WO2016043275A1

WO2016043275A1 - Surface-protective film

Info

Publication number: WO2016043275A1
Application number: PCT/JP2015/076512
Authority: WO
Inventors: 雄一倉田; 克彦堀米; 仁大橋; 剛史安齋
Original assignee: リンテック株式会社
Priority date: 2014-09-19
Filing date: 2015-09-17
Publication date: 2016-03-24
Also published as: JP6756429B2; TWI673174B; TW201625409A; JPWO2016043275A1

Abstract

　A surface-protective film affixed to an optical member or an electronic member and used for protecting a surface thereof, wherein the surface-protective film is provided with a substrate including a polyethylene terephthalate film, an adhesive layer provided on one side of the substrate, and a release film provided on the adhesive layer, and the surface-protective film satisfies (A) through (D). (A): The bending resistance of the substrate is 5000-85000 mN∙cm. (B): The elastic modulus of the adhesive layer is 1.0×10⁴ to 1.0×10⁷ Pa. (C): The thickness of the release film is at least 20 µm. (D): The ratio of the bending resistance of the substrate and the bending resistance of the release film [Substrate bending resistance/Release film bending resistance] is 1.0 to 4.0. The surface-protective film has excellent working efficiency during affixing and release, and minimal burden on an adherend during releasing therefrom.

Description

Surface protection film

The present invention relates to a surface protective film that is applied to the surface of various optical members and electronic members and used to protect the surface.

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. At this time, optical and electronic components such as unitized imaging modules, camera lens units, motor units such as communication / sensor modules and vibrators are prevented from being scratched during processing, assembly, inspection, transportation, etc. In order to do this, a surface protective film may be stuck on the exposed surface. The surface protective film is peeled off from the optical member or the electronic member when the surface protection is no longer necessary.

Moreover, as a base material of such a surface protective film, for example, it is known to use a polyethylene terephthalate film from the viewpoint of obtaining transparency and a base material such as polyimide or polyethylene naphthalate from the viewpoint of heat resistance. (See Patent Document 1).

JP 2005-341520 A

In recent years, optical members and electronic members as described above have been reduced in size, and the size of the surface protection film has been reduced accordingly. Moreover, since attachment and peeling of a surface protective film are normally performed manually, it is calculated | required that workability | operativity of attachment and peeling is made favorable. Specifically, since the film is small in size, misalignment tends to occur at the time of attachment, and the frequency of reattachment increases. In order to reduce the frequency of re-sticking, improvement in the ease of sticking has been demanded. In addition, if the surface protective film is difficult to peel from the adherend, an excessive load is applied to the optical member or electronic member that is the adherend, and the delicate member is damaged (distortion, scratches, etc.). there is a possibility. Therefore, it is required to improve the peeling performance of the surface protective film.
However, for example, Patent Document 1 does not discuss workability such as sticking and peeling of the surface protective film.

The present invention has been made in view of the above problems, and an object of the present invention is an optical member that is excellent in workability at the time of pasting and peeling, and has a low load on an adherend at the time of peeling work. Or it is providing the surface protection film for electronic members.

As a result of intensive studies, the present inventors have found that the surface protective film has a base material having a specific bending resistance, a pressure-sensitive adhesive layer having a specific elastic modulus provided on one surface of the base material, and the pressure-sensitive adhesive layer. A release film with a thickness of 20 μm or more provided on the agent layer, and the ratio of the bending resistance of the substrate to the bending resistance of the peeling film [the bending resistance of the substrate / the bending resistance of the peeling film It was found that the above problem can be solved when the degree] is 1 or more, and the present invention has been completed.
That is, the present invention provides the following [1] to [8].
[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 including a polyethylene terephthalate film, a pressure-sensitive adhesive layer provided on one surface of the base material, and a release film provided on the pressure-sensitive adhesive layer,
A surface protective film satisfying the following (A) to (D).
(A) The bending resistance of the base material is 5000 to 85000 mN · cm.
(B) The elastic modulus of the pressure-sensitive adhesive layer is 1.0 × 10 ⁴ to 1.0 × 10 ⁷ Pa.
(C) The thickness of the release film is 20 μm or more. (D) The ratio of the stiffness of the substrate to the stiffness of the release film [the stiffness of the substrate / the stiffness of the release film] is 1. .0 to 4.0
[2] The surface protective film according to [1], wherein the pressure-sensitive adhesive layer is made of a pressure-sensitive adhesive composition containing an acrylic copolymer.
[3] The surface protective film according to [2], wherein the pressure-sensitive adhesive composition containing the acrylic copolymer further contains a silane coupling agent.
[4] The surface protective film according to any one of [1] to [3], wherein the bending resistance of the base material is 50000 mN · cm or less.
[5] The above [1] to [1], wherein the adhesive strength of the surface protective film to the liquid crystal plastic under conditions of 80 ° C. and 23 ° C. before and after heating for 2 hours and 50% RH (relative humidity) is 400 to 1000 mN / 25 mm. [4] The surface protective film according to any one of [4].
[6] The surface protective film according to any one of the above [1] to [5], wherein the peeling film has a peeling force of 50 to 200 mN / 50 mm.
[7] The surface protective film according to any one of [1] to [6] above, wherein the size of the surface protective film is 100 mm ² or less.
[8] A method of protecting the surface protective film according to any one of [1] to [7] by attaching the surface protective film to the surface of an optical member or an electronic member after peeling the release film.

According to the present invention, it is possible to provide a surface protective film for an optical member or an electronic member that is excellent in workability at the time of pasting and peeling and has a small load on the adherend during the peeling work.

