WO2016157921A1

WO2016157921A1 - Surface protecton film

Info

Publication number: WO2016157921A1
Application number: PCT/JP2016/050286
Authority: WO
Inventors: 剛史安齋; 雄一倉田; 克彦堀米
Original assignee: リンテック株式会社
Priority date: 2015-03-31
Filing date: 2016-01-07
Publication date: 2016-10-06
Also published as: TWI697538B; TW201700665A; JP6139808B2; JPWO2016157921A1

Abstract

The surface protection film of the present invention is a surface protection film that is applied to an optical component or an electronic component and used for protecting the surface thereof, the surface protection film comprising: a substrate having a Young's modulus of 2500 MPa or less and a thickness of 50 μm or more; and an adhesive layer provided on one surface of the substrate, and having a storage modulus of 0.1 MPa or more.

Description

Surface protection film

The present invention relates to a surface protective film in which a pressure-sensitive adhesive is laminated on one surface of a substrate, and in particular, a surface that is used to protect the surface by being affixed to the surface of various optical members and electronic members. It relates to a protective film.

2. Description of the Related Art Conventionally, when assembling an electronic device or the like, a method of previously uniting various electric components and optical components and mounting them on a substrate or the like is widely known. As such a unitized optical member and electronic member, there are many known units such as a motor unit including an imaging module, a camera lens unit, a communication module, a sensor module, and a vibrator. In these optical members and electronic members, a surface protective film may be attached in order to prevent scratches on the surface during processing, assembly, inspection, transportation, and the like.

The surface protective film is formed by providing a pressure-sensitive adhesive layer on one surface of a base material, and is adhered to an adherend such as an optical member or an electronic member by the pressure-sensitive adhesive layer to protect the surface of the adherend. At the same time, it is peeled off from the adherend when it is no longer necessary to protect the surface. Conventionally, surface protective films for optical members or electronic members have been made of ester-based materials such as polyethylene terephthalate and polyethylene naphthalate as a base material, and acrylic pressure-sensitive adhesives and silicone pressure-sensitive adhesives are used for pressure-sensitive adhesive layers. Is known to be used (see, for example, Patent Document 1).

JP 2005-341520 A

By the way, the above-mentioned optical member and electronic member have been miniaturized year by year, and the size of the surface protective film has been reduced accordingly. Such a small-sized surface protective film is difficult to automate the pasting and peeling operations, and is currently performed manually.

However, small-sized surface protective films may have problems that do not occur with normal label sizes when applied and peeled off manually. For example, substrates and adhesives that are widely used for adhesive sheets Even if an agent is used, adhesive residue may occur at the time of peeling. Even with a small amount of the adhesive residue, there is a risk of quality deterioration or malfunction in a miniaturized optical member or electronic member.
Therefore, it is conceivable to reduce the adhesive strength to prevent adhesive residue, but if the adhesive strength is simply reduced, the small size surface protective film will be easily peeled off from the adherend, providing sufficient protection performance. It becomes difficult to secure. Moreover, when the base material is made thin, it is considered that the above-mentioned adhesive residue hardly occurs, but when the base material is made extremely thin with a small-sized surface protective film, the handling property is lowered.

The present invention has been made in view of the above-mentioned problems, and the problem of the present invention is that even if the size of the surface protective film is reduced, it is possible to ensure an appropriate adhesive force and improve the handling property while peeling. It is to provide a surface protective film that sometimes does not cause adhesive residue.

The present inventors considered the mechanism of the occurrence of adhesive residue. Generally, since the base material has a relatively strong waist, when a small-sized surface protective film is manually peeled off, It was found that the substrate locally pushed the adherend. And, such an indentation force is relatively large in a small-sized surface protection film with a large substrate thickness that requires a large bending force at the time of peeling. Scratched the adherend and considered that adhesive residue was generated.
Therefore, as a result of intensive studies, the present inventors have found that when the Young's modulus of the base material is lowered while increasing the storage elastic modulus of the pressure-sensitive adhesive, the above-mentioned scratch is almost eliminated, thereby preventing adhesive residue and adhesion. The inventors have found that the force becomes an appropriate value and the adhesive performance is also improved, and the following invention has been completed. That is, the present invention provides the following (1) to (17).
(1) A surface protective film that is applied to an optical member or an electronic member and used to protect the surface thereof,
A base material having a Young's modulus of 2900 MPa or less and a thickness of 50 μm or more;
A surface protective film comprising: a pressure-sensitive adhesive layer provided on one surface of the substrate and having a storage elastic modulus of 0.1 MPa or more.
(2) The surface protective film according to (1), wherein the film area is 20 cm ² or less.
(3) The surface protective film according to (1) or (2), wherein the base material has a thickness of 300 μm or less.
(4) The surface protective film according to any one of (1) to (3) above, wherein the storage layer has a storage elastic modulus of 1 MPa or less.
(5) The surface protective film according to any one of (1) to (4), wherein the substrate has a Young's modulus of 500 MPa or more.
(6) The surface protective film according to any one of (1) to (5), wherein the adhesive strength is 0.1 to 1.0 N / 25 mm.
(7) The surface protective film according to any one of (1) to (6) above, wherein the pressure-sensitive adhesive layer has a thickness of 3 to 45 μm.
(8) The surface protective film according to any one of (1) to (7), wherein the substrate is a laminate comprising at least a polyethylene terephthalate film and a polyolefin film.
(9) The surface protective film according to any one of (1) to (8), wherein the pressure-sensitive adhesive layer is formed from an acrylic pressure-sensitive adhesive composition containing an acrylic polymer.
(10) The acrylic polymer comprises an alkyl (meth) acrylate having 1 to 20% by mass of an alkyl group having 1 or 2 carbon atoms and an alkyl (meth) acrylate 60 having an alkyl group having 3 to 8 carbon atoms. The surface protective film according to (9) above, which is a copolymer of monomers containing at least 92% by mass.
(11) The acrylic polymer is a copolymer of monomers containing at least 0.1 to 2.5% by mass of a carboxyl group-containing monomer and 0.5 to 15% by mass of a hydroxyl group-containing (meth) acrylate. The surface protective film as described in said (9) or (10).
(12) The surface protective film according to any one of (9) to (11), wherein the acrylic pressure-sensitive adhesive composition contains 3 to 20 parts by mass of a crosslinking agent with respect to 100 parts by mass of the acrylic polymer. .
(13) The surface protective film according to any one of (1) to (12), wherein the pressure-sensitive adhesive layer is formed from a non-energy ray curable pressure-sensitive adhesive composition.
(14) The surface protective film according to any one of (1) to (13), which is attached to the imaging module and used to protect the light receiving portion of the imaging module.
(15) The base material has a Young's modulus of 1000 to 2000 MPa and a thickness of 60 to 150 μm, the adhesive layer has a storage elastic modulus of 0.15 to 0.35 MPa, a thickness of 5 to 45 μm, and The surface protective film according to any one of (1) to (14), wherein the adhesive strength is 0.1 to 0.6 N / 25 mm.
(16) With a surface protective film comprising a member selected from either an optical member or an electronic member and the surface protective film according to any one of (1) to (15) attached to the surface of the member Element.
(17) A method for protecting the surface of the optical member or electronic member by applying the surface protective film according to any one of (1) to (15) above to the surface thereof.

