JP2008194886A - Surface protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protective film which has excellent optical characteristics where an appearance of a material to be protected is hardly deteriorated and the surface protective film where the appearance of the material to be protected is hardly deteriorated and which has an adhesive layer capable of being peeled at high speed when being used as the surface protective film. <P>SOLUTION: The surface protective film has the adhesive layer on one surface side of a base material film containing a lactone ring-containing polymer as a main component. The surface protective film roll is characterized by having a mold releasing layer on one side surface of the base material film containing the lactone ring-containing polymer as the main component, and the sheet having the adhesive layer is wound on the other surface in a roll shape with the adhesive layer as the inner side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface protective film for preventing blocking when a resin film, a resin sheet, or a coated processed product is stacked or rolled up, or for protecting a product surface. Mainly masking optical films such as polarizing plates that conduct product inspections with surface protective films attached, and film resists that carry out precise secondary processing, as well as finished products that are important in color and appearance. The present invention relates to a surface protective film used as a surface protective material that is used for applications and peeled off during actual use of these products.

  As a surface protection film used for surface protection of various materials (metal plate, resin plate, various display devices, etc.), it adheres to polyolefin resin such as polyethylene (hereinafter abbreviated as PE) and polypropylene (hereinafter abbreviated as PP). A film obtained by laminating an acrylic pressure-sensitive adhesive on a polyester film such as a melt coextruded film with a conductive elastomer or polyethylene terephthalate (hereinafter abbreviated as PET) is generally used. It is known that the polymer used for the base material of these surface protective films has a relatively high molecular weight and melting temperature, and easily causes fish eyes (projections) due to gels and the like.

  In particular, optical films such as polarizing plates for liquid crystal panels are used only for surface protective films with few fish eyes and excellent appearance characteristics because the optical film is inspected while the surface protective film is attached in the manufacturing process. in use. Surface protective films based on PE or PP are inexpensive, but they are not suitable for polarizing plates because they are inferior to PET based films in terms of light transmittance and appearance such as fish eyes. Yes.

  Focusing on such problems, Patent Document 1 proposes a technique for removing the cause of fish eyes using a melt extruder equipped with a filter. However, the effect of reducing fish eyes is still not improved. There was room.

  On the other hand, PET-based films have relatively good appearance characteristics. However, since manganese, antimony compounds, and the like are used as reaction catalysts during the production of PET resins, the metal compounds are convex. It may be deposited in the shape of a film and appear on the film surface. Therefore, with the recent increase in size and quality of flat panel displays, further improvement in appearance characteristics is required even for PET films.

  As a method for improving this problem, Patent Document 2 discloses a method of highly smoothing a PET film by a combination of an addition amount of a reaction catalyst used during the production of a PET resin and a stabilizer.

  Moreover, as for the surface protection film which uses PET as a base film, the PET film which gave the mold release process as a separator is normally laminated | stacked on the adhesive layer apply | coated and formed on the PET base material. At this time, if fish eyes (projections) are present in the separator, bubbles may be generated at the interface between the pressure-sensitive adhesive layer and the separator, and a dent may be formed on the surface of the pressure-sensitive adhesive layer. When such a surface protective film is used to protect the polarizing plate, if the separator is peeled off and the adhesive surface is attached to the polarizing plate, bubbles are generated at the interface between the adhesive layer and the polarizing plate, so the inspection of the polarizing plate is accurate. The problem of being unable to do so occurs. Since such a problem becomes more conspicuous as the film is thinner, it is also considered to use a thick film or to adopt a molding method (such as a solvent casting method) that can obtain a film with good smoothness. However, it is not an economic measure, and further consideration is required.

  Furthermore, regarding the surface protective film used for protecting the polarizing plate, a method of using a resin film with little optical anisotropy as a base material in order to reduce the influence of optical distortion on the inspection of the polarizing plate (patent) Reference 3) has also been proposed. However, sufficient studies have not been made on the problems of light transmittance and fish eye.

Moreover, the refractive index of the PET base material generally used as a base material is around 1.66. Therefore, the surface protective film in which an acrylic pressure-sensitive adhesive layer (refractive index: 1.47 to 1.51) is laminated on this PET base material has a large refractive index difference between the base film and the pressure-sensitive adhesive layer. It is difficult to inspect the optical properties of the protective film itself or foreign matter, or interference fringes are generated due to uneven thickness of the adhesive layer. If the surface protective film remains attached, the optical properties of optical products such as polarizing plates In addition, there has been a problem that the accuracy of inspection of foreign matter is lowered.
JP 9-314642 A JP-A-2005-97466 Japanese Patent Laid-Open No. 4-30120

  This invention was made paying attention to the said situation, and the objective is to provide the surface protection film which is excellent in an optical characteristic and cannot produce the appearance fall of a to-be-protected material. Another object of the present invention is to provide a surface protective film having an adhesive layer that is less likely to cause a decrease in the appearance of a material to be protected and can be peeled at a high speed when used as a surface protective film.

  The present inventors have repeatedly studied to solve the above problems, and as a base material, the surface smoothness is high in transparency, has small optical anisotropy, and has few fish eyes and surface protrusions. If it is a surface protective film that uses a film mainly composed of a lactone ring-containing polymer, and has a pressure-sensitive adhesive layer with excellent peeling properties on one side, it is fine when pasted on the surface of the material to be protected. It is possible to protect the surface without deteriorating the appearance, and even when attached to an optical film such as a polarizing plate, the surface protective film is not peeled off in the inspection process However, the present inventors have found that the inspection can be performed without hindrance and completed the present invention.

  That is, the surface protective film according to the present invention is characterized by having a pressure-sensitive adhesive layer on one side of a base film mainly composed of a lactone ring-containing polymer.

  In the surface protective film of the present invention, the thickness of the base film is 5 to 50 μm, the thickness of the pressure-sensitive adhesive layer is 5 to 30 μm, and the visible light transmittance is 90% or more. Is preferred.

  The lactone ring-containing polymer preferably has a lactone ring structure represented by the following formula (1).

[Wherein, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms]

  The pressure-sensitive adhesive layer is preferably formed from a (meth) acrylic pressure-sensitive adhesive. In particular, the (meth) acrylic pressure-sensitive adhesive has a high Tg polymer (A) having a glass transition temperature (Tg) of 0 ° C. or higher and a Tg lower than the high Tg polymer, and has pressure-sensitive adhesiveness. In the pressure-sensitive adhesive layer, the high Tg polymer (A) and the low Tg polymer (B) form a sea-island structure without being compatible with each other. preferable.

  The surface protective film further includes a separator having a release layer formed on one side of a film mainly containing a lactone ring-containing polymer, and includes a base film, an adhesive layer, and a separator in this order. Are also preferred embodiments of the present invention.

  Furthermore, a sheet having a release layer on one side of a base film mainly composed of a lactone ring-containing polymer and having an adhesive layer on the other side is wound in a roll shape with the adhesive layer as the inside. The surface protective film raw material obtained is also included in the scope of the present invention. The film original fabric does not require a separator and can be automatically attached to a material to be protected.

  Hereinafter, the term “polymer” includes not only homopolymers but also copolymers and copolymers of three or more.

  According to the present invention, by using a base film mainly composed of a lactone ring-containing polymer, in addition to excellent film physical properties such as heat resistance and surface hardness, optical characteristics and appearance defects due to fish eyes are improved. We were able to. Therefore, when used as a surface protective film for an optical film such as an image display material, the object to be protected can be inspected without hindrance while the surface protective film is stuck in the inspection process. It can also be used for masking in semiconductor manufacturing processes and for surface protection of products whose appearance and color tone are important.

  Hereinafter, the present invention will be described in detail. However, the scope of the present invention is not limited to these descriptions, and modifications other than the following examples can be made as appropriate without departing from the spirit of the present invention.

  The surface protective film of the present invention is characterized by having a pressure-sensitive adhesive layer on one side of a base film mainly composed of a lactone ring-containing polymer. First, the lactone ring-containing polymer that is the main component of the base film according to the present invention will be described.

[Lactone ring-containing polymer]
The lactone ring-containing polymer that is the main component of the base film preferably has a lactone ring structure represented by the following general formula (1).

[Wherein, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. ]

  In the present specification, examples of the “organic residue having 1 to 20 carbon atoms” include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, and a cyclohexyl group. Examples thereof include an alkyl group having 1 to 20 carbon atoms, an aryl group such as a phenyl group, and an aralkyl group such as a benzyl group. In addition, these organic residues may contain nitrogen, oxygen, and sulfur atoms (hereinafter, the same applies to formulas (1a) and (2a)).

  In the structure of the lactone ring-containing polymer, the content of the lactone ring structure represented by the general formula (1) is preferably 5 to 90% by mass, more preferably 10 to 70% by mass, and still more preferably 10 to 70% by mass. 60% by mass, particularly preferably 10 to 50% by mass. If the content of the lactone ring structure represented by the general formula (1) is less than 5% by mass, the obtained polymer may have insufficient heat resistance, solvent resistance and surface hardness. On the other hand, when the content ratio of the lactone ring structure represented by the general formula (1) is more than 90% by mass, the moldability of the obtained polymer may be deteriorated. In addition, the content rate of the said lactone ring structure can be measured by a well-known method, for example, it is calculated from the mass reduction by the dynamic TG measurement (150-300 degreeC) of NMR and the (co) polymer which has a lactone ring structure. The dealcoholization reaction rate and the molar ratio of the raw material monomer having a hydroxy group in the used raw material monomer.

  The lactone ring-containing polymer may have a structure other than the lactone ring structure represented by the general formula (1). The structure other than the lactone ring structure represented by the general formula (1) is not particularly limited. For example, a (meth) acrylic compound exemplified in the method for producing a lactone ring-containing polymer described later is used. Polymer formed by polymerizing at least one monomer selected from the group consisting of acid esters, hydroxyl group-containing monomers, unsaturated carboxylic acids, and monomers represented by the following general formula (2a) It is preferably a structural unit (repeating structural unit).

[Wherein, R ⁴ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an —OAc group, a —CN group, a —CO—R ⁵ group, or —C It represents -O-R ⁶ group, Ac group represents an acetyl group, R ⁵ and R ⁶ represents a hydrogen atom or an organic residue having 1 to 20 carbon atoms. ]

  The content ratio of the structure other than the lactone ring structure represented by the general formula (1) in the lactone ring-containing polymer structure is a polymer structural unit (repeated structural unit) constructed by polymerizing (meth) acrylic acid ester. ) Is preferably 10 to 95% by mass, more preferably 30 to 90% by mass, still more preferably 40 to 90% by mass, particularly preferably 50 to 90% by mass, and a hydroxyl group-containing monomer is polymerized. In the case of the polymer structural unit to be formed (repeating structural unit), it is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, further preferably 0 to 15% by mass, and particularly preferably 0 to 10% by mass. is there. In the case of a polymer structural unit (repeating structural unit) formed by polymerizing an unsaturated carboxylic acid, it is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, even more preferably 0 to 15% by mass, particularly Preferably it is 0-10 mass%. Furthermore, in the case of a polymer structural unit (repeating structural unit) formed by polymerizing the monomer represented by the general formula (2a), preferably 0 to 30% by mass, more preferably 0 to 20% by mass. More preferably, it is 0-15 mass%, Most preferably, it is 0-10 mass%.

  The method for producing the lactone ring-containing polymer is not particularly limited. For example, in the polymerization step, after the polymer (a) having a hydroxyl group and an ester group in the molecular chain is obtained, It can be obtained by carrying out a lactone cyclization condensation step for introducing a lactone ring structure into the polymer by heat-treating the compound (a).

  In the polymerization step, for example, a polymer having a hydroxyl group and an ester group in the molecular chain can be obtained by performing a polymerization reaction of a monomer component containing a monomer represented by the following general formula (1a). .

[Wherein, R ⁷ and R ⁸ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. ]

  Examples of the monomer represented by the general formula (1a) include methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, 2- Examples thereof include n-butyl (hydroxymethyl) acrylate, t-butyl 2- (hydroxymethyl) acrylate, and the like. As for the monomer represented by the general formula (1a), only one type may be used, or two or more types may be used in combination. Among these, methyl 2- (hydroxymethyl) acrylate and 2- (hydroxymethyl) ethyl acrylate are preferable, and methyl 2- (hydroxymethyl) acrylate is particularly preferable because of its high effect of improving heat resistance.

  The content ratio of the monomer represented by the general formula (1a) in the monomer component to be subjected to the polymerization step is preferably 5 to 90% by mass, more preferably 10 to 70% by mass, and still more preferably 10 to 10% by mass. 60% by mass, particularly preferably 10 to 50% by mass. When the content ratio of the monomer represented by the general formula (1a) is less than 5% by mass, the obtained polymer may have insufficient heat resistance, solvent resistance, and surface hardness. On the other hand, when the content ratio of the monomer represented by the general formula (1a) is more than 90% by mass, gelation occurs in the polymerization step or the lactone cyclization step, or the obtained polymer is molded. May decrease.

  You may mix | blend monomers other than the monomer represented with General formula (1a) with the monomer component with which it uses for a superposition | polymerization process. Such a monomer is not particularly limited. For example, a (meth) acrylic acid ester, a hydroxyl group-containing monomer, an unsaturated carboxylic acid, and a single monomer represented by the following general formula (2a) A body etc. are mentioned preferably. These monomers may be used alone or in combination of two or more.

