JP2024008691A - Protective sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: 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

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a protective sheet.

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

Among the above-mentioned manufacturing of electronic components, manufacturing of semiconductor chips is usually carried out by dividing (cutting) one semiconductor wafer (for example, Patent Document 2 below).
For example, Patent Document 2 below discloses that a semiconductor chip is manufactured in the following manner.

(1) A plurality of dividing lines are formed in a grid 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 pattern by the plurality of planned dividing lines (hereinafter also referred to as grid partition areas). In this way, a semiconductor wafer for obtaining semiconductor chips is manufactured.
(3) Divide (cut) the semiconductor wafer along the plurality of planned dividing lines, in other words, divide (cut) the semiconductor wafer into each of the lattice-shaped partitioned areas to form a plurality of semiconductor chips. obtain.

Japanese Patent Application Publication No. 2021-161735 Japanese Patent Application Publication No. 2012-119670

As mentioned above, when dividing (cutting) one semiconductor wafer to obtain multiple semiconductor chips, a small amount of dust is generated as a part of the semiconductor wafer near the dividing part (cutting part) is pulverized. This may occur.
If such dust adheres to one surface side of the semiconductor chip (the side on which the circuit pattern is formed), there is a risk that the operational reliability of the circuit included in the circuit pattern formed on the one surface side may decrease. That's why I don't like it.
Therefore, when manufacturing a semiconductor chip, it is conceivable to protect the semiconductor chip by attaching the protective sheet to one surface side (the side on which the circuit pattern is formed) of the one semiconductor wafer.
As such a protective sheet, one having a water-soluble protective layer that can be easily removed from an adherend such as a semiconductor wafer after use is considered useful.

By the way, when attaching a protective sheet to an adherend such as a semiconductor wafer, the protective sheet cut into a predetermined shape may be set in a laminating machine and attached to the adherend, or the protective sheet cut into a predetermined shape may be placed on the adherend. A possible method is to attach it directly to the wearer.
In order to easily align the protective layer and peel the release liner from the protective layer when setting it in a laminating device or directly attaching it to an adherend, it is recommended to provide a gripping margin on the release liner. It is considered to be effective.
However, this will cause the release liner to protrude beyond the outer periphery of the protective layer, and the outer periphery of the release liner and the outer periphery of the protective layer will not match, so it is difficult to accurately position the protective layer from the release liner side. This may make it difficult to grasp and position 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, and the like.

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 contains a water-soluble polymer,
The release liner includes an inner surface facing the protective layer and an outer surface opposite to the inner surface,
The light transmittance from the outer surface of the release liner to the protective layer is 15% or more lower than the light transmittance of the release liner at at least one wavelength.

Moreover, the protective sheet according to the present invention is
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 includes a water-soluble polymer compound,
Each of the first release liner and the second release liner includes an inner surface facing the protective layer and an outer surface opposite to 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.

According to the present invention, it is possible to provide a protective sheet whose protective layer can be easily aligned with respect to a transfer device, an adherend, and the like.

FIG. 1 is a schematic cross-sectional view showing the configuration of a protective sheet according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing the configuration of a protective sheet according to another embodiment of the present invention. FIG. 1 is a schematic cross-sectional view showing one aspect of cutting a protective layer in a protective sheet according to an embodiment of the present invention. FIG. 7 is a schematic cross-sectional view showing one aspect of cutting a protective layer when obtaining a protective sheet according to another embodiment of the present invention. FIG. 7 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 the protective layer. FIG. 3 is a schematic cross-sectional view showing how a sensing device is used to detect the position of a protective layer obtained by post-precutting. FIG. 2 is a schematic cross-sectional view showing how a protective layer obtained by post-precutting is attached to a surface to be protected of a semiconductor wafer using a mounting device. FIG. 2 is a schematic cross-sectional view showing a protective layer bonded to a surface to be protected of a semiconductor wafer. FIG. 3 is a schematic cross-sectional view showing how a sensing device is used to detect the position of a protective layer obtained by pre-cutting. FIG. 2 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. FIG. 2 is a schematic cross-sectional view showing a protective layer bonded to a surface to be protected of a semiconductor wafer.

An embodiment of the present invention will be described below.

[Protective sheet according to first embodiment]
As shown in FIGS. 1A and 1B, the protective sheet 10 according to the first embodiment of the present invention includes a protective layer 1, a first release liner 2 disposed on one surface of the protective layer 1, and a protective sheet 10. A second release liner 3 disposed on the other surface.
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 has water solubility.
On the other hand, the first release liner 2 and the second release liner 3 are water-insoluble.

The protective layer 1 of this embodiment has adhesiveness to the extent that it can be attached to an adherend.
It is preferable that the protective layer 1 of this embodiment has tackiness (pressure-sensitive adhesiveness).
The protective sheet 10 of this embodiment can be applied to the surface of the adherend while performing various treatments on the adherend by attaching the protective layer 1 to an adherend (in this embodiment, a "semiconductor wafer"). It is used to prevent foreign matter from adhering to the surface.

The first release liner 2 and the second release liner 3 are each bonded to the protective layer 1 in order to prevent foreign matter from adhering to the protective layer 1 before being bonded to the semiconductor wafer.
Each of the first release liner 2 and the second release liner 3 includes an inner surface facing the protective layer 1 and an outer surface opposite to the inner surface.
The protective sheet 10 of this embodiment is used by peeling off the second release liner 3 and adhering the other surface of the protective layer 1 to a semiconductor wafer.

In this embodiment, as will be described later, the protective layer 1 is attached to the protected surface of the adherend after the protective layer 1 is accurately positioned.
Positioning may be indirect rather than direct.
For example, when setting the protective layer 1 in a laminating device in which the adherend is scheduled to be placed in a predetermined position and laminating the protective layer 1 to the adherend in the laminating device, the laminating device The protective layer 1 may be positioned on the adherend by positioning the protective layer 1 in .

In this embodiment, the protective layer 1 is not attached to the entire surface of the second release liner 3 at the time of positioning, but is provided so as to partially cover the inner surface of the second release liner 3.
The protective sheet 10 during positioning in this embodiment has a laminated area where the second release liner 3 and the protective layer 1 are laminated, and a laminated area where the protective layer 1 is not laminated on the second release liner 3. 2, a single-layer region including only the release liner 3, and the single-layer region is provided so as to surround the laminated region.

In the protective sheet 10 according to the first embodiment, the light transmittance of the second release liner 3 is higher than that of the protective layer 1, the first release liner 2, or the laminate of the protective layer 1 and the first release liner 2. The transmittance is higher than that of
More specifically, in this embodiment, the transmittance of light from the outer surface of the second release liner to the point where it passes through the protective layer 1 is higher than the light transmittance of the second release liner 3 in 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. It is 15% or more lower than the transmittance.

In the protective sheet 10 according to the first embodiment, the transmittance T A of the second release liner 3 measured at one wavelength included in the near-infrared region and the transmittance T _A of the protective layer 1 measured at the one wavelength ΔT _AB is the difference between the transmittance T _A and the transmittance T C of the first release liner 2 measured at the one wavelength, and ΔT _AC is the difference between the transmittance T _A and the transmittance T _C of the first release liner ₂ measured at the one wavelength. When the difference between the measured transmittance T _D of the laminate of the protective layer 1 and the first release liner 2 is ΔT _AD , the ΔT _AB , the ΔT _AC , or the ΔT _AD is 15% or more. It is.

Note that in this specification, the near-infrared region means a region with a wavelength of 800 nm or more and 2500 nm or less.
Further, 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.

The protective layer 1 is used by being attached to a surface of an electronic component to be protected.
Examples of the electronic component include semiconductor wafers.
The semiconductor wafer is a semiconductor wafer in which a grid-shaped partitioned area (hereinafter also referred to as grid-shaped partitioned area) is formed on one surface side, and a circuit pattern is formed in each of the grid-shaped partitioned area. An example of this is a semiconductor wafer in which an electrode part is arranged.
When the electronic component is a semiconductor wafer as described above, the protective layer 1 is used by being attached to one surface of the semiconductor wafer.
In this way, by bonding the protective layer 1 to one surface of the semiconductor wafer, when dividing (cutting) the semiconductor wafer to obtain a plurality of semiconductor chips, the semiconductor wafer near the dividing part (cutting part) Fine foreign matter generated when a part of It is possible to suppress adhesion to each electrode portion arranged (electrode portion arranged for each grid-like partitioned region).

