JP2024007757A - Protective sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective sheet that includes release sheets on both sides of a protective layer, and prevents the protective layer from lifting from the other release sheet when one release sheet is peeled off, and that can sufficiently suppress the separation of the protective layer.

SOLUTION: A protective sheet according to the present invention includes a protective layer, a first release liner disposed on one surface of the protective layer, and a second release liner disposed on the other surface of the protective layer, and the protective layer includes a water-soluble polymer compound, and when the release force of the first release liner against the protective layer is P_A, and the release force of the second release liner against the protective layer is P_B, the peeling force P_A and the peeling force P_B satisfy the following relational expressions. P_A<P_B. P_B≤2000 mN/25 mm.

SELECTED DRAWING: Figure 1

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 in order 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.

Further, 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 regions partitioned in a grid pattern by the plurality of planned dividing lines (hereinafter also referred to as grid partitioned regions). 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 regions to form a plurality of semiconductor chips. obtain.

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

By the way, as mentioned above, when dividing (cutting) a semiconductor wafer to obtain a plurality of semiconductor chips, a part of the semiconductor wafer near the dividing part (cutting part) is pulverized and small foreign particles are generated. may occur.
If such minute foreign matter 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 be reduced. This is not desirable because of the
Therefore, manufacturing of semiconductor chips is often carried out by bonding the protective layer of the protective sheet to one surface side (the side on which the circuit pattern is formed) of the semiconductor wafer.

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

The one release sheet is peeled off from the protective layer by applying an external force such as a suction force from the outside of the one release sheet (the side on which the protective layer is not provided). When the protective layer is peeled off, the protective layer may float off the other of the two release sheets.
Further, when the protective layer is peeled off from the one release sheet, although no lifting of the protective layer from the other sheet is observed, a part of the protective layer remains attached to the one release sheet. may be peeled off. That is, the protective layer may separate (cohesive failure or the like may occur in the protective layer).

However, in a protective sheet provided with release sheets on both sides of the protective layer, it is necessary to suppress the lifting of the protective layer from the other release sheet when one release sheet is peeled off, and to prevent the protective layer from separating. It cannot be said that sufficient consideration has been given to achieving a sufficient balance between suppressing the storage of waste.

Therefore, the present invention provides release sheets on both sides of the protective layer, and suppresses the lifting of the protective layer from the other release sheet when one release sheet is peeled off. It is an object of the present invention to provide a protective sheet capable of sufficiently suppressing tearful separation.

The protective sheet according to the present invention includes:
a protective layer;
a first release liner disposed on one surface of the protective layer;
a second release liner disposed on the other surface of the protective layer,
The protective layer includes a water-soluble polymer compound,
When the release force of the first release liner with respect to the protective layer is P _A , and the release force of the second release liner with respect to the protective layer is P _B ,
A protective sheet in which peeling force P _A and peeling force P _B satisfy the following relational expression.
P _A < P _B
P _B ≦2000mN/25mm

According to the present invention, release sheets are provided on both sides of the protective layer, and when one release sheet is peeled off, lifting of the protective layer from the other release sheet is suppressed, and the protective layer is It is possible to provide a protective sheet that can sufficiently suppress the occurrence of tearful separation.

FIG. 1 is a schematic cross-sectional view showing the configuration of a protective sheet according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the configuration of a mounting device for bonding a protective layer of a protective sheet to a surface to be protected of an electronic component such as a semiconductor wafer.

An embodiment of the present invention will be described below.

[Protection sheet]
As shown in FIG. 1, a protective sheet 10 according to an 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 first release liner 2 disposed on the other surface of the protective layer 1. A second release liner 3 is provided.
Note that, hereinafter, one embodiment of the present invention will simply be referred to as the present embodiment.
In the protective sheet 10 according to this embodiment, the protective layer 1 contains a water-soluble polymer compound.
That is, the protective layer 1 has water solubility.
On the other hand, the first release liner 2 and the second release liner 3 are water-insoluble.

As shown in FIG. 1, in the protective sheet 10 according to the present embodiment, the protective layer 1, the first release liner 2, and the second release liner 3 have substantially the same dimensions in plan view.
Specifically, in the protective sheet 10 according to one embodiment, the inner surface of the first release liner 2 (the surface facing one surface of the protective layer) and the one surface of the protective layer 1 are in the shape where the edges are joined together. The inner surface of the second release liner 3 (the surface facing the other surface of the protective layer 1) and the other surface of the protective layer 1 overlap almost the entire area with their edges together. has been done.