In the present invention, even when the surface protective film is small, it is possible to provide a surface protective film that ensures an appropriate adhesive force and improves handling properties, and that does not generate adhesive residue at the time of peeling.

In the following description, “weight average molecular weight” is a value in terms of polystyrene measured by a gel permeation chromatography (GPC) method, specifically a value measured based on the method described in the examples. .
In the description of the present specification, for example, “(meth) acrylate” is used as a word indicating both “acrylate” and “methacrylate”, and the same applies to other similar terms.

Hereinafter, the present invention will be described in more detail using embodiments.
The surface protective film of the present invention is applied to an adherend selected from an optical member or an electronic member and used to protect the surface, and has a Young's modulus of 2900 MPa or less and a thickness of 50 μm or more. And a pressure-sensitive adhesive layer provided on one surface of the substrate and having a storage elastic modulus of 0.1 MPa or more. This surface protective film is used by being attached to an adherend through an adhesive layer.

The surface protective film of the present invention is used to protect a relatively small optical member or electronic member, and has a relatively small size. Furthermore, the base material of the surface protective film is relatively thick in order to improve handling properties. That is, the surface protective film of the present invention has a small size, a thick base material, and adhesive residue is relatively likely to occur, but the Young's modulus of the base material and the storage elastic modulus of the pressure-sensitive adhesive layer are a constant value. By doing so, it becomes difficult to generate adhesive residue when the surface protective film is peeled off from the adherend while improving the adhesive strength.

In the present invention, as described above, the Young's modulus of the substrate is 2900 MPa or less and preferably 500 MPa or more. When the base material has a Young's modulus greater than 2900 MPa, the base material pushes the adherend with a strong force when the surface protective film is peeled off, and adhesive residue is likely to occur. Moreover, when Young's modulus becomes larger than 2900 MPa, it exists in the tendency for the adhesive force of the surface protection film mentioned later to fall. On the other hand, by setting the Young's modulus of the base material to 500 MPa or more, a certain degree of rigidity is imparted to the base material, and the handleability of the surface protective film is improved. Moreover, it becomes easy to adjust the adhesive force mentioned later to the desired range.
The Young's modulus of the substrate is more preferably from 600 to 2800 MPa, and even more preferably from 1000 to 2000 MPa, in order to ensure the handling property and adhesive force and to prevent adhesive residue.
The Young's modulus of the base material is a value measured according to JISK-7127 (1999).

In addition, the thickness of the base material is 50 μm or more as described above, but if it is less than 50 μm, the handling property is deteriorated, and the surface protective film is manually attached to the adherend or peeled off. It becomes difficult to do. Moreover, when carrying out the punching process mentioned later, it may be difficult to cut only the surface protective film without cutting the release sheet. On the other hand, the upper limit value of the thickness of the base material is not particularly limited, but is preferably 300 μm or less from the viewpoint of improving handling properties and the like.
From the above viewpoint, the thickness of the base material is more preferably 55 to 200 μm, still more preferably 60 to 150 μm.

In addition, the storage elastic modulus of the pressure-sensitive adhesive layer in the present invention is 0.1 MPa or more as described above. When the storage elastic modulus is less than 0.1 MPa, the pressure-sensitive adhesive layer becomes too soft, and when the Young's modulus of the base material is low as described above, the adhesive force increases and the peel performance of the surface protective film decreases. To do. Furthermore, adhesive residue may easily occur. The storage elastic modulus of the pressure-sensitive adhesive layer is preferably 1 MPa or less. By setting the pressure to 1 MPa or less, the pressure-sensitive adhesive layer easily exhibits good adhesiveness, and the adherend is easily protected appropriately.
The storage elastic modulus of the pressure-sensitive adhesive layer is preferably 0.12 to 0.5 MPa, and more preferably 0.15 to 0.35 MPa in order to improve adhesiveness while preventing adhesive residue.
The storage elastic modulus can be adjusted by changing the material of the pressure-sensitive adhesive. For example, as will be described later, it is possible to increase the storage elastic modulus by adding a reactive functional group to the main polymer and increasing the amount of the crosslinking agent. Further, if the amount of the crosslinking agent is reduced, the storage elastic modulus can be lowered. Furthermore, it can also be adjusted by appropriately changing the type of monomer constituting the main polymer such as an acrylic polymer and the weight average molecular weight of the main polymer.
The storage elastic modulus of the pressure-sensitive adhesive layer is a storage elastic modulus G ′ measured by a torsional shear method in an environment of 23 ° C. at 1 Hz, as will be described later.

When the pressure-sensitive adhesive layer is thinned, the adhesive strength decreases, and when it is thickened, the adhesive strength increases. The thickness of the pressure-sensitive adhesive layer is usually adjusted to about 2 to 50 μm. The thickness of the pressure-sensitive adhesive layer is preferably 3 to 45 μm and more preferably 5 to 25 μm in order to easily adjust the adhesive force to a desired range described later.

