JP2010248489A - Protective adhesive film - Google Patents

Abstract

[Problem] While using an acrylic pressure-sensitive adhesive, wetting of the pressure-sensitive adhesive layer to the object to be adhered proceeds favorably at the time of pasting, and bubbles can be easily removed when pasting on the surface of the object to be adhered. The present invention provides a protective adhesive film that hardly causes contamination on the surface to be deposited after peeling with a plasticizer in an adhesive layer even under a wet heat environment.
A protective adhesive film having a substrate and an adhesive layer, the adhesive layer comprising an acrylic adhesive composition containing an acrylic copolymer and a plasticizer, wherein the plasticizer is saturated or An ester formed from a mono- or dicarboxylic acid having an unsaturated hydrocarbon group and an alcohol having a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms, or an unsaturated group in the unsaturated hydrocarbon group is an epoxy The protective film which consists of converted ester and has a solubility parameter (SP value) of 8.5 or less.
[Selection figure] None

Description

  The present invention relates to a protective adhesive film for protecting a display such as a mobile phone, a personal computer, a television, etc., which is applied to prevent scratching and contamination of the surface during processing, assembly, and transportation.

  The surface protective film is generally composed of a plastic film substrate and an adhesive layer provided on one side of the substrate. For example, it is used to prevent the surface of an optical component having a display such as a television, a personal computer, a mobile phone, or a car navigation system from being scratched, dusty, and dirty. For the display, various materials, for example, resins such as acrylic, polycarbonate, and polyester, and a panel of a highly rigid glass plate are used. Since a display becomes a product defect when the surface is scratched or soiled, an adhesive film is generally affixed to the display surface for the purpose of preventing scratches and contamination during assembly and various processing.

  In addition, once the surface protective film is applied, it is transported and stored in a state where it is applied until the next manufacturing process, or it is molded and applied with the protective film applied during processing. In some cases, missing parts are inspected, and peeling and pasting are repeated many times to confirm the surface. In addition, when used as a protective application for the final product, the inclusion of bubbles causes poor appearance, and therefore it is necessary to be able to affix bubbles without involving bubbles on a smooth or rough surface. At this time, the processing process becomes higher, and the shape to be protected becomes uneven and has a complicated structure, which causes air entrainment when pasted with a machine. In some cases, the film is attached by hand.

  Since air bubbles are likely to be caught when manually pasting, a protective adhesive film in which a silicone-based adhesive layer in which bubbles are easily removed is widely used as a protective adhesive film for such applications. Yes. However, since this silicone adhesive is expensive, a protective adhesive film using an inexpensive acrylic adhesive is required.

  As a protective film using an acrylic adhesive, for example, a display surface protecting adhesive film using an adhesive layer containing a plasticizer having a constant solubility parameter is disclosed (see Patent Document 1). The display surface protecting pressure-sensitive adhesive film improves the wettability of the pressure-sensitive adhesive layer by containing a plasticizer in the pressure-sensitive adhesive layer, and has suitable bubble removal. However, the adhesive film for protecting the surface of the display does not have sufficient stain resistance on the adherend surface, and the adherend surface may be contaminated in a long-term high temperature, high humidity, or high temperature and high humidity environment. there were.

JP 2007-327012 A

  The problem to be solved by the present invention is that, while using an acrylic pressure-sensitive adhesive, air bubbles are easily removed when pasted on the surface of the object to be adhered, and the surface of the object to be adhered after peeling even in a long-time humid heat environment An object of the present invention is to provide a protective adhesive film that hardly causes contamination.

  The present invention is a protective pressure-sensitive adhesive film having a base material and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer comprises an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer and a plasticizer, and the plasticizer is An ester formed from a mono- or dicarboxylic acid having a saturated or unsaturated hydrocarbon group and an alcohol having a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms, or unsaturated in the unsaturated hydrocarbon group It is a protective film having a solubility parameter (SP value) of 8.5 or less, wherein the group is composed of an epoxidized ester and is calculated by the Small formula. In the present invention, by using the acrylic pressure-sensitive adhesive composition containing the plasticizer as a pressure-sensitive adhesive layer, even when an acrylic composition is used as the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is attached to an object to be adhered. The wettability can be improved. Moreover, the said plasticizer is excellent in compatibility with an acrylic adhesive composition, and is easily hold | maintained suitably in the adhesive layer which consists of an acrylic adhesive composition. As a result, the protective adhesive film of the present invention is less susceptible to air bubble entrainment when the adhesive film is attached, and the adhesive layer is not easily entrapped, and the adhesive film can be used in a wet heat environment. It is difficult for the adherend to be contaminated by the plasticizer in the agent layer.

  Since the protective adhesive film of the present invention has good wettability with respect to the object to be adhered, there is little entrapment of bubbles even when affixed at a high affixing speed, and contamination of the object to be adhered is difficult to occur even in a long-term wet heat environment. The visibility of the image display unit is excellent.

