Adhesive sheet

Abstract

To provide an adhesive sheet having good expandability.SOLUTION: An adhesive sheet includes a base material and an adhesive layer, wherein the base material is a resin film having no chlorine atom, the resin constituting the resin film is at least one of a thermoplastic polyurethane elastomer obtained by reacting long chain polyol, a chain extender and polyisocyanate, and a polyester-based resin, all of tensile stresses from 10% elongation to 100% elongation in a predetermined first measurement direction are settled within a range of 8 to 30 MPa, and all of tensile stresses from 100% elongation to 200% elongation in the first measurement direction are settled within a range of 10 to 40 MPa.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an adhesive sheet that can be suitably used as a workpiece processing sheet used in processing workpieces such as semiconductor wafers. [Background technology]

[0002] Semiconductor wafers such as silicon and gallium arsenide and various packages are manufactured in large diameters, cut into chips (diced), peeled off (picked up), and then transferred to the next process, the mounting process. At this time, the workpieces such as semiconductor wafers are attached to an adhesive sheet (hereinafter sometimes referred to as a "workpiece processing sheet") that has a base material and an adhesive layer, and undergo processing such as backgrinding, dicing, cleaning, drying, expanding, picking up, and mounting.

[0003] One of the above-mentioned dicing methods is a method of cutting a workpiece using a rotating circular blade (dicing blade). In this method, it is common to partially cut the workpiece together with the workpiece processing sheet to which the workpiece is attached, in order to ensure that the workpiece is cut reliably. When the workpiece processing sheet is cut together with the workpiece in this way, cutting chips made of the material that constitutes the adhesive layer and the base material may be generated from the workpiece processing sheet.

[0004] If a chip is sealed with a large amount of chip debris attached to it, the chip debris will decompose due to the heat of sealing, and the resulting thermal decomposition products may destroy the package or cause malfunctions in the resulting device. Because these debris are difficult to remove by cleaning, the generation of debris significantly reduces the yield of the dicing process. Therefore, when dicing with a rotating circular blade, it is necessary to prevent the generation of debris.

[0005] With the aim of suppressing the generation of cutting waste, Patent Document 1 discloses an invention in which a polyolefin film irradiated with electron beams or gamma (γ) rays at 1 to 80 Mrad is used as the base film of a dicing sheet. In this invention, it is believed that irradiation with electron beams or gamma rays forms covalent crosslinks in the resin that constitutes the base film, suppressing the generation of cutting waste. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 5-211234 Summary of the Invention [Problem to be solved by the invention]

[0007] In the above-mentioned pickup process, in order to facilitate the pickup of semiconductor chips, the semiconductor chips may be individually pushed up from the side of the workpiece processing sheet opposite to the side on which the semiconductor chips are stacked. In particular, to prevent collisions between semiconductor chips during pickup and to facilitate pickup, the workpiece processing sheet is usually stretched (expanded) to separate the semiconductor chips. Therefore, the workpiece processing sheet is required to have excellent flexibility to enable good expansion.

[0008] However, conventional dicing sheets such as those disclosed in Patent Document 1 do not have sufficient expandability.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pressure-sensitive adhesive sheet having good expandability. [Means for solving the problem]

[0010] In order to achieve the above object, first, the present invention provides a pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer laminated on one side of the substrate, wherein the substrate is a resin film containing no chlorine atoms, the resin constituting the resin film is at least one of a thermoplastic polyurethane elastomer obtained by reacting a long-chain polyol, a chain extender and a polyisocyanate, and a polyester-based resin, and wherein an arbitrary direction in a plan view of the substrate is taken as a reference direction, and the angle formed by the reference direction in the plan view with the reference direction is 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, 170°, 180°, 190°, 210°, 220°, 230°, 240°, 250°, 260°, 270°, 280°, 290°, 300°, 310°, 320°, 330°, 340°, 350°, 360°, 370°, 380°, 390°, 410°, 420°, 430°, 440°, 450°, 460°, 470°, 480°, 490°, 500°, 510°, 520°, 530°, 540°, 550°, 560°, 570°, 580°, 590°, 610°, 620°, 630°, 640°, 650°, 660° The adhesive sheet is characterized in that, when the first measurement direction is defined as the direction in which the increase in tensile stress, obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation, is the smallest among a total of 18 directions, namely 20°, 130°, 140°, 150°, 160°, and 170°, the tensile stresses of the substrate from 10% elongation to 100% elongation in the first measurement direction all fall within the range of 8 MPa or more and 30 MPa or less, and the tensile stresses of the substrate from 100% elongation to 200% elongation in the first measurement direction all fall within the range of 10 MPa or more and 40 MPa or less (Invention 1).

[0011] The pressure-sensitive adhesive sheet according to the above invention (Invention 1) has excellent flexibility and can perform good expansion because the substrate satisfies the above-mentioned tensile stress conditions.

[0012] In the above invention (Invention 1), the polyester resin preferably contains, as monomer units constituting the polyester resin, a dicarboxylic acid having an alicyclic structure, a diol having an alicyclic structure, and a dimer acid obtained by dimerizing an unsaturated fatty acid (Invention 2).

[0013] In the above inventions (Inventions 1 and 2), it is preferable that the increase in tensile stress of the substrate in the first measurement direction, obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation, is 1 MPa or more and 20 MPa or less (Invention 3).

[0014] In the above inventions (Inventions 1 to 3), when a second measurement direction is defined as one direction in a plan view of the substrate that forms an angle of 90° with the first measurement direction, it is preferable that the tensile stress of the substrate in the second measurement direction from 10% elongation to 100% elongation all fall within a range of 5 MPa or more and 30 MPa or less, and the tensile stress of the substrate in the second measurement direction from 100% elongation to 200% elongation all fall within a range of 10 MPa or more and 40 MPa or less (Invention 4).

[0015] In the above invention (Invention 4), it is preferable that the increase in tensile stress of the substrate in the second measurement direction, obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation, is 1 MPa or more and 20 MPa or less (Invention 5).

[0016] In the above inventions (Inventions 1 to 5), the tensile modulus of the substrate in the first measurement direction is preferably 100 MPa or more and 1000 MPa or less (Invention 6).

[0017] In the above inventions (Inventions 1 to 6), the breaking elongation of the substrate in the first measurement direction is preferably 100% or more and 1000% or less (Invention 7).

[0018] In the above inventions (Inventions 1 to 7), it is preferable that, when the results measured when a tensile test is performed on the substrate in the first measurement direction are plotted on a coordinate plane with tensile elongation (unit: %) on the horizontal axis and tensile stress (unit: MPa) on the vertical axis, a curve is obtained in which either there is no maximum point on the curve, or there is at least one maximum point and one minimum point on the curve, and the absolute value of the difference between the value of the tensile stress at the maximum point where the tensile elongation value is smallest and the value of the tensile stress at the minimum point where the tensile elongation value is smallest is 2.0 MPa or less (Invention 8).

[0019] In the above inventions (Inventions 1 to 8), it is preferable that the substrate does not contain halogen atoms (Invention 9).

[0020] In the above inventions (Inventions 1 to 9), it is preferable that the sheet is used as a workpiece processing sheet (Invention 10).

[0021] In the above invention (Invention 10), the workpiece processing sheet is preferably a dicing sheet (Invention 11). [Effects of the Invention]

[0022] The pressure-sensitive adhesive sheet according to the present invention has good expandability. [Brief explanation of the drawings]

[0023] [Figure 1] 4 is a curve illustrating the physical properties of the substrate in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, an embodiment of the present invention will be described. The adhesive sheet according to the present embodiment comprises a substrate and an adhesive layer laminated on one side of the substrate. While the adhesive sheet can be used for various purposes, similar to general adhesive sheets, it is particularly suitable for use as a workpiece processing sheet used for processing workpieces such as semiconductor wafers. In particular, the adhesive sheet according to the present embodiment is suitable for use as a sheet for picking up workpieces such as semiconductor chips.

