JP2017066395A - Laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate excellent in adhesion characteristics when bonding adherends having various surface shapes, and hard to increase adhesive strength excessively and contaminate an adherend even if stored under a severe condition such as a high temperature and a high pressure.SOLUTION: The laminate having an adhesive layer at least on one surface of a base material has a nanoindentation hardness, measured from an adhesive layer side under a condition of 32°C and 2 mN of a maximum weight, of not less than 20 MPa; and an average value of tanδ of the adhesive layer at 20-40°C in 1 Hz of not less than 0.20.SELECTED DRAWING: None

Description

  The present invention is excellent in adhesive properties when bonded to adherends having various surface shapes, and has an excessive increase in adhesive force even when stored under severe conditions of high temperature and high pressure. The present invention relates to a laminate that hardly causes contamination.

  Products made of various materials such as synthetic resin, metal, and glass are often handled with a material that protects the surface in order to prevent scratches and dirt during processing, transportation, and storage. A typical example is a surface protective film, which generally uses a support substrate made of thermoplastic resin or paper, with an adhesive layer formed on it, and attaches the adhesive layer surface to the adherend. Then, the surface is protected by coating with a supporting substrate.

  Particularly in recent years, liquid crystal displays and touch panel devices have been widely used, and these are composed of a number of members such as optical sheets and optical films made of synthetic resin. Since such optical members need to reduce defects such as optical distortion as much as possible, surface protection films are frequently used to prevent scratches and dirt that may cause defects.

  The characteristics of the surface protective film are that it is not easily peeled off from the adherend when it is subjected to environmental changes such as temperature and humidity or small stress, and the adhesive and the adhesive on the adherend when peeled off from the adherend. It is required that no components remain.

  Among the above optical members, in the case of a member having an uneven surface such as a diffusion plate or a prism sheet, the adhesive layer does not sufficiently follow the uneven portion immediately after the surface protective film is bonded, and the desired adhesive The force may not be obtained and may peel off. For such a problem, a method for softening the pressure-sensitive adhesive layer, a method for increasing the adhesive force using a tackifier, and the like are known (for example, Patent Documents 1 to 3).

  However, when the uneven portion of the adherend is flexible, it is difficult to obtain a sufficient contact area by adjusting the softness of the adhesive layer as in Patent Documents 1 and 2, and the adhesive force may be insufficient. there were. Even if the adhesive layer is made extremely soft and a sufficient contact area is obtained, the contact area tends to increase with time, and as a result, it becomes difficult to peel off due to an excessive increase in adhesive force, In some cases, adhesive residue was left on the body.

  Moreover, in patent document 3, the method of controlling adhesive force is shown by adjusting the compounding quantity of the tackifier in an adhesion layer. By adding a large amount of tackifier, sufficient tackiness can be obtained even when the contact area is small immediately after pasting, but the tackifier does not stick when stored under time, high temperature or high pressure. There are cases where the adherend is contaminated by bleeding out on the surface of the layer, or the adhesive force is increased and it becomes difficult to peel off the adherend.

  Conventionally, when attaching a surface protective film to an adherend that is difficult to adhere, generally, the adhesive layer is softened as described above, or the amount of tackifier is increased to increase the adhesive strength. there were. However, in such a method, the adhesive strength increases excessively due to aging or heat storage, and peeling may become difficult, or adhesive residue may be generated on the adherend after peeling.

  Moreover, in order to improve sticking property, it was a general method to lower the nanoindentation hardness of the laminate.

JP 2005-298630 A JP 2012-77244 A JP 2012-111793 A

  An object of the present invention is to solve the above-described problems. In other words, it achieves moderate adhesive strength to protect various adherends with uneven surfaces, and excessive increase in adhesive strength even when stored under severe conditions of high temperature and high pressure. And to prevent contamination of the adherend.

  The above-described problem is a laminate having an adhesive layer on at least one surface of a substrate, and the nanoindentation hardness of the laminate measured from the adhesive layer side at 32 ° C. and a maximum load of 2 mN is 20 MPa or more. Yes, it can be achieved by a laminate in which the average value of tan δ at 1 Hz of the adhesive layer at 20 to 40 ° C. is 0.20 or more.

  According to the present invention, in view of the above-described problems, the adhesive has appropriate adhesive properties for various adherends having irregularities on the surface, and is stored under severe conditions of high temperature and high pressure. However, it is possible to provide a laminate in which an excessive increase in adhesive force and contamination of the adherend are unlikely to occur.