In the protective sheet 10 according to the present embodiment, the protective layer 1 has adhesiveness to the extent that it can be attached to an adherend.
In the protective sheet 10 according to this embodiment, the protective layer 1 preferably has tackiness (pressure-sensitive adhesiveness).
By attaching the protective layer 1 to an adherend (for example, an electronic component such as a semiconductor wafer), the protective sheet 10 of this embodiment protects the surface of the adherend while performing various treatments on the adherend. It is used to prevent foreign matter from adhering.

In the protective sheet 10 according to the present embodiment, the protective layer 1 (more specifically, the exposed surface of the protective layer 1) is mounted on an electronic device such as a semiconductor wafer using a mounting device 200 as shown in FIG. 2, for example. Affixed to the protected surface of the component.
As shown in FIG. 2, the mounting device 200 includes a chamber 201, an electrostatic chuck table 202 disposed at the bottom of the chamber 201, 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 addition, in the mounting device 200, an electronic component such as a semiconductor wafer is attached to the electrostatic chuck table 202, and a protective sheet 10 is attached to the head section 203.
In addition, in the mounting device 200, the protective sheet 10 and electronic components such as semiconductor wafers are mounted on the head section 203 and the electrostatic chuck table 202 in such a manner that the exposed surface of the protective layer 1 and the surface to be protected face each other. Each can be installed.
Furthermore, as shown in FIG. 2, the protective sheet 10 may be attached to the holding table 101 after the holding table 101 is attached to the head portion 203.

The vertical direction (vertical direction) is the Z-axis direction, and the horizontal direction along the cut surface when the electrostatic chuck table 202 and head section 203 are cut on a plane parallel to the Z-axis (horizontal direction along the paper surface in FIG. 2) ) is the X-axis direction, and the direction perpendicular to both the Z-axis and the By moving it to one side and further moving it in the Z-axis direction, the exposed surface of the protective layer 1 attached to the head section 203 is attached to the electrostatic chuck table 202 to protect the electronic components such as semiconductor wafers. It can be attached to the surface.

When the holding table 101 is not attached to the head section 203, the electrostatic chuck table 202 may be kept in a heated state when attaching the exposed surface of the protective layer 1 to the surface to be protected.
Furthermore, when the holding table 101 is attached to the head section 203, at least one of the holding table 101 and the electrostatic chuck table 202 is heated when attaching the exposed surface of the protective layer 1 to the surface to be protected. You can leave it as

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 an adherend.
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 according to this embodiment is used by peeling off the first release liner 2 to expose one surface of the protective layer 1, and then adhering the one surface to the surface to be protected of an adherend.
The protective sheet 10 according to the present embodiment is manufactured by attaching one surface of the protective layer 1 to the surface to be protected of an adherend, and then peeling off the second release liner 3 from the other surface of the protective layer 1. It may also be used with other surfaces exposed.
That is, in the protective sheet 10 according to the present embodiment, the first release liner 2 is peeled off to expose one surface of the protective layer 1, and the one surface is adhered to the surface to be protected of the adherend, and then the protective sheet 10 is removed. The layer 1 may be used with the other surface of the layer 1 covered with the second release liner 3, or the second release liner 3 may be peeled off from the other surface of the protective layer 1 to expose the other surface of the protective layer 1. may be used in

In the protective sheet 10 according to the present embodiment, when attaching one surface of the protective layer 1 to the surface to be protected of the adherend, at least the protective layer 1 has approximately the same planar dimension as the adherend. It is cut etc.

In the protective sheet 10 according to the present embodiment, when the peeling force of the first release liner 2 to the protective layer 1 is P _A and the peeling force of the second release liner 3 to the protective layer 1 is P _B , the peeling force P It is important that _A and the peeling force P _B satisfy the following relational expression.

