JP2011190370A - Surface protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protective film that is excellent in spreadability and suppresses adhesion enhancing even when applied to an adherend whose surface has very small unevenness. <P>SOLUTION: In the surface protective film, a self-adhesive layer contains: a propylene-based polymer and an aromatic alkenyl block polymer. The aromatic alkenyl block polymer includes: a polymer block A having a continued aromatic alkenyl compound unit as a main component; and a polymer block B which is an aromatic alkenyl-conjugated diene copolymer block randomly including a conjugated diene unit and an aromatic alkenyl compound unit, a content of the aromatic alkenyl compound unit being 10-35 wt.%, wherein the content of the total aromatic alkenyl compound unit is 30-50 wt.%, and a weight ratio (A:B) of the total amount of the polymer block A to the total amount of the polymer block B is 5:95 to 25:75. A ratio of the propylene-based polymer of the total weight of the aromatic alkenyl block polymer and the propylene-based polymer is 25-60 wt.%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface protective film.

  Conventionally, a surface in which an adhesive layer is laminated on one side of a film-like substrate to protect the surface of various members such as optical devices, metal plates, painted metal plates, resin plates, glass plates, etc. Protective films (generally called protective tapes, masking tapes, or surface protective sheets) are widely used. In particular, surface protective films have recently been used for optical members for liquid crystal displays such as optical sheets.

By the way, generally, the surface protection film is industrially manufactured as a wound body obtained by winding a long film in a roll shape. It is known that the surface protection film as such a wound body has a high force (deployment force) necessary for unwinding the wound body, and the deployment force tends to increase with time. There is a strong demand for a small force, that is, the ability to easily rewind the wound body.
Further, since the surface protective film is peeled off after use, smooth peelability and the like are required.

On the other hand, as a material for the optical sheet, acrylic resins, polycarbonate resins, and polar polymers such as PET are frequently used. These optical sheets are shipped to an optical device manufacturer after a surface protective film is attached, but may be exposed to high temperatures during transportation, storage, and the like.
Here, there is a problem of so-called adhesive progress, that is, an increase in adhesive force due to an increase in the contact area between the adherend and the adhesive layer due to external factors such as time and temperature.

  In general, acrylic pressure-sensitive adhesives are widely used as pressure-sensitive adhesives, but acrylic pressure-sensitive adhesives have a particularly large increase in adhesive strength over time.

  For these reasons, in particular, in the case of a surface protective film applied to an optical sheet, a rubber-based pressure-sensitive adhesive is mainly used instead of an acrylic pressure-sensitive adhesive for the pressure-sensitive adhesive layer constituting the surface protective film. Thus, an increase in adhesive force with time is avoided, and the surface protective film is smoothly peeled off from the optical member surface.

  However, since rubber adhesive is generally a solution-coated type, there are problems such as environmental pollution and energy waste during solvent drying, and the back side of the olefin base material layer (the side on which the adhesive layer is laminated) It is also necessary to perform a mold release process on the opposite surface. Moreover, if it is a hot-melt-type adhesive, the former problem can be eliminated or reduced, but the back surface release treatment cannot be avoided. Furthermore, even if it is a rubber-based adhesive, in the case of a conventional rubber-based adhesive, the adhesive strength is too heavy for an adherend having extremely small surface irregularities, for example, an adherend having a surface roughness Ra of 2.0 μm or less. And could not be used practically.

For the problem of improving the unwinding property, for example, a laminate in which a base layer composed of a polyorganosiloxane having one or more intramolecular double bonds and a polyolefin resin and an adhesive layer are laminated A method for producing a surface protective film in which an electron beam or γ-ray is irradiated on the surface of a film base layer has been proposed (Patent Document 1).
In addition, a surface layer containing a polyolefin resin and a pressure-sensitive adhesive layer containing a thermoplastic elastomer are laminated and formed by a coextrusion method, and then a release layer is formed on the back surface of the surface layer by a coating method. A surface protective film has been proposed (Patent Document 2).
Moreover, it is a surface protection film formed by co-extrusion with an olefin base material layer using an adhesive layer mainly composed of a styrene elastomer instead of natural rubber, and the back surface of the base material layer is subjected to friction treatment. A surface protective film excellent in unwinding properties has been proposed (Patent Document 3).

  On the other hand, for the problem of suppressing the adhesion progress, for example, the initial adhesive force to the adherend is obtained by mixing polyethyleneimine having a higher alkyl group introduced into the base material layer and bleeding out to the surface of the adhesive layer. Attempts have been made to suppress the adhesion progress while ensuring the above (Patent Document 4).

Japanese Patent Laid-Open No. 2-252783 JP 2003-41216 A JP 07-62311 A JP 09-188857 A

However, the above prior art still has the following problems.
Even with the surface protective film of Patent Document 1 or 3, the developing force cannot be sufficiently reduced only by the back surface treatment, the rewinding property of the wound body is not sufficient, and the workability may be lowered.
In the release treatment method of Patent Document 2, sufficient feeding property can be ensured even when the back surface of the substrate is rough, but the release agent is transferred to the adhesive layer, and the adhesiveness to the adherend may be reduced. .
The surface protective film disclosed in Patent Document 4 has a case where the amount of polyethyleneimine that bleeds out to the surface is stored in a normal environment when stored in an extremely high temperature environment (for example, a tropical region or a subtropical region). On the other hand, there is a possibility that the effect of suppressing the adhesion progress sufficiently cannot be exhibited.
Further, any of the surface protective films disclosed in any of the patent documents has a problem that the adhesive strength is too heavy for an adherend having a surface roughness Ra of 2.0 μm or less.

