JP2010100788A - Surface protection film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protection film for protecting a prism sheet scarcely damaging a lens part even if small protrusions and fish-eyes are present on the surface protection film on a flat face of the prism sheet or a load is applied in lamination stage. <P>SOLUTION: The surface protection film for protecting the prism sheet comprising a sheet and a plurality of prismatic lens parts essentially composed of a triangular prism, is pasted to an outer surface of the lens part. The multiple lens parts are fixed to one surface of the sheet in such a manner that ridges extending along the length of the triangular prism are arranged parallel to each other and the face of the prism opposite to the ridge is fixed to one surface of the sheet. The protection film comprises a polyolefin substrate layer and a tacky adhesive layer composed mainly of a rubbery resin component laminated on one surface of the polyolefin substrate layer, the surface roughness Ra of a surface of the polyolefin substrate layer opposite to the tacky adhesive layer is 0.7 μm≤Ra≤2.0 μm, and the penetrating depth of the prism lens to the tacky adhesive layer is ≥1% and <100% of the thickness of the tacky adhesive layer measured by pasting the protection film to the outer face of the lens part and pressing a protrusion having a diameter of 400 μm and a height of 10 μm with a force of 0.8 N/cm<SP>2</SP>for 24 h in an atmosphere of 50°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface protective film for protecting the outer surface of a prism type lens portion of a prism sheet used in an optical device.

  In order to protect the surface of various adherends, a surface protective film in which an adhesive layer is laminated on one surface of a sheet-like substrate is widely used. On the other hand, prism sheets in which a plurality of substantially prismatic prisms are fixed to one surface of a sheet are used in various optical devices. In this type of prism sheet, it is necessary to protect the outer surface of the lens part until it is used. Therefore, the surface protective film is also used for such applications.

  By the way, in the surface protective film for protecting the surface of the prism sheet, when the increase in the adhesive force with time is large, it is difficult to smoothly peel the protective film from the surface of the lens portion of the prism sheet. Therefore, an acrylic pressure-sensitive adhesive having a large increase in adhesive strength with time is not used, and a natural rubber-based pressure-sensitive adhesive is mainly used.

On the other hand, prism sheets with a 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, due to the load of the prism sheet disposed above, the ridge line of the prism of the lens portion of the prism sheet disposed below (that is, the top of the lens portion) may be destroyed, and the optical quality may deteriorate. there were. This is because the top of the lens part of the prism sheet 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 dispersion / relaxation effect of the load by the adhesive layer. This is thought to be due to 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 from the viewpoint of manufacturing cost, but also the depth of biting into the pressure-sensitive adhesive layer of the lens portion is increased, and there is a possibility that the increase in pressure-sensitive adhesive force will increase with time.

In order to solve such a problem, the following Patent Document 1 discloses a surface protective film in which an adhesive layer having a thickness of 10 μm or more mainly composed of a styrene-based elastomer is used instead of natural rubber, It is described that a sufficient protective function for the adherend and appropriate adhesive properties can be satisfied at the same time. However, as a result of testing by the present inventors, even when the adhesive layer using the styrene-based elastomer described in Patent Document 1 is used for protecting the surface of the prism sheet, depending on the selection of the material used for the adhesive layer, Bite into the adhesive layer, increasing the adhesive force, and it has been found that the top of the lens part may be destroyed.
In the following Patent Document 2, a surface protective film having an adhesive layer using a styrene elastomer is disclosed. By adjusting the elastic modulus of the adhesive, the prism lens is 12.5 g / cm ² in a 60 ° C. atmosphere. The depth of penetration into the adhesive layer of the prism lens at the portion pressed for 3 days by the force of 90% or less is less than 90% of the thickness of the adhesive layer, and prism sheets each having a surface protective film attached to the prism sheet are stacked in units of several tens. It is described that a good surface protective film can be obtained without damage to the top of the lens part even when stored in the storage.
By the way, the opposite side of the surface having the prism shape of a general prism sheet is often a flat surface, and generally a surface protective film is also used for the flat surface. That is, when the prism sheets are stacked and stored, the surface protective film on the flat surface opposite to the prism surface of the prism sheet is in contact with the protective film of the prism sheet. As a result of investigations by the present inventors, fish eye (FE
) Or a biting foreign matter or the like, stress concentrates on the protruding portion, and therefore, when stored in a stacked state, the top of the lens portion is broken even under the conditions described in Patent Document 2. It was found to occur.