In the description of the present specification, “weight average molecular weight (Mw)” is a value in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method, specifically, the method described in the examples. Based on the measured value.
In addition, in the description in the present specification, for example, “(meth) acrylate” is a term meaning both “acrylate” and “methacrylate”, and other similar terms are also the same.

[Surface protection film]
The surface protective film of the present invention is used to protect the surface of an optical member or an electronic member, and is provided on a base material including a polyethylene terephthalate film and one surface of the base material. And a release film provided on the pressure-sensitive adhesive layer and satisfying the following (A) to (D).
(A) The bending resistance of the base material is 5000 to 85000 mN · cm.
(B) The elastic modulus of the pressure-sensitive adhesive layer is 1.0 × 10 ⁴ to 1.0 × 10 ⁷ Pa.
(C) The thickness of the release film is 20 μm or more. (D) The ratio of the stiffness of the substrate to the stiffness of the release film [the stiffness of the substrate / the stiffness of the release film] is 1. .0 to 4.0
Hereinafter, each member of the surface protective film will be described. In the following, the “adhesive film” refers to a configuration composed of a portion of the surface protective film excluding the release film.

<Base material>
The substrate possessed by the surface protective film of the present invention is a substrate including a polyethylene terephthalate film, and has a bending resistance of 5000 to 85000 mN · cm.
When a base material having a bending resistance of less than 5000 mN · cm is used, when the obtained surface protection film is applied to the surface of an optical member or an electronic member, the surface protection film is weak, so it is applied to the target application position. It becomes difficult to work and the workability is inferior.
Further, when a base material having a bending resistance exceeding 85000 mN · cm is used, when the adhesive film affixed to the surface of the optical member or electronic member is peeled off from the surface of the member, the adhesive film is too strong to be easily peeled off. Workability is inferior. Furthermore, when an adhesive film is peeled off, an unnecessary load is applied to the optical member or the electronic member, which may damage the member.
In particular, in the case of performing manual attachment and peeling work, the sticking and peeling work described above becomes more difficult because a small-sized surface protective film is handled using a tool such as tweezers.
From such a viewpoint, the bending resistance of the substrate is preferably 10,000 mN · cm or more, more preferably 15000 mN · cm or more, and preferably 50000 mN · cm or less, more preferably 45000 mN · cm or less. .
The bending resistance is a value measured by a method according to JIS L 1913. More specifically, the bending resistance is a value measured and calculated based on a method described in Examples described later.

The polyethylene terephthalate film may further be laminated with a film made of one or more resins selected from the following resins.
The resin film laminated on the polyethylene terephthalate film is not particularly limited as long as the bending resistance of the substrate is in the above range. For example, polyester such as polyethylene naphthalate, polybutylene terephthalate, wholly aromatic polyester, polyamide, polyimide , Resin films made of polyacetal, polycarbonate, modified polyphenylene oxide, polyphenylene sulfide, polysulfone, polyether ketone, polypropylene, polyethylene, or biaxially stretched films thereof.

Moreover, the base material used in the present invention may contain a filler, a colorant, an antistatic agent, a flame retardant, an antioxidant, an organic lubricant, a catalyst, and the like as long as the effects of the present invention are not impaired.
Further, the substrate may be transparent or opaque, and may be colored or vapor-deposited as desired.
In addition, in order to improve the adhesiveness with the pressure-sensitive adhesive layer, at least one surface of the substrate used in the present invention may be subjected to an adhesion treatment such as a corona treatment, or may be provided with an easy adhesion layer described later. Good.
Further, the thickness of the substrate is not particularly limited as long as the bending resistance of the substrate is in the above range, but the workability at the time of attaching and peeling the surface protective film of the present invention to the optical member or the electronic member is improved. From the viewpoint of improving the thickness, the thickness is preferably 40 to 150 μm, more preferably 50 to 130 μm, and still more preferably 70 to 110 μm.

<Adhesive layer>
The adhesive layer of the surface protective film of the present invention has an elastic modulus of 1.0 × 10 ⁴ to 1.0 × 10 ⁷ Pa.
When a pressure-sensitive adhesive layer having an elastic modulus of less than 1.0 × 10 ⁴ Pa is used, the difference in pressure-sensitive adhesive strength before and after heating at 80 ° C. of the obtained surface protective film becomes large. It becomes difficult.
Moreover, when an adhesive layer having an elastic modulus exceeding 1.0 × 10 ⁷ Pa is used, the adhesive layer becomes too hard when the adhesive film attached to the optical member or electronic member surface is peeled off from the member surface. Therefore, it becomes difficult to peel off and workability is inferior. Furthermore, when an adhesive film is peeled off, an unnecessary load is applied to the optical member or the electronic member, which may damage the member.
From such a viewpoint, the elastic modulus of the pressure-sensitive adhesive layer is preferably 1.0 × 10 ⁵ to 1.5 × 10 ⁶ Pa, more preferably 1.5 × 10 ⁵ to 1.2 × 10 ⁶ Pa. is there.
More specifically, the above-described elastic modulus is a value measured based on the method described in Examples described later.

Although it does not specifically limit as an adhesive which forms the adhesive layer which the surface protection film of this invention has, For example, an acrylic adhesive, a urethane adhesive, a silicone adhesive, a rubber adhesive, a polyester adhesive Is mentioned.
These pressure-sensitive adhesives may be used alone or in combination of two or more.