Therefore, an object of the present invention is to provide a surface protective film that eliminates the above-mentioned drawbacks of the prior art and ensures an appropriate initial adhesive force, is excellent in developability and adhesive force, and prevents the adhesion from progressing. is there.
A further object of the present invention is to provide a surface protective film for an optical sheet that suppresses the progress of adhesion even under an extremely high temperature (eg, 60 ° C.) environment while ensuring an appropriate initial adhesive force. That is.

  As a result of intensive studies, the present inventors have used a specific multi-block copolymer having an aromatic alkenyl polymer block and an aromatic alkenyl-conjugated diene copolymer block for the pressure-sensitive adhesive layer, and thereby suitable initial stage. The present inventors have found that a surface protective film that is excellent in developability and prevents adhesion progress can be obtained while ensuring adhesive strength, and as a result of further studies, the present invention has been completed.

The surface protective film of the present invention is
A surface protective film having a base material layer and an adhesive layer,
The pressure-sensitive adhesive layer comprises an aromatic alkenyl block polymer, a tackifier, and a styrenic block phase reinforcing agent,
The aromatic alkenyl block polymer is
Polymer (i): comprising the following polymer block A and the following polymer block B, the general formula [AB] n (wherein A is the polymer block A, B is the polymer block B, n is A copolymer (I) having a structure represented by the formula (1) or a hydrogenated product thereof:
Polymer (ii): Including the following polymer block A and the following polymer block B, the general formula A-B-A (the symbols in the formula are as defined above) or the general formula (A-B) x A copolymer (II) having a structure represented by -Y (wherein x represents an integer of 1 or more, Y represents a coupling agent residue, and other symbols are as defined above), Containing the hydrogenated product,
The overall aromatic alkenyl compound unit content (St (A + B)) of the polymer (i) and the polymer (ii) is 30 to 50% by weight,
The weight ratio (A: B) of the total amount of the polymer block A and the total amount of the polymer block B contained in each of the polymer (i) and the polymer (ii) is in the range of 5:95 to 25:75. And
The content of the styrenic block phase reinforcing agent is 5 to 50 parts by weight with respect to 100 parts by weight of the aromatic alkenyl block polymer, and satisfies the following formula (1).
Styrenic block phase reinforcing agent / tackifier ≧ 1 (1)
Polymer block A:
Polymer block having a series of aromatic alkenyl compound units and mainly consisting of aromatic alkenyl compound units Polymer block B:
An aromatic alkenyl-conjugated diene copolymer block containing a conjugated diene unit and an aromatic alkenyl compound unit at random, wherein the aromatic alkenyl compound unit content (St (b)) is 10 to 35% by weight. Combined block

The surface protective film of the present invention is excellent in developability.
Furthermore, since the surface protective film of one embodiment of the present invention can secure an appropriate initial adhesive force and suppresses adhesive progress even under extremely high temperature (eg, 60 ° C.) environment, It can be secured.

<Definition of symbols and terms in this specification>
The symbol “˜” used to represent a numerical range in this specification is used with the intention that the numerical range includes the numerical values at both ends unless otherwise specified.
In the present specification, the “content” of the repeating unit of the polymer used in the term “aromatic alkenyl compound unit content” or the like means the weight ratio in terms of the monomer from which the repeating unit is derived, that is, the polymer. The ratio (wt%) of the weight of the monomer from which the repeating unit is derived to the weight of all monomers to be formed, that is, the alkenyl aromatic compound content of the polymer. Here, the “weight of all monomers for forming the polymer” approximates the weight of the polymer. Similarly, in the present specification, the “content ratio” of the repeating unit of the polymer block is the weight ratio converted to the monomer from which the repeating unit is derived, that is, the total monomer for forming the polymer block. It means the ratio (% by weight) of the weight of the monomer from which the repeating unit is derived to the weight. Here, the “weight of all monomers for forming the polymer block” approximates the weight of the polymer block.
In the present specification, the “vinyl bond content” means the total content of 1,2-vinyl bonds and 3,4-vinyl bonds calculated by the Morero method using an infrared absorption spectrum method.
In this specification, “surface roughness Ra” is “arithmetic average height” defined in JIS B0601: 2001.

<Surface protection film>
The surface protective film of this invention has a base material layer and an adhesive layer.
Preferably, the pressure-sensitive adhesive layer is laminated on one surface of the base material layer.

<Adhesive layer>
The pressure-sensitive adhesive layer contains an aromatic alkenyl block polymer, a tackifier, and a styrenic block phase reinforcing agent.
The pressure-sensitive adhesive composition includes a softener, an antioxidant, a light stabilizer, an ultraviolet absorber, a filler, a pigment, an anti-adhesive agent, an olefin resin, a silicone polymer, a liquid acrylic copolymer, as necessary. You may contain well-known additives, such as a coalescence and a phosphate ester type compound, suitably.

  Although the thickness in particular of an adhesive layer is not restrict | limited, For example, it is about 0.5-50 micrometers normally, Preferably it is 1-40 micrometers, More preferably, it is 2-30 micrometers.

