Base film and workpiece processing sheet

Abstract

To provide a base material film and a sheet for workpiece processing which can achieve both antistatic properties and mechanical strength.SOLUTION: A base material film has a resin layer containing a polyester resin, a polymer type antistatic agent and a carbon nanotube. The content of the polymer type antistatic agent in the resin layer is preferably 0.1 mass% or more and 50 mass% or less, and the content of the carbon nanotube in the resin layer is preferably 0.001 mass% or more and 1 mass% or less. The polyester resin preferably has an alicyclic structure, and has a heat quantity of melting measured at a rate of temperature rise of 20°C / min by differential scanning calorimetry of 2 J / g or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a base film that can be suitably used as a base film for a workpiece processing sheet used for processing workpieces such as semiconductor wafers, and to the workpiece processing sheet itself. [Background technology]

[0002] Semiconductor wafers such as silicon and gallium arsenide, as well as various packages, are manufactured in a large diameter state, cut into chips (dicing), and then peeled off (picked up) before being moved to the next process, the mounting process. During this process, the semiconductor wafer and other workpieces are attached to an adhesive sheet (hereinafter sometimes referred to as a "workpiece processing sheet") which has a base film and an adhesive layer, and then processed with backgrinding, dicing, washing, drying, expanding, picking up, and mounting.

[0003] In this process, the workpiece processing sheet is peeled off from the workpiece after the predetermined processing steps are completed. At this time, static electricity called peeling charge may be generated between the workpiece processing sheet and the workpiece. Such static electricity can cause dust and other debris to adhere to the workpiece and equipment, and can also cause damage to the workpiece. Therefore, antistatic properties are required for workpiece processing sheets.

[0004] Patent Document 1 discloses a substrate for adhesive tape containing a resin material and a conductive material, with specified surface resistivity and volume resistivity, in order to effectively suppress or prevent static electricity from being generated on the attached substrate (workpiece). Examples of the conductive material disclosed include conductive polymers and permanent antistatic polymers (IDPs). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-015953 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, generally speaking, when the proportion of conductive materials, particularly permanent antistatic polymers, blended into a resin material increases, the mechanical strength of the resulting resin film tends to decrease. Therefore, in the adhesive tape substrate disclosed in Patent Document 1, if a large amount of permanent antistatic polymer is blended to obtain sufficient antistatic properties, the mechanical strength of the substrate film for workpiece processing will decrease, and there is a risk of breakage during processes such as the aforementioned expansion.

[0007] This invention has been made in view of the above circumstances, and aims to provide a base film and a workpiece processing sheet that can achieve both antistatic properties and mechanical strength. [Means for solving the problem]

[0008] To achieve the above objective, firstly, the present invention provides a base film comprising a resin layer containing a polyester resin, a polymer-type antistatic agent, and carbon nanotubes (Invention 1).

[0009] In the above invention (Invention 1), by blending a polymer-type antistatic agent and carbon nanotubes with a polyester resin matrix, conductive paths are efficiently formed, and the surface resistivity is effectively reduced. Therefore, to obtain the desired antistatic properties, it is sufficient to blend only small amounts of the polymer-type antistatic agent and carbon nanotubes. This suppresses a decrease in the mechanical strength of the base film, particularly the elongation at break, caused by these components, and prevents breakage during processes such as expansion. Thus, the base film according to the above invention makes it possible to achieve both antistatic properties and mechanical strength.

[0010] In the above invention (Invention 1), it is preferable that the content of the polymer-type antistatic agent in the resin layer is 0.1% by mass or more and 50% by mass or less, and the content of the carbon nanotubes in the resin layer is 0.001% by mass or more and 1% by mass or less (Invention 2).

[0011] In the above inventions (Inventions 1 and 2), it is preferable that the polyester resin has an alicyclic structure and that the heat of fusion measured by differential scanning calorimetry at a heating rate of 20°C / min is 2 J / g or more (Invention 3).

[0012] In the above invention (Invention 3), it is preferable that the polyester resin contains the dicarboxylic acid having the alicyclic structure as a monomer unit constituting the polyester resin (Invention 4).

[0013] In the above inventions (Inventions 3 and 4), it is preferable that the polyester resin contains a diol having the alicyclic structure as a monomer unit constituting the polyester resin (Invention 5).

[0014] In the above inventions (inventions 3 to 5), it is preferable that the number of carbon atoms constituting the ring of the alicyclic structure is 6 or more and 14 or less (invention 6).

[0015] In the above inventions (Inventions 1 to 6), it is preferable that the polyester resin contains a dimer acid obtained by dimerizing an unsaturated fatty acid as a monomer unit constituting the polyester resin, and that the number of carbon atoms of the unsaturated fatty acid is 10 or more and 30 or less (Invention 7).

[0016] In the above invention (Invention 7), it is preferable that the ratio of the dimer acid as a monomer unit constituting the polyester resin to the total dicarboxylic acid as a monomer unit constituting the polyester resin is 2 mol% or more and 25 mol% or less (Invention 8).

[0017] In the above inventions (Inventions 1 to 8), it is preferable that the polymer type antistatic agent contains a polymer compound, and the polymer compound is a polymer containing a polyether segment (Invention 9).

[0018] In the above inventions (Inventions 1 to 9), the surface resistivity on at least one side of the base film is 1×10

[0024] , , , , , ,

[0023] , , , Ω / □ or more and 5×10 11 Ω / □ or less (Invention 10).

[0019] In the above inventions (Inventions 1 to 10), it is preferable that the thickness of the base film is 20 μm or more and 600 μm or less (Invention 11).

[0020] Second, the present invention provides a work processing sheet characterized by including the base film (Inventions 1 to 11) and an adhesive layer laminated on one side of the base film (Invention 12).

[0021] In the above invention (Invention 12), it is preferable that the work processing sheet is a dicing sheet (Invention 13).

Effect of the Invention

[0022] According to the base film and the work processing sheet according to the present invention, it is possible to achieve both antistatic properties and mechanical strength.

Embodiment for Carrying out the Invention

[0023] Hereinafter, embodiments of the present invention will be described. 〔Base Film〕 The base film according to the present embodiment includes a resin layer containing a polyester resin, a polymer type antistatic agent, and carbon nanotubes (hereinafter sometimes referred to as “resin layer R”). The base film according to the present embodiment may consist only of the resin layer R, or may include other layers in addition to the resin layer R.

[0024] In the base film according to this embodiment, by blending a polymer-type antistatic agent and carbon nanotubes with the polyester resin matrix, conductive paths are efficiently formed, and the surface resistivity is effectively reduced. Therefore, to obtain the desired antistatic properties, it is sufficient to blend only small amounts of the polymer-type antistatic agent and carbon nanotubes. This suppresses a decrease in the mechanical strength of the base film, particularly the elongation at break, caused by these components, and prevents breakage during processes such as expansion. Thus, the base film according to this embodiment makes it possible to achieve both antistatic properties and mechanical strength.