[0025] 1. Composition of adhesive sheet (1) Base material The substrate in this embodiment does not contain chlorine atoms. By not containing chlorine atoms, the pressure-sensitive adhesive sheet according to this embodiment is more likely to reduce the environmental impact. Here, "not containing chlorine atoms" also includes substantially not containing chlorine atoms. That is, the substrate in this embodiment may be one in which a trace amount of a component containing chlorine atoms has been unintentionally mixed during the manufacturing process, for example. In this case, the content of chlorine atoms in the substrate may be 0.005% by mass or less, particularly 0.003% by mass or less, and even 0.0001% by mass or less.

[0026] In the substrate of this embodiment, when a predetermined direction in a plan view is defined as a first measurement direction, the tensile stress in the first measurement direction from 10% elongation to 100% elongation all falls within a range of 8 MPa or more and 30 MPa or less, and the tensile stress in the first measurement direction from 100% elongation to 200% elongation all falls within a range of 10 MPa or more and 40 MPa or less.

[0027] The adhesive sheet according to the present embodiment has excellent flexibility because the substrate satisfies these conditions. Therefore, when the adhesive sheet according to the present embodiment is used for processing a workpiece, it is possible to perform good expansion. As a result, in the subsequent pick-up process, it becomes easier to push up the chip from the backside, and good pick-up is possible.

[0028] Here, the above-mentioned first measurement direction simply refers to the tensile direction in which the increase in tensile stress from 100% elongation to 200% elongation is smallest when a tensile test is performed on a substrate. More specifically, with any one direction in a plan view of the substrate as a reference direction, the first measurement direction is the direction in which the increase in tensile stress, obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation, is smallest among 18 directions that form angles of 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, and 170° with respect to the reference direction in a plan view.

[0029] When the substrate is a resin film as described below, the direction perpendicular to the flow direction during production (TD direction) usually coincides with the first measurement direction.

[0030] From the viewpoint of more effectively realizing good expandability, the lower limit of the range of the tensile stress from 10% elongation to 100% elongation described above is preferably 9 MPa or more, and more preferably 10 MPa or more, and the upper limit of this range is preferably 25 MPa or less, more preferably 20 MPa or less, and even more preferably 15 MPa or less.

[0031] From the same viewpoint, the lower limit of the range of the tensile stress from 100% elongation to 200% elongation is preferably 11 MPa or more, and more preferably 12 MPa or more, and the upper limit of the range is preferably 30 MPa or less, and more preferably 20 MPa or less.

[0032] The details of the method for measuring the tensile stress are as described in the test examples below.

[0033] (1-1) Physical properties of the substrate In the substrate of this embodiment, the increase in tensile stress in the first measurement direction, obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation, is preferably 1 MPa or more, particularly preferably 1.5 MPa or more, and even more preferably 1.8 MPa or more. Furthermore, the increase is preferably 20 MPa or less, more preferably 15 MPa or less, particularly preferably 10 MPa or less, and even more preferably 5 MPa or less. Having the increase of 1 MPa or more makes it difficult for stress to concentrate on a portion of the substrate when expanding the pressure-sensitive adhesive sheet of this embodiment, making it easier to effectively suppress breakage of the substrate. On the other hand, having the increase of 20 MPa or less makes it easier for the substrate to expand uniformly when expanding the pressure-sensitive adhesive sheet of this embodiment, making it easier to effectively separate the chips from each other. Therefore, by satisfying the above-mentioned increase, the pressure-sensitive adhesive sheet of this embodiment has better expandability.

[0034] Furthermore, the substrate in this embodiment preferably has an increase in tensile stress in the first measurement direction, obtained by subtracting the tensile stress at 10% elongation from the tensile stress at 200% elongation, of 0.5 MPa or more, more preferably 1 MPa or more, particularly preferably 1.5 MPa or more, and even more preferably 2 MPa or more. Furthermore, the increase is preferably 25 MPa or less, particularly preferably 15 MPa or less, and even more preferably 5 MPa or less. Having the increase of 0.5 MPa or more makes it difficult for stress to concentrate on a portion of the substrate when expanding the pressure-sensitive adhesive sheet according to this embodiment, making it easier to effectively suppress breakage of the substrate. On the other hand, having the increase of 25 MPa or less makes it easier for the substrate to expand uniformly when expanding the pressure-sensitive adhesive sheet according to this embodiment, making it easier to effectively separate the chips from each other. Therefore, by satisfying the above-mentioned increase, the pressure-sensitive adhesive sheet according to this embodiment has better expandability.

[0035] Furthermore, the base material in this embodiment preferably has a ratio of the tensile stress at 200% elongation to the tensile stress at 100% elongation in the first measurement direction of 0.5 or more, particularly preferably 0.75 or more, and even more preferably 1 or more. Furthermore, this ratio is preferably 3 or less, more preferably 2.5 or less, particularly preferably 2 or less, and even more preferably 1.5 or less. Having this ratio of 0.5 or more makes it difficult for stress to concentrate on a portion of the base material when expanding the pressure-sensitive adhesive sheet according to this embodiment, making it easier to effectively suppress breakage of the base material. On the other hand, having this ratio of 3 or less makes it easier for the base material to expand uniformly when expanding the pressure-sensitive adhesive sheet according to this embodiment, making it easier to effectively separate the chips from each other. Therefore, by satisfying the above ratio, the pressure-sensitive adhesive sheet according to this embodiment has better expandability.

[0036] Furthermore, the substrate in this embodiment preferably has a tensile modulus in the first measurement direction of 100 MPa or more, particularly preferably 200 MPa or more, and even more preferably 300 MPa or more. The tensile modulus is preferably 1000 MPa or less, particularly preferably 800 MPa or less, and even more preferably 600 MPa or less. Having a tensile modulus of 100 MPa or more makes the substrate in this embodiment more likely to have adequate strength, resulting in good handleability of the adhesive sheet and facilitating successful desired workpiece processing. Additionally, when expanding the adhesive sheet according to this embodiment, stress is less likely to concentrate on a portion of the substrate, making it easier to effectively suppress breakage of the substrate. Furthermore, having a tensile modulus of 1000 MPa or less makes it easier to uniformly stretch the substrate when expanding the adhesive sheet according to this embodiment, making it easier to effectively separate chips from each other. Therefore, by ensuring that the tensile modulus in the first measurement direction of the substrate is within the above-mentioned upper and lower limit values, the adhesive sheet according to this embodiment has better expandability. The details of the method for measuring the tensile modulus are as described in the test examples below.

[0037] Furthermore, the substrate in this embodiment preferably has a breaking elongation in the first measurement direction of 100% or more, particularly preferably 200% or more, and even more preferably 300% or more. Furthermore, the breaking elongation is preferably 1000% or less, particularly preferably 800% or less, and even more preferably 600% or less. When the breaking elongation is 100% or more, the substrate in this embodiment is more likely to have the desired extensibility, and the pressure-sensitive adhesive sheet according to this embodiment is more likely to achieve excellent expandability and pick-up properties. When the breaking elongation is 1000% or less, the processability of the substrate is more excellent, and the desired pressure-sensitive adhesive sheet can be easily produced. Details of the method for measuring the breaking elongation are as described in the test examples below.

[0038] Furthermore, it is preferable that the substrate in this embodiment satisfies either of the following two conditions for the curve obtained by plotting the results measured when a tensile test is performed on the previous substrate in the first measurement direction on a coordinate plane with tensile elongation (unit: %) on the horizontal axis and tensile stress (unit: MPa) on the vertical axis. (Condition 1) There is no maximum point (hereinafter sometimes referred to as "maximum point") in the curve. (Condition 2) There is at least one maximum point and one minimum point (hereinafter sometimes referred to as "minimum point") in the curve, and the absolute value of the difference between the tensile stress value at the maximum point where the tensile elongation value is smallest and the tensile stress value at the minimum point where the tensile elongation value is smallest is 2.0 MPa or less.

