JP2007009109A - Pressure-sensitive adhesive surface protection film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive surface protection film with superior removability that has moderate low pressure-sensitive adhesive property required for removal reuse and does not damage removability due to increased adhesive strength when left under a high temperature environment, in which a pressure-sensitive adhesive is not fallen upon the removal and even when an impact is added after application of the film, the film is not stripped as easily due to the impact. <P>SOLUTION: This pressure-sensitive adhesive surface protection film is used for protection of a substrate surface through its application, provided with (1) adhesive strength A to polymethylmethacrylate resin surface with a smooth surface of 0.05-1.0 N/25 mm, (2) adhesive strength B after heating at 90°C for 168 h of ≤1.0 N/25 mm, (3) a parameter α of wear resistance of ≤0.05, and (4) the removal is carried out without a slip-stick phenomenon at a peel rate of 1,000 mm/min. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an adhesive film for surface protection for protecting a plastic molded product such as a display panel of a mobile electronic device.

  In order to prevent scratches on the surface of the molded product in an assembly process or a transfer process of various plastic molded products, a surface protective film is generally attached to the surface of the molded product. Accordingly, many surface protective films have been developed for various applications (for example, Patent Documents 1, 2, or 3). In recent years, the demand for mobile electronic devices such as mobile phones and portable game machines has been growing, and the demand for surface protection films for the purpose of preventing scratches on the display panel surface and the like has increased due to the increase in the size and transparency of the display part. ing. In the assembly process, since the appearance inspection is performed with the protective film applied to the surface of the molded product, transparency of the surface protective film after being applied to the molded product is required. In many cases, a polyester film excellent in workability and friction resistance is used. Due to the diversification of mobile electronic device designs, there are an increasing number of molded products with quadratic or cubic curved surfaces. Polyester film base films are not very flexible, and floats and peels off the curved surfaces of molded products after application. It's easy to do. In some cases, dust, dust or the like enters from the peeled portion and adheres to the surface of the molded product, thereby impairing the appearance of the molded product. Patent Document 1 describes a surface protective film that is flexible and has excellent adhesion to a third-order curved surface, but emphasizes that the surface protective film does not peel off when used outdoors. Sex is not considered.

  The surface protective film generally has a configuration in which a plastic film is used as a base material and an adhesive layer is provided on one surface of the film. Typical adhesive layers include acrylic adhesives, rubber adhesives, and silicone adhesives, but acrylic adhesives are used because of their availability, transparency, and ease of adhesion control. Often done. In particular, in order to moderately lower the adhesive strength and provide removability, it is common to set the degree of crosslinking of the adhesive to a high level. A low-adhesive adhesive film with moderate adhesive strength as a re-peelable adhesive film has good re-working work when the adhesive film is applied to a molded product, and when the adhesive film is no longer needed Peelability is good. However, if the pressure-sensitive adhesive is reduced by simply curing the pressure-sensitive adhesive excessively, when the pressure-sensitive adhesive becomes too brittle and peels, a part of the pressure-sensitive adhesive drops off and the pressure-sensitive adhesive remains on the surface of the molded product. The appearance will be significantly impaired. Furthermore, a method of increasing the glass transition temperature (Tg) of the pressure-sensitive adhesive is used in order to make it difficult for the pressure-sensitive adhesive to fall off. In this case, the adhesive strength of the surface protective film is greatly influenced by the peeling speed, and the pulling speed is increased. The phenomenon of extreme strength in the adhesive force (slipstick phenomenon) occurs due to the magnitude of the peeling speed, and the edge of the surface protective film peels off with a slight impact during assembly process or transportation, etc. There may be dirt and dust in between. Conversely, if the adhesive has a low glass transition temperature (Tg) in order to make it difficult for the adhesive to fall off, even if the adhesive strength is moderately low at the beginning of application to the surface of the molded product, If left in a high-temperature environment, such as when left in a ship during overseas export, the adhesive strength increases and some of the adhesive drops off and remains on the surface of the molded product, resulting in heavy peeling There are some defects that are difficult to remove. Patent Document 2 states that the adhesive strength is 400 gf / 50 mm at a peeling speed of 20 m / min. However, the adhesive strength after heating is suppressed, and the adhesive does not fall off and does not cause the slip stick phenomenon. There is no mention of a practical approach. Further, Patent Document 3 states that the adhesive strength is 1.5 N / 25 mm or less when heated at 95 ° C. for 4 hours. It does not describe a specific method for preventing the slip stick phenomenon.

JP2003-165959A JP 2001-323239 A JP 09-208910 A

  Therefore, the object of the present invention is to provide removability by increasing the adhesive force even when left in a high temperature environment while having an appropriate low adhesiveness, which is necessary for use in re-peeling applications. In addition, the adhesive does not fall off when peeled off, and even when an impact is applied after application, it is excellent in removability that does not easily peel off due to the impact. Another object is to provide an adhesive film for protecting the surface.

