CN114867804A

CN114867804A - Adhesive sheet

Info

Publication number: CN114867804A
Application number: CN202180007680.8A
Authority: CN
Inventors: 佐佐木辽; 川田智史; 河原田有纪
Original assignee: Lintec Corp
Current assignee: Lintec Corp
Priority date: 2020-03-30
Filing date: 2021-03-29
Publication date: 2022-08-05
Also published as: TW202142658A; WO2021200786A1; KR20220158677A; JPWO2021200786A1

Abstract

An adhesive sheet comprising a base material and an adhesive layer, wherein the base material does not contain chlorine atoms and any direction in a plane viewed from above of the base material is set as a reference direction, and the angle formed by the reference direction in the plane of view is 18 directions of 0 degree, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, 70 degrees, 80 degrees, 90 degrees, 100 degrees, 110 degrees, 120 degrees, 130 degrees, 140 degrees, 150 degrees, 160 degrees and 170 degrees, when 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 is the first measurement direction, in the first measurement direction, the tensile stress from 10% elongation to 100% elongation is in the range of 8 to 30MPa, and the tensile stress in the first measurement direction is within the range of 10 to 40MPa from 100% elongation to 200% elongation. The adhesive sheet has good expansibility.

Description

Adhesive sheet

Technical Field

The present invention relates to an adhesive sheet which can be suitably used as a workpiece processing sheet used for processing a workpiece such as a semiconductor wafer.

Background

Semiconductor wafers such as silicon and gallium arsenide, and various packages (packages) are manufactured in a large-diameter state, cut (diced) into chips, and then peeled (picked up), and then transferred to a mounting (mount) step which is a next step. In this case, a work such as a semiconductor wafer is subjected to processing such as back grinding, dicing, cleaning, drying, spreading, picking up, and mounting in a state of being attached to an adhesive sheet (hereinafter, sometimes referred to as a "work processing sheet") provided with a base material and an adhesive layer.

As one of the cutting methods, there is a method of cutting a workpiece with a rotating circular blade (cutting blade). In this method, in order to ensure that the workpiece is cut, the workpiece processing sheet attached to the workpiece is also partially cut together with the workpiece. When the workpiece-processing sheet is cut together with the workpiece in this manner, chips formed of the materials constituting the adhesive layer and the base material may be generated from the workpiece-processing sheet.

If the chip is sealed in a state where a large amount of chips are attached to the chip, the chips attached to the chip are decomposed by the heat energy of the sealing, and such a thermal decomposition product may damage the package or cause an operation failure of the obtained device. Since it is difficult to remove the chips by cleaning, the yield of the cutting process is significantly reduced by the generation of chips. Therefore, in the case of cutting with a rotating circular blade, it is necessary to prevent the generation of cutting chips.

In order to suppress the generation of the cutting chips, patent document 1 discloses an invention using a polyolefin film irradiated with an electron beam or Gamma ray of 1 to 80Mrad as a base film of a dicing sheet. In this invention, it is considered that the crosslinking by covalent bonds is formed in the resin constituting the base film by irradiation with electron beams or γ rays, and the generation of cutting chips is suppressed.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 5-211234

Disclosure of Invention

Technical problem to be solved by the invention

In the pickup step, in order to facilitate the pickup of the semiconductor chips, the semiconductor chips may be lifted one by one from a surface of the work processing sheet opposite to the surface on which the semiconductor chips are stacked. In particular, in order to suppress collision between the semiconductor chips at the time of pickup and at the same time facilitate pickup, the work processing sheet is generally stretched (expanded) so that the semiconductor chips are separated from each other. Therefore, the work processing sheet is required to have excellent flexibility that can be well spread.

However, the conventional dicing sheet as disclosed in patent document 1 does not have sufficient expandability.

The present invention has been made in view of such circumstances, and an object thereof is to provide an adhesive sheet having good stretchability.

Means for solving the problems

In order to achieve the above object, the present invention provides an adhesive sheet comprising a substrate and an adhesive layer laminated on one surface side of the substrate, wherein the substrate does not contain a chlorine atom, any one direction of a plane viewed from above of the substrate is taken as a reference direction, and a direction in which an increase in tensile stress obtained by subtracting a tensile stress at 100% from a tensile stress at 200% elongation is smallest in a total of 18 directions at an angle of 0 °, 10 °, 20 °, 30 °, 40 °, 50 °, 60 °, 70 °, 80 °, 90 °, 100 °, 110 °, 120 °, 130 °, 140 °, 150 °, 160 °, and 170 ° from the reference direction in a tensile stress at 100% elongation is set as a first measurement direction, and the tensile stress from 10% elongation to 100% elongation is in a range of 8MPa to 30MPa in the first measurement direction, the substrate has a tensile stress in the first measurement direction from 100% elongation to 200% elongation in the range of 10MPa to 40MPa (invention 1).

The adhesive sheet of the invention (invention 1) has excellent flexibility and can be satisfactorily stretched since the substrate satisfies the above-mentioned condition of tensile stress.

In the above invention (invention 1), the substrate is preferably such that an increase in tensile stress obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation in the first measurement direction is 1MPa to 20MPa (invention 2).

In the above inventions (inventions 1 and 2), when a direction which is one direction in a plane view of the base material and forms an angle of 90 ° with the first measurement direction is set as a second measurement direction, it is preferable that the tensile stress from 10% elongation to 100% elongation in the second measurement direction is in a range of 5MPa or more and 30MPa or less for the base material, and the tensile stress from 100% elongation to 200% elongation in the second measurement direction is in a range of 10MPa or more and 40MPa or less for the base material (invention 3).

In the above invention (invention 3), the base material is preferably such that an increase in tensile stress obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation in the second measurement direction is 1MPa or more and 20MPa or less (invention 4).

In the above inventions (inventions 1 to 4), the tensile modulus of the base material in the first measurement direction is preferably 100MPa or more and 1000MPa or less (invention 5).

In the above inventions (inventions 1 to 5), the elongation at break of the base material in the first measurement direction is preferably 100% or more and 1000% or less (invention 6).

In the above inventions (inventions 1 to 6), a curve is obtained by plotting a result obtained when a tensile test of the base material is performed in the first measurement direction on a coordinate plane having a tensile elongation (unit:%) as a horizontal axis and a tensile stress (unit: MPa) as a vertical axis, and in the curve, a point which becomes a maximum value does not exist, or at least one point which becomes a maximum value and one point which becomes a minimum value exist, and an absolute value of a difference between a value of the tensile stress at a point at which the tensile elongation becomes a minimum value among the points which become maximum values and a value of the tensile stress at a point at which the tensile elongation becomes a minimum value among the points which become minimum values is preferably 2.0MPa or less (invention 7).

In the above inventions (inventions 1 to 7), it is preferable that the base material does not contain a halogen atom (invention 8).

In the above inventions (inventions 1 to 8), the pressure-sensitive adhesive sheet is preferably used as a sheet for processing a workpiece (invention 9).

In the above invention (invention 9), the work processing sheet is preferably a dicing sheet (invention 10).

Effects of the invention

The adhesive sheet of the present invention has good spreadability.

Drawings

FIG. 1 is a graph for illustrating the physical properties of the substrate according to the present embodiment.

Detailed Description

Hereinafter, embodiments of the present invention will be described.

The adhesive sheet of the present embodiment includes a substrate and an adhesive layer laminated on one surface of the substrate. The adhesive sheet can be used for various purposes as in a general adhesive sheet, but is particularly suitable for use as a workpiece processing sheet used for processing a workpiece such as a semiconductor wafer. In particular, the adhesive sheet of the present embodiment is suitable for use as a sheet for picking up a workpiece such as a semiconductor chip.

