JP6636346B2 - Electrostatic suction sheet and method of manufacturing the same - Google Patents

Description

  The present invention relates to an electrostatic attraction sheet provided with a protective sheet that can be electrostatically attracted to an adherend.

  A protective film for protecting a metal foil is attached to a flexible printed circuit board (FPC) having a metal foil as a conductor during its production, processing, production, or storage. As such a protective film, a polyethylene film having an adhesive layer to which an adhesive is applied and which is attached to a metal foil via the adhesive layer is used. However, the polyethylene film having the adhesive layer has a problem that the surface state of the metal foil changes when peeled off as an effect on the metal foil as an adherend. Therefore, a polyethylene film that is attached to a metal foil through a pressure-sensitive adhesive layer coated with a removable adhesive is used.A polyethylene film having this pressure-sensitive adhesive layer is also a metal foil under a high-temperature environment. There were problems such as a change in the surface condition.

  Meanwhile, as a film having no adhesive layer or pressure-sensitive adhesive layer, a protective film made of a polypropylene film, which has self-adhesiveness due to electrostatic adsorption and can be attached to an adherend, is known. In addition, a polypropylene film having improved adhesive properties by providing a layer containing a polypropylene elastomer as an adhesive layer has been developed (see Patent Document 1).

JP 2014-200955 A

  The self-adhesive protective film made of a polypropylene film as described above does not cause a change in the surface state of the metal foil, but has a physical property of being thermally deformed or contracted in a high-temperature environment. For this reason, when the temperature of the adherend is high, the protective film is deflected due to the deformation of the protective film, and thus peels off from the adherend. In addition, the protective film made of a polypropylene film does not have sufficient charge holding power, and when the temperature of the adherend becomes high, the charge is released to lower the adsorption performance.

  In a manufacturing process of a flexible printed circuit board, for example, a process of forming a resin layer, the protective film may be exposed to a high-temperature environment while being attached to a metal foil. In such a high-temperature environment, when a self-adhesive protective film made of a conventional polypropylene film is used, since the adsorption performance is reduced as described above, sufficient performance for protecting the adherend is required. I could not say it did.

  The present invention has been made in view of such background art. It is an object of the present invention to provide an electrostatic attraction sheet that has a small dimensional change even under a high-temperature environment and can maintain an attraction performance.

  The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that by using a polyolefin resin having a specific melting point, dimensional changes are small even under a high-temperature environment, and it is possible to maintain adsorption performance. Thus, the present invention has been completed.

That is, the present invention provides various specific embodiments described below.
[1] A protective sheet that can be electrostatically adsorbed to an adherend, and a substrate that is electrostatically adsorbed to the protective sheet, wherein the protective sheet is provided on a surface in contact with the substrate and is at least one type. an adsorption layer containing the above polyolefin resin, at least one or more of the melting point of the having a substrate and in contact with the side surface and the coating layer provided on the opposite side of the front Kipo Li olefin resin 200 An electrostatic adsorption sheet characterized by a temperature of at least ℃.

[2] The electrostatic adsorption sheet according to the above [1], wherein the polyolefin resin having a melting point of 200 ° C or higher contains a polyolefin (co) polymer containing 4-methyl-1-pentene as a monomer component.
[3] The adsorption layer has a melting point of 50 to 100% by mass of a polyolefin resin having a melting point of 200 ° C. or more, and a polyolefin resin having a melting point of 200 ° C. or more, other than a polyolefin resin having a melting point of 50 to 0% based on the total amount of the polyolefin resin. % Of the electrostatic adsorption sheet according to the above [1] or [2].
[4] The protective sheet has a surface resistivity of 1 × 10 ^{13 to} 9 × 10 ¹⁷ Ω on the surface on the adsorption layer side, and the substrate has a surface resistivity on a surface in contact with the adsorption layer. The electrostatic attraction sheet according to any one of the above [1] to [3], which has a resistance of 1 × 10 ^{13 to} 9 × 10 ¹⁷ Ω.
[5] The surface resistivity of the surface of the coat layer side is ^{1 × 10 -1 Ω~9 × 10 12} Ω, the surface resistivity of the surface of the substrate side 1 × 10 ^-1 Ω~9 × 10 The electrostatic adsorption sheet according to any one of the above [1] to [4], which is ¹² Ω.
[6] The electrostatic attraction sheet according to any one of [1] to [5], wherein the protective sheet has a center surface average roughness (SRa) of 0.01 to 5 μm on the side of the attraction layer. .
[7] The method for producing an electrostatic attraction sheet according to any one of the above [1] to [6] , wherein the base material is electrostatically charged after subjecting the protective sheet to charge injection by DC corona discharge. A method for producing an electrostatic attraction sheet to be adsorbed.

  ADVANTAGE OF THE INVENTION According to this invention, the dimensional change is small even in a high temperature environment, and the electrostatic adsorption sheet which can maintain adsorption | suction performance can be provided.

It is a sectional view showing typically an electrostatic attraction sheet of an embodiment. It is a perspective view which shows typically the sample for evaluation used in the Example. It is a perspective view which shows typically the adsorption-force measuring device used in the Example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are exemplifications for describing the present invention, and the present invention is not limited to only the embodiments. In the following description, unless otherwise specified, the positional relationship such as up, down, left, and right is based on the positional relationship shown in the drawings. The dimensional ratios in the drawings are not limited to the illustrated ratios. In addition, in this specification, the numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit and an upper limit.

[Electrostatic suction sheet]
As shown in FIG. 1, the electrostatic attraction sheet 1 of the present embodiment includes a protection sheet 11 and a base material 41, and the protection sheet 11 and the base material 41 are stacked by electrostatic attraction. The protective sheet 11 has an adsorbing layer 31 provided on a surface 11b on the side in contact with the base material 41 and a coat layer 21 provided on a surface 11a opposite to the surface 11b on the side in contact with the base material 41. That is, the electrostatic adsorption sheet 1 includes the coat layer 21, the adsorption layer 31, and the base material 41 in this order. Then, in the electrostatic adsorption sheet 1, the base material 41 is removed as a release sheet at the time of use, the surface 31 a of the protection sheet 11 on the adsorption layer 31 side is exposed, and the exposed surface (surface 31 a) is used as an adherend. The adherend is protected by electrostatic attraction. Hereinafter, each member constituting the electrostatic adsorption sheet 1 will be described in detail.

<Adsorption layer>
The attraction layer 31 constitutes the protection sheet 11, holds electric charge, and enables electrostatic attraction of the protection sheet 11 by the electrostatic charge.

(Specific polyolefin resin)
The adsorption layer 31 contains at least a polyolefin resin having a melting point of 200 ° C. or higher (hereinafter, also referred to as “specific polyolefin resin”). This specific polyolefin resin is excellent in heat resistance, insulation, workability, etc., so it has a small dimensional change in a high temperature environment, and maintains its adsorption performance even when electrostatically adsorbed to an adherend in a high temperature environment. Can be. In addition, since the polyolefin resin has insulating properties and can hold an electric charge therein, it enables electrostatic adsorption of the protective sheet 11 to an adherend.

  The melting point of the specific polyolefin resin is preferably 220 ° C. or higher, more preferably 230 ° C. or higher. The upper limit of the melting point of the specific polyolefin resin is not particularly limited, but is usually 300 ° C or lower, preferably 250 ° C or lower. When the melting point of the specific polyolefin resin is in the above range, the dimensional change of the adsorption layer 31 is reduced even in a high temperature environment. Therefore, the amount of deformation of the protective sheet 11 in a high-temperature environment is small, and it is difficult for the warp to occur, and the adsorption performance of the protective sheet 11 can be maintained. Further, it is presumed that a small amount of charge release even when the temperature of the adherend becomes high contributes to maintaining the adsorption performance. In addition, in this specification, a melting point means the melting temperature measured based on JISK7121: 2012.

  As the specific polyolefin resin, a (co) polymer of ethylene or an α-olefin having 3 to 20 carbon atoms and having a melting point of 200 ° C. or more can be used. Examples of the α-olefin having 3 to 20 carbon atoms include propylene, butene, hexene, octene, butadiene, and isoprene, but are not particularly limited thereto. Here, the (co) polymer is a concept that includes both a homopolymer and a copolymer of the above-mentioned monomers, and the specific polyolefin resin includes other copolymer components other than these olefins (hereinafter simply referred to as “others”). May also be included.). Other monomer components include styrenes such as styrene and α-methylstyrene; vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl laurate, vinyl stearate, vinyl benzoate, and butyl benzoate. Carboxylic acid vinyl esters such as vinyl acrylate and vinyl cyclohexanecarboxylate (or vinyl alcohol obtained by saponifying these carboxylic acid vinyl esters after copolymerization); acrylic acid, methacrylic acid, methyl (meth) acrylate, ethyl (meth) ) Acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) (Meth) acrylic esters such as acrylate, isobonyl (meth) acrylate, dicyclopentanyl (meth) acrylate; (meth) acrylamides such as (meth) acrylamide and N-methalol (meth) acrylamide; methyl vinyl ether, ethyl vinyl ether And vinyl ethers such as propyl vinyl ether, butyl vinyl ether, cyclopentyl vinyl ether, cyclohexyl vinyl ether, benzyl vinyl ether, and phenyl vinyl ether, but are not particularly limited thereto. One or more kinds of other monomer components can be appropriately selected and used as needed.

