Protective sheet

Abstract

This protective sheet is provided with: a protective layer; a first release liner disposed on a surface of the protective layer; the first release liner is arranged on one surface of the protective layer, the second release liner is arranged on the other surface of the protective layer, the protective layer contains a water-soluble polymer compound, and when the release force of the first release liner to the protective layer is PA and the release force of the second release liner to the protective layer is PB, the release force PA and the release force PB satisfy the following relational expressions: PA < PB, PB < = 2000 mN / 25 mm.

Description

[0001] Cross-references of related applications

[0002] This application claims the benefit of priority based on Japanese Patent Application No. 2022-109059, the disclosure of which is incorporated herein by reference. Technical Field

[0003] The invention relates to a protective sheet. Background Art

[0004] Conventionally, it is known that in the manufacture of semiconductor elements such as semiconductor chips and electronic components such as liquid crystal display devices, a protective sheet having adhesive properties is used to prevent foreign matter from adhering to the electronic components (for example, Patent Document 1 listed below).

[0005] Patent Document 1 listed below discloses, as the protective sheet, a protective sheet including a protective layer formed of a resin composition containing an oxyalkylene group-containing polyvinyl alcohol-based resin and two release sheets disposed on both surfaces of the protective layer.

[0006] In the production of the above-mentioned electronic components, the production of semiconductor chips is generally carried out by dividing (cutting) one semiconductor wafer (for example, see Patent Document 2 below).

[0007] For example, Patent Document 2 listed below discloses that semiconductor chips are manufactured in the following manner.

[0008] (1) A plurality of planned dividing lines are formed in a grid pattern on one surface side of a silicon wafer.

[0009] (2) Circuit patterns are formed and electrodes are arranged in each of the regions divided into a grid shape by the plurality of planned dividing lines (hereinafter also referred to as grid-shaped divided regions). In this way, a semiconductor wafer for obtaining semiconductor chips is manufactured.

[0010] (3) The semiconductor wafer is divided (cut) along the plurality of planned dividing lines, in other words, the semiconductor wafer is divided (cut) according to the grid-shaped divided regions to obtain a plurality of semiconductor chips.

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: Japanese Patent Application Publication No. 2021-161735

[0014] Patent Document 2: Japanese Patent Application Publication No. 2012-119670 Summary of the invention

[0015] Problems to be solved by the invention

[0016] Furthermore, as described above, when a semiconductor wafer is divided (cut) to obtain a plurality of semiconductor chips, a part of the semiconductor wafer near the divided portion (cut portion) may be powdered to generate fine foreign matter.

[0017] Furthermore, if such fine foreign matter adheres to one surface side (the side where the circuit pattern is formed) of the semiconductor chip, the operational reliability of the circuit included in the circuit pattern formed on the one surface side may be reduced, which is not preferable.

[0018] Therefore, the production of semiconductor chips is often carried out by bonding the protective layer of the protective sheet to one surface side (the side where the circuit pattern is formed) of the semiconductor wafer.

[0019] When using a protective sheet as described above that has a protective layer comprising a water-soluble polymer compound such as a polyvinyl alcohol-based resin containing an oxyalkylene group and two release sheets arranged on both sides of the protective layer, when the protective layer is attached to one surface side of the semiconductor wafer, it is necessary to peel off one of the two release sheets from the protective sheet to expose the surface of the protective layer.

[0020] The peeling sheet on one side is peeled off from the protective layer by an external force such as suction being applied from the outer side (the side without the protective layer) of the peeling sheet on the other side. However, when the peeling sheet on one side is peeled off from the protective layer, the protective layer sometimes lifts up from the peeling sheet on the other side of the two peeling sheets.

[0021] In addition, when the protective layer and the release sheet on one side are peeled off, it is not confirmed that the protective layer is lifted from the other side, but sometimes the release sheet on one side is peeled off with a part of the protective layer attached. In other words, sometimes the protective layer is separated unintentionally. In other words, sometimes cohesive failure occurs in the protective layer.

[0022] However, in the case of a protective sheet having release sheets on both sides of the protective layer, it is difficult to say that sufficient research has been conducted to achieve both sufficient balance between suppressing the protective layer from lifting from the other release sheet when one release sheet is peeled off and suppressing unintentional separation of the protective layer.

[0023] Therefore, the technical problem of the present invention is to provide a protective sheet having release sheets on both sides of a protective layer, which can fully take into account both the suppression of the protective layer from warping from the other release sheet when one release sheet is peeled off and the suppression of unintentional separation of the protective layer.

[0024] Solutions for solving problems

[0025] The protective sheet of the present invention comprises: a protective layer; a first release liner disposed on one surface of the protective layer; and a second release liner disposed on the other surface of the protective layer, wherein the protective layer comprises a water-soluble polymer compound, and when the release force of the first release liner on the protective layer is set to P A , the peeling force of the second release liner on the protective layer is set to P B When the peeling force P A and peeling force P B Satisfies the following relationship: P A <P B , P B ≤2000mN / 25mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic cross-sectional view showing the structure of a protection sheet according to one embodiment of the present invention.

[0027] Figure 2 It is a cross-sectional view showing the structure of a mounting device for bonding a protective layer of a protective sheet to a surface to be protected of an electronic component such as a semiconductor wafer. DETAILED DESCRIPTION

[0028] Hereinafter, one embodiment of the present invention will be described.

[0029] [Protective film]

[0030] like Figure 1 As shown, a protective sheet 10 according to one embodiment of the present invention includes: a protective layer 1 ; a first release liner 2 disposed on one surface of the protective layer 1 ; and a second release liner 3 disposed on the other surface of the protective layer 1 .

[0031] It should be noted that, hereinafter, one embodiment of the present invention is simply referred to as this embodiment.

[0032] In the protective sheet 10 of the present embodiment, the protective layer 1 contains a water-soluble polymer compound.

[0033] That is, the protective layer 1 is water-soluble.

[0034] On the other hand, the first release liner 2 and the second release liner 3 are water-insoluble.

[0035] like Figure 1 As shown, in the protective sheet 10 of the present embodiment, the protective layer 1, the first release liner 2, and the second release liner 3 have substantially the same size in a plan view.

[0036] Specifically, in a protective sheet 10 according to one embodiment, the inner surface of the first release liner 2 (the surface opposite to one surface of the protective layer) and one surface of the protective layer 1 overlap substantially the entire area in a manner such that the end edges are aligned with each other, and the inner surface of the second release liner 3 (the surface opposite to the other surface of the protective layer 1) and the other surface of the protective layer 1 overlap substantially the entire area in a manner such that the end edges are aligned with each other.