<Aromatic alkenyl block polymer>
The aromatic alkenyl block polymer contains a polymer (i) and a polymer (ii).
<Polymers (i) and (ii)>
In the present specification, the “polymer (i)” includes the following polymer block A and the following polymer block B, and is represented by the general formula [AB] n (wherein A represents the polymer block A and B represents The polymer block B is a copolymer (I) having a structure represented by n represents an integer of 1 to 3) or a hydrogenated product thereof.
In the present specification, the “polymer (ii)” includes the following polymer block A and the following polymer block B, and is represented by the general formula A-B-A (the symbols in the formula are as defined above) or General formula (AB) xY (wherein x represents an integer of 2 or more, Y represents a coupling agent residue, and other symbols are as defined above).
Or a hydrogenated product thereof.
In the present specification, a composition comprising the polymer (i) and the polymer (ii) may be simply referred to as a “copolymer composition”.
The overall aromatic alkenyl compound unit content of the polymer (i) and the polymer (ii) is 30 to 50% by weight,
The weight ratio of the total amount of the polymer block A and the total amount of the polymer block B contained in the polymer (i) and the polymer (ii) is in the range of 5:95 to 25:75.
In the present specification, the “polymer block A” is a polymer block in which aromatic alkenyl compound units are continuous and mainly composed of aromatic alkenyl compound units.
In the present specification, the “polymer block B” is an aromatic alkenyl-conjugated diene copolymer block in which a conjugated diene unit and an aromatic alkenyl compound unit are randomly included, and the aromatic alkenyl compound unit content (St (B)) is a polymer block of 10 to 35% by weight.

<Polymer block A>
As described above, the “polymer block A” is a polymer block in which aromatic alkenyl compound units are continuous and mainly composed of aromatic alkenyl compound units.

  The “aromatic alkenyl compound unit” is a repeating unit derived from an aromatic alkenyl compound. Examples of the “aromatic alkenyl compound” include styrene, tert-butylstyrene, α-methylstyrene, p-methylstyrene, p-ethylstyrene, divinylbenzene, 1,1-diphenylethylene, vinylnaphthalene, vinylanthracene, N , N-Jetyl-p-aminoethylstyrene, vinylpyridine and the like. Among them, the “aromatic alkenyl compound unit” is preferably a styrene unit because the raw materials are easily industrially available.

  The “polymer block A” needs to be composed of an aromatic alkenyl compound unit as a main repeating unit. Specifically, the aromatic alkenyl compound unit content is 80% by weight or more. By making the aromatic alkenyl compound unit content as high as 80% by weight or more, there is an advantage that the thermoplasticity of the pressure-sensitive adhesive composition can be improved and recycling of the pressure-sensitive adhesive composition becomes easier. The repeating unit other than the aromatic alkenyl compound unit that may be contained in an amount of less than 20% by weight includes a repeating unit derived from a compound copolymerizable with the aromatic alkenyl compound, such as a conjugated diene compound or (meth). Mention may be made of repeating units derived from acrylic ester compounds. Of these, 1,3-butadiene and isoprene are preferred because of their high copolymerizability with aromatic alkenyl compounds.

<Polymer block B>
As described above, the “polymer block B” is an aromatic alkenyl-conjugated diene copolymer block in which conjugated diene units and aromatic alkenyl compound units are randomly included, and the aromatic alkenyl compound unit content (St (B)) is a polymer block of 10 to 35% by weight.

  The “conjugated diene compound unit” constituting the “polymer block B” is a repeating unit derived from a conjugated diene compound. Examples of the “conjugated diene compound” include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-octadiene, 1,3- Examples include hexadiene, 1,3-cyclohexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, myrcene, and chloroprene. Among them, the “conjugated diene compound unit” is at least one repeating unit selected from the group of 1,3-butadiene units and isoprene units because of high polymerization reactivity and easy availability of raw materials industrially. It is preferable.

  The “polymer block B” needs to be composed of a conjugated diene compound unit as a main repeating unit. From the viewpoint of exerting the effects of the present invention, the conjugated diene compound unit content is preferably in the range of 65 to 90% by weight.

Further, from the viewpoint of obtaining the effects of the present invention, the “polymer block B” needs to have an aromatic alkenyl compound unit content (St (b)) in the range of 10 to 35% by weight, and 13 to 33. It is preferably in the range of wt%, more preferably in the range of 16-30 wt%. When the aromatic alkenyl compound unit content is less than 10% by weight, the developability may be inferior and the handling property may be deteriorated. On the other hand, when it exceeds 35% by weight, the flexibility of the pressure-sensitive adhesive composition is inferior, and sufficient adhesive force important for the surface protective film may not be ensured.
The “polymer block B” may also contain a repeating unit other than the conjugated diene compound unit and the aromatic alkenyl compound unit as long as the effects of the present invention are not hindered.

  The “polymer block B” preferably has a vinyl bond content in the range of 50 to 90% and more preferably in the range of 60 to 80% from the viewpoint of exerting the effects of the present invention. preferable. Moreover, there exists an advantage that the adhesive composition excellent in the balance of tack | tuck and adhesive force can be comprised by making a vinyl bond content rate into 50% or more.

<Copolymer (I)>
The “copolymer (I)” includes a polymer block A and a polymer block B, and is represented by the general formula [AB] n (wherein A represents the polymer block A, B represents the polymer block B, n represents an integer of 1 to 3.).

  As “n” represents an integer of 1 to 3, as is clear, examples of the “structure represented by the formula [A-B] n” include AB, ABAB, And a structure represented by A-B-A-B-A-B. In these block copolymers, A and B may be the same or different in repetition.

