JP7319815B2 - Surface protection film and optical components - Google Patents

Description

The present invention relates to surface protective films and optical components.

A surface protection film (also referred to as a surface protection sheet) generally has a structure in which an adhesive is provided on a film-like substrate (support). The protective film is attached to an adherend through the pressure-sensitive adhesive, and is used for the purpose of protecting the adherend from scratches and stains during processing, transportation, and the like. For example, a polarizing plate to be attached to a liquid crystal cell in the manufacture of a liquid crystal display panel is once manufactured in a roll form, is unwound from the roll, and is cut into a desired size according to the shape of the liquid crystal cell. . Here, in order to prevent the polarizing plate from being damaged by being rubbed with a transport roll or the like in an intermediate process, a measure is taken to attach a surface protective film to one side or both sides (typically one side) of the polarizing plate. .

The above-mentioned protective film is required to have the ability to stably adhere to the adherend so as to achieve the purpose of protection during the protection period (attachment period). It must have good releasability from adherends. For example, the pressure-sensitive adhesive for protective films used for optical applications should have sufficient pressure-sensitive adhesive strength to prevent problems such as lifting or peeling off from optical components such as polarizing films, which are adherends, during display panel assembly or inspection. is given. Also, the adhesive strength is limited to a level that allows good peeling and removal from the optical component. Patent Documents 1 to 4 are cited as technical documents relating to such surface protective films. Patent Documents 5 and 6 disclose a laminated polyester film, and describe forming an antistatic layer and a cured layer on one surface of the polyester film.

Japanese Patent Application Laid-Open No. 2003-41205 Japanese Patent Application Laid-Open No. 2003-320631 JP 2018-180512 A JP 2019-12127 A JP 2018-43448 A JP 2009-256623 A

As a method for peeling and removing the protective film from the adherend after the protection period is over, a method is adopted in which an adhesive tape is attached to the back surface of the protective film and the protective film is peeled off using the adhesive force of the adhesive tape. (Patent Documents 1 to 4). Specifically, the adhesive tape is attached to the back of the protective film attached to the adherend, and the protective film is lifted from the end of the protective film (pick-up operation), so that the protective film is peeled off from the adherend. be done. According to this method, the protective film can be peeled and removed with good workability. An adhesive tape used for peeling and removing such a protective film is called an adhesive tape for pickup (pickup tape).

As the pickup tape, rubber-based adhesive tapes and acrylic-based adhesive tapes, which are excellent in versatility and cost, are often used. Rubber-based adhesive tapes are widely used as pickup tapes because they tend to have high adhesive strength (for example, Patent Documents 1 and 2). Acrylic pressure-sensitive adhesive tapes have the advantage of being easy to obtain good processability (e.g., cutting processability) based on cohesive force due to cross-linking, etc., and are often used (e.g., Patent Document 3). There is a tendency to prefer adherends, such as those tending to have lower forces. Therefore, when using an acrylic pick-up tape, it may be necessary to pay more attention to the material of the surface of the adherend and the pressure-bonding conditions so as not to cause pick-up defects, compared to the case of using a rubber-based pick-up tape.

In recent years, automation of the protective film peeling and removing process as described above has progressed, and the peeling and removing is performed by an automatic peeling device equipped with a pick-up tape. According to the automatic peeling device, the protective film peeled from the adherend can be recovered in a series of processes using a pick-up tape, which is efficient. In addition, peeling and removal of the protective film tends to be speeded up for the purpose of further improving production efficiency, and the time from pressing the pickup tape to the protective film to peeling when removing the protective film tends to be shortened. Even in such a case, the protective film must be reliably picked up by the pick-up tape and peeled off. In production sites where rubber-based or acrylic-based pickup tapes are used, it would be significant if a protective film that could be reliably peeled off from the adherend in a short time after the pickup tape was pressed was provided, regardless of the type of pickup tape. .

The present invention has been created in view of the above circumstances. An object of the present invention is to provide a peelable surface protection film. Another object of the present invention is to provide an optical component to which the surface protection film is adhered.

According to this specification, there is provided a surface protective film having an adhesive layer, a substrate layer, and a topcoat layer in this order. In this surface protective film, the topcoat layer constitutes the back surface of the surface protective film. In addition, the surface protective film has the following characteristics: (A) 180 degree peel strength of a standard acrylic pressure-sensitive adhesive tape against the back surface measured under the conditions of 23°C, 1 minute after application, and a tensile speed of 0.3 m/min (standard Back peel strength of acrylic pressure-sensitive adhesive tape) A is 3.5 N/19 mm or more; The peel strength (peel strength against PET) B is less than 3.5 N/19 mm.

Regarding the pick-up of the surface protective film, the acrylic adhesive tape tends to have less adhesion to the back surface of the protective film in a short application time than the rubber adhesive tape. is reliably picked up and peeled off by the pick-up tape even when the acrylic pick-up tape is pressure-bonded to its back surface for a short period of time or when the film is peeled immediately after pressure-bonding the pickup tape. Such a protective film can be reliably peeled off by applying the pickup tape for a short period of time regardless of the type of pickup tape. That is, by using the protective film, there is no need to worry about the type of pickup tape to be used (rubber-based, acrylic-based, etc.). Also, even if the type of pickup tape is changed in the middle of the process, it can be handled well without problems such as poor peeling. These have great practical advantages as they lead to maintenance of flexibility in coping with situations at the production site and improvement in workability. Moreover, the protective film can be continuously collected after being peeled off from the adherend with a pick-up tape. The surface protective film may be particularly suitable for use in which it is peeled from an adherend at a relatively high speed, for example using an automatic peeling device .

In a typical embodiment, the surface protection film further has the following characteristics: (C) 180 of a standard rubber-based adhesive tape against the back surface measured under the conditions of 23°C, 1 minute after application, and a tensile speed of 0.3 m/min. The degree peel strength (back peel strength of standard rubber pressure-sensitive adhesive tape) C is 3.5 N/19 mm or more. A surface protective film that satisfies the property (C) is easily peeled off from an adherend in a mode in which the rubber-based pickup tape is pressure-bonded to its back surface for a short period of time or in a mode in which the film is peeled immediately after the pressure-bonding of the pickup tape.

In some preferred embodiments, the topcoat layer includes an acrylic binder. By providing a top coat layer containing an acrylic binder, the surface protective film preferably satisfies the above characteristic (A) , and even if the pressure bonding time of the pickup tape is short or the pickup tape is peeled off immediately after pressure bonding. can be reliably peeled off with an acrylic pick-up tape.

In the surface protective film according to some aspects, the surface resistivity of the back surface is 1.0×10 ¹³ Ω/□ or less. By setting the surface resistivity to 1.0×10 ¹³ Ω/□ or less, it is possible to prevent or suppress electrification when the surface protective film is peeled off.

In some preferred embodiments, the topcoat layer comprises at least one selected from quaternary ammonium salts and conductive polymers. By containing a quaternary ammonium salt or a conductive polymer, the surface resistivity of the topcoat layer is reduced, and for example, static charging of the surface protective film can be preferably prevented or suppressed without providing an additional antistatic layer. . In a particularly preferred embodiment, the topcoat layer contains a conductive polymer, and the conductive polymer contains at least one selected from poly(3,4-ethylenedioxythiophene) and polyaniline sulfonic acid.

In some preferred embodiments, the topcoat layer is a layer formed from a coating material containing a curing agent. The curing agent is at least one selected from the group consisting of melamine curing agents, isocyanate curing agents, epoxy curing agents, oxazoline curing agents, aziridine curing agents and carbodiimide curing agents. preferable. By providing the topcoat layer formed using the curing agent, the surface protection film can preferably satisfy properties required for the protection film, such as scratch resistance.

In some preferred embodiments, the adhesive layer is an acrylic adhesive layer. The effects of the technique disclosed herein can be preferably realized in a mode using an acrylic pressure-sensitive adhesive layer. For example, according to acrylic adhesives that are easy to molecularly design and easy to adjust adhesive properties, while having good adhesive strength necessary for protecting the adherend, the peel strength B against PET is reduced, and when peeled off It is possible to preferably prevent peeling defects in. In addition, since the acrylic pressure-sensitive adhesive has excellent transparency, it is suitable as a surface protective film material for optical parts.

In a typical aspect, the substrate layer is made of a resin film. As the resin film, for example, a resin film (polyester resin film) made of a resin material containing polyester as a main component (a component containing more than 50% by weight) can be preferably employed. In other words, the substrate layer is preferably made of a polyester resin film. A surface protective film having a base layer made of a polyester resin film can have mechanical strength suitable for a protective film and can have excellent adhesion to a topcoat layer. In addition, the base material layer made of a polyester resin film is transparent and can have good optical properties (less anisotropy, etc.), so it is suitable as a surface protection film material for optical parts.

Further, according to this specification, there is provided an optical component with a surface protective film, which includes an optical component and a surface protective film that protects the optical component. In this optical component with a surface protective film, the surface protective film comprises an adhesive layer to be attached to the optical component, a substrate layer, and a topcoat layer constituting the back surface of the surface protective film in this order. have. In addition, the surface protective film has the following properties: (A) 180 degree peel strength of a standard acrylic pressure-sensitive adhesive tape against the back surface measured under the conditions of 23°C, 1 minute after application, and a tensile speed of 0.3 m/min ( The back peel strength A of a standard acrylic pressure-sensitive adhesive tape is 3.5 N/19 mm or more. Furthermore, when the surface protection film is peeled from the optical component under conditions of 23° C., a peeling angle of 90°, and a tensile speed of 0.3 m/min, the surface protective film adheres to the optical component with a trigger peel strength of less than 3.5 N/19 mm. attached. The surface protective film is attached to an optical component (for example, an optical component used as a constituent element of a liquid crystal display panel such as a polarizing plate and a wavelength plate) to suitably protect the surface of the optical component during processing or transportation. be able to. In addition, for example, after the protection period has ended, the surface protective film attached to the optical component may be peeled off from the adherend, the optical component, by pressure-bonding an acrylic pickup tape to its back surface. Even if the pressure-bonding time is short or the pressure-bonding is immediately followed by peeling, the pick-up tape can reliably peel and even collect the tape. Regardless of the type of pickup tape, such a protective film can be reliably peeled off from the optical component to be protected by attaching the pickup tape for a short period of time. A suitable example of the optical component is a reflective polarizing film .

1 is a schematic cross-sectional view showing a configuration example of a surface protective film according to one embodiment; FIG. It is a typical sectional view showing the type of use of the surface protection film concerning one embodiment. FIG. 2 is a schematic cross-sectional view showing the form of a surface protection film according to one embodiment before use.

Preferred embodiments of the present invention are described below. Matters other than those specifically referred to in this specification that are necessary for the implementation of the present invention are applicable based on the teaching of the implementation of the invention described in this specification and the common general knowledge as of the filing. understandable to traders. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field.
In the drawings below, members and portions having the same function are 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 are not intended to accurately represent the size or scale of the products and parts actually provided.

The surface protection film disclosed here can be in the form of a commonly called pressure-sensitive adhesive sheet. The concept of the adhesive sheet as used herein can include what is called an adhesive tape, an adhesive label, an adhesive film, and the like. The pressure-sensitive adhesive layer is typically formed continuously, but is not limited to such a form. For example, the pressure-sensitive adhesive layer is formed in a regular or random pattern such as dots or stripes. may be Moreover, the adhesive sheet disclosed herein may be in the form of a roll or sheet. Alternatively, it may be a pressure-sensitive adhesive sheet processed into various shapes.

<Structure of Surface Protection Film>
A structural example of the surface protection film disclosed herein is schematically shown in FIG. The surface protective film 1 includes a substrate layer 12, a topcoat layer 14 provided on one surface (12A; also referred to as the first surface) of the substrate layer 12, and the other surface of the substrate layer 12 ( 12B; also referred to as a second surface) and an adhesive layer 20 provided on the second surface. In other words, the pressure-sensitive adhesive layer 20 is provided on the surface 12B of the surface of the base material layer 12 opposite to the topcoat layer side surface 12A. The surface protective film 1 has a first surface 1A and a second surface 1B opposite to the first surface 1A. ) constitutes 1A. In other words, the first surface 1A is the front surface (back surface) 14A of the topcoat layer 14 . The second surface (back surface) 1B of the surface protection film 1 is the adhesive surface 20A of the adhesive layer 20 . In this configuration example, the topcoat layer 14 is directly provided on the back surface 12A of the base material layer 12, and another layer (for example, an antistatic layer) is provided between the back surface 12A of the base material layer and the topcoat layer 14. not intervening.

As schematically shown in FIG. 2, the surface protective film 1 is used by attaching the adhesive surface 20A of the adhesive layer 20 to the surface of an adherend (object to be protected, for example, an optical component such as a polarizing plate) 50. be. Before use (that is, before sticking to an adherend), the surface protective film 1 typically has an adhesive surface 20A (sticking surface to the adherend) of the adhesive layer 20 as shown in FIG. At least the pressure-sensitive adhesive layer 20 side may be protected by a release liner 30 that serves as a release surface. Alternatively, the surface protective film 1 is wound in a roll so that the back surface 10A (topcoat layer surface 14A) of the topcoat layer-attached film 10 is brought into contact with the pressure-sensitive adhesive layer 20 to protect the surface. may

Another structural example of the surface protective film includes a structure having one or more additional layers in addition to the topcoat layer, base layer and pressure-sensitive adhesive layer. Such additional layers may be disposed between the first side (back) of the base layer and the topcoat layer, between the second side (front) of the base layer and the adhesive layer, and the like. The layer arranged between the back surface of the substrate layer and the topcoat layer can be, for example, a layer containing an antistatic component (antistatic layer). The layer arranged between the front surface of the substrate layer and the pressure-sensitive adhesive layer may be, for example, an undercoat layer (anchor layer) that enhances the anchoring property of the pressure-sensitive adhesive layer to the second surface, an antistatic layer, or the like. The surface protection film may have a structure in which an antistatic layer is arranged on the front surface of the base material layer, an anchor layer is arranged on the antistatic layer, and a pressure-sensitive adhesive layer is arranged thereon.

<Characteristics of Surface Protection Film>
The surface protective film disclosed herein has a 180-degree peel strength of a standard acrylic pressure-sensitive adhesive tape against the back surface of the surface protective film measured under the conditions of 23°C, 1 minute after application, and a tensile speed of 0.3 m/min (standard acrylic Back peel strength of adhesive tape) A [N / 19 mm] and 90 degree trigger peel strength against polyethylene terephthalate film measured under conditions of 23 ° C. and tensile speed of 0.3 m / min (PET trigger peel strength) B [N /19 mm] is characterized by satisfying A>B. By satisfying the above conditions (A>B), the surface protective film can be peeled off from an adherend using a pickup tape in a short time after the pickup tape is crimped, even when an acrylic pickup tape is used. It is picked up and peeled off.

The first technical significance of the back peel strength A of the standard acrylic pressure-sensitive adhesive tape is that the standard acrylic pressure-sensitive adhesive tape is attached to the back surface of the surface protective film (topcoat layer surface) and the peel strength is measured after 1 minute. at the point. The fact that a peel strength greater than the PET trigger peel strength B is exhibited by pasting for a short period of time means that, in peeling using a pickup tape, the time from pressure bonding of the pickup tape to the back of the surface protective film to peeling is short. However, even if it is typically peeled immediately after crimping, it may mean that the back surface of the surface protective film and the pickup tape adhere well and the surface protective film is easily picked up by the pickup tape. Such a surface protection film can be peeled off in a mechanized, automated protective film peeling removal process with a short pick-up application, and thus can be well suited for speeding up the process. For example, it is particularly suitable for use in peeling the surface protective film from the adherend at a relatively high speed using an automatic peeling device.

Another technical significance of the back surface peel strength A of the standard acrylic pressure-sensitive adhesive tape is that the standard acrylic pressure-sensitive adhesive tape is used as a pickup tape for this characteristic evaluation. This point will be explained. As the pick-up tape, a rubber-based adhesive tape or an acrylic-based adhesive tape, which is excellent in versatility, cost, etc., is often used. However, acrylic adhesive tapes tend to be more selective in their adherends than rubber-based adhesive tapes, as they tend to have lower adhesive strength to low-polarity adherends. tends to be difficult. However, it goes without saying that in production sites where various pickup tapes such as rubber-based and acrylic-based pickup tapes are used, the surface protection film must be reliably peeled from the adherend regardless of the type of pickup tape. The surface protective film, in which the back surface peel strength A of the standard acrylic pressure-sensitive adhesive tape is relatively greater than the PET trigger peel strength B, even if the acrylic pickup tape, which is more disadvantageous than the rubber-based tape in terms of peelability, is used, Since pick-up peeling is possible, regardless of the type of pickup tape, it can be peeled off by sticking the pickup tape in a short period of time.

The range of the back peel strength A of the standard acrylic pressure-sensitive adhesive tape is not particularly limited as long as it exhibits a relatively larger value than the PET trigger peel strength B, and approximately 0.5 N/19 mm or more is appropriate. , approximately 1 N/19 mm or greater (eg, approximately 2.5 N/19 mm or greater). In order to improve the certainty of peeling of the pickup, the adhesive strength between the pickup tape and the back surface of the surface protective film should be high. From such a point of view, the surface protective film according to some preferred embodiments has the property (A): Standard The 180-degree peel strength A of the acrylic pressure-sensitive adhesive tape is 3.5 N/19 mm or more. The back peel strength A of the standard acrylic pressure-sensitive adhesive tape is preferably about 4.5 N/19 mm or more, more preferably about 5.5 N/19 mm or more, still more preferably about 6 N/19 mm or more, and particularly preferably about 6.5 N. /19 mm or more. The upper limit of the back peel strength A of the standard acrylic adhesive tape is not particularly limited, and can be about 15 N/19 mm or less, about 12 N/19 mm or less (for example, about 10 N/19 mm or less, typically 8 N/19 mm). below) is appropriate.