[Wherein, R ⁴ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an —OAc group, a —CN group, a —CO—R ⁵ group, or —C It represents -O-R ⁶ group, Ac group represents an acetyl group, R ⁵ and R ⁶ represents a hydrogen atom or an organic residue having 1 to 20 carbon atoms. ]

  The (meth) acrylic acid ester is not particularly limited as long as it is a (meth) acrylic acid ester other than the monomer represented by the general formula (1a). For example, methyl acrylate, acrylic Acrylic acid esters such as ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, benzyl acrylate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, Methacrylic acid esters such as isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate; and the like. These (meth) acrylic acid esters may be used alone or in combination of two or more. You may use together. Among these, methyl methacrylate is particularly preferable from the viewpoint of excellent heat resistance and transparency of the obtained polymer.

  When a (meth) acrylic acid ester other than the monomer represented by the general formula (1a) is used, the content ratio in the monomer component to be subjected to the polymerization step is sufficient to exert the effect of the present invention. And preferably 10 to 95% by mass, more preferably 30 to 90% by mass, still more preferably 40 to 90% by mass, and particularly preferably 50 to 90% by mass.

  The hydroxyl group-containing monomer is not particularly limited as long as it is a hydroxyl group-containing monomer other than the monomer represented by the general formula (1a). For example, α-hydroxymethylstyrene, α-hydroxyethylstyrene, 2- (hydroxyalkyl) acrylic acid esters such as methyl 2- (hydroxyethyl) acrylate; 2- (hydroxyalkyl) acrylic acids such as 2- (hydroxyethyl) acrylic acid; and the like. These may be used alone or in combination of two or more.

  In the case of using a hydroxyl group-containing monomer other than the monomer represented by the general formula (1a), the content ratio in the monomer component to be subjected to the polymerization step is sufficient to exert the effect of the present invention. Preferably it is 0-30 mass%, More preferably, it is 0-20 mass%, More preferably, it is 0-15 mass%, Most preferably, it is 0-10 mass%.

  Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, α-substituted methacrylic acid and the like. These unsaturated carboxylic acids may be used alone or in combination of two or more. Among these, acrylic acid and methacrylic acid are preferable because the effects of the present invention are sufficiently exhibited.

  When the unsaturated carboxylic acid is used, the content of the unsaturated carboxylic acid in the monomer component to be subjected to the polymerization step is preferably 0 to 30% by mass, more preferably, in order to sufficiently exhibit the effects of the present invention. It is 0-20 mass%, More preferably, it is 0-15 mass%, Most preferably, it is 0-10 mass%.

  Examples of the monomer represented by the general formula (2a) include styrene, vinyl toluene, α-methyl styrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, and vinyl acetate. These may be used alone or in combination of two or more. Among these, styrene and α-methylstyrene are particularly preferable in that the effects of the present invention are sufficiently exhibited.

  When using the monomer represented by the general formula (2a), the content ratio in the monomer component to be subjected to the polymerization step is preferably 0 to 30% by mass in order to sufficiently exhibit the effects of the present invention. More preferably, it is 0-20 mass%, More preferably, it is 0-15 mass%, Most preferably, it is 0-10 mass%.

  The form of the polymerization reaction for polymerizing the monomer component to obtain a polymer having a hydroxyl group and an ester group in the molecular chain is preferably a polymerization form using a solvent, and solution polymerization is particularly preferred.

  The polymerization temperature and polymerization time vary depending on the type of monomer used, the ratio of use, and the like. For example, the polymerization temperature is preferably 0 to 150 ° C., and the polymerization time is 0.5 to 20 hours, more preferably. The polymerization temperature is 80 to 140 ° C., and the polymerization time is 1 to 10 hours.

  In the case of a polymerization form using a solvent, the polymerization solvent is not particularly limited. For example, aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ether solvents such as tetrahydrofuran And so on. These solvents may be used alone or in combination of two or more. Moreover, since the residual volatile matter of the lactone ring containing polymer finally obtained will increase when the boiling point of the solvent to be used is too high, the solvent whose boiling point is 50-200 degreeC is preferable.

  During the polymerization reaction, a polymerization initiator may be added as necessary. The polymerization initiator is not particularly limited. For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t- Organic peroxides such as amylperoxy-2-ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2 , 4-dimethylvaleronitrile) and the like; and the like. These may use only 1 type and may use 2 or more types together. The amount of the polymerization initiator used is not particularly limited as long as it is appropriately set according to the combination of the monomers used and the reaction conditions.

  When performing the polymerization, it is preferable to control the concentration of the produced polymer in the polymerization reaction mixture to be 50% by mass or less in order to suppress gelation of the reaction solution. Specifically, when the concentration of the produced polymer in the polymerization reaction mixture exceeds 50% by mass, a polymerization solvent is appropriately added to the polymerization reaction mixture so that the polymer concentration becomes 50% by mass or less. It is preferable to control. The concentration of the polymer formed in the polymerization reaction mixture is more preferably 45% by mass or less, and further preferably 40% by mass or less. Note that, if the concentration of the polymer produced in the polymerization reaction mixture is too low, the productivity is lowered. Therefore, the concentration of the polymer produced in the polymerization reaction mixture is preferably 10% by mass or more, more preferably It is 20 mass% or more.

  The form in which the polymerization solvent is appropriately added to the polymerization reaction mixture is not particularly limited, and for example, the polymerization solvent may be added continuously or the polymerization solvent may be added intermittently. By controlling the concentration of the polymer formed in the polymerization reaction mixture in this way, the gelation of the reaction solution can be more sufficiently suppressed, and in particular, to increase the lactone ring content and improve the heat resistance. Even when the ratio between the hydroxyl group and the ester group in the molecular chain is increased, gelation can be sufficiently suppressed. As the polymerization solvent to be added, for example, the same type of solvent as the solvent used at the initial charging of the polymerization reaction or a different type of solvent may be used, but the solvent used at the initial charging of the polymerization reaction It is preferable to use the same type of solvent. Further, the polymerization solvent to be added may be only one kind of single solvent or two or more kinds of mixed solvents.

  The polymerization reaction mixture obtained when the above polymerization step is completed usually contains a solvent in addition to the produced polymer, but it is necessary to completely remove the solvent and take out the polymer in a solid state. However, it is preferably introduced into the subsequent lactone cyclization condensation step in a state containing a solvent. Further, if necessary, after taking out in a solid state, a suitable solvent may be added again in the subsequent lactone cyclization condensation step.

  The polymer obtained in the polymerization step is a polymer (a) having a hydroxyl group and an ester group in the molecular chain, and the weight average molecular weight of the polymer (a) is preferably 1,000 to 2,000,000. 000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000, particularly preferably 50,000 to 500,000. The polymer (a) obtained in the polymerization step is subjected to heat treatment in the subsequent lactone cyclization condensation step, whereby a lactone ring structure is introduced into the polymer to become a lactone ring-containing polymer.

  The reaction for introducing a lactone ring structure into the polymer (a) is a reaction in which a hydroxyl group and an ester group present in the molecular chain of the polymer (a) are cyclized and condensed to form a lactone ring structure by heating. Yes, alcohol is by-produced by the cyclocondensation. By forming the lactone ring structure in the molecular chain of the polymer (in the main skeleton of the polymer), high heat resistance is imparted. If the reaction rate of the cyclization condensation reaction leading to the lactone ring structure is insufficient, the heat resistance will not be improved sufficiently, or the condensation reaction will occur during the molding process due to the heat treatment during molding, and the resulting alcohol will be contained in the molded product. May exist as bubbles or silver streaks.

  The lactone ring-containing polymer obtained in the lactone cyclization condensation step preferably has a lactone ring structure represented by the following general formula (1).

[Wherein, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. ]

  The method for heat-treating the polymer (a) is not particularly limited, and a conventionally known method can be used. For example, you may heat-process the polymerization reaction mixture containing the solvent obtained in the superposition | polymerization process as it is. Moreover, you may heat-process using a ring-closing catalyst as needed in presence of a solvent. Moreover, it can also heat-process using the heating furnace and reaction apparatus provided with the vacuum apparatus or devolatilization apparatus for removing a volatile component, the extruder provided with the devolatilization apparatus, etc.

  In carrying out the cyclization condensation reaction, in addition to the polymer (a), another thermoplastic resin may coexist. Further, when performing the cyclization condensation reaction, if necessary, an esterification catalyst or a transesterification catalyst such as p-toluenesulfonic acid generally used as a catalyst for the cyclization condensation reaction may be used. Organic carboxylic acids such as propionic acid, benzoic acid, acrylic acid, and methacrylic acid may be used as a catalyst. Furthermore, for example, basic compounds, organic carboxylates, carbonates and the like may be used as disclosed in JP-A-61-254608 and JP-A-61-261303.

  In carrying out the cyclization condensation reaction, it is preferable to use an organic phosphorus compound as a catalyst. By using an organophosphorus compound as a catalyst, the cyclization condensation reaction rate can be improved, and coloring of the resulting lactone ring-containing polymer can be greatly reduced. Moreover, when an organophosphorus compound is used as a catalyst, since the molecular weight fall which can occur when using the below-mentioned devolatilization process is suppressed, the outstanding mechanical strength of a lactone ring containing polymer is securable.

  Examples of the organic phosphorus compound used as a catalyst in the cyclocondensation reaction include alkyl (aryl) phosphonous acids such as methylphosphonous acid, ethylphosphonous acid, and phenylphosphonous acid (however, these are tautomers) May be an alkyl (aryl) phosphinic acid which is a natural product) and monoesters or diesters thereof; dialkyl (such as dimethylphosphinic acid, diethylphosphinic acid, diphenylphosphinic acid, phenylmethylphosphinic acid, phenylethylphosphinic acid) Aryl) phosphinic acid and esters thereof; alkyl (aryl) phosphonic acids such as methylphosphonic acid, ethylphosphonic acid, trifluoromethylphosphonic acid, and phenylphosphonic acid; and monoesters or diesters thereof; methylphosphinic acid Alkyl (aryl) phosphinic acids such as ethylphosphinic acid and phenylphosphinic acid and esters thereof; methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite, diethyl phosphite, phosphorus phosphite Phosphorous acid monoester or diester or triester such as diphenyl acid, trimethyl phosphite, triethyl phosphite, triphenyl phosphite; methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, octyl phosphate, phosphorus Isodecyl phosphate, lauryl phosphate, stearyl phosphate, isostearyl phosphate, phenyl phosphate, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, phosphorus Diisostearyl acid, diphenyl phosphate, phosphoric acid Phosphoric monoesters or diesters or triesters such as limethyl, triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, triphenyl phosphate; methylphosphine, ethylphosphine, phenylphosphine, Mono- or di- or tri-alkyl (aryl) phosphine such as dimethylphosphine, diethylphosphine, diphenylphosphine, trimethylphosphine, triethylphosphine, triphenylphosphine; methyldichlorophosphine, ethyldichlorophosphine, phenyldichlorophosphine, dimethylchlorophosphine, Alkyl (aryl) halogen phosphines such as diethyl chlorophosphine and diphenylchlorophosphine; Mono-, di- or tri-alkyl (aryl) phosphine oxides such as fin, ethyl phosphine oxide, phenyl phosphine oxide, dimethyl phosphine oxide, diethyl phosphine oxide, diphenyl phosphine oxide, trimethyl phosphine oxide, triethyl phosphine oxide, triphenyl phosphine oxide Halogenated tetraalkyl (aryl) phosphonium such as tetramethylphosphonium chloride, tetraethylphosphonium chloride, tetraphenylphosphonium chloride; and the like. These organic phosphorus compounds may be used alone or in combination of two or more. Among these, alkyl (aryl) phosphonous acid, phosphorous acid monoester or diester, phosphoric acid monoester or diester, and alkyl (aryl) phosphonic acid are preferable because of high catalytic activity and low colorability. Aryl) phosphonous acid, phosphorous acid monoester or diester, phosphoric acid monoester or diester are more preferred, and alkyl (aryl) phosphonous acid, phosphoric acid monoester or diester is particularly preferred.

  Although the usage-amount of the catalyst used in the case of a cyclization condensation reaction is not specifically limited, For example, Preferably it is 0.001-5 mass% with respect to a polymer (a), More preferably, it is 0.01-2.5. % By mass, more preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. If the amount of the catalyst used is less than 0.001% by mass, the reaction rate of the cyclization condensation reaction may not be sufficiently improved. On the other hand, when the usage-amount of a catalyst exceeds 5 mass%, it may become a cause of coloring of the obtained polymer, or a polymer may bridge | crosslink and it may become difficult to carry out melt molding.

  The addition timing of the catalyst is not particularly limited, and may be added at the beginning of the reaction, may be added during the reaction, or may be added in both of them.

  It is preferable to carry out the cyclization condensation reaction in the presence of a solvent and to use a devolatilization step in combination with the cyclization condensation reaction. In this case, a mode in which the devolatilization step is used throughout the cyclization condensation reaction and a mode in which the devolatilization step is not used over the entire cyclization condensation reaction but only in a part of the process. In the method using the devolatilization step, the alcohol produced as a by-product in the condensation cyclization reaction is forcibly devolatilized and removed, so that the equilibrium of the reaction is advantageous to the product side.

  The devolatilization step refers to a step of removing volatile components such as a solvent and residual monomers and alcohol produced as a by-product by a cyclocondensation reaction leading to a lactone ring structure, if necessary under reduced pressure heating conditions. If this alcohol removal treatment is insufficient, residual volatile components in the produced polymer increase, and coloring may occur due to deterioration during molding, or molding defects such as bubbles and silver streaks may occur.

  In the case of a form in which a devolatilization step is used throughout the cyclization condensation reaction, the apparatus to be used is not particularly limited, but for performing the present invention more effectively, for example, from a heat exchanger and a devolatilization tank. It is preferable to use a devolatilizing device, an extruder with a vent, or a device in which the devolatilizing device and an extruder are arranged in series, and a devolatilizing device or a vented extruder comprising a heat exchanger and a devolatilizing tank is used. More preferably, it is used.