Further, the adhesive force of the protective surface film can be used as long as it is about 1.5 N / 25 mm or less, but preferably 0.1 to 1.0 N / 25 mm. Since the protective surface film has an adhesive strength of 0.1 N / 25 mm or more, it is prevented from being unexpectedly peeled off from the adherend after being attached to the adherend, and appropriately protects the adherend. It becomes possible. Moreover, the protective surface film can be peeled from the adherend manually by setting it to 1.5 N / 25 mm or less, and further, the protective surface film can be easily peeled manually by setting it to 1.0 N / 25 mm or less. It becomes possible to do. The adhesive force can be appropriately adjusted by appropriately changing the material constituting the adhesive as described later, or changing the thickness of the adhesive, the Young's modulus of the base material, and the like as described above.
The adhesive strength of the protective surface film is more preferably 0.2 to 0.9 N / 25 mm, and more preferably 0.25 to 0.6 N / 25 mm in order to improve both the protective performance and the peelability in a well-balanced manner. More preferably.
In addition, as shown in the Example mentioned later, the adhesive force of a protective surface film means the adhesive force measured when a protective surface film was affixed on a specific adherend and it peeled after that.

Moreover, although the surface protective film of this invention is a small size as mentioned above, the film area becomes 20 cm < ² > or less normally. By setting it to 20 cm ² or less, it can be appropriately used as a surface protective film for a miniaturized electronic member or optical member. On the other hand, the lower limit of the film area is not particularly limited, but is preferably 0.05 cm ² or more from the viewpoint of practicality.
Further, the film area is more preferably 0.1 to 10 cm ² , and further preferably 0.2 to 4 cm ² in order to improve the practicality while easily exerting the effects of the present invention.
In addition, in this invention, although a film area means the area of a base material, for example, when a part of base material has an unevenness | corrugation, it is an apparent area of a base material when planarly viewed.

The shape of the surface protective film is not limited, but is processed into, for example, a circle, a square, a rectangle, or the like. The surface protective film is usually one in which a pressure-sensitive adhesive layer is provided on the entire surface of the substrate, but there may be a portion where the pressure-sensitive adhesive layer is not provided. For example, there may be a non-adhesive region where the pressure-sensitive adhesive layer is not provided at the center in the surface direction of the substrate. Moreover, although a base material is a plane normally, it may have the shape where one part swelled. For example, only the central part of the base material may bulge, and the part surrounding the central part may be a flat surface.
As described above, when a non-adhesive region or a bulging portion is provided in the central portion of the surface protective film, the central portion of the surface protective film does not contact the adherend. Therefore, the protective surface film of the present invention can be used even in the case where a part of the adherend is composed of precision parts that cause problems by contacting the pressure-sensitive adhesive layer.
Moreover, in order to improve the visibility of the surface protective film, the base material and the pressure-sensitive adhesive layer may be colored with a pigment or a dye.

In the present invention, the base material has a Young's modulus of 500 to 2900 MPa, a thickness of 50 to 300 μm, and a pressure-sensitive adhesive layer in order to improve the balance of adhesive residue properties, protective performance, handling suitability, and peelability. Preferably, the storage elastic modulus is 0.1 to 1 MPa, the thickness is 3 to 45 μm or less, and the adhesive strength of the surface protective film is 0.1 to 1.0 N / 25 mm.
Further, in order to further improve the balance of adhesive residue characteristics, handling suitability and peelability, the base material has a Young's modulus of 1000 to 2000 MPa and a thickness of 60 to 150 μm, and the adhesive layer has a storage elastic modulus of 0.1. More preferably, the thickness is 15 to 0.35 MPa, the thickness is 5 to 45 μm, and the adhesive strength of the surface protective film is 0.1 to 0.6 N / 25 mm.

Next, the material which comprises a base material and an adhesive layer is demonstrated in detail.
<Base material>
As long as the base material has a Young's modulus within a predetermined range as described above, it may be composed of a single-layer resin film or a multilayer resin film. In order to improve the handling property while making the rate appropriate, it is better to be composed of a plurality of layers.
When the substrate is a single layer film, a resin film having a relatively low Young's modulus is selected as a general film. Specifically, a low density polyethylene (LDPE, density: 0.910 g / cm ³ or more and less than 0.930 g / cm ³ ), medium density polyethylene (density: 0.930 g / cm ³ or more and less than 0.942 g / cm ³ ), high density polyethylene (HDPE, density: 0.942 g / cm ³ or more) Examples thereof include polyolefin films such as polyethylene films composed of polyethylene such as polyethylene and polypropylene films, polybutylene terephthalate films, urethane acrylate cured films, and unstretched polypropylene films.

Further, when the substrate is composed of a plurality of layers, the substrate is a laminate including a resin film having a relatively high Young's modulus and a resin film having a relatively low Young's modulus. A laminate including each of the above-described resin films that can be used in a film and a resin film having a higher Young's modulus than the resin film is preferable. Here, examples of the resin film having a high Young's modulus include a polyethylene terephthalate film, a polyethylene naphthalate film, a polyphenylene sulfide film, a polystyrene film, a polycarbonate film, and a biaxially stretched polypropylene film, and polyethylene terephthalate is preferable.

The base material is more preferably a laminate including a polyethylene terephthalate film and a polyolefin film in order to improve the handling property while maintaining a suitable Young's modulus, and a laminate including a polyethylene terephthalate film and a low-density polyethylene film. More preferably, it is a body.
Furthermore, when the resin film is composed of a plurality of layers, it may have a two-layer structure of a resin film having a relatively high Young's modulus and a resin film having a relatively low Young's modulus. A three-layer structure in which one resin film having a relatively high Young's modulus is provided between resin films having a relatively low Young's modulus is preferable. Preferable examples of the three-layer structure include those in which a low density polyethylene film, a polyethylene terephthalate film, and a low density polyethylene film are provided in this order.

Further, the base material may be appropriately subjected to surface treatment or the like, and a film or the like may be formed on the surface of the resin film. For example, an easy-adhesion layer for improving the adhesiveness with the pressure-sensitive adhesive layer may be formed on the surface of the substrate on which the pressure-sensitive adhesive layer is provided. The easy adhesion layer is formed of, for example, a polyester resin, a urethane resin, a polyester urethane resin, an acrylic resin, or the like.
In addition, the thickness of a base material means the whole thickness which comprises a base material. For example, when it is composed of a plurality of resin films, the total thickness of all the resin films is the thickness of the base material. For a base material having a coating layer such as an easy-adhesion layer, the thickness of the coating layer It is the thickness including.