In the said adhesive, it is preferable that it is an acrylic adhesive. Moreover, when it is the said acrylic adhesive, it is generally an acrylic adhesive (henceforth an "acrylic adhesive composition") containing an acrylic copolymer.
The acrylic copolymer usually constitutes a pressure-sensitive adhesive component in the pressure-sensitive adhesive layer, and is hereinafter also referred to as “main polymer”.
In the following description, an example in the case of an acrylic pressure-sensitive adhesive will be mainly described, but the same applies to other types of pressure-sensitive adhesives. In this case, the main polymer constituting the pressure-sensitive adhesive component is acrylic. A polymer other than the copolymer is used.
The acrylic copolymer is obtained by copolymerizing a monomer component containing alkyl (meth) acrylate as a main monomer (hereinafter also referred to as “copolymer component”). Examples of the alkyl (meth) acrylate include those having 1 to 18 carbon atoms in the alkyl group, such as methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, and butyl. (Meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate Etc.
The acrylic copolymer preferably contains 50% by mass or more, more preferably 50 to 99% by mass of alkyl (meth) acrylate as a copolymer component with respect to the total amount of the copolymer component.

The acrylic copolymer contains, as a copolymer component, an alkyl (meth) acrylate having an alkyl group having 3 or more carbon atoms among alkyl (meth) acrylates in an amount of 30 to 98 mass based on the total amount of the copolymer component. % Content is preferable. By making content of the alkyl (meth) acrylate whose carbon number of an alkyl group is 3 or more into such a range, it becomes easy to provide suitable adhesive performance and peeling performance to a surface protection film. From such a viewpoint, the content of the alkyl (meth) acrylate having 3 or more carbon atoms in the alkyl group is more preferably 40 to 97% by mass, and further preferably 45 to 96% by mass.

The alkyl (meth) acrylate having 3 or more carbon atoms in the alkyl group is preferably an alkyl (meth) acrylate in which the alkyl group has 3 to 8 carbon atoms, and the alkyl group has 4 to 8 carbon atoms. Alkyl (meth) acrylates are more preferred, and alkyl acrylates having an alkyl group with 4 to 8 carbon atoms are even more preferred. Specifically, n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, and the like are preferable.

The acrylic copolymer contains 5 alkyl (meth) acrylates having 1 or 2 carbon atoms in the alkyl group among the alkyl (meth) acrylate as a copolymer component, based on the total amount of the copolymer component. It may be contained in an amount of up to 50% by mass.
More preferably, the acrylic copolymer contains 10 to 40% by mass of an alkyl (meth) acrylate having 1 or 2 carbon atoms in the alkyl group as a copolymer component, based on the total amount of the copolymer component. 15 to 35% by mass is more preferable.
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 acrylate and methyl methacrylate are preferable.

The acrylic copolymer preferably contains a polymerizable monomer other than alkyl (meth) acrylate as the copolymer component, and specifically contains a functional group-containing monomer. The functional group-containing monomer provides a functional group necessary for reaction with a cross-linking agent described later. 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.

The acrylic copolymer is preferably a copolymer component obtained by copolymerizing a copolymer component containing 0.1 to 40% by mass of a functional group-containing monomer with respect to the total amount of the copolymer component. When the content of the functional group-containing monomer is within the above range, the acrylic copolymer can be appropriately crosslinked with a crosslinking agent described later.
The content of the functional group-containing monomer is more preferably 0.2 to 30% by mass. When the functional group-containing monomer is 0.2 to 30% by mass, it is possible to appropriately crosslink the acrylic copolymer with a cross-linking agent to be described later while ensuring appropriate adhesive performance.

Here, examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, and itaconic acid.
Specific examples of the hydroxyl group-containing (meth) acrylate include hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2 -Hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and the like.
Moreover, as a monomer which has an epoxy group in a molecule | numerator, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether etc. are mentioned, for example.
The above functional group-containing monomers may be used alone or in combination of two or more.

In addition to the above monomers, the acrylic copolymer is a copolymer of (meth) acrylic acid esters, dialkyl (meth) acrylamides, vinyl formate, vinyl acetate, and styrene other than alkyl (meth) acrylate and functional group-containing monomers. It may be included as a coalescence component. As (meth) acrylic acid esters other than (meth) acrylic acid alkyl esters and functional group-containing monomers, (meth) acrylic acid alkoxyalkyl esters, (meth) acrylic acid alkyleneoxyalkyl esters, (meth) acrylic acid nonylphenoxy polyethylene Glycol, tetrahydrofuran furfuryl acrylate, diacrylates which are esters of polyether and acrylic acid, and the like may also 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 copolymer is preferably 100,000 or more, more preferably 100,000 to 1500,000, and still more preferably 150,000 to 1,000,000.

Moreover, when using the adhesive composition containing an acryl-type copolymer, it is preferable to contain a silane coupling agent further.
As the silane coupling agent, an organosilicon compound having at least one alkoxysilyl group in the molecule, having good compatibility with the pressure-sensitive adhesive component and having light transmittance, for example, a substantially transparent one. Is preferred. The amount of such a silane coupling agent is preferably 0.01 to 1.5 parts by weight, particularly 0.05 to 1.0 parts by weight, based on 100 parts by weight of the acrylic copolymer. It is preferable.
Examples of the silane coupling agent include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, (meth) acryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 2 Silicon compounds having an epoxy structure such as-(3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- ( Examples include amino group-containing silicon compounds such as 2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, and 3-isocyanatopropyltriethoxysilane. You may use these 1 type or in combination of 2 or more types.

The pressure-sensitive adhesive layer may have a crosslinked structure in which an acrylic copolymer is crosslinked. Examples of the crosslinking agent contained in the pressure-sensitive adhesive composition for crosslinking include an organic polyvalent isocyanate compound, an organic polyvalent epoxy compound, and an organic polyvalent imine compound.

