JP2011057992A - Surface protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protective film which has excellent expandability and prevents paste residues after being peeled off to an adherend while ensuring appropriate initial tack force. <P>SOLUTION: An adhesive composition comprises a polymer (i), which is a copolymer (I) containing polymer blocks A and B and represented by general formula [A-B]n (wherein n=1-3) or hydrogenated product thereof, and a polymer (ii), which is a copolymer (II) represented by formula A-B-A or formula (A-B)x-Y (wherein x≥1 and Y represents a residue of a coupling agent) or hydrogenated product thereof, wherein the total aromatic alkenyl compound unit content in the polymers (i) and (ii) is 30-50 wt.%, and the weight ratio of the total amount of block A to the total amount of block B contained in the polymers (i) and (ii) is within the range of from 5:95-25:75. The block A represents a polymer composed mainly of aromatic alkenyl compound units, and the block B represents a polymer which is an aromatic alkenyl-conjugated diene random copolymer having an aromatic alkenyl compound unit content of 10-35 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. Some optical members have an uneven surface, such as a prism sheet or a diffusion film. In order not to damage the irregularities, the surface (especially the outer surface of the irregularities) is protected by a surface protective film before use, and a surface protective film is applied to the irregular surface. When attaching, since a large contact area cannot be obtained, it is necessary to form an adhesive layer having a strong adhesive force.

  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 and removed after use, it is required to have smooth peelability and no adherend adherence due to adhesive residue.

  On the other hand, polar materials such as acrylic resins and polycarbonate resins are frequently used as materials such as prism sheets and diffusion films. 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, particularly when the surface of the adherend has an uneven shape, 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, so-called There is a problem of adhesive progress.

  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 lens portion (prism) surface of the optical sheet.

  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.

  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).

  By the way, the prism sheets with the surface protective film attached are generally stacked and stored in units of several tens of sheets until they are incorporated into a product.

  In this case, the top of the unevenness of the prism sheet disposed below may be destroyed by the load of the prism sheet disposed above, and the optical quality may deteriorate. This means that the top part bites into the adhesive layer of the surface protective film due to the load, reaches the base material of the surface protective film, and no longer exceeds the limit of the effect of dispersing and relaxing the load by the adhesive layer. It is thought that. In order to solve this problem, it is considered that the thickness of the pressure-sensitive adhesive layer may be sufficiently increased. However, increasing the thickness of the pressure-sensitive adhesive layer is not only disadvantageous in terms of manufacturing cost, but also increases the depth of penetration of the lens part (prism) into the pressure-sensitive adhesive layer, which may increase the adhesive force with time. was there.

  For this reason, there is an example of a surface protective film in which a styrene elastomer is used instead of natural rubber. For example, Patent Document 5 discloses a surface protective film using a pressure-sensitive adhesive layer having a thickness of 10 μm or more mainly composed of a styrene-based elastomer. It is described that a sufficient protective function for the adherend and an appropriate adhesive property can be satisfied at the same time.

Japanese Patent Laid-Open No. 2-252783 JP 2003-41216 A JP 07-62311 A JP 09-188857 A JP 2000-80336 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.

  In addition, the surface protective film disclosed in Patent Document 5 is applied to a harsh state, for example, in particular, on the prism surface of the prism sheet, and the surface opposite to the prism surface side (that is, the outer surface of the surface protective film). In the case where a projection such as a so-called fish eye is pressed against the surface, there is room for further improvement from the viewpoint of protecting the shape of the top of the irregularities of the prism portion.

  Accordingly, an object of the present invention is to provide a surface protective film that eliminates the above-mentioned drawbacks of the prior art, has an excellent initial adhesive force, has excellent developability, and prevents adhesive residue after peeling on the adherend. Is to provide.

  A further object of the present invention is to provide a surface protective film for a prism sheet, in which an adequate initial adhesive force is ensured, and the adhesive progress is suppressed even under an extremely high temperature (eg, 70 ° C.) environment. That is.

  In addition, a further object of the present invention is to be applied to a harsh state, for example, particularly on the surface of the prism sheet that is affixed to the prism surface and opposite to the prism surface (that is, the outer surface of the surface protective film). An object of the present invention is to provide a surface protective film capable of protecting the top and bottom shapes of the prism portions even when a projection such as a so-called fish eye is pressed.

  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 inventors have found that a surface protective film that is excellent in developability and prevents adhesive residue after peeling from the adherend can be obtained while ensuring adhesive strength, and as a result of further studies, the present invention has been completed.

The pressure-sensitive adhesive composition of the present invention 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 2 or more, Y represents a coupling agent residue, and other symbols are as defined above) or 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. It is characterized by being.

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 protection film of this invention has a base material layer and the adhesive layer which consists of an adhesive composition of the said this invention.

  By using the pressure-sensitive adhesive composition of the present invention, the surface protective film of the present invention has excellent developability and prevents adhesive residue after peeling from the adherend.

Preferably, in the surface protective film,
The substrate layer is a polyolefin substrate layer;
The pressure-sensitive adhesive composition further contains a tackifier, and the maximum temperature of tan δ obtained by measuring dynamic viscoelasticity at −50 ° C. to 80 ° C. of the pressure-sensitive adhesive layer is −10 ° C. to 20 ° C. It is.

  Thereby, the said surface protective film can have the further expansion | deployment property and initial stage adhesive force of a more preferable balance.

Preferably, in the surface protective film,
The substrate layer is a polyolefin substrate layer;
The pressure-sensitive adhesive composition further contains a tackifier and a styrenic block phase reinforcing agent,
The ratio of the weight of the aromatic alkenyl compound unit in the polymer (i), the polymer (ii) and the styrenic block phase reinforcing agent to the weight of the pressure-sensitive adhesive layer (aromatic alkenyl compound unit content) is 20 ~ 50% by weight.

  Thereby, the progress of the adhesive force with time can be further suitably suppressed.

Preferably, in the surface protective film, the storage modulus G at 70 ° C. of the pressure-sensitive adhesive layer 'is ^{4.5 × 10 5 Pa~6.0 × 10 5} Pa.

  Thereby, the progress of the adhesive force with time can be further suitably suppressed.

Preferably, when the surface protective film is used for protecting the surface of the prism surface of the prism sheet, the surface protective film is affixed to the prism surface and a load of 0.3 N / cm ² is applied for 24 hours in an atmosphere at 70 ° C. The depth of penetration of the prism apex angle of the prism surface into the adhesive is 1% or more and less than 40% of the thickness of the adhesive layer.

  Thereby, damage to the prism can be suitably suppressed while ensuring an appropriate adhesive force.

  Preferably, when the surface protective film is for protecting the prism surface of the prism sheet, a protrusion having a diameter of 400 μm and a height of 12 μm is attached to the surface opposite to the prism surface. The depth of penetration of the prism apex angle of the prism surface into the pressure-sensitive adhesive layer when pressed is 1% or more and less than 100% of the pressure-sensitive adhesive layer thickness.

  Thereby, damage to the prism can be suitably suppressed while ensuring an appropriate adhesive force.

  Preferably, when the surface protective film is for protecting the prism surface of the prism sheet, the outer surface of the base material layer has a surface roughness Ra of 0.7 to 2.0 μm, an average height of undulation motif of 3 μm or more. And an average length of waviness motif of 350 μm or more and 600 μm or less.

  Thereby, while ensuring an appropriate adhesive force, in a harsh state, for example, in particular, it is affixed to the prism surface of the prism sheet, and the surface opposite to the prism surface side (that is, the outer surface of the surface protective film) In addition, even when a projection such as a so-called fish eye is pressed, it is possible to protect the top and bottom shapes of the prism portions.