JP 2000-80336 A JP 2007-332329 A

  An object of the present invention is to solve the above-mentioned disadvantages of the prior art, and a prism sheet in which a plurality of substantially triangular prisms are fixed to one surface of the sheet without increasing the thickness of the adhesive layer. The outer surface of the lens part can be reliably protected, and even when microprojections and FE are present on the surface protective film on the flat surface of the prism sheet, and when a load is applied during lamination, An object of the present invention is to provide a surface protective film that is not easily damaged.

The surface protective film of the present invention has a sheet and a plurality of prism-shaped lens portions each substantially consisting of a triangular prism, and the plurality of lens portions has one ridge line extending in the length direction of the triangular prism. A surface protective film that is affixed to the outer surface of the lens portion of the prism sheet that is fixed to one surface of the sheet on the side surface facing the ridge line so as to be substantially parallel to each other,
A polyolefin substrate layer;
An adhesive layer mainly composed of a rubber-based resin component laminated on one surface of the polyolefin base layer;
Consists of.
Further, after pasting on the outer surface of the lens part, a projection having a diameter of 400 μm and a height of 10 μm was pressed against the surface protective film of the present invention with a force of 0.8 N / cm ^{2 in} an atmosphere of 50 ° C. for 24 hours. In this case, the depth of penetration of the prism lens into the adhesive layer is 1% or more and less than 100% of the adhesive layer thickness.
Thereby, damage in the ridge line part located in the top part of a lens part does not arise easily. Further, the surface protective film having a depth of less than 1% may not have sufficient adhesion to the lens portion.

本明細書中、「うねりモチーフ平均長さ」および「うねりモチーフ平均高さ」は、それぞれＪＩＳ Ｂ０６０１：２００１に規定されている「輪郭曲線要素の平均長さ」および「輪郭曲線要素の平均高さ」である。
また、本発明の表面保護フィルムの粘着層厚みは３〜１０μｍに設定されることが望ましい。
本発明に係る表面保護フィルムでは、上記ゴム系樹脂成分は、好ましくは、（１）スチレン系重合体ブロック（Ａ）と共役ジエン系重合体ブロック（Ｂ）とのブロック共重合体、（２）スチレン系重合体ブロック（Ａ）とスチレン系モノマーと共役ジエン系モノマーとのランダム共重合体ブロック（Ｂ’）とのブロック共重合体、または（３）これらの水添物を主骨格とするスチレン系エラストマーである。
本明細書中、「スチレン系重合体ブロック」とは、主骨格がスチレンモノマーの重合体である重合体を意味する。 The above is achieved by setting the surface roughness Ra of the surface of the polyolefin substrate layer opposite to the adhesive layer to 0.7 μm ≦ Ra ≦ 2.0.
In this specification, “surface roughness Ra” is “arithmetic average height” defined in JIS B0601: 2001.
More preferably, the average height of the undulation motif shown by the surface of the polyolefin substrate layer on which the pressure-sensitive adhesive layer is not formed is 3 μm or more, and the average length of the motif is 400 to 600 μm.
The average height W of the swell motif is
As an average value of Wj in the schematic diagram showing the undulation of the polyolefin substrate layer surface of FIG.
The motif average length AW is the average value of AWj.
It is calculated by the following formula.

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. Is.
Moreover, as for the adhesion layer thickness of the surface protection film of this invention, it is desirable to set to 3-10 micrometers.
In the surface protective film according to the present invention, the rubber-based resin component is preferably (1) a block copolymer of a styrene polymer block (A) and a conjugated diene polymer block (B), (2) A block copolymer of a styrene polymer block (A) and a random copolymer block (B ′) of a styrene monomer and a conjugated diene monomer, or (3) styrene having a hydrogenated product thereof as a main skeleton Based elastomer.
In the present specification, the “styrene polymer block” means a polymer whose main skeleton is a polymer of a styrene monomer.

  In the surface protective film according to the present invention, preferably, in the styrene elastomer, the content ratio of the component derived from the styrene monomer is in the range of 5 to 20% by weight. In this case, adhesive residue at the time of peeling from the prism sheet can be surely prevented, and further, it can be easily and reliably attached to the lens surface of the prism sheet.