[0037] In the protective sheet 10 of the present embodiment, the protective layer 1 has adhesiveness to such an extent that it can be attached to an adherend.

[0038] In the protective sheet 10 of the present embodiment, the protective layer 1 preferably has adhesiveness (pressure-sensitive adhesiveness).

[0039] The protective sheet 10 of the present embodiment is used to prevent foreign matter from being attached to the surface of an adherend (for example, an electronic component such as a semiconductor wafer) by attaching the protective layer 1 to the adherend while various processes are being performed on the adherend.

[0040] In the protective sheet 10 of the present embodiment, the protective layer 1 (more specifically, the exposed surface of the protective layer 1) is formed by, for example, Figure 2 The mounting device 200 shown is attached to a surface to be protected of an electronic component such as a semiconductor wafer.

[0041] The installation device 200 is as follows Figure 2 As shown, it includes: a chamber 201; an electrostatic chuck stage 202, which is arranged at the bottom of the chamber 201; a head 203, which is arranged above the electrostatic chuck stage 202 and in the chamber 201; and a pump P for decompressing the interior of the chamber 201.

[0042] It should be noted that in the mounting device 200 , electronic components such as semiconductor wafers are mounted on the electrostatic chuck stage 202 , and the protection sheet 10 is mounted on the head 203 .

[0043] In the mounting device 200 , the protective sheet 10 and the electronic component such as the semiconductor wafer are mounted on the head 203 and the electrostatic chuck stage 202 , respectively, in such a manner that the exposed surface of the protective layer 1 faces the surface to be protected.

[0044] Furthermore, if Figure 2 As shown, when the holding base 101 is mounted on the head 203 , the protection sheet 10 may be mounted on the holding base 101 .

[0045] The vertical direction (vertical direction) is defined as the Z-axis direction, and the horizontal direction ( Figure 2 The horizontal direction along the paper surface) is set as the X-axis direction, and the direction perpendicular to both the Z-axis and the X-axis ( Figure 2The direction perpendicular to the paper surface) is set as the Y-axis direction. At this time, on the basis of moving the head 203 in at least one of the X-axis direction and the Y-axis direction, it is further moved in the Z-axis direction, thereby enabling the exposed surface of the protective layer 1 installed on the head 203 to adhere to the protection target surface of the electronic component such as the semiconductor wafer installed on the electrostatic chuck table 202.

[0046] When the head 203 is not equipped with the holding table 101, the electrostatic chuck table 202 may be heated in advance when the exposed surface of the protective layer 1 is attached to the surface to be protected.

[0047] Furthermore, when the holding table 101 is attached to the head 203 , at least one of the holding table 101 and the electrostatic chuck table 202 may be heated in advance when the exposed surface of the protective layer 1 is attached to the protection target surface.

[0048] The first release liner 2 and the second release liner 3 are each attached to the protective layer 1 in order to prevent foreign matter from being attached to the protective layer 1 before being attached to an adherend.

[0049] Each of the first release liner 2 and the second release liner 3 includes an inner surface facing the protective layer 1 and an outer surface opposite to the inner surface.

[0050] The protective sheet 10 of the present embodiment is used by peeling off the first release liner 2 to expose one surface of the protective layer 1, and affixing the one surface to a surface to be protected of an adherend.

[0051] The protective sheet 10 of the present embodiment may be used by attaching one surface of the protective layer 1 to the protection target surface of an adherend, and then peeling off the second release liner 3 from the other surface of the protective layer 1 to expose the other surface of the protective layer 1 .

[0052] That is, the protective sheet 10 of the present embodiment can be used in a state where the other surface of the protective layer 1 is covered with the second release liner 3 after the first release liner 2 is peeled off to expose one surface of the protective layer 1, and the one surface is adhered to the protection target surface of the adherend, or the second release liner 3 can be peeled off from the other surface of the protective layer 1 to expose the other surface of the protective layer 1.

[0053] In the protection sheet 10 of the present embodiment, when one surface of the protection layer 1 is attached to the protection target surface of the adherend, at least the protection layer 1 is cut to have substantially the same size as the plane size of the adherend.

[0054] In the protective sheet 10 of the present embodiment, the peeling force of the first release liner 2 to the protective layer 1 is represented by P A , the peeling force of the second release liner 3 on the protective layer 1 is defined as PB When the peeling force P A and peeling force P B The following relationship is satisfied.

[0055] P A <P B ,

[0056] P B ≤2000mN / 25mm.

[0057] By making the peeling force P B When the force is 2000 mN / 25 mm or less, excessive adhesion of the second release liner 3 to the protective layer 1 can be suppressed.

[0058] Thus, after the first release liner 2 is peeled off to expose one surface of the protective layer 1, and the one surface is adhered to the protection target surface of the semiconductor wafer as the adherend, when the second release liner 3 is peeled off from the other surface of the protective layer 1, the second release liner 3 can be prevented from being peeled off in a state where a part of the protective layer 1 is attached.

[0059] That is, when the second release liner 3 is peeled off, unintentional separation of the protective layer 1 can be suppressed.

[0060] In addition, by making the peeling force P A and peeling force P B Satisfy P A <P B In this relationship, when the first release liner 2 is peeled off to expose one surface of the protective layer 1, the second release liner 3 can be prevented from rising on the other surface side of the protective layer 1.

[0061] It should be noted that from the viewpoint of properly balancing the adhesion force of the first release liner 2 to the protective layer 1 and the adhesion force of the second release liner 3 to the protective layer 1, the release force P is B and peeling force P A The ratio (P B / P A ) is preferably 1.1 or more, more preferably 1.2 or more.

[0062] Furthermore, the R is more preferably 2.0 or more, more preferably 3.0 or more, more preferably 4.0 or more, and more preferably 5.0 or more. The upper limit of the R is usually 100.

[0063] By setting the R to be 2.0 or more, the peeling force P can be sufficiently increased. A The value of peeling force P B Therefore, when the first release liner 2 is peeled off from the protective layer 1, it is possible to sufficiently suppress the protective layer 1 from lifting off from the second release liner 3.

[0064] In order to make the protective sheet 10 of this embodiment satisfy the above relationship, that is, P A <P B And P B ≤2000mN / 25mm, it is necessary to perform surface treatment on the inner surface of the first release liner 2 so that the inner surface of the first release liner 2 has an appropriate adhesion force to one surface of the protective layer 1, and on this basis, the inner surface of the second release liner 3 is surface treated so that the inner surface of the second release liner 3 has an appropriate adhesion force to the other surface of the protective layer 1.