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

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

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

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

In the protective sheet 10 shown in FIG. 1A, the first release liner 2 and the second release liner 3 have substantially the same dimensions in plan view, and this planar dimension is larger than the surface to be protected of the electronic component. ing.
On the other hand, in the protective sheet 10 shown in FIG. 1B, the protective layer 1 has substantially the same dimensions as the surface to be protected of the electronic component in plan view.
Specifically, the protective layer 1 is formed into a laminate with one release liner, for example, the first release liner 2, and then cut (see FIG. 2B) so that the protective layer 1 has approximately the same planar dimensions as the surface to be protected of the electronic component. has been done.
That is, in the protective sheet 10 shown in FIG. 1B, the protective layer 1 is made to have substantially the same dimensions as the surface to be protected of the electronic component by the pre-precut method.
Note that the other release liner, for example, the second release liner 3, is bonded to the exposed surface of the protective layer 1 after the protective layer 1 is cut (see FIG. 2C).

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 includes one strip-shaped second release liner 3 and a plurality of protective layers 1 having the same shape as the surface to be protected, and the plurality of protective layers 1 are arranged in the longitudinal direction of the second release liner 3. The protective layers 1 may be arranged in such a manner that a certain interval may be provided between adjacent protective layers 1 in the longitudinal direction.
Further, in that 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.

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, even if the protective sheet 10 has the second release liner 3 protruding outward from the outer peripheral edge of the protective layer 1, and the second release liner 3 protrudes over the entire circumference of the protective layer 1, good.

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 is applied onto the first release liner 2 to a predetermined thickness (for example, 10 μm).
(2) The water-soluble resin composition after application is dried at a predetermined temperature for a predetermined time (eg, 110° C. for 2 minutes). As a result, the protective layer 1 containing the water-soluble polymer compound is formed on the first release liner 2.
(3) A second release liner 3 is attached to the surface of the protective layer 1 opposite to the surface on which the first release liner 2 is arranged (the exposed surface of the protective layer 1).

In the production of the protective sheet 10 shown in FIG. 1B, between the above step (2) and the above step (3), the protective layer 1 is formed so as to have approximately the same planar dimension as the surface to be protected of the electronic component. (step (2'), see FIG. 2B).

In the protective sheet 10 according to the first embodiment, the protective layer 1 has a water-soluble polymer compound dispersed in water (hereinafter referred to as a water-soluble resin composition containing a water-soluble polymer compound and an excess liquid). , a 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, and 10 parts by mass or more and 70 parts by mass or less, per 100 parts by mass of water. More preferably, the content is 15 parts by mass or more and 60 parts by mass or less.
Further, in the protective layer forming composition, it is preferable that the water-soluble polymer compound is dissolved in water.
In the protective layer forming composition, the water-soluble polymer compound can be dissolved in water by being treated at a temperature of 20 to 90°C.
Furthermore, the viscosity of the protective layer forming composition at 25° C. is preferably 0.03 Pa·s or more, more preferably 0.05 Pa·s or more, and preferably 0.1 Pa·s or more. More preferred.
When the viscosity at 25° C. is equal to or higher than the above lower limit, when the protective layer forming composition is applied onto the first release liner 2 to form the protective layer 1 on the first release liner 2, It is possible to prevent the thickness of the layer 1 from easily fluctuating.
Further, the viscosity of the protective layer forming composition at 25° C. is preferably 15 Pa·s or less, more preferably 10 Pa·s or less, and even more preferably 5 Pa·s or less.
When the viscosity at 25° C. is at least the above-mentioned upper limit, the coating properties of the protective layer forming composition when applied onto the first release liner 2 can be improved.
The viscosity of the protective layer forming composition at 25°C was measured using a digital viscometer manufactured by Hideko Seiki Co., Ltd. (product name "DV-I Prime") and an LV-3 spindle. , the rotation speed is 50 rpm.

Examples of the water-soluble polymer compound include polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), water-soluble polyester (PES), and polyethylene oxide (PEO).
As the water-soluble polymer compound, polyvinyl alcohol, polyvinylpyrrolidone, water-soluble polyester, polyethylene oxide, etc. may be used alone, or two or more of these may be used in combination.
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.

The degree of saponification of the polyvinyl alcohol is preferably 50 or more and 98 or less, more preferably 60 or more and 90 or less.
By having a saponification degree within the above numerical range, the polyvinyl alcohol can exhibit sufficient water solubility, and when the polyvinyl alcohol is included in the protective layer forming composition, the first The protective layer forming composition can be applied onto the release liner 2 with good workability.
The degree of saponification of the polyvinyl alcohol can be measured by proton magnetic resonance spectroscopy ( ¹ H-NMR measurement).
In addition, if the measurement sample contained an additive and the peak derived from the additive overlapped with the peak used for calculating the degree of saponification, the measurement sample was subjected to methanol extraction etc. to separate the additive. Afterwards, 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 Heavy water or heavy dimethyl sulfoxide (heavy DMSO)
・Measurement temperature 80℃
・Chemical shift standard External standard TSP-d4 (0.00ppm) (when measuring heavy water)
Measurement solvent (2.50ppm) (during heavy DMSO measurement)

The degree of saponification of the polyvinyl alcohol is determined by the peak derived from the methylene group of the vinyl alcohol unit (VOH) (heavy water: 2.0 to 1.0 ppm, heavy DMSO: 1.9 to 1.0 ppm) and the peak derived from the acetyl group of the vinyl acetate unit (VAc). It is calculated based on the following formula using the peak of (heavy water: around 2.1 ppm, heavy DMSO: around 2.0 ppm).
In the following formula, [VOH(-CH ₂ )-] means the intensity of the peak derived from -CH ₂ - in the vinyl alcohol unit, and [VAc(CH ₃ CO-)] means the intensity of the peak derived from -CH 2 - in the vinyl alcohol unit. It means the peak intensity derived from CH ₃ CO-.

The average degree of polymerization of the polyvinyl alcohol is preferably 100 or more and 1000 or less, more preferably 100 or more and 800 or less.
By having an average degree of polymerization within the above numerical range, the polyvinyl alcohol can exhibit sufficient water solubility, and when the polyvinyl alcohol is included in the protective layer forming composition, the polyvinyl alcohol can exhibit sufficient water solubility. 1. The protective layer forming composition can be applied onto the 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
・Column TSKgel G6000PWXL (manufactured by Tosoh Corporation) and TSKgel G3000PWXL (manufactured by Tosoh Corporation)
The above two columns are connected in series.
・Column temperature 40℃
・Eluent: 0.2M sodium nitrate aqueous solution ・Injection volume: 100μL
・Detector Differential refractometer (RI)
・Standard sample PEG standard sample and PVA standard sample

Specific measurements are performed as follows.

(1) Calculate the mass average molecular weight Mw of the sample to be measured (PVA) and the PVA standard sample by GPC measurement using a PEG standard sample. Note that the PVA standard sample has a known average degree of polymerization.
(2) Create a calibration curve using the average degree of polymerization of the PVA standard sample and the calculated mass average molecular weight Mw of the PVA standard sample.
(3) Using the created calibration curve, determine the average degree of polymerization of the sample to be measured (PVA) from the mass average molecular weight Mw of the sample to be measured (PVA).

Further, when the 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. good.

The water-soluble polyester has a polyhydric carboxylic acid residue and a polyol residue.
The water-soluble polyester is, for example, a polymerization product of monomer components containing a polyhydric carboxylic acid component and a polyol component.
In addition, whether the water-soluble polyester has water solubility can be determined based on common technical knowledge.

