Protective sheet

Abstract

To provide a protective sheet that allows easy positioning of a protective layer with respect to a transfer device, an adherend and the like.SOLUTION: A protective sheet according to the present invention comprises a protective layer attached to an adherend, and a release liner provided on a surface of the protective layer. The protective layer contains a water-soluble polymer. The release liner is provided with an inner surface that faces the protective layer, and an outer surface that serves as an opposite surface from the inner surface. An optical transmittance of transmission from the outer surface of the release liner through the protective layer is at least 15% lower than an optical transmittance of the release liner at least at one wavelength.SELECTED DRAWING: Figure 1A

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 manufacturing methods of the above electronic components, the manufacturing method 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] As described above, when one semiconductor wafer is divided (cleaved) to obtain a plurality of semiconductor chips, a part of the semiconductor wafer near the divided portion (cleaved portion) may be pulverized, generating a small amount of dust. Furthermore, if such dust 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. Therefore, when manufacturing semiconductor chips, it is conceivable to protect the semiconductor chips by attaching the protective sheet to one surface side (the side on which a circuit pattern is formed) of one of the semiconductor wafers. It is believed that such a protective sheet having a water-soluble protective layer that can be easily removed from an adherend such as a semiconductor wafer after use is useful.

[0006] When adhering a protective sheet to an adherend such as a semiconductor wafer, possible methods include placing the protective sheet cut to a specified shape in a laminating device and adhering it to the adherend, or directly adhering the protective sheet cut to a specified shape to the adherend. Furthermore, it is believed that providing a gripping area on the release liner is effective in facilitating alignment of the protective layer and peeling the release liner from the protective layer when setting it in a laminating device or directly attaching it to an adherend. However, doing so would cause the release liner to extend outward beyond the outer edge of the protective layer, and the outer edges of the release liner and the protective layer would no longer coincide, making it difficult to accurately determine the position of the protective layer from the release liner side, which could make it difficult to align the protective layer. Therefore, an object of the present invention is to provide a protective sheet that allows easy alignment of the protective layer with respect to a transfer device, an adherend, etc. [Means for solving the problem]

[0007] That is, the protective sheet according to the present invention is A protective layer attached to the adherend; A release liner disposed on the surface of the protective layer, the protective layer comprises a water-soluble polymer, the release liner has an inner surface facing the protective layer and an outer surface opposite the inner surface, The light transmittance of the release liner from the outer surface through the protective layer is at least 15% lower than the light transmittance of the release liner at at least one wavelength.

[0008] The protective sheet according to the present invention further comprises: A protective layer attached to the adherend; 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, each of the first release liner and the second release liner has an inner surface facing the protective layer and an outer surface opposite the inner surface; The light transmittance from the outer surface of the second release liner to the outer surface of the first release liner is at least 15% less than the light transmittance of the second release liner at at least one wavelength. Effect of the Invention

[0009] According to the present invention, it is possible to provide a protective sheet that allows easy alignment of the protective layer with respect to a transfer device, an adherend, etc. [Brief description of the drawings]

[0010] [Figure 1A] FIG. 1 is a schematic cross-sectional view showing a configuration of a protective sheet according to one embodiment of the present invention. [Figure 1B]FIG. 4 is a schematic cross-sectional view showing the configuration of a protective sheet according to another embodiment of the present invention. [Figure 2A] FIG. 3 is a schematic cross-sectional view showing one embodiment of cutting a protective layer in a protective sheet according to one embodiment of the present invention. [Figure 2B] FIG. 4 is a schematic cross-sectional view showing one embodiment of cutting a protective layer to obtain a protective sheet according to another embodiment of the present invention. [Figure 2C] FIG. 4 is a schematic cross-sectional view showing an example of obtaining a protective sheet according to another embodiment by laminating a first release liner to the exposed surface of a protective layer. [Figure 3A] FIG. 13 is a schematic cross-sectional view showing a state in which the position of a protective layer obtained by post-precutting is detected by using a sensing device. [Figure 3B] 1 is a schematic cross-sectional view showing how a protective layer obtained by post-precutting is bonded to a surface to be protected of a semiconductor wafer using a mounting device. [Figure 3C] 1 is a schematic cross-sectional view showing a state in which a protective layer is bonded to a surface to be protected of a semiconductor wafer. [Figure 4A] FIG. 13 is a schematic cross-sectional view showing how the position of a protective layer obtained by pre-cutting is detected by using a sensing device. [Figure 4B] 1 is a schematic cross-sectional view showing how a protective layer obtained by pre-cutting is bonded to a surface to be protected of a semiconductor wafer using a laminating device. [Figure 4C] 1 is a schematic cross-sectional view showing a state in which a protective layer is bonded to a surface to be protected of a semiconductor wafer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, one embodiment of the present invention will be described.

[0012] [Protective sheet according to the first embodiment] As shown in Figures 1A and 1B, the protective sheet 10 according to the first 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 protective sheet 10 according to the first 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.

[0013] The protective layer 1 of this embodiment has sufficient adhesiveness to allow it to be attached to an adherend. The protective layer 1 of the present embodiment 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 (in this embodiment, a "semiconductor wafer") by adhering the protective layer 1 to the adherend while various treatments are being performed on the adherend.

[0014] 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 a semiconductor wafer. 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. The protective sheet 10 of this embodiment is used by peeling off the second release liner 3 and attaching the other surface of the protective layer 1 to a semiconductor wafer.

[0015] In this embodiment, as described later, the surface to be protected of the adherend and the protective layer 1 are accurately positioned, and then the protective layer 1 is attached to the surface to be protected. Positioning may be indirect rather than direct. For example, when protective layer 1 is set in a laminating device in which the adherend is planned to be placed at a predetermined position and protective layer 1 is bonded to the adherend using the laminating device, the positioning of protective layer 1 on the adherend can be performed by positioning the protective layer 1 in the laminating device.

[0016] In this embodiment, at the time of positioning, protective layer 1 is not attached to the entire surface of second release liner 3, but is provided so as to cover only a portion of the inner surface of second release liner 3. In this embodiment, when positioned, the protective sheet 10 has a laminated region where the second release liner 3 and the protective layer 1 are laminated, and a single-layer region where the protective layer 1 is not laminated on the second release liner 3 and only the second release liner 3 is present, and the single-layer region is arranged to surround the laminated region.

[0017] In the protective sheet 10 according to the first embodiment, the light transmittance of the second release liner 3 is higher than the light transmittance of any of the protective layer 1, the first release liner 2, or the laminate of the protective layer 1 and the first release liner 2. More specifically, in this embodiment, the light transmittance from the outer surface of the second release liner to the protective layer 1 is at least 15% lower than the light transmittance of the second release liner 3 at at least one wavelength, or the light transmittance from the outer surface of the second release liner 3 to the outer surface of the first release liner 2 is at least 15% lower than the light transmittance of the second release liner 3 at at least one wavelength.

[0018] In the protective sheet 10 according to the first embodiment, the transmittance T of the second release liner 3 measured at a wavelength included in the near infrared region is A and the transmittance T of the protective layer 1 measured at the one wavelength. B The difference between AB and the transmittance T A and the transmittance T of the first release liner 2 measured at the one wavelength. C The difference between AC and the transmittance T A and the transmittance T of the laminate of the protective layer 1 and the first release liner 2 measured at the one wavelength. D The difference between AD When the above ΔT AB , the ΔT AC , or the ΔT AD However, it is more than 15%.

[0019] In this specification, the near-infrared region refers to a region having a wavelength of 800 nm or more and 2500 nm or less. In the first embodiment of the present invention, it is preferable to use a wavelength of 1060 nm as one wavelength included in the near infrared region.

[0020] The protective layer 1 is used by being attached to the surface of an electronic component to be protected. The electronic component may be, for example, 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).

[0021] In protective sheet 10 shown in FIG. 1A, protective layer 1, first release liner 2, and second release liner 3 have approximately the same dimensions in a plan view. In addition, the protective layer 1 usually has a size larger than the surface of the electronic component to be protected in a plan view.