P _A < P _B
P _B ≦2000mN/25mm

By setting the peeling force P _B to 2000 mN/25 mm or less, it is possible to prevent the second release liner 3 from being excessively adhered to the protective layer 1 .
As a result, after peeling off the first release liner 2 to expose one surface of the protective layer 1 and adhering the one surface to the surface to be protected of the semiconductor wafer as the adherend, the other surface of the protective layer 1 is removed. When the second release liner 3 is peeled off, it is possible to prevent the second release liner 3 from being peeled off with part of the protective layer 1 attached.
That is, it is possible to prevent the protective layer 1 from tearing apart when the second release liner 3 is peeled off.
Furthermore, since the peeling force P _A and the peeling force P _B satisfy the relationship P _A < _PB , when the first release liner 2 is peeled off to expose one surface of the protective layer 1 , the protective layer 1 It is possible to prevent the second release liner 3 from floating up on the other surface side.
In addition, from the viewpoint of appropriately balancing the adhesion force of the first release liner 2 to the protective layer 1 and the adhesion force of the second release liner 3 to the protective layer 1, the ratio of the release force P _B to the release force P _A (P _B / P _A ) is preferably 1.1 or more, and more preferably 1.2 or more.
Further, the R is more preferably 2.0 or more, more preferably 3.0 or more, more preferably 4.0 or more, and even more preferably 5.0 or more. The upper limit of R is usually 100.
When R is 2.0 or more, the difference between the value of peeling force P _A and the value of peeling force P _B can be made sufficiently large, so that the first release liner 2 can be peeled off from the protective layer 1 . It is possible to sufficiently suppress the protective layer 1 from lifting off from the second release liner 3 during the release process.

In order for the protective sheet 10 according to the present embodiment to satisfy the above relational expression, that is, P _A < P _B and P _B ≦2000 mN/25 mm, the first release liner 2 on one surface of the protective layer 1 must be The inner surface of the first release liner 2 is subjected to a surface treatment so that the inner surface of the second release liner 3 has an appropriate adhesion force to the other surface of the protective layer 1. It is necessary to perform a surface treatment on the inner surface of the second release liner 3 so that it becomes .

In the protective sheet 10 according to the present embodiment, the peeling force _PA is preferably 5 mN/25 mm or more, more preferably 10 mN/25 mm or more, and even more preferably 15 mN or more.
Further, in the protective sheet 10 according to the present embodiment, the peeling force P _A is preferably 1000 mN/25 mm or less, more preferably 500 mN/25 mm or less, and even more preferably 300 mN/25 mm or less. , 200 mN/25 mm or less is even more preferable.

In the protective sheet 10 according to the present embodiment, the peeling force P _B is preferably 70 mN/25 mm or more, and preferably 80 mN/25 mm or more.
Further, in the protective sheet 10 according to the present embodiment, the peeling force P _B is preferably 1500 mN/25 mm or less, and more preferably 1000 mN/25 mm or less.

The peeling force P _A and the peeling force P _B can be measured using a tensile tester (trade name "Autograph AG-IS", manufactured by Shimadzu Corporation).
Regarding the peeling force P _A using the tensile tester, a sample with a length of 150 mm and a width of 100 mm was cut out from the protective sheet 10, and then the second release liner 3 was peeled off from the sample. A specimen (hereinafter referred to as the first specimen).
Regarding the peel force P _B using the tensile tester, a sample with a length of 150 mm and a width of 100 mm was cut out from the protective sheet 10, and then the first release liner 2 was peeled off from the sample. Let this be the specimen (hereinafter referred to as the second specimen).
Note that the unit of "mN/25 mm" for the peeling force P _A and the peeling force P _B is the value measured at a width of 100 mm converted to a width of 25 mm.

The peeling force _P was measured by attaching the exposed surface of the protective layer in the first specimen to the surface of the bare wafer with a double-sided tape (for example, Nitto Denko's product name "No. 500") interposed. A 180° peel test can be performed using a tensile tester (for example, "Autograph AG-IS" manufactured by Shimadzu Corporation).
Note that the 180° peel test is performed by pulling the first release liner 2 in the length direction under the conditions of a temperature of 23 ± 2 ° C., a relative humidity of 55 ± 5% RH, and a peeling speed of 300 mm/min. Can be done.
In addition, the measurement of the peel force P _B was carried out in the same manner as the measurement of the peel force P _A , except that the first specimen was replaced with the second specimen and the target to be pulled in the length direction was replaced with the second release liner 3. can do.
Furthermore, the peeling force P _A and the peeling force P _B are average values of values within a range from the start point of 30 mm to the end point of 120 mm from the start of measurement.

Examples of the surface treatment include performing a mold release treatment on the inner surface of the first release liner 2 and the inner surface of the second release liner 3 using a release agent.
As the release agent, any suitable release agent can be used as long as the effects of the present invention are not impaired.
Examples of such release agents include ethylene-vinyl alcohol copolymers, fatty acid amide additives, low molecular weight polyolefin waxes, long-chain alkyl additives, polymethylpentene, fluorine release agents, silicone release agents, etc. can be mentioned.