Examples of organic polyvalent isocyanate compounds include aromatic polyvalent isocyanate compounds, aliphatic polyvalent isocyanate compounds, alicyclic polyvalent isocyanate compounds, trimers of these organic polyvalent isocyanate compounds, and these organic polyvalent isocyanate compounds. Examples thereof include terminal isocyanate urethane prepolymers obtained by reacting with a polyol compound.

Further specific examples of the organic polyvalent isocyanate compound 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, tolylene diisocyanate Examples include adducts of trimethylolpropane.

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

Specific examples of the organic polyvalent imine compound include N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, tetra Examples include methylolmethane-tri-β-aziridinylpropionate and N, N′-toluene-2,4-bis (1-aziridinecarboxamide) triethylenemelamine.

The content of the crosslinking agent is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, and still more preferably 0.5 to 8 parts by mass with respect to 100 parts by mass of the acrylic copolymer. It is used in the ratio. When the content of the cross-linking agent is not more than the above upper limit value, the pressure-sensitive adhesive layer is prevented from being excessively cross-linked, and appropriate adhesive force is easily obtained. Moreover, by making the usage-amount of a crosslinking agent more than the said lower limit, it is prevented that an adhesive adheres to an electronic member or an optical member.

Moreover, the pressure-sensitive adhesive layer may be colored so that the light transmittance of the surface protective film is less than 80%. The visibility of the surface protective film is improved by coloring the pressure-sensitive adhesive layer. Therefore, for example, when the surface protective film is peeled off manually from a release film described later, or because the surface protective film is easily attached to the adherend to be protected, it is easy to peel off, and , Can also prevent forgetting to peel off. The light transmittance of the surface protective film is measured with a spectrophotometer UV-3600 manufactured by Shimadzu Corporation at a wavelength of 600 nm. The light transmittance is preferably about 30 to 70%.
In order to color the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition usually contains a dye and a pigment, and among them, a blue dye and a blue pigment are preferably contained.

In addition, the above-mentioned pressure-sensitive adhesives include antioxidants, softeners (plasticizers), deterioration inhibitors, antistatic agents, flame retardants, rust inhibitors, fillers, silicone compounds, chain transfer agents, and other components other than those described above. Components may be appropriately contained.

<Peeling film>
A release film is affixed to the pressure-sensitive adhesive layer side of the surface protective film of the present invention.
The release film of the surface protective film of the present invention has a thickness of 20 μm or more.
When a release film having a thickness of less than 20 μm is used, when performing the punching process of the surface protective film to be obtained, even when only the portion composed of the base material layer and the pressure-sensitive adhesive layer in the surface protective film is to be extracted, Problems such as extraction of the release film (all extraction) are likely to occur, and the punching processability is poor.
From such a viewpoint, the thickness of the release film is preferably 30 μm or more, more preferably 50 μm or more. Moreover, Preferably it is 150 micrometers or less, More preferably, it is 100 micrometers or less.
As the release film of the present invention, a release film that has been subjected to a double-sided release process, a release film that has been subjected to a single-sided release process, or the like is used, and examples include those in which a release agent is applied on the surface of a release film substrate.
As the substrate for the release film, a resin film is preferable. Examples of the resin constituting the resin film include a polyester resin such as a polyethylene terephthalate resin, a polybutylene terephthalate resin, and a polyethylene naphthalate resin, a polypropylene resin, and a polyethylene resin. Examples include polyolefin resins.
Examples of the release agent include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long chain alkyl resins, alkyd resins, and fluorine resins.

The release film of the surface protective film of the present invention preferably has a bending resistance of 2000 to 42500 mN · cm.
When the bending softness of the release film is 2000 mN · cm or more, the stiffness does not become too weak, and the surface protection film can be easily handled. Moreover, when the bending softness of the release film is 42500 mN · cm or less, the stiffness does not become too strong, and the release film is easily peeled off from the adhesive film manually.
From such a viewpoint, the bending resistance of the release film is more preferably 6000 mN · cm or more. More preferably, it is 30000 mN / cm or less.
The bending resistance is a value measured by a method according to JIS L 1913. More specifically, the bending resistance is a value measured and calculated based on a method described in Examples described later.
The release film of the surface protective film of the present invention preferably has a peel strength of 50 mN / 50 mm or more and 200 mN / 50 mm or less.
In the punching process, a punching blade is inserted so as to reach the release film from the surface of the surface protective film on the base material side, and only the adhesive film is punched into a predetermined shape. After extracting the punching blade from the surface protective film, an unnecessary portion of the adhesive film is peeled off and removed, but at this time, a necessary portion as the adhesive film may be removed together (hereinafter, “ It is also called “to rise.”
If the release force of the release film is 50 mN / 50 mm or more, it is possible to prevent an increase during the punching process. Moreover, if peeling force is 200 mN / 50 mm or less, peeling of a peeling film will become easy and the workability | operativity at the time of bonding work will improve.
From such a viewpoint, the peeling force of the release film is more preferably 70 mN / 50 mm or more, and still more preferably 100 mN / 50 mm or more.
The above-described peeling force is a value measured based on the method described in Examples described later.