1. Structure of adhesive sheet

(1) Base material

The substrate of the present embodiment does not contain a chlorine atom. Since the adhesive sheet of the present embodiment does not contain a chlorine atom, the environmental load is easily reduced. The phrase "not containing a chlorine atom" as used herein also includes the case where a chlorine atom is not substantially contained. That is, the base material of the present embodiment may be, for example, a very small amount of a component containing a chlorine atom unintentionally mixed in during the production process. In this case, the content of chlorine atoms in the base material may be 0.005% by mass or less, particularly may be 0.003% by mass or less, and further may be 0.0001% by mass or less.

When the predetermined direction in the plan view of the base material of the present embodiment is set as the first measurement direction, the tensile stress from 10% elongation to 100% elongation in the first measurement direction is within a range of 8MPa or more and 30MPa or less, and the tensile stress from 100% elongation to 200% elongation in the first measurement direction is within a range of 10MPa or more and 40MPa or less.

Since the substrate of the adhesive sheet of the present embodiment satisfies these conditions, the adhesive sheet of the present embodiment has very excellent flexibility. Therefore, when the adhesive sheet of the present embodiment is used for processing a workpiece, the expansion can be performed well. Meanwhile, in the subsequent picking process, the chip is easy to be pushed up from the back surface of the chip, and good picking can be performed.

Here, the first measurement direction means, in short, a tensile direction in which an increase in tensile stress from 100% elongation to 200% elongation is smallest when a tensile test of the base material is performed. More specifically, the first measurement direction is the direction in which the smallest increase in tensile stress, which is obtained by subtracting the tensile stress at 100% from the tensile stress at 200% elongation, is the tensile stress at 100% elongation, among 18 directions in total of 0 °, 10 °, 20 °, 30 °, 40 °, 50 °, 60 °, 70 °, 80 °, 90 °, 100 °, 110 °, 120 °, 130 °, 140 °, 150 °, 160 °, and 170 ° in any one direction in the plane of the base material as the reference direction, and the angles formed with the reference direction in the plane of the base material are the first direction.

In the case where the substrate is a resin film as described later, a direction (TD direction) perpendicular to a flow direction in the production of the resin film often coincides with the first measurement direction.

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 is preferably 9MPa or more, and particularly preferably 10MPa or more. The upper limit of this range is preferably 25MPa or less, particularly preferably 20MPa or less, and more preferably 15MPa or less.

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

The details of the method of measuring the tensile stress are described in the test examples described later.

(1-1) physical Properties of base Material

In the substrate of the present embodiment, the increase of the tensile stress obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation in the first measurement direction is preferably 1MPa or more, particularly preferably 1.5MPa or more, and more preferably 1.8MPa or more. The increase is preferably 20MPa or less, more preferably 15MPa or less, particularly preferably 10MPa or less, and further preferably 5MPa or less. When the above increase amount is 1MPa or more, stress is less likely to concentrate on a part of the substrate when the pressure-sensitive adhesive sheet of the present embodiment is expanded, and the substrate is likely to be effectively inhibited from breaking. On the other hand, when the amount of increase is 20MPa or less, the adhesive sheet of the present embodiment is expanded, the substrate is easily uniformly stretched, and the chips are easily separated from each other well. Therefore, by satisfying the above increase amount, the adhesive sheet of the present embodiment has more excellent spreadability.

In the substrate of the present embodiment, the increase of the tensile stress obtained by subtracting the tensile stress at 10% elongation from the tensile stress at 200% elongation in the first measurement direction is preferably 0.5MPa or more, more preferably 1MPa or more, particularly preferably 1.5MPa or more, and further preferably 2MPa or more. The increase is preferably 25MPa or less, particularly preferably 15MPa or less, and more preferably 5MPa or less. When the above increase amount is 0.5MPa or more, stress is not easily concentrated on a part of the substrate when the pressure-sensitive adhesive sheet of the present embodiment is expanded, and the substrate is easily and effectively prevented from being broken. On the other hand, when the amount of increase is 25MPa or less, the adhesive sheet of the present embodiment is expanded, the substrate is easily uniformly stretched, and the chips are easily separated from each other well. Therefore, by satisfying the above increase amount, the adhesive sheet of the present embodiment has more excellent spreadability.

In addition, the ratio of the tensile stress at 200% elongation to the tensile stress at 100% elongation in the first measurement direction of the substrate of the present embodiment is preferably 0.5 or more, particularly preferably 0.75 or more, and more preferably 1 or more. The ratio is preferably 3 or less, more preferably 2.5 or less, particularly preferably 2 or less, and further preferably 1.5 or less. When the ratio is 0.5 or more, the pressure-sensitive adhesive sheet of the present embodiment is expanded, stress is less likely to concentrate on a part of the substrate, and the substrate is likely to be effectively inhibited from breaking. On the other hand, when the adhesive sheet of the present embodiment is expanded by setting the ratio to 3 or less, the base material is easily uniformly stretched, and the chips are easily separated from each other well. Therefore, by satisfying the above ratio, the adhesive sheet of the present embodiment has more excellent extensibility.

In addition, the tensile modulus in the first measurement direction of the substrate of the present embodiment is preferably 100MPa or more, particularly preferably 200MPa or more, and more preferably 300MPa or more. The tensile modulus is preferably 1000MPa or less, particularly preferably 800MPa or less, and more preferably 600MPa or less. By setting the tensile modulus to 100MPa or more, the substrate of the present embodiment is likely to have appropriate strength, and the adhesive sheet is likely to perform desired work processing with good workability. In addition, when the pressure-sensitive adhesive sheet of the present embodiment is expanded, stress is less likely to concentrate on a part of the substrate, and the substrate is likely to be effectively inhibited from breaking. Further, when the tensile modulus is 1000MPa or less, the adhesive sheet of the present embodiment is easily stretched uniformly when stretched, and the chips are easily separated from each other well. Therefore, the adhesive sheet of the present embodiment has more excellent extensibility by setting the tensile modulus of the base material in the first measurement direction within the above upper limit and lower limit. The details of the method for measuring the tensile modulus are described in the test examples described later.

In addition, the elongation at break in the first measurement direction of the substrate of the present embodiment is preferably 100% or more, particularly preferably 200% or more, and further preferably 300% or more. The elongation at break is preferably 1000% or less, particularly preferably 800% or less, and more preferably 600% or less. By setting the elongation at break to 100% or more, the substrate of the present embodiment is likely to have desired extensibility, and the adhesive sheet of the present embodiment is likely to realize excellent extensibility and pickup properties. By setting the elongation at break to 1000% or less, the processability of the base material becomes more excellent, and a desired adhesive sheet can be easily produced. The details of the method for measuring the elongation at break are described in the test examples described later.

Further, with respect to the substrate of the present embodiment, it is preferable that a curve obtained by plotting the results obtained when the tensile test of the substrate is performed in the first measurement direction on a coordinate plane having a tensile elongation (unit:%) as a horizontal axis and a tensile stress (unit: MPa) as a vertical axis satisfies any one of the following two conditions with respect to the curve.

(condition 1) there is no point that becomes a maximum value (hereinafter, sometimes referred to as "maximum value point") in the curve.

(condition 2) the curve has at least one point having a maximum value and one point having a minimum value (hereinafter, sometimes referred to as "minimum value point") and the absolute value of the difference between the value of the tensile stress at the point having the minimum tensile elongation among the points having the maximum value and the value of the tensile stress at the point having the minimum tensile elongation among the points having the minimum value is 2.0MPa or less.