  The laminate of the present invention is a laminate having an adhesive layer on at least one surface of a substrate, and has a nanoindentation hardness of 20 MPa or more measured from the adhesive layer side at 32 ° C. and a maximum load of 2 mN. And the average value of 20-40 degreeC of tan-delta in 1 Hz of the said adhesion layer is 0.20 or more. Here, the pressure-sensitive adhesive layer refers to a layered layer having a finite thickness having adhesiveness, and refers to a layer that can be distinguished from a supporting substrate when observed with a microscope or the like. Further, the nanoindentation hardness of the laminate and the tan δ of the adhesive layer can be calculated by the methods described later.

  In the laminate of the present invention, when the nanoindentation hardness is less than 20 MPa, the adhesive force may easily increase over time. On the other hand, when the nanoindentation hardness is 20 MPa or more, the adherend is hardly pushed into the adhesive layer even when heat or pressure is applied during storage, and thus the adhesive force is hardly increased. From the viewpoint of suppressing the increase in adhesive strength during storage at high temperatures and high pressures, the nanoindentation hardness is preferably higher than 20 MPa, but if it is too hard, the adhesive layer is less likely to follow the adherend during bonding. Since sufficient adhesive strength may not be obtained, the upper limit is substantially about 100 MPa.

  Examples of the method for controlling the nanoindentation hardness include a method for controlling the hardness and thickness of the adhesive layer and the substrate and the lamination ratio. For example, the higher the hardness of the adhesive layer, the higher the nanoindentation hardness. In general, since the adhesive layer is softer than the base material, the thinner the adhesive layer is, the more easily affected by the base material, and the higher the nanoindentation hardness.

  The pressure-sensitive adhesive layer of the present invention preferably has an average value of tan δ at 1-40 Hz of 20 to 40 ° C. obtained by dynamic viscoelasticity measurement of 0.20 or more. By controlling the average value of tan δ (hereinafter sometimes simply referred to as tan δ) to 0.20 or more, the laminate of the present invention is preferable because it exhibits good adhesion to an adherend. In particular, it is preferable because an adherend having unevenness on the surface and an adherend on which the surface unevenness portion is soft and hardly exhibit adhesiveness exhibit good adhesiveness.

  When the tan δ is less than 0.20 in the laminate of the present invention, it is difficult to stick when the laminate is bonded to the adherend, and it may be peeled off immediately or a part of the attached portion may float. There is a case. The higher the tan δ is 0.20 or higher, the more easily the laminate of the present invention adheres to the adherend. However, in consideration of the properties of the resin used for the adhesive layer, the substantial upper limit of tan δ is about 3.0. It is.

  As a method for controlling the average value of tan δ at 20 to 40 ° C. of the adhesive layer to 0.20 or more, for example, a resin having a glass transition point around -20 to 60 ° C. or a resin having high stress absorption is used for the adhesive layer. The method to use is mentioned. Specifically, for example, styrene / isoprene copolymer, styrene / butadiene copolymer, styrene / isobutylene copolymer, hydrogenated products thereof, low crystalline polypropylene, amorphous polypropylene, and low crystalline polybutene. , Amorphous polybutene and 4-methyl-1-pentene / α-olefin copolymer can be used.

  In the present invention, it is easy to follow the adherend by controlling the tan δ of the adhesive layer, while the nanoindentation hardness of the laminate is controlled to be equal to or higher than the above value so that the sticking property is not deteriorated. It has been found that it is possible to obtain a laminate that does not easily cause excessive increase in adhesive strength or contamination of the adherend during storage at high temperature and high pressure.

  Although the base material which comprises the laminated body of this invention is not specifically limited, For example, polyolefin and polyester can be used. Especially, it is preferable that polyolefin is a main component from viewpoints of productivity, processability, etc. Here, having polyolefin as a main component means that the ratio of polyolefin is 50% by mass or more, more preferably 70% by mass or more, when the whole substrate is 100% by mass.

  Examples of the polyolefin include, for example, low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, low crystalline or amorphous ethylene / α-olefin copolymer, polypropylene, propylene / ethylene copolymer. Polymer (random copolymer and / or block copolymer), propylene / α-olefin copolymer, propylene / ethylene / α-olefin copolymer, ethylene / ethyl (meth) acrylate copolymer, ethylene / methyl ( Examples include a (meth) acrylate copolymer, an ethylene / n-butyl (meth) acrylate copolymer, and an ethylene / vinyl acetate copolymer. These may be used alone or in combination. The α-olefin is not particularly limited as long as it can be copolymerized with propylene or ethylene. For example, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-pentene, 1-heptene can be mentioned. Among the above-mentioned polyolefins, polypropylene, propylene / ethylene copolymer (random copolymer and / or block copolymer), propylene / ethylene / α-olefin copolymer, propylene / α-olefin can be obtained with high rigidity. A propylene-based material such as a copolymer is more preferable.