  The reaction treatment temperature in the case of using a devolatilizer comprising the heat exchanger and the devolatilization tank is preferably 150 to 350 ° C, more preferably 200 to 300 ° C. If the reaction treatment temperature is lower than 150 ° C, the cyclization condensation reaction may be insufficient, and the residual volatile matter may increase. On the other hand, if the reaction treatment temperature is higher than 350 ° C, coloring or decomposition may occur. is there.

  When using a devolatilizer comprising the heat exchanger and the devolatilizer, the pressure during the reaction treatment is preferably 931 to 1.33 hPa (700 to 1 mmHg), more preferably 798 to 66.5 hPa (600). ~ 50mmHg). If the pressure during the reaction treatment is higher than 931 hPa (700 mmHg), volatile components including alcohol may easily remain. On the other hand, if the pressure during the reaction treatment is lower than 1.33 hPa (1 mmHg), industrial implementation may be difficult.

  When using the extruder with a vent, one or a plurality of vents may be used, but it is preferable to have a plurality of vents.

  The reaction treatment temperature when using the extruder with a vent is preferably 150 to 350 ° C, more preferably 200 to 300 ° C. If the temperature is lower than 150 ° C, the cyclization condensation reaction may be insufficient and the residual volatile content may increase. On the other hand, if the temperature is higher than 350 ° C, the obtained polymer may be colored or decomposed. is there.

  The pressure during the reaction treatment when using the extruder with a vent is preferably 931 to 1.33 hPa (700 to 1 mmHg), more preferably 798 to 13.3 hPa (600 to 10 mmHg). When the pressure during the reaction process is higher than 931 hPa (700 mmHg), there is a problem that volatile components including alcohol easily remain, and when it is lower than 1.33 hPa (1 mmHg), industrial implementation may be difficult. .

  In the case of using the devolatilization step throughout the cyclization condensation reaction, as described later, the physical properties of the lactone ring-containing polymer obtained may be deteriorated under severe heat treatment conditions. It is preferable to use a catalyst for the dealcoholization reaction and under the mildest conditions possible, for example, using a vented extruder or the like.

  In the case where the devolatilization step is used throughout the cyclization condensation reaction, the polymer (a) obtained in the polymerization step is preferably introduced into the cyclization condensation reaction device together with a solvent. Depending on the situation, it may be passed once again through a cyclocondensation reaction apparatus such as an extruder with a vent.

  The devolatilization step may be performed in a form that is not used together over the entire process of the cyclization condensation reaction but is used together only in a part of the process. For example, the apparatus for producing the polymer (a) is further heated to advance the cyclization condensation reaction to some extent in advance (at this time, a part of the devolatilization step may be used in combination if necessary) Subsequently, the cyclization condensation reaction and the devolatilization step are simultaneously performed to complete the reaction.

  In the embodiment in which the devolatilization step is used throughout the cyclization condensation reaction described above, for example, when the polymer (a) is heat-treated at a high temperature of about 250 ° C. or higher using a twin-screw extruder. In addition, due to the difference in heat history, partial decomposition or the like may occur before the cyclization condensation reaction occurs, and the physical properties of the resulting lactone ring-containing polymer may be deteriorated. Therefore, if the cyclization condensation reaction is allowed to proceed to some extent before performing the cyclization condensation reaction combined with the devolatilization process, the reaction conditions in the latter half can be eased, and the physical property deterioration of the resulting lactone ring-containing polymer is suppressed. It is preferable because it is possible. As a particularly preferred form, for example, a form in which the devolatilization step is started after a lapse of time from the start of the cyclization condensation reaction, that is, a hydroxyl group and an ester present in the molecular chain of the polymer (a) obtained in the polymerization step A mode in which a group is preliminarily subjected to a cyclization condensation reaction to increase the cyclization condensation reaction rate to some extent, and then a cyclization condensation reaction and a devolatilization step are simultaneously performed. Specifically, for example, a cyclization condensation reaction is allowed to proceed to a certain reaction rate in the presence of a solvent in advance using a kettle reactor, and then a reactor equipped with a devolatilizer, for example, a heat Preferred is a mode in which the cyclization condensation reaction is completed with a devolatilizer comprising an exchanger and a devolatilization tank, an extruder with a vent, or the like. Particularly in the case of this form, it is more preferable that a catalyst for the cyclization condensation reaction is present in the reaction system.

  As described above, the hydroxyl group and ester group present in the molecular chain of the polymer (a) obtained in the polymerization step are preliminarily subjected to a cyclization condensation reaction to increase the cyclization condensation reaction rate to some extent. The method of carrying out the cyclization condensation reaction using the steps at the same time is a preferred form in obtaining a lactone ring-containing polymer in the present invention. With this configuration, a lactone ring-containing polymer having a higher cyclization condensation reaction rate, a higher glass transition temperature, and excellent heat resistance can be obtained. In this case, as a measure of the cyclization condensation reaction rate, for example, the mass reduction rate in the range of 150 to 300 ° C. in the dynamic TG measurement shown in the examples is preferably 2% or less, more preferably 1. It is 5% or less, more preferably 1% or less.

  The reactor that can be employed in the case of the cyclization condensation reaction carried out in advance before the cyclization condensation reaction using the devolatilization process at the same time is not particularly limited. For example, an autoclave, a kettle reactor, a heat exchanger and a devolatilization tank A vented extruder suitable for a cyclocondensation reaction in which a devolatilization step is simultaneously used can also be used. Of these reactors, autoclaves and kettle reactors are preferred. However, even when a reactor such as an extruder with a vent is used, by adjusting the temperature condition, barrel condition, screw shape, screw operation condition, etc. It is possible to carry out the cyclization condensation reaction in the same state as the reaction state in the kettle reactor.

  In the case of the cyclization condensation reaction performed in advance before the cyclization condensation reaction using the devolatilization step at the same time, preferably, a mixture containing the polymer (a) obtained in the polymerization step and the solvent is used as (i). Examples thereof include a method in which a catalyst is added and subjected to a heat reaction, (ii) a method in which a heat reaction is performed without a catalyst, and a method in which the above (i) or (ii) is performed under pressure.

  In addition, as the “mixture containing the polymer (a) and the solvent” which is the starting material of the cyclization condensation reaction in the lactone cyclization condensation step, the polymerization reaction mixture obtained in the polymerization step may be used as it is. Alternatively, the solvent once removed from the polymerization reaction mixture and then re-added with a solvent suitable for the cyclization condensation reaction may be used.

  The solvent that can be re-added in the cyclization condensation reaction that is carried out in advance before the cyclization condensation reaction simultaneously used in the devolatilization step is not particularly limited, for example, aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; Ketones such as methyl ethyl ketone and methyl isobutyl ketone; chloroform, dimethyl sulfoxide (DMSO), tetrahydrofuran and the like. These solvents may be used alone or in combination of two or more. It is preferable to use the same type of solvent that can be used in the polymerization step.

  Examples of the catalyst added in the above method (i) include esterification catalysts such as p-toluenesulfonic acid or transesterification catalysts, basic compounds, organic carboxylates, carbonates and the like that are generally used. Is preferably the above-described organophosphorus compound. The addition timing of the catalyst is not particularly limited. For example, the catalyst may be added at the initial stage of the reaction, may be added during the reaction, or may be added in both of them. Although the addition amount of a catalyst is not specifically limited, For example, Preferably it is 0.001-5 mass% with respect to the mass of a polymer (a), More preferably, it is 0.01-2.5 mass%, More preferably, it is 0.00. It is 01-0.1 mass%, Most preferably, it is 0.05-0.5 mass%. Although the heating temperature and heating time of method (i) are not particularly limited, for example, the heating temperature is preferably room temperature to 180 ° C, more preferably 50 ° C to 150 ° C, and the heating time is preferably 1 to 20 hours, more preferably 2 to 10 hours. When the heating temperature is low or when the heating time is short, the cyclization condensation reaction rate may decrease. If the heating time is too long, the resulting polymer may be colored or decomposed.

  Examples of the method (ii) include a method of heating the polymerization reaction mixture obtained in the polymerization step as it is using a pressure-resistant kettle reactor or the like. The heating temperature is, for example, preferably 100 ° C to 250 ° C, more preferably 150 ° C to 230 ° C. The heating time is preferably 1 to 20 hours, more preferably 2 to 10 hours. When the heating temperature is low or the heating time is short, the cyclization condensation reaction rate may decrease. On the other hand, when the heating temperature is high or the heating time is too long, the resin may be colored or decomposed.

  Both the above methods (i) and (ii) have no problem even under pressure depending on conditions.

  In the case of the cyclization condensation reaction performed in advance before the cyclization condensation reaction using the devolatilization step at the same time, there is no problem even if part of the solvent volatilizes spontaneously during the reaction.

  The mass reduction rate between 150 and 300 ° C. in the dynamic TG measurement at the end of the cyclization condensation reaction performed in advance before the cyclization condensation reaction simultaneously using the devolatilization step, that is, immediately before the start of the devolatilization step is 2% or less is preferable, More preferably, it is 1.5% or less, More preferably, it is 1% or less. If the mass reduction rate is higher than 2%, the cyclization condensation reaction rate does not rise to a sufficiently high level even if the cyclization condensation reaction is performed simultaneously with the devolatilization step, and the physical properties of the resulting lactone ring-containing polymer. May decrease. In addition, when performing said cyclization condensation reaction, in addition to a polymer (a), you may coexist other thermoplastic resins.

  The hydroxyl group and ester group present in the molecular chain of the polymer (a) obtained in the polymerization step were subjected to a cyclization condensation reaction in advance to increase the cyclization condensation reaction rate to some extent, and then the devolatilization step was simultaneously used in combination. In the case of a form in which a cyclization condensation reaction is performed, a polymer obtained by a cyclization condensation reaction performed in advance (a polymer in which at least a part of a hydroxyl group and an ester group present in a molecular chain undergoes a cyclization condensation reaction) and a solvent, The devolatilization step may be used as it is, and may be introduced into the cyclization condensation reaction. If necessary, the polymer (a polymer obtained by cyclization condensation reaction of at least a part of hydroxyl groups and ester groups present in the molecular chain) may be used. It may be introduced into a cyclization condensation reaction in which a devolatilization step is used at the same time after other treatment such as re-addition of a solvent.

  The end timing of the devolatilization process is not particularly limited, and the devolatilization process and the cyclization condensation reaction may be completed at the same time, or the devolatilization process may be terminated after a while from the end of the cyclization condensation reaction. I do not care.

  The weight average molecular weight of the lactone ring-containing polymer obtained by the cyclization condensation reaction is preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, and still more preferably 10,000. ˜500,000, particularly preferably 50,000 to 500,000.

  The lactone ring-containing polymer preferably has a mass reduction rate in the range of 150 to 300 ° C. in dynamic TG measurement of 1% or less, more preferably 0.5% or less, and even more preferably 0.3% or less. It is.

  Since the lactone ring-containing polymer according to the present invention has a high cyclization condensation reaction rate, it is possible to avoid the disadvantage that bubbles and silver streaks enter the molded product after molding. Further, since the lactone ring structure is sufficiently introduced into the polymer due to a high cyclization condensation reaction rate, the obtained lactone ring-containing polymer has sufficiently high heat resistance.

  The lactone ring-containing polymer that is the main component of the base film according to the present invention preferably has a coloring degree (YI) of 6 or less, more preferably 3 or less, even more preferably in a chloroform solution having a concentration of 15% by mass. Is 2 or less, most preferably 1 or less. If the coloring degree (YI) exceeds 6, transparency may be impaired due to coloring, and it may not be used for the intended purpose.

  The lactone ring-containing polymer preferably has a 5% mass reduction temperature in thermal mass spectrometry (TG) of 330 ° C. or higher, more preferably 350 ° C. or higher, and still more preferably 360 ° C. or higher. The 5% mass reduction temperature in thermal mass spectrometry (TG) is an indicator of thermal stability, and if it is less than 330 ° C., sufficient thermal stability may not be exhibited.

  The lactone ring-containing polymer has a glass transition temperature (Tg) of preferably 115 ° C. or higher, more preferably 125 ° C. or higher, further preferably 130 ° C. or higher, more preferably 135 ° C. or higher, and most preferably 140 ° C. or higher. .

  The total amount of residual volatile components contained in the lactone ring-containing polymer is preferably 1,500 ppm or less, more preferably 1,000 ppm or less. If the total amount of residual volatile components is more than 1,500 ppm, it may cause molding defects such as coloring, foaming or silver streak due to alteration during molding.

  The lactone ring-containing polymer has a visible light transmittance measured by a method according to ASTM-D-1003 of a molded product having a thickness of 100 μm obtained by extrusion molding, preferably 85% or more, more preferably It is 90% or more, more preferably 91% or more. Visible light transmittance is a measure of transparency, and if it is less than 85%, the transparency is lowered and there is a possibility that it cannot be used for the intended purpose.

[Base film mainly composed of a lactone ring-containing polymer]
The base film used for the surface protective film according to the present invention contains the above-mentioned lactone ring-containing polymer as a main component.

  The content of the lactone ring-containing polymer in the base film is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, still more preferably 70 to 100% by mass, and particularly preferably 80 to 100% by mass. is there. When the content ratio of the lactone ring-containing polymer in the base film is less than 50% by mass, the effects of the present invention may not be sufficiently exhibited.

  The base film according to the present invention may contain a polymer other than the lactone ring-containing polymer (hereinafter, also referred to as “other polymer”) as other components.

  Examples of other polymers include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, poly (4-methyl-1-pentene); halogens such as vinyl chloride, vinylidene chloride, and chlorinated vinyl resins. Acrylic polymers such as polymethyl methacrylate; Styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer Polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; polyamides such as nylon 6, nylon 66 and nylon 610; polyacetals; polycarbonates; polyphenylene oxides; Polyether ether ketone; polysulfones; polyethersulfones; polyoxyethylene benzylidene alkylene; polyamideimide; polybutadiene rubber, rubber-like polymer such as ABS resin or ASA resin containing an acrylic rubber; and the like.

