroprene foam; of fibrous substances (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, semi-synthetic fibers such as acetate, etc.) Woven fabrics and non-woven fabrics made by single or blended spinning, etc.; Japanese paper, fine paper, paper such as kraft paper and crepe paper; metal foil such as aluminum foil, copper foil, and stainless steel (SUS); A suitable material can be selected from the above and used as the base material layer material. Examples of the base material layer of the composite structure include a laminated base material (multilayer structure base material) having a structure in which a metal foil and the resin film are laminated, and a resin sheet reinforced with inorganic fibers such as glass cloth. be done.

Various films (hereinafter also referred to as base films) can be preferably used as the material for the base layer. The base film may be a porous film such as a foam film or a non-woven fabric sheet, or may be a film having a structure in which a porous layer and a non-porous layer are laminated. In some embodiments, as the base film, a base film containing a resin film capable of independently maintaining its shape (self-supporting or independent) can be preferably used. By "resin film" is meant a non-porous structure, typically a substantially voidless resin film. Therefore, the resin film is a concept distinguished from foam films and non-woven fabrics. The resin film may have a single-layer structure or a multilayer structure of two or more layers (for example, a three-layer structure).

Examples of the resin material constituting the resin film include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers. Polyolefins such as coalescence; polycycloolefins derived from monomers having an alicyclic structure such as norbornene structure; polyamides (PA) such as nylon 6, nylon 66, and partially aromatic polyamides; polyimides (PI) such as transparent polyimides (CPI) Polyether sulfone (PES); Polyphenylene sulfide (PPS); Polycarbonate (PC); Polyurethane (PU); Ethylene-vinyl acetate copolymer (EVA); polyvinyl alcohol (PVA); polystyrene; ABS resin; polyvinyl chloride; polyvinylidene chloride; fluorine resin such as polytetrafluoroethylene (PTFE); Resins such as cellulose-based polymer; vinyl butyral-based polymer; arylate-based polymer; polyoxymethylene-based polymer; and epoxy-based polymer can be used. The substrate layer disclosed herein may have a surface composed of the above resin material. The resin film that can be used as the substrate layer is suitably selected from those formed using a resin material containing one of the above resins alone and those formed using a resin material in which two or more of the above resins are blended. material can be selected and used. The resin film is a composite resin film in which a resin layer containing one or more resin materials and a resin layer containing one or more resin materials of the same or different type as the resin layer are laminated. There may be. The resin film may be unstretched or may be 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 a polyolefin resin film, it is possible to preferably obtain a surface protection sheet that exhibits suitable properties (e.g., adhesive strength F1 after immersion in warm water for 30 minutes and degree of decrease in water peel strength after immersion in warm water for 30 minutes) with an appropriate thickness. . Here, the polyolefin resin means a resin containing more than 50% by weight of polyolefin. As the polyolefin resin, one type of polyolefin can be used alone, or two or more types of polyolefin can be used in combination. The polyolefin may be, for example, an α-olefin homopolymer, a copolymer of two or more α-olefins, a copolymer of one or more α-olefins and other vinyl monomers, and the like. Specific examples include PE, PP, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymers such as ethylene-propylene rubber (EPR), ethylene-propylene-butene copolymers, ethylene -butene copolymer, ethylene-vinyl alcohol copolymer, ethylene-ethyl acrylate copolymer, and the like. Both low density (LD) and high density (HD) polyolefins can be used. Examples of polyolefin resin films include unstretched polypropylene (CPP) film, biaxially stretched polypropylene (OPP) film, low density polyethylene (LDPE) film, linear low density polyethylene (LLDPE) film, medium density polyethylene (MDPE). films, high-density polyethylene (HDPE) films, polyethylene (PE) films obtained by blending two or more kinds of polyethylene (PE), PP/PE blend films 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 suitable examples of the resin material that constitutes the resin film include polyvinylidene chloride resin, PPS resin, polyurethane resin, EVA resin, and fluorine resin such as PTFE. Here, the polyvinylidene chloride resin refers to a resin containing polyvinylidene chloride in a proportion exceeding 50% by weight. Similarly, PPS resin means a resin containing PPS in a proportion exceeding 50% by weight. The same applies to polyurethane resin, EVA resin, and fluororesin. The polyolefin resins (PE, PP), polyvinylidene chloride resins, PPS resins, polyurethane resins, EVA resins, and fluorine resins exemplified above may be used in combination with other materials, and each may be used alone. You may use it as a base material layer.

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

The method of manufacturing 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, and calendar roll molding can be appropriately employed.

The base material layer may be substantially composed of such a resin film. Alternatively, the substrate layer may contain an auxiliary layer in addition to the resin film. Examples of the auxiliary layers include optical property adjusting layers (e.g., colored layers, antireflection layers), printed layers and laminate layers for imparting desired appearance, antistatic layers, undercoat layers, release layers, etc. A processing layer may be mentioned.

In some other aspects, the substrate layer has a layer containing an inorganic material (inorganic material-containing layer). By adopting a substrate layer including an inorganic material-containing layer, the effects of the technology disclosed herein can also be achieved. Arranging the inorganic material-containing layer tends to improve barrier properties (moisture permeation prevention properties). In some aspects, the substrate layer having an inorganic material-containing layer includes the above-described resin film or the like as a substrate main layer, and an inorganic material-containing layer provided on at least one surface of the substrate main layer. A configuration having In some other aspects, the substrate layer may consist essentially of the inorganic material-containing layer.

Inorganic materials used for the inorganic material-containing layer include various metal materials including simple substances and alloys of transition metal elements and metalloid elements, and materials capable of forming a hydrophilic surface from among inorganic compounds such as inorganic oxides. is used. The above inorganic materials can be used singly or in combination of two or more. Suitable examples of inorganic materials include 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. (inorganic oxides, typically metal oxides). Among them, an inorganic oxide such as silicon oxide is used as a preferable inorganic material. Other preferred examples of inorganic materials include metal foils (metal materials) such as aluminum foil, copper foil, and stainless steel (SUS). The inorganic material-containing layer may or may not contain various organic materials including organic polymer compounds that can be used as coating agents and binders, in addition to the above inorganic materials.

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

The method of forming the layer containing the inorganic material is not particularly limited, and can be formed by an appropriate method depending on the desired thickness and the like. For example, it is possible to use an inorganic material formed in a layer using a known film forming method such as a vacuum vapor deposition method, a sputtering method, or a plating method. When an inorganic compound is used as the inorganic material, various vapor deposition methods can be used, for example, physical vapor deposition (PVD) such as vacuum vapor deposition, sputtering, ion plating, atomic layer deposition, etc. chemical vapor deposition (CVD) or the like can be employed. A coating layer containing an inorganic polymer such as polysiloxane can be formed by appropriately selecting from known coating agents that provide a surface exhibiting a desired water contact angle and using a conventional method.

The thickness of the inorganic material-containing layer is not particularly limited. In the embodiment in which the substrate layer has a substrate main layer and an inorganic material-containing layer, the thickness of the inorganic material-containing layer is Specifically, about 5 μm or less (for example, less than 5000 nm) is suitable, and about 2 μm or less (for example, less than 2000 nm) may be used. In some aspects, the inorganic material-containing layer has a thickness of less than 1000 nm, more preferably less than 500 nm, even more preferably less than 100 nm, particularly preferably less than 50 nm, and may be about 30 nm or less, about 20 nm. 15 nm or less (for example, less than 10 nm). By forming such a thin inorganic material-containing layer, desired properties such as barrier properties (anti-moisture permeation) can be imparted to the base layer without impairing the function of the base layer (main layer of the base layer). can do. A thin inorganic material-containing layer is also advantageous from the viewpoint of lightness and optical properties. In addition, the thickness of the inorganic material-containing layer is appropriately 1 nm or more (for example, 3 nm or more). .

In the aspect in which the substrate layer has a substrate main layer and an inorganic material-containing layer, the thickness of the substrate main layer (when it has a plurality of layers other than the inorganic material-containing layer, the layers other than the inorganic material-containing layer The total thickness of the substrate layer) is suitably 50% or more, preferably 70% or more, more preferably 90% or more, and 97% or more (for example, 99% or more) of the total thickness of the base layer. may

The base material layer may have a single-layer structure, or may have a multi-layer structure of two or more layers. Examples of the substrate layer having a single-layer structure include a substrate layer made of a resin film. A substrate layer composed of a resin film is suitable for a surface protection sheet for chemical treatment such as an etchant. It also tends to be superior in flexibility and flexibility. Examples of the substrate layer having a multilayer structure include a structure composed of a resin film having a multilayer structure, and a structure having a substrate main layer and an inorganic material-containing layer.