  Above all, from the viewpoint of heat resistance, the specific polyolefin resin preferably contains a polyolefin (co) polymer containing an α-olefin having 5 to 8 carbon atoms as a copolymer component. Examples of the α-olefin having 5 to 8 carbon atoms include 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 4,4dimethyl-1-pentene, and 3-ethyl. -1-pentene, 3-methyl-1-hexene, 4-methyl-1-hexene, 4-ethyl-1-hexene and the like. That is, as a homopolymer of the above monomers, poly (3-methyl-1-butene), poly (3-methyl-1-pentene), poly (4-methyl-1-pentene), poly4,4 (dimethyl- 1-pentene), poly (3-ethyl-1-pentene), poly (3-methyl-1-hexene), poly (4-methyl-1-hexene), poly (4-ethyl-1-hexene), etc. A polyolefin resin having a melting point of 200 ° C. or more, which is a polymer, can be used. Further, as the copolymer of the above-mentioned monomers, one obtained by copolymerizing two or more kinds of the above-mentioned monomers or one obtained by copolymerizing one or more kinds of the above-mentioned monomers and another monomer is used. Thus, a polyolefin resin having a melting point of 200 ° C. or more can be used. Examples of such a copolymer include a copolymer of an α-olefin having 5 to 8 carbon atoms and another α-olefin. These copolymers may be binary, ternary or higher, and may be random copolymers or block copolymers. Among these polyolefin resins, since the production of the monomer is relatively easy, a (co) polymer of 4-methyl-1-pentene, that is, poly (4-methyl-1-pentene), which is a homopolymer of 4-methyl-1-pentene, is used. Methyl-1-pentene), and a copolymer of 4-methyl-1-pentene and another α-olefin are preferred.

  The content of each of the above monomer components constituting the specific polyolefin resin can be changed within a range where the melting point is 200 ° C. or higher, and is not particularly limited. For example, in a copolymer of an α-olefin having 5 to 8 carbon atoms and another α-olefin, the content of each monomer component is (molar basis) (content of α-olefin having 5 to 8 carbon atoms). / (Content of other α-olefin) is preferably in the range of 80/20 to 100/0, more preferably in the range of 90/20 to 100/0, and still more preferably in the range of 95/5 to 100/0. .

  As the specific polyolefin resin contained in the adsorption layer 31, a functional group-containing polyolefin resin into which a functional group has been introduced can also be used.

  Specific examples of the functional group-containing polyolefin-based resin include a copolymer of the olefin with a functional group-containing monomer copolymerizable with the olefin. Examples of such functional group-containing monomers include styrenes such as styrene and α-methylstyrene; vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl laurate, vinyl stearate, vinyl benzoate, and butyl. Vinyl carboxylate such as vinyl benzoate and vinyl cyclohexanecarboxylate (or vinyl alcohol obtained by saponifying these vinyl carboxylate after copolymerization); acrylic acid, methacrylic acid, methyl (meth) acrylate, ethyl ( (Meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (Meth) acrylic esters such as (meth) acrylate, isobonyl (meth) acrylate, and dicyclopentanyl (meth) acrylate; (meth) acrylamides such as (meth) acrylamide and N-methanol (meth) acrylamide; methyl vinyl ether And vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, cyclopentyl vinyl ether, cyclohexyl vinyl ether, benzyl vinyl ether and phenyl vinyl ether. One or more of these functional group-containing monomers may be appropriately selected and copolymerized as necessary.

In addition, as the specific polyolefin resin, a graft-modified product thereof can be used as necessary.
Known techniques can be used for graft modification of the resin. Specific examples include graft modification with an unsaturated carboxylic acid or a derivative thereof. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid and the like. Examples of the derivative of the unsaturated carboxylic acid include acid anhydrides, esters, amides, imides, and metal salts.

  Specific examples of unsaturated carboxylic acids include maleic anhydride, itaconic anhydride, citraconic anhydride, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylic acid. Glycidyl, maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, itaconic acid monomethyl ester, itaconic acid diethyl ester, (meth) acrylamide, maleic monoamide, maleic diamide, maleic acid-N Monoethylamide, maleic acid-N, N-diethylamide, maleic acid-N-monobutylamide, maleic acid-N, N-dibutylamide, fumaric acid monoamide, fumaric diamide, fumaric acid-N-monoethylamide, Fumaric acid-N, N-diethyl Amide, fumaric acid-N-monobutylamide, fumaric acid-N, N-dibutylamide, maleimide, N-butylmaleimide, N-phenylmaleimide, sodium (meth) acrylate, potassium (meth) acrylate, and the like. Can be.

  The graft-modified product may be a graft-modified product obtained by using a graft monomer in an amount of usually 0.005 to 10% by mass, preferably 0.01 to 5% by mass, based on various polyolefin resins.

(Optional polyolefin resin)
The adsorption layer 31 may contain another polyolefin resin (hereinafter, also simply referred to as “optional polyolefin resin”) other than the specific polyolefin resin described above. The optional polyolefin resin is a (co) polymer of ethylene or an α-olefin having 3 to 20 carbon atoms and having a melting point of less than 200 ° C. Specific examples of the optional polyolefin resin include a part of an ethylene homopolymer such as high-density polyethylene and low-density polyethylene, and a propylene homopolymer, but are not particularly limited thereto. One of the optional polyolefin resins may be selected and used alone, or two or more may be selected and used in combination.

  When the specific polyolefin resin and the optional polyolefin resin are used in combination, the content thereof is not particularly limited, but the content of the specific polyolefin resin is preferably 50 to 100 parts by mass with respect to the total amount of the polyolefin resin, The amount is more preferably 60 to 100 parts by mass, and even more preferably 70 to 100 parts by mass. Further, the content of the optional polyolefin resin is preferably 50 to 0 parts by mass, more preferably 40 to 0 parts by mass, and more preferably 30 to 0 parts by mass with respect to the total amount of the specific polyolefin resin. Is more preferred. When the content of the specific polyolefin resin is within the above range, the resistance of the adsorption layer 31 to high temperatures is exhibited, the dimensional change is small even in a high temperature environment, and the adsorption performance of the protective sheet 11 can be maintained.

  Further, the adsorption layer 31 may contain a resin other than the specific polyolefin resin and the optional polyolefin resin. Other resins include polyamide resins such as nylon-6 and nylon-6,6; polyethylene terephthalate and copolymers thereof, aromatic polyesters such as polybutylene terephthalate, and fats such as polybutylene succinate and polylactic acid. Thermoplastic polyester resins such as aromatic polyesters; and thermoplastic resins such as polycarbonate, atactic polystyrene, and syndiotactic polystyrene, but are not particularly limited thereto.

  When the adsorption layer 31 contains another resin, it is not particularly limited, but the content of the other resin is preferably 0.1 to 30 parts by mass with respect to 100 parts by mass of the above-mentioned polyolefin resin. 0.1-20 parts by mass, more preferably 0.1-10 parts by mass.

(Inorganic fine powder and organic filler)
The adsorption layer 31 may include at least one of an inorganic fine powder and an organic filler. By containing the inorganic fine powder or the organic filler, the adsorption layer 31 becomes milky white and translucent, and the presence of the protective sheet 11 is easily visually recognized, so that the handleability can be improved. Further, by including the inorganic fine powder or the organic filler, the dielectric constant of the adsorption layer 31 can be adjusted, and the mechanical strength of the protective sheet 11 can be improved. In addition, by containing the inorganic fine powder or the organic filler, undulations are formed on the surface of the adsorption layer 31, and the sheets can be made difficult to stick together when the adsorption layer 31 or the protective sheet 11 is manufactured.

Examples of the inorganic fine powder include calcium carbonate, calcined clay, silica, diatomaceous earth, clay, talc, titanium oxide, barium sulfate, barium titanate, alumina, zeolite, mica, sericite, bentonite, sepiolite, vermiculite, and dolomite. , Wollastonite, glass fiber and the like, but are not particularly limited thereto. When adding an inorganic fine powder, those having an average particle size of usually 0.01 to 15 μm, preferably 0.1 to 5 μm are used. In the present specification, the average particle diameter refers to a volume-based median diameter (D ₅₀ ) measured using a particle size distribution measuring device by a laser diffraction method.

  When adding an organic filler, it is preferable to select a different type of resin from the specific polyolefin resin contained in the adsorption layer 31. Since the adsorption layer 31 of the present embodiment contains at least one or more specific polyolefin resins, as the organic filler, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon-6, nylon-6,6, cyclic polyolefin, polystyrene , A polymer such as polymethacrylate, which has a melting point higher than the melting point of the specific polyolefin resin (for example, 200 to 300 ° C.), and can be finely dispersed in a phase by melt-kneading with the specific polyolefin resin. And incompatible ones can be used.

  The content of the inorganic fine powder and the organic filler in the adsorption layer 31 may be appropriately set according to the desired performance, and is not particularly limited, but is 0 to 50% by mass with respect to the total amount of the adsorption layer 31. Is preferably 0 to 30% by mass, and more preferably 0 to 10% by mass. When the content of the inorganic fine powder and the organic filler in the adsorption layer 31 is equal to or less than the upper limit of the above range, the mechanical strength of the protective sheet 11 is improved, and the charged electric charge is hard to escape and is retained inside. Tend to be able to.