  The melt flow rate (measured under the conditions of MFR, 230 ° C. and 2.16 kg) of the polyolefin mainly used for the substrate of the present invention is preferably in the range of 2 to 30 g / min, particularly preferably in the range of 5 to 30 g / min. If the MFR is less than 2 g / min, the melt viscosity is too high, and the productivity may decrease. On the other hand, if the MFR is larger than 30 g / min, the base material becomes brittle and it may be difficult to handle at the time of manufacturing or using the laminate.

  The base material in this invention can also be comprised from two or more layers, for example, you may provide the contact bonding layer for making the adhesion layer and a base material contact | adhere well.

  Further, in the composition constituting the substrate of the present invention, a lubricant, an antioxidant, a weathering agent, an antistatic agent, a crystal nucleating agent, a pigment, etc., as long as the properties as the laminate of the present invention are not impaired. Various additives may be added as appropriate.

  Although the thickness of a base material can be suitably adjusted according to the required characteristic of a laminated body, 5-200 micrometers is preferable, More preferably, it is 10-100 micrometers, More preferably, it is 10-80 micrometers. If it is thinner than 5 μm, the strength may be insufficient, and it may be difficult to convey in the manufacturing process, or may be torn during processing or use. If it is thicker than 200 μm, the transparency of the film may be insufficient or the productivity may be reduced.

  The composition for constituting the pressure-sensitive adhesive layer of the present invention is not particularly limited as long as the effects of the present invention are not impaired, and for example, a styrene-based elastomer can be used. Specifically, styrene / conjugated diene copolymers such as styrene / butadiene copolymer (SBR), styrene / isoprene / styrene copolymer (SIS), styrene / butadiene / styrene copolymer (SBS), and the like. Hydrogenated products (for example, hydrogenated styrene / butadiene copolymer (HSBR) and styrene / ethylene / butylene / styrene copolymer (SEBS)) and styrene / isobutylene copolymers (for example, styrene / isobutylene / styrene triblock) A copolymer (SIBS), a styrene / isobutylene diblock copolymer (SIB), or a mixture thereof). Among these, hydrogenated styrene / butadiene copolymers (HSBR), styrene / ethylene / butylene / styrene copolymers (SEBS), and styrene / isobutylene copolymers are preferably used, and more preferably styrene / isobutylene copolymers. A polymer is used. Only one kind of the styrenic elastomer described above may be used, or two or more kinds may be used in combination. Moreover, you may use together materials other than a styrene-type elastomer as needed.

  The weight average molecular weight of the styrenic elastomer is preferably in the range of 50,000 to 400,000, more preferably in the range of 50,000 to 200,000. When the weight average molecular weight is less than 50,000, the cohesive force of the pressure-sensitive adhesive layer may be reduced, and adhesive residue may be generated when peeled from the adherend. When the weight average molecular weight exceeds 400,000, the viscosity increases and the productivity decreases. There is.

  The styrene content in the styrenic elastomer is preferably in the range of 5 to 50% by mass, and more preferably in the range of 8 to 40% by mass. If the styrene content is less than 5% by mass, the cohesive force of the adhesive layer is reduced, and adhesive residue may be generated when it is peeled off from the adherend. If it exceeds 50% by mass, the adherence to the adherend may be increased. In particular, the adhesiveness may be insufficient for an adherend having unevenness.

  In addition to the styrene-based elastomer described above, polyolefin may be added to the pressure-sensitive adhesive layer of the present invention. For example, low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, low crystalline or amorphous ethylene / α-olefin copolymer, crystalline polypropylene, low crystalline polypropylene, amorphous Polypropylene, propylene / ethylene copolymer (random copolymer and / or block copolymer), propylene / α-olefin copolymer, propylene / ethylene / α-olefin copolymer, polybutene, 4-methyl-1- Pentene / α-olefin copolymer, ethylene / ethyl (meth) acrylate copolymer, ethylene / methyl (meth) acrylate copolymer, ethylene / n-butyl (meth) acrylate copolymer, ethylene / vinyl acetate copolymer These may be combined, and these may be used alone or in combination. The α-olefin is not particularly limited as long as it is copolymerizable with ethylene, propylene, and 4-methyl-1-pentene. For example, ethylene, propylene, 1-butene, 1-hexene, 4-methyl- Examples thereof include 1-pentene, 1-octene, 1-pentene, and 1-heptene.

  Among the above-mentioned polyolefins, low density polyethylene, linear low density polyethylene, ethylene / α-olefin copolymer, polypropylene, propylene / α-olefin copolymer, polybutene, low crystalline polypropylene, amorphous polypropylene, A 4-methyl-1-pentene / α-olefin copolymer is preferably used.