In addition, the fact that the PET trigger peel strength B is relatively smaller than the back peel strength A of the standard acrylic pressure-sensitive adhesive tape means that the maximum peel strength of the surface protective film from the adherend is relatively high. It means that it is relatively low and good releasability is easily obtained. Here, the peel strength to PET starting peel strength B means the maximum value (maximum stress) of the peel strength recorded at the initial stage of peeling of the surface protective film from the PET film. If the trigger peel strength is high, even if the normal peel strength to the adherend (the stable peel strength after the initial peak) is limited, initial stress stress can cause peel failure. According to the technology disclosed herein, the PET trigger peel strength B shows a low value in the relative relationship with the back peel strength A of the standard acrylic pressure-sensitive adhesive tape. It is picked up and peeled off in peeling from the adherend.

In addition, the peeling angle of 90 degrees in the evaluation of the PET trigger peel strength B is a peeling angle corresponding to the peeling mode by the actual pickup tape including manual peeling and automatic peeling, and in particular, an automatic peeling device to which the pickup tape is attached. can correspond well to the peel angle during peel removal by . The fact that the PET starting peel strength B is lower than the back peel strength A of the standard acrylic pressure-sensitive adhesive tape can lead to the fact that the surface protective film can be easily peeled off and removed using an automatic peeler. Furthermore, the peelability from the PET film at the PET initial peel strength B can well represent the peelability of the surface protection film disclosed herein from the object to be protected. For example, many optical parts (typically optical films such as polarizing films), which are suitable examples of objects to be protected by the surface protection film disclosed herein, have surfaces formed of a resin such as polyester. The peel strength of the surface protection film to the PET film tends to show a high correlation with the peel strength of the surface protection film to the object to be protected.

The range of the PET trigger peel strength B is not particularly limited as long as it exhibits a relatively smaller value than the back peel strength A of the standard acrylic pressure-sensitive adhesive tape. It may be less than 19mm (eg less than 5N/19mm). The lower the trigger peel strength B to PET, the higher the certainty of preventing peel failure. From such a viewpoint, the surface protective film according to some preferred embodiments has a property (B): 90-degree trigger peel strength B against a PET film measured under conditions of 23°C and a tensile speed of 0.3 m/min is 3 is less than .5 N/19 mm; The trigger peel strength B to PET is preferably less than 3 N/19 mm, more preferably less than 2.5 N/19 mm, even more preferably less than 2 N/19 mm, particularly preferably less than 1.5 N/19 mm. In a particularly preferred embodiment, the trigger peel strength B to PET may be less than 1.2 N/19 mm, less than 0.8 N/19 mm, or less than 0.5 N/19 mm. The lower limit of the PET trigger peel strength B is not particularly limited, and may be about 0.1 N/19 mm or more, and may be about 0.2 N/19 mm or more (for example, about 0.3 N/19 mm or more). .

In addition, the surface protective film disclosed in the present specification includes embodiments without the above conditions (A>B), and in such embodiments, the surface protective film is not limited to those satisfying the above conditions. .

The surface protective film disclosed herein has the above PET trigger peel strength B [N / 19 mm] and the surface protective film back surface measured under the conditions of 23 ° C., 1 minute after application and a tensile speed of 0.3 m / min. The relationship between the 180-degree peel strength of the standard rubber pressure-sensitive adhesive tape (the back peel strength of the standard rubber pressure-sensitive adhesive tape) C [N/19 mm] may satisfy C>B. A surface protective film that satisfies the above conditions (C>B) can be peeled off from the adherend in a mode in which the rubber-based pickup tape is pressure-bonded to the back surface for a short period of time or in a mode in which it is peeled off immediately after pressure-bonding the pickup tape. obtain. A surface protection film that satisfies the condition (C>B) in addition to the condition (A>B) can be peeled off from both rubber-based and acrylic-based pickup tapes by attaching the pickup tape for a short period of time.

The back peel strength C of the standard rubber-based pressure-sensitive adhesive tape is not particularly limited, and is suitably about 0.5 N/19 mm or more, and may be about 1 N/19 mm or more (for example, about 2.5 N/19 mm or more). The surface protective film according to some preferred embodiments further has the following properties: (C) Standard rubber-based adhesion to the back surface of the surface protective film measured under the conditions of 23°C, 1 minute after application, and a tensile speed of 0.3 m/min. 180 degree peel strength of the tape (back peel strength of standard rubber adhesive tape) C is 3.5 N/19 mm or more. For example, a surface protective film that satisfies the property (C) in addition to the above property (B) can be adhered in a mode in which the rubber-based pickup tape is pressed onto the back surface for a short period of time, or in a mode in which the pickup tape is peeled off immediately after being pressed. It can be reliably detached from the body. By satisfying, for example, the above-mentioned characteristic (A) while having such characteristics, the surface protective film can be reliably applied to both rubber-based and acrylic-based pickup tapes in a short period of time. can be stripped.

From the viewpoint of improving the certainty of pick-up peeling by the pickup tape, the back peel strength C of the standard rubber adhesive tape in the characteristic (C) is preferably about 4.5 N/19 mm or more, more preferably about 5.5 N/19 mm or more. , more preferably about 6 N/19 mm or more, particularly preferably about 6.5 N/19 mm or more (for example, about 7 N/19 mm or more). The upper limit of the back peel strength C of the standard rubber pressure-sensitive adhesive tape is not particularly limited, and may be about 15 N/19 mm or less, preferably about 12 N/19 mm or less (for example, about 10 N/19 mm or less).

The larger the difference between the back surface peel strength A [N/19 mm] of the standard acrylic pressure-sensitive adhesive tape and the PET trigger peel strength B [N/19 mm], the greater the tendency to improve the certainty of preventing the occurrence of peeling defects. There is From such a point of view, the difference (AB) between A [N / 19 mm] and B [N / 19 mm] can be 0.1 or more, and 1 or more (for example, 3 or more) is suitable. , preferably 4 or more, more preferably 5 or more, still more preferably 5.5 or more, and particularly preferably 6 or more (for example, 6.5 or more). The upper limit of the difference (A - B) is not particularly limited, and may be less than 15, suitably less than 10, and preferably less than 9, more preferably less than 9 in consideration of adhesion to adherends and the like. is less than 8, more preferably less than 7.5 (eg less than 7), and may be less than 6.

Further, in the surface protection film disclosed herein, the difference between the back peel strength A [N/19 mm] of the standard acrylic adhesive tape and the back peel strength C [N/19 mm] of the standard rubber adhesive tape| AC| is preferably within a predetermined range. The back surface of the surface protective film, which has a small difference between the two, exhibits similar adhesiveness and pick-up peelability to both rubber-based and acrylic-based pickup tapes, and is easy to handle. From such a viewpoint, the difference |AC| can be 5 or less, suitably 3 or less, preferably 2.5 or less, more preferably 2 or less, and further preferably 1.5 or less. (for example, 1 or less). The lower limit of the difference |A−C| is not particularly limited, and if it is about 0.3 or more (for example, 0.5 or more), there is no practical disadvantage.

The back peel strength A of the standard acrylic pressure-sensitive adhesive tape, the peel strength B against PET, and the back peel strength C of the standard rubber pressure-sensitive adhesive tape can be measured by the method described in Examples below.

In some preferred embodiments, the surface resistivity of the back surface of the surface protection film (thus the surface of the topcoat layer) is 1.0×10 ¹³ Ω/□ or less. By setting the surface resistivity to 1.0×10 ¹³ Ω/□ or less, it is possible to suitably prevent or suppress electrification when the surface protective film is peeled off. The surface resistivity is more preferably less than 1.0×10 ¹² Ω/square, still more preferably less than 5.0×10 ¹¹ Ω/square, and particularly preferably less than 1.0×10 ¹¹ Ω/square. A surface protective film exhibiting the above-described surface resistivity can be suitably used as a surface protective film used in processing or transporting articles that should not be subjected to static electricity, such as liquid crystal cells and semiconductor devices. The lower limit of the surface resistivity is not particularly limited, and is approximately 5×10 ⁶ Ω/□ or more, for example 1.0×10 ⁷ Ω/□ or more. The surface resistivity of the back surface of the surface protective film (topcoat layer surface) can be measured by the method described in Examples below.

In some aspects, the surface resistivity of the adhesive surface (and thus the adhesive layer) of the surface protection film can be 1.0×10 ¹³ Ω/□ or less. By setting the surface resistivity to 1.0×10 ¹³ Ω/□ or less, it is possible to suitably prevent or suppress electrification when the surface protective film is peeled off. The surface resistivity is preferably less than 1.0×10 ¹² Ω/□, more preferably less than 5.0×10 ¹¹ Ω/□. A surface protective film exhibiting the above-described surface resistivity can be suitably used as a surface protective film used in processing or transporting articles that should not be subjected to static electricity, such as liquid crystal cells and semiconductor devices. The lower limit of the surface resistivity is not particularly limited, and is 5×10 ⁶ Ω/□ or more, for example 1.0×10 ⁹ Ω/□ or more, and 1.0×10 ¹⁰ Ω/□ or more (for example, 1.0×10 Ω/□ or more). × 10 ¹¹ Ω/square or more), or about 1.0 × 10 ¹³ Ω/square or more in an embodiment in which antistatic property is not imparted to the pressure-sensitive adhesive layer. The surface resistivity of the adhesive surface (adhesive layer) of the surface protection film can be measured by the method described in Examples below.

<Base material layer>
A resin film can be preferably employed as the material of the substrate layer (film substrate) used as the support of the surface protective film disclosed herein. Such a resin film may be obtained by molding various resin materials into a film shape. As the resin material, those capable of forming a resin film excellent in one or more of properties such as transparency, mechanical strength, thermal stability, moisture shielding property, and isotropy are preferred. For example, polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate; celluloses such as diacetyl cellulose and triacetyl cellulose; polycarbonates; acrylic polymers such as polymethyl methacrylate; A resin film composed of a resin material as a component (that is, a component contained in an amount of more than 50% by weight) can be preferably used as the film substrate. Other examples of the resin material constituting the resin film include styrenes such as polystyrene and acrylonitrile-styrene copolymers; olefins such as polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, ethylene-propylene copolymers; Polyvinyl chlorides; Polyamides such as nylon 6, nylon 6,6, and aromatic polyamides; Alternatively, polyimides, polysulfones, polyethersulfones, polyetheretherketones, polyphenylene sulfides, polyvinyl alcohols, polyvinylidene chlorides, polyvinyl butyrals, polyarylates, polyoxymethylenes, epoxies, etc. A resin film composed of a resin material as a main component may be used as the substrate layer. The resin material constituting the resin film may be a blend of two or more of these.

As the resin film for the substrate layer, a film having transparency and less anisotropy in optical properties (retardation, etc.) is preferably employed. In general, the smaller the anisotropy, the better. In particular, it is significant to reduce the optical anisotropy of the resin film used as the substrate layer of the surface protection film for optical parts. The resin film may have a single-layer structure, or may have a structure in which a plurality of layers having different compositions are laminated. Generally, a resin film having a single-layer structure can be preferably employed. Therefore, the substrate layer may also have a single-layer structure, or may have a structure in which a plurality of layers having different compositions are laminated.

From the viewpoint of appearance characteristics, the refractive index of the base layer (typically a resin film) is usually in the range of about 1.43 to 1.7, and 1.45 to 1.67. A range of degrees is preferred. A manufacturer's nominal value can be adopted as the value of the refractive index. If there is no nominal value, the value measured by JIS K 7142 A method can be adopted. In addition, the base material layer (typically a resin film) preferably has transparency with a total light transmittance of about 70% or more in the visible light wavelength region. More preferably, the transparent resin film has a total light transmittance of 80% or more (for example, 85% or more). The upper limit of the total light transmittance is ideally 100%. Practically, it can be preferably used as a transparent resin film. A manufacturer's nominal value can be adopted as the value of the total light transmittance. If there is no nominal value, the value measured according to JIS K 7361-1 can be adopted.

In some preferred embodiments, the film substrate is a resin film (polyester resin film) in which a resin (polyester resin) containing polyester as a main component (a component containing more than 50% by weight) is molded into a film shape. use. For example, a resin film (PET film) in which the polyester is mainly PET, a resin film (PEN film) in which the polyester is mainly PEN, or the like can be preferably employed.

Various additives such as antioxidants, ultraviolet absorbers, antistatic components, plasticizers, colorants (pigments, dyes, etc.) are blended in the resin material constituting the base material layer as necessary. good too. The first surface (the back surface, i.e., the surface on which the topcoat layer is provided) of the substrate layer (film substrate) is subjected to, for example, corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, undercoat agent. A known or conventional surface treatment such as coating may be applied. Such a surface treatment may be, for example, a treatment for enhancing adhesion between the back surface of the base material layer and the topcoat layer. A surface treatment that introduces a polar group such as a hydroxyl group (--OH group) to the back surface of the base material layer can be preferably employed. Further, in the surface protection film disclosed herein, the second surface of the substrate layer (the front surface, i.e., the surface on which the pressure-sensitive adhesive layer is formed) may be subjected to the same surface treatment as the back surface. good. Such a surface treatment may be a treatment for enhancing the adhesion between the substrate layer and the pressure-sensitive adhesive layer (the anchoring property of the pressure-sensitive adhesive layer).

In addition, the thickness of the substrate layer can be appropriately selected in consideration of the application, purpose, usage pattern, etc. of the surface protective film. From the standpoint of workability such as strength and handleability, a film substrate having a thickness of about 10 μm or more is suitable, preferably about 15 μm or more, more preferably about 20 μm or more, even more preferably about 30 μm or more (for example, 35 μm or more). The thickness of the base material layer is suitably about 200 μm or less, preferably about 150 μm or less, more preferably about 100 μm or less, still more preferably about 75 μm or less (for example, 50 μm or less), from the viewpoint of cost, transparency, etc. is.

<Top coat layer>
A top coat layer is typically formed from resin. As the resin constituting the topcoat layer, one or more resin materials that can satisfy the property (A) can be used. Such resins can be of various types, such as heat-curable resins, UV-curable resins, electron-beam-curable resins, two-component resins, and the like. The resin to be selected and used is more preferably a resin that is excellent in scratch resistance, capable of forming a layer having sufficient strength, and excellent in light transmittance.

Specific examples of thermosetting resins include polysiloxane-based, polysilazane-based, polyurethane-based, acrylic-urethane-based, acrylic-styrene-based, fluororesin-based, acrylic silicon-based, acrylic-based, polyester-based, and polyolefin-based resins. What is to be mentioned. Specific examples of UV-curable resins include monomers, oligomers, polymers, and mixtures thereof of various resins such as polyester, acrylic, urethane, amide, silicone, and epoxy resins. From the viewpoint of adhesion to the substrate layer, it is advantageous to use a thermosetting resin rather than an ultraviolet curable resin.

(Binder)
The topcoat layer typically contains a binder. Here, the "binder" contained in the topcoat layer refers to a basic component that contributes to the formation of the topcoat layer. As the binder, one or more of various resin materials that can satisfy the above property (A) can be used. Such resins include polyester resins, acrylic resins (including acrylic resins, urethane-acrylic resins, and styrene-acrylic resins), acrylic-silicone resins, silicone resins, polysilazane resins, polyurethane resins, fluororesins, polyolefin resins. Resin etc. are mentioned.

A topcoat layer according to some preferred embodiments contains an acrylic resin (also referred to as an acrylic binder) as a binder (binder resin). By providing a topcoat layer containing an acrylic binder, it is easy to increase the back peel strength A of the standard acrylic pressure-sensitive adhesive tape, even if the pressure bonding time of the pickup tape is short or the pickup tape peels off immediately after pressure bonding. can be reliably peeled off with an acrylic pickup tape.
The term "acrylic resin" used as a binder in this specification refers to a resin containing an acrylic polymer as a main component (a component contained in the resin in the largest proportion). The term "acrylic polymer" refers to a monomer having at least one (meth)acryloyl group in one molecule (hereinafter sometimes referred to as "acrylic monomer") as the main constituent monomer component (monomer The main component of the acrylic polymer, that is, the component that is the most contained among the total amount of monomers constituting the acrylic polymer). The above-mentioned "(meth)acryloyl group" is meant to comprehensively refer to acryloyl groups and methacryloyl groups. Similarly, "(meth)acrylate" is meant to collectively refer to acrylates and methacrylates.

The acrylic monomer that is the main monomer component of the acrylic polymer contained in the acrylic binder is not particularly limited, and monomers having (meth)acryloyl groups such as alkyl (meth)acrylates and (meth)acrylic acid. One or two or more of are preferably used. The number of carbon atoms in the alkyl group of the alkyl (meth)acrylate is typically 1 to 20, preferably 1 to 12, more preferably 1 to 11, for example 1 to 10 (further 2 to 10). . The above alkyl groups include chain (linear and branched) alkyl groups and alicyclic alkyl groups. From the viewpoint of adhesion performance, etc., the monomer component forming the acrylic polymer contains less than 30% by weight (for example, less than 15% by weight) of alkyl (meth)acrylate having 12 or more carbon atoms in the alkyl group. Suitably, the proportion may be less than 10 wt% (eg less than 3 wt%, typically less than 1 wt%).