  If necessary, additives such as a heat stabilizer (antioxidant), a light stabilizer, a dispersant, a lubricant, and a nucleating agent can be added to the adsorption layer 31. When a heat stabilizer is added, it is usually used in the range of 0.001 to 1% by mass based on the total amount of the adsorption layer 31. As the heat stabilizer, for example, stabilizers such as a sterically hindered phenol antioxidant, a phosphorus antioxidant, an amine antioxidant, and a sulfur antioxidant can be used. When a light stabilizer is added, it is usually used in the range of 0.001 to 1% by mass based on the total amount of the adsorption layer 31. As the light stabilizer, for example, a light stabilizer such as a sterically hindered amine light stabilizer, a benzotriazole light stabilizer, and a benzophenone light stabilizer can be used. The dispersant and the lubricant are used, for example, for the purpose of dispersing the inorganic fine powder. When adding a dispersant or a lubricant, it is used within a range of 0.01 to 4% by mass based on the total amount of the adsorption layer 31. As the dispersant, for example, a silane coupling agent, higher fatty acids such as oleic acid and stearic acid, metal soap, polyacrylic acid, polymethacrylic acid or salts thereof can be used.

(Surface resistivity)
It is preferable that the adsorption layer 31 of the protection sheet 11 has a structure that is easy to perform a charging process and easily retains the charge due to the charging process in order to provide the electrostatic adsorption capability. The ease of performing the charging process and the charge retention performance of the adsorption layer 31 can be indicated by the surface resistivity. In the present specification, the term “surface resistivity” refers to a double ring method under the conditions of a temperature of 23 ° C. and a relative humidity of 50% according to JIS K 6911 when the surface resistivity is 1 × 10 ⁷ Ω or more. Means the value measured by using the electrode. When the surface resistivity is less than 1 × 10 ⁷ Ω, it means a value measured with a four-end needle at a temperature of 23 ° C. and a relative humidity of 50% in accordance with JIS K 7194.

The surface resistivity of the surface 11b of the adsorbing layer 31 on the side in contact with the base material 41 is preferably in the range of 1 × 10 ^{13 to} 9 × 10 ¹⁷ Ω, and in the range of 5 × 10 ^{13 to} 9 × 10 ¹⁶ Ω. More preferably, it is more preferably in the range of 1 × 10 ^{14 to} 9 × 10 ¹⁵ Ω. When the surface resistivity of the surface 11b is equal to or more than the lower limit of the above range, the charge given during the charging process is hard to escape along the surface, and the charging process tends to be easily performed. In addition, it is difficult for the charge once applied to the adsorption layer 31 to escape along the surface of the adsorption layer 31 to the outside (in the air or the like), and since the adsorption layer 31 can retain the electric charge for a long period of time, the electrostatic adsorption force of the protective sheet 11 is reduced. It tends to be easy to maintain. If the surface resistivity of the surface 11b exceeds the upper limit of the above range, there is no problem in performance, but it is preferable that the surface resistivity is equal to or less than the upper limit of the above range from the viewpoint of manufacturing cost. The protective sheet 11 having such a surface resistivity can be achieved by selecting a resin constituting the protective sheet, and by performing surface treatment on the protective sheet 11 or the like.

(Thickness)
The thickness of the adsorption layer 31 may be appropriately set according to desired performance, and is not particularly limited, but is preferably in a range of 20 to 220 μm. It is more preferably in the range of 35 to 200 μm, further preferably in the range of 55 to 180 μm, and particularly preferably in the range of 90 to 160 μm. When the thickness of the adsorptive layer 31 is equal to or more than the lower limit of the above range, sufficient mechanical strength is obtained, wrinkles are less likely to occur when the protective sheet 11 is attached to the adherend, and the protective sheet 11 can be adhered well. Will be excellent. When the thickness of the attraction layer 31 is equal to or less than the upper limit of the above range, electrostatic charges can be charged, and the self-weight of the protective sheet 11 is suppressed, and the self-weight is held by the Can be prevented from falling.

(Basis weight)
The adsorption layer 31 is not particularly limited, but preferably has a basis weight in the range of 5 to 200 g / m ² . The basis weight of the adsorbent layer 31 is more preferably in the range of 7~150g / m ^2, more preferably in the range of 10 to 100 g / m ^2. The grammage of the adsorption layer 31 is proportional to the capacitance of the electrostatic charge that can be held inside the adsorption layer 31. Therefore, when the grammage of the adsorption layer 31 is equal to or more than the lower limit of the above range, the capacitance of the protection sheet 11 increases, and the adhesion of the protection sheet 11 to the adherend is easily maintained. When the grammage of the adsorbent layer 31 is equal to or less than the upper limit of the above range, the calorific value of the protective sheet 11 including the adsorbent layer 31 (e.g., represented by the total calorific value of the cone calorimeter) can be suppressed. it can.

(Surface roughness)
The surface roughness of the surface 11b of the adsorption layer 31 on the side in contact with the base material 41 is not particularly limited, but is preferably 0.01 to 5 μm, more preferably 0.05 to 2 μm, and 0.1 More preferably, it is 1 μm. When the surface roughness of the surface 11b is within the above range, higher smoothness of the surface where the adsorption layer 31 and the adherend are in contact is obtained. Thereby, the protective sheet 11 is brought into close contact with the adherend, whereby the electrostatic attraction force is sufficiently exhibited, and the attraction performance is improved. In addition, in this specification, surface roughness means the center-surface average roughness (SRa) of a surface measured using a stylus type three-dimensional surface roughness meter. For the measurement of the center plane average roughness (SRa), it is preferable to use an apparatus having a measurement accuracy of 0.01 μm or less.

(Formation of adsorption layer)
The method for forming the adsorption layer 31 is not particularly limited. For example, various known moldings such as cast molding, calender molding, rolling molding, and inflation molding for extruding a molten polyolefin resin into a sheet using a single-layer or multilayer T-die or I-die connected to a screw type extruder. By the method, the adsorption layer 31 can be formed. Further, the obtained adsorption layer 31 may be stretched. Further, the adsorption layer 31 may be subjected to a discharge surface treatment.

(Multilayer)
The adsorption layer 31 may have a single-layer structure, a two-layer structure, or a multi-layer structure of three or more layers. Various functions such as improvement of withstand voltage performance and improvement of suitability for secondary processing can be added to the adsorption layer 31 by forming a multilayer structure. When the adsorption layer 31 has a multilayer structure, various known methods can be used. Specific examples include a dry lamination method, a wet lamination method, and a melt lamination method using various adhesives, and a feed block. And a multilayer die system (co-extrusion system) using a multi-manifold, an extrusion lamination system using a plurality of dies, and a coating method using various coaters. It is also possible to use a combination of a multilayer die and an extrusion lamination.

  When the adsorption layer 31 has a multilayer structure, at least one layer preferably contains a specific polyolefin resin, and more preferably all layers contain a specific polyolefin resin. In addition, when the adsorption layer 31 has a multilayer structure, the content of the specific polyolefin resin and the content of the optional polyolefin resin with respect to the total amount of the polyolefin resin described above may be satisfied as the entire adsorption layer 31 having the multilayer structure. preferable.

<Coat layer>
The coat layer 21 constitutes the protective sheet 11 and is provided for the purpose of imparting antistatic performance to one surface of the adsorption layer 31.

  The coating layer 21 preferably contains, as its composition, 0.1 to 100% by mass of an antistatic agent, 0 to 99.9% by mass of a polymer binder, and 0 to 70% by mass of pigment particles. The coating layer 21 may be provided as a coating agent containing these components by directly coating on the adsorption layer 31 or may be previously coated on another film to form the coating layer 21, 31 can be provided.

  The antistatic agent is for imparting antistatic performance to the coat layer 21. Specifically, low molecular weight organic compound type antistatic agents represented by stearic acid monoglyceride, alkyldiethanolamine, sorbitan monolaurate, alkylbenzenesulfonate, alkyldiphenylethersulfonate, etc .; ITO (indium-doped tin oxide) , ATO (antimony-doped tin oxide), conductive whiskers, etc .; conductive inorganic fillers; so-called electron conductive polymers, such as polythiophene, polypyrrole, and polyaniline, which exhibit conductivity by pi electrons in their molecular chains; polyethylene glycol And non-ionic polymer antistatic agents such as polyoxyethylenediamine; quaternary ammonium salts such as polyvinylbenzyltrimethylammonium chloride and polydimethylaminoethyl methacrylate quaternary compounds; Coalescing; Although polymers having an antistatic function typified by alkali metal salts containing polymers such as alkali metal ions additives to alkylene oxide groups and / or hydroxyl group-containing polymers include, but are not particularly limited thereto.

  Each of these antistatic agents has characteristics. For example, a low molecular weight organic compound-based antistatic agent is likely to be greatly affected by the environmental humidity. On the other hand, a quaternary ammonium salt type copolymer or an alkali metal salt-containing polymer is preferable because it has good antistatic performance and the influence of environmental humidity on the antistatic performance is small.