  When polyolefin is used for the adhesive layer, from the viewpoint of controlling the elastic modulus of the adhesive layer and adjusting the adhesive strength, and from the viewpoint of obtaining good film forming properties, the content of the polyolefin is 100% by mass of the entire adhesive layer. Is preferably 50% by mass or less, and more preferably 40% by mass or less.

  Further, from the viewpoint of controlling the average value of tan δ at 20 to 40 ° C. of the adhesive layer to 0.20 or more, low crystalline polypropylene, amorphous polypropylene, low crystalline polybutene, amorphous polybutene, 4-methyl A resin having a glass transition point (Tg) in the vicinity of -20 to 60 ° C. such as a -1-pentene / α-olefin copolymer or a resin having high stress absorption is more preferable, and 4-methyl-1-pentene / α- An olefin copolymer is particularly preferably used. The addition amount of the resin having a glass transition point (Tg) in the range of -20 to 60 ° C is usually 0 to 100% by mass, preferably 5 to 70% by mass when the entire adhesive layer is 100% by mass. More preferably, it is 10-50 mass%.

  In addition to the above, the pressure-sensitive adhesive layer of the present invention may be appropriately added with other components such as wax, tackifier, lubricant, and other additives as long as the object of the present invention is not impaired.

  As the above-mentioned wax, for example, paraffin wax, olefin wax, and modified waxes thereof can be used. For example, in the case of olefin wax, polyethylene wax, polypropylene wax, polybutene wax, and modified waxes thereof can be used. Moreover, it is preferable that melting | fusing point of the wax used for this invention is 70-170 degreeC, 90-160 degreeC is more preferable, and 110-160 degreeC is further more preferable. If the melting point is less than 70 ° C., stickiness may occur. If the melting point is higher than 170 ° C., moldability may be deteriorated, and handling may be difficult. The content of the wax is preferably 10% by mass or less when the entire adhesive layer is 100% by mass. When it is more than 10% by mass, the tackiness may be lowered.

  Examples of the tackifier include petroleum resins such as aliphatic copolymers, aromatic copolymers, aliphatic / aromatic copolymer systems and alicyclic copolymers, terpene resins, and terpenes. Phenol resins, rosin resins, alkylphenol resins, xylene resins, or hydrogenated products thereof can be used. The content of the tackifier is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 3% by mass or less when the entire adhesive layer is 100% by mass. When the content of the tackifier is more than 10% by mass, when the pressure-sensitive adhesive layer is molded by a melt extrusion method, a part of the tackifier sublimates to contaminate the die and may adhere to the product. is there. Also, after pasting the laminate of the present invention to the adherend, a part of the tackifier is used when the adhesive residue is contaminated when peeled off from the laminate, or when the adherend is contaminated or when stored over time or heated. May bleed out to the surface of the adhesive layer, resulting in excessive adhesion.

  Examples of the lubricant include fatty acids, fatty acid amides, and fatty acid metal salts having at least one alkyl group or alkenyl group having 4 to 60 carbon atoms, particularly at least one linear alkyl group or linear alkenyl group having 4 to 30 carbon atoms in the molecule. For example, fatty acids such as lauric acid, palmitic acid, stearic acid, behenic acid, oleic acid and erucic acid, and metal salts and amide compounds of these fatty acids can be mentioned. The content of the lubricant is preferably 2% by mass or less, and more preferably 1% by mass or less, when the entire adhesive layer is 100% by mass. When the content of the lubricant is more than 2% by mass, it may bleed out on the surface and contaminate the adherend, or the adhesiveness may decrease.

  Examples of other additives described above include antioxidants, weathering agents, and antistatic agents. These additives may be used alone or in combination, but the total content is preferably 3% by mass or less, and more preferably 2% by mass or less when the entire adhesive layer is 100% by mass. When the total content of the additives is more than 3% by mass, the product may bleed out from the adhesive layer to cause defects in the product, or the adherend may be contaminated.

  Although the thickness of the adhesion layer in this invention can be suitably adjusted according to the material of an adherend, thickness, surface shape, and a required level, 1-20 micrometers is preferable, 2-10 micrometers is more preferable, and 2-8 micrometers is especially preferable. If the thickness of the adhesive layer is less than 1 μm, the nanoindentation hardness may be too high to exhibit sufficient adhesive force on the adherend, and if it is greater than 20 μm, the adhesive force may be excessive or In some cases, the adhesive strength may increase excessively when heated and stored, or the productivity may decrease.

  Although the laminated body of this invention is a laminated body which has a base material and an adhesion layer at least, you may provide a mold release layer in the surface on the opposite side to the adhesion layer of a base material. The material, thickness, and surface shape constituting the release layer may be selected and adjusted from the viewpoint of the adhesive strength of the adhesive layer and the processing suitability during the production and use of the laminate, and use techniques known in the art. be able to. Preferably, from the viewpoint of satisfactorily controlling the releasability, a propylene-based resin containing 0.5 to 10% by mass of a fluorine-containing compound having both a polyfluorohydrocarbon group and a polyoxyethylene group is mainly constituted. It is preferable.