[0022] The protective sheet 10 of this embodiment is used to protect a semiconductor wafer, for example, in the following manner. (a) After one and the other release liners (2, 3) are laminated on both sides of the protective layer 1 to obtain the protective sheet, the laminate of one release liner (first release liner 2) and the protective layer 1 is cut so that the planar dimensions of the laminate are approximately the same as the planar dimensions of one semiconductor wafer (post-precut method). That is, in the post-precut method, the protective sheet 10 is configured such that the protective layer 1 is sandwiched between another release liner (second release liner 3) having planar dimensions larger than the protective layer 1, and one release liner (first release liner 2) having planar dimensions approximately the same as those of the protective layer 1.

[0023] The protective sheet 10 of this embodiment is also used to protect a semiconductor wafer in the following manner. (b) After one release liner (first release liner 2) is laminated on one surface of the protective layer 1, only the protective layer 1 is cut so that its planar dimensions are approximately the same as those of the semiconductor wafer (pre-cut method). Then, the other release liner having a planar dimension larger than that of the protective layer 1 (for example, a release liner (second release liner 3) having approximately the same planar dimensions as the one release liner) is laminated on the other surface of the cut protective layer 1. That is, in the pre-cut method, the protective sheet 10 is configured such that the protective layer 1 is sandwiched between two release liners (one and the other release liner) having planar dimensions larger than that of the protective layer 1.

[0024] As described above in (a), in one aspect of this embodiment, when the protective layer 1 is bonded to the surface of the electronic component to be protected, the protective layer 1, in a laminated state with the first release liner 2, is cut from the first release liner 2 side so that it has approximately the same planar dimensions as the surface of the electronic component to be protected (see Figure 2A). That is, in protective sheet 10 shown in FIG. 1A, protective layer 1 is made to have substantially the same dimensions as the surface of the electronic component to be protected by a post-precutting method.

[0025] In protective sheet 10 shown in FIG. 1A, first release liner 2 and second release liner 3 have approximately the same dimensions in a plan view, and these plan dimensions are larger than the surface of the electronic component to be protected. In contrast, in protective sheet 10 shown in FIG. 1B, protective layer 1 has, in plan view, approximately the same dimensions as the surface of the electronic component to be protected. In detail, the protective layer 1 is laminated with one of the release liners, for example the first release liner 2, and then cut (see FIG. 2B) to have approximately the same planar dimensions as the surface of the electronic component to be protected. That is, in protective sheet 10 shown in FIG. 1B, protective layer 1 is precut to have approximately the same dimensions as the surface of the electronic component to be protected. The other release liner, for example, second release liner 3, is attached to the exposed surface of protective layer 1 after protective layer 1 is cut (see FIG. 2C).

[0026] 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, or may have the same shape as the surface to be protected like the protective layer 1.

[0027] 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 .

[0028] 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 the first release liner 2 to a predetermined thickness (for example, 10 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 first release liner 2. (3) A second release liner 3 is attached to the surface of protective layer 1 opposite to the surface on which first release liner 2 is disposed (the exposed surface of protective layer 1). In the production of protective sheet 10 shown in FIG. 1B, between steps (2) and (3), a step (step (2'), see FIG. 2B) of cutting protective layer 1 so that the protective layer has approximately the same planar dimensions as the surface of the electronic component to be protected is carried out.

[0029] In the protective sheet 10 according to the first embodiment, the protective layer 1 is preferably prepared using a water-soluble resin composition containing an excess liquid component together with the water-soluble polymer compound, 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. When the viscosity at 25° C. is equal to or greater 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.

[0030] 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.

[0031] 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(-CH2)-] means the peak intensity derived from -CH2- in the vinyl alcohol unit, and [VAc(CH3CO-)] means the peak intensity derived from CH3CO- in the vinyl acetate unit.

[0032]

number

[0033] 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).

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] An example of the first release liner 2 is a resin sheet made of a resin such as polyethylene terephthalate (PET). At least the surface of the resin sheet to be bonded to the protective layer 1 may be subjected to a release treatment. The release treatment may be a silicone release treatment. Also, the second release liner 3 may be the same as the first release liner 2 .

[0039] The thickness of the first release liner 2 and the second release liner 3 is preferably 15 μm or more and 75 μm or less, and more preferably 20 μm or more and 60 μm or less. The first release liner 2 and the second release liner 3 may have the same thickness or different thicknesses. 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 .

[0040] As described above, in the protective sheet 10 according to the first embodiment, the transmittance of the second release liner 3 is higher than the transmittance of either the protective layer 1, the first release liner 2, or the laminate of the protective layer 1 and the first release liner 2. In addition, in the protective sheet 10 according to the first embodiment, the transmittance T A and the transmittance T of the protective layer 1 measured at the one wavelength. B The difference between AB and the transmittance T Aand the transmittance T of the first release liner 2 measured at the one wavelength. C The difference between AC and the transmittance T A and the transmittance T of the laminate of the protective layer 1 and the first release liner 2 measured at the one wavelength. D The difference between AD When the above ΔT AB , the ΔT AC , or the ΔT AD However, it is more than 15%. In addition, the transmittance T A means the ratio when the light of the one wavelength is transmitted through the second release liner 3 in the thickness direction, and the transmittance T B means the ratio when the light of the one wavelength is transmitted through the protective layer 1 in the thickness direction, and the transmittance T C means the ratio when the light of the one wavelength is transmitted through the first release liner 2 in the thickness direction, and the transmittance T D means the ratio at which light of one wavelength passes through a laminate of protective layer 1 and first release liner 2 in the direction parallel to the thickness direction. That is, the transmittance T A ~T D means the parallel beam transmittance.

[0041] Light included in the near-infrared region, that is, near-infrared light, has an extremely long wavelength and therefore tends to pass through an object in a direction parallel to the thickness direction when the object is irradiated with the light. Therefore, the above ΔT AB In order to make ΔT 15% or more, it is necessary to prevent light of one wavelength included in the near infrared region from passing through the protective layer 1 in a direction parallel to the thickness direction. AC In order to make the ΔT 15% or more, it is necessary to prevent the light of one wavelength from passing through the first release liner 2 in a direction parallel to the thickness direction. AD In order to make the transmittance 15% or more, it is necessary to prevent the light of one wavelength from transmitting through the laminate of protective layer 1 and first release liner 2 in a direction parallel to the thickness direction. Specifically, it is necessary to absorb a portion of the light of one wavelength that passes parallel to the thickness direction in the protective layer 1 or the first release liner 2, or to diffusely reflect a portion of the light of one wavelength that passes parallel to the thickness direction in the protective layer 1 or the first release liner 2.

[0042] As an example of the treatment for preventing the light of one wavelength from passing through the protective layer 1 in a direction parallel to the thickness direction, a pigment may be included in the protective layer forming composition for forming the protective layer 1. By including a pigment in the protective layer 1, even if the light is near-infrared light such as the light of the one wavelength, the pigment can absorb a part of the light of the one wavelength. Moreover, the pigment can cause a portion of the light of the one wavelength to be diffusely reflected.

[0043] As the pigment, any pigment known in the art can be used. Examples of the pigment include inorganic pigments such as zinc carbonate, zinc oxide, zinc sulfide, talc, kaolin, calcium carbonate, titanium oxide, silica, lithium fluoride, calcium fluoride, barium sulfate, alumina, zirconia, iron oxide, iron hydroxide, chromium oxide, spinel-type fired system, chromate system, chrome vermilion system, Prussian blue system, aluminum powder system, bronze powder system, and calcium phosphate, and organic pigments such as phthalocyanine system, azo system, condensed azo system, azo lake system, anthraquinone system, perylene-perinone system, indigo-thioindigo system, isoindolinone system, azomethane system, and carbon black system.

