JP2023136637A - Base material film and sheet for workpiece processing - Google Patents

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

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 a workpiece such as a semiconductor wafer, and the workpiece processing sheet.

Semiconductor wafers and various packages made of silicon, gallium arsenide, etc. are manufactured in a large diameter state, diced into chips, peeled off (picked up), and then transferred to the next process, the mounting process. At this time, the workpiece such as a semiconductor wafer is attached to an adhesive sheet (hereinafter sometimes referred to as a "workpiece processing sheet") comprising a base film and an adhesive layer, and is subjected to back grinding, dicing, cleaning, etc. Processing such as drying, expanding, picking up, and mounting is performed.

Here, the workpiece processing sheet is peeled off from the adherend after a predetermined processing step is completed, but at this time, static electricity called peeling charge is generated between the workpiece processing sheet and the adherend. There is. Such static electricity causes dust and the like to adhere to the work and the device, and also causes damage to the work and the like. Therefore, sheets for workpiece processing are required to have antistatic properties.

Patent Document 1 describes an adhesive that contains a resin material and a conductive material and has a defined surface resistivity and volume resistivity in order to accurately suppress or prevent static electricity from being generated on the adhered substrate (workpiece). A substrate for a tape is disclosed. As the conductive material, conductive polymers, permanently antistatic polymers (IDP), and the like are disclosed.

JP 2021-015953 Publication

However, in general, as the proportion of a conductive material, particularly a permanently antistatic polymer, added to a resin material increases, the mechanical strength of the resulting resin film tends to decrease. Therefore, in the adhesive tape base material disclosed in Patent Document 1, if a large amount of permanently antistatic polymer is blended in order to obtain sufficient antistatic properties, the mechanical strength as a base film for processing workpieces will decrease. Therefore, there is a risk that it will break during the process such as the above-mentioned expansion.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a base film and a workpiece processing sheet that can achieve both antistatic properties and mechanical strength.

In order to achieve the above object, the present invention first provides a base film including a resin layer containing a polyester resin, a polymeric antistatic agent, and carbon nanotubes (Invention 1).

In the above invention (invention 1), conductive paths are efficiently formed and the surface resistivity is effectively reduced by blending a polymeric antistatic agent and carbon nanotubes with the polyester resin as the matrix. descend. Therefore, in order to obtain the desired antistatic property, it is sufficient to mix a small amount of each of the polymer type antistatic agent and carbon nanotubes. Thereby, it is possible to suppress a decrease in the mechanical strength, particularly the elongation at break, of the base film due to these components, and it is possible to prevent the base film from being broken in a process such as expanding. Thus, according to the base film according to the above invention, it is possible to achieve both antistatic properties and mechanical strength.

In the above invention (invention 1), the content of the polymer 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 The amount is preferably 0.001% by mass or more and 1% by mass or less (Invention 2).

In the above inventions (Inventions 1 and 2), the polyester resin has an alicyclic structure and has 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 is preferable (Invention 3).

In the invention (invention 3), the polyester resin preferably contains the dicarboxylic acid having the alicyclic structure as a monomer unit constituting the polyester resin (invention 4).

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).

In the above inventions (Inventions 3 to 5), the number of carbon atoms constituting the ring of the alicyclic structure is preferably 6 or more and 14 or less (Invention 6).

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

In the invention (invention 7), the proportion of the dimer acid as a monomer unit constituting the polyester resin is 2 mol% or more and 25 mol% or less with respect to all dicarboxylic acids as monomer units composing the polyester resin. It is preferable that (Invention 8).

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).

In the above inventions (Inventions 1 to 9), the surface resistivity on at least one side of the front base film is preferably 1×10 ⁶ Ω/□ or more and 5×10 ¹¹ Ω/□ or less (Invention 10) .

In the above inventions (Inventions 1 to 10), the thickness of the base film is preferably 20 μm or more and 600 μm or less (Invention 11).

Second, the present invention provides a workpiece processing sheet comprising the base film (inventions 1 to 11) and an adhesive layer laminated on one side of the base film ( Invention 12).

In the invention (invention 12), it is preferable that the workpiece processing sheet is a dicing sheet (invention 13).