  The content of the other polymer in the base film is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, further preferably 0 to 30% by mass, and particularly preferably 0 to 20% by mass. .

  The base film used for the surface protective film according to the present invention may contain other additives. Examples of other additives include hindered phenol-based, phosphorus-based and sulfur-based antioxidants; light-resistant stabilizers, weather-resistant stabilizers, heat-stabilizers, and other stabilizers; reinforcing materials such as glass fibers and carbon fibers. UV absorbers such as phenyl salicylate, (2,2′-hydroxy-5-methylphenyl) benzotriazole, 2-hydroxybenzophenone; near infrared absorbers; tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide Flame retardants such as: antistatic agents such as anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; organic fillers and inorganic fillers; resin modifiers; Inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants; These additives can contain a particle size that does not impair the smoothness of the base film, if necessary.

  The content of other additives in the base film is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, and still more preferably 0 to 0.5% by mass.

  The production method of the base film used in the surface protective film according to the present invention is not particularly limited. For example, a lactone ring-containing polymer and, if necessary, other polymers and additives are mixed in a conventionally known mixture. A method in which the thermoplastic resin composition is mixed in advance and then softened and melted to form a film; a lactone ring-containing polymer and other polymers and additives are used as a solvent. Examples thereof include a method of dissolving or dispersing each of them and then mixing them to obtain a uniform mixed solution, which is then formed into a film. Moreover, it is good also as a stretched film by extending | stretching the unstretched film obtained as mentioned above.

  Specific film forming methods include conventionally known film forming methods such as a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Among these, the solution casting method (solution casting method) and the melt extrusion method are preferable.

  Solvents used in the solution casting method (solution casting method) include, for example, chlorine-based solvents such as chloroform and dichloromethane; aromatic solvents such as toluene, xylene, benzene, and mixed solvents thereof; cyclohexane, decalin, and the like Aliphatic hydrocarbon solvents; alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, 2-butanol, methyl cellosolve, ethyl cellosolve, butyl cellosolve; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone; tetrahydrofuran, dioxane, And ethers such as ethyl acetate and diethyl ether; dimethylformamide; dimethyl sulfoxide, cyclohexanone; and the like. These solvents may be used alone or in combination of two or more.

  Examples of the apparatus for performing the solution casting method (solution casting method) include a drum casting machine, a band casting machine, and a spin coater.

  Examples of the melt extrusion method include a T-die method and an inflation method. In this case, the film forming temperature is preferably 150 to 350 ° C., more preferably 200 to 300 ° C.

  When forming a film by the T-die method, a roll-shaped film can be obtained by attaching a T-die to the tip of a known single-screw extruder or twin-screw extruder and winding the film extruded into a film. it can. At this time, it is also possible to perform uniaxial stretching by appropriately adjusting the temperature of the winding roll and adding stretching in the extrusion direction. Also, simultaneous biaxial stretching, sequential biaxial stretching, and the like can be performed by stretching the film in a direction perpendicular to the extrusion direction.

  As a method of stretching, conventionally known stretching methods can be applied, and for example, uniaxial stretching, sequential biaxial stretching, simultaneous biaxial stretching, etc. can be used (uniaxially stretched film, sequential biaxially stretched film or simultaneous biaxial stretch) Stretched film). In the case of biaxial stretching, mechanical strength is improved and film performance is improved.

  The stretching temperature is preferably in the vicinity of the glass transition temperature of the polymer that is the film raw material. Specifically, the stretching temperature is preferably (glass transition temperature−30 ° C.) to (glass transition temperature + 100 ° C.), more preferably. Is (glass transition temperature−20 ° C.) to (glass transition temperature + 80 ° C.). If the stretching temperature is lower than (glass transition temperature-30 ° C.), a sufficient stretching ratio may not be obtained. On the other hand, when the stretching temperature is higher than (glass transition temperature + 100 ° C.), resin flow may occur and stable stretching may not be performed.

  The draw ratio defined by the area ratio is preferably in the range of 1.1 to 25 times, more preferably in the range of 1.3 to 10 times. If the draw ratio is less than 1.1 times, it may not lead to an improvement in toughness accompanying the drawing. On the other hand, when the draw ratio is larger than 25 times, the effect of increasing the draw ratio may not be recognized.

  The stretching speed is unidirectional, preferably in the range of 10 to 20,000% / min, more preferably in the range of 100 to 10,000% / min. If it is slower than 10% / min, it takes time to obtain a sufficient draw ratio, and the production cost may increase. On the other hand, if the stretching speed (one direction) is faster than 20,000% / min, the stretched film may be broken.

  In order to stabilize the optical isotropy and mechanical properties of the film, a heat treatment (annealing) or the like may be performed after the stretching treatment. The heat treatment conditions may be appropriately selected in the same manner as the heat treatment conditions performed on a conventionally known stretched film, and are not particularly limited.

  In addition, the base film according to the present invention is not limited to a single layer, and has a multilayer (laminated) structure of two or more layers as long as the performance as a base film is not impaired. May be.

  Various molded functional coating layers such as an antistatic layer, an easy-adhesion layer, an antifouling layer, and a hard coat layer are laminated and coated on the molded base film, or the base material according to the present invention. The laminated body which laminated | stacked the member by which each individual functional coating layer was coated on the film via the adhesive or the adhesive agent may be sufficient. In addition, the stacking order of each layer is not particularly limited, and the stacking method is not particularly limited. Further, the surface of the base film can be subjected to surface modification treatment such as corona discharge treatment, metal vacuum deposition, and electron beam irradiation.

  In addition, the base film according to the present invention containing the lactone ring-containing polymer as a main component is excellent in adhesiveness with an acrylic pressure-sensitive adhesive to be described later even if the base film surface is not subjected to corona discharge treatment. is there. Therefore, the corona discharge treatment on the surface of the base film can be omitted, and the manufacturing process is not complicated and is economically preferable.

  The film thickness of the base film is preferably 1 μm to 200 μm, more preferably 5 μm to 100 μm, and still more preferably 5 μm to 50 μm. A base film having a film thickness of less than 1 μm may be difficult to ensure sufficient strength for practical use, and breakage or the like is likely to occur when stretching. On the other hand, if the film thickness is larger than 200 μm, there may be a problem in cost.

  Although the base film used for the surface protective film according to the present invention has high transparency, from the viewpoint of use as a surface protective film of an image display device such as a liquid crystal display or a flat panel display, ASTM-D The visible light transmittance measured by a method according to −1003 is preferably 85% or more, more preferably 90% or more, and particularly preferably 92% or more.

  The base film according to the present invention preferably has a tensile strength measured based on ASTM-D-882-61T of 10 MPa to 300 MPa, more preferably 30 MPa to 250 MPa. If it is less than 10 MPa, it is not preferable because sufficient mechanical strength may not be exhibited. When it exceeds 300 MPa, workability is deteriorated, which is not preferable.

  It is preferable that the base film which concerns on this invention is 1% or more of the elongation rate measured based on ASTM-D-882-61T. Although an upper limit is not specifically limited, Usually, 100% or less is preferable. If it is less than 1%, it is not preferable because it lacks toughness.

  The base film according to the present invention preferably has a refractive index of 1.43 to 1.55 as measured with an Abbe refractometer (for example, measured with “DR-M2” manufactured by Atago Co., Ltd.). . More preferably, it is 1.45 to 1.53, and further preferably 1.47 to 1.52. As a surface protection film, if there is a difference in the refractive index between the adhesive and substrate film described later, not only the performance inspection of the surface protection film itself, but also the performance inspection of the object to which the surface protection film is attached. In some cases, the accuracy of the test is lowered and accurate inspection cannot be performed. In addition, the refractive index of a base film can be adjusted with the kind of monomer which comprises the polymer used for a base film, and the content rate of a lactone ring structure.

(Adhesive layer)
Next, the pressure-sensitive adhesive layer will be described. The surface protective film of the present invention has a pressure-sensitive adhesive layer on one side of a base film mainly composed of the lactone ring-containing polymer. When used as a surface protection film, the pressure-sensitive adhesive layer has transparency that does not interfere with performance inspection, adhesion that does not allow air bubbles, etc., and increased adhesion after application to the adherend and adherend. It is required that there is no adhesive residue. In addition, since the surface protective film has also increased in size with the recent increase in size of displays, the fact that the surface protective film can be peeled at high speed by a machine in the peeling process is also counted as an important required characteristic.

  As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, known ones can be used as long as they can be formed by coating such as a solvent type, a solventless type, (meth) acrylic resin, (meth) acrylic ester resin, or Examples thereof include rubbers such as these copolymers, styrene-butadiene copolymers, polyisoprene rubber and polyisobutylene rubber, and polyvinyl ether, silicone, maleimide, and cyanoacrylate adhesives. These may be used alone, but may be used as a pressure-sensitive adhesive composition by blending a crosslinking agent and a tackifier. In view of optical properties such as light resistance and transparency, a (meth) acrylic pressure-sensitive adhesive which is a copolymer containing a (meth) acrylic acid alkyl ester monomer as a main component is preferable.

  As the solvent-type pressure-sensitive adhesive (composition), it is preferable to use a (meth) acrylic pressure-sensitive adhesive from the viewpoint of durability in addition to optical characteristics. The (meth) acrylic pressure-sensitive adhesive is an acrylic polymer comprising a (meth) acrylic acid alkyl ester as a main component and copolymerizing a polar monomer component or the like by a known polymerization method as required, Preferred are those obtained by solution polymerization using toluene or ethyl acetate.

  The (meth) acrylic acid alkyl ester is an alkyl ester of acrylic acid or methacrylic acid, and is not particularly limited. For example, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, acrylic acid Examples include isobutyl, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, and lauryl (meth) acrylate.

  The (meth) acrylic pressure-sensitive adhesive is used as a composition that can be mixed with a crosslinking agent to crosslink the acrylic polymer. As the crosslinking agent, for example, polyisocyanate compounds such as aliphatic diisocyanates, aromatic diisocyanates, and aromatic triisocyanates are used. The compounding quantity of a crosslinking agent is about 0.1-10 mass parts with respect to 100 mass parts of acrylic polymers, and can provide a tackifier and a plasticizer as needed.

  Among the solvent-type pressure-sensitive adhesives, a solvent-type pressure-sensitive adhesive (composition) that forms a sea-island structure when the pressure-sensitive adhesive layer is formed is particularly preferable.

  The solvent-type pressure-sensitive adhesive forming the sea-island structure has a high Tg polymer (A) having a glass transition temperature (Tg) of 0 ° C. or higher, and a Tg lower than this high Tg polymer, and is pressure-sensitive adhesive. And a low Tg polymer (B) showing

  In the following description of the solvent-type pressure-sensitive adhesive that forms the sea-island structure, the term “polymer” includes not only homopolymers but also copolymers and ternary or higher copolymers. In addition, the term “monomer” used in the description of the solvent-type pressure-sensitive adhesive forming the sea-island structure means an addition polymerization type monomer.

  First, the 1st essential component in the solvent-type adhesive which forms the said sea-island structure is a high Tg polymer (A) whose glass transition temperature (Tg) is 0 degreeC or more. The presence of the high Tg polymer suppresses an increase in the adhesive strength during high-speed peeling (hereinafter sometimes referred to as high-speed adhesive strength).

Here, the Tg of the polymer can be determined by DSC (differential scanning calorimeter), DTA (differential thermal analyzer), and TMA (thermomechanical measuring device). In addition, since the Tg of the homopolymer is described in various documents (for example, polymer handbooks), the Tg of the copolymer is determined by the Tg _n (K) of various homopolymers and the mass fraction (W _n ) of the monomer. Can also be obtained from the following equation.

ここで Ｗ_ｎ ；各単量体の質量分率
Ｔｇ_ｎ；各単量体のホモポリマーのＴｇ（Ｋ）

Where W _n ; mass fraction of each monomer
Tg _n : Tg (K) of homopolymer of each monomer

  The Tg of the main homopolymer is 106 ° C. for polyacrylic acid, 8 ° C. for polymethyl acrylate, −22 ° C. for polyethyl acrylate, −54 ° C. for poly n-butyl acrylate, and −70 ° C. for poly 2-ethylhexyl acrylate. Poly-2-hydroxyethyl acrylate is −32 ° C., poly 2-hydroxyethyl methacrylate is 71 ° C., polymethyl methacrylate is 105 ° C., polyvinyl acetate is 32 ° C., polyacrylonitrile is 125 ° C., and polystyrene is 100 ° C.

  The high Tg polymer (A) used for the solvent-type adhesive forming the sea-island structure is not particularly limited as long as Tg is 0 ° C. or higher, and even a homopolymer is obtained by copolymerizing two or more monomers. A polymer may be used. In order to further improve the high-speed peelability, Tg is preferably 10 ° C or higher, more preferably 20 ° C or higher, and further preferably 30 ° C or higher. However, if the Tg of the high Tg polymer (A) is too high, although it may be a slightly adhesive type for re-peeling, the adhesive strength may be insufficient. Therefore, it is preferably less than 80 ° C, preferably 75 ° C or less, 70 More preferably, it is not more than ℃

  The surface protective film of the present invention is used for optical applications, and since the optical performance and the like are inspected while the film is attached to a protected body, the pressure-sensitive adhesive layer has a small haze. Is preferred. In order to reduce the haze of the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition, the high Tg polymer (A) preferably has units derived from vinyl acetate. The refractive index of the vinyl acetate polymer and the refractive index of the (meth) acrylate polymer (especially a polymer containing 2-ethylhexyl acrylate or butyl acrylate) that is the main component of the low Tg polymer (B) are approximate. This is because the haze is reduced. Therefore, the high Tg polymer (A) is preferably obtained from a monomer having 70% by mass or more of vinyl acetate. As for vinyl acetate, 90 mass% or more is more preferable. The most preferred high Tg polymer (A) is polyvinyl acetate (vinyl acetate homopolymer). Other monomers that can be used in combination with vinyl acetate are (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and acrylonitrile, which have a high homopolymer Tg. Styrene and the like are preferable, but a monomer that can be used as a raw material monomer for the low Tg polymer described later can also be used if the type and amount are selected so that the Tg of the high Tg polymer is 25 ° C. or higher. is there. The molecular weight of the high Tg polymer is preferably about 2000 to 100,000 in terms of mass average molecular weight (Mw).