<Adhesive layer>
Although it does not specifically limit as an adhesive which forms an adhesive layer, For example, an acrylic adhesive, a urethane adhesive, a silicone adhesive, a rubber adhesive, and a polyester adhesive are mentioned, for example. These pressure-sensitive adhesives may be used alone or in combination of two or more. The pressure-sensitive adhesive is usually formed from a pressure-sensitive adhesive composition containing main polymer components such as acrylic resin (that is, acrylic polymer), urethane resin, silicone resin, rubber component, and polyester resin. Among these pressure-sensitive adhesives, an acrylic pressure-sensitive adhesive is preferable in order to easily make the storage elastic modulus 0.1 MPa or more while setting the pressure-sensitive adhesive strength to 0.1 to 1 N / 25 mm.

Hereinafter, the case where an acrylic adhesive is used as an adhesive is demonstrated in detail.
An acrylic pressure-sensitive adhesive (hereinafter, also referred to as “acrylic pressure-sensitive adhesive composition”) includes an acrylic polymer as a main polymer that imparts adhesiveness, and the acrylic polymer is used in the acrylic pressure-sensitive adhesive composition. It is the main component. That is, the acrylic polymer is usually contained in an amount of 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more of the total amount of the composition.
The acrylic polymer is obtained by polymerizing a monomer containing at least an alkyl (meth) acrylate. Examples of the alkyl (meth) acrylate include those having an alkyl group having 1 to 18 carbon atoms, such as methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n -Butyl (meth) methacrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) ) Acrylate and the like.
The alkyl (meth) acrylate is usually 50% by mass or more, preferably 60 to 99% by mass, more preferably 70 to 97%, based on the total amount of monomers constituting the acrylic polymer (hereinafter also simply referred to as “monomer total amount”). Contains by mass%.

The acrylic polymer is an alkyl (meth) acrylate having 1 or 20 mass of alkyl (meth) acrylate having 1 or 2 carbon atoms as the monomer component constituting the polymer, based on the total amount of monomers. The alkyl (meth) acrylate having 3 to 8 carbon atoms in the alkyl group is preferably contained in an amount of 60 to 92% by mass based on the total amount of monomers. By using a predetermined alkyl (meth) acrylate at such a ratio, the adhesive strength can be easily adjusted to 0.1 to 1 N / 25 mm while the storage elastic modulus is set to 0.1 to 1 MPa or more as described above. .
Further, in the acrylic polymer, as a monomer component, alkyl (meth) acrylate having an alkyl group having 1 or 2 carbon atoms is contained in an amount of 3 to 15% by mass based on the total amount of monomers, and the number of carbon atoms in the alkyl group. It is more preferable that 75 to 90% by mass of alkyl (meth) acrylate in which is 3 to 8 is contained.
Further, in order to adjust the glass transition temperature of the pressure-sensitive adhesive and improve the pressure-sensitive adhesiveness of the acrylic polymer, the alkyl (meth) acrylate having 1 or 2 carbon atoms as described above is an alkyl methacrylate. It is preferable. On the other hand, an alkyl (meth) acrylate having an alkyl group with 3 to 8 carbon atoms is preferably an alkyl acrylate in order to develop excellent tackiness, and the alkyl group has 4 to 6 carbon atoms. It is preferable that

Examples of the alkyl (meth) acrylate having 1 or 2 carbon atoms in the alkyl group include methyl (meth) acrylate and ethyl (meth) acrylate. Among these, methyl methacrylate is preferable.
The alkyl (meth) acrylate having an alkyl group with 3 to 8 carbon atoms is preferably n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, or the like, and more preferably n-butyl acrylate.

The acrylic polymer is preferably a copolymer obtained by copolymerizing a monomer further containing a polymerizable monomer other than the above-described alkyl (meth) acrylate, and such a monomer is preferably a functional group-containing monomer. The functional group-containing monomer provides, for example, a functional group necessary for reaction with a cross-linking agent described later, or adjusts the adhesive force. The functional group-containing monomer is a monomer having a polymerizable double bond and a functional group such as a hydroxyl group, a carboxyl group, an amino group, a substituted amino group, and an epoxy group in the molecule. A carboxyl group is preferred.

The functional group-containing monomer preferably contains a carboxyl group-containing monomer in order to increase the adhesive strength of the surface protective film. The carboxyl group-containing monomer is preferably from 0.1 to 2.5% by mass, more preferably from 0.5 to 2.0% by mass, based on the total amount of monomers. Thus, by using a small amount of the carboxyl group-containing monomer, it is possible to appropriately increase the adhesive force while adjusting the storage elastic modulus to an appropriate value. Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, and itaconic acid, but acrylic acid is preferable.

The functional group-containing monomer preferably further contains a hydroxyl group-containing compound, more preferably a hydroxyl group-containing (meth) acrylate. The hydroxyl group-containing (meth) acrylate is preferably 0.5 to 15% by mass relative to the total amount of monomers. By making the content of the hydroxyl group-containing (meth) acrylate within the above range, the acrylic polymer can be appropriately cross-linked with a cross-linking agent described later, and the storage elastic modulus and adhesive force are set to appropriate values. Easy to adjust. The content of the hydroxyl group-containing (meth) acrylate is more preferably 2 to 10% by mass.
Specific examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and the like. Can be mentioned.
These hydroxyl group-containing (meth) acrylates may be used alone or in combination of two or more.

In addition to the above monomers, acrylic polymers include (meth) acrylic esters other than alkyl (meth) acrylates and functional group-containing monomers, dialkyl (meth) acrylamides, vinyl formate, vinyl acetate, styrene, vinyl acetate, etc. Copolymerized monomers containing Examples of (meth) acrylic acid esters other than alkyl (meth) acrylate and functional group-containing monomers include (meth) acrylic acid alkoxyalkyl esters, (meth) acrylic acid alkyleneoxyalkyl esters, (meth) acrylic acid nonylphenoxypolyethylene glycols, Tetrahydrofuranfuryl acrylate, diacrylates which are esters of polyether and acrylic acid, and the like may be used.
As the dialkyl (meth) acrylamide, dimethyl (meth) acrylamide, diethyl (meth) acrylamide and the like are used.
The weight average molecular weight of the acrylic polymer is preferably 100,000 or more, more preferably 100,000 to 1,500,000, and further preferably 200,000 to 1,200,000. By making the range of a weight average molecular weight into the above range, it becomes easy to adjust the storage elastic modulus and adhesive force of an adhesive layer to a desired range.