[0065] In the protective sheet 10 of this embodiment, the peeling force P A It is preferably 5 mN / 25 mm or more, more preferably 10 mN / 25 mm or more, and further preferably 15 mN or more.

[0066] In the protective sheet 10 of the present embodiment, the peeling force P A It is preferably 1000 mN / 25 mm or less, more preferably 500 mN / 25 mm or less, further preferably 300 mN / 25 mm or less, and further preferably 200 mN / 25 mm or less.

[0067] In the protective sheet 10 of this embodiment, the peeling force P B It is preferably 70 mN / 25 mm or more, and more preferably 80 mN / 25 mm or more.

[0068] In the protective sheet 10 of the present embodiment, the peeling force P B It is preferably 1500 mN / 25 mm or less, and more preferably 1000 mN / 25 mm or less.

[0069] Peel force P A and peeling force P B The tensile strength can be measured using a tensile testing machine (trade name: "Autograph AG-IS", manufactured by Shimadzu Corporation).

[0070] The peel force P obtained using the tensile tester A A sample having a length of 150 mm and a width of 100 mm was cut out from the protective sheet 10 , and the second release liner 3 was peeled off from the sample to obtain a sample to be used as a test piece (hereinafter referred to as a first test piece).

[0071] In addition, the peeling force P obtained using the tensile tester is B A sample having a length of 150 mm and a width of 100 mm was cut out from the protective sheet 10 , and the first release liner 2 was peeled off from the sample to form a test piece (hereinafter referred to as a second test piece).

[0072] It should be noted that the peeling force P A and peeling force P B The unit "mN / 25 mm" is obtained by converting the value measured at a width of 100 mm to a width of 25 mm.

[0073] Peel force P A The measurement can be carried out by a 180° peel test using a tensile testing machine (for example, Autograph AG-IS, manufactured by Shimadzu Corporation) with a double-sided tape (for example, "No. 500", manufactured by Nitto Denko Corporation) sandwiched therebetween so that the exposed surface of the protective layer of the first specimen is in contact with the surface of the bare wafer.

[0074] It should be noted that the 180° peel test can be performed by stretching the first release liner 2 in the longitudinal direction under the conditions of a temperature of 23±2° C., a relative humidity of 55±5% RH, and a peeling speed of 300 mm / min.

[0075] In addition, the peel force P B In addition to replacing the first specimen with the second specimen and replacing the object stretched in the longitudinal direction with the second release liner 3, the peel force P can also be measured. A The determination of is carried out in the same manner.

[0076] In addition, the peel force P A and peeling force P B The value was set as the average value of the range with 30 mm as the starting point and 120 mm as the end point from the start of the measurement.

[0077] Examples of the surface treatment include a release treatment of the inner surface of the first release liner 2 and the inner surface of the second release liner 3 using a release agent.

[0078] As the release agent, any appropriate release agent may be used within a range not impairing the effects of the present invention.

[0079] Examples of such a release agent include ethylene-vinyl alcohol copolymers, fatty acid amide-based additives, low molecular weight polyolefin waxes, long chain alkyl-based additives, polymethylpentene, fluorine-based release agents, and silicone-based release agents.

[0080] As the ethylene-vinyl alcohol copolymer, for example, an ethylene-vinyl alcohol copolymer obtained by saponifying a copolymer of ethylene and at least one selected from the group consisting of vinyl acetate, vinyl formate, and vinyl propionate can be used.

[0081] Examples of the fatty acid amide additive include methylene bisstearic acid amide, ethylene bisstearic acid amide, ethylene bisoleic acid amide, N,N-dioleyl adipamide, and N-stearyl-N'-stearic acid amide (eg, N-stearyl-N'-stearyl urea).

[0082] These fatty acid amide-based additives may be used alone or in combination of two or more.

[0083] Examples of the low molecular weight polyolefin wax include low molecular weight products of polyethylene wax and low molecular weight products of polypropylene wax.

[0084] Examples of the long-chain alkyl-based additive include additives containing a long-chain alkyl side chain polymer.

[0085] Examples of commercially available products of such long-chain alkyl additives include PEELOIL (registered trademark) 1010 (manufactured by Ipposha Oils & Fats Industrial Co., Ltd.) and PEELOIL (registered trademark) 1010S (manufactured by Ipposha Oils & Fats Industrial Co., Ltd.).

[0086] Examples of the polymethylpentene include olefin copolymers based on 4-methyl-1-pentene.

[0087] Examples of commercially available products of such polymethylpentene include TPX (registered trademark) MX001 (manufactured by Mitsui Chemicals, Inc.) and TPX (registered trademark) 0004 (manufactured by Mitsui Chemicals, Inc.).

[0088] The fluorine-based release agent includes a fluorine-based resin.

[0089] Examples of the fluorine-based resins include PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride), PCTFE (polychlorotrifluoroethylene), PVF (polyvinyl fluoride), PFA (copolymer of tetrafluoroethylene and perfluoroalkoxyethylene), FEP (copolymer of tetrafluoroethylene and hexafluoropropylene), ETFE (copolymer of tetrafluoroethylene and ethylene), ECTFE (copolymer of chlorotrifluoroethylene and ethylene), terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride, and fluororubber.

[0090] These various fluorine-based resins may be used alone or in combination of two or more.

[0091] Examples of the silicone-based release agent include oil-based, baking-based, and emulsion-based release agents.

[0092] As the oil-type silicone release agent, liquid silicone compounds such as polyalkylsiloxane, modified polyalkylsiloxane, and resin modified with polyalkylsiloxane can be used.

[0093] Examples of the polyalkylsiloxane include dimethylsilicone in which all the side chains and terminals are methyl groups, methylphenylsilicone in which a part of the side chains is phenyl groups, and methylhydrogensilicone in which a part of the side chains is hydrogen.

[0094] In addition, dimethyl silicone, methylphenyl silicone, and methyl hydrogen silicone are all called linear silicones in which silicon (Si) is bonded to each other via oxygen (O) in a linear chain.

[0095] Examples of the modified polyalkylsiloxane include those obtained by introducing an organic group into a part of the side chain of the polysiloxane.

[0096] Examples of the organic group include a monoamine group, a diamine group, an amino group, an epoxy group, a carbinol group, a mercapto group, a carboxyl group, a polyether group, an aralkyl group, and a fluoroalkyl group.