[0044] The protective layer 1 preferably contains 0.1 part by mass or more of the pigment per 100 parts by mass of the water-soluble polymer compound, more preferably 0.5 part by mass or more, and even more preferably 1.0 part by mass or more. Furthermore, the protective layer 1 preferably contains 30 parts by mass or less of the pigment per 100 parts by mass of the water-soluble polymer compound, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. The pigment means a colorant that is insoluble in organic solvents such as water and alcohol.

[0045] As another example of the treatment for preventing the light of one wavelength from passing through the protective layer 1 in a direction parallel to the thickness direction, a foaming treatment may be performed on the protective layer-forming composition for forming the protective layer 1. The protective layer 1 formed from the protective layer-forming composition that has been subjected to such foaming treatment contains a plurality of bubbles. This allows diffuse reflection to occur in the multiple air bubbles contained in the protective layer 1, thereby reducing the proportion of near-infrared light such as the one-wavelength light that passes through the protective layer 1 parallel to the thickness direction.

[0046] As explained above, when the first release liner 2 is a resin sheet made using a resin such as polyethylene terephthalate (PET), an example of a treatment that prevents the light of one wavelength from passing through the first release liner 2 parallel to the thickness direction is to subject the resin composition used to make the resin sheet to a foaming treatment. The resin sheet (resin foam sheet) obtained by subjecting the resin composition to foaming treatment contains a plurality of bubbles, and therefore the plurality of bubbles can cause diffuse reflection. This makes it possible to reduce the proportion of near-infrared light, such as the light of one wavelength, that is transmitted through the first release liner 2 in the direction parallel to the thickness direction. Furthermore, when the first release liner 2 is a resin sheet made of a resin such as polyethylene terephthalate (PET), the resin sheet may be subjected to a foaming treatment. For example, the resin sheet may be stretched and subjected to a foaming treatment to generate voids during the stretching.

[0047] In addition, an example of a treatment that prevents the light of one wavelength from passing through the first release liner 2 parallel to the thickness direction is coating at least one surface of the first release liner 2 with an ink containing a pigment such as titanium oxide. By forming a coating layer containing a pigment on at least one surface (the inner surface, the outer surface, or both surfaces) of the first release liner 2, even in the case of near-infrared light such as the light of the one wavelength, a portion of the light of the one wavelength can be absorbed by the pigment contained in the coating layer. Moreover, the pigment can cause a portion of the light of the one wavelength to be diffusely reflected.

[0048] Furthermore, the first release liner 2 may be constructed using a resin containing a pigment, and the proportion of the light of said wavelength that transmits through the first release liner 2 parallel to the thickness direction may be reduced by having the pigment absorb a portion of the light of said wavelength or by having the pigment diffusely reflect a portion of the light of said wavelength.

[0049] Furthermore, examples of the treatment that prevents light of one wavelength from passing through the first release liner 2 parallel to the thickness direction include matting or embossing at least one surface of the first release liner 2 . By subjecting at least one surface of the first release liner 2 to a matte finish or embossing finish, it is possible to generate diffuse reflection at the irregularities on the surface of the first release liner 2 . This makes it possible to reduce the proportion of near-infrared light, such as the light of one wavelength, that is transmitted through the first release liner 2 in the direction parallel to the thickness direction.

[0050] The first release liner 2 may be a laminate film having a layer for blocking light. The first release liner 2 may be a laminate film having a resin layer and a metal deposition layer, or may be an aluminum laminate film or the like.

[0051] The light of the one wavelength is prevented from passing through the laminate of the protective layer 1 and the first release liner 2 in the thickness direction, and the transmittance T A and the transmittance T of the laminate of the protective layer 1 and the first release liner 2 D The difference between AD In order to make the transmittance T Aand the transmittance T of protective layer 1 B The difference between AB , and the transmittance T of the second release liner 3 A and the transmittance T of the first release liner 2 C The difference between AC The combined value of these factors must be 15% or more. For example, ΔT AB With ΔT set to 5% or more, AC or 10% or more, or ΔT AB With ΔT set to 10% or more, AC can be set to 5% or more. Transmittance of protective layer 1 T B and the transmittance T of the first release liner C can be adjusted in a similar manner as described above. Of course, as explained above, ΔT AB and ΔT AC By setting at least one of the above to 15% or more, the above ΔT AD can be set to 15% or more.

[0052] The difference in transmittance for determining the presence of protective layer 1 and first release liner 2 through second release liner 3 is preferably 20% or more, and more preferably 25% or more. The difference in transmittance may be 30% or more, 40% or more, or 50% or more. Incidentally, it is also preferable for there to be such a difference in transmittance in other embodiments described later.

[0053] The transmittance T of the protective layer 1 measured at the one wavelength B , the transmittance T of the first release liner 2 measured at the one wavelength C , and the transmittance T of the laminate of the protective layer 1 and the first release liner 2 measured at the one wavelength. D From the viewpoint of making the difference as large as possible between the transmittance T A It is preferable that the transmittance of the light of the one wavelength is high. The transmittance T of the second release liner 3 measured at the one wavelength A is preferably 65% ​​or more, more preferably 75% or more, and even more preferably 85% or more. The transmittance T of the second release liner 3 measured at the one wavelength A may be 100% or less, or may be 95% or less.

[0054] The transmittance T of the second release liner 3 at the one wavelength A , the transmittance T of the protective layer 1 at the one wavelength B , the transmittance T of the first release liner 2 at the one wavelength C , and the transmittance T of the laminate of the protective layer 1 and the first release liner 2 at the one wavelength. D can be obtained by measuring the parallel ray transmittance at the one wavelength using a spectrophotometer (manufactured by JASCO Corporation, product name "V-670"). In the measurement of parallel ray transmittance using a spectrophotometer, the measurement wavelength can be in the range of 190 nm to 3000 nm. Furthermore, the second release liner 3 can be measured with a thickness of approximately 50 μm, the protective layer 1 can be measured with a thickness of approximately 10 μm, and the first release liner 2 can be measured with a thickness of approximately 40 μm. The parallel ray transmittance is measured using a spectrophotometer without using an integrating sphere.

[0055] [Protective sheet according to the second embodiment] The protective sheet 10 according to the second embodiment of the present invention has a transmittance T A’ and the transmittance T of the protective layer 1 measured at the one wavelength. B’ The difference between A’B’ and the transmittance T A’ and the transmittance T of the first release liner 2 measured at the one wavelength. C’ The difference between A’C’ and the transmittance T A’and the transmittance T of the laminate of the protective layer 1 and the first release liner 2 measured at the one wavelength. D’ The difference between A’D’ When the above ΔT A’B’ , the ΔT A’C’ , or the ΔT A’D’ The protective sheet 10 has the same structure as the protective sheet 10 according to the first embodiment described above, except that the percentage of the protective sheet 10 is 15% or more.

[0056] In this specification, the ultraviolet region refers to a region having a wavelength of 200 nm or more and less than 380 nm. In the second embodiment of the present invention, it is preferable to use a wavelength of 330 nm as the wavelength included in the ultraviolet region.

[0057] The transmittance T A’ ~T D’ is the transmittance T A ~T D Similarly, it means the parallel ray transmittance. In addition, the transmittance T of the second release liner 3 at a wavelength included in the ultraviolet region A’ , the transmittance T of the protective layer 1 at the one wavelength B’ , the transmittance T of the first release liner 2 at the one wavelength C’ , and the transmittance T of the laminate of the protective layer 1 and the first release liner 2 at the one wavelength. D’ can be measured in the same manner as described above.

[0058] Light in the ultraviolet range, i.e., ultraviolet light (ultraviolet rays), has an extremely short wavelength, and therefore when irradiated onto an object, is less likely to pass through the object than light with an extremely long wavelength as described above, i.e., near-infrared light. Therefore, by subjecting the protective layer 1 to the same treatment as described in the first embodiment, the ΔT A’B’ can be 15% or more, and by subjecting the first release liner 2 to the same treatment as described in the first embodiment above, the ΔT A’C’can be 15% or more, and by subjecting a laminate of the protective layer 1 and the first release liner 2 to the same treatment as described in the first embodiment above, the ΔT A’D’ can be set to 15% or more.