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

Embodiments of the present invention will be described below.
[Base film]
The base film according to this embodiment includes a resin layer (hereinafter sometimes referred to as "resin layer R") containing a polyester resin, a polymer type antistatic agent, and carbon nanotubes. The base film according to this embodiment may consist of only the resin layer R, or may include other layers in addition to the resin layer R.

In the base film according to this embodiment, conductive paths are efficiently formed and the surface resistivity is effectively improved by combining a polymer antistatic agent and carbon nanotubes with the polyester resin as the matrix. decreases. Therefore, in order to obtain the desired antistatic property, it is sufficient to mix a small amount of each of the polymer type antistatic agent and carbon nanotubes. Thereby, it is possible to suppress a decrease in the mechanical strength, particularly the elongation at break, of the base film due to these components, and it is possible to prevent the base film from being broken in a process such as expanding. In this manner, the base film according to this embodiment can achieve both antistatic properties and mechanical strength.

The content of the 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 0.001% by mass. The above content is preferably 1% by mass or less. When the contents of the polymer type antistatic agent and the carbon nanotubes are within the above ranges, excellent antistatic properties can be obtained, and mechanical strength, especially elongation at break, can be improved.

From the viewpoint of antistatic properties, the content of the polymer type antistatic agent in the resin layer R is preferably 0.1% by mass or more, more preferably 1% by mass or more, particularly 3% by mass. It is preferably at least 5% by mass, and more preferably at least 5% by mass. In addition, from the viewpoint of mechanical strength, the content of the polymeric antistatic agent in the resin layer R is preferably 50% by mass or less, more preferably 40% by mass or less, particularly 30% by mass. It is preferably at most 25% by mass, more preferably at most 25% by mass.

From the viewpoint of antistatic properties, the content of carbon nanotubes in the resin layer R is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, particularly 0.01% by mass. It is preferably at least 0.03% by mass, and more preferably at least 0.03% by mass. Further, from the viewpoint of mechanical strength, the content of carbon nanotubes in the resin layer R is preferably 1% by mass or less, more preferably 0.7% by mass or less, particularly 0.5% by mass. It is preferably at most 0.3% by mass, more preferably at most 0.3% by mass.

1. Each component (1) Polyester resin The polyester resin in this embodiment is particularly suitable as long as it exhibits the antistatic effect of the above-mentioned polymer type antistatic agent and carbon nanotubes, and can also exhibit the desired mechanical strength. Not limited.

Among these, the polyester resin in this embodiment is a polyester resin that has an alicyclic structure and has a heat of fusion of 2 J/g or more as measured by differential scanning calorimetry at a heating rate of 20° C./min (hereinafter referred to as "polyester resin P"). ) is preferable. As a result, the antistatic effect of the polymer type antistatic agent and carbon nanotubes is well exhibited, and the elongation at break becomes even more excellent. Furthermore, the workpiece processing sheet comprising a base film using the polyester resin P described above can effectively suppress the generation of cutting waste when used for dicing a workpiece using a rotating round blade. .

The following is expected to be the reason why the cutting debris suppressing effect is obtained as described above. However, it is not excluded that the above effects may be obtained due to a combination of the following reasons and other reasons, nor is it excluded that the above effects may be obtained due to reasons other than the following reasons.

First, polyester resin is expected to be easily cut at ester bond positions when dicing force is applied to a base material made using the polyester resin. As described above, the polyester resin P has an alicyclic structure and exhibits the above-mentioned heat of fusion, so that it has an appropriate structure (lamellar structure) in which a portion of its polymer chains are regularly folded. Therefore, when a dicing force is applied, it is expected that the polyester resin P will be easily cut even at the position of the lamella structure. As described above, the polyester resin P is more likely to be cut at specific positions when a dicing force is applied, compared to resins used in conventional base films.

Here, the mechanism by which cutting chips are generated from the base material of a general dicing sheet is that the base material is softened by the frictional heat generated during dicing, and then the rotating round blade comes into contact with the base material and cuts the cut portion of the base material. It is thought that this is because the cut portion of the base material is stretched and scraped off by applying the pulling force. In particular, most of the cutting debris thus generated has a thread-like form.