[0039] The above-mentioned conditions 1 and 2 will be explained in more detail using FIG. 1. FIG. 1 shows the state where curves C1 and C2 exist on a coordinate plane with tensile elongation (unit: %) on the horizontal axis and tensile stress (unit: MPa) on the vertical axis. First, curve C1 is an example where the above-mentioned condition 1 is satisfied. In curve C1, as the tensile elongation is increased from 0%, the tensile stress also increases accordingly (however, the increase becomes more difficult as the tensile stress approaches a predetermined value). Therefore, curve C1 does not have a point where the tensile stress changes from increasing to decreasing, i.e., a maximum point.

[0040] On the other hand, curve C2 is an example where condition 2 is satisfied. In curve C2, when the tensile elongation is increased from 0%, the tensile stress first increases up to point A. Then, at point A, the tensile stress starts to decrease. In other words, curve C2 has a maximum point at point A. When the tensile elongation is further increased after passing point A, the tensile stress starts to increase from a decrease at point B, and then continues to increase. In other words, curve C2 has a minimum point at point B. Here, curve C2 satisfies condition 2 when the absolute value of the difference in tensile stress between point A and point B (the value indicated by "Δ" in Figure 1) is 2.0 MPa or less.

[0041] Although curve C2 in Figure 1 has one maximum point and one minimum point, condition 2 may be satisfied even when there are multiple maximum points or multiple minimum points. In this case, the maximum point and the minimum point with the smallest tensile elongation value are selected from the multiple maximum points and multiple minimum points, and whether condition 2 is satisfied is determined based on whether the absolute value of the difference between these points is 2.0 MPa or less.

[0042] The substrate in this embodiment satisfies at least one of the above-mentioned conditions 1 and 2, which makes it easier for the pressure-sensitive adhesive sheet according to this embodiment to have excellent expandability. From this perspective, the absolute value difference (Δ) under condition 2 is preferably 1.8 MPa or less, more preferably 1.6 MPa or less, particularly preferably 1.5 MPa or less, even more preferably 1.3 MPa or less, and most preferably 1.0 MPa or less. Meanwhile, the lower limit of the above-mentioned absolute value difference (Δ) is not particularly limited and may be, for example, greater than 0. Details of the method for determining whether the above-mentioned conditions 1 and 2 are satisfied are as described in the test examples below.

[0043] In the substrate of this embodiment, when the second measurement direction is one direction in a plan view of the substrate that is at an angle of 90° with the first measurement direction, it is preferable that the tensile stresses from 10% elongation to 100% elongation in the second measurement direction all fall within a range of 5 MPa to 30 MPa, and the tensile stresses from 100% elongation to 200% elongation in the second measurement direction all fall within a range of 10 MPa to 40 MPa. By satisfying these conditions, the substrate is more likely to have excellent flexibility and to obtain better expandability.

[0044] From the viewpoint of more effectively realizing good expandability, the lower limit of the range of the tensile stress from 10% elongation to 100% elongation in the second measurement direction is particularly preferably 7.5 MPa or more, more preferably 10 MPa or more, and the upper limit of this range is particularly preferably 25 MPa or less, more preferably 20 MPa or less.

[0045] From the same viewpoint, the lower limit of the range of the tensile stress in the second measurement direction from 100% elongation to 200% elongation is preferably 11 MPa or more, more preferably 12 MPa or more, and the upper limit of the range is preferably 35 MPa or less, more preferably 30 MPa or less.

[0046] Details of the method for measuring the tensile stress in the second measurement direction are as described in the test examples below.

[0047] Furthermore, the substrate in this embodiment preferably has an increase in tensile stress in the second measurement direction, obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation, of 1 MPa or more, particularly preferably 2 MPa or more, and even more preferably 3 MPa or more. Furthermore, the increase is preferably 20 MPa or less, particularly preferably 15 MPa or less, and even more preferably 10 MPa or less. Having the increase of 1 MPa or more makes it difficult for stress to concentrate on a portion of the substrate when expanding the pressure-sensitive adhesive sheet according to this embodiment, making it easier to effectively suppress breakage of the substrate. On the other hand, having the increase of 20 MPa or less makes it easier for the substrate to expand uniformly when expanding the pressure-sensitive adhesive sheet according to this embodiment, making it easier to effectively separate the chips from each other. Therefore, by satisfying the above-mentioned increase, the pressure-sensitive adhesive sheet according to this embodiment has better expandability.

[0048] Furthermore, in the substrate of this embodiment, the increase in tensile stress in the second measurement direction, obtained by subtracting the tensile stress at 10% elongation from the tensile stress at 200% elongation, is preferably 1 MPa or more, more preferably 2 MPa or more, particularly preferably 3 MPa or more, and even more preferably 4 MPa or more. Furthermore, the increase is preferably 30 MPa or less, particularly preferably 25 MPa or less, and even more preferably 20 MPa or less. Having the increase of 1 MPa or more makes it difficult for stress to concentrate on a portion of the substrate when expanding the pressure-sensitive adhesive sheet of this embodiment, making it easier to effectively suppress breakage of the substrate. On the other hand, having the increase of 30 MPa or less makes it easier for the substrate to expand uniformly when expanding the pressure-sensitive adhesive sheet of this embodiment, making it easier to effectively separate the chips from each other. Therefore, by satisfying the above-mentioned increase, the pressure-sensitive adhesive sheet of this embodiment has better expandability.

[0049] Furthermore, in the substrate of this embodiment, the increase in tensile stress in the second measurement direction, obtained by subtracting the tensile stress at 50% elongation from the tensile stress at 150% elongation, is preferably 0.5 MPa or more, more preferably 1 MPa or more, particularly preferably 1.5 MPa or more, and even more preferably 2 MPa or more. Furthermore, the increase is preferably 20 MPa or less, particularly preferably 15 MPa or less, and even more preferably 10 MPa or less. When the increase is 0.5 MPa or more, stress is less likely to concentrate on a portion of the substrate when the pressure-sensitive adhesive sheet of this embodiment is expanded, making it easier to effectively suppress breakage of the substrate. On the other hand, when the increase is 20 MPa or less, the substrate is more likely to expand uniformly when the pressure-sensitive adhesive sheet of this embodiment is expanded, making it easier to effectively separate the chips from each other. Therefore, by satisfying the above-mentioned increase, the pressure-sensitive adhesive sheet of this embodiment has better expandability.

[0050] Furthermore, the substrate in this embodiment preferably has an increase in tensile stress in the second measurement direction, obtained by subtracting the tensile stress at 50% elongation from the tensile stress at 250% elongation, of 2 MPa or more, particularly preferably 4 MPa or more, even more preferably 5 MPa or more, and even more preferably 6 MPa or more. Furthermore, the increase is preferably 30 MPa or less, particularly preferably 25 MPa or less, and even more preferably 20 MPa or less. Having the increase of 2 MPa or more makes it difficult for stress to concentrate on a portion of the substrate when expanding the pressure-sensitive adhesive sheet according to this embodiment, making it easier to effectively suppress breakage of the substrate. On the other hand, having the increase of 30 MPa or less makes it easier for the substrate to expand uniformly when expanding the pressure-sensitive adhesive sheet according to this embodiment, making it easier to effectively separate the chips from each other. Therefore, by satisfying the above-mentioned increase, the pressure-sensitive adhesive sheet according to this embodiment has better expandability.