The water-soluble polyester preferably satisfies at least one of the following (1) to (4).
(1) When water at room temperature (23±2° C.) is sprayed for 20 minutes at a spray pressure of 0.005 MPa over the entire surface of a 20 μm thick thin film made of the water-soluble polyester, the entire thin film dissolves in water.
(2) When water at 50° C. is sprayed at a spray pressure of 0.005 MPa for 10 minutes over the entire surface of a 20 μm thick thin film made of the water-soluble polyester, the entire thin film dissolves in water.
(3) When the water-soluble polyester and room temperature water are mixed at a mass ratio of water-soluble polyester: room temperature water = 1:5 to obtain a mixed solution, and when the mixed solution is irradiated with ultrasound for 20 minutes, The water-soluble polyester is completely dissolved in water.
(4) Mix the water-soluble polyester and 50°C water at a mass ratio of water-soluble polyester: 50°C water = 1:5 to obtain a mixed solution, and irradiate the mixed solution with ultrasound for 10 minutes. Then, all of the water-soluble polyester is dissolved in water.

The thickness of the protective layer 1 is preferably 2 μm or more and 70 μm or less, more preferably 3 μm or more and 50 μm or less, and even more preferably 5 μm or more and 40 μm or less.
The thickness of the protective layer 1 can be determined by, for example, measuring the thickness at five randomly selected points using a dial gauge (manufactured by PEACOCK, model R-205), and calculating the arithmetic average of these thicknesses. It can be found by

Examples of the first release liner 2 include a resin sheet made using a resin such as polyethylene terephthalate (PET).
The resin sheet may be subjected to a release treatment at least on the surface to be bonded to the protective layer 1.
Examples of the mold release treatment include silicone mold release treatment.
Furthermore, the second release liner 3 can also be the same as the first release liner 2.

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, more preferably 20 μm or more and 60 μm or less.
The thickness of the first release liner 2 and the second release liner 3 may be the same or different.
The thickness of the first release liner 2 and the second release liner 3 can be determined in the same manner as the thickness of the protective layer 1.

As explained above, in the protective sheet 10 according to the first embodiment, the transmittance of the second release liner 3 is higher than that of the protective layer 1, the first release liner 2, or the protective layer 1 and the first release liner 2. The transmittance is higher than that of any of the laminates.
In the protective sheet 10 according to the first embodiment, the transmittance T A of the second release liner 3 measured at one wavelength included in the near-infrared region and the transmittance T _A of the protective layer 1 measured at the one wavelength ΔT _AB is the difference between the transmittance T _B and the transmittance T _C of the first release liner 2 measured at the one wavelength, and ΔT _AC is the difference between the transmittance T A and the transmittance T _C of the first release liner 2 measured at the _one wavelength. When the difference between the transmittance T _D of the laminate of the protective layer 1 and the first release liner 2 measured at the wavelength is ΔT _AD , the ΔT _AB , the ΔT _AC , or the ΔT _AD is 15 % or more.
Note that the transmittance T _A means the ratio when the light of one wavelength is transmitted through the second release liner 3 in parallel to the thickness direction, and the transmittance T _B is the ratio when the light of one wavelength is transmitted through the second release liner 3 in parallel to the thickness direction. The transmittance _TC means the ratio when the light of one wavelength is transmitted through the first release liner 2 parallel to the thickness direction, and the transmittance T The ratio T _D means the ratio at which the light of one wavelength is transmitted through the laminate of the protective layer 1 and the first release liner 2 in parallel to the thickness direction.
That is, the transmittances T _A to T _D mean parallel line transmittances.

Light included in the near-infrared region, that is, near-infrared light, has an extremely long wavelength, so when it is irradiated onto an object, it easily passes through the object in parallel to the thickness direction.
Therefore, in order to set the ΔT _AB to 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 parallel to the thickness direction, and the ΔT _AC In order to make ΔT AD 15% or more, it is necessary to prevent the light of one wavelength from passing through the first release liner 2 in parallel with the thickness direction, and in order to make ΔT _AD 15% or more, It is necessary to prevent light of one wavelength from passing through the laminate of the protective layer 1 and the first release liner 2 in parallel to the thickness direction.
Specifically, in the protective layer 1 and the first release liner 2, a part of the light of one wavelength transmitted in parallel to the thickness direction is absorbed, and in the protective layer 1 and the first release liner 2, the thickness It is necessary to diffusely reflect a part of the light of one wavelength that is transmitted parallel to the direction.

The treatment for preventing the light of one wavelength from passing through the protective layer 1 in parallel to the thickness direction includes including a pigment in the protective layer forming composition for forming the protective layer 1. .
By including the pigment in the protective layer 1, even if it is near-infrared light such as the one-wavelength light, the pigment can absorb a part of the one-wavelength light.
Furthermore, the pigment can diffusely reflect a portion of the light of one wavelength.

As the pigment, conventionally known pigments can be used.
The pigments include 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, Inorganic pigments such as chromium oxide type, spinel fired type, chromic acid type, chrome vermilion type, navy blue type, aluminum powder type, bronze powder type, calcium phosphate, phthalocyanine type, azo type, condensed azo type, azo lake type, anthracite type, etc. Examples include organic pigments such as quinone, perylene/perinone, indigo/thioindigo, isoindolinone, azomethane, and carbon black.

The protective layer 1 preferably contains 0.1 parts by mass or more of the pigment, more preferably 0.5 parts by mass or more, and 1.0 parts by mass of the pigment based on 100 parts by mass of the water-soluble polymer compound. It is more preferable that the content is more than 1 part by mass.
The protective layer 1 preferably contains 30 parts by mass or less of the pigment, more preferably 20 parts by mass or less, and 10 parts by mass or less of the pigment based on 100 parts by mass of the water-soluble polymer compound. It is more preferable that the
Note that the term "pigment" refers to a coloring agent that does not dissolve in organic solvents such as water and alcohol.

Further, as the treatment for preventing the light of one wavelength from passing through the protective layer 1 in parallel to the thickness direction, it is also possible to perform a foaming treatment on the protective layer forming composition for forming the protective layer 1. .
The protective layer 1 formed from the protective layer forming composition subjected to such foaming treatment comes to contain a plurality of air bubbles.
As a result, diffuse reflection can be caused in the plurality of bubbles included in the protective layer 1, so even near-infrared light such as the one-wavelength light can be transmitted through the protective layer 1 in parallel to the thickness direction. It is possible to reduce the ratio of

As explained above, when the first release liner 2 is a resin sheet made using a resin such as polyethylene terephthalate (PET), the light of one wavelength is applied to the first release liner 2 in parallel to the thickness direction. Examples of the treatment that prevents the permeation of the resin include foaming treatment of the resin composition for producing the resin sheet.
Since the resin sheet (resin foam sheet) obtained by subjecting the resin composition to foaming treatment includes a plurality of bubbles, diffused reflection can be caused in the plurality of bubbles.
As a result, even near-infrared light such as the one-wavelength light can be transmitted through the first release liner 2 in parallel to the thickness direction.
Further, when the first release liner 2 is a resin sheet made using 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 that generates voids during the stretching.

Further, as a treatment for preventing the light of one wavelength from passing through the first release liner 2 in parallel to the thickness direction, at least one surface of the first release liner 2 is coated with ink containing a pigment such as titanium oxide. There are many things you can do.
By forming a coating layer containing a pigment on at least one surface (inner surface, outer surface, or both surfaces) of the first release liner 2, near-infrared light such as the one wavelength light can be emitted. Also, part of the light of one wavelength can be absorbed by the pigment contained in the coating layer.
Furthermore, the pigment can diffusely reflect a portion of the light of one wavelength.

Furthermore, the first release liner 2 is configured using a resin containing a pigment, so that the pigment absorbs a portion of the one wavelength light, or the pigment diffusely reflects a portion of the one wavelength light. By doing so, the ratio of the light of one wavelength passing through the first release liner 2 in parallel to the thickness direction may be reduced.

Further, as the treatment for preventing the light of one wavelength from passing through the first release liner 2 in parallel with the thickness direction, it is also possible to perform matte processing or embossing on at least one surface of the first release liner 2. .
By applying matte processing or embossing to at least one surface of the first release liner 2, diffused reflection can be caused in the uneven portions of the surface of the first release liner 2.
Thereby, even near-infrared light such as the one-wavelength light described above can reduce the rate of transmission through the first release liner 2 in parallel to the thickness direction.

The first release liner 2 may be a laminated film having a layer for blocking light. The first release liner 2 may be a laminated film having a resin layer and a metal deposited layer, or may be an aluminum laminate film.