The above conditions 1 and 2 are explained in more detail with reference to fig. 1. In FIG. 1, it is shown that a curve C exists in a coordinate plane having a horizontal axis of tensile elongation (unit:%) and a vertical axis of tensile stress (unit: MPa) ₁ And curve C ₂ The state of (1). First, curve C ₁ An example of the case where the above condition 1 is satisfied. At curve C ₁ In (b), as the tensile elongation increases from 0%, the tensile stress also increases accordingly (however, as the value gradually approaches the prescribed tensile stress, it becomes less likely to increase). Thus, curve C ₁ There is no point where the tensile stress transitions from increasing to decreasing, i.e., the maximum point.

On the other hand, curve C ₂ An example of the case where condition 2 is satisfied. At curve C ₂ When the tensile elongation is increased from 0%, the tensile stress is first increased to the position of point a. Then, with this point a as a boundary, the tensile stress becomes reduced. I.e. curve C ₂ With the maximum point being point a. When the tensile elongation is further increased beyond point a, then the tensile stress shifts from decreasing to increasing, and then continues to increase, bounded by point B. I.e. curve C ₂ With a minimum point as point B. Here, the curve C is a curve in which the absolute value of the difference between the values of tensile stresses at the points A and B (the value indicated by "Δ" in FIG. 1) is 2.0MPa or less ₂ Condition 2 is satisfied.

In addition, curve C in FIG. 1 ₂ In (1), there is a maximum pointAnd one minimum point, even in the case where there are a plurality of maximum points and minimum points, the condition 2 is sometimes satisfied. In this case, from among the plurality of maximum and minimum points, the maximum point at which the tensile elongation is the smallest and the minimum point at which the tensile elongation is the smallest are selected, and whether or not the condition 2 is satisfied is determined based on whether or not the absolute value of the difference between the maximum point and the minimum point is 2.0MPa or less.

By allowing the substrate of the present embodiment to satisfy at least one of the above conditions 1 and 2, the adhesive sheet of the present embodiment is likely to have excellent extensibility. From this viewpoint, the difference in absolute value (Δ) in condition 2 is preferably 1.8MPa or less, more preferably 1.6MPa or less, particularly preferably 1.5MPa or less, further preferably 1.3MPa or less, and most preferably 1.0MPa or less. On the other hand, the lower limit of the absolute difference (Δ) is not particularly limited, and may be, for example, greater than 0. The details of the measurement method as to whether or not the above conditions 1 and 2 are satisfied are described in the test examples described later.

In the substrate of the present embodiment, when a direction which is one direction in a plane view of the substrate and forms an angle of 90 ° with the first measurement direction is set as the second measurement direction, the tensile stress from 10% elongation to 100% elongation in the second measurement direction is preferably within a range of 5MPa or more and 30MPa or less, and the tensile stress from 100% elongation to 200% elongation in the second measurement direction is preferably within a range of 10MPa or more and 40MPa or less. By satisfying these conditions, the base material tends to have further excellent flexibility and to have further excellent extensibility.

From the viewpoint of more effectively achieving 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 7.5MPa or more, and more preferably 10MPa or more. The upper limit of this range is particularly preferably 25MPa or less, and more preferably 20MPa or less.

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

The details of the method for measuring the tensile stress in the second measurement direction are described in the test examples described later.

Further, in the substrate of the present embodiment, the increase of the tensile stress obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation in the second measurement direction is preferably 1MPa or more, particularly preferably 2MPa or more, and more preferably 3MPa or more. The increase is preferably 20MPa or less, particularly preferably 15MPa or less, and more preferably 10MPa or less. When the above increase amount is 1MPa or more, stress is less likely to concentrate on a part of the substrate when the pressure-sensitive adhesive sheet of the present embodiment is expanded, and the substrate is likely to be effectively inhibited from breaking. On the other hand, when the amount of increase is 20MPa or less, the adhesive sheet of the present embodiment is expanded, the substrate is easily uniformly stretched, and the chips are easily separated from each other well. Therefore, by satisfying the above increase amount, the adhesive sheet of the present embodiment has more excellent spreadability.

In addition, in the substrate of the present embodiment, the increase of the tensile stress obtained by subtracting the tensile stress at 10% elongation from the tensile stress at 200% elongation in the second measurement direction is preferably 1MPa or more, more preferably 2MPa or more, particularly preferably 3MPa or more, and further preferably 4MPa or more. The increase is preferably 30MPa or less, particularly preferably 25MPa or less, and more preferably 20MPa or less. When the above increase amount is 1MPa or more, stress is less likely to concentrate on a part of the substrate when the pressure-sensitive adhesive sheet of the present embodiment is expanded, and the substrate is likely to be effectively inhibited from breaking. On the other hand, when the amount of increase is 30MPa or less, the adhesive sheet of the present embodiment is expanded, the substrate is easily uniformly stretched, and the chips are easily separated from each other well. Therefore, by satisfying the above increase amount, the adhesive sheet of the present embodiment has more excellent spreadability.

In addition, in the substrate of the present embodiment, in the second measurement direction, the increase of the tensile stress obtained by subtracting the tensile stress at 50% elongation from the tensile stress at 150% elongation is preferably 0.5MPa or more, more preferably 1MPa or more, particularly preferably 1.5MPa or more, and further preferably 2MPa or more. The increase is preferably 20MPa or less, particularly preferably 15MPa or less, and more preferably 10MPa or less. When the above increase amount is 0.5MPa or more, stress is not easily concentrated on a part of the substrate when the pressure-sensitive adhesive sheet of the present embodiment is expanded, and the substrate is easily and effectively prevented from being broken. On the other hand, when the amount of increase is 20MPa or less, the adhesive sheet of the present embodiment is expanded, the substrate is easily uniformly stretched, and the chips are easily separated from each other well. Therefore, by satisfying the above increase amount, the adhesive sheet of the present embodiment has more excellent spreadability.

In addition, in the substrate of the present embodiment, the increase of the tensile stress obtained by subtracting the tensile stress at 50% elongation from the tensile stress at 250% elongation in the second measurement direction is preferably 2MPa or more, particularly preferably 4MPa or more, more preferably 5MPa or more, and still more preferably 6MPa or more. The increase is preferably 30MPa or less, particularly preferably 25MPa or less, and more preferably 20MPa or less. When the above increase amount is 2MPa or more, stress is not easily concentrated on a part of the substrate when the pressure-sensitive adhesive sheet of the present embodiment is expanded, and the substrate is easily and effectively prevented from being broken. On the other hand, when the amount of increase is 30MPa or less, the adhesive sheet of the present embodiment is expanded, the substrate is easily uniformly stretched, and the chips are easily separated from each other well. Therefore, by satisfying the above increase amount, the adhesive sheet of the present embodiment has more excellent spreadability.

In addition, the tensile modulus in the second measurement direction of the substrate of the present embodiment is preferably 100MPa or more, particularly preferably 200MPa or more, and more preferably 300MPa or more. The tensile modulus is preferably 1000MPa or less, particularly preferably 800MPa or less, and more preferably 600MPa or less. By setting the tensile modulus to 100MPa or more, the substrate of the present embodiment is likely to have appropriate strength, and the adhesive sheet is likely to perform desired work processing with good workability. In addition, when the pressure-sensitive adhesive sheet of the present embodiment is expanded, stress is less likely to concentrate on a part of the substrate, and the substrate is likely to be effectively inhibited from breaking. Further, when the tensile modulus is 1000MPa or less, the adhesive sheet of the present embodiment is easily stretched uniformly when stretched, and the chips are easily separated from each other well. Therefore, by setting the tensile modulus of the base material in the second measurement direction within the above upper limit and lower limit, the pressure-sensitive adhesive sheet of the present embodiment has more excellent extensibility. The details of the method for measuring the tensile modulus are described in the test examples described later.

(1-2) composition of the substrate

The composition of the substrate of the present embodiment is not limited as long as it substantially contains no chlorine atom and satisfies the physical properties described above with respect to the tensile stress from 10% elongation to 100% elongation and the tensile stress from 100% elongation to 200% elongation.