[0025] The content of polymer-type antistatic agent in the resin layer R is preferably 0.1% by mass or more and 50% by mass or less, and the content of carbon nanotubes in the resin layer R is preferably 0.001% by mass or more and 1% by mass or less. By having the content of polymer-type antistatic agent and carbon nanotubes within the above ranges, excellent antistatic properties can be obtained, as well as good mechanical strength, especially elongation at break.

[0026] From the viewpoint of antistatic properties, the content of polymeric antistatic agent in the resin layer R is preferably 0.1% by mass or more, more preferably 1% by mass or more, particularly preferably 3% by mass or more, and even more preferably 5% by mass or more. Furthermore, from the viewpoint of mechanical strength, the content of polymeric antistatic agent in the resin layer R is preferably 50% by mass or less, more preferably 40% by mass or less, particularly preferably 30% by mass or less, and even more preferably 25% by mass or less.

[0027] From the viewpoint of antistatic properties, the carbon nanotube content in the resin layer R is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, particularly preferably 0.01% by mass or more, and even more preferably 0.03% by mass or more. Furthermore, from the viewpoint of mechanical strength, the carbon nanotube content in the resin layer R is preferably 1% by mass or less, more preferably 0.7% by mass or less, particularly preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less.

[0028] 1. Each ingredient (1) Polyester resin The polyester resin in this embodiment is not particularly limited, as long as it exhibits the antistatic effect of the polymer-type antistatic agent and carbon nanotubes, and can also exhibit the desired mechanical strength.

[0029] In particular, the polyester resin in this embodiment is preferably a polyester resin (hereinafter sometimes referred to as "polyester resin P") that has an alicyclic structure and a heat of fusion of 2 J / g or more, as measured by differential scanning calorimetry at a heating rate of 20°C / min. This allows the antistatic effect of the polymer-type antistatic agent and carbon nanotubes to be effectively exhibited, and also results in superior elongation at break. Furthermore, when a workpiece processing sheet comprising a base film using the polyester resin P is used for dicing a workpiece with a rotating circular blade, the generation of cutting chips can be effectively suppressed.

[0030] The following are expected to be the reasons why the chip suppression effect described above is obtained. However, the possibility that the above effect is obtained through a combination of the following reasons and other reasons cannot be ruled out, nor can the possibility that the above effect is obtained through reasons other than those listed below be ruled out.

[0031] First, it is expected that polyester resin will be easily cleaved at the ester bond when a dicing force is applied to a substrate made using the polyester resin. The polyester resin P, as described above, has an alicyclic structure and exhibits the above-mentioned heat of fusion, resulting in a moderately regular folded structure (lamellar structure) in which a portion of its polymer chains are folded. Therefore, it is expected that when a dicing force is applied, the polyester resin P will also be easily cleaved at the location of the lamellar structure. Thus, compared to resins used in conventional substrate films, polyester resin P is more prone to cleavage at specific locations when a dicing force is applied.

[0032] The mechanism by which cutting chips are generated from a typical dicing sheet substrate is thought to be that the frictional heat generated during dicing softens the substrate, and then the rotating circular blade makes contact, applying a pulling force to the cut portion of the substrate, causing the cut portion to be stretched and scraped away. In particular, much of the cutting chips generated in this way have a thread-like form.

[0033] On the other hand, in the base film using the polyester resin P described above, it is thought that cutting occurs effectively near the ester bonds and lamellar structure before stretching as described above, resulting in the suppression of cutting debris generation.

[0034] From the viewpoint of making it easier to achieve the aforementioned chip suppression effect, the amount of heat of fusion of the polyester resin P, measured by differential scanning calorimetry at a heating rate of 20°C / min, is preferably 5 J / g or more, particularly preferably 10 J / g or more, and even more preferably 15 J / g or more. On the other hand, the upper limit of the amount of heat of fusion is not particularly limited, and may be, for example, 150 J / g or less, 100 J / g or less, particularly 70 J / g or less, even more preferably 50 J / g or less, and especially 30 J / g or less. Details of the method for measuring the amount of heat of fusion described above are as described in the Examples section below.

[0035] The specific composition of the polyester resin P described above is not particularly limited, as long as it has an alicyclic structure and satisfies the conditions that the polyester resin exhibits the above-mentioned heat of fusion.

[0036] From the viewpoint of obtaining a better chip suppression effect, it is preferable that the alicyclic structure of the polyester resin P has 6 or more carbon atoms constituting the ring. Furthermore, it is preferable that the number of carbon atoms be 14 or less, and particularly preferable that it be 10 or less. In particular, it is preferable that the number of carbon atoms be 6. Furthermore, the alicyclic structure may be a monocyclic structure consisting of one ring, a bicyclic structure consisting of two rings, or a structure consisting of three or more rings.

[0037] Furthermore, from the viewpoint of easily satisfying the two conditions mentioned above, it is preferable that the polyester resin P contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting the polyester resin. Also, from the same viewpoint, it is preferable that the polyester resin P contains a diol having an alicyclic structure as a monomer unit constituting the polyester resin. Although only one of such dicarboxylic acids and diols may be contained in the polyester resin P, from the viewpoint of more easily satisfying the above conditions, it is preferable that the polyester resin P contains both such dicarboxylic acids and diols.

[0038] The structure of the dicarboxylic acid described above is not particularly limited as long as it has an alicyclic structure and two carboxyl groups. For example, the dicarboxylic acid may have a structure in which two carboxyl groups are bonded to an alicyclic structure, or it may have a structure in which an alkyl group or the like is further inserted between such an alicyclic structure and carboxyl groups. Preferred examples of such dicarboxylic acids include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,4-decahydronaphthalenedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid, and 2,7-decahydronaphthalenedicarboxylic acid, and among these, 1,4-cyclohexanedicarboxylic acid is preferred. These dicarboxylic acids may also be derivatives of alkyl esters, etc. Such alkyl ester derivatives may be, for example, alkyl esters having 1 to 10 carbon atoms. More specific examples include dimethyl esters and diethyl esters, with dimethyl esters being particularly preferred.

[0039] When the polyester resin P contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting it, the proportion of the dicarboxylic acid monomer to the total monomer units constituting the polyester resin P is preferably 20 mol% or more, more preferably 25 mol% or more, particularly preferably 30 mol% or more, and even more preferably 35 mol% or more. Furthermore, the proportion is preferably 60 mol% or less, more preferably 55 mol% or less, particularly preferably 50 mol% or less, and even more preferably 45 mol% or less. Being within these ranges makes the polyester resin P more likely to exhibit the aforementioned heat of fusion, and as a result, the workpiece processing sheet obtained using the base film according to this embodiment is more likely to achieve a better chip suppression effect.

