Protective sheet

Abstract

The protective sheet of the present invention comprises: a protective layer; a first release paper disposed on one surface of the protective layer; and a second release paper disposed on the other surface of the aforementioned protective layer; wherein the aforementioned protective layer contains a water-soluble polymer compound; when the peel force of the aforementioned first release paper on the aforementioned protective layer is PA and the peel force of the aforementioned second release paper on the aforementioned protective layer is PB, the peel forces PA and PB satisfy the following relationship: PA<P BP B≦2000mN / 25mm.

Description

Technical Field

[0001] The present invention relates to a protective sheet. Prior Art

[0002] Conventionally, it is known to use a protective sheet having adhesive properties for preventing foreign matter from adhering to electronic components such as semiconductor elements such as semiconductor chips or liquid crystal display devices during the manufacture of the electronic components (e.g., Patent Document 1 below). Patent Document 1 below discloses a protective sheet comprising a protective layer formed of a resin composition containing an oxyalkylene group-containing polyvinyl alcohol-based resin, and two release sheets disposed on both sides of the protective layer.

[0003] Furthermore, in the manufacture of the above-mentioned electronic components, the manufacture of semiconductor chips is usually carried out by dividing (cutting) a semiconductor wafer (for example, the following Patent Document 2). For example, the following patent document 2 discloses a method for manufacturing a semiconductor chip using the following method: (1) A plurality of predetermined dividing lines are formed on one surface side of a silicon wafer to form a grid pattern. (2) While forming circuit patterns in each of the grid-shaped regions (hereinafter also referred to as grid-shaped divided regions) divided by the plurality of predetermined dividing lines, an electrode portion is arranged. Thus, a semiconductor wafer for obtaining a semiconductor chip is manufactured. (3) The semiconductor wafer is divided (cut) along the aforementioned plurality of predetermined dividing lines, in other words, the semiconductor wafer is divided (cut) according to each of the aforementioned grid-shaped divided areas to obtain a plurality of semiconductor chips. [Prior Art Literature] [Patent Document]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2021-161735 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-119670 Summary of the Invention

[0005] [Technical Problems to be Solved by the Invention]

[0006] However, as described above, when a semiconductor wafer is divided (cut) to obtain a plurality of semiconductor chips, a portion of the semiconductor wafer near the divided portion (cut portion) may be powdered, thereby generating fine foreign matter. Furthermore, when such fine foreign matter adheres to one surface side of the semiconductor chip (the side where the circuit pattern is formed), there is a concern that the operational reliability of the circuit included in the circuit pattern formed on the one surface side may be reduced, which is not ideal. Therefore, the manufacture of semiconductor chips is often carried out by laminating the aforementioned protective layer of the aforementioned protective sheet to one surface side (the side where the circuit pattern is formed) of the aforementioned semiconductor wafer.

[0007] When the protective layer is attached to one surface of the semiconductor wafer using the protective sheet having the protective layer containing a water-soluble polymer compound such as a polyvinyl alcohol-based resin containing an oxyalkylene group and two release sheets disposed on both sides of the protective layer, one of the two release sheets needs to be peeled off from the protective sheet to expose the protective layer on the surface.

[0008] The release sheet on the one side is peeled off from the protective layer by applying an external force such as an attractive force from the outer side of the release sheet on that side (the side not provided with the protective layer). However, when the release sheet on the one side is peeled off from the protective layer, the protective layer may float off the release sheet on the other side of the two release sheets. Furthermore, when the protective layer is peeled off from the release sheet on one side, there are cases where the protective layer does not lift off from the other side, but the release sheet on the other side is peeled off with a portion of the protective layer still attached. In other words, there are cases where the protective layer is undesirably peeled off. In other words, there are cases where cohesive failure, etc., occurs in the protective layer.

[0009] However, for protective sheets having release sheets on both sides of the protective layer, it is difficult to say that sufficient research has been conducted to achieve a good balance between suppressing the occurrence of the protective layer lifting off the release sheet on one side when peeling the release sheet on the other side and suppressing the undesired peeling of the protective layer.

[0010] Therefore, the object of the present invention is to provide a protective sheet having release sheets on both sides of a protective layer, which can fully balance the prevention of the protective layer from floating off the release sheet on the other side when the release sheet on one side is peeled off, and the prevention of undesired peeling of the protective layer. [Technical means]

[0011] The protective sheet of the present invention comprises: protective layer; a first release paper disposed on one surface of the protective layer; and The second release paper is disposed on the other surface of the protective layer; and The aforementioned protective layer contains a water-soluble polymer compound; When the peeling force of the first release paper on the protective layer is PA and the peeling force of the second release paper on the protective layer is PB, The peeling force PA and the peeling force PB satisfy the following relationship: PA <P B PB≦2000mN / 25mm. Simple diagram description

[0012] FIG1 is a schematic cross-sectional view showing the structure of a protective sheet according to one embodiment of the present invention. FIG2 is a cross-sectional view showing the structure of a mounting device for attaching a protective layer of a protective sheet to a surface to be protected of an electronic component such as a semiconductor wafer. Implementation Method

[0013] Hereinafter, one embodiment of the present invention will be described.

[0014] [Protective sheet] As shown in FIG. 1 , a protective sheet 10 according to an embodiment of the present invention comprises a protective layer 1 , a first release paper 2 disposed on one surface of the protective layer 1 , and a second release paper 3 disposed on the other surface of the protective layer 1 . Hereinafter, one embodiment of the present invention will be referred to as simply this embodiment. In the protective sheet 10 of this embodiment, the protective layer 1 contains a water-soluble polymer compound. That is, the protective layer 1 is water-soluble. On the other hand, the first release paper 2 and the second release paper 3 are water-insoluble.