Examples of the ethylene-vinyl alcohol copolymer include ethylene obtained by saponifying a copolymer of ethylene and at least one member selected from the group consisting of vinyl acetate, vinyl formate, and vinyl propionate. - Vinyl alcohol copolymer etc. can be used.

Examples of the fatty acid amide additives include methylene bisstearamide, ethylene bisstearamide, ethylene bisoleic acid amide, N,N-dioleyladipic acid amide, N-stearyl-N'-stearylic acid amide ( For example, N-stearyl-N'-stearylurea, etc.).
These fatty acid amide additives may be used alone or in combination of two or more.

Examples of the low molecular weight polyolefin wax include low molecular weight polyethylene waxes, low molecular weight polypropylene waxes, and the like.

Examples of the long-chain alkyl additive include those containing long-chain alkyl pendant polymers.
Commercially available products of such long-chain alkyl additives include Pearoyl (registered trademark) 1010 (manufactured by Ichigosha Yushi Kogyo Co., Ltd.), Pearoyl (registered trademark) 1010S (manufactured by Ichigosha Yushi Kogyo Co., Ltd.), and the like.

Examples of the polymethylpentene include olefin copolymers based on 4-methyl-1-pentene.
Commercially available products of such polymethylpentene include TPX (registered trademark) MX001 (manufactured by Mitsui Chemicals, Inc.) and TPX (registered trademark) 0004 (manufactured by Mitsui Chemicals, Inc.).

The fluorine-based release agent contains a fluorine-based resin.
Examples of the fluororesin include PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride), PCTFE (polychlorotrifluoroethylene), PVF (polyvinyl fluoride), and PFA (a combination of tetrafluoroethylene and perfluoroalkoxyethylene). copolymer), FEP (copolymer of tetrafluoroethylene and hexafluoropropylene), ETFE (copolymer of tetrafluoroethylene and ethylene), ECTFE (copolymer of chlorotrifluoroethylene and ethylene), Examples include a terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, and fluororubber.
These various fluororesins may be used alone or in combination of two or more.

Examples of the silicone release agent include oil type, baking type, and emulsion type release agents.

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

Examples of the polyalkylsiloxane include dimethyl silicone in which all of the side chains and terminals are methyl groups, methylphenyl silicone in which part of the side chain is a phenyl group, and methylhydrogen silicone in which part of the side chain is hydrogen. Can be mentioned.
Note that dimethyl silicone, methylphenyl silicone, and methyl hydrogen silicone are all called straight silicones in which silicon (Si) is linearly bonded via oxygen (O).

Examples of the modified polyalkylsiloxane include those in which an organic group is introduced into a part of the side chain of the polysiloxane.
Examples of the organic group include a monoamine group, a diamine group, an amino group, an epoxy group, a carbinol group, a mercapto group, a carboxyl group, a polyether group, an aralkyl group, and a fluoroalkyl group.
Among the modified polyalkylsiloxanes, those having reactive organic groups such as monoamine groups, diamine groups, amino groups, epoxy groups, carbinol groups, mercapto groups, and carboxyl groups are called reactive silicones. Among the modified polyalkylsiloxanes, those having non-reactive organic groups such as polyether groups, aralkyl groups, and fluoroaralkyl groups are called non-reactive silicones.

The baking-type silicone release agent is a liquid silicone compound such as the above-mentioned polyalkylsiloxane, the modified polyalkylsiloxane, and a resin modified with polyalkylsiloxane, and a peroxide or a peroxide-containing silicone compound. Examples include those containing a crosslinking agent.

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

The silicone compound such as the polyalkylsiloxane has thermal crosslinkability.
In such a silicone compound, the degree of peeling force can be easily adjusted by adjusting the degree of thermal crosslinking.
Therefore, in consideration of the above, it is preferable to use a silicone-based release agent among the various release agents described above.

Note that the release agent is usually in liquid form, and is used in a form that is applied to the object from which it is desired to improve releasability.
Various known coating methods can be employed as the method for coating the release agent.
Examples of various known coating methods include roll coating methods such as gravure coating and reverse coating, barcode methods such as Meyer bar, spray coating, and air knife coating.
Note that the above-mentioned release agent may be diluted with an organic solvent (for example, ethyl methyl ketone) and then applied to the object.
Further, the release agent is preferably applied so that the thickness after drying is in the range of 0.05 μm or more and 1 μm or less.