[0040] Furthermore, if the polyester resin P contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting it, the proportion of the dicarboxylic acid having an alicyclic structure to the total dicarboxylic acid having a cyclic structure constituting the polyester resin P is preferably 60 mol% or more, more preferably 70 mol% or more, particularly preferably 80 mol% or more, and even more preferably 90 mol% or more. By having the above proportion of 60% or more, the workpiece processing sheet obtained using the base film according to this embodiment is more likely to achieve a better chip suppression effect. The upper limit of this proportion is not particularly limited, and may be, for example, 100 mol% or less. The above dicarboxylic acid having a cyclic structure includes not only dicarboxylic acids having an alicyclic structure but also dicarboxylic acids having an aromatic ring structure, etc.

[0041] The structure of the diol described above is not particularly limited as long as it has an alicyclic structure and two hydroxyl groups. For example, the diol may have a structure in which two hydroxyl groups are bonded to an alicyclic structure, or it may have a structure in which an alkyl group is further inserted between such an alicyclic structure and hydroxyl groups. Preferred examples of such diols include 1,2-cyclohexanediol (especially 1,2-cyclohexanedimethanol), 1,3-cyclohexanediol (especially 1,3-cyclohexanedimethanol), 1,4-cyclohexanediol (especially 1,4-cyclohexanedimethanol), and 2,2-bis-(4-hydroxycyclohexyl)-propane, and among these, 1,4-cyclohexanedimethanol is preferred.

[0042] When the polyester resin P contains a diol having an alicyclic structure as a monomer unit constituting it, the proportion of the diol monomer to the total monomer units constituting the polyester resin is preferably 35 mol% or more, particularly preferably 40 mol% or more, and even more preferably 45 mol% or more. Furthermore, the proportion is preferably 65 mol% or less, particularly preferably 60 mol% or less, and even more preferably 55 mol% or less. Being within these ranges makes the polyester resin P more likely to exhibit the aforementioned heat of fusion, and as a result, the workpiece processing sheet obtained using the base film according to this embodiment is more likely to achieve a better chip suppression effect.

[0043] From the viewpoint of making the base material more easily able to achieve the desired flexibility, the above-mentioned polyester resin P may also preferably contain dimer acid obtained by dimerizing an unsaturated fatty acid as a monomer unit constituting the polyester resin P. Here, the number of carbon atoms of the unsaturated fatty acid is preferably 10 or more, and particularly preferably 15 or more. Furthermore, the number of carbon atoms is preferably 30 or less, and particularly preferably 25 or less. Examples of such dimer acid include a 36-carbon dicarboxylic acid obtained by dimerizing an 18-carbon unsaturated fatty acid such as oleic acid or linoleic acid, and a 44-carbon dicarboxylic acid obtained by dimerizing an 22-carbon unsaturated fatty acid such as erucic acid. When obtaining the above-mentioned dimer acid, a small amount of trimer acid obtained by trimmerizing the above-mentioned unsaturated fatty acid may also be produced. The polyester resin P may contain such trimer acid along with the above-mentioned dimer acid.

[0044] When the polyester resin P contains the dimer acid as a monomer unit, the ratio of the dimer acid to the total dicarboxylic acid units constituting the polyester resin P is preferably 2 mol% or more, particularly preferably 5 mol% or more, and even more preferably 10 mol% or more. Furthermore, the ratio is preferably 25 mol% or less, particularly preferably 23 mol% or less, and even more preferably 20 mol% or less. Within these ranges, the polyester resin P is more likely to have the desired flexibility, and as a result, the workpiece processing sheet obtained using the base film according to this embodiment can achieve excellent expandability and pick-up properties.

[0045] The polyester resin P described above may contain monomers other than the dicarboxylic acids, diols, and dimer acids mentioned above as constituent monomer units. 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. It may also contain diol components other than diols having an alicyclic structure. For example, it may contain ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, decanediol; ethylene oxide adducts such as bisphenol A and bisphenol S; and trimethylolpropane.

[0046] However, in the above-mentioned polyester resin P, from the viewpoint of easily achieving an excellent chip suppression effect, it is preferable that monomers having an alicyclic structure (as mentioned above, dicarboxylic acids having an alicyclic structure and diols having a fatty structure) are present in greater quantities than monomers having an aromatic ring structure. In particular, among the monomer units constituting the polyester resin P, the molar ratio of monomer units having an aromatic ring structure to monomer units 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, especially preferably 0.005 or less, even more preferably 0.001 or less, and most preferably 0.

[0047] The method for producing the polyester resin P described above is not particularly limited, and the polyester resin P can be obtained by polymerizing the aforementioned monomer components using a known catalyst.

[0048] In this embodiment, the proportion of polyester resin to the total components constituting the resin layer R is preferably 50% by mass or more, particularly preferably 60% by mass or more, and even more preferably 70% by mass or more. A proportion of 50% by mass or more makes it easier to achieve a superior chip suppression effect in the workpiece processing sheet obtained using the base film according to this embodiment. The upper limit of the above proportion is not particularly limited; for example, it may be 100% by mass or less.

[0049] (2) Polymer-type antistatic agent The polymer-type antistatic agent in this embodiment is an antistatic agent containing at least a polymer compound. Preferably, the polymer-type antistatic agent in this embodiment is an ion-conducting polymer-type antistatic agent (hereinafter sometimes referred to as "polymer-type antistatic agent A") containing a polymer compound and an organic salt or inorganic protonic acid salt composed of an organic cation and an organic anion (such as an alkali metal salt, alkaline earth metal, zinc salt, or ammonium salt).

[0050] The substrate film according to this embodiment exhibits excellent antistatic properties and can achieve the surface resistivity described later by using a polymer-type antistatic agent, particularly polymer-type antistatic agent A, together with carbon nanotubes.

[0051] The polymer compound contained in the polymer-type antistatic agent in this embodiment is a compound having at least two repeating units. The weight-average molecular weight of the polymer compound is preferably 300 or more, and particularly preferably 1000 or more. Furthermore, the weight-average molecular weight is preferably 100,000 or less, particularly preferably 75,000 or less, and even more preferably 50,000 or less. Note that the weight-average molecular weight in this specification is the value on a standard polystyrene basis measured by gel permeation chromatography (GPC).

[0052] The above polymer compound is not particularly limited, but from the viewpoint of easily exhibiting excellent antistatic properties, it is preferable that it is a polymer containing a polyether segment. Examples of polymers containing a polyether segment include polymers containing a polyether segment and a polyolefin segment, and polymers containing a polyether segment and an amide segment (hereinafter sometimes referred to as "polyether ester amide").

[0053] Examples of the polyether segments mentioned above include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyhexamethylene glycol; polyoxyalkylene polyoxyalkylene glycols such as polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, and polyoxyethylene-polyoxypropylene glycol; and polyalkylene ether diols. These segments may be arranged randomly in the polymer or in a block-like arrangement.

