Protective sheet

Abstract

To provide a protective sheet that includes release sheets on both sides of a protective layer, and prevents the protective layer from lifting from the other release sheet when one release sheet is peeled off, and that can sufficiently suppress the separation of the protective layer.SOLUTION: A protective sheet according to the present invention includes 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, and the protective layer includes a water-soluble polymer compound, and when the release force of the first release liner against the protective layer is PA, and the release force of the second release liner against the protective layer is PB, the peeling force PA and the peeling force PB satisfy the following relational expressions. PA<PB. PB≤2000 mN / 25 mm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a protective sheet. [Background technology]

[0002] Conventionally, in the manufacture of electronic components such as semiconductor elements such as semiconductor chips and liquid crystal display devices, it has been known to use an adhesive protective sheet to prevent foreign matter from adhering to the electronic components (for example, Patent Document 1 below). The following Patent Document 1 discloses the protective sheet comprising a protective layer formed from a resin composition containing an oxyalkylene group-containing polyvinyl alcohol-based resin, and two release sheets arranged on both sides of the protective layer.

[0003] Among the methods for producing the above electronic components, the production of semiconductor chips is usually carried out by dividing (breaking) one semiconductor wafer (for example, Patent Document 2 below). For example, Patent Document 2 below discloses a method for manufacturing a semiconductor chip as follows. (1) A plurality of dividing lines are formed in a lattice pattern on one surface of a silicon wafer. (2) A circuit pattern is formed and an electrode portion is arranged in each of the areas partitioned into a grid by the plurality of planned division lines (hereinafter also referred to as grid-shaped partitioned areas), thereby producing a semiconductor wafer for obtaining semiconductor chips. (3) The semiconductor wafer is divided (cut) along the plurality of planned dividing lines, in other words, the semiconductor wafer is divided (cut) into the grid-shaped partition areas to obtain a plurality of semiconductor chips. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-161735 A [Patent Document 2] JP 2012-119670 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when a semiconductor wafer is divided (cut) to obtain a plurality of semiconductor chips as described above, a portion of the semiconductor wafer near the dividing portion (cut portion) may be pulverized, resulting in the generation of minute foreign matter. Furthermore, if such microscopic foreign matter adheres to one surface side of the semiconductor chip (the side on which the circuit pattern is formed), this is undesirable because it may reduce the operational reliability of the circuit contained in the circuit pattern formed on the one surface side. For this reason, semiconductor chips are often manufactured by attaching the protective layer of the protective sheet to one surface side (the side on which a circuit pattern is formed) of the semiconductor wafer.

[0006] When using a protective sheet comprising a protective layer containing a water-soluble polymer compound such as an oxyalkylene group-containing polyvinyl alcohol resin as described above and two release sheets arranged on both sides of the protective layer to bond the protective layer to one surface side of the semiconductor wafer, it is necessary to peel one of the two release sheets from the protective sheet to expose the protective layer on the surface.

[0007] One of the release sheets is peeled off from the protective layer by application of an external force such as suction force from the outside of the one release sheet (the side without the protective layer), but when one of the release sheets is peeled off from the protective layer, the protective layer may float off from the other of the two release sheets. Furthermore, when the protective layer is peeled off from one of the release sheets, the protective layer may not be lifted off from the other sheet, but the one release sheet may be peeled off with part of the protective layer still attached, i.e., the protective layer may come apart (cohesive failure or the like may occur in the protective layer).

[0008] However, in a protective sheet having release sheets on both sides of a protective layer, it cannot be said that sufficient consideration has yet been given to sufficiently achieving both preventing the protective layer from lifting off from one release sheet when the other release sheet is peeled off, and preventing the protective layer from becoming separated.

[0009] Therefore, an object of the present invention is to provide a protective sheet which has release sheets on both sides of a protective layer and which can sufficiently suppress the protective layer from lifting off from one release sheet when the other release sheet is peeled off, and which can suppress the protective layer from becoming separated. [Means for solving the problem]

[0010] The protective sheet according to the present invention comprises: A protective layer; a first release liner disposed on one surface of the protective layer; A second release liner is disposed on the other surface of the protective layer, the protective layer contains a water-soluble polymer compound, The peel strength of the first release liner to the protective layer is P A and the peeling force of the second release liner with respect to the protective layer is P B When Peeling force P A , and peel force P B satisfies the following relation: Protective sheet. P A <P B P B≦2000mN / 25mm Effect of the Invention

[0011] According to the present invention, it is possible to provide a protective sheet which has release sheets on both sides of a protective layer and which can satisfactorily suppress the protective layer from lifting off from one release sheet when the other release sheet is peeled off, and which can also suppress the protective layer from becoming separated. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a configuration of a protective sheet according to one embodiment of the present invention. [Diagram 2] 1 is a cross-sectional view showing the configuration of a mounting device that bonds a protective layer of a protective sheet to a surface to be protected of an electronic component such as a semiconductor wafer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 one embodiment of the present invention comprises 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. In the following, one embodiment of the present invention will be simply referred to as the present embodiment. In the protective sheet 10 according to 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 liner 2 and the second release liner 3 are water-insoluble.