When the release agent is used to release the inner surface of the first release liner 2 and the inner surface of the second release liner 3, the type of release agent applied to the inner surface of the first release liner 2 and the If the type of release agent applied to the inner surface of the second release liner 3 is different, the release force P _A of the inner surface of the first release liner 2 to the protective layer 1 and the inner surface of the second release liner 3 to the protective layer 1 can be changed. The peeling force _PB of the surface can be made different.
Furthermore, when a silicone release agent is used as both the release agent applied to the inner surface of the first release liner 2 and the release agent applied to the inner surface of the second release liner 3, as explained above, If the degree of thermal crosslinking of the silicone release agent applied to the inner surface of the first release liner 2 is different from the degree of thermal crosslinking of the silicone release agent applied to the inner surface of the second release liner 3, , the release force P _A of the inner surface of the first release liner 2 against the protective layer 1 and the release force P _B of the inner surface of the second release liner 3 against the protective layer 1 can be made different.
Note that the degree of thermal crosslinking can be adjusted by varying the heating temperature or heating time.
Furthermore, when the release agent applied to the inner surface of the first release liner 2 and the release agent applied to the inner surface of the second release liner 3 are of the same type, the dilution ratio with an organic solvent etc. The inner surface of the first release liner 2 and the inner surface of the second release liner 3 may each be coated using different release agents. Even when the coating process is performed in this manner, the peeling force P A of the inner surface of the first release liner 2 with respect to the protective layer 1 and the peeling force P _B of the inner surface of the second release liner 3 with respect to the protective layer ₁ are can be made different.

Further, as the surface treatment, for example, unevenness may be provided on the inner surface of the first release liner 2 (the surface on which the protective layer 1 is disposed) and the inner surface of the second release liner 3 by matting, embossing, etc. can be mentioned.
In the case where the inner surface of the first release liner 2 and the inner surface of the second release liner 3 are provided with irregularities, the arithmetic mean roughness Ra of the inner surface of the first release liner 2 is preferably 0.1 μm or more. , more preferably 0.5 μm or more, and even more preferably 1.0 μm or more.
Further, the arithmetic mean roughness Ra of the inner surface of the first release liner 2 is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 10 μm or less.
Furthermore, the arithmetic mean roughness Ra of the inner surface of the second release liner 3 is preferably 0.050 μm or more, more preferably 0.075 μm or more, and even more preferably 0.100 μm or more.

The arithmetic mean roughness Ra of the inner surface of the first release liner 2 and the arithmetic mean roughness Ra of the inner surface of the second release liner 3 are determined using a confocal laser microscope (for example, trade name "OPTELICS H300", manufactured by Lasertech). It can be measured using

The larger the value of the arithmetic mean roughness Ra, the smaller the contact area between the inner surface of the first release liner 2 and the inner surface of the second release liner 3 and the surface of the protective layer 1.
Therefore, the larger the value of the arithmetic mean roughness Ra, the more the peeling force P _A of the inner surface of the first release liner 2 with respect to the protective layer 1 and the peeling force P _B of the inner surface of the second release liner 3 with respect to the protective layer 1. becomes smaller (can be easily peeled off).
Therefore, by making the value of the arithmetic mean roughness Ra of the inner surface of the first release liner 2 larger than the value of the arithmetic mean roughness Ra of the inner surface of the second release liner 3, release force P _A < release force P Relationship _B will be satisfied.
Furthermore, since the arithmetic mean roughness Ra of the inner surface of the first release liner 2 is within the above numerical range and the arithmetic mean roughness Ra of the inner surface of the second release liner 3 is within the above numerical range, this implementation is possible. It becomes easy to make the protective sheet 10 according to this embodiment satisfy each of the above-mentioned relational expressions.

As explained above, the protective layer 1 is used by being attached to the surface of the adherend to be protected.
Examples of the adherend include electronic components, and examples of the electronic components 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).

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.

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 second release liner 3 to a predetermined thickness (for example, 5 μm to 30 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 second release liner 3.
(3) In the protective layer 1, the first release liner 2 is attached to the surface opposite to the surface on which the second release liner 3 is arranged (the exposed surface of the protective layer 1) at a predetermined temperature (for example, 70° C.) .

In the protective sheet 10 according to the present embodiment, the protective layer 1 is a water-soluble resin composition containing a water-soluble polymer compound and an excess liquid, in which the water-soluble polymer compound is dispersed in water (hereinafter referred to as It is preferable to use a protective layer forming composition (referred to as 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 below the above-mentioned upper limit, the coating properties when coating the protective layer forming composition on 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 prepared 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 including 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 taking the arithmetic average of these thicknesses. Can be done.