The acrylic pressure-sensitive adhesive composition preferably contains a crosslinking agent. By using the crosslinking agent, the acrylic polymer has a crosslinked structure in the pressure-sensitive adhesive layer. Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, a metal chelate crosslinking agent, and the like. Among these, an isocyanate crosslinking agent is preferable, and an isocyanate crosslinking agent and other crosslinking agents are used. A combination of agents is also preferred.

Examples of the isocyanate-based crosslinking agent include organic polyvalent isocyanate compounds, specifically, aromatic polyvalent isocyanate compounds, aliphatic polyvalent isocyanate compounds, alicyclic polyvalent isocyanate compounds, and these organic polyvalent isocyanate compounds. And terminal isocyanate urethane prepolymers obtained by reacting these organic polyvalent isocyanate compounds and polyol compounds.

Specific examples of the isocyanate-based crosslinking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4 ′. Diisocyanate, diphenylmethane-2,4′-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, dicyclohexylmethane-2,4′-diisocyanate; Trimethylolpropane modified tolylene diisocyanate such as adduct of tolylene diisocyanate and trimethylol propane, xylene diisocyanate and trimethylo Trimethylolpropane modified xylene diisocyanate such as an adduct of propane. Among these, trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylene diisocyanate are preferable.

Specific examples of the epoxy-based crosslinking agent include 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, ethylene Examples include glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, and diglycidyl amine.

Specific examples of the aziridine-based crosslinking agent include diphenylmethane-4,4′-bis (1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethane tri-β- Aziridinylpropionate, toluene-2,4-bis (1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1- (2-methylaziridine), tris-1- (2-methylaziridine) ) Phosphine, trimethylolpropane tri-β- (2-methylaziridine) propionate and the like.
Metal chelate crosslinking agents include chelate compounds whose metal atoms are aluminum, zirconium, titanium, zinc, iron, tin, etc., but aluminum chelate compounds are preferred from the viewpoint of performance. Examples of the aluminum chelate compound include diisopropoxy aluminum monooleyl acetoacetate, monoisopropoxy aluminum bis oleyl acetoacetate, monoisopropoxy aluminum monooleate monoethyl acetoacetate, diisopropoxy aluminum monolauryl acetoacetate, diisopropoxy Aluminum monostearyl acetoacetate, diisopropoxy aluminum monoisostearyl acetoacetate, monoisopropoxy aluminum mono-N-lauroyl-β-alanate monolauryl acetoacetate, aluminum trisacetylacetonate, monoacetylacetonate aluminum bis (isobutylacetate Acetate) chelate, monoacetylacetonate aluminum Bis (2-ethylhexyl acetoacetate) chelate, monoacetylacetonate aluminum bis (dodecyl acetoacetate) chelate, monoacetylacetonate aluminum bis (oleyl acetoacetate) chelate and the like, among aluminum tris acetylacetonate is preferred.

The content of the crosslinking agent in the acrylic pressure-sensitive adhesive composition is preferably 3 to 20 parts by mass with respect to 100 parts by mass of the acrylic polymer. When the content of the crosslinking agent is not less than the above lower limit value, the acrylic polymer is appropriately crosslinked, and the storage elastic modulus can be easily adjusted to 0.1 MPa or more. Moreover, by setting it as an upper limit value or less, it prevents that it bridge | crosslinks excessively and prevents that a storage elastic modulus becomes high too much or adhesive force falls.
In order to make the storage elastic modulus and the adhesive strength easy to achieve the above-mentioned preferable values, the content of the crosslinking agent is more preferably 4 to 15 parts by mass, and further preferably 5 to 9 parts by mass.

The acrylic pressure-sensitive adhesive composition may contain additives in addition to the crosslinking agent as long as the effects of the present invention are not impaired. Examples of such additives include antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, energy ray polymerizable compounds, photopolymerization initiators, and the like.

The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer is preferably a non-energy ray curable pressure-sensitive adhesive composition. The non-energy ray curable pressure-sensitive adhesive composition does not include a component that is cured by energy rays in the composition, as in the energy ray-curable pressure-sensitive adhesive composition described later, and the composition is applied even when irradiated with energy rays. It means that the adhesive strength of the pressure-sensitive adhesive layer formed from an object does not change. In the present invention, the surface protective film is peeled off by adjusting the Young's modulus of the base material and the storage elastic modulus of the pressure-sensitive adhesive layer as described above without imparting energy ray curability to the pressure-sensitive adhesive layer. Adhesive residue can be prevented while improving the peeling performance. Specific examples of energy rays include ultraviolet rays and electron beams.

However, the energy ray-curable pressure-sensitive adhesive composition may be used as the pressure-sensitive adhesive composition. The energy ray-curable pressure-sensitive adhesive composition is not particularly limited as long as it has energy ray curability, but an X-type one is used as a preferred embodiment.
The X-type energy ray-curable pressure-sensitive adhesive composition is one in which the main polymer (for example, acrylic polymer) of the pressure-sensitive adhesive itself has energy ray-curing properties. For example, in the case of an acrylic pressure-sensitive adhesive composition, at least a part of the above-mentioned acrylic polymer is an energy ray curable acrylic polymer having an unsaturated group in the side chain.

However, the energy beam curable pressure-sensitive adhesive composition may be a Y-type energy beam curable pressure-sensitive adhesive composition. The Y-type energy ray-curable pressure-sensitive adhesive composition has energy ray-curing properties by blending an energy ray-polymerizable compound separately from the main polymer (for example, acrylic polymer) for exhibiting adhesiveness. It has been granted. As the energy ray polymerizable compound, energy ray polymerizable oligomers such as epoxy acrylate, urethane acrylate, polyester acrylate, and polyether acrylate, and energy ray polymerizable monomers are used. These energy beam polymerizable compounds have at least two photopolymerizable carbon-carbon double bonds in the molecule. Further, the energy ray curable pressure-sensitive adhesive composition may be a combination of X type and Y type. That is, the energy ray curable pressure-sensitive adhesive composition contains an energy ray polymerizable compound in addition to the main polymer, and at least a part of the main polymer has an unsaturated group in the side chain. Also good.
When the pressure-sensitive adhesive layer is formed from an energy ray-curable pressure-sensitive adhesive composition, it may be cured by being irradiated with energy rays after being attached to the adherend and before being peeled off from the adherend. In this case, the adherend is appropriately protected with a high adhesive strength at the time of application, and the adhesive strength is reduced when peeled off from the adherend, so that it is easy to prevent adhesive residue. In this case, the above-mentioned adhesive strength means the adhesive strength before the energy ray is irradiated, but even if the adhesive strength is high, the peelability is good, so the upper limit value may be higher than 1.5 N / 25 mm. Good.
When the pressure-sensitive adhesive layer is formed from an energy ray-curable pressure-sensitive adhesive composition, the surface protective film may be irradiated with energy rays before being attached to the adherend.