In some embodiments, the base layer (base film used as the base layer) preferably has a moisture permeability of 24 g/(m ² ·day) or less as measured by the cup method. With such a structure having a limited moisture permeability, even if it is used in a mode of contact with an aqueous liquid such as chemical treatment or hot water immersion, the presence of the low moisture permeability base layer allows water to pass through to the pressure-sensitive adhesive layer. Infiltration of liquids is appropriately prevented, and deterioration of adhesive strength due to water releasability does not occur, or deterioration of adhesive strength is suppressed. As a result, the adhesive force to the adherend is maintained, and the surface protective sheet can maintain the state of close contact with the adherend. In some preferred embodiments, the moisture permeability of the base material layer is about 18 g/(m ² ·day) or less, more preferably about 14 g/(m ² ·day) or less, even more preferably about 10 g/( m ² ·day) or less, particularly preferably approximately 8 g/(m ² ·day) or less, and may be approximately 5 g/(m ² ·day) or less (for example, approximately 3 g/(m ² ·day) or less). Further, when the surface protective sheet is exposed to heat such as warm water, if the moisture permeability is excessively low, the water releasability may not be effectively exhibited due to aging due to heat. From such a viewpoint, in some aspects, the moisture permeability of the base material layer is suitably 1 g/(m ² ·day) or more, preferably about 3 g/(m ² ·day) or more. Yes, for example greater than 5 g/(m ² ·day).

More specifically, the moisture permeability of the substrate layer is, for example, 23 g/(m ² ·day) or more or less, 22 g/(m ² ·day) or more or less, or 21 g/(m ² ·day) or more. or less, 20 g/(m ² ·day) or more or less, 19 g/(m ² ·day) or more or less, 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 or less, 15 g/(m ² ·day) or more or less, 14 g/(m ² ·day) or more or less, 13 g/(m ² ·day) or more or 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) or more or less.

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

The 25° C. bending rigidity value of the substrate layer (substrate film used as the substrate layer) can be in the same range as the range of the 25° C. bending rigidity value that can be taken by the surface protective sheet described above. Description is omitted. Similarly, the ranges of the 25°C tensile modulus, the stress at 25°C 100% elongation, the 25°C breaking stress, and the 25°C breaking strain that the base material layer can take are also the 25°C tensile elastic modulus of the surface protective sheet, the 25°C 100 The ranges of stress at % elongation, stress at break at 25° C. and strain at break at 25° C. can be the same ranges, respectively, so repeated explanations are omitted. The 25° C. flexural rigidity value, 25° C. tensile modulus, 25° C. 100% elongation stress, 25° C. breaking stress and 25° C. breaking strain of the base material layer were measured using the base material layer as a test piece (the base material used as the base layer Film) is used, but the 25° C. flexural rigidity, 25° C. tensile modulus, 25° C. 100% elongation stress, 25° C. breaking stress and 25° C. breaking strain of the surface protective sheet are measured in the same manner. The thickness and cross-sectional area of the test piece used to calculate the 25° C. bending stiffness value, 25° C. tensile modulus, stress at 25° C. 100% elongation and 25° C. breaking stress were as follows: Used. The 25° C. bending rigidity value of the base material layer may be the MD 25° C. bending rigidity value or the TD 25° C. bending rigidity value, like the 25° C. bending rigidity value of the surface protection sheet. , Therefore, it may be at least one of the 25 ° C. bending stiffness value of MD and the 25 ° C. bending stiffness value of TD, or any one direction regardless of whether it is MD or TD may be the 25° C. bending stiffness value of Similarly, the 25° C. tensile modulus of the substrate layer may be the 25° C. tensile modulus in MD or the 25° C. tensile modulus in TD, thus 25° C. tensile modulus in MD and It may be at least one 25° C. tensile modulus of TD, or it may be a 25° C. tensile modulus in any one direction, whether MD or TD. . Similarly, the stress at 100% elongation, stress at break and strain at break of the substrate layer may each be a measured value of MD (stress at 100% elongation, stress at break or strain at break), and a measured value of TD and thus may be a measurement in MD and/or a measurement in TD, or any one-way measurement, whether MD or TD. may

The thickness of the base material layer is not particularly limited, and can be selected according to the purpose of protection, mode of use, and the like. The thickness of the substrate layer may be, for example, about 1000 μm or less, or about 300 μm or less, and from the viewpoint of weight reduction and thinning, about 100 μm or less is suitable, preferably about 75 μm or less (typically less than 75 μm), more preferably approximately 50 μm or less, may be 40 μm or less, or may be 30 μm or less. When the thickness of the base material layer is reduced, the flexibility of the surface protection sheet and the followability to the surface shape of the adherend tend to be improved. In addition, since the deformation (expansion and shrinkage) of the base material layer due to heating is suppressed by limiting the thickness of the base material layer, for example, when used in a heated manner such as immersion in warm water. Even if there is, there is a tendency that the state of adhesion to the adherend is likely to be maintained. Moreover, from the viewpoint of handleability, processability, etc., 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 may be about 30 μm or more, or even 40 μm or more. It may be 50 μm or more. As the thickness of the substrate layer increases, the adherend tends to be more protected against permeation of chemicals.

Conventionally known surface treatments such as corona treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of an undercoat (primer), etc. may be applied to the adhesive layer side surface of the substrate layer, if necessary. may be applied. Such a surface treatment can 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 composition of the primer is not particularly limited, and can be appropriately selected from known ones. Although the thickness of the undercoat layer is not particularly limited, it is suitably about 0.01 μm to 1 μm, preferably about 0.1 μm to 1 μm. In addition, the surface of the base material main layer (typically, the inorganic material-containing layer side surface) may be subjected to the various surface treatments described above, antistatic treatment, and other surface treatments.

The surface of the substrate layer opposite to the pressure-sensitive adhesive layer side (hereinafter also referred to as the back surface) is optionally subjected to conventionally known surface treatments such as peeling treatment and antistatic treatment. good too. For example, by surface-treating the back surface of the base material layer with a release agent, the unwinding force of the surface protective sheet wound into a roll can be reduced. Examples of release agents that can be used include silicone-based release agents, long-chain alkyl-based release agents, olefin-based release agents, fluorine-based release agents, fatty acid amide-based release agents, molybdenum sulfide, and silica powder. .

<Total thickness>
The thickness of the surface protection sheet disclosed herein (including the pressure-sensitive adhesive layer and the base material layer, but not including the release liner) is not particularly limited, and may be 3 μm or more, and may be 5 μm or more. , 10 μm or more is appropriate, and from the viewpoint of adhesion to the adherend such as step conformability, it is preferably 20 μm or more, more preferably 30 μm or more, still more preferably 40 μm or more, and may be 45 μm or more. As the thickness of the surface protection sheet increases, there is a tendency that the protection of the adherend against penetration of chemical solutions and the like improves. In some aspects, the thickness of the surface protection sheet is greater than 50 μm, may be 60 μm or greater, may be 70 μm or greater, or may be 80 μm or greater. The upper limit of the thickness of the surface protective sheet is, for example, 5 mm or less, may be 3 mm or less, or may be 1 mm or less. In some aspects, the thickness of the surface protective sheet is suitably 300 μm or less (for example, 200 μm or less), preferably 100 μm or less, more preferably 75 μm or less, and further preferably 65 μm or less. Preferably, it may be, for example, 55 μm or less. By limiting the thickness of the surface protective sheet to a predetermined value or less, the surface protective sheet is prevented from being deformed (expansion and contraction) due to heating, and tends to easily maintain the state of adhesion to the adherend. . Reducing the thickness of the adhesive sheet is advantageous in terms of thinning, miniaturization, weight reduction, resource saving, and the like.

<Release liner>
The release liner used in the surface protection sheet disclosed herein is not particularly limited, and may be, for example, a release liner in which the surface of a liner substrate such as a resin film or paper is subjected to a release treatment, or a fluoropolymer (polytetrafluoroethylene etc.) or a release liner made of a low-adhesive material such as polyolefin resin (polyethylene, polypropylene, etc.). For the release treatment, for example, a release treatment agent such as a silicone-based agent or a long-chain alkyl-based agent may be used. In some embodiments, a release-treated resin film can be preferably employed as a release liner.