[0054] Examples of the polyolefin segments mentioned above include homopolymers of alphaolefins having 2 to 10 carbon atoms, or copolymers of at least one alphaolefin and at least one other copolymerizable monomer. Examples of alphaolefins include ethylene, propylene, 1-butene, 2-methylpropene, 1-pentene, 3-methyl l-butene, 1-hexene, 4-methyl l-pentene, 3-methyl l-pentene, and 1-octene. These segments may be arranged randomly in the polymer or in a block-like arrangement.

[0055] The above-mentioned polyether ester amide is not particularly limited as long as it is a polymer comprising amide segments having amide bonds and ether segments having ether bonds. These segments may be arranged randomly in the polymer or in a block-like arrangement. Furthermore, these segments may be linked to each other by ester bonds, amide bonds, or the like.

[0056] The above amide segments include, for example, dicarboxylic acids (e.g., oxalic acid, succinic acid, adipic acid, sebacic acid, dodecanediic acid, terephthalic acid, isophthalic acid, 1,4-cyclohexanedicarboxylic acid, etc.) and diamines (e.g., ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, decamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane) These amide segments are obtained by condensation and polycondensation with methylenebis(4-aminocyclohexane), m-xylylenediamine, p-xylylenediamine, etc., ring-opening polymerization of lactams such as ε-caprolactam and ω-dodecalactam, polycondensation of aminocarboxylic acids such as 6-aminocaproic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid, or by condensation of the ring-opened product of the above lactam or an aminocarboxylic acid with a dicarboxylic acid, or by polycondensation of the ring-opened product of the above lactam or an aminocarboxylic acid with a diamine. Examples of such amide segments include nylon 4, nylon 6, nylon 46, nylon 66, nylon 610, nylon 612, nylon 6T, nylon 11, nylon 12, nylon 6 / 66, nylon 6 / 12, nylon 6 / 610, nylon 66 / 12, nylon 6 / 66 / 610, etc., with nylon 11 and nylon 12 being particularly preferred. The molecular weight of the amide segment is preferably, for example, around 100 to 5000.

[0057] The organic cations and organic anions constituting the organic salt contained in the above polymer-type antistatic agent A are not particularly limited, as long as they are ionized organic compounds. Examples of such organic cations include those derived from at least one of the following: imidazolium cation, pyridinium cation, pyrrolidinium cation, ammonium cation, sulfonium cation, phosphonium cation, etc. Examples of such organic anions include linear alkylbenzene sulfonic acid and sulfonate anion (RSO 3- ), carboxylate anion (RCOO -), alkoxide or phenoxide anion (RO - ), organic imide anion (R2N - ), Methido (R3C - ) Anions, organic borates (R4B - ) Examples include those derived from at least one type of anion, etc.

[0058] The above-mentioned inorganic protonic acid salts are not particularly limited and include, for example, alkali metal salts, alkaline earth metals, zinc salts, or ammonium salts. Examples of alkali metal salts include salts having alkali metals such as lithium, sodium, and potassium as cationic components. Examples of alkaline earth metal salts include salts having alkaline earth metals such as magnesium and calcium as cationic components.

[0059] In this embodiment, the polymeric antistatic agent, particularly polymeric antistatic agent A, preferably has a 5% weight loss temperature of 200°C or higher in an atmospheric environment, and more preferably 250°C or higher. Having a 5% weight loss temperature of 200°C or higher makes it difficult for the polymeric antistatic agent to decompose even when heated during the mixing or film formation of the base film material, thus making it easier to exhibit sufficient antistatic properties. The upper limit of the 5% weight loss temperature is not particularly limited; for example, it may be 1000°C or lower, more preferably 900°C or lower, and even more preferably 700°C or lower.

[0060] Furthermore, the polymeric antistatic agent in this embodiment, particularly polymeric antistatic agent A, preferably has a 5% weight loss temperature of 250°C or higher under a nitrogen atmosphere, more preferably 270°C or higher, and even more preferably 300°C or higher. Having a 5% weight loss temperature of 250°C or higher makes it difficult for the polymeric antistatic agent to decompose even when heated during the mixing or film formation of the base film material, thus making it easier to exhibit sufficient antistatic properties. The upper limit of the 5% weight loss temperature is not particularly limited; for example, it may be 1000°C or lower, more preferably 900°C or lower, and even more preferably 700°C or lower.

[0061] Details of the measurement method for the 5% weight loss temperature under the above-mentioned atmospheric and nitrogen atmospheres are described in the examples below.

[0062] In this embodiment, the polymer-type antistatic agent may be, in addition to the polymer-type antistatic agent A described above, for example, an ether-based antistatic agent, an ester-based antistatic agent, a polyamide-based antistatic agent, an acrylic-based antistatic agent, or a polyether ester amide-based antistatic agent. Note that polyether ester amide-based antistatic agents are classified as either ether-based antistatic agents, ester-based antistatic agents, or polyamide-based antistatic agents.

[0063] (3) Carbon nanotubes In this embodiment, the carbon nanotube may be a single-walled carbon nanotube having a structure in which one layer of graphite forms a cylinder, or a multi-walled carbon nanotube having a structure in which two or more layers of graphite each form a cylinder and these cylinders are stacked. However, from the viewpoint of efficiently forming conductive paths when used in combination with a polymer-type antistatic agent, a single-walled carbon nanotube is preferred. Note that a structure in which the graphite layer is rolled into a roughly conical shape is called a carbon nanohorn, and the carbon nanotube in this embodiment also includes carbon nanohorns.

[0064] In this embodiment, the average length of the carbon nanotubes is preferably 1 μm or more, more preferably 3 μm or more, particularly preferably 8 μm or more, and even more preferably 10 μm or more. Furthermore, the average length is preferably 30 μm or less, more preferably 25 μm or less, particularly preferably 20 μm or less, and even more preferably 15 μm or less. By having the average length of the carbon nanotubes within the above range, conductive paths can be formed more efficiently when used in combination with a polymer-type antistatic agent, and the mechanical strength of the substrate film is less likely to be adversely affected.

[0065] In this embodiment, the average outer diameter of the carbon nanotubes is preferably 0.0001 μm or more, more preferably 0.0003 μm or more, particularly preferably 0.0006 μm or more, and even more preferably 0.001 μm or more. Furthermore, the average outer diameter is preferably 0.05 μm or less, more preferably 0.03 μm or less, particularly preferably 0.01 μm or less, and even more preferably 0.005 μm or less. By having the average outer diameter of the carbon nanotubes within the above range, conductive paths can be formed more efficiently when used in combination with a polymer-type antistatic agent, and the mechanical strength of the base film is less likely to be adversely affected.

[0066] In this embodiment, the aspect ratio of the carbon nanotube is preferably 100 or more, more preferably 250 or more, particularly preferably 500 or more, and even more preferably 1000 or more. Furthermore, the aspect ratio is preferably 25000 or less, more preferably 20000 or less, particularly preferably 15000 or less, and even more preferably 10000 or less. By having the aspect ratio of the carbon nanotube within the above range, conductive paths are formed more efficiently when used in combination with a polymer-type antistatic agent, and the mechanical strength of the base film is less likely to be adversely affected.