  Next, the second essential component contained in the solvent-type pressure-sensitive adhesive is a low Tg polymer (B) exhibiting pressure-sensitive adhesiveness. The low Tg polymer (B) is required to be lower than the Tg (0 ° C. or higher) of the high Tg polymer (A), and Tg is 0 in order to say “shows pressure-sensitive adhesiveness”. It is preferable that it is less than ° C. More preferably, it is -20 degrees C or less, More preferably, it is -35 degrees C or less. However, if the Tg of the low Tg polymer (B) is lower than -80 ° C, the cohesive force tends to decrease, and adhesive residue tends to occur, which is not preferable.

  In order to obtain this low Tg polymer (B), it is preferable to use a combination of alkyl (meth) acrylate (b-1) and functional group-containing monomer (b-2). The alkyl (meth) acrylate (b-1) is necessary for ensuring adhesive strength, and the functional group-containing monomer (b-2) is a low Tg polymer having a functional group for reacting with a crosslinking agent described later. It is a monomer for introduction into (B).

  In the alkyl (meth) acrylate (b-1), the alkyl group preferably has 4 to 12 carbon atoms from the viewpoint of adhesive properties. This carbon number is preferably 4 to 10, more preferably 4 to 8. If the carbon number is less than 4 (3 or less) or more than 12 (13 or more), the adhesive strength may be reduced. Specifically, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, (meth) acryl Isoamyl acid, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) Nonyl acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, etc. Among them, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate and isooctyl acrylate are more. preferable. These may be used alone or in combination of two or more, and is not limited.

  As the functional group-containing monomer (b-2), 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, caprolactone-modified hydroxy (meth) acrylate, α- ( Hydroxymethyl) methyl acrylate, α- (hydroxymethyl) ethyl acrylate, hydroxyl-containing (meth) acrylates such as mono (meth) acrylate of polyester diol obtained from phthalic acid and propylene glycol; (meth) acrylic acid, Unsaturated monocarboxylic acids such as cinnamic acid and crotonic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid and citraconic acid; carboxyl group-containing monomers such as monoesters of these unsaturated dicarboxylic acids; amino Groups, amide groups, epoxy groups, etc. Examples include (meth) acrylates having any of them. Of these, hydroxyl group-containing (meth) acrylates are preferred.

  The alkyl (meth) acrylate (b-1) is preferably used in the range of 50 to 99.9% by mass in 100% by mass of the raw material monomer of the low Tg polymer (B). More preferably, it is 60-99.7 mass%, More preferably, it is 70-99.5 mass%. If the usage-amount of alkyl (meth) acrylate (b-1) is in the said range, the obtained adhesive will show sufficient adhesive force and tack, However, If less than 50 mass%, adhesive strength and There is a possibility that the wettability to the adherend may be insufficient, and if it exceeds 99.9% by mass, the amount of the functional group-containing monomer (b-2) that becomes a crosslinking point is too small, and the high-speed adhesive force is increased. There is a risk of passing.

  The functional group-containing monomer (b-2) is preferably 0.1 to 10% by mass. If there are few functional groups, the speed of crosslinking reaction will become slow, or high-speed adhesive force will become large too much, but if it exceeds 10 mass%, the adhesive strength of adhesive and the wettability to the adherend will tend to decrease. Therefore, it is not preferable. As for the usage-amount of a functional group containing monomer (b-2), 0.3-8 mass% is more preferable, and 0.5-6 mass% is still more preferable.

  In synthesizing the low Tg polymer, another monomer (b-3) may be copolymerized. The other monomer (b-3) can be copolymerized with the alkyl (meth) acrylate (b-1) and the functional group-containing monomer (b-2), and (b-1) ) And (b-2). For example, alkyl (meth) acrylates other than the alkyl (meth) acrylate (b-1); halogen-substituted products of aliphatic unsaturated hydrocarbons such as ethylene and butadiene, and aliphatic unsaturated hydrocarbons such as vinyl chloride; Aromatic unsaturated hydrocarbons such as styrene and α-methylstyrene; vinyl esters such as vinyl acetate; vinyl ethers; esters of allyl alcohol and various organic acids; ethers of allyl alcohol and various alcohols; acrylonitrile, etc. Of unsaturated cyanide compounds. These may be used alone or in combination of two or more, and is not limited.

  The other monomer (b-3) is preferably 0 to 49.9% by mass in 100% by mass of the raw material monomer mixture. If the content exceeds 49.9% by mass, the amount of the alkyl (meth) acrylate (b-1) or the functional group-containing monomer (b-2) will be reduced, resulting in failure to obtain desired adhesive properties. . A more preferred upper limit is 40% by mass, and a still more preferred upper limit is 30% by mass.

  The most preferred embodiment of the low Tg polymer (B) is a polymer obtained from a raw material monomer mixture containing 2-ethylhexyl acrylate, butyl acrylate, and hydroxyethyl acrylate. This polymer has good adhesive properties and has a refractive index close to that of polyvinyl acetate, which is the best mode of the high-Tg polymer (A), thus reducing the haze of the resulting adhesive layer. Because it can. When the total of 2-ethylhexyl acrylate, butyl acrylate, and hydroxyethyl acrylate is 100% by mass, 2-ethylhexyl acrylate is 20 to 80% by mass, butyl acrylate is 20 to 80% by mass, and hydroxyethyl acrylate is 0.8%. 5-5 mass% is preferable. Of course, (b-1) to (b-3) described above can also be used in combination, but when applied to applications in which haze is important, other than 2-ethylhexyl acrylate, butyl acrylate, and hydroxyethyl acrylate The monomer is preferably 10% by mass or less.

  The low Tg polymer (B) preferably has an Mw of 200,000 or more from the viewpoint of improving the adhesive properties. In addition, when employ | adopting the manufacturing method mentioned later, although the molecular weight of only a low Tg polymer (B) cannot be measured, in the whole mixture of the high Tg polymer (A) and low Tg polymer (B) of this invention Mw is preferably 100,000 to 800,000.

  The high Tg polymer (A) and the low Tg polymer (B) are incompatible because of different Tg and different compositions. In the pressure-sensitive adhesive layer according to the present invention, the high Tg polymer (A) and the low Tg polymer (B) preferably form a sea-island structure. The sea-island structure is in a micro phase-separated state, and a larger amount becomes the sea (continuous phase). However, in the pressure-sensitive adhesive layer according to the present invention, a high Tg polymer (A) and a low Tg polymer (B). When the total amount is 100% by mass, the high Tg polymer (A) is preferably 4 to 35% by mass and the low Tg polymer (B) is preferably 65 to 96% by mass. (B) becomes a continuous phase, and the high Tg polymer (A) becomes an island and is dispersed. The action of the high-Tg polymer (A) dispersed in the form of islands suppresses the increase in adhesive strength during high-speed peeling and the zipping phenomenon (a phenomenon in which peeling does not occur smoothly but makes a noise). be able to. In order to exert this effect, the high Tg polymer is preferably 4 to 35% by mass. If the amount is too small, the above effect will be insufficient. If the amount is too large, the adhesive strength and wettability to the adherend may be insufficient.

  In order to produce the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer, a blending method and a two-stage polymerization method can be adopted as described in detail later. The preferred amount of the high Tg polymer (A) when the blend method is employed is about 4 to 20% by mass, and the preferred amount of the high Tg polymer (A) when the two-stage polymerization method is adopted is 10 to 35. It was found by the present inventors that it is about mass%. This is because the diameter of the island made of the high Tg polymer (A) is about 1.0 to 100 μm in the case of the blending method and about 0.5 to 50 μm in the case of the two-stage polymerization method. Since the blend method having a larger size is more likely to exhibit the effect of the high Tg polymer (A), it is presumed that the high-speed peelability may be improved even if the amount is somewhat small.

  In the present invention, the pressure-sensitive adhesive layer obtained by applying and drying the pressure-sensitive adhesive composition is used for an optical microscope, a transmission electron microscope, a scanning electron microscope, a phase contrast microscope, a polarizing microscope, a scanning tunnel microscope, a microscope The presence or absence of sea-island structure is judged by observing with Raman. The preferred form of the sea-island structure is such that the island-like portions are almost spherical and dispersed in the continuous phase (sea), and the average diameter of each island-like substance is about 0.1 to 100 μm. The presence or absence of such a sea-island structure can also be observed using an optical microscope, a phase contrast microscope, and a polarizing microscope.

  A pressure-sensitive adhesive composition having a sea-island structure by a blend method and a pressure-sensitive adhesive composition having a sea-island structure by a two-stage polymerization method can be clearly distinguished by performing the following separation degree check. That is, a solution having a non-volatile content of 30% by mass was prepared from the high Tg polymer (A), the low Tg polymer (B) and the solvent, and poured into, for example, a test tube and sealed at 25 ° C. It is only necessary to check the separation state when left for 24 hours. When the high-Tg polymer (A) and the low-Tg polymer (B) have a sea-island structure that is easy to phase-separate obtained by the blending method, they are separated after standing for 24 hours. If the obtained sea-island structure is difficult to separate, it does not separate at all in 24 hours. The solution prepared by the above method may be cloudy as long as the cloudy state is uniform throughout the solution. After leaving for 24 hours under the above conditions, if a transparent part is generated in the upper part or the lower part of the liquid column or if the liquid column is separated into two phases having different turbidity, it is judged as “separated”. In addition, the mass ratio of the high Tg polymer (A) and the low Tg polymer (B) in the solution is within the above-described preferable range.

  The solvent that can be used for the separation degree check is not particularly limited as long as it is a solvent used at the time of coating. However, aromatic hydrocarbons such as toluene and xylene; aliphatic esters such as ethyl acetate and butyl acetate; cyclohexane and the like Alicyclic hydrocarbons; aliphatic hydrocarbons such as hexane and pentane, and the like may be mentioned, and these may be used alone or in admixture of two or more.

  In order to confirm that the composition does not separate in the above separation degree check but contains two types of polymers, for example, two Tg are observed in the measurement of tan δ of dynamic viscoelasticity. You can check whether or not. The tan δ of the dynamic viscoelasticity is, for example, an angular vibration frequency of 6.28 rad / s by using a rheometer (manufactured by T.A. Instruments; “ARES”) by a shear mode, a paraplate method (8 mmφ), It may be measured at a measurement temperature range of −50 to 150 ° C.

  As described above, if a high Tg polymer (A) and a low Tg polymer (B) having an approximate refractive index are used, the haze is 3% or less in both the blending method and the two-stage polymerization method. An adhesive product excellent in transparency can be obtained. The haze is preferably as small as possible, and can be measured, for example, with a turbidimeter. In this specification, “haze” refers to a turbidimeter (Nippon Denshoku) in the state of a surface protective film in which an adhesive layer (thickness 20 μm) is provided on the base film (thickness 45 μm or 25 μm). The value when measured using “NDH-2000 type” manufactured by Kogyo Co., Ltd. is employed.

  Next, the manufacturing method of the solvent-type adhesive (composition) which forms the said sea island structure is demonstrated. First, the blending method is a method in which a high Tg polymer (A) and a low Tg polymer (B) are separately polymerized, and then both are mixed (blended). The polymerization method is not particularly limited, but solution polymerization is simple. If the high Tg polymer (A) and the low Tg polymer (B) are polymerized with the same or compatible solvent, the solvent-removing step is unnecessary at the time of blending, which is more convenient. In addition, when blending, it is preferable to stir at high speed with a disper or the like.

  On the other hand, in the two-stage polymerization method, first, a monomer for the high Tg polymer (A) (hereinafter referred to as “monomer (A)”) is polymerized by solution polymerization, and then the high Tg polymer. (A) A method of polymerizing a monomer for a low Tg polymer (B) (hereinafter referred to as “monomer (B)”) in the presence of a solution. Although the pressure-sensitive adhesive composition obtained by this two-stage polymerization method does not cause separation even in the above-described separation degree check, this is because when the monomer (B) is polymerized, the high Tg polymer (A) is converted into a low Tg polymer ( It is thought that a polymer such as B) is partially grafted, and this is to stabilize the island by exerting a surfactant action having affinity for both the sea and the island. . For this reason, it is considered that the island diameter is smaller than that of the blend method.

  In the two-stage polymerization method, it is preferable to start adding the monomer (B) to the reactor after the polymerization rate of the monomer (A) reaches about 70 to 95% by mass. This is because separation does not occur. The polymerization rate (mass%) is a ratio of the mass of the monomer in the reaction vessel converted into a polymer (nonvolatile content), and can be easily obtained by measuring the nonvolatile content. The low Tg monomer (B) is preferably added dropwise to the reactor together with the polymerization initiator. The molecular weight can be increased.

  The high Tg polymer (A) polymerized separately may be added after the two-stage polymerization of the high Tg polymer (A) and the low Tg polymer (B) is completed. The composition of the post-added high Tg polymer (A) is preferably the same as the initially polymerized high Tg polymer (A) from the viewpoint of dispersion stability, but the molecular weight may be different. Thereby, the adhesive force reduction effect of high-speed peeling appears further.