On the other hand, in the base film using the above-mentioned polyester resin P, before being stretched as described above, cutting occurs effectively in the vicinity of the ester bond and the lamella structure, and as a result, it is thought that the generation of cutting debris is suppressed. .

From the viewpoint of more easily achieving the above-mentioned cutting debris suppression effect, the 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 more preferably 15 J/g or more. On the other hand, the upper limit of the 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, and even 50 J/g. It may be less than or equal to 30 J/g, especially less than or equal to 30 J/g. The details of the method for measuring the heat of fusion described above are as described in the Examples section below.

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

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

Moreover, from the viewpoint of easily satisfying the above two conditions, it is preferable that the polyester resin P contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting the polyester resin. Moreover, 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 easier satisfying the above conditions, it is preferable that the polyester resin P contains both such dicarboxylic acids and diols. It is preferable to include.

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

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 with respect to all the monomer units constituting the polyester resin P is 20 mol% or more. It is preferably at least 25 mol%, more preferably at least 30 mol%, and even more preferably at least 35 mol%. Further, 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. Within these ranges, the polyester resin P tends to exhibit the above-mentioned heat of fusion, and as a result, the sheet for workpiece processing obtained using the base film according to the present embodiment has a superior cutting waste suppression effect. becomes easier to achieve.

In addition, when the polyester resin P contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting it, the dicarboxylic acid having an alicyclic structure relative to the entire dicarboxylic acid having a ring structure constituting the polyester resin P The proportion 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. When the ratio is 60% or more, the workpiece processing sheet obtained using the base film according to the present embodiment can easily achieve a better cutting waste suppression effect. Note that the upper limit of the ratio is not particularly limited, and may be, for example, 100 mol% or less. Note that the dicarboxylic acids having a ring structure include dicarboxylic acids having an aromatic ring structure in addition to dicarboxylic acids having an alicyclic structure.

The structure of the diol described above is not particularly limited as long as it has an alicyclic structure and two hydroxy groups. For example, a diol may have a structure in which two hydroxy 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 a hydroxy group. It's okay. Preferred examples of such diols include 1,2-cyclohexanediol (especially 1,2-cyclohexanedimethanol), 1,3-cyclohexanediol (especially 1,3-cyclohexanedimethanol), and 1,4-cyclohexanediol. (especially 1,4-cyclohexanedimethanol), 2,2-bis-(4-hydroxycyclohexyl)-propane, etc. Among these, it is preferable to use 1,4-cyclohexanedimethanol.

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 all monomer units constituting the polyester resin may be 35 mol% or more. It is preferably at least 40 mol%, particularly preferably at least 45 mol%. Further, the proportion is preferably 65 mol% or less, particularly preferably 60 mol% or less, and even more preferably 55 mol% or less. Within these ranges, the polyester resin P tends to exhibit the above-mentioned heat of fusion, and as a result, the sheet for workpiece processing obtained using the base film according to the present embodiment has a superior cutting waste suppression effect. becomes easier to achieve.

It is also preferable that the polyester resin P contains a dimer acid obtained by dimerizing an unsaturated fatty acid as a monomer unit constituting the polyester resin P, from the viewpoint that the base material can easily have desired flexibility. Here, the number of carbon atoms in the unsaturated fatty acid is preferably 10 or more, particularly preferably 15 or more. Moreover, it is preferable that the said carbon number is 30 or less, and it is especially preferable that it is 25 or less. Examples of such dimer acids include dicarboxylic acids with 36 carbon atoms obtained by dimerizing unsaturated fatty acids with 18 carbon atoms such as oleic acid and linoleic acid, and unsaturated fatty acids with 22 carbon atoms such as erucic acid. Examples include dicarboxylic acids having 44 carbon atoms obtained by dimerization. In addition, when obtaining the above-mentioned dimer acid, a small amount of trimer acid formed by trimerizing the above-mentioned unsaturated fatty acid may also be produced. The polyester resin P may contain such a trimer acid together with the above dimer acid.