  In the structure represented by [A-B] n, it is preferable that the terminal polymer block B occupies 2% by weight or more of the entire copolymer from the viewpoint of reliably exhibiting the effect of the polymer block B. Even when the terminal of some of the copolymers (I) has a structure of -A, the content of the terminal polymer block A is less than 2% by weight of the entire copolymer (I). Can exhibit the same effect as the terminal being the polymer block B. That is, the structure can be regarded as having a polymer block B at the end.

n needs to be an integer of 1 to 3. Industrial productivity becomes favorable by making n into this range. In addition, from the viewpoint of improving adhesive strength and material strength, n is more preferably 1 to 2, and particularly preferably 1. That is, as the “copolymer having a structure represented by the general formula [AB] n”, a block copolymer having a structure represented by the general formula AB is particularly preferable.

  The lower limit of the aromatic alkenyl compound unit content of the copolymer (I) or its hydrogenated product (polymer (i)) is required to be 30 weights, preferably 33. On the other hand, the upper limit needs to be 50 weight, and it is preferable that it is 45 weight%. By setting the aromatic alkenyl compound unit content in this range, it is possible to constitute a pressure-sensitive adhesive composition having an appropriate holding power and followability to the unevenness of the adherend surface, and having excellent spreadability. It becomes possible.

  The molecular weight of the polymer (i) is not particularly limited, but the weight average molecular weight is preferably 30,000 to 500,000, more preferably 80,000 to 300,000, and 100,000 to 200,000. Is particularly preferred. By setting the weight average molecular weight in the range of 30,000 to 500,000, the polymer (i), and thus the polymer (i) and the copolymer (II) or a hydrogenated product thereof (polymer (ii)) are formed. Industrial production of the copolymer composition can be facilitated. When the weight average molecular weight is less than 30,000, the polymer adheres to the production equipment or the like in the step of removing the solvent and drying the polymer, and industrial production of the polymer (i) may be difficult. On the other hand, when the weight average molecular weight is 500,000 or more, the solubility in a solvent and the heat melting property are deteriorated, and it may be difficult to process the pressure-sensitive adhesive body.

Since the hydrogenated copolymer (I) has excellent heat resistance and weather resistance, the double bond derived from the conjugated diene monomer is 80% or more, preferably 90% or more, more preferably 95%. As described above, a hydrogenated product in which an unsaturated bond is hydrogenated to a saturated bond by hydrogenation is preferable.
. In the present specification, the hydrogenation ratio (hydrogenation rate) means a hydrogenation rate calculated from a 270 MHz, ¹ H-NMR spectrum using carbon tetrachloride as a solvent.
The polymer (i) may be a single type (one type) or a combination of two or more types.

<Copolymer (II)>
The “copolymer (II)” includes the following polymer block A and the following polymer block B, and is represented by the general formula ABA (the symbols in the formula are as defined above) or the general formula (A -B) x-Y (wherein x represents an integer of 2 or more, Y represents a coupling agent residue, and other symbols are as defined above).
It is a copolymer which has a structure represented by these.

As is apparent from the above general formula, the copolymer (II) has a polymer block A at all molecular terminals.
The terminal polymer block A preferably accounts for 2% by weight or more of the entire copolymer (II). This is to ensure that the effect of the polymer block A is exhibited. Even if the terminal of some of the copolymers (II) has a structure of -B, the content of the terminal polymer block B is less than 2% by weight of the entire copolymer (II). Can exhibit the same effect as that of the polymer block A at the end. That is, the structure can be regarded as having the polymer block A at the end.
A structure represented by the general formula (AB) xY (wherein x represents an integer of 2 or more, Y represents a coupling agent residue, and other symbols are as defined above). In other words, the copolymer having has a structure in which the copolymer (I) is coupled by Y. Therefore, in the case of (AB) x-Y, the mixture of (I) and (II) can be synthesized in the same reaction kettle.
From the industrial viewpoint, (AB) xY is preferred. When x is 3 or more, the copolymer is a so-called star polymer. x is preferably 2 to 4 from the viewpoint of suppressing side reactions during the production of the copolymer and controlling the physical properties of the copolymer.

  The copolymer (II) or its hydrogenated product (polymer (ii)) also has an aromatic alkenyl compound unit content in the range of 30 to 50 weights for the same reason as the polymer (i). Is preferable, and it is more preferable that it is 33 to 45 weight%.

  Since the polymer (ii) has excellent heat resistance and weather resistance, the double bond derived from the conjugated diene monomer is 80% or more, preferably 90% or more, more preferably 95% or more. It is preferable that the unsaturated bond is a hydrogenated product obtained by hydrogenating the saturated bond.

The molecular weight of the polymer (ii) is not particularly limited, but the weight average molecular weight is preferably 50,000 to 500,000, and more preferably 50,000 to 300,000. By making the weight average molecular weight in the range of 50,000 to 500,000, industrial production of the polymer (ii), and thus the copolymer composition comprising the polymer (i) and the polymer (ii) can be facilitated. Can be. When the weight average molecular weight is less than 30,000, the polymer adheres to the production equipment in the process of removing the solvent and drying the polymer, making it difficult to industrially produce the copolymer (II) or its hydrogenated product. There is a case. On the other hand, when the weight average molecular weight is 500,000 or more, the solubility in a solvent and the heat melting property are deteriorated, and it may be difficult to process the pressure-sensitive adhesive body.
The polymer (ii) may be a single type (one type) or a combination of two or more types.

