CN114902378A

CN114902378A - Base material film and sheet for processing workpiece

Info

Publication number: CN114902378A
Application number: CN202180007739.3A
Authority: CN
Inventors: 佐佐木辽; 田矢直纪
Original assignee: Lintec Corp
Current assignee: Lintec Corp
Priority date: 2020-03-30
Filing date: 2021-03-26
Publication date: 2022-08-12
Also published as: KR20220159344A; WO2021200619A1; JPWO2021200619A1; TW202200684A

Abstract

The present invention provides a base film made of a material containing a polyester resin, wherein a measurement result of a tensile test of the base film at a tensile speed of 406 mm/min in an environment of 23 ℃ is plotted on a coordinate plane having a tensile elongation (unit:%) as a horizontal axis and a tensile stress (unit: MPa) as a vertical axis, and with respect to a curve obtained by the plotting, there is no point having a maximum value in the curve, or there is at least one point having a maximum value and one point having a minimum value in the curve, and an absolute value of a difference between a value of the tensile stress at a point having a minimum value of the tensile elongation among the points having a maximum value and a value of the tensile stress at a point having a minimum value of the tensile elongation among the points having a minimum value is 2.0MPa or less. The base film has excellent flexibility enabling good expansion, and a sheet for processing a workpiece which can be expanded well can be obtained from the base film.

Description

Base material film and sheet for processing workpiece

Technical Field

The present invention relates to a base material film and a sheet for processing a workpiece, which can be suitably used as a base material film for a sheet 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, and after being cut (diced) into chips and peeled (picked up), the semiconductor wafers are 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 "work processing sheet") provided with a base material and an adhesive layer.

In the above-described picking-up step, in order to facilitate the picking-up 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 semiconductor chips at the time of picking up and facilitate picking up, the work processing sheet is generally stretched (expanded) to separate the semiconductor chips from each other. Therefore, the workpiece-processing sheet is required to have excellent flexibility that enables good expansion.

Patent documents 1 and 2 disclose inventions based on a workpiece processing sheet developed for the purpose of achieving good expansion. In particular, cited document 1 discloses a dicing film having a base layer and an adhesive layer, the base layer containing a predetermined random polypropylene and a predetermined olefin elastomer under predetermined conditions. Further, reference 2 discloses an adhesive tape in which an adhesive layer, an adhesive coated layer, a thermoplastic elastomer layer and a resin layer are laminated in this order, wherein the thermoplastic elastomer layer is composed of a predetermined resin composition.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5494132

Patent document 2: japanese laid-open patent publication No. 11-199840

Disclosure of Invention

Technical problem to be solved by the invention

The present inventors have studied to use a base film formed using a predetermined polyester resin as a main material as a base film of a sheet for processing a workpiece. The inventors of the present invention have confirmed that such a work processing sheet has various excellent effects including an effect of suppressing the occurrence of cutting pieces at the time of cutting. Further, the inventors of the present invention have found that the usefulness of the base material film can be further improved by improving the expandability of the base material film.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a base film having excellent flexibility which enables good expansion, and a sheet for processing a workpiece which enables good expansion.

Means for solving the problems

In order to achieve the above object, the present invention provides a substrate film comprising a material containing a polyester resin, wherein the measurement result of a tensile test of the substrate film at a tensile rate of 406 mm/min in an environment of 23 ℃ is plotted on a coordinate plane having a tensile elongation (unit:%) as a horizontal axis and a tensile stress (unit: MPa) as a vertical axis, for the curve obtained by drawing, there is no point that becomes a maximum value in the curve, or there is at least one point that becomes a maximum value and one point that becomes a minimum value in the curve, and the absolute value of the difference between the value of the tensile stress at the point at which the tensile elongation is the minimum value among the points having the maximum value and the value of the tensile stress at the point at which the tensile elongation is the minimum value among the points having the minimum value is 2.0MPa or less (invention 1).

The base film of the invention (invention 1) is made of a material containing a polyester resin, and the curve obtained by the tensile test satisfies the above conditions, so that the base film has excellent flexibility, and a sheet for processing a workpiece using the base film can be favorably spread.

In the above invention (invention 1), it is preferable that: a tensile modulus measured in a tensile test of the base film at a tensile rate of 406 mm/min in an environment of 23 ℃ is 50MPa or more and 800MPa or less (invention 2).

In the above inventions (inventions 1 and 2), it is preferable that: a tensile modulus measured in a tensile test of the base film at a tensile rate of 200 mm/min in an environment of 23 ℃ is 50MPa or more and 800MPa or less (invention 3).

In the above invention (inventions 1 to 3), it is preferable that: the elongation at break measured when the substrate film is subjected to a tensile test at a tensile rate of 406 mm/min in an environment of 23 ℃ is 150% or more and 800% or less (invention 4).

In the above inventions (inventions 1 to 4), it is preferable that: the elongation at break measured when the substrate film is subjected to a tensile test at a tensile rate of 200 mm/min in an environment of 23 ℃ is 150% to 800% (invention 5).

In the above invention (inventions 1 to 5), it is preferable that: the content of the polyester resin in the material is 55 mass% or more and 96 mass% or less (invention 6).

In the above inventions (inventions 1 to 6), it is preferable that: the polyester resin has an alicyclic structure (invention 7).

In the above invention (invention 7), it is preferable that: the polyester resin contains a dicarboxylic acid having the alicyclic structure as a monomer unit constituting the polyester resin (invention 8).