[Base material]
As a base material used for this invention, if it is a base material generally used for a protective adhesive film, it will not specifically limit, Any of a biaxially stretched film, a uniaxially stretched film, and an unstretched film can be used. For such a plastic film, a polyolefin-based resin film is preferably used. For example, a resin such as a low-density polyethylene resin, a linear low-density polyethylene resin, a high-density polyethylene resin, a polypropylene resin, or an ethylene-propylene copolymer resin. A film etc. are mentioned. More specifically, polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, diacetyl cellulose film, triacetyl cellulose film, acetyl cellulose butyrate film, polyvinyl chloride film, polyvinyl chloride Vinylidene film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, polymethylpentene film, polysulfone film, polyetheretherketone film, polyethersulfone film, polyetherimide film, polyimide film, fluorine Resin film, nylon film, acrylic resin film, etc. Door can be. Of these, resin films such as linear low-density polyethylene resin and ethylene-propylene copolymer resin, which are excellent in transparency, are more preferable, and among them, PET film has good handling without using additives such as slip agents. Therefore, the possibility of contamination of the adherend surface by the additive can be reduced, and since it has high transparency, there is an advantage that the inspection can be performed in a state where the protective adhesive film is stuck, so that it can be particularly preferably used. Furthermore, since the tensile strength is strong and there is a waist, it is difficult for air bubbles to be generated when a part of the protective adhesive film other than the affixed part comes into contact with the adherend during application, and biaxially stretched that has excellent handling properties during processing. A PET film is more preferable.

  Although it does not specifically limit as thickness of the said base material, 10-150 micrometers is preferable, 25-100 micrometers is still more preferable, 38-100 micrometers is especially preferable. If it is thicker than 10 μm, the film strength is durable enough to obtain a protective performance, so that problems such as tearing of the film at the time of peeling hardly occur, and if it is 25 μm or more, flexibility suitable for manual attachment can be obtained. On the other hand, if the thickness is less than 150 μm, the problem of peeling due to catching of the edge portion hardly occurs, and if it is 100 μm or less, the light transmittance of the film is good, and the problem that the film itself becomes expensive does not occur.

  The elastic modulus of the substrate of the present invention is preferably 1 to 7 GPa. When the elastic modulus is 1 GPa or more, deformation of the film substrate hardly occurs when the protective adhesive film is formed, and when it is 7 GPa or less, the film substrate follows even when the protective adhesive film is attached to a gently curved surface. It has enough hardness.

  When printing is performed for the purpose of providing a display function such as POP on the surface of the substrate described above, an anchor coat layer can be provided in order to improve ink adhesion.

  A hard coat layer can be provided on the surface of the substrate described above for the purpose of preventing scratches on the surface.

  On the base film surface described above, an antistatic layer may be provided on either the base film surface in contact with the pressure-sensitive adhesive layer or the base film surface that does not form the pressure-sensitive adhesive layer when antistatic purposes are intended. .

  In order to improve the adhesion between the base film surface and the pressure-sensitive adhesive layer, and to improve the adhesion when laminating the anchor coat layer, hard coat layer, antistatic layer and pressure-sensitive adhesive layer, sandblasting, solvent treatment, etc. Surface treatments such as corrugated surface treatment by, or surface oxidation treatment such as corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment, etc. can be performed.

  The surface protective film of the present invention preferably has high transparency when it is subjected to product inspection of optical components in a state of being attached to the display surface. In this application, it is preferable to use a transparent substrate as the substrate. The transparent substrate preferably has a visible light transmittance of 85% or more, and particularly preferably 90% or more.

[Adhesive layer]
The pressure-sensitive adhesive layer in the protective pressure-sensitive adhesive film of the present invention is a pressure-sensitive adhesive layer formed from an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer and a plasticizer. Although the thickness of an adhesive layer is not specifically limited, It is preferable that it is 5-50 micrometers, It is more preferable that it is 10-35 micrometers, It is still more preferable that it is 10-25 micrometers. When the thickness of the pressure-sensitive adhesive is 5 μm or more, coating stripes hardly occur, and when it is 50 μm or less, higher transparency can be obtained. Furthermore, when the thickness of the pressure-sensitive adhesive is 10 to 25 μm, it is possible to provide suitable air escape performance without depending on the surface unevenness.

[Acrylic copolymer]
The acrylic pressure-sensitive adhesive composition used for the pressure-sensitive adhesive layer contains an acrylic copolymer as a main component. The acrylic copolymer can be copolymerized by a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an ultraviolet irradiation method, or an electron beam irradiation method.

  Among these, an acrylic copolymer containing a (meth) acrylic acid ester having an alkyl group having 1 to 14 carbon atoms as a monomer component is preferable. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) Examples thereof include acrylate and n-lauryl (meth) acrylate, and can be used alone or in combination of two or more. Among them, n-butyl acrylate, 2-ethylhexyl acrylate, or a monomer using them in combination is preferably a main component, and the amount used is more preferably 50% by mass or more in the pressure-sensitive adhesive composition. It is particularly preferably 90% by mass or more. By using in this range, it is difficult for the plasticizer to bleed out, and when the pressure-sensitive adhesive composition is prepared, the crosslinking is moderately performed. The rest can be reduced.