[0015] As shown in FIG. 1 , in the protective sheet 10 of this embodiment, the protective layer 1 , the first release paper 2 , and the second release paper 3 have approximately the same size when viewed from above. Specifically, in one embodiment of the protective sheet 10, the inner surface of the first release paper 2 (the surface opposite to one surface of the protective layer) and one surface of the protective layer 1 overlap with each other in a manner that aligns their edges over approximately the entire area; and the inner surface of the second release paper 3 (the surface opposite to the other surface of the protective layer 1) and the other surface of the protective layer 1 overlap with each other in a manner that aligns their edges over approximately the entire area.

[0016] In the protective sheet 10 of this embodiment, the protective layer 1 has adhesiveness sufficient to adhere to an adherend. In the protective sheet 10 of this embodiment, the protective layer 1 is preferably adhesive (pressure-sensitive adhesive). The protective sheet 10 of this embodiment is used to attach the protective layer 1 to an adherend (eg, an electronic component such as a semiconductor wafer) to prevent foreign matter from adhering to the surface of the adherend during various treatments of the adherend.

[0017] In the protective sheet 10 of this embodiment, the protective layer 1 (more specifically, the exposed surface of the protective layer 1) is attached to the protection target surface of an electronic component such as a semiconductor wafer using, for example, a mounting device 200 as shown in FIG. 2 . As shown in FIG2 , the mounting device 200 comprises a chamber 201 , an electrostatic chuck 202 disposed at the bottom of the chamber 201 , a head 203 disposed in the chamber 201 and above the electrostatic chuck 202 , and a pump P for decompressing the interior of the chamber 201 . In the mounting device 200 , electronic components such as semiconductor wafers are mounted on the electrostatic chuck 202 , and the protective sheet 10 is mounted on the head 203 . In addition, in the mounting device 200, the protective sheet 10 and electronic components such as semiconductor wafers are respectively mounted on the head 203 and the electrostatic chuck 202 in a form facing the exposed surface of the protective layer 1 and the aforementioned protection object surface. Furthermore, as shown in FIG. 2 , when the holding platform 101 is mounted on the head 203 , the protective sheet 10 can also be mounted on the holding platform 101 .

[0018] When the up-down direction (vertical direction) is the Z-axis direction, the horizontal direction along the cut surface when the electrostatic chuck 202 and the head 203 are cut along a plane parallel to the Z-axis (the horizontal direction along the paper surface of Figure 2) is the X-axis direction, and the direction perpendicular to both the Z-axis and the X-axis (the direction perpendicular to the paper surface of Figure 2) is the Y-axis direction, the head 203 is moved toward at least one of the X-axis direction and the Y-axis direction, and then further moved toward the Z-axis direction, so that the exposed surface of the protective layer 1 mounted on the head 203 can be attached to the protection target surface of the electronic component such as the semiconductor wafer mounted on the electrostatic chuck 202.

[0019] When the holding platform 101 is not mounted on the head 203 and the exposed surface of the protective layer 1 is placed against the aforementioned surface to be protected, the electrostatic chuck 202 may be heated in advance. In addition, when the holding platform 101 is installed on the head 203 and the exposed surface of the protective layer 1 is attached to the aforementioned protection target surface, at least one of the holding platform 101 and the electrostatic suction cup 202 can be heated in advance.

[0020] The first release paper 2 and the second release paper 3 are respectively attached to the protective layer 1 in order to prevent foreign matter from adhering to the protective layer 1 before being attached to the adherend. The first release paper 2 and the second release paper 3 each include an inner surface facing the protective layer 1 and an outer surface opposite to the inner surface.

[0021] The protective sheet 10 of this embodiment is used by peeling off the first release paper 2 to expose one surface of the protective layer 1, and then sticking the surface to be protected on the adherend. The protective sheet 10 of this embodiment can also be used by attaching one surface of the protective layer 1 to the protection target surface of the adherend, and then peeling off the second release paper 3 from the other surface of the protective layer 1 to expose the other surface of the protective layer 1. That is, the protective sheet 10 of this embodiment can be used with the second release paper 3 covering the other surface of the protective layer 1 after peeling off the first release paper 2 to expose one surface of the protective layer 1, which is then attached to the protected surface of the adherend. Alternatively, the second release paper 3 can be peeled off from the other surface of the protective layer 1 to expose the other surface of the protective layer 1.

[0022] In the protective sheet 10 of this embodiment, when one surface of the protective layer 1 is attached to the protection target surface of the adherend, the protective layer 1 is at least cut to have a size that is approximately the same as the plane size of the adherend.

[0023] In the protective sheet 10 of this embodiment, when the peeling force of the first release paper 2 on the protective layer 1 is PA and the peeling force of the second release paper 3 on the protective layer 1 is PB, it is important that the peeling force PA and the peeling force PB satisfy the following relationship: PA <P B PB≦2000mN / 25mm.

[0024] By setting the peel force PB to be 2000 mN / 25 mm or less, the second release paper 3 can be prevented from being excessively adhered to the protective layer 1 . Thereby, when peeling off the first release paper 2 to expose one surface of the protective layer 1 and adhering the one surface to the surface to be protected of the semiconductor wafer as the adherend, when peeling off the second release paper 3 from the other surface of the protective layer 1, it is possible to suppress the case where the second release paper 3 is peeled off with a part of the protective layer 1 attached thereto. That is, when peeling off the second release paper 3, it is possible to suppress the case where the protective layer 1 is peeled off undesirably. In addition, by the relationship that the peeling force P A and the peeling force P B satisfy P A < P B, when peeling off the first release paper 2 to expose one surface of the protective layer 1, it is possible to suppress the case where the second release paper 3 floats on the other surface side of the protective layer 1. Also, from the viewpoint of appropriately balancing the adhesion force of the first release paper 2 to the protective layer 1 and the adhesion force of the second release paper 3 to the protective layer 1, as R which is the ratio of the peeling force P B to the peeling force P A (P B / P A), it is preferably 1.1 or more, more preferably 1.2 or more. In addition, the aforementioned R is more preferably 2.0 or more, more preferably 3.0 or more, more preferably 4.0 or more, more preferably 5.0 or more. The upper limit of the aforementioned R is usually 100. By the aforementioned R being 2.0 or more, a sufficient difference can be generated between the value of the peeling force P A and the value of the peeling force P B. Therefore, when peeling off the first release paper 2 from the protective layer 1, it is possible to sufficiently suppress the case where the protective layer 1 floats from the second release paper 3.