[0015] As shown in FIG. 1, in the protective sheet 10 according to this embodiment, the protective layer 1, the first release liner 2, and the second release liner 3 have approximately the same dimensions in a plan view. More specifically, in protective sheet 10 according to one embodiment, the inner surface of first release liner 2 (the surface facing one surface of protective layer) and one surface of protective layer 1 are overlapped over substantially the entire area with their edges aligned, and the inner surface of second release liner 3 (the surface facing the other surface of protective layer 1) and the other surface of protective layer 1 are overlapped over substantially the entire area with their edges aligned.

[0016] In the protective sheet 10 according to this embodiment, the protective layer 1 has sufficient adhesiveness to allow it to be attached to an adherend. In the protective sheet 10 according to this embodiment, the protective layer 1 preferably has tackiness (pressure-sensitive adhesiveness). The protective sheet 10 of this embodiment is used to prevent foreign matter from adhering to the surface of an adherend (e.g., an electronic component such as a semiconductor wafer) while various treatments are being performed on the adherend by adhering the protective layer 1 to 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 surface to be protected of an electronic component, such as a semiconductor wafer, using, for example, a mounting device 200 as shown in FIG. As shown in FIG. 2, the mounting device 200 includes a chamber 201, an electrostatic chuck table 202 disposed at the bottom of the chamber 201, a head portion 203 disposed within the chamber 201 above the electrostatic chuck table 202, and a pump P for reducing the pressure inside the chamber 201. In the mounting apparatus 200 , an electronic component such as a semiconductor wafer is mounted on the electrostatic chuck table 202 , and a protective sheet 10 is attached to the head portion 203 . In the mounting device 200, the protective sheet 10 and electronic components such as semiconductor wafers are mounted on the head unit 203 and electrostatic chuck table 202, respectively, in such a manner that the exposed surface of the protective layer 1 faces the surface to be protected. Furthermore, as shown in FIG. 2, after the holding table 101 is attached to the head unit 203, the protective sheet 10 may be attached to the holding table 101.

[0018] When the up-down direction (vertical direction) is defined as the Z-axis direction, the horizontal direction along the cut surface when the electrostatic chuck table 202 and the head unit 203 are cut along a plane parallel to the Z-axis (the horizontal direction along the paper surface in FIG. 2) is defined as the X-axis direction, and the direction perpendicular to both the Z-axis and the X-axis (the direction perpendicular to the paper surface in FIG. 2) is defined as the Y-axis direction, by moving the head unit 203 in at least one of the X-axis direction and the Y-axis direction and then further moving it in the Z-axis direction, the exposed surface of the protective layer 1 attached to the head unit 203 can be attached to the surface to be protected of an electronic component, such as a semiconductor wafer, attached to the electrostatic chuck table 202.

[0019] In the case where the holding table 101 is not attached to the head unit 203, the electrostatic chuck table 202 may be kept in a heated state when the exposed surface of the protective layer 1 is attached to the surface to be protected. In addition, when the holding table 101 is attached to the head portion 203, at least one of the holding table 101 and the electrostatic chuck table 202 may be kept in a heated state when adhering the exposed surface of the protective layer 1 to the surface to be protected.

[0020] 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 adhering to the protective layer 1 before it is attached to an adherend. Each of the first release liner 2 and the second release liner 3 has an inner surface facing the protective layer 1 and an outer surface opposite the inner surface.

[0021] Protective sheet 10 according to this embodiment is used by peeling off first release liner 2 to expose one surface of protective layer 1, and attaching that surface to the surface to be protected of an adherend. The protective sheet 10 of this embodiment may be used by adhering one surface of the protective layer 1 to the surface of an adherend to be protected, and then peeling the second release liner 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 may be used in a state in which the first release liner 2 is peeled off to expose one surface of the protective layer 1 and that surface is adhered to the surface of the adherend to be protected, and then the other surface of the protective layer 1 is covered with the second release liner 3, or the second release liner 3 is peeled off from the other surface of the protective layer 1 to expose the other surface of the protective layer 1.

[0022] In protective sheet 10 according to this embodiment, when one surface of protective layer 1 is attached to the surface to be protected of an adherend, at least protective layer 1 is cut or otherwise made to have approximately the same planar dimensions as the adherend.

[0023] In the protective sheet 10 according to this embodiment, the peel strength of the first release liner 2 to the protective layer 1 is P A The peel force of the second release liner 3 against the protective layer 1 is P B When the peel force P A , and peel force P B It is important that the following relation is satisfied: P A <P B P B ≦2000mN / 25mm

[0024] Peeling force P B By making the compressive strength 2000 mN / 25 mm or less, it is possible to prevent the second release liner 3 from being excessively adhered to the protective layer 1. This makes it possible to prevent the second release liner 3 from being peeled off with part of the protective layer 1 still attached when 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 surface to be protected of the semiconductor wafer as the adherend, and then the second release liner 3 is peeled off from the other surface of the protective layer 1. That is, when the second release liner 3 is peeled off, the protective layer 1 can be prevented from being torn apart. In addition, the peeling force P A and peeling force P B But, P A <P BBy satisfying 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 floating up on the other surface side of the protective layer 1. From the viewpoint of appropriately balancing the adhesion of the first release liner 2 to the protective layer 1 and the adhesion of the second release liner 3 to the protective layer 1, the release force P A Peel force P B Ratio (P B / P A ) is preferably 1.1 or more, and more preferably 1.2 or more. Moreover, the R is more preferably 2.0 or more, more preferably 3.0 or more, more preferably 4.0 or more, and even more preferably 5.0 or more. The upper limit of the R is usually 100. By the R being 2.0 or more, the peeling force P A and peel force P B Since the difference between the values ​​can be made sufficiently large, when the first release liner 2 is peeled off from the protective layer 1, the protective layer 1 can be sufficiently prevented from lifting up from the second release liner 3.