The ratio of the stiffness of the substrate and the stiffness of the release film [the stiffness of the substrate / the stiffness of the release film] of the surface protective film of the present invention is 1.0 to 4.0. It is.
When the ratio is less than 1.0, when the film is a small size, when the release film of the surface protection film is folded, the adhesive film partially peeled from the release film is peeled off at the time of application. As a trigger), it is difficult to peel off the adhesive film from the release film (also referred to as “cueing”), so it is easy to cause misalignment when sticking to the adherend, and the frequency of reattachment increases. Workability at the time of pasting is inferior.
In general, the thicker the substrate, the higher the bending resistance of the substrate. The same applies to the release film.
Therefore, if the ratio exceeds 4.0, the effect of the thickness difference between the part with the adhesive film and the part without the adhesive film (part of the release film only) becomes large, and the surface protective film becomes difficult to handle. The workability at the time of peeling the release film from the adhesive film is reduced. For example, a bundle of several surface protection films of the present invention, gripping both ends thereof by hand, and work for aligning the ends of the bundled surface protection films (eg, grasping a bundle of surface protection films gripping both ends) For example, when one side of the non-side is slightly dropped on the cutter board several times to align the edges, the gap between the surface protection films is large if there is a large difference in thickness between the part with and without the adhesive film. Becomes wider, the surface protective films are easily displaced, and the working efficiency is reduced. From such a viewpoint, the ratio is preferably 1.0 or more and 3.0 or less.

<Easily adhesive layer>
The base material of the present invention may have an easy adhesion layer on the surface on which the pressure-sensitive adhesive layer is provided in order to improve adhesion.
Although it does not specifically limit as a composition for easy-adhesion layer formation which forms an easy-adhesion layer, For example, the composition containing a polyester-type resin, a urethane-type resin, a polyester urethane-type resin, an acrylic resin etc. is mentioned.
The easy-adhesion layer-forming composition contains a crosslinking agent, a photopolymerization initiator, an antioxidant, a softening agent (plasticizer), a filler, a rust inhibitor, a pigment, a dye, and the like as necessary. May be.
The thickness of the easy adhesion layer is preferably 0.01 to 10 μm, more preferably 0.03 to 5 μm.

The size of the surface protective film is preferably 100 mm ² or less, more preferably about 10 to 80 mm ² . In addition, the size of the surface protective film here refers to the area of the adhesive film portion. The size of the adhesive film is reduced depending on the optical member and the electronic member. Generally, when the size of the surface protective film is reduced, operations such as pasting and peeling become difficult. Since the surface protective film of the present invention has good peeling performance as described above, it is easy to peel off even by manual work. The shape of the adhesive film is not limited, but is processed into, for example, a circle, a square, a rectangle, an annular shape, or the like.

The surface protective film preferably has an adhesive strength to liquid crystal plastic of 400 to 1000 mN / 25 mm under conditions of 23 ° C. and 50% RH (relative humidity) before and after heating at 80 ° C. for 2 hours.
When the adhesive strength before and after heating at 80 ° C. for 2 hours is 400 mN / 25 mm or more, the adhesive strength of the surface protective film to the optical member and the electronic member is increased, and the protective performance is improved. In addition, the adhesive force before and after heating at 80 ° C. for 2 hours is 1000 mN / 25 mm or less, so that the adhesive film can be easily peeled off from the optical member or the electronic member as the adherend, It is possible to prevent an excessive load from being applied to the adherend. Moreover, the optical member or the electronic member to which the adhesive film is attached may be heated in processes such as processing, attachment, inspection, or conveyance. When the adhesive strength of the adhesive film is increased by heating, workability at the time of peeling the adhesive film is lowered. Therefore, the adhesive strength of the surface protective film before and after heating the surface protective film at 80 ° C. for 2 hours is 400 to The range is preferably 1000 mN / 25 mm.
From such a point of view, the adhesive strength to liquid crystal plastics under conditions of 23 ° C. and 50% RH (relative humidity) before and after heating for 2 hours at 80 ° C. is preferably 450 to 800 mN / 25 mm, more preferably 500 to 800 mN / 25 mm.
The above-mentioned adhesive strength can be adjusted by the kind and blending ratio of the monomers constituting the main polymer constituting the aforementioned pressure-sensitive adhesive layer, the amount of the crosslinking agent used, and the like. It is also affected by the bending resistance of the substrate.
More specifically, the above-mentioned adhesive strength of the surface protective film is a value measured based on the method described in Examples described later.