  The propylene-based resin may be the same as or different from the resin constituting the substrate, but at least 20% by mass of a copolymer of propylene and ethylene and / or α-olefin. It is preferable to contain the above in order to roughen the surface roughness of the release layer described later to Rz of 3.0 μm or more. When the propylene-based polymer is a copolymer with ethylene and / or α-olefin, the higher the comonomer content, the lower the melting point of the copolymer. Therefore, the comonomer content is more preferably in the range of 3 to 7% by mass. In addition, when adding heat resistance to a mold release layer, it can also select suitably so that a comomer content may be decreased and desired heat resistance may be acquired.

  Further, the MFR measured under the conditions of 230 ° C. and 2.16 kg of the propylene-based resin is preferably in the range of 3 to 40 g / 10 min. In particular, those having an MFR in the range of 10 to 40 g / 10 min are more preferable because they can be extruded at low temperature and are easy to roughen the release layer when combined with low density polyethylene.

  In order to roughen the release layer, it is preferable to contain at least 4% by mass of high-pressure low-density polyethylene that is poorly compatible with the propylene resin.

  Further, the release layer is preferably composed of a propylene-based resin containing 0.5% by mass to 10% by mass of a fluorine-containing compound containing a polyfluorohydrocarbon group and a polyoxyethylene group at the same time. The fluorohydrocarbon group and the polyoxyethylene group-containing fluorine compound can include, for example, a (meth) acrylic acid ester having a C 1-18 perfluoroalkyl group as the monomer (a). It can be obtained by copolymerizing the (meth) acrylic acid ester having a polyoxyethylene group of the bodies (b) and (c).

  The perfluoroalkyl group of the monomer (a) preferably has 1 to 18 carbon atoms, more preferably 1 to 6 carbon atoms. The perfluoroalkyl group may be linear or branched. These may be used alone or in combination of two or more.

  The (meth) acrylic acid ester having a perfluoroalkyl group is commercially available from Kyoeisha Chemical Co., Ltd. or the like, but can also be synthesized by a known method using a fluorine-containing compound as a raw material.

As the monomer (b) containing a polyoxyethylene group, those having a structure in which oxyethylene units (—CH ₂ —CH ₂ —O—) are linked in an amount of 1 to 30 are preferable, and in particular, the units are 1 to 20 Are more preferred. An oxypropylene unit (—CH ₂ —CH (CH ₃ ) —O—) may be contained in the chain. For example, polyethylene glycol monomethacrylate having 8 oxyethylene units can be mentioned. The monomer (b) may be used alone or in combination of two or more.

  Another monomer (c) containing a polyoxyethylene group is a di (meta) having a structure in which 1 to 30 oxyethylene units are linked and having double bonds at both ends. ) A preferred specific example is acrylate, polyethylene glycol dimethacrylate having 8 linkages. A monomer (c) can also be used individually by 1 type or in combination of 2 or more types.

  As the ratio of each of the monomers (a), (b), and (c), the monomer (a) is 1 to 80% by mass, the monomer (b) is 1 to 80% by mass, the monomer (C) is preferably 1 to 50% by mass.

  The fluorine-containing compound having a polyfluorohydrocarbon group and a polyoxyethylene group includes, in addition to the above three monomers, a monomer copolymerizable with these in a range of less than 50% by mass. For example, methylene, vinyl acetate, vinyl chloride, vinyl fluoride, vinyl halide, styrene, methylstyrene, (meth) acrylic acid and its ester, (meth) acrylamide monomer, (meth) allyl Monomer.

  The polymerization method for obtaining a fluorine-containing compound having a polyfluorohydrocarbon group and a polyoxyethylene group using the monomer may be any of bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization, and heat. In addition to polymerization, photopolymerization and energy beam polymerization can also be employed.

  As the polymerization initiator, existing organic azo compounds, peroxides, persulfates and the like can be used.

  The weight average molecular weight of the fluorine-containing compound used in the present invention is preferably from 1,000 to 100,000, particularly preferably from 5,000 to 20,000. The weight average molecular weight can be adjusted with a polymerization chain transfer agent such as thiol, mercaptan, or α-methylstyrene.

  The proportion of the fluorine-containing compound in the release layer of the present invention is preferably 0.5% by mass to 10% by mass. If it is less than 0.5% by mass, blocking with the adhesive layer is likely to occur, and it may be difficult to obtain a desired unwinding force. In addition, if the content exceeds 10% by mass, since the solubility in the resin is low, it is difficult to mix uniformly, the propylene-based resin for forming the release layer at the time of melt extrusion is affected by the fluorine-containing compound, It may be difficult to slip and uniformly discharge at the extrusion screw portion.