<Peeling method>
According to this specification, a method for peeling a surface protective sheet attached to an adherend (object to be protected) is provided. In the peeling method, in a state where an aqueous liquid is present at the interface between the adherend and the surface protective sheet on the peeling front of the surface protective sheet from the adherend, the peeling front follows the movement of the peeling front. It includes a water-peeling step of peeling the surface protective sheet from the adherend while allowing the aqueous liquid to enter the interface. According to the water peeling step, the surface protective sheet can be peeled from the adherend by effectively using the aqueous liquid.

As the aqueous liquid, it is possible to use water or a mixed solvent containing water as a main component containing a small amount of additive as necessary. As a solvent other than water that constitutes the mixed solvent, a lower alcohol (eg, ethyl alcohol) or a lower ketone (eg, acetone) that can be uniformly mixed with water can be used. A known surfactant or the like can be used as the additive. From the viewpoint of avoiding contamination of the adherend, in some embodiments, an aqueous liquid containing substantially no additives can be preferably used. From the viewpoint of environmental hygiene, it is particularly preferable to use water as the aqueous liquid. The water is not particularly limited, and in consideration of the purity required according to the application, availability, etc., for example, distilled water, ion-exchanged water, tap water, etc. can be used.

In some embodiments, the peeling method includes supplying an aqueous liquid onto the adherend near the outer edge of the surface protection sheet attached to the adherend, for example, in the same manner as when measuring the normal water peeling force FW0, After 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, without supplying new water (that is, before starting peeling, it is applied to the adherend. It can be preferably carried out in a mode in which peeling of the surface protection sheet is promoted using only the supplied aqueous liquid. In the middle of the water peeling step, if the water that follows the movement of the peeling front and enters the interface between the surface protective sheet and the adherend is depleted in the middle, intermittent water peeling after the start of the water peeling step. Alternatively, additional water may be supplied continuously. For example, when the adherend has water absorbability, or when aqueous liquid tends to remain on the surface of the adherend or adhesive surface after peeling, it is preferable to adopt a mode of additionally supplying water after starting the water peeling step. obtain.

The amount of the aqueous liquid to be supplied before starting peeling is not particularly limited as long as the amount is sufficient to introduce the aqueous liquid to the interface between the surface protection sheet and the adherend from outside the attachment range of the surface protection sheet. The amount of the aqueous liquid may be, for example, 5 μL or more, usually 10 μL or more, and may be 20 μL or more. Moreover, there is no particular limitation on the upper limit of the amount of the aqueous liquid. In some embodiments, the amount of the aqueous liquid may be, for example, 10 mL or less, 5 mL or less, 1 mL or less, 0.5 mL or less, or 0.1 mL or less from the viewpoint of improving workability. or less than 0.05 mL. By reducing the amount of the aqueous liquid, it is possible to omit or simplify the operation of removing the aqueous liquid by drying, wiping, or the like after peeling the surface protective sheet.

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 can be performed, for example, by inserting a jig such as a cutter knife or a needle into the interface at the outer edge of the surface protective sheet. insert the tip of the surface protection sheet, scratch the outer edge of the surface protection sheet with a hook or nail, etc., attach a strong adhesive tape or suction cup, etc. to the back surface near the outer edge of the surface protection sheet It can be carried out in a manner such as lifting. By forcing the aqueous liquid to enter the interface from the outer edge of the surface protective sheet in this way, it is possible to efficiently create a state in which the aqueous liquid exists at the interface between the adherend and the surface protective sheet. In addition, both good water releasability after an operation for forcing an aqueous liquid to enter the interface to create a trigger for delamination and high water resistance reliability when no such operation is performed are preferably compatible. can be done.

<Application>
The surface protective sheet disclosed here can be used as a surface protective sheet for various uses. For example, in various treatments such as chemical treatment of glass, semiconductor wafers, metal plates, etc. using chemical solutions and physical treatments such as cutting and polishing, the surface protection sheet disclosed herein For example, it can be used by being attached to the non-processed surface of the object to be processed.

The type of adherend (also called an object to be protected; it can be an object to be treated) is not particularly limited. The surface protective sheet disclosed herein can be used to protect various members and materials. The surface protective sheet disclosed herein can be peeled off using an aqueous liquid without damaging or deforming the adherend, so it is suitable for protecting glass materials such as alkali glass, semiconductor wafers, and the like. be. These materials usually have a limited thickness and are brittle materials (also called hard brittle materials) that are likely to crack, chip, or crack due to external force during handling or peeling. By applying peeling using an aqueous liquid to such an adherend, it is possible to suitably prevent damage to the adherend during peeling. The glass material to be the adherend is, for example, a transparent conductive film (e.g., ITO (indium tin oxide) film) or FPC, which is used for tablet personal computers, mobile phones, organic LEDs (light emitting diodes), etc. It may be a glass plate having a surface provided on the Preferred examples of adherends include glass plates such as window glass and cover glass used in foldable displays and rollable displays. These glass plates are thin (e.g., 100 μm or less in thickness) and have a higher risk of breakage. Also, damage to the adherend can be prevented at the time of peeling.

The water contact angle of the adherend surface to which the surface protection sheet is attached is not particularly limited. In some embodiments, the adherend surface can be a hydrophilic surface with a water contact angle of, 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 small, water tends to spread along the surface of the adherend, and desired water removability tends to be obtained. The surface protective sheet disclosed herein is, for example, a surface made of a material (for example, glass such as an alkali glass plate or alkali-free glass) having a water contact angle of about 20 degrees or less (for example, 15 degrees or less, further 10 degrees or less). can be preferably used to protect members having In principle, the lower limit of the water contact angle on the surface of the adherend is 0 degree. In some aspects, the water contact angle of the adherend surface may be greater than 0 degrees, 1 degree or more, 3 degrees or more, or 5 degrees or more. In some other embodiments, the water contact angle of the adherend surface may be greater than 30 degrees, greater than 50 degrees, or greater than 60 degrees (e.g., 70 degrees or greater). . The surface protective sheet disclosed herein can be used for various materials with different water contact angles. The water contact angle on the surface of the adherend is measured by a method similar to the contact angle measuring method described in Examples below.

The thickness of the adherend (for example, glass plate or semiconductor wafer) is not particularly limited, and is, for example, approximately 1 mm or less, and may be approximately 500 μm or less or approximately 300 μm or less. Since the effect of the technology disclosed herein (prevention of breakage during peeling) is more effectively exhibited for thin adherends, the thickness may be, for example, about 150 μm or less, It may be about 100 μm or less. The lower limit of the thickness is, for example, approximately 10 μm or more (eg, 30 μm or more).

In some preferred embodiments, for example, it is suitable as a surface protective sheet used in a process of chemically and/or physically treating an object to be treated such as glass or a semiconductor wafer in a liquid. In the above applications, the surface protective sheet disclosed herein can have the adhesiveness necessary for protecting the object to be treated during the treatment, and when peeled off after the treatment, the object to be treated (attached) (body) can be smoothly peeled off using an aqueous liquid. The chemical treatment includes treatment with a chemical solution containing an acid or an alkali, such as an etching solution such as an aqueous hydrofluoric acid solution. For example, etching processing that dissolves glass with a chemical solution (etching solution) to adjust the thickness of the glass and remove burrs and microcracks formed on the cut edge of the glass, anti-glare processing, chemical solution (etching solution) on the surface of the metal Etching treatment that partially corrodes with, plating treatment that partially plating the connection terminal part of the circuit board (printed circuit board, flexible printed circuit board (FPC), etc.) with a chemical solution (plating solution), etc. disclosed here A surface protection sheet can be preferably used. Among others, it can be particularly preferably applied to an application in which an etching treatment is performed using an acidic chemical solution such as a hydrofluoric acid solution. Physical processing includes polishing and cutting of the surface of the object to be processed.

The surface protective sheet disclosed here is preferably used for glass slimming treatment. For example, a glass plate used as an optical member can be thinned by glass slimming treatment using a chemical such as a hydrofluoric acid solution. In this glass slimming process, a surface protective sheet can be used to protect the non-processed surface of the glass. Although not particularly limited, in the glass slimming process, the glass plate is thinned to, for example, about 150 μm or less (eg, about 100 μm or less). The thickness of the glass plate before the glass slimming process is, for example, about 0.15 mm to 5 mm, and can be about 300 μm or more (for example, about 500 μm to 1000 μm). Such thin glass tends to break due to external force when peeled off, but by using the surface protective sheet disclosed herein, the problem of glass breakage during peeling of the surface protective sheet can be solved, or the problem can be solved. Risk can be greatly reduced.