The light of one wavelength is prevented from transmitting through the laminate of the protective layer 1 and the first release liner 2 in parallel with the thickness direction, and the transmittance _TA of the second release liner 3 and the protective layer 1 and the first release liner are In order to make _{ΔTAD, which is the difference between the transmittance TD of} the laminate of the liner 2, 15% or more, the difference between the transmittance TA of the second release liner ₃ and the transmittance TB of the protective layer 1 must be 15 _% or more. It is sufficient that the total value of a certain ΔT _AB and ΔT _AC , which is the difference between the transmittance T _A of the second release liner 3 and the transmittance T _C of the first release liner 2, is 15% or more.
For example, ΔT _AB may be set to 5% or more, and ΔT _AC may be set to 10% or more, or ΔT _AB may be set to 10% or more, and ΔT _AC may be set to 5% or more.
The transmittance T _B of the protective layer 1 and the transmittance T _C of the first release liner can be adjusted in the same manner as explained above.
Of course, as explained above, the ΔT _AD can also be made 15% or more by setting at least one of ΔT _AB and ΔT _AC to 15% or more.

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

The transmittance T _B of the protective layer 1 measured at the one wavelength, the transmittance T _C of the first release liner 2 measured at the one wavelength, and the protective layer 1 and the first release liner measured at the one wavelength. From the viewpoint of maximizing the difference between the transmittance _TD of the laminate of the liner 2 and the transmittance TA of the second release liner 3 measured at the one wavelength, the transmittance _TA of the second release liner 3 measured at the one wavelength is Higher is preferable.
The transmittance T _A of the second release liner 3 measured at the one wavelength is preferably 65% or more, more preferably 75% or more, and even more preferably 85% or more.
The transmittance T _A of the second release liner 3 measured at the one wavelength may be 100% or less, or 95% or less.

The transmittance T _A of the second release liner 3 at the one wavelength, the transmittance T _B of the protective layer 1 at the one wavelength, the transmittance T _C of the first release liner 2 at the one wavelength, and the protection at the one wavelength. The transmittance _TD of the laminate of the layer 1 and the first release liner 2 is determined by measuring the parallel light transmittance at one wavelength using a spectrophotometer (manufactured by JASCO Corporation, trade name "V-670"). It can be found by
When measuring parallel light transmittance using a spectrophotometer, the measurement wavelength can be in the range of 190 nm to 3000 nm.
The second release liner 3 can be measured with a thickness of about 50 μm, the protective layer 1 can be measured with a thickness of about 10 μm, and the first release liner 2 can be measured with a thickness of about 10 μm. A sample having a thickness of about 40 μm can be used as a measurement sample.
Note that parallel ray transmittance is measured using a spectrophotometer without using an integrating sphere.

[Protection sheet according to second embodiment]
The protective sheet 10 according to the second embodiment of the present invention has a transmittance T _A' of the second release liner 3 measured at one wavelength included in the ultraviolet region and a transmittance of the protective layer 1 measured at the one wavelength. The difference between the transmittance _{TA' and} the transmittance TC _' of the first release liner 2 measured at the one wavelength is ΔT _{A'C' ,} When the difference between the transmittance T _A' and the transmittance T _D' of the laminate of the protective layer 1 and the first release liner 2 measured at one wavelength is ΔT _A'D' , the ΔT _A' The protective sheet 10 is configured in the same manner as the protective sheet 10 according to the first embodiment described above, except that _B' , the ΔT _A'C' , or the ΔT _A'D' is 15% or more.

In this specification, the ultraviolet region means a region with a wavelength of 200 nm or more and less than 380 nm.
Moreover, in the second embodiment of the present invention, it is preferable to use a wavelength of 330 nm as one wavelength included in the ultraviolet region.

The transmittances T _A' to T _D' mean parallel line transmittances, similarly to the transmittances T _A to T _D.
Further, the transmittance T _A' of the second release liner 3 at one wavelength included in the ultraviolet region, the transmittance T _B' of the protective layer 1 at the one wavelength, and the transmittance T _C of the first release liner 2 at the one wavelength. _' and the transmittance _TD' of the laminate of the protective layer 1 and the first release liner 2 at one wavelength can also be measured in the same manner as described above.

Light in the ultraviolet region, that is, ultraviolet light (ultraviolet light), has an extremely short wavelength, so when it is irradiated onto an object, it is more sensitive than light that has an extremely long wavelength as explained above, that is, near-infrared light. It is also difficult for light to pass through the object.
Therefore, by subjecting the protective layer 1 to the same treatment as explained in the section of the first embodiment above, the ΔT _A'B' can be made 15% or more, and the first release liner 2 is By performing the same treatment as explained in the section of the first embodiment, the ΔT _A'C' can be made 15% or more, and the laminate of the protective layer 1 and the first release liner 2 is By performing the same processing as explained in the section of the first embodiment, the ΔT _A'D' can be made 15% or more.

Further, by performing processing other than the above, the ΔT _A'B' , ΔT _A'C' , and ΔT _A'D' can be made 15% or more.
For example, by forming the protective layer 1 with the protective layer forming composition containing an ultraviolet absorber, or forming the first release liner 2 with a resin containing an ultraviolet absorber, the ΔT _A'B' , the ΔT _A'C' , and ΔT _A'D' can be 15% or more.

Examples of the UV absorbers include triazine UV absorbers, benzotriazole UV absorbers, benzophenone UV absorbers, oxybenzophenone UV absorbers, salicylic acid ester UV absorbers, cyanoacrylate UV absorbers, and the like. Can be mentioned.
These various ultraviolet absorbers may be used alone or in combination of two or more.

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; The content is more preferably .5 parts by mass or more, and even more preferably 1.0 parts by mass or more.
Further, 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, and preferably contains 15 parts by mass or less of the UV absorber. It is more preferable that the amount is contained in an amount of 10 parts by mass or less, and even more preferably 10 parts by mass or less.

In addition, instead of the ultraviolet absorber, the protective layer 1 may be formed of the protective layer forming composition containing an azo dye, which will be described later, or the first release liner 2 may be formed using a resin containing the azo dye. By doing so, the ΔT _A'B' , the ΔT _A'C' , and the ΔT _A'D' can be made 15% or more.
Note that examples of the azo dye include yellow dyes that exhibit yellow color.

When the protective layer 1 contains the azo dye, its content can be the same as the content of the ultraviolet absorber described above.

The protective layer 1 may be formed of the protective layer forming composition containing the azo dye in addition to the ultraviolet absorber, or may be formed using a resin containing the azo dye in addition to the ultraviolet absorber. Also by configuring the release liner 2, the ΔT _A'B' , the ΔT _A'C' , and the ΔT _A'D' can be made 15% or more.

[Protection sheet according to third embodiment]
The protective sheet 10 according to the third embodiment of the present invention has a transmittance T A'' of the second release liner 3 measured at one wavelength included in the visible region and a transmittance T _A'' of the protective layer 1 measured at the one wavelength. The difference between the transmittance T _B'' and the transmittance T B'' is ΔT _A''B'' , and the difference between the transmittance T _A'' and the transmittance T _C'' of the first release liner 2 measured at one wavelength is ΔT _A''C'' , and the difference between the transmittance T _A'' and the transmittance T _D'' of the laminate of the protective layer 1 and the first release liner 2 measured at the one wavelength is ΔT _A''D'' , as described above, except that the ΔT _A''B'' , the ΔT _A''C'' , or the ΔT _A''D'' is 15% or more. It is configured similarly to the protective sheet 10 according to the first embodiment.

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

The transmittances T _A'' to T _D'' mean parallel line transmittances, similarly to the transmittances T _A to T _D.
Further, the transmittance T _A'' of the second release liner 3 at one wavelength included in the visible region, the transmittance T _B'' of the protective layer 1 at the one wavelength, and the transmittance of the first release liner 2 at the one wavelength. T _C'' and the transmittance T _D'' of the laminate of the protective layer 1 and the first release liner 2 at one wavelength can also be measured in the same manner as described above.

Light included in the visible region, that is, visible light (visible light), has a shorter wavelength than near-infrared light, so when it is irradiated onto an object, it is less likely to pass through the object than near-infrared light. It has become.
Therefore, by subjecting the protective layer 1 to the same treatment as described in the section of the first embodiment above, the ΔT _A''B'' can be made 15% or more, and the first release liner 2 By performing the same treatment as described in the first embodiment above, the ΔT _A''C'' can be made 15% or more, and the protective layer 1 and the first release liner 2 can be By subjecting the laminate to the same treatment as described in the section of the first embodiment above, the ΔT _A''D'' can be made 15% or more.