The ratio of the acrylic monomer to the monomer components constituting the acrylic polymer contained in the acrylic binder may vary depending on the content of other copolymerizable monomers, but may be, for example, more than 25% by weight, or even 34% by weight. greater than, typically greater than 50% by weight. The proportion of the acrylic monomer in the monomer components constituting the acrylic polymer may be approximately 70% by weight or more, may be approximately 90% by weight or more, and may be approximately 95% by weight or more (e.g., 99 to 100% by weight). ).

In some aspects, the amount of the monomer component that constitutes the acrylic polymer contained in the acrylic binder is limited to a monomer having a homopolymer glass transition temperature (Tg) of 0° C. or higher from the viewpoint of adhesion performance. ing. The proportion of monomers having a homopolymer Tg of 0° C. or higher in all monomer components is suitably about 50% by weight or less, and may be about 30% by weight or less (for example, about 10% by weight or less). In the present specification, the glass transition temperature of the homopolymer used for calculating Tg is the value described in publicly known materials such as "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). shall be used. For monomers for which multiple values are listed in this document, the highest value is adopted. If the Tg of the homopolymer is not described in known documents, the value obtained by the measurement method described in JP-A-2007-51271 shall be used.

In the acrylic polymer, the type of copolymerizable monomer to be copolymerized with the acrylic monomer is not particularly limited. Examples include vinyl esters such as vinyl acetate; aromatic vinyl compounds such as styrene; vinyl ethers; (meth)acrylonitrile; be done. These copolymerizable monomers can be used singly or in combination of two or more.

From the viewpoint of adhesiveness, etc., the acrylic polymer contained in the acrylic binder disclosed herein has a (meth)acrylate having silicone in the side chain or a fluoroalkyl group such as a perfluoroalkyl group in the side chain ( Suitably, the copolymerization proportion of meth)acrylate is less than 10% by weight. The copolymerization ratio of these silicone (meth)acrylates and fluoroalkyl (meth)acrylates in the acrylic polymer may be less than 3% by weight (less than 1% by weight). The technology disclosed herein can be preferably practiced in a mode in which an acrylic polymer in which silicone (meth)acrylate and fluoroalkyl (meth)acrylate are not substantially copolymerized is used as the acrylic binder.

In some preferred embodiments, a carboxy group-containing polymer is used as the acrylic binder. The acid value of the carboxy group-containing polymer is not particularly limited, and one having about 10 mgKOH/g or more (for example, about 30 mgKOH/g or more, preferably about 50 mgKOH/g or more) is preferably used. The upper limit of the acid value may be about 250 mgKOH/g or less (eg, about 200 mgKOH/g or less, preferably about 100 mgKOH/g or less). As the acid value, a value measured by the potentiometric titration method specified in JIS K0070:1992 can be adopted. Examples of carboxy group-containing polymers include "ARUFON UC-3000 series" and "ARUFON UC-5000 series" available from Toagosei.

In some other preferred embodiments, a hydroxyl-containing polymer is used as the acrylic binder. The hydroxyl value of the hydroxyl group-containing polymer is not particularly limited, and one having about 10 mgKOH/g or more (for example, about 50 mgKOH/g or more, preferably about 70 mgKOH/g or more) is preferably used. The upper limit of the hydroxyl value may be about 250 mgKOH/g or less (eg, about 150 mgKOH/g or less, preferably about 100 mgKOH/g or less). As the hydroxyl value, a value measured by a potentiometric titration method specified in JIS K0070:1992 can be adopted. Examples of hydroxyl group-containing polymers include "ARUFON UH-2000 series" available from Toagosei Co., Ltd., and "Oricox KC-7000", "Oricox KC-700" and "Oricox KC-7025T" available from Kyoeisha Chemical Co., Ltd. ” is mentioned.

In some other preferred embodiments, an acrylic copolymer containing quaternary ammonium groups in the side chains is used as the acrylic binder. Such acrylic copolymers not only function as binders, but can also serve as antistatic agents. Examples of such a quaternary ammonium group-containing acrylic copolymer include "Bondip" available from Konishi Co., Ltd.

The molecular weight of the acrylic binder (specifically, the acrylic polymer) should be an appropriate molecular weight in consideration of adhesiveness, pick-up peelability, topcoat layer formability, and handleability (dispersibility, etc.). Not limited to a specific range. The molecular weight of the acrylic binder (specifically acrylic polymer) is, for example, approximately 1500 or more, approximately 5000, as a standard polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC). Above is suitable, preferably about 8000 or more, and about 10000 or more (for example, about 12000 or more) may be used. The molecular weight is suitably about 15×10 ⁴ or less, preferably about 5×10 ⁴ or less, and may be about 3×10 ⁴ or less, for example.

The glass transition temperature (Tg) of the acrylic binder (specifically, the acrylic polymer) is not limited to a specific range, and a suitable Tg is used in consideration of adhesiveness, pick-up peelability, and the like. The Tg of the acrylic binder (specifically acrylic polymer) can be approximately 0° C. or higher, suitably approximately 20° C. or higher, preferably approximately 40° C. or higher (for example, approximately 50° C. or higher). be. The Tg is, for example, approximately 120° C. or lower, and is suitably approximately 100° C. or lower (for example, approximately 80° C. or lower). In this specification, unless otherwise specified, Tg refers to Tg obtained from the Fox formula based on the composition of the monomer components.

The proportion of the acrylic polymer, which is the main component of the acrylic resin, when the acrylic resin contains a plurality of components, is, for example, more than 25% by weight, more than 34% by weight, typically more than 34% by weight, in the acrylic resin. It can be greater than 50% by weight. The proportion of the acrylic polymer in the acrylic resin may be approximately 70% by weight or more, approximately 90% by weight or more, or approximately 95% by weight or more (for example, 99 to 100% by weight).

The proportion of the acrylic binder contained in the topcoat layer is not particularly limited, and may be approximately 10% by weight or more, and approximately 20% by weight or more is suitable, and the effect of containing the acrylic binder is preferably expressed. From the viewpoint of It may be 90% by weight or more. In addition, the proportion of the acrylic binder in the topcoat layer is appropriately about 95% by weight or less (for example, 85% by weight or less), preferably about 65% by weight or less, in consideration of scratch resistance, antistatic properties, etc. , more preferably about 60% by weight or less, still more preferably about 55% by weight or less (for example, about 50% by weight or less, furthermore 45% by weight or less).

In the embodiment in which the topcoat layer contains an acrylic binder, the topcoat layer contains, as the binder, a resin other than an acrylic resin (e.g., polyester resin, acrylic-silicone resin, silicone resin, polysilazane resin, polyurethane resin, fluororesin, polyolefin resin). (1 or 2 or more resins selected from resins, etc.). The content of the non-acrylic resin is suitably less than 100 parts by weight with respect to 100 parts by weight of the acrylic resin. It may be 30 parts by weight or less, or about 10 parts by weight or less (for example, about 3 parts by weight or less). In some preferred embodiments, the binder contained in the topcoat layer consists essentially of acrylic resin.

The proportion of the binder in the entire topcoat layer (total amount of binder) is set in consideration of film formability, scratch resistance, antistatic properties, etc., and is not limited to a specific range. The binder content in the topcoat layer can be, for example, approximately 10% by weight or more, suitably approximately 20% by weight or more, preferably approximately 30% by weight or more, more preferably approximately 35% by weight or more ( For example, about 40% by weight or more), may be about 50% by weight or more, may be about 70% by weight or more, or may be about 90% by weight or more. In addition, the upper limit of the proportion of the binder in the topcoat layer is appropriately about 95% by weight or less (for example, 85% by weight or less), preferably about 65% by weight or less, more preferably about 60% by weight or less, and even more preferably about 60% by weight or less. It is about 55% by weight or less (for example, about 50% by weight or less, further 45% by weight or less).

(Antistatic component)
The technology disclosed herein can be preferably implemented in a mode in which the topcoat layer contains an antistatic component. The antistatic component is a component capable of preventing or suppressing the charging of the surface protection film. When the topcoat layer contains an antistatic component, for example, an organic or inorganic conductive substance, various antistatic agents, and the like can be used as the antistatic component.

Examples of the organic conductive substance include quaternary ammonium salts, pyridinium salts, cationic antistatic agents having cationic functional groups such as primary amino groups, secondary amino groups, and tertiary amino groups; sulfonates and sulfuric acid. Anionic antistatic agents having anionic functional groups such as ester salts, phosphonates, and phosphate ester salts; Alkylbetaine and its derivatives, imidazoline and its derivatives, alanine and its derivatives, etc. amphoteric antistatic agents; amino Nonionic antistatic agents such as alcohols and derivatives thereof, glycerin and derivatives thereof, polyethylene glycol and derivatives thereof; monomers having the above cationic, anionic and zwitterionic ion conductive groups (e.g., quaternary ammonium bases) and conductive polymers such as polythiophene, polyaniline, polypyrrole, polyethyleneimine, and allylamine-based polymers. A quaternary ammonium group-containing acrylic copolymer exemplified as a binder can also be used as an antistatic agent. Such antistatic agents may be used alone or in combination of two or more.

Examples of the above inorganic conductive substances include tin oxide, antimony oxide, indium oxide, cadmium oxide, titanium oxide, zinc oxide, indium, tin, antimony, gold, silver, copper, aluminum, nickel, chromium, titanium, iron, Cobalt, copper iodide, ITO (indium oxide/tin oxide), ATO (antimony oxide/tin oxide), and the like. Such inorganic conductive substances may be used singly or in combination of two or more.

Examples of the antistatic agent include cationic antistatic agents, anionic antistatic agents, amphoteric antistatic agents, nonionic antistatic agents, and the above cationic, anionic, and amphoteric ion conductive groups. ion-conductive polymers obtained by polymerizing or copolymerizing monomers having

In some preferred embodiments, the antistatic component used in the topcoat layer comprises an organic conductive material. Various conductive polymers can be preferably used as the organic conductive substance. A topcoat layer containing a conductive polymer tends to achieve both good antistatic properties and high scratch resistance. Examples of conductive polymers include polythiophene, polyaniline, polypyrrole, polyethyleneimine, and allylamine-based polymers. Such conductive polymers may be used singly or in combination of two or more. It may also be used in combination with other antistatic components (inorganic conductive substances, antistatic agents, etc.).

Polythiophene (thiophene-based polymer) and polyaniline (aniline-based polymer) are exemplified as conductive polymers that can be preferably employed in the technology disclosed herein. Polythiophene preferably has a polystyrene-equivalent Mw of 40×10 ⁴ or less, more preferably 30×10 ⁴ or less. Polyaniline preferably has an Mw of 50×10 ⁴ or less, more preferably 30×10 ⁴ or less. Moreover, the Mw of these conductive polymers is usually preferably 0.1×10 ⁴ or more, more preferably 0.5×10 ⁴ or more. As used herein, polythiophene refers to a polymer of unsubstituted or substituted thiophene. One suitable example of the substituted thiophene polymer in the technology disclosed herein is poly(3,4-ethylenedioxythiophene). A suitable example of polyaniline is polyaniline sulfonic acid.

The content of the organic conductive substance (typically a conductive polymer) can be about 10 parts by weight or more with respect to 100 parts by weight of the binder contained in the topcoat layer from the viewpoint of antistatic. Part by weight or more is suitable, preferably 40 parts by weight or more, more preferably 50 parts by weight or more (for example, more than 50 parts by weight), still more preferably 60 parts by weight or more. When emphasizing antistatic properties, the content of the organic conductive substance (typically a conductive polymer) may be 70 parts by weight or more (for example, 90 parts by weight or more) with respect to 100 parts by weight of the binder. Considering the compatibility of the organic conductive substance (typically a conductive polymer) in the topcoat layer and the property change due to the decrease in compatibility, the content of the organic conductive substance (typically a conductive polymer) is , 200 parts by weight or less (for example, 150 parts by weight or less), preferably 120 parts by weight or less (for example, 100 parts by weight or less) with respect to 100 parts by weight of the binder. It is also possible to set the content of the organic conductive substance (typically conductive polymer) to 80 parts by weight or less (for example, 60 parts by weight or less) with respect to 100 parts by weight of the binder.

The amount of the inorganic conductive substance used can be, for example, about 5 parts by weight or more, and usually 10 parts by weight or more (for example, 100 parts by weight or more) per 100 parts by weight of the resin component constituting the topcoat layer. It is suitable that the upper limit is about 500 parts by weight or less.

As a method for forming the topcoat layer, when a method of applying a coating material for forming a topcoat layer to a film substrate and drying or curing is adopted, the conductive polymer used for preparing the coating material may be the conductive A conductive polymer dissolved or dispersed in water (aqueous conductive polymer solution) can be preferably used. Such a conductive polymer aqueous solution can be prepared, for example, by dissolving or dispersing a conductive polymer having a hydrophilic functional group (which can be synthesized by a technique such as copolymerizing a monomer having a hydrophilic functional group in the molecule) in water. can be prepared by Examples of the hydrophilic functional groups include sulfo group, amino group, amide group, imino group, hydroxyl group, mercapto group, hydrazino group, carboxyl group, quaternary ammonium group, sulfate ester group (--O--SO ₃ H), Phosphate ester groups (such as —O—PO(OH) ₂ ) are exemplified. Such hydrophilic functional groups may form salts. Examples of commercially available polythiophene aqueous solutions include the product name "Denatron" series manufactured by Nagase Chemtech. Moreover, as a commercially available polyaniline sulfonic acid aqueous solution, Mitsubishi Chemical Corporation's trade name "Aquapass" is exemplified.

In some preferred embodiments, an aqueous polythiophene solution is used to prepare the coating material. The use of an aqueous polythiophene solution containing polystyrene sulfonate (PSS) (which may be in the form of polythiophene to which PSS is added as a dopant) is preferred. Such aqueous solutions may contain polythiophene:PSS in a weight ratio of 1:1 to 1:10. The total content of polythiophene and PSS in the aqueous solution can be, for example, about 1 to 5% by weight. Commercially available polythiophene aqueous solutions include H.I. C. Stark's trade name "Baytron" is exemplified.
When using a polythiophene aqueous solution containing PSS as described above, the total amount of polythiophene and PSS is 5 parts by weight or more (typically 10 parts by weight or more, for example 25 parts by weight) with respect to 100 parts by weight of the binder. parts or more), preferably 40 parts by weight or more (for example, 50 parts by weight or more). The total amount of polythiophene and PSS is suitably 200 parts by weight or less, preferably 120 parts by weight or less (for example, 100 parts by weight or less), or 80 parts by weight, per 100 parts by weight of the binder. or less (for example, 60 parts by weight or less).

The topcoat layer disclosed herein optionally contains a conductive polymer and one or more other antistatic components (organic conductive substances other than conductive polymers, inorganic conductive substances, antistatic agents, etc.). In some preferred embodiments, the topcoat layer is substantially free of antistatic components other than the conductive polymer. That is, the technology disclosed herein can be preferably implemented in a mode in which the antistatic component contained in the topcoat layer consists essentially of the conductive polymer.

(curing agent)
In some preferred embodiments, the topcoat layer contains a curing agent. The curing agent can be a cross-linking agent that cures the topcoat layer through a chemical reaction such as a cross-linking reaction. By using a curing agent, the back side performance of the protective film can be favorably improved, such as improved scratch resistance and solvent resistance. Curing agents include isocyanate, epoxy, oxazoline, aziridine, melamine, carbodiimide, hydrazine, amine, imine, peroxide, metal chelate, metal alkoxide, and metal salt. Various compounds are used. These can be used individually by 1 type or in combination of 2 or more types. Preferred examples include melamine-based curing agents, oxazoline-based curing agents, aziridine-based curing agents, epoxy-based curing agents, and carbodiimide-based curing agents. Among these, melamine-based curing agents, oxazoline-based curing agents, and aziridine-based curing agents are preferred, and aziridine-based curing agents are more preferred.

As the melamine-based curing agent, methylolmelamine such as hexamethylolmelamine and various melamine-based curing agents such as butylated melamine resin can be used. The melamine-based curing agents can be used singly or in combination of two or more. For example, "Nika resin series" available from Nippon Carbide Industry Co., Ltd. and trade name "Super Beccamin J-820-60N" available from DIC Corporation can be mentioned.

As the oxazoline curing agent, those having one or more oxazoline groups in one molecule can be used without particular limitation. The oxazoline group may be any of 2-oxazoline group, 3-oxazoline group and 4-oxazoline group. An oxazoline curing agent having a 2-oxazoline group can be preferably used. Specific examples of oxazoline-based curing agents include compounds containing a main chain composed of a (meth)acrylic skeleton or a styrene skeleton and having an oxazoline group in the side chain of the main chain. A preferred example is an oxazoline group-containing (meth)acrylic polymer that includes a main chain composed of a (meth)acrylic skeleton and has an oxazoline group in the side chain of the main chain. The oxazoline curing agents can be used singly or in combination of two or more.

The molecular weight of the oxazoline-based curing agent (typically, an oxazoline group-containing polymer) is, for example, about 0.2×10 ³ or more, suitably about 0.5×10 ³ or more, preferably about 1×10 ³ . (for example, 1.5×10 ³ or more), about 100×10 ⁴ or less (for example, about 50×10 ⁴ or less) is suitable, and about 10×10 ⁴ or less (for example, about 5×10 ^{4 or less} ) is preferable. below). The above molecular weight is a standard polystyrene equivalent number average molecular weight (Mn) obtained by GPC.

The Tg of the oxazoline curing agent (typically an oxazoline group-containing polymer) is, for example, about 0° C. or higher, suitably about 20° C. or higher, preferably about 40° C. or higher (for example, about 50° C. or higher). be. The Tg is, for example, approximately 120° C. or less, and is suitably approximately 100° C. or less (for example, approximately 90° C. or less).