In addition, the surface protection sheet can also be preferably used for the production of 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), etc.), a compound semiconductor wafer such as a gallium arsenide wafer, or the like. In the manufacture of the above semiconductor, for example, semiconductor wafer processing such as a step of thinning a semiconductor wafer (more specifically, a back grinding step of polishing the back surface of a semiconductor wafer) and a step of cutting a semiconductor wafer (for example, a dicing step) The surface protective sheet disclosed herein can be preferably used in a process (typically silicon wafer processing). Although not particularly limited, in the back grinding process, the semiconductor wafer is thinned to, for example, about 150 μm or less (eg, about 100 μm or less). The thickness of the semiconductor wafer before back grinding can be about 300 μm or more (for example, about 500 μm to 1000 μm). Since the semiconductor manufacturing process can be exposed to temperatures higher than room temperature (for example, 40° C. to 90° C., preferably 40° C. to 60° C.), good properties (adhesion and water removability) against such heating are required. Of particular interest is the use of surface protective sheets that can be retained. Surface protective sheets used for such purposes are sometimes simply referred to as backgrinding sheets or dicing sheets.

In some aspects, the surface protection sheet used for the above-mentioned various surface protection applications is a state in which one surface protection sheet is attached to one side of one or more processing objects, and a conveying means such as a roller is applied. It can be used in such a manner that a plurality of objects to be treated (also objects to be protected) are transported continuously or individually into water such as a chemical tank or a cleaning tank, and the intended treatment is carried out. In the process during and after transportation (including placement and setting in equipment, etc.), external forces such as impact, vibration, deformation, etc. may be applied unavoidably or unintentionally to the object to be processed. be. For example, a plurality of rollers arranged at predetermined intervals can be used as a conveying means used in chemical liquid processing and cleaning processing. of peeling load is likely to be applied continuously. Since the surface protection sheet disclosed herein is excellent in preventing peeling of the edges against external forces such as vibration, the object to be treated can be treated, for example, in a liquid while being attached to the object to be treated as described above. Even when it is used in a process including a step of cleaning, it has the advantage that it is less likely to come off from the edge due to external forces such as vibration during the process. In addition, in the aspect of performing physical treatment such as cutting and polishing on an object to be treated such as a semiconductor wafer, the external force in the physical treatment becomes a peeling load. As a result, even when a physical load is applied in a physical treatment process, peeling from the edge is less likely to occur. The vibration in the transporting process and the physical load (also referred to as peeling load) in the physical treatment process typically include the load applied in the thickness direction of the surface protective sheet.

Further, the adherend is, for example, a liquid crystal display device, an organic EL (electroluminescence) display device, a PDP (plasma display panel), a display device (image display device) such as electronic paper, or an input device such as a touch panel. It can be a member constituting a device (optical device), particularly a portable electronic device such as a foldable display or a rollable display.

Examples of the above portable electronic devices include, for example, mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wrist wear types worn on the wrist like wristwatches, Modular type to be worn on the body, eyewear type including glasses type (monocular type and binocular type, including head-mounted type), clothing type to be attached to shirts, socks, hats, etc. in the form of accessories, earphones earwear type, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, vehicle information Equipment, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. In this specification, the term “portable” means not only being able to be carried around, but also having a level of portability that allows an individual (a typical adult) to carry it relatively easily. shall mean.

<Protection method>
From the above, according to the present specification, there is provided a surface protection method using the surface protection sheet disclosed herein. This surface protection method includes a step of attaching a surface protection sheet to at least a part of an object to be protected (a surface to be protected or a portion to be protected); treatment, warm water immersion treatment, water immersion treatment, physical treatment such as cutting and polishing, etc.); Here, the step of peeling the surface protection sheet from the object to be protected is preferably carried out in the presence of water, and may include, for example, the water peeling step described above. The protection method is also called a treatment method because it includes treatment of the object to be protected (object to be treated). The details of the surface protective sheet, the water-peeling step, the object to be protected, the treatment (glass slimming treatment, semiconductor wafer thinning treatment, etc.), and other matters (applications, etc.) are as described above, and therefore repeated descriptions will be omitted. Typical examples of objects to be protected include glass plates, semiconductor wafers, and the like to which processing such as glass slimming is performed. Therefore, according to the present specification, a glass slimming method and a semiconductor manufacturing method including the above steps can be provided.

<Processing method>
Also, from the above, the present specification provides a treatment method using the surface protective sheet disclosed herein. This treatment method includes a step of attaching a surface protective sheet to the surface of the object to be treated; a step of treating the object to which the surface protective sheet is attached; and treating the surface protective sheet after the above treatment. and a step of removing from the object (processed object). In the object to be treated, the surface to which the surface protection sheet is attached is typically a surface having a water contact angle of 20 degrees or less. In addition, in the above treatment process, the object to be treated typically comes into contact with a liquid (for example, an aqueous solution). The step of removing the surface protective sheet from the object to be treated (processed object) is preferably a step of peeling and removing the surface protective sheet from the object to be treated (processed object) in the presence of water. The treatment methods disclosed herein may include at least one of the steps of the protection methods described above. As the surface protective sheet, the surface protective sheet disclosed herein is used. Examples of processing include glass slimming processing and semiconductor processing, and typical examples of processing objects include glass plates and semiconductor wafers on which processing such as glass slimming is performed. Therefore, according to the present specification, a glass slimming method and a semiconductor manufacturing method including the above steps can be provided. The details of the surface protection sheet, water peeling, removal step, object to be treated, treatment (glass slimming treatment, semiconductor wafer thinning treatment, etc.), and other matters (applications, etc.) are as described above, so repeated explanations are omitted. do.

Several examples of the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

<Evaluation method>
[Normal adhesive strength F0]
A surface protective sheet to be measured is cut into a size of 20 mm in width and 100 mm in length to prepare a test piece. In an environment of 23 ° C. and 50% RH, the release liner covering the adhesive surface (adhesive layer surface) was peeled off from the test piece, and the exposed adhesive surface was attached to an alkali glass plate (water contact angle of 20 degrees) as an adherend. A 2-kg rubber roller is made to reciprocate once against the surface of the alkali glass having the following surface) and pressed against it. The sample for evaluation thus obtained is autoclaved (50° C., 0.5 MPa, 15 minutes). After holding the evaluation sample taken out of the autoclave for 1 hour in an environment of 23 ° C. and 50% RH, under the same environment, JIS Z0237: 2009 10.4.1 Method 1: 180 ° peeling off from the test plate According to the adhesive strength, using a tensile tester, the peel strength of the test piece from the adherend under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees (however, until the following water peel strength measurement is performed, that is, the peel interface Measure the peel strength for the period until distilled water is supplied to. The measurement is performed three times, and the average value thereof is taken as the normal state adhesive strength F0 [N/20 mm]. The normal state adhesive force F0 is measured so that the peeling of the test piece attached to the adherend progresses from the bottom to the top. As the adherend, an alkali glass plate (product name “Microslide Glass S200423”, manufactured by Matsunami Glass Industry Co., Ltd.) can be used. As the tensile tester, a universal tensile/compression tester (equipment name “Tensile/Compression Tester, TCM-1kNB” manufactured by Minebea Co., Ltd.) or its equivalent can be used.
In the measurement, if necessary, the test piece may be reinforced by attaching an appropriate backing material to the opposite surface of the surface protective sheet (the surface opposite to the adhesive surface). As the backing material, for example, a polyethylene terephthalate (PET) film having a thickness of about 25 μm can be used.

[Normal water peeling force FW0]
In the measurement of the normal state adhesive strength F0, during the measurement of the peel strength of the test piece from the adherend, 20 μL of distilled water is supplied to the point where the test piece starts to separate from the adherend (peeling front), Measure the peel strength after supplying distilled water. The measurement is performed each time the normal state adhesive strength F0 is measured (that is, three times), and the average value thereof is taken as the normal state water peel strength FW0 [N/20 mm].
The conditions for measuring the peel strength after supplying distilled water shall comply with JIS Z0237:2009, 10.4.1 Method 1: 180° peeling adhesive strength to test plate. Specifically, the test temperature is 23° C., the tensile speed is 300 mm/min, and the peel angle is 180 degrees using a tensile tester.
In addition, the measurement of the normal state water peeling force FW0 may be performed by continuously measuring the normal state adhesive force F0 and the normal water peeling force FW0 for each test piece. The measurement of the water peel force FW0 may be performed using a different specimen. For example, in a case where it is difficult to prepare test strips having a sufficient length for continuous measurement, it is possible to employ a mode in which different test strips are used for measurement. The adherend, tensile tester, and other matters are the same as those for the normal state adhesive strength F0 measurement.