  Preferably, the hydrogenated structure of the conjugated diene unit of the styrenic elastomer is ethylene and butylene, and the ratio of ethylene and butylene is in the range of 0.6-3. In this case, the tackiness of the styrene-based elastomer becomes an appropriate value, the handling at the time of manufacture becomes easy, and the elastic modulus of the elastomer can be set to an appropriate size. Can be made more suitable.

  Details of the present invention will be described below.

(Prism sheet)
The adherend to which the surface protective film of the present invention is applied is a prism sheet. A prism sheet is a side surface in which a plurality of substantially prismatic prism-shaped lenses on one surface of the sheet are parallel to each other with one ridge line extending in the length direction of the prism. And has a fixed structure. Such prism sheets are widely used in optical devices such as liquid crystal displays.

  Examples of the material constituting the prism-shaped lens unit include, but are not limited to, a resin having translucency, such as an acrylic resin or polycarbonate.

  Moreover, although the material which comprises the said sheet | seat generally uses polyester and a polycarbonate widely, what is necessary is just a thing excellent in the optical characteristic, and it does not restrict | limit.

  Examples of a method for producing a prism sheet to which the surface protective film of the present invention is applied include, for example, a method of forming a lens portion made of an electromagnetic radiation curable resin on a sheet, and a sheet and a thermoplastic resin for lens portion formation in a sheet form. And a method of embossing the lens shape after melt extrusion. In the latter method, the difference between the sheet and the lens portion forming resin does not matter.

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. More specifically, as shown in FIG. 1, 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 cross-sectional view in FIG. 2, 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 lens portions 3 of the prism sheet 1 from the adhesive layer 6 side. It is affixed to the side where 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. The triangular cross-sectional shape of the lens portion 3 of the triangular prism is a triangle, and this triangle is preferably an isosceles triangle with the side fixed to the sheet as the base, and the apex angle is about 90 ± 10 degrees. Is preferable, and about 90 ± 5 degrees is more preferable.
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 the plurality of substantially triangular prisms of the prism sheet to which the surface protective film according to the present invention is applied, the distance between adjacent prisms, that is, the prism pitch is preferably about 10 to 1000 μm, more preferably. 10 to 500 μm. Further, the height of the triangular prism is determined by the pitch and apex angle of each triangular prism.

(Configuration of surface protection film)
In the surface protective film of the present invention, an adhesive layer mainly composed of a rubber-based resin component is laminated on one surface of the polyolefin base material layer. That is, the surface protective film according to the present invention is an adhesive film having a peelable adhesive layer on one side.

In the present invention, after a surface protective film is attached to the prism lens, a protrusion having a diameter of 400 μm and a height of 10 μm is pressed with a force of 0.8 N / cm ² for 24 hours in a 50 ° C. atmosphere. The surface of the polyolefin substrate layer on which the adhesive layer is not formed so that the depth of penetration of the prism lens into the adhesive layer is 1% or more and less than 100% of the adhesive layer thickness (that is, opposite to the adhesive layer) The surface roughness of the side surface is set.
In addition, the surface protective film of the present invention has a diameter of 500 μm or less (eg, 400 μm or less, 100 to 300 μm) and a height of 5 μm or more (eg, 10 μm) after being attached to the outer surface of the lens part.
m) or more) is pressed against the surface protective film of the present invention for 24 hours under a force of 0.8 N / cm ² in an atmosphere of 50 ° C. It is predicted to be 1% or more and less than 100% of the layer thickness.
Thereby, it is hard to produce the damage in the ridgeline part located in the top part of a lens part.
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 on the surface protective film, the surface of the substrate layer of the surface protective film on the prism lens surface is rough, so the protrusion on the surface protective film on the smooth sheet surface is It is possible to enter a minute recess on the surface of the base material layer. As a result, excessive biting of the lens portion of the prism sheet into the adhesive layer of the surface protective film can be reliably suppressed. Thereby, the lens surface of the prism sheet is hardly damaged. In the present invention, more preferably, a swell motif is set on the surface of the polyolefin base layer on which the pressure-sensitive adhesive layer is not formed (that is, the surface opposite to the pressure-sensitive adhesive layer).
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 on the surface protection film, the surface of the substrate layer of the surface protection film on the prism lens surface is wavy, so the protrusions on the surface protection film on the smooth sheet surface are Stress that concentrates on the protrusions on the surface protection film on the smooth sheet surface than when the surface of the surface protection film on the prism lens surface is flat because it can penetrate into the undulation valley on the surface of the substrate layer Can be reduced. As a result, excessive biting of the lens portion of the prism sheet into the adhesive layer of the surface protective film can be reliably suppressed. Thereby, the lens surface of the prism sheet is hardly damaged.