  The acrylic copolymer is a monomer that gives a functional group, and a (meth) acrylic acid ester monomer or other vinyl monomer having a polar group such as a hydroxyl group, a carboxyl group, or an amino group in the side chain. It is preferable to contain. The content of the monomer having a polar group is preferably from 0.1 to 15% by mass, more preferably from 1 to 10% by mass, based on the monomer component constituting the acrylic copolymer. By containing in the said range, it is easy to adjust the cohesive force and adhesiveness of an adhesive to a suitable range.

  Examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, hydroxypropyl (meth) acrylate, and caprolactone-modified (meth) acrylate. Hydroxyl group-containing (meth) acrylates such as polyethylene glycol mono (meth) acrylate and polypropylene glycol (meth) acrylate can be used, among which 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxy It is preferred to use hexyl (meth) acrylate as a copolymerization component.

  As the monomer having a carboxyl group, acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, (meth) acrylic acid dimer, ethylene oxide-modified succinic acid acrylate, etc. can be used. It is preferable to use it as a copolymerization component.

  Examples of the monomer having a nitrogen atom include N-vinyl-2-pyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, N, N-dimethylacrylamide, and 2- (perhydrophthalimido-N-yl) ethyl acrylate. An amide group-containing vinyl monomer can be used, and among these, N-vinyl-2-pyrrolidone, N-vinylcaprolactam, and acryloylmorpholine are preferably used as the copolymerization component.

  Examples of vinyl monomers having other polar groups include vinyl acetate, acrylonitrile, maleic anhydride, itaconic anhydride and the like.

  The acrylic copolymer preferably has a weight average molecular weight in the range of 300,000 to 1,400,000. A weight average molecular weight can be measured using a gel permeation chromatography (GPC), and shows the weight average molecular weight converted into standard polystyrene (PS). When the weight average molecular weight is 300,000 or more, contamination of the adherend surface with a low molecular weight product tends to be difficult to occur. Furthermore, when the weight average molecular weight is suppressed to 1.4 million or less, there is an advantage that problems such as streaks during coating work due to an increase in the viscosity of the adhesive solution do not occur.

In this invention, it is preferable that the glass transition temperature of the said acrylic copolymer calculated | required by the Fox formula shown below is -70 to -20 degreeC, and it is more preferable that it is -70 to -50 degreeC.
Fox formula: 1 / Tg = Σ (Wn / Tgn)
(In the above formula, Tg (K) is the glass transition temperature of the copolymer, Wn is the weight fraction of the monomer, Tgn (K) is the glass transition temperature of the homopolymer of each monomer, and n is the type of each monomer. )

[Plasticizer]
In the present invention, as a plasticizer, an ester formed from a mono- or dicarboxylic acid having a saturated or unsaturated acyclic hydrocarbon group and an alcohol having an acyclic hydrocarbon group having 1 to 20 carbon atoms, Alternatively, a plasticizer comprising an ester obtained by epoxidizing an unsaturated group in the unsaturated acyclic hydrocarbon group is used. In the present invention, by using an ester having no cyclic skeleton as a plasticizer, the wettability of the pressure-sensitive adhesive layer to the adherend can be improved, and it is difficult to cause entrainment of bubbles at the time of attachment. Further, bleeding out of the plasticizer from the pressure-sensitive adhesive layer hardly occurs, and adherend contamination can be suitably reduced.

  As the saturated or unsaturated acyclic hydrocarbon group in the mono- or dicarboxylic acid component constituting the ester, an alkyl group or an alkylene group can be used, among which an alkyl group or alkylene group having 1 to 20 carbon atoms is preferable. It is more preferable that it is a C4-C18 alkyl group, and a C4-C14 alkyl group is especially preferable. The mono- or dicarboxylic acid having such a saturated or unsaturated acyclic hydrocarbon group has a carbon number close to that of the acrylic monomer constituting the acrylic copolymer used in the pressure-sensitive adhesive layer. As a result, the compatibility with the pressure-sensitive adhesive composition is improved and the plasticizer acrylic pressure-sensitive adhesive composition is suitably held, so that bleeding out is suppressed.

  Examples of the monocarboxylic acid and dicarboxylic acid having a saturated or unsaturated acyclic hydrocarbon group include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacin. Acids, mono- or polyesters of linear aliphatic dicarboxylic acids such as dodecanedioic acid, acetic acid, propionic acid, butyric acid, chitosulic acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecyl acid, lauric acid, tridecyl Acids, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, and other saturated fatty acids, crotonic acid, angelic acid, lindelic acid, myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, gadole Acid, eicosenoic acid, erucic acid, nervonic acid, linault Examples include unsaturated fatty acids such as acid, eicosadienoic acid, docosadienoic acid, linolenic acid, pinolenic acid, eleostearic acid, mead acid, stearidonic acid, arachidonic acid, eicosatetraenoic acid, adrenic acid, elaidic acid, docosahexaenoic acid, etc. It is done.