As a result of intensive studies to solve the above problems, the present inventors have solved the problem by using the following adhesive film. That is, it is a pressure-sensitive adhesive film for surface protection for adhering to the surface of an adherend and protecting the surface of the adherend,
(1) The adhesive force A to the surface of the smooth polymethyl methacrylate resin is 0.05 to 1.0 N / 25 mm,
(2) Adhesive force B after heating at 90 ° C. for 168 hours is 1.0 N / 25 mm or less,
(3) The wear resistance parameter α is 0.05 or less,
Furthermore,
(4) The present invention provides a pressure-sensitive adhesive film for surface protection, which peels without causing a slip stick phenomenon when peeled at a tensile speed of 1000 mm / min.

  Moreover, this invention provides the electronic device with which the said adhesive film for surface protection was affixed.

  When the surface protective adhesive film of the present invention is applied to the surface of a molded product for the purpose of protecting the surface of a display panel or a casing part of a mobile electronic device such as a mobile phone or a portable game machine, the molded product is being assembled. It is difficult to peel off due to impacts during transportation or during transportation, and there is little increase in adhesive strength even after leaving in a high-temperature environment due to leaving it in a car under hot weather or exporting it overseas, etc. The adhesive does not fall off and does not contaminate the surface of the adherend, and exhibits excellent removability. Furthermore, since the surface protective adhesive film of the present invention has moderate low adhesiveness as a re-peelable adhesive film, the reworkability when attaching the adhesive film to a molded product is good, The peelability when the film becomes unnecessary is good.

  Hereinafter, the adhesive film for surface protection of the present invention (hereinafter referred to as the adhesive film of the present invention) will be specifically described. The basic structure of the adhesive film of the present invention is a structure in which a plastic film is used as a base material and an adhesive layer is provided on one surface of the film. In order to attach to the surface of the molded product and use it for the purpose of protecting the surface of the molded product, peeling may occur when the consumer uses the mobile electronic device while it is still attached in some cases, such as during the assembly process or transportation process of the molded product. If it is no longer necessary, it should be easy to peel off and remain free of adhesive residue and contamination of the surface of the molded product. Most of the display panels of mobile electronic devices are resin molded products with polymethyl methacrylate or silicone-modified acrylic hard coat. Therefore, the initial adhesive force (180 degree peeling adhesive force) with respect to the polymethylmethacrylate resin surface of the adhesive film of the present invention is 0.05 to 1.0 N / 25 mm. The adhesive strength is preferably 0.1 to 0.6 N / 25 mm, and particularly preferably 0.2 to 0.4 N / 25 mm. If the adhesive strength is less than 0.05 N / 25 mm, the molded product is easily peeled off during the assembly process or the transportation process of the molded product, and the molded product having a small curved surface is lifted from the end. On the other hand, when the thickness exceeds 1.0 N / 25 mm, it is difficult to reattach when the adhesive film is applied to a molded product, and the attaching workability is remarkably deteriorated.

  When a sticky film is stuck on a molded product and exported overseas by ship, or when a consumer is left in a car under hot weather with a sticky film stuck on a molded product, a temperature of around 90 ° C is applied. In this case, the adhesion between the adhesive and the molded product is increased, and an increase in the adhesive force is likely to occur. When peeling an unnecessary adhesive film, it is necessary that the peeling resistance is small and there is no residue or contamination of the adhesive on the surface of the molded product. Therefore, the 180 ° peel adhesion after leaving the adhesive film of the present invention on the polymethyl methacrylate resin surface and leaving it at 90 ° C. for 168 hours is 1.0 N / 25 mm or less. It is preferable that it is 0.2N-0.8N / 25mm, and it is especially preferable that it is 0.2-0.5N / 25mm. When the adhesive strength exceeds 1.0 N / 25 mm, when the adhesive film is peeled off from the molded product, workability is remarkably reduced, and the adhesive is likely to remain on the surface of the molded product.

  The abrasion resistance parameter α in the pressure-sensitive adhesive film of the present invention is 0.05 or less. The abrasion resistance parameter α is a physical property parameter that represents the difficulty of the adhesive remaining on the surface of the molded product when the adhesive film is peeled off from the molded product. The abrasion resistance parameter α of the pressure-sensitive adhesive film of the present invention is preferably 0.04 or less, and particularly preferably 0.03 or less. When it exceeds 0.05, when the pressure-sensitive adhesive film is peeled off from the molded product, the pressure-sensitive adhesive comes off from the pressure-sensitive adhesive film, and the pressure-sensitive adhesive remains on the surface of the molded product. Further, when the pressure-sensitive adhesive film is punched into a label shape or when the pressure-sensitive adhesive film is attached to a molded product, the pressure-sensitive adhesive comes off from the end of the pressure-sensitive adhesive film and adheres to the surface of the pressure-sensitive adhesive film or the surface of the pressure-sensitive adhesive.

  The impact speed generated in the assembling process and the transport process of the molded product corresponds to a speed that is slightly higher than the normal tensile speed of 300 mm / min. When the adhesive film of the present invention is peeled 180 ° from the surface of the polymethylmethacrylate resin at a tensile speed of 1000 mm / min, a slip stick phenomenon does not occur. When the slip stick phenomenon occurs, the edge of the adhesive film is peeled off by a slight impact during the assembly process or transportation, and dust and dust are mixed between the adhesive film and the molded product.