  The polymer binder is used to give good adhesion between the coat layer 21 and the adsorption layer 31 on which the coat layer 21 is provided by its binding force or cohesive force. Specific examples of the polymer binder include polyethyleneimine, an alkyl-modified polyethyleneimine having 1 to 12 carbon atoms, poly (ethyleneimine-urea), an ethyleneimine adduct of poly (ethyleneimine-urea), polyamine polyamide, and polyamine polyamide. Polyethyleneimine polymers such as ethyleneimine adducts and epichlorohydrin adducts of polyamine polyamides; acrylic ester copolymers, methacrylic ester copolymers, acrylic acid amide-acrylic acid ester copolymers, acrylic acid amide-acrylic acid Ester-methacrylic ester copolymers, polyacrylamide derivatives, and acrylate polymers such as oxazoline group-containing acrylate polymers; polyvinylpyrrolidone, polyethylene glycol, and the like, Vinyl acid resin, urethane resin, polyether resin, polyester resin, urea resin, terpene resin, petroleum resin, ethylene-vinyl acetate copolymer, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer resin, vinylidene chloride resin, chloride Vinyl-vinylidene chloride copolymer resin, chlorinated ethylene resin, chlorinated propylene resin, butyral resin, silicone resin, nitrocellulose resin, styrene-acryl copolymer resin, styrene-butadiene copolymer resin, acrylonitrile-butadiene copolymer Examples thereof include polymers, but are not particularly limited thereto.

  One of these polymer binders may be used alone, or two or more thereof may be used in combination. These polymer binders can be used in a form diluted or dispersed in an organic solvent or water. Among them, urethane resins such as polyethyleneimine polymers, polyether urethanes, polyester polyurethanes, and acrylic urethanes, or acrylate copolymers have good compatibility (compatibility) with the above-mentioned polymer having an antistatic function. It is stable when melted into a paint, and is preferable because it is easy to apply.

  The coat layer 21 may or may not include pigment particles. It is possible to improve performance such as blocking prevention by imparting unevenness on the surface of the coat layer 21 formed by adding pigment particles to the coat layer 21, and to impart performance such as light resistance and weather resistance as an ultraviolet reflecting material. The pigment particles are appropriately selected and used in consideration of these required properties, and are added as necessary.

  Known organic or inorganic fine particles can be used as the pigment particles. Specific examples include silicon oxide, calcium carbonate, calcined clay, titanium oxide, zinc oxide, barium sulfate, diatomaceous earth, acrylic particles, styrene particles, polyethylene particles, polypropylene particles, and the like. The particle size of the pigment particles is preferably 20 μm or less, more preferably 15 μm or less, and further preferably 3 μm or less. Further, the particle size of the pigment particles is preferably 0.01 μm or more, more preferably 0.1 μm or more. When the particle diameter of the pigment molecules is equal to or less than the above upper limit, the falling off of the pigment particles from the formed coat layer 21 and the accompanying reduction in powder blowing can be suppressed. Further, when the particle diameter of the pigment molecule is equal to or more than the above lower limit value, undulations are formed on the surface of the coat layer 21, and there is a tendency that blocking when the electrostatic adsorption sheet 1 is stored in a stacked state is prevented. The pigment particle content in the coat layer 21 is preferably from 0 to 70% by mass, more preferably from 0 to 60% by mass, and still more preferably from 0 to 50% by mass. When the content of the pigment particles is equal to or less than the above range, the amount of the binder resin is sufficient, so that the cohesive force of the coat layer 21 is improved, and the adhesive strength to the adsorption layer 31 and the interlayer strength of the protective sheet 11 are improved. Can be improved.

  The coating layer 21 can be provided as a coating layer by preparing a coating liquid containing the above components, coating the coating liquid on the adsorption layer 31, drying and solidifying the coating liquid. Conventionally known methods and devices can be used for coating.

  Further, the coat layer 21 can be provided on the adsorption layer 31 by lamination. In this case, another film provided with the coat layer 21 in advance may be prepared and laminated on the adsorption layer 31. Lamination processing can be performed by a method such as ordinary dry lamination or melt lamination.

  It is preferable to install the coat layer 21 on the adsorption layer 31 before performing a charging process described later. Due to the antistatic performance of the coat layer 21, it is possible to suppress the electrostatic attraction force of the electrostatic attraction sheet 1 to the outside even after the charging process.

(Surface resistivity)
The coating layer 21 imparts antistatic performance to one surface of the adsorption layer 31. The surface resistivity of the coat layer 21 is preferably in the range of 1 × 10 ^{−1 to} 9 × 10 ¹² Ω, more preferably in the range of 1 × 10 ^{3 to} 9v × 10 ¹¹ Ω, and more preferably 1 × 10 Ω. More preferably, it is in the range of ^{6 to} 9 × 10 ¹⁰ Ω. When the surface resistivity of the coat layer 21 is equal to or less than the upper limit of the above range, sufficient antistatic performance is provided, and the electrostatic attraction force of the protection sheet 11 and the electrostatic attraction sheet 1 is sufficiently suppressed. Therefore, troubles such as sticking to a roll and sticking between sheets can be suppressed when the protective sheet 11 is stuck, and sticking between the electrostatic adsorption sheets 1 can be suppressed. Although there is no problem in performance even if the surface resistivity is lower than the lower limit of the above range, it is preferable that the surface resistivity is higher than the lower limit of the above range from the viewpoint of manufacturing cost. It is preferable from the viewpoint that the force can be held.

(Thickness)
The thickness of the coat layer 21 may be appropriately set according to desired performance, and is not particularly limited, but is preferably in the range of 0.001 to 50 μm. It is more preferably in the range of 0.1 to 20 μm, and still more preferably in the range of 1 to 10 μm. When the thickness of the coat layer 21 is equal to or more than the lower limit of the above range, the uniformity of the coat layer 21 can be maintained, and the antistatic performance can be stably exhibited. Further, when the thickness of the coat layer 21 is equal to or less than the upper limit of the above range, the self-weight of the protective sheet 11 is suppressed, and the self-weight is held by the electrostatic attraction force to prevent the protection sheet 11 from dropping from the adherend. it can.

(Basis weight)
The basis weight (coating amount) of the coat layer 21 is preferably 0.01 to 50 g / m ² , more preferably 0.05 to 30 g / m ² , in terms of solid content, and more preferably 0.1 to 30 g / m ^2. further preferably to 10 g / m ^2, and particularly preferably 0.3~8g / m ^2. When the grammage of the coat layer 21 is equal to or more than the lower limit of the above range, the uniformity of the coat layer 21 can be maintained, and the antistatic performance can be stably exhibited. Further, when the grammage of the coat layer 21 is equal to or less than the upper limit of the above range, it is possible to prevent the electrostatic attraction force of the adsorbent layer 31 from being impaired when the adsorbent layer 31 is provided on the adsorbent layer 31. , And can be prevented from peeling off from the adherend by supporting its own weight by the electrostatic attraction force, and a decrease in the electrostatic attraction force between the attraction layer 31 and the base material 41 can be suppressed.

<Protective sheet>
As shown in FIG. 1, the protective sheet 11 has a configuration in which a coat layer 21 is disposed on an upper surface side and an adsorption layer 31 is disposed on a lower surface side. For this reason, the surface resistivity and the surface roughness of the surface 31 a of the protective sheet 11 are in the same range as the surface resistivity and the surface roughness of the surface 11 b of the adsorption layer 31 described above. Thus, the protective sheet 11 having the surface 31a having the above-described preferable surface resistivity has the electrostatic attraction ability on the surface 31a on the attraction layer 31 side. Therefore, the protective sheet 11 is peeled off from the base material 41 at the time of use, and can be attached to the adherend by the electrostatic attraction ability of the surface 31a.

(Thickness)
The thickness of the protective sheet 11 is appropriately set according to the thicknesses of the coat layer 21 and the adsorption layer 31, and is not particularly limited, but is preferably 20 to 250 μm, more preferably 35 to 220 μm, and more preferably 60 to 200 μm. Is more preferable, and particularly preferably 90 to 170 μm. When the thickness of the protective sheet 11 is equal to or greater than the lower limit of the above range, wrinkles are less likely to be formed when the protective sheet 11 is attached to an adherend, and the protective sheet 11 can be attached well and the appearance is excellent. When the thickness of the attraction layer 31 is equal to or less than the upper limit of the above range, the self-weight of the protective sheet 11 is suppressed, and the self-weight is held by the electrostatic attraction force to prevent the protection sheet 11 from falling from the adherend. it can.

<Substrate>
The base material 41 constituting the electrostatic attraction sheet 1 of the present embodiment is laminated on one surface of the protection sheet 11 by the electrostatic attraction force of the protection sheet 11 or the own electrostatic attraction force. The base material 41 is removed like a release paper of a pressure-sensitive adhesive label when the protective sheet 11 is used.

  The base material 41 is used to prevent the charge stored in the protection sheet 11 from leaking to the outside until the protection sheet 11 is used, and to keep the electrostatic attraction force inside the protection sheet 11 inside. This is to make the protection sheet 11 easy to handle.