  Preferably, the surface protective film is for protecting the surface of a diffusion film.

  The surface protective film of the present invention is excellent in developability and prevents adhesive residue after peeling from the adherend.

  Furthermore, the surface protective film of one embodiment of the present invention has suppressed adhesion progress even in an environment of extremely high temperature (eg, 70 ° C.) while ensuring appropriate initial adhesive strength.

  Furthermore, the surface protective film of one embodiment of the present invention is applied to a harsh state, for example, the surface of the prism sheet, particularly the surface opposite to the prism surface (that is, the outer surface of the surface protective film). In the case where a projection such as a so-called fish eye is pressed, the shape of the top of the projections and depressions of the prism portion can be protected.

It is a schematic diagram which shows the wave | undulation of the outer surface of a base material layer. It is a perspective view of the prism sheet to which the surface protection film of one mode of the present invention is applied. A structure in which a surface protective film of one embodiment of the present invention is attached to a prism sheet

<Definition of symbols 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.

<Adhesive composition>
The pressure-sensitive adhesive composition of the present invention contains the following polymer (i) and the following polymer (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”.

In the pressure-sensitive adhesive composition of the present invention, the total 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 is heavy 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 the following polymer block A and the following polymer block B, and is represented by the general formula [AB] n (wherein A is the polymer block A and B is 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 copolymer (I) or its hydrogenated product (polymer (i)) preferably has an aromatic alkenyl compound unit content in the range of 30 to 50% by weight, and is preferably 33 to 45% by weight. More preferred. 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>
As described above, the pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing a copolymer composition composed of the polymer (i) and the polymer (ii) as a constituent component. In this copolymer composition, the weight ratio of the polymer (i) and the polymer (ii) needs to be within the range of 90:10 to 10:90. 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), when the film is peeled off from the surface of the adherend, It is possible to exert a preferable effect that it is possible to effectively prevent a problem (glue residue) that the adhesive remains on the surface of the adherend and contaminates the surface of the adherend.

  From the viewpoint of more reliably preventing the pressure-sensitive adhesive layer from being lifted and remaining glue, 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 the unevenness of the adherend surface. Therefore, it is possible to exert a preferable effect that the surface of the adherend can be surely protected. The weight ratio of the total amount of the polymer block A and the total amount of the polymer block B is preferably in the range of 5:95 to 25:75, and more preferably in the range of 7:93 to 23:77. A range of 10:90 to 21:79 is particularly preferable.

<Surface protection film>
The surface protective film of this invention has a base material layer and the adhesive layer which consists of an adhesive composition of this invention demonstrated above.

  Preferably, the pressure-sensitive adhesive layer is laminated on one surface of the base material layer.

<Base material layer>
The base material layer is preferably a polyolefin base material layer.

  Examples of the “polyolefin” 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 thereof include a copolymer, an ethylene-methyl acrylate copolymer, an ethylene-n-butyl acrylate copolymer, and polypropylene (homopolymer, random copolymer, block copolymer).

  These can be used alone or in combination of two or more. The “polyolefin” may be a polyolefin having a substituent, and a resin other than the polyolefin may be added. Furthermore, the end material of the polyolefin base material layer and the end material of the surface protection film which were produced 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.

  Preferably, the outer surface of the base material layer (that is, the surface opposite to the pressure-sensitive adhesive layer side) has a surface roughness Ra of 0.7 to 2.0 μm, a waviness motif average height of 3 μm or more, and 350 μm. The swell motif average length is 600 μm or less.

  Thereby, even when the surface protective film of this embodiment is stuck on the surface of the prism sheet and stored in a stacked manner, damage to the lens portion (prism) of the prism sheet can be made difficult to occur. It can be suitably used for protection.

  In particular, the surface roughness of the back surface of the base material layer, the waviness motif average height, and the waviness motif average length are in the predetermined range, and a plurality of prism sheets with a surface protective film attached thereon are stored in a stacked manner. Even if there is a minute biting foreign matter, the fine biting foreign matter can enter the undulation valley of the surface, so the stress concentrated on the lens part of the prism sheet is greater than when the surface is smooth. It is thought that it can be reduced.

  In the present specification, “surface roughness Ra” is “arithmetic average height” defined in JIS B0601: 2001. The average swell motif height W is calculated as the average value of Wj in the schematic diagram showing the swell of the polyolefin substrate layer surface of FIG. 2, and the average swell motif length AW is calculated as the average value of AWj by the following formula. Is done.

In the present specification, “average swell motif length” and “average swell motif height” are “average length of contour curve element” and “average height of contour curve element” defined in JIS B0601: 2001, respectively. It is.

<Adhesive layer>
The said adhesive layer consists of an adhesive composition of this invention. In addition to the polymer (i) and the polymer (ii), the pressure-sensitive adhesive composition includes a tackifier, a styrene block phase reinforcing agent, a softening agent, an antioxidant, and a light stabilizer, as necessary. , UV absorbers, fillers, pigments, adhesion promoters, olefin resins, silicone polymers, liquid acrylic copolymers, phosphate ester compounds, and the like may be contained as appropriate.

  Examples of the tackifier used in the present invention include petroleum resins such as aliphatic copolymers, aromatic copolymers, aliphatic / aromatic copolymers and alicyclic copolymers, Generally adhesives such as coumarone-indene resin, terpene resin, terpene-phenol resin, polymerized rosin resin such as rosin resin, (alkyl) phenol resin, xylene resin or hydrogenated products thereof What is used for can be used without a restriction | limiting in particular. 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 tackifier in the present invention means a compound that is compatible with a rubber layer that is a conjugated diene system or a hydrogenated soft segment thereof in an aromatic alkenyl block copolymer and can control the adhesive force. .

  “Compatible” means that the tan δ peak temperature of a blend obtained by blending a tackifier with the copolymer composition is different from the tan δ peak temperature of the copolymer composition. That means. In the present specification, “tan δ peak temperature” means a temperature at which tan δ is maximized.

  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 used in the present invention include styrene and α-methylstyrene, p-methylstyrene, p-chlorostyrene, chloromethylstyrene, tert-butylstyrene, and p-ethylstyrene as monomer units. And styrenic compounds such as divinylbenzene. 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.

  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.

  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.

In a preferred embodiment of the surface protective film of the present invention,
The substrate layer is a polyolefin substrate layer;
The pressure-sensitive adhesive composition further contains a tackifier, and the maximum temperature of tan δ obtained by measuring dynamic viscoelasticity at −50 ° C. to 80 ° C. of the pressure-sensitive adhesive layer is −10 ° C. to 20 ° C. It is.

  Here, as the tackifier, those exemplified above can be used.

  It is suitable to use the tackifier in an amount that can prevent adhesive residue when the surface protective film is peeled off from the adherend. For example, when used as a surface protective film for a prism sheet, the compounding ratio of the tackifier is a rubber-based resin component [the polymer (i) and the polymer (ii) (hereinafter collectively referred to as these). , May be referred to as an aromatic alkenyl block copolymer.)] The amount is preferably 5 to 50 parts by weight, more preferably 10 to 40 parts by weight with respect to 100 parts by weight.

  The tan δ peak temperature obtained by measuring dynamic viscoelasticity at −50 ° C. to 80 ° C. of the pressure-sensitive adhesive layer is preferably in the range of −10 ° C. to 20 ° C. The tan δ peak temperature adjusts the rubber-based resin component in the pressure-sensitive adhesive layer, for example, the range of the aromatic alkenyl compound unit content in the random block of the aromatic alkenyl block copolymer, the blending ratio of the tackifier, and the like. Or it can adjust to a preferable range by selecting the tackifier to use in consideration of softening temperature etc.