<Method for producing surface protective film>
There is no restriction | limiting in particular as a manufacturing method of the surface protection film of this invention, It can manufacture by a well-known method.
For example, a pressure-sensitive adhesive composition diluted with an appropriate solvent as required is applied on a release film so as to have a predetermined dry film thickness, and then dried to form a pressure-sensitive adhesive layer. What is necessary is just to form a material by bonding together. Moreover, the adhesive composition diluted with a suitable solvent as needed may be directly applied to the substrate, and then dried to form an adhesive layer, and a release film may be bonded thereon.
Moreover, a surface protection film may provide an adhesive layer partially on a support body (the said base material or peeling film), and may form a non-adhesion part with an adhesion part on a support body. In order to create a surface protective film partially provided with an adhesive layer, screen printing or inkjet printing may be performed. The adhesive portion and the non-adhesive portion may be arranged in any pattern selected from a stripe shape, a lattice shape, a dot shape, a shape in which a plurality of wavy lines are arranged, a checkered pattern, and a shape in which various patterns are arranged in a plurality. Other shapes may be preferable.
In addition, when an adhesive layer is partially provided in pattern shape, the pattern is normally provided in the whole surface of a support body.
In addition, the surface protective film may be provided with a pressure-sensitive adhesive layer on the entire surface of the substrate, and a partially non-adhesive resin layer may be further formed on the pressure-sensitive adhesive layer. In order to create the non-adhesive resin layer, screen printing or inkjet printing may be performed. The non-adhesive resin layer is arranged in any pattern selected from a stripe shape, a lattice shape, a dot shape, a shape in which a plurality of wavy lines are arranged, a checkered pattern, and a shape in which various patterns are arranged in a plurality. Is preferable, and other shapes may be used.
Furthermore, in each pattern that can be taken by the adhesive part and the non-adhesive part of the adhesive layer partially provided on the support, and in each pattern that the non-adhesive resin layer can take, the pitch of the pattern (that is, The distance between adjacent adhesive parts or the distance between adjacent non-adhesive parts is preferably 10 to 500 μm, more preferably 10 to 300 μm, and particularly preferably 10 to 250 μm.
That is, the width of each stripe and the interval between stripes, the width of each wavy line and the interval between wavy lines, the width of each line forming the lattice, the interval between adjacent lines constituting the lattice, the interval between dots The width and height of the dots, or the height and width of each square constituting the checkered pattern is preferably 10 to 500 μm, more preferably 10 to 300 μm, and particularly preferably 10 to 250 μm.
Further, the punching process may be performed before or after the pressure-sensitive adhesive layer is formed. For example, the punching process may be performed on the laminate of the base material and the pressure-sensitive adhesive layer provided on the release film. By the punching process, as described above, the shape of the pressure-sensitive adhesive film is circular, square, rectangular, or annular. The shape such as the shape can be adjusted. In the punching process, a punching blade is inserted so as to reach the release film from the surface of the surface protective film on the base material side, and only the adhesive film is punched into a predetermined shape. After extracting the punching blade from the surface protective film, the surface protective film can be obtained by removing unnecessary portions of the adhesive film. Moreover, you may form an unevenness | corrugation suitably in a surface protection film by stamping etc. at arbitrary timings.
In the surface protective film thus obtained, for example, a plurality of pressure-sensitive adhesive films (for example, circular pressure-sensitive adhesive films) are provided on a single release film, and then the release film portion is appropriately removed with a cutter or the like. It can cut | disconnect and it can also process a surface protection film (a peeling film is included) into a desired shape.

[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 protecting the surface of the optical member or electronic member by attaching the surface protective film after peeling the release film. Specifically, an optical member or an electronic member (hereinafter, also simply referred to as “member with a surface adhesive film”) to which an adhesive film is attached is processed, attached to another member, inspected, transported, or the like. Although it is a thing, an adhesive film protects the surface of an optical member or an electronic member in these processes. Further, the adhesive 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, sticking and peeling of a surface protection film are normally performed manually. At that time, by using the surface protective film of the present invention, it is difficult to cause a shift in the attaching position when attaching to the surface of the optical member or the electronic member, so that the frequency of reattaching is reduced. Moreover, since the adhesive film once pasted can be peeled off without applying an excessive load even when peeled off from the adherend, it damages the optical member and electronic member which are adherends (causes distortion). , Etc.) can be prevented.
In addition, the member with an adhesive film may be heated in processes, such as an above-described process, attachment, an inspection, or conveyance. The heating temperature at that time is not particularly limited, but is about 60 to 200 ° C., preferably about 70 to 150 ° C.

It is preferable that the optical member or the electronic member (the member with the adhesive film) to which the adhesive film is attached is attached to another member such as a substrate with an adhesive, for example. At this time, a thermosetting adhesive is used, and in order to cure the adhesive, the member with a surface protective film is usually at a temperature of 60 to 200 ° C. or higher, preferably about 70 to 150 ° C. as described above. Heating is preferred. Then, when surface protection becomes unnecessary, the adhesive film is peeled from the optical member or the electronic member.

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 adhesive 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. Since the adhesive film adheres to the light receiving portion and the surface of the casing or package around the light receiving portion with high adhesion, it is possible to appropriately protect the light receiving portion provided on one surface of the imaging module. Moreover, the adhesive film can be easily peeled off from the imaging module, and an excessive load is prevented from being applied to the light receiving portion and the like.
In addition, as above-mentioned, it is preferable that the imaging module with which the adhesive film was stuck is heated for hardening of a thermosetting adhesive, and is attached to other members, such as a board | substrate.

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.
[Measuring method]
<Weight average molecular weight of acrylic copolymer (Mw)>
Using a gel permeation chromatograph, measurement was performed under the following conditions, and values measured in terms of standard polystyrene were 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
<Flexibility of base material>
By a method according to JIS L 1913, the flow direction (Machine Direction; hereinafter referred to as “MD direction”) during molding of the substrate and the direction perpendicular to the flow direction during molding of the substrate (Transverse Direction. , “TD direction”), and measurement was performed for each. However, a 45 ° cantilever type tester was used, and the substrate was cut into 20 mm × 150 mm test pieces. Two test pieces used for the measurement were prepared in each of the MD direction and the TD direction. Here, the test piece in the MD direction means that the longitudinal direction of the test piece is the MD direction of the substrate. Similarly, the test piece in the TD direction indicates that the longitudinal direction of the test piece is the TD direction of the substrate.
For each test piece, the bending length (mN · cm) was measured four times in total, twice on the front surface (both ends) and twice on the back surface (both ends). The average value was calculated for the measurement results for the four times.
From the measured value of the bending length of two test pieces in the MD direction and the mass per unit area (g / m ² ) of the test piece used for the measurement, the calculation formula described in JIS L 1913 is used. MD bending resistance was calculated. Similarly, in the TD direction, the TD bending resistance was calculated using the measurement values of the bending lengths of two test pieces.
The calculated values of MD bending resistance and TD bending resistance were averaged to obtain the bending resistance (mN · cm) of the base material.
<Bending softness of release film>
The bending length (mN · cm) in the MD direction and the TD direction of the release film was measured using the same method as the measurement method described in “Bending and bending resistance of base material”. And the bending softness (mN * cm) of a peeling film was computed using the method similar to the calculation method of "the bending softness of a base material".