Examples of the first release liner 2 include a resin sheet made using a resin such as polyethylene terephthalate (PET).
When the first release liner 2 is made of a resin sheet as described above, the resin sheet has a layer on at least the surface to be bonded to the protective layer 1 in order to appropriately adjust the adhesion to the protective layer 1. Surface treatments as described may be applied.
Further, as the second release liner 3, like the first release liner 2, for example, a resin sheet made using a resin such as polyethylene terephthalate (PET) can be mentioned.
When the second release liner 3 is made of a resin sheet as described above, in the resin sheet, at least the surface to be bonded to the protective layer 1 is coated with an adhesive layer on the surface of the resin sheet in order to appropriately adjust the adhesion to the protective layer 1. Surface treatments as described may be applied.

When the thickness of the first release liner 2 is T _A and the thickness of the second release liner 3 is T _B , it is preferable that the thickness T _A and the thickness T _B satisfy the following relational expression.

T _A < T _B
35μm<T _B <80μm

Generally, the thicker the release liner, the higher the waist strength (flexural rigidity).
The higher the release liner's waist strength, the more difficult it becomes to bend in the thickness direction.
Here, as explained above, one surface of the protective layer 1 exposed by peeling off the first release liner 2 is bonded to the surface to be protected of an adherend such as a semiconductor wafer.
Then, the first release liner 2 is peeled off from one surface of the protective layer 1 by applying an external force such as a suction force from the outside (the side on which the protective layer 1 is not disposed).
In the above case, the first release liner 2 is deflected due to suction or the like, and this deflection causes a part of the first release liner 2 to rise from one surface of the protective layer 1. Become.
Then, the first release liner 2 is peeled off from one surface of the protective layer 1 using the raised portion as a starting point.
As described above, when the first release liner 2 is peeled off from one surface of the protective layer 1, the second release liner 3 also tends to bend inward (toward the side on which the protective layer 1 is disposed). Therefore, it is not preferable that the second release liner 3 rises from the other surface of the protective layer 1.
Therefore, it is preferable that the thickness T _A of the first release liner 2 and the thickness T _B of the second release liner 3 satisfy the relational expression T _A <T _B as described above.
Further, after one surface of the protective layer 1 is bonded to the surface to be protected, the second release liner 3 is usually peeled off from the other surface of the protective layer 1.
Therefore, from the viewpoint of making it easier to peel off the second release liner 3 after bonding one surface of the protective layer 1 to the surface to be protected, the thickness T _B of the second release liner 3 is set to 35 μm<T as described above. It is preferable that the relational expression _B <80 μm is satisfied.
This allows the second release liner 3 to have appropriate stiffness, so that when the second release liner 3 is peeled off from the other surface of the protective layer 1, a part of the protective layer 1 may adhere. It is possible to prevent the second release liner 3 from being peeled off in this state, that is, from tearing apart.

Furthermore, by making the thickness _TA of the first release liner 2 and the thickness _TB of the second release liner 3 different, when the protective sheet 10 is viewed from the side, the first release liner 2 and the second release liner 3 becomes easier to identify.

The thickness T _A of the first release liner 2 may be 15 μm or more, 20 μm or more, or 25 μm or less.
Further, the thickness T _A of the first release liner 2 may be less than 40 μm or 35 μm or less.
Furthermore, the thickness T _B of the second release liner 3 may be 40 μm or more, 45 μm or more, 50 μm or more, or 60 μm or more.
Further, the thickness T _B of the second release liner 3 may be 75 μm or less, or 70 μm or less.
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.

From the viewpoint of making it easier to visually identify the first release liner 2 and the second release liner 3, the first release liner 2 and the second release liner 3 may have different colors.
For example, both the first release liner 2 and the second release liner 3 are colored, such as the first release liner 2 is colored black and the second release liner 3 is colored white. 2 and the second release liner 3 may be visually distinguishable from each other.
In addition, when both the first release liner 2 and the second release liner 3 are colorless and transparent, one of the first release liner 2 and the second release liner 3 is colored, and the first release liner 2 and the second release liner 3 are colored. Distinguishability from the release liner 3 may be improved.
As the coloring agent for coloring the first release liner 2 and the second release liner 3, various known coloring agents can be used.
Examples of the coloring agent include dyes and pigments.
Note that the term "dye" refers to a coloring agent that has the property of being soluble in water, organic solvents, etc., and the term "pigment" refers to a coloring agent that does not dissolve in water, organic solvents, or the like.

Matters disclosed by this specification include the following.