[0025] In order for the protective sheet 10 of the present embodiment to satisfy the above relational expressions, that is, to satisfy P A < P B and P B ≤ 2000 mN / 25 mm, it is necessary to perform a surface treatment on the inner surface of the first release paper 2 so that the inner surface of the first release paper 2 has an appropriate adhesion force to one surface of the protective layer 1, and then perform a surface treatment on the inner surface of the second release paper 3 so that the inner surface of the second release paper 3 has an appropriate adhesion force to the other surface of the protective layer 1.

[0026] In the protective sheet 10 of the present embodiment, the peeling force P A is preferably 5 mN / 25 mm or more, more preferably 10 mN / 25 mm or more, and even more preferably 15 mN or more. In addition, in the protective sheet 10 of the present embodiment, the peeling force P A is preferably 1000 mN / 25 mm or less, more preferably 500 mN / 25 mm or less, even more preferably 300 mN / 25 mm or less, and further preferably 200 mN / 25 mm or less.

[0027] In the protective sheet 10 of this embodiment, the peeling force PB is preferably 70 mN / 25 mm or more, and preferably 80 mN / 25 mm or more. Furthermore, in the protective sheet 10 of this embodiment, the peeling force PB is preferably 1500 mN / 25 mm or less, and more preferably 1000 mN / 25 mm or less.

[0028] The peel force PA and the peel force PB can be measured using a tensile testing machine (trade name: "Autograph AG-IS", manufactured by Shimadzu Corporation). Regarding the peel force PA using the aforementioned tensile tester, a sample having a length of 150 mm and a width of 100 mm was cut out from the protective sheet 10 and the sample after peeling off the second release paper 3 was used as a sample (hereinafter referred to as the first sample). In addition, regarding the peel force PB using the aforementioned tensile tester, a sample having a length of 150 mm and a width of 100 mm was cut out from the protective sheet 10 and the sample after peeling off the first release paper 2 was used as a sample (hereinafter referred to as the second sample). The unit of peel force PA and peel force PB is "mN / 25mm", which is the value measured at a width of 100mm converted to a width of 25mm.

[0029] The peel force PA can be measured by a 180° peel test using a tensile testing machine (e.g., "Autograph AG-IS," manufactured by Shimadzu Corporation) with the exposed surface of the protective layer of the first sample placed against the surface of the bare wafer, with double-sided tape (e.g., Nitto Denko Corporation's "No. 500" tape) sandwiched between the two. The 180° peel test can be performed by stretching the first release paper 2 in the longitudinal direction at a temperature of 23±2°C, a relative humidity of 55±5% RH, and a peeling speed of 300 mm / min. In addition, the measurement of the peel force PB can be carried out in the same manner as the measurement of the peel force PA, except that the second sample is used instead of the first sample and the object stretched in the longitudinal direction is replaced by the second release paper 3. The peel force PA and the peel force PB are the average values ​​of the values ​​in the range from 30 mm as the starting point to 120 mm as the end point from the start of the measurement.

[0030] As the surface treatment, for example, a release treatment may be performed on the inner surface of the first release paper 2 and the inner surface of the second release paper 3 using a release agent. As the aforementioned release agent, any appropriate release agent may be used within the range not impairing the effects of the present invention. Examples of such release agents 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.

[0031] 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.

[0032] Examples of the fatty acid amide additive include methylene bis-stearylamide, ethylene bis-stearylamide, ethylene bis-oleylamide, N,N-dioleyl adipamide, and N-stearyl-N'-stearylamide (e.g., N-stearyl-N'-stearyl urea). These fatty acid amide additives can be used alone or in combination of two or more.

[0033] Examples of the low molecular weight polyolefin wax include low molecular weight polyethylene wax products and low molecular weight polypropylene wax products.

[0034] Examples of the long-chain alkyl additive include those containing a long-chain alkyl side chain polymer. Examples of commercially available long-chain alkyl additives include Peeloil (registered trademark) 1010 (manufactured by Ippo-sha Oil & Fats Industry Co., Ltd.) and Peeloil (registered trademark) 1010S (manufactured by Ippo-sha Oil & Fats Industry Co., Ltd.).

[0035] Examples of the polymethylpentene include olefin copolymers based on 4-methyl-1-pentene. 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.).

[0036] The aforementioned fluorine-based stripping agent contains a fluorine-based resin. Examples of the fluorine-based resin 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), ternary copolymers of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride, and fluororubber. These various fluorine-based resins can be used alone or in combination of two or more.

[0037] Examples of the silicone-based release agent include oil-based, baking-based, and emulsion-based release agents.

[0038] As oil-type silicone strippers, liquid silicone compounds such as polyalkylsiloxane, modified polyalkylsiloxane, and resins modified with polyalkylsiloxane can be used.

[0039] Examples of the polyalkylsiloxane include dimethylsilicone in which all side chains and terminals are methyl groups, methylphenylsilicone in which a portion of the side chains are phenyl groups, and methylhydrogensilicone in which a portion of the side chains are hydrogen groups. Furthermore, dimethyl silicone, methylphenyl silicone, and methylhydrogen silicone are all ordinary silicones (straight silicones) in which silicon (Si) is bonded to each other via oxygen (O) in a straight chain.