  In addition to the fluorine-containing compound, the release layer of the present invention more preferably contains 0.1% by mass to 10% by mass of inorganic particles and / or organic particles having an average particle diameter of 1 to 20 μm at the same time. The average particle size of the inorganic particles and the organic particles is particularly preferably 3 to 15 μm from the viewpoint of slipperiness and blocking properties.

  Examples of the inorganic particles include silica, calcium carbonate, magnesium carbonate, titanium oxide, clay, talc, magnesium hydroxide, aluminum hydroxide, zeolite, and the like, among which silica is more preferable.

  Examples of the organic particles include polystyrene and polymethyl methacrylate.

  Due to the synergistic effect of the fluorine-containing compound, the inorganic or organic particles, and the surface roughness of the release layer, which will be described later, blocking becomes difficult and good unwinding property can be easily obtained.

  The surface roughness of the release layer of the present invention is preferably 3 μm or more in terms of 10-point average roughness (Rz). If Rz is less than 3 μm, wrinkles are likely to occur when the laminate is wound into a roll, and the quality may be lowered. Examples of a method for controlling Rz to 3 μm or more include a method in which a small amount of an ethylene resin having poor compatibility is added to the propylene resin as described above.

  The laminate of the present invention is preferably in the form of a film from the viewpoint of use purpose and ease of handling. The thickness of the laminate is preferably 10 to 250 μm, more preferably 10 to 150 μm, and particularly preferably 10 to 100 μm. If the thickness is less than 10 μm, the strain may be insufficient and handling during manufacture or use may be difficult. On the other hand, when the thickness is greater than 250 μm, it may be difficult to follow the adherend when bonded to the adherend, or productivity may be reduced.

  The laminate of the present invention preferably has a tensile modulus of 200 to 10,000 MPa. When the tensile elastic modulus is less than 200 MPa, the laminate is easily deformed, which may cause wrinkles and tears. On the other hand, when the tensile elastic modulus is greater than 10,000 MPa, the film is too hard to follow the adherend, and a good adhesive force may not be obtained.

  Next, the manufacturing method of the laminated body of this invention is demonstrated.

  The production method of the laminate of the present invention is not particularly limited. For example, in the case of a three-layer laminated structure of a base material, an adhesive layer, and a release layer, the resin composition constituting each is melt-extruded from an individual extruder, and a die is formed. The so-called coextrusion method for laminating and integrating the above, and the method of laminating by laminating after individually melting and extruding the base material, the adhesive layer, and the release layer are mentioned. Preferably, it is manufactured by the method. As the material constituting each layer, a material mixed with a Henschel mixer or the like may be used, or a material obtained by kneading all or a part of materials of each layer in advance may be used. As the co-extrusion method, known methods such as an inflation method and a T-die method are used. From the viewpoint of excellent thickness accuracy and surface shape control, a hot-melt co-extrusion method by the T-die method is particularly preferable.

  The laminate of the present invention can be used as a surface protection film for the prevention of scratches and the adhesion of dirt during the manufacture, processing, and transportation of synthetic resin plates, metal plates, glass plates, etc. It is preferably used for the body. For example, it is used for a diffusion plate or a prism sheet which is a display member made of a synthetic resin, and is particularly preferable for a prism sheet having a nano-indentation hardness of a prism portion of 100 MPa or less measured at 32 ° C. and a maximum load of 2 mN. Used.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples. Various physical properties were measured and evaluated by the following methods.

(1) Thickness of laminated body Using a microtome method, an ultrathin section having a cross section in the die width direction of the laminated body-the thickness direction of the laminated body was prepared, and the cross section was coated with platinum to obtain an observation sample. Next, the cross section of the laminate was observed at an acceleration voltage of 1.0 kV using a Hitachi Field Emission Scanning Electron Microscope (S-4800), and an adhesive layer, a base material, and a release layer were observed from any part of the observed image. Each thickness was measured. The observation magnification was 10,000 times for the adhesive layer and the release layer, and 1,000 times for the substrate. Furthermore, the same measurement was performed 5 times in total, and the average value was used as the thickness of the adhesive layer, the substrate, and the release layer. The total thickness of the laminate was determined by adding the thicknesses of the adhesive layer, the base material, and the release layer.