[0097] It should be noted that among the modified polyalkylsiloxanes, those having reactive organic groups such as monoamine, diamine, amino, epoxy, methanol, mercapto, and carboxyl groups are referred to as reactive silicones, and those having non-reactive organic groups such as polyether, aralkyl, and fluoroaralkyl groups are referred to as non-reactive silicones.

[0098] Examples of the baked silicone release agent include silicone release agents prepared by blending a crosslinking agent such as a peroxide or a peroxide-containing silicone compound into a liquid silicone compound such as the polyalkylsiloxane, the modified polyalkylsiloxane, and a resin modified with a polyalkylsiloxane described above.

[0099] The emulsion-type silicone release agent is an aqueous dispersion of an organosilicon compound in which an organosilicon compound is dispersed in an aqueous medium.

[0100] The emulsion-type silicone release agent is also called a silicone-based water-dispersible resin.

[0101] Examples of the organic silicon compound include liquid organic silicon compounds such as the polyalkylsiloxane, modified polyalkylsiloxane, and resin modified with polyalkylsiloxane described above.

[0102] The organic silicon compound such as polyalkylsiloxane has thermal crosslinking property.

[0103] Furthermore, in such an organic silicon compound, the degree of the peeling force can be easily adjusted by adjusting the degree of thermal crosslinking.

[0104] Therefore, considering the above, it is preferable to use a silicone-based release agent among the various release agents described above.

[0105] In addition, a release agent is usually in a liquid state, and is used in a form applied to an object whose release properties are to be improved.

[0106] As a method for applying the release agent, various known coating methods can be adopted.

[0107] Examples of various known coating methods include roll coating methods such as gravure coating and reverse coating methods; rod coating methods such as a Meyer rod; spray coating methods; and air knife coating methods.

[0108] In addition, the above-mentioned release agent may be applied to the object after being diluted with an organic solvent (for example, ethyl methyl ketone) or the like.

[0109] Furthermore, the release agent is preferably applied so that the thickness after drying is in a range of 0.05 μm to 1 μm.

[0110] When the inner surface of the first release liner 2 and the inner surface of the second release liner 3 are subjected to a release treatment using the release agent, if the type of the release agent applied to the inner surface of the first release liner 2 is different from the type of the release agent applied to the inner surface of the second release liner 3, the release force P of the inner surface of the first release liner 2 to the protective layer 1 can be increased. A The peeling force P of the inner surface of the second release liner 3 to the protective layer 1 is B different.

[0111] Furthermore, when a silicone-based release agent is used as the release agent applied to the inner surface of the first release liner 2 and the release agent applied to the inner surface of the second release liner 3, as described above, if the degree of thermal crosslinking of the silicone-based release agent applied to the inner surface of the first release liner 2 and the degree of thermal crosslinking of the silicone-based release agent applied to the inner surface of the second release liner 3 are made different, the release force P of the inner surface of the first release liner 2 to the protective layer 1 can be made greater. A The peeling force P of the inner surface of the second release liner 3 to the protective layer 1 is B different.

[0112] In addition, the degree of thermal crosslinking can be adjusted by varying the heating temperature or the heating time.

[0113] Furthermore, when the release agent coated on the inner surface of the first release liner 2 and the release agent coated on the inner surface of the second release liner 3 are the same, the inner surface of the first release liner 2 and the inner surface of the second release liner 3 can be coated respectively with a release agent obtained by changing the dilution ratio using an organic solvent or the like. When the coating treatment is performed in this manner, the release force P of the inner surface of the first release liner 2 to the protective layer 1 can be increased. AThe peeling force P of the inner surface of the second release liner 3 to the protective layer 1 is B different.

[0114] Examples of the surface treatment include providing projections and depressions on the inner surface of the first release liner 2 (the surface on which the protective layer 1 is disposed) and the inner surface of the second release liner 3 by matte processing, embossing processing, or the like.

[0115] When the inner surfaces of first release liner 2 and second release liner 3 are provided with irregularities, the arithmetic mean roughness Ra of the inner surface of first release liner 2 is preferably 0.1 μm or more, more preferably 0.5 μm or more, and further preferably 1.0 μm or more.

[0116] Furthermore, the arithmetic mean roughness Ra of the inner surface of the first release liner 2 is preferably 50 μm or less, more preferably 30 μm or less, and further preferably 10 μm or less.

[0117] Furthermore, the arithmetic mean roughness Ra of the inner surface of the second release liner 3 is preferably 0.050 μm or more, more preferably 0.075 μm or more, and further preferably 0.100 μm or more.

[0118] The arithmetic mean roughness Ra of the inner surface of the first release liner 2 and the arithmetic mean roughness Ra of the inner surface of the second release liner 3 can be measured using a confocal laser microscope (for example, trade name “OPTELICS H300”, manufactured by Lasertec Corporation).

[0119] The larger the value of the arithmetic mean roughness Ra, the smaller the contact area between the inner surface of the first release liner 2 and the inner surface of the second release liner 3 and the surface of the protective layer 1 .

[0120] Therefore, the larger the value of the arithmetic mean roughness Ra, the greater the peeling force P of the inner surface of the first release liner 2 to the protective layer 1. A The peeling force P of the inner surface of the second release liner 3 to the protective layer 1 B That is, the first release liner 2 and the second release liner 3 can be easily peeled off from the protective layer 1 .

[0121] Therefore, by making the value of the arithmetic mean roughness Ra of the inner surface of the first release liner 2 larger than the value of the arithmetic mean roughness Ra of the inner surface of the second release liner 3, the release force P A <Peeling force P B relationship.

[0122] Furthermore, when the arithmetic mean roughness Ra of the inner surface of the first release liner 2 and the arithmetic mean roughness Ra of the inner surface of the second release liner 3 are within the above numerical ranges, it is easy to set the protective sheet 10 of the present embodiment to satisfy the above relational expressions.

[0123] As described above, the protective layer 1 is bonded to the protection target surface of the adherend for use.

[0124] Examples of the adherend include electronic components, and examples of the electronic components include semiconductor wafers.

[0125] Examples of the semiconductor wafer include a semiconductor wafer having regions divided into a grid shape (hereinafter also referred to as grid-shaped divided regions) formed on one surface side, and a circuit pattern is formed in each of the grid-shaped divided regions and an electrode portion is arranged.

[0126] When the electronic component is a semiconductor wafer as described above, the protective layer 1 is used by being attached to one surface of the semiconductor wafer.