[Adhesive strength F1 after immersion in hot water for 30 minutes]
Adhesion F1 after immersion in hot water for 30 minutes was measured by immersing an evaluation sample (an alkali glass plate to which a test piece (surface protective sheet) was attached) in hot water at 60°C ± 2°C for 30 minutes, and then pulling it out of the hot water. Except for measuring the peel strength after wiping off the adhering water, it is measured in the same manner as the normal adhesive strength F0.
Specifically, similarly to the measurement of the normal state adhesive strength F0, the surface protection sheet to be measured is cut into a size of 20 mm in width and 100 mm in length to prepare a test piece. In an environment of 23 ° C. and 50% RH, the release liner covering the adhesive surface (adhesive layer surface) was peeled off from the test piece, and the exposed adhesive surface was applied to an alkali glass plate as an adherend, and a 2 kg rubber roller. to crimp once. The sample for evaluation thus obtained is autoclaved (50° C., 0.5 MPa, 15 minutes). A sample for evaluation taken out from the autoclave is immersed in a water bath containing hot water at a set temperature of 60° C.±2° C. for 30 minutes. As hot water, deionized water or distilled water is used. The sample for evaluation is held horizontally in warm water with the adhesive layer facing upward. The distance (immersion depth) from the upper surface of the evaluation sample to the water surface is set to 10 mm or more (for example, about 10 mm to 100 mm). Next, pull up the evaluation sample from the hot water, gently wipe off the water adhering to the evaluation sample, and then in an environment of 23 ° C. and 50% RH, JIS Z0237: 2009 10.4.1 Method 1 : According to the 180° peeling adhesive strength to the test plate, using a tensile tester, the peel strength from the adherend of the test piece under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees (however, the following water peel strength measurement , that is, until distilled water is supplied to the peel interface). The measurement is performed three times, and the average value thereof is defined as the adhesive strength F1 [N/20 mm] after immersion in warm water for 30 minutes. The time from when the evaluation sample is pulled out of the hot water to when the peel strength is measured is within 10 minutes. The adherend, tensile tester, and other matters are the same as those for the normal state adhesive strength F0 measurement.

[Water peeling force FW1 after immersion in hot water for 30 minutes]
Water peel strength FW1 after immersion in hot water for 30 minutes is measured by immersing an evaluation sample (an alkali glass plate to which a test piece (surface protective sheet) is attached) in hot water at 60°C ± 2°C for 30 minutes, and then pulling it out of the hot water. Except for measuring the water peeling force after wiping off the adhering water, it is measured in the same manner as the normal water peeling force FW0.
Specifically, in the measurement of the adhesive strength F1 after immersion in hot water for 30 minutes, the test piece separated from the adherend during measurement of the peel strength of the test piece from the adherend after immersion in hot water for 30 minutes. 20 μL of distilled water is supplied to the starting point (peeling front), and the peel strength after supplying the distilled water is measured. The measurement is performed each time the adhesive strength F1 is measured after immersion in warm water for 30 minutes (that is, three times), and the average value thereof is taken as the water peel strength FW1 [N/20 mm] after immersion in warm water for 30 minutes.
The conditions for measuring the peel strength after supplying distilled water shall comply with JIS Z0237:2009, 10.4.1 Method 1: 180° peeling adhesive strength to test plate. Specifically, the test temperature is 23° C., the tensile speed is 300 mm/min, and the peel angle is 180 degrees using a tensile tester.
The water peel strength FW1 after immersion in hot water for 30 minutes was measured by continuously measuring the adhesive strength F1 after immersion in hot water for 30 minutes and the peel strength FW1 after immersion in hot water for 30 minutes for each test piece. Alternatively, the measurement of the adhesive strength F1 after immersion in warm water for 30 minutes and the measurement of the water peel strength FW1 after immersion in warm water for 30 minutes may be performed using different test pieces. The adherend, tensile tester, and other matters are the same as those for the normal state adhesive strength F0 measurement.

[Adhesive strength F2 after immersion in warm water for 1 hour]
The adhesive strength F2 after immersion in warm water for 1 hour is measured in the same manner as the adhesive strength F1 after immersion in warm water for 30 minutes, except that the time of immersion in hot water is 1 hour.
Specifically, similarly to the measurement of the normal state adhesive strength F0, the surface protection sheet to be measured is cut into a size of 20 mm in width and 100 mm in length to prepare a test piece. In an environment of 23 ° C. and 50% RH, the release liner covering the adhesive surface (adhesive layer surface) was peeled off from the test piece, and the exposed adhesive surface was applied to an alkali glass plate as an adherend, and a 2 kg rubber roller. to crimp once. The sample for evaluation thus obtained is autoclaved (50° C., 0.5 MPa, 15 minutes). A sample for evaluation taken out of the autoclave is immersed in a water bath containing hot water at a set temperature of 60° C.±2° C. for 1 hour. The conditions for hot water immersion are the same as those for the adhesive strength F2 after 30 minutes hot water immersion. Next, pull up the evaluation sample from the hot water, gently wipe off the water adhering to the evaluation sample, and then in an environment of 23 ° C. and 50% RH, JIS Z0237: 2009 10.4.1 Method 1 : According to the 180° peeling adhesive strength to the test plate, using a tensile tester, the peel strength from the adherend of the test piece under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees (however, the following water peel strength measurement , that is, until distilled water is supplied to the peel interface). The measurement is performed three times, and the average value thereof is taken as the adhesive strength F2 [N/20 mm] after immersion in hot water for 1 hour. The adherend, tensile tester, and other matters are the same as those for the measurement of the adhesive force F2 after immersion in hot water for 30 minutes.

[Water peeling force FW2 after immersion in warm water for 1 hour]
The water peel strength FW2 after immersion in warm water for 1 hour is measured in the same manner as the peel strength FW1 after immersion in warm water for 30 minutes, except that the time of immersion in warm water is 1 hour.
Specifically, in the measurement of the adhesive strength F2 after immersion in hot water for 1 hour, the test piece separated from the adherend during measurement of the peel strength of the test piece from the adherend after immersion in hot water for 1 hour. 20 μL of distilled water is supplied to the starting point (peeling front), and the peel strength after supplying the distilled water is measured. The measurement is performed each time the adhesive strength F2 after immersion in warm water for 1 hour is measured (that is, 3 times), and the average value thereof is taken as the water peel strength FW2 [N/20 mm] after immersion in warm water for 1 hour.
The adherend, tensile tester, and other matters are the same as those for the measurement of water peel strength FW1 after immersion in hot water for 30 minutes.

In the above measurements (measurements of F0, FW0, F1, FW1, F2 and FW2), the adherend has a contact angle of 20 degrees or less (for example, 5 degrees to 10 degrees) to distilled water on the surface where the test piece is attached. Use what is Specifically, the adherend is an alkali glass plate produced by the float method, and the contact angle of the surface to which the test piece is attached to distilled water is 20 degrees or less (for example, 5 degrees to 10 degrees). can be used. As such an adherend, the alkali glass plate manufactured by Matsunami Glass Industry Co., Ltd. can be used, but the present invention is not limited to this. It is also possible to use

Also, the contact angle of the alkali glass plate is measured by the following method. That is, in a measurement atmosphere of 23 ° C. and 50% RH, a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., trade name “DMo-501 type”, control box “DMC-2”, control / analysis software “FAMAS (version 5.0.30)”) is carried out by the droplet method. The amount of distilled water dropped is 2 μL, and the contact angle is calculated by the Θ/2 method from the image 5 seconds after dropping (performed with N5).

The present inventors have confirmed that the adhesive strength and water peeling strength after immersion in warm water exhibit a certain high correlation with the adhesive strength and water peeling strength after immersion in a hydrofluoric acid aqueous solution, respectively. Based on this finding, the adhesive strength and water peeling strength after immersion in hot water are used as evaluation indices for the applicability of the surface protective sheet in liquid treatment applications including immersion in chemical solutions.