  The base material 41 is made of a resin film layer, and this resin film layer preferably contains a thermoplastic resin, and is more preferably a dielectric material, and more preferably contains a resin that is insulative and can hold charges inside. The surface 41a of the substrate 41 on the side in contact with the adsorption layer 31 is adhered to the adsorption layer 31 by the adsorption layer 31 or its own electrostatic adsorption force.

  The substrate 41 may have a single-layer structure or a multilayer structure including two or more layers. The base material 41 is preferably configured such that the surface 41a is in contact with the adsorption layer 31 so as to be electrostatically attractable and the surface 41b opposite to the surface 41a has antistatic performance. Is preferred.

(Thermoplastic resin)
The kind of the thermoplastic resin that can be used for the base material 41 is not particularly limited. For example, high-density polyethylene, medium-density polyethylene, low-density polyethylene, propylene-based resin, polyolefin-based resin such as polymethylpentene; ethylene / vinyl acetate Functional group-containing polyolefin resins such as copolymers, ethylene / acrylic acid copolymers, maleic acid-modified polyethylene, and maleic acid-modified polypropylene; polyamide resins such as nylon-6, nylon-6,6; polyethylene terephthalate and copolymers thereof. Thermoplastic polyester resins containing aliphatic polyesters such as polymers, polybutylene terephthalate, polybutylene succinate, and polylactic acid; polycarbonate, atactic polystyrene, syndiotactic polystyrene, and the like.

  Among them, it is preferable to use a polyolefin-based resin, a functional group-containing polyolefin-based resin, a polyamide-based resin, a thermoplastic polyester-based resin, or the like, which is excellent in workability, and more preferably a polyolefin-based resin.

(Relative permittivity)
The base material 41 has a role of sealing the charge of the adsorption layer 31 in the protective sheet 11 so as not to escape to the outside. The ability to confine this charge can be indicated by the relative dielectric constant of the base material 41 (the ratio of the dielectric constant ε of the base material 41 to the dielectric constant ε ₀ of vacuum (ε / ε ₀ )). The relative dielectric constant of the base material 41 is preferably in the range of 1.1 to 5.0, more preferably 1.2 to 4.0, and still more preferably 1.5 to 3.0. When the relative dielectric constant of the base material 41 is equal to or less than the upper limit of the above range, the adsorbing layer 31 can hold a charge for a long period of time, and tends to easily maintain the electrostatic attraction force of the protective sheet 11. If the relative permittivity of the base material 41 is lower than the lower limit of the above range, there is no problem in performance, but the material is lower than the relative permittivity of air (vacuum). It is difficult to obtain. Such a relative dielectric constant can be achieved in a desired range by forming the base material 41 from the above-described resin, forming a gap therein, or the like.

  For the measurement of the relative permittivity, a measurement method suitable for the measurement frequency range is selected. If the measurement frequency is 10 Hz or less, use an ultra-low frequency bridge. If it is 10 Hz to 3 MHz, use a transformer bridge. If it exceeds 1 MHz, use a parallel T-type bridge, high-frequency Schering bridge, Q meter, resonance method. It is preferable to use a standing wave method and a cavity resonance method. In addition, for an AC signal of a measurement frequency, a voltage / current vector for a circuit component is measured, and an LCR meter or the like that calculates a capacitance from this value can be used.

  As a measuring device for measuring the relative dielectric constant of the base material 41, a sample is sandwiched between a plate-shaped applying electrode and a plate-shaped guard electrode arranged in parallel at a constant pressure, and a voltage of about 5 V can be applied. Is preferred. According to such a measuring instrument, by changing the frequency, the frequency dependence of the sample can be grasped, and can be used as an index of the appropriate use range. The sample preferably has a thickness as uniform as possible and a smooth surface. If the surface condition is poor, a gap (air layer) is formed between the sample and the electrode, giving a large error to the measured value. In this case, it is preferable to apply a silver conductive paint such as a silver paste or to perform vacuum deposition in order to complete electrical contact between the sample and the electrode.

(Surface resistivity)
The surface 41a of the base material 41 on the side in contact with the adsorption layer 31 is preferably higher in surface resistivity as in the case of the adsorption layer 31, from the viewpoint of reducing the movement of charges. Specifically, the surface resistivity of the surface 41a is preferably in the range of 1 × 10 ^{13 to} 9 × 10 ¹⁷ Ω, more preferably in the range of 5 × 10 ^{13 to} 9 × 10 ¹⁶ Ω, and more preferably 1 × 10 ^{13 to} 9 × 10 ¹⁶ Ω. More preferably, it is in the range of 10 ^{14 to} 9 × 10 ¹⁵ Ω. When the surface resistivity of the surface 41a is equal to or more than the lower limit of the above range, when the substrate 41 and the adsorption layer 31 come into contact with each other, it is difficult for the charge of the adsorption layer 31 to escape to the outside through the substrate 41, Since the layer 31 can hold a charge for a long time, the electrostatic attraction of the protective sheet 11 tends to be easily maintained. Although there is no problem in performance even if the surface resistivity of the surface 41a exceeds the upper limit of the above range, it is preferable that the surface resistivity is equal to or less than the upper limit of the above range from the viewpoint of manufacturing cost.

  On the other hand, it is preferable that the base material 41 has antistatic performance on the surface 41b opposite to the surface 41a for the purpose of improving the handling property when the electrostatic suction sheet 1 is formed. Thereby, the outermost surface 1b of the electrostatic attraction sheet 1 combined with the base material 41 and the protection sheet 11 has antistatic performance.

  The provision of antistatic performance to the base material 41 can be achieved by a method using a resin film in which an antistatic agent is kneaded, or by direct evaporation, transfer evaporation, or lamination of an evaporation film on the surface 41b. A method of providing a metal thin film, a paper having an antistatic treatment or having an antistatic performance, a synthetic paper, a resin film, a woven fabric, or a nonwoven fabric, or a resin film in which an antistatic agent is kneaded and laminated to form a multilayer structure. And the like.

  In an embodiment using a resin film in which an antistatic agent is kneaded, an antistatic effect may not be exhibited unless a corona discharge surface treatment or a frame surface treatment is performed on the film surface. In some cases, the anti-static effect differs greatly from that of the untreated surface. By taking advantage of this phenomenon, the base material 41 is formed by stretching a thermoplastic resin into which an antistatic agent is kneaded, and a surface treatment such as corona discharge is performed on one side of the base material 41, so that the antistatic performance is provided on one side despite the single-layer structure. It is also possible to form the base material 41 having.

According to the various methods described above, the surface resistivity of the surface 41b of the base material 41 is preferably in the range of 1 × 10 ^{−1 to} 9 × 10 ¹² Ω, preferably 1 × 10 ^{0 to} 9 × 10 ¹² Ω. More preferably, it is within the range. When the surface resistivity of the surface 41b is equal to or less than the upper limit of the above range, sufficient antistatic performance is provided, and sticking to the periphery of the electrostatic adsorption sheet 1 and sticking between sheets are suppressed, Handleability is improved. Further, if the surface resistivity of the surface 41b is lower than the lower limit of the above range, there is no problem in performance, but it is preferable that the surface resistivity is more than the lower limit of the above range from the viewpoint of manufacturing cost.

(Thickness)
The thickness of the substrate 41 may be appropriately set according to the desired performance, and is not particularly limited, but is preferably in the range of 1 to 200 μm. The range is more preferably from 10 to 150 μm, and even more preferably from 60 to 110 μm. When the thickness of the base material 41 is equal to or more than the lower limit of the above range, when the base material 41 and the protective sheet 11 are bonded, it is possible to prevent the charge from flowing out from the surface 41a through the thickness of the base material 41, The electric charge in the electrostatic attraction sheet 1 is contained, and the electrostatic attraction force of the protection sheet 11 can be maintained. Further, when the thickness of the base material 41 is equal to or less than the upper limit of the above range, the thickness of the electrostatic adsorption sheet 1 is suppressed, and the workability in the printing process and the cutting process can be improved.

(Basis weight)
The substrate 41 preferably has a basis weight in the range of ²⁰ to 500 g / m ² . The basis weight of the substrate 41, more preferably in the range of 30 to 400 g / m ^2, more preferably in the range of 40~300g / m ^2. The base material 41 desirably retains a charge equivalent to the charge held by the adsorbing layer 31. However, when the basis weight of the base material 41 is equal to or greater than the lower limit of the above range, the electrostatic charge of the base material 41 is reduced. The capacity is increased, and the charge is easily held. Thereby, when the protective sheet 11 and the base material 41 are electrostatically adsorbed, the electric charge held by the adsorbing layer 31 can be maintained, and the adhesion of the protective sheet 11 to the adherend can be easily maintained. Further, when the basis weight of the base material 41 is equal to or less than the upper limit of the above range, the weight of the electrostatic adsorption sheet 1 is suppressed, and the handleability is improved.

<Electrification treatment>
The electrostatic adsorption sheet 1 of the present embodiment is obtained by applying a charging treatment to at least one of the surface 31a of the protection sheet 11 and the surface 41a of the base material 41, and then bonding the both by an electrostatic adsorption force. It has a laminate of the sheet 11 and the base material 41. The charging process is performed to inject an electric charge into the interior of the adsorption layer 31 or the base material 41 to give the electrostatic adsorption force to the electric charge.