The substrate of the present embodiment is preferably a resin film containing a resin-based material as a main component, from the viewpoint that the adhesive sheet of the present embodiment easily exhibits a desired function when used as a sheet for processing a workpiece.

Examples of the resin include polyolefins such as polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, an ethylene-norbornene copolymer, and a norbornene resin; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; ethylene-vinyl acetate copolymers; ethylene copolymers such as ethylene- (meth) acrylic acid copolymers, ethylene- (meth) acrylic acid methyl ester copolymers, and other ethylene- (meth) acrylic acid ester copolymers; (meth) acrylate ester copolymers; a polyurethane; a polyimide; polystyrene; a polycarbonate; fluorine resins, and the like. Further, a modified resin such as a crosslinked resin or an ionomer resin of these resins may be used. In the present specification, "(meth) acrylic" refers to both acrylic and methacrylic. The same is true for other similar terms. In addition, "polymer" in the present specification also includes the concept of "copolymer".

The substrate of the present embodiment may be a laminated film formed by laminating a plurality of films of the above-described resins. In this laminated film, the materials constituting the respective layers may be the same kind or different kinds.

Among the above resins, at least one of a fluororesin, a polyurethane and a polyester resin is preferably used. In particular, in the film using these resins, the main component resin (fluororesin, polyurethane or polyester resin) is preferably contained in an amount of 50 mass% or more, more preferably 60 mass% or more, particularly preferably 70 mass% or more, and further preferably 80 mass% or more. By using these films, the above-described physical properties relating to tensile stress can be easily satisfied.

Examples of the fluororesin include Polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene (ETFE), tetrafluoroethylene-hexafluoroethylene (FEP), Perfluoroalkoxyalkane (PFA), polyvinylidene fluoride (PVdF), and the like. Among them, Polytetrafluoroethylene (PTFE) is particularly preferable.

Examples of the polyurethane include polyurethane elastomers, and among them, thermoplastic polyurethane elastomers (TPU) are preferably used.

The thermoplastic polyurethane elastomer is generally obtained by reacting a long-chain polyol, a chain extender, and a polyisocyanate, and is composed of a soft segment (soft segment) having a structural unit derived from the long-chain polyol, and a hard segment (hard segment) having a polyurethane structure obtained by the reaction of the chain extender and the polyisocyanate.

The thermoplastic polyurethane elastomer can be classified into a polyester polyurethane elastomer, a polyether polyurethane elastomer, a polycarbonate polyurethane elastomer, and the like, according to the type of the long-chain polyol used as the soft segment component. The substrate of the present embodiment preferably uses a polyether urethane elastomer therein.

Specific examples of the long-chain polyol include polyester polyols such as lactone-type polyols and adipate-type polyols; polyether polyols such as polypropylene (ethylene) polyol and polytetramethylene ether glycol; polycarbonate polyols, and the like. Among them, polyether polyols having a number average molecular weight of usually 600 to 5000 are preferably used.

Examples of the polyisocyanate include 2, 4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, 4' -diphenylmethane diisocyanate (pure MDI), hexamethylene diisocyanate, and the like.

Among them, pure MDI is preferably used.

Examples of the chain extender include low-molecular-weight polyols such as 1, 4-butanediol and 1, 6-hexanediol, and aromatic diamines.

As examples of the polyester-based resin, in addition to the above-mentioned resins, polyester resins having an alicyclic structure can be cited.

In addition, when the adhesive sheet of the present embodiment is used as a dicing sheet, the number of carbon atoms constituting the ring of the alicyclic structure of the polyester resin is preferably 6 or more, from the viewpoint of easily suppressing the generation of cutting chips. The number of carbon atoms is preferably 14 or less, and particularly preferably 10 or less. The number of carbon atoms is particularly preferably 6. The alicyclic structure may be a monocyclic structure composed of one ring, a bicyclic structure composed of two rings, or an alicyclic structure composed of three or more rings.

In addition, from the viewpoint that the base material of the present embodiment is likely to have more excellent 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. The polyester resin may contain only one of such dicarboxylic acid and diol, but from the viewpoint of facilitating better flexibility, it is preferable that the polyester resin contains both such dicarboxylic acid and diol.

The structure of the dicarboxylic acid is not particularly limited as long as it has two carboxyl groups in addition to the alicyclic structure. For example, the dicarboxylic acid may have a structure in which two carboxyl groups are bonded to an alicyclic structure, or may have a structure in which an alkyl group or the like is further inserted between such an alicyclic structure and a carboxyl group. Preferred examples of such dicarboxylic acids include 1, 2-cyclohexanedicarboxylic acid, 1, 3-cyclohexanedicarboxylic acid, 1, 4-cyclohexanedicarboxylic acid, decahydronaphthalene-1, 4-dicarboxylic acid, decahydronaphthalene-1, 5-dicarboxylic acid, decahydronaphthalene-2, 6-dicarboxylic acid, decahydronaphthalene-2, 7-dicarboxylic acid, and the like, and among these, 1, 4-cyclohexanedicarboxylic acid is preferably used. These dicarboxylic acids may be derivatives of alkyl esters and the like. Such an alkyl ester derivative may be, for example, an alkyl ester having 1 to 10 carbon atoms. More specific examples thereof include dimethyl ester and diethyl ester, and dimethyl ester is particularly preferable.

The structure of the diol is not particularly limited as long as it has two hydroxyl groups in addition to the alicyclic structure. For example, the diol may have a structure in which two hydroxyl groups are bonded to an alicyclic structure, or may have a structure in which an alkyl group is further inserted between such an alicyclic structure and a hydroxyl 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, and among these, 1, 4-cyclohexanedimethanol is preferably used.

The polyester resin preferably further contains a dimer acid obtained by dimerization of an unsaturated fatty acid as a monomer unit constituting the polyester resin, from the viewpoint that the base material easily has desired flexibility and more excellent expandability can be easily realized. Here, the number of carbon atoms of the unsaturated fatty acid is preferably 10 or more, and particularly preferably 15 or more. The number of carbon atoms is preferably 30 or less, and particularly preferably 25 or less. Examples of such dimer acids include dicarboxylic acids having 36 carbon atoms obtained by dimerizing unsaturated fatty acids having 18 carbon atoms such as oleic acid and linoleic acid, and dicarboxylic acids having 44 carbon atoms obtained by dimerizing unsaturated fatty acids having 22 carbon atoms such as erucic acid. In addition, when the dimer acid is obtained, a small amount of trimer acid formed by trimerization of the unsaturated fatty acid may be generated. The polyester resin may contain the above dimer acid and such trimer acid.

The polyester resin may contain monomers other than the dicarboxylic acid, the diol, and the dimer acid as monomer units constituting the polyester resin. 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; aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, 2, 6-naphthalenedicarboxylic acid, 1, 4-naphthalenedicarboxylic acid, and 4, 4' -diphenyldicarboxylic acid. Further, a diol component other than the diol having an alicyclic structure may be contained. For example, ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, octylene glycol, and decylene glycol; ethylene oxide adducts of bisphenol a, bisphenol S and the like; trimethylolpropane, and the like.

The heat of fusion of the polyester resin measured by differential scanning calorimetry at a temperature rise rate of 20 ℃/min is preferably 2J/g or more, more preferably 5J/g or more, particularly preferably 10J/g or more, and still more preferably 15J/g or more. By setting the heat of fusion to 2J/g or more, the crystallinity of the base material of the present embodiment is suitably improved, and the base material has more favorable workability and processability. The heat of fusion is preferably 150J/g or less, more preferably 100J/g or less, particularly preferably 70J/g or less, further preferably 50J/g or less, and particularly preferably 30J/g or less. By setting the heat of fusion to 150J/g or less, the substrate of the present embodiment is likely to have more excellent flexibility.