In the above inventions (inventions 7 and 8), it is preferable that: the polyester resin contains a diol having the alicyclic structure as a monomer unit constituting the polyester resin (invention 9).

In the above invention (inventions 7 to 9), it is preferable that: the alicyclic structure has 6 to 14 carbon atoms constituting the ring (invention 10).

In the above invention (inventions 1 to 10), it is preferable that: the polyester resin contains, as a monomer unit constituting the polyester resin, a dimer acid obtained by dimerization of an unsaturated fatty acid having 10 or more and 30 or less carbon atoms (invention 11).

In the above inventions (inventions 1 to 11), it is preferable that: the thickness of the base film is 20 μm or more and 600 μm or less (invention 12).

In the above inventions (inventions 1 to 12), it is preferable that: the substrate film is used as a substrate film constituting a sheet for processing a workpiece (invention 13)

The second aspect of the present invention provides a sheet for processing a workpiece, comprising the base film (aspects 1 to 13) and an adhesive layer (aspect 14) laminated on one surface side of the base film.

Effects of the invention

The substrate film of the present invention has excellent flexibility enabling good stretching. Further, the sheet for processing a workpiece of the present invention can be expanded favorably.

Drawings

Fig. 1 is a graph for illustrating the physical properties of the substrate film of the present embodiment.

Detailed Description

Hereinafter, embodiments of the present invention will be described.

[ base film ]

The base film of the present embodiment is composed of a material containing a polyester resin. Further, the measurement results of the tensile test of the substrate film at a tensile rate of 406 mm/min in an environment of 23 ℃ are plotted on a coordinate plane having a tensile elongation (unit:%) as a horizontal axis and a tensile stress (unit: MPa) as a vertical axis, and the obtained curve satisfies any of the following 2 conditions.

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

(condition 2) the curve has at least one point which is a maximum value and one point which is 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 where the tensile elongation is the minimum value among the points which are maximum values and the value of the tensile stress at the point where the tensile elongation is the minimum value among the points which are minimum values is 2.0MPa or less.

The conditions 1 and 2 are described more specifically 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 changes from increasing to decreasing, i.e., there is no 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 is turned to decrease. I.e. curve C ₂ With the maximum point being point a. When the tensile elongation is further increased beyond point a, the tensile stress is shifted from decreasing to increasing and then continues to increase, with point B as a boundary. I.e. curve C ₂ With a minimum point as point B. Here, since the absolute value of the difference between the tensile stress values at the points A and B (the value indicated by "Δ" in FIG. 1) is 2.0MPa or less, the curve C ₂ Condition 2 is satisfied.

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

The base film of the present embodiment is made of a material containing a polyester resin and satisfies either of the above conditions 1 or 2, and therefore has very excellent flexibility. Therefore, when the substrate film of the present embodiment is used as a substrate film of a semiconductor processing sheet, the semiconductor processing sheet can be expanded well. Accordingly, the chip can be easily lifted from the back surface of the chip in the subsequent pickup step, and good pickup can be performed.

However, when neither the above condition 1 nor the above condition 2 is satisfied, for example, when the difference (Δ) in absolute value is greater than 2.0MPa although there is a maximum point, the flexibility of the base material film becomes insufficient, and the stretchability of the semiconductor processing sheet using the base material film also becomes insufficient. Therefore, from the viewpoint of obtaining higher flexibility, the difference (Δ) in absolute value 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 difference (Δ) in absolute value is not particularly limited, and may be, for example, greater than 0.

In addition, in general, when the tensile elongation of the base material film is increased from 0%, even when the tensile stress initially reaches the maximum value, the tensile stress finally continues to increase until the base material film breaks. Therefore, a curve in which the maximum point exists but the minimum point does not exist (i.e., a curve in which the tensile stress is continuously reduced with the maximum point as a boundary) is not generally generated. The details of the measurement method for determining whether or not the above conditions 1 and 2 are satisfied are described in the test examples described below.

The base film of the present embodiment can be used for various purposes, but can achieve the above-described effects, and is particularly suitable as a base for a workpiece processing sheet used in processing a workpiece such as a semiconductor wafer, and particularly suitable as a base for a dicing sheet used in dicing the workpiece.

Further, since the base film of the present embodiment is made of a material containing a polyester resin, the generation of cutting chips can be favorably suppressed even when the work processing sheet made of the base film is used for cutting a work by a rotating circular blade. Such a chip-suppressing effect can be achieved without irradiating the base film of the present embodiment with radiation such as electron beam or γ ray. Therefore, according to the substrate film of the present embodiment, the work processing sheet can be produced at a production cost suppressed to be low as compared with the conventional substrate film produced by the method including the step of irradiating with radiation.

Further, the base film of the present embodiment using the polyester resin as a material has good transparency, and therefore, the work can be easily observed or inspected through the work processing sheet provided with the base film.

1. Material for substrate film

As described above, the base film of the present embodiment is composed of a material containing a polyester resin.

(1) Polyester resin

The specific structure of the polyester resin is not particularly limited, but a polyester resin which easily satisfies the above conditions 1 and 2 and further easily gives a more excellent flexibility to the base film is preferable. From this viewpoint, the polyester resin preferably has an alicyclic structure.