Alternatively, the protective layer 1 may be formed using the protective layer forming composition containing a component that absorbs visible light, or the first release liner 2 may be formed using a resin containing a component that absorbs visible light. , the ΔT _A''B'' , the ΔT _A''C'' , and the ΔT _A''D'' can be 15% or more.
Examples of components that absorb visible light include dyes.
Note that the term "dye" refers to a coloring agent that has the property of being soluble in water, organic solvents, and the like.

Examples of the dye include azo dyes, anthraquinone, quinone phthalone, styryl, diphenylmethane, triphenylmethane, oxazine, triazine, xanthan, methane, azomethine, acridine, and diazine.

When the protective layer 1 contains the dye, the protective layer 1 preferably contains 0.1 part by mass or more of the dye, and preferably 0.5 part by mass, based on 100 parts by mass of the water-soluble polymer compound. It is more preferable that the amount is more than 1.0 parts by mass, and even more preferably 1.0 parts by mass or more.
When the protective layer 1 contains the dye, the protective layer 1 preferably contains 30 parts by mass or less, and preferably 20 parts by mass or less, of the dye per 100 parts by mass of the water-soluble polymer compound. It is more preferable that the content is 10 parts by mass or less.

In the protective sheet 10 according to the first to third embodiments above, the second release liner 3 and the protective layer 1 can be distinguished from each other, or the second release liner 3 and the first release liner 2 can be distinguished from each other by the transmittance difference. An example of identifying the second release liner 3 and the laminate of the protective layer 1 and the first release liner 2 has been described.
On the other hand, identification of the second release liner 3 and the protective layer 1, identification of the second release liner 3 and the first release liner 2, and lamination of the second release liner 3, the protective layer 1, and the first release liner 2 are performed. Identification from the body may be performed based on a difference in haze (cloudiness) or a difference in brightness (L value) in addition to a difference in transmittance.

In distinguishing between the first release liner 2 and the second release liner 3 based on the difference in haze (haze), it is preferable that the haze of the first release liner 2 is as high as possible; It is preferable that the haze of is 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. Preferably, it is particularly preferably 98% or more.
Further, the upper limit value 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 preferably 3% or less. Particularly preferred.
Note that the haze of the first release liner 2 and the haze of the second release liner 3 mean haze in the thickness direction, and the haze in the thickness direction is a value measured in accordance with JIS K 7136.
Moreover, the haze in the thickness direction can be measured using a turbidity meter (manufactured by Nippon Denshoku Co., Ltd., trade name "NDH2000").

Further, 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 is as high as possible, and the haze of the second release liner 3 is preferably as high as possible. is preferably 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, it is preferable that the upper limit value of the haze of the second release liner 3 is set as explained above.
Note that the haze of the protective layer 1 also means the haze in the thickness direction, and the haze in the thickness direction can be measured in the same manner as the first release liner 2 and the second release liner 3.

In identifying the first release liner 2 and the second release liner 3 from the difference in lightness (L value), the lightness (L value) of the first release liner 2 is preferably as low as possible, The lightness (L value) of the second release liner 3 is preferably 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.
Further, 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 shall be measured using a color meter (manufactured by Suga Test Instruments Co., Ltd., trade name "SM-T"). Can be done.
In addition, 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 be measured at the same time. .

Furthermore, in identifying the protective layer 1 and the second release liner 3 based on the difference in lightness (L value), the lightness (L value) of the protective layer 1 is preferably as low as possible; The lightness (L value) of the release liner 3 is preferably as high as possible.
The upper limit of the brightness (L value) of the protective layer 1 is preferably 70 or less, more preferably 65 or less.
Further, the lower limit of the lightness (L value) of the second release liner 3 is preferably 80 or more, more preferably 90 or more.
The lightness (L value) of the protective layer 1 can also 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 addition, 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.

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

Next, using a semiconductor wafer as an example of an electronic component, we will explain an example of bonding the protective layer 1 obtained by the post-precut method (see FIG. 2A) to the surface to be protected of the semiconductor wafer, and also explain An example of bonding the protected layer 1 (see 2B) to the surface to be protected of a semiconductor wafer will be described.
Below, first, an example will be described in which the protective sheet 10 including the protective layer 1 obtained by the post-precut method is used to bond the protective layer 1 to the surface to be protected of a semiconductor wafer.

The bonding of the protective layer 1 to the surface to be protected of the semiconductor wafer using the protective sheet 10 including the protective layer 1 obtained by the post-precut method is performed using a sensing device 100 that detects the position of the protective layer 1 on the protective sheet 10. and a mounting device 200 that attaches the protective layer 1 to the surface to be protected of the semiconductor wafer based on the position of the protective layer 1 detected by the sensing device 100.

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 first release liner 2 side, and an interval between the holding surfaces 1011 of the holding table 101. A position detecting section 102 is provided which is spaced apart and detects the position of the protective layer 1 on the protective sheet 10.
The position detection unit 102 includes a camera 1021 for capturing an image of the protective sheet 10 from the second release liner 3 side, 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 on the protective sheet 10 using an image captured by the camera 1021 from the second release liner 3 side.
Note that, as indicated by the broken line in FIG. 3A, the imaging field of view of the camera 1021 is expanded to cover the entire protective sheet 10 by the lens 1022.
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.

Here, as explained above, in the protective sheet 10 according to the first embodiment, the transmittance _TA of the second release liner 3 at one wavelength included in the near-infrared region and the protective layer at the one wavelength ΔT _AB , which is the difference between the transmittance T _B of the first release liner 2 at one wavelength, is 15% or more, or ΔT _AC , which is the difference between the transmittance T _A and the transmittance T _C of the first release liner 2 at one wavelength. is 15% or more, or ΔT _AD , which is the difference between the transmittance T _A and the transmittance T _D of the laminate of the protective layer 1 and the first release liner 2 at one wavelength, is 15% or more. It becomes.
In the protective sheet 10 according to the first embodiment, there is a region with a single-layer structure of only the second release liner 3 (single-layer region), and a region with a laminate structure of the first release liner 2 and the protective layer 1 (laminated region). ) is provided.
The intensity of the light transmitted through the protective sheet 10 from the side where the protective layer 1 is provided is different between the transmitted light transmitted through the single-layer region and the transmitted light transmitted through the laminated region.
In this embodiment, the light transmittance from the outer surface of the second release liner to the point where it passes through the protective layer 1, that is, the transmittance in the laminated region, is the light transmittance of only the second release liner 3 (single layer The transmittance of the area is 15% or more lower than the transmittance of the area.
Therefore, in this embodiment, by photographing the protective sheet 10 from the outer surface side of the second release liner 3 with the camera 1021 (near infrared camera), the single layer area is made into a bright area, and the laminated area is made into a brighter area than the bright area. It can be understood as a dark dark area.
In this embodiment, by having a difference in transmittance of 15% or more, sufficient contrast is formed between the dark part and the bright part, and the outer periphery of the laminated region can be detected with high accuracy.
Therefore, in the protective sheet 10 according to the first embodiment, the position of the protective layer 1 can be identified.
Thereby, the position of the protective layer 1 on the protective sheet 10 according to the first embodiment can be detected, and also the position on the holding surface 1011 of the holding table 101 where the protective layer 1 is placed can be detected. Can be done.