  The charging treatment can be performed according to various known methods. Examples of the treatment method include a method of forming a film and then applying a corona discharge or a pulsed high voltage to the surface of the film (electro-electret method), holding both surfaces of the film with a dielectric, and applying a direct current to both surfaces. A method of applying a voltage (electro electret method) and a method of irradiating the same film with ionizing radiation such as γ-rays or electron beams to form an electret (radio electret method) are exemplified.

  The charging treatment of the protective sheet 11 or the base material 41 is preferably performed by an electro-electret forming method in which corona discharge or high voltage is applied. Preferred examples of the electro-electretization method include a method of applying a voltage by fixing a film between an application electrode connected to a DC high-voltage power supply and an earth electrode (batch type), and a method of applying a voltage by passing through a film ( Continuous type). When using this method, a main electrode (applied electrode) with many needle-shaped ones arranged at equal intervals, or a metal wire is used, and a flat metal plate or metal roll is used for the counter electrode (earth electrode). It is desirable to use.

  In the present embodiment, the charging process is preferably a DC corona discharge process. The DC corona discharge treatment uses a device in which a needle-shaped or wire-shaped main electrode (applied electrode) and a plate-shaped or roll-shaped counter electrode (earth electrode) are connected to a DC high-voltage power supply. In the direct current corona discharge treatment, the protective sheet 11 or the base material 41 is placed on the counter electrode, and the corona discharge generated by applying a high DC voltage between the main electrode and the counter electrode causes the protective sheet 11 or the base material 41. Charge is injected into the

At this time, the distance between the main electrode and the counter electrode is preferably 1 to 50 mm, more preferably 2 to 30 mm, and still more preferably 5 to 20 mm. When the distance between the main electrode and the counter electrode is within the above range, the corona discharge is generated stably, the distance between the electrodes is kept uniform, the charging process is performed uniformly in the width direction, and the uniform charging process is performed. Can be applied.
There are cases.

The voltage applied between the two electrodes is determined by the electrical characteristics of the protective sheet 11 and the base material 41, the shapes and materials of the main electrode and the counter electrode, and the distance between the main electrode and the counter electrode. -100 kV is preferred, 3-70 kV is more preferred, 5-50 kV is still more preferred, 10-40 kV is particularly preferred, and 16-30 kV is most preferred. The polarity of the main electrode may be positive or negative, but it is preferable to make the main electrode side a negative polarity because a relatively stable corona discharge state results.
The materials of the main electrode and the counter electrode are appropriately selected from conductive substances, and are preferably made of metal such as iron, stainless steel, copper, brass, and tungsten, or made of carbon.

  The amount of electric charge introduced into the protective sheet 11 or the base material 41 by these charging processes depends on the amount of current flowing between the main electrode and the counter electrode during the processing. Since the amount of current increases as the voltage between the two electrodes increases, it is preferable that the applied voltage be set high enough to prevent dielectric breakdown of the protective sheet 11 or the base material 41.

  The protection sheet 11 and / or the base material 41 constituting the electrostatic adsorption sheet 1 according to the present embodiment may be subjected to a charge elimination process after the charging process. By performing the charge elimination process, it is possible to remove excessive charge and avoid troubles in processing steps such as a cutting step and a printing step. A known method such as a voltage application type static eliminator (ionizer) or a self-discharge static eliminator can be used for such static elimination processing. These general static eliminators can remove the charge on the surface, but cannot remove the charge accumulated inside the adsorption layer 31 or the base material 41. Therefore, the electrostatic attraction force of the adsorption layer 31 or the base material 41 is not significantly impaired by the charge removal processing.

<Electrostatic suction sheet>
The electrostatic attraction sheet 1 is obtained by contacting the base sheet 41 with the protection sheet 11 on which the attraction layer 31 has been subjected to charging treatment. In this case, the electric charge accumulated inside the adsorption layer 31 causes the base material 41 in contact with the dielectric layer to be dielectrically, that is, electrostatically polarized, and both are adhered by an electrostatic adsorption force. Alternatively, the electrostatic attraction sheet 1 is obtained by bringing the base material 41 subjected to the charging treatment into contact with the attraction layer 31 of the protection sheet 11 and electrostatically adsorbing the same. In this case, the electric charge accumulated inside the base material 41 causes the adsorbing layer 31 that comes into contact with the electric charge to be insulated, and the two adhere to each other by electrostatic attraction. It should be noted that the electrostatic suction sheet 1 having the same performance can be obtained by either method.

  As shown in FIG. 1, the electrostatic adsorption sheet 1 is provided with a coat layer 21 on its upper surface and a base material 41 on its lower surface. Therefore, the surface resistivity of the outermost surface 1a on the coat layer 21 side of the electrostatic adsorption sheet 1 is in the same range as the surface resistivity of the coat layer 21 described above. In addition, the surface resistivity of the outermost surface 1b on the substrate 41 side of the electrostatic attraction sheet 1 is in the same range as the surface resistivity of the surface 41b of the substrate 41 described above. Thereby, the electrostatic attraction sheet 1 having the outermost surfaces 1a and 1b having the above-described preferable surface resistivity has a high electrostatic attraction layer 31 in the form of the electrostatic attraction sheet 1 before the protective sheet 11 is peeled off. The antistatic performance is imparted to both surfaces while maintaining the suction force. Therefore, the electrostatic attraction sheet 1 has a reduced electrostatic attraction force to the outside, and sticks to the surroundings during handling of the electrostatic attraction sheet 1 during transportation, storage, printing, and the like, and between the electrostatic attraction sheets 1. Sticking is unlikely to occur and handling is good.

[Use]
The protective sheet 11 constituting the electrostatic adsorption sheet 1 of the present embodiment can be used as a sheet for protecting the adherend by peeling it off from the base material 41 and attaching it to the adherend. At this time, since the protective sheet 11 is adhered to the adherend by the electrostatic attraction force, reattachment is easy, and even if air pockets are formed between the adherend and the adherend, it can be removed from any direction by hand. Also, there is an advantage that the air can be easily removed and the final finish is good. In addition, the protective sheet 11 has a high electrostatic attraction force when used, has sufficient durability of the electrostatic attraction force, and can be used for display on an adherend for a long period of time. , And can be easily separated from the adherend.

  Further, the protective sheet 11 can be attached as long as the adhered surface of the adherend is a smooth material. For example, metals such as copper, silver, gold, iron, stainless steel, and aluminum, glass, resin, and ceramics It can be attached to a surface made of tiles or the like. Examples of the adherend of the protection sheet 11 include a signboard, a signboard, a signboard, a whiteboard, a wall, a ceiling, a pillar, a door, a partition, a floor, a locker, a desk, a shelf, a window (made of glass and resin), Refrigerators (metallic surfaces, glass surfaces, plastic surfaces), showcases, various devices (machine tools, printing machines, molding machines, etc.), and in-cars (automobiles, buses, trains), ships, airplanes, etc. .

  Furthermore, since the protective layer 11 includes the polyolefin resin having the predetermined melting point, the protective layer 11 has resistance to high temperatures, has a small dimensional change even in a high-temperature environment, and can maintain the adsorption performance. it can. For this reason, the protection sheet 11 can be suitably used in a field in which the protection sheet 11 is exposed to a high temperature due to the high temperature of the adherend or the environment around the adherend. Examples of the use of such a protective sheet 11 include, for example, protection of a metal foil, and particularly, it can be suitably used for protection of a copper foil provided on a flexible substrate. In addition, high temperature here means 100 degreeC or more.

  Hereinafter, the present invention will be specifically described with reference to Production Examples and Examples. In addition, the materials, usage amounts, ratios, processing contents, processing procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the present invention is not limited to the following examples.

[Evaluation method]
The electrostatic adsorbing sheets obtained in each of the examples and comparative examples were evaluated by the following methods.

<Thickness>
The thickness of the adsorption layer obtained in each of the production examples and examples was measured using a constant-pressure thickness gauge (trade name: PG-01J, manufactured by Tech Rock Co., Ltd.) in accordance with JIS K 7130: 1999. did.

<Surface roughness>
The center surface average roughness (SRa) of the protective sheet obtained in each production example was measured using a three-dimensional surface roughness meter (trade name: Surfcom 1500DX3, manufactured by Tokyo Seimitsu Co., Ltd.) at a measurement speed of 0.2 mm. / Sec, measurement length: 5 mm, and feed pitch: 20 μm. The measurement of the surface roughness was performed on the surface of the protective sheet on the adsorption layer side.

<Surface resistivity>
The surface resistivity of the protective sheet obtained in each production example and each example was measured using a double-ring method electrode at a temperature of 23 ° C. and a relative humidity of 50% in accordance with JIS K 6911: 1995. Measured. The surface resistivity is measured by measuring the surface of the protective sheet on the side of the adsorbing layer and the side of the coating layer, and the surface of the substrate that is in contact with the adsorbing layer and the surface of the substrate that is opposite to the surface that is in contact with the adsorbing layer I went about.