In addition, the above heat of fusion can be measured using a differential scanning calorimeter (for example, DSC manufactured by TA instruments, product name "DSC Q2000") according to JIS K7121: 2012.

From the viewpoint of easily realizing desired tensile physical properties, it is also preferable that the film containing a polyester resin as a main component further contains an elastomer in addition to the polyester resin. The elastomer is not particularly limited, and may be a thermosetting elastomer or a thermoplastic elastomer, but a thermoplastic elastomer is preferable because the base material of the present embodiment is likely to have more excellent flexibility.

Examples of the thermoplastic elastomer are also not particularly limited, and for example, styrene-based elastomers, olefin-based elastomers, polyester-based elastomers, silicone-based elastomers, and the like can be used. The thermoplastic elastomer may be used alone, or two or more of them may be used in combination. Among the above elastomers, styrene-based elastomers are preferably used in view of facilitating more excellent flexibility.

Examples of the styrene-based elastomer include a styrene-conjugated diene copolymer and a styrene-olefin copolymer. Specific examples of the styrene-conjugated diene copolymer include unhydrogenated styrene-conjugated diene copolymers such as styrene-butadiene copolymer, styrene-butadiene-styrene copolymer (SBS), styrene-butadiene-butylene-styrene copolymer, styrene-isoprene-styrene copolymer (SIS), and styrene-ethylene-isoprene-styrene copolymer; hydrogenated styrene-conjugated diene copolymers such as styrene-ethylene/propylene-styrene copolymers (SEPS) and styrene-ethylene/butylene-styrene copolymers (SEBS). These styrene-based elastomers may be used alone, or two or more thereof may be used in combination. Among the above styrene-based elastomers, from the viewpoint of easily achieving more favorable flexibility, styrene-conjugated diene copolymers are preferred, hydrogenated styrene-conjugated diene copolymers are preferred, and styrene-ethylene/butylene-styrene copolymers are more preferably used.

From the viewpoint of facilitating further reduction of environmental load, it is also preferable that the base material of the present embodiment does not contain a halogen atom. Examples of the halogen atom include a fluorine atom, a bromine atom, an iodine atom, and the like, in addition to the chlorine atom. In addition, "not containing a halogen atom" herein may mean that a halogen atom is not substantially contained, as in the case of the chlorine atom. In this case, the content of the halogen atom in the base material may be 0.005% by mass or less, particularly may be 0.003% by mass or less, and further may be 0.0001% by mass or less.

Further, additives such as flame retardants, plasticizers, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, and ion scavengers may be added to the base material of the present embodiment. The content of these additives is not particularly limited, but is preferably set within a range in which the base material exerts a desired function.

The layer structure of the substrate of the present embodiment may be a single layer or a plurality of layers. In addition, in order to improve adhesion to the adhesive layer, the surface of the substrate on which the adhesive layer is to be laminated may be subjected to surface treatment such as primer treatment, corona treatment, or plasma treatment.

(1-3) method for producing substrate

The method for producing the base material of the present embodiment is not particularly limited, and for example, a melt extrusion method such as a T die method or a circular die method; a rolling method; solution methods such as dry method and wet method. Among them, from the viewpoint of efficiently producing the base material, a melt extrusion method or a rolling method is preferably employed.

When a substrate composed of a single layer is produced by a melt extrusion method, a substrate material is kneaded and a film is formed directly from the obtained kneaded product using a known extruder, or a mixture obtained by kneading a substrate material and previously producing pellets (pellet) is kneaded and a film is formed using a known extruder. In the case of producing a substrate composed of a plurality of layers by the melt extrusion method, it is sufficient to knead the components constituting each layer separately and extrude a plurality of layers simultaneously from the obtained kneaded mass directly using a known extruder to form a film, or to knead the components constituting each layer separately and produce the obtained kneaded mass into pellets first and then extrude a plurality of layers simultaneously using a known extruder to form a film.

(1-4) thickness of base Material

The thickness of the substrate in the present embodiment is preferably 20 μm or more, particularly preferably 40 μm or more, and further preferably 60 μm or more. The thickness of the base material is preferably 600 μm or less, particularly preferably 300 μm or less, and more preferably 200 μm or less. By setting the thickness of the base material to 20 μm or more, the adhesive sheet can easily have appropriate strength, and the work fixed to the adhesive sheet can be easily and satisfactorily held. As a result, chipping (chipping) and the like can be effectively suppressed during dicing. Further, by setting the thickness of the base material to 600 μm or less, the above-described physical properties with respect to the tensile stress from 10% elongation to 100% elongation and the tensile stress from 100% elongation to 200% elongation are easily satisfied. Further, the thickness of the base material film is set to 600 μm or less, whereby the base material film has more excellent processability.

(2) Adhesive layer

The adhesive constituting the adhesive layer of the present embodiment is not particularly limited as long as it can exhibit sufficient adhesive force to an adherend (particularly, has sufficient adhesive force to a work to process the work). Examples of the adhesive constituting the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, and polyvinyl ether adhesives. Among these, acrylic adhesives are preferably used because they are easy to exert desired adhesive force.

The adhesive constituting the adhesive layer of the present embodiment may be an adhesive having no active energy ray-curing property, but is preferably an adhesive having an active energy ray-curing property (hereinafter, may be referred to as "active energy ray-curing adhesive"). When the adhesive layer is made of an active energy ray-curable adhesive, the adhesive layer can be cured by irradiation with an active energy ray, and the adhesive force of the adhesive sheet to the adherend can be easily reduced. In particular, when the adhesive sheet of the present embodiment is used as a workpiece processing sheet, the processed workpiece can be easily separated from the adhesive sheet by irradiation with active energy rays.

The active energy ray-curable adhesive constituting the adhesive layer may contain, as a main component, a polymer having active energy ray-curability, or may contain, as a main component, a mixture of a non-active energy ray-curable polymer (a polymer having no active energy ray-curability) and a monomer and/or oligomer having at least one or more active energy ray-curable groups.

The active energy ray-curable polymer is preferably a (meth) acrylate polymer having a functional group curable with an active energy ray (active energy ray-curable group) introduced into a side chain thereof (hereinafter, sometimes referred to as "active energy ray-curable polymer"). Preferably, the active energy ray-curable polymer is 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 the present specification, (meth) acrylic acid refers to both acrylic acid and methacrylic acid. The same is true for other similar terms. Further, "polymer" also includes the concept of "copolymer".

The weight average molecular weight of the active energy ray-curable polymer is preferably 1 ten thousand or more, particularly preferably 15 ten thousand or more, and more preferably 20 ten thousand or more. The weight average molecular weight is preferably 250 ten thousand or less, particularly preferably 200 ten thousand or less, and more preferably 150 ten thousand or less. The weight average molecular weight (Mw) in the present specification is a value in terms of standard polystyrene measured by Gel Permeation Chromatography (GPC).

On the other hand, when the active energy ray-curable adhesive contains, as a main component, a mixture of an inactive energy ray-curable polymer and a monomer and/or oligomer having at least one or more active energy ray-curable groups, the above-mentioned acrylic copolymer before the reaction with the unsaturated group-containing compound can be used as the inactive energy ray-curable polymer component. As the active energy ray-curable monomer and/or oligomer, for example, an ester of a polyol and (meth) acrylic acid, or the like can be used.

The weight average molecular weight of the acrylic polymer as the non-active energy ray-curable polymer component is preferably 1 ten thousand or more, particularly preferably 15 ten thousand or more, and more preferably 20 ten thousand or more. The weight average molecular weight is preferably 250 ten thousand or less, particularly preferably 200 ten thousand or less, and more preferably 150 ten thousand or less.