Such a thing is achieved by making the base layer waviness motif average depth of the surface protection film of the prism lens surface W ≧ 3.0 μm and the waviness motif average length 400 ≦ AW ≦ 600 μm. When the average undulation motif depth W is less than 3.0 μm, the effect of relieving the stress concentrated on the protrusions is small, and the biting into the adhesive layer cannot be suppressed. In addition, when the average swell motif length is 400 μm or less, the protrusions on the surface protective film having a smooth sheet surface may not enter the valleys of the swell motif. On the other hand, if the average length of the swell motif is 600 μm or more, there is a high probability that the projections on the surface protective film having a smooth sheet surface will hit the peak of the swell motif, and the lens part surface of the prism sheet may be damaged.
Moreover, as for the adhesion layer thickness of the surface protection film of this invention, it is desirable to set to 3-10 micrometers.
In setting the hardness range of the adhesive layer, the thickness of the adhesive layer is set to 3 μm or more and 10 μm or less for the following reason.
When the thickness of the pressure-sensitive adhesive layer exceeds 10 μm, the depth of penetration of the prism sheet into the lens portion is increased, the pressure-sensitive adhesive force may be excessively increased with time, and the cost of the surface protective film is increased. On the other hand, when the thickness of the pressure-sensitive adhesive layer is reduced to less than 3 μm, the function of dispersing and relaxing external stress by the pressure-sensitive adhesive layer is not sufficient, and the protective effect by the surface protective film may be reduced.

In the present invention, the adhesive layer mainly comprises a rubber-based resin component, and the rubber-based resin component is preferably a block copolymer of a styrene-based polymer block (A) and a conjugated diene-based polymer block (B). A block copolymer of a styrene polymer block (A) and a random copolymer block (B ′) of a styrene monomer and a conjugated diene monomer, or a styrene elastomer having a hydrogenated product thereof as a main skeleton It is comprised using.
“Mainly from a rubber-based resin component” means that 60% by weight or more (preferably 90% by weight or more) of the entire pressure-sensitive adhesive layer in the present invention is a rubber-based resin component.

  More specifically, the styrene elastomer is the following styrene elastomers (1) to (3).

(1) A styrene elastomer having a main skeleton of a block copolymer of a styrene polymer block (A) and a conjugated diene copolymer block (B). For example, it can be represented by a general formula of _AB , _ABAA , (AB) _n , or (AB) _nX . However, X shows the residue of a coupling agent and n is an integer greater than or equal to 1.

(2) A styrene elastomer having a main skeleton of a block copolymer comprising a styrene polymer block (A) and a random copolymer block (B ′) of a styrene monomer and a conjugated diene monomer.
For example,
(2-1) (A) and (B ′) 1 block each bonded: AB ′ block copolymer, (2-2) (A) and (B ′) 1 block each, A random copolymer of a styrene monomer and an isobutylene monomer, comprising a tapered block (C) in which the content of styrene (St) monomer units gradually increases: an AB′-C block copolymer,
(2-3) What contains a styrenic polymer block (A) instead of the tapered block (C) of (2-2) above: an AB′-A block copolymer,
(2-4) These repeated and the coupled _{ones: (A-B ') n} , (A-B') n X, (A-B'-C) n X, (A-B'-A) A copolymer that can be represented by a general formula such as nX. However, in these general formulas, X represents a residue of a coupling agent, and n is an integer of 1 or more.

  (3) A styrenic elastomer comprising a hydrogenated product of the styrenic elastomers of (1) and (2) above.