Commercially available oxazoline curing agents include, for example, Nippon Shokubai Co., Ltd. under the trade names of "Epocross WS-500", "Epocross WS-700", "Epocross K-2010E", "Epocross K-2020E", and "Epocross K- 2030E" and the like.

As the aziridine-based curing agent, for example, a compound having two or more aziridyl groups in one molecule (bifunctional, trifunctional or higher polyfunctional aziridine compound) can be used. Suitable examples include an aziridine content of about 1 to 15 mmol/g (preferably 3 to 10 mmol/g, typically 5 to 8 mmol/g) and a molecular weight of 100 to 10,000 (preferably 200 to 1,000, typically is about 300 to 600). Specific examples include tris(1-aziridinepropionic acid) 1,1,1-propanetriyltrismethylene, trimethylolpropanetris[3-(1-aziridinyl)propionate], trimethylolpropanetris[3-(1- (2-methyl)aziridinylpropionate)], tetramethylromethane-tri-β-aziridinylpropionate, 1,1,-isophthaloyl bis(2-methylaziridine), and the like. The aziridine-based curing agents can be used singly or in combination of two or more. Examples of aziridine curing agents include Chemitite series such as "Chemitite PZ-33" and "Chemitite DZ-22E" available from Nippon Shokubai Co., Ltd., "CROSSLINKER CL-427" available from Sogo Pharmaceutical Co., Ltd., "BIA" can be used.

As the epoxy-based curing agent, a compound having two or more epoxy groups in one molecule can be used without particular limitation. Epoxy curing agents having 3 to 5 epoxy groups in one molecule are preferred. Epoxy curing agents may be used singly or in combination of two or more. Specific examples of the epoxy curing agent include, but are not limited to, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl ) cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether and the like. Commercially available epoxy-based curing agents include Mitsubishi Gas Chemical Co., Ltd.'s trade name "TETRAD-C" and trade name "TETRAD-X", DIC's trade name "Epiclon CR-5L", and Nagase ChemteX Co., Ltd. product name "Denacol EX-512" manufactured by Nissan Chemical Industries, Ltd.; product name "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd.;

A carbodiimide-based curing agent is a compound having at least one, typically two or more carbodiimide groups as crosslinkable functional groups. The carbodiimide group is a functional group (-N=C=NH) obtained by removing one hydrogen atom from carbodiimide (HN=C=NH), or a functional group obtained by removing two hydrogen atoms (-N=C= N-). This carbodiimide group can react with a carboxyl group. The carbodiimide-based curing agents can be used singly or in combination of two or more. Carbodiimide-based curing agents include, for example, Carbodilite V series such as "Carbodilite V-02", "Carbodilite V-02-L2" and "Carbodilite V-04"; "Carbodilite E-01" and "Carbodilite E-02". , Carbodilite E series such as "Carbodilite E-04"; and Carbodilite series (manufactured by Nisshinbo Co., Ltd.).

The content of the curing agent is set in consideration of pickup releasability, scratch resistance, anchoring property, etc., and is not limited to a specific range. With respect to 100 parts by weight of the binder contained in the topcoat layer, it can be about 1 part by weight or more, and about 10 parts by weight or more is suitable. 20 parts by weight or more (for example, approximately 30 parts by weight or more). In addition, the upper limit of the content of the curing agent can be, for example, about 100 parts by weight or less with respect to 100 parts by weight of the binder contained in the topcoat layer, and about 80 parts by weight or less is suitable. and antistatic properties, it is preferably about 65 parts by weight or less (e.g. about 60 parts by weight or less), more preferably 55 parts by weight or less, still more preferably 50 parts by weight or less (e.g. about 45 parts by weight or less). .

(Slip agent)
The topcoat layer may contain a slip agent. As used herein, the term "slipping agent" refers to a component that, when contained in the topcoat layer, can exhibit the action of improving the slipperiness of the topcoat layer. In some embodiments, for example, esters of fatty acids and alcohols (hereinafter also referred to as “fatty acid esters”) are used as slip agents. The fatty acid is preferably a carboxylic acid (typically a monovalent carboxylic acid) having 8 or more carbon atoms (typically 10 or more, more preferably 10 or more and 40 or less). The alcohol preferably has 6 or more carbon atoms (typically 10 or more, more preferably 10 or more and 40 or less) (typically a monohydric or dihydric alcohol, preferably a monohydric alcohol). ). Specific examples of fatty acid esters include myricyl cerotate, myricyl palmitate, cetyl palmitate, and stearyl stearate. The slip agents can be used singly or in combination of two or more.

In some other embodiments, a natural wax containing a fatty acid ester can be used as a raw material for the topcoat layer. As such a natural wax, the content ratio of the fatty acid ester (when two or more kinds of fatty acid esters are included, the total content ratio thereof) is more than 50% by weight (more preferably 65% by weight or more, for example 75% by weight or more) can be preferably employed. For example, carnauba wax (generally containing 60% by weight or more, preferably 70% by weight or more, typically 80% by weight or more of myricyl cerotinate), vegetable waxes such as palm wax; beeswax, whale Animal waxes such as waxes; natural waxes such as waxes can be used. The melting point of the natural wax used is preferably 50° C. or higher (more preferably 60° C. or higher, still more preferably 70° C. or higher, for example 75° C. or higher). As a raw material for the topcoat layer, a chemically synthesized fatty acid ester may be used, or a fatty acid ester obtained by purifying natural wax to increase the purity of the fatty acid ester may be used. These raw materials can be used alone or in combination as appropriate.

In some other embodiments, the topcoat layer contains petroleum wax (paraffin wax, etc.), mineral wax (montan wax, etc.), higher fatty acid (cerotic acid, etc.), neutral fat (palmitic acid triglyceride, etc.) as a slip agent. etc.), various waxes other than fatty acid esters. Alternatively, general silicone-based lubricants, fluorine-based lubricants, and the like may be contained. These can be used individually by 1 type or in combination of 2 or more types.

The amount of the slipping agent to be added in the topcoat layer can be, for example, approximately 1% by weight or more, suitably approximately 3% by weight or more, and preferably approximately 5% by weight or more ( For example, about 10% by weight or more). The upper limit of the amount of the slipping agent added can be, for example, about 50% by weight or less, suitably about 20% by weight or less, and from the viewpoint of pick-up peelability, etc., preferably about 15% by weight or less, more preferably about 15% by weight or less. It is about 10% by weight or less, more preferably about 3% by weight or less, and may be about 1% by weight or less. The technology disclosed herein can be preferably implemented in a mode in which the topcoat layer does not substantially contain a slip agent.

The topcoat layer in the technology disclosed herein optionally contains antioxidants, colorants (pigments, dyes, etc.), fluidity modifiers (thixotropic agents, thickeners, etc.), film-forming aids, interface Additives such as activators (antifoaming agents, dispersants, etc.), preservatives and the like may be contained.

The technology disclosed herein can be preferably implemented in a mode in which the topcoat layer contains a binder (typically an acrylic binder), an antistatic component (preferably a conductive polymer) and a curing agent. As a result, the effect (reliable pick-up peelability) of the technology disclosed herein is preferably exhibited. In some aspects, a surface protective film having a topcoat layer substantially composed of the above three components may be used. From the viewpoint of effectively obtaining the certainty of pick-up peeling by the technology disclosed herein, the content of components (other components) other than the binder, antistatic component and curing agent in the topcoat layer is, for example, about 30% by weight or less. 10% by weight or less is suitable, preferably about 3% by weight or less, more preferably about 1% by weight or less (for example, 0.1% by weight or less). The technology disclosed herein can be preferably carried out in a mode in which the topcoat layer does not substantially contain the above other components.

(Method for forming topcoat layer)
The topcoat layer is formed by applying a liquid composition (coating material for forming a topcoat layer) in which the resin component and optional additives are dispersed or dissolved in an appropriate solvent to the film substrate. It can be preferably formed by a technique including. For example, a method of applying the above coating material to the first surface of the film base material, drying it, and subjecting it to curing treatment (heat treatment, ultraviolet treatment, etc.) as necessary can be preferably adopted. The NV of the coating material can be, for example, 5% by weight or less (typically 0.05 to 5% by weight), and usually 1% by weight or less (typically 0.10 to 1% by weight). It is appropriate to When forming a thin topcoat layer, the NV of the coating material is preferably 0.05 to 0.50% by weight (eg, 0.10 to 0.30% by weight). By using such a low NV coating material, a more uniform topcoat layer can be formed.

As the solvent constituting the coating material for forming the topcoat layer, a solvent capable of stably dissolving or dispersing the components for forming the topcoat layer is preferable. Such solvents can be organic solvents, water, or mixtures thereof. Examples of the organic solvent include esters such as ethyl acetate; ketones such as methyl ethyl ketone, acetone and cyclohexanone; cyclic ethers such as tetrahydrofuran (THF) and dioxane; hydrocarbons; aromatic hydrocarbons such as toluene and xylene; aliphatic or alicyclic alcohols such as methanol, ethanol, n-propanol, isopropanol and cyclohexanol; alkylene glycol monoalkyl ethers (e.g., ethylene glycol monomethyl ether , ethylene glycol monoethyl ether), glycol ethers such as dialkylene glycol monoalkyl ether; and the like. In some preferred embodiments, the solvent of the coating material is water or a mixed solvent containing water as a main component (for example, a mixed solvent of water and ethanol).

(thickness of topcoat layer)
The thickness of the topcoat layer in the technology disclosed herein is suitably 3 nm or more (for example, 7 nm or more) from the viewpoint of suitably exhibiting the function of the topcoat layer. Uniform formation of the topcoat layer is preferably realized by setting the topcoat layer to a predetermined thickness or more. From such a viewpoint, the thickness of the topcoat layer is preferably 10 nm or more, more preferably 15 nm or more, still more preferably 20 nm or more, and may be 25 nm or more. In some aspects, the thickness of the topcoat layer may be 30 nm or greater, 80 nm or greater, or 150 nm or greater (eg, 180 nm or greater). The thickness of the topcoat layer is suitably 500 nm or less (eg, 300 nm or less) from the viewpoint of transparency, etc., preferably 100 nm or less (eg, 100 nm or less), more preferably 90 nm or less (eg, 80 nm or less). It is preferably 50 nm or less, particularly preferably 40 nm or less (for example, 30 nm or less). By thinning the topcoat layer, the influence on the properties (optical properties, dimensional stability, etc.) of the surface protective film can be reduced.

The thickness of the topcoat layer can be determined by observing a cross section of the topcoat layer with a transmission electron microscope (TEM). For example, the target surface protection film sample is subjected to heavy metal staining treatment for the purpose of clarifying the top coat layer, then embedded in resin, and the results obtained by performing TEM observation of the sample cross section by the ultra-thin section method. , can be preferably employed as the thickness of the topcoat layer in the technology disclosed herein. As the TEM, a TEM manufactured by Hitachi, model "H-7650" or the like can be used. If the topcoat layer can be observed clearly enough without heavy metal staining, the heavy metal staining treatment may be omitted. Alternatively, the correlation between the thickness grasped by the TEM and the detection results by various thickness detection devices (e.g., surface roughness meter, interference thickness meter, infrared spectrometer, various X-ray diffraction devices, etc.) is calibrated. The thickness of the topcoat layer may be determined by drawing a line and performing a calculation.

<Adhesive layer>
The pressure-sensitive adhesive layer disclosed herein has characteristics suitable for a surface protection film (for example, the adhesive strength to the adherend is not too high, the adhesive strength does not increase with time, the adherend is not contaminated, etc.). The type of adhesive that constitutes the adhesive layer is not particularly limited. For example, acrylic, polyester, urethane, polyether, rubber, silicone, polyamide, fluorine, etc., one or more selected from various known pressure-sensitive adhesives. It can be an adhesive layer.

(Acrylic adhesive)
In some preferred embodiments, the pressure-sensitive adhesive layer is composed of an acrylic pressure-sensitive adhesive. Acrylic pressure-sensitive adhesives are generally excellent in transparency, and are therefore preferable as the pressure-sensitive adhesive layer of the optical surface protection film. Hereinafter, the technology disclosed herein will be described in more detail, taking as a main example a surface protective film in which the pressure-sensitive adhesive layer is composed of an acrylic pressure-sensitive adhesive. is not intended to be limited to
The term "acrylic pressure-sensitive adhesive" refers to a pressure-sensitive adhesive that uses an acrylic polymer as a base polymer (the main component of the polymer components contained in the acrylic pressure-sensitive adhesive, i.e., a component containing more than 50% by weight). say. The term "acrylic polymer" refers to a monomer having at least one (meth)acryloyl group in one molecule (hereinafter sometimes referred to as "acrylic monomer") as the main constituent monomer component (monomer It refers to the polymer that is the main component of

(acrylic polymer)
The acrylic polymer, which is the base polymer of the acrylic pressure-sensitive adhesive, is typically a polymer containing alkyl (meth)acrylate as a main constituent monomer component. As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably used.
_CH2 =C( ^R1 ) ^COOR2 (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. R ² is an alkyl group having 1 to 20 carbon atoms (meaning that it includes a chain alkyl group and an alicyclic alkyl group). Since it is easy to obtain an adhesive with excellent adhesive properties, R ² is a chain alkyl having 1 to 14 carbon atoms (hereinafter, such a carbon atom number range may be referred to as C _1-14 ). Alkyl (meth)acrylates, which are groups (meaning including linear alkyl groups and branched alkyl groups), are preferred. Specific examples of the C _1-14 chain alkyl group include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group, isoamyl group, neopentyl group, n-hexyl group, n-heptyl group, n-octyl group, isooctyl group, 2-ethylhexyl group, n-nonyl group, isononyl group, n-decyl group, isodecyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, and the like. Alicyclic alkyl groups that can be selected as R ² include a cyclohexyl group, an isobornyl group, and the like.

In some preferred embodiments, 50% by weight or more (typically 50 to 99.9% by weight) of the total amount of monomers used to synthesize the acrylic polymer (hereinafter also referred to as "all raw material monomers"), more Preferably 70% by weight or more (typically 70 to 99.9% by weight), for example 85% by weight or more (typically 85 to 99.9% by weight), R ² in the above formula (1) is C _1-14 chain alkyl (meth)acrylates (more preferably C _2-12 chain alkyl acrylates, more preferably C _4-10 chain alkyl acrylates such as one of n-butyl acrylate and 2-ethylhexyl acrylate) or both). An acrylic polymer obtained from such a monomer composition is preferred because it facilitates the formation of a pressure-sensitive adhesive exhibiting adhesive properties suitable for use as a surface protective film.

As the acrylic polymer in the technology disclosed herein, one obtained by copolymerizing an acrylic monomer having a hydroxyl group (--OH) can be preferably used. Such a copolymer composition (monomer composition) can be preferably employed particularly when a solution polymerization method is used as a method for synthesizing the acrylic polymer. Specific examples of acrylic monomers having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4- Hydroxybutyl (meth)acrylate, 2-hydroxyhexyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl ( meth)acrylate, (4-hydroxymethylcyclohexyl)methylacrylate, polypropylene glycol mono(meth)acrylate, N-hydroxyethyl(meth)acrylamide, N-hydroxypropyl(meth)acrylamide and the like. Such hydroxyl group-containing acrylic monomers may be used alone or in combination of two or more. An acrylic polymer obtained by copolymerizing such a monomer is preferable because it tends to provide a pressure-sensitive adhesive exhibiting adhesive properties suitable for use as a surface protective film. For example, since it becomes easy to control the release force to the adherend to be low, it is easy to obtain a pressure-sensitive adhesive with excellent removability. Particularly preferred hydroxyl-containing acrylic monomers include hydroxyl-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxy Butyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate can be mentioned.

From the viewpoint of sufficiently exhibiting the effect of using the monomer, such a hydroxyl group-containing acrylic monomer is preferably used at a rate of about 0.1% by weight or more of the total amount of the monomers used for synthesizing the acrylic polymer. Preferably, the amount of hydroxyl group-containing acrylic monomer used is more preferably about 0.2% by weight or more, and still more preferably about 0.3% by weight or more. In a particularly preferred embodiment, the amount of the hydroxyl group-containing acrylic monomer in the total amount of monomers used for synthesizing the acrylic polymer is 1% by weight or more (for example, 3% by weight or more, typically 6% by weight or more). In addition, the amount of the hydroxyl group-containing acrylic monomer in the total amount of monomers used in the synthesis of the acrylic polymer is about 15% by weight or less, considering the cohesiveness of the adhesive and the wettability (adhesion) to the adherend. is preferably about 12% by weight or less, more preferably 10% by weight or less.

As the acrylic polymer in the technology disclosed herein, one having a Tg of about 0° C. or less (typically −100° C. to 0° C.) is used because it is easy to balance adhesion performance. An acrylic polymer having a Tg in the range of about -80°C to -5°C is suitable. From the viewpoint of the initial adhesiveness in use at room temperature and the workability of attaching the protective film, the Tg of the acrylic polymer is preferably about −30° C. or less, more preferably about −50° C. or less, and even more preferably about −50° C. or less. −60° C. or less (for example, about −65° C. or less). The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the types and usage ratios of the monomers used in synthesizing the polymer).