A release sheet may be attached to the pressure-sensitive adhesive layer of the surface protective film in order to protect the pressure-sensitive adhesive layer. As the release sheet, a resin film such as polyethylene terephthalate, polyethylene naphthalate, polypropylene, polyethylene, etc., which has been subjected to a release treatment with a release agent such as a silicone resin can be used, but is not limited thereto. A plurality of surface protective films may be provided on one release sheet having a size sufficiently larger than the surface protective film.

The method for forming the pressure-sensitive adhesive layer is not particularly limited. After the pressure-sensitive adhesive composition diluted with an appropriate solvent is applied onto the release sheet as necessary, and then heated and dried to form the pressure-sensitive adhesive layer. What is necessary is just to form a base material together on an adhesive layer.
Moreover, you may apply | coat the adhesive composition diluted with the appropriate solvent as needed directly to a base material, and heat and dry after that, and may form an adhesive layer. It is preferable that a release sheet is further bonded onto the pressure-sensitive adhesive layer thus formed.

The laminate (also referred to as “pressure-sensitive adhesive sheet”) having the base material, the pressure-sensitive adhesive layer, and the release sheet manufactured as described above is cut so as to surround a predetermined portion (surface protective film portion) from the base material side. It is preferable to insert and punch. Here, the cut is formed by cutting the base material and the pressure-sensitive adhesive layer while not cutting the release sheet. After this punching process, the surface protective film having a predetermined shape is formed on the release sheet by removing the laminate of the adhesive layer and the substrate other than the surface protective film part from the release sheet. .

[Optical member or electronic member]
As an optical member or an electronic member protected by the surface protective film of the present invention, an imaging module in which one or more lenses and an imaging sensor such as a CCD or CMOS are housed in a casing or a package; a plurality of lenses is a lens mirror Examples include a lens unit held in a tube and housed in a housing or a package as necessary; a light emitting element unit having a light emitting element such as an LED; a motor unit such as a vibrator; a communication module, a sensor module, and the like. These optical members and electronic members are preferably members that are used by being attached to other members such as a substrate.

The optical member refers to an optical component that receives or emits light, or includes an optical component that transmits light. Among the above, an imaging module, a lens unit, a light emitting element unit, a communication module that transmits or receives an optical signal, An example of the optical member is an optical sensor module. The electronic member usually includes at least a part of an electric circuit and includes an electronic component that transmits or receives an electric signal, an electronic component that processes an electric signal, an electronic component that operates by an electric signal or electric power, and the like. Among them, a motor unit such as an imaging module, a light emitting element unit, and a vibrator, a communication module that transmits or receives an electrical signal, various sensor modules, and the like are specific examples of the electronic member. Note that a communication module, an optical sensor module, an imaging module, a light emitting element unit, and the like that transmit or receive optical signals are members that are both electronic members and optical members.
Moreover, it is preferable that the optical member or the electronic member is, for example, one in which the electronic component or the optical component is housed in a package or a housing or supported by a support member. Moreover, it is preferable that a part of electronic component or optical component is exposed on the surface, and the surface protection film is used, for example, to protect the exposed component.

[Usage of surface protection film]
The surface protective film of the present invention is used for affixing to the surface of an adherend selected from an optical member or an electronic member and protecting the surface. Specifically, an optical member or an electronic member (hereinafter also referred to as “member with a surface protective film”) to which a surface protective film is attached is processed, attached to another member, inspected, transported, or the like. Although it is a thing, a surface protection film protects the surface of an optical member or an electronic member in these processes. Further, the surface protective film is peeled off from the optical member or the electronic member when these steps are finished and the surface protection is no longer necessary.
In addition, the surface of the adherend to which the surface protective film is affixed may be flat, but may have steps or irregularities. If there is a level difference or unevenness, adhesive residue is likely to occur at the level difference or uneven part, but the surface protective film of the present invention prevents the occurrence of adhesive residue even in such a case.

The application of the surface protective film to the adherend and the peeling from the adherend are usually performed manually. These operations may be performed by directly gripping the surface protection film with a finger or may be performed by gripping with a tool such as tweezers.
Moreover, the member with a surface protective film may be heated in the processes such as processing, attachment, inspection, or conveyance described above. The heating temperature at that time is not particularly limited, but is about 60 to 200 ° C., preferably about 70 to 150 ° C. In addition, heating is performed in order to harden the thermosetting adhesive agent for attaching an optical member or an electronic member (member with a surface protection film) to another member, for example.

Further, the surface protective film is particularly preferably used as a surface protective film for an imaging module in the above-described optical member or electronic member.
The imaging module is usually provided with a light receiving portion for receiving light from the outside on one surface and guiding the light to the imaging device via a lens inside the module. The light receiving unit is provided on a part (for example, the center) of one surface of the imaging module and is made of glass or transparent resin. The surface protective film is preferably attached to one surface of the imaging module where the light receiving part is provided so as to cover the light receiving part.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

The measurement method and evaluation method in the present invention are as follows.
[Weight average molecular weight (Mw)]
Using gel permeation chromatography (GPC), the value measured under the following conditions and measured in terms of standard polystyrene was used.
(Measurement condition)
Measuring device: product name “HLC-8220GPC”, manufactured by Tosoh Corporation Column: product name “TSKGel SuperHZM-M”, developed by Tosoh Corporation Solvent: tetrahydrofuran column temperature: 40 ° C.
Flow rate: 1.0 mL / min
[Measurement of Young's modulus of substrate]
The Young's modulus of the substrate was measured in accordance with JISK-7127 (1999) at a test speed of 200 mm / min.
[Measurement of storage modulus of adhesive]
Using a viscoelasticity measuring device (Anton Paar, device name “MCR300”), a sample of an adhesive layer having a diameter of 8 mm × thickness of 1 mm is torsionally sheared with a storage elastic modulus G ′ at 1 Hz in an environment of 23 ° C. Measured by the method. In the examples and comparative examples described later, the above samples were obtained by laminating pressure-sensitive adhesive layers formed under the same conditions as in the examples and comparative examples from the solution of the pressure-sensitive adhesive composition.
[Thickness of base material and pressure-sensitive adhesive layer]
According to JIS K7130, measurement was performed using a constant pressure thickness measuring instrument (product name “PG-02” manufactured by Teclock Co., Ltd.). In addition, the thickness of an adhesive layer is the value which measured the thickness of the adhesive sheet and subtracted the thickness of a base material and a peeling sheet from the thickness.