[Moisture Permeability]
The moisture permeability of the substrate (layer) and surface protection sheet is measured according to JIS Z0208 moisture permeability test (cup method). A method for measuring the moisture permeability of the substrate is as follows. That is, the base material according to each example is cut into a circle of 7 cmΦ, and this is used as an evaluation sample. Then, a predetermined amount of calcium chloride is put inside a test cup (made of aluminum, a moisture permeable cup defined by JIS Z0208), and the mouth of the cup is sealed with the above evaluation sample. Specifically, the evaluation sample was placed on the test cup so as to cover the mouth of the test cup, and the edge of the opening of the test cup (circular shape with an inner diameter of 6 cm, an outer diameter of 9 cm, and an edge width of 1.5 cm) was measured. A shaped annular packing and lid are overlaid and screwed on to seal the interior of the test cup. Next, the cup covered with the evaluation sample is stored at 40 ° C. and 92% RH for 24 hours, and the change in total weight before and after storage (specifically, the weight change based on the amount of water absorbed by calcium chloride) is measured. Then, the moisture permeability [g/(m ² ·day)] is obtained. The moisture permeability of the surface protection sheet is the same as the moisture permeability measurement method of the base material, except that instead of the base material, the surface protection sheet is placed so that the cup side is the adhesive surface, and the mouth of the cup is closed and the measurement is performed. measured by the method of

[60° C. loss elastic modulus G″]
The 60° C. loss elastic modulus G″ [Pa] of the pressure-sensitive adhesive layer is determined by dynamic viscoelasticity measurement. The pressure-sensitive adhesive layer is punched out into a disk shape with a diameter of 7.9 mm, and the sample is sandwiched between parallel plates and fixed. or its equivalent), perform dynamic viscoelasticity measurement under the following conditions to determine the loss elastic modulus G″ [Pa] at 60°C.
・Measurement mode: Shear mode ・Temperature range: -70°C to 150°C
・Temperature increase rate: 5°C/min
・Measurement frequency: 1Hz
The pressure-sensitive adhesive layer to be measured can be formed by applying the corresponding pressure-sensitive adhesive composition in layers and drying or curing.

[Tensile test]
A test piece is prepared by cutting the surface protective sheet into a strip having a width of 10 mm. According to JIS K 7161, this test piece is stretched under the following conditions to obtain a stress-strain curve.
(Stretching conditions)
Measurement temperature: 25°C
Tensile speed: 300 mm/min Distance between chucks: 50 mm
As the tensile tester, a universal tensile/compression tester (equipment name “Tensile/Compression Tester, TCM-1kNB” manufactured by Minebea Co., Ltd.) or its equivalent can be used.
The 25° C. tensile modulus [Pa] is obtained from linear regression of the stress-strain curve. The 25° C. tensile modulus is based on the value obtained by subtracting the thickness of the pressure-sensitive adhesive layer from the measured thickness of the surface protection sheet, or the value obtained by measuring the thickness of the base layer itself. and converted into a value per cross-sectional area of the base material layer.
Also, from the above tensile test, the stress at 100% elongation [N/mm ² ], breaking stress [N/mm ² ] and breaking strain [%] at 25° C. are measured.
The stress at 100% elongation is a value obtained by dividing the load [N] measured when the test piece is elongated 100% in the tensile test by the base layer cross-sectional area [mm ² ] of the test piece. The breaking stress is a value obtained by dividing the load [N] when the test piece breaks in the tensile test by the base layer cross-sectional area [mm ² ] of the test piece, and the breaking strain [%] is the test piece. Elongation at break [%].
Note that the measured values (tensile modulus, stress at 100% elongation, breaking stress and breaking strain) in the present examples are obtained by comparing the MD of the surface protective sheet (more specifically, the base material layer) with the tensile direction of the tensile test. The above tensile test can be performed on the MD of the surface protective sheet, and by changing the method of cutting out the test piece, the above tensile test can be performed on the TD of the surface protective sheet. can be performed to obtain a measure of TD. Alternatively, the above tensile test can be performed in any one direction, whether MD or TD, to obtain measurements.

[25°C bending stiffness value]
The 25° C. bending rigidity value D [Pa·m ³ ] of the surface protection sheet is obtained by the formula:
D=Eh ³ /12(1−ν ² );
requested from. In the above formula, E is the 25° C. tensile elastic modulus [Pa] of the surface protective sheet, and h is the thickness [m] of the base material layer. ν is Poisson's ratio, and ν=0.35 in the above equation.
The 25° C. bending rigidity value in this example is the 25° C. bending rigidity value of MD, but by changing the method of cutting out the test piece as described above, not only the 25° C. bending rigidity value of MD but also TD 25° bending stiffness values can be obtained, or 25° bending stiffness values in any one direction, whether MD or TD, can be obtained.

[Underwater trigger peel force]
A surface protection sheet to be measured is cut into a size of 10 mm in width and 100 mm in length to prepare a test piece. In an environment of 23 ° C. and 50% RH, the release liner covering the adhesive surface (adhesive layer surface) was peeled off from the test piece, and the exposed adhesive surface was attached to an alkali glass plate (water contact angle of 20 degrees) as an adherend. A 2-kg rubber roller is made to reciprocate once against the surface of the alkali glass having the following surface) and pressed against it. 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 thus obtained is autoclaved (50° C., 0.5 MPa, 15 minutes). A sample for evaluation taken out of the autoclave is held in an environment of 23° C. and 50% RH for 1 hour, and then immersed in water at room temperature (23° C. to 25° C.). As water, ion-exchanged water or distilled water is used. In water, the sample for evaluation is held horizontally with the surface to which the test piece is attached facing up. The distance (immersion depth) from the upper surface of the evaluation sample to the water surface is set to 10 mm or more (for example, about 10 mm to 100 mm). In this way, with the evaluation sample placed in water, within 1 minute from the start of immersion in water, using a tensile tester, in an environment of 23 ° C. and 50% RH, the longitudinal direction of the test piece A peeling test is performed from one end (one end protruding from the adherend) under the conditions of a tensile speed of 1000 mm/min and a peeling angle of 20 degrees, and the maximum stress applied at the initial peeling stage is recorded. The measurement is performed three times, and the average value of the above maximum stresses is taken as the triggering peel force in water [N/10 mm].
There is a tendency that the higher the water-triggered peeling force is, the more excellent the end peeling prevention property against external force such as vibration during the transportation process is. In processes such as transportation, external forces such as vibrations that can cause edge peeling of the surface protective sheet are considered to be high-speed peeling loads applied at a relatively shallow angle to the object to be protected. The surface protective sheet that exhibits a peeling force in water of 20 degrees and a peeling speed of 1000 mm/min. It tends to be highly resistant to edge peeling.
In the above test, an alkali glass plate (product name: "Microslide Glass S200423", manufactured by Matsunami Glass Industry Co., Ltd.) is used as the adherend. As the tensile tester, a universal tensile/compression tester (equipment name “Tensile/compression tester, TCM-1kNB” manufactured by Minebea Co., Ltd.) or its equivalent is used.
In the measurement, if necessary, the test piece may be reinforced by attaching an appropriate backing material to the opposite surface of the surface protection sheet (the surface opposite to the adhesive surface). As the backing material, for example, a PET film having a thickness of about 25 μm can be used.

[20 degree trigger release force]
A surface protection sheet to be measured is cut into a size of 10 mm in width and 100 mm in length to prepare a test piece. In an environment of 23 ° C. and 50% RH, the release liner covering the adhesive surface (adhesive layer surface) was peeled off from the test piece, and the exposed adhesive surface was attached to an alkali glass plate (water contact angle of 20 degrees) as an adherend. A 2-kg rubber roller is made to reciprocate once against the surface of the alkali glass having the following surface) and pressed against it. At this time, one end of the test piece in the longitudinal direction is attached so as to protrude from the adherend. After holding the evaluation sample thus obtained in an environment of 23 ° C. and 50% RH for 24 hours, the adhesive surface of the test piece protruding from the adherend and the adherend (the above 20 μL of distilled water is dropped on the end of the adherend), and one end of the test piece in the longitudinal direction (one end protruding from the adherend) is measured using a tensile tester in an environment of 23 ° C. and 50% RH. Then, a peel test is performed under the conditions of a temperature of 23° C., a peel angle of 20 degrees, and a tensile speed of 1000 mm/min, and the maximum stress applied at the initial stage of peeling is recorded. The measurement is performed three times, and the average value of the maximum stresses is defined as the 20-degree trigger peel force [N/10 mm].
The 20-degree trigger peel force was measured by dripping water at the starting point of peeling. As described above, the trigger peel force is the maximum stress applied at the initial stage of peeling, and the water peelability (decrease in peel force due to the presence of water) in the technology disclosed herein is measured after the start of peeling (after detection of the trigger peel force). ), and the water peel strength is the peel strength measured after the start of peeling. The higher the 20-degree trigger peel force, the more the surface protective sheet tends to be excellent in preventing peeling at the edges against the physical load applied in the thickness direction of the surface protective sheet, regardless of whether or not water is present. be.
In the above test, an alkali glass plate (product name “Microslide Glass S200423”, manufactured by Matsunami Glass Industry Co., Ltd.) is used as the adherend. As the tensile tester, a universal tensile/compression tester (equipment name “Tensile/compression tester, TCM-1kNB” manufactured by Minebea Co., Ltd.) or its equivalent is used.
In the measurement, if necessary, the test piece may be reinforced by attaching an appropriate backing material to the opposite surface of the surface protective sheet (the surface opposite to the adhesive surface). As the backing material, for example, a PET film having a thickness of about 25 μm can be used.