The number of carbon atoms constituting the ring of the alicyclic structure of the polyester resin is preferably 6 or more, from the viewpoint that the base film tends to have more excellent flexibility. 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 having 1 ring, a bicyclic structure having 2 rings, or an alicyclic structure having 3 or more rings.

In addition, from the viewpoint that the base film tends 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 2 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 include dimethyl ester and diethyl ester, and dimethyl ester is particularly preferable.

When the polyester resin in the present embodiment contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting the polyester resin, the ratio of the dicarboxylic acid monomer to all monomer units constituting the polyester resin is preferably 20 mol% or more, more preferably 25 mol% or more, particularly preferably 30 mol% or more, and further preferably 35 mol% or more. The ratio is preferably 60 mol% or less, more preferably 55 mol% or less, particularly preferably 50 mol% or less, and further preferably 45 mol% or less. By making it within these ranges, the substrate film of the present embodiment is liable to have more excellent flexibility.

When the polyester resin in the present embodiment contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting the polyester resin, the proportion of the dicarboxylic acid having an alicyclic structure to the whole dicarboxylic acid having a ring structure constituting the polyester resin is preferably 60% or more, more preferably 70% or more, particularly preferably 80% or more, and further preferably 90% or more. By setting the above ratio to 60% or more, the substrate film of the present embodiment is likely to have more excellent flexibility. The upper limit of the ratio is not particularly limited, and may be, for example, 100% or less. Further, the dicarboxylic acid having a ring structure includes a dicarboxylic acid having an aromatic ring structure, in addition to a dicarboxylic acid having an alicyclic structure.

The structure of the diol is not particularly limited as long as it has 2 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 or the like 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.

When the polyester resin in the present embodiment contains a diol having an alicyclic structure as a monomer unit constituting the diol, the proportion of the diol monomer to all monomer units constituting the polyester resin is preferably 35 mol% or more, particularly preferably 40 mol% or more, and further preferably 45 mol% or more. The ratio is preferably 65 mol% or less, particularly preferably 60 mol% or less, and further preferably 55 mol% or less. By making it within these ranges, the substrate film of the present embodiment is liable to have more excellent flexibility.

In the polyester resin of the present embodiment, it is preferable that the polyester resin 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 film is likely to have more excellent flexibility. 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 dimerization of unsaturated fatty acids having 18 carbon atoms such as oleic acid and linoleic acid; dicarboxylic acid having 44 carbon atoms obtained by dimerization of unsaturated fatty acid 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 in the present embodiment may contain such a trimer acid in addition to the above dimer acid.

When the polyester resin in the present embodiment contains the dimer acid as a monomer unit constituting the dimer acid, the ratio of the dimer acid to all dicarboxylic acid units constituting the polyester resin is preferably 2 mol% or more, particularly preferably 5 mol% or more, and more preferably 10 mol% or more. The ratio is preferably 25 mol% or less, particularly preferably 23 mol% or less, and further preferably 20 mol% or less. When the amount of the organic solvent is within these ranges, the polyester resin tends to have desired flexibility, and as a result, the base film of the present embodiment tends to have more excellent flexibility.

The polyester resin in the present embodiment may contain monomers other than the above-mentioned dicarboxylic acid, diol and dimer acid as monomer units constituting the same. 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.

However, in the polyester resin in the present embodiment, it is preferable that the alicyclic structure-containing monomer (the alicyclic structure-containing dicarboxylic acid or the aliphatic structure-containing diol) is contained in a larger amount than the aromatic ring structure-containing monomer in view of easily achieving more excellent flexibility. In particular, in the monomer units constituting the polyester resin in the present embodiment, the molar ratio of the monomer unit having an aromatic ring structure to the monomer unit having an alicyclic structure is preferably less than 1, more preferably 0.5 or less, more preferably 0.2 or less, more preferably 0.1 or less, more preferably 0.05 or less, more preferably 0.03 or less, more preferably 0.01 or less, particularly preferably 0.005 or less, further preferably 0.001 or less, and most preferably 0.

Further, the heat of fusion of the polyester resin in the present embodiment, which is 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 further preferably 15J/g or more. When the heat of fusion is 2J/g or more, the crystallinity of the base film is moderately increased, and the base film has more excellent handling properties 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 most preferably 30J/g or less. By making the heat of fusion 150J/g or less, the substrate film of the present embodiment is liable to have more excellent flexibility. The details of the method for measuring the heat of fusion are described in the section of examples below.

The method for producing the polyester resin in the present embodiment is not particularly limited, and the polyester resin can be obtained by polymerizing the monomer components using a known catalyst.

The content of the polyester resin in the material constituting the base film of the present embodiment is preferably 55% by mass or more, particularly preferably 60% by mass or more, and more preferably 65% by mass or more. The content is preferably 96% by mass or less, particularly preferably 94% by mass or less, and more preferably 92% by mass or less. When the content of the polyester resin in the material is within the above range, the base film formed using the material tends to have more excellent flexibility.

(2) Elastic body

The material for producing the base film of the present embodiment preferably contains an elastomer in addition to the polyester resin. By containing an elastomer in the material, the above conditions 1 and 2 are easily satisfied, and the base material film is easily provided with more excellent flexibility.