  In both the blending method and the two-stage polymerization method, the solvent used in the solution polymerization specifically includes, for example, aromatic hydrocarbons such as toluene and xylene; aliphatic esters such as ethyl acetate and butyl acetate. Alicyclic hydrocarbons such as cyclohexane; aliphatic hydrocarbons such as hexane and pentane, and the like, but not particularly limited as long as the polymerization reaction is not inhibited. These solvents may be used alone or in combination of two or more. What is necessary is just to determine the usage-amount of a solvent suitably. Although the said solvent-type adhesive composition has a solvent as an essential component, it is preferable to use the same solvent as a polymerization solvent. This is because the product obtained upon completion of the polymerization can be used as a raw material for the solvent-type pressure-sensitive adhesive composition as it is.

  Reaction conditions such as polymerization reaction temperature and reaction time may be appropriately set according to, for example, the composition and amount of the monomer, and are not particularly limited. Further, the reaction pressure is not particularly limited, and may be any of normal pressure (atmospheric pressure), reduced pressure, and increased pressure. The polymerization reaction is desirably performed in an atmosphere of an inert gas such as nitrogen gas.

  Examples of the polymerization catalyst (polymerization initiator) include, but are not limited to, methyl ethyl ketone peroxide, benzoyl peroxide, dicumyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxy octoate, organic peroxides such as t-butylperoxybenzoate, lauroyl peroxide, trade name “NIPPER BMT-K40” (manufactured by NOF Corporation; mixture of m-toluoyl peroxide and benzoyl peroxide), azobisisobutyrate Known compounds such as nitriles and azo compounds such as trade name “ABN-E” (Nippon Hydrazine Kogyo; 2,2′-azobis (2-methylbutyronitrile)) can be used. Further, for example, a known molecular weight regulator represented by mercaptans such as dodecyl mercaptan may be used.

  It is preferable to mix | blend a crosslinking agent with the said solvent-type adhesive composition. As the crosslinking agent, a compound having two or more functional groups capable of reacting with the functional group of the high Tg polymer (A) and / or the low Tg polymer (B) is used.

  For example, if the low Tg polymer (B) has a hydroxyl group, an isocyanate compound is preferable, and if it has a carboxyl group, an isocyanate compound or an epoxy compound is preferable. In terms of reactivity, a combination of a hydroxyl group and an isocyanate compound is most preferable.

  Examples of the isocyanate compound include tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate, 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, Diisocyanate compounds such as hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, and isophorone diisocyanate; Burette polyisocyanate compounds such as “Sumijour N” (manufactured by Sumitomo Bayer Urethane Co., Ltd .; Sumijoule is a registered trademark); "Death Module HL" (both manufactured by Bayer AG; Death Module is a registered trademark), "Coronate EH" (Nippon Polyureta Manufactured by Kogyo Co., Ltd .; a polyisocyanate compound having an isocyanurate ring known as Coronate is a registered trademark; an adduct polyisocyanate compound such as “Sumijour L” (manufactured by Sumitomo Bayer Urethane Co., Ltd.); “Coronate L” (manufactured by Nippon Polyurethane Co., Ltd.) And polyisocyanate compounds such as “Duranate D201” (manufactured by Asahi Kasei Corporation; Duranate is a registered trademark). These can be used alone or in combination of two or more. In addition, so-called blocked isocyanates in which the isocyanate groups of these compounds are inactivated by reacting with a masking agent having active hydrogen can also be used.

  Examples of the epoxy compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A type epoxy resin, N, N, N ′, N′-tetraglycidyl-m-xylenediamine. 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N-diglycidylaniline, N, N-diglycidyltoluidine and the like.

  These crosslinking agents are preferably added so as to be 0.1 to 5 equivalents when the total of the functional groups of the high Tg polymer (A) and the low Tg polymer (B) is 1 equivalent. . If the amount of the cross-linking agent is too small, the resulting adhesive may have insufficient cohesive force and cause adhesive residue, but if it is too large, the adhesive force will be insufficient or the wettability to a rough surface will be reduced. A more preferable amount of the crosslinking agent is 0.2 to 4 equivalents, and further preferably 0.3 to 2 equivalents.

  The non-volatile content of the solvent-type pressure-sensitive adhesive composition is not particularly limited, but is preferably, for example, 10 to 80% by mass, more preferably 20 to 60% by mass, and further preferably 25 to 45% by mass. . When the non-volatile content is less than 10% by mass, drying after application or the like takes a long time, which may reduce productivity. Moreover, when it exceeds 80 mass%, the viscosity of the whole composition will become high, handling property and applicability | paintability may lack, and there exists a possibility that it may become impractical. As the solvent for the pressure-sensitive adhesive composition, any of the polymerization solvents described above can be used, and as described above, the same solvent as the polymerization solvent is preferable.

  In the solvent-type pressure-sensitive adhesive composition, known crosslinking accelerators, tackifiers, modifiers, pigments, colorants, fillers, anti-aging agents, ultraviolet absorbers, ultraviolet stabilizers, etc. You may add in the range which does not inhibit the objective of invention.

  Further, a compatibilizing agent may be added as long as it does not destroy the sea-island structure. The compatibilizer is not particularly limited. For example, a block copolymer or graft copolymer of (meth) acrylate and vinyl acetate, a compatibilizer (compound or polymer having a specific functional group) by ionic interaction, etc. Can be used. The addition amount of the compatibilizer is preferably about 0 to 20 parts by mass per 100 parts by mass of the resin component (total amount of the polymer (A) and the polymer (B)) in the solvent-type pressure-sensitive adhesive composition.

  Examples of the solventless adhesive include a melt-type adhesive and a curable adhesive. Examples of the melt-type pressure-sensitive adhesive include a thermoplastic pressure-sensitive adhesive composition in which a tackifier and a plasticizer are blended with a base polymer containing a thermoplastic elastomer.

  Examples of the thermoplastic elastomer include copolymers or block copolymers of styrenes such as styrene and methylstyrene and conjugated dienes such as butadiene and isoprene. Further, as the thermoplastic elastomer, hydride of styrene-butadiene copolymer, hydride of styrene-isoprene copolymer, hydride of SBS {(styrene / ethylene)-(butylene / styrene) copolymer} (SEBS ), Hydrogenated SIS {(styrene / ethylene)-(propylene / styrene) copolymer} (SEPS) and the like, and those obtained by hydrogenating the block copolymer or modified products thereof. The hydrogenation rate of the copolymer or block copolymer is not particularly limited, and as a modified product, a polar group such as a carboxyl group or a hydroxyl group is added to a part of the copolymer or block copolymer. Various modified products such as those introduced may be mentioned. Among these, hydrides of styrene-conjugated diene block copolymers such as SEBS and SEPS and / or modified products thereof are preferable because they are excellent in light resistance.

  As the curable pressure-sensitive adhesive composition, those obtained by adding a polyfunctional acrylate to bulk partially polymerized acrylic syrup and those obtained by introducing a double bond into the main chain of the polymer are preferable.

  The pressure-sensitive adhesive composition can adjust the monomer composition, the crosslinking density and the gel fraction so that no adhesive residue is generated on the adherend when the pressure-sensitive adhesive is peeled off or the pressure-sensitive adhesive layer is peeled off. preferable.

  You may mix | blend a tackifier and a plasticizer with each said adhesive composition as needed. Examples of the tackifier include terpene resin, terpene phenol resin, phenol resin, aromatic hydrocarbon modified terpene resin, rosin resin, modified rosin resin, synthetic petroleum resin (aliphatic, aromatic and alicyclic synthetic petroleum resin). Etc.), coumarone-indene resins, xylene resins, styrene resins, dicyclopentadiene resins, and those having unsaturated double bonds that can be hydrogenated include hydrogenated products thereof. . One type of tackifier may be used, or two or more types may be used in combination. The amount of the tackifying resin used is usually 50% or less based on the mass of the polymer constituting the pressure-sensitive adhesive, and preferably 1 to 25% from the viewpoint of the pressure-sensitive adhesive strength and tack of the pressure-sensitive adhesive.

  Examples of the plasticizer include hydrocarbon plasticizers. Specific examples of the hydrocarbon plasticizer include liquid paraffin, polybutene, and liquid polybutadiene. Moreover, various well-known plasticizers, such as a phthalic acid ester, an aliphatic dibasic acid ester, glycol ester, phosphoric acid ester, an epoxy plasticizer, are mentioned. The amount of the plasticizer used is usually 20% or less based on the mass of the polymer constituting the adhesive, and preferably 1 to 15% from the viewpoint of the adhesive strength and tack of the adhesive.

[Method for producing surface protective film]
The surface protective film of the present invention can be obtained by forming a pressure-sensitive adhesive layer on the surface of a base film mainly composed of a lactone ring-containing polymer. The method for forming the pressure-sensitive adhesive layer is not particularly limited, and any conventionally known method in the art can be adopted. For example, in the case of employing a solvent-type pressure-sensitive adhesive composition, a pressure-sensitive adhesive composition solution obtained by dissolving or dispersing the solvent-type pressure-sensitive adhesive composition in a solvent is applied onto a substrate film or a separator and dried. You can do it. On the other hand, in the case of a solvent-free pressure-sensitive adhesive composition, if it is a melt-type pressure-sensitive adhesive composition, a thermoplastic resin composition containing a lactone ring-containing polymer used as a base film as a main component (the lactone ring-containing weight). And a thermoplastic pressure-sensitive adhesive composition can be employed, and if it is a curable pressure-sensitive adhesive composition, the curable pressure-sensitive adhesive composition is applied onto a substrate film or a separator to form a coating film Examples of the method include drying as necessary and curing by heating or irradiation with energy rays such as ultraviolet rays or electron beams.

  The method for applying the pressure-sensitive adhesive composition to the substrate film is not particularly limited, and a known method such as a roll coating method, a spray coating method, or a dipping method can be employed. In this case, any of a method for directly applying the pressure-sensitive adhesive composition to the substrate, a method for applying the pressure-sensitive adhesive composition to a release paper, and then transferring the coated material onto the substrate can be employed. After apply | coating an adhesive composition, an adhesive layer is formed on a base film by making it dry.

  In forming the pressure-sensitive adhesive layer, it is desirable to perform heat drying under conditions in which the solvent scatters (volatilizes) (for example, at 50 to 120 ° C. for about 60 to 180 seconds).

  The thickness of the pressure-sensitive adhesive layer is preferably 3 to 50 μm, and more preferably 5 to 30 μm. If the thickness is less than 3 μm, the adhesive strength is insufficient, and partial lifting may occur. If the thickness is larger than 50 μm, the peeling force becomes unnecessarily large, and further, there is a problem in terms of cost.

  A separator 3 (release paper) may be adhered to the surface of the pressure-sensitive adhesive formed on the base film as shown in FIG. Thereby, the adhesive surface can be suitably protected and preserved. The separator (release paper) is peeled off from the pressure-sensitive adhesive surface when the surface protective film is used. The separator is not particularly limited. For example, it is preferable to use a separator that has been subjected to a mold release treatment in advance on one surface of a film containing the lactone ring-containing polymer as a main component.

  In addition, when the adhesive surface is formed on one side of the base film such as a sheet or tape, a known release agent is applied to the back of the base film to form a release agent layer. In this case, as shown in FIG. 2, the base film 1 (surface protective film) may be wound into a roll shape with the pressure-sensitive adhesive layer 2 inside, so that the original film 4 can be obtained. Thereby, since an adhesive layer will contact | abut with the mold release agent layer of a base film back surface, an adhesive surface is protected and preserve | saved.

  A well-known method can be employ | adopted for the mold release process of the said film. In the release treatment, it is preferable to use a release agent containing, as a main component, at least one selected from the group consisting of a silicone resin, a fluororesin, an aliphatic wax, and an olefin resin, for example. Depending on the type of pressure-sensitive adhesive, there is a case where the mold release treatment of the base film is unnecessary.

  As the silicone resin, a silicone resin generally used as a release agent can be used. For example, the silicone resin is used in the technical field described in “Silicone Material Handbook” (Toray Dow Corning, 19933.8). It can be selected from silicone resins. Specifically, a thermosetting or ionizing radiation curable silicone resin is preferable. Examples of the thermosetting silicone resin include a condensation reaction type or addition reaction type silicone resin, and examples of the ionizing radiation curable silicone resin include an ultraviolet curable type or an electron beam curable type silicone resin. A release layer is formed by applying these on a base film and drying or curing.

  In the surface protective film of the present invention, fish eyes of the base film, and bubbles at the interface between the pressure-sensitive adhesive layer and the separator or the back face of the base film (release treatment surface) are difficult to be confirmed by visual inspection. . However, in order to prevent the appearance of dust and foreign matters that cause poor appearance, it is preferable that the surface protective film manufacturing process is also performed in a clean room of class 1000 or higher according to JIS B9920.

[Surface protection film]
The surface protective film of the present invention preferably has a visible light transmittance of 90% or more as measured according to ASTM-D-1003. More preferably, it is 91% or more, More preferably, it is 92% or more. If the visible light transmittance is less than 90%, the inspection performance of the optical film or the like that is the object to be protected is inferior, and an accurate inspection result may not be obtained.