[0051] Furthermore, the substrate in this embodiment preferably has a tensile modulus in the second measurement direction of 100 MPa or more, particularly preferably 200 MPa or more, and even more preferably 300 MPa or more. The tensile modulus is preferably 1000 MPa or less, particularly preferably 800 MPa or less, and even more preferably 600 MPa or less. Having a tensile modulus of 100 MPa or more makes the substrate in this embodiment more likely to have appropriate strength, resulting in good handleability of the pressure-sensitive adhesive sheet and facilitating successful desired workpiece processing. Additionally, when expanding the pressure-sensitive adhesive sheet according to this embodiment, stress is less likely to concentrate on a portion of the substrate, making it easier to effectively prevent breakage of the substrate. Furthermore, having a tensile modulus of 1000 MPa or less makes it easier to uniformly stretch the substrate when expanding the pressure-sensitive adhesive sheet according to this embodiment, making it easier to effectively separate chips from each other. Therefore, by ensuring that the tensile modulus in the second measurement direction of the substrate is within the above-mentioned upper and lower limits, the pressure-sensitive adhesive sheet according to this embodiment has better expandability. The details of the method for measuring the tensile modulus are as described in the test examples below.

[0052] (1-2) Composition of the base material The composition of the base material in this embodiment is not limited as long as it is substantially free of chlorine atoms and satisfies the above-described physical properties regarding the tensile stress from 10% elongation to 100% elongation and the tensile stress from 100% elongation to 200% elongation.

[0053] From the viewpoint of easily achieving the desired function when using the adhesive sheet of this embodiment as a work processing sheet, it is preferable that the substrate in this embodiment is a resin film whose main material is a resin-based material.

[0054] Examples of the resin include polyolefins such as polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, ethylene-norbornene copolymers, and norbornene resins; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; ethylene-vinyl acetate copolymers; ethylene copolymers such as ethylene-(meth)acrylic acid copolymers, ethylene-methyl(meth)acrylate copolymers, and other ethylene-(meth)acrylic acid ester copolymers; (meth)acrylic acid ester copolymers; polyurethanes; polyimides; polystyrene; polycarbonates; and fluororesins. Modified resins such as crosslinked resins and ionomer resins of these resins may also be used. Note that, in this specification, "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, in this specification, "polymer" also includes the concept of "copolymer."

[0055] The substrate in this embodiment may be a laminated film formed by laminating a plurality of films of the above-mentioned resin. In this laminated film, the materials constituting the respective layers may be the same or different.

[0056] Among the above-mentioned resins, it is preferable to use at least one of fluororesin, polyurethane, and polyester-based resin. In particular, in films using these, the main resin (fluororesin, polyurethane, or polyester-based resin) is preferably contained in an amount of 50% by mass or more, more preferably 60% by mass or more, particularly preferably 70% by mass or more, and even more preferably 80% by mass or more. By using these films, the physical properties related to the tensile stress described above can be easily satisfied.

[0057] Examples of fluororesins include polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene (ETFE), tetrafluoroethylene-hexafluoroethylene (FEP), perfluoroalkoxyalkane (PFA), polyvinylidene fluoride (PVdF), etc. Among these, polytetrafluoroethylene (PTFE) is particularly preferred.

[0058] Examples of the polyurethane include polyurethane elastomers, and among these, thermoplastic polyurethane elastomers (TPU) are preferred.

[0059] Thermoplastic polyurethane elastomers are generally obtained by reacting a long-chain polyol, a chain extender, and a polyisocyanate, and consist of soft segments having structural units derived from the long-chain polyol and hard segments having a polyurethane structure obtained from the reaction of the chain extender and the polyisocyanate.

[0060] Thermoplastic polyurethane elastomers can be classified according to the type of long-chain polyol used as the soft segment component into polyester-based polyurethane elastomers, polyether-based polyurethane elastomers, polycarbonate-based polyurethane elastomers, etc. Of these, polyether-based polyurethane elastomers are preferably used for the substrate in this embodiment.

[0061] Specific examples of the long-chain polyol include polyester polyols such as lactone-based polyester polyols and adipate-based polyester polyols, polyether polyols such as polypropylene (ethylene) polyols and polytetramethylene ether glycol, polycarbonate polyols, etc. Among these, polyether polyols are preferably used, and their number average molecular weight is usually 600 to 5,000.

[0062] Examples of the polyisocyanate include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate (pure MDI), hexamethylene diisocyanate, etc. Of these, pure MDI is preferably used.

[0063] Examples of the chain extender include low molecular weight polyhydric alcohols such as 1,4-butanediol and 1,6-hexanediol, and aromatic diamines.

[0064] Examples of the polyester resin include those mentioned above as well as polyester resins having an alicyclic structure.

[0065] Furthermore, from the viewpoint of easily suppressing the generation of cutting waste when the pressure-sensitive adhesive sheet according to this embodiment is used as a dicing sheet, it is preferable that the alicyclic structure of the polyester resin has 6 or more carbon atoms constituting the ring. Furthermore, the number of carbon atoms is preferably 14 or less, and particularly preferably 10 or less. In particular, the number of carbon atoms is preferably 6. Furthermore, the alicyclic structure may be a monocyclic structure consisting of one ring, a bicyclic structure consisting of two rings, or a structure consisting of three or more rings.

[0066] In addition, from the viewpoint of making the base material in this embodiment more likely to have good flexibility, the polyester resin preferably contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting the polyester resin. From the same viewpoint, the polyester resin preferably contains a diol having an alicyclic structure as a monomer unit constituting the polyester resin. While only one of the dicarboxylic acid and the diol may be contained in the polyester resin, from the viewpoint of making the base material in this embodiment more likely to have good flexibility, it is preferable that the polyester resin contain both the dicarboxylic acid and the diol.

[0067] The structure of the dicarboxylic acid described above is not particularly limited as long as it has an alicyclic structure and two carboxy groups. For example, the dicarboxylic acid may have a structure in which two carboxy groups are bonded to an alicyclic structure, or a structure in which an alkyl group or the like is further inserted between the alicyclic structure and the carboxy group. Preferred examples of such dicarboxylic acids include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,4-decahydronaphthalenedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid, and 2,7-decahydronaphthalenedicarboxylic acid. Among these, 1,4-cyclohexanedicarboxylic acid is preferred. These dicarboxylic acids may also be derivatives such as alkyl esters. Examples of such alkyl ester derivatives include alkyl esters having 1 to 10 carbon atoms. More specific examples include dimethyl esters and diethyl esters, with dimethyl esters being particularly preferred.

[0068] The structure of the diol is not particularly limited as long as it has an alicyclic structure and two hydroxy groups. For example, the diol may have a structure in which two hydroxy groups are bonded to an alicyclic structure, or a structure in which an alkyl group is further inserted between the alicyclic structure and the hydroxy group. Preferred examples of such diols include 1,2-cyclohexanediol (particularly 1,2-cyclohexanedimethanol), 1,3-cyclohexanediol (particularly 1,3-cyclohexanedimethanol), 1,4-cyclohexanediol (particularly 1,4-cyclohexanedimethanol), and 2,2-bis-(4-hydroxycyclohexyl)-propane. Among these, 1,4-cyclohexanedimethanol is preferably used.

[0069] The polyester resin preferably contains, as a monomer unit constituting the polyester resin, a dimer acid obtained by dimerizing an unsaturated fatty acid, from the viewpoint of making it easier for the substrate to have the desired flexibility and to achieve better expandability. The unsaturated fatty acid preferably has 10 or more carbon atoms, particularly 15 or more. The carbon number is preferably 30 or less, particularly 25 or less. Examples of such dimer acids include 36-carbon dicarboxylic acids obtained by dimerizing 18-carbon unsaturated fatty acids such as oleic acid and linoleic acid, and 44-carbon dicarboxylic acids obtained by dimerizing 22-carbon unsaturated fatty acids such as erucic acid. When obtaining the dimer acid, a small amount of trimer acid obtained by trimerizing the unsaturated fatty acid may also be produced. The polyester resin may contain such trimer acid in addition to the dimer acid.

[0070] The polyester resin may contain, as its constituent monomer units, a monomer other than the dicarboxylic acid, diol, and dimer acid described above. Examples of such monomers include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid; and aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and 4,4'-diphenyldicarboxylic acid. The polyester resin may also contain a diol component other than a diol having an alicyclic structure. For example, the polyester resin may contain ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, decanediol; ethylene oxide adducts of bisphenol A, bisphenol S, and the like; trimethylolpropane, and the like.