  As a C1-C20 acyclic hydrocarbon group in the alcohol which comprises ester, a C1-C20 alkyl group and an alkylene group, especially an alkyl group can be used conveniently, Especially, C4-C4 An 18 alkyl group is preferable, and an alkyl group having 4 to 14 carbon atoms is particularly preferable. Such an alcohol having a saturated or unsaturated acyclic hydrocarbon group has a carbon number close to the carbon number of the acrylic monomer constituting the acrylic copolymer used in the pressure-sensitive adhesive layer. Since the compatibility with the agent composition is improved and is suitably retained in the plasticizer acrylic pressure-sensitive adhesive composition, bleeding out is suppressed. In the present invention, as compared with the carboxylic acid component constituting the ester, the number of carbon atoms of the hydrocarbon group of the alcohol component is the carbon of the acrylic monomer constituting the acrylic copolymer used in the pressure-sensitive adhesive layer. By setting the number of carbons to be close to the number, it is particularly easy to suppress adherend contamination.

  Examples of the alcohol having such an acyclic hydrocarbon group include methyl alcohol, ethyl alcohol, propanol, butanol, pentanol, hexanol, heptanol, octyl alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, dodecyl alcohol, Examples include tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, octadecyl alcohol, nonadecyl alcohol, and straight chain or branched alcohol of aralkyl alcohol. Of these, butanol, pentanol, hexanol, heptanol, octyl alcohol, nonyl alcohol, and decyl alcohol can be particularly preferably used.

  In the present invention, an ester formed from the above mono- or dicarboxylic acid and an alcohol is used as a plasticizer. The ester may have a skeleton composed of a saturated or unsaturated hydrocarbon group, but is preferably an ester not having a skeleton composed of an unsaturated hydrocarbon group. Moreover, an epoxidized ester in which an unsaturated bond of an ester having a skeleton composed of the unsaturated hydrocarbon group is epoxidized can also be preferably used. Among the esters, adipic acid monoester, sebacic acid monoester, and epoxidized fatty acid monoester can be particularly preferably used.

  The ester used as the plasticizer may be either a monoester or a polyester, but it is easy to control the SP value within a suitable range and easily improve the compatibility with the pressure-sensitive adhesive. The ester having a weight average molecular weight of 1000 or less is preferable, and an ester having a weight average molecular weight of 300 to 800 is particularly preferable.

  In the present invention, a plasticizer having a solubility parameter (SP value) of 8.5 or less is used as the plasticizer. Especially, it is preferable that it is 7.0-8.4. If the SP value of the plasticizer is 8.5 or less, it is excellent in compatibility with the acrylic pressure-sensitive adhesive copolymer. In this case, the surface of the deposition target is less likely to be clouded when peeled off from the surface of the deposition target. As the SP value of the plasticizer, a plasticizer having a value larger than 7.0 is generally used. The SP value is the value of J.P. The Small formula [P. A. J. et al. Small: J.M. Appl. Chem. , 3, 71 (1953)].

  The viscosity of the plasticizer is preferably 2500 mPa · s or less, more preferably 10 mPa · s to 1000 mPa · s, and particularly preferably 10 mPa · s to 100 mPa · s, and 15 mPa · s. It is particularly preferable that it is ˜30 mPa · s. When the viscosity of the plasticizer is greater than 10 mPa · s, the display surface is not fogged when peeled from the display surface, and problems such as contamination of the resin surface of the display do not occur. Further, when the viscosity of the plasticizer is 2500 mPa · s or less, bubbles are easily removed when the plasticizer is manually attached. The above viscosity is a value measured using a B-type viscometer at a temperature of 25 ° C.

  The plasticizer is preferably added in an amount of 0.5 to 30 parts by weight with respect to 100 parts by weight of the (meth) acrylic copolymer constituting the acrylic pressure-sensitive adhesive. It is more preferable to add below, and it is especially preferable to add 1 to 10 parts by weight. When the added amount of the plasticizer is more than 0.5 parts by weight, the bubbles are easily removed when manually pasted. Further, when the amount is less than 30 parts by weight, the display surface is less likely to fog up even in a high temperature and high humidity environment.

[Crosslinking agent]
In order to increase the cohesive strength of the pressure-sensitive adhesive layer, it is preferable to add a crosslinking agent to the acrylic pressure-sensitive adhesive composition. Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, a chelate crosslinking agent, and an aziridine crosslinking agent. Among these, when an isocyanate crosslinking agent is used, it can be preferably used because the air release property of the obtained protective film is easily improved.