The acrylic polymer in the technique disclosed herein may be copolymerized with monomers other than the above (other monomers) within a range that does not significantly impair the effects of the present invention. The above-mentioned other monomers can be used, for example, for the purpose of adjusting the Tg of the acrylic polymer, adjusting the adhesion performance (for example, releasability), and the like. For example, monomers capable of improving the cohesive strength and heat resistance of the adhesive include sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, vinyl esters, aromatic vinyl compounds, and the like. In addition, monomers that introduce functional groups that can serve as cross-linking base points into the acrylic polymer or that can contribute to improving adhesion include carboxyl group-containing monomers, acid anhydride group-containing monomers, amide group-containing monomers, amino group-containing monomers, Examples include imide group-containing monomers, epoxy group-containing monomers, (meth)acryloylmorpholine, vinyl ethers, and the like. These can be used individually by 1 type or in combination of 2 or more types.

Sulfonic acid group-containing monomers include styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxy Examples include naphthalenesulfonic acid, sodium vinylsulfonate, and the like.
Examples of phosphoric acid group-containing monomers include 2-hydroxyethyl acryloyl phosphate.
Examples of cyano group-containing monomers include acrylonitrile and methacrylonitrile.
Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl laurate, and the like.
Examples of aromatic vinyl compounds include styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene and other substituted styrenes.

Examples of carboxyl group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.
Acid anhydride group-containing monomers include maleic anhydride, itaconic anhydride, acid anhydrides of the above carboxyl group-containing monomers, and the like.
Amide group-containing monomers include acrylamide, methacrylamide, diethylacrylamide, N-vinylpyrrolidone, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, Examples include N,N'-methylenebisacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, diacetoneacrylamide and the like.
Examples of amino group-containing monomers include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate and the like.
Examples of imide group-containing monomers include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide and itaconimide.
Examples of epoxy group-containing monomers include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, and allyl glycidyl ether.
Examples of vinyl ethers include methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether and the like.

Such "other monomers" may be used singly or in combination of two or more. The content (total amount) of the above other monomers is preferably about 40% by weight or less (typically, 0.001 to 40% by weight) of the total amount of monomers used for synthesizing the acrylic polymer. More preferably, it is 30% by weight or less (typically 0.001 to 30% by weight). In addition, a monomer composition containing no other monomers (for example, using only C _1-14 alkyl (meth) acrylate as a monomer, or using only C _1-14 alkyl (meth) acrylate and hydroxyl group-containing (meth) acrylate) It may be an acrylic polymer.

The initiator used for polymerization is not particularly limited, and one or more of various polymerization initiators can be used. For example, an azo polymerization initiator can be preferably used. Specific examples of azo polymerization initiators include 2,2′-azobisisobutyronitrile, 2,2′-azobis(2-methylpropionamidine) disulfate, 2,2′-azobis(2-amidino propane) dihydrochloride, 2,2′-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2′-azobis(N,N′-dimethyleneisobutyramidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'- azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis (2, 4,4-trimethylpentane), dimethyl-2,2′-azobis(2-methylpropionate) and the like.

Other examples of polymerization initiators include persulfates such as potassium persulfate and ammonium persulfate; benzoyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxybenzoate, dicumyl Peroxides, such as peroxides, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, and hydrogen peroxide Initiators; substituted ethane-based initiators such as phenyl-substituted ethane; aromatic carbonyl compounds; Still other examples of polymerization initiators include redox initiators based on combinations of peroxides and reducing agents. Examples of such redox initiators include a combination of peroxide and ascorbic acid (such as a combination of aqueous hydrogen peroxide and ascorbic acid), a combination of peroxide and iron (II) salt (aqueous hydrogen peroxide, and an iron (II) salt), a combination of a persulfate and sodium hydrogen sulfite, and the like.

Such polymerization initiators can be used singly or in combination of two or more. The amount of the polymerization initiator to be used can be selected, for example, from the range of about 0.005 to 1 part by weight (typically 0.01 to 1 part by weight) per 100 parts by weight of all raw material monomers.

The method for obtaining the acrylic polymer having the monomer composition as described above is not particularly limited, and the polymer is obtained by applying various polymerization methods such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization. be able to. Alternatively, photopolymerization performed by irradiating light such as UV (typically performed in the presence of a photopolymerization initiator), or radiation polymerization performed by irradiating radiation such as β rays and γ rays Active energy ray irradiation polymerization may be employed. Moreover, the acrylic polymer may be a random copolymer, a block copolymer, a graft copolymer, or the like. A random copolymer is preferred from the viewpoint of productivity and the like.

In some preferred embodiments, a solution polymerization method can be preferably employed as a technique for synthesizing the base polymer (typically an acrylic polymer). An embodiment employing a solution polymerization method can be advantageous from the viewpoint of the transparency and adhesion performance of the surface protection film. As a method of supplying the monomers when carrying out solution polymerization, it is possible to appropriately adopt a batch charging method in which all the monomer raw materials are supplied at once, a continuous supply (dropping) method, a divided supply (dropping) method, or the like. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and may be, for example, about 20° C. to 170° C. (typically 40° C. to 140° C.). can.

The solvent (polymerization solvent) used for solution polymerization is not particularly limited, and examples include aromatic compounds (typically aromatic hydrocarbons) such as toluene and xylene; acetic esters such as ethyl acetate; hexane and cyclohexane. , aliphatic or alicyclic hydrocarbons such as methylcyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); Any one solvent selected from ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; and the like, or a mixed solvent of two or more can be used. It is preferable to use an organic solvent (which may be a mixed solvent) having a boiling point in the range of 20 to 200° C. (more preferably 25 to 150° C.) at a total pressure of 1 atm.

According to solution polymerization, a polymerization reaction liquid in which a base polymer (typically an acrylic polymer) is dissolved in an organic solvent is obtained. As the base polymer, it is possible to preferably use the above polymerization reaction solution or a product obtained by subjecting the reaction solution to an appropriate post-treatment. Typically, the base polymer-containing solution after post-treatment is adjusted to an appropriate viscosity (concentration) before use. Alternatively, a base polymer is synthesized using a polymerization method other than the solution polymerization method (e.g., emulsion polymerization, photopolymerization, bulk polymerization, etc.), and the polymer is dissolved in an organic solvent to prepare a solution. may

The acrylic polymer suitably has an Mw of 10×10 ⁴ or more in terms of standard polystyrene obtained by GPC, preferably 20×10 ⁴ or more, more preferably 30×10 4 from the viewpoint of cohesiveness and the like. ⁴ or more (for example, 40×10 ⁴ or more). The Mw is preferably 500×10 ⁴ or less, more preferably 400×10 ⁴ or less, still more preferably 300×10 ⁴ or less, and 200×10 ⁴ or less (for example, 100×10 ⁴ or less). may be

Specifically, the Mw of the acrylic polymer can be obtained by measuring under the following conditions using a GPC measuring device, trade name "HLC-8220GPC" (manufactured by Tosoh Corporation).
[Measurement conditions of GPC]
Sample concentration: 0.2% by weight (tetrahydrofuran solution)
Sample injection volume: 10 μL
Eluent: Tetrahydrofuran (THF)
Flow rate (flow rate): 0.6 mL/min Column temperature (measurement temperature): 40°C
column:
Sample column: 1 product name “TSKguardcolumn SuperHZ-H” + 2 product name “TSKgel SuperHZM-H” (manufactured by Tosoh Corporation)
Reference column: Product name "TSKgel SuperH-RC" 1 column (manufactured by Tosoh Corporation)
Detector: differential refractometer (RI)
Standard sample: polystyrene

By setting the Mw of the acrylic polymer to a predetermined value or more, the cohesive force of the pressure-sensitive adhesive is improved, and it is easy to prevent the occurrence of adhesive residue on the surface of the adherend. By setting the Mw to a predetermined value or less, the pressure-sensitive adhesive tends to have appropriate fluidity and wettability (adhesion) to the adherend is likely to be obtained. By having good wettability, the surface protective film attached to the adherend is not peeled off from the adherend during use, and can fulfill its protective function. It is particularly significant that the Mw of the acrylic polymer obtained by the solution polymerization method is within the preferred range described above.

(Antistatic component of adhesive layer)
The surface protective film disclosed herein can be preferably implemented in a mode in which the pressure-sensitive adhesive layer contains an antistatic component. Examples of the antistatic component include the materials described above as the antistatic component that can be contained in the topcoat layer, as well as ionic liquids and alkali metal salts. These antistatic components may be used singly or in combination of two or more. In some preferred embodiments, the antistatic component contained in the pressure-sensitive adhesive layer contains at least one of an ionic liquid and an alkali metal salt. The term “ionic liquid” (sometimes referred to as room temperature molten salt) refers to a molten salt that exhibits a liquid state at any temperature of 100° C. or lower. Since the ionic liquid is liquid at any temperature of 100° C. or lower, it can be easily added to the pressure-sensitive adhesive and dispersed or dissolved in that temperature range, compared to a solid salt. Furthermore, since the ionic liquid has no vapor pressure (non-volatile), it does not disappear over time, and has the characteristic that antistatic properties can be continuously obtained.

(ionic liquid)
As the ionic liquid, one or more of nitrogen-containing onium salts, sulfur-containing onium salts and phosphorus-containing onium salts can be preferably used. In some preferred embodiments, the pressure-sensitive adhesive layer contains an ionic liquid having at least one organic cationic component represented by any one of the following general formulas (A) to (E). With such an ionic liquid, a surface protective film having particularly excellent antistatic performance can be realized.

Here, in formula (A) above, R _a represents a hydrocarbon group having 4 to 20 carbon atoms or a functional group containing a heteroatom. R _b and R _c may be the same or different and each represents a hydrogen atom, a hydrocarbon group having 1 to 16 carbon atoms, or a functional group containing a heteroatom. However, when the nitrogen atom contains a double bond, there is no _Rc .
In formula (B) above, R _d represents a hydrocarbon group having 2 to 20 carbon atoms or a functional group containing a hetero atom. R _e , R _f and R _g may be the same or different and each represents a hydrogen atom, a hydrocarbon group having 1 to 16 carbon atoms, or a functional group containing a heteroatom.
In formula (C) above, R _h represents a hydrocarbon group having 2 to 20 carbon atoms or a functional group containing a hetero atom. R _i , R _j and R _k may be the same or different and each represents a hydrogen atom, a hydrocarbon group having 1 to 16 carbon atoms, or a functional group containing a heteroatom.
In formula (D) above, Z represents a nitrogen atom, a sulfur atom, or a phosphorus atom. R _l , R _m , R _n and R _o may be the same or different and each represents a hydrocarbon group having 1 to 20 carbon atoms or a functional group containing a heteroatom. However, when Z is a sulfur atom, there is no _Ro .
In formula (E) above, R _p represents a hydrocarbon group having 1 to 18 carbon atoms or a functional group containing a hetero atom.

Examples of cations represented by formula (A) include pyridinium cations, pyrrolidinium cations, piperidinium cations, cations having a pyrroline skeleton, cations having a pyrrole skeleton, and the like.

Specific examples of pyridinium cations include 1-methylpyridinium, 1-ethylpyridinium, 1-propylpyridinium, 1-butylpyridinium, 1-pentylpyridinium, 1-hexylpyridinium, 1-heptylpyridinium, 1-octylpyridinium, 1 -nonylpyridinium, 1-decylpyridinium, 1-allylpyridinium, 1-propyl-2-methylpyridinium, 1-butyl-2-methylpyridinium, 1-pentyl-2-methylpyridinium, 1-hexyl-2-methylpyridinium, 1-heptyl-2-methylpyridinium, 1-octyl-2-methylpyridinium, 1-nonyl-2-methylpyridinium, 1-decyl-2-methylpyridinium, 1-propyl-3-methylpyridinium, 1-butyl-3 -methylpyridinium, 1-butyl-4-methylpyridinium, 1-pentyl-3-methylpyridinium, 1-hexyl-3-methylpyridinium, 1-heptyl-3-methylpyridinium, 1-octyl-3-methylpyridinium, 1-octyl-4-methylpyridinium, 1-nonyl-3-methylpyridinium, 1-decyl-3-methylpyridinium, 1-propyl-4-methylpyridinium, 1-pentyl-4-methylpyridinium, 1-hexyl-4 -methylpyridinium, 1-heptyl-4-methylpyridinium, 1-nonyl-4-methylpyridinium, 1-decyl-4-methylpyridinium, 1-butyl-3,4-dimethylpyridinium and the like.

Specific examples of pyrrolidinium cations include 1,1-dimethylpyrrolidinium, 1-ethyl-1-methylpyrrolidinium, 1-methyl-1-propylpyrrolidinium, 1-methyl-1-butylpyrrolidinium. nium, 1-methyl-1-pentylpyrrolidinium, 1-methyl-1-hexylpyrrolidinium, 1-methyl-1-heptylpyrrolidinium, 1-methyl-1-octylpyrrolidinium, 1-methyl- 1-nonylpyrrolidinium, 1-methyl-1-decylpyrrolidinium, 1-methyl-1-methoxyethoxyethylpyrrolidinium, 1-ethyl-1-propylpyrrolidinium, 1-ethyl-1-butylpyrrolidinium dinium, 1-ethyl-1-pentylpyrrolidinium, 1-ethyl-1-hexylpyrrolidinium, 1-ethyl-1-heptylpyrrolidinium, 1,1-dipropylpyrrolidinium, 1-propyl- 1-butylpyrrolidinium, 1,1-dibutylpyrrolidinium, pyrrolidinium-2-one and the like.

Specific examples of piperidinium cations include 1-propylpiperidinium, 1-pentylpiperidinium, 1,1-dimethylpiperidinium, 1-methyl-1-ethylpiperidinium, 1-methyl-1- propylpiperidinium, 1-methyl-1-butylpiperidinium, 1-methyl-1-pentylpiperidinium, 1-methyl-1-hexylpiperidinium, 1-methyl-1-heptylpiperidinium, 1 -methyl-1-octylpiperidinium, 1-methyl-1-decylpiperidinium, 1-methyl-1-methoxyethoxyethylpiperidinium, 1-ethyl-1-propylpiperidinium, 1-ethyl-1 -butylpiperidinium, 1-ethyl-1-pentylpiperidinium, 1-ethyl-1-hexylpiperidinium, 1-ethyl-1-heptylpiperidinium, 1,1-dipropylpiperidinium, 1 -Propyl-1-butylpiperidinium, 1-propyl-1-pentylpiperidinium, 1-propyl-1-hexylpiperidinium, 1-propyl-1-heptylpiperidinium, 1,1-dibutylpiperidinium 1-butyl-1-pentylpiperidinium, 1-butyl-1-hexylpiperidinium, 1-butyl-1-heptylpiperidinium and the like.

Specific examples of cations having a pyrroline skeleton include 2-methyl-1-pyrroline. Specific examples of cations having a pyrrole skeleton include 1-ethyl-2-phenylindole, 1,2-dimethylindole, 1-ethylcarbazole and the like.

Examples of cations represented by formula (B) include imidazolium cations, tetrahydropyrimidinium cations, dihydropyrimidinium cations, and the like.

Specific examples of imidazolium cations include 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-methyl-3-ethylimidazolium, 1-methyl-3-hexylimidazolium, 1-ethyl-3 -methylimidazolium, 1-propyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-pentyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-heptyl- 3-methylimidazolium, 1-octyl-3-methylimidazolium, 1-nonyl-3-methylimidazolium, 1-decyl-3-methylimidazolium, 1-dodecyl-3-methylimidazolium, 1-tetradecyl- 3-methylimidazolium, 1-hexadecyl-3-methylimidazolium, 1-octadecyl-3-methylimidazolium, 1,2-dimethyl-3-propylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium, 1-hexyl-2,3-dimethylimidazolium, 1-(2-methoxyethyl)-3-methylimidazolium and the like.

Specific examples of tetrahydropyrimidinium cations include 1,3-dimethyl-1,4,5,6-tetrahydropyrimidinium and 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidinium. , 1,2,3,4-tetramethyl-1,4,5,6-tetrahydropyrimidinium, 1,2,3,5-tetramethyl-1,4,5,6-tetrahydropyrimidinium, etc. mentioned.

Specific examples of dihydropyrimidinium cations include 1,3-dimethyl-1,4-dihydropyrimidinium, 1,3-dimethyl-1,6-dihydropyrimidinium, 1,2,3-trimethyl-1 ,4-dihydropyrimidinium, 1,2,3-trimethyl-1,6-dihydropyrimidinium, 1,2,3,4-tetramethyl-1,4-dihydropyrimidinium, 1,2,3 ,4-tetramethyl-1,6-dihydropyrimidinium and the like.

A pyrazolium cation, a pyrazolinium cation, etc. are illustrated as a cation represented by Formula (C).

Specific examples of pyrazolium cations include 1-methylpyrazolium, 3-methylpyrazolium, 1-ethyl-2,3,5-trimethylpyrazolium, 1-propyl-2,3,5-trimethyl pyrazolium, 1-butyl-2,3,5-trimethylpyrazolium, 1-(2-methoxyethyl)pyrazolium and the like. Specific examples of pyrazolinium cations include 1-ethyl-2-methylpyrazolinium.

Examples of cations represented by formula (D) include cations in which R _l , R _m , R _n and R _o are the same or different and are all alkyl groups having 1 to 20 carbon atoms. Examples of such cations are tetraalkylammonium cations, trialkylsulfonium cations and tetraalkylphosphonium cations. Other examples of cations represented by formula (D) include those in which a portion of the above alkyl group is substituted with an alkenyl group, an alkoxy group, or an epoxy group. Also, one or more of R _l , R _m , R _n and R _o may contain an aromatic ring or an aliphatic ring.