[0059] In addition, the above ΔT can also be reduced by performing other processes. A’B’ , ΔT A’C’ , and ΔT A’D’ can be set to 15% or more. For example, the protective layer 1 may be formed from the protective layer-forming composition containing an ultraviolet absorbent, or the first release liner 2 may be formed from a resin containing an ultraviolet absorbent, thereby making it possible to reduce the ΔT A’B’ , the ΔT A’C’ , and ΔT A’D’ can be set to 15% or more.

[0060] Examples of the ultraviolet absorbing agent include triazine-based ultraviolet absorbing agents, benzotriazole-based ultraviolet absorbing agents, benzophenone-based ultraviolet absorbing agents, oxybenzophenone-based ultraviolet absorbing agents, salicylic acid ester-based ultraviolet absorbing agents, and cyanoacrylate-based ultraviolet absorbing agents. These various ultraviolet absorbents may be used alone or in combination of two or more.

[0061] When the protective layer 1 contains the ultraviolet absorber, the protective layer 1 preferably contains 0.1 part by mass or more of the ultraviolet absorber per 100 parts by mass of the water-soluble polymer compound, more preferably contains 0.5 part by mass or more, and even more preferably contains 1.0 part by mass or more. Furthermore, when the protective layer 1 contains the ultraviolet absorber, the protective layer 1 preferably contains 20 parts by mass or less of the ultraviolet absorber per 100 parts by mass of the water-soluble polymer compound, more preferably contains 15 parts by mass or less, and even more preferably contains 10 parts by mass or less.

[0062] In addition, the protective layer 1 may be formed from the protective layer-forming composition containing an azo-based dye, which will be described later, instead of the ultraviolet absorbing agent, or the first release liner 2 may be formed from a resin containing the azo-based dye, so that the ΔT A’B’ , the ΔT A’C’ , and ΔT A’D’ can be set to 15% or more. Examples of the azo dye include yellow dyes that exhibit a yellow color.

[0063] When the protective layer 1 contains the azo dye, the content thereof can be the same as the content of the ultraviolet absorbing agent described above.

[0064] In addition, the protective layer 1 may be formed from the protective layer-forming composition containing the azo dye in addition to the ultraviolet absorbent, or the first release liner 2 may be formed from a resin containing the azo dye in addition to the ultraviolet absorbent, thereby making it possible to reduce the ΔT A’B’ , the ΔT A’C’ , and ΔT A’D’ can be set to 15% or more.

[0065] [Protective sheet according to the third embodiment] The protective sheet 10 according to the third embodiment of the present invention has a transmittance T A’’ and the transmittance T of the protective layer 1 measured at the one wavelength. B’’ The difference between A’’B’’ and the transmittance T A’’ and the transmittance T of the first release liner 2 measured at the one wavelength. C’’ The difference between A’’C’’ and the transmittance T A’’ and the transmittance T of the laminate of the protective layer 1 and the first release liner 2 measured at the one wavelength. D’’ The difference between A’’D’’ When the above ΔT A’’B’’ , the ΔT A’’C’’ , or the ΔT A’’D’’The protective sheet 10 has the same structure as the protective sheet 10 according to the first embodiment described above, except that the percentage of the protective sheet 10 is 15% or more.

[0066] In this specification, the visible region refers to a wavelength region of 380 nm or more and less than 800 nm. In the third embodiment of the present invention, it is preferable to use a wavelength within the range of 550 nm to 650 nm as the wavelength included in the visible region.

[0067] Transmittance T A’’ ~T D’’ is the transmittance T A ~T D Similarly, it means the parallel ray transmittance. In addition, the transmittance T of the second release liner 3 at one wavelength included in the visible range A’’ , the transmittance T of the protective layer 1 at the one wavelength B’’ , the transmittance T of the first release liner 2 at the one wavelength C’’ , and the transmittance T of the laminate of the protective layer 1 and the first release liner 2 at the one wavelength. D’’ can be measured in the same manner as described above.

[0068] Light included in the visible region, that is, visible light (visible rays), has a shorter wavelength than near-infrared light, and therefore when irradiated onto an object, is less likely to pass through the object than near-infrared light. Therefore, by subjecting the protective layer 1 to the same treatment as described in the first embodiment, the ΔT A’’B’’ can be 15% or more, and by subjecting the first release liner 2 to the same treatment as described in the first embodiment above, the ΔT A’’C’’ can be 15% or more, and by subjecting a laminate of the protective layer 1 and the first release liner 2 to the same treatment as described in the first embodiment above, the ΔT A’’D’’ can be set to 15% or more.

[0069] In addition, the protective layer 1 may be formed from the protective layer-forming composition containing a component that absorbs visible light, or the first release liner 2 may be formed from a resin containing a component that absorbs visible light, thereby reducing the ΔT A’’B’’ , the ΔT A’’C’’ , and ΔT A’’D’’ can be set to 15% or more. An example of a component that absorbs visible light is a dye. The dye refers to a colorant that is soluble in water, organic solvents, and the like.

[0070] Examples of the dye include azo dyes, anthraquinone, quinonephthalone, styryl, diphenylmethane, triphenylmethane, oxazine, triazine, xanthan, methane, azomethine, acridine, and diazine.

[0071] When the dye is contained in the protective layer 1, the protective layer 1 preferably contains 0.1 part by mass or more of the dye per 100 parts by mass of the water-soluble polymer compound, more preferably 0.5 part by mass or more, and even more preferably 1.0 part by mass or more. When the dye is contained in the protective layer 1, the protective layer 1 preferably contains 30 parts by weight or less of the dye per 100 parts by weight of the water-soluble polymer compound, more preferably 20 parts by weight or less, and even more preferably 10 parts by weight or less.

[0072] In the protective sheets 10 according to the first to third embodiments described above, examples have been described in which the difference in transmittance is used to distinguish between the second release liner 3 and the protective layer 1, between the second release liner 3 and the first release liner 2, or between the second release liner 3 and the laminate of the protective layer 1 and the first release liner 2. On the other hand, the second release liner 3 may be distinguished from the protective layer 1, the second release liner 3 from the first release liner 2, and the second release liner 3 from the laminate of the protective layer 1 and the first release liner 2 by differences in haze (cloudiness) or brightness (L value) in addition to differences in transmittance.

[0073] When distinguishing between the first release liner 2 and the second release liner 3 based on the difference in haze (cloudiness), it is preferable that the haze of the first release liner 2 be as high as possible, and it is preferable that the haze of the second release liner 3 be as low as possible. The lower limit of the haze of the first release liner 2 is preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, even more preferably 93% or more, and particularly preferably 98% or more. Furthermore, the upper limit of the haze of the second release liner 3 is preferably 10% or less, more preferably 7% or less, even more preferably 5% or less, and particularly preferably 3% or less. The haze of the first release liner 2 and the haze of the second release liner 3 refer to the haze in the thickness direction, and the haze in the thickness direction is a value measured in accordance with JIS K 7136. The haze in the thickness direction can be measured using a turbidity meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH2000").

[0074] Furthermore, when distinguishing between the protective layer 1 and the second release liner 3 based on the difference in haze (cloudiness), it is preferable that the haze of the protective layer 1 be as high as possible, and the haze of the second release liner 3 be as low as possible. The lower limit of the haze of the protective layer 1 is preferably 15% or more, more preferably 25% or more, and even more preferably 35% or more. Moreover, the upper limit of the haze of the second release liner 3 is preferably set as explained above. The haze of the protective layer 1 also refers to the haze in the thickness direction, and the haze in the thickness direction can be measured in the same manner as that of the first release liner 2 and the second release liner 3.