  FIG. 1 shows a graph of an adhesive force-peeling time curve when measured by a 180 ° peel adhesive strength measurement test in the case of peeling while the slip stick phenomenon occurs. As shown in Fig. 1, after holding a certain maximum value of adhesive strength for a certain period of time, the adhesive strength suddenly decreases and then peels off while repeating the adhesive force returning several times immediately. This is called “slipstick”. “Slipstick phenomenon does not occur” in the adhesive film of the present invention means that the amplitude of the adhesive force is less than 30% with respect to the maximum adhesive force. When the amplitude is less than 30%, it is in a state of peeling continuously, and this state is not peeling by “slip stick”.

  The base film of the pressure-sensitive adhesive film of the present invention preferably has a tensile modulus of 0.4 to 1.0 GPa and a thickness of 40 to 80 μm. When the tensile modulus and thickness are in this range, the followability to the small curved surface of the molded product is better, and peeling is less likely to occur from the end of the adhesive film. In addition, the workability of attaching to a molded product is significantly improved.

  As the material of the base film used for the adhesive film of the present invention, a polyolefin resin film is preferably used because it can be easily obtained in the above-mentioned range of tensile elastic modulus. Examples thereof include resin films such as chain low density polyethylene resin, high density polyethylene resin, polypropylene resin, and ethylene-propylene copolymer resin. Preferred are resin films such as linear low density polyethylene resin and ethylene-propylene copolymer resin, which are excellent in transparency. The ethylene copolymerization ratio in the ethylene-propylene copolymer resin is not particularly limited, but is preferably 5 to 10 mol%. The base film used in the pressure-sensitive adhesive film of the present invention may have a single layer structure or a multilayer structure. For example, a single layer structure film formed by appropriately mixing a low density polyethylene resin and an ethylene-propylene copolymer resin, or a linear low film A three-layer structure film in which an ethylene-propylene copolymer resin is laminated on both sides of a density polyethylene resin may be used.

  The base film used for the pressure-sensitive adhesive film of the present invention can be produced by a known method. For example, heat-melt linear low density polyethylene or ethylene-propylene copolymer resin, etc., and continuously extrude with a single layer or multilayer structure T die, circular die, etc., and then cool to form a base film can do.

  When printing on the surface of the base film of the pressure-sensitive adhesive film of the present invention for the purpose of providing a display function such as a caution note or POP, the surface can be corona-treated or an anchor coat layer can be provided. It is preferable to make it easy to adhere the printed layer such as to the base film. Similarly, the adhesion between the surface of the base film and the pressure-sensitive adhesive layer can be improved by performing corona treatment or providing an anchor coat layer on the surface on which the pressure-sensitive adhesive layer is laminated.

The anchor coat layer can be formed by applying an anchor coat agent composed of a resin that accepts printing ink and a dispersion medium to the surface of the base film and drying. As a resin for receiving printing ink, a known acrylic resin, polyvinyl alcohol resin, polyurethane resin, polyester resin, nitrocellulose and the like can be used. A dispersion medium that does not dissolve the substrate film is selected. For example, what mainly has alcohol, such as isopropyl alcohol and ethanol, is mentioned. Moreover, you may use the emulsion which emulsified resin which receives printing ink using water for a dispersion medium using a well-known emulsifier. Moreover, when it is necessary to wind the base film provided with the anchor coat layer in a roll shape, an anti-blocking agent may be added when the base film is unnecessarily adhered by the anchor coat layer. . As an anti-blocking agent, known synthetic silica, calcium carbonate, inorganic additives such as titanium oxide, and organic additives such as polyethylene wax resin can be used. The blending of the anchor coating agent is preferably 20 to 30 parts by mass of the resin that receives the printing ink, 60 to 70 parts by mass of the dispersion medium, and 1 to 5 parts by mass of the antiblocking agent. The coating amount of the anchor coat layer is preferably 0.5 to 3.0 g / m ² , more preferably 1.0 to 2.0 g / m ² in terms of dry weight.

  Instead of the anchor coat layer, an antistatic layer for antistatic purposes may be applied to either the base film surface in contact with the adhesive layer or the base film surface not forming the adhesive layer.

  The antistatic layer is composed of an ion conductive resin and a moisture diffusion preventing resin. The ion conductive resin is composed of a polymer compound having an acidic group such as a carboxyl group or a sulfone group in the side chain, or a polymer compound having a basic group such as an amino group or an N-substituted amino group in the side chain. Obtained by neutralization with a compound or acidic compound. The ion conductive resin is required to have high conductivity and high adhesion to the substrate, and an acrylic acid copolymer having an N, N-disubstituted amino group in the side chain is used as quaternary ammonium. Most preferred is a chlorinated polyelectrolyte. Examples of the moisture diffusion prevention resin include polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), polycarbonate (PC), ethylene-vinyl acetate resin (EVA), thermoplastic resin such as acrylic resin, urethane resin, and alkyd resin. Thermosetting resins such as epoxy resins, unsaturated polyester resins, melamine resins, and urea resins can be used. PVDC, EVA, acrylic resin, and urethane resin are preferable from the viewpoint of transparency, flexibility, and adhesiveness with the pressure-sensitive adhesive layer, and PVDC with low moisture permeability is most preferable. The thickness of the antistatic layer is preferably from 0.1 to 5.0 μm, more preferably from 0.2 to 1.0 μm.