When the polyester resin P contains the dimer acid as a monomer unit constituting it, the proportion of the dimer acid with respect to all the dicarboxylic acid units constituting the polyester resin P is preferably 2 mol% or more. In particular, it is preferably 5 mol% or more, and more preferably 10 mol% or more. Further, the proportion 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 tends to have the desired flexibility, and as a result, the workpiece processing sheet obtained using the base film according to this embodiment has excellent expandability and pick-up properties. It is also possible to achieve sexuality.

The polyester resin P may contain monomers other than the above-mentioned dicarboxylic acid, diol, and dimer acid as monomer units constituting it. Examples of such monomers include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid; phthalic acid, terephthalic acid, isophthalic acid, 2,6-naphthalene Examples include aromatic dicarboxylic acids such as dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, and 4,4'-diphenyldicarboxylic acid. Further, it may contain a diol component other than the diol 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; trimethylolpropane, and the like.

However, in the above-mentioned polyester resin P, monomers having an alicyclic structure (the above-mentioned dicarboxylic acids having an alicyclic structure and diols having an aliphatic structure) are aromatic, from the viewpoint of easily achieving an excellent cutting debris suppressing effect. It is preferable that it is contained in a larger amount than the monomer having a ring structure. In particular, among the monomer units constituting the polyester resin P, the molar ratio of the monomer units having an aromatic ring structure to the monomer units having an alicyclic structure is preferably less than 1, and more preferably 0.5 or less. preferably 0.2 or less, more preferably 0.1 or less, more preferably 0.05 or less, more preferably 0.03 or less, 0.01 or less More preferably, it is 0.005 or less, further preferably 0.001 or less, and most preferably 0.

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

The proportion of the polyester resin to all components constituting the resin layer R in this embodiment is preferably 50% by mass or more, particularly preferably 60% by mass or more, and further preferably 70% by mass or more. is preferred. When the above ratio is 50% by mass or more, the sheet for workpiece processing obtained using the base film according to the present embodiment can easily achieve a better cutting waste suppression effect. Note that the upper limit of the above ratio is not particularly limited, and may be, for example, 100% by mass or less.

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

The base film according to this embodiment exhibits excellent antistatic properties by using a polymeric antistatic agent, particularly the polymeric antistatic agent A described above, together with carbon nanotubes, and has a surface resistivity as described below. can be achieved.

The polymer compound contained in the polymer type antistatic agent in this embodiment is a compound having at least two or more repeating units. The weight average molecular weight of the polymer compound is preferably 300 or more, particularly preferably 1000 or more. Further, 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 a value measured by gel permeation chromatography (GPC method) in terms of standard polystyrene.

The above-mentioned polymer compound is not particularly limited, but is preferably a polymer containing a polyether segment from the viewpoint of easily exhibiting excellent antistatic properties. Examples of the above-mentioned polymer containing a polyether segment include a polymer containing a polyether segment and a polyolefin segment, a polymer containing a polyether segment and an amide segment (hereinafter sometimes referred to as "polyether ester amide"), etc. It will be done.

Examples of the polyether segments include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyhexamethylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, polyoxyethylene glycol, etc. Examples include polyoxyalkylene glycols such as polyoxypropylene glycol, polyalkylene ether diols, and the like. These segments may be arranged randomly or in blocks in the polymer.

Examples of the polyolefin segment include homopolymers of alpha olefins having 2 to 10 carbon atoms or copolymers of at least one alpha olefin and at least one other copolymerizable monomer. Examples of alpha olefins include ethylene, propylene, 1-butene, 2-methylpropene, 1-pentene, 3-methyl l-butene, 1-hexene, 4-methyl l-pentene, 3-methyl l-pentene, 1 - Examples include octene. These segments may be arranged randomly or in blocks in the polymer.

The polyether ester amide is not particularly limited as long as it is a polymer comprising an amide segment having an amide bond and an ether segment having an ether bond. These segments may be arranged randomly or in blocks in the polymer. Further, these segments may be connected to each other by an ester bond, an amide bond, or the like.