[0025] The protective sheet 10 according to this embodiment satisfies the above relational expression, i.e., P A <P B , and P B In order to satisfy the requirement of ≦2000 mN / 25 mm, it is necessary to apply a surface treatment to the inner surface of the first release liner 2 so that the adhesion force of the inner surface of the first release liner 2 to one surface of the protective layer 1 is appropriate, and then apply a surface treatment to the inner surface of the second release liner 3 so that the adhesion force of the inner surface of the second release liner 3 to the other surface of the protective layer 1 is appropriate.

[0026] In the protective sheet 10 according to this embodiment, the peel 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 according to this embodiment, the peel 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 even more preferably 200 mN / 25 mm or less.

[0027] In the protective sheet 10 according to this embodiment, the peel force P B is preferably 70 mN / 25 mm or more, and more preferably 80 mN / 25 mm or more. In addition, in the protective sheet 10 according to this embodiment, the peel force P B is preferably 1500 mN / 25 mm or less, and more preferably 1000 mN / 25 mm or less.

[0028] Peeling force P A and peeling force P B can be measured using a tensile tester (product name "Autograph AG-IS", manufactured by Shimadzu Corporation). The peeling force P A Regarding the above, a sample measuring 150 mm in length and 100 mm in width is cut out from the protective sheet 10, and the second release liner 3 is peeled off from the sample to obtain a test piece (hereinafter referred to as the first test piece). In addition, the peel force P B Regarding the second test piece, a sample measuring 150 mm in length and 100 mm in width was cut out from the protective sheet 10, and the first release liner 2 was then peeled off from the sample to obtain a test piece (hereinafter referred to as the second test piece). In addition, the peeling force P A and peeling force P B The unit "mN / 25mm" is the value measured at a width of 100 mm converted to a width of 25 mm.

[0029] Peeling force P AThe measurement can be performed by attaching the exposed surface of the protective layer of the first specimen to the surface of a bare wafer with a double-sided tape (e.g., "No. 500" manufactured by Nitto Denko Corporation) between them, and then performing a 180° peel test using a tensile tester (e.g., "Autograph AG-IS" manufactured by Shimadzu Corporation). The 180° peel test can be carried out by pulling the first release liner 2 in the length direction under conditions of a temperature of 23±2° C., a relative humidity of 55±5% RH, and a peel speed of 300 mm / min. In addition, the peeling force P B The measurement of the peel force P was performed by changing the first test piece to the second test piece and changing the object to be pulled in the longitudinal direction to the second release liner 3. A The measurement can be carried out in the same manner as in In addition, the peeling force P A and peeling force P B is the average value of the range beginning 30 mm from the start of measurement and ending 120 mm.

[0030] The surface treatment may be, for example, 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. As the release agent, any appropriate release agent can be used as long as it does not impair the effects of the present invention. Examples of such release agents include ethylene-vinyl alcohol copolymers, fatty acid amide additives, low molecular weight polyolefin waxes, long chain alkyl 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 additives include methylene bisstearic acid amide, ethylene bisstearic acid amide, ethylene bisoleic acid amide, N,N-dioleyl adipamide, and N-stearyl-N'-stearyl acid amide (for example, N-stearyl-N'-stearyl urea). These fatty acid amide-based additives may 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 and low molecular weight polypropylene wax.

[0034] The long-chain alkyl additives include, for example, those containing long-chain alkyl pendant polymers. Commercially available products of such long-chain alkyl additives include Peloil (registered trademark) 1010 (manufactured by Ipposha Yushi Kogyo Co., Ltd.) and Peloil (registered trademark) 1010S (manufactured by Ipposha Yushi Kogyo Co., Ltd.).

[0035] The polymethylpentene includes an olefin copolymer based on 4-methyl-1-pentene. 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 fluorine-based release agent includes 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), a ternary copolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride, and fluororubber. These various fluorine-based resins may be used alone or in combination of two or more kinds.

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

[0038] As the oil-type silicone release agent, 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 of the side chains and terminals are methyl groups, methylphenylsilicone in which part of the side chains are phenyl groups, and methylhydrogensilicone in which part of the side chains are hydrogen. Dimethyl silicone, methyl phenyl silicone, and methyl hydrogen silicone are all called straight silicones in which silicon (Si) atoms are bonded in a straight chain via oxygen (O).

[0040] The modified polyalkylsiloxane may be one in which an organic group has been 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. Among the modified polyalkylsiloxanes, those having a reactive organic group such as a monoamine group, a diamine group, an amino group, an epoxy group, a carbinol group, a mercapto group, or a carboxyl group are called reactive silicones, and among the modified polyalkylsiloxanes, those having a non-reactive organic group such as a polyether group, an aralkyl group, or a fluoroaralkyl group are called non-reactive silicones.