<Preparation of evaluation sample>
The electrostatic adsorption sheets of Examples and Comparative Examples were cut into a shape of 10 cm × 11 cm, and stored for one day under an atmosphere of a relative humidity of 50%. Thereafter, under the same atmosphere, the protective sheet 11 was peeled off from the electrostatic attracting sheet, and as shown in FIG. 2, the protective sheet 11 was attached to a mirror-finished copper foil 52 having a thickness of 200 μm. At this time, the attachment was performed so that the adsorption area became 10 cm × 10 cm, and the 1 cm width of one end of the protection sheet 11 protruded from the copper foil 52. Furthermore, the inside air was evacuated using a rubber roll to obtain a sample 51 for evaluation. After the obtained evaluation sample 51 was stored in an atmosphere of 50% relative humidity for 1 day, it was heated in an oven at 150 ° C. for 5 minutes, taken out of the oven, and cooled at room temperature for 10 minutes to obtain the following appearance, The evaluation of the adsorption force and the change in the surface state were performed in order.

<Appearance>
The appearance of the protective sheet was visually observed, and a two-step evaluation was performed based on the following criteria.
：: good (no wrinkling occurred and no peeling from the adherend was observed)
×: Not possible (wrinkles are generated and peeling from the adherend is observed)

<Adsorption power>
After the appearance was evaluated, the attraction force was evaluated using an attraction force measuring device 61 as shown in FIG. The suction force measuring device 61 holds both ends of the glass plate 64 in a state of being vertically erected by the columns 62 and 63. The upper end of the copper foil 52 of the evaluation sample 51 is attached to the glass plate 64 with the fixing adhesive tape 65 such that the protruding end of the evaluation sample 51 is on the lower side. In this state, the clip 66 is attached to the protruding lower end portion of the protection sheet 11. 10 g of weights 68 are added to the clip 66 one by one via the thread 67 attached to the clip 66, and the weight of the weight 68 when the protective sheet 11 slides down from the copper foil 52 is calculated based on the weight of the weight 68 per square meter. The value converted to kilograms (kgf / m ² ) was determined as an adsorption force and evaluated according to the following criteria.
：: good (adsorption force is 5 kgf / m ² or more)
×: defective (adsorption force is less than 5 kgf / m ² )

<Change in surface condition>
After the evaluation of the attraction force, the surface state of the copper foil after peeling the protective sheet was visually observed, and the adhesive residue was evaluated according to the following criteria.
：: Good (the glossiness is not changed between the surface where the protective sheet is adsorbed and the surface where the protective sheet is not adsorbed)
×: Not possible (the glossiness differs between the surface where the protective sheet was adsorbed and the surface where it was not adsorbed)

[Manufacture of adsorption layer]
Table 1 shows details of the thermoplastic resins a to d used as the raw material resins in the production examples of the adsorption layer.

<Production example 1 of adsorption layer>
The resin a (polymethylpentene (trade name: TPX MX004, manufactured by Mitsui Chemicals, Inc.)) was melt-kneaded using an extruder set at 290 ° C., and extruded into a sheet shape from an extrusion die set at 290 ° C. The extruded sheet was cooled by a cooling roll set at 60 ° C. Both ends of this sheet were slit, and then one surface of the sheet was subjected to a corona discharge treatment to obtain an adsorption layer a of Production Example 1. The thickness of the adsorption layer a was 50 μm.

<Production Example 2 of adsorption layer>
Adsorption layer b of Production Example 2 was obtained in the same manner as in Production Example 1, except that resin b (polymethylpentene (trade name: TPX DX845) manufactured by Mitsui Chemicals, Inc.) was used instead of resin a. . The thickness of the adsorption layer b was 100 μm.

<Production example 3 of adsorption layer>
An adsorption layer c of Production Example 3 was obtained in the same manner as in Production Example 1, except that resin c (polymethylpentene (trade name: TPX MX002) manufactured by Mitsui Chemicals, Inc.) was used instead of resin a. . The thickness of the adsorption layer c was 30 μm.

<Production Example 4 of adsorption layer>
Production was performed except that a blend of 70% by mass of resin a and 30% by mass of resin d (propylene homopolymer (trade name: Novatec PP FY4) manufactured by Nippon Polychem Co., Ltd.) was used instead of resin a. In the same manner as in Example 1, an adsorption layer d of Production Example 4 was obtained. The thickness of the adsorption layer d was 50 μm.

<Production Example 5 of Adsorption Layer>
The adsorption layer e of Production Example 5 was obtained in the same manner as in Production Example 1 except that the temperature of the extruder was changed to 250 ° C. and the temperature of the extrusion die was changed to 250 ° C. using resin d instead of resin a. Was. The thickness of the adsorption layer e was 100 μm.

<Production Example 6 of adsorption layer>
Corona discharge treatment is also applied to the untreated surface of the adsorbing layer e that has not been subjected to corona discharge treatment, and an adhesive (a 1: 1 mixture of TM320 and CAT-13B, manufactured by Toyo Ink Mfg. Co., Ltd.) is applied to one surface. Coating was performed so that the thickness after drying became 2 μm, and the corona discharge surface-treated surface of the adsorption layer a was bonded to the coated surface after drying. Next, an adhesive (trade name: 1: 1 mixture of TM320 and CAT-13B, manufactured by Toyo Ink Mfg. Co., Ltd.) is applied to the other surface of the adsorption layer e so that the thickness after drying becomes 2 μm. The treated surface of the adsorbent layer a was subjected to a corona discharge treatment on the coated surface after drying. Further, the surface of one adsorbing layer a was subjected to corona discharge surface treatment to obtain an adsorbing layer f having a layer configuration (adsorbing layer a / adsorbing layer e / adsorbing layer a (resin a / resin d / resin a)). . The thickness of the adsorption layer f was 154 μm, and the content of the resin a was 63%.

[Preparation of coating agent]
<Example of preparation of antistatic agent>
100 parts by mass of polyethylene glycol monomethacrylate (manufactured by NOF Corporation, trade name: Blemmer PE-350), 20 parts by mass of lithium perchlorate (manufactured by Wako Pure Chemical Industries, Ltd.), 1 part by mass of hydroquinone, and 400 parts by mass of methyl ethyl ketone was introduced into a four-necked flask equipped with a stirrer, a condenser, a nitrogen inlet tube, and a thermometer, and the inside of the system was purged with nitrogen and reacted at 60 ° C. for 40 hours. To this, 20 parts by mass of stearyl methacrylate, 20 parts by mass of n-butyl methacrylate, and 1 part by mass of azobisisobutyronitrile were added, and after a polymerization reaction at 80 ° C. for 3 hours, methyl ethyl ketone was added to reduce the solid content to 20% by mass. To obtain an antistatic solution having a mass average molecular weight of about 300,000 and a lithium concentration of 0.8 wt% in solids.

<Preparation example of polymer binder>
15 parts by mass of 2-hydroxyethyl methacrylate, 50 parts by mass of methyl methacrylate, 35 parts by mass of ethyl acrylate, and 100 parts by mass of toluene were charged into a three-necked flask equipped with a stirrer, a reflux condenser, and a thermometer, and then purged with nitrogen. , 2,2'-azobisisobutyronitrile was added as an initiator and polymerized at 80 ° C for 4 hours. The obtained solution was a 50% by mass toluene solution of a hydroxyl group-containing (meth) acrylate copolymer resin having a hydroxyl value of 65. Next, 40 parts by mass of a 20 mass% methyl ethyl ketone solution of a vinyl chloride-vinyl acetate copolymer (trade name: ZESTC150ML, manufactured by Shin-Daiichi Vinyl Co., Ltd.) was added to 100 parts by mass of this solution, and hexamethylene diisocyanate (Nippon Polyurethane Industry Co., Ltd.) Co., Ltd., trade name: Coronate HL) 20 parts by mass of a 75% by mass ethyl acetate solution, and a solvent obtained by mixing toluene and methyl ethyl ketone at a ratio of 1: 1 to this mixture was added to adjust the solid content to 20% by mass. Thus, a polymer binder solution was obtained.

<Example of preparation of coating agent>
While gently stirring 8 kg of methyl ethyl ketone with a Cowles mixer, 1 kg of sedimentable silica (Mizukasil P-527, manufactured by Mizusawa Chemical Industry Co., Ltd., trade name: 1.6 μm in average particle size, oil absorption: 180 cc / 100 g) was averaged. 1 kg of barium sulfate having a particle diameter of 0.3 μm (trade name: BARIACE B-32, manufactured by Sakai Chemical Industry Co., Ltd.) was added little by little, and adjusted to a solid concentration of 20% by mass. The rotation speed of the Cowles mixer was increased and the mixture was stirred for 30 minutes to obtain a pigment dispersion.

  Next, the number of revolutions of the Cowles mixer was reduced, and 11.8 kg of the polymer binder solution obtained in the above-described preparation example of the polymer binder and the charge obtained in the above-described preparation example of the antistatic agent solution were added to the pigment dispersion. 2.5 kg of an inhibitor solution and 0.8 kg of hexamethylene diisocyanate (trade name: Coronate HL, manufactured by Nippon Polyurethane Industry Co., Ltd.) previously diluted to a solid content of 20% by mass with ethyl acetate are added in this order, and 20 The mixture was stirred for minutes and mixed, and then passed through a 100-mesh filter to remove coarse particles, thereby obtaining a coating agent.