[0040] Examples of the modified polyalkylsiloxane include those in which an organic group is introduced into a portion of the side chain of the polysiloxane. 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. Furthermore, the aforementioned modified polyalkylsiloxanes containing reactive organic groups such as monoamine, diamine, amino, epoxy, carbinol, mercapto, and carboxyl groups are referred to as reactive silicones; while the aforementioned modified polyalkylsiloxanes containing non-reactive organic groups such as polyether, aralkyl, and fluoroalkyl groups are referred to as non-reactive silicones.

[0041] Examples of baking-type silicone release agents include liquid silicone compounds such as the polyalkylsiloxanes described above, the modified polyalkylsiloxanes described above, and resins modified with polyalkylsiloxanes, combined with crosslinking agents such as peroxides or peroxide-containing silicone compounds.

[0042] Emulsion-type silicone stripping agent is an aqueous dispersion of silicone compounds dispersed in an aqueous medium. The aforementioned emulsion-type silicone stripping agent is also called a silicone-based water-dispersible resin. Examples of the silicone compound include the liquid silicone compounds such as the polyalkylsiloxanes, modified polyalkylsiloxanes, and resins modified with polyalkylsiloxanes described above.

[0043] The aforementioned silicone compounds such as polyalkylsiloxane are thermally cross-linkable. Furthermore, in such a silicone compound, the degree of peeling force can be easily adjusted by adjusting the degree of thermal crosslinking. Therefore, considering the above factors, among the various stripping agents mentioned above, it is ideal to use a silicone-based stripping agent.

[0044] Furthermore, release agents are usually in liquid form and are used by applying them to an object whose release properties are to be enhanced. As a method for applying the release agent, various well-known coating methods can be adopted. Examples of various well-known coating methods include roll coating methods such as gravure coating and reverse coating, rod coating methods such as Meyer bar coating, spray coating, and air knife coating. Furthermore, the above-mentioned stripping agent may be applied to the above-mentioned object after being diluted with an organic solvent (such as ethyl methyl ketone). Furthermore, the aforementioned release agent is preferably applied so that the thickness after drying is in the range of 0.05 μm to 1 μm.

[0045] When the release agent is used to release the inner surface of the first release liner 2 and the inner surface of the second release liner 3, the release force PA of the inner surface of the first release liner 2 against the protective layer 1 and the release force PB of the inner surface of the second release liner 3 against the protective layer 1 can be made different by simply using different types of release agent applied to the inner surface of the first release liner 2 and the inner surface of the second release liner 3. Furthermore, when a silicone release agent is used as the release agent applied to the inner surface of the first release liner 2 and the inner surface of the second release liner 3, as described above, by making the degree of thermal crosslinking of the silicone release agent applied to the inner surface of the first release liner 2 and the degree of thermal crosslinking of the silicone release agent applied to the inner surface of the second release liner 3 different, the release force PA of the inner surface of the first release liner 2 against the protective layer 1 and the release force PB of the inner surface of the second release liner 3 against the protective layer 1 can be made different. Furthermore, the degree of thermal crosslinking can be adjusted by varying the heating temperature or the heating time. Furthermore, when 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 are the same, the release agent can be applied at varying dilution ratios using an organic solvent or the like, and then applied to the inner surface of the first release liner 2 and the inner surface of the second release liner 3, respectively. This coating process can create a difference between the release force PA of the inner surface of the first release liner 2 and the release force PB of the inner surface of the second release liner 3.

[0046] In addition, examples of the surface treatment include providing concavities and convexities on the inner surface of the first release paper 2 (the surface on which the protective layer 1 is disposed) and the inner surface of the second release paper 3 by matte processing or embossing processing. When the inner surface of the first release paper 2 and the inner surface of the second release paper 3 are provided with projections and depressions, the arithmetic mean roughness Ra of the inner surface of the first release paper 2 is preferably not less than 0.1 μm, more preferably not less than 0.5 μm, and even more preferably not less than 1.0 μm. Furthermore, the arithmetic mean roughness Ra of the inner surface of the first release paper 2 is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 10 μm or less. Furthermore, the arithmetic mean roughness Ra of the inner surface of the second release paper 3 is preferably not less than 0.050 μm, more preferably not less than 0.075 μm, and even more preferably not less than 0.100 μm.

[0047] The arithmetic mean roughness Ra of the inner surface of the first release paper 2 and the arithmetic mean roughness Ra of the inner surface of the second release paper 3 can be measured using a conjugate laser microscope (eg, trade name "OPTELICS H300", manufactured by Lasertec Corporation).

[0048] The larger the value of the arithmetic mean roughness Ra is, the smaller the contact area between the inner surface of the first release paper 2 and the inner surface of the second release paper 3 and the surface of the protective layer 1 will be. Therefore, the greater the arithmetic mean roughness Ra, the smaller the peel force PA of the inner surface of the first release liner 2 against the protective layer 1, and the peel force PB of the inner surface of the second release liner 3 against the protective layer 1. In other words, the first and second release liner 2, 3 can be easily peeled from the protective layer 1. Therefore, by making the arithmetic mean roughness Ra of the inner surface of the first release paper 2 greater than the arithmetic mean roughness Ra of the inner surface of the second release paper 3, the relationship of peeling force PA < peeling force PB can be satisfied. In addition, by having the arithmetic mean roughness Ra of the inner surface of the first release paper 2 and the arithmetic mean roughness Ra of the inner surface of the second release paper 3 within the above numerical range, it is easy to make the protective sheet 10 of this embodiment satisfy the above-mentioned relationship expressions.

[0049] As described above, the protective layer 1 is applied to the surface to be protected of the adherend. Examples of the adhered body include electronic components, and examples of the electronic components include semiconductor wafers. As the aforementioned semiconductor wafer, a semiconductor wafer can be cited, which has a grid-divided area (hereinafter also referred to as a grid-divided area) formed on one surface side, and each of the grid-divided areas is formed with a circuit pattern and is configured with an electrode portion. 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. In this way, when the protective layer 1 is adhered to one surface of the aforementioned semiconductor wafer and the aforementioned semiconductor wafer is divided (cut) to obtain a plurality of semiconductor chips, fine foreign matter produced by the pulverization of a portion of the aforementioned semiconductor wafer near the dividing portion (cutting portion) can be suppressed from adhering to the circuit patterns formed on the aforementioned surface (the circuit patterns formed in each of the aforementioned grid-shaped divided areas) and the electrode portions arranged on the aforementioned surface (the electrode portions arranged in each of the aforementioned grid-shaped divided areas).