(2) Nanoindentation Hardness of Laminate Using an Elionix nanoindentation tester ENT-2100, under the following conditions, using a Berkovich indenter (triangular pyramid), load-exclusion from the adhesive layer side of the laminate An indentation test by a load test was performed five times for each type of laminate. Subsequently, the average value of the indentation hardness (H _IT ) obtained by the measurement was calculated and used as the nanoindentation hardness of the laminate.
Temperature: 32 ° C
Maximum load: 2mN
Load speed: 0.2 mN / s
Holding time at maximum load: 1 second Surface detection method: Inclination method Surface detection threshold coefficient: 2.0
Spring compensation: None.

(3) Prism Nanoindentation Hardness Under the same conditions as in (2) above, an indentation test was performed on the ridge line portion of the prism tip, and the average value of the obtained indentation hardness (H _IT ) was calculated as prism nanoindentation. Hardness.

(4) Average value of tan δ at 20 to 40 ° C. of adhesive layer Only a predetermined amount of the adhesive layer was peeled off from the laminates shown in the following examples and comparative examples, and the resulting adhesive layer composition was melt-molded to a thickness of 2 mm. Using a rheometer AR2000ex manufactured by TA Instruments Inc., the viscoelasticity of the kneaded material in shear mode at a temperature of 15 to 45 ° C., a heating rate of 3 ° C./min, a frequency of 1 Hz, and a strain of 0.01%. evaluated. The viscoelastic data was collected at 0.2 ° C. intervals. From the obtained results, an average value of tan δ was calculated by arithmetically averaging all data obtained at intervals of 0.2 ° C. at 20.0 ° C. or higher and 40.0 ° C. or lower, and 20-40 of the adhesive layer. The average value of tan δ at ° C. was used.

(5) Bonding to prism After the laminate was cut to a width of 40 mm and bonded to a prism sheet having a width of 25 mm by reciprocating a pressure roller (rubber hardness A80, roller mass 4 kg) three times in a direction perpendicular to the width direction. The laminate that protruded from the prism sheet was removed. The prism sheet used had a length between prism ridges of 50 μm and a prism nanoindentation hardness of 30 MPa.

(6) Initial adhesive strength The adhesive strength after storing the sample obtained by said (5) in the room | chamber interior of 25 degreeC for 24 hours was measured, and it evaluated in the following five steps. The adhesive strength was measured using a tensile testing machine (Orientec “Tensilon” universal testing machine) at a tensile speed of 300 mm / min and a peeling angle of 180 °.
A: Adhesive strength of 0.5 g / 25 mm or more and less than 5 g / 25 mm B: Adhesive strength of 5 g / 25 mm or more and less than 10 g / 25 mm C: Adhesive strength of 10 g / 25 mm or more and less than 15 g / 25 mm D: Adhesion Force is less than 0.5 g / 25 mm E: Adhesive strength is 15 g / 25 mm or more.

(7) Adhesive strength after heat storage The sample obtained in (5) above was taken out after being stored in a hot air dryer at 50 ° C under a load of 10 g / cm ² for 3 days, and was taken out in a room at 25 ° C. The adhesive strength after storage for a period of time was measured and evaluated in five stages as described in (6) above.

(8) Contamination property Contamination property to the prism surface after peeling an adhesive film by said (7) was confirmed visually, and it evaluated as follows.
A: No contamination at all B: Contamination is observed.

Example 1
The constituent resin of each layer was prepared as follows.

  Adhesive layer: SEBS (“Tough Tech” H1052 manufactured by Asahi Kasei Chemicals; styrene content 20% by mass, MFR 13 g / 10 min (measured at 230 ° C., 2.16 kg)) 80% by mass, 4-methyl-1-pentene / propylene 20% by mass of polymer was used. The 4-methyl-1-pentene / propylene copolymer has a copolymerization ratio of 73% by mole of 4-methyl-1-pentene and 27% by mole of propylene, and is described in (4) above. The average value of tan δ at 20 to 40 ° C. measured in the same manner as the average value of tan δ at 20 to 40 ° C. of the adhesive layer was 1.7.

  Base material: A commercially available homopolypropylene having an MFR of 5 g / 10 min (measured at 230 ° C. and 2.16 kg) was used.

Release layer: 45% by mass of the same homopolypropylene used for the base material and 24% by mass (ethylene content) of propylene-ethylene random copolymer having an MFR of 35 g / 10 min (measured at 230 ° C. and 2.16 kg) 5% by mass), low density polyethylene having a density of 920 kg / m ³ having an MFR of 2 g / 10 min (measured at 190 ° C. and 2.16 kg) is added to 6% by mass, and the average particle is previously added to 90% by mass of the homopolypropylene. A mixed composition comprising 4% by mass of silica having a diameter of 11 μm and 6% by mass of a fluorine-containing compound having a polyfluorohydrocarbon group and a polyoxyethylene group was prepared as a master batch, and 25% by mass was uniformly mixed with a Henschel mixer. .