  Here, tan δ means a loss tangent (= loss elastic modulus / storage elastic modulus) in a dynamic viscoelastic spectrum measured under the following conditions in a measurement temperature range of −50 ° C. to 80 ° C.

Viscoelastic spectrometer: Trade name “DVA-200” (manufactured by IT Measurement & Control Co., Ltd.)
Sample size of the pressure-sensitive adhesive layer: thickness of about 1.5 mm × 5 mm × 10 mm
Set temperature rise rate: 6 ° C / min Measurement frequency: 10Hz
Measurement mode: shear

  By setting the tan δ peak temperature thus measured within this range, the cohesive force of the pressure-sensitive adhesive layer can be improved in combination with the action of the tackifier. Thereby, even when the pressure-sensitive adhesive layer is adhered to the back surface of the base material layer of the surface protection film to form a wound body, the surface protection film can be easily peeled from the back surface of the base material layer. That is, the wound body can be rewound without difficulty. Moreover, even when applied to an adherend having irregularities on the surface, the irregularities can be followed, and the surface protection of the adherend can be ensured.

In another preferred embodiment of the surface protective film of the present invention,
The substrate layer is a polyolefin substrate layer;
The pressure-sensitive adhesive composition further contains a tackifier and a styrenic block phase reinforcing agent, and the polymer (i) and the aromatic alkenyl compound unit in the polymer (ii) and the styrenic block phase reinforcing agent. The ratio of the weight to the weight of the pressure-sensitive adhesive layer (aromatic alkenyl compound unit content) is 20 to 50% by weight. When the proportion is less than 20% by weight, the adhesive strength with time may be easily increased, and when the proportion exceeds 50% by weight, high adhesive strength may not be obtained.
Here, as the tackifier, those exemplified above can be used.

  The tackifier is preferably used in an amount that can prevent adhesive residue when the surface protective film is peeled off from the adherend. For example, the tackifier is preferably contained in an amount of about 5 to 50 parts by weight, more preferably 10 parts by weight to 100 parts by weight of the rubber-based resin component (aromatic alkenyl block copolymer). About 40 parts by weight.

  Here, as the styrene block phase reinforcing agent, those exemplified above can be used.

  The styrenic block phase reinforcing agent is, for example, preferably blended in an amount of about 40 parts by weight or less, more preferably about 30 parts by weight or less based on 100 parts by weight of the aromatic alkenyl block copolymer. Moreover, although it should just be mix | blended more than 0 weight part, 1 weight part or more is preferable.

  By using the styrenic block phase reinforcing agent, the cohesive force of the pressure-sensitive adhesive layer can be improved by being compatible with the styrene (St) phase in the styrene copolymer block. Thereby, the surface protective film adhered from the back surface of the polyolefin base material layer can be easily peeled off, and the wound body can be easily rewound. Moreover, the adhesive residue at the time of peeling a surface protection film from a to-be-adhered body can be prevented, and it becomes possible to peel with a comparatively small force.

In the surface protective film of the present invention, the storage modulus G at 70 ° C. of the pressure-sensitive adhesive layer 'is preferably ^{4.5 × 10 5 Pa~6.0 × 10 5} Pa.

When the storage elastic modulus G ′ is 4.5 × 10 ⁵ Pa or more, undesirable adhesion progress is suppressed even in a high temperature environment, while the storage elastic modulus G ′ is 6.0 × 10 ⁵ Pa or less. In some cases, appropriate adhesive strength can be obtained.

  In order to adjust the storage elastic modulus G ′ of the pressure-sensitive adhesive, the cohesive strength of the aromatic alkenyl block copolymer is adjusted by adjusting the aromatic alkenyl compound unit content of the pressure-sensitive adhesive layer in the surface protective film of the present invention. It may be within an appropriate range. The content can be adjusted by using an aromatic alkenyl block copolymer having a content of a component derived from an appropriate aromatic alkenyl monomer and / or adding a styrenic block phase reinforcing agent to the pressure-sensitive adhesive layer. Can be implemented. The styrenic block phase reinforcing agent is an agent that reinforces the island phase of the sea-island structure formed by the aromatic alkenyl block copolymer, and has a property of being compatible with the domain made of the aromatic alkenyl block copolymer.

  The amount of the styrenic block phase reinforcing agent used is preferably 40 parts by weight or less, more preferably 30 parts by weight or less, based on 100 parts by weight of the aromatic alkenyl block copolymer. When the amount used is too large, the adhesive strength is insufficient, and the fluidity may be deteriorated in the case of extrusion molding. The lower limit of the amount used is not particularly limited, and when there is no need to adjust the aromatic alkenyl compound unit content as described above, addition is unnecessary, but it is preferably 1 part by weight or more.

In another preferred embodiment, the surface protective film of the present invention is for protecting the surface of the prism surface of the prism sheet, and is affixed to the prism surface and is 0.3 N / cm ² under an atmosphere of 70 ° C. The depth of penetration of the prism apex angle of the prism surface into the adhesive when the load is applied for 24 hours is 1% or more and less than 40% of the thickness of the adhesive layer.

  The bite depth is measured by the following method.

The surface protection film to be tested is attached to the surface of the prism sheet at a speed of 300 mm / min using a 2 kg pressure rubber roller in an environment of a room temperature of 23 ° C. and a relative humidity of 50%. A prism sheet having a prism center distance of 50 μm and a height of 25 μm is used. Thereafter, a prism sheet with a surface protective film attached is sandwiched between polycarbonate plates (thickness 2 mm), a pressure of 0.3 N / cm ² is applied, and the mixture is allowed to stand in an environment of 70 ° C. for 24 hours. Thereafter, the surface protective film is peeled off at a peeling angle of 180 degrees, the surface of the pressure-sensitive adhesive layer is observed with a laser microscope, and the depth of biting into the pressure-sensitive adhesive layer at the apex angle of the lens portion (prism) of the prism sheet is measured.

  Adhesion when the penetration depth is 1% or more and less than 40% of the thickness of the pressure-sensitive adhesive layer without being adversely affected by adhesive physical properties such as adhesive strength in a high temperature (eg, 70 ° C.) environment. Progress is suppressed.

  Setting the bite depth to 1% or more and less than 40% of the thickness of the pressure-sensitive adhesive layer is achieved, for example, by controlling the storage elastic modulus G ′ of the pressure-sensitive adhesive layer at 70 ° C. to the above-mentioned preferable range. Is done.

In another preferred embodiment, the surface protective film of the present invention is for protecting the prism surface of the prism sheet,
Depth of biting into the pressure-sensitive adhesive layer of the prism apex angle of the prism surface when a projection having a diameter of 400 μm and a height of 12 μm is pressed against the surface opposite to the prism surface side. Is not less than 1% and less than 100% of the thickness of the pressure-sensitive adhesive layer.

Here, the condition for pressing the protrusion is preferably 24 hours with a force of 0.8 N / cm ^{2 in} an atmosphere of 50 ° C.

  In addition, when the protrusion has a diameter of 400 μm or less and a height of 12 μm or less, the upper limit of the biting depth is similarly predicted to be less than 100% of the pressure-sensitive adhesive layer thickness.

  Therefore, when the surface protective film of the present invention is affixed to the prism sheet and another surface protective film is affixed to the smooth sheet surface, for example, when several tens of prism sheets are stacked and stored, the smooth sheet surface Even if there are protrusions such as FE and biting foreign matter in the surface protective film, the aromatic alkenyl compound unit content of the adhesive in the adhesive layer of the surface protective film is set to an appropriate amount. The agent layer becomes hard, and excessive biting of the lens portion of the prism sheet into the pressure-sensitive adhesive layer of the surface protective film is surely suppressed. Thereby, the lens surface (prism surface) of the prism sheet is hardly damaged.