Furthermore, as explained above, in the protective sheet 10 according to the second embodiment, the transmittance T A' of the second release liner 3 at one wavelength included in the ultraviolet region and the transmittance T _A' of the protective layer 1 at the one wavelength are Whether the difference ΔT _A'B' from the transmittance T _B' is 15% or more, or the difference between the transmittance T _A' and the transmittance T _C' of the first release liner 2 at one wavelength. ΔT _A'C' is 15% or more, or the difference between the transmittance T _A' and the transmittance T _D' of the laminate of the protective layer 1 and the first release liner 2 at one wavelength is The difference ΔT _A'D' is 15% or more.
That is, in the protective sheet 10 according to the second embodiment, the intensity of the ultraviolet rays transmitted is different between the laminated region and the single layer region.
Therefore, similarly to the first embodiment, by photographing the protective sheet 10 from the outer surface side of the second release liner 3 with the camera 1021 (ultraviolet camera), the single layer area is made into a bright area, and the laminated area is made from the bright area. It can also be understood as a dark dark area.
Therefore, by identifying the bright and dark parts in the image, the position of the protective layer 1 can be identified also in the protective sheet 10 according to the second embodiment.
Thereby, the position of the protective layer 1 on the protective sheet 10 according to the second embodiment can be detected, and also the position on the holding surface 1011 of the holding table 101 where the protective layer 1 is placed can be detected. Can be done.

Furthermore, as explained above, in the protective sheet 10 according to the third embodiment, the transmittance T _A'' of the second release liner 3 at one wavelength included in the visible region and the protective layer 1 at the one wavelength are ΔT _A''B'' , which is the difference between the transmittance T _B'' , is 15% or more, or the transmittance T of the first release liner 2 between the transmittance T _A'' and the one wavelength ΔT _A''C'' which is the difference from _C' ' is 15% or more, or the transmittance T _A'' and the lamination of the protective layer 1 and the first release liner 2 at one wavelength The difference ΔT _A''D'' from the body transmittance T _D'' is 15% or more.
That is, in the protective sheet 10 according to the third embodiment, the intensity of visible light transmitted through the laminated region and the single layer region is different.
Therefore, similarly to the first embodiment, by photographing the protective sheet 10 from the outer surface side of the second release liner 3 with the camera 1021 (visible light camera), the single layer area is defined as a bright area, and the laminated area is defined as the bright area. It can be understood as a dark area that is darker than the actual image.
Therefore, by identifying the bright and dark portions, the position of the protective layer 1 can be identified also in the protective sheet 10 according to the third embodiment.
Thereby, the position of the protective layer 1 on the protective sheet 10 according to the third embodiment can be detected, and also the position of the protective layer 1 on the holding surface 1011 of the holding table 101 can be detected. Can be done.

In this embodiment, a backlight may be provided to improve the detection performance by the camera 1021, and light containing 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.
Note that 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 released. Then, one surface of the protective layer 1 is exposed.

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, and a head section disposed in the chamber 201 above the electrostatic chuck table 202. 203, and a pump P for reducing the pressure inside the chamber 201.
In the following, the up-down direction (vertical direction) is taken as the Z-axis direction, and the horizontal direction along the cut surface when the electrostatic chuck table 202 and the head section 203 are cut along a plane parallel to the Z-axis (the paper surface in FIG. 3B In the following description, the direction (horizontal direction along the plane of FIG. 3B) will be referred to as the X-axis direction, and the direction perpendicular to both the Z-axis and the X-axis (the direction perpendicular to the plane of the paper in FIG. 3B) will be referred to as the Y-axis direction.

As shown in FIG. 3B, in the mounting apparatus 200, the electrostatic chuck table 202 holds the dicing die bond film D to which the semiconductor wafer W is attached by electrostatic force.
Note that the dicing die bond film D includes a die bond film in which an adhesive layer is laminated on a base material, and a die bond layer disposed on the 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.
Furthermore, 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 section 203 suctions the holding table 101 holding the laminate of the protective layer 1 and the first release liner 2 from the first release liner 2 side. and hold it.
Furthermore, in the mounting device 200, the head section 203 is configured to be movable within the chamber 201 along the X-axis direction, the Y-axis direction, and the Z-axis direction.

In the mounting device 200, the inside of the chamber 201 is maintained at atmospheric pressure before the head section 203 holds the holding table 101, and is depressurized by the pump P after the head section 203 holds the holding table 101. Ru.
That is, the holding table 101 is held by the head section 203 under atmospheric pressure, and the bonding of the protective layer 1 to the surface to be protected of the semiconductor wafer W is performed under reduced pressure.

In the mounting device 200 configured as described above, information on the position of the protective layer 1 detected by the sensing device 100, more specifically, where on the holding surface 1011 of the holding table 101 the protective layer 1 is arranged. The protective layer 1 is attached to the surface of the semiconductor wafer W to be protected based on the information (hereinafter also simply referred to as the positional information of the protective layer on the holding table).

Specifically, based on the positional information of the protective layer on the holding table, the head section 203 is moved in the X-axis direction and the Y-axis direction so that the outer periphery of the semiconductor wafer W and the outer periphery of the protective layer 1 are approximately aligned. Thereafter, the head portion 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.
It is preferable that the exposed surface of the protective layer 1 be bonded together while applying a pressure of about 0.3 MPa.
Thereby, the exposed surface of the protective layer 1 can be sufficiently bonded to the surface to be protected of the semiconductor wafer W.
After the exposed surface of the protective layer 1 is sufficiently bonded to the surface to be protected of the semiconductor wafer W, the first release liner 2 is peeled off from the protective layer 1 by moving the head portion 203 upward in the Z-axis direction. .
Thereby, as shown in FIG. 3C, the protective layer 1 can be provided on the surface to be protected of the semiconductor wafer W.
Note that when bonding the exposed surface of the protective layer 1 to the surface to be protected of the semiconductor wafer W, at least one of the holding table 101 and the electrostatic chuck table 202 may be heated.

Next, an example of bonding the protective layer 1 to the surface to be protected of a semiconductor wafer using a protective sheet including the protective layer 1 obtained by the pre-precut method will be described.

When bonding a semiconductor wafer to a surface to be protected using a protective sheet 10 having a protective layer 1 obtained by the pre-cutting method as shown in FIG. 1B, a first release liner 2 or a second release liner With one of the liners 3 peeled off and the surface of the protective layer 1 exposed, the position of the protective layer 1 relative to the bonded release liner is detected.
Therefore, in this embodiment, there needs to be a difference in transmittance between the release liner bonded to one side of the protective layer 1 and the protective layer 1.

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 of the second release liner 3 at one wavelength included in the near-infrared region ΔT _AB , which is the difference between T _A and the transmittance T _B of the protective layer 1 at one wavelength, must be 15% or more, and the second release liner 3 at one wavelength included in the ultraviolet region must be 15% or more. ΔT _A'B ', which is the difference between the transmittance T _A' and the transmittance T _B' of the protective layer 1 at one wavelength, must be 15% or more, and at one wavelength included in the visible region, The difference between the transmittance T _A'' of the second release liner 3 and the transmittance T _B'' of the protective layer 1 at one wavelength, ΔT _A''B'' , must be 15% or more. There is.
In the following, in a state where 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 position of the protective layer 1 with respect to the second release liner 3 is detected, and then the protective An example in which layer 1 is bonded to a surface to be protected of a semiconductor wafer will be described.

The attachment of the protective layer 1 to the surface to be protected of the semiconductor wafer using the protective sheet 10 provided with the protective layer 1 obtained by the tip pre-cutting method is performed by adjusting the position of the protective layer 1 relative to the second release liner 3 and the position of the semiconductor wafer. A sensing device 300 that detects the position, and a laminate that adheres the protective layer 1 to the surface to be protected of the semiconductor wafer based on the position of the protective layer 1 with respect to the second release liner 3 and the position of the semiconductor wafer detected by the sensing device 300. This is implemented using the device 400.

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, and a protective layer 1 and a second release liner 3 disposed above the wafer holding table 301. a gripper 302 that grips the laminate from both edges of the laminate; and a position detector disposed above the gripper 302 to detect the position of the protective layer 1 and the semiconductor wafer W with respect to the second release liner 3. 303.
In the following, the up-down direction (vertical direction) is taken as the Z-axis direction, and the horizontal direction along the cut surface when the wafer holding table 301 etc. is cut on a plane parallel to the Z-axis (horizontal direction along the plane of the paper in FIG. 4A) is referred to as the Z-axis direction. In the following description, the direction (direction) is assumed to be the X-axis direction, and the direction perpendicular to both the Z-axis and the X-axis (the direction perpendicular to the plane of the paper in FIG. 4A) is the Y-axis.
Also, in FIG. 4B below, the X-axis direction, Y-axis direction, and Z-axis direction mean the same directions as the X-axis direction, Y-axis direction, and Z-axis direction in FIG. 4A.