  In the styrene elastomer (including hydrogenated product), the content ratio of the styrene monomer and the conjugated diene monomer, which are constituent components, is preferably 5:95 to 20:80 by weight. When the styrene monomer content is less than 5% by weight, the cohesive strength of the pressure-sensitive adhesive is reduced, so that adhesive residue may be formed on the adherend during re-peeling. When the content exceeds 20% by weight, the pressure-sensitive adhesive has insufficient adhesive strength. As a result, sticking to the adherend may be difficult.

  In the hydrogenated product of (1) and (2) above, a conjugated diene moiety in a conjugated diene polymer block (B) and a random copolymer block (B ′) of the styrene monomer and conjugated diene monomer. It is preferable that at least 80% of the double bond is saturated by hydrogenation, more preferably 90% or more, still more preferably 95 to 100%. If the ratio of hydrogenation is less than 80%, heat resistance and weather resistance may be deteriorated.

  The weight average molecular weight of the styrene elastomer is preferably 30,000 to 40,000, more preferably 50,000 to 200,000 in terms of polystyrene by the GPC method. When the weight average molecular weight is less than 30,000, the cohesive force of the adhesive is reduced, and thus adhesive residue may be generated on the adherend during re-peeling. When the weight average molecular weight exceeds 400,000, the adhesive force may be insufficient and the fluidity may deteriorate. There is.

The conjugated diene polymer block of the styrene elastomer preferably has an ethylene / butylene structure in which polybutadiene is hydrogenated, and the molar ratio of ethylene to butylene (ethylene / butylene) is preferably from 0.6 to 3. When the molar ratio of ethylene and butylene is less than 0.6, the tackiness of the resulting elastomer is too high, and handling during production may be deteriorated. If the molar ratio of ethylene to butylene exceeds 3, the resulting styrene elastomer has an excessively high elastic modulus, and thus may not be used as a pressure-sensitive adhesive.

The composition of the pressure-sensitive adhesive layer is, for example, using SEBS as a styrene elastomer and adding 3 to 40 parts by weight, preferably 5 to 30 parts by weight of a tackifier to 100 parts by weight of the styrene elastomer. Composition can be used.

  Examples of the tackifier include petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic / aromatic copolymer systems and alicyclic copolymers, and coumarone-indene resins. , Terpene resin, terpene phenol resin, rosin resin such as polymerized rosin, (alkyl) phenol resin, xylene resin or hydrogenated products thereof, etc. Things can be used without any particular restrictions. As for these tackifiers, only 1 type may be used or 2 or more types may be used together.

  In addition, in order to improve peelability and weather resistance, a hydrogenated tackifier is preferable. In addition, as a tackifier, what is marketed as a blend with an olefin resin can also be used.

  A softening agent may be added to the adhesive layer of the surface protective film according to the present invention. By adding a softening agent, the adhesive force of the pressure-sensitive adhesive layer can be increased. Examples of the softening agent include low molecular weight diene polymers, polyisobutylene, hydrogenated polyisoprene, hydrogenated polybutadiene, and derivatives thereof. Examples of the derivative include those having an OH group or a COOH group at one or both ends, and specifically, hydrogenated polybutadiene diol, hydrogenated polybutadiene monool, hydrogenated polyisoprene diol, hydrogenated polyisoprene. Monool etc. are mentioned. In particular, hydrogenated products of diene polymers such as hydrogenated polybutadiene and hydrogenated polyisoprene, olefinic softeners, and the like are preferable for the purpose of suppressing improvement in adhesion to an adherend. Specifically, “Kuraprene LIR-200” manufactured by Kuraray Co., Ltd. is available. These softeners may be used alone or in combination of two or more.

  The molecular weight of the softening agent is not particularly limited. However, if the molecular weight is too small, the softening agent may move from the adhesive layer to the adherend side, or the peeling force may increase. Conversely, if the molecular weight of the softening agent becomes too large, the effect of improving the adhesive strength may be reduced. Accordingly, the number average molecular weight of the softening agent is preferably about 5,000 to 100,000, more preferably 10,000 to 50,000.

  If the amount of the softener added is too large, adhesive residue tends to occur at high temperatures. Accordingly, the softening agent is preferably 40 parts by weight or less, more preferably 20 parts by weight or less, still more preferably 10 parts by weight or less, with respect to 100 parts by weight of the total of the styrene-based elastomer and the softening agent.