[0071] Furthermore, the heat of fusion of the polyester resin measured by differential scanning calorimetry at a heating rate of 20°C / min is preferably 2 J / g or more, more preferably 5 J / g or more, particularly preferably 10 J / g or more, and even more preferably 15 J / g or more. When the heat of fusion is 2 J / g or more, the crystallinity of the substrate in this embodiment is appropriately improved, and the substrate has better handleability and processability. Furthermore, the heat of fusion is preferably 150 J / g or less, more preferably 100 J / g or less, particularly preferably 70 J / g or less, even more preferably 50 J / g or less, and especially preferably 30 J / g or less. When the heat of fusion is 150 J / g or less, the substrate according to this embodiment is more likely to have excellent flexibility.

[0072] The heat of fusion can be measured using a differential scanning calorimeter (for example, DSC, manufactured by TA Instruments, product name "DSC Q2000") in accordance with JIS K 7121:2012.

[0073] The above-mentioned film containing a polyester resin as a main material preferably contains an elastomer together with the polyester resin, from the viewpoint of easily achieving the desired tensile properties. The elastomer is not particularly limited and may be a thermosetting elastomer or a thermoplastic elastomer, but is preferably a thermoplastic elastomer from the viewpoint of easily providing the substrate in this embodiment with superior flexibility.

[0074] Examples of the thermoplastic elastomer are not particularly limited, and examples thereof include styrene-based elastomers, olefin-based elastomers, polyester-based elastomers, and silicone-based elastomers. These may be used alone or in combination of two or more. Among the above-mentioned elastomers, it is preferable to use styrene-based elastomers because they tend to have superior flexibility.

[0075] Examples of the styrene-based elastomer include styrene-conjugated diene copolymers and styrene-olefin copolymers. Specific examples of styrene-conjugated diene copolymers include unhydrogenated styrene-conjugated diene copolymers such as styrene-butadiene copolymer, styrene-butadiene-styrene copolymer (SBS), styrene-butadiene-butylene-styrene copolymer, styrene-isoprene copolymer, styrene-isoprene-styrene copolymer (SIS), and styrene-ethylene-isoprene-styrene copolymer; and hydrogenated styrene-conjugated diene copolymers such as styrene-ethylene / propylene-styrene copolymer (SEPS) and styrene-ethylene / butylene-styrene copolymer (SEBS). These may be used alone or in combination. Among the above-mentioned styrene-based elastomers, styrene-conjugated diene copolymers are preferred from the viewpoint of achieving better flexibility, with hydrogenated styrene-conjugated diene copolymers being particularly preferred, and styrene-ethylene / butylene-styrene copolymers being even more preferred.

[0076] In order to further reduce the environmental impact, the substrate in this embodiment preferably does not contain halogen atoms. Examples of the halogen atoms include fluorine atoms, bromine atoms, and iodine atoms, in addition to the chlorine atoms described above. Note that "does not contain halogen atoms" here may mean that the substrate does not substantially contain halogen atoms, as in the case of chlorine atoms described above. In this case, the content of halogen atoms in the substrate may be 0.005% by mass or less, particularly 0.003% by mass or less, and even 0.0001% by mass or less.

[0077] The substrate in this embodiment may contain additives such as a flame retardant, a plasticizer, a lubricant, an antioxidant, a colorant, an infrared absorber, an ultraviolet absorber, an ion scavenger, etc. The content of these additives is not particularly limited, but is preferably set within a range in which the substrate exhibits the desired function.

[0078] The layer structure of the substrate in this embodiment may be a single layer or multiple layers. Furthermore, the surface of the substrate on which the pressure-sensitive adhesive layer is to be laminated may be subjected to a surface treatment such as a primer treatment, a corona treatment, or a plasma treatment in order to improve adhesion to the pressure-sensitive adhesive layer.

[0079] (1-3) Manufacturing method of substrate The method for producing the substrate in this embodiment is not particularly limited, and for example, melt extrusion methods such as a T-die method or a round die method, a calender method, a solution method such as a dry method or a wet method, etc. Among these, it is preferable to adopt the melt extrusion method or the calender method from the viewpoint of efficiently producing the substrate.

[0080] When a substrate consisting of a single layer is produced by melt extrusion, the materials of the substrate are kneaded, and the resulting kneaded mixture is directly or once produced into pellets, and then film-formed using a known extruder. When a substrate consisting of multiple layers is produced by melt extrusion, the components constituting each layer are kneaded, and the resulting kneaded mixture is directly or once produced into pellets, and then film-formed by simultaneously extruding the multiple layers using a known extruder.

[0081] (1-4) Thickness of the substrate In this embodiment, the thickness of the substrate is preferably 20 μm or more, particularly preferably 40 μm or more, and even more preferably 60 μm or more. Furthermore, the thickness of the substrate is preferably 600 μm or less, particularly preferably 300 μm or less, and even more preferably 200 μm or less. A substrate thickness of 20 μm or more facilitates the adhesive sheet to have appropriate strength and facilitates favorable support of the workpiece fixed on the adhesive sheet. As a result, it becomes possible to effectively suppress the occurrence of chipping during dicing. Furthermore, a substrate thickness of 600 μm or less facilitates the satisfaction of the above-described physical properties regarding the tensile stress from elongation to 100% elongation and the tensile stress from 100% elongation to 200% elongation. Furthermore, a substrate film thickness of 600 μm or less provides better processability for the substrate film.

[0082] (2) Adhesive layer The adhesive constituting the adhesive layer in this embodiment is not particularly limited as long as it can exert sufficient adhesive strength to the adherend (particularly, adhesive strength to the workpiece sufficient for processing the workpiece). Examples of adhesives constituting the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, polyvinyl ether adhesives, etc. Among these, it is preferable to use acrylic adhesives because they can easily exert the desired adhesive strength.

[0083] The adhesive constituting the adhesive layer in this embodiment may be an adhesive that does not have active energy ray curability, but is preferably an adhesive that has active energy ray curability (hereinafter, may be referred to as an "active energy ray curable adhesive"). When the adhesive layer is composed of an active energy ray curable adhesive, the adhesive layer can be cured by irradiation with active energy rays, and the adhesive strength of the adhesive sheet to the adherend can be easily reduced. In particular, when the adhesive sheet according to this embodiment is used as a workpiece processing sheet, irradiation with active energy rays makes it possible to easily separate the processed workpiece from the adhesive sheet after processing.

[0084] The active energy ray-curable adhesive constituting the adhesive layer may be one whose main component is a polymer having active energy ray curability, or one whose main component is a mixture of a non-active energy ray-curable polymer (a polymer not having active energy ray curability) and a monomer and / or oligomer having at least one active energy ray-curable group.

[0085] The active energy ray-curable polymer is preferably a (meth)acrylic acid ester polymer (hereinafter sometimes referred to as "active energy ray-curable polymer") having an active energy ray-curable functional group (active energy ray-curable group) introduced into its side chain. This active energy ray-curable polymer is preferably one obtained by reacting an acrylic copolymer having a functional group-containing monomer unit with an unsaturated group-containing compound having a functional group bonded to the functional group. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, the term "polymer" also includes the concept of "copolymer."

[0086] The weight-average molecular weight of the active energy radiation-curable polymer is preferably 10,000 or more, particularly preferably 150,000 or more, and even more preferably 200,000 or more. The weight-average molecular weight is preferably 2,500,000 or less, particularly preferably 2,000,000 or less, and even more preferably 1,500,000 or less. The weight-average molecular weight (Mw) in this specification is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0087] On the other hand, when the active energy ray-curable adhesive is mainly composed of a mixture of an active energy ray non-curable polymer component and a monomer and / or oligomer having at least one active energy ray-curable group, the active energy ray non-curable polymer component can be, for example, the above-mentioned acrylic copolymer before being reacted with an unsaturated group-containing compound.Furthermore, the active energy ray-curable monomer and / or oligomer can be, for example, an ester of a polyhydric alcohol and (meth)acrylic acid.