The cation represented by formula (D) may be a symmetrical cation or an asymmetrical cation. Symmetrical ammonium cations include alkyl groups in which R _l , R _m , R _n and R _o are the same (e.g., methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, , nonyl group, decyl group, dodecyl group, hexadecyl group, or octadecyl group).

Representative examples of asymmetric ammonium cations include tetraalkylammonium cations in which three of R _l , R _m , R _n and R _o are the same and the remaining one is different, specific examples being trimethylethylammonium and trimethylpropylammonium. , trimethylbutylammonium, trimethylpentylammonium, trimethylhexylammonium, trimethylheptylammonium, trimethyloctylammonium, trimethylnonylammonium, trimethyldecylammonium, triethylmethylammonium, triethylpropylammonium, triethylbutylammonium, triethylpentylammonium, triethylhexylammonium, triethyl heptylammonium, triethyloctylammonium, triethylnonylammonium, triethyldecylammonium, tripropylmethylammonium, tripropylethylammonium, tripropylbutylammonium, tripropylpentylammonium, tripropylhexylammonium, tripropylheptylammonium, tripropyloctylammonium, Tripropylnonyl ammonium, tripropyldecylammonium, tributylmethylammonium, tributylethylammonium, tributylpropylammonium, tributylpentylammonium, tributylhexylammonium, tributylheptylammonium, tripentylmethylammonium, tripentylethylammonium, tripentylpropylammonium, tri Pentylbutylammonium, tripentylhexylammonium, tripentylheptylammonium, trihexylmethylammonium, trihexylethylammonium, trihexylpropylammonium, trihexylbutylammonium, trihexylpentylammonium, trihexylheptylammonium, triheptylmethylammonium, tri Heptylethylammonium, triheptylpropylammonium, triheptylbutylammonium, triheptylpentylammonium, triheptylhexylammonium, trioctylmethylammonium, trioctylethylammonium, trioctylpropylammonium, trioctylbutylammonium, trioctylpentylammonium, trio Non-symmetrical tetraalkylammonium cations such as cetylhexylammonium, trioctylheptylammonium, trioctyldodecylammonium, trioctylhexadecylammonium, trioctyloctadecylammonium, trinonylmethylammonium, tridecylmethylammonium and the like.

Other examples of asymmetric ammonium cations are dimethyldiethylammonium, dimethyldipropylammonium, dimethyldibutylammonium, dimethyldipentylammonium, dimethyldihexylammonium, dimethyldiheptylammonium, dimethyldioctylammonium, dimethyldinonylammonium, dimethyldidecylammonium, Dipropyldiethylammonium, dipropyldibutylammonium, dipropyldipentylammonium, dipropyldihexylammonium, dimethylethylpropylammonium, dimethylethylbutylammonium, dimethylethylpentylammonium, dimethylethylhexylammonium, dimethylethylheptylammonium, dimethylethylnonyl ammonium, dimethyl Propylbutylammonium, dimethylpropylpentylammonium, dimethylpropylhexylammonium, dimethylpropylheptylammonium, dimethylbutylhexylammonium, dimethylbutylheptylammonium, dimethylpentylhexylammonium, dimethylhexylheptylammonium, diethylmethylpropylammonium, diethylmethylpentylammonium, diethyl Methylheptylammonium, diethylpropylpentylammonium, dipropylmethylethylammonium, dipropylmethylpentylammonium, dipropylbutylhexylammonium, dibutylmethylpentylammonium, dibutylmethylhexylammonium, methylethylpropylbutylammonium, methylethylpropylpentylammonium, methyl Tetraalkylammonium cations such as ethylpropylhexylammonium; Ammonium cations containing cycloalkyl groups such as trimethylcyclohexylammonium; ammonium cations containing; , an ammonium cation containing an alkoxy group; an ammonium cation containing an epoxy group, such as glycidyltrimethylammonium;

The symmetrical sulfonium cation is a trialkylsulfonium cation in which R _l , R _m and R _n are the same alkyl group (eg, any one of a methyl group, an ethyl group, a propyl group, a butyl group and a hexyl group). exemplified. Asymmetric sulfonium cations include asymmetric trialkylsulfonium cations such as dimethyldecylsulfonium, diethylmethylsulfonium, dibutylethylsulfonium, and the like.

Symmetrical phosphonium cations include alkyl groups in which R _l , R _m , R _n and R _o are the same (e.g., methyl group, ethyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, , a decyl group) are exemplified. Asymmetric phosphonium cations include tetraalkylphosphonium cations in which three of R _l , R _m , R _n and R _o are the same and the remaining one is different. Heptylphosphonium, trimethyloctylphosphonium, trimethylnonylphosphonium, trimethyldecylphosphonium, triethylmethylphosphonium, tributylethylphosphonium, tributyl-(2-methoxyethyl)phosphonium, tripentylmethylphosphonium, trihexylmethylphosphonium, triheptylmethylphosphonium, trioctyl methylphosphonium, trinonylmethylphosphonium, tridecylmethylphosphonium and the like. Other examples of asymmetric phosphonium cations include asymmetric tetraalkylphosphonium cations such as trihexyltetradecylphosphonium, dimethyldipentylphosphonium, dimethyldihexylphosphonium, dimethyldiheptylphosphonium, dimethyldioctylphosphonium, dimethyldinonylphosphonium, dimethyldidecylphosphonium, etc. sulfonium cations containing alkoxy groups, such as trimethyl(methoxyethoxyethyl)phosphonium and dimethylethyl(methoxyethoxyethyl)phosphonium;

Preferred examples of the cation represented by formula (D) include the above-described asymmetric tetraalkylammonium cations, asymmetric trialkylsulfonium cations, and asymmetric tetraalkylphosphonium cations.

Examples of cations represented by formula (E) include sulfonium cations in which R _p is an alkyl group having 1 to 18 carbon atoms. Specific examples of R _p include methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, nonyl group, decyl group, dodecyl group, tridecyl group, tetradecyl group, octadecyl group, and the like.

The anion component of the ionic liquid is not particularly limited as long as a salt with any of the cations disclosed herein can form an ionic liquid. Specific examples include Cl ⁻ , Br ⁻ , I ⁻ , AlCl ₄ ⁻ , Al ₂ Cl ₇ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , NO ₃ ⁻ , CH ₃ COO ⁻ , CF ₃ COO ⁻ , CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , (FSO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , NbF ₆ ⁻ , TaF ₆ ⁻ , F(HF) _n ⁻ , (CN) ₂ N ⁻ , C ₄ F ₉ SO ₃ ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , C ₃ F ₇ COO ⁻ , (CF ₃ SO ₂ )(CF ₃ CO)N ⁻ , C ₉ H ₁₉ COO ⁻ , (CH ₃ ) ₂ PO ₄ ⁻ , (C ₂ H ₅ ) ₂ PO ₄ ⁻ , C ₂ H ₅ OSO ₃ ⁻ , C ₆ H ₁₃ OSO ₃ ⁻ , C ₈ H ₁₇ OSO ₃ ⁻ , CH ₃ (OC ₂ H ₄ ) ₂ OSO ₃ ⁻ , C ₆ H ₄ (CH ₃ )SO ₃ ⁻ , (C ₂ F ₅ ) ₃ PF ₃ ⁻ , CH ₃ Examples include CH(OH)COO ⁻ and anions represented by the following formula (F).

Among them, the hydrophobic anionic component tends not to bleed to the pressure-sensitive adhesive surface, and is preferably used from the viewpoint of low staining. In addition, an anionic component containing a fluorine atom (for example, an anionic component containing a perfluoroalkyl group) is preferably used since an ionic compound with a low melting point can be obtained. Preferred examples of such anion components include bis(perfluoroalkylsulfonyl)imide anions (eg, (FSO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ ). and fluorine-containing anions such as perfluoroalkylsulfonium anions (eg, CF ₃ SO ₃ ⁻ ). The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 3, more preferably 1 or 2.

The ionic liquid used in the technology disclosed herein can be an appropriate combination of the cationic component and the anionic component. As an example, when the cationic component is a pyridinium cation, specific combinations with the above-described anionic components include 1-butylpyridinium tetrafluoroborate, 1-butylpyridinium hexafluorophosphate, 1-butyl-3-methylpyridinium tetra fluoroborate, 1-butyl-3-methylpyridinium trifluoromethanesulfonate, 1-butyl-3-methylpyridinium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylpyridinium bis(pentafluoroethanesulfonyl)imide, 1- hexylpyridinium tetrafluoroborate, 1-allylpyridinium bis(trifluoromethanesulfonyl)imide, and the like. Similarly, for each of the other cations described above, ionic liquids in combination with any of the anion components disclosed herein can be used.

Such an ionic liquid can be commercially available or can be easily synthesized by a known method. The method for synthesizing the ionic liquid is not particularly limited as long as the desired ionic liquid can be obtained. In general, the halide method, hydroxide method, acid ester method, complex formation method, as described in the well-known document "Ionic liquids - the front line of development and the future -" (published by CMC Publishing) , and neutralization methods, etc. are used.

The appropriate amount of the ionic liquid to be blended is 0.01 to 5 parts by weight per 100 parts by weight of the base polymer (typically an acrylic polymer). , preferably 0.03 to 3 parts by weight, more preferably 0.05 to 2.5 parts by weight, still more preferably 0.1 to 2 parts by weight.

(alkali metal salt)
Typical examples of alkali metal salts used as antistatic components in pressure-sensitive adhesive layers include lithium salts, sodium salts and potassium salts. For example, Li ⁺ , Na ⁺ or K ⁺ as cationic components and Cl ⁻ , Br ⁻ , I ⁻ , BF ₄ − , PF ₆ ⁻ , SCN ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , as anionic components. Metal salts consisting of (FSO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₂ N ^- , (C ₂ F ₅ SO ₂ ) ₂ N ^- or (CF ₃ SO ₂ ) ₃ C ^- can be used. The use of lithium salts is preferred due to their high dissociation. Preferred specific _examples include LiBr, LiI, _LiBF4 , _LiPF6 , LiSCN _{, LiClO4} , _LiCF3SO3 , Li( _{CF3SO2 ) 2N} , Li( _{C2F5SO2 ) 2N} , Li( Lithium salts such as CF ₃ SO ₂ ) ₃ C are included. Above all, lithium salts (e.g., Li(FSO ₂ ) ₂ N ⁻ , Li(CF ₃ SO ₂ ), in which the anion component is a fluorine-containing anion such as bis(perfluoroalkylsulfonyl)imide anion, perfluoroalkylsulfonium anion, etc.) _2N , Li( _C2F5SO2 ) _{2N , LiCF3SO3} ) _{are preferred} . Such alkali metal salts may be used singly or in combination of two or more.

The appropriate amount of the alkali metal salt (eg, lithium salt) is 0.01 to 5 parts by weight per 100 parts by weight of the base polymer (typically an acrylic polymer). Considering the above, it is preferably 0.03 to 3 parts by weight, more preferably 0.05 to 2.5 parts by weight, and still more preferably 0.1 to 2 parts by weight.

(Adhesive composition)
In the technology disclosed herein, the form of the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer is not particularly limited. For example, an adhesive composition containing an adhesive component in an organic solvent (solvent-type adhesive composition), an adhesive composition in which an adhesive component is dispersed in an aqueous solvent (water-dispersed adhesive composition, typically water-based emulsion-type adhesive composition), adhesive composition in which the adhesive component is dissolved in water (aqueous solution-type adhesive composition), solvent-free adhesive composition (e.g., ultraviolet rays, electron beams, etc.) It may be a type of pressure-sensitive adhesive composition that is cured by irradiation with active energy rays, a hot-melt type pressure-sensitive adhesive composition), or the like. The technique disclosed herein can be preferably implemented in a mode provided with an adhesive layer formed from a solvent-type adhesive composition. The organic solvent contained in the solvent-based pressure-sensitive adhesive composition may be, for example, a single solvent consisting of any one of toluene, xylene, ethyl acetate, hexane, cyclohexane, methylcyclohexane, heptane and isopropyl alcohol. It may be a mixed solvent containing as a main component. In some other preferred embodiments, the surface protective film comprises a pressure-sensitive adhesive layer formed from a water-dispersible pressure-sensitive adhesive composition.

In the technique disclosed herein, the adhesive composition (preferably a solvent-based or water-dispersed adhesive composition) used for forming the adhesive layer includes a base polymer contained in the composition (typically (acrylic polymer) can be suitably crosslinked. As a specific cross-linking means, a cross-linking base point is introduced into a base polymer (typically an acrylic polymer) by copolymerizing a monomer having an appropriate functional group (hydroxyl group, carboxyl group, etc.). A method of adding a compound (crosslinking agent) capable of reacting with a group to form a crosslinked structure to a base polymer (typically an acrylic polymer) and allowing the reaction to occur can be preferably employed. The cross-linking agent is not particularly limited, and for example, isocyanate compounds, epoxy compounds, melamine-based resins, aziridine compounds and the like can be used. Such cross-linking agents may be used singly or in combination of two or more.

As the cross-linking agent, an isocyanate compound is particularly preferably used because it facilitates adjustment of the peeling force from the adherend to an appropriate range. Examples of such isocyanate compounds include: aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate; More specifically: lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; 2,4-tolylene diisocyanate, 4 , 4'-diphenylmethane diisocyanate, xylylene diisocyanate and other aromatic diisocyanates; trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate L"), trimethylolpropane/hexamethylene diisocyanate 3 Isocyanate adducts such as a mer adduct (manufactured by Tosoh Corporation, trade name "Coronate HL") and an isocyanurate form of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX"); Such an isocyanate compound may be used individually by 1 type, and may be used in combination of 2 or more type.

Epoxy compounds used as cross-linking agents include N,N,N',N'-tetraglycidyl-m-xylenediamine (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "TETRAD-X"), 1,3-bis (N,N-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company, trade name “TETRAD-C”) and the like are exemplified. Examples of melamine-based resins include hexamethylolmelamine. As the aziridine derivative, commercially available products such as "HDU", "TAZM" and "TAZO" manufactured by Sogo Yakuko Co., Ltd. can be mentioned.

The amount of the cross-linking agent to be used can be appropriately selected according to the composition and structure (molecular weight, etc.) of the base polymer (typically an acrylic polymer), the mode of use of the surface protective film, and the like. It is appropriate to use about 0.01 to 15 parts by weight of the cross-linking agent with respect to 100 parts by weight of the base polymer (typically an acrylic polymer), and about 0.1 to 10 parts by weight (for example, about 0.1 part by weight). 2 to 5 parts by weight). By adjusting the amount of the cross-linking agent to be used in an appropriate range, it is possible to increase the cohesive strength of the pressure-sensitive adhesive and prevent the occurrence of adhesive residue on the adherend. There is a tendency for good wettability and, in turn, adhesion to the In the technique disclosed herein, the amount of the cross-linking agent used is preferably more than 1 part by weight, more preferably 1.5 parts by weight, based on 100 parts by weight of the base polymer, in consideration of the releasability from the adherend. Part by weight or more, more preferably 2 parts by weight or more (for example, 2.5 parts by weight or more).

The pressure-sensitive adhesive composition may further contain a cross-linking catalyst (also referred to as a cross-linking accelerator). The type of cross-linking catalyst can be appropriately selected according to the type of cross-linking agent used. In this specification, the cross-linking catalyst refers to a catalyst that increases the speed of the cross-linking reaction by the cross-linking agent. Such cross-linking accelerators include, for example, tin (Sn)-containing compounds such as dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diacetylacetonate, tetra-n-butyltin, and trimethyltin hydroxide; Organometallic compounds such as titanium-containing compounds such as isopropyl titanate and tetra-n-butyl titanate; Nitrogen (N)-containing compounds such as amines such as N,N,N',N'-tetramethylhexanediamine and triethylamine, and imidazoles Compound; basic compounds such as lithium hydroxide, potassium hydroxide, sodium methylate; and the like. These can be used individually by 1 type or in combination of 2 or more types. Among them, Sn-containing compounds are preferred. The amount of the crosslinking catalyst contained in the adhesive composition is, for example, about 0.001 to 10 parts by weight (preferably 0.005 to 5 parts by weight) relative to 100 parts by weight of the base polymer (typically an acrylic polymer). part).

In addition, the adhesive composition disclosed herein may contain a cross-linking retarder depending on the purpose. The crosslinking retarder is not particularly limited, and examples thereof include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate; acetylacetone, 2,4-hexanedione, β-diketones such as benzoylacetone; A crosslinking retarder can be used individually by 1 type or in combination of 2 or more types. Acetylacetone may be used as a preferred example. The content (amount used) of the cross-linking retarder is not particularly limited, and from the viewpoint of ensuring the pot life of the adhesive, it is approximately 0.1 to 10 parts by weight (for example, approximately 0.1 ~5 parts by weight).

Also, the technology disclosed herein can be implemented in a mode in which the pressure-sensitive adhesive layer contains a release modifier. By including a release modifier (typically, an adhesive strength reducing agent) in the adhesive layer, it is easy to obtain an adhesive with well-balanced adhesion to the adherend and releasability. The release modifier is not particularly limited, and one or more of known materials that can be used as release modifiers in the field of pressure-sensitive adhesives can be used without particular limitation. When the technique disclosed herein is carried out in a mode comprising a pressure-sensitive adhesive layer formed from a solvent-based pressure-sensitive adhesive composition, the solvent-based pressure-sensitive adhesive composition contains an anionic surfactant, a nonionic surfactants such as cationic surfactants and cationic surfactants. Of these, anionic surfactants and nonionic surfactants are preferred. The release modifiers can be used singly or in combination of two or more.