The above amide segment is, for example, dicarboxylic acid (e.g. oxalic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, 1,4-cyclohexanedicarboxylic acid, etc.) and diamine (e.g. ethylenediamine, Tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, decamethylene diamine, 2,2,4-trimethylhexamethylene diamine, 2,4,4-trimethylhexamethylene diamine, 1,3-bis(aminomethyl)cyclohexane, 1 , 4-bis(aminomethyl)cyclohexane, methylenebis(4-aminocyclohexane), m-xylylenediamine, p-xylylenediamine, etc.), and polycondensation of lactams such as ε-caprolactam and ω-dodecalactam. Ring-opening polymerization, polycondensation of aminocarboxylic acids such as 6-aminocaproic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid, or ring-opening products of the above lactams or combinations of aminocarboxylic acids and dicarboxylic acids. It is obtained by condensation, a ring-opened product of the above-mentioned lactam, or polycondensation of an aminocarboxylic acid, a dicarboxylic acid, and a diamine. 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., and nylon 11, nylon 12, etc. are particularly preferred. The molecular weight of the amide segment is preferably about 100 to 5,000, for example.

The organic cation and organic anion constituting the organic salt contained in the polymeric antistatic agent A are not particularly limited as long as they are ionized organic compounds. Examples of the organic cation include those derived from at least one of imidazolium cations, pyridinium cations, pyrrolidinium cations, ammonium cations, sulfonium cations, and phosphonium cations. Examples of the organic anions include linear alkylbenzene sulfonic acid, sulfonate anion (RSO ^3- ), carboxylate anion (RCOO ^- ), alkoxide or phenoxide anion (RO ^- ), and organic imide anion (R ₂ N ^- ). , methide (R ₃ C ⁻ ) anion, organic borate (R ₄ B ⁻ ) anion, and the like.

The salt of the inorganic protonic acid is not particularly limited, and examples thereof include alkali metal salts, alkaline earth metal salts, zinc salts, and ammonium salts. Examples of the alkali metal salt include salts having an alkali metal such as lithium, sodium, and potassium as a cation component. Further, examples of the alkaline earth metal salts include salts having alkaline earth metals such as magnesium and calcium as a cation component.

The polymeric antistatic agent in this embodiment, particularly the polymeric antistatic agent A, preferably has a 5% weight loss temperature of 200°C or higher, particularly preferably 250°C or higher, in the air. Since the above 5% weight loss temperature is 200°C or higher, the polymeric antistatic agent is difficult to decompose even when heated during kneading and film forming of the base film material, and sufficient antistatic properties are achieved. It becomes easier to express one's sexuality. The upper limit of the 5% weight loss temperature is not particularly limited, and may be, for example, 1000°C or lower, particularly 900°C or lower, and even 700°C or lower.

Further, the polymer type antistatic agent in this embodiment, particularly the polymer type antistatic agent A, preferably has a 5% weight loss temperature of 250°C or higher in a nitrogen atmosphere, particularly preferably 270°C or higher. Preferably, the temperature is more preferably 300°C or higher. Since the above 5% weight loss temperature is 250°C or higher, the polymer type antistatic agent is difficult to decompose even if heated during kneading or film forming of the base film material, and sufficient antistatic properties are achieved. It becomes easier to express one's sexuality. The upper limit of the 5% weight loss temperature is not particularly limited, and may be, for example, 1000°C or lower, particularly 900°C or lower, and even 700°C or lower.

The details of the method for measuring the 5% weight loss temperature in the air atmosphere and nitrogen atmosphere are as described in Examples below.

In addition to the above-mentioned polymeric antistatic agent A, the polymeric antistatic agent in this embodiment includes, for example, an ether antistatic agent, an ester antistatic agent, a polyamide antistatic agent, and an acrylic antistatic agent. etc., or a polyether ester amide type antistatic agent. The polyether ester amide antistatic agent is classified as an ether antistatic agent, an ester antistatic agent, and a polyamide antistatic agent.

(3) Carbon nanotubes The carbon nanotubes in this embodiment may be single-walled carbon nanotubes having a structure in which one graphite layer forms a cylinder, or two or more graphite layers each forming a cylinder. However, from the viewpoint of efficient formation of conductive paths when used in combination with a polymeric antistatic agent, single-walled carbon nanotubes are preferable. preferable. Note that a carbon nanohorn has a structure in which a graphite layer is rounded into a substantially conical shape, but the carbon nanotubes in this embodiment also include carbon nanohorns.