  The anchor coat agent or the antistatic agent is applied to the base film by a known method. For example, it can coat using a knife coater, a gravure coater, a roll coater, etc. A gravure coater is preferable.

  As an adhesive which comprises the adhesive layer used for the adhesive film of this invention, well-known acrylic type, silicone type, and rubber-type adhesive resin can be used. As the rubber-based adhesive, block copolymer systems such as styrene-isoprene-styrene, synthetic rubber-based adhesives such as polybutadiene and polybutylene, natural rubber, and the like can be used. In addition, as the silicone-based pressure-sensitive adhesive, a peroxide crosslinking type or an addition condensation type may be used alone or as a mixture. An acrylic pressure-sensitive adhesive is preferred from the viewpoint of availability, transparency, and ease of adhesion control.

As the acrylic adhesive resin, it is preferable to use a resin obtained by reacting a radical polymerizable monomer containing an acrylate ester having an alkyl chain having 1 to 14 carbon atoms as a monomer component. As an acrylate ester having an alkyl chain having 1 to 14 carbon atoms, for example,
(Group 1) methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, lauryl acrylate methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, cyclohexyl Methacrylate, n-octyl methacrylate, isooctyl meta Relate, 2-ethylhexyl methacrylate, isononyl methacrylate, isodecyl methacrylate, lauryl methacrylate and the like. Among them, it is preferable to use a methacrylic acid alkyl ester having an alkyl chain having 4 to 9 carbon atoms or an acrylic acid alkyl ester having an alkyl chain having 4 to 9 carbon atoms. Among them, it is more preferable to use an acrylic acid alkyl ester having an alkyl chain having 4 to 9 carbon atoms.

  As the monomer component, it is preferable to add an acrylate ester or other vinyl monomer having a polar group such as a hydroxyl group, a carboxyl group, or an amino group.

As a monomer containing a hydroxyl group,
(Group 2) 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, hydroxypropyl (meth) acrylate, caprolactone-modified (meth) acrylate, polyethylene glycol mono (meth) ) Acrylate, polypropylene glycol (meth) acrylate, and the like. Preferred examples include 4-hydroxybutyl (meth) acrylate and 6-hydroxyhexyl (meth) acrylate.

In addition, as a monomer having a polar group other than a hydroxyl group,
(Group 3) A monomer having a carboxyl group such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, acrylic acid dimer, ethylene oxide-modified succinic acid acrylate, N-vinyl-2-pyrrolidone, n-vinylcaprolactam, Examples thereof include monomers having an amide group such as acryloylmorpholine, acrylamide, N, N-dimethylacrylamide, 2- (perhydrophthalimido-N-yl) ethyl acrylate, acrylonitrile, maleic anhydride, itaconic anhydride and the like.

  In particular, as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer used in the pressure-sensitive adhesive film of the present invention, in addition to the monomer (group 1) above, the formula (I)

（式中、Ｘは水素原子又はメチル基、Ｒ_１は分岐鎖を有していてもよい炭素数１〜１２のアルキレン基、Ｒ_２は分岐鎖を有していてもよい炭素数１〜１２のアルキル基を表す。）で表される化合物、式（II）

(In the formula, X is a hydrogen atom or a methyl group, R ₁ is an alkylene group having 1 to 12 carbon atoms that may have a branched chain, and R ₂ is an alkyl group having 1 to 12 carbon atoms that may have a branched chain. A compound represented by formula (II):

（式中、Ｘは水素原子又はメチル基、Ｒ_１は分岐鎖を有していてもよい炭素数１〜１２のアルキレン基を表す。）で表される化合物及び式（III）

(Wherein X represents a hydrogen atom or a methyl group, R ₁ represents an optionally substituted alkylene group having 1 to 12 carbon atoms) and formula (III)

（式中、Ｘは水素原子又はメチル基を表す。）で表される化合物を含有する重合性モノマーを反応して得られる粘着性樹脂を用いることが好ましい。

It is preferable to use an adhesive resin obtained by reacting a polymerizable monomer containing a compound represented by the formula (wherein X represents a hydrogen atom or a methyl group).

As a compound represented by the above formula (I), in formula (I), X is a hydrogen atom, R ₁ is —CH ₂ CH ₂ —, R ₂ is —CH ₃ , —CH ₂ CH _3. , —CH ₂ CH ₂ CH ₃ , —CH ₂ CH ₂ CH ₂ CH ₃ are preferred, X is a hydrogen atom, R ₁ is —CH ₂ CH ₂ —, and R ₂ is —CH ₃ . It is particularly preferred. The compound represented by the above-mentioned formula (II), wherein (II), X is a hydrogen atom, R ₁ is _{-CH 2 CH 2 -, - CH} 2 CH 2 CH 2 -, - CH 2 CH ₂ CH ₂ CH ₂ — is preferred, X is a hydrogen atom, and R ₁ is particularly preferably —CH ₂ CH ₂ —. Further, in the formula (III), X is preferably a hydrogen atom.