  The addition amount of the crosslinking agent is preferably adjusted so that the gel fraction of the pressure-sensitive adhesive layer is 80 to 99%. A more preferable gel fraction is 90 to 99%. By setting it as the range of the said gel fraction, the ratio of a low molecular weight component decreases, it becomes easy to prevent easy drop-off of an adhesive layer, and it can reduce especially adhesive residue suitably. In addition, a gel fraction immerses the adhesive layer composition after curing in toluene, measures the mass after drying of the insoluble part which remained after leaving for 24 hours, and represents it as a percentage with respect to the original mass.

[Other additives]
Various additives such as a tackifier, an antifoaming agent, an antioxidant, an ultraviolet absorber, a filler, a pigment, an antistatic agent, etc. are added to the adhesive layer as necessary, as long as the performance is not impaired. Also good.

[Release liner]
A release liner may be laminated on the protective film of the present invention for the purpose of protecting the adhesive layer. As a base material for the release liner, there are paper, plastic film, and the like, and a plastic film having particularly excellent surface smoothness is generally applied. The film material is not particularly limited, and examples thereof include a polyethylene film, a polypropylene film, and a polyethylene terephthalate film. It is preferable to use a general release agent such as a silicone resin, a fluorine resin, a long chain alkyl resin, an olefin resin, or the like on the bonding surface between the pressure-sensitive adhesive and the release liner.

  The thickness of the release liner is preferably 5 to 100 μm, and more preferably 25 to 100 μm. When the thickness of the release liner is 25 μm or more, it is possible to suppress cutting to the release liner when half-cutting during processing from the viewpoint of workability.

[Protective adhesive film]
(Constitution)
The protective pressure-sensitive adhesive film of the present invention comprises an acrylic pressure-sensitive adhesive composition containing an ester plasticizer having a main chain structure composed of the above-mentioned continuous carbon-carbon bonds on a substrate and having a low solubility parameter. By using it as an adhesive layer, suitable wetting characteristics can be realized without causing contamination of the adherend.

  The structure of the protective adhesive film of this invention should just be a structure which has the said base material layer and an adhesive layer, for example, the structure by which the said adhesive layer was provided in the single side | surface or both surfaces of the said base material can be illustrated. Moreover, a release liner may be laminated on the pressure-sensitive adhesive layer surface as necessary.

  In order to form the pressure-sensitive adhesive layer on the substrate, the solid content of the acrylic pressure-sensitive adhesive composition is adjusted to 20 to 60% by mass, and the pressure-sensitive adhesive composition is directly applied to the substrate with a roll coater or a die coater. The method of apply | coating to a base material and the method of once forming an adhesive layer on a release liner, and transferring to a base material are used.

  The wetting speed of the protective adhesive film of the present invention is preferably 0.5 cm / sec or more, more preferably 0.75 cm / sec, and particularly preferably 1.0 cm / sec. When the wetting speed is high, wetting progresses faster than the descending speed of the tip of the base material, so even when sticking a large area of the adhesive film, the edge of the adhesive film touches the surface of the adherend, causing bubbles to enter. Not likely to occur.

  The initial adhesive force (180 ° peel adhesive strength) of the protective adhesive film of the present invention is preferably 0.01 to 1.0 N / 25 mm. The adhesive force is preferably 0.01 to 0.6 N / 25 mm, and particularly preferably 0.05 to 0.4 N / 25 mm. If the adhesive force is 0.01 N / 25 mm or more, peeling during the processing step is difficult to occur. In addition, when the thickness is 1.0 N / 25 mm or less, it is easy to re-attach even when the protective adhesive film is attached to a molded product, and the attaching workability is good.

  The adhesive strength (180 ° peel adhesive strength) of the protective adhesive film of the present invention is preferably 0.01 to 1.0 N / 25 mm even after being left in a humid heat environment for a long time, 0.01 to 0 .6 N / 25 mm is more preferable, and 0.02 to 0.4 N / 25 mm is particularly preferable. If the adhesive force is within this range, it is difficult for adhesive force to suddenly increase or adhesive residue, and it can be easily peeled off and pasted even when the protective surface film is replaced or inspected even after storage in a warehouse or the like. it can.

(Usage mode)
As the surface to be protected by the protective adhesive film of the present invention, a TV, a personal computer, or the like, which is made of a transparent resin such as polymethyl methacrylate resin, polycarbonate resin, polystyrene resin or the like and a hard coat layer such as silicone-modified acrylic resin on the surface of these transparent resins, An optical component display having a display such as a mobile phone or a car navigation is preferred.

Example 1
[Acrylic copolymer A]
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 was dissolved in 100 parts of ethyl acetate, and after substitution with nitrogen, polymerization was carried out at 80 ° C. for 8 hours to prepare an acrylic copolymer A having a weight average molecular weight of 600,000. A solution was obtained. The calculation Tg of the acrylic copolymer A was -69 ° C. Ethyl acetate was added to the solution and mixed uniformly to obtain a pressure-sensitive adhesive main agent having a solid content of 40%.