Examples of anionic surfactants used as release modifiers include alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate; alkylsulfates such as sodium laurylsulfate and ammonium laurylsulfate; (poly)oxyethylene laurylamine, (poly) (Poly)ether amines such as oxyethylene stearylamine; sodium (poly) oxyethylene alkyl ether sulfate, ammonium (poly) oxyethylene alkyl phenyl ether sulfate, (poly) oxyethylene alkyl alkenyl phenyl ether ammonium sulfate, (poly) oxyethylene alkylphenyl (Poly)ether sulfate such as sodium ether sulfate; sodium (poly)oxyethylene alkyl sulfosuccinate, (poly)oxyethylene alkyl ether phosphate, and the like.
Examples of nonionic surfactants used as release modifiers include (poly)oxyethylene alkyl ethers, (poly)oxyethylene alkylphenyl ethers, (poly)oxyethylene fatty acid esters, polyoxyethylene polyoxypropylene block polymers, and the like. mentioned.

The release modifier is used in an appropriate amount capable of exhibiting a release control effect, and its content is not limited to a specific range. For example, the content of the release modifier with respect to 100 parts by weight of the base polymer (typically an acrylic polymer) is appropriately about 0.01 parts by weight or more (for example, about 0.05 parts by weight or more), preferably about 0.05 parts by weight or more. It is 0.1 part by weight or more. From the viewpoint of maintaining adhesion to the adherend, the content of the release modifier should be approximately 15 parts by weight or less per 100 parts by weight of the base polymer (typically an acrylic polymer). Yes, preferably about 10 parts by weight or less (eg, about 5 parts by weight or less, typically about 1 part by weight or less).

Various conventionally known additives can be further blended into the pressure-sensitive adhesive composition, if necessary. Examples of such additives include surface lubricants, leveling agents, plasticizers, softeners, fillers, antioxidants, preservatives, light stabilizers, ultraviolet absorbers, polymerization inhibitors, silane coupling agents, and the like. be done. In addition, a known or commonly used tackifying resin may be blended in a pressure-sensitive adhesive composition having an acrylic polymer as a base polymer. Furthermore, the pressure-sensitive adhesive layer disclosed herein may or may not contain an alkylene oxide compound such as polypropylene glycol for the purpose of adjusting removability and hygroscopicity. Furthermore, when synthesizing the adhesive polymer by emulsion polymerization, an emulsifier or a chain transfer agent (which can also be understood as a molecular weight modifier or polymerization degree modifier) is preferably used. The content of these optional additives can be appropriately determined according to the purpose of use. The amount of the optional additive used is approximately 5 parts by weight or less, and is suitably approximately 3 parts by weight or less (for example, approximately 1 part by weight or less) with respect to 100 parts by weight of the base polymer.

(Method for Forming Adhesive Layer)
The pressure-sensitive adhesive layer in the technique disclosed herein can be formed, for example, by a method of directly applying the pressure-sensitive adhesive composition as described above to the second surface of the film substrate and drying or curing (direct method). . Alternatively, the pressure-sensitive adhesive composition is applied to the surface (release surface) of a release liner and dried or cured to form a pressure-sensitive adhesive layer on the surface. It may be formed by a method of transferring an adhesive layer (transfer method). From the viewpoint of the anchoring property of the pressure-sensitive adhesive layer, the direct method can be preferably employed. Various methods such as roll coating, gravure coating, reverse coating, roll brushing, spray coating, air knife coating, and coating using a die coater can be used to apply (typically apply) the pressure-sensitive adhesive composition. can be adopted as appropriate. Drying of the pressure-sensitive adhesive composition can be performed under heating (for example, by heating to about 60° C. to 150° C.), if necessary. Ultraviolet rays, laser rays, α rays, β rays, γ rays, X rays, electron beams, and the like can be appropriately employed as means for curing the pressure-sensitive adhesive composition.

(Thickness of adhesive layer)
Although not particularly limited, the thickness of the pressure-sensitive adhesive layer can be, for example, approximately 0.1 μm or more, suitably approximately 1 μm or more, and preferably approximately 3 μm or more (for example, approximately 5 μm or more). From the viewpoint of adhesion to an object to be protected, etc., the thickness is preferably about 10 μm or more, more preferably about 14 μm or more, and even more preferably about 17 μm or more. The thickness can be, for example, approximately 100 μm or less, suitably approximately 50 μm or less (eg, approximately 30 μm or less), and preferably approximately 20 μm or less (eg, approximately 18 μm or less).

<Release liner>
The surface protective film disclosed herein comprises, if necessary, a release liner attached to the adhesive surface for the purpose of protecting the adhesive surface (the surface of the adhesive layer that is attached to the adherend). It can be provided in the form of a surface protective film with a release liner. As the substrate constituting the release liner, paper, synthetic resin film, etc. can be used, and synthetic resin film is preferably used because of its excellent surface smoothness. For example, various resin films (for example, polyester film) can be preferably used as the substrate of the release liner. The thickness of the release liner can be, for example, about 5 μm to 200 μm, preferably about 10 μm to 100 μm. The surface of the release liner to be bonded to the pressure-sensitive adhesive layer is treated with a release agent (e.g., silicone, fluorine, long-chain alkyl, fatty acid amide, etc.), silica powder, or the like for release or antifouling treatment. may be applied.

<Application>
The protection target of the surface protection film disclosed herein is not particularly limited. It can be used as a protective film for various products, parts and the like. For example, the surface protective film is particularly suitable as a surface protective film for protecting the surface of optical parts (for example, optical parts used as liquid crystal display panel components such as polarizing plates and wavelength plates) during processing and transportation. is. More specifically, the surface protective film is used as a constituent element of liquid crystal display panels, plasma display panels (PDP), organic electroluminescence (EL) displays, etc., during the production of optical members, during transportation, etc., when the optical parts ( It is also called an optical member.). In particular, surfaces applied to optical parts such as polarizing plates (polarizing films, e.g., reflective polarizing films) for liquid crystal display panels, wavelength plates, retardation plates, optical compensation films, brightness enhancement films, light diffusion sheets, reflection sheets, etc. Useful as a protective film.

After the protection period ends, the surface protection film can be peeled off from the optical component by attaching a pick-up tape to the back surface of the protection film and using the adhesive force of the adhesive tape. A preferred mode of use of the surface protective film in the technology disclosed herein is that after using the surface protective film (after the protection period ends), the surface protective film is peeled off and removed by the pickup tape in an automatic peeling device to which a pickup tape is attached. It encompasses the aspects to be described. According to the automatic peeling device, the surface protective film peeled from the adherend can be collected in a state of being attached to the pick-up tape through a series of processes. In such a mode of use, the surface protection film disclosed herein can be reliably peeled off from the adherend in a short time after pressure bonding with the pickup tape, regardless of the type of pickup tape such as rubber-based or acrylic-based.

<Optical parts>
The technique disclosed here includes provision of a novel optical component with a surface protective film. The optical component with a surface protective film includes an optical component and a surface protective film that protects the optical component. The surface protective film has, in this order, a pressure-sensitive adhesive layer to be attached to the optical component, a base layer, and a topcoat layer forming the back surface of the surface protective film. Since the surface protective film and the optical parts are as described above, redundant description is omitted. An example of the configuration of the optical component with the surface protection film is as shown in FIG. 2, so the description is omitted.

One of the features of the optical component with a surface protective film disclosed herein is the state of adhesion (specifically, releasability) between the surface protective film and the optical component. Specifically, the surface protective film attached to the optical component has a peel strength D [N/19 mm when peeled from the optical component under the conditions of 23° C., a peeling angle of 90 degrees, and a tensile speed of 0.3 m/min. ] satisfies the condition: A [N/19 mm]>D [N/19 mm]; Here, A [N/19 mm] is the 180-degree peel strength of a standard acrylic pressure-sensitive adhesive tape against the back surface of a surface protection film measured under the conditions of 23°C, 1 minute after application, and a tensile speed of 0.3 m/min (standard acrylic Peeling strength on the back surface of the adhesive tape) [N/19 mm]. By satisfying the above condition (A>D), when peeling the surface protective film from the optical component using the pickup tape, even when using the acrylic pickup tape, the surface protective film is pressure-bonded to the pickup tape. is picked up in a short period of time and peeled off from the optical component.

In some preferred embodiments, the surface protection film has a trigger peel strength of less than 3.5 N/19 mm (peel It is attached to the optical component with a strength D). The lower the peel strength D, the higher the certainty of preventing poor peeling. It is less than 5N/19mm. In a particularly preferred embodiment, the peel strength D may be less than 1.2 N/19 mm, less than 0.8 N/19 mm, or less than 0.5 N/19 mm. The lower limit of the peel strength D is not particularly limited, and may be about 0.1 N/19 mm or more, or about 0.2 N/19 mm or more (for example, about 0.3 N/19 mm or more). The method for measuring the peel strength D is the same as the peel strength against PET in the examples described later, except that an optical component to which a surface protective film is already attached is used instead of the PET film as the adherend. can be measured in In the measurement of the peel strength D, the time from pressing (sticking) the surface protective film to the optical component to peeling is not particularly limited.

Also, from the viewpoint of pick-up peelability, it is suitable that the back surface peel strength A of the standard acrylic pressure-sensitive adhesive tape is 3.5 N/19 mm or more, and the preferred range is as described above. description is omitted.

Several examples related to the present invention are described below, but are not intended to limit the present invention to those shown in the examples. "Parts" and "%" in the following description are by weight unless otherwise specified.

<Evaluation method>
[Back Peel Strength A of Standard Acrylic Adhesive Tape]
The surface protective film is cut into a size of 70 mm in width and 100 mm in length, and the adhesive layer side surface (adhesive surface) is an acrylic plate (manufactured by Mitsubishi Rayon Co., Ltd., trade name “Acrylite”, thickness 2 mm, width 70 mm, length 100 mm) double-sided adhesive tape (trade name "No. 500" manufactured by Nitto Denko Corporation, double-sided adhesive tape with a thickness of 0.17 mm having an acrylic adhesive on both sides of the non-woven fabric substrate 180 degree peel strength: about 12.5 N /20 mm) to prepare a test piece. As a standard acrylic adhesive tape, an acrylic adhesive tape manufactured by Nitto Denko (trade name “No. It is pressed onto the topcoat layer of the surface protective film at a pressure of 0.25 MPa and a speed of 0.3 m/min. After leaving this in the same environment for 1 minute, using a universal tensile tester, under the same environment, a standard acrylic adhesive tape was applied under the conditions of a tensile speed of 0.3 m / min and a peeling angle of 180 degrees. The peel strength measured at this time is taken as the back peel strength A [N/19 mm] of the standard acrylic pressure-sensitive adhesive tape.
"No. 31B" manufactured by Nitto Denko Co., Ltd. is an acrylic single-sided adhesive tape with a polyester film base. 19 mm. The 180-degree peel strength is measured by using a stainless steel plate (SUS304) as an adherend based on JIS Z 0237: 2009, and pressing a 2 kg roller back and forth once under a measurement environment of 23 ° C. to the adherend. It is the peel strength when peeled in the direction of 180 degrees under the condition of a tensile speed of 300 mm/min after 30 minutes. The 180-degree peel strength of "No. 500", "CT-24" manufactured by Nichiban Co., Ltd., and "NO. 315" manufactured by Nitto Denko Co., Ltd., which will be described later, are also measured in the same manner as described above.
The back surface peel strength A [N/19 mm] was measured in the same manner as above except that standard acrylic adhesive tapes with different widths were used, and the obtained measured value was converted to 19 mm width. may In addition, the double-sided adhesive tape used for fixing the surface protective film and the acrylic plate is not limited to "No. 500", and in the measurement of the back peel strength A of the standard acrylic adhesive tape, Various known double-sided adhesive pressure-sensitive adhesive tapes capable of holding a fixing function can be used without particular limitation.

[Back Peel Strength C of Standard Rubber Adhesive Tape]
The surface protective film is cut into a size of 70 mm in width and 100 mm in length, and the adhesive layer side surface (adhesive surface) is an acrylic plate (manufactured by Mitsubishi Rayon Co., Ltd., trade name “Acrylite”, thickness 2 mm, width 70 mm, length 100 mm) double-sided adhesive tape (trade name "No. 500" manufactured by Nitto Denko Corporation, double-sided adhesive tape with a thickness of 0.17 mm having an acrylic adhesive on both sides of the non-woven fabric substrate 180 degree peel strength: about 12.5 N /20 mm) to prepare a test piece. As a standard rubber adhesive tape, Nichiban's rubber adhesive tape (trade name "CT-24", 24 mm width) was prepared, and the standard rubber adhesive tape was applied to the surface in an environment of 23 ° C. × 50% RH. It is pressed onto the topcoat layer of the protective film at a pressure of 0.25 MPa and a speed of 0.3 m/min. After leaving it in the same environment for 1 minute, using a universal tensile tester, a standard rubber adhesive tape was applied to the back of the surface protective film under the same environment at a tensile speed of 0.3 m / min and a peeling angle of 180 degrees. (top coat layer side surface), and the back peel strength [N/24 mm] at this time is measured. By converting the obtained value to a width of 19 mm, the back peel strength C [N/19 mm] of the standard rubber adhesive tape is obtained.
"CT-24" manufactured by Nichiban Co., Ltd. is a rubber-based single-sided pressure-sensitive adhesive tape with a cellophane base material. be.
The back peel strength C [N / 19 mm] may be measured using a standard rubber adhesive tape with a width of 19 mm, and the obtained value may be used as it is as the back peel strength [N / 19 mm]. Aside from using standard rubber-based pressure-sensitive adhesive tapes having different widths as described above, the same measurement as above may be carried out, and the obtained measured value may be converted to a width of 19 mm to adopt a value. In addition, the double-sided adhesive tape used for fixing the surface protective film and the acrylic plate is not limited to "No. 500". Various known double-sided adhesive pressure-sensitive adhesive tapes capable of holding a fixing function can be used without particular limitation.

[Peeling strength against PET trigger B]
One side of the substrate-less transparent double-sided pressure-sensitive adhesive sheet (trade name “LUCIACS CS9862UAS” manufactured by Nitto Denko, tape thickness 50 μm, both adhesive surfaces coated with PET release liner (thickness 75 μm)) was peeled off. , Toray Co., Ltd. PET film (product name “Lumirror S-10” thickness 188 μm) is pressed at a pressure of 0.25 MPa and a speed of 0.3 m/min to obtain a laminate. A surface protection film is press-bonded to the PET film side surface of this laminate at a pressure of 0.25 MPa and a speed of 0.3 m/min. The obtained laminate is cut into a size of 50 mm in width and 100 mm in length with a push-cut type paper cutter. The other release liner of the cut laminate was peeled off, and an acrylic plate (manufactured by Mitsubishi Rayon Co., Ltd., trade name “Acrylite”, thickness 2 mm, width 70 mm, length 100 mm) was applied with a pressure of 0.25 MPa and a pressure of 0.3 m. / min to prepare a test piece. In an environment of 23° C. and 50% RH, a hand roller was used to crimp Nitto Denko's product name “NO. . Under the same environment, the surface protection film is peeled from the PET film under the conditions of a tensile speed of 0.3 m/min and a peel angle of 90 degrees, and the maximum stress applied at the beginning of peeling is recorded as the trigger peel strength [N/50 mm]. By converting the obtained value to a width of 19 mm, the trigger peel strength against PET B [N/19 mm] is obtained.
In the above measurement, the time from pressure bonding of the surface protective film to the PET film until peeling is 3 days in this test. Even if the measurement results are different, the difference is at a negligible level, so after leaving for 3 days or more, the value of the trigger peel strength measured by performing the above peel test may be adopted as the trigger peel strength B against PET. good.
"NO.315" manufactured by Nitto Denko Co., Ltd. is a rubber-based single-sided adhesive tape with a polyester base material, the base material thickness is about 25 μm, the total thickness is about 60 μm, and the 180 degree peel strength is about 12.0 N. /19 mm.
In addition, the substrate-less transparent double-sided adhesive sheet used for fixing the PET film and the acrylic plate is not limited to "LUCIACS CS9862UAS", and in the measurement of the PET trigger peel strength B, the fixing function between the PET film and the acrylic plate is Various known double-sided adhesive pressure-sensitive adhesive tapes capable of being held can be used without particular limitation.

[Peelability of surface protective film]
The surface protective film is press-bonded to a reflective polarizing film ("APF-V3" manufactured by 3M, thickness 26 µm) at a pressure of 0.25 MPa and a speed of 0.3 m/min. The resulting laminate (polarizing film with surface protective film) is cut into a size of 50 mm wide and 100 mm long with a push-cut paper cutter. The polarizing film side surface of the cut laminate was attached to an acrylic plate (manufactured by Mitsubishi Rayon Co., Ltd., product name "Acrylite", thickness 2 mm, width 70 mm, length 100 mm) and double-sided adhesive tape (product name "Nitto Denko"). No. 500", a double-sided adhesive tape having a thickness of 0.17 mm and having an acrylic adhesive on both sides of a non-woven fabric substrate. In an environment of 23 ° C. × 50% RH, acrylic adhesive tape (trade name “No. Immediately after, the surface protective film is manually peeled off from the polarizing film at a peeling angle of approximately 90 degrees and a tensile speed of 0.3 m/min. If the surface protective film could be peeled off from the polarizing film, the peeling was successful, and if the acrylic pressure-sensitive adhesive tape was peeled off from the surface protective film and the surface protective film could not be peeled off from the polarizing film, the peeling was unsuccessful. This test is performed 10 times, and the number of times the surface protective film is successfully peeled off is counted. The results are shown in Table 1 as [number of successes/10 (times)].