[0067] The carbon nanotubes in this embodiment can be manufactured by conventional methods. For example, they can be manufactured by the arc discharge method, laser evaporation method, thermal decomposition method, etc., as described in Saito and Bando, "Fundamentals of Carbon Nanotubes" (pp. 23-57, Corona Publishing Co., Ltd., 1998). Furthermore, if necessary, they can be purified by hydrothermal methods, centrifugal separation, ultrafiltration, oxidation, etc., to increase their purity.

[0068] (4) Other ingredients The resin layer R in this embodiment may contain other components besides the polyester resin, polymer antistatic agent, and carbon nanotubes described above. Examples of other components include those commonly used in base films for workpiece processing sheets, and specifically include various additives such as flame retardants, plasticizers, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, and ion scavengers. While there are no particular limitations on the content of these additives, it is preferable to set it within a range that allows the base film to exhibit the desired function.

[0069] 2. Composition of the base film In this embodiment, the layer structure of the base film may be a single layer or multiple layers, as long as it comprises the aforementioned polyester resin, polymer-type antistatic agent, and a resin layer R containing carbon nanotubes, but a single layer of resin layer R is preferred.

[0070] On the other hand, when multiple layers are used, multiple resin layers R may be laminated, or a resin layer R may be laminated with other layers. When other layers are expanded together with the resin layer R, it is preferable that these layers have a fracture elongation equal to or greater than that of the resin layer R.

[0071] In this embodiment, the surface of the base film on which the adhesive layer is laminated may be subjected to surface treatments such as primer treatment, corona treatment, or plasma treatment in order to improve adhesion with the adhesive layer.

[0072] 3. Physical properties of the base film (1) Thickness In this embodiment, the thickness of the base film is preferably 20 μm or more, particularly preferably 40 μm or more, and even more preferably 60 μm or more. Also, in this embodiment, the thickness of the base film is preferably 600 μm or less, particularly preferably 300 μm or less, and even more preferably 200 μm or less. When the thickness of the base film is within the above range, the sheet for workpiece processing has appropriate strength, and it becomes easier to favorably support the workpiece fixed on the sheet for workpiece processing. Also, it is likely to have a desired elongation at break and is likely to be excellent in expandability.

[0073] (2) Surface resistivity In the base film according to this embodiment, the surface resistivity on at least one side thereof is preferably 5×10 11 Ω / sq or less, more preferably 4×10 11 Ω / sq or less, particularly preferably 3×10 11 Ω / sq or less, and even more preferably 2×10 11 Ω / sq or less. When the base film according to this embodiment has such a surface resistivity, the sheet for workpiece processing constituted by using the base film is less likely to be charged during storage or use, and it is possible to favorably suppress the adhesion of dust to the sheet for workpiece processing caused by charging. The base film according to this embodiment can achieve the above low surface resistivity without reducing the mechanical strength by using the polymer type antistatic agent and the carbon nanotube in combination as described above.

[0074] The lower limit value of the above surface resistivity is not particularly limited. For example, it may be 1×10 6 Ω / sq or more, or may be 1×10 7 Ω / sq or more, and particularly may be 1×10 8 Ω / sq or more. Note that the method for measuring the surface resistivity in this specification is as shown in the test example described later.

[0075] (3) Elongation at break The elongation at break of the base film in the MD direction according to this embodiment is preferably 200% or more, more preferably 220% or more, particularly preferably 240% or more, and even more preferably 260% or more. Furthermore, the elongation at break of the base film in the TD direction according to this embodiment is preferably 200% or more, more preferably 220% or more, particularly preferably 250% or more, and even more preferably 300% or more. By having the above elongation at break of the base film, it is possible to effectively prevent breakage during processes such as expansion. As described above, by using a polymer-type antistatic agent and carbon nanotubes in combination, the base film according to this embodiment can achieve the above-mentioned large elongation at break while keeping the surface resistivity low. Here, the MD direction refers to the flow direction during film formation of the base film (resin layer R), and the TD direction refers to the direction perpendicular to the MD direction.

[0076] The upper limit of the elongation at break in the MD direction of the base film according to this embodiment is not particularly limited and may be 600% or less, 550% or less, or particularly 500% or less. Similarly, the upper limit of the elongation at break in the TD direction of the base film according to this embodiment is not particularly limited and may be 600% or less, 550% or less, or particularly 500% or less. The method for measuring elongation at break in this specification conforms to JIS K7127:1999, and is specifically as shown in the test examples described later.

[0077] 4. Method for manufacturing the base film The method for manufacturing the base film in this embodiment is not particularly limited as long as the material containing the aforementioned polyester resin, polymer-type antistatic agent, and carbon nanotubes is used. For example, melt extrusion methods such as the T-die method and circular die method; calendering; and solution methods such as the dry method and wet method can be used. Among these, from the viewpoint of efficiently manufacturing the base film, it is preferable to employ the melt extrusion method or the calendering method.

[0078] When manufacturing a base film consisting of a single layer of resin layer R by melt extrusion, the raw materials for the resin layer R (including the aforementioned polyester resin, polymer antistatic agent, and carbon nanotubes) are kneaded together, and the resulting mixture is used to form a film either directly or after first producing pellets, using a known extruder. During the kneading process, it is preferable to first knead the polyester resin and carbon nanotubes (masterbatch) together to obtain a carbon nanotube mixture, and then knead this carbon nanotube mixture with the polyester resin and polymer antistatic agent. This ensures good dispersibility of the carbon nanotubes.

[0079] Furthermore, when manufacturing a base film consisting of multiple layers by melt extrusion, the components constituting each layer can be kneaded separately, and the multiple layers can be extruded simultaneously using a known extruder, either directly from the resulting kneaded material or after first producing pellets, to form the film.

[0080] Furthermore, if the base film has multiple layers, a coating solution containing the raw materials for the resin layer R (including the aforementioned polyester resin, polymer antistatic agent, and carbon nanotubes) may be applied to one side of a predetermined layer that has been formed into a film beforehand, and then dried or cured to form the resin layer R on the predetermined layer. This makes it possible to obtain a base film comprising the predetermined layer and the resin layer R.

[0081] [Sheet for workpiece processing] The workpiece processing sheet according to this embodiment comprises the aforementioned base film and an adhesive layer laminated on one side of the base film.

[0082] 1. Configuration of the workpiece processing sheet The following describes the components of the workpiece processing sheet according to this embodiment, excluding the base film mentioned above.

[0083] (1) Adhesive layer The adhesive constituting the above adhesive layer is not particularly limited, as long as it can exert sufficient adhesive force to the adherend (especially sufficient adhesive force to the workpiece for processing the workpiece). Examples of adhesives constituting the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, and polyvinyl ether adhesives. Among these, it is preferable to use an acrylic adhesive because it is easier to exert the desired adhesive force.