[Acrylic adhesive composition A]
10 parts of an adipic acid monoester plasticizer (monosizer W-242, manufactured by DIC Corporation) having an SP value of 8.5 and a viscosity of 25 mPa · s with respect to 100 parts of the acrylic copolymer A as a main component of the adhesive. Add 1.5 parts of isocyanate-based crosslinking agent (“Coronate HX” manufactured by Nippon Polyurethane Industry) and 1.0 part of chelate-based crosslinking agent (“curing agent M-5A” manufactured by Soken Chemical) for 15 minutes. The mixture was stirred to obtain an acrylic pressure-sensitive adhesive composition A.

[Protective adhesive film]
The above-mentioned acrylic pressure-sensitive adhesive composition A is dried on a 50 μm-thick biaxially stretched polyester film separator (“SP-PET-01-BU” manufactured by Tosero Co., Ltd.) coated with a silicone-based release agent. The coating was dried. Furthermore, a transparent biaxially stretched polyester film (Mitsubishi Resin, “T100G”) having a thickness of 50 μm was bonded to the pressure-sensitive adhesive surface to prepare a protective pressure-sensitive adhesive film. Furthermore, this protective adhesive film was used for the test after aging in a 40 ° C. RH environment for 2 days.

(Example 2)
The same procedure as in Example 1 except that 10 parts by weight of a sebacic acid ester plasticizer (Monocizer W-280 (DOS), manufactured by DIC Corporation) having an SP value of 8.4 and a viscosity of 22 mPa · s was used as a plasticizer. A protective adhesive film was prepared.

(Example 3)
A protective adhesive film was prepared in the same manner as in Example 1 except that 10 parts by weight of an epoxidized fatty acid plasticizer (Eposizer W-121, manufactured by DIC Corporation) having an SP value of 8.1 and a viscosity of 12 mPa · s was used as a plasticizer. Produced.

Example 4
Protective adhesive in the same manner as in Example 1 except that 10 parts by weight of an epoxidized fatty acid plasticizer (Eposizer W-128-S, manufactured by DIC Corporation) having an SP value of 8.1 and a viscosity of 19 mPa · s was used as a plasticizer. A film was prepared.

(Example 5)
A protective adhesive film was prepared in the same manner as in Example 1 except that 10 parts by weight of an epoxidized fatty acid plasticizer (Eposizer W-131, manufactured by DIC Corporation) having an SP value of 7.9 and a viscosity of 26 mPa · s was added as a plasticizer. Produced.

(Example 6)
A protective adhesive film was prepared in the same manner as in Example 1 except that 20 parts by weight of an epoxidized fatty acid plasticizer (Eposizer W-131, manufactured by DIC Corporation) having an SP value of 7.9 and a viscosity of 26 mPa · s was added as a plasticizer. Produced.

(Example 7)
[Acrylic copolymer B]
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 96.9 parts of n-butyl acrylate, 0.1 part of acrylic acid, 3.0 parts of 4-hydroxybutyl acrylate, and 2,2 as a polymerization initiator Dissolve 0.2 parts of '-azobisisobutylnitrile in 150 parts of ethyl acetate, and after purging with nitrogen, polymerize at 80 ° C. for 8 hours to obtain an adhesive copolymer B of acrylic copolymer B having a solid content of 40%. It was.

[Acrylic adhesive composition B]
7.0 parts by weight of the epoxidized fatty acid ester plasticizer W-121 (manufactured by DIC Corporation) is blended into the above-mentioned pressure-sensitive adhesive main agent B with respect to 100 parts by weight of the solid content of the acrylic copolymer B. An acrylic pressure-sensitive adhesive composition B was obtained.

[Protective adhesive film]
1.5 parts of isocyanate crosslinking agent Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.) and 1.0 part of chelating crosslinking agent M-5A (manufactured by Soken Chemical Co., Ltd.) are added to the acrylic adhesive composition B, and 15 After stirring for a minute, it was coated on a 75 μm thick polyester film subjected to a release treatment so that the thickness after drying was 20 μm, and dried at 80 ° C. for 90 seconds to obtain an adhesive layer. This was affixed to a 50 μm PET film and aged for 3 days in a 40 ° C. RH environment to obtain a protective adhesive film.

(Example 8)
A protective adhesive film was prepared in the same manner as in Example 7 except that the content of the epoxidized fatty acid ester plasticizer W-121 (manufactured by DIC Corporation) was changed from 7.0 parts by weight to 10.0 parts by weight. Produced.

Example 9
[Acrylic copolymer C]
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 96.9 parts of 2-ethylhexyl acrylate, 0.1 part of acrylic acid, 3.0 parts of 4-hydroxybutyl acrylate, and 2,2 as a polymerization initiator '-Azobisisobutylnitrile (0.2 parts) was dissolved in ethyl acetate (150 parts), purged with nitrogen, and then polymerized at 80 ° C for 8 hours to obtain an adhesive copolymer C of acrylic copolymer C having a solid content of 40%. .