[0075] When distinguishing the first release liner 2 and the second release liner 3 based on the difference in lightness (L value), it is preferable that the lightness (L value) of the first release liner 2 is as low as possible, and it is preferable that the lightness (L value) of the second release liner 3 is as high as possible. The upper limit of the lightness (L value) of the first release liner 2 is preferably 10 or less, more preferably 7 or less, and even more preferably 5 or less. Furthermore, the lower limit of the lightness (L value) of the second release liner 3 is preferably 70 or more, more preferably 80 or more, and even more preferably 90 or more. The lightness (L value) of the first release liner 2 and the lightness (L value) of the second release liner 3 can be measured using a color meter (manufactured by Suga Test Instruments Co., Ltd., product name "SM-T"). In the measurement using the color meter, the chromaticity (a value and b value) of the first release liner 2 and the chromaticity (a value and b value) of the second release liner 3 can also be measured simultaneously.

[0076] Furthermore, when distinguishing between the protective layer 1 and the second release liner 3 based on the difference in lightness (L value), it is preferable that the lightness (L value) of the protective layer 1 is as low as possible, and the lightness (L value) of the second release liner 3 is as high as possible. The upper limit of the lightness (L value) of the protective layer 1 is preferably 70 or less, and more preferably 65 or less. The lower limit of the lightness (L value) of the second release liner 3 is preferably 80 or more, and more preferably 90 or more. The lightness (L value) of the protective layer 1 can be measured using the color meter in the same manner as the lightness (L value) of the first release liner 2 and the lightness (L value) of the second release liner 3. In the measurement using the color meter, the chromaticity (a value and b value) of the protective layer 1 can also be measured at the same time.

[0077] The protective layer 1 and the first and second release liners 2 and 3 can also be distinguished by the difference in gloss (hereinafter also referred to as gloss difference). For example, the gloss difference can be determined by measuring the gloss when light is incident at an angle of 60° (gloss at an incident angle of 60°) on a laminate in which a first release liner 2 is laminated on one side of a protective layer 1 and a second release liner 3 is laminated on the other side of the protective layer 1. The light incident at an angle of 60° can be white light. The gloss at an incident angle of 60° can be measured using a spectrophotometer CM-26dG manufactured by Konica Minolta. The gloss difference of the laminate is preferably 20 GU or more, more preferably 30 GU or more, even more preferably 50 GU or more, and even more preferably 90 GU or more. When the gloss difference of the laminate is within the above range, the protective layer 1 can be sufficiently distinguished from the first release liner 2 and the second release liner 3.

[0078] Next, using a semiconductor wafer as an example of an electronic component, an example of bonding a protective layer 1 (see FIG. 2A) obtained by the post-precut method to the surface of the semiconductor wafer to be protected will be described, as well as an example of bonding a protective layer 1 (see FIG. 2B) obtained by the pre-precut method to the surface of the semiconductor wafer to be protected. In the following, first, an example will be described in which protective sheet 10 having protective layer 1 obtained by the post-precut method is used to attach protective layer 1 to the surface to be protected of a semiconductor wafer.

[0079] The bonding of protective layer 1 to the surface to be protected of a semiconductor wafer using protective sheet 10 having protective layer 1 obtained by the post-precut method is carried out using a sensing device 100 that detects the position of protective layer 1 in protective sheet 10, and a mounting device 200 that bonds protective layer 1 to the surface to be protected of the semiconductor wafer based on the position of protective layer 1 detected by the sensing device 100.

[0080] As shown in FIG. 3A, the sensing device 100 includes a holding table 101 having a holding surface 1011 that holds the protective sheet 10 from the side of the first release liner 2, and a position detection unit 102 that is arranged at a distance opposite to the holding surface 1011 of the holding table 101 and detects the position of the protective layer 1 in the protective sheet 10. The position detection unit 102 includes a camera 1021 for capturing an image of the protective sheet 10 from the side of the second release liner 3, and a lens 1022 for widening the imaging field of the camera 1021. That is, the sensing device 100 detects the position of the protective layer 1 in the protective sheet 10 using an image captured by the camera 1021 from the side of the second release liner 3. As indicated by the dashed line in FIG. 3A, the imaging field of view of camera 1021 is expanded by lens 1022 to cover the entire protection sheet 10. That is, in the sensing device 100, the camera 1021 is capable of capturing an image of the entire protective sheet 10 from the second release liner 3 side.

[0081] As described above, in the protective sheet 10 according to the first embodiment, the transmittance T A and the transmittance T of the protective layer 1 at the one wavelength. B The difference between AB is 15% or more, or the transmittance T A and the transmittance T of the first release liner 2 at the one wavelength. C The difference between AC is 15% or more, or A and the transmittance T of the laminate of the protective layer 1 and the first release liner 2 at the one wavelength. D The difference between AD is more than 15%. The protective sheet 10 in the first embodiment has an area (single layer area) having a single layer structure consisting of only the second release liner 3, and an area (laminate area) having a laminate structure consisting of the first release liner 2 and protective layer 1. The intensity of light transmitted through protective sheet 10 from the side where protective layer 1 is provided differs between the light transmitted through the single-layer region and the light transmitted through the laminated region. In this embodiment, the light transmittance from the outer surface of the second release liner through the protective layer 1, i.e., the transmittance in the laminated region, is 15% or more lower than the light transmittance of the second release liner 3 alone (the transmittance in the single layer region). Therefore, in this embodiment, by photographing the protective sheet 10 with a camera 1021 (near-infrared camera) from the outer surface side of the second release liner 3, the single-layer region can be identified as a bright area, and the laminated region can be identified as a dark area that is darker than the bright area. In this embodiment, by having a difference in transmittance of 15% or more, sufficient contrast is formed between the dark and bright areas, and the outer periphery of the laminated region can be detected with high accuracy. Therefore, in protective sheet 10 according to the first embodiment, the position of protective layer 1 can be identified. This makes it possible to detect the position of the protective layer 1 on the protective sheet 10 in the first embodiment, and also makes it possible to detect at which position on the holding surface 1011 of the holding table 101 the protective layer 1 is disposed.

[0082] As described above, in the protective sheet 10 according to the second embodiment, the transmittance T A’ and the transmittance T of the protective layer 1 at the one wavelength. B’ The difference between A’B’ is 15% or more, or the transmittance T A’ and the transmittance T of the first release liner 2 at the one wavelength. C’ The difference between A’C’ is 15% or more, or A’ and the transmittance T of the laminate of the protective layer 1 and the first release liner 2 at the one wavelength. D’ The difference between A’D’ is more than 15%. That is, in protective sheet 10 according to the second embodiment, the intensity of ultraviolet light transmitted through the laminated region and the single-layer region differs. Therefore, as in the first embodiment, by photographing the protective sheet 10 from the outer surface side of the second release liner 3 with a camera 1021 (ultraviolet camera), the single-layer area can be seen as a bright area, and the laminated area can be seen as a dark area that is darker than the bright area. Therefore, by identifying the light and dark areas in the image, it is possible to identify the position of protective layer 1 in protective sheet 10 according to the second embodiment as well. This makes it possible to detect the position of the protective layer 1 on the protective sheet 10 in the second embodiment, and also makes it possible to detect at which position on the holding surface 1011 of the holding table 101 the protective layer 1 is disposed.

[0083] Furthermore, as described above, in the protective sheet 10 according to the third embodiment, the transmittance T A’’ and the transmittance T of the protective layer 1 at the one wavelength. B’’ The difference between A’’B’’ is 15% or more, or the transmittance T A’’ and the transmittance T of the first release liner 2 at the one wavelength. C’’ The difference between A’’C’’ is 15% or more, or A’’ and the transmittance T of the laminate of the protective layer 1 and the first release liner 2 at the one wavelength. D’’ The difference between A’’D’’ is more than 15%. That is, in the protective sheet 10 according to the third embodiment, the intensity of visible light transmitted through the laminated region differs from that transmitted through the single-layer region. Therefore, as in the first embodiment, by photographing the protective sheet 10 with a camera 1021 (visible light camera) from the outer surface side of the second release liner 3, the single-layer area can be seen as a bright area, and the laminated area can be seen as a dark area that is darker than the bright area. Therefore, by identifying the light and dark areas, the position of the protective layer 1 can also be identified in the protective sheet 10 according to the third embodiment. This makes it possible to detect the position of the protective layer 1 on the protective sheet 10 in the third embodiment, and also makes it possible to detect at which position on the holding surface 1011 of the holding table 101 the protective layer 1 is disposed.