  The surface protective film of the present invention is attached to the surface of the object to be protected by the pressure-sensitive adhesive layer provided therein, and protects the surface of the object to be protected (display etc.) in the manufacturing process or the distribution process. Is premised on being peeled off. However, after affixing to a non-protective body as a surface protective film, it is preferable that the film does not peel off under use conditions or over time, or does not cause an extreme increase in peel strength. Therefore, for example, it is preferable that the 180 ° adhesive strength at low-speed peeling (0.3 m / min) with respect to an acrylic plate measured by the conditions described later is 0.05 to 0.3 N / 25 mm, more preferably 0.07. It is -0.2N / 25mm, and is 0.3-2.0N / 25mm in high-speed peeling (30m / min), and it is more preferable that it is 0.5-1.5N / 25mm. If the low-speed peel adhesive strength is in the above range, it is sufficient as a surface protective sheet for an optical member, and if the high-speed peel adhesive strength is in the above range, it can be smoothly peeled without causing inconvenience such as zipping. . Moreover, it can be said that the increase in the adhesive force at the time of high speed peeling was able to be suppressed as the value which remove | divided high speed peeling adhesive force by the low speed peeling adhesive force is 15.0 or less. The 180 ° adhesive strength is a value obtained when the 180 ° adhesive strength for an acrylic plate is measured at 23 ° C. using a surface protective film having a 20 μm thick adhesive layer formed on a 25 μm thick substrate. Is adopted. In the unit “N / 25 mm”, the “/ 25 mm” portion means the width of the surface protective film that is pressure-bonded to the adherend.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these. Hereinafter, for convenience, “parts by mass” may be referred to as “parts” and “liters” may be simply referred to as “L”.

  First, the evaluation method of a lactone ring containing polymer and a base film is demonstrated.

<Polymerization reaction rate, polymer composition analysis>
The reaction rate during the polymerization reaction and the content of the specific monomer unit in the polymer were determined by gas chromatography (manufactured by Shimadzu Corporation, apparatus name: GC17A) based on the amount of unreacted monomer in the obtained polymerization reaction mixture. ) And measured.

<Dynamic TG>
The polymer (or polymer solution or pellet) is once dissolved or diluted in tetrahydrofuran, poured into excess hexane or methanol for reprecipitation, and the taken out precipitate is vacuum dried (1 mmHg (1.33 hPa), 80 ° C. Volatile components and the like were removed by conducting the reaction for 3 hours or more, and the obtained white solid resin was analyzed by the following method (dynamic TG method).
Measuring apparatus: differential type differential thermal balance (Thermo Plus 2 TG-8120 Dynamic TG, manufactured by Rigaku Corporation)
Measurement conditions: Sample amount 5-10 mg
Temperature increase rate: 10 ° C / min
Atmosphere: Nitrogen flow 200 mL / min
Method: Step-like isothermal control method (controlled to a mass reduction rate value of 0.005% / s or less within a range of 60 ° C to 500 ° C)

<Dealcoholization reaction rate and content ratio of lactone ring structure>
First, based on the amount of mass reduction that occurs when all hydroxyl groups are dealcoholated as methanol from the obtained polymer composition, 300 before the start of decomposition of the polymer from 150 ° C. before the mass reduction starts in dynamic TG measurement. The dealcoholization reaction rate was determined from the mass reduction due to the dealcoholization reaction up to ° C.

That is, in the dynamic TG measurement of the polymer having a lactone ring structure, the mass reduction rate between 150 ° C. and 300 ° C. is measured, and the obtained actual mass reduction rate is defined as (X). On the other hand, from the composition of the polymer, the mass reduction rate when assuming that all the hydroxyl groups contained in the polymer composition become alcohol and de-alcoholate because they participate in the formation of the lactone ring (that is, in the composition) The mass reduction rate calculated assuming that 100% dealcoholization reaction has occurred is defined as the theoretical mass reduction rate (Y). The theoretical mass reduction rate (Y) is more specifically the molar ratio of the raw material monomers having a structure (hydroxyl group) involved in the dealcoholization reaction in the polymer, that is, the raw material unit in the polymer composition. It can be calculated from the content of the monomer. These values (X, Y) are calculated from the dealcoholization formula:
1- (actual mass reduction rate (X) / theoretical mass reduction rate (Y))
Substituting for, the value is obtained and expressed in percentage (%), the dealcoholization reaction rate is obtained. Then, the content (mass ratio) in the polymer composition of the raw material monomer having a structure (hydroxyl group) involved in lactone cyclization, assuming that the predetermined lactone cyclization has been performed by the dealcoholization reaction rate. The ratio of the lactone ring structure in the polymer can be calculated by multiplying the reaction rate by the dealcoholization reaction rate.

  As an example, the content ratio of the lactone ring structure is calculated by taking the pellet (lactone ring-containing polymer) obtained in the production example described later as an example. When the theoretical mass reduction rate (Y) of this polymer was determined, the molecular weight of methanol was 32, the molecular weight of methyl 2- (hydroxymethyl) acrylate was 116, and methyl 2- (hydroxymethyl) acrylate. Since the content (mass ratio) in the polymer is 25.0% by mass in terms of composition, (32/116) × 25.0≈6.90% by mass. On the other hand, the actual mass reduction rate (X) by dynamic TG measurement was 0.22% by mass. When these values are applied to the above-described dealcoholization calculation formula, 1− (0.22 / 6.90) ≈0.968 is obtained, so that the dealcoholization reaction rate is 96.8%. Then, in the polymer, the content (25.0% by mass) of 2- (hydroxymethyl) methyl acrylate in the polymer is assumed to have been subjected to predetermined lactone cyclization by the dealcoholization reaction rate. When the dealcoholization reaction rate (96.8% = 0.968) is multiplied, the content of the lactone ring structure in the polymer is 24.2 (25.0 × 0.968) mass%.

<Weight average molecular weight>
The weight average molecular weight of the polymer was determined in terms of polystyrene using a gel permeation chromatograph (GPC system, manufactured by Tosoh Corporation).

<Melt flow rate>
The melt flow rate was measured at a test temperature of 240 ° C. and a load of 10 kg in accordance with JIS-K6874.

<Thermal analysis of polymer>
The thermal analysis of the polymer was performed using a differential scanning calorimeter (DSC-8230, manufactured by Rigaku Corporation) under the conditions of about 10 mg of sample, a heating rate of 10 ° C./min, and a nitrogen flow of 50 cc / min. The glass transition temperature (Tg) was determined by the midpoint method according to ASTM-D-3418.

<Pencil hardness>
The surface hardness of the base film was measured using a pencil scratch tester based on JIS K-5400.

<Optical characteristics>
Refractive index anisotropy (retardation: Re) was measured using an automatic birefringence measuring apparatus (KOBRA-21ADH, manufactured by Oji Scientific Instruments). Visible light transmittance was measured using a turbidimeter (NDH-1001DP, manufactured by Nippon Denshoku Industries Co., Ltd.).

<Mechanical properties>
The tensile strength, elongation rate, and tensile elastic modulus of the base film were measured based on ASTM-D-882-61T.

  Below, the manufacturing method of a base film and an adhesive composition is demonstrated in order.

[Production of lactone ring-containing polymer and substrate film]
[Production Example 1]
To a 30 L reaction kettle equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction pipe, 9,000 g of methyl methacrylate (MMA), 1,000 g of methyl 2- (hydroxymethyl) methyl acrylate (MHMA), 10, 000 g of 4-methyl-2-pentanone (methyl isobutyl ketone, MIBK), 5 g of n-dodecyl mercaptan were charged, and the temperature was raised to 105 ° C. while passing nitrogen through the mixture. Of t-butylperoxyisopropyl carbonate (trade name: Kaya-Carbon BIC-75, manufactured by Kayaku Akzo Co., Ltd.) and simultaneously adding 4 g of a solution comprising 10.0 g of t-butylperoxyisopropyl carbonate and 230 g of MIBK. While dropping over time, solution polymerization is performed under reflux (about 105 to 120 ° C.), Aging was carried out over a period of 4 hours in La.

  30 g of stearyl phosphate / distearyl phosphate mixture (manufactured by Sakai Chemical Industry Co., Ltd., trade name: Phoslex A-18) was added to the resulting polymer solution, and the mixture was refluxed (about 90 to 120 ° C.) for 5 Cyclocondensation reaction was performed for a time. Next, the obtained polymer solution was a vent type screw twin screw extruder having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1, and a forevent number of 4. (Φ = 29.75 mm, L / D = 30), by introduction of resin at a processing rate of 2.0 kg / h, cyclization condensation reaction and devolatilization in the extruder, and extrusion. A lactone ring-containing polymer was obtained as a transparent pellet (1A).

  When the obtained pellet (1A) was subjected to dynamic TG measurement, a mass loss of 0.35% by mass was detected. The obtained polymer had a mass average molecular weight of 156,000, a melt flow rate of 3.9 g / 10 min, and a glass transition temperature of 123 ° C.

  The obtained pellet (1A) was melt-extruded from a coat hanger type T die having a width of 150 mm using a twin screw extruder having a 20 mmφ screw to produce a film (1B) having a thickness of about 100 μm. Next, a base film (1C) having a thickness of 25 μm was obtained from the film (1B) using a tenter type biaxial stretching machine. The physical properties of the substrate film (1C) were tensile strength 160 MPa, elongation 40%, pencil hardness 4H, visible light transmittance 93.5%, and Re (550) 8 nm.

[Production Example 2]
A lactone ring-containing polymer was obtained as a transparent pellet (2A) in the same manner as in Production Example 1 except that the amount of MMA was changed to 8,000 g and the amount of MHMA was changed to 2,000 g in Production Example 1.

  When the obtained pellet (2A) was measured for dynamic TG, a mass reduction of 0.64% by mass was detected. Moreover, the mass average molecular weight of the pellet was 144,000, the melt flow rate was 9.2 g / 10 min, and the glass transition temperature was 131 ° C.

  The obtained pellet (2A) was melt-extruded by the same method as the above pellet (1A) to produce a film (2B) having a thickness of about 100 μm, and then a thickness of 45 μm by a tenter type biaxial stretching machine. A base film (2C) was obtained. The physical properties of the substrate film (2C) were tensile strength 181 MPa, elongation 40%, pencil hardness 4H, visible light transmittance 93%, and Re (550) 5 nm.

[Release processing of base film]
Corona discharge treatment is applied to one side of a 25 μm-thick base film (1C), and a thermosetting silicone release agent (product name “LTC750A” manufactured by Toray Dow Corning Silicone Co., Ltd.) is dried on the treated surface. Was applied so that the coating amount was 0.3 g / m ² , and dried to obtain a separator (1S) made of a film mainly composed of a lactone ring-containing polymer.

  Next, the manufacturing method of an adhesive composition is demonstrated.

[Adhesive composition 1]
Re-peeling slightly-adhesive solvent-type acrylic adhesive (manufactured by Nippon Shokubai Co., Ltd., trade name “Acryset (registered trademark) AST-8220R”, solid content 40%, viscosity 1000 mPa · s), 100 parts of acetic acid 20 parts of ethyl and 2 parts of a polyisocyanate cross-linking agent (“Coronate L-55E” manufactured by Nippon Polyurethane Industry Co., Ltd.), passed through a filter with an opening of 5 μm, and removed foreign substances and gels are pressure-sensitive adhesive compositions. It was set as thing 1.

[Adhesive composition 2, 3]
The pressure-sensitive adhesive compositions 2 and 3 were polymer solutions No. 1 prepared in Synthesis Examples 1 and 2. 1 and no. 2 was used for adjustment.

[Synthesis Example 1 (two-stage polymerization)]
Use 70 parts of vinyl acetate (VAC) as the monomer for the high Tg polymer and 210 parts of ethyl acetate as the solvent, mix well, and add thermometer, stirrer, inert gas inlet tube, reflux condenser and dropping funnel. Added to the equipped flask. While circulating nitrogen gas, the internal temperature of the flask was raised to 75 ° C., and “Niper (registered trademark) BMT-K40” (manufactured by NOF Corporation; m-toluoyl peroxide and benzoyl peroxide) as a polymerization initiator. 0.09 part of the mixture) was charged into the flask to initiate the polymerization.

  After 1.5 hours from the start of the reaction, “ABN-E” (manufactured by Nippon Hydrazine Kogyo; 2,2′-azobis (2-methylbutyronitrile)) 0.25 is used as a booster (post-initiator). After the addition of a portion, the mixture was further aged at 76 ° C. for 1.5 hours to obtain a polyvinyl acetate solution. At this time, the polymerization rate of vinyl acetate was 73%.

  Subsequently, in the same flask, 120 parts of n-butyl acrylate, 268 parts of 2-ethylhexyl acrylate and 12 parts of 2-hydroxyethyl acrylate, and 0.5 parts of “Nyper BMT-K40” as a monomer for a low Tg polymer. Then, 105 parts of ethyl acetate was mixed well to prepare a monomer solution, which was dropped evenly from the dropping funnel over 1 hour. After the completion of the dropping, after 1.5 hours, 0.2 part of the “ABN-E” was added as a booster together with 200 parts of ethyl acetate, and further aged at 78 ° C. for 2.5 hours, and 200 parts of ethyl acetate was added. Polymer solution No. 1 was obtained. As a result of observation using an optical microscope, it was confirmed that the structure was a sea-island structure.

[Synthesis Example 2]
250 parts of vinyl acetate and 1.25 parts of “thiocalcol (registered trademark) -20” (manufactured by Kao Corporation; n-dodecyl mercaptan) were weighed and mixed well to prepare a monomer mixture. 50% of this monomer mixture and 375 parts of ethyl acetate were added to a flask equipped with a thermometer, stirrer, inert gas inlet tube, reflux condenser and dropping funnel. The remaining monomer mixture and the monomer mixture for dropping composed of 0.16 part of the above-mentioned “Nyper BMT-K40” were put into a dropping funnel and mixed well. While circulating nitrogen gas, the internal temperature of the flask was raised to 73 ° C., and 0.32 part of “Nyper BMT-K40” was charged into the flask to initiate polymerization. After 10 minutes had passed since the polymerization initiator was added, the dropping of the monomer mixture for dropping was started. The monomer mixture for dripping was dripped uniformly over 1 hour. After completion of the dropwise addition, 38 parts of ethyl acetate was added to the flask. Further, 1 hour after the completion of the dropwise addition, 0.125 part of the “ABN-E” was added as a booster, and further aged at 76 ° C. for 1.5 hours to obtain a polyvinyl acetate solution. At this time, the polymerization rate of vinyl acetate was 82%.