[Acrylic adhesive composition C]
10.0 parts by weight of the epoxidized fatty acid ester plasticizer W-121 (manufactured by DIC Corporation) is blended into the above-mentioned pressure-sensitive adhesive main agent C with respect to 100 parts by weight of the solid content of the acrylic copolymer C. An acrylic pressure-sensitive adhesive composition C was obtained.

[Protective adhesive film]
1.5 parts of isocyanate crosslinking agent Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.) and 1.0 part of chelating crosslinking agent M-5A (manufactured by Soken Chemical Co., Ltd.) are added to the acrylic pressure-sensitive adhesive composition C, and 15 After stirring for a minute, it was coated on a 75 μm thick polyester film subjected to a release treatment so that the thickness after drying was 20 μm, and dried at 80 ° C. for 90 seconds to obtain an adhesive layer. This was affixed to a 50 μm PET film and aged for 3 days in a 40 ° C. RH environment to obtain a protective adhesive film.

(Example 10)
A protective adhesive film was prepared in the same manner as in Example 7 except that the content of the epoxidized fatty acid ester plasticizer W-121 (manufactured by DIC Corporation) was changed from 10.0 parts by weight to 2.2 parts by weight. Produced.

(Example 11)
A protective adhesive film was prepared in the same manner as in Example 7 except that the content of the epoxidized fatty acid ester plasticizer W-121 (manufactured by DIC Corporation) was changed from 10.0 parts by weight to 6.6 parts by weight. Produced.

(Comparative Example 1)
A protective adhesive film was produced in the same manner as in Example 1 except that the plasticizer was changed to 0 part by weight.

(Comparative Example 2)
Protective adhesive film in the same manner as in Example 1 except that 10 parts by weight of a benzoate plasticizer (Polysizer W-83, manufactured by DIC Corporation) having an SP value of 9.8 and a viscosity of 700 mPa · s was added as a plasticizer. Was made.

(Comparative Example 3)
Protected in the same manner as in Example 1 except that 10 parts by weight of a phthalate ester plasticizer (Polysizer W-23-S, manufactured by DIC Corporation) having an SP value of 9.2 and a viscosity of 976 mPa · s was used as a plasticizer. An adhesive film was prepared.

(Comparative Example 4)
Protected in the same manner as in Example 1 except that 10 parts by weight of pyromellitic acid ester plasticizer (Monocizer W-7010, manufactured by DIC Corporation) having an SP value of 8.6 and a viscosity of 460 mPa · s was used as a plasticizer. An adhesive film was prepared.

(Comparative Example 5)
A protective adhesive film in the same manner as in Example 1 except that 10 parts by weight of an ether ester plasticizer (Monocizer W-262, manufactured by DIC Corporation) having an SP value of 8.5 and a viscosity of 26 mPa · s was used as a plasticizer. Was made.

(Comparative Example 6)
A protective adhesive film was prepared in the same manner as in Example 1 except that 10 parts by weight of an ether ester plasticizer (Polysizer AS-200, manufactured by DIC Corporation) having an SP value of 8.4 and a viscosity of 72 mPa · s was added as a plasticizer. Produced.

(Comparative Example 7)
Protected in the same manner as in Example 1 except that 10 parts by weight of an adipate ester plasticizer (Polysizer W-23-H, manufactured by DIC Corporation) having an SP value of 9.2 and a viscosity of 210 mPa · s was used as a plasticizer. An adhesive film was prepared.

(Comparative Example 8)
Protected in the same manner as in Example 1 except that 10 parts by weight of an adipate ester plasticizer (Polysizer W-1020-EL, manufactured by DIC Corporation) having an SP value of 8.9 and a viscosity of 198 mPa · s was used as a plasticizer. An adhesive film was prepared.

(Comparative Example 9)
Protected in the same manner as in Example 1 except that 10 parts by weight of an adipate ester plasticizer (Polysizer W-2520-EL, manufactured by DIC Corporation) having an SP value of 8.9 and a viscosity of 4700 mPa · s was used as a plasticizer. An adhesive film was prepared.

(Comparative Example 10)
Protective adhesive film in the same manner as in Example 1 except that 10 parts by weight of epoxidized soybean oil (Eposizer W-100-EL, manufactured by DIC Corporation) having an SP value of 8.0 and a viscosity of 370 mPa · s was added as a plasticizer. Was made.

(Evaluation methods)
About the protective adhesive film obtained in the said Example and comparative example, the following matters were evaluated and the obtained result was shown to Tables 1-3.

1. Air bubble contamination When both sides of a protective adhesive film with a length of 90 mm and a width of 40 mm are attached and the center part is attached to a glass plate, the presence or absence of air bubbles after the entire surface is adhered is visually observed. did. The evaluation criteria are as follows.
○: No bubbles are mixed.
X: Air bubbles are mixed.