[0084] In this embodiment, in order to improve the detectability of the camera 1021, a backlight may be provided and light including any one of near infrared rays, ultraviolet rays, and visible rays may be irradiated from the inner surface side of the second release liner 3. After the position of the protective layer 1 on the protective sheet 10 is detected and the position of the protective layer 1 on the holding surface 1011 of the holding table 101 is detected, the second release liner 3 is peeled off and one side of the protective layer 1 is exposed.

[0085] As shown in FIG. 3B, 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 following description, 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. 3B) 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. 3B) is defined as the Y-axis direction.

[0086] As shown in FIG. 3B, in the mounting apparatus 200, an electrostatic chuck table 202 holds the dicing die bond film D to which the semiconductor wafer W is attached by electrostatic force. The dicing die bond film D includes a die bond film in which a pressure-sensitive adhesive layer is laminated on a substrate, and a die bond layer disposed on the pressure-sensitive adhesive layer of the die bond film. The semiconductor wafer W is bonded to the die bond layer of the dicing die bond film D. In addition, a dicing ring R is attached to the edge side of the dicing die bond film D. Furthermore, as shown in FIG. 3B, in the mounting device 200, the head portion 203 holds, for example by suction, the holding table 101 which holds the laminate of the protective layer 1 and the first release liner 2 from the side of the first release liner 2. In addition, in the mounting device 200, the head unit 203 is configured to be movable within the chamber 201 along the X-axis direction, the Y-axis direction, and the Z-axis direction.

[0087] In the mounting apparatus 200, the inside of the chamber 201 is maintained at atmospheric pressure before the head unit 203 holds the holding table 101, and the pressure is reduced by the pump P after the head unit 203 holds the holding table 101. That is, the holding table 101 is held on the head portion 203 under atmospheric pressure, and the protective layer 1 is bonded to the surface to be protected of the semiconductor wafer W under reduced pressure.

[0088] In the mounting device 200 configured as described above, the protective layer 1 is bonded to the surface to be protected of the semiconductor wafer W based on information on the position of the protective layer 1 detected by the sensing device 100, more specifically, information on at which position on the holding surface 1011 of the holding table 101 the protective layer 1 is located (hereinafter simply referred to as position information of the protective layer on the holding table).

[0089] Specifically, based on the position information of the protective layer on the holding table, the head unit 203 is moved in the X-axis or Y-axis direction until the outer periphery of the semiconductor wafer W and the outer periphery of the protective layer 1 approximately coincide with each other, and then the head unit 203 is moved downward in the Z-axis direction to bond the exposed surface of the protective layer 1 to the surface of the semiconductor wafer W to be protected. The exposed surface of the protective layer 1 is preferably attached while applying a pressure of about 0.3 MPa. This allows the exposed surface of the protective layer 1 to be bonded sufficiently to the surface of the semiconductor wafer W to be protected. Then, after the exposed surface of the protective layer 1 has been thoroughly bonded to the surface to be protected of the semiconductor wafer W, the head portion 203 is moved upward in the Z-axis direction to release the first release liner 2 from the protective layer 1. This allows the protective layer 1 to be provided on the surface to be protected of the semiconductor wafer W, as shown in FIG. 3C. When bonding the exposed surface of the protective layer 1 to the surface of the semiconductor wafer W to be protected, at least one of the holding table 101 and the electrostatic chuck table 202 may be kept in a heated state.

[0090] Next, an example will be described in which a protective sheet having a protective layer 1 obtained by a pre-cut method is used to attach the protective layer 1 to the surface to be protected of a semiconductor wafer.

[0091] When a protective sheet 10 having a protective layer 1 obtained by the pre-cut method as shown in Figure 1B is used to bond to the surface of a semiconductor wafer to be protected, either the first release liner 2 or the second release liner 3 is peeled off to expose the surface of protective layer 1, and the position of protective layer 1 relative to the bonded release liner is detected. Therefore, in this embodiment, a difference in transmittance must occur between protective layer 1 and the release liner attached to one side of protective layer 1 .

[0092] For example, when the first release liner 2 is peeled off from the protective layer 1 and the second release liner 3 is bonded to the protective layer 1, the transmittance T A and the transmittance T of the protective layer 1 at the one wavelength. B The difference between AB must be 15% or more, and the transmittance T A’ and the transmittance T of the protective layer 1 at the one wavelength. B’ The difference between A’B’ must be 15% or more, and the transmittance T A’’ and the transmittance T of the protective layer 1 at the one wavelength.B’’ The difference between A’’B’’ must be 15% or more. Below, we will explain an example in which a first release liner 2 is peeled off from a protective layer 1, a second release liner 3 is bonded to the protective layer 1, the position of the protective layer 1 relative to the second release liner 3 is detected, and then the protective layer 1 is bonded to the surface of a semiconductor wafer to be protected.

[0093] The bonding of protective layer 1 to the surface to be protected of a semiconductor wafer using protective sheet 10 having protective layer 1 obtained by the pre-cut method is carried out using a sensing device 300 that detects the position of protective layer 1 relative to second release liner 3 and the position of the semiconductor wafer, and a laminating device 400 that bonds protective layer 1 to the surface to be protected of the semiconductor wafer based on the position of protective layer 1 relative to second release liner 3 and the position of the semiconductor wafer detected by sensing device 300.

[0094] As shown in FIG. 4A, the sensing device 300 includes a wafer holding table 301 having a holding surface 3011 for holding a semiconductor wafer W, a gripping tool 302 arranged above the wafer holding table 301 for gripping a laminate of a protective layer 1 and a second release liner 3 from both end edge sides of the laminate, and a position detection unit 303 arranged above the gripping tool 302 for detecting the position of the protective layer 1 relative to the second release liner 3 and the position of the semiconductor wafer W. In the following description, the up-down direction (vertical direction) is defined as the Z-axis direction, the horizontal direction along the cut surface when wafer holding table 301, etc. is cut along a plane parallel to the Z-axis (the horizontal direction along the paper surface in FIG. 4A) 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. 4A) is defined as the Y-axis. In addition, in the following FIG. 4B, the X-axis direction, the Y-axis direction, and the Z-axis direction refer to the same directions as the X-axis direction, the Y-axis direction, and the Z-axis direction in FIG. 4A.

[0095] The position detection unit 303 is equipped with a camera 3031 for capturing images of the laminate of the protective layer 1 and the second release liner 3, as well as the semiconductor wafer W, from the second release liner 3 side, and a lens 3032 for widening the imaging field of view of the camera. That is, the sensing device 300 detects the position of the protective layer 1 and the position of the semiconductor wafer W relative to the second release liner 3 using an image captured by the camera 3031 from the second release liner 3 side. As indicated by the dashed line in FIG. 4A, the imaging field of view of camera 3031 is expanded by lens 3032 to the vicinity of the area grasped by grasper 302. That is, in the sensing device 300, the camera 3031 is capable of imaging the laminate of the protective layer 1 and the first release liner 2 from the second release liner 3 side to the vicinity of the area gripped by the gripping tool 302, as well as imaging the semiconductor wafer W.

[0096] The gripper 302 is attached to an arm (not shown) and is movable by the arm in the X-axis, Y-axis, and Z-axis directions.