When ultraviolet rays are used as active energy rays for curing the active energy ray-curable adhesive, a photopolymerization initiator is preferably added to the adhesive. In addition, an inactive energy ray-curable polymer component, an oligomer component, a crosslinking agent, or the like may be added to the adhesive.

The thickness of the adhesive agent layer of the present embodiment is preferably 1 μm or more, particularly preferably 2 μm or more, and more preferably 3 μm or more. The thickness of the adhesive layer is preferably 50 μm or less, particularly preferably 40 μm or less, and more preferably 30 μm or less. When the thickness of the adhesive layer is 1 μm or more, the adhesive sheet of the present embodiment easily exhibits desired adhesiveness. Further, when the thickness of the adhesive agent layer is 50 μm or less, the adherend can be easily separated from the cured adhesive agent layer.

(3) Release sheet

In the pressure-sensitive adhesive sheet of the present embodiment, before a surface of the pressure-sensitive adhesive layer on the opposite side to the substrate (hereinafter, sometimes referred to as "pressure-sensitive adhesive surface") is attached to an adherend, a release sheet may be laminated on the surface for the purpose of protecting the surface.

The release sheet is optionally configured, and for example, a release sheet obtained by peeling a plastic film with a release agent or the like is exemplified. 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. As the release agent, silicones, fluorines, long-chain alkyl groups, and the like can be used, and among them, silicones which are inexpensive and can obtain stable performance are preferable.

The thickness of the release sheet is not particularly limited, and may be, for example, 20 μm or more and 250 μm or less.

(4) Others

In the adhesive sheet of the present embodiment, a pressure-sensitive adhesive layer may be laminated on the surface of the pressure-sensitive adhesive layer opposite to the substrate. In this case, the adhesive sheet of the present embodiment can be used as a dicing die. A work is attached to the surface of the adhesive layer of the sheet opposite to the adhesive layer, and the adhesive layer is cut together with the work, whereby a chip having a singulated adhesive layer laminated thereon can be obtained. The chip can be easily fixed to an object to which the chip is to be mounted by the singulated adhesive layer. As a material constituting the pressure-sensitive adhesive layer, a material containing a thermoplastic resin and a low-molecular-weight thermosetting pressure-sensitive adhesive component, a material containing a B-stage (semi-cured) thermosetting pressure-sensitive adhesive component, or the like is preferably used.

In the adhesive sheet of the present embodiment, a protective film-forming layer may be laminated on the adhesive surface of the adhesive layer. In this case, the adhesive sheet of the present embodiment can be used as a protective film forming and cutting sheet. A work is attached to the surface of the protective film forming layer of the sheet opposite to the adhesive layer, and the protective film forming layer is cut together with the work, whereby a chip in which the singulated protective film forming layers are stacked can be obtained. In this case, a protective film forming layer is generally laminated on the surface opposite to the surface on which the circuit is formed. By curing the singulated protective film forming layer at a predetermined timing, a protective film having sufficient durability can be formed on the chip. The protective film-forming layer is preferably composed of an uncured curable adhesive.

2. Method for producing adhesive sheet

The method for producing the adhesive sheet of the present embodiment is not particularly limited. For example, it is preferable that after the adhesive layer is formed on the release sheet, one surface of the substrate is laminated on the surface of the adhesive layer opposite to the release sheet to obtain an adhesive sheet.

The adhesive layer can be formed by a known method. For example, a coating liquid containing an adhesive composition for forming an adhesive layer and further containing a solvent or a dispersion medium as necessary is prepared. Then, the coating liquid is applied to a releasable surface (hereinafter, sometimes referred to as a "releasable surface") of a release sheet. Next, the obtained coating film is dried, whereby an adhesive layer can be formed.

The coating liquid can be applied by a known method, and for example, it can be applied by a bar coating method, a blade coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like. The coating liquid is not particularly limited as long as it can be applied, and may contain a component for forming the adhesive layer as a solute or a component for forming the adhesive layer as a dispersion medium. The release sheet may be released as a process material, or may protect the adhesive layer until the adhesive layer is attached to an adherend.

When the adhesive composition for forming the adhesive agent layer contains the above-mentioned crosslinking agent, it is preferable to cause the polymer component in the coating film and the crosslinking agent to undergo a crosslinking reaction by changing the above-mentioned drying conditions (temperature, time, etc.) or by additionally providing a heating treatment, to form a crosslinked structure in the adhesive agent layer at a desired existing density. Further, in order to sufficiently progress the crosslinking reaction, the adhesive layer may be attached to the substrate and then aged by standing for several days, for example, in an environment of 23 ℃ and a relative humidity of 50%.

3. Method for using adhesive sheet

The adhesive sheet of the present embodiment can be used for various purposes as in a general adhesive sheet, but is particularly suitable for use as a workpiece processing sheet used for processing a workpiece such as a semiconductor wafer. In this case, the work may be processed on the adhesive sheet after the adhesive surface of the adhesive sheet of the present embodiment is attached to the work. The pressure-sensitive adhesive sheet of the present embodiment can be used as a sheet for processing a workpiece such as a back-grinding sheet, a dicing sheet, an expanding sheet, or a picking-up sheet. Examples of the work include semiconductor wafers, semiconductor members such as semiconductor packages, and glass members such as glass plates.

As described above, the adhesive sheet of the present embodiment can be favorably spread. Therefore, the adhesive sheet of the present embodiment is particularly suitable for use as a sheet to be expanded (a dicing sheet, an expanding sheet, a picking sheet, etc.) among the above-described sheets for processing a workpiece.

In addition, when the adhesive sheet of the present embodiment includes the adhesive layer, the adhesive sheet can be used as a dicing die. Further, when the adhesive sheet of the present embodiment includes the protective film forming layer, the adhesive sheet can be used as a protective film forming and dicing sheet.

In addition, when the adhesive layer in the adhesive sheet of the present embodiment is composed of the above-mentioned active energy ray-curable adhesive, it is also preferable to irradiate the following active energy rays at the time of use. That is, when the work is processed on the adhesive sheet and the processed work is separated from the adhesive sheet, it is preferable to irradiate the adhesive layer with an active energy ray before the separation. This cures the adhesive layer, thereby reducing the adhesive force of the adhesive sheet to the processed work satisfactorily, and facilitating the separation of the processed work.

The embodiments described above are described for easy understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiments also includes all design changes and equivalents within the technical scope of the present invention.

Examples

The present invention will be described in more detail with reference to examples and the like, but the scope of the present invention is not limited to these examples and the like.

[ example 1]

(1) Preparation of adhesive composition

160 parts of a silicone-based resin having a product name of "DOWSIL SD 4580", 40 parts of a silicone-based resin having a product name of "DOWSIL 7646", and 1.5 parts of a silicone-based resin having a product name of "DOWSIL SRX 212" (each manufactured by Dow Toray Co., Ltd.) were mixed to obtain a silicone-based adhesive composition.

(2) Formation of adhesive layer

The silicone-based adhesive composition obtained above was applied to a release-treated surface of a release sheet (manufactured by linec Corporation, product name "SP-PET 50E-0010 YC") having a thickness of 50 μm and obtained by subjecting one surface of a polyethylene terephthalate film to a release treatment using a fluorine-based release agent, and the resulting coating film was dried at 100 ℃ for 1 minute. Thus, a laminate in which an adhesive layer having a thickness of 10 μm was formed on the release surface of the release sheet was obtained.

(3) Production of adhesive sheet

One surface of a Polytetrafluoroethylene (PTFE) sheet (manufactured by nicias Corporation, product name "NAFLON PTFE Tape TOMBO 9001", thickness: 100 μm) as a base material was bonded to the adhesive layer side surface of the laminate obtained in the above step (2), thereby obtaining an adhesive sheet.