[0084] The adhesive constituting the adhesive layer in this embodiment may be an adhesive that does not have active energy ray curability, but it is preferable that it is an adhesive that has active energy ray curability (hereinafter sometimes referred to as "active energy ray curable adhesive"). Because the adhesive layer is composed of an active energy ray curable adhesive, the adhesive layer can be cured by irradiation with active energy rays, and the adhesive force of the workpiece processing sheet to the adherend can be easily reduced. In particular, irradiation with active energy rays makes it possible to easily separate the processed workpiece from the workpiece processing sheet.

[0085] The active energy ray curable adhesive constituting the adhesive layer may be mainly composed of an active energy ray curable polymer, or it may be mainly composed of a mixture of an active energy ray non-curable polymer (a polymer that does not possess active energy ray curability) and a monomer and / or oligomer having at least one active energy ray curable group.

[0086] The polymer having active energy ray curability is preferably a (meth)acrylic acid ester polymer (hereinafter sometimes referred to as "active energy ray curable polymer") in which a functional group having active energy ray curability (active energy ray curable group) is introduced into the side chain. This active energy ray curable polymer is preferably obtained by reacting an acrylic copolymer having a functional group-containing monomer unit with an unsaturated group-containing compound having a functional group that is bonded to that functional group. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, the concept of "polymer" is also included in the concept of "copolymer".

[0087] The weight-average molecular weight of the above-mentioned active energy ray-curable polymer is preferably 10,000 or more, particularly preferably 150,000 or more, and even more preferably 200,000 or more. Furthermore, the weight-average molecular weight is preferably 2,500,000 or less, particularly preferably 2,000,000 or more, and even more preferably 1,500,000 or less. In this specification, the weight-average molecular weight (Mw) is the value on a standard polystyrene basis measured by gel permeation chromatography (GPC).

[0088] On the other hand, when an active energy ray-curable adhesive mainly consists of a mixture of an active energy ray-non-curable polymer component and a monomer and / or oligomer having at least one active energy ray-curable group, the active energy ray-non-curable polymer component can be, for example, the acrylic copolymer before reacting with an unsaturated group-containing compound. Furthermore, as the active energy ray-curable monomer and / or oligomer, for example, an ester of a polyhydric alcohol and (meth)acrylic acid can be used.

[0089] The weight-average molecular weight of the acrylic polymer used as the active energy ray non-curable polymer component is preferably 10,000 or more, particularly preferably 150,000 or more, and even more preferably 200,000 or more. Furthermore, the weight-average molecular weight is preferably 2,500,000 or less, particularly preferably 2,000,000 or more, and even more preferably 1,500,000 or less.

[0090] Furthermore, when ultraviolet light is used as the active energy ray for curing an active energy ray-curable adhesive, it is preferable to add a photopolymerization initiator to the adhesive. In addition, active energy ray-non-curable polymer components or oligomer components, crosslinking agents, etc., may be added to the adhesive.

[0091] In this embodiment, the thickness of the adhesive layer is preferably 1 μm or more, particularly preferably 2 μm or more, and even more preferably 3 μm or more. Furthermore, the thickness of the adhesive layer is preferably 50 μm or less, particularly preferably 40 μm or less, and even more preferably 30 μm or less. A thickness of 1 μm or more in the adhesive layer makes it easier for the workpiece processing sheet according to this embodiment to exhibit the desired adhesiveness. Furthermore, a thickness of 50 μm or less in the adhesive layer makes it easier to separate the adherend from the adhesive layer after curing.

[0092] (2) Release sheet In the workpiece processing sheet according to this embodiment, a release sheet may be laminated on the side of the adhesive layer opposite to the base film (hereinafter sometimes referred to as the "adhesive side") for the purpose of protecting that side until it is attached to the adherend.

[0093] The composition of the release sheet described above is arbitrary, and examples include plastic films that have been treated with a release agent. Specific examples of such plastic films include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; and polyolefin films such as polypropylene and polyethylene. As the release agent, silicone-based, fluorine-based, and long-chain alkyl-based agents can be used, and among these, silicone-based agents are preferred because they are inexpensive and provide stable performance.

[0094] There are no particular restrictions on the thickness of the release sheet mentioned above; for example, it may be between 20 μm and 250 μm.

[0095] (3) Others In the workpiece processing sheet according to this embodiment, the adhesive layer may be laminated on the side of the adhesive layer opposite to the base film. In this case, the workpiece processing sheet according to this embodiment can be used as a dicing / die bonding sheet. With this sheet, a workpiece can be attached to the side of the adhesive layer opposite to the adhesive layer, and by dicing the adhesive layer together with the workpiece, a chip can be obtained in which individual pieces of the adhesive layer are laminated. The chip can be easily fixed to the object on which it is mounted by these individual pieces of adhesive layer. As the material constituting the adhesive layer described above, it is preferable to use one that contains a thermoplastic resin and a low molecular weight thermosetting adhesive component, or one that contains a B-stage (semi-cured) thermosetting adhesive component.

[0096] Furthermore, in the workpiece processing sheet according to this embodiment, a protective film forming layer may be laminated on the adhesive surface of the adhesive layer. In this case, the workpiece processing sheet according to this embodiment can be used as a protective film forming and dicing sheet. With such a sheet, a workpiece is attached to the side of the protective film forming layer opposite to the adhesive layer, and the protective film forming layer is diced together with the workpiece to obtain a chip with individual pieces of the protective film forming layer laminated on it. Preferably, a workpiece with a circuit formed on one side is used, and in this case, the protective film forming layer is usually laminated on the side opposite to the side with the circuit formed. By curing the individual pieces of the protective film forming layer at a predetermined timing, a protective film with sufficient durability can be formed on the chip. Preferably, the protective film forming layer is made of an uncured curable adhesive.

[0097] 2. Method for manufacturing sheets for workpiece processing The method for manufacturing the workpiece processing sheet according to this embodiment is not particularly limited. For example, it is preferable to obtain the workpiece processing sheet by forming an adhesive layer on a release sheet, and then laminating one side of a base film onto the side of the adhesive layer opposite to the release sheet.

[0098] The adhesive layer described above can be formed by known methods. For example, a coating solution containing an adhesive composition for forming the adhesive layer, and optionally a solvent or dispersion medium, can be prepared. Then, the coating solution is applied to the release surface of the release sheet (hereinafter sometimes referred to as the "release surface"). Subsequently, the adhesive layer can be formed by drying the resulting coating film.

[0099] The coating solution described above can be applied by known methods, such as bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, etc. The properties of the coating solution are not particularly limited as long as it can be applied, and it may contain components for forming the adhesive layer as a solute or as a dispersed phase. The release sheet may be peeled off as a process material, or it may protect the adhesive layer until it is attached to the substrate.