  The compound represented by the above formula (I) is preferably used in an amount of 2 to 15% by mass, more preferably 5 to 10% by mass, based on all monomers. Moreover, it is preferable to use 0.5-15 mass% for the compound represented by the said formula (II) with respect to all the monomers, and it is more preferable to use 2-10 mass%. Furthermore, it is preferable to use 0.05-5 mass% of compounds represented by Formula (III) with respect to all the monomers, and it is more preferable to use 0.1-3 mass%.

  As the resin used for the pressure-sensitive adhesive layer used in the pressure-sensitive adhesive film of the present invention, when a resin obtained by reacting the monomers represented by the formulas (I) to (III) as described above is used, the adhesive strength of the pressure-sensitive adhesive layer is set to 0. Even when it is set to 05 to 1 N / 25 mm, the breaking elongation of the pressure-sensitive adhesive layer does not become extremely small, and even if it receives mechanical share such as friction or scratching, the pressure-sensitive adhesive layer is dropped or damaged. Deficiency is difficult to occur.

  The weight average molecular weight of the adhesive resin is preferably 700,000 to 1,100,000 (Mw). Among these, it is more preferable that it is 800,000-900,000. When the weight average molecular weight (Mw) is less than 700,000, the adhesive strength becomes high, and the degree of crosslinking must be set high in order to achieve low adhesion, and the adhesive is likely to fall off. Furthermore, there is a case where a slip stick phenomenon is likely to occur due to the lack of flexibility due to the advanced three-dimensional adhesive resin. When the weight average molecular weight (Mw) exceeds 1,100,000, the pressure-sensitive adhesive is similarly inflexible and a slip stick phenomenon is likely to occur.

  The glass transition temperature (Tg) of the adhesive resin is preferably −70 to −50 ° C., more preferably −70 to −60 ° C. If the glass transition temperature (Tg) is less than -70 ° C, even if the initial adhesive strength is low, if left in a car under a hot weather or left in a ship when exported overseas, Adhesive strength increases and a part of the pressure-sensitive adhesive drops off and remains on the surface of the molded product, or a defect that is difficult to peel off due to heavy peeling. On the other hand, when the glass transition temperature (Tg) exceeds −50 ° C., the adhesive resin becomes inflexible and a slip stick phenomenon is likely to occur.

  The acrylic copolymer can be obtained by copolymerization by a known polymerization method such as a solution polymerization method, a cage polymerization method, a suspension polymerization method, or an emulsion polymerization method. Polymerization can be initiated by peroxides such as benzoyl peroxide and lauroyl peroxide, thermal initiation using azo-based thermal polymerization initiators such as azobisisobutylnitrile, acetophenone-based, benzoin ether-based, benzyl A starting method by ultraviolet irradiation using a ketal-based, acylphosphine oxide-based, benzoin-based or benzophenone-based photopolymerization initiator, or a method by electron beam irradiation can be arbitrarily selected.

  Moreover, in order to raise the cohesion force of an adhesive layer, you may add a crosslinking agent to an adhesive. Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, a chelate crosslinking agent, and a photocurable crosslinking agent. As the addition amount of the crosslinking agent, the pressure-sensitive adhesive layer is preferably adjusted to have a gel fraction of 70 to 99%, and most preferably 80 to 99%. The gel fraction is obtained by immersing the composition of the pressure-sensitive adhesive layer after curing in toluene, measuring the mass after drying of the unnecessary portion remaining after standing for 24 hours, and expressing it as a percentage of the original weight.

  Various additives such as tackifier resins, antioxidants, ultraviolet absorbers, fillers, pigments, thickeners, antistatic agents, etc., are added to the adhesive layer as necessary, as long as the performance is not impaired. Also good.

  The coating solution for the pressure-sensitive adhesive layer is prepared by dissolving the above pressure-sensitive adhesive and, if necessary, other additives in an organic solvent. The organic solvent is not particularly limited as long as the above-described blending components are dissolved, but a known and commonly used organic solvent such as ethyl acetate, toluene, xylene, hexane, methanol, isopropyl alcohol is used alone or in combination. Can be used.

  In order to form a pressure-sensitive adhesive layer on a base film, a method of directly applying a pressure-sensitive adhesive solution adjusted to a solid content of 20 to 60% by weight on a base film with a roll coater or a die coater, or on a release liner First, after forming the pressure-sensitive adhesive layer, a method of transferring to the base film is used. As the release liner, known ones can be used. For example, polyethylene laminate paper, glassine paper, clay coat paper, polyester film, polypropylene film, etc., on which a release layer of a silicone compound is formed can be suitably used. The preferable thickness of the pressure-sensitive adhesive layer after drying is 3 to 30 μm, preferably 10 to 20 μm. When the thickness of the pressure-sensitive adhesive layer exceeds 30 μm, the pressure-sensitive adhesive layer easily falls off from the base film.