<Copolymer composition>
In the copolymer composition comprising the polymer (i) and the polymer (ii), the weight ratio of the polymer (i) and the polymer (ii) is in the range of 90:10 to 10:90. It is necessary. By including 10 parts by weight or more of the polymer (i) in 100 parts by weight of the total amount of the polymer (i) and the polymer (ii), the pressure-sensitive adhesive layer is lifted from the surface of the adherend, and the film is peeled off. It is possible to exert a preferable effect that it is possible to effectively prevent problems (floating) that occur. On the other hand, by including 10 parts by weight or more of the polymer (ii) in 100 parts by weight of the total amount of the polymer (i) and the polymer (ii), it is possible to effectively prevent the adhesion progress. It can be demonstrated.
From the viewpoint of more reliably preventing the pressure-sensitive adhesive layer from being lifted and the pressure-sensitive adhesive progressing, the weight ratio of the polymer (i) to the polymer (ii) is preferably in the range of 50:50 to 15:85.

  From the viewpoint of achieving the effect of the present invention, the weight ratio of the total amount of the polymer block A and the total amount of the polymer block B contained in the polymer (i) and the polymer (ii) is 5:95 to 25:75. It is necessary to be within the range. In addition, by containing 5 parts by weight or more of the polymer block A in 100 parts by weight of the total amount of the polymer block A and the polymer block B, it is possible to impart an appropriate holding force to the formed pressure-sensitive adhesive layer. The preferable effect of becoming can be exhibited. On the other hand, by including 75 parts by weight or more of the polymer block B in 100 parts by weight of the total amount of the polymer block A and the polymer block B, the pressure-sensitive adhesive layer to be formed is good against unevenness on the surface of the adherend. Therefore, it is possible to exert a preferable effect that the surface of the adherend can be surely protected. The lower limit of the weight ratio between the total amount of the polymer block A and the total amount of the polymer block B needs to be 5:95, preferably 7:93, and more preferably 10:90. The upper limit of the weight ratio between the total amount of the polymer block A and the total amount of the polymer block B needs to be 25:75, preferably 23:77, and more preferably 21:79.

  Examples of the tackifier include petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic / aromatic copolymers and alicyclic copolymers, and coumarone-indene resins. , Terpene resins, terpene-phenolic resins, rosin resins such as polymerized rosin, (alkyl) phenolic resins, xylene resins or hydrogenated products thereof, etc. Can be used without particular limitation. It is more preferable to use a tackifier having a softening point of 90 to 140 ° C. These tackifiers may be used alone or in combination of two or more. In order to improve peelability and weather resistance, it is more preferable to use a hydrogenated tackifier. Moreover, you may use the tackifier marketed as a blend with an olefin resin.

The styrenic block phase reinforcing agent is used to suppress the adhesion progress of the adhesive layer.
Examples of the styrenic block phase reinforcing agent include monomer units such as styrene and α-methylstyrene, p-methylstyrene, p-chlorostyrene, chloromethylstyrene, tert-butylstyrene, p-ethylstyrene, and divinylbenzene. A styrene-type compound is mentioned. These can be used alone or in combination of two or more. That is, the styrenic block phase reinforcing agent can be obtained by polymerizing these monomers. In the case of a copolymer composed of two or more types of monomers, it may be a block copolymer or a random copolymer. Among them, the styrenic block phase reinforcing agent preferably has a softening point of about 100 ° C. or higher, and more preferably 150 ° C. or higher. Specifically, trade names “ENDEX 155” (softening point 155 ° C.), “ENDEX 160” (softening point 160 ° C.) manufactured by Eastman Chemical Co., Ltd. are preferably used.
The content of the styrenic block phase reinforcing agent is 5 to 50 parts by weight with respect to 100 parts by weight of the aromatic alkenyl block polymer.
If it is 5 parts by weight or less, the effect of adding the styrenic block phase reinforcing agent is small, and the adhesive strength with time may increase excessively. On the other hand, if it is 50 parts by weight or more, molding may be worse and molding may not be possible.
Furthermore, it is preferable that the amount of the tackifier and the styrene block phase reinforcing agent satisfy the following formula (1).
Styrenic block phase reinforcing agent / tackifier ≧ 1 (1)
If the styrene block phase reinforcing agent / tackifier <1, the adhesive strength with time may increase excessively.

<Additives>
Softeners are usually effective in improving adhesive strength. Examples of the softener include low molecular weight diene polymer, polyisobutylene, hydrogenated polyisoprene, hydrogenated polybutadiene, paraffinic process oil, naphthenic process oil, aromatic process oil, castor oil, tall oil, natural oil, What is generally used for an adhesive, such as liquid polyisobutylene resin, polybutene, or hydrogenated products thereof, can be used without any particular limitation. These softeners may be used alone or in combination of two or more.

The antioxidant is not particularly limited, and examples thereof include commonly used ones such as phenolic (monophenolic, bisphenolic, and polymeric phenolic), sulfur, and phosphorus.
Examples of the light stabilizer include hindered amine compounds.
The ultraviolet absorber is not particularly limited, and examples thereof include salicylic acid series, benzophenone series, benzotriazole series, and cyanoacrylate series.

Examples of the filler include calcium carbonate, magnesium carbonate, silica, zinc oxide, and titanium oxide.
Examples of the anti-adhesive agent include fatty acid amides, polyethyleneimine long-chain alkyl grafts, soybean oil-modified alkyd resins (for example, Arakawa Chemical Industries, trade name “Arachid 251”, etc.), tall oil-modified alkyd resins (for example, Arakawa Chemical Industries, trade name “Arachid 6300”, etc.).
These additives may be used alone or in combination of two or more.