  Making the penetration depth 1% or more and less than 100% of the pressure-sensitive adhesive layer thickness is mainly that the aromatic alkenyl compound unit content of the aromatic alkenyl block copolymer is 30 to 50% by weight, Has been achieved. If this content is less than 30% by weight, the cohesive force of the pressure-sensitive adhesive is low, so that the depth of biting into the pressure-sensitive adhesive layer of the prism lens may not be suppressed. Conversely, if this content exceeds 50% by weight, the cohesive force of the pressure-sensitive adhesive is too high, and the prism lens is difficult to bite into the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive force becomes too low, so that it can be used as a protective film. It may not be possible.

  The lens portion of the prism sheet to which the surface protective film of the present invention is applied has a prism shape substantially consisting of a triangular prism. In the present specification, a surface having such a prism-shaped lens portion is referred to as a prism surface. More specifically, as shown in FIG. 2, the prism sheet 1 has a structure in which a plurality of triangular prism-shaped lens portions 3 are integrated on one surface of a flat sheet 2. The lens unit 3 has a substantially triangular prism shape. A plurality of lens portions 3 are closely arranged in parallel so that the ridge lines of the triangular prism are parallel to each other. The outer surface of the prism-shaped lens portion 3 is protected by the surface protective film of the present invention.

  For example, as shown in a sectional view in FIG. 3, the first surface protective film 4 (surface protective film of the present invention) is affixed to the portion of the prism sheet 1 where the lens portion 3 is provided. The first surface protective film 4 has a base material layer 5 and an adhesive layer 6 provided on one surface of the base material layer 5, and the plurality of lenses of the prism sheet 1 from the adhesive layer 6 side. It is affixed to the side where the part 3 is provided. Therefore, the surface protective film of the present invention is stuck so as to be in contact with the plurality of apexes 3 a of the triangular prism-shaped lens unit 3. Further, the cross-sectional shape of the lens portion 3 of this triangular prism is a triangle, but this triangle is preferably an isosceles triangle with the side fixed to the sheet as the base.

  On the other hand, a second surface protective film 7 is attached to the flat surface of the prism sheet 1 opposite to the side on which the lens portion 3 is provided, if desired. If projections such as fish eyes (FE) or biting foreign matter are present on the surface protective film 7, it may cause damage to the top of the lens portion.

  In addition, the side surface in the prism shape of a triangular prism shall mean the three side surfaces extended in the length direction of a triangular prism.

  In a suitable prism sheet to which the surface protective film of the present invention is applied, it is preferable that the distance between adjacent prisms in a plurality of substantially prismatic prisms, that is, the prism pitch is about 10 to 1000 μm, More preferably, the thickness is 10 to 500 μm, but the adherend to which the surface protective film of the present invention is applied is not limited thereto.

<Manufacturing method>
In the pressure-sensitive adhesive composition of the present invention, for example, copolymer (I) and copolymer (II) are synthesized by block polymerization, blended at a predetermined mass ratio, and then hydrogenated as desired. , Copolymer (I) or a hydrogenated product thereof, and a mixture of copolymer (I) or the hydrogenated product thereof, and an additive to be blended if desired is mixed by a conventional method .

  As the hydrogenation catalyst, a compound containing any one of Group Ib, IVb, Vb, VIb, VIIb, and Group VIII 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 of the present invention. The composition 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 can be suitably used for an uneven adherend such as an optical plate, a prism sheet, and a diffusion film, but is not limited to this, for example, a sheet having a smooth surface It can also be used for surface protection.

Although it does not specifically limit as a material which comprises the sheet | seat used as a to-be-adhered body, Resin which has translucency, for example, acrylic resin, a polycarbonate, etc. are mentioned.

  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).

  Hereinafter, the desired copolymer composition was obtained in the same manner (Synthesis Examples 2 to 24 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]

(Examples 1-8, Comparative Examples 1-7)
100 parts by weight of each copolymer composition (Table 2) obtained by the above synthesis methods, 30 parts by weight of Alcon P100 (manufactured by Arakawa Chemical Industries) as a tackifier, and Irganox 1010 as an antioxidant 1 weight part (made by Ciba Specialty Chemicals) was mix | blended and each adhesive composition was obtained. The composition is shown in Table 2 below.

  Polypropylene (J715M manufactured by Prime Polymer Co., Ltd.) is used as the base material, and the base material and each pressure-sensitive adhesive composition are coextruded by the T-die method, so that the base material layer has a thickness of 34 μm and the pressure-sensitive adhesive layer has a thickness of 6 μm. The surface protection films of Examples 1 to 8 and Comparative Examples 1 to 7, which were laminated and integrated, were molded and wound bodies wound on a paper core having an inner diameter of 3 inches were 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.

(2) Initial adhesive force Each surface protection film was affixed so that the lens surface of the prism sheet which has an unevenness | corrugation might be covered. A prism sheet made of acrylic resin having a thickness of 130 μm and having a prism pitch of 50 μm and a height of 25 μm was prepared. 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 25 mm width was measured at a speed of 300 mm / min. The peeling direction at this time was the ridge line direction of the prism. The peel strength measured in this manner was taken as the initial adhesive strength.

(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 is sandwiched between polycarbonate plates (thickness 2 mm), a pressure of 6.0 × 10 ⁻³ MPa is applied, and in this state, the environment is 60 ° C. and a relative humidity of 90% for 48 hours. I left it alone. After taking this out to room temperature and leaving it for 30 minutes, according to JISZ0237, 180 degree peel strength in 25 mm width was measured at the speed of 300 mm / min.

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) = (adhesive force with time / initial adhesive force) × 100

(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]

[Table 3]

<Criteria>
Adhesive strength (initial)
○ (Good): 0.1 N / 25 mm or more x (Bad): Less than 0.1 N / 25 mm adhesive force (rate of change)
◎ (excellent): less than 200% ○ (good): 200% or more and 500% or less × (defect): over 500% deployability ◎ (excellent): less than 2.0 N / 50 mm ○ (good): 2.0 N / 50 mm More than 3.5N / 50mm or less x (defect): More than 3.5N / 50mm

Example 9
100 parts by weight of the copolymer composition of Synthesis Example 4, 18 parts by weight of Alcon P100 (Arakawa Chemical Industries) as a tackifier, and 1 part by weight of Irganox 1010 (manufactured by Ciba Specialty Chemicals) as an antioxidant Then, 0.5 part by weight of Tinuvin 326 (manufactured by Ciba Specialty Chemicals) was blended as an ultraviolet absorber and kneaded to obtain a pressure-sensitive adhesive composition.
Polypropylene (J715M manufactured by Prime Polymer Co., Ltd.) is used as the base material, and the base material and the pressure-sensitive adhesive composition are coextruded by the T-die method, so that the base material layer having a thickness of 34 μm and the pressure-sensitive adhesive layer having a thickness of 6 μm A surface protection film was formed by laminating and integrating, and a wound body wound around a paper core having an inner diameter of 3 inches was obtained.
(Examples 10, 11, and 13 and Comparative Examples 8 to 10)
As shown in Table 4, the pressure-sensitive adhesive composition was blended, and a wound body of the surface protective film was obtained in the same manner as in Example 9.
(Example 12)
In the same manner as in Example 9, except that 100 parts by weight of the copolymer composition of Synthesis Example 7 and 40 parts by weight of Clearon P125 (manufactured by Yasuhara Chemical Co., Ltd.) as a tackifier were used. A wound body of the surface protective film was obtained.

(Evaluation)
The following items were evaluated for each surface protective film obtained as described above.
The results are shown in Table 5.