[Repulsion resistance (aluminum repulsion resistance)]
The pressure-sensitive adhesive layer protected with a release film is cut into a size of 10 mm wide and 110 mm long. The surface of an aluminum plate with a width of 10 mm, a length of 110 mm, and a thickness of 0.03 mm was washed with toluene, the release liner covering one adhesive surface of the pressure-sensitive adhesive layer was peeled off, and the exposed adhesive surface was applied to the surface of the aluminum plate. By bonding, a measurement sample (a laminate of an aluminum plate and an adhesive layer) having an adhesive layer lined with an aluminum plate is prepared. After this measurement sample was allowed to stand at 23° C. for 1 day, the aluminum plate side of the measurement sample was placed inside, and the longitudinal direction of the measurement sample was placed along the outer periphery of a cylindrical glass tube with a radius of 17 mm for 10 seconds. bend. Next, the other release liner covering the pressure-sensitive adhesive layer of the measurement sample was peeled off, and the sample was applied to the surface of an alkali glass plate as an adherend using a laminator under the conditions of a lamination pressure of 0.25 MPa and a lamination speed of 0.3 m/min. It is crimped and observed at 23° C. and 50% RH. For example, 1 hour after pressure bonding to the adherend, the distance (length of peeling from one end) [mm] at which the measurement sample was peeled off from the adherend was measured and used as the result of repulsion resistance evaluation.
The above-mentioned repulsion resistance test evaluates the resistance to peeling of the adhesive against a physical load (peel load) in the direction perpendicular to the surface direction of the surface protective sheet (thickness direction of the surface protective sheet) at the edge of the surface protective sheet. It is a test to In the above-mentioned repulsion resistance test, a PSA with little or no edge peeling is evaluated as having excellent edge peeling-preventing properties against physical loads applied in the thickness direction.
The present inventors have confirmed that the peel length in the repulsion resistance test correlates with the 20-degree trigger peel force. Specifically, in the repulsion resistance test, it was confirmed that the shorter the edge peeling length, the higher the 20-degree trigger peel force. In peeling at a peeling angle of 20 degrees, the peeling stress of the pressure-sensitive adhesive is considered to be due to the high ratio of components acting in the vertical direction (90 degrees). The reason why water is not added in the repulsion resistance test is to eliminate the influence of swelling of the pressure-sensitive adhesive due to water in the evaluation of repulsion resistance over time.

<Production of adhesive>
(Adhesive E1)
2-ethylhexyl acrylate (2EHA) 85 parts, methyl acrylate (MA) 13 parts, acrylic acid (AA) 1.2 parts, methacrylic acid (MAA) 0.75 parts, 3-glycidoxypropyltrimethoxysilane (Shin-Etsu Chemical Kogyo Co., Ltd., KBM-403) 0.01 parts, t-dodecyl mercaptan 0.05 parts as a chain transfer agent and emulsifier (Kao Corporation, Latemul E-118B) 1.9 parts, in 100 parts of ion-exchanged water An aqueous emulsion of the monomer mixture (monomer emulsion) was prepared by mixing and emulsifying with.
The above monomer emulsion was placed in a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer and a stirrer, and stirred at room temperature for 1 hour or more while introducing nitrogen gas. Then, the system is heated to 60 ° C., 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate as a polymerization initiator (manufactured by Wako Pure Chemical Industries, Ltd., VA-057 ) was added and reacted at 60° C. for 6 hours to obtain an aqueous dispersion of acrylic polymer e1. After cooling the system to room temperature, 10% aqueous ammonia as a pH adjuster and polyacrylic acid (aqueous solution with 36% non-volatile content) as a thickener were used to adjust the pH to about 7.5 and the viscosity to about 9 Pa.・Emulsion-type PSA composition E1 was prepared by adjusting to s.

A 38 μm thick release film (manufactured by Mitsubishi Plastics Co., Ltd., MRF #38) in which one side of the polyester film is a release surface and a 38 μm thick release film in which one side of the polyester film is a release surface (Mitsubishi Plastics Co., Ltd. manufactured by MRE #38). The adhesive composition E1 was applied to the release surface of one release film (MRF#38) and dried at 120° C. for 3 minutes to form an adhesive layer E1 having a thickness of 25 μm. The release surface of the other release film (MRE #38) was adhered to this adhesive layer for protection. Thus, the pressure-sensitive adhesive layer E1 whose surface was protected by two release films was obtained.

(Adhesives E2 to E7)
For 100 parts of the solid content of the aqueous dispersion of the acrylic polymer e1, a tackifier resin emulsion (manufactured by Arakawa Chemical Industries, Ltd., Super Ester E-865NT, a water dispersion of a polymerized rosin ester having a softening point of 160 ° C., hereinafter "adhesive 10 parts (adhesive E2), 20 parts (adhesive E3), 25 parts (adhesive E4), 30 parts (adhesive E5), 35 parts in terms of solid content (Adhesive E6) or 50 parts (Adhesive E7) were added in the same manner as in the preparation of the emulsion-type PSA composition E1 to prepare emulsion-type PSA compositions E2 to E7, and the resulting emulsion type Adhesive layers E2 to E7 having a thickness of 25 μm were obtained in the same manner as in the production of the above adhesive layer E1, except that the adhesive compositions E2 to E7 were used. The 60° C. loss elastic modulus G″ of the adhesive layer E2 was 12.3 kPa.

(Adhesive E8)
The monomer composition of the acrylic polymer was changed to 49 parts of 2EHA, 49 parts of n-butyl methacrylate (BMA), and 2 parts of AA. Two parts were used per part. Otherwise, an aqueous emulsion of the monomer mixture (monomer emulsion) was prepared in the same manner as the preparation of the acrylic polymer e1 in the adhesive E1, and a polymerization reaction was performed to obtain an aqueous dispersion of the acrylic polymer e2. After cooling the system to room temperature, 20 parts of tackifier resin A in terms of solid content per 100 parts of solid content in the aqueous dispersion of acrylic polymer e2, and an oxazoline-based cross-linking agent (manufactured by Nippon Shokubai Co., Ltd., Epocross WS-500). The two parts were mixed. Furthermore, the pH is adjusted to about 7.5 and the viscosity to about 9 Pa s using 10% aqueous ammonia as a pH adjuster and polyacrylic acid (an aqueous solution with a non-volatile content of 36%) as a thickener. to prepare an emulsion-type pressure-sensitive adhesive composition E8. A pressure-sensitive adhesive layer E8 having a thickness of 25 μm was obtained in the same manner as in the preparation of the pressure-sensitive adhesive layer E1 except that the emulsion-type pressure-sensitive adhesive composition E8 was used.

(Adhesive E9)
Instead of 20 parts of tackifying resin A, 20 parts of tackifying resin B (manufactured by Arakawa Chemical Industries, Ltd., Superester NS-121, aqueous dispersion of rosin resin (acid value imparting) with softening point of 120 ° C.) in terms of solid content. used. Otherwise, a 25 μm-thick pressure-sensitive adhesive layer E9 was obtained in the same manner as the pressure-sensitive adhesive layer E8.

(Adhesive S1)
In a reaction vessel equipped with a condenser, a nitrogen inlet, a thermometer and a stirrer, 72 parts of 2EHA, 14 parts of N-vinyl-2-pyrrolidone (NVP), 13 parts of 2-hydroxyethyl acrylate (HEA) and methyl 1 part of methacrylate (MMA), 0.12 parts of α-thioglycerol as a chain transfer agent, and ethyl acetate as a polymerization solvent are charged, and 0.2 parts of AIBN is added as a thermal polymerization initiator to carry out solution polymerization under a nitrogen atmosphere. Thus, a solution containing acrylic polymer s1 with Mw of 300,000 was obtained.