<Base material layer>
The material of the base material layer is preferably a polyolefin resin.
Examples of the polyolefin resin include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-α-olefin copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, Examples include ethylene-methyl acrylate copolymer, ethylene-n-butyl acrylate copolymer, and polypropylene (homopolymer, random copolymer, block copolymer).
These can be used alone or in combination of two or more. Moreover, the polyolefin resin which has a substituent may be sufficient, and resin other than polyolefin resin may be added. Furthermore, the end material of the base material layer which uses the polyolefin resin as a raw material, and the end material of the surface protection film which arose in the manufacturing process of the surface protection film may be added.
The base material layer may be a single layer or a layer having two or more multilayer structures having different compositions.

  The thickness of the base material layer can be appropriately adjusted depending on the use of the surface protective film. Usually, it is suitable to set the thickness to about 10 to 100 μm.

<Manufacturing method>
As for the aromatic alkenyl block polymer, for example, the copolymer (I) and the copolymer (II) are respectively synthesized by block polymerization, blended at a predetermined mass ratio, and then hydrogenated as desired. The copolymer (I) or a hydrogenated product thereof, and a mixture of the copolymer (I) or the hydrogenated product thereof are obtained, and an additive to be blended as desired is mixed by a conventional method.
As the hydrogenation catalyst, the periodic table Ib, IVb, Vb, VIb, VIIb, VIII
A compound containing any of group metals can be used. Examples thereof include compounds containing Ti, V, Co, Ni, Zr, Ru, Rh, Pd, Hf, Re, and Pt atoms, and more specifically, Ti, Zr, Hf, Co, Ni, Rh. And metallocene compounds such as Ru, and supported heterogeneous catalysts in which metals such as pd, Ni, Pt, Rh and Ru are supported on a support such as carbon, silica, alumina, diatomaceous earth, and basic activated carbon. it can.
Specific examples of the metallocene compounds include a Kaminsky catalyst having two ligands in which hydrogen on the cyclopentagenyl ring (Cp ring) or Cp ring is substituted with an alkyl group, and ansa. Examples thereof include a type metallocene catalyst, a non-crosslinked half metallocene catalyst, and a crosslinked half metallocene catalyst.
Specific examples include JP-A-1-275605, JP-A-5-271326, JP-A-5-271325, JP-A-5-222115, JP-A-11-292924, and JP-A-11-292924. JP 2000-37632 A, JP 59-133203 A, JP 63-5401 A, JP 62-218403 A, JP 7-90017 A, JP 43-19960 A, Mention may be made of the catalysts described in JP-B 47-40473. These various catalysts may be used alone or in combination of two or more.

  Alternatively, when the copolymer (II) has a structure represented by the general formula (AB) xY (wherein the symbols are as defined above), the pressure-sensitive adhesive composition is It may be produced by the following method (coupling method). In the coupling method, copolymer (I) or a hydrogenated product thereof (polymer (i)) and copolymer (II) or a hydrogenated product thereof (polymer (ii)) can be synthesized in one pot. Therefore, the production process is simple, the production cost is low, and the ratio of the polymer (i) to the polymer (ii) can be controlled by the kind and amount of the coupling agent.

The coupling method is
1st process: The process which synthesize | combines the copolymer which has a structure of [AB] by block polymerization,
Second step: the part of the copolymer having the structure of [A-B], a coupling agent Y-Z _x (where "Y" coupling agent residue, "Z" is a leaving group, “X” represents an integer of 2 or more.) To synthesize a copolymer having a structure of {[AB] _x —Y},
When obtaining a hydrogenated product,
Third step: Hydrogenation of the copolymer having the structure [AB] and the copolymer having the structure {[AB] _x -Y} to form hydrogenated copolymer And a step of obtaining a copolymer composition comprising the combination (I) and the copolymer (II).

  Examples of the “coupling agent” include methyldichlorosilane, dimethyldichlorosilane, methyltrichlorosilane, butyltrichlorosilane, tetrachlorosilane, dibromoethane, tetrachlorotin, butyltrichlorotin, tetrachlorogermanium, bis (trichlorosilyl) ethane. Halogen compounds such as epoxidized soybean oil; carbonyl compounds such as diethyl adipate, dimethyl adipate, dimethyl terephthalic acid and diethyl terephthalic acid; polyvinyl compounds such as divinylbenzene; polyisocyanates; . Of these, methyldichlorosilane, dimethyldichlorosilane, methyltrichlorosilane, and tetrachlorosilane are preferred because they are easily industrially available and have high reactivity.

  The surface protective film of the present invention is, for example, a method in which a base sheet (base layer) is produced by extrusion molding and then a liquid obtained by melting or dissolving the pressure-sensitive adhesive composition is applied or sprayed on the base sheet, or The base material sheet obtained by the inflation method and the pressure-sensitive adhesive sheet can be bonded together, or the base material and the pressure-sensitive adhesive composition can be coextruded using a T die having a multilayer manifold. Especially, since the multilayer sheet | seat with which the base material layer and the adhesive layer contact | adhered is obtained, the method of manufacturing by coextrusion is preferable. A liquid obtained by melting or dissolving the pressure-sensitive adhesive composition of the present invention is also included in the pressure-sensitive adhesive composition of the present invention.