[0088] The weight-average molecular weight of the acrylic polymer as the non-active energy ray-curable polymer component is preferably 10,000 or more, particularly preferably 150,000 or more, and even more preferably 200,000 or more, and is preferably 2,500,000 or less, particularly preferably 2,000,000 or less, and even more preferably 1,500,000 or less.

[0089] When ultraviolet rays are used as the active energy rays for curing the active energy ray-curable adhesive, it is preferable to add a photopolymerization initiator to the adhesive. In addition, the adhesive may also contain an active energy ray-non-curable polymer component or oligomer component, a crosslinking agent, etc.

[0090] The thickness of the pressure-sensitive adhesive layer in this embodiment is preferably 1 μm or more, particularly preferably 2 μm or more, and even more preferably 3 μm or more. The thickness of the pressure-sensitive adhesive layer is also preferably 50 μm or less, particularly preferably 40 μm or less, and even more preferably 30 μm or less. Having a thickness of 1 μm or more makes it easier for the pressure-sensitive adhesive sheet according to this embodiment to exhibit the desired adhesive properties. Having a thickness of 50 μm or less makes it easier for the pressure-sensitive adhesive layer to be separated from the adherend after curing.

[0091] (3) Release sheet In the pressure-sensitive adhesive sheet according to this embodiment, a release sheet may be laminated on the surface of the pressure-sensitive adhesive layer opposite the substrate (hereinafter sometimes referred to as the "adhesive surface") in order to protect that surface until it is attached to the adherend.

[0092] The release sheet may have any configuration, and may be, for example, a plastic film that has been subjected to a release treatment using a release agent or the like. Specific examples of the plastic film include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; and polyolefin films such as polypropylene and polyethylene. Silicone-based, fluorine-based, and long-chain alkyl-based release agents can be used, and among these, silicone-based release agents are preferred because they are inexpensive and provide stable performance.

[0093] There are no particular limitations on the thickness of the release sheet, and it may be, for example, 20 μm or more and 250 μm or less.

[0094] (4) Other In the pressure-sensitive adhesive sheet according to this embodiment, an adhesive layer may be laminated on the surface of the adhesive layer opposite the substrate. In this case, the pressure-sensitive adhesive sheet according to this embodiment can be used as a dicing / die-bonding sheet. In this sheet, a workpiece is attached to the surface of the adhesive layer opposite the adhesive layer, and the adhesive layer is diced together with the workpiece to obtain a chip on which the individualized adhesive layer is laminated. The individualized adhesive layer allows the chip to be easily fixed to the object on which the chip is to be mounted. As a material for constituting the adhesive layer, it is preferable to use a material containing a thermoplastic resin and a low-molecular-weight thermosetting adhesive component, or a material containing a B-stage (semi-cured) thermosetting adhesive component.

[0095] Furthermore, in the pressure-sensitive adhesive sheet according to this embodiment, a protective film-forming layer may be laminated on the adhesive surface of the adhesive layer. In this case, the pressure-sensitive adhesive sheet according to this embodiment can be used as a sheet for both protective film formation and dicing. In such a sheet, a workpiece is attached to the surface of the protective film-forming layer opposite the adhesive layer, and the protective film-forming layer is diced together with the workpiece to obtain a chip on which a singulated protective film-forming layer is laminated. It is preferable that the workpiece has a circuit formed on one side. In this case, the protective film-forming layer is typically laminated on the surface opposite the surface on which the circuit is formed. The singulated protective film-forming layer can be cured at a predetermined timing to form a protective film with sufficient durability on the chip. The protective film-forming layer is preferably made of an uncured curable adhesive.

[0096] 2. Manufacturing method of adhesive sheet The method for producing the pressure-sensitive adhesive sheet according to the present embodiment is not particularly limited. For example, it is preferable to obtain the pressure-sensitive adhesive sheet by forming a pressure-sensitive adhesive layer on a release sheet and then laminating one side of a substrate on the surface of the pressure-sensitive adhesive layer opposite the release sheet.

[0097] The pressure-sensitive adhesive layer can be formed by a known method. For example, a coating liquid containing a pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer and, if desired, a solvent or dispersion medium is prepared. The coating liquid is then applied to the release surface of a release sheet (hereinafter sometimes referred to as the "release surface"). The resulting coating film is then dried to form the pressure-sensitive adhesive layer.

[0098] The coating of the coating liquid described above can be carried out by a known method, such as bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, etc. The properties of the coating liquid are not particularly limited as long as it can be applied, and the coating liquid may contain components for forming the pressure-sensitive adhesive layer as a solute or as a dispersoid. The release sheet may be peeled off as a processing material, or may protect the pressure-sensitive adhesive layer until it is attached to the adherend.

[0099] When the adhesive composition for forming the adhesive layer contains the above-mentioned crosslinking agent, it is preferable to change the above-mentioned drying conditions (temperature, time, etc.) or to separately perform a heat treatment to promote the crosslinking reaction between the polymer component in the coating film and the crosslinking agent, thereby forming a crosslinked structure with a desired density in the adhesive layer. Furthermore, in order to promote the above-mentioned crosslinking reaction sufficiently, after laminating the adhesive layer and the substrate, curing may be performed, for example, by leaving them to stand in an environment of 23°C and a relative humidity of 50% for several days.

[0100] 3. How to use the adhesive sheet The adhesive sheet according to this embodiment can be used for various purposes, similar to general adhesive sheets, but is particularly suitable for use as a workpiece processing sheet used for processing workpieces such as semiconductor wafers. In this case, the adhesive surface of the adhesive sheet according to this embodiment is attached to the workpiece, and then the workpiece can be processed on the adhesive sheet. Depending on the processing, the adhesive sheet according to this embodiment can be used as a workpiece processing sheet such as a backgrinding sheet, dicing sheet, expanding sheet, or pickup sheet. Examples of workpieces include semiconductor components such as semiconductor wafers and semiconductor packages, and glass components such as glass plates.

[0101] As described above, the pressure-sensitive adhesive sheet according to this embodiment can perform good expansion, and therefore, among the above-mentioned workpiece processing sheets, the pressure-sensitive adhesive sheet according to this embodiment is particularly suitable for use as a sheet to be expanded (such as a dicing sheet, an expanding sheet, or a pickup sheet).

[0102] When the pressure-sensitive adhesive sheet according to this embodiment includes the adhesive layer described above, the pressure-sensitive adhesive sheet can be used as a dicing / die bonding sheet. Furthermore, when the pressure-sensitive adhesive sheet according to this embodiment includes the protective film-forming layer described above, the pressure-sensitive adhesive sheet can be used as a sheet for both protective film formation and dicing.

[0103] Furthermore, when the adhesive layer in the adhesive sheet according to this embodiment is composed of the above-mentioned active energy ray-curable adhesive, it is also preferable to irradiate the adhesive layer with active energy rays as follows during use. That is, when processing of a workpiece on the adhesive sheet is completed and the processed workpiece is to be separated from the adhesive sheet, it is preferable to irradiate the adhesive layer with active energy rays before the separation. This hardens the adhesive layer, effectively reducing the adhesive strength of the adhesive sheet to the processed workpiece, and facilitating separation of the processed workpiece.

[0104] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention. [Example]

[0105] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0106] Example 1 (1) Preparation of adhesive composition A silicone-based adhesive composition was obtained by mixing 160 parts of product name "DOWSIL SD 4580", 40 parts of product name "DOWSIL 7646", and 1.5 parts of product name "DOWSIL SRX 212" (all products manufactured by Dow Toray Industries, Inc.), each of which is a silicone-based resin.