<Elastic modulus>
The storage elastic modulus (G ′) of the pressure-sensitive adhesive layer was obtained by laminating a layer of a pressure-sensitive adhesive composition having a thickness of 30 μm, producing a cylindrical test piece having a thickness of 8 mmφ × 3 mm, and using a torsional shear method under the following conditions: It is measured.
Measuring device: Dynamic viscoelasticity measurement “Physica MCR 300” manufactured by Anton Paar
Frequency: 1Hz
Temperature: 23 ° C

<Measurement of normal adhesive strength (adhesive strength before heating)>
After cutting the surface protective film into a 25 mm x 250 mm shape, the sample from which the surface protective film was peeled off was cut into a 3 mm x 70 mm x 150 mm shape with a 2 kg roller. , Manufactured by Polyplastics Co., Ltd.) to prepare a tensile test piece. The test piece was stored for 24 hours in an environment of 23 ° C. and 50% RH (relative humidity). Thereafter, the test piece was pulled using a tensile tester (trade name: “RTG-1225”, manufactured by A & D Co., Ltd.) in an environment of 23 ° C. and 50% RH (relative humidity). The adhesive force when the sample was peeled off from the adherend at a speed of 300 mm / min and a peeling direction of 180 ° was measured to obtain a normal state adhesive force (adhesive force before heating).
<Measurement of adhesive strength after heating>
After cutting the surface protective film into a 25 mm × 250 mm shape, the sample from which the surface protective film was peeled off was cut with a 2 kg roller into a 3 mm × 70 mm × 150 mm shape liquid crystal plastic “Vectra LCP” (trade name, A tensile test piece was prepared by pasting onto Polyplastics Co., Ltd. The test piece was stored for 24 hours in an environment of 23 ° C. and 50% RH (relative humidity), and then heated in an oven at 80 ° C. for 2 hours. The heated test piece was further stored for 24 hours in an environment of 23 ° C. and 50% RH (relative humidity). Thereafter, the test piece was used in an environment of 23 ° C. and 50% RH (relative humidity) using a tensile tester (trade name: “RTG-1225”, manufactured by A & D Co., Ltd.) The adhesive strength when the sample was peeled from the adherend at a pulling speed of 300 mm / min and a peeling direction of 180 ° was measured and used as the adhesive strength after heating.

<Measurement of peel strength of release film>
After the surface protective film is cut into a shape of 50 mm × 250 mm, one of the short sides of the release film of the surface protective film is peeled off and bent, and the tensile speed is 300 mm / min in an environment of 23 ° C. and 50% RH (relative humidity). The peel strength of the peeled film was measured by measuring the adhesive strength when the sample was peeled from the adherend in a peel direction of 180 °.

[Method for evaluating surface protective film]
<Attachment workability>
The adhesive film that had been punched into a size of 9 mmφ (63.6 mm ² ) was peeled from the release film using tweezers, and the workability when it was attached to the camera module was evaluated according to the following criteria. The evaluation was performed by five workers, and each worker determined 1 point or 0 point, and the evaluation was performed with a total of 0 to 5 points.
1 point: Easy to work.
0 points: Difficult to work.
<Peeling workability>
The adhesive film punched into a size of 9 mmφ (63.6 mm ² ) was bonded to a camera module to produce a sample for evaluation. The evaluation sample was heated at 80 ° C. for 2 hours, and then allowed to stand until the temperature of the evaluation sample reached room temperature. Then, the workability | operativity when peeling an adhesive film from a camera module with a finger was evaluated on the following references | standards. The evaluation was performed by five workers, and each worker determined 1 point or 0 point, and the evaluation was performed with a total of 0 to 5 points.
1 point: Easy to work.
0 points: Difficult to work.
<Module failure prevention degree>
An adhesive film die-cut to a size of 9 mmφ (63.6 mm ² ) was bonded to the camera module to produce a sample for evaluation. The sample was heated at 80 ° C. for 2 hours and then allowed to stand until the sample temperature reached room temperature. Then, the adhesive film was peeled from the camera module with a finger. Defects in the camera module after peeling the adhesive film (the spring in the camera module was completely damaged) were confirmed and evaluated according to the following criteria. Five camera modules were used in one test, 1 point or 0 point was determined for each camera module, and evaluation was made with a total of 0 to 5 points.
1 point: No problem.
0 point: There is a defect.

[Example 1]
Copolymerization of 68.6 parts by mass of 2-ethylhexyl acrylate (2EHA), 30 parts by mass of methyl acrylate (MA), 0.2 parts by mass of glycidyl methacrylate (GMA), and 1.2 parts by mass of acrylic acid (AA) 1 part by mass of 3-glycidoxypropyltrimethoxysilane (GPTMS) as a silane coupling agent and trimethylolpropane-trimethyl as a crosslinking agent with respect to 100 parts by mass of the acrylic copolymer (weight average molecular weight 750,000) Coating solution prepared by adding 0.5 parts by mass of β-aziridinylpropionate in a dry weight ratio and diluted to 30% by weight with a mixed solvent of toluene: methyl ethyl ketone = 90: 10 (mass ratio) It was.
This coating liquid is applied to the release surface of a 75 μm-thick polyester film “SP-PET752150” (trade name, manufactured by Lintec Co., Ltd.) as a release film so that the thickness after drying with a roll knife coater is 18 μm. After coating and drying at 90 ° C. for 1 minute, the substrate is bonded to an adhesive polyester film “Cosmo Shine A4300” (trade name, manufactured by Toyobo Co., Ltd.) having a thickness of 75 μm, and then 7 days at 23 ° C. A surface protective film was obtained by aging.
The elastic modulus of the pressure-sensitive adhesive layer was 1.2 × 10 ⁶ Pa.