(1) tan δ peak temperature The viscoelastic spectrum of the pressure-sensitive adhesive layer is −50 at a frequency of 10 Hz and a temperature increase rate of 6 ° C./min using a dynamic viscoelastic spectrum measuring apparatus (product number: DVA-200, manufactured by IT Measurement Control Co., Ltd.). The temperature was measured in the range of 80 ° C. to 80 ° C., and the temperature at which tan δ was maximized (tan δ peak temperature) was determined.

(2) Initial adhesive strength Each surface protection film of an Example and a comparative example was affixed so that the lens surface of the prism sheet which has an unevenness | corrugation might be covered. A prism sheet made of acrylic resin having a thickness of 130 μm and having a prism pitch of 50 μm and a height of 30 μm was prepared. 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 25 mm width was measured at a speed of 300 mm / min. The peeling direction at this time was the ridge line direction of the prism. The peel strength measured in this manner was taken as the initial adhesive strength.

(3) Unfolding force Except for changing the unwinding speed of the 50 mm-wide wound bodies of the surface protective films of Examples and Comparative Examples, high-speed unwinding force at a unwinding speed of 20 m / min in accordance with JIS Z0237. Was measured as the deployment force.
[Table 4]

[Table 5]

<Criteria>
Initial adhesive strength ○ (good): 0.1 N / 25 mm or more × (defect): Less than 0.1 N / 25 mm deployment force ◎ (excellent): 2.5 N / 50 mm or less ○ (good): 3.5 N / 50 mm or less × (Bad): Over 3.5N / 50mm

(Example 14)
Adhesive layer:
100 parts by weight of the copolymer composition of Synthesis Example 4, 50 parts by weight of Alcon P100 (manufactured by Arakawa Chemical Industries) as a tackifier, and 10 parts by weight of ENDEX 155 (manufactured by Eastman Chemical) as a styrene block phase reinforcing agent 1 part by weight of Irganox 1010 (manufactured by Ciba Specialty Chemicals) as an antioxidant was mixed and kneaded to obtain a pressure-sensitive adhesive composition.
Base material layer:
A base material made of polypropylene (J715M manufactured by Prime Polymer Co., Ltd.) and the pressure-sensitive adhesive composition obtained above were coextruded by a T-die method, and a 34 μm-thick polypropylene base material layer and a 6 μm-thick pressure-sensitive adhesive were laminated. The integrated surface protective adhesive sheet was wound around a paper core having an inner diameter of 3 inches to obtain a wound body.

(Examples 15-19, Comparative Examples 11-14)
As shown in Table 6 below, the pressure-sensitive adhesive composition was blended, and a wound body of the surface protective film was obtained in the same manner as in Example 14.
In Table 6, “St / adhesive layer (% by weight)” is the ratio of the total weight of the aromatic alkenyl compound units of the copolymer composition and the styrenic block phase reinforcing agent to the weight of the adhesive ( Aromatic alkenyl compound unit content). In addition, “St / adhesive layer (—TF) (% by weight)” is the total amount of the copolymer composition and the styrene block phase reinforcing agent relative to the total weight of the copolymer composition and the styrene block phase reinforcing agent. The ratio of the total weight of the aromatic alkenyl units is shown.

(Evaluation)
The following items were evaluated for each surface protective film obtained as described above. The results are shown in Table 7.

(1) tan δ peak temperature The viscoelastic spectrum of the pressure-sensitive adhesive layer is −50 at a frequency of 10 Hz and a temperature increase rate of 6 ° C./min using a dynamic viscoelastic spectrum measuring apparatus (product number: DVA-200, manufactured by IT Measurement Control Co., Ltd.). The temperature was measured in the range of 80 ° C. to 80 ° C., and the temperature at which tan δ was maximized was determined.

(2) Initial adhesive strength Each surface protection film of an Example and a comparative example was affixed so that the lens surface of the prism sheet which has an unevenness | corrugation might be covered. A prism sheet made of acrylic resin having a thickness of 130 μm and having a prism pitch of 50 μm and a height of 30 μm was prepared. 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 25 mm width was measured at a speed of 300 mm / min. The peeling direction at this time was the ridge line direction of the prism. The peel strength measured in this manner was taken as the initial adhesive strength.

(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 is sandwiched between polycarbonate plates (thickness 2 mm), a pressure of 6.0 × 10 ⁻³ MPa is applied, and in this state, the environment is 60 ° C. and a relative humidity of 90% for 48 hours. I left it alone. After taking this out to room temperature and leaving it for 30 minutes, according to JISZ0237, 180 degree peel strength in 25 mm width was measured at the speed of 300 mm / min.

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) = (adhesive force with time / initial adhesive force) × 100

［表７］

(4) Unfolding force A high-speed unwinding force at a rewinding speed of 20 m / min, in accordance with JIS Z0237, except that the unwinding speed was changed for the wound bodies with a width of 50 mm of the surface protective films of the examples and comparative examples. Was measured as the deployment force.
[Table 6]

[Table 7]

<Criteria>
Adhesive strength (initial)
○ (good): 0.1 N / 25 mm or more Δ (possible): 0.05 N / 25 mm or more and less than 0.1 N / 25 mm x (impossible): less than 0.05 N / 25 mm adhesive force (change rate)
◎ (excellent): Less than 200% ○ (good): 200% or more and 500% or less × (defect): over 500% deployment force ○ (good): 3.5 N / 50 mm or less × (defect): 3.5 N / 50 mm Super

(Example 20)
Coextruded by the T-die method to form a surface protection film (width 700 mm) for a prism sheet with a base material layer (thickness 34 μm) / adhesive layer (thickness 6 μm) to obtain a wound body having a winding length of 100 m It was. The material for forming the pressure-sensitive adhesive layer is 30 parts by weight of an alicyclic saturated petroleum resin Alcon P125 (manufactured by Arakawa Chemical Industries, Ltd.) having a softening point of 125 ° C. as a tackifier in 100 parts by weight of the copolymer composition of Synthesis Example 13. 20 parts by weight of ENDEX155 (manufactured by Eastman Chemical Co.) as a styrene block phase reinforcing agent, 1 part by weight of Irganox 1010 (manufactured by Ciba Specialty Chemicals) as an antioxidant, and Tinuvin 326 (Ciba Specialty) as an ultraviolet absorber (Chemicals Co., Ltd.) 0.5 parts by weight was blended, kneaded with a twin screw extruder, and pelletized. The material for forming the base material layer includes 100 parts by weight of block PP and 100 parts by weight of a film (block polypropylene (block PP) as the base material), and the copolymer composition of Synthesis Example 13 as the pressure sensitive adhesive layer. Parts, and 30 parts of Alcon P125 (made by Arakawa Chemical Industries) as a tackifier, 20 parts by weight of ENDEX 155 (made by Eastman Chemical Co.) as a styrenic block phase reinforcing agent, and Irganox 1010 (Ciba Specialty Chemicals) as an antioxidant 1 part by weight, containing 0.5 part by weight of Tinuvin 326 (manufactured by Ciba Specialty Chemicals) as an ultraviolet absorber) 10 parts by weight of the film trimmed at both ends to adjust the winding shape of the roll during molding Are mixed with a twin screw extruder and pelletized. It had.

(Examples 21 to 25)
Except for changing the amount of tackifier and the amount of styrenic block phase reinforcing agent (may be abbreviated as St block reinforcing agent in this specification) as shown in Table 8 below. A wound body of a surface protective film for a prism sheet was obtained in the same manner as in Example 20.
“St / adhesive (% by weight)” in Table 8 is the ratio of the total weight of aromatic alkenyl units of the copolymer composition and the styrene block phase reinforcing agent to the weight of the adhesive (aromatic Alkenyl compound unit content).