2. Wetability Measures the time until the entire surface sticks when the hands are released with both ends of a protective adhesive film 90mm long and 40mm wide, with the center part attached to a glass plate, and the speed of wetting speed Was evaluated. The evaluation criteria are as follows.
◎: Within 4 seconds ○: 4-5 seconds △: 5-7 seconds ×: More than 7 seconds

3. Contamination resistance Polymethylmethacrylate (PMMA) plate and polycarbonate (PC) plate were each attached with protective adhesive film with release film peeled off in a deliberate state with air bubbles, high temperature and high humidity (α: 40 ° C, 60% RH, β: 60 ° C./90%) After being left in an environment for 5 days and then left for 1 week, the surface of the PMMA plate and PC plate after being allowed to cool in an environment of 23 ° C./50% for 1 hour was observed. . The evaluation criteria are as follows.
A: No fogging or sticking marks are formed on the adherend surface.
○: After peeling of the protective adhesive film, there is no fogging or sticking marks that can be easily visually recognized on the surface to be coated.
X: After peeling off the protective adhesive film, fogging or sticking marks that can be easily visually recognized are formed on the adherend surface.
XX: The fogging and sticking marks on the adherend surface are severe, and contamination can be confirmed even when the protective adhesive film is attached.

4. Compatibility The compatibility at the time of mixing a plasticizer with the adhesive main ingredient containing the said acrylic copolymer A is shown. The evaluation criteria are as follows.
○: Compatible and the adhesive is transparent.
X: Not compatible and white turbidity of the adhesive occurs.

5). Adhesive force A test piece having a width of 25 mm and a length of 80 mm is prepared. Using an application method defined in JIS Z0237 (2000 edition) to a SUS plate (hairline) in an environment of a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 5% RH, that is, using a 2 kg roller, the bonding speed is 5 mm / s, with one reciprocation, and attached to a stainless steel plate polished in a hairline shape. 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.

6). Removability A test piece having a width of 25 mm and a length of 80 mm is prepared. JIS Z0237 (2000 version) against SUS plate (hairline), polymethylmethacrylate (PMMA) plate, polycarbonate (PC) plate, polystyrene (PS) plate in an environment of temperature 23 ± 2 ° C and relative humidity 50 ± 5% RH ) Tensillon manufactured by A & D Co., Ltd. after the application by the application method specified in), and after standing for 1 week in a wet heat (60 ° C., 90% RH) environment. Measurement was performed using a universal testing machine “RTA-100”. Moreover, the presence or absence of the adhesive residue at the time of peeling was confirmed visually.
◯: No adhesive residue after peeling is confirmed on all adherend surfaces.
X: The adhesive residue after peeling is confirmed on the surface of one or more adherends.

  As apparent from Tables 1 to 3 above, the protective adhesive film of the present invention using an ester having a SP value of 8.5 or less and having a specific structure as a plasticizer is free of bubbles due to good wettability. Attaching was possible without mixing, contamination to the adherend hardly occurred, and good removability. On the other hand, in the protective adhesive film of Comparative Example 1 containing no plasticizer, mixing of bubbles occurred. The protective adhesive film of Comparative Example 2 that uses an ester having a cyclic structure and the protective adhesive film of Comparative Example 10 that does not use an ester having a specific structure were mixed with bubbles and caused adherend contamination. Further, the protective adhesive films of Comparative Examples 3 to 4 and Comparative Examples 6 to 8 using esters having a high SP value are insufficient in suppressing air bubbles, and those of Comparative Examples 3 and 6 to 8 are attached. Contamination to the body could not be suppressed. In addition, the protective adhesive films of Comparative Examples 5 to 6 using an ester having a low SP value but not having a specific structure showed adherence contamination although improvement in wettability was observed. The thing of the comparative example 9 was not compatible, and the suitable protective adhesive film was not obtained.

Claims (4)

A protective adhesive film having a substrate and an adhesive layer,
The pressure-sensitive adhesive layer comprises an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer and a plasticizer,
The plasticizer is an ester formed from a mono- or dicarboxylic acid having a saturated or unsaturated acyclic hydrocarbon group and an alcohol having an acyclic hydrocarbon group having 1 to 20 carbon atoms; A protective adhesive film comprising a plasticizer having an unsaturated group in a saturated hydrocarbon group comprising an epoxidized ester and a solubility parameter (SP value) calculated by the Small formula of 8.5 or less. 2. The protective adhesive film according to claim 1, wherein the plasticizer has a viscosity measured by a B-type viscometer at a temperature of 25 ° C. of 5 to 500 mPa · s. Content of the plasticizer in the said acrylic adhesive composition is 0.5-30 mass parts with respect to 100 mass parts of said acrylic copolymers, The protective adhesive film characterized by the above-mentioned. The protective adhesive film according to claim 1 or 2, wherein the acrylic copolymer contains 50% by mass or more of at least one of 2-ethylhexyl acrylate and n-butyl acrylate as a monomer component.