[ example 2]

(1) Preparation of adhesive composition

A (meth) acrylate polymer was obtained by polymerizing 95 parts by mass of n-butyl acrylate and 5 parts by mass of acrylic acid by a solution polymerization method. The weight average molecular weight (Mw) of the acrylic polymer measured by the method described later was 50 ten thousand.

100 parts by mass of the (meth) acrylate polymer obtained in the above-described manner (hereinafter, the same applies in terms of solid content), 120 parts by mass of urethane acrylate oligomer (Mw: 8,000), 5 parts by mass of an isocyanate-based crosslinking agent (product name "CORONATE L", manufactured by TOSOH CORPORATION) and 4 parts by mass of a photopolymerization initiator (product name "Omnirad 184", manufactured by IGM res b.v.) were mixed to obtain an active energy ray-curable adhesive composition.

(2) Formation of adhesive layer

The adhesive composition obtained in the step (1) was applied to a release-treated surface of a release sheet (manufactured by LINTEC Corporation, product name "SP-PET 381031") having a thickness of 38 μm and obtained by subjecting one surface of a polyethylene terephthalate film to a release treatment using a silicone-based release agent, and the obtained coating film was dried at 100 ℃ for 1 minute. Thus, a laminate in which an adhesive layer having a thickness of 10 μm was formed on the release surface of the release sheet was obtained.

(3) Production of adhesive sheet

One surface of a thermoplastic polyurethane elastomer (TPU) sheet (product name "Elastollan 1164D" manufactured by basf corporation, thickness: 80 μm) as a substrate was bonded to the adhesive layer side surface of the laminate obtained in the step (2), thereby obtaining an adhesive sheet.

Here, the weight average molecular weight (Mw) is a weight average molecular weight in terms of standard polystyrene measured by Gel Permeation Chromatography (GPC) under the following conditions (GPC measurement).

< measurement Condition >

The measurement device: HLC-8320, manufactured by TOSOH CORPORATION

GPC column (run through in the following order): TOSOH CORPORATION, Inc

TSK gel super H-H

TSK gel super HM-H

TSK gel super H2000

Determination of the solvent: tetrahydrofuran (THF)

Measurement temperature: 40 deg.C

[ example 3]

12.90kg of dimethyl 1, 4-cyclohexanedicarboxylate (the proportion of the trans isomer was 98%), 11.47kg of 1, 4-cyclohexanedimethanol, 0.3kg of ethylene glycol and 0.11kg of an ethylene glycol solution containing 10% manganese acetate tetrahydrate were charged into a reactor equipped with a stirrer, a distillation tube and a pressure reducing device, and after heating to 200 ℃ under a nitrogen stream, the temperature was raised to 230 ℃ over 1 hour. After the transesterification was carried out while maintaining this state for 2 hours, 10.30kg of an erucic acid-derived dimer acid (having 44 carbon atoms, manufactured by Croda International Plc, and having a product name of "PRIPOL 1004") and 0.11kg of an ethylene glycol solution containing 10% trimethyl phosphate were added to the reaction system, followed by esterification at 230 ℃ for 1 hour. Then, 300ppm germanium dioxide was added as a polycondensation catalyst and stirred, and then the pressure was reduced to 133Pa or less over 1 hour, during which the internal temperature was raised from 230 ℃ to 270 ℃, and stirred until the viscosity became a predetermined viscosity under high vacuum of 133Pa or less, to perform the polycondensation reaction. The resulting polymer was extruded in water into strands (strand) and cut into pellets.

Pellets of the polyester resin (PEs) obtained in the above manner were dried at 85 ℃ for 4 hours or more, and then placed in a hopper of a single-screw extruder equipped with a T-die. Then, the resin was extruded from the T die in a melt-kneaded state under conditions of a cylinder temperature of 220 ℃ and a die temperature of 220 ℃ and cooled by a cooling roll, thereby obtaining a sheet-like substrate having a thickness of 80 μm. An adhesive sheet was obtained in the same manner as in example 2, except that this substrate was used.

In addition, the above polyester resin contains about 50 mol% of 1, 4-cyclohexanedimethanol, about 40.5 mol% of dimethyl 1, 4-cyclohexanedicarboxylate, and 9.5 mol% of erucic acid-derived dimer acid as monomers constituting the resin. Further, the proportion of the dimer acid to all the dicarboxylic acid units constituting the polyester resin was 19.1 mol%.

Further, the heat of fusion of the above polyester resin measured using a differential scanning calorimeter (DSC manufactured by TA instruments, product name "DSC Q2000") according to JIS K7121: 2012 was 20J/g. In this measurement, first, the sample was heated from room temperature to 250 ℃ at a temperature rising rate of 20 ℃/min and maintained at 250 ℃ for 10 minutes, and then, the temperature was lowered to-60 ℃ at a temperature lowering rate of 20 ℃/min and maintained at-60 ℃ for 10 minutes. Then, the mixture was heated to 250 ℃ again at a temperature rise rate of 20 ℃ per minute to obtain a DSC curve, and the melting point was measured.

[ example 4]

Pellets of polyester resins (PEs) were obtained in the same manner as in example 3. The granules were then dried at 85 ℃ for 4 hours or more. Then, 70 parts by mass of the dried pellets were kneaded with 30 parts by mass of a styrene-ethylene/butylene-styrene copolymer (SBES) (styrene/ethylene-butylene ratio: 20/80, Melt Flow Rate (MFR): 13.0g/10 min (measured at 230 ℃ under a load of 2.16kg according to ISO 1133) as a styrene-based elastomer, using a twin-screw kneader. The granules thus obtained were placed in the hopper of a single screw extruder provided with a T-die. Then, the pellets were extruded from the T-die in a melt-kneaded state under conditions of a cylinder temperature of 220 ℃ and a die temperature of 220 ℃ and cooled by a cooling roll, thereby obtaining a sheet-like substrate having a thickness of 80 μm. An adhesive sheet was obtained in the same manner as in example 2, except that this substrate was used.

Comparative example 1

An adhesive sheet was obtained in the same manner as in example 2, except that a substrate (thickness: 80 μm) composed of an ethylene-methacrylic acid copolymer (EMAA) was used as the substrate.

Comparative example 2

An adhesive sheet was obtained in the same manner as in example 2, except that a substrate (thickness: 80 μm) composed of EMAA and having one surface treated with electron beam irradiation (EB) was used as the substrate, and an adhesive layer was laminated on the surface of the substrate subjected to electron beam irradiation.

[ test example 1] (measurement of tensile Properties of base Material)

With respect to the substrates produced in examples and comparative examples, a total of 18 directions in which the angle formed with the reference direction in the plane of depression is 0 °, 10 °, 20 °, 30 °, 40 °, 50 °, 60 °, 70 °, 80 °, 90 °, 100 °, 110 °, 120 °, 130 °, 140 °, 150 °, 160 °, and 170 ° were determined, with any one direction in the plane of depression of the substrate as the reference direction.

Subsequently, the substrate was cut to obtain 18 kinds of test pieces (15 mm. times.150 mm). In this cutting, the test piece was cut so that the long side of the test piece was parallel to one of the 18 directions.

These test pieces were subjected to a tensile test in the longitudinal direction at a speed of 200 mm/min in an environment of 23 ℃ with a collet pitch of 100mm using a tensile tester (manufactured by Shimadzu Corporation, product name: "Autograph AG-X plus 100N") in accordance with JIS K7127: 1999.

Next, from the results of the above tests, the amount of increase in tensile stress obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation was calculated. Then, for the test piece with the smallest increase, the direction parallel to the long side of the test piece (1 direction out of the above 18 directions) is set as the first measurement direction. In addition, a direction having an angle of 90 ° with respect to the first measurement direction in the plane of view is defined as a second measurement direction. The second measurement direction is substantially parallel to the MD direction of the base material (the flow direction when the base material is manufactured), and the first measurement direction is substantially parallel to the TD direction of the base material (the direction perpendicular to the MD direction).