The position detection unit 303 includes a camera 3031 for capturing an image 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 camera 3031 for capturing an image of the semiconductor wafer W, and a camera 3031 for widening the imaging field of the camera. A lens 3032 is provided.
That is, the sensing device 300 detects the position of the protective layer 1 and the position of the semiconductor wafer W with respect to the second release liner 3 using an image captured by the camera 3031 from the second release liner 3 side.
Note that, as shown by the broken line in FIG. 4A, the imaging field of view of the camera 3031 is expanded by the lens 3032 to the vicinity of the area gripped by the gripper 302.
That is, in the sensing device 300, the camera 3031 can image the stack 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 gripper 302, and can also image the semiconductor wafer W. It is now possible to take images.

The gripping tool 302 is attached to an arm (not shown), and is movable by the arm in the X-axis direction, Y-axis direction, and Z-axis direction.

Here, as described above, the semiconductor wafer W has a circuit pattern formed on one surface side and electrode portions arranged thereon.
Further, the semiconductor wafer W usually has a thickness of about several tens of micrometers (for example, 50 micrometers).
Therefore, even near-infrared light having an extremely long wavelength is difficult to pass through the semiconductor wafer W.
Therefore, using any of a near-infrared camera, an ultraviolet camera, or a visible light camera as the camera 3031, the laminate of the protective layer 1 and the second release liner 3 and the semiconductor wafer W are inspected from the second release liner 3 side. Even if an image is taken, the protective layer 1 and the semiconductor wafer W are shown as a shaded part (dark part) in any of the taken images.
Thereby, the position of the protective layer 1 with respect to the second release liner 3 and the position of the semiconductor wafer W can be detected by identifying a shaded part (dark part) in the image.
Then, based on the information on the position of the protective layer 1 with respect to the second release liner 3 and the 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. The outer periphery of the semiconductor wafer W and the outer periphery of the protective layer 1 are made substantially coincident.
Next, the gripper 302 is moved downward in the Z-axis direction to bond the protective layer 1 of the laminate of the protective layer 1 and the second release liner 3 to the surface of the semiconductor wafer W to be protected.

As shown in FIG. 4B, the laminating apparatus 400 rotates and presses a roller 401 in contact with the second release liner 3 of the laminate of the protective layer 1 and the second release liner 3. We are prepared.
In the laminating apparatus 400, as shown in FIG. 4B, the roller 401 protects the semiconductor wafer W by pressing the stack of the protective layer 1 and the second release liner 3 while rotating and moving in the X-axis direction. The protective layer 1 is attached to the target surface.
The pressing is preferably performed while applying a pressure of about 0.3 MPa.
Thereby, the exposed surface of the protective layer 1 can be sufficiently bonded to the surface to be protected of the semiconductor wafer W.

After the exposed surface of the protective layer 1 is sufficiently 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. .
Thereby, as shown in FIG. 4C, the protective layer 1 can be provided on the surface to be protected of the semiconductor wafer W.

The attachment of the protective layer 1 to the surface to be protected of the semiconductor wafer W may be carried out using a vacuum diaphragm type laminator device that laminates the protective layer 1 to the surface to be protected of the semiconductor wafer W under vacuum.
Further, the bonding of the protective layer 1 to the surface to be protected of the semiconductor wafer W may be carried out using a differential pressure press in a chamber where the pressure can be adjusted.

Matters disclosed by this specification include the following.

(1)
a protective layer attached to the adherend;
a release liner disposed on the surface of the protective layer,
the protective layer contains a water-soluble polymer,
The release liner includes an inner surface facing the protective layer and an outer surface opposite to the inner surface,
The light transmittance of the release liner from the outer surface to the protective layer is 15% or more lower than the light transmittance of the release liner in at least one wavelength.

According to such a configuration, the position of the protective layer can be accurately determined from the release liner side.
Thereby, the protective layer can be easily aligned with respect to the transfer device, the adherend, and the like.

(2)
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 includes an inner surface facing the protective layer and an outer surface opposite to 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 15% or more lower than the light transmittance of the second release liner in at least one wavelength.

According to such a configuration, the positions of the protective layer and the first release liner can be accurately grasped from the second release liner side.
Therefore, especially when the protective layer and the first release liner are pre-cut so that they have substantially the same dimensions in a plan view, the position of the protective layer can be accurately determined with respect to the position of the first release liner. can be grasped.
Thereby, the protective layer can be easily aligned with respect to the transfer device, the adherend, and the like.

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

Note that the protective sheet according to the present invention is not limited to the above embodiment. Moreover, the protective sheet according to the present invention is not limited to the above-mentioned effects. The protective sheet according to the present invention can be modified in various ways without departing from the gist of the present invention.

For example, in the protective sheet according to the present invention, the adherend is not limited to a semiconductor wafer, but may be other than a semiconductor as the adherend to be protected.
Further, in this embodiment, an embodiment is exemplified in which a protective layer is provided between two release liners, a first release liner and a second release liner, but the protective sheet of the present invention can be applied to a single release liner. It may have a two-layer structure of a liner and a protective layer.
Furthermore, the protective sheet of the present invention is not limited to the above examples in any way other than these.

Next, the present invention will be described in more detail with reference to Examples. The following examples are intended to explain the invention in more detail and are not intended to limit the scope of the invention.

[Example 1]
In a container, an aqueous dispersion solution was prepared by dispersing polyvinyl alcohol (solubility degree: 65, average degree of polymerization: 240) in water.
Note that hereinafter, polyvinyl alcohol is also referred to as PVA.
Next, the container containing the aqueous dispersion solution was placed in a 90° C. water bath, and the aqueous dispersion solution was stirred to dissolve PVA in water, thereby obtaining a PVA-dissolved composition.
Next, the PVA-dissolved composition was applied using an applicator onto the release-treated surface of a second release liner (manufactured by Mitsubishi Chemical Corporation, product name MRA50, thickness 50 μm), which had a silicone release-treated surface. It was applied to a thickness of 10 μm.
Next, the second release liner coated with the PVA-dissolved 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., trade name "CRISPR (registered trademark) K1211", thickness 38 μm) was laminated on the protective layer to obtain a protective sheet according to Example 1. Ta.
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 by reducing the permeability of the first release liner.

The saponity degree and average degree of polymerization of the polyvinyl alcohol were measured according to the method described in the above embodiment section.

[Example 2]
In the same manner as in Example 1, except that a PET film (manufactured by Fujiko Co., Ltd., trade name "PET38-SCA1", thickness 38 μm) having a coating layer containing titanium oxide on one side was used as the first release liner. A protective sheet according to Example 2 was obtained.
Note that the first release liner had been subjected to a release treatment on the other surface (the surface opposite to the surface having the coating layer).
In the protective sheet according to Example 2, after forming a protective layer on the second release liner, the release-treated surface (the surface without the coating layer) of the first release liner is bonded to the protective layer. It was made by
The protective sheet according to Example 2 as described above was also produced in such a way as to reduce the permeability of the first release liner.

[Example 3]
Except that a layer containing silica was used as the protective layer, and a release liner (manufactured by Mitsubishi Chemical Corporation, product name MRA38, thickness 38 μm) having a surface treated with silicone mold release treatment was used as the first release liner. A protective sheet according to Example 3 was obtained in the same manner as in Example 1.
In the protective sheet according to Example 3, the protective layer is formed by applying a silica-containing composition obtained by adding silica to the PVA-dissolved composition onto the release-treated surface of the second release liner to a thickness of 10 μm using an applicator. After coating, a second release liner coated with the silica-containing composition was formed by drying at 110° C. for 2 minutes.
As the silica, the product name "Snowtech (registered trademark) MP-2040" manufactured by Nissan Chemical Co., Ltd. was used.
Further, the concentration of the silica in the silica-containing composition was 30% by mass.
Further, the first release liner was attached to the protective layer by attaching the surfaces that had been subjected to the release treatment.
The protective sheet according to Example 3 as described above was produced so as to reduce the transmittance of the protective layer.