[0127] In this way, by adhering the protective layer 1 to one surface of the semiconductor wafer, when the semiconductor wafer is divided (cut) to obtain a plurality of semiconductor chips, it is possible to prevent fine foreign matter produced by pulverization of a portion of the semiconductor wafer near the dividing portion (cutting portion) and the like from adhering to each circuit pattern formed on the one surface (circuit pattern formed in each of the grid-shaped divided areas) and each electrode portion arranged on the one surface (electrode portion arranged in each of the grid-shaped divided areas).

[0128] The second release liner 3 may be in the form of an elongated tape having a long dimension and a short dimension.

[0129] The protective sheet 10 includes a strip-shaped second release liner 3 and a plurality of protective layers 1 having the same shape as the protection target surface. The plurality of protective layers 1 may be arranged in the longitudinal direction of the second release liner 3 or a certain interval may be provided between adjacent protective layers 1 in the longitudinal direction.

[0130] In this case, the first release liner 2 may be in a tape shape similarly to the second release liner 3 .

[0131] The second release liner 3 may be larger than the protective layer 1 in both the longitudinal direction and the transverse direction.

[0132] That is, in the protective sheet 10 , the second release liner 3 may protrude outward from the outer peripheral edge of the protective layer 1 , and the second release liner 3 may protrude over the entire circumference of the protective layer 1 .

[0133] The protection sheet 10 can be produced, for example, in the following manner.

[0134] (1) Using an applicator or the like, a water-soluble resin composition containing a water-soluble polymer compound together with the remaining liquid component is applied to the second release liner 3 to a predetermined thickness (eg, 5 μm to 30 μm).

[0135] (2) The applied water-soluble resin composition is dried at a predetermined temperature for a predetermined time (eg, 110° C. for 2 minutes). Thus, a protective layer 1 containing a water-soluble polymer compound is formed on the second release liner 3 .

[0136] (3) The first release liner 2 is bonded to the surface of the protective layer 1 opposite to the surface on which the second release liner 3 is disposed (the exposed surface of the protective layer 1 ) at a predetermined temperature (eg, 70° C.).

[0137] In the protective sheet 10 of this embodiment, the protective layer 1 is preferably produced using a composition in which the water-soluble polymer compound is dispersed in water (hereinafter referred to as a protective layer-forming composition) as a water-soluble resin composition containing the water-soluble polymer compound and the remaining liquid component.

[0138] In the protective layer forming composition, the water-soluble polymer is preferably contained in an amount of 5 parts by mass or more and 80 parts by mass or less, more preferably 10 parts by mass or more and 70 parts by mass or less, and further preferably 15 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of water.

[0139] Furthermore, in the protective layer-forming composition, it is preferred that the water-soluble polymer compound is dissolved in water.

[0140] In addition, in the protective layer forming composition, the water-soluble polymer compound can be dissolved in water by treating at a temperature of 20° C. to 90° C.

[0141] Furthermore, the viscosity of the protective layer-forming composition at 25° C. is preferably 0.03 Pa·s or more, more preferably 0.05 Pa·s or more, and even more preferably 0.1 Pa·s or more.

[0142] By setting the viscosity at 25° C. to be equal to or higher than the above lower limit, when the protective layer-forming composition is applied onto the first release liner 2 to form the protective layer 1 on the first release liner 2 , the thickness of the protective layer 1 can be prevented from easily varying.

[0143] Furthermore, the viscosity of the protective layer-forming composition at 25° C. is preferably 15 Pa·s or less, more preferably 10 Pa·s or less, and even more preferably 5 Pa·s or less.

[0144] By setting the viscosity at 25° C. to be equal to or less than the above upper limit, the coating properties when the protective layer-forming composition is applied onto the first release liner 2 can be improved.

[0145] The viscosity of the protective layer forming composition at 25° C. can be measured by using a digital viscometer (product name “DV-I Prime”) manufactured by Eiko Seiki Co., Ltd. as a measuring device and using an LV-3 spindle at a rotation speed of 50 rpm.

[0146] Examples of the water-soluble polymer compound include polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), water-soluble polyester (PES), and polyethylene oxide (PEO).

[0147] As the water-soluble polymer compound, polyvinyl alcohol, polyvinyl pyrrolidone, water-soluble polyester, polyethylene oxide, etc. may be used alone or in combination of two or more thereof.

[0148] As the water-soluble polymer compound, at least one selected from the group consisting of polyvinyl alcohol, water-soluble polyester and polyethylene oxide is preferably used, and polyvinyl alcohol is more preferably used.

[0149] The saponification degree of the polyvinyl alcohol is preferably 50 or more and 98 or less, and more preferably 60 or more and 90 or less.

[0150] When the degree of saponification is within the above numerical range, the polyvinyl alcohol can exhibit sufficient water solubility. In addition, when the protective layer forming composition contains the polyvinyl alcohol, the protective layer forming composition can be applied to the first release liner 2 with good workability.

[0151] The saponification degree of the polyvinyl alcohol can be determined by proton nuclear magnetic resonance spectroscopy ( 1 H-NMR measurement method).

[0152] When the measurement sample contains an additive and a peak derived from the additive overlaps with a peak for calculating the saponification degree, the saponification degree of the polyvinyl alcohol is measured after the additive is separated by subjecting the measurement sample to methanol extraction or the like.

[0153] The saponification degree of the polyvinyl alcohol can be measured under the following conditions.

[0154] <Measurement conditions>

[0155] Analytical equipment FT-NMR: Bruker Biospin, AVANCE III-400.

[0156] Observation frequency 400MHz(1H).

[0157] The test solvent is heavy water or deuterated dimethyl sulfoxide (DMSO).

[0158] ·Measurement temperature: 80℃.

[0159] Chemical shift reference external standard TSP-d4 (0.00ppm) (for heavy water determination);

[0160] Measurement solvent (2.50 ppm) (in the case of measurement with deuterated DMSO).

[0161] It should be noted that the saponification degree of the polyvinyl alcohol is calculated based on the following formula using the peak of the methylene group derived from the vinyl alcohol unit (VOH) (heavy water; 2.0 to 1.0 ppm, deuterated DMSO; 1.9 to 1.0 ppm) and the peak of the acetyl group derived from the vinyl acetate unit (VAc) (heavy water; around 2.1 ppm, deuterated DMSO; around 2.0 ppm).

[0162] In the following formula, [VOH(-CH2)-] refers to the intensity of the peak derived from -CH2- in the vinyl alcohol unit, and [VAc(CH3CO-)] refers to the intensity of the peak derived from CH3CO- in the vinyl acetate unit.

[0163]

[0164] The average degree of polymerization of the polyvinyl alcohol is preferably 100 or more and 1000 or less, and more preferably 100 or more and 800 or less.