Then, the base materials prepared in examples and comparative examples were cut again so that the long sides thereof were parallel to the first measurement direction, thereby obtaining test pieces of 15mm × 150 mm. The tensile modulus and elongation at break of the test piece were measured according to JIS K7127: 1999. Specifically, the tensile test was performed on the test piece in a first measurement direction of the base film at a rate of 200 mm/min under an environment of 23 ℃ after setting the collet pitch to 100mm by using a tensile tester (manufactured by Shimadzu Corporation, product name "Autograph AG-Xplus 100N"), and the tensile modulus (MPa) and the elongation at break (%) were measured. These results are shown in table 1 as the tensile modulus and the elongation at break in the first measurement direction.

Further, with respect to the test piece obtained in the same manner as described above, a tensile test of stretching the test piece in the first measurement direction of the base material film was performed at a speed of 200 mm/min under an environment of 23 ℃, and a change in tensile stress (MPa) at which the tensile elongation (%) increased from 0% to 250% was measured.

Then, the tensile stress (MPa) at the time points of 10%, 50%, 100%, 150%, 200% and 250% of the tensile elongation was recorded. Further, an increase (MPa) in tensile stress from a time point when the tensile elongation is 10% to a time point when the tensile elongation is 200% and an increase (MPa) in tensile stress from a time point when the tensile elongation is 100% to a time point when the tensile elongation is 200% were calculated, respectively. Further, the ratio of the tensile stress at the time point when the tensile elongation was 200% to the tensile stress at the time point when the tensile elongation was 100% was calculated. These results are also shown in table 1 as measured values of the tensile physical properties in the first measurement direction.

Further, the tensile stress (MPa) measured in the above manner was plotted on a coordinate plane having the tensile elongation (unit:%) as the horizontal axis and the tensile stress (unit: MPa) as the vertical axis, to prepare a curve. The presence or absence of a maximum point at which the tensile stress becomes maximum in this curve was confirmed, and the results are shown in table 1. Further, when the maximum point exists, it is confirmed that there is a minimum point where the tensile stress becomes a minimum value, and then the absolute value (MPa) of the difference in tensile stress between the maximum point (the maximum point where the tensile elongation is the smallest when there are a plurality of maximum points) and the minimum point (the minimum point where the tensile elongation is the smallest when there are a plurality of minimum points) is determined.

The results are also shown in Table 1.

Further, in the same manner as the above-described method for obtaining a test piece, a test piece for measuring tensile physical properties in the second measurement direction was obtained. That is, a test piece of 15mm × 150mm was cut by cutting the base material so that the 150mm side was parallel to the second measurement direction.

For the test piece thus obtained, the tensile modulus (MPa) was measured in the same manner as described above, and the change in tensile stress (MPa) at the time when the tensile elongation (%) was increased from 0% to 250% was measured. Then, the tensile stress (MPa) at the time points of 10%, 50%, 100%, 150%, 200% and 250% of the tensile elongation was determined from the change in tensile stress (MPa), and the increase (MPa) in tensile stress was calculated from these values. As the increase amounts, four increase amounts of an increase amount from a 10% time point to a 200% time point, an increase amount from a 50% time point to a 150% time point, an increase amount from a 50% time point to a 250% time point, and an increase amount from a 100% time point to a 200% time point were calculated. These results are also shown in table 2 as measured values of the tensile physical properties in the second measurement direction.

[ test example 2] (evaluation of expandability)

The release sheet was peeled from the adhesive sheet produced in examples and comparative examples, and the exposed surface of the exposed adhesive layer was attached to one surface of a silicon wafer having a thickness of 40 μm, and then a dicing ring frame was attached to the peripheral portion of the exposed surface of the adhesive sheet (a position not overlapping with the silicon wafer). Next, the silicon wafer was diced using a dicing saw (manufactured by DISCO Corporation, product name "DFD 6362") under the following conditions.

Workpiece (adherend): silicon wafer

Workpiece size: 6 inches in diameter and 40 μm thick

Cutting blade: manufactured by DISCO Corporation, product name "27 HECC", Diamond blade

Blade rotation speed: 50,000rpm

Cutting speed: 100 mm/sec

Cutting depth: cutting from the surface of the substrate film to a depth of 20 μm

Cut size: 8mm

Then, the adhesive sheet to which the chip obtained by dicing and the loop frame were attached was set in an expanding device (product name "ME-300B" manufactured by JCM, ltd.) and the loop frame was pulled down at a rate of 2 mm/sec until the pull-down amount became 40 mm.

Next, the amount of pull-down (mm) at which the fracture occurred was recorded. Then, 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 pull-down amount (mm) is 40mm or more.

F: the pull-down (mm) is less than 40 mm.

As can be seen from tables 1 and 2, the adhesive sheets produced in the examples exhibited excellent spreadability.

Industrial applicability

The adhesive sheet of the present invention can be suitably used as a workpiece processing sheet used for processing a workpiece such as a semiconductor wafer.

Claims

1. An adhesive sheet comprising a base and an adhesive layer laminated on one surface of the base,

the base material does not contain a chlorine atom,

when any one direction of the plane of the base material is taken as a reference direction, and the direction in which the increase of tensile stress obtained by subtracting the tensile stress at 100% elongation from the tensile stress at 200% elongation is smallest among 18 directions in total of 0 °, 10 °, 20 °, 30 °, 40 °, 50 °, 60 °, 70 °, 80 °, 90 °, 100 °, 110 °, 120 °, 130 °, 140 °, 150 °, 160 °, and 170 ° in the plane of the base material and the reference direction is taken as a first measurement direction,

wherein the tensile stress from 10% elongation to 100% elongation of the base material in the first measurement direction is in the range of 8MPa or more and 30MPa or less,

the substrate has a tensile stress in the first measurement direction from 100% elongation to 200% elongation in a range of 10MPa or more and 40MPa or less.

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

3. The pressure-sensitive adhesive sheet according to claim 1, wherein when a direction which is one direction of a plane of the substrate and forms an angle of 90 ° with the first measurement direction is set as the second measurement direction,

wherein the tensile stress from 10% elongation to 100% elongation of the base material in the second measurement direction is in the range of 5MPa or more and 30MPa or less,

the substrate has a tensile stress in the second measurement direction from 100% to 200% elongation in the range of 10MPa or more and 40MPa or less.

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

5. The adhesive sheet according to any one of claims 1 to 4, wherein the tensile modulus of the substrate in the first measurement direction is 100MPa or more and 1000MPa or less.

6. The adhesive sheet according to any one of claims 1 to 5, wherein the substrate has an elongation at break in the first measurement direction of 100% or more and 1000% or less.

7. The adhesive sheet according to any one of claims 1 to 6, wherein a curve is obtained by plotting the results obtained in a tensile test of the substrate in the first measurement direction on a coordinate plane having a horizontal axis of tensile elongation (unit:%) and a vertical axis of tensile stress (unit: MPa), and wherein, for the curve,

there is no point in the curve that becomes a maximum value, or

At least one point which becomes a maximum value and one point which becomes a minimum value are present in the curve, and the absolute value of the difference between the value of the tensile stress at the point where the tensile elongation is the minimum value among the points which become maximum values and the value of the tensile stress at the point where the tensile elongation is the minimum value among the points which become minimum values is 2.0MPa or less.

8. The adhesive sheet according to any one of claims 1 to 7, wherein the substrate does not contain a halogen atom.

9. The adhesive sheet according to any one of claims 1 to 8, which is used as a sheet for processing a workpiece.

10. The adhesive sheet according to claim 9, wherein the workpiece processing sheet is a dicing sheet.