The average length of the carbon nanotubes in this embodiment 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. Further, 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. When the average length of the carbon nanotubes is within the above range, a conductive path can be formed more efficiently when used in combination with a polymeric antistatic agent, and the mechanical strength of the base film is less likely to be adversely affected.

The average outer diameter of the carbon nanotubes in this embodiment 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. It is preferable that Further, 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. preferable. When the average outer diameter of the carbon nanotubes is within the above range, a conductive path can be formed more efficiently when used in combination with a polymeric antistatic agent, and the mechanical strength of the base film is less likely to be adversely affected.

The aspect ratio of the carbon nanotubes in this embodiment is preferably 100 or more, more preferably 250 or more, particularly preferably 500 or more, and even more preferably 1000 or more. Further, the aspect ratio is preferably 25,000 or less, more preferably 20,000 or less, particularly preferably 15,000 or less, and even more preferably 10,000 or less. When the aspect ratio of the carbon nanotubes is within the above range, a conductive path can be formed more efficiently when used in combination with a polymeric antistatic agent, and the mechanical strength of the base film is less likely to be adversely affected.

The carbon nanotubes in this embodiment can be manufactured by a conventional method. For example, it can be manufactured by the arc discharge method, laser evaporation method, pyrolysis method, etc. described in Saito and Bando "Basics of Carbon Nanotubes" (P23-P57, published by Coronasha Publishing, 1998), and if necessary, the purity It can also be purified by hydrothermal methods, centrifugal separation methods, ultrafiltration methods, oxidation methods, etc. in order to increase the

(4) Other components The resin layer R in this embodiment may contain components other than the above-mentioned polyester resin, polymeric antistatic agent, and carbon nanotubes. Other components include, for example, components used in the base film of general workpiece processing sheets, specifically flame retardants, plasticizers, lubricants, antioxidants, colorants, and infrared absorbers. , ultraviolet absorbers, ion scavengers, and other additives. Although the content of these additives is not particularly limited, it is preferably within a range that allows the base film to exhibit desired functions.

2. Structure of Base Film The layer structure of the base film in this embodiment may be a single layer as long as it includes the resin layer R containing the above-mentioned polyester resin, polymeric antistatic agent, and carbon nanotubes. Although the resin layer R may have multiple layers, it is preferable that the resin layer R is a single layer.

On the other hand, in the case of multiple layers, a plurality of resin layers R may be laminated, or the resin layer R and other layers may be laminated. When other layers are expanded together with the resin layer R, it is preferable that the layer has a breaking elongation equal to or higher than that of the resin layer R.

The surface of the base film in this embodiment on which the adhesive layer is laminated may be subjected to surface treatment such as primer treatment, corona treatment, plasma treatment, etc., in order to increase the adhesion with the adhesive layer. .

3. Physical Properties of Base Film (1) Thickness The thickness of the base film in this embodiment is preferably 20 μm or more, particularly preferably 40 μm or more, and even more preferably 60 μm or more. Further, the thickness of the base film in this embodiment 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 workpiece processing sheet has appropriate strength, and the workpiece fixed on the workpiece processing sheet can be easily supported well. Moreover, it tends to have a desired elongation at break and has excellent expandability.

(2) Surface resistivity The surface resistivity of the base film according to this embodiment on at least one side thereof is preferably 5×10 ¹¹ Ω/□ or less, and preferably 4×10 ¹¹ Ω/□ or less. is more preferable, particularly preferably 3×10 ¹¹ Ω/□ or less, and even more preferably 2×10 ¹¹ Ω/□ or less. Since the base film according to the present embodiment has such a surface resistivity, the workpiece processing sheet formed using the base film is difficult to be charged during storage or use, and is not easily charged. It is possible to satisfactorily suppress the adhesion of dust to the workpiece processing sheet caused by this. As described above, the base film according to this embodiment can achieve the low surface resistivity as described above without reducing mechanical strength by using a polymer antistatic agent and carbon nanotubes together. I can do it.

The lower limit value of the surface resistivity is not particularly limited, and may be, for example, 1×10 ⁶ Ω/□ or more, or 1×10 ⁷ Ω/□Ω/□, particularly 1 It may be ×10 ⁸ Ω/□Ω/□ or more. Note that the method for measuring surface resistivity in this specification is as shown in the test example described below.