[0165] When the average degree of polymerization is within the above numerical range, the polyvinyl alcohol can exhibit sufficient water solubility. In addition, when the protective layer forming composition contains the polyvinyl alcohol, the protective layer forming composition can be applied to the first release liner 2 with good workability.

[0166] The average degree of polymerization of the polyvinyl alcohol can be measured by aqueous GPC (Gel Permeation Chromatography).

[0167] The average degree of polymerization of the polyvinyl alcohol can be measured under the following conditions.

[0168] <Measurement conditions>

[0169] ·Analytical device: Agilent, 1260 Infinity.

[0170] ·Chromatographic columns: TSKgel G6000PWXL (manufactured by TOSOH Corporation) and TSKgel G3000PWXL (manufactured by TOSOH Corporation).

[0171] The above two chromatographic columns are connected in series.

[0172] Column temperature: 40°C.

[0173] · Eluent: 0.2 M sodium nitrate aqueous solution.

[0174] Injection volume: 100 μL.

[0175] · Detector Differential Refractometer (RI).

[0176] Standard samples: PEG standard sample and PVA standard sample.

[0177] The specific measurement was performed as follows.

[0178] (1) The mass average molecular weight Mw of the sample to be measured (PVA) and the PVA standard sample are calculated by GPC measurement using a PEG standard sample. The average degree of polymerization of the PVA standard sample is known.

[0179] (2) A calibration curve is prepared using the average degree of polymerization of the PVA standard sample and the calculated mass average molecular weight Mw of the PVA standard sample.

[0180] (3) Using the prepared calibration curve, the average degree of polymerization of the sample (PVA) to be measured is determined from the mass average molecular weight Mw of the sample (PVA) to be measured.

[0181] When the polyvinyl alcohol is used as the water-soluble polymer, a plurality of polyvinyl alcohols having different saponification degrees may be used in combination, or a plurality of polyvinyl alcohols having different average polymerization degrees may be used in combination.

[0182] The water-soluble polyester has a residue of a polycarboxylic acid and a residue of a polyol.

[0183] The water-soluble polyester is, for example, a polymerization product of monomer components including a polycarboxylic acid component and a polyol component.

[0184] It should be noted that the water-soluble polyester is water-soluble based on common technical knowledge.

[0185] The water-soluble polyester preferably satisfies at least one of the following (1) to (4).

[0186] (1) When water at room temperature (23±2° C.) was sprayed in a mist form at a spray pressure of 0.005 MPa on the entire surface of a film having a thickness of 20 μm formed of the water-soluble polyester for 20 minutes, the film was completely dissolved in the water.

[0187] (2) When water at 50° C. was sprayed in a mist form at a spray pressure of 0.005 MPa for 10 minutes on the entire surface of a film having a thickness of 20 μm formed of the water-soluble polyester, the film was completely dissolved in the water.

[0188] (3) When the water-soluble polyester and water at room temperature are mixed in a mass ratio of water-soluble polyester:water at room temperature=1:5 to obtain a mixed solution, and the mixed solution is irradiated with ultrasonic waves for 20 minutes, the water-soluble polyester is completely dissolved in the water.

[0189] (4) When the water-soluble polyester and 50°C water are mixed at a mass ratio of water-soluble polyester:50°C water=1:5 to obtain a mixed solution, and the mixed solution is irradiated with ultrasonic waves for 10 minutes, the water-soluble polyester is completely dissolved in the water.

[0190] The thickness of the protective layer 1 is preferably 2 μm or more and 70 μm or less, more preferably 3 μm or more and 50 μm or less, and further preferably 5 μm or more and 40 μm or less.

[0191] The thickness of the protective layer 1 can be obtained, for example, by measuring the thickness at five randomly selected points using a micrometer (manufactured by PEACOCK, Model R-205) and calculating the arithmetic average of these thicknesses.

[0192] As the first release liner 2 , for example, there can be mentioned a resin sheet produced using a resin such as polyethylene terephthalate (PET).

[0193] When the first release liner 2 is composed of the above-mentioned resin sheet, in order to appropriately adjust the adhesion force with the protective layer 1, at least the surface of the resin sheet that is to be bonded to the protective layer 1 may be subjected to the surface treatment as described above.

[0194] Moreover, as the second release liner 3 , similarly to the first release liner 2 , for example, a resin sheet produced using a resin such as polyethylene terephthalate (PET) can be cited.

[0195] When the second release liner 3 is composed of the above-mentioned resin sheet, in order to appropriately adjust the adhesion force with the protective layer 1 , at least the surface of the resin sheet that is to be bonded to the protective layer 1 may be subjected to the surface treatment as described above.

[0196] When the thickness of the first release liner 2 is set to T A , the thickness of the second release liner 3 is set to T BWhen the thickness T A and thickness T B It is preferable that the following relationship is satisfied.

[0197] T A <T B ,

[0198] 35μm<T B <80μm.

[0199] Generally, the thicker the release liner is, the higher its toughness (bending rigidity) is.

[0200] Furthermore, the higher the toughness strength of the release liner is, the less likely it is to bend in the thickness direction.

[0201] Here, as described above, one surface of the protective layer 1 exposed by peeling off the first release liner 2 is bonded to the protection target surface of the adherend such as a semiconductor wafer.

[0202] Then, the first release liner 2 is peeled off from one surface of the protective layer 1 by an external force such as suction force being applied from the outside (the side where the protective layer 1 is not arranged).

[0203] In such a case, the first release liner 2 is bent due to suction or the like, and a part of the first release liner 2 is lifted from one surface of the protective layer 1 due to the bending.

[0204] Then, the first release liner 2 is peeled off from one surface of the protective layer 1 with the lifted portion as a base point.

[0205] As described above, when first release liner 2 is peeled off from one surface of protective layer 1, second release liner 3 is easily bent toward the inside (the side where protective layer 1 is arranged), and second release liner 3 is lifted from the other surface of protective layer 1, which is not preferable.

[0206] Therefore, the thickness T of the first release liner 2 is A and the thickness T of the second release liner 3 B As mentioned above, it is preferred to satisfy T A <T B The relationship formula.

[0207] Furthermore, after one surface of the protective layer 1 is bonded to the surface to be protected, the second release liner 3 is usually peeled off from the other surface of the protective layer 1 .

[0208] Therefore, from the viewpoint of facilitating the removal of the second release liner 3 after the one surface of the protective layer 1 is attached to the surface to be protected, the thickness T of the second release liner 3 is B As described above, it is preferable to satisfy 35 μm<T B <80μm.