  Thus, the surface protective pressure-sensitive adhesive film of the present invention is obtained, and such surface protective pressure-sensitive adhesive film is applied as a surface protection to a display panel of a mobile electronic device such as a mobile phone or a portable game machine. Because it does not slip stick, it does not easily peel off during the assembly process of the molded product or during transportation, etc., has excellent curved surface followability to the molded product, has little increase in adhesive strength even after being left to heat, and has a pressure sensitive adhesive. Dropout is difficult to occur.

  The pressure-sensitive adhesive film of the present invention is processed into a label shape by the following steps. A base film is applied to a roll product of the pressure-sensitive adhesive film of the present invention in which a base film, a pressure-sensitive adhesive and a release liner are laminated (for example, a scroll having a width of 50 to 200 mm and a length of 100 to 800 m is a conventional use size). After that, the unnecessary part is removed after the laminated part up to the adhesive is punched out with a mainspring blade or the like. Thus, a roll product in which necessary portions (labels) are arranged in the longitudinal direction of the release liner is produced, and is cut into a sheet as necessary. When printing is performed on the surface of the base film, an ink-colored layer is provided on the surface of the base film with a printing machine, and then the laminated part from the ink-colored layer through the base film to the adhesive is used as a spring After punching out with, remove unnecessary parts.

  The molded product protected with the adhesive film of the present invention is preferably a molded product made of a transparent resin such as polymethyl methacrylate resin, polycarbonate resin, polystyrene resin or the like and provided with a hard coat layer such as silicone-modified acrylic resin on the surface of these transparent resins. A display panel of a mobile electronic device such as a mobile phone or a portable game machine is particularly preferable.

  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. In the examples, “parts” and “%” are based on mass unless otherwise specified.

(1) Preparation of base film [Base film A]
An ethylene-propylene copolymer resin (“PC630A” manufactured by Sun Allomer) having a melting point of 142 ° C. is supplied to an extruder, melted at 200 ° C., continuously extruded by a T-die and rapidly cooled to obtain a polyolefin substrate film A having a thickness of 80 μm. Produced.

[Base film B]
A polyolefin-based substrate film B having a thickness of 40 μm was obtained by the same composition and method as those of the substrate film A.

[Base film C]
30 parts of an acrylic resin (“Thermolac EF-32” manufactured by Soken Chemical Co., Ltd.) as an ink-accepting resin, 65 parts of a 4: 1 mixed solvent of ethanol and isopropyl alcohol as a dispersion medium, and synthetic silica (Fuji Silysia) as an antiblocking agent 5 parts of “Cylicia 350” manufactured by Kagaku Co., Ltd. was added to prepare a total of 100 parts of the blended solution. The compounded liquid was dispersed for 20 minutes using a paint conditioner to obtain an anchor coating agent I having a solid content of 35%. An original film having a thickness of 80 μm was produced by the same composition and method as the base film A. A polyolefin system in which a corona treatment of 420 mN was applied to one side of the original film, and then an anchor coating agent I was applied with a gravure coater, and after drying, an anchor coating layer having a coating amount of 1.5 g / m ² was provided. A film substrate C was obtained.

[Base film D]
As the polyester base film D, “Embret T-50” (50 μm) manufactured by Unitika Ltd. was used.

(2) Synthesis of adhesive main agent [adhesive main agent A]
In a reaction vessel equipped with a condenser, stirrer, thermometer, and dropping funnel, 89 parts of 2-ethylhexyl acrylate, 5 parts of β-hydroxyethyl acrylate, 5 parts of 2-methoxyethyl acrylate, 1 part of acrylic acid and a polymerization initiator 0.2 part of 2,2′-azobisisobutylnitrile was dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization was carried out at 80 ° C. for 8 hours to obtain an acrylic copolymer solution having a weight average molecular weight of 900,000. . The calculated Tg of the acrylic copolymer is -66 ° C. Ethyl acetate was added and mixed uniformly to obtain an adhesive main agent A having a solid content of 30%.

[Adhesive main agent B]
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 88 parts of 2-ethylhexyl acrylate, 3 parts of 4-hydroxybutyl acrylate, 8 parts of 2-methoxyethyl acrylate, 1 part of acrylic acid and a polymerization initiator 0.2 part of 2,2′-azobisisobutylnitrile was dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization was carried out at 80 ° C. for 8 hours to obtain an acrylic copolymer solution having a weight average molecular weight of 900,000. . The calculated Tg of the acrylic copolymer is -66 ° C. Ethyl acetate was added and mixed uniformly to obtain an adhesive main agent B having a solid content of 30%.

[Adhesive main agent C]
Polymerization started with 87.9 parts of 2-ethylhexyl acrylate, 10 parts of n-butyl acrylate, 2 parts of 4-hydroxybutyl acrylate and 0.1 part of acrylic acid in a reaction vessel equipped with a condenser, stirrer, thermometer and dropping funnel As an agent, 0.2 part of 2,2′-azobisisobutylnitrile is dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization is carried out at 80 ° C. for 8 hours to obtain an acrylic copolymer solution having a weight average molecular weight of 600,000. Obtained. The acrylic copolymer calculation Tg is -69 ° C.
Ethyl acetate was added and mixed uniformly to obtain an adhesive main agent C having a solid content of 40%.