[0050] The second release paper 3 may also be in the form of a long strip with a long side and a short side. The protective sheet 10 may include a strip-shaped second release paper 3 and a plurality of protective layers 1 having the same shape as the protected surface. The plurality of protective layers 1 may be arranged in the longitudinal direction of the second release paper 3, or a certain interval may be set between adjacent protective layers 1 in the longitudinal direction. In addition, in this case, the first release paper 2 can also be in a strip shape like the second release paper 3.

[0051] The second release paper 3 may be larger than the protective layer 1 not only in the long side direction but also in the short side direction. That is, in the protective sheet 10 , the second release paper 3 may extend beyond the outer periphery of the protective layer 1 , and the extended portion of the second release paper 3 extends along the entire periphery of the protective layer 1 .

[0052] The protective sheet 10 can be made, for example, by the following method. (1) Using a coater or the like, a water-soluble resin composition containing a water-soluble polymer compound and excess liquid components is coated on the second release paper 3 to a specified thickness (e.g., 5 μm to 30 μm). (2) The coated water-soluble resin composition is dried at a specified temperature for a specified time (e.g., 110° C. for 2 minutes). Thus, a protective layer 1 containing a water-soluble polymer compound is formed on the second release paper 3. (3) In the protective layer 1, the first release paper 2 is bonded to the opposite side of the side where the second release paper 3 is arranged (the exposed side of the protective layer 1) at a predetermined temperature (for example, 70°C).

[0053] In the protective sheet 10 of this embodiment, the protective layer 1 is a water-soluble resin composition containing a water-soluble polymer compound and an excess liquid component, and is preferably made by dispersing the water-soluble polymer compound in water (hereinafter referred to as a protective layer forming composition). The protective layer-forming composition preferably contains 5 to 80 parts by mass of the water-soluble polymer compound per 100 parts by mass of water, more preferably 10 to 70 parts by mass, and even more preferably 15 to 60 parts by mass. Furthermore, in the protective layer forming composition, it is ideal that the water-soluble polymer compound is dissolved in water. Furthermore, in the protective layer forming composition, the water-soluble polymer compound may be dissolved in water by being treated at a temperature of 20 to 90°C. Furthermore, the viscosity of the protective layer forming composition at 25° C. is preferably 0.03 Pa·s or higher, more preferably 0.05 Pa·s or higher, and even more preferably 0.1 Pa·s or higher. By having a viscosity at 25° C. of at least the lower limit, when the protective layer forming composition is coated on the first release paper 2 to form the protective layer 1 on the first release paper 2 , the thickness of the protective layer 1 can be prevented from easily fluctuating. Furthermore, the protective layer forming composition preferably has a viscosity at 25° C. of 15 Pa·s or less, more preferably 10 Pa·s or less, and even more preferably 5 Pa·s or less. By setting the viscosity at 25° C. to be below the aforementioned upper limit, the coating properties of the protective layer forming composition when applied to the first release paper 2 can be improved. The viscosity of the protective layer-forming composition at 25°C was measured using a digital viscometer (product name "DV-I Prime") manufactured by Eikon Seiki Co., Ltd., using an LV-3 spindle at a rotation speed of 50 rpm.

[0054] Examples of the water-soluble polymer compound include polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), water-soluble polyester (PES), and polyethylene oxide (PEO). The aforementioned water-soluble polymer compound may be polyvinyl alcohol, polyvinyl pyrrolidone, water-soluble polyester, polyethylene oxide, etc., used alone or in combination of two or more thereof. As the water-soluble polymer compound, it is desirable to use at least one selected from the group consisting of polyvinyl alcohol, water-soluble polyester, and polyethylene oxide, and it is more desirable to use polyvinyl alcohol.

[0055] The polyvinyl alcohol preferably has a saponification degree of 50 or more and 98 or less, more preferably 60 or more and 90 or less. When the saponification degree is within the above numerical range, the polyvinyl alcohol can be sufficiently water-soluble, and when the protective layer forming composition contains the polyvinyl alcohol, the coating of the protective layer forming composition on the first release liner 2 can be carried out with good workability. The saponification degree of the polyvinyl alcohol can be measured by proton nuclear magnetic resonance spectroscopy ( 1H-NMR measurement method). Furthermore, when the measurement sample contains an additive and the peak originating from the additive overlaps with the peak used to calculate the saponification degree, the saponification degree of the polyvinyl alcohol is measured after the additive is separated from the measurement sample by methanol extraction or the like. The saponification degree of the aforementioned polyvinyl alcohol can be measured using the following conditions. <Measurement Conditions> Analytical equipment FT-NMR: Bruker Biospin, AVANCE III-400 Observation frequency 400MHz (1H) Determination of solvent heavy water or heavy dimethyl sulfoxide (heavy DMSO) ·Measurement temperature 80℃ Chemical shift reference external standard TSP-d4 (0.00 ppm) (for heavy water measurement) Measurement solvent (2.50 ppm) (for heavy DMSO measurement) The saponification degree of 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: 2.0-1.0 ppm, heavy DMSO: 1.9-1.0 ppm) and the peak of the acetyl group derived from the vinyl acetate unit (VAc) (heavy water: around 2.1 ppm, heavy DMSO: around 2.0 ppm). In the following formula, [VOH(-CH2-)] refers to the peak intensity of -CH2- derived from vinyl alcohol units; [Vac(CH3CO-)] refers to the peak intensity of CH3CO- derived from vinyl acetate units.