[Reference example 1]
A protective sheet according to Reference Example 1 was obtained in the same manner as in Example 3 except that a dye-containing protective layer was used.
In the protective sheet according to Reference Example 1, the protective layer is formed by applying a dye-containing composition in which a dye is dissolved in the PVA-dissolved composition onto the release-treated surface of the second release liner to a thickness of 10 μm using an applicator. After coating, a second release liner coated with the dye-containing composition was formed by drying at 110° C. for 2 minutes.
As the dye, the product name "Lina Blue (registered trademark)" (blue pigment) manufactured by DIC Corporation was used.
Further, the concentration of the dye in the dye-containing composition was 5%.
The protective sheet according to Reference Example 1 as above was also produced in such a way as to reduce the transmittance of the protective layer.

[Comparative example 1]
Comparative Example 1 was carried out in the same manner as in Example 1, except that a release liner (manufactured by Mitsubishi Chemical Corporation, product name MRA38, thickness 38 μm) having a surface treated with silicone mold release treatment was used as the first release liner. Such a protective sheet was obtained.
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 surfaces that had been subjected to the release treatment.
The protective sheet according to Comparative Example 1 as described above was produced without reducing the transmittance of either the protective layer or the first release liner.

<Transmittance>
Regarding the protective sheet according to each example, the transmittance of the first release liner, the protective layer, and the second release liner was measured.
The transmittance measurement was performed using light with a wavelength of 1060 nm (near infrared rays), light with a wavelength of 330 nm (ultraviolet rays), 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 peeling off the second release liner from the laminate after obtaining a laminate of the second release liner and the protective layer.
The measurement of the transmittance was performed using the method described in the embodiment section above.
The results are shown in Table 1 below.

In Table 1 below, the transmittance of the second release liner measured using light with a wavelength of 1060 nm is expressed as T _A , and the transmittance of the protective layer measured using light with a wavelength of 1060 nm is expressed as T _B. The transmittance of the first release liner measured using light with a wavelength of 1060 nm is expressed as _TC .
In addition, the transmittance of the second release liner measured using light with a wavelength of 330 nm is expressed as 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 is expressed as T _C' .
Furthermore, the transmittance of the second release liner measured using light with a wavelength of 550 nm is expressed as 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 expressed as T _C''1 .
In addition, the transmittance of the second release liner measured using light with a wavelength of 650 nm is expressed as 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 expressed as T _C''2 .
Furthermore, the difference between the transmittance T _A and the transmittance T _B (TA - _{T B} ) is expressed as ΔT _AB , and the difference between the transmittance T _A and the transmittance T _C ( _TA - T _C ) is expressed as ΔT _AC The difference between the transmittance T _A' and the transmittance T _B' (T _A' - T _B' ) is written as ΔT _A'B' , and the difference between the transmittance T _A' and the transmittance T _C' is expressed as ΔT A'B'. The difference (T _A' - _{T C'} ) is expressed as ΔT ^A'C' , and the difference between the transmittance T _A''1 and the transmittance T _B''1 (T _A''1 - _{T B''1} ) is expressed as ΔT _A''1B''1 , and the difference between the transmittance T _A''1 and the transmittance T _C''1 (T _A''1 - T _C''1 ) is expressed as ΔT _A''1C''1 is written, and the difference between the transmittance T _A''2 and the transmittance T _B''2 (T _A''2 - T _B''2 ) is written as ΔT _A''2B''2 . However, the difference between the transmittance T _A''2 and the transmittance T _C''2 (T _A''2 - T _C''2 ) is expressed as ΔT _A''2C''2 .

<Haze>
Regarding the protective sheet according to each example, the haze of the first release liner, the protective layer, and the second release liner was measured.
The haze measurement was performed using the method described in the embodiment section above.
The results are shown in Table 1 below.

<Gloss at an incident angle of 60°>
Regarding the protective sheet according to each example, the gloss when light was incident on the first release liner, the protective layer, and the second release liner at an angle of 60° (gloss at an incident angle of 60°) was measured.
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 spectral colorimeter CM-26dG manufactured by Konica Minolta.
The results are shown in Table 1 below.
In Table 1, "GU" (Gloss Unit) shown in parentheses is a unit of gloss.

<Lightness (L value)>
Regarding the protective sheet according to 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.
Note that when measuring brightness (L value) using a color meter, chromaticity (a value and b value) is 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, the protective layer, and the second release liner for the protective sheet according to each example.
Table 1 below also shows the measured values of lightness (L value) and chromaticity (a value and b value) of the first release liner, protective layer, and second release liner for the protective sheets according to each example. From this, the value of (L ² +a ² +b ² ) ^1/2 was calculated.
The results are also shown in Table 1 below.

<Identification>
Regarding the protective sheet according to each example, the distinguishability of the protective layer or the first release liner was evaluated.
In the evaluation of identifiability, the protective layer and first release liner were pre-cut and used as test specimens.
Furthermore, the evaluation of identifiability was carried out using a transmission type photoelectric sensor (manufactured by KEYENCE, product name "PR-G51N") that includes a light emitting part and a light receiving part.
Specifically, for the protective sheet according to each example, the light emitting part is placed outside the second release sheet, and the light receiving part is placed outside the first release sheet, and then the light emitting part is placed outside the first release sheet. This was carried out by evaluating whether or not the protective layer or the first release liner was identified as a shadow area (dark area) in the light receiving section when laser light was irradiated.
When the protective layer or the first release liner was identified as a shadow area (dark area), it was evaluated as "excellent", and when it was not identified as a shadow area, it was evaluated as "poor".
Note that as the laser light irradiated from the light projecting section, a laser light with a wavelength of 550 nm and a laser light with a wavelength of 650 nm were used.
Table 1 below shows the results of evaluating the identifiability of the protective layer or the first release liner using a 550 nm laser beam and a 650 nm laser beam.

From Table 1, in Examples 1 and 2 in which ΔT _A''2C''2 is 15% or more, the evaluation of distinguishability when irradiated with a laser beam with a wavelength of 650 nm is "Excellent". It can be seen that in Example 3 and Reference Example 1, in which ΔT _A''2B''2 is 15% or more, the evaluation of distinguishability when irradiated with a laser beam with a wavelength of 650 nm is "Excellent". .
On the other hand, in Comparative Example 1 in which both ΔT _A''2C''2 and ΔT _A''2B''2 are less than 15%, the discriminability when irradiated with laser light with a wavelength of 650 nm is It can be seen that the evaluation is "unacceptable".
In addition, in Examples 1 and 2 in which ΔT _A''1C''1 is 15% or more, the evaluation of distinguishability when irradiated with a laser beam with a wavelength of 550 nm is "Excellent", and ΔT _A''1C''1 is 15% or more. It can be seen that in Example 3 in which _{``1B'' 1} is 15% or more, the evaluation of distinguishability when irradiated with a laser beam with a wavelength of 550 nm is "excellent".
On the other hand, in Reference Example 1 and Comparative Example 1, ΔT _A''1B''1 was less than 15%, and the evaluation of identifiability when irradiated with a laser beam with a wavelength of 550 nm was "impossible". I can see that
From these results, when visible light is irradiated as a laser beam, 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 separated. It is understood that when 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.
Furthermore, even when near-infrared light or ultraviolet light is used as the laser beam instead of visible light, the difference between the transmittance of the second release liner and the transmittance of the protective layer is 15% or more. and, as in the case of visible light, the second release liner and the protective layer can be sufficiently distinguished, and the difference between the transmittance of the second release liner and the transmittance of the first release liner is 15% or more, As with visible light, it is believed that the second release liner and the first release liner can be sufficiently distinguished.

Reference Signs List 1: protective layer, 2: first release liner, 3: second release liner, 10: protective sheet.

Claims (3)

a protective layer attached to the adherend;
a release liner disposed on the surface of the protective layer,
the protective layer contains a water-soluble polymer,
The release liner includes an inner surface facing the protective layer and an outer surface opposite to the inner surface,
The light transmittance of the release liner from the outer surface to the protective layer is 15% or more lower than the light transmittance of the release liner in at least one wavelength. 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 includes a water-soluble polymer compound,
Each of the first release liner and the second release liner includes an inner surface facing the protective layer and an outer surface opposite to 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 15% or more lower than the light transmittance of the second release liner in at least one wavelength. The protective sheet according to claim 1 or 2, wherein the one wavelength is a wavelength in an ultraviolet region, a visible region, or a near-infrared region.