[0097] Here, as described above, the semiconductor wafer W has a circuit pattern formed on one surface side and an electrode portion disposed thereon. Moreover, the semiconductor wafer W usually has a thickness of about several tens of μm (for example, 50 μm). Therefore, even near-infrared rays having an extremely long wavelength are unlikely to pass through the semiconductor wafer W. Therefore, regardless of whether a near-infrared camera, an ultraviolet camera, or a visible light camera is used as camera 3031 to image the laminate of protective layer 1 and second release liner 3, and the semiconductor wafer W, from the side of second release liner 3, in all images captured, protective layer 1 and semiconductor wafer W will be shown as shaded areas (dark areas). This makes it possible to detect the position of the protective layer 1 relative to the second release liner 3 and the position of the semiconductor wafer W by identifying shaded areas (dark areas) in the image. Then, based on information on the position of the protective layer 1 relative to the second release liner 3 and information on the position of the semiconductor wafer W, the gripping tool 302 is moved in the X-axis direction, Y-axis direction, Z-axis direction, etc., until the outer periphery of the semiconductor wafer W and the outer periphery of the protective layer 1 are approximately aligned. Next, the gripping tool 302 is moved downward in the Z-axis direction, and the protective layer 1 of the laminate of the protective layer 1 and the second release liner 3 is bonded to the surface of the semiconductor wafer W to be protected.

[0098] As shown in FIG. 4B, laminating apparatus 400 includes roller 401 which rotates and presses the laminate of protective layer 1 and second release liner 3 while being in contact with second release liner 3 of the laminate. In the laminating device 400, the roller 401 rotates and moves in the X-axis direction, as shown in FIG. 4B, while pressing the laminate of the protective layer 1 and the second release liner 3, thereby bonding the protective layer 1 to the surface to be protected of the semiconductor wafer W. The pressing is preferably carried out while applying a pressure of about 0.3 MPa. This allows the exposed surface of the protective layer 1 to be bonded sufficiently to the surface of the semiconductor wafer W to be protected.

[0099] Then, after the exposed surface of the protective layer 1 has been thoroughly bonded to the surface to be protected of the semiconductor wafer W, the second release liner 3 is peeled off from the protective layer 1 by moving the gripper 302 upward in the Z-axis direction. This allows the protective layer 1 to be provided on the surface to be protected of the semiconductor wafer W, as shown in FIG. 4C.

[0100] The protective layer 1 may be bonded to the surface of the semiconductor wafer W to be protected by using a vacuum diaphragm type laminator device that bonds the protective layer 1 to the surface of the semiconductor wafer W to be protected under vacuum. Furthermore, the bonding of the protective layer 1 to the surface to be protected of the semiconductor wafer W may be performed by a differential pressure press in a chamber capable of adjusting the pressure.

[0101] The matters disclosed in this specification include the following.

[0102] (1) A protective layer attached to the adherend; A release liner disposed on the surface of the protective layer, the protective layer comprises a water-soluble polymer, the release liner has an inner surface facing the protective layer and an outer surface opposite the inner surface, The light transmittance of the release liner from the outer surface through the protective layer is at least 15% lower than the light transmittance of the release liner at at least one wavelength. Protective sheet.

[0103] According to this configuration, the position of the protective layer can be accurately grasped from the release liner side. This makes it possible to easily align the protective layer with the transfer device, the adherend, and the like.

[0104] (2) A protective layer attached to the adherend; 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, each of the first release liner and the second release liner has an inner surface facing the protective layer and an outer surface opposite the inner surface; the light transmittance from the outer surface of the second release liner to the outer surface of the first release liner is at least 15% lower than the light transmittance of the second release liner at at least one wavelength; Protective sheet.

[0105] According to this configuration, the positions of the protective layer and the first release liner can be accurately grasped from the second release liner side. Therefore, particularly when the protective layer and the first release liner are pre-cut so that they have approximately the same dimensions in a planar view, the position of the protective layer can be accurately determined based on the position of the first release liner. This makes it possible to easily align the protective layer with the transfer device, the adherend, and the like.

[0106] (3) The protective sheet according to (1) or (2) above, wherein the one wavelength is any one of a wavelength in the ultraviolet region, the visible region, and the near-infrared region.

[0107] 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.

[0108] For example, the protective sheet according to the present invention is not limited to protecting semiconductor wafers, but may also protect objects other than semiconductors. Furthermore, although the present embodiment illustrates an embodiment in which a protective layer is provided between two release liners, the first release liner and the second release liner, the protective sheet of the present invention may also have a two-layer structure consisting of one release liner and a protective layer. Furthermore, the protective sheet of the present invention is not limited to the above examples. EXAMPLES

[0109] 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.

[0110] [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 was stirred to dissolve the PVA in water, thereby obtaining a PVA dissolved composition. Next, the PVA solution composition was applied to a thickness of 10 μm using an applicator onto the release-treated surface of a second release liner (manufactured by Mitsubishi Chemical Corporation, product name MRA50, thickness 50 μm) having a surface that had been subjected to a silicone release treatment. Next, the second release liner coated with the PVA solution composition was dried at 110° C. for 2 minutes to form a protective layer on the second release liner. That is, a laminate of the second release liner and the protective layer was obtained. Next, a foamed first release liner (manufactured by Toyobo Co., Ltd., product name "Crisper (registered trademark) K1211", thickness 38 μm) was attached onto the protective layer to obtain a protective sheet according to Example 1. The first release sheet was foamed by generating voids during stretching, and no release treatment was applied to the surface. The protective sheet according to Example 1 as described above was produced so as to reduce the permeability of the first release liner.

[0111] The saponification degree and average polymerization degree of the polyvinyl alcohol were measured in accordance with the method described in the above embodiment section.

[0112] [Example 2] A protective sheet of Example 2 was obtained in the same manner as Example 1, except that a PET film having a coating layer containing titanium oxide on one side (manufactured by Fujiko Co., Ltd., product name "PET38-SCA1", thickness 38 μm) was used as the first release liner. The first release liner had the other surface (the surface opposite to the surface having the coating layer) subjected to release treatment. The protective sheet of Example 2 was produced by forming a protective layer on a second release liner and then laminating the release-treated surface of the first release liner (the surface not having a coating layer) to the protective layer. The protective sheet according to Example 2 above was also produced so as to reduce the permeability of the first release liner.

[0113] [Example 3] A protective sheet according to Example 3 was obtained in the same manner as in Example 1, except that a protective layer containing silica was used and a release liner having a surface treated with a silicone release agent (product name MRA38, manufactured by Mitsubishi Chemical Corporation, thickness 38 μm) was used as the first release liner. In the protective sheet of Example 3, the protective layer was formed by applying a silica-containing composition, in which silica was added to the PVA dissolution composition, to a release-treated surface of the second release liner with an applicator to a thickness of 10 μm, and then drying the second release liner to which the silica-containing composition had been applied at 110° C. for 2 minutes. As the silica, "Snowtec (registered trademark) MP-2040" manufactured by Nissan Chemical Industries, Ltd. was used. The concentration of the silica in the silica-containing composition was 30% by mass. Furthermore, the first release liner was attached to the protective layer by attaching the release-treated surface thereof. The protective sheet according to Example 3 as described above was produced so as to reduce the transmittance of the protective layer.

[0114] [Reference example 1] A protective sheet according to Reference Example 1 was obtained in the same manner as in Example 3, except that a protective layer containing a dye was used. In the protective sheet of Reference Example 1, the protective layer was formed by applying a dye-containing composition, in which a dye was dissolved in the PVA dissolution composition, to a thickness of 10 μm on the release-treated surface of the second release liner using an applicator, and then drying the second release liner to which the dye-containing composition had been applied at 110°C for 2 minutes. As the dye, "Linablue (registered trademark)" (blue pigment) manufactured by DIC Corporation was used. The concentration of the dye in the dye-containing composition was 5%. The protective sheet according to Reference Example 1 as described above was also produced so as to reduce the transmittance of the protective layer.

[0115] [Comparative Example 1] A protective sheet according to Comparative Example 1 was obtained in the same manner as in Example 1, except that a release liner having a surface treated with a silicone release agent (product name MRA38, manufactured by Mitsubishi Chemical Corporation, thickness 38 μm) was used as the first release liner. In Comparative Example 1, the first release sheet was attached to the protective layer in the same manner as in Example 3, by attaching the release-treated surface to the protective layer. The protective sheet according to Comparative Example 1 described above was produced without reducing the transmittance of either the protective layer or the first release liner.