<Application>
The surface protective film of the present invention includes an adherend having extremely fine surface irregularities (eg, a light diffusion plate (light diffusion film) (including a diffusion plate (diffusion film) with a prism having a prism on one side)) and the like. However, it can also be used on an adherend having a larger surface roughness.
More specifically, the surface protective film of the present invention is preferably used for protecting a surface having a surface roughness Ra of 2.6 μm or less. The surface protective film of the present invention may be inferior in peelability when applied to an optical sheet having a completely smooth surface. Therefore, it is preferably used for protecting a surface having a surface roughness Ra of 0.3 μm or more.
Although it does not specifically limit as a material which comprises the optical sheet used as a to-be-adhered body, Resin which has translucency, for example, acrylic resin, a polycarbonate, etc. are mentioned.
The optical sheet whose surface is protected by the surface protective film of the present invention is usually stored as a wound body. Such a wound body is manufactured by the following manufacturing method, for example.
(1) affixing the surface protective film of the present invention to the first main surface of the optical sheet having the first main surface with a surface roughness Ra of 0.3 μm to 2.6 μm; and (2) the surface protective film. The manufacturing method of the wound body of the optical film by which the surface was protected including winding the optical sheet on which the was affixed in roll shape.
In addition, it is also usual to stack and store optical films with protected surfaces obtained by unwinding such wound bodies and cutting them to a certain size.
Such an optical film with the surface protected can be manufactured by a manufacturing method including cutting the wound body of the optical film with the surface protected in a direction parallel to the axis of the wound body. .
In this way,
An optical sheet having a first principal surface with a surface roughness Ra of 0.3 μm to 2.6 μm;
The surface-protected optical film having the surface protective film according to the present invention attached to the first main surface is also an embodiment of the present invention.

  Hereinafter, although the surface protection film of this invention is demonstrated in detail based on an Example, this invention is not limited to a following example.

(Synthesis example of copolymer composition)
Polymer block A
A nitrogen-substituted reaction vessel is charged with 500 parts by mass of degassed / dehydrated cyclohexane, 20 parts by mass of styrene and 5 parts by mass of tetrahydrofuran, and 0.13 parts by mass of n-butyllithium is added at a polymerization start temperature of 40 ° C. Then, temperature rising polymerization was performed.
Polymer block B
After the polymerization conversion rate of the polymer A reached approximately 100%, the reaction solution was cooled to 15 ° C., and then 70 parts by mass of 1,3-butadiene and 10 parts by mass of styrene were added, followed by further temperature rising polymerization. .

  After the polymerization conversion rate reached almost 100%, 0.06 parts by mass of methyldichlorosilane was added as a coupling agent to carry out a coupling reaction. After the coupling reaction was completed, it was left for 10 minutes while supplying hydrogen gas at a pressure of 0.4 MPa-Gauge. A partially extracted polymer had a vinyl content of 64%, a weight average molecular weight of about 110,000, and a coupling rate of 60%.

Thereafter, 0.03 parts by mass of diethylaluminum chloride and 0.06 parts by mass of bis (cyclopentadienyl) titanium furfuryloxychloride were added to the reaction vessel and stirred. The hydrogenation reaction was started at a hydrogen gas supply pressure of 0.7 MPa-Gauge and a reaction temperature of 80 ° C., and when the hydrogen absorption was completed, the reaction solution was returned to room temperature and normal pressure, and the polymer was removed from the reaction vessel. A copolymer composition comprising (i) and a polymer (ii) was obtained (Synthesis Example 1 in Table 1).
Thereafter, the desired copolymer composition was obtained in the same manner (Synthesis Example 2 in Table 1). The properties of these copolymer compositions are shown in Table 1.

In Table 1, “St (A + B)”, “St (B)”, “St (A)”, and “St (b)” represent numerical values defined as follows. In the definition, “total polymer” means the whole of the polymer (i) and the polymer (ii).
“St (A + B)” is the aromatic alkenyl compound unit content of the whole polymer, and means a numerical value represented by the following formula. This is equal to the sum of the following “St (B)” and the following “St (A)”.
formula:
St (A + B) = (aromatic alkenyl compound unit weight in all polymers) / (total monomer unit weight in all polymers) × 100 (% by weight)
“St (B)” means a numerical value represented by the following equation.
formula:
St (B) = (aromatic alkenyl compound unit weight in all polymer blocks B) / (total monomer unit weight in all polymers) × 100 (% by weight)
“St (A)” means a numerical value represented by the following formula.
formula:
St (A) = (aromatic alkenyl compound unit weight in all polymer blocks A) / (total monomer unit weight in all polymers) × 100 (% by weight)

“St (b)” is the aromatic alkenyl compound unit content of the polymer block B, and means a numerical value represented by the following formula.
formula:
St (b) = (aromatic alkenyl compound unit weight in all polymer blocks B) / (total monomer unit weight in all polymer blocks B) × 100 (% by weight)
In Table 1, “A: B” represents a weight ratio between the total amount of the polymer block A and the total amount of the polymer block B.
In Table 1, “(i) :( ii)” represents the weight ratio of the polymer (i) to the polymer (ii).
Further, in Table 1, “conjugated diene content” represents the conjugated diene unit content of the polymer block B.
In Table 1, “Vinyl bond content” represents the vinyl bond content of the polymer block B.

[Table 1]

Example 1
A base material layer having a thickness of 36 μm is obtained by coextruding the base material and the pressure-sensitive adhesive composition prepared in the ratio shown in Table 2 by a T-die method using polypropylene (J715M manufactured by Prime Polymer Co., Ltd.) as the base material. And a 4 μm thick adhesive layer were laminated and integrated to form a surface protective film, and a wound body wound around a paper core having an inner diameter of 3 inches was obtained.