(3) Elongation at break The elongation at break in the MD direction of the base film according to this embodiment is preferably 200% or more, more preferably 220% or more, and particularly preferably 240% or more. Preferably, it is more preferably 260% or more. Further, the elongation at break in the TD direction of the base film according to the present embodiment is preferably 200% or more, more preferably 220% or more, particularly preferably 250% or more, and It is preferable that it is 300% or more. When the elongation at break of the base film is within the above range, it is possible to effectively prevent breakage during steps such as expanding. As described above, the base film according to the present embodiment can achieve a high elongation at break while keeping the surface resistivity low by using a polymer antistatic agent and carbon nanotubes together. It is possible. 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.

The upper limit of the elongation at break in the MD direction of the base film according to the present embodiment is not particularly limited, and may be 600% or less, 550% or less, and particularly 500% or less. It's okay. Further, the upper limit of the elongation at break in the TD direction of the base film according to the present embodiment is not particularly limited, and may be 600% or less, or 550% or less, particularly 500% or less. It may be. Note that the method for measuring the elongation at break in this specification is based on JIS K7127:1999, and specifically as shown in the test example described below.

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 above-mentioned polyester resin, polymer antistatic agent, and carbon nanotube-containing material is used. For example, the T-die method , a melt extrusion method such as a round die method; a calendar method; a solution method such as a dry method or a wet method. Among these, from the viewpoint of efficiently manufacturing the base film, it is preferable to employ the melt extrusion method or the calender method.

When producing a base film consisting of a single layer of the resin layer R by a melt extrusion method, the raw materials for the resin layer R (including the aforementioned polyester resin, polymeric antistatic agent, and carbon nanotubes) are kneaded, and the obtained The film may be formed directly from the kneaded material or after once producing pellets using a known extruder. At the time of the above kneading, the polyester resin and carbon nanotubes (masterbatch) may be kneaded in advance to obtain a carbon nanotube kneaded product, and then the carbon nanotube kneaded product, the polyester resin, and the polymer type antistatic agent are kneaded. preferable. This improves the dispersibility of carbon nanotubes.

In addition, when producing a base film consisting of multiple layers by melt extrusion, the components constituting each layer may be kneaded, and the resulting kneaded product may be used directly, or once pellets are produced, using a known extruder. Then, a plurality of layers may be simultaneously extruded to form a film.

In addition, when the base film has multiple layers, the raw materials for the resin layer R (including the aforementioned polyester resin, polymer type antistatic agent, and carbon nanotubes) are added to one side of a predetermined layer formed in advance into a film shape. The resin layer R may be formed on a predetermined layer by applying a coating liquid containing the following and drying or curing the coating liquid. Thereby, a base film including the predetermined layer and the resin layer R can be obtained.

[Work processing sheet]
The workpiece processing sheet according to the present embodiment includes the base film described above and an adhesive layer laminated on one side of the base film.

1. Structure of Workpiece Processing Sheet Among the members constituting the workpiece processing sheet according to the present embodiment, the structure other than the above-mentioned base film will be described below.

(1) Adhesive layer The adhesive constituting the above-mentioned adhesive layer must exhibit sufficient adhesion to the adherend (especially adhesion to the workpiece that is sufficient for processing the workpiece). There is no particular limitation as long as it is possible. Examples of the adhesive constituting the adhesive layer include acrylic adhesive, rubber adhesive, silicone adhesive, urethane adhesive, polyester adhesive, polyvinyl ether adhesive, and the like. Among these, it is preferable to use acrylic pressure-sensitive adhesives from the viewpoint of easily exhibiting desired adhesive strength.

The adhesive constituting the adhesive layer in this embodiment may be an adhesive that does not have active energy ray curability, but may be an adhesive that has active energy ray curability (hereinafter referred to as "active energy ray curable adhesive"). ) is preferable. Since the adhesive layer is composed of an active energy ray-curable adhesive, the adhesive layer can be cured by irradiation with active energy rays, and the adhesive strength of the workpiece processing sheet to the adherend can be easily reduced. I can do it. In particular, by irradiating with active energy rays, it becomes possible