[Adhesive agent D]
In a reaction vessel equipped with a condenser, stirrer, thermometer, and dropping funnel, 85 parts of 2-ethylhexyl acrylate, 5 parts of β-hydroxyethyl methacrylate, 10 parts of acrylic acid and 2,2′-azobisisobutylnitrile as a polymerization initiator 0.2 part was dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization was carried out at 80 ° C. for 8 hours to obtain an acrylic copolymer solution having a weight average molecular weight of 600,000. The acrylic copolymer calculation Tg is -56 ° C. Ethyl acetate was added and mixed uniformly to obtain an adhesive base D having a solid content of 30%.

About the above adhesive main agents AD, Tg calculated ratio using the Tg value of the homopolymer of each monomer. The Tg value of the homopolymer is as follows.
2-ethylhexyl acrylate-70 ° C, β-hydroxyethyl acrylate-15 ° C, 2-methoxyethyl acrylate-50 ° C, acrylic acid 106 ° C, 4-hydroxybutyl acrylate-80 ° C, n-butyl acrylate-55 ° C.

(3) Preparation of adhesive [adhesive a]
2.5 parts of an isocyanate-based crosslinking agent (“Bernock NC-40” manufactured by Dainippon Ink & Chemicals, Inc.) was added to 100 parts of the pressure-sensitive adhesive main agent A, and stirred for 15 minutes to obtain pressure-sensitive adhesive a.

[Adhesive b]
2.5 parts of an isocyanate-based crosslinking agent (“Bernock NC-40” manufactured by Dainippon Ink & Chemicals, Inc.) was added to 100 parts of the pressure-sensitive adhesive main agent B, and stirred for 15 minutes to obtain pressure-sensitive adhesive b.

[Adhesive c]
To 100 parts of the pressure-sensitive adhesive main agent C, 1.5 parts of an isocyanate-based crosslinking agent (“Coronate HX” manufactured by Nippon Polyurethane Industry) and 1.0 part of a chelate-based crosslinking agent (“curing agent M-5A” manufactured by Soken Chemical) The mixture was added and stirred for 15 minutes to obtain an adhesive c.

[Adhesive d]
1100 parts of an isocyanate-based crosslinking agent (“Bernock NC-40” manufactured by Dainippon Ink & Chemicals, Inc.) was added to 100 parts of the pressure-sensitive adhesive main agent D and stirred for 15 minutes to obtain a pressure-sensitive adhesive d.

Example 1
A pressure-sensitive adhesive a was applied to a release liner of a polyester film substrate having a silicone compound release layer formed on the surface and dried at 80 ° C. for 90 seconds to form a pressure-sensitive adhesive layer having a dry weight of 15 g / m ² . A pressure-sensitive adhesive film was prepared by performing a corona treatment of 420 μN / cm on one side of the base film A and then bonding it to the pressure-sensitive adhesive layer. In addition, the obtained adhesive film was used for the test after curing at 40 ° C. for 2 days.

(Example 2)
A pressure-sensitive adhesive film of Example 2 was produced in the same manner as Example 1 except that the pressure-sensitive adhesive b was used.

(Example 3)
A pressure-sensitive adhesive film of Example 3 was produced in the same manner as in Example 1 except that the base film B was used.

Example 4
A pressure-sensitive adhesive film of Example 4 was produced in the same manner as in Example 1 except that the surface having no anchor coat layer of the base film C was subjected to a corona treatment of 420 μN / cm.

(Example 5)
A pressure-sensitive adhesive film of Example 5 was produced in the same manner as in Example 1 except that the base film D was used.

(Comparative Example 1)
A pressure-sensitive adhesive film of Comparative Example 1 was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive c was used and a pressure-sensitive adhesive layer having a dry weight of 30 g / m ² was formed.

(Comparative Example 2)
A pressure-sensitive adhesive film of Comparative Example 2 was produced in the same manner as Example 1 except that the pressure-sensitive adhesive d was used.

The evaluation measurement method will be described below.

[Base film thickness]
The measurement was performed by the method (Method A) defined in JIS K7130 in an environment of 23 ° C. and 50% RH. Using a thickness meter (Tester Sangyo Co., Ltd. Film Thickness Measuring Machine “TH-102”), the thickness of 10 locations was measured at equal intervals in the width direction of the base film, and the average value was taken as the thickness. .

[Tensile modulus]
A test piece having a width of 10 mm and a length of 270 mm is prepared. In an environment of 23 ° C. and 50% RH, the tensile modulus was measured by the method specified in JIS K7113 (tensile speed: 1 mm / min, shape of test piece: No. 4 type test piece). A & D Tensilon Universal Tester “RTA-100” was used as a measuring instrument, and the distance between the marked lines of the test piece was 100 mm, the distance between the grips was 170 mm, and the grip part length was 50 mm.

[Initial adhesive strength]
A test piece having a width of 25 mm and a length of 100 mm is prepared. It affixed with the sticking method prescribed | regulated to JISZ0237 with respect to the polymethylmethacrylate resin board in the environment of 23 degreeC50% RH. One hour after application, the film was peeled off in the 180 ° direction at a tensile speed of 300 mm / min, and the peel strength (unit: N / 25 mm) was measured. As a measuring instrument, A & D Tensilon universal testing machine “RTA-100” was used.