[0056] [Number 1]

[0057] The polyvinyl alcohol preferably has an average degree of polymerization of 100 to 1000, more preferably 100 to 800. By having an average degree of polymerization within the above numerical range, the polyvinyl alcohol can exhibit sufficient water solubility, and when the protective layer forming composition contains the polyvinyl alcohol, the protective layer forming composition can be coated on the first release paper 2 with good operability. The average degree of polymerization of the polyvinyl alcohol can be measured by aqueous gel permeation chromatography (GPC). The average degree of polymerization of the polyvinyl alcohol can be measured under the following conditions. <Measurement Conditions> Analytical equipment: Agilent, 1260 Infinity Columns: TSKgel G6000PWXL (manufactured by Tosoh Corporation) and TSKgel G3000PWXL (manufactured by Tosoh Corporation) The above two pipe columns are connected in series. Column temperature 40℃ ·Dissolution solution 0.2M sodium nitrate aqueous solution Injection volume 100μL Detector differential refractometer (RI) Standard samples: PEG standard samples and PVA standard samples The specific determination was carried out using the following method. (1) By GPC measurement using a PEG standard sample, the mass average molecular weight (Mw) of the sample being measured (PVA) and the PVA standard sample are calculated. The average degree of polymerization of the PVA standard sample is known. (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. (3) Using the prepared calibration curve, the average degree of polymerization of the sample (PVA) to be measured is calculated from the mass average molecular weight Mw of the sample (PVA) to be measured.

[0058] Furthermore, when the polyvinyl alcohol is used as the water-soluble polymer, a plurality of polyvinyl alcohols having different saponification degrees or a plurality of polyvinyl alcohols having different average polymerization degrees may be used in combination.

[0059] The water-soluble polyester has residues of polycarboxylic acids and residues of polyols. The water-soluble polyester is, for example, a polymerization product of monomer components containing a polycarboxylic acid component and a polyol component. Furthermore, the water-soluble polyester is water-soluble, which can be determined based on common technical knowledge.

[0060] The aforementioned water-soluble polyester preferably satisfies at least one of the following (1) to (4). (1) When the entire surface of a film with a thickness of 20 μm formed from the aforementioned water-soluble polyester is sprayed with water at room temperature (23±2°C) at a spray pressure of 0.005 mpA for 20 minutes, the film is completely dissolved in the water. (2) When the entire surface of a 20 μm thick film formed of the aforementioned water-soluble polyester was sprayed with 50°C water at a spray pressure of 0.005 mpA for 10 minutes, the film was completely dissolved in the water. (3) The water-soluble polyester and room temperature water are mixed at a mass ratio of water-soluble polyester:room temperature water = 1:5 to obtain a mixed solution. When the mixed solution is irradiated with ultrasonic waves for 20 minutes, the water-soluble polyester is completely dissolved in the water. (4) The water-soluble polyester and 50°C water are mixed in a mass ratio of 1:5 to obtain a mixed solution. When the mixed solution is irradiated with ultrasonic waves for 10 minutes, the water-soluble polyester is completely dissolved in the water.

[0061] The thickness of the protective layer 1 is preferably not less than 2 μm and not more than 70 μm, more preferably not less than 3 μm and not more than 50 μm, and even more preferably not less than 5 μm and not more than 40 μm. The thickness of the protective layer 1 can be determined by measuring the thickness at five randomly selected points using, for example, a needle-dial gauge (manufactured by PEACOCK, model R-205) and averaging these thicknesses.

[0062] Examples of the first release paper 2 include resin sheets made of resins such as polyethylene terephthalate (PET). When the first release paper 2 is formed of the resin sheet as described above, in order to properly adjust the adhesion with the protective layer 1, at least the surface of the resin sheet that contacts the protective layer 1 may be subjected to the surface treatment described above. In addition, as the second release paper 3, similar to the first release paper 2, for example, a resin sheet made of a resin such as polyethylene terephthalate (PET) can be cited. When the second release paper 3 is constituted by the resin sheet as described above, in the resin sheet, in order to appropriately adjust the adhesion force to the protective layer 1, at least the surface adhered to the protective layer 1 is subjected to the surface treatment as described above.

[0063] When the thickness of the first release paper 2 is TA and the thickness of the second release paper 3 is TB, the thickness TA and the thickness TB preferably satisfy the following relational expression: TA < TB 35 μm < TB < 80 μm.

[0064] For release paper, generally, the thicker the thickness, the higher the bending strength (flexural rigidity). Moreover, for release paper, the higher the elastic strength, the more difficult it is to bend in the thickness direction. Here, as described above, on the surface to be protected of an adherend such as a semiconductor wafer, one surface of the protective layer 1 exposed by peeling off the first release paper 2 is adhered. Moreover, the first release paper 2 is peeled off from one surface of the protective layer 1 by applying an external force such as an attractive force from the outside (the side where the protective layer 1 is not disposed). In the case as described above, when the first release paper 2 is bent due to attraction or the like, a part of the first release paper 2 floats up from one surface of the protective layer 1 due to this bending. Moreover, with this floating part as a starting point, the first release paper 2 can be peeled off from one surface of the protective layer 1. As described above, when peeling off the first release paper 2 from one surface of the protective layer 1, it is not desirable that the second release paper 3 also easily bends inward (the side where the protective layer 1 is disposed) and the second release paper 3 floats up from the other surface of the protective layer 1. Therefore, the thickness TA of the first release paper 2 and the thickness TB of the second release paper 3, as described above, preferably satisfy the relational expression TA < TB. In addition, after adhering one surface of the protective layer 1 to the surface to be protected, the second release paper 3 is usually peeled off from the other surface of the protective layer 1. Therefore, from the viewpoint that the second release paper 3 is easily peeled off after adhering one surface of the protective layer 1 to the surface to be protected, the thickness TB of the second release paper 3, as described above, preferably satisfies the relational expression 35 μm < TB < 80 μm. Thus, since the second release paper 3 can have appropriate elastic strength, when peeling the second release paper 3 from the other surface of the protective layer 1, the second release paper 3 can be prevented from being peeled off while being partially attached to the protective layer 1, that is, the occurrence of undesired peeling can be suppressed.