(1)
a protective layer;
a first release liner disposed on one surface of the protective layer;
a second release liner disposed on the other surface of the protective layer,
The protective layer includes a water-soluble polymer compound,
When the release force of the first release liner with respect to the protective layer is P _A , and the release force of the second release liner with respect to the protective layer is P _B ,
A protective sheet in which peeling force P _A and peeling force P _B satisfy the following relational expression.
P _A < P _B
P _B ≦2000N/25mm

According to such a configuration, when one release sheet is peeled off, it is possible to suppress the lifting of the protective layer from the other release sheet, and to suppress the protective layer from being separated. It is possible to achieve both.

(2)
When the thickness of the first release liner is T _A and the thickness of the second release liner is T _B ,
The protective sheet according to claim 1, wherein the thickness T _A and the thickness T _B satisfy the following relational expression.
T _A < T _B
35μm<T _B <80μm

According to such a configuration, when one release sheet is peeled off, it is possible to suppress the lifting of the protective layer from the other release sheet, and to suppress the protective layer from being separated. It is possible to achieve both of these requirements even more fully.
Moreover, it becomes easier to visually distinguish one release sheet from the other release sheet.

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.

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 water dispersion solution was placed in a 90° C. water bath, and the water dispersion container was stirred to dissolve PVA in water, thereby obtaining a PVA-dissolved composition.
Next, a second release liner (trade name "Diafoil MRV75" manufactured by Mitsubishi Chemical Corporation, thickness 75 μm) having a surface treated with silicone mold release treatment (hereinafter also referred to as silicone mold release treatment surface) was subjected to mold release treatment. The PVA-dissolved composition was applied onto the surface using an applicator to a thickness of 5 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.
Next, a first release liner (trade name "Diafoil MRA25" manufactured by Mitsubishi Chemical Corporation, thickness 25 μm) having a silicone release treated surface is superimposed on the protective layer, and the second release liner and the protective After obtaining a laminate in which the layers and the first release liner were laminated in this order, the laminate was heat-treated at 70°C.
Note that the first release liner had a silicone release-treated surface superimposed on the exposed surface of the protective layer.
Thereby, a protective sheet according to Example 1 was obtained.
Further, in the following, the diafoil MRV75 is simply referred to as "MRV75", and the diafoil MRA25 is simply referred to as "MRA25".

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]
As the second release liner, "CRISPR CN500-50" (trade name, manufactured by Toyobo Co., Ltd.) was used, as the first release liner, "Diafoil MRA38" (trade name, manufactured by Mitsubishi Chemical Corporation) was used, and the thickness of the protective layer was adjusted. A protective sheet according to Example 2 was obtained in the same manner as Example 1 except that the thickness was 10 μm.
The second release liner, CRISPR CN500-50, has a surface that has been subjected to a release treatment with a non-silicone release agent that does not contain a silicone compound (hereinafter also referred to as a non-silicone release treatment surface). The thickness was 50 μm.
Further, the diafoil MRA38, which is the first release liner, had a silicone release treatment surface, like the MRV75 and the MRA25, and had a thickness of 38 μm.
Furthermore, the silicone release treated surface of the first release liner was bonded to one surface of the protective layer, and the non-silicone release treated surface of the second release liner was bonded to the other surface of the protective layer.
Further, in the following, CRISPR CN500-50 is simply written as "CN500-50", and Diafoil MRA38 is simply written as "MRA38".

[Example 3]
A protective sheet according to Example 3 was prepared in the same manner as in Example 2, except that the first release liner was "CRISPR CN100-38" manufactured by Toyobo Co., Ltd., and the thickness of the protective layer was 30 μm. Obtained.
The first release liner, CRISPAR CN100-38, had a non-silicone release treated surface, like CRISPAR CN500-50, and had a thickness of 38 μm.
Further, in the following, CRISPR CN100-38 is simply referred to as "CN100-38".

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

[Comparative example 1]
As the first release liner, "Lumirror (registered trademark) #38-S10" manufactured by Toray Industries, Inc. was used, and as the second release liner, "Lumirror (registered trademark) #50-" manufactured by Toray Industries, Inc. was used. A protective sheet according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the protective layer was made to have a thickness of 10 μm.
Note that the first release liner, Lumirror (registered trademark) #38-S10, was not subjected to any release treatment and had a thickness of 38 μm.
The second release liner, Lumirror (registered trademark) #50-S10, was also not subjected to any release treatment and had a thickness of 50 μm.
Furthermore, below, Lumirror (registered trademark) #38-S10 is simply described as "#38-S10", and Lumirror (registered trademark) #50-S10 is simply described as "#50-S10".
Note that both “#38-S10” and “#50-S10” are polyester films.