[0100] If the adhesive composition for forming the adhesive layer contains the aforementioned crosslinking agent, it is preferable to promote the crosslinking reaction between the polymer components in the coating film and the crosslinking agent by changing the drying conditions (temperature, time, etc.) or by separately performing a heat treatment, thereby forming a crosslinked structure with a desired density in the adhesive layer. Furthermore, in order to allow the above-mentioned crosslinking reaction to proceed sufficiently, curing may be performed after bonding the adhesive layer and the base film, for example, by leaving it undisturbed for several days in an environment of 23°C and 50% relative humidity.

[0101] 3. How to use the workpiece processing sheet The workpiece processing sheet according to this embodiment can be used for processing workpieces such as semiconductor wafers. In this case, after attaching the adhesive surface of the workpiece processing sheet according to this embodiment to the workpiece, processing of the workpiece can be performed on the workpiece processing sheet. Depending on the processing, the workpiece processing sheet according to this embodiment can be used as a workpiece processing sheet such as a backgrind sheet, dicing sheet, expand sheet, or pickup sheet. Examples of workpieces include semiconductor wafers, semiconductor components such as semiconductor packages, and glass components such as glass plates.

[0102] The workpiece processing sheet according to this embodiment is constructed using the base film according to the aforementioned embodiment, and therefore exhibits excellent antistatic properties and good mechanical strength, particularly elongation at break. Accordingly, the workpiece processing sheet according to this embodiment is particularly suitable as an expanded sheet or a dicing sheet used in a dicing-to-expand process.

[0103] Furthermore, if the workpiece processing sheet according to this embodiment includes the aforementioned adhesive layer, the workpiece processing sheet can be used as a dicing and die bonding sheet. In addition, if the workpiece processing sheet according to this embodiment includes the aforementioned protective film forming layer, the workpiece processing sheet can be used as a protective film forming and dicing sheet.

[0104] Furthermore, if the adhesive layer in the workpiece processing sheet according to this embodiment is composed of the aforementioned active energy ray curable adhesive, it is also preferable to irradiate it with the following active energy rays during use. That is, when the processing of the workpiece is completed on the workpiece processing sheet and the processed workpiece is to be separated from the workpiece processing sheet, it is preferable to irradiate the adhesive layer with active energy rays before the separation. This hardens the adhesive layer, which reduces the adhesive force of the workpiece processing sheet to the processed workpiece, making it easier to separate the processed workpiece.

[0105] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Accordingly, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention. [Examples]

[0106] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0107] [Example 1] (1) Preparation of base film In a reactor equipped with a stirrer, distillation tube, and vacuum device, 12.90 kg of dimethyl 1,4-cyclohexanedicarboxylate (98% trans isomer ratio), 11.47 kg of 1,4-cyclohexanedimethanol, 0.3 kg of ethylene glycol, and 0.11 kg of an ethylene glycol solution containing 10% Mn acetate tetrahydrate were charged. The mixture was heated to 200°C under a nitrogen flow, and then the temperature was increased to 230°C over 1 hour. After holding the mixture for 2 hours to carry out the transesterification reaction, 10.30 kg of erucic acid-derived dimer acid (44 carbon atoms, manufactured by Croda, product name "PRIPOL1004") and 0.11 kg of an ethylene glycol solution containing 10% trimethyl phosphate were added to the system, and the esterification reaction was carried out at 230°C for 1 hour. Next, 300 ppm germanium dioxide was added as a polycondensation catalyst and stirred. The pressure was then reduced to below 133 Pa for 1 hour, during which time the internal temperature was raised from 230°C to 270°C. The polycondensation reaction was carried out under high vacuum below 133 Pa, stirring until the desired viscosity was achieved. The resulting polymer was extruded into water in strand form, cut, and formed into pellets.

[0108] The resulting polyester resin pellets were dried at 85°C for at least 4 hours. Subsequently, 90 parts by mass of the dried pellets and 5 parts by mass of a carbon nanotube masterbatch (manufactured by OCSiAl, product name "TUBALL 0540") were kneaded in a twin-screw kneader to obtain carbon nanotube compound (A).

[0109] Next, 85 parts by mass of the above polyester resin pellets, 10 parts by mass of a polyether ester amide polymer antistatic agent (manufactured by Sanyo Chemical Industries, Ltd., product name "Pelektron AS"), and 5 parts by mass of the above carbon nanotube mixture (A) were kneaded in a twin-screw kneader (240°C, 12 minutes) to obtain pellets. The carbon nanotube content in these pellets was 0.05% by mass.

[0110] The pellets obtained above were fed into the hopper of a single-screw extruder equipped with a T-die. Then, under conditions of cylinder temperature 220°C and die temperature 220°C, the pellets were extruded from the T-die in a melted and kneaded state, and cooled with a cooling roll to obtain a sheet-like base film with a thickness of 80 μm.

[0111] The polyester resin described above contained approximately 50 mol% of 1,4-cyclohexanedimethanol, approximately 40.5 mol% of 1,4-cyclohexanedicarboxylate dimethyl, and 9.5 mol% of erucic acid-derived dimer acid as monomers constituting the resin. The ratio of the dimer acid to the total dicarboxylic acid units constituting the polyester resin was 19.1 mol%. Furthermore, the heat of fusion of the polyester resin was measured by the method described later and was found to be 20 J / g.

[0112] Furthermore, when the 5% weight loss temperature of the above polymer-type antistatic agent was measured by the method described later, it was 260°C in an atmospheric environment and 333°C in a nitrogen atmosphere.

[0113] (2) Preparation of adhesive composition 95 parts by mass of n-butyl acrylate and 5 parts by mass of acrylic acid were polymerized by solution polymerization to obtain a (meth)acrylic acid ester polymer. The weight-average molecular weight (Mw) of this acrylic polymer was measured by the method described later and was found to be 500,000.

[0114] As described above, 100 parts by mass (on a solid content basis, the same applies hereafter) of the (meth)acrylic acid ester polymer obtained, 120 parts by mass of urethane acrylate oligomer (Mw: 8,000), 5 parts by mass of isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L"), and 4 parts by mass of photopolymerization initiator (manufactured by IGM Resins BV, product name "Omnirad 184") were mixed to obtain an energy ray-curable adhesive composition.

[0115] (3) Formation of the adhesive layer The adhesive composition obtained in step (2) above was applied to the release surface of a release sheet (Lintec Corporation, product name "SP-PET381031"), which was a 38 μm thick polyethylene terephthalate film with one side released using a silicone-based release agent. The resulting coating was dried at 100°C for 1 minute. This resulted in a laminate in which a 10 μm thick adhesive layer was formed on the release surface of the release sheet.

[0116] (4) Preparation of workpiece processing sheets A workpiece processing sheet was obtained by bonding one side of the base film obtained in step (1) above with the adhesive layer side of the laminate obtained in step (3) above.