[0065] Furthermore, by making the thickness TA of the first release paper 2 and the thickness TB of the second release paper 3 different from each other, the first release paper 2 and the second release paper 3 can be easily distinguished when the protective sheet 10 is visually checked from the side.

[0066] The thickness TA of the first release paper 2 may be greater than 15 μm, greater than 20 μm, or less than 25 μm. In addition, the thickness TA of the first release paper 2 may be less than 40 μm, or may be less than 35 μm. Furthermore, the thickness TB of the second release paper 3 may be greater than 40 μm, greater than 45 μm, greater than 50 μm, or greater than 60 μm. In addition, the thickness TB of the second release paper 3 may be less than 75 μm, or less than 70 μm. The thickness of the first release paper 2 and the second release paper 3 can be obtained in the same manner as the thickness of the protective layer 1 .

[0067] From the perspective of facilitating visual identification of the first release paper 2 and the second release paper 3 , the first release paper 2 and the second release paper 3 may have different colors. Alternatively, both the first release paper 2 and the second release paper 3 may be colored, for example, the first release paper 2 may be colored black and the second release paper 3 may be colored white, so that the visual recognition of the first release paper 2 and the second release paper 3 is improved. In addition, when both the first release paper 2 and the second release paper 3 are colorless and transparent, one of the first release paper 2 or the second release paper 3 can be colored to improve the identification of the first release paper 2 and the second release paper 3. As the coloring agent for coloring the first release paper 2 and the second release paper 3, various well-known coloring agents can be used. Examples of the colorant include dyes and pigments. Furthermore, a dye refers to a coloring agent that is soluble in water or an organic solvent, and a pigment refers to a coloring agent that is insoluble in water or an organic solvent.

[0068] The matters disclosed in this specification include the following.

[0069] (1) A protective sheet material, comprising: protective layer; A first release paper disposed on one surface of the protective layer; and The second release paper is disposed on the other surface of the protective layer; and The aforementioned protective layer contains a water-soluble polymer compound; When the peeling force of the first release paper on the protective layer is PA and the peeling force of the second release paper on the protective layer is PB, The peeling force PA and the peeling force PB satisfy the following relationship: PA <P B。

[0070] According to this configuration, it is possible to achieve both sufficient control over the occurrence of the protective layer being lifted off the release sheet on the other side when the release sheet on one side is peeled off and the prevention of unintended peeling of the protective layer.

[0071] (2) The protective sheet as described in (1), wherein: When the thickness of the first release paper is TA and the thickness of the second release paper is TB, The thickness TA and the thickness TB satisfy the following relationship: TA <T B 35μm <T B<80μm。

[0072] According to this configuration, it is possible to more satisfactorily achieve both suppression of the protective layer from being lifted off the release sheet on the other side when the release sheet on one side is peeled off and suppression of unintended peeling of the protective layer. In addition, it is easy to visually distinguish between the release sheet on one side and the release sheet on the other side.

[0073] Furthermore, the protective sheet of the present invention is not limited to the aforementioned embodiments. Furthermore, the protective sheet of the present invention is not limited to the aforementioned functions and effects. Various modifications can be made to the protective sheet of the present invention without departing from the spirit of the present invention. [Example]

[0074] The following examples are provided to further illustrate the present invention, but are not intended to limit the scope of the present invention.

[0075] [Example 1] An aqueous dispersion solution was prepared by dispersing polyvinyl alcohol (degree of saponification 65, average degree of polymerization 240) in water in a container. In addition, hereinafter, polyvinyl alcohol is also referred to as PVA. Next, the container containing the aqueous dispersion solution was placed in a water bath at 90° C., and the PVA was dissolved in water by stirring the aqueous dispersion container to obtain a PVA dissolved composition. Next, the PVA dissolving composition was applied to the release-treated surface of a second release paper (trade name "DIAFOIL MRV75" manufactured by Mitsubishi Chemical Corporation, thickness 75 μm) having a silicone release-treated surface (hereinafter also referred to as the silicone release-treated surface) using an applicator to a thickness of 5 μm. Then, the second release paper coated with the PVA dissolved composition was dried at 110° C. for 2 minutes to form a protective layer on the second release paper. Next, a first release paper having a silicone release-treated surface (trade name "DIAFOIL MRA25" manufactured by Mitsubishi Chemical Corporation, thickness 25 μm) was laminated onto the protective layer to obtain a laminate comprising the second release paper, the protective layer, and the first release paper in this order. This laminate was then heat-treated at 70°C. Furthermore, the first release paper is formed by overlapping the silicone release treated surface with the exposed surface of the protective layer. In this way, the protective sheet of Example 1 was obtained. In the following, DIAFOIL MRV75 is abbreviated as "MRV75," and DIAFOIL MRA25 is abbreviated as "MRA25."

[0076] The saponification degree and average polymerization degree of the polyvinyl alcohol are measured according to the method described in the above embodiment.

[0077] [Example 2] The 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 paper, "DIAFOIL MRA38" manufactured by Mitsubishi Chemical Corporation was used as the first release paper, and the thickness of the protective layer was 10 μm. Furthermore, the second release paper, Crisper CN500-50, has a surface that has been release-treated with a non-silicone release agent that does not contain a silicone compound (hereinafter also referred to as the non-silicone release-treated surface), and has a thickness of 50 μm. In addition, DIAFOIL MRA38, the first release paper, has a silicone release-treated surface like the MRA75 and MRA25, and is 38 μm thick. Furthermore, the silicone release-treated surface of the first release paper is attached to one surface of the protective layer, and the non-silicone release-treated surface of the second release paper is attached to the other surface of the protective layer. In the following, Crisper CN500-50 is abbreviated as "CN500-50" and DIAFOIL MRA38 is abbreviated as "MRA38".