[0209] Thus, the second release liner 3 can have appropriate toughness strength, so when the second release liner 3 is peeled off from the other surface of the protective layer 1, the second release liner 3 can be prevented from being peeled off with a part of the protective layer 1 attached, that is, unintentional separation can be prevented.

[0210] Furthermore, by making the thickness T of the first release liner 2 A and the thickness T of the second release liner 3 B On the contrary, when the protective sheet 10 is visually confirmed from the side, the first release liner 2 and the second release liner 3 are easily distinguished.

[0211] Thickness T of the first release liner 2 A The thickness may be 15 μm or more, 20 μm or more, or 25 μm or less.

[0212] In addition, the thickness T of the first release liner 2 is A It may be less than 40 μm, or may be less than 35 μm.

[0213] Furthermore, the thickness T of the second release liner 3 is B The thickness may be 40 μm or more, 45 μm or more, 50 μm or more, or 60 μm or more.

[0214] In addition, the thickness T of the second release liner 3 is B The thickness may be 75 μm or less, or 70 μm or less.

[0215] The thickness of the first release liner 2 and the second release liner 3 can be determined in the same manner as the thickness of the protective layer 1 .

[0216] From the viewpoint of making it easy to visually distinguish between the first release liner 2 and the second release liner 3 , the first release liner 2 and the second release liner 3 may have different colors.

[0217] For example, the first release liner 2 and the second release liner 3 may be colored in black and white, respectively, to improve visual distinction between the first release liner 2 and the second release liner 3 .

[0218] Furthermore, when both the first release liner 2 and the second release liner 3 are colorless and transparent, one of the first release liner 2 or the second release liner 3 may be colored to improve the distinguishability of the first release liner 2 and the second release liner 3 .

[0219] As the coloring agent for coloring the first release liner 2 and the second release liner 3 , various known coloring agents can be used.

[0220] Examples of the colorant include dyes and pigments.

[0221] It should be noted that a dye refers to a colorant having a property of being soluble in water, an organic solvent, or the like, and a pigment refers to a colorant having a property of being insoluble in water, an organic solvent, or the like.

[0222] Matters disclosed by this specification include the following. (1)

[0224] A protective sheet comprising: a protective layer; a first release liner disposed on one surface of the protective layer; and a second release liner disposed on the other surface of the protective layer, wherein the protective layer comprises a water-soluble polymer compound, and when the release force of the first release liner on the protective layer is set to P A , the peeling force of the second release liner on the protective layer is set to P B When the peeling force P A and peeling force P B Satisfies the following relationship: P A <P B .

[0225] According to the above configuration, it is possible to sufficiently achieve both suppression of the occurrence of warping of the protective layer from the other release sheet when peeling off one release sheet and suppression of unintentional separation of the protective layer. (2)

[0227] The protective sheet according to the above (1), wherein, when the thickness of the first release liner is T A , the thickness of the second release liner is set to T B When the thickness T A and thickness T B Satisfies the following relationship: T A <T B ; 35μm<T B <80μm.

[0228] According to the above configuration, it is possible to more fully achieve both suppression of the protective layer from being lifted from the other release sheet when the one release sheet is peeled off and suppression of the protective layer from being unintentionally separated.

[0229] In addition, it is easy to visually distinguish one release sheet from the other release sheet.

[0230] It should be noted that the protection sheet of the present invention is not limited to the above-mentioned embodiments. In addition, the protection sheet of the present invention is not limited to the above-mentioned effects. The protection sheet of the present invention can be modified in various ways without departing from the scope of the present invention.

[0231] Example

[0232] Next, the present invention will be described in more detail with reference to the following examples. The following examples are provided to further illustrate the present invention in detail, but are not intended to limit the scope of the present invention.

[0233] [Example 1]

[0234] An aqueous dispersion solution was prepared in a container by dispersing polyvinyl alcohol (degree of saponification: 65, average degree of polymerization: 240) in water.

[0235] In addition, polyvinyl alcohol is also referred to as PVA hereinafter.

[0236] Next, the container containing the aqueous dispersion was placed in a water bath at 90° C., and the aqueous dispersion was stirred to dissolve PVA in water, thereby obtaining a PVA dissolved composition.

[0237] Next, the PVA dissolving composition was applied to a release-treated surface of a second release liner (trade name "DIAFOIL MRV75" manufactured by MITSUBISHI CHEMICAL, thickness 75 μm) having a silicone release-treated surface (hereinafter also referred to as silicone release-treated surface) with a thickness of 5 μm using an applicator.

[0238] Next, the second release liner coated with the PVA dissolved composition was dried at 110° C. for 2 minutes, thereby forming a protective layer on the second release liner.

[0239] Next, a first release liner having a silicone release-treated surface (trade name "DIAFOIL MRA25" manufactured by MITSUBISHI CHEMICAL, thickness 25 μm) was laminated on the protective layer to obtain a laminate having the second release liner, the protective layer and the first release liner laminated in this order, and then the laminate was heat-treated at 70°C.

[0240] It should be noted that, in the first release liner, the silicone release-treated surface is overlapped with the exposed surface of the protective layer.

[0241] Thus, the protective sheet of Example 1 was obtained.

[0242] In addition, hereinafter, DIAFOIL MRV75 is simply described as “MRV75”, and DIAFOIL MRA25 is simply described as “MRA25”.

[0243] The saponification degree and average polymerization degree of the polyvinyl alcohol are measured according to the method described in the above embodiment.

[0244] [Example 2]

[0245] A protective sheet of Example 2 was obtained in the same manner as in Example 1 except that "CRISPER CN500-50" manufactured by Toyobo Co., Ltd. was used as the second release liner, "DIAFOIL MRA38" manufactured by Mitsubishi Chemical Co., Ltd. was used as the first release liner, and the thickness of the protective layer was set to 10 μm.

[0246] The second release liner CRISPER CN500-50 has a surface subjected to a release treatment using a non-silicone release agent containing no silicone compound (hereinafter also referred to as a non-silicone release treated surface) and has a thickness of 50 μm.

[0247] In addition, DIAFOIL MRA38 as the first release liner has a silicone release-treated surface similarly to the MRV75 and the MRA25, and has a thickness of 38 μm.

[0248] Furthermore, the silicone release-treated surface of the first release liner is bonded to one surface of the protective layer, and the non-silicone release-treated surface of the second release liner is bonded to the other surface of the protective layer.

[0249] In addition, hereinafter, CRISPER CN500-50 is simply described as “CN500-50”, and DIAFOIL MRA38 is simply described as “MRA38”.