[0107] (2) Formation of adhesive layer The silicone-based adhesive composition obtained above was applied to the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET 50E-0010YC"), one side of which had been treated with a fluorine-based release agent to form a 50 μm-thick polyethylene terephthalate film, and the resulting coating was dried for 1 minute at 100° C. This produced a laminate in which a 10 μm-thick adhesive layer was formed on the release surface of the release sheet.

[0108] (3) Preparation of adhesive sheet An adhesive sheet was obtained by bonding one side of a polytetrafluoroethylene (PTFE) sheet (manufactured by Nichias Corporation, product name "Naflon PTFE Tape TOMBO 9001", thickness: 100 μm) as a substrate to the adhesive layer side of the laminate obtained in the above step (2).

[0109] Example 2 (1) Preparation of adhesive composition 95 parts by mass of n-butyl acrylate and 5 parts by mass of acrylic acid were polymerized by solution polymerization to obtain a (meth)acrylic acid ester polymer. The weight average molecular weight (Mw) of this acrylic polymer was measured by the method described below and was found to be 500,000.

[0110] 100 parts by mass (solid content equivalent, same below) of the (meth)acrylic acid ester polymer obtained as described above, 120 parts by mass of a urethane acrylate oligomer (Mw: 8,000), 5 parts by mass of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L"), and 4 parts by mass of a photopolymerization initiator (manufactured by IGM Resins BV, product name "Omnirad 184") were mixed to obtain an active energy ray-curable adhesive composition.

[0111] (2) Formation of adhesive layer The adhesive composition obtained in the above step (1) was applied to the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031"), one side of which was a 38 μm-thick polyethylene terephthalate film treated with a silicone-based release agent, and the resulting coating was dried for 1 minute at 100° C. This resulted in a laminate in which a 10 μm-thick adhesive layer was formed on the release surface of the release sheet.

[0112] (3) Preparation of adhesive sheet An adhesive sheet was obtained by bonding one side of a thermoplastic polyurethane elastomer (TPU) sheet (manufactured by BASF, product name "Elastollan 1164D", thickness: 80 μm) as a substrate to the adhesive layer side of the laminate obtained in the above step (2).

[0113] Here, the weight average molecular weight (Mw) is a weight average molecular weight measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement) and converted into standard polystyrene. <Measurement conditions> Measuring device: Tosoh Corporation, HLC-8320 GPC columns (passed in the following order): Tosoh Corporation TSK gel superH-H TSK gel super HM-H TSK gel superH2000 Measurement solvent: tetrahydrofuran ·Measurement temperature: 40℃

[0114] Example 3 A reactor equipped with a stirrer, distillation tube, and pressure regulator was charged with 12.90 kg of dimethyl 1,4-cyclohexanedicarboxylate (trans isomer ratio 98%), 11.47 kg of 1,4-cyclohexanedimethanol, 0.3 kg of ethylene glycol, and 0.11 kg of an ethylene glycol solution containing 10% manganese acetate tetrahydrate. The mixture was heated to 200°C under a nitrogen flow and then increased to 230°C over 1 hour. After maintaining the temperature for 2 hours to allow for transesterification, 10.30 kg of erucic acid-derived dimer acid (44 carbon atoms, Croda, product name "PRIPOL 1004") and 0.11 kg of an ethylene glycol solution containing 10% trimethyl phosphate were added to the system, and the esterification reaction was continued at 230°C for 1 hour. Next, 300 ppm of germanium dioxide was added as a polycondensation catalyst and stirred, after which the pressure was reduced to 133 Pa or less over 1 hour, during which time the internal temperature was raised from 230°C to 270°C, and the polycondensation reaction was carried out by stirring until a predetermined viscosity was reached under a high vacuum of 133 Pa or less. The resulting polymer was extruded into water in the form of a strand, cut, and pelletized.

[0115] The polyester resin (PEs) pellets thus obtained were dried at 85°C for 4 hours or more and then placed in the hopper of a single-screw extruder equipped with a T-die. The resin was then extruded from the T-die in a melt-kneaded state under conditions of a cylinder temperature of 220°C and a die temperature of 220°C, and cooled with a cooling roll to obtain a sheet-like substrate with a thickness of 80 μm. A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 2, except that this substrate was used.

[0116] The polyester resin contained approximately 50 mol% of 1,4-cyclohexanedimethanol, approximately 40.5 mol% of dimethyl 1,4-cyclohexanedicarboxylate, and 9.5 mol% of a dimer acid derived from erucic acid as its constituent monomers, and the proportion of the dimer acid to the total dicarboxylic acid units constituting the polyester resin was 19.1 mol%.

[0117] Furthermore, the heat of fusion of the polyester resin was measured in accordance with JIS K7121:2012 using a differential scanning calorimeter (DSC, manufactured by TA Instruments, product name "DSC Q2000") and found to be 20 J / g. In this measurement, the resin was first heated from room temperature to 250°C at a heating rate of 20°C / min, held at 250°C for 10 minutes, cooled to -60°C at a heating rate of 20°C / min, and held at -60°C for 10 minutes. The resin was then heated again to 250°C at a heating rate of 20°C / min to obtain a DSC curve, and the melting point was measured.

[0118] Example 4 Polyester resin (PEs) pellets were obtained in the same manner as in Example 3. The pellets were then dried at 85°C for at least 4 hours. Subsequently, 70 parts by mass of the dried pellets and 30 parts by mass of a styrene-ethylene / butylene-styrene copolymer (SBES) (styrene / ethylene-butylene ratio = 20 / 80, melt flow rate (MFR) = 13.0 g / 10 min (measured in accordance with ISO 1133 at 230°C and a load of 2.16 kg)) serving as a styrene-based elastomer were kneaded in a twin-screw kneader. The pellets thus obtained were placed in the hopper of a single-screw extruder equipped with a T-die. The pellets were then extruded from the T-die in a molten state under conditions of a cylinder temperature of 220°C and a die temperature of 220°C, and cooled on a cooling roll to obtain a sheet-like substrate with a thickness of 80 μm. A PSA sheet was obtained in the same manner as in Example 2, except for using this substrate.

[0119] Comparative Example 1 A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 2, except that a substrate (thickness: 80 μm) made of ethylene-methacrylic acid copolymer (EMAA) was used as the substrate.

[0120] Comparative Example 2 An adhesive sheet was obtained in the same manner as in Example 2, except that a substrate (thickness: 80 μm) made of EMAA, one surface of which had been treated with electron beam irradiation (EB), was used as the substrate, and an adhesive layer was laminated on the electron beam irradiated surface of the substrate.

[0121] [Test Example 1] (Measurement of tensile properties of substrate) For the substrates prepared in the examples and comparative examples, a total of 18 directions were determined, with one arbitrary direction in a planar view being set as the reference direction, and the angles formed with the reference direction in a planar view were 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, and 170°.

[0122] Next, the substrate was cut to obtain 18 test pieces (15 mm × 150 mm) such that the long side of each test piece was parallel to one of the 18 directions.

[0123] These test pieces were subjected to a tensile test in accordance with JIS K7127:1999 using a tensile testing machine (Shimadzu Corporation, product name "Autograph AG-Xplus 100N"), in which the test pieces were pulled in the long side direction at a speed of 200 mm / min in an environment of 23°C with a chuck distance of 100 mm.

[0124] Next, from the results of the above tests, the increase in tensile stress, obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation, was calculated for each test piece. Then, for the test piece with the smallest increase, the direction parallel to the long side of the test piece (one of the 18 directions mentioned above) was designated as the first measurement direction. The direction forming an angle of 90° with the first measurement direction in a plan view was designated as the second measurement direction. The second measurement direction was approximately parallel to the MD direction of the substrate (the flow direction during the production of the substrate), and the first measurement direction was approximately parallel to the TD direction of the substrate (the direction perpendicular to the MD direction).