[Surface resistivity of topcoat layer]
Under the atmosphere of 23 ° C. and 50% RH, using a commercially available resistivity meter, under the conditions of 23 ° C. and 50% RH, based on JIS K 6911, the applied voltage is 100 V and the applied time is 30 seconds. The resistivity of the layer surface (back surface of the surface protective film) is measured. As the resistivity meter, a trade name "Hiresta UP MCP-HT450 type" manufactured by Mitsubishi Chemical Analytic Co., Ltd. or its equivalent can be used. The surface resistivity was measured immediately after the topcoat layer was applied (initial surface resistivity) and after it was left to stand after ultraviolet irradiation (UV irradiation) in an environment of 23 ° C. × 50% RH, and the initial surface resistivity [Ω /□], surface resistivity after UV irradiation [Ω/□]. The UV irradiation conditions are the use of a metal halide lamp, an illuminance of 90 mW/cm ² and an integrated amount of light of 3000 mJ/cm ² . The illuminance and the integrated amount of light are measured using an ultraviolet illuminometer (trade name “EYE UVMETER UVPF-A1”, Headsensor “PD-365” manufactured by Eye Graphics Co., Ltd.).

[Surface resistivity of adhesive layer]
Using a commercially available resistivity meter, the surface (adhesive surface) of the adhesive layer of the surface protective film is subjected to an applied voltage of 500 V and an applied time of 30 based on JIS K 6911 under an atmosphere of 23 ° C. and 50% RH. The resistivity [Ω/□] of the pressure-sensitive adhesive layer surface is measured under the condition of seconds. As the resistivity meter, a trade name "Hiresta UP MCP-HT450 type" manufactured by Mitsubishi Chemical Analytech Co., Ltd. or its equivalent can be used.

<Preparation of coating material>
(Coating material E1)
An aqueous solution containing 0.5% poly(3,4-ethylenedioxythiophene) (PEDOT) as a conductive polymer and 0.8% polystyrene sulfonate (number average molecular weight 150,000) (PSS) (manufactured by Heraeus, trade name "Clevios P"; hereinafter also referred to as "aqueous conductive polymer solution A1") was prepared. In addition, an acrylic resin (trade name “ARUFON UC-3000” manufactured by Toagosei Co., Ltd. (solid content 98%, molecular weight 10,000, Tg 65° C., acid value 74 mgKOH/g) was prepared as the acrylic binder B1.
In a mixed solvent of water and ethanol, 100 parts of the conductive polymer aqueous solution A1 in solid content, 100 parts of the acrylic binder B1 in solid content, and a melamine curing agent (manufactured by Nippon Carbide Industry Co., Ltd., trade name " 40 parts of Nika Resin S-176") was added and thoroughly mixed by stirring for about 20 minutes. Thus, NV 0.3% coating material E1 was prepared.

(Coating material E2)
A coating material E2 with NV of 0.3% was prepared in the same manner as the coating material E1 except that the acrylic binder B1 was changed to the acrylic binder B2. As the acrylic binder B2, a styrene acrylic resin (manufactured by Toagosei Co., Ltd., trade name "ARUFON UH-2170" (solid content 98%, molecular weight 14,000, Tg 60°C, hydroxyl value 88 mgKOH/g) was used.

(Coating material E3)
Coating material E1 except that the melamine-based curing agent was changed to oxazoline-based curing agent (A) (Nippon Shokubai Co., Ltd., trade name "Epocross WS-300" (10% non-volatile aqueous solution Tg 90 ° C., Mn 40,000, Mw 120,000) In the same manner, NV 0.3% coating material E3 was prepared.

(Coating material E4)
Coating material E1 except that the melamine curing agent was changed to oxazoline curing agent (B) (manufactured by Nippon Shokubai Co., Ltd., trade name "Epocross WS-700" (25% non-volatile aqueous solution Tg 50 ° C., Mn 20,000, Mw 40,000) In the same manner, NV 0.3% coating material E4 was prepared.

(Coating material E5)
NV 0.3% in the same manner as coating material E1 except that the melamine-based curing agent was changed to an aziridine-based curing agent (manufactured by Nippon Shokubai Co., Ltd., trade name "Kemitite PZ-33", nonvolatile content > 99%, molecular weight 425) of coating material E5 was prepared.

(Coating material E6)
A coating material E6 with NV of 0.3% was prepared in the same manner as the coating material E1 except that the number of parts of the melamine curing agent was changed from 40 parts to 20 parts.

(Coating material E7)
A coating material E7 with NV of 0.3% was prepared in the same manner as the coating material E1 except that the number of parts of the melamine curing agent was changed from 40 parts to 50 parts.

(Coating material E8)
A 0.3% NV coating material E8 was prepared in the same manner as the coating material E1 except that the conductive polymer aqueous solution A1 was changed to the conductive polymer aqueous solution A2. As the conductive polymer aqueous solution A2, a 5% aqueous solution of polyaniline sulfonic acid (manufactured by Mitsubishi Chemical Corporation, product name “Aquapass-01X”, molecular weight 10,000 to 20,000) was used.

(Coating material E9)
An acrylic copolymer containing a quaternary ammonium group in the side chain (trade name “Bondip-PA100 main agent” manufactured by Konishi Co., Ltd., non-volatile content 32%) and an epoxy resin (trade name “Bondip” manufactured by Konishi Co., Ltd. -PA100 curing agent", non-volatile content 8.8%), and the above acrylic copolymer and epoxy resin are mixed in a mixed solvent of water and isopropyl alcohol at a weight ratio of 1: 1, and acrylic A 0.3% NV coating material E9 was prepared with a copolymer:epoxy resin solids ratio of 100:28. The acrylic copolymer can function as both an antistatic agent and a binder (acrylic antistatic agent/binder).

(Coating material E10)
A coating material E10 with NV 0.3% was prepared in the same manner as the coating material E1, except that the acrylic binder B1 was changed to a polyester binder B3, and 40 parts of a solid content of an aqueous dispersion of carnauba wax as a lubricant was added. prepared. As the polyester-based binder B3, Toyobo Co., Ltd. trade name "Binalol MD-1480" (25% aqueous dispersion of saturated copolyester resin) was used.

(Coating material E11)
A toluene solution (NV 0.3%) of a copolymer of octadecyl methacrylate, acrylonitrile and methacrylic acid (molar ratio: octadecyl methacrylate/acrylonitrile/methacrylic acid=18/82/35, Mw 70,000) was prepared as coating material E11. The copolymer used for the coating material E11 is a copolymer whose main monomer component is acrylonitrile, which does not have a (meth)acryloyl group, and does not correspond to an acrylic binder. Also, this copolymer has a long-chain alkyl group in its side chain.

(Preparation of adhesive F1)
200 parts of 2-ethylhexyl acrylate (2EHA), 8 parts of 2-hydroxyethyl acrylate (HEA), and 2,2 as a polymerization initiator are placed in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. 0.4 parts of '-azobisisobutyronitrile (AIBN) and 312 parts of ethyl acetate as a solvent were charged, nitrogen gas was introduced while gently stirring, and the liquid temperature in the flask was maintained at around 65°C for 6 hours. A polymerization reaction was carried out to prepare an acrylic polymer solution (NV 40%). The acrylic polymer had an Mw of 540,000 and a Tg of -68°C.
The above acrylic polymer solution was diluted with ethyl acetate to 20%, and polyoxyethylene nonylpropenylphenyl ether ammonium sulfate (trade name), which is an anionic surfactant, was added on a solid basis to 100 parts of the solid content in this solution. "Aqualon HS-10", Daiichi Kogyo Seiyaku Co., Ltd.) 0.3 parts, isocyanurate of hexamethylene diisocyanate as a cross-linking agent (trifunctional isocyanate compound, trade name "Coronate HX", Tosoh Corporation) 3 parts, cross-linking 0.03 part of dioctyltin dilaurate (trade name: "Envirizer OL-1", manufactured by Tokyo Fine Chemical Co., Ltd., 1% toluene solution) was added as a catalyst, and 3 parts of acetylacetone was added as a cross-linking retarder to 100 parts of the total solvent. were added and mixed and stirred to prepare an acrylic pressure-sensitive adhesive solution F1.

(Preparation of adhesive F2)
91 parts of 2EHA, 9 parts of 4-hydroxybutyl acrylate (4HBA), 0.2 parts of AIBN as a polymerization initiator, and 150 parts of ethyl acetate were placed in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler. After charging, nitrogen gas was introduced while gently stirring, and the liquid temperature in the flask was maintained at around 60° C., and the polymerization reaction was carried out for 6 hours to prepare an acrylic polymer solution (NV 40%). Mw of this acrylic polymer was 500,000.
The above acrylic polymer solution is diluted with ethyl acetate to 20%, and based on the solid content of 100 parts of this solution, the isocyanurate of hexamethylene diisocyanate (trifunctional isocyanate compound, trade name “ Coronate HX", manufactured by Tosoh Corporation) 3 parts, 0.03 parts of dioctyltin dilaurate as a cross-linking catalyst (manufactured by Tokyo Fine Chemical Co., Ltd., trade name "Envirizer OL-1", 1% toluene solution), lithium bis (trifluoromethane 0.5 parts of polyether-modified silicone (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KF-353") were added, and acetylacetone was added as a cross-linking retarder. 5 parts were added to 100 parts of the solvent and mixed and stirred to prepare an acrylic adhesive solution F2.

(Preparation of adhesive F3)
The acrylic polymer solution (NV40%) used in the preparation of PSA F1 was diluted with ethyl acetate to 20% by weight, and hexamethylene diisocyanate was used as a cross-linking agent on a solid basis with respect to 100 parts of the solid content in this solution. 2 parts of isocyanurate (trifunctional isocyanate compound, trade name "Coronate HX", manufactured by Tosoh Corporation), dioctyl tin dilaurate as a cross-linking catalyst (trade name "Envilizer OL-1" manufactured by Tokyo Fine Chemical Co., Ltd., 1% toluene 0.03 part of solution) was added, and 3 parts of acetylacetone as a cross-linking retarder was added to 100 parts of the total solvent, and mixed and stirred to prepare acrylic adhesive solution F3.

(Preparation of Adhesive F4)
The acrylic polymer solution (NV40%) used for the preparation of PSA F1 was diluted with ethyl acetate to 20%, and hexamethylene diisocyanate was added as a cross-linking agent on a solid basis to 100 parts of the solid content in this solution. 1 part of isocyanurate (trade name: "Coronate HX", manufactured by Tosoh Corporation), 0.03 part of dioctyltin dilaurate (trade name: "Envilizer OL-1", manufactured by Tokyo Fine Chemical Co., Ltd., 1% toluene solution) as a cross-linking catalyst was added, and 3 parts of acetylacetone as a cross-linking retarder was added to 100 parts of the total solvent, and mixed and stirred to prepare an acrylic pressure-sensitive adhesive solution F4.

<Example 1>
A transparent PET film with a thickness of 38 μm was prepared. The coating material E1 was applied to the PET film with a bar coater, and dried by heating at 130° C. for 30 seconds. Thus, a film with a topcoat layer having a topcoat layer with a thickness of 24 nm on one side of the PET film was produced.
The acrylic pressure-sensitive adhesive solution F1 was applied to the opposite side of the topcoat layer-attached film to the topcoat layer and heated at 130° C. for 20 seconds to form a pressure-sensitive adhesive layer having a thickness of 20 μm. Next, a silicone-treated surface of a release liner made of a PET film (thickness: 25 μm) having one surface silicone-treated was attached to the surface of the pressure-sensitive adhesive layer to prepare a surface protective film (adhesive sheet) according to this example. .

<Examples 2 to 12, 16 to 18>
A surface protective film (adhesive sheet) according to each example was prepared in the same manner as in Example 1, except that the coating material, the thickness of the topcoat layer, the adhesive solution, and the thickness of the adhesive layer were changed to those shown in Table 1. made.

<Examples 13-15>
A transparent PET film with a thickness of 38 μm was prepared. One side of this PET film was subjected to corona treatment, and the coating material E9 was applied with a bar coater so that the thickness after drying would be 208 nm (Example 13), 104 nm (Example 14) or 26 nm (Example 15). and dried for 30 seconds. In this manner, a film with a topcoat layer according to each example was produced. A surface protection film (adhesive sheet) according to each example was produced in basically the same manner as in Example 1, except that the obtained film with a topcoat layer was used.

Schematic structure of the surface protective film according to each example, back peel strength A [N / 19 mm] of standard acrylic adhesive tape, back peel strength C [N / 19 mm] of standard rubber adhesive tape, PET trigger peel strength B [ N / 19 mm], peelability of the surface protective film [success times / 10 (times)], initial surface resistivity of the top coat layer [Ω / □], surface resistivity after UV irradiation [Ω / □], and adhesive layer Table 1 shows the evaluation results of the surface resistivity [Ω/□]. In Table 1, the back peel strength A of the standard acrylic adhesive tape is indicated as "back peel strength (standard acrylic)", and the back peel strength C of the standard rubber adhesive tape is indicated as "back peel strength (standard rubber)". , the surface resistivity is simply written as resistivity.

As shown in Table 1, the surface protective films of Examples 1 to 15 satisfying the properties (A) and (B) were subjected to a peelability evaluation test in which an acrylic pressure-sensitive adhesive tape for pick-up was adhered to the back surface and immediately peeled off. , the success rate of peeling from the polarizing film, which is the adherend, was 100% . In contrast, Examples 16 to 18, which did not satisfy the characteristics (A) and (B) , had a low peeling success rate in the peelability evaluation test. In Examples 1 to 18, the back peel strength of the standard rubber-based pressure-sensitive adhesive tapes was all 3.5 N/19 mm or more, and the surface protection films of these examples are considered to have good peelability from the rubber-based pressure-sensitive adhesive tape for pick-up. be done.
From the above results, according to the surface protective film that satisfies the above characteristics (A) and (B) , in peeling from the adherend using the pickup tape, even when using the acrylic pickup tape, the pickup tape pressure bonding It can be seen that it can be reliably peeled off by the pick-up tape in a short period of time.

1: Surface protective film 1A: First surface (back surface) of surface protective film
1B: Second surface of surface protective film 12: Base material layer 12A: First surface (back surface) of base material layer
12B: Second surface (front surface) of base material layer
14: Topcoat layer 14A: Topcoat layer surface 20: Adhesive layer 20A: Surface (adhesive surface)
30: release liner 50: adherend (optical component)

Claims (9)

A surface protection film having an adhesive layer, a substrate layer, and a topcoat layer in this order,
The top coat layer constitutes the back surface of the surface protection film,
The pressure-sensitive adhesive layer is formed from a solvent-based pressure-sensitive adhesive composition,
The pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing a crosslinked acrylic polymer as a base polymer,
The topcoat layer contains an acrylic binder,
The topcoat layer has a thickness of 12 nm or more,
The following properties:
(A) The 180 degree peel strength A of the standard acrylic pressure-sensitive adhesive tape against the back surface measured under the conditions of 23 ° C., 1 minute after application and a tensile speed of 0.3 m / min is 3.5 N / 19 mm or more; and ( B) The 90-degree trigger peel strength B to a polyethylene terephthalate film measured under conditions of 23° C. and a tensile speed of 0.3 m/min is less than 3.5 N/19 mm;
A surface protection film that satisfies Additionally the following properties:
(C) The 180-degree peel strength C of the standard rubber-based pressure-sensitive adhesive tape against the back surface measured under the conditions of 23° C., 1 minute after application, and a tensile speed of 0.3 m/minute is 3.5 N/19 mm or more;
The surface protection film according to claim 1, which satisfies The surface protective film according to claim 1 or 2, wherein the back surface has a surface resistivity of 1.0 × 10 ¹³ Ω/□ or less. The surface protection film according to any one of claims 1 to 3, wherein the topcoat layer contains at least one selected from quaternary ammonium salts and conductive polymers. the topcoat layer comprises a conductive polymer;
5. The surface protective film according to any one of claims 1 to 4, wherein the conductive polymer contains at least one selected from poly(3,4-ethylenedioxythiophene) and polyaniline sulfonic acid. The topcoat layer is a layer formed from a coating material containing a curing agent,
2. The curing agent is at least one selected from the group consisting of melamine curing agents, isocyanate curing agents, epoxy curing agents, oxazoline curing agents, aziridine curing agents and carbodiimide curing agents. 6. The surface protection film according to any one of -5. 7. The surface protective film according to any one of claims 1 to 6 , wherein the base layer is made of a polyester resin film. Equipped with an optical component and a surface protection film that protects the optical component,
The surface protection film is
an adhesive layer to be attached to the optical component;
a base layer;
a topcoat layer constituting the back surface of the surface protection film;
in that order, and
The pressure-sensitive adhesive layer is formed from a solvent-based pressure-sensitive adhesive composition,
The pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing a crosslinked acrylic polymer as a base polymer,
The topcoat layer contains an acrylic binder,
The topcoat layer has a thickness of 12 nm or more,
The surface protection film has the following properties:
(A) The 180-degree peel strength A of the standard acrylic pressure-sensitive adhesive tape against the back surface measured under the conditions of 23°C, 1 minute after application, and a tensile speed of 0.3 m/min is 3.5 N/19 mm or more;
satisfies the
When the surface protective film is peeled from the optical component under conditions of 23° C., a peeling angle of 90 degrees, and a tensile speed of 0.3 m/min, the surface protective film is attached to the optical component with a trigger peel strength of less than 3.5 N/19 mm. optical components with surface protection film. 9. The optical component with a surface protection film according to claim 8 , wherein said optical component is a reflective polarizing film.

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