Moreover, you may add another additive to the adhesion layer of the surface protection film of this invention as needed in the range which does not inhibit achievement of the subject of this invention. Examples of such additives include ultraviolet absorbers, antioxidants, and adhesion progress inhibitors. The UV absorber is not particularly limited, and examples thereof include commonly used ones such as salicylic acid UV absorbers, benzophenone UV absorbers, benzotriazole UV absorbers, and cyanoacrylate UV absorbers. The antioxidant is not particularly limited, and for example, phenolic (monophenolic, bisphenolic, polymeric phenolic) antioxidants, sulfur antioxidants, phosphorus antioxidants and the like are usually used. Things. Examples of the anti-adhesion progress agent include fatty acid amides, polyethyleneimine long-chain alkyl grafts, soybean oil-modified alkyd resins (for example, Arakawa Chemical Co., Ltd., trade name “Arachid 251”, etc.), tall oil-modified alkyd resins (for example, Arakawa Chemical Co., Ltd., trade name “Arachid 6300”, etc.).
Moreover, it is preferable that the hardness of the adhesive layer of the surface protective film of the present invention is 5 × 10 ⁵ Pa or more at 70 ° C. in terms of shear storage elastic modulus at a frequency of 10 Hz. By setting the shear storage elastic modulus of the adhesive layer to the above value, stability with time of the adhesive force is imparted.

  The surface protective film according to the present invention can be obtained by laminating a rubber-based adhesive layer made of the above-mentioned adhesive composition on a polyolefin substrate.

  The material of the polyolefin substrate is not particularly limited, and examples thereof include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-α-olefin copolymer, propylene-α-olefin copolymer. Polymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer, polypropylene homopolymer, random copolymer, block copolymer Examples thereof include olefinic resins such as coalescence. These may be used independently and 2 or more types may be used together. Of these, polyethylene and polypropylene are preferred.

  The thickness of the polyolefin substrate may be designed to have sufficient strength to protect the lens portion of the prism sheet, and it varies depending on the dimensions and surface properties of the prism lens, but is designed in the range of 20 to 100 μm. It only has to be done.

The manufacturing method of the surface protection film of this invention is not specifically limited. For example, a method of laminating and integrating the materials used for the polyolefin base material and the adhesive layer by co-extrusion, a method of laminating an adhesive layer on one side of a polyolefin base material previously formed, and a method of laminating and integrating It is done.
Moreover, surface roughness Ra of the polyolefin base material layer surface in which the adhesive layer of the surface protection film of this invention is not formed is 0.7 micrometer <= Ra <= 2.0micrometer. The surface roughness of the polyolefin substrate layer can be adjusted by the resin composition, molding conditions and molding method of the polyolefin substrate layer.
In addition, the average depth of the waviness motif on the surface of the surface protective film of the present invention on which the pressure-sensitive adhesive layer of the polyolefin base layer is not formed is W ≧ 3 μm, and the average length of the waviness motif is 400 ≦ AW ≦ 600. It is. The surface state (swelling state) of the polyolefin substrate layer can be adjusted by the resin composition, molding conditions and molding method of the polyolefin substrate layer.
Although the composition of the polyolefin base layer varies depending on the setting of molding conditions, it is preferable to contain 5 to 30 parts by weight of a polyethylene polymer with respect to 100 parts by weight of the polypropylene polymer. The polypropylene polymer is a blend of two or more of a block polymer of polypropylene, a homopolymer of polypropylene, or a random polypropylene containing ethylene and propylene as rubber components.
Molding conditions vary depending on the molding machine used, but it is preferable to mold at the lowest possible temperature.
Examples of the molding method for forming a desired undulation on the surface include embossing molding in which a resin film is transferred to an embossing roll that has been processed into an arbitrary shape in advance.

  As a method of laminating and integrating the polyolefin base material and the pressure-sensitive adhesive layer by coextrusion, a known method such as an inflation method or a T-die method is used. As a method of laminating the pressure-sensitive adhesive layer on the base material layer, A solution coating method for applying a pressure-sensitive adhesive solution, a dry lamination method, an extrusion coating method using a T-die, or the like can be used. Among these, coextrusion by the T-die method is preferable from the viewpoint of quality and economy. In the case of the solution coating method, it is preferable to perform a surface treatment such as primer application on the base material in advance in order to increase the bonding strength between the base material layer and the pressure-sensitive adhesive layer.