(Evaluation)
About the item described in the following (1)-(4), the surface protection film of Examples 20-25 was evaluated and tested. The results are shown in Table 9.

(1) Initial adhesive strength Each surface protection film of an Example and a comparative example was affixed so that the lens surface of the prism sheet which has an unevenness | corrugation might be covered. As the prism sheet, a prism sheet made of acrylic resin having a thickness of 130 μm and having a prism pitch of 50 μm and a height of 30 μm was used. Affixing conditions are room temperature 23 ° C. and relative humidity 50%, respectively, using a 2 kg pressure-bonded rubber roller, affixed at a speed of 300 mm / min, left in that state for 1 hour, and then compliant with JIS Z0237 The 180 degree peel strength at a width of 25 mm was measured at a speed of 300 mm / min. The peel strength measured in this manner was taken as the initial adhesive strength.

(2) Adhesive strength with time 2 kg of each surface protective film of Examples and Comparative Examples was applied to the surface of the prism sheet used for the initial adhesive strength evaluation of (1) under the environment of room temperature 23 ° C. and relative humidity 50%. Using a pressure-bonded rubber roller, it was attached 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), a pressure of 0.3 N / cm ² was applied, and the mixture was allowed to stand in an environment of 70 ° C. for 24 hours. Then, after leaving still for 1 hour in the environment of room temperature 23 degreeC and relative humidity 50%, based on JISZ0237, 180 degree peel strength in 25 mm width was measured at the speed | rate of 300 mm / min. 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) = (adhesive force with time / initial adhesive force) × 100

(3) Storage elastic modulus G ′
The storage elastic modulus of the pressure-sensitive adhesive layer is in the range of −50 ° C. to + 150 ° C. at a frequency of 1 Hz and a temperature increase rate of 3 ° C./min using a dynamic viscoelasticity spectrum measurement device (IT Measurement Control, product number: DVA200). The storage elastic modulus G ′ at 70 ° C. was determined.

(4) Amount of biting The surface protective film was affixed to the surface of the prism sheet at a speed of 300 mm / min using a 2 kg pressure rubber roller in an environment of a room temperature of 23 ° C. and a relative humidity of 50%. A prism sheet having a prism pitch of 50 μm and a height of 30 μm was used. Thereafter, a prism sheet with a surface protective film attached thereto was sandwiched between polycarbonate plates (thickness 2 mm), a pressure of 0.3 N / cm ² was applied, and the mixture was allowed to stand in an environment of 70 ° C. for 24 hours. Thereafter, the surface protective film was peeled off at a peeling angle of 180 °, the surface of the pressure-sensitive adhesive layer was observed with a laser microscope, and the depth of biting into the pressure-sensitive adhesive layer of the lens portion of the prism sheet was measured.

The amount of biting in was calculated by the following formula.
Encroachment (%)
= (Depth of biting into the pressure-sensitive adhesive layer of the lens portion of the prism sheet) / (pressure-sensitive adhesive layer thickness: 6 μm) × 100
[Table 8]

[Table 9]

<Criteria>
Amount of bite ○ (excellent): 1% or more and less than 40% △ (good): 40% or more and less than 80% × (defect): 80% or more adhesive strength (rate of change)
◎ (excellent): less than 150% ○ (good): 150% to 300%

(Example 26)
As shown in Table 10 below, 100 parts by weight of the copolymer composition of Synthesis Example 14 was mixed with 30 parts by weight of Alcon P-125 (manufactured by Arakawa Chemical Industries), which is an alicyclic saturated petroleum resin, as a tackifier. This was added to obtain a pressure-sensitive adhesive composition.
On the other hand, a pressure-sensitive adhesive layer made of the above pressure-sensitive adhesive composition, a base material made of a resin composition containing 75 parts by weight of block polypropylene (block PP) shown in Table 10 and 25 parts by weight of low-density polyethylene (LDPE). The surface protective film was co-extruded by a T-die method, and a 40 μm thick polypropylene base material and a 6 μm thick adhesive layer were laminated and integrated.

(Examples 27-28 and Comparative Examples 15-19)
A surface protective film was prepared and evaluated in the same manner as in Example 25 except that the composition and thickness of the pressure-sensitive adhesive layer were changed as shown in Table 10 below. All tackifiers were Alcon P-125.

  In Comparative Example 18, the film formability was poor.

(Evaluation)
About these surface protection films,
1) The lens part of a prism sheet when a projection having a diameter of 400 μm and a height of 12 μm is pressed against a prism sheet with a surface protective film attached thereto at a force of 0.8 N / cm ^{2 in} a 50 ° C. atmosphere for 24 hours. Of bite into the adhesive,
2) Initial adhesive strength (against the prism surface), and 3) Initial adhesive strength (against the flat surface)
Were measured and evaluated as follows.

Further, when evaluating the bite of the prism sheet of 1) above,
4) Prism scratches,
5) Adhesive strength over time (against the prism surface)
6) The adhesive residue was measured and evaluated as follows.

further,
7) The deployment force was measured and evaluated as follows.

  The results are shown in Table 11 below.

1) Encroaching amount The surface protective film obtained above was attached so that the pressure-sensitive adhesive layer surface thereof was in contact with the lens surface of the prism sheet, to prepare a test piece. A prism sheet (BEF, Sumitomo 3M) having a lens portion made of acrylic resin, a sheet made of polyethylene terephthalate having a thickness of 150 μm, a prism pitch of 50 μm, and a height of 23 μm was prepared. In pasting, a pressure of 5.9 × 10 ⁵ Pa was applied from the outside of the surface protective film (that is, the side opposite to the pressure-sensitive adhesive layer surface) and pasted at a speed of 2 m / min. The following laminator was used for pasting, and the pasting pressure was measured using a prescale ultra-low pressure manufactured by Fuji Film Business Supply Co., Ltd.

Laminator Manufacturer: MCK Corporation
Model: MRK-600
Roll: Heat-resistant silicone rubber roll Roll diameter: Φ80
The obtained test piece was cut into a size of 3 cm × 8 cm to prepare a sample piece.

  Moreover, in order to prepare the projection used for the evaluation test, a nylon fiber having a diameter of 0.2 mm is cut into a length of 11 to 13 μm by a cryomicrotome, and a cut piece obtained on the slide glass is fixed. The cut piece was fixed between the slide glass and the surface protective film by sticking the surface protective film obtained above to the slide glass with a 2 kg roller. The resulting convex shape (that is, the protrusion) was observed with a laser microscope, and its diameter and height were determined.

  The diameter and height of the convex shape used for evaluation are shown below.

Diameter: 400μm
Height: 12 μm
The slide glass with a surface protective film having the above convex shape is set on the sample piece so that the sample piece and the surface protective film having the above convex shape are in contact with each other, and a weight of 200 g is placed on the slide glass (0 8 N / cm 2) and left in an oven at 50 ° C. for 24 hours. After 24 hours, the sample piece was taken out, the cross section was cut, the cross section was observed with a scanning electron microscope (SEM), and the depth of penetration (μm) of the lens portion of the prism sheet into the adhesive layer was measured.

  The amount of biting (%) was calculated from the actually measured biting depth (μm) by the following formula.

Encroachment (%)
= (Depth of biting into the pressure-sensitive adhesive layer of the lens portion of the prism sheet) / (pressure-sensitive adhesive layer thickness: 6 μm) × 100

2) Initial adhesive strength (to prism surface)
The surface protective film obtained above was attached so as to cover the lens surface of the prism sheet. At the time of pasting, as in 1), a pressure of 5.9 × 10 ⁵ Pa was applied from the outside of the surface protective film, pasted at a speed of 2 m / min, and left in a room at 23 ° C. ± 2 ° C. for 30 minutes.