  Polymer solution No. manufactured in Synthesis Example 1 Both were mixed so that the nonvolatile content of the polyvinyl acetate solution was 10 parts with respect to 100 parts of the nonvolatile content of 1, and the mixture was stirred well. 2 was obtained. It was confirmed by an optical microscope that it has a sea-island structure.

  The polymer solution No. About 1 and 2, it was set as the adhesive composition with the following method.

  Each polymer solution obtained in the above synthesis example was taken, and the nonvolatile content was adjusted to 34% with ethyl acetate. For 100 parts of polymer, 250 parts by weight of dibutyltin dilaurate as a crosslinking accelerator and 10 parts of “Duranate (registered trademark) D-201” (hexamethylene diisocyanate; bifunctional; manufactured by Asahi Kasei Co., Ltd.) as a crosslinking agent. The amount corresponding to was added and stirred well to obtain pressure-sensitive adhesive compositions (2 and 3).

  Each polymer solution No. The synthesis methods for 1 and 2 are summarized in Table 1, and each characteristic is shown in Table 2. In addition, each characteristic value in following Table 2 is the value measured in the adhesive or polymer solution state before adding a crosslinking agent. The characteristic evaluation method is as follows.

<Tg>
The Tg of the polymer refers to the values described in various documents (for example, the polymer handbook) for the Tg of the homopolymer, and the Tg _n (K) of the various homopolymers and the mass fraction of the monomer ( W _n ) and the following formula.

ここで Ｗ_ｎ ；各単量体の質量分率
Ｔｇ_ｎ；各単量体のホモポリマーのＴｇ（Ｋ）

Where W _n ; mass fraction of each monomer
Tg _n : Tg (K) of homopolymer of each monomer

In Table 1, each monomer and molecular weight modifier are abbreviated as follows. The numbers on the right are the Tg (K) values of homopolymers listed in the polymer handbook.
VAC: Vinyl acetate 305K
BA: n-butyl acrylate 219K
2EHA: 2-ethylhexyl acrylate 203K
HEA: 2-hydroxyethyl acrylate 241K
DM: Dodecyl mercaptan (molecular weight regulator)

<Mass average molecular weight (Mw)>
GPC measuring apparatus: Liquid Chromatography Model 510 (manufactured by Waters) was used under the following conditions.
Detector: M410 differential refractometer Column: Ultra Styragel Linear (7.8 mm × 30 cm)
Ultra Styragel 100Å (7.8mm × 30cm)
Ultra Styragel 500Å (7.8mm × 30cm)
Solvent: Tetrahydrofuran (abbreviated as THF)
The sample concentration was 0.2%, the injection amount was 200 microliters / time, and the polystyrene standard sample conversion value was Mw.

  In the case of two-stage polymerization, the high Tg polymer (A) was sampled and Mw was measured before adding the second-stage monomer to the flask. Moreover, Mw of the whole polymer mixture was measured after completion | finish of two-stage polymerization.

<Tan δ>
Using rheometer (manufactured by TA Instruments Inc .; “ARES”), measured by shear mode, paraplate method (8 mmφ), angular vibration frequency 6.28 rad / s, measurement temperature range −50 to 150 ° C. did.

<Presence / absence of separation>
The following polymer solution No. For 1 and 2, the concentration is adjusted with ethyl acetate so that the nonvolatile content is 30% by mass, and 50 g is collected in a beaker. After sufficiently stirring by hand, pour into a 12 mmφ test tube until the height of the liquid column reaches 100 mm, and seal the opening of the test tube so that the solvent does not volatilize. Stand in a test tube stand, leave it in an atmosphere of 25 ° C. for 24 hours, and visually observe the state of separation. The case where the degree of turbidity was uniform throughout the solution and no separation boundary was observed was defined as “no separation”. When a transparent part is generated at the upper or lower part of the liquid column, or when two phases having different turbidity are formed (for example, the upper 90 mm of the liquid column is strongly turbid, and the lower 10 mm is higher than the upper part, In the case of a slightly less turbid state), it was judged as “separated”.

[Production of surface protective film]
[Example 1]
One side of the base film (2C) obtained in Production Example 2 is subjected to corona discharge treatment, and the pressure-sensitive adhesive composition 1 is applied to the treated surface so as to have a dry film thickness of 20 μm. (1S) was bonded to obtain a surface protective film (P1) in which the base film (2C), the pressure-sensitive adhesive layer, and the separator (1S) were laminated in this order.

[Example 2]
The adhesive composition 2 was applied to one side of the base film (1C) obtained in Production Example 1 so that the dry film thickness was 20 μm. Next, corona discharge treatment was performed on both surfaces of the base film (1C), and first, an antistatic agent (Bondip-P standard blend manufactured by Konishi Co., Ltd.) was applied on one surface to a dry film thickness of 0.3 μm. Next, as an antifouling agent, polyethyleneimine octadecyl carbamate (manufactured by Nippon Shokubai Co., Ltd., RP-20) 10 parts, saturated polyester resin (Hitachi Chemical Industry Co., Ltd. Espel 9940E-37) 175 And 2 parts of a 50% isopropanol solution of paratoluenesulfonic acid to 100 parts of a mixture obtained by mixing 40 parts of melamine resin and 40 parts of melamine resin (Nicarac MS-11 manufactured by Sanwa Chemical Co., Ltd.) The antistatic layer film (1D) having an antistatic layer and an antifouling layer was obtained by coating on the antistatic layer so as to have a dry film thickness of 0.3 μm (second layer).

  Next, the surface on the pressure-sensitive adhesive layer side of the base film (1C) provided with the pressure-sensitive adhesive layer and the surface on which the anti-static layer of the anti-static base film (1D) is not provided are bonded together to form an antistatic base material. A surface protective film (P2) obtained by laminating the film (1D), the pressure-sensitive adhesive layer, and the base film (1C) in this order was obtained.

Example 3
The non-release treatment surface of the separator (1S) is subjected to corona discharge treatment, and the pressure-sensitive adhesive composition 1 is applied to the corona discharge treatment surface so as to have a dry film thickness of 20 μm. The film was wound up so as to abut on the surface to be released from the mold to obtain a surface protective film original. A film having a size of 200 × 200 mm was cut out from the surface protective film original fabric to obtain a surface protective film (P3) sample having an adhesive layer on the base film (1S).

[Comparative Example 1]
A surface protective film (CP1) was prepared in the same manner as in Example 1 except that a polyester film (“Lumirror (registered trademark)” manufactured by Toray Industries, Inc., 25 μm thick) was used as the base film. The physical properties of the substrate film (PET film) used at this time are as follows: glass transition temperature 110 ° C., tensile strength 160 MPa, elongation 40%, pencil hardness F, visible light transmittance 90%, Re (550) 700 nm. there were.

  Table 3 shows the results of visual inspection, optical properties, and adhesive properties of the obtained films P1 to 3 and CP1. In addition, the characteristic evaluation method regarding these films is as follows.

<Adhesive properties>
After applying the pressure-sensitive adhesive composition to a base film or the like so as to have a predetermined thickness after drying by the method shown in the above examples, it was dried at 100 ° C. for 2 minutes and then cured in an atmosphere at 40 ° C. for 3 days. . The pressure-sensitive adhesive film after curing was conditioned for 24 hours in an atmosphere of 23 ° C. and a relative humidity of 65%, and then cut into an appropriate length with a width of 25 mm to prepare a test tape. The release film was peeled off during the test.

  A surface protective film of each of the above Examples and Comparative Examples was prepared by using an acrylic plate (standard test plate made by Nippon Test Panel Co., Ltd.) having a thickness of 3 mm as an adherend, and an acrylic plate in an atmosphere of 23 ° C. and 65% relative humidity. The test tape of 25 mm × 100 mm cut out from 1 is reciprocated once with a 2 kg rubber roller, and is crimped. After leaving for 25 minutes after pressure bonding, the peeling speed was 0.3 m / min for low speed peeling and 30 m / min for high speed peeling, and 180 ° peeling adhesive strength was measured in an atmosphere of 23 ° C. according to JIS K 6854. . In Table 3, the low-speed peel adhesive strength, the high-speed peel adhesive strength, and the value obtained by dividing the high-speed peel adhesive strength by the low-speed peel adhesive strength (shown as “high speed / low speed”) are also shown.

<Haze (%)>
Using a turbidimeter (manufactured by JEOL Ltd .; “NDH-2000”), haze (%) of the surface protective film was measured according to JIS K 7105.

<Durability test>
The surface protective film cut out to a size of 50 × 50 mm was pressure-bonded to a 3 mm thick acrylic plate (standard test plate manufactured by Nippon Test Panel Co., Ltd.) to obtain a test piece. After leaving this test piece in an oven at 70 ° C. for 7 days, it was taken out and visually checked for the presence of bubbles and lift-off.
○ (Good): No bubbles and no peeling × (No): Bubbles and no peeling

<Polarizer inspection>
Two polarizers were placed in a crossed Nicol state on a white light source. The position and number of bright spots that can be confirmed at this time were confirmed in advance. Next, a surface protective film sample (200 × 200 mm) was sandwiched between two polarizers, and the number of bright spots in the range where the surface protective film sample was present was counted visually.
○ (Good): The number of bright spots increased by inserting a surface protective film between the polarizers is 0-2. Δ (possible): The number of bright spots increased by inserting the surface protective film between the polarizers is 3-5. X (impossible): The number of bright spots increased by inserting a surface protective film between the polarizers is 6 or more.

<Appearance inspection>
Fish eyes present in the surface protective film (base film) and bubbles in the pressure-sensitive adhesive layer were visually observed. The number and size of defects existing per 1 m ^{2 of the} surface protective film were measured and evaluated based on the following criteria.
Evaluation criteria ○ (good): The number of defects having a size of 0.7 mm ² or more is 0, and the number of defects having a size of 0.3 mm ² or more is 5 or less. The number of defects of 7 mm ² or more is less than 5 and the number of defects of size 0.3 mm ² or more is 10 or less × (impossible): The number of defects of size 0.7 mm ² or more is 5 The number of defects having a size of 0.3 mm ² or more is 11 or more. Table 3 summarizes the structures of the films P1 to 3 and CP1 and the evaluation results of each physical property.

  In Table 3, “pressure-sensitive adhesive 1” means pressure-sensitive adhesive composition 1, “pressure-sensitive adhesive 2” means pressure-sensitive adhesive composition 2, and “pressure-sensitive adhesive 3” means pressure-sensitive adhesive composition 3. To do.

  From the above Tables 2 and 3, it can be seen that the surface protective films of Examples 1 to 3 have excellent appearance inspection properties because the fisheye is reduced and the optical properties are good. Moreover, since the heat resistance of a base film is excellent, even when the thickness of a base film is 25 micrometers (Example 2), it turns out that the surface protection film after a durability test does not arise easily and peeling.

  Furthermore, the pressure-sensitive adhesive composition used in Examples 2 and 3 was produced by carrying out two-stage polymerization, but it was excellent in storage stability without causing separation (Table 2). In addition, since high Tg polymer and low Tg polymer are blended in a balanced manner, the high-speed peel adhesive strength is small, the high-speed / low-speed value is 15.0 or less, and it has excellent high-speed peelability. I understand.

  In addition, since the surface hardness of the substrate film is high, it is considered that the scratch resistance is excellent even when the hard coat treatment is not performed.

  Since the surface protective film of the present invention is excellent in optical properties and appearance and excellent in high-speed peelability, surface protective materials for various products, such as optical films and functions for flat displays such as liquid crystal display devices, plasma displays, and organic EL display devices. It is suitable as a surface protective material for products that are required to have high quality in appearance, such as masking of resist films and film resists that perform precise secondary processing, and products in which color tone and appearance are important. In particular, it is suitable for optical applications such as a polarizing plate and a retardation film that are inspected with a surface protective film attached.

It is a schematic diagram which shows an example of the surface protection film of this invention. It is a schematic diagram which shows the other example of the surface protection film (film raw fabric) of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base film 2 Adhesive layer 3 Separator 4 Film raw material

Claims (7)

  A surface protective film comprising a pressure-sensitive adhesive layer on one side of a base film mainly comprising a lactone ring-containing polymer.   The surface protective film according to claim 1, wherein the thickness of the base film is 5 to 50 µm, the thickness of the pressure-sensitive adhesive layer is 5 to 30 µm, and the visible light transmittance is 90% or more. The surface protection film according to claim 1 or 2, wherein the lactone ring-containing polymer has a lactone ring structure represented by the following formula (1).

[Wherein, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms]   The surface protection film according to claim 1, wherein the pressure-sensitive adhesive layer is formed of a (meth) acrylic pressure-sensitive adhesive.   The (meth) acrylic pressure-sensitive adhesive has a high Tg polymer (A) having a glass transition temperature (Tg) of 0 ° C. or higher and a Tg lower than the high Tg polymer, and exhibits low pressure-sensitive adhesiveness. A Tg polymer (B), and in the pressure-sensitive adhesive layer, the high Tg polymer (A) and the low Tg polymer (B) form a sea-island structure without compatibility. 5. The surface protective film according to any one of 4 above.   The surface protective film further includes a separator having a release layer formed on one side of a film mainly containing a lactone ring-containing polymer, and includes a base film, an adhesive layer, and a separator in this order. The surface protective film of any one of Claims 1-5.   A sheet having a release layer on one side of a base film mainly composed of a lactone ring-containing polymer and having an adhesive layer on the other side is wound into a roll shape with the adhesive layer as the inside. A surface protective film original fabric characterized by comprising.

Images