[0250] [Example 3]

[0251] A protective sheet of Example 3 was obtained in the same manner as in Example 2 except that “CRISPER CN100-38” manufactured by Toyobo Co., Ltd. was used as the first release liner and the thickness of the protective layer was set to 30 μm.

[0252] It should be noted that CRISPER CN100-38 as the first release liner has a non-silicone release treated surface similarly to CRISPER CN500-50 and has a thickness of 38 μm.

[0253] In addition, hereinafter, CRISPER CN100-38 is simply described as “CN100-38”.

[0254] [Example 4]

[0255] A protective sheet of Example 4 was obtained in the same manner as in Example 3 except that "CRISPER CN100-38" manufactured by Toyobo Co., Ltd. was used as the second release liner and the thickness of the protective layer was set to 5 μm.

[0256] [Comparative Example 1]

[0257] A protective sheet of Comparative Example 1 was obtained in the same manner as in Example 1 except that “Lumirror (registered trademark) #38-S10” manufactured by TORAY was used as the first release liner, “Lumirror (registered trademark) #50-S10” manufactured by TORAY was used as the second release liner, and the thickness of the protective layer was set to 10 μm.

[0258] It should be noted that Lumirror (registered trademark) #38-S10 as the first release liner was not subjected to any release treatment and had a thickness of 38 μm.

[0259] Furthermore, Lumirror (registered trademark) #50-S10 as the second release liner was also not subjected to release treatment and had a thickness of 50 μm.

[0260] Furthermore, hereinafter, Lumirror (registered trademark) #38-S10 is simply described as “#38-S10”, and Lumirror (registered trademark) #50-S10 is simply described as “#50-S10”.

[0261] It should be noted that both "#38-S10" and "#50-S10" are polyester films.

[0262] [Comparative Example 2]

[0263] A protective sheet of Comparative Example 2 was obtained in the same manner as in Example 2 except that "DIAFOIL MRA50" (trade name) manufactured by MITSUBISHI CHEMICAL CO., LTD. was used as the second release liner.

[0264] It should be noted that DIAFOIL MRA50 as the second release liner has a silicone release-treated surface similarly to the MRV75, the MRA25, and the MRA38, and has a thickness of 50 μm.

[0265] In addition, DIAFOIL MRA50 is hereinafter referred to as simply “MRA50”.

[0266] <Peel force>

[0267] For each protective sheet, the peeling force P of the first release liner to the protective layer was measured. A and the peeling force P of the second release liner to the protective layer B .

[0268] Peel force P A and peeling force P BThe measurement is carried out according to the method described in the above-mentioned embodiment.

[0269] In the following Table 1, the measured peeling force P is shown for each protective sheet. A and peeling force P B result.

[0270] In addition, in the following Table 1, the peeling force P B and peeling force P A The ratio of R.

[0271] <Unintentional separation of protective layer>

[0272] The surface of the release liner peeled from the protective layer during the measurement of the peeling force was visually observed, and the unintentional separation of the protective layer was evaluated according to the following criteria.

[0273] Good: No protective layer was visually confirmed on the surface of the release liner.

[0274] Unacceptable: A portion of the protective layer was visually observed on the surface of the release liner.

[0275] The following Table 1 shows the results of evaluating the unintentional separation of the protective layer.

[0276] <Warping of protective layer>

[0277] The protective sheet of each example was left to stand for 24 hours in an environment of a temperature of 23±2° C. and a relative humidity of 55±5% RH, and then visually observed to see whether lifting of the protective layer from each release liner (the first release liner and the second release liner) was confirmed.

[0278] Then, the lifting of the protective layer was evaluated according to the following criteria.

[0279] Excellent: No lifting of the protective layer from the first release liner or the second release liner was observed visually. In addition, even after the protective sheet was exposed to the above environment (temperature 23±2°C and relative humidity 55±5%RH) for 24 hours, the first release liner was peeled off from the protective layer by hand, and no lifting of the protective layer from the second release liner was observed visually.

[0280] Good: No lifting of the protective layer from the first release liner or the second release liner was observed visually. On the other hand, after the protective sheet was exposed to the above environment for 24 hours, when the first release liner was peeled off from the protective layer by hand, slight lifting of the protective layer from the second release liner was observed visually.

[0281] Unacceptable: The protective layer was visually confirmed to be lifted from at least one of the first release liner and the second release liner.

[0282] The following Table 1 shows the results of evaluating the lifting of the protective layer.

[0283] [Table 1]

[0284]

[0285] According to Table 1, as for the protective sheets of each embodiment, the peeling force P of the first release liner to the protective layer is A and the peeling force P of the second release liner to the protective layer B , satisfying P A <P B And P B The protective sheet with a relation of ≤2000mN / 25mm can take into account both suppressing the unintentional separation of the protective layer and suppressing the warping of the protective layer.

[0286] On the other hand, it is understood that the protective sheets that do not satisfy the above relationship, such as the protective sheets of the comparative examples, cannot achieve both suppression of unintentional separation of the protective layer and suppression of warping of the protective layer.

[0287] Furthermore, it is found that when the evaluation results of the lifting of the protective layer of the protective sheets of Examples 1 to 3 having a comparison R of 2.0 or more are compared with the evaluation results of the lifting of the protective layer of the protective sheets of Comparative Examples having a comparison R of less than 2.0, particularly good results are obtained in the protective sheets of Examples 1 to 3.

[0288] It should be noted that in the protective sheet of Comparative Example 1, the peeling force P A The value and peel force P B The value of was too high, so the evaluation of the lifting of the protective layer could not be performed.

[0289] Therefore, regarding the protective sheet of Comparative Example 1, the evaluation of the lifting of the protective layer was described as “cannot be evaluated” in Table 1.

[0290] Description of Reference Numerals

[0291] 1: protective layer; 2: first release liner; 3: second release liner; 10: protective sheet.

Claims

1. A protective sheet, wherein: The protective sheet has: Protective layer; A first release liner is disposed on a surface of the protective layer; and A second release liner is disposed on the other surface of the protective layer, The protective layer comprises a water-soluble polymer compound, When the peeling force of the first release liner on the protective layer is set to P A , the peeling force of the second release liner on the protective layer is set to P B hour, Peel force P A and peeling force P B Satisfies the following relationship: P A <P B 、 P B ≤2000mN / 25mm。 2. The protective sheet according to claim 1, wherein: When the thickness of the first release liner is set to T A , the thickness of the second release liner is set to T B hour, Thickness T A and thickness T B Satisfies the following relationship: T A <T B 、 35μm<T B <80μm。

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