In the surface protective film according to the present invention, after the surface protective film is attached to the prism lens, a protrusion having a diameter of 400 μm and a height of 10 μm is 0.8 N / cm in an atmosphere of 50 ° C.
The surface roughness of the polyolefin substrate surface is set so that the depth of penetration of the prism lens into the adhesive layer when pressed for ² hours with a force of ² is not less than 1% and less than 100% of the adhesive layer thickness, more preferably Since the surface roughness of the polyolefin substrate surface and the average height and average length of the swell motif are set, even if a large number of prism sheets to which a surface protective film is applied are stacked and stored, the prism sheet lens Damage at the top of the part is unlikely to occur.

  Hereinafter, the present invention will be clarified by giving specific examples and comparative examples of the present invention. In addition, this invention is not limited to a following example.

Example 1
As shown in Table 1 below, 100 parts by weight of a styrene elastomer (hydrogenated from Kraton Polymer, product number: Kraton G1657, ethylene / butylene ratio = 2.6) made by hydrogenation of a styrene-butadiene copolymer is adhered to 100 parts by weight. As an imparting agent, 20 parts by weight of Alcon P-125 manufactured by Arakawa Chemical Industries, which is an alicyclic petroleum resin, was blended to obtain a pressure-sensitive adhesive composition. The ethylene / butylene ratio of the styrene elastomer was measured as follows.

Ethylene / butylene ratio (E / B ratio)
10 mg of a hydrogenated styrene-butadiene copolymer was dissolved in chloroform, and H-NMR was measured. The E / B ratio (molar ratio) was calculated by the following formula. S _1.24 indicates an integrated value of the peak area with a chemical shift of _1.24 ppm.

_S1.4 = _S1.85 + _{S1.42- S1.24} x 5/3-( _S7.08 + _S6.54 ) x _3/5
S _1.2 = S _0.82 × _8/3
E / B ratio = 2 × S _1.4 / S _1.2
The results are shown in Table 1 below.

On the other hand, a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition, a base material made of a resin composition containing 75 parts by weight of block polypropylene shown in Table 1, and 25 parts by weight of low-density polyethylene are coextruded by a T-die method, A surface protective film in which a polypropylene substrate having a thickness of 40 μm and an adhesive layer having a thickness of 6 μm were laminated and integrated was produced.
About this surface protective film, 1) The prism sheet on which the surface protective film was affixed with projections having an arbitrary diameter and height was pressed for 24 hours, and the amount of biting into the adhesive of the prism sheet at that time, 2) Initial adhesive strength ( The prism surface) and 3) initial adhesive strength (versus flat surface) were evaluated in the following manner. Furthermore, the lens flaw evaluation of the prism sheet (BEF, Sumitomo 3M) of 1) was evaluated in the following manner, and 5) prism damage was evaluated. Moreover, 6) adhesive strength with time (to the prism surface) and 7) adhesive residue were evaluated as follows.
1) Amount of biting The obtained surface protective film was attached so as to cover the lens surface of the prism sheet to prepare a test piece. As the prism sheet, a lens part was made of acrylic resin, the sheet was made of polyethylene terephthalate having a thickness of 150 μm, and a prismatic lens part having a height of 23 μm and a width of 50 μm was prepared. In 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 glass slide and the surface protective film. Thereafter, the convex shape was observed with a laser microscope, and the diameter and height were determined.
The slide glass with the surface protective film was set on the sample piece so that the surface protective film and the sample piece overlapped, and a 140 g weight was placed on the slide glass and left in an oven at 50 ° C. for 24 hours. After 24 days, the test piece was taken out, the cross section was cut, the cross section was observed with a scanning electron microscope (SEM), and the depth of biting into the adhesive layer of the lens portion of the prism sheet was measured.

2) Initial adhesive strength (to prism surface)
The obtained surface protective film was attached so as to cover the lens surface of the prism sheet. At the time of sticking, a pressure of 5.9 × 10 ⁵ Pa is applied from the outside of the surface protective film to 2 m /
It was pasted at a rate of minutes 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)
The obtained surface protective film was applied to a flat acrylic resin plate using a 2 kg rubber roller under the 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 1 below, a sample in which many scratches are observed is marked with ×, Δ when slightly observed, and ○ when not observed at all.
Further, when the peel strength was measured when evaluating the initial adhesive strength (to the prism surface), the presence or absence of adhesive residue on the lens surface of the prism sheet after peeling was visually observed.