[Comparative example 2]
A protective sheet according to Comparative Example 2 was obtained in the same manner as in Example 2, except that "Diafoil MRA50" (trade name, manufactured by Mitsubishi Chemical Corporation) was used as the second release liner.
Note that the diafoil MRA50, which is the second release liner, had a silicone release-treated surface and had a thickness of 50 μm, similarly to the MRV75, the MRA25, and the MRA38.
Further, in the following, the diafoil MRA50 is simply referred to as "MRA50".

<Peeling force>
For the protective sheet according to each example, the peel force P _A of the first release liner with respect to the protective layer and the peel force P _B of the second release liner with respect to the protective layer were measured.
The peeling force P _A and the peeling force P _B were determined according to the method described in the embodiment section above.
Table 1 below shows the results of measuring the peeling force P _A and the peeling force P _B for the protective sheets according to each example.
Further, Table 1 below also shows R, which is the ratio of the peeling force P _B to the peeling force _PA , for the protective sheets according to each example.

<The tearful farewell of the protective layer>
In measuring the peel force, the surface of the release liner peeled off from the protective layer was visually observed, and the separation of the protective layer was evaluated according to the following criteria.

Excellent: No protective layer is visually observed on the surface of the release liner.
Not acceptable: Part of the protective layer is visually confirmed on the surface of the release liner.

Table 1 below shows the results of evaluating the quality of the protective layer.

<Lifting of the protective layer>
After leaving the protective sheet according to each example in an environment with a temperature of 23 ± 2°C and a relative humidity of 55 ± 5% RH for 24 hours, the protective layer from each release liner (first release liner and second release liner) was removed. Visual observation was made to see if any floating was observed.
Then, the lifting of the protective layer was evaluated according to the following criteria.

Excellent: No lifting of the protective layer is visually observed from either the first release liner or the second release liner. Furthermore, even if the first release liner is manually peeled off from the protective layer after exposing the protective sheet to the above environment (temperature 23 ± 2°C and relative humidity 55 ± 5% RH), the second release liner No lifting of the protective layer from the release liner is visually observed.
Good: No lifting of the protective layer is visually observed in either the first release liner or the second release liner. On the other hand, when the first release liner is manually peeled off from the protective layer after exposing the protective sheet to the above environment for 24 hours, slight lifting of the protective layer from the second release liner is visually confirmed.
Not acceptable: Lifting of the protective layer is visually confirmed from at least one of the first release liner and the second release liner.

Table 1 below shows the results of evaluating the lifting of the protective layer.

From Table 1, as in the protective sheets of each example, the peel force P _A of the first release liner with respect to the protective layer and the peel force P _B of the second release liner with respect to the protective layer are such that P _A <P _B , and , P _B ≦2000 mN/25 mm, it can be seen that it is possible to suppress both the tearing of the protective layer and the lifting of the protective layer.
On the other hand, it can be seen that protective sheets in which the above relational expression is not satisfied, such as the protective sheets of the comparative examples, are unable to simultaneously suppress the separation of the protective layer and suppress the lifting of the protective layer.
In addition, the evaluation results of the lifting of the protective layer of the protective sheets of Examples 1 to 3 with a ratio R of 2.0 or more and the lifting of the protective layer of the protective sheets of each comparative example with a ratio R of less than 2.0 are also shown. A comparison with the evaluation results shows that particularly good results are obtained with the protective sheets according to Examples 1 to 3.
In addition, in the protective sheet of Comparative Example 1, the peeling force P _A value and the peeling force P _B value were too high, so it was not possible to evaluate the lifting of the protective layer.
Therefore, regarding the protective sheet of Comparative Example 1, the evaluation of lifting of the protective layer is described as "Evaluation not possible" in Table 1.

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

Claims (2)

a protective layer;
a first release liner disposed on one surface of the protective layer;
a second release liner disposed on the other surface of the protective layer,
The protective layer includes a water-soluble polymer compound,
When the release force of the first release liner with respect to the protective layer is P _A , and the release force of the second release liner with respect to the protective layer is P _B ,
A protective sheet in which peeling force P _A and peeling force P _B satisfy the following relational expression.
P _A < P _B
P _B ≦2000mN/25mm When the thickness of the first release liner is T _A and the thickness of the second release liner is T _B ,
The protective sheet according to claim 1, wherein the thickness T _A and the thickness T _B satisfy the following relational expression.
T _A < T _B
35μm<T _B <80μm

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