The elastomer in the present embodiment is not particularly limited, and may be a thermosetting elastomer or a thermoplastic elastomer, but a thermoplastic elastomer is preferable because the base film in 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, acrylic elastomers, urethane-based elastomers, olefin-based elastomers, polyester-based elastomers, silicone-based elastomers and the like can be used. These elastomers may be used alone, or two or more of them may be used in combination. Among the above elastomers, from the viewpoint of facilitating more excellent flexibility, at least 1 of styrene-based elastomers, acrylic elastomers, urethane-based elastomers and olefin-based elastomers is preferably used, particularly at least 1 of styrene-based elastomers, acrylic elastomers and urethane-based elastomers is preferably used, and styrene-based elastomers are more preferably used. In addition, a urethane elastomer is preferably used because it is easy to adjust the physical properties of the base film to a desired range.

In the present specification, the "styrene-based elastomer" is a copolymer containing a structural unit derived from styrene or a derivative thereof (styrene-based compound), and is a material having rubbery elasticity and having thermoplastic properties in a temperature region including normal temperature.

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 achieving more satisfactory flexibility, styrene-conjugated diene copolymers are preferred, hydrogenated styrene-conjugated diene copolymers are preferred, and styrene-ethylene/butylene-styrene copolymers are more preferably used.

When a styrene-ethylene/butylene-styrene copolymer is used, the styrene content in the copolymer is preferably 3% by mass or more, particularly preferably 5% by mass or more, and more preferably 10% by mass. The styrene content is preferably 60% by mass or less, particularly preferably 50% by mass or less, and more preferably 40% by mass or less. By using the styrene-ethylene/butylene-styrene copolymer having the styrene content within the above range, the substrate film of the present embodiment is liable to have more excellent flexibility.

In the present specification, the "acrylic elastomer" is a copolymer containing a structural unit derived from acrylic acid or a derivative thereof (acrylic compound), and is a material having rubbery elasticity and having thermoplasticity in a temperature region including normal temperature.

Examples of the acrylic elastomer include (meth) acrylic diblock copolymers and (meth) acrylic triblock copolymers. The copolymer has the following structure: a structure in which a hard segment (hard segment) made of polymethyl methacrylate (PMMA) and capable of simulating crosslinking is connected to one end or both ends of a relatively soft segment (soft segment) made of polybutyl acrylate (PBA) or 2-ethylhexyl acrylate (2 EHA). Among them, from the viewpoint of the strength of the film, a (meth) acrylic triblock copolymer is preferable.

Examples of the (meth) acrylic triblock copolymer include polymethyl methacrylate (PMMA) -polybutyl acrylate (PBA) -polymethyl methacrylate (PMMA), polymethyl methacrylate (PMMA) -poly (2-ethylhexyl acrylate) -polymethyl methacrylate (PMMA), and the like.

When the (meth) acrylic triblock copolymer having a segment of PMMA as described above is used as the acrylic elastomer, the ratio of the methyl methacrylate monomer to all monomers constituting the copolymer (MMA ratio) is preferably 10% by weight or more, particularly preferably 20% by weight or more, and further preferably 30% by weight or more. The MMA ratio is preferably 80% or less, particularly preferably 70% or less by weight, and more preferably 60% or less by weight. By using a (meth) acrylic triblock copolymer having an MMA ratio within the above range, the substrate film of the present embodiment tends to have more excellent flexibility.

In the present specification, the "urethane-based elastomer" is a copolymer containing a structural unit derived from a urethane compound or a derivative thereof (urethane-based compound), and is a material having rubbery elasticity and having thermoplasticity in a temperature range including normal temperature.

In particular, urethane elastomers are generally obtained by reacting a long-chain polyol, a chain extender, and a polyisocyanate, and are composed of a soft segment having a structural unit derived from the long-chain polyol, and a hard segment having a polyurethane structure obtained by reacting the chain extender and the polyisocyanate.

When urethane elastomers are classified according to the type of long-chain polyol used as a soft segment component thereof, they can be classified into polyester polyurethane elastomers, polyether polyurethane elastomers, polycarbonate polyurethane elastomers, and the like.

Examples of the long-chain polyol include polyester polyols such as lactone-type polyester polyol and adipate-type polyester polyol; polyether polyols such as polypropylene (ethylene) polyol and polytetramethylene ether glycol; polycarbonate polyols, and the like.

Examples of the polyisocyanate include 2, 4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, 4' -diphenylmethane diisocyanate, and hexamethylene diisocyanate.

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

In the present specification, the "olefin-based elastomer" is a copolymer containing a structural unit derived from an olefin or a derivative thereof (olefin-based compound), and is a material having rubber-like elasticity and having thermoplastic properties in a temperature range including normal temperature.

As the olefinic elastomer, olefinic elastomers containing at least 1 resin selected from the group consisting of ethylene- α -olefin copolymers, propylene- α -olefin copolymers, butene- α -olefin copolymers, ethylene-propylene- α -olefin copolymers, ethylene-butene- α -olefin copolymers, propylene-butene- α -olefin copolymers, and ethylene-propylene-butene- α -olefin copolymers are cited.

The content of the elastomer in the material constituting the substrate film of the present embodiment is preferably 4% by mass or more, particularly preferably 6% by mass or more, and more preferably 8% by mass or more. By setting the content of the elastomer in the material to 4 mass% or more, the base film formed using the material tends to have more excellent flexibility. The content is preferably 45% by mass or less, particularly preferably 40% by mass or less, and more preferably 35% by mass or less. When the content of the elastomer in the material is 45 mass% or less, the material can be used to easily form a base film and can easily achieve an excellent blade-suppressing effect.