To the solution obtained above, per 100 parts of the monomer component used to prepare the solution, maleated rosin ester as a tackifier (manufactured by Harima Kasei Co., Ltd., Haritak 4740, softening point 115 to 125 ° C., hereinafter “tackifier 20 parts in solid content, an isocyanate-based cross-linking agent (trimethylolpropane/xylylene diisocyanate adduct, manufactured by Mitsui Chemicals, trade name: Takenate D-110N, solid content concentration 75 %) as a solid content, 0.01 part of dioctyltin dilaurate (manufactured by Tokyo Fine Chemical Co., Ltd., trade name: Envirizer OL-1) as a cross-linking accelerator, 3 parts of acetylacetone as a cross-linking retarder, and a hydrophilic agent. 0.5 parts of a nonionic surfactant (polyoxyethylene sorbitan monolaurate, HLB 16.7, trade name: Rhodol TW-L120, manufactured by Kao Corporation) is added and uniformly mixed to form a solvent-type adhesive composition. S1 was prepared.

A 38 μm thick release film (manufactured by Mitsubishi Plastics Co., Ltd., MRF #38) in which one side of the polyester film is a release surface and a 38 μm thick release film in which one side of the polyester film is a release surface (Mitsubishi Plastics Co., Ltd. manufactured by MRE #38). The solvent-based adhesive composition S1 prepared above was applied to the release surface of one release film (MRF #38) and dried at 60°C for 3 minutes and then at 120°C for 3 minutes to form an adhesive with a thickness of 25 µm. A layer was formed. The release surface of the other release film (MRE #38) was adhered to this adhesive layer for protection. Thus, a pressure-sensitive adhesive layer S1 whose surface was protected by two release films was obtained.

<Examples 1 to 8 and Comparative Examples 1 to 2>
A 60 μm-thick OPP film (product name “Torayfan #60-2500” manufactured by Toray Industries, Inc., biaxially oriented PP film, moisture permeability 2.1 g/(m ² ·day)) was prepared as a base layer material. . Peel off the release liner covering one surface of the pressure-sensitive adhesive layers E1 to E9 with release liner obtained above and S1, and the exposed surface (adhesive surface) is reciprocated twice with a 2 kg rubber roller on the surface of the OPP film. crimped. In this way, a surface protection sheet (single-sided pressure-sensitive adhesive sheet with a base layer) according to each example, the adhesive surface of which was protected with a release liner, was obtained. The 25° C. bending rigidity value of the surface protection sheet of each example is 1.2×10 ⁻⁴ Pa·m ³ , the stress at 100% elongation at 25° C. is 83 N/mm ² , the breaking stress at 25° C. is 131 N/mm ² , The 25°C breaking strain was 232%. In addition, the moisture permeability of the surface protection sheet according to each example was within the range of ±1.5 g/(m ² ·day) of the moisture permeability of the substrate layer.

<Performance evaluation>
For the surface protection sheet according to each example, normal state adhesive strength F0 [N / 20 mm], normal state water peel strength FW0 [N / 20 mm], adhesive strength F1 [N / 20 mm] after immersion in hot water for 30 minutes, water after immersion in hot water for 30 minutes A peel force FW1 [N/20 mm] was measured. Further, the degree of decrease in water peel strength [%] was determined from the formula: FW/F×100 for the adhesive strength and water peel strength at each stage (normal state, after immersion in warm water for 30 minutes). In the above formula, F is the adhesive force [N/20 mm] and is F0 or F1. FW is the water peeling force [N/20mm] and is FW0 or FW1. The results are shown in Table 1 together with an overview of each example.

As shown in Table 1, the surface protective sheets according to Examples 1 to 8 and Comparative Examples 1 and 2 achieved a degree of water peel strength reduction (FW1/F1) of 50% or less, It was possible to peel off the adherend without damaging or deforming the adherend at the time of peeling, while adhering well to it. Further, in Examples 1 to 5 in which more than 10 parts of the tackifier was used with respect to 100 parts of the base polymer, compared to Comparative Examples 1 to 2 in which the tackifier was not used or was used at a rate of 10 parts or less, A tendency for the adhesive strength F0 to improve was recognized, and in particular, a high adhesive strength F1 after hot water immersion was obtained. Even in Examples 6 to 8 in which the polymer species, polymerization method, and tackifier species were changed, high adhesive strength F0 and adhesive strength after hot water immersion F1 were obtained by using more than 10 parts of tackifier.

Although not shown in the table, in Examples 1, 3, 6 to 8, the 20-degree trigger peel force was 0.7 N/10 mm or more, and the repulsion resistance (peeling length after 1 hour of crimping) was 0.0 mm. Met.

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

Reference Signs List

1, 2

Surface protection sheet

1A,

2A Adhesion surface

1B, 2B Back surface 10 Base material layer 10A One surface 10B Other surface 11 First layer 12 Second layer (inorganic material-containing layer)
20 adhesive layer 20A adhesive surface 30 release liner 50 surface protective sheet with release liner

Claims

A surface protective sheet comprising a substrate layer and a pressure-sensitive adhesive layer provided on one surface of the substrate layer,
The surface protective sheet has a water peeling force FW0 of 50% or less of the adhesive force F0,
here,
The water peeling force FW0 was determined by bonding an adhesive surface of a surface protective sheet to an alkali glass surface having a water contact angle of 20 degrees or less, and holding the surface in an environment of 23°C and 50% RH for 1 hour. After that, 20 μL of distilled water was supplied between the alkali glass and the adhesion surface, and the distilled water was allowed to enter one end of the interface between the alkali glass and the adhesion surface. water peeling force [N/20 mm] measured under the conditions of degree and speed of 300 mm / min,
The adhesive force F0 is measured after bonding the adhesive surface of the surface protective sheet to the surface of alkali glass having a water contact angle of 20 degrees or less and holding the adhesive surface in an environment of 23° C. and 50% RH for 1 hour. , the peel strength [N / 20 mm] measured under the conditions of a temperature of 23 ° C., a peel angle of 180 degrees and a speed of 300 mm / min,
The pressure-sensitive adhesive layer contains a base polymer and a tackifier,
The surface protective sheet, wherein the content of the tackifier in the adhesive layer is more than 10 parts by weight with respect to 100 parts by weight of the base polymer.
The surface protective sheet according to claim 1, wherein the content of the tackifier in the adhesive layer is more than 10 parts by weight and less than 100 parts by weight with respect to 100 parts by weight of the base polymer.
The surface protection sheet according to claim 1 or 2, wherein the adhesive layer contains at least one selected from tackifier resins and acrylic oligomers as the tackifier.
Any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer contains, as the tackifier, at least one tackifier resin selected from rosin-based tackifier resins, rosin derivative tackifier resins and terpene phenol resins. The surface protection sheet described in the paragraph.
The surface protection sheet according to any one of claims 1 to 4, wherein the adhesive layer is an acrylic adhesive layer containing an acrylic polymer as the base polymer.
The surface protection sheet according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive layer contains a water affinity agent.
The surface protective sheet according to any one of claims 1 to 6, wherein the pressure-sensitive adhesive layer has a thickness of more than 10 µm and not more than 100 µm.
a step of attaching a surface protection sheet to the surface of an object to be treated having a surface with a water contact angle of 20 degrees or less;
a step of performing a treatment on the object to be treated to which the surface protection sheet is attached, wherein the object to be treated contacts a liquid in the treatment;
a step of removing the surface protective sheet from the treated object in the presence of water by peeling;
including
The surface protection sheet comprises a base layer and an adhesive layer provided on one side of the base layer,
The surface protective sheet has a water peeling force FW0 of 50% or less of the adhesive force F0,
here,
The water peeling force FW0 was determined by bonding an adhesive surface of a surface protective sheet to an alkali glass surface having a water contact angle of 20 degrees or less, and holding the surface in an environment of 23°C and 50% RH for 1 hour. After that, 20 μL of distilled water was supplied between the alkali glass and the adhesion surface, and the distilled water was allowed to enter one end of the interface between the alkali glass and the adhesion surface. water peeling force [N/20 mm] measured under the conditions of degree and speed of 300 mm / min,
The adhesive force F0 is measured after bonding the adhesive surface of the surface protective sheet to the surface of alkali glass having a water contact angle of 20 degrees or less and holding the adhesive surface in an environment of 23° C. and 50% RH for 1 hour. , the peel strength [N / 20 mm] measured under the conditions of a temperature of 23 ° C., a peel angle of 180 degrees and a speed of 300 mm / min,
The pressure-sensitive adhesive layer comprises a base polymer and a tackifier,
The processing method, wherein the content of the tackifier in the adhesive layer is more than 10 parts by weight with respect to 100 parts by weight of the base polymer.
The processing method according to claim 8, wherein the liquid is an aqueous solution.
A surface protection sheet used in the treatment method according to claim 8 or 9.