[Example 2]
A surface protective film was produced in the same manner as in Example 1 except that an easily adhesive polyester film “Cosmo Shine A4300” (trade name, manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm was used as the substrate.

[Example 3]
48 parts by mass of 2-ethylhexyl acrylate (2EHA), 48 parts by mass of n-butyl acrylate (BA), 3.64 parts by mass of acrylic acid (AA), 0.36 parts by mass of 2-hydroxypropyl acrylate (2HPA), Trimethylolpropane adduct tolylene diisocyanate (trade name: “Coronate L”, manufactured by Nippon Polyurethane Industry Co., Ltd.) as a crosslinking agent for 100 parts by mass of an acrylic copolymer (weight average molecular weight 600,000) ) Was added at a dry weight ratio of 6.6 parts by mass, and diluted with a mixed solvent of toluene: methyl ethyl ketone = 90: 10 (mass ratio) to a solid content of 30% by mass. In the same manner as in Example 1, a surface protective film was produced.
The elastic modulus of the pressure-sensitive adhesive layer was 7.2 × 10 ⁴ Pa.

[Example 4]
A 50 μm thick easily adhesive polyester film “Cosmo Shine A4300” (trade name, manufactured by Toyobo Co., Ltd.) is used as the base material, and a 38 μm thick polyester film “SP-PET 382150” (trade name) is used as the release film. A surface protective film was produced in the same manner as in Example 1 except that the product was manufactured by Lintec Corporation.

[Comparative Example 1]
A surface protective film was produced in the same manner as in Example 1 except that a 38 μm thick polyester film “Diafoil PET” (trade name, manufactured by Mitsubishi Resin Co., Ltd.) was used as the base material.

[Comparative Example 2]
A 150 μm thick easily adhesive polyester film “Cosmo Shine A4300” (trade name, manufactured by Toyobo Co., Ltd.) is used as the base material, and a 50 μm thick polyester film “SP-PET502150” (trade name) is used as the release film. A surface protective film was produced in the same manner as in Example 1 except that the product was manufactured by Lintec Corporation.

[Comparative Example 3]
A surface protective film was produced in the same manner as in Example 1 except that a polyester film “SP-PET502150” (trade name, manufactured by Lintec Corporation) having a thickness of 38 μm was used as the release film.

[Comparative Example 4]
A surface protective film was produced in the same manner as in Example 1, except that an easily adhesive polyester film “Cosmo Shine A4300” (trade name, manufactured by Toyobo Co., Ltd.) having a thickness of 188 μm was used as the substrate.

From Table 1, it can be seen that the surface protective films prepared in Examples 1 to 4 are excellent in both attachment workability and peeling workability, and no module failure occurs.
On the other hand, the surface protective film produced in Comparative Example 1 has no problem in peeling workability, and no module failure has occurred. However, since the bending resistance of the substrate is low and the bending resistance ratio is less than 1.0, the stiffness of the substrate is weak and the workability is poor.
Moreover, the surface protection film produced in Comparative Example 3 has no difference in peeling workability from the surface protection film produced in Example 3, and no module failure has occurred. However, since the bending resistance ratio exceeded 4.0, the result was inferior to the workability of pasting.
Moreover, since the surface protection film produced in Comparative Examples 2 and 4 has a bending resistance ratio exceeding 4.0, it is inferior in sticking workability, and further, the bending work is too high because the bending resistance of the base material is too high. As a result, the module malfunctioned.

The surface protective film of the present invention is excellent in workability at the time of sticking and peeling, and has a small load on the adherend during the peeling work.
Therefore, the surface protective film of the present invention can be suitably used as, for example, a surface protective film that protects the surface of an optical member or an electronic member. It is possible to effectively prevent damage to the adherend when it is peeled off from the adherend and the frequency of reattachment due to.

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 including a polyethylene terephthalate film, a pressure-sensitive adhesive layer provided on one surface of the base material, and a release film provided on the pressure-sensitive adhesive layer,
A surface protective film satisfying the following (A) to (D).
(A) The bending resistance of the base material is 5000 to 85000 mN · cm.
(B) The elastic modulus of the pressure-sensitive adhesive layer is 1.0 × 10 4 to 1.0 × 10 7 Pa.
(C) The thickness of the release film is 20 μm or more. (D) The ratio of the stiffness of the substrate to the stiffness of the release film [the stiffness of the substrate / the stiffness of the release film] is 1. .0 to 4.0
The surface protective film according to claim 1, wherein the pressure-sensitive adhesive layer is made of a pressure-sensitive adhesive composition containing an acrylic copolymer.
The surface protective film according to claim 2, wherein the pressure-sensitive adhesive composition containing the acrylic copolymer further contains a silane coupling agent.
The surface protective film according to any one of claims 1 to 3, wherein the bending resistance of the base material is 50000 mN · cm or less.
The adhesive strength of the surface protective film to the liquid crystal plastic under conditions of 23 ° C and 50% RH before and after heating at 80 ° C for 2 hours is 400 to 1000 mN / 25 mm, respectively. Surface protection film.
6. The surface protective film according to claim 1, wherein the peeling film has a peeling force of 50 to 200 mN / 50 mm.
The surface protective film according to claim 1, wherein the size of the surface protective film is 100 mm 2 or less.
A method for protecting the surface protective film according to any one of claims 1 to 7 by attaching it to the surface of an optical member or an electronic member after peeling the release film.