[0117] (5)Various measurement methods The heat of fusion of the aforementioned polyester resin was measured in accordance with JIS K 7121:2012 using a differential scanning calorimeter (DSC, manufactured by T.A. Instruments, product name "DSC Q2000"). Specifically, the sample was first heated from room temperature to 250°C at a heating rate of 20°C / min, held at 250°C for 10 minutes, then cooled to -60°C at a cooling rate of 20°C / min, and held at -60°C for 10 minutes. After that, it was heated again to 250°C at a heating rate of 20°C / min to obtain a DSC curve and measure the melting point.

[0118] The 5% weight loss temperature of the polymer-type antistatic agent described above was determined using a differential thermal and thermogravimetric simultaneous measurement device (Shimadzu Corporation, product name "DTG-60") in accordance with JIS K7120:1987. Specifically, using air or nitrogen as the inflow gas, thermogravimetric measurements were performed by raising the temperature from 40°C to 550°C at a gas inflow rate of 100 ml / min and a heating rate of 20°C / min. From the obtained thermogravimetric curve, the temperature at which the mass decreases by 5% compared to the mass at 100°C (5% weight loss temperature) was determined.

[0119] Furthermore, the weight-average molecular weight (Mw) mentioned above is the weight-average molecular weight on a standard polystyrene basis, measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement). <Measurement conditions> • Measuring device: Tosoh Corporation, HLC-8320 • GPC column (passes through in the following order): Manufactured by Tosoh Corporation TSK Gel Super H-H TSK gel superHM-H TSK Gel Super H2000 • Measurement solvent: tetrahydrofuran ·Measurement temperature: 40℃

[0120] [Example 2, Comparative Examples 1-6] A workpiece processing sheet was obtained in the same manner as in Example 1, except that the amounts of polyester resin, polymer-type antistatic agent, and carbon nanotube masterbatch (carbon nanotubes) were changed as shown in Table 1.

[0121] [Test Example 1] (Measurement of surface resistivity) The surface resistivity of one side of the substrate films prepared in the examples and comparative examples was measured. Specifically, the surface resistivity (Ω / □) of samples cut from the substrate film to a size of 100 mm x 100 mm was measured using an ultra-high resistance / micro-current meter (ADC Corporation, product name "Digital Ultra-High Resistance / Micro-Current Meter 5450") under the conditions of an applied voltage of 100 V and an applied time of 60 sec. The results are shown in Table 1.

[0122] Based on the above measurement results, the surface resistivity (antistatic properties) was evaluated according to the following criteria. The results are shown in Table 1. ○...Surface resistivity is 5 × 10 11 Ω / □ or less ×...Surface resistivity is 5 × 10 11 Ω / □Super

[0123] [Test Example 2] (Measurement of elongation at break) The base films prepared in the examples and comparative examples were cut to a size of 15 mm × 140 mm to obtain test specimens. At this time, two types of test specimens were obtained: one for the MD direction, where the longer side (the 140 mm side) was parallel to the MD direction of the base film, and another for the TD direction, where the longer side was parallel to the TD direction.

[0124] For the two types of test specimens described above, the elongation at break at 23°C was measured in accordance with JIS K7127:1999. Specifically, the above test specimens were subjected to a tensile test at a speed of 200 mm / min using a tensile testing machine (Shimadzu Corporation, product name "Autograph AG-XPlus") with a chuck distance of 100 mm, and the elongation at break (%) when the test specimen broke was measured. At this time, the elongation at break (%) in the MD direction was measured using the test specimen for the MD direction, and the elongation at break (%) in the TD direction was measured using the test specimen for the TD direction. The results are shown in Table 1.

[0125] Based on the above measurement results, the elongation at break (mechanical strength) was evaluated according to the following criteria. The results are shown in Table 1. ○...Elongation at break is 200% or more ×...Elongation at break is less than 200%

[0126] [Table 1]

[0127] As can be seen from Table 1, the base film of the workpiece processing sheet manufactured in the examples had a low surface resistivity, exhibited excellent antistatic properties, and had a high elongation at break, showing good mechanical strength. [Industrial applicability]

[0128] The base film of the present invention can be suitably used as a base film for a workpiece processing sheet, particularly a dicing sheet, used in the processing of workpieces such as semiconductor wafers.

Claims

1. The resin layer comprises a polyester resin, a polymer-type antistatic agent, and carbon nanotubes. The content of the polymer-type antistatic agent in the resin layer is 0.1% by mass or more and 25% by mass or less. The carbon nanotube content in the resin layer is 0.001% by mass or more and 1% by mass or less. The polyester resin contains a dimer acid obtained by dimerizing an unsaturated fatty acid as a monomer unit constituting the polyester resin. The number of carbon atoms in the aforementioned unsaturated fatty acid is 10 or more and 30 or less. A base film characterized by the following features.

2. The resin layer comprises a polyester resin, a polymer-type antistatic agent, and carbon nanotubes. The content of the polymer-type antistatic agent in the resin layer is 0.1% by mass or more and 25% by mass or less. The carbon nanotube content in the resin layer is 0.001% by mass or more and 1% by mass or less. The polyester resin contains a dimer acid obtained by dimerizing an unsaturated fatty acid as a monomer unit constituting the polyester resin. The ratio of the dimer acid as a monomer unit constituting the polyester resin to the total dicarboxylic acid as a monomer unit constituting the polyester resin is 2 mol% or more and 25 mol% or less. A base film characterized by the following features.

3. The base film according to claim 1 or 2, characterized in that the polyester resin has an alicyclic structure and the heat of fusion measured by differential scanning calorimetry at a heating rate of 20°C / min is 2 J / g or more.

4. The base film according to claim 3, characterized in that the polyester resin contains a dicarboxylic acid having the alicyclic structure as a monomer unit constituting the polyester resin.

5. The base film according to claim 3 or 4, characterized in that the polyester resin contains a diol having the alicyclic structure as a monomer unit constituting the polyester resin.

6. The base film according to any one of claims 3 to 5, characterized in that the number of carbon atoms constituting the ring of the alicyclic structure is 6 or more and 14 or less.

7. The unsaturated fatty acid has 10 or more carbon atoms and 30 or less. The base film according to feature 2.

8. The base film according to claim 1, characterized in that the ratio of the dimer acid as a monomer unit constituting the polyester resin to the total dicarboxylic acid as a monomer unit constituting the polyester resin is 2 mol% or more and 25 mol% or less.

9. The polymer-type antistatic agent contains a polymer compound, The polymer compound is a polymer containing a polyether segment. A base film according to any one of claims 1 to 8.

10. The surface resistivity on at least one side of the pre-substrate film is 1 × 10 ６ Ω / □ or more, 5×10 １１ A base film according to any one of claims 1 to 9, characterized in that it is Ω / □ or less.

11. The base film according to any one of claims 1 to 10, characterized in that the thickness of the base film is 20 μm or more and 600 μm or less.

12. A base film according to any one of claims 1 to 11, An adhesive layer laminated on one side of the base film and A workpiece processing sheet characterized by having the following features.

13. The workpiece processing sheet according to claim 12, characterized in that the workpiece processing sheet is a dicing sheet.

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