[0125] The substrates prepared in the examples and comparative examples were then cut again so that their long sides were parallel to the first measurement direction to obtain 15 mm × 150 mm test pieces. The tensile modulus and elongation at break of the test pieces were measured in accordance with JIS K7127:1999. Specifically, the test pieces were subjected to a tensile test using a tensile tester (Shimadzu Corporation, product name "Autograph AG-Xplus 100N") with a chuck distance of 100 mm, and then a tensile test was performed in which the test pieces were pulled in the first measurement direction of the substrate film at a rate of 200 mm / min under an environment of 23°C, and the tensile modulus (MPa) and elongation at break (%) were measured. The results are shown in Table 1 as the tensile modulus and elongation at break in the first measurement direction.

[0126] In addition, a tensile test was performed on the test pieces obtained in the same manner as above, in which the test pieces were pulled in the first measurement direction of the base film at a speed of 200 mm / min in an environment of 23°C, and the change in tensile stress (MPa) was measured as the tensile elongation (%) was increased from 0% to 250%.

[0127] The tensile stress (MPa) was recorded at tensile elongation points of 10%, 50%, 100%, 150%, 200%, and 250%. Furthermore, the increase in tensile stress (MPa) from 10% to 200% tensile elongation and the increase in tensile stress (MPa) from 100% to 200% tensile elongation were calculated. The ratio of the tensile stress at 200% tensile elongation to that at 100% tensile elongation was also calculated. These results are also shown in Table 1 as the measured values ​​of each tensile property in the first measurement direction.

[0128] Furthermore, the tensile stress (MPa) measured as described above was plotted on a coordinate plane with the tensile elongation (unit: %) on the horizontal axis and the tensile stress (unit: MPa) on the vertical axis to create a curve. The presence or absence of a maximum point where the tensile stress was at a local maximum was confirmed on the curve, and the results are shown in Table 1. Furthermore, if such a maximum point was present, the presence or absence of a minimum point where the tensile stress was at a local minimum was also confirmed, and the absolute value (MPa) of the difference in tensile stress between the maximum point (if multiple points exist, the maximum point where the tensile elongation value was minimum) and the minimum point (if multiple points exist, the minimum point where the tensile elongation value was minimum) was determined. The results are also shown in Table 1.

[0129] In addition, a test piece for measuring the tensile properties in the second measurement direction was obtained in the same manner as described above, i.e., a 15 mm × 150 mm test piece was cut so that the 150 mm side was parallel to the second measurement direction of the substrate.

[0130] The resulting test specimens were also measured for tensile modulus (MPa) in the same manner as described above, and the change in tensile stress (MPa) was measured as the tensile elongation (%) was increased from 0% to 250%. The tensile stress (MPa) values ​​at 10%, 50%, 100%, 150%, 200%, and 250% elongation points were determined from the change in tensile stress (MPa), and the increase in tensile stress (MPa) was calculated from these values. The increase was calculated in four ways: from 10% to 200%, from 50% to 150%, from 50% to 250%, and from 100% to 200%. These results are also shown in Table 2 as the measured values ​​of each tensile property in the second measurement direction.

[0131] [Test Example 2] (Evaluation of expandability) The release sheet was peeled off from the pressure-sensitive adhesive sheet produced in the Examples and Comparative Examples, and the exposed surface of the pressure-sensitive adhesive layer was attached to one side of a 40 μm thick silicon wafer. A dicing ring frame was then attached to the periphery of the exposed surface of the pressure-sensitive adhesive sheet (at a position that did not overlap with the silicon wafer). The silicon wafer was then diced using a dicing saw (manufactured by Disco Corporation, product name "DFD6362") under the following conditions: Workpiece (substrate): Silicon wafer Work size: 6 inch diameter, 40μm thickness Dicing blade: DISCO Corporation, product name "27HECC", diamond blade Blade rotation speed: 50,000 rpm Dicing speed: 100mm / sec Cutting depth: Cut to a depth of 20 μm from the surface of the base film Dicing size: 8mm x 8mm

[0132] The chips obtained by dicing and the adhesive sheet with the ring frame attached were then placed in an expanding device (manufactured by JCM Corporation, product name "ME-300B"), and the ring frame was pulled down at a speed of 2 mm / sec until the pulling distance reached 40 mm.

[0133] The amount of pull-down (mm) when breakage occurred was recorded. The expandability was evaluated based on the following criteria. The results are shown in Tables 1 and 2 (the results shown in Tables 1 and 2 are the same). A: The withdrawal amount (mm) was 40 mm or more. F: The amount of withdrawal (mm) was less than 40 mm.

[0134] [Table 1]

[0135] [Table 2]

[0136] As is clear from Tables 1 and 2, the pressure-sensitive adhesive sheets produced in the examples exhibited excellent expandability. [Industrial Applicability]

[0137] The pressure-sensitive adhesive sheet of the present invention can be suitably used as a workpiece processing sheet used in processing workpieces such as semiconductor wafers.

Claims

1. A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer laminated on one side of the substrate, the substrate is a resin film containing no chlorine atoms, the resin constituting the resin film is at least one of a thermoplastic polyurethane elastomer obtained by reacting a long-chain polyol, a chain extender, and a polyisocyanate, and a polyester-based resin; When any one direction in a plan view of the substrate is taken as a reference direction, and among 18 directions in total, whose angles with respect to the reference direction in a plan view are 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, and 170°, the direction in which the increase in tensile stress, obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation, is the smallest, For the substrate, the tensile stress in the first measurement direction from 10% elongation to 100% elongation is all within a range of 8 MPa or more and 30 MPa or less, The tensile stress of the substrate in the first measurement direction from 100% elongation to 200% elongation is all within the range of 10 MPa or more and 40 MPa or less. A pressure-sensitive adhesive sheet characterized by:

2. The pressure-sensitive adhesive sheet according to claim 1, characterized in that the polyester-based resin contains, as monomer units constituting the polyester-based resin, a dicarboxylic acid having an alicyclic structure, a diol having an alicyclic structure, and a dimer acid obtained by dimerizing an unsaturated fatty acid.

3. 2. The adhesive sheet according to claim 1, wherein the increase in tensile stress of the substrate in the first measurement direction, obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation, is 1 MPa or more and 20 MPa or less.

4. When a direction in a plan view of the substrate, which is at an angle of 90° with respect to the first measurement direction, is defined as a second measurement direction, For the substrate, the tensile stress in the second measurement direction from 10% elongation to 100% elongation is all within a range of 5 MPa or more and 30 MPa or less, For the substrate, the tensile stress in the second measurement direction from 100% elongation to 200% elongation is all within the range of 10 MPa or more and 40 MPa or less. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3.

5. 5. The adhesive sheet according to claim 4, wherein the increase in tensile stress of the substrate in the second measurement direction, obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation, is 1 MPa or more and 20 MPa or less.

6. 6. The pressure-sensitive adhesive sheet according to claim 1, wherein the substrate has a tensile modulus in the first measurement direction of 100 MPa or more and 1000 MPa or less.

7. 7. The pressure-sensitive adhesive sheet according to claim 1, wherein the substrate has a breaking elongation in the first measurement direction of 100% or more and 1000% or less.

8. The results measured when a tensile test is performed on the substrate in the first measurement direction are plotted on a coordinate plane with tensile elongation (unit: %) on the horizontal axis and tensile stress (unit: MPa) on the vertical axis, and the resulting curve is: There is no maximum point in the curve, or The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, characterized in that there is at least one maximum point and one minimum point in the curve, and the absolute value of the difference between the value of the tensile stress at the point among the maximum points where the tensile elongation value is smallest and the value of the tensile stress at the point among the minimum points where the tensile elongation value is smallest is 2.0 MPa or less.

9. 9. The pressure-sensitive adhesive sheet according to claim 1, wherein the substrate does not contain halogen atoms.

10. The adhesive sheet according to any one of claims 1 to 9, which is used as a workpiece processing sheet.

11. The adhesive sheet according to claim 10, wherein the workpiece processing sheet is a dicing sheet.

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