[Adhesive force]
The adhesive strength was measured according to JISZ0237 at a width of 25 mm. However, the adherend is LCP Vectra A130 (trade name, manufactured by Polyplastics Co., Ltd.), and the adhesive sheet (surface protective film) cut to a width of 25 mm is moved back and forth by a 2 kg roller, and applied to the adherend by pressing. Affixed. The adhesive strength was measured when the adhesive was peeled off at a peeling angle of 180 ° using a Tensilon universal tensile tester after being left for 24 hours in an environment of 23 ° C. and 50% relative humidity.
In each of the following examples and comparative examples, the surface protective film is small in size, and the sample cannot be collected. Therefore, the pressure-sensitive adhesive sheet before punching is cut into samples.
[Adhesive residue evaluation]
After the surface protective film is attached to soda lime glass, it is left in a dry environment at 85 ° C. (relative humidity 0%) for 4 hours, and then further left at 23 ° C. and 50% relative humidity for 24 hours. Was peeled off. The adhesive residue on the glass was observed with a wide-field confocal microscope “HD100D” (manufactured by Laser Rack Co., Ltd.), and the state was evaluated according to the following criteria.
A: No glue residue B: There is some glue residue but no problem C: Many glue residues are present and there are problems in actual use [Handling suitability evaluation]
<Attachment workability>
The surface protection film obtained by punching to a size of 7 mm (38.5 mm ² ) in diameter was peeled off from the release film using tweezers, and the workability at the time of attaching to the optical member was evaluated according to the following criteria.
A: Good workability with no film sag B: Level of difficulty in working but can be applied C: Large sag of film and poor workability

[Example 1]
Using 86 parts by mass of n-butyl acrylate, 8 parts by mass of methyl methacrylate, 1 part by mass of acrylic acid, and 5 parts by mass of 2-hydroxyethyl acrylate as solution monomers, solution polymerization was performed in an ethyl acetate solvent to obtain an acrylic polymer (weight average A solution having a molecular weight of 800,000) was obtained.
In this acrylic polymer solution, an isocyanate-based crosslinking agent (trade name “Coronate L” manufactured by Nippon Polyurethane Co., Ltd.) is added in an amount of 7.5% by mass with respect to 100 parts by mass of the acrylic polymer (solid content). It mix | blended so that it might become a ratio of a part, and the solution of the adhesive composition (1) was obtained.
Release treatment of PET film (trade name “SP-PET751031”, manufactured by Lintec Corporation) that has been subjected to silicone release treatment as a release sheet so that the thickness after drying of the pressure-sensitive adhesive composition (1) is 20 μm. After coating on the surface, it was dried at 100 ° C. for 1 minute to form an adhesive layer.
Next, a low density polyethylene film (density: 0.923 g / m ³ , thickness 27.5 μm) / polyethylene terephthalate film (thickness 25.0 μm) / low density polyethylene film (density: 0.923 g / m ³ , thickness: 27 A resin film having a total thickness of 80 μm consisting of three layers (.5 μm) was prepared as the substrate A, and this substrate A was bonded to the adhesive layer to obtain an adhesive sheet. Thereafter, punching was performed to obtain a circular surface protective film (film area: 0.38 cm ² ) having a diameter of 7 mm. Table 1 shows the evaluation results of the surface protective film.

[Example 2]
The amount of the isocyanate-based crosslinking agent added to the pressure-sensitive adhesive composition (1) was changed to a solid content ratio of 4 parts by mass to obtain a pressure-sensitive adhesive composition (1) ′. Using this pressure-sensitive adhesive composition (1) ′ and the substrate A, a pressure-sensitive adhesive tape was obtained in the same manner as in Example 1. Thereafter, punching was performed to obtain a circular surface protective film having a diameter of 7 mm as in Example 1.

[Example 3]
A pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that the base material to be bonded to the pressure-sensitive adhesive layer was changed to base material C made of unstretched polypropylene film (trade name “Pyrene Film CT P1147” thickness 80 μm, manufactured by Toyobo Co., Ltd.). Obtained. Thereafter, punching was performed to obtain a circular surface protective film having a diameter of 7 mm as in Example 1.

[Example 4]
The base material to be bonded to the adhesive layer is a low density polyethylene film (density: 0.923 g / m ³ , thickness 27.5 μm) / polyethylene terephthalate film (thickness 50.0 μm) / low density polyethylene film (density: 0.923 g). / M ³ , thickness: 27.5 μm) A pressure-sensitive adhesive tape was obtained in the same manner as in Example 1, except that the resin film substrate D was changed to a total thickness of 105 μm. Thereafter, punching was performed to obtain a circular surface protective film having a diameter of 7 mm as in Example 1.

[Example 5]
Using 75.5 parts by mass of n-butyl acrylate, 18.9 parts by mass of 2-ethylhexyl acrylate, and 5.6 parts by mass of 4-hydroxybutyl acrylate as raw material monomers, solution polymerization was performed in an ethyl acetate solvent to obtain an acrylic polymer (weight An average molecular weight: 700,000) solution was obtained. In this acrylic polymer solution, an isocyanate crosslinking agent (trade name “Duranate 24A-100”, manufactured by Asahi Kasei Chemicals Corporation) was added at a solid content ratio of 3. with respect to 100 parts by mass of the acrylic polymer (solid content). 75 parts by mass, aluminum chelate-based crosslinking agent (manufactured by Soken Chemical Co., Ltd., trade name “M-2A”) at a ratio of 0.25 parts by mass to 100 parts by mass of acrylic polymer (solids) It mix | blended so that it might become, and the solution of the adhesive composition (3) was obtained.
This pressure-sensitive adhesive composition (3) was bonded to the substrate A in the same manner as in Example 1 to obtain a pressure-sensitive adhesive tape. Thereafter, punching was performed to obtain a circular surface protective film having a diameter of 7 mm as in Example 1.