[0041] Examples of the baked silicone release agent include those obtained by blending a liquid silicone compound, such as the polyalkylsiloxane, the modified polyalkylsiloxane, or a resin modified with a polyalkylsiloxane, described above, with a crosslinking agent, such as a peroxide or a peroxide-containing silicone compound.

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

[0043] The silicone compound such as the polyalkylsiloxane has a thermal crosslinking property. In such a silicone compound, the degree of release force can be easily adjusted by adjusting the degree of thermal crosslinking. Therefore, taking the above into consideration, it is preferable to use a silicone-based release agent among the various release agents mentioned above.

[0044] The release agent is usually in a liquid form and is used by applying it to an object to which it is desired to improve the release properties. As a method for applying the release agent, various known application methods can be adopted. Examples of the various known coating methods include roll coating methods such as gravure coating and reverse coating, bar code methods such as Mayer bar, spray coating, and air knife coating. The stripping agent may be diluted with an organic solvent (eg, ethyl methyl ketone) and then applied to the object. The 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 inner surface of the first release liner 2 and the inner surface of the second release liner 3 are subjected to release treatment using the release agent, if the type of release agent applied to the inner surface of the first release liner 2 is different from the type of release agent applied to the inner surface of the second release liner 3, the peel force P A and the peel force P of the inner surface of the second release liner 3 to the protective layer 1. B It is possible to make them different. Furthermore, when a silicone-based release agent is used as both 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 explained above, if the degree of thermal crosslinking of the silicone-based release agent applied to the inner surface of the first release liner 2 is made different from the degree of thermal crosslinking of the silicone-based release agent applied to the inner surface of the second release liner 3, the peel force P A and the peel force P of the inner surface of the second release liner 3 to the protective layer 1 B It is possible to make them different. The degree of thermal crosslinking can be adjusted by varying the heating temperature or 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 type, the release agents diluted with an organic solvent or the like at different ratios may be used to apply the release agents to the inner surfaces of the first release liner 2 and the second release liner 3. Even when the application process is performed in this manner, the peel force P A and the peel force P of the inner surface of the second release liner 3 to the protective layer 1 B It is possible to make them different.

[0046] The surface treatment may be, for example, by providing irregularities 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 matting or embossing. When unevenness is provided on the inner surface of the first release liner 2 and the inner surface of the second release liner 3, the arithmetic mean roughness Ra of the inner surface of the first release liner 2 is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1.0 μm or more. 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 even more preferably 10 μm or less. 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 even more preferably 0.100 μm or more.

[0047] 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, product name "OPTELICS H300", manufactured by Lasertec Corporation).

[0048] 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 . Therefore, the larger the value of the arithmetic mean roughness Ra, the greater the peel force P A , and the peel force P of the inner surface of the second release liner 3 to the protective layer 1 B becomes smaller (enabling lighter peeling). 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 peel force P A <Peeling force P B The relationship between the two is fulfilled. Furthermore, since the arithmetic mean roughness Ra of the inner surface of the first release liner 2 is within the above numerical range, and the arithmetic mean roughness Ra of the inner surface of the second release liner 3 is within the above numerical range, it becomes easier to make the protective sheet 10 in this embodiment satisfy the above relational expressions.

[0049] As described above, the protective layer 1 is used by being attached to the surface to be protected of an adherend. The adherend may be an electronic component, and an example of the electronic component may be a semiconductor wafer. The semiconductor wafer may be a semiconductor wafer having a grid-shaped partitioned area (hereinafter also referred to as grid-shaped partitioned area) formed on one surface side, in which a circuit pattern is formed in each of the grid-shaped partitioned areas and an electrode portion is disposed. 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 manner, by bonding protective layer 1 to one surface of the semiconductor wafer, it is possible to prevent minute foreign matter that is generated when the semiconductor wafer is divided (fractured) to obtain multiple semiconductor chips, and when a portion of the semiconductor wafer near the divided portion (fractured portion) is powdered, from adhering to each circuit pattern formed on the one surface (the circuit pattern formed for each of the lattice-shaped partition areas) and each electrode portion arranged on the one surface (the electrode portion arranged for each of the lattice-shaped partition areas).

[0050] The second release liner 3 may be in the form of a long strip having a longitudinal direction and a lateral direction. The protective sheet 10 comprises a strip-shaped second release liner 3 and multiple protective layers 1 having the same shape as the surface to be protected, and the multiple protective layers 1 may be arranged side by side in the longitudinal direction of the second release liner 3, or a fixed gap may be provided between adjacent protective layers 1 in the longitudinal direction. In this case, the first release liner 2 may be strip-shaped like the second release liner 3 .

[0051] The second release liner 3 may be larger than the protective layer 1 not only in the longitudinal direction but also in the lateral direction. That is, protective sheet 10 may be one in which second release liner 3 protrudes outward beyond the outer peripheral edge of protective layer 1 , and such protrusion of second release liner 3 occurs along the entire periphery of protective layer 1 .

[0052] The protective sheet 10 can be produced, for example, as follows. (1) Using an applicator or the like, a water-soluble resin composition containing a water-soluble polymer compound and an excess liquid portion is applied onto second release liner 3 to a predetermined thickness (for example, 5 μm to 30 μm). (2) The applied water-soluble resin composition is dried at a predetermined temperature for a predetermined time (for example, 2 minutes at 110° C.), thereby forming a protective layer 1 containing a water-soluble polymer compound on the second release liner 3. (3) The first release liner 2 is attached 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.).