[Adhesive strength after heating]
A sample prepared by the same method as in the previous section was allowed to stand in an environment of 90 ° C. for 168 hours and then left in an environment of 23 ° C. and 50% RH for 1 hour, and the peel strength (unit: N / N) was determined in the same manner as in the previous section. 25 mm).

[Slipstick]
When a sample produced by the same method as the initial adhesive strength was peeled off in the 180 ° direction at a tensile speed of 1000 mm / min, the presence or absence of the occurrence of the slip stick phenomenon was evaluated according to the following criteria.
○: Slip stick phenomenon does not occur (the amplitude is less than 30% with respect to the maximum adhesive force).
X: Slip stick phenomenon occurs.

[Abrasion resistance parameter α]
A sample is prepared by cutting it into a circular shape with a diameter of 110 mm and opening a hole with a diameter of 10 mm in the center. Further, only the release liner of the adhesive film is cut out in a donut shape between the diameters of 60 mm and 90 mm from the center to obtain a test piece. The mass of this test piece is measured with an electronic balance. Next, an abrasion test was performed under the following conditions according to JIS K5600-5-9 using an abrasion tester in an environment of 23 ° C. and 50% RH. A Taber type abrasion tester “AB-101” manufactured by Tester Sangyo Co., Ltd. was used as a measuring instrument.
Wear wheel: CS-17
Load: 250g (arm only)
Rotational speed: 60 revolutions / minute Rotational speed: 5 times Abrasive paper: No. 360 After completion of the test, the removed or missing adhesive is removed using an adhesive film (single-sided tape PF-025H manufactured by Dainippon Ink & Chemicals, Inc.) The mass of the piece was measured with an electronic balance, and the amount of the adhesive removed was calculated. The wear resistance parameter was calculated by the following formula.
Abrasion resistance parameter α = Amount of adhesive falling off (g) / [Amount of adhesive applied (g / m ² ) × 0.0026 (m ² )]
* Area where wear ring rotates: 26cm ²

[Dropping defect]
Place the adhesive liner on the rubber mat so that the adhesive side of the adhesive film is facing up, and use a spatula (a spatula for weighing reagents, etc. with a circular tip) that applies a load of 250 g. Scratch the adhesive surface. After changing the scratching location and repeating the process 5 times, an adhesive film having an adhesive force of less than 0.5 N / 25 mm is once attached to the adhesive surface. The attached adhesive film was peeled off again, and the state of transfer of the drop-off defect to the adhesive film by scratching was evaluated according to the following criteria.
○: Dropping defect due to scratching is not visible.
X: A drop-off defect is visible in all five scratches.

[Curved surface tracking]
A test piece having a width of 10 mm and a length of 25 mm is prepared. The test piece is attached with the long side direction aligned with the circumferential direction of a cylinder made of polymethyl methacrylate resin having a diameter of 50 mm. The condition of floating after being left for 168 hours in a 40 ° C. environment was evaluated according to the following criteria.
○: Floating off is not visible.
X: The floating peeling of 3 mm or more can be visually recognized at one side edge part.

[Gel fraction]
A test piece having a width of 40 mm and a length of 50 mm is prepared. The weight of the test piece was measured in advance with an electronic balance, then immersed in toluene and left in a 23 ° C. room for 24 hours. After standing, the test piece was filtered with a paper filter, dried in a thermostat at 105 ° C. for 1 hour, and then the weight was measured. The weight of the base film not coated with the same size adhesive as the test piece was measured, and the gel fraction was calculated by the following formula.
Gel fraction (%) = 100 × [(weight of test piece after test) − (weight of base film)] / [(weight of test piece before test) − (weight of base film)]

  The evaluation results of Examples and Comparative Examples are shown in Table 1.

The graph of the adhesive force-peeling time curve when the adhesive sheet of this invention is measured on 180 degree peeling adhesive force measurement test conditions with respect to the test board as described in JIS-Z0237 is shown.

Claims (4)

A pressure-sensitive adhesive film for protecting a surface to be adhered to the surface of an adherend and protecting the surface of the adherend,
(1) The adhesive force A to the surface of the smooth polymethyl methacrylate resin is 0.05 to 1.0 N / 25 mm,
(2) Adhesive force B after heating at 90 ° C. for 168 hours is 1.0 N / 25 mm or less,
(3) The wear resistance parameter α is 0.05 or less,
Furthermore,
(4) An adhesive film for surface protection, which peels without causing a slip stick phenomenon when peeled at a tensile speed of 1000 mm / min. The pressure-sensitive adhesive film for surface protection according to claim 1, wherein the base film has a tensile modulus of 0.4 to 1.0 GPa and a thickness of 40 to 80 µm. The adhesive film for surface protection according to claim 1 or 2, wherein the base film is a polyolefin resin film. The electronic device with which the adhesive film for surface protection in any one of Claim 1, 2 or 3 was stuck.

Images