(3) Other ingredients

The material for producing the base film of the present embodiment may contain other components than the polyester resin and the elastomer. In particular, the material may contain a component of a base film generally used for a sheet for processing a workpiece.

Examples of such components include various additives such as flame retardants, plasticizers, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, and ion scavengers. The content of these additives is not particularly limited, but is preferably within a range in which the base film exhibits a desired function.

(4) Constitution of substrate film

The layer structure of the base film of the present embodiment may be a single layer or a plurality of layers as long as it includes a layer made of a material containing the polyester resin (hereinafter, sometimes referred to as "resin layer a"). The substrate film in the present embodiment is preferably a single layer (only the resin layer a) from the viewpoint of reduction in manufacturing cost. On the other hand, in the case of a plurality of layers, a plurality of resin layers a may be stacked, or a resin layer a and layers other than the same may be stacked.

In addition, the surface of the base film on which the adhesive layer is laminated may be subjected to surface treatment such as undercoating treatment, corona treatment, or plasma treatment in order to improve adhesion to the adhesive layer.

2. Physical properties of the base film and the like

The tensile modulus of the substrate film in the present embodiment measured in a tensile test at a tensile rate of 200 mm/min in an environment of 23 ℃ is preferably 800MPa or less, particularly preferably 600MPa or less, and more preferably 500MPa or less. When the tensile modulus is 800MPa or less, the above conditions 1 and 2 are easily satisfied, and the substrate film of the present embodiment is easily made to have more excellent flexibility. The tensile modulus is preferably 50MPa or more, more preferably 100MPa or more, particularly preferably 150MPa or more, further preferably 200MPa or more, further more preferably 250MPa or more, and most preferably 300MPa or more. Further, by setting the tensile modulus to 100MPa or more, the base film of the present embodiment is likely to have an appropriate strength, and a sheet for workpiece processing provided with the base film has good handling properties and is likely to perform desired workpiece processing well.

The tensile modulus of the substrate film in the present embodiment measured in a tensile test at a tensile rate of 406 mm/min in an environment of 23 ℃ is preferably 800MPa or less, particularly preferably 600MPa or less, and more preferably 500MPa or less. When the tensile modulus is 800MPa or less, the above-mentioned conditions 1 and 2 are easily satisfied, and the substrate film of the present embodiment is easily provided with more excellent flexibility. The tensile modulus is preferably 50MPa or more, more preferably 100MPa or more, particularly preferably 150MPa or more, further preferably 200MPa or more, further more preferably 250MPa or more, and most preferably 300MPa or more. Further, by setting the tensile modulus to 50MPa or more, the base film of the present embodiment is likely to have an appropriate strength, and a sheet for workpiece processing provided with the base film has good handling properties and is likely to perform desired workpiece processing well. In the present specification, the drawing speed of 406 mm/min represents a value obtained by converting the stress speed of the workpiece-processing sheet under normal stretching conditions into a drawing speed.

The substrate film in the present embodiment preferably has a stress at break point of 60MPa or less, particularly preferably 50MPa or less, and more preferably 40MPa or less, as measured in a tensile test at a tensile rate of 200 mm/min in an environment of 23 ℃. By setting the breaking point stress to 60MPa or less, the substrate film of the present embodiment has better workability. The breaking point stress is preferably 5MPa or more, more preferably 10MPa or more, particularly preferably 15MPa or more, further preferably 20MPa or more, and most preferably 25MPa or more. By setting the breaking point stress to 15MPa or more, the base film of the present embodiment is likely to have an appropriate strength, and a sheet for workpiece processing having the base film has good handling properties and is likely to perform desired workpiece processing well. Further, the substrate film of the present embodiment has good extensibility by setting the breaking point stress to 15MPa or more.

The breaking point stress of the substrate film in the present embodiment measured in a tensile test at a tensile rate of 406 mm/min in an environment of 23 ℃ is preferably 60MPa or less, particularly preferably 50MPa or less, and more preferably 40MPa or less. By setting the breaking point stress to 60MPa or less, the substrate film of the present embodiment has better workability. The breaking point stress is preferably 5MPa or more, particularly preferably 10MPa or more, further preferably 15MPa or more, preferably 20MPa or more, and preferably 25MPa or more. By setting the breaking point stress to 5MPa or more, the base film of the present embodiment is likely to have an appropriate strength, and a sheet for workpiece processing having the base film has good handling properties and is likely to perform desired workpiece processing well. Further, the base material film of the present embodiment has good extensibility by setting the breaking point stress to 5MPa or more.

The elongation at break of the substrate film in the present embodiment is preferably 150% or more, more preferably 200% or more, particularly preferably 250% or more, further preferably 300% or more, and most preferably 350% or more, as measured in a tensile test at a tensile rate of 200 mm/min in an environment of 23 ℃. By setting the elongation at break to 200% or more, the base material film in the present embodiment is likely to have desired extensibility, and a work processing sheet provided with the base material film is likely to realize excellent extensibility and pickup properties. The elongation at break is preferably 800% or less, more preferably 700% or less, particularly preferably 600% or less, and further preferably 500% or less. By setting the elongation at break to 800% or less, the processability of the base film is further improved, and the desired sheet for processing a workpiece can be easily produced.