[0053] In the protective sheet 10 according to this embodiment, the protective layer 1 is preferably prepared using a water-soluble resin composition containing a water-soluble polymer compound together with an excess liquid content, the water-soluble polymer compound being dispersed in water (hereinafter referred to as the protective layer-forming composition). In the protective layer forming composition, the water-soluble polymer compound 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 even more preferably 15 parts by mass or more and 60 parts by mass or less, per 100 parts by mass of water. In the protective layer-forming composition, the water-soluble polymer compound is preferably dissolved in water. In the protective layer-forming composition, the water-soluble polymer compound can be dissolved in water by treating at a temperature of 20 to 90°C. Furthermore, the protective layer-forming composition has a viscosity at 25° C. of 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. By having a viscosity at 25°C that is equal to or greater than the above-mentioned lower limit, when the protective layer forming composition is applied onto a first release liner 2 to form a protective layer 1 on the first release liner 2, it is possible to prevent the thickness of the protective layer 1 from easily varying. 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 ensuring that the viscosity at 25° C. is equal to or less than the above upper limit, the coatability of the protective layer-forming composition when it is applied onto the first release liner 2 can be improved. The viscosity of the protective layer forming composition at 25°C can be measured using a digital viscometer (product name "DV-I Prime") manufactured by Eiko Seiki Co., Ltd. as the measuring device, using an LV-3 spindle and adopting conditions of a rotation speed of 50 rpm.

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

[0055] The polyvinyl alcohol preferably has a degree of saponification of 50 or more and 98 or less, and more preferably 60 or more and 90 or less. By having a degree of saponification within the above numerical range, the polyvinyl alcohol can exhibit sufficient water solubility, and in addition, when the polyvinyl alcohol is contained in the protective layer forming composition, the protective layer forming composition can be applied onto the first release liner 2 with good workability. The degree of saponification of the polyvinyl alcohol was measured by proton magnetic resonance spectroscopy ( 1 It can be measured by H-NMR measurement. In addition, when the measurement sample contains an additive and a peak derived from the additive overlaps with a peak used for calculating the degree of saponification, the measurement sample is subjected to methanol extraction or the like to separate the additive, and then the degree of saponification of the polyvinyl alcohol is measured. The degree of saponification of the polyvinyl alcohol can be measured under the following conditions. <Measurement conditions> ·Analyzer FT-NMR: Bruker Biospin, AVANCE III-400 Observation frequency: 400MHz (1H) Measurement solvent: deuterium oxide or deuterium dimethyl sulfoxide (DMSO) ·Measurement temperature 80℃ ·Chemical shift standard External standard TSP-d4 (0.00ppm) (when measuring heavy water) Measurement solvent (2.50 ppm) (when measuring deuterated DMSO) The degree of saponification of the polyvinyl alcohol is calculated based on the following formula using the peaks derived from the methylene groups of the vinyl alcohol unit (VOH) (heavy water: 2.0 to 1.0 ppm, deuterated DMSO: 1.9 to 1.0 ppm) and the peaks derived from the acetyl groups of the vinyl acetate unit (VAc) (heavy water: around 2.1 ppm, deuterated DMSO: around 2.0 ppm). In the following formula, [VOH(-CH 2 )-] is the -CH 2 -means the intensity of the peak derived from, [VAc(CH 3 CO-)] is the CH 3 The peak intensity derived from CO-

[0056]

number

[0057] The polyvinyl alcohol preferably has an average degree of polymerization of 100 or more and 1,000 or less, and more preferably 100 or more and 800 or less. Because the average degree of polymerization is within the above numerical range, the polyvinyl alcohol can exhibit sufficient water solubility, and in addition, when the polyvinyl alcohol is contained in the protective layer forming composition, the protective layer forming composition can be applied onto the first release liner 2 with good workability. The average degree of polymerization of the polyvinyl alcohol can be measured by aqueous GPC. The average degree of polymerization of the polyvinyl alcohol can be measured under the following conditions. <Measurement conditions> ·Analyzer Agilent, 1260Infinity Columns: TSKgel G6000PWXL (Tosoh Corporation) and TSKgel G3000PWXL (Tosoh Corporation) The two columns are connected in series. Column temperature: 40℃ Eluent: 0.2M aqueous sodium nitrate solution ·Injection volume 100μL Detector: Differential refractometer (RI) Standard samples: PEG standard sample and PVA standard sample The specific measurement is carried out as follows. (1) The weight average molecular weight Mw of the sample (PVA) and the PVA standard sample are calculated by GPC measurement using a PEG standard sample. The PVA standard sample has a known average degree of polymerization. (2) A calibration curve is prepared using the average degree of polymerization of the PVA standard samples and the calculated mass average molecular weight Mw of the PVA standard samples. (3) Using the created calibration curve, the average degree of polymerization of the sample (PVA) is calculated from the mass average molecular weight Mw of the sample (PVA).

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

[0059] The water-soluble polyester has a residue of a polycarboxylic acid and a residue of a polyol. The water-soluble polyester is, for example, a polymerization product of monomer components including a polyvalent carboxylic acid component and a polyol component. Whether the water-soluble polyester has water solubility can be determined based on common general technical knowledge.