[Manufacture of protective sheet]
<Production example 1 of protective sheet>
The coating agent obtained in the above-mentioned preparation example of the coating agent was applied to the corona discharge surface-treated surface of the adsorption layer a so that the thickness after drying would be the thickness shown in Table 2, and set at 70 ° C. After drying in an oven for 60 seconds, a protective sheet a of Production Example 1 was obtained.

<Production Examples 2 to 6 of protective sheet>
A production example except that a coating agent was applied to the corona discharge surface-treated surface so that the thickness after drying became the thickness shown in Table 2 using the adsorption layer shown in Table 2 instead of the protective sheet a. In the same manner as in Example 1, protective sheets b to f of Production Examples 2 to 6 were obtained.

  Table 2 shows the physical properties of the protective sheet.

[Manufacture of base material]
<Example 1 of manufacturing base material>
An adhesive (a 1: 1 mixture of Toyo Ink Mfg. Co., Ltd., trade name: TM320, CAT-13B) was applied to one side of a synthetic paper (trade name: FPG60, manufactured by Yupo Corporation) having a thickness of 60 μm. Coating is performed so that the thickness after drying becomes 2 μm, and the corona discharge treated surface of a biaxially stretched polypropylene film having a thickness of 20 μm (manufactured by Toyobo Co., Ltd., trade name: P2102) is applied to the coated surface after drying. The base material A of Production Example 1 was obtained.

<Example 2 of manufacturing base material>
An adhesive (manufactured by Toyo Ink Mfg. Co., Ltd., trade names: TM329, CAT-18B) was applied to the corona discharge treated surface of a biaxially stretched polypropylene film (manufactured by Futamura Chemical Co., Ltd., trade name: FOP-K) having a thickness of 50 μm. (1: 1 mixture), and bonded to the coated surface after drying such that the aluminum-deposited surface of a 12 μm-thick aluminum-deposited PET film (trade name: Tetraite PC, manufactured by Oike Industry Co., Ltd.) is on the outside. Thus, a base material B of Production Example 2 was obtained.

  Table 3 shows the contents of the materials used as the raw material resins in the production examples of the base material and the physical properties of the base material. In the case of the substrate A, the surface resistivity was indicated such that the side of the biaxially oriented polypropylene film having a high surface resistivity was in contact with the adsorbing layer, and the side of the synthetic paper was on the side opposite to the side in contact with the adsorbing layer. Further, in the base material B, the surface resistivity was indicated such that the side of the biaxially stretched polypropylene film having a high surface resistivity was in contact with the adsorption layer, and the side of the aluminum vapor-deposited PET film was in the opposite side to the side in contact with the adsorption layer.

[Manufacture of electrostatic attraction sheet]
<Example 1>
The charge injection process by the DC corona discharge process was performed on the surface of the protective sheet a opposite to the surface on the coat layer side. First, in order to set the conditions for the charge injection process, the surface of the protective sheet a on the coat layer side was placed on the earth electrode board of the electretization apparatus in which the distance between the needles of the main electrode was set to 10 mm and the distance between the main electrode and the ground electrode was set to 10 mm. Was placed in contact with the ground electrode surface. In this state, the voltage applied to the surface on the adsorption layer side is gradually increased from 1 KV to measure the voltage at which the protective sheet a is destroyed by the local spark discharge, and a voltage 1 kv lower than the spark discharge voltage is injected. The discharge voltage of the treatment was used. Then, using the discharge voltage under the processing conditions described in Table 4, the charge injection process by the DC corona discharge process was performed on the surface on the adsorption layer side. Subsequently, the surface of the protective sheet a subjected to the charge injection treatment and the surface of the substrate A having the higher surface resistivity (the biaxially oriented polypropylene film side) are laminated so that they are in contact with each other. The electrostatic adhesion sheet of Example 1 was obtained by pressure bonding.

<Example 2>
Example 2 was repeated except that the base material B was used in place of the base material A, the protection sheet b was used in place of the protection sheet a, and the discharge voltage under the processing conditions shown in Table 4 was used. Was obtained.

<Example 3>
An electrostatic attraction sheet of Example 3 was obtained in the same manner as in Example 1, except that a protective sheet c was used instead of the protective sheet a and discharge voltages under processing conditions shown in Table 4 were used.

<Example 4>
An electrostatic attraction sheet of Example 4 was obtained in the same manner as in Example 1 except that the protection sheet d was used instead of the protection sheet a.

<Example 5>
Example 5 was repeated except that the base material B was used in place of the base material A, the protection sheet f was used in place of the protection sheet a, and the discharge voltage under the processing conditions shown in Table 4 was used. Was obtained.

<Comparative Example 1>
An electrostatic attraction sheet of Comparative Example 1 was obtained in the same manner as in Example 1, except that the protective sheet e was used instead of the protective sheet a, and the discharge voltage under the processing conditions shown in Table 4 was used.

<Comparative Example 2>
A commercially available PET adhesive protection sheet (trade name: 50AN, manufactured by Okamoto Co., Ltd.) was used as the electrostatic adsorption sheet of Comparative Example 2.

[Evaluation]
Table 4 shows the physical properties and evaluation results of the electrostatic adsorption sheet.
The electrostatic adsorption sheets of Examples 1 to 5 include an adsorption layer containing a polyolefin resin having a melting point of 200 ° C. or higher. As shown in Table 4, in the electrostatic suction sheets of Examples 1 to 5, the protection sheet was stuck to the adherend without sticking while having excellent adhesion even in a high temperature environment by sticking the protective sheet to a copper foil. In this state, excellent adsorption performance was maintained. In addition, there was no change in the surface state when peeled off, and no contamination of the copper foil occurred.

  Further, in the electrostatic attraction sheets of Examples 1 to 5, the surface resistivity of the surface of the protective sheet on the coat layer side is lower than that of the surface on the attraction layer side. Further, the surface resistivity of the surface of the base material on the side not in contact with the adsorption layer is suppressed more than the surface on the side in contact with the adsorption layer. Thereby, in a mode in which the protective sheet and the base material are bonded, the outermost surface of the electrostatic attraction sheet has a reduced surface resistivity on both sides. Therefore, the performance of the protective sheet is favorable as described above, while the electrostatic suction sheets of Examples 1 to 5 have good handling properties.

  In the electrostatic adsorption sheet of Comparative Example 1, since the adsorption layer was made of only a propylene homopolymer and could be electrostatically adsorbed to an adherend, there was no problem that the surface state of the metal foil was changed. However, when placed in a high-temperature environment, not only is the adsorption power inferior, but also wrinkles are generated due to shrinkage after high-temperature treatment, and the adhered state cannot be maintained.

  Since the PET pressure-sensitive adhesive protective sheet of Comparative Example 2 enables the adhesion to the copper foil with the pressure-sensitive adhesive layer, when placed in a high-temperature environment, the adsorptive power was sufficient and no wrinkles were generated. However, the gloss of the surface was changed due to the adhesive layer, and contamination of the copper foil was caused.

Reference Signs List 1 electrostatic adsorption sheet 1a outermost surface 1b on coat layer side outermost surface 11 on base material side protective sheet 11a surface 11b opposite to surface in contact with substrate 21b surface in contact with substrate 21 coating layer 31 adsorption layer 31a adsorption Layer-side surface 41 Base material 41a Surface 41b in contact with the adsorption layer 41b Surface opposite to the surface in contact with the adsorption layer

Claims (7)

A protective sheet that can be electrostatically adsorbed to the adherend, and a substrate that is electrostatically adsorbed to the protective sheet,
The protective sheet, an adsorption layer provided on a surface in contact with the base material and containing at least one or more polyolefin resin, and a coat layer provided on a surface side opposite to the surface in contact with the base material And
The melting point of at least one kind of the polyolefin resin is 200 ° C. or more. The polyolefin resin having a melting point of 200 ° C. or more includes a polyolefin (co) polymer containing 4-methyl-1-pentene as a monomer component,
The electrostatic attraction sheet according to claim 1. The adsorption layer, based on the total amount of the polyolefin resin, the melting point is 50 to 100% by mass of a polyolefin resin having a melting point of 200 ° C or more, and the melting point is 50 to 0% by mass of a polyolefin resin other than the polyolefin resin having a melting point of 200 ° C or more. contains,
The electrostatic adsorption sheet according to claim 1. The protective sheet has a surface resistivity of 1 × 10 ^{13 to} 9 × 10 ¹⁷ Ω on the surface on the adsorption layer side,
The substrate has a surface resistivity of 1 × 10 ^{13 to} 9 × 10 ¹⁷ Ω on a surface in contact with the adsorption layer,
The electrostatic adsorption sheet according to claim 1. The surface resistivity of the surface on the coat layer side is 1 × 10 ⁻¹ Ω to 9 × 10 ¹² Ω,
The surface resistivity of the substrate-side surface is 1 × 10 ⁻¹ Ω to 9 × 10 ¹² Ω,
The electrostatic attraction sheet according to claim 1. The protective sheet has a center plane average roughness (SRa) of 0.01 to 5 μm on a surface on the adsorption layer side.
The electrostatic attraction sheet according to claim 1. It is a manufacturing method of the electrostatic attraction sheet according to any one of claims 1 to 6,
A method for manufacturing an electrostatically attracting sheet, wherein the substrate is electrostatically attracted after charge injection by DC corona discharge is performed on the protective sheet.

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