The elongation at break of the substrate film in the present embodiment is preferably 150% or more, particularly preferably 200% or more, further preferably 250% or more, preferably 300% or more, and preferably 350% or more, as measured in a tensile test at a tensile rate of 406 mm/min in an environment of 23 ℃. By setting the elongation at break to 150% or more, the base material film in the present embodiment is likely to have desired extensibility, and a work processing sheet provided with the base material film is likely to realize excellent extensibility and pickup properties. The elongation at break is preferably 800% or less, particularly preferably 700% or less, further preferably 600% or less, and preferably 500% or less. By setting the elongation at break to 800% or less, the processability of the base film is further improved, and the desired sheet for processing a workpiece can be easily produced.

The details of the methods for measuring the tensile modulus, the stress at break and the elongation at break are described in the test examples below.

The thickness of the substrate film of 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 film 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 film to 20 μm or more, the workpiece-processing sheet provided with the base material film is likely to have appropriate strength, and the workpiece fixed to the workpiece-processing sheet is likely to be supported well. As a result, occurrence of chipping (chipping) during dicing can be effectively suppressed. Further, the above elongation at break can be easily achieved by setting the thickness of the base film to 600 μm or less. Further, the thickness of the base film is set to 600 μm or less, whereby the base film has more excellent workability.

3. Method for producing base material film

The method for producing the base film of the present embodiment is not particularly limited as long as the material containing the polyester resin is used, 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 film composed of a single layer is produced by a melt extrusion method, a material of the substrate film (a material containing the polyester resin and the elastomer) is kneaded and film-formed directly from the obtained kneaded product by using a known extruder, or a mixture obtained by kneading a material of the substrate film is previously produced into pellets (pellets) and film-formed by using a known extruder.

In the case of producing a substrate film composed of a plurality of layers by the melt extrusion method, the components constituting each layer may be kneaded and the plurality of layers may be simultaneously extruded directly from the obtained kneaded mass by using a known extruder to form a film, or the components constituting each layer may be kneaded and the obtained kneaded mass may be granulated and then the plurality of layers may be simultaneously extruded by using a known extruder to form a film.

[ sheet for processing work ]

The work processing sheet of the present embodiment includes the base film and an adhesive layer laminated on one surface of the base film.

1. Structure of sheet for working workpiece

Hereinafter, the structure of the member constituting the sheet for processing a workpiece according to the present embodiment, excluding the base film, will be described.

(1) Adhesive layer

The adhesive constituting the adhesive layer is not particularly limited as long as it can exhibit sufficient adhesive force to an adherend (particularly, 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 them, acrylic adhesives are preferably used from the viewpoint of easily exhibiting a 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 strength of the work processing sheet to the adherend can be easily reduced. In particular, the workpiece after processing 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 an active energy ray-curable polymer 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, the term (meth) acrylic acid means acrylic acid and methacrylic acid. The same is true for other similar terms. Further, "polymer" also encompasses 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 more, and more preferably 150 ten thousand or less.

When ultraviolet rays are used as the active energy ray 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 in 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 work processing sheet of the present embodiment easily exhibits desired adhesiveness. Further, by setting the thickness of the adhesive agent layer to 50 μm or less, separation of the adherend from the cured adhesive agent layer is facilitated.

(2) Release sheet

In the work processing sheet of the present embodiment, before a surface of the adhesive agent layer opposite to the base film (hereinafter, sometimes referred to as "adhesive surface") is attached to an adherend, a release sheet may be laminated on the surface for the purpose of protecting the surface.

The above-mentioned release sheet is optional, and for example, a release sheet obtained by peeling a plastic film with a peeling agent or the like can be 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 provide 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.

(3) Others

In the work processing sheet of the present embodiment, the pressure-sensitive adhesive layer may be laminated on the surface of the pressure-sensitive adhesive layer opposite to the base film. In this case, the work processing 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 work processing 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 work processing 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 manufacturing sheet for processing workpiece

The method for producing the workpiece-processing sheet of the present embodiment is not particularly limited. For example, it is preferable to obtain a sheet for processing a work by forming an adhesive layer on a release sheet and then laminating one surface of a base film on a surface of the adhesive layer opposite to the release 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 sheet for processing workpiece

The workpiece processing sheet of the present embodiment can be used for processing a workpiece such as a semiconductor wafer. In this case, the workpiece can be processed on the workpiece processing sheet after the adhesive surface of the workpiece processing sheet of the present embodiment is attached to the workpiece. The work processing sheet of the present embodiment can be used as a work processing sheet such as a back grinding sheet, a dicing sheet, an expanding sheet, a picking sheet, and the like. Examples of the work include semiconductor wafers, semiconductor members such as semiconductor packages, and glass members such as glass plates.

As described above, the sheet for processing a workpiece according to the present embodiment can be favorably expanded because the base film has favorable flexibility. Therefore, the sheet for workpiece processing of the present embodiment is particularly suitable for use as a dicing sheet, an expanding sheet, or a pickup sheet.

In addition, when the work processing sheet of the present embodiment is provided with the above adhesive agent layer, the work processing sheet can be used as a dicing die. Further, when the work processing sheet of the present embodiment is provided with the above-described protective film forming layer, the work processing sheet can be used as a protective film forming and cutting sheet.