[Example 6]
It implemented similarly to Example 2 except the point which made thickness of an adhesive layer 50 micrometers.
[Example 7]
The same operation as in Example 1 was performed except that the thickness of the pressure-sensitive adhesive layer was 2 μm.
[Example 8]
The same operation as in Example 2 was performed except that the thickness of the pressure-sensitive adhesive layer was 5 μm.
[Example 9]
The same operation as in Example 1 was performed except that the thickness of the pressure-sensitive adhesive layer was 10 μm.
[Example 10]
The same operation as in Example 1 was performed except that the thickness of the pressure-sensitive adhesive layer was 25 μm.
[Example 11]
The same operation as in Example 5 was performed except that the thickness of the pressure-sensitive adhesive layer was 45 μm.

[Comparative Example 1]
Solution polymerization of 68.6 parts by mass of 2-ethylhexyl acrylate, 30 parts by mass of methyl acrylate, 0.2 parts by mass of glycidyl methacrylate, 1.2 parts by mass of acrylic acid, and 1 part by mass of glycidylpropyltrimethoxysilane in an ethyl acetate solvent As a result, a solution of an acrylic polymer (weight average molecular weight: 800,000) was obtained.
To this acrylic polymer solution, an aziridine crosslinking agent (trade name “BXX5172” manufactured by Toyochem Co., Ltd.) is added in an amount of 0.5 part by mass with respect to 100 parts by mass of the acrylic polymer (solid content). Were mixed so as to obtain a solution of the pressure-sensitive adhesive composition (2). In the same manner as in Example 1, this pressure-sensitive adhesive composition (2) was coated on a release film to form a pressure-sensitive adhesive layer. A polyethylene terephthalate film with an easy-adhesion layer (Toyobo Co., Ltd.) was formed on the pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet was obtained by laminating the surface of the base material B made of company-made product name “Cosmo Shine A4300”, thickness: 100 μm) on the easy adhesion layer side. Thereafter, punching was performed to obtain a circular surface protective film having a diameter of 7 mm as in Example 1.

[Comparative Example 2]
Except for the point that the base material bonded to the adhesive layer was changed to the base material B, the same procedure as in Example 1 was performed to obtain an adhesive sheet. Thereafter, punching was performed to obtain a circular surface protective film having a diameter of 7 mm as in Example 1.

[Comparative Example 3]
The adhesive sheet was obtained by carrying out in the same manner as in Comparative Example 1 except that the substrate to be bonded to the adhesive layer was changed to the substrate A. Thereafter, punching was performed, and a circular surface protective film having a diameter of 7 mm was obtained in the same manner as in Comparative Example 1.

As apparent from Table 1 above, the surface protective films of Examples 1 to 11 were small in size and large in substrate thickness, but the Young's modulus of the substrate and the storage elastic modulus of the adhesive layer were low. Since it was a predetermined value, no adhesive residue was generated when it was peeled off from the adherend. In addition, since the adhesive strength of Example 6 was higher than 1.0 N / 25 mm, the peeling performance was lower than that of the other examples. Further, in Example 7, the adhesive strength was lower than 0.1 N / 25 mm, and the protective performance was high. Not as good as the other examples.
On the other hand, in Comparative Examples 1 to 3, since at least one of the Young's modulus of the base material or the storage elastic modulus of the pressure-sensitive adhesive layer was outside the predetermined range, adhesive residue was generated, or the adhesive strength was too high. The peeling performance deteriorated.

Claims

A surface protective film that is applied to an optical member or an electronic member and used to protect the surface thereof,
A base material having a Young's modulus of 2900 MPa or less and a thickness of 50 μm or more;
A surface protective film comprising: an adhesive layer provided on one surface of the substrate and having a storage elastic modulus of 0.1 MPa or more.
The surface protective film according to claim 1, wherein the film area is 20 cm 2 or less.
The surface protective film according to claim 1 or 2, wherein the substrate has a thickness of 300 µm or less.
The surface protective film according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer has a storage elastic modulus of 1 MPa or less.
The surface protective film according to any one of claims 1 to 4, wherein the substrate has a Young's modulus of 500 MPa or more.
The surface protective film according to any one of claims 1 to 5, wherein the adhesive strength is 0.1 to 1.0 N / 25 mm.
The surface protective film according to any one of claims 1 to 6, wherein the pressure-sensitive adhesive layer has a thickness of 3 to 45 µm.
The surface protective film according to any one of claims 1 to 7, wherein the substrate is a laminate including at least a polyethylene terephthalate film and a polyolefin film.
The surface protective film according to any one of claims 1 to 8, wherein the pressure-sensitive adhesive layer is formed from an acrylic pressure-sensitive adhesive composition containing an acrylic polymer.
The acrylic polymer comprises 1 to 20% by mass of an alkyl (meth) acrylate having an alkyl group having 1 or 2 carbon atoms and 60 to 92% by mass of an alkyl (meth) acrylate having an alkyl group having 3 to 8 carbon atoms. The surface protective film according to claim 9, which is a copolymer of a monomer containing at least%.
10. The copolymer of a monomer containing at least 0.1 to 2.5% by mass of a carboxyl group-containing monomer and 0.5 to 15% by mass of a hydroxyl group-containing (meth) acrylate. Or the surface protection film of 10.
The surface protective film according to any one of claims 9 to 11, wherein the acrylic pressure-sensitive adhesive composition contains 3 to 20 parts by mass of a crosslinking agent with respect to 100 parts by mass of the acrylic polymer.
The surface protective film according to any one of claims 1 to 12, wherein the pressure-sensitive adhesive layer is formed from a non-energy ray curable pressure-sensitive adhesive composition.
The surface protective film according to any one of claims 1 to 13, which is attached to an imaging module and used to protect a light receiving portion of the imaging module.
The base material has a Young's modulus of 1000 to 2000 MPa and a thickness of 60 to 150 μm.
15. The pressure-sensitive adhesive layer has a storage elastic modulus of 0.15 to 0.35 MPa, a thickness of 5 to 45 μm, and an adhesive force of 0.1 to 0.6 N / 25 mm. 2. The surface protective film according to item 1.
A member with a surface protective film, comprising: a member selected from either an optical member or an electronic member; and the surface protective film according to any one of claims 1 to 15 attached to a surface of the member.
A method for protecting the surface of the optical member or electronic member by applying the surface protective film according to any one of claims 1 to 15 on the surface thereof.