  Thereafter, in accordance with JIS Z0237, the 180 degree peel strength at 25 mm (unit: N) was measured in the direction parallel to the ridge line of the prism at a peel rate of 300 mm / min and 30 m / min, respectively. ).

3) Initial adhesive strength (vs flat surface)
As in 1), the surface protective film obtained above was attached to a flat acrylic resin plate under conditions of pressure 5.9 × 10 ⁵ Pa and speed 2 m / min, and placed in a room at 23 ° C. ± 2 ° C. for 30 After leaving for a minute, in accordance with JIS Z0237, the 180-degree peel strength (unit: N) at a width of 25 mm was measured under the condition of a peel rate of 30 m / min.

4) Evaluation of Prism Scratch During the test in 1), the surface protective film taken out from the oven was peeled off from the prism sheet, and the presence or absence of a bright spot generated by the scratch on the lens surface of the prism sheet was visually observed.

  In Table 10 below, X marks are given to samples in which many scratches are observed, Δ marks are given when they are slightly observed, and ○ marks are given when no scratches are observed.

5) Adhesive strength over time (against the prism surface)
The obtained surface protective film was applied to the surface of the prism sheet used in the initial adhesive strength evaluation of 2) under the conditions of pressure 5.9 × 10 ⁵ Pa and speed 2 m / min, as in 1). After standing for 1 week in an atmosphere of ± 2 ° C., 180 degree peel strength at 25 mm width was measured at a peel speed of 300 mm / min in accordance with JIS Z0237. The peel strength measured in this manner was taken as the adhesive strength with time, and the change rate (adhesion progress rate) of the adhesive strength with time was calculated from the initial adhesive strength (against the prism surface, peeling speed 300 mm / min) by the following equation.

Change rate (adhesion progress rate) = (adhesive force with time / initial adhesive force (against the prism surface, peeling speed 300 mm / min)) × 100
6) Adhesive residue In the test of 5), the presence or absence of adhesive residue on the lens surface of the prism sheet after peeling was visually observed together with the measurement of the peel strength. When the adhesive residue was observed on the lens surface, it was marked with x, and when it was not observed at all, it was marked with ○. The results are shown in Table 11 below.

7) Unfolding force Except for changing the unwinding speed of each of the surface protective films of the examples and comparative examples, the unwinding speed was changed according to JIS Z0237, and a high-speed unwinding force was achieved at a unwinding speed of 20 m / min. Measured and used as deployment force.
[Table 10]

[Table 11]

<Criteria>
Amount of bite ○ (good): 1% or more and less than 100% × (bad): less than 1%, 100%
Initial adhesive strength (against prism surface) Peeling speed: 300 mm / min. ○ (good): 0.05 N / 25 mm or more x (defect): less than 0.05 N / 25 mm adhesive strength (rate of change, against prism surface)
◎ (excellent): Less than 200% ○ (good): 200% or more and 500% or less × (defect): 500% super-prism scratch evaluation ○: scratches cannot be visually confirmed ×: adhesive residue evaluation capable of visually confirming scratches ○: The occurrence of adhesive residue cannot be confirmed visually. ×: The developing force capable of confirming the occurrence of adhesive residue visually. ○ (good): 3.5 N / 50 mm or less × (defect): more than 3.5 N / 50 mm

(Example 29)
Coextruded by the T-die method to form a surface protection film (width 700 mm) for a prism sheet with a base material layer (thickness 34 μm) / adhesive layer (thickness 6 μm) to obtain a wound body having a winding length of 100 m It was.

As a material for forming the pressure-sensitive adhesive layer, 100 parts by weight of the copolymer composition of Synthesis Example 13 and 30 parts by weight of an alicyclic saturated petroleum resin Alcon P125 (manufactured by Arakawa Chemical Industries) having a softening point of 125 ° C. as a tackifier. 10 parts by weight of ENDEX155 (manufactured by Eastman Chemical Co.) as a styrene block phase reinforcing agent, 1 part by weight of Irganox 1010 (manufactured by Ciba Specialty Chemicals) as an antioxidant, and Tinuvin 326 (Ciba Specialty Chemicals) as an ultraviolet absorber 0.5 parts by weight was added, and the mixture was kneaded with a twin screw extruder and pelletized.
The material for forming the base material layer includes 75 parts by weight of block PP, 25 parts by weight of low density polyethylene (LDPR), and a part where both ends of the film are trimmed to adjust the roll shape during film forming (as the base material) 100 parts by weight of block polypropylene (block PP), and 100 parts by weight of the copolymer composition of Synthesis Example 13 as an adhesive, 30 parts of Alcon P125 (manufactured by Arakawa Chemical Industries) as a tackifier, and styrene 20 parts by weight of ENDEX155 (manufactured by Eastman Chemical Co., Ltd.) as a block phase reinforcing agent, 1 part by weight of Irganox 1010 (manufactured by Ciba Specialty Chemicals) as an antioxidant, and Tinuvin 326 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as an ultraviolet absorber ) 0.5 parts by weight) 10 parts by weight mixed Thereafter, the mixture was kneaded with a twin screw extruder and pelletized.

  In Table 12, “St / adhesive (% by weight)” is the ratio of the total weight of the aromatic alkenyl compound units of the copolymer composition and the styrenic block phase reinforcing agent to the weight of the adhesive (aromatic alkenyl). Compound unit content).

(Examples 30 to 31, Comparative Examples 20 to 22)
As shown in Table 12 below, the amount and type of polyolefin in the base layer, the pressure-sensitive adhesive layer, the copolymer composition, the amount of styrene, the amount of tackifier, and the styrenic block phase reinforcing agent (that is, St block) A wound body of the surface protective film for a prism sheet was obtained in the same manner as in Example 29 except that the amount of the reinforcing agent was changed.

(Evaluation)
About the item described in the following (1)-(6), the evaluation test of the surface protection film of Examples 29-31 and Comparative Examples 20-22 was carried out. The results are shown in Table 13.
(1) Using surface roughness Ra (Surf Test SJ-301, manufactured by Mitsutoyo), measurement was performed under the following measurement conditions.
(Measurement condition)
Measurement length: 7.2mm
λc: 0.8mm
λs: 2.5 μm
Measurement speed: 0.5mm / s

In addition, according to JIS B0601: 2001, the swell motif average height and the swell motif average length were calculated from the profile measured under the measurement conditions.

(2) Adhesive strength Each surface protective film of Examples and Comparative Examples was attached so as to cover the lens surface of the prism sheet having irregularities. As the prism sheet, a prism sheet made of acrylic resin having a thickness of 130 μm and having a prism pitch of 50 μm and a height of 30 μm was used. Affixing conditions are room temperature 23 ° C. and relative humidity 50%, respectively, using a 2 kg pressure-bonded rubber roller, affixing at a speed of 300 mm / min, and standing in that state for 1 hour, and then conforming to JIS Z0237 The 180 degree peel strength at a width of 25 mm was measured at a speed of 300 mm / min. The peel strength measured in this way was defined as the adhesive strength.

(3) Initial deployment force The initial deployment force was measured in accordance with JIS Z0237 except that the rewind speed was changed for each surface protective film 50 mm wide wound body, and the high speed rewind force was measured at a rewind speed of 15 m / min. did. The high-speed unwinding force measured in this way was used as the initial deployment force.