[0060] The water-soluble polyester preferably satisfies at least one of the following (1) to (4). (1) When room temperature (23±2° C.) water is sprayed onto the entire surface of a 20 μm-thick thin film formed from the water-soluble polyester at a spray pressure of 0.005 MPa for 20 minutes, the thin film dissolves entirely in water. (2) When water at 50° C. is sprayed onto the entire surface of a 20 μm-thick thin film formed from the water-soluble polyester for 10 minutes at a spray pressure of 0.005 MPa, the thin film dissolves entirely in water. (3) The water-soluble polyester is mixed with water at room temperature in a mass ratio of water-soluble polyester:water at room temperature=1:5 to obtain a mixed liquid, and when the mixed liquid is irradiated with ultrasound for 20 minutes, the water-soluble polyester is completely dissolved in the water. (4) The water-soluble polyester is mixed with 50°C water in a mass ratio of water-soluble polyester:50°C water=1:5 to obtain a mixed liquid, and when the mixed liquid is irradiated with ultrasound for 10 minutes, the water-soluble polyester is completely dissolved in the water.

[0061] The thickness of the protective layer 1 is preferably from 2 μm to 70 μm, more preferably from 3 μm to 50 μm, and further preferably from 5 μm to 40 μm. The thickness of the protective layer 1 can be determined, for example, by measuring the thickness at five randomly selected points using a dial gauge (Model R-205, manufactured by PEACOCK) and calculating the arithmetic average of these thicknesses.

[0062] An example of the first release liner 2 is a resin sheet made of a resin such as polyethylene terephthalate (PET). When the first release liner 2 is composed of a resin sheet as described above, at least the surface of the resin sheet that is bonded to the protective layer 1 may be subjected to a surface treatment as described above in order to appropriately adjust the adhesion to the protective layer 1. Similarly to the first release liner 2, the second release liner 3 may be a resin sheet made from a resin such as polyethylene terephthalate (PET). When the second release liner 3 is composed of a resin sheet as described above, at least the surface of the resin sheet that is bonded to the protective layer 1 may be subjected to a surface treatment as described above in order to appropriately adjust the adhesion to the protective layer 1.

[0063] The thickness of the first release liner 2 is T A The thickness of the second release liner 3 is T B Then, the thickness T A and thickness T B It is preferable that the following relational expression is satisfied: T A <T B 35μm <T B <80 μm

[0064] Generally, the thicker the release liner is, the higher its bending strength (flexural rigidity). The higher the stiffness of the release liner, the less likely it is to bend in the thickness direction. Here, as explained above, one surface of protective layer 1 exposed by peeling off first release liner 2 is bonded to the surface to be protected of an adherend such as a semiconductor wafer. Then, the first release liner 2 is peeled off from one surface of the protective layer 1 by application of an external force such as suction force from the outside (the side on which the protective layer 1 is not disposed). In the above case, the first release liner 2 is bent due to suction or the like, and this bending causes a portion of the first release liner 2 to lift off from one surface of the protective layer 1 . Then, the first release liner 2 is peeled off from one surface of the protective layer 1 using this lifted portion as a base point. As described above, when the first release liner 2 is peeled off from one surface of the protective layer 1, the second release liner 3 is also likely to bend toward the inside (the side on which the protective layer 1 is arranged), and it is undesirable for the second release liner 3 to lift off from the other surface of the protective layer 1. Therefore, the thickness T of the first release liner 2 A and the thickness T of the second release liner 3 B As mentioned above, T A <T B It is preferable that the following relation is satisfied. After one surface of protective layer 1 has been bonded to the surface to be protected, second release liner 3 is usually peeled off from the other surface of protective layer 1. Therefore, in order to facilitate peeling off the second release liner 3 after bonding one surface of the protective layer 1 to the surface to be protected, the thickness T B As mentioned above, 35 μm <T B It is preferable that the relation <80 μm is satisfied. This allows the second release liner 3 to have appropriate stiffness, so that when the second release liner 3 is peeled off from the other surface of the protective layer 1, it is possible to prevent the second release liner 3 from being peeled off with part of the protective layer 1 still attached, i.e., to prevent separation from occurring.

[0065] In addition, the thickness T of the first release liner 2 A and the thickness T of the second release liner 3 B By making them different, it becomes easier to distinguish between the first release liner 2 and the second release liner 3 when the protective sheet 10 is viewed from the side.

[0066] Thickness T of the first release liner 2 A may be 15 μm or more, may be 20 μm or more, or may be 25 μm or less. In addition, the thickness T of the first release liner 2 A may be less than 40 μm, or may be 35 μm or less. Furthermore, the thickness T of the second release liner 3 B may be 40 μm or more, 45 μm or more, 50 μm or more, or 60 μm or more. In addition, the thickness T of the second release liner 3 B may be 75 μm or less, or may be 70 μm or less. The thicknesses 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 .

[0067] In order to make the first release liner 2 and the second release liner 3 easier to visually distinguish, the first release liner 2 and the second release liner 3 may have different colors. For example, both the first release liner 2 and the second release liner 3 may be colored, such as coloring the first release liner 2 black and the second release liner 3 white, to improve visual distinction between the first release liner 2 and the second release liner 3. 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 between the first release liner 2 and the second release liner 3. As a colorant for coloring the first release liner 2 and the second release liner 3, various known colorants can be used. The colorant may be a dye or a pigment. It should be noted that the dye refers to a colorant that has the property of being soluble in water, organic solvents, etc., and the pigment refers to a colorant that has the property of not being soluble in water, organic solvents, etc.