When the adhesive layer in the work processing sheet of the present embodiment is composed of the active energy ray-curable adhesive, it is also preferable to perform the following irradiation with an active energy ray during use. That is, when the workpiece is machined on the workpiece-machining sheet and the machined workpiece is separated from the workpiece-machining sheet, it is preferable that the adhesive agent layer is irradiated with an active energy ray before the separation. This cures the adhesive layer, thereby reducing the adhesive force of the work processing sheet to the processed work satisfactorily, and facilitating 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) Production of substrate film

12.90kg of dimethyl 1, 4-cyclohexanedicarboxylate (the ratio of trans-isomer: 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, under the product name "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.

The pellets of the polyester resin thus obtained were 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 (SEBS) (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 by using a twin-screw kneader. The pellets thus obtained were fed into the hopper of a single screw extruder provided with a T-die. Then, the pellets were extruded from a T-die in a melt-kneaded state under conditions of a cylinder (cylinder) temperature of 220 ℃ and a die temperature of 220 ℃ and were cooled by a cooling roll, thereby obtaining a sheet-like substrate film having a thickness of 80 μm.

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 polyester resin was measured by the method described later, and the result was 20J/g.

(2) 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 was measured by the method described below, and found to be 50 ten thousand.

An energy ray-curable adhesive composition was obtained by mixing 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 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 b.v., company, product name "Omnirad 184").

(3) Formation of adhesive layer

The adhesive composition obtained in the step (2) was applied to a release-treated surface of a release sheet (product name "SP-PET 381031" manufactured by linetec Corporation) 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, the thickness of which was 38 μm. 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.

(4) Production of sheet for workpiece processing

The sheet for processing a workpiece is obtained by bonding one surface of the base film obtained in the step (1) to the surface of the adhesive layer side of the laminate obtained in the step (3).

Here, the heat of fusion of the polyester resin was measured using a differential scanning calorimeter (DSC, manufactured by TA Instruments, product name "DSC Q2000") in accordance with JIS K7121: 2012.

Specifically, first, the steel sheet is heated from room temperature to 250 ℃ at a temperature rising rate of 20 ℃/min and maintained at 250 ℃ for 10 minutes, and is reduced 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.

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 2]

A base material film was produced in the same manner as in example 1, except that the ratio of the mass parts of the dried polyester resin particles to SEBS was changed to 80:20 in the step of producing the base material film, and a sheet for workpiece processing was obtained in the same manner as in example 1 using this base material film.

[ example 3]

A base material film was produced in the same manner as in example 1, except that the ratio of the mass parts of the dried polyester resin particles to SEBS was changed to 90:10 in the step of producing the base material film, and a sheet for workpiece processing was obtained in the same manner as in example 1 using this base material film.

[ example 4]

In the same manner as in the step (1) of example 1, pellets of the completely dried polyester resin were obtained. 80 parts by mass of the pellets were kneaded with 20 parts by mass of a triblock copolymer of Polymethacrylate (PMMA) -Polybutylacrylate (PBA) -Polymethacrylate (PMMA) as an acrylic elastomer (pellets, MMA ratio: 50 wt%, Melt Flow Rate (MFR) 31.0g/10 min (measured at 230 ℃ C. under a load of 2.16kg according to ISO 1133)) 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 a 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 film having a thickness of 80 μm. A sheet for workpiece processing was obtained in the same manner as in example 1, except that this base material film was used.

[ example 5]

In the same manner as in the step (1) of example 1, pellets of the completely dried polyester resin were obtained. 80 parts by mass of the pellets were kneaded with 20 parts by mass of a thermoplastic polyurethane elastomer (manufactured by BASF JAPAN company, product name "Elastollan ET 164D") as a urethane-based elastomer using a twin-screw kneader. The pellets thus obtained were fed into the hopper of a single screw extruder provided with a T-die. Then, the pellets were extruded from a 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 film having a thickness of 80 μm. A sheet for workpiece processing was obtained in the same manner as in example 1, except that this base material film was used.

Comparative example 1

A base material film was produced in the same manner as in example 1, except that in the step of producing a base material film, a base material film was produced without using SEBS (the base material film was produced by separately feeding pellets of the dried polyester resin into a hopper of a single screw extruder provided with a T-die), and a sheet for processing a workpiece was obtained in the same manner as in example 1 using the base material film.

Comparative example 2

A sheet for workpiece processing was obtained in the same manner as in example 1, except that a resin sheet having a thickness of 80 μm produced using an alcohol-modified polyester resin having a structure represented by the following general formula (1) was used as a base material. The heat of fusion of the above alcohol-modified polyester resin was measured by the aforementioned method and found to be 0J/g.

[ chemical formula 1]

Comparative example 3

A sheet for workpiece processing was obtained in the same manner as in example 1, except that a resin sheet having a thickness of 80 μm, which was produced using an amorphous polyester resin having a structure represented by the following general formula (2), was used as a base material. The heat of fusion of the amorphous polyester resin was measured by the method described above, and the result was 0J/g.

[ chemical formula 2]

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

The substrate films prepared in examples and comparative examples were cut into test pieces of 15mm × 150 mm. At this time, the cutting was performed so that the 150mm side was parallel to the MD direction of the base material film (longitudinal direction when the base material film was produced), and the 15mm side was parallel to the TD direction of the base material film (direction perpendicular to the MD direction). Then, the tensile modulus, elongation at break and stress at break of the test piece were measured in accordance with JIS K7127: 1999.