(4) Time-lapse deployment force The time-lapse deployment force conforms to JIS Z0237 except that the 50 mm width wound body of each surface protection film is cured for one week in a room at 40 ° C. ± 2 ° C. and then the rewind speed is changed. The high-speed rewinding force at a rewinding speed of 15 m / min was measured. The high-speed unwinding force measured in this way was defined as the time-development force. In the table, when the time-development force is 3 N / 50 mm or less, it is evaluated that the feeding property is good, and a mark is given, and when it exceeds 3 N / 50 mm, the feeding property is evaluated as poor. Was attached.

(5) Prism scratch evaluation Each surface protection film of an Example and a comparative example was affixed so that the lens surface of the prism sheet which has an unevenness | corrugation might be covered, and the test piece was produced. As the prism sheet, the same one as used for the adhesive strength evaluation in (2) was used. At the time of pasting, a pressure of 5.9 × 10 ⁵ Pa was applied from the outside of the surface protective film and pasted at a speed of 2 m / min. The test piece was cut into a size of 3 cm × 8 cm to prepare a sample piece.

In addition, a nylon fiber having a diameter of 0.2 mm is cut into a length of 8 to 10 μm by a cryomicrotome, a cut piece is fixed on the slide glass, and the obtained surface protective film is pasted on the slide glass with a 2 kg roller. The piece was fixed between the slide glass and the surface protective film to prepare a convex sample having a diameter of 400 μm and a height of 10 μm.
The convex sample is set on the sample piece covering the lens part with the surface protective film so as to overlap the surface protective film covering the lens part, and a weight of 140 g is placed on the slide glass, It was allowed to stand for 24 hours in an oven. After 24 hours, the test piece was taken out, the surface protective film was peeled off from the prism sheet, and the presence or absence of bright spots generated by scratches on the lens surface of the prism sheet was visually observed. In Table 13 below, samples with a lot of scratches are marked with x (defect), Δ (good) when slightly observed, and ○ (excellent) when not observed at all.

[Table 12]

[Table 13]

(Examples 32-38, Comparative Examples 23-29)
100 parts by weight of the copolymer composition obtained by the above synthesis method, 5 parts by weight of Alcon P125 (Arakawa Chemical Industries) as a tackifier, and Irganox 1010 (manufactured by Ciba Specialty Chemicals) as an antioxidant ) 1 part by weight was blended to obtain an adhesive composition.

  Polypropylene (J715M manufactured by Prime Polymer Co., Ltd.) is used as the base material, and the base material and the pressure-sensitive adhesive composition are coextruded by the T-die method. A surface protection film was formed by laminating and integrating, 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 15.

(1) Film-forming property The appearance of the surface protective film formed by coextrusion was evaluated by visual observation.
(2) Initial adhesive strength Each surface protection film of an Example and a comparative example was affixed so that the lens surface of a diffusion film (3M company make, DBEF) 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 25 mm width was measured at a speed of 300 mm / min. The peeling direction at this time was the MD (machine direction) direction of the surface protective film. The peel strength measured in this manner was taken as the initial adhesive strength.

(3) Adhesive strength with time 2 kg of each surface protective film of Examples and Comparative Examples was applied to the surface of the diffusion film used for the initial adhesive strength evaluation in (1) under the environment of room temperature 23 ° C. and relative humidity 50%. Using a pressure-bonded rubber roller, it was attached at a speed of 300 mm / min. Thereafter, a diffusion film having a surface protective film attached thereto is sandwiched between polycarbonate plates (thickness 2 mm), a pressure of 6.0 × 10 ⁻³ MPa is applied, and in that state, an environment of 60 ° C. and a relative humidity of 90% is used for 48 hours. I left it alone. After taking this out to room temperature and leaving it for 30 minutes, according to JISZ0237, 180 degree peel strength in 25 mm width was measured at the speed of 300 mm / min.

The peel strength measured in this way was used as the adhesive strength with time, and the rate of progress of the adhesive strength with time was calculated from the initial adhesive strength by the following equation.
Rate of change (adhesion progress rate) = (adhesive force with time / initial adhesive force) × 100

(4) Unfolding force According to JIS Z0237 except that the unwinding speed of the 50 mm-wide wound bodies of the respective surface protective films of Examples and Comparative Examples was changed at a rewinding speed of 5 m / min and 15 m / min. The unwinding force was measured and used as the deploying force.
[Table 14]

[Table 15]

<Criteria>
Adhesive strength (initial)
○ (good): 0.05 N / 25 mm or more and less than 0.35 N / 25 mm x (defect): less than 0.05 N / 25 mm or 0.35 N / 25 mm or more adhesive force (change rate)
◎ (excellent): less than 200% ○ (good): 200% or more and 500% or less × (defect): over 500% deployability ◎ (excellent): less than 2.0 N / 50 mm ○ (good): 2.0 N / 50 mm More than 3.5N / 50mm or less x (defect): More than 3.5N / 50mm

  The pressure-sensitive adhesive composition of the present invention is suitably used for a pressure-sensitive adhesive layer of a surface protective film such as a prism sheet or a diffusion film.

  The surface protective film of this invention is used suitably for surface protection, such as a prism sheet and a diffusion film.

1 Prism sheet 2 Sheet 3 Lens part (prism)
3a Top of lens part (prism apex angle)
4 First surface protective film 5 Base material layer 6 Adhesive layer 7 Second surface protective film

Claims (9)

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. A pressure-sensitive adhesive composition characterized by
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, and the aromatic alkenyl compound unit content (St (b)) is 10 to 35% by weight, Polymer block with vinyl bond content in the range of 50-90%   The surface protection film which has a base material layer and the adhesive layer which consists of an adhesive composition of Claim 1. The substrate layer is a polyolefin substrate layer;
The pressure-sensitive adhesive composition further contains a tackifier, and the maximum temperature of tan δ obtained by measuring dynamic viscoelasticity at −50 ° C. to 80 ° C. of the pressure-sensitive adhesive layer is −10 ° C. to 20 ° C. The surface protective film according to claim 2, wherein The substrate layer is a polyolefin substrate layer;
The pressure-sensitive adhesive composition further contains a tackifier and a styrenic block phase reinforcing agent,
The ratio of the weight of the aromatic alkenyl compound unit in the polymer (i), the polymer (ii) and the styrenic block phase reinforcing agent to the weight of the pressure-sensitive adhesive layer (aromatic alkenyl compound unit content) is 20 The surface protective film according to claim 2, which is ˜50 wt%. According to any one of claims 2-4, wherein the storage modulus G at 70 ° C. of the pressure-sensitive adhesive layer 'is ^{4.5 × 10 5 Pa~6.0 × 10 5} Pa Surface protective film. For protecting the prism surface of the prism sheet, the prism apex angle of the prism surface is affixed to the prism surface and subjected to a load of 0.3 N / cm ² for 24 hours in an atmosphere at 70 ° C. 6. The surface protective film according to claim 5, wherein the depth of penetration into the pressure-sensitive adhesive is 1% or more and less than 40% of the thickness of the pressure-sensitive adhesive layer. For protecting the prism surface of the prism sheet,
Depth of biting into the pressure-sensitive adhesive layer of the prism apex angle of the prism surface when a projection having a diameter of 400 μm and a height of 12 μm is pressed against the surface opposite to the prism surface side. The surface protective film according to claim 2, wherein the thickness is 1% or more and less than 100% of the thickness of the pressure-sensitive adhesive layer.   For protecting the prism surface of the prism sheet, the outer surface of the base material layer has a surface roughness Ra of 0.7 to 2.0 μm, an average height of a waviness motif of 3 μm or more, and a waviness motif of 350 μm or more and 600 μm or less. It has an average length, The surface protection film of any one of Claims 2-6 characterized by the above-mentioned.   It is an object for surface protection of a diffusion film, The surface protection film of any one of Claims 2-5.

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