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

[0069] (1) A protective layer; a first release liner disposed on one surface of the protective layer; A second release liner is disposed on the other surface of the protective layer, the protective layer contains a water-soluble polymer compound, The peel strength of the first release liner to the protective layer is P A and the peeling force of the second release liner with respect to the protective layer is P B When Peeling force P A , and peel force P B satisfies the following relation: Protective sheet. P A <P B P B ≦2000N / 25mm

[0070] With this configuration, it is possible to sufficiently achieve both preventing the protective layer from lifting off from one release sheet when the other release sheet is peeled off, and preventing the protective layer from becoming separated.

[0071] (2) The thickness of the first release liner is T A The thickness of the second release liner is T B When Thickness T A and thickness T B satisfies the following relation: The protective sheet according to claim 1. T A <T B 35μm <T B <80 μm

[0072] With this configuration, it is possible to more effectively prevent the protective layer from lifting off from one release sheet when the other release sheet is peeled off, and to more effectively prevent the protective layer from becoming separated. Moreover, one release sheet can be easily visually distinguished from the other release sheet.

[0073] The protective sheet according to the present invention is not limited to the above-described embodiment. The protective sheet according to the present invention is also not limited by the above-described effects. The protective sheet according to the present invention can be modified in various ways without departing from the gist of the present invention. EXAMPLES

[0074] The present invention will now be described in more detail with reference to examples. The following examples are provided to further explain the present invention in detail, and are not intended to limit the scope of the present invention.

[0075] [Example 1] In a container, polyvinyl alcohol (saponification degree 65, average polymerization degree 240) was dispersed in water to prepare an aqueous dispersion solution. In the following, polyvinyl alcohol is also referred to as PVA. Next, the container containing the aqueous dispersion was placed in a water bath at 90° C., and the aqueous dispersion container was stirred to dissolve the PVA in the water, thereby obtaining a PVA dissolved composition. Next, the PVA dissolution composition was applied to a thickness of 5 μm using an applicator onto the release-treated surface of a second release liner (manufactured by Mitsubishi Chemical Corporation under the trade name "Diafoil MRV75", thickness 75 μm) having a surface that had been subjected to a silicone release treatment (hereinafter also referred to as the silicone release-treated surface). Next, the second release liner on which the PVA dissolved composition was applied was dried at 110° C. for 2 minutes to form a protective layer on the second release liner. Next, a first release liner having a silicone release treated surface (manufactured by Mitsubishi Chemical Corporation under the trade name "Diafoil MRA25", thickness 25 μm) was superimposed on the protective layer to obtain a laminate in which the second release liner, the protective layer, and the first release liner were laminated in this order, and the laminate was then heat-treated at 70°C. The silicone release treated surface of the first release liner was laminated onto the exposed surface of the protective layer. In this way, the protective sheet according to Example 1 was obtained. In addition, hereinafter, Diafoil MRV75 will be referred to simply as "MRV75", and Diafoil MRA25 will be referred to simply as "MRA25".

[0076] The saponification degree and average polymerization degree of the polyvinyl alcohol were measured in accordance with the method described in the above embodiment section.

[0077] [Example 2] A protective sheet according to Example 2 was obtained in the same manner as in Example 1, except that a product manufactured by Toyobo Co., Ltd. under the trade name "Crisper CN500-50" was used as the second release liner, a product manufactured by Mitsubishi Chemical Corporation under the trade name "Diafoil MRA38" was used as the first release liner, and the thickness of the protective layer was 10 μm. The second release liner, CRISPER CN500-50, had a surface that had been release-treated with a non-silicone release agent that did not contain silicone compounds (hereinafter also referred to as the non-silicone release-treated surface), and had a thickness of 50 μm. Moreover, Diafoil MRA38, which is the first release liner, had a silicone release treated surface, similar to the MRV75 and MRA25, and had a thickness of 38 μm. Furthermore, the silicone release treated surface of the first release liner was bonded to one surface of the protective layer, and the silicone release non-treated surface of the second release liner was bonded to the other surface of the protective layer. In addition, hereinafter, CRISPR CN500-50 will be simply referred to as "CN500-50", and Diafoil MRA38 will be simply referred to as "MRA38".

[0078] [Example 3] A protective sheet according to Example 3 was obtained in the same manner as in Example 2, except that a product named "Crisper CN100-38" manufactured by Toyobo Co., Ltd. was used as the first release liner and the thickness of the protective layer was 30 μm. The first release liner, CRISPER CN100-38, had a non-silicone release treated surface, similar to CRISPER CN500-50, and had a thickness of 38 μm. In addition, hereinafter, CRISPR CN100-38 will be referred to simply as "CN100-38".

[0079] [Example 4] A protective sheet according to Example 4 was obtained in the same manner as in Example 3, except that a product manufactured by Toyobo Co., Ltd. under the trade name "Crisper CN100-38" was used as the second release liner and the thickness of the protective layer was 5 μm.