Here, the fluorine-containing compound having a polyfluorohydrocarbon group and a polyoxyethylene group is a C ₆ F ₁₃ perfluoroalkyl acrylate (CH ₂ ═CHCOOC ₂ H ₄ C ₆ F ₁₃ ) as the monomer (a). 25% by mass, monomer (b), 50% by mass of polyethylene glycol monoacrylate {CH ₂ ═CHCOO (CH ₂ CH ₂ O) ₈ H} having ₈ oxyethylene repeating units, and monomer (c) As an example, a polyethylene glycol dimethacrylate having eight oxyethylene repeating units {CH ₂ ═C (CH ₃ ) COO (CH ₂ CH ₂ O) ₈ COC (CH ₃ ) ═CH ₂ } in a proportion of 25% by mass in a solvent Using fluorotoluene, 2,2'-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator, Using lauryl mercaptan as a chain transfer agent, under nitrogen stream, stirring was polymerized for 5 hours at 60 ° C., after which was precipitated, filtered with methanol used was dried under reduced pressure.

  Next, the constituent resin of each layer is put into each extruder of a T-die composite film forming machine having three extruders, and the discharge amount of each extruder is adjusted so as to obtain a desired lamination ratio. The film was extruded from a T-die at an extrusion temperature of 200 ° C. and molded into a film.

  Thereafter, the thickness of the pressure-sensitive adhesive layer, the total thickness of the layered product, nanoindentation hardness, initial pressure-sensitive adhesive strength, pressure-sensitive adhesive strength after heat storage, and contamination were evaluated for the obtained layered product by the method described above. Moreover, the average value of 20-40 degreeC tan-delta of the adhesion layer was evaluated by the method as described above.

(Example 2)
As a resin constituting the adhesive layer, 70% by mass of styrene / isobutylene block copolymer (“Shibustar” 062M manufactured by Kaneka; styrene content 23% by mass, MFR 15 g / 10 min (measured at 230 ° C., 2.16 kg))) This was the same as Example 1 except that 30% by mass of the same 4-methyl-1-pentene / propylene copolymer as used in Example 1 was used.

(Example 3)
As a resin constituting the adhesive layer, 70% by mass of the same styrene / isobutylene block copolymer as used in Example 2, 4-methyl-1-pentene / propylene similar to that used in Example 1 was used. Example 1 except that 10% by mass of linear low density polyethylene having a copolymer content of 20% by mass, a density of 921 kg / m ³ and an MFR of 5 g / 10 min (measured at 190 ° C. and 2.16 kg) was used. And the same.

(Comparative Example 1)
70% by mass of SEBS similar to that used in Example 1 as a resin constituting the adhesive layer, 10% by mass of linear low density polyethylene similar to that used in Example 3, hydrogenated terpene phenol (Yasuhara Chemical) The same procedure as in Example 1 was performed except that 20% by mass of YS “Polyster” TH130) was used and the resin constituting these adhesive layers was previously melt-kneaded with a twin-screw extruder and pelletized.

(Comparative Example 2)
As a resin constituting the adhesive layer, 80% by mass of the same styrene / isobutylene block copolymer as used in Example 2 and 20% by mass of hydrogenated terpene phenol similar to those used in Comparative Example 1 were used. Except for this, it was the same as Comparative Example 1.

  Examples 1 to 3 satisfying the requirements of the present invention all showed good initial adhesive strength and were excellent in sticking to a prism sheet. Further, even after heat storage, the adhesive strength was not significantly increased compared to the initial stage, and the film was able to be peeled well and was excellent in contamination. On the other hand, Comparative Example 1 had a low initial adhesive force and had a part that was partially peeled off. Comparative Example 2 had a high adhesive force after heat storage and was inferior in peelability. Further, both Comparative Examples 1 and 2 were inferior in contamination.

  The laminate of the present invention is used not only as a surface protective film for preventing scratches and dirt on the adherend having irregularities on the surface, but also as a surface protective film for various products made of various materials such as synthetic resin, metal, and glass. It can be preferably used.

Claims (4)

  A laminate having an adhesive layer on at least one surface of a substrate, having a nanoindentation hardness of 20 MPa or more measured from the adhesive layer side at 32 ° C. and a maximum load of 2 mN, and 1 Hz of the adhesive layer An average value of tan δ at 20 to 40 ° C. is 0.20 or more.   The laminate according to claim 1, wherein the adhesive layer contains a styrene-based elastomer.   The laminate according to claim 1, wherein the adhesive layer contains a polyolefin.   The laminate according to any one of claims 1 to 3, wherein the laminate is used for surface protection of a prism sheet having a prism portion having a nanoindentation hardness of 100 MPa or less measured at 32 ° C and a maximum load of 2 mN. .