[0116] <Transmittance> For the protective sheet of each example, the transmittance of the first release liner, the protective layer, and the second release liner was measured. The transmittance was measured using light with a wavelength of 1060 nm (near infrared light), light with a wavelength of 330 nm (ultraviolet light), light with a wavelength of 550 nm (visible light), and light with a wavelength of 650 nm (visible light). The transmittance of the protective layer was measured using a protective layer obtained by obtaining a laminate of the second release liner and the protective layer and then peeling the second release liner from the laminate. The transmittance was measured by the method described in the embodiment section above. The results are shown in Table 1 below.

[0117] In Table 1 below, the transmittance of the second release liner measured using light with a wavelength of 1060 nm is T A and the transmittance of the protective layer measured using light with a wavelength of 1060 n is expressed as T B The transmittance of the first release liner measured using light with a wavelength of 1060 nm is denoted as TC It is written as follows. The transmittance of the second release liner measured using light with a wavelength of 330 nm was T A’ and the transmittance of the protective layer measured using light with a wavelength of 330 nm is expressed as T B’ The transmittance of the first release liner measured using light with a wavelength of 330 nm is denoted as T C’ It is written as follows. Furthermore, the transmittance of the second release liner measured using light with a wavelength of 550 nm was T A’’1 and the transmittance of the protective layer measured using light with a wavelength of 550 nm is expressed as T B’’1 The transmittance of the first release liner measured using light with a wavelength of 500 nm is denoted as T C’’1 It is written as follows. The transmittance of the second release liner measured using light with a wavelength of 650 nm was T A’’2 and the transmittance of the protective layer measured using light with a wavelength of 650 nm is expressed as T B’’2 The transmittance of the first release liner measured using light with a wavelength of 650 nm is denoted as T C’’2 It is written as follows. Furthermore, the transmittance T A and transmittance T B Difference from (T A -T B ) to ΔT AB and transmittance T A and transmittance T C Difference from (T A -T C ) to ΔT AC and transmittance T A’ and transmittance T B’ Difference from (T A’ -T B’ ) to ΔT A’B’ and transmittance T A’ and transmittance T C’ Difference from (T A’ -T C’ ) to ΔT A’C’ and transmittance T A’’1 and transmittance T B’’1 Difference from (T A’’1 -T B’’1 ) to ΔT A’’1B’’1 and transmittance T A’’1 and transmittance TC’’1 Difference from (T A’’1 -T C’’1 ) to ΔT A’’1C’’1 and transmittance T A’’2 and transmittance T B’’2 Difference from (T A’’2 -T B’’2 ) to ΔT A’’2B’’2 and transmittance T A’’2 and transmittance T C’’2 Difference from (T A’’2 -T C’’2 ) to ΔT A’’2C’’2 It is written as follows.

[0118] <Haze> For the protective sheet of each example, the haze of the first release liner, the protective layer, and the second release liner was measured. The haze was measured by the method described in the embodiment section above. The results are shown in Table 1 below.

[0119] <Gloss at an incidence angle of 60°> For the protective sheet of each example, the gloss was measured when light was incident on the first release liner, protective layer, and second release liner at an angle of 60° (gloss at an incident angle of 60°). White light was used as the light incident at an angle of 60°. The gloss at an incident angle of 60° was measured using a spectrophotometer CM-26dG manufactured by Konica Minolta. The results are shown in Table 1 below. In Table 1, the "GU" (Gloss Unit) in parentheses is a unit of gloss.

[0120] <Lightness (L value)> For the protective sheet of each example, the lightness (L value) of the first release liner, the protective layer, and the second release liner was measured. The lightness (L value) was measured using a color meter as described in the embodiment section above. The results are shown in Table 1 below. When measuring lightness (L value) using a color meter, chromaticity (a value and b value) are also measured at the same time. Therefore, Table 1 below also shows the measurement results of the chromaticity (a value and b value) of the first release liner, protective layer, and second release liner for the protective sheet according to each example. In addition, Table 1 below shows the lightness (L value) and chromaticity (a value and b value) of the first release liner, protective layer, and second release liner for each example of the protective sheet. 2 +a 2 +b 2 ) 1 / 2 The value was calculated. The results are also shown in Table 1 below.

[0121] <Distinguishing property> For the protective sheet of each example, the distinguishability of the protective layer or first release liner was evaluated. In the evaluation of the distinguishability, the protective layer and the first release liner were precut and used as the test specimen. The evaluation of the discrimination ability was carried out using a transmission type photoelectric sensor (manufactured by KEYENCE Corporation, product name "PR-G51N") equipped with a light projecting part and a light receiving part. Specifically, for the protective sheet of each example, a light-projecting portion was arranged outside the second release sheet and a light-receiving portion was arranged outside the first release sheet, and then when laser light was irradiated from the light-projecting portion, an evaluation was conducted as to whether the protective layer or the first release liner was identified as a shaded portion (dark portion) in the light-receiving portion. If the protective layer or the first release liner was discernible as a shaded area (dark area), it was rated as "excellent," and if it was not discernible as a shaded area, it was rated as "poor." The laser light emitted from the light projecting unit had a wavelength of 550 nm and a wavelength of 650 nm. The distinguishability of the protective layer or the first release liner was evaluated using a 550 nm laser beam and a 650 nm laser beam, and the results are shown in Table 1 below.

[0122] [Table 1]

[0123] From Table 1, ΔT A’’2C’’2 In Examples 1 and 2, where the difference is 15% or more, the evaluation of the discrimination ability when irradiated with a laser beam having a wavelength of 650 nm is "excellent," and ΔT A’’2B’’2 It can be seen that in Example 3 and Reference Example 1, where the difference is 15% or more, the evaluation of the discrimination ability when irradiated with a laser beam having a wavelength of 650 nm is "excellent." In contrast, ΔT A’’2C’’2 and ΔT A’’2B’’2 However, in Comparative Example 1, where both values ​​are less than 15%, the evaluation of distinguishability when irradiated with laser light having a wavelength of 650 nm is "fail." Also, ΔT A’’1C’’1 In Examples 1 and 2, where the difference is 15% or more, the evaluation of the discrimination ability when irradiated with a laser beam having a wavelength of 550 nm is "excellent," and ΔT A’’1B’’1 It can be seen that in Example 3, where the difference is 15% or more, the evaluation of the distinguishability when irradiated with a laser beam having a wavelength of 550 nm is "excellent." In contrast, in Reference Example 1 and Comparative Example 1, ΔT A’’1B’’1 It can be seen that the discrimination ability when irradiated with a laser beam having a wavelength of 550 nm was evaluated as “unacceptable.” From these results, it can be seen that when visible light is irradiated as laser light, if the difference between the transmittance of the second release liner and the transmittance of the protective layer is 15% or more, the second release liner and the protective layer can be sufficiently distinguished, and if the difference between the transmittance of the second release liner and the first release liner is 15% or more, the second release liner and the first release liner can be sufficiently distinguished. Furthermore, even if near-infrared light or ultraviolet light is used as the laser light instead of visible light, it is believed that if the difference between the transmittance of the second release liner and the transmittance of the protective layer is 15% or more, the second release liner and the protective layer can be sufficiently distinguished, as in the case of visible light, and if the difference between the transmittance of the second release liner and the transmittance of the first release liner is 15% or more, the second release liner and the first release liner can be sufficiently distinguished, as in the case of visible light. [Explanation of symbols]

[0124] 1 protective layer, 2 first release liner, 3 second release liner, 10 protective sheet.

Claims

1. a protective layer attached to the adherend; 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, each of the first release liner and the second release liner has an inner surface facing the protective layer and an outer surface opposite the inner surface; the second release liner has a higher light transmittance than the first release liner; The light transmittance from the outer surface of the second release liner to the outer surface of the first release liner is at least 15% lower than the light transmittance of the second release liner at at least one wavelength. Protective sheet.

2. 2. The protective sheet according to claim 1, wherein the one wavelength is a wavelength in any of the ultraviolet region, the visible region, and the near-infrared region.

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