[0080] [Comparative Example 1] A protective sheet according to Comparative Example 1 was obtained in the same manner as in Example 1, except that a product manufactured by Toray Industries, Inc. under the product name "Lumirror (registered trademark) #38-S10" was used as the first release liner, a product manufactured by Toray Industries, Inc. under the product name "Lumirror (registered trademark) #50-S10" was used as the second release liner, and the thickness of the protective layer was 10 μm. The first release liner, Lumirror (registered trademark) #38-S10, was not subjected to any release treatment and had a thickness of 38 μm. Furthermore, the second release liner, Lumirror (registered trademark) #50-S10, was also not subjected to any release treatment and had a thickness of 50 μm. Furthermore, hereinafter, Lumirror (registered trademark) #38-S10 will be simply referred to as "#38-S10," and Lumirror (registered trademark) #50-S10 will be simply referred to as "#50-S10." Both "#38-S10" and "#50-S10" are polyester films.

[0081] [Comparative Example 2] A protective sheet according to Comparative Example 2 was obtained in the same manner as in Example 2, except that a product manufactured by Mitsubishi Chemical Corporation under the trade name "Diafoil MRA50" was used as the second release liner. The second release liner, Diafoil MRA50, had a silicone release treated surface, similar to the MRV75, MRA25, and MRA38, and had a thickness of 50 μm. In the following, Diafoil MRA50 will simply be referred to as "MRA50".

[0082] <Peeling force> For each protective sheet example, the peel force P of the first release liner to the protective layer A and the peel force P of the second release liner to the protective layer. B was measured. Peeling force P A and peeling force P B was carried out according to the method described in the embodiment section above. The peel strength P for each protective sheet in each example is shown in Table 1 below. A and peeling force P B The measurement results are shown below. In addition, the peel strength P A Peel force P B The ratio R is also shown.

[0083] <The sad farewell to the protective layer> In the measurement of the peeling force, the surface of the release liner peeled from the protective layer was visually observed and the separation of the protective layer was evaluated according to the following criteria. Excellent: No protective layer is visually observed on the surface of the release liner. Unacceptable: Part of the protective layer is visually confirmed on the surface of the release liner. Table 1 below shows the evaluation results of the separation of the protective layer.

[0084] <Protective layer lifting> The protective sheet of each example was left for 24 hours in an environment of 23±2°C and 55±5%RH relative humidity, and then visually observed to see whether or not the protective layer had lifted off from each release liner (first release liner and second release liner). The protective layer lifting was evaluated according to the following criteria. Excellent: No lifting of the protective layer is visually observed from either the first or second release liner. Furthermore, even when the protective sheet is exposed to the above environment (temperature 23±2°C and relative humidity 55±5% RH) for 24 hours and then the first release liner is peeled off from the protective layer by hand, no lifting of the protective layer from the second release liner is visually observed. Good: No lifting of the protective layer is visually observed from either the first or second release liner. However, when the protective sheet is exposed to the above environment for 24 hours and then the first release liner is peeled off from the protective layer by hand, slight lifting of the protective layer from the second release liner is visually observed. Poor: Lifting of the protective layer from at least one of the first release liner and the second release liner is visually confirmed. Table 1 below shows the evaluation results of the protective layer lifting.

[0085] [Table 1]

[0086] From Table 1, as in the protective sheets of each example, the peel force P of the first release liner to the protective layer A , and the peel force P of the second release liner to the protective layer B About P A <P B , and P B It is understood that when the relational expression of ≦2000 mN / 25 mm is satisfied, both the separation of the protective layer and the lifting of the protective layer can be suppressed. In contrast, in the case of the protective sheets of the comparative examples, which do not satisfy the above relationship, it is clear that it is not possible to simultaneously prevent separation of the protective layer and prevent lifting of the protective layer. Furthermore, when comparing the evaluation results of the protective layer lifting of the protective sheets of Examples 1 to 3, in which the ratio R is 2.0 or more, with the evaluation results of the protective layer lifting of the protective sheets of each comparative example, in which the ratio R is less than 2.0, it is found that the protective sheets of Examples 1 to 3 gave particularly good results. In addition, in the protective sheet of Comparative Example 1, the peel force P A Value of and peel force P B Since the value was too high, it was not possible to evaluate the lifting of the protective layer. For that reason, the protective sheet of Comparative Example 1 is marked in Table 1 with respect to the evaluation of protective layer lifting as "evaluation not possible." [Explanation of symbols]

[0087] 1 protective layer, 2 first release liner, 3 second release liner, 10 protective sheet.

Claims

1. A protective layer; a first release liner disposed on one surface of the protective layer; a second release liner disposed on the other surface of the protective layer; the protective layer contains a water-soluble polymer compound, The peeling force of the first release liner from the protective layer is P Ａ and the peeling force of the second release liner with respect to the protective layer is P Ｂ When Peeling force P Ａ , and peel force P Ｂ satisfies the following relation: Protective sheet. P Ａ <P Ｂ 70mN / 25mm≦P Ｂ ≦2000mN / 25mm

2. The thickness of the first release liner is T Ａ and the thickness of the second release liner is T Ｂ When Thickness T Ａ and thickness T Ｂ satisfies the following relation: The protective sheet according to claim 1 . T Ａ <T Ｂ 35μm<T Ｂ <80μm

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