[0078] [Example 3] The 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 paper and the thickness of the protective layer was 30 μm. In addition, Crisper CN100-38, the first release paper mentioned above, has a non-silicone release treatment surface like Crisper CN500-50 and a thickness of 38 μm. In addition, below, Crisper CN100-38 is abbreviated as "CN100-38".

[0079] [Example 4] The 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 paper and the thickness of the protective layer was 5 μm.

[0080] [Comparative Example 1] 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 Industries, Inc. was used as the first release liner, "Lumirror (registered trademark) #50-S10" manufactured by Toray Industries, Inc. was used as the second release liner, and the thickness of the protective layer was 10 μm. Furthermore, the first release paper, Lumirror (registered trademark) #38-S10, was not subjected to any release treatment and had a thickness of 38 μm. In addition, the second release paper, Lumirror (registered trademark) #50-S10, was not subjected to any release treatment and had a thickness of 50 μm. Furthermore, hereinafter, Lumirror (registered trademark) #38-S10 is abbreviated as "#38-S10", and Lumirror (registered trademark) #50-S10 is abbreviated as "#50-S10". In addition, "#38-S10" and "#50-S10" are also polyester films.

[0081] [Comparative Example 2] A protective sheet of Comparative Example 2 was obtained in the same manner as in Example 2 except that "DIAFOIL MRA50" manufactured by Mitsubishi Chemical Corporation was used as the second release paper. Furthermore, DIAFOIL MRA50, the second release paper, has a silicone release-treated surface similar to the MRV75, MRA25, and MRA38, and has a thickness of 50 μm. In the following, DIAFOIL MRA50 is abbreviated as "MRA50".

[0082] <Peel Force> For each protective sheet, the peeling force PA of the first release paper on the protective layer and the peeling force PB of the second release paper on the protective layer were measured. The peeling force PA and the peeling force PB are implemented according to the method described in the above implementation items. Table 1 below shows the results of measuring the peeling force PA and the peeling force PB for each protective sheet. In addition, the following Table 1 also shows the ratio R of the peeling force PB to the peeling force PA for each protective sheet.

[0083] Undesirable peeling of protective layer In the measurement of the peeling force, the surface of the release paper peeled from the protective layer was visually observed, and the unintended peeling of the protective layer was evaluated according to the following criteria. Excellent: No protective layer was visually observed on the surface of the release paper. Poor: A portion of the protective layer can be visually confirmed on the surface of the release paper. Table 1 below shows the evaluation results of the undesired peeling of the protective layer.

[0084] <Floating of protective layer> After placing the protective sheet materials of each example for 24 hours in an environment of a temperature of 23 ± 2°C and a relative humidity of 55 ± 5%RH, visually observe whether the protective layer has lifted from each release paper (the first release paper and the second release paper). Next, evaluate the lifting of the protective layer according to the following criteria. Excellent: No lifting of the protective layer is visually confirmed from either the first release paper or the second release paper. In addition, even after exposing the protective sheet material to the above environment (temperature 23 ± 2°C and relative humidity 55 ± 5%RH) for 24 hours, when peeling the first release paper from the protective layer by hand, no lifting of the protective layer from the second release paper is visually confirmed. Good: No lifting of the protective layer is visually confirmed from either the first release paper or the second release paper. On the other hand, after exposing the protective sheet material to the above environment for 24 hours, when peeling the first release paper from the protective layer by hand, a slight lifting of the protective layer from the second release paper is visually confirmed. Poor: Lifting of the protective layer is visually confirmed from at least one of the first release paper and the second release paper. The evaluation results of the lifting of the protective layer are shown in Table 1 below.

[0085] [Table 1]

[0086] As can be seen from Table 1, for the protective sheet materials of each embodiment, for the peeling force P A of the protective layer from the first release paper and the peeling force P B of the protective layer from the second release paper, those satisfying the relational expression of P A < P B and P B ≦ 2000 mN / 25 mm can balance the suppression of the undesired peeling of the protective layer and the suppression of the lifting of the protective layer. In contrast, it can be seen that for the protective sheet materials of each comparative example, those not satisfying the above relational expression cannot balance the suppression of the undesired peeling of the protective layer and the suppression of the lifting of the protective layer. In addition, after comparing the evaluation results of the lifting of the protective layer of the protective sheet materials of Examples 1 to 3 with a ratio R of 2.0 or more and the evaluation results of the lifting of the protective layer of the protective sheet materials of each comparative example with a ratio R of less than 2.0, it can be seen that the protective sheet materials of Examples 1 to 3 can obtain particularly good results. Also, for the protective sheet material of Comparative Example 1, since the values of the peeling force P A and the peeling force P B are too high, the lifting of the protective layer cannot be evaluated. Therefore, for the protective sheet material of Comparative Example 1, the evaluation of the lifting of the protective layer is recorded as "unable to evaluate" in Table 1.

[0087] 1:Protective layer 2: First release paper 3:Second release paper 10: Protective material

Claims

1. A protective sheet comprising: a protective layer; a first release paper disposed on one surface of the protective layer; and a second release paper disposed on the other surface of the protective layer; wherein the protective layer contains a water-soluble polymer compound; wherein the peel force of the first release paper on the protective layer is PA, and the peel force of the second release paper on the protective layer is PB, and the peel forces PA and PB satisfy the following relationship: 1.1 ≦ (PB / PA) 70mN / 25mm ≦ PB ≦ 2000mN / 25mm.

2. The protective sheet as described in claim 1, wherein, When the thickness of the first release paper is TA and the thickness of the second release paper is TB, the thicknesses TA and TB satisfy the following relationship: TA < TB 35μm < TB < 80μm.

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