(Examples 2-8, Comparative Examples 1-7)
A surface protective film was molded in the same manner as in Example 1 except that the pressure-sensitive adhesive composition was changed to the composition described in Table 2, and a wound body wound around a paper core having an inner diameter of 3 inches was obtained.

(Evaluation)
The following items were evaluated for each surface protective film obtained as described above. The results are shown in Table 3.

(1) Film-formability The appearance of each surface protective film formed by coextrusion as described above was evaluated visually, and “◯” was given if there was no problem in appearance. In Comparative Example 7, a surface protective film could not be formed.
(2) Initial adhesive strength Each surface protective film was affixed so that the lens surface of the optical sheet which has an unevenness | corrugation whose surface roughness Ra is 1.5 micrometers might be covered. Affixing conditions were as follows: a room temperature of 23 ° C. and a relative humidity of 50%, each using a 2 kg pressure-bonded rubber roller, affixed at a speed of 300 mm / min, left in that state for 30 minutes, and conformed to JIS Z0237. The 180 degree peel strength at a width of 25 mm was measured at the speed shown in Table 2.
(3) Adhesive strength with time Each surface protective film was used in an environment of a room temperature of 23 ° C. and a relative humidity of 50% using a 2 kg pressure-bonded rubber roller on the surface of the prism sheet used for the initial adhesive strength evaluation in (2). Affixed at a speed of 300 mm / min. Thereafter, a prism sheet with a surface protective film attached thereto was sandwiched between polycarbonate plates (thickness 2 mm) and left in an environment at 60 ° C. for 30 minutes. After taking this out to room temperature and leaving it for 30 minutes, according to JIS Z0237, 180 degree peel strength in 25 mm width was measured at the speed | rate shown in Table 2.
The peel strength measured in this manner was taken as the adhesive strength with time, and the change rate of adhesive strength with time (adhesion progress rate) was calculated from the initial adhesive strength by the following equation.

Rate of change (adhesion progress rate) = time-dependent adhesive force / initial adhesive force

(4) Unfolding force Except for changing the unwinding speed of the 50 mm-wide wound bodies of the surface protective films of the examples and comparative examples, the unwinding force was applied at a unwinding speed of 15 m / min in accordance with JIS Z0237. Measured and used as deployment force.

[Table 2]
J715M: Polypropylene (manufactured by Prime Polymer, “J715M”)

<Criteria>
Adhesive strength (initial)
○ (good): 0.02 N / 25 mm or more, less than 0.50 N / 25 mm × (defect): less than 0.02 N / 25 mm, 0.5 N / 25 mm or more Adhesion progress rate ◎ (excellent): less than 150% ○ (good ): 150% or more, less than 300% × (defect): 300% or more deployment force ◎ (excellent): less than 2.0 N / 50 mm ○ (good): 2.0 N / 50 mm or more, less than 4.0 N / 50 mm × ( Defect): 4.0 N / 50 mm or more

Claims (4)

A surface protective film having a base material layer and an adhesive layer,
The pressure-sensitive adhesive layer contains an aromatic alkenyl block polymer, a tackifier, and a styrenic block phase reinforcing agent,
The aromatic alkenyl block polymer is
Polymer (i): comprising the following polymer block A and the following polymer block B, the general formula [AB] n (wherein A is the polymer block A, B is the polymer block B, n is A copolymer (I) having a structure represented by the formula (1) or a hydrogenated product thereof:
Polymer (ii): Including the following polymer block A and the following polymer block B, the general formula A-B-A (the symbols in the formula are as defined above) or the general formula (A-B) x A copolymer (II) having a structure represented by -Y (wherein x represents an integer of 1 or more, Y represents a coupling agent residue, and other symbols are as defined above), Containing the hydrogenated product,
The overall aromatic alkenyl compound unit content (St (A + B)) of the polymer (i) and the polymer (ii) is 30 to 50% by weight,
The weight ratio (A: B) of the total amount of the polymer block A and the total amount of the polymer block B contained in each of the polymer (i) and the polymer (ii) is in the range of 5:95 to 25:75. And
The content of the styrenic block phase reinforcing agent is 5 to 50 parts by weight with respect to 100 parts by weight of the aromatic alkenyl block polymer, and satisfies the following formula (1).
Styrenic block phase reinforcing agent / tackifier ≧ 1 (1)
Polymer block A:
Polymer block having a series of aromatic alkenyl compound units and mainly consisting of aromatic alkenyl compound units Polymer block B:
An aromatic alkenyl-conjugated diene copolymer block containing a conjugated diene unit and an aromatic alkenyl compound unit at random, wherein the aromatic alkenyl compound unit content (St (b)) is 10 to 35% by weight. Combined block (1) Affixing the surface protective film according to claim 1 to the first main surface of an optical sheet having a first main surface having a surface roughness Ra of 0.3 μm to 2.6 μm, and (2) A method for producing a wound body of an optical film with a protected surface, comprising winding an optical sheet on which a surface protective film is attached in a roll shape.   A wound body of an optical film, the surface of which is obtained by the production method according to claim 2. An optical sheet having a first principal surface with a surface roughness Ra of 0.3 μm to 2.6 μm;
An optical film having a surface protected, comprising the surface protective film according to claim 1 attached to the first main surface.