5) Adhesive strength over time (against the prism surface)
The obtained surface protective film was affixed to the surface of the prism sheet used in the initial adhesive strength evaluation in 1) using a 2 kg rubber roller under the conditions of pressure 5.9 × 10 ⁵ Pa and speed 2 m / min, 60 After leaving for 1 week in a room with a temperature of ± 2 ° C., the 180-degree peel strength at a width of 25 mm was measured at a peel speed of 30 m / min according to JIS Z0237. When the obtained 180-degree peel strength, that is, the adhesive strength with time, is 2 times or less of the initial adhesive strength measured in 1), ◯ is given, and when it exceeds 2 times, X is marked.
6) Adhesive residue At the time of the test in 4), the case where the adhesive residue was observed on the lens surface was marked with x, and when it was not observed at all, the mark was marked with. The results are shown in Table 1 below.
7) Surface roughness and undulation Using a surface roughness measuring machine (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
The results are shown in Table 1 below.
(Examples 2 to 5 and Comparative Examples 1 and 2)
A surface protective film was prepared and evaluated in the same manner as in Example 1 except that the composition and thickness of the adhesive layer were changed as shown in Table 1 below. In Table 1, 1321P indicates “Dynalon 1321P” (an elastomer having a styrene polymer block and a hydrogenated random copolymer block of styrene and butadiene) manufactured by JSR. All tackifiers were Alcon P-125.

It is a perspective view of a prism sheet to which the present invention is applied. It is sectional drawing of the structure where the surface protection film of one Embodiment of this invention was affixed on the prism sheet. It is a schematic diagram which shows the wave | undulation of the polyolefin base material layer surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Prism sheet 2 Sheet 3 Lens part 3a Top part 4 of lens part 1st surface protection film 5 Base material layer 6 Adhesive layer 7 2nd surface protection film

Claims (6)

A sheet and a plurality of prism-shaped lens portions each substantially consisting of a triangular prism, and the plurality of lens portions are arranged such that one ridge line extending in the length direction of the triangular prism is substantially parallel to each other. A surface protective film that is affixed to the outer surface of the lens portion of the prism sheet that is fixed to one surface of the sheet on the side surface facing the ridgeline,
A polyolefin substrate layer;
An adhesive layer mainly composed of a rubber-based resin component laminated on one surface of the polyolefin base layer;
Consists of
The surface roughness Ra of the surface of the polyolefin base layer opposite to the adhesive layer is 0.7 μm ≦ Ra ≦ 2.0, and after pasting on the outer surface of the lens part, the diameter is 400 μm, the height Is a 10μm protrusion at 50 ° C
A surface protective film having a depth of biting into the adhesive layer of the prism lens when pressed with a force of 0.8 N / cm ² for 24 hours in an atmosphere of 1 to 100% of the thickness of the adhesive layer.   The surface protective film according to claim 1, wherein the average height of the swell motif on the surface of the polyolefin substrate layer opposite to the adhesive layer is 3 μm or more and the average length of the motif is 400 to 600 μm.   The rubber resin component is (1) a block copolymer of a styrene polymer block (A) and a conjugated diene polymer block (B), (2) a styrene polymer block (A) and a styrene monomer. The surface according to claim 1 or 2, which is a block copolymer with a random copolymer block (B ') with a conjugated diene monomer, or (3) a styrene elastomer having these hydrogenated products as a main skeleton. Protective film.   The surface protection film according to any one of claims 1 to 3, wherein the styrene-based elastomer has a content of a styrene-based monomer-derived component in the range of 5 to 20% by weight.   The hydrogenated structure of the conjugated diene unit of the styrene-based elastomer is ethylene and butylene, and the ratio of ethylene and butylene is in the range of 0.6 to 3 in terms of molar ratio. The surface protective film as described.   The surface protection film according to claim 1, wherein the polyolefin base material and the pressure-sensitive adhesive layer are laminated and integrated by coextrusion.

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