Specifically, the tensile modulus (MPa), the elongation at break (%), and the stress at break (MPa) were measured by subjecting the test piece to a tensile test in which the test piece was pulled in the MD direction of the base film at a speed of 200 mm/min under an environment of 23 ℃ after setting the collet pitch to 100mm using a tensile tester (manufactured by Shimadzu Corporation, product name "Autograph AG-X plus 100N"). These results are shown in Table 1 as the results of the drawing speed of 200 mm/min.

Further, a tensile test was performed in the same manner as described above except that the speed of stretching was changed to 406 mm/min, and the tensile modulus (MPa), elongation at break (%), and stress at break (MPa) were measured. These results are shown in Table 1 as the results of the drawing speed of 406 mm/min. In comparative examples 2 and 3, the absolute value of the difference in tensile stress between the maximum value point and the minimum value point described below was finally significantly higher than 2.0. Therefore, comparative examples 2 and 3 were not measured because it was judged that it is not important to investigate in detail the tensile modulus, elongation at break and stress at break at a tensile rate of 406 mm/min.

Further, a test piece was obtained from the base film in the same manner as described above except that the TD direction and the MD direction were interchanged (i.e., a test piece having a side parallel to the MD direction and a side parallel to the TD direction and having a length of 150mm was obtained). With respect to this test piece, a tensile test was conducted by stretching the test piece in the TD direction of the base film at a stretching speed of 406 mm/min, and the variation of tensile stress (MPa) was measured when the tensile elongation (%) was increased from 0% to 640% (when the base film was judged before reaching 640%, the tensile elongation (%) was increased from 0% to breakage). Then, the measurement results were plotted on a coordinate plane having a tensile elongation (unit:%) as a horizontal axis and a tensile stress (unit: MPa) as a vertical axis, to prepare a curve. The curve was checked for the presence of a maximum point at which the tensile stress was maximum, 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.

[ test example 2] (evaluation of expandability)

The release sheet was peeled from the workpiece processing sheets manufactured in examples and comparative examples, 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 (a position not overlapping with the silicon wafer) of the exposed surface of the workpiece processing sheet. Next, the silicon wafer was cut 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 work piece processing sheet to which the chip obtained by dicing and the ring frame were attached was set in an expanding apparatus (product name "ME-300B" manufactured by JCM) and the ring frame was pulled down at a speed of 2 mm/sec until the pull-down amount became 40 mm.

Then, the amount of pull-down (mm) at which the fracture occurred was recorded. The results are shown in table 1 as the ultimate pull-down amounts. Further, the work piece was shown to be "40 or more" which did not break even when the pull-down amount reached 40 mm.

As can be seen from table 1, the workpiece-processing sheets produced in the examples exhibited excellent expandability.

Industrial applicability

The base material film of the present invention can be suitably used as a base material film constituting a sheet for processing a workpiece used in processing a workpiece such as a semiconductor wafer.

Claims

1. A substrate film comprising a material containing a polyester resin,

the measurement results of the tensile test of the base film at a tensile speed of 406 mm/min in an environment of 23 ℃ were plotted on a coordinate plane having a horizontal axis of tensile elongation (unit:%) and a vertical axis of tensile stress (unit: MPa), and for the obtained curve,

there is no point in the curve that becomes maximum, 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.

2. The substrate film according to claim 1, wherein a tensile modulus measured when the substrate film is subjected to a tensile test at a tensile rate of 406 mm/min in an environment of 23 ℃ is 50MPa or more and 800MPa or less.

3. The substrate film according to claim 1 or 2, wherein a tensile modulus measured when the substrate film is subjected to a tensile test at a tensile rate of 200 mm/min in an environment of 23 ℃ is 50MPa or more and 800MPa or less.

4. The substrate film according to any one of claims 1 to 3, wherein the elongation at break measured when the substrate film is subjected to a tensile test at a tensile rate of 406 mm/min in an environment of 23 ℃ is 150% or more and 800% or less.

5. The substrate film according to any one of claims 1 to 4, wherein the elongation at break measured when the substrate film is subjected to a tensile test at a tensile rate of 200 mm/min in an environment of 23 ℃ is 150% or more and 800% or less.

6. The base material film according to any one of claims 1 to 5, wherein the content of the polyester resin in the material is 55 mass% or more and 96 mass% or less.

7. The substrate film according to any one of claims 1 to 6, wherein the polyester resin has an alicyclic structure.

8. The substrate film according to claim 7, wherein the polyester resin contains a dicarboxylic acid having the alicyclic structure as a monomer unit constituting the polyester resin.

9. The substrate film according to claim 7 or 8, wherein the polyester resin contains a diol having the alicyclic structure as a monomer unit constituting the polyester resin.

10. The substrate film according to any one of claims 7 to 9, wherein the number of carbon atoms constituting a ring of the alicyclic structure is 6 or more and 14 or less.

11. The substrate film according to any one of claims 1 to 10, wherein the polyester resin contains, as a monomer unit constituting the polyester resin, a dimer acid obtained by dimerization of an unsaturated fatty acid,

the unsaturated fatty acid has 10 to 30 carbon atoms.

12. The substrate film according to any one of claims 1 to 11, wherein the thickness of the substrate film is 20 μm or more and 600 μm or less.

13. The substrate film according to any one of claims 1 to 12, which is used as a substrate film constituting a sheet for processing a workpiece.

14. A sheet for processing a workpiece, comprising the base film according to any one of claims 1 to 13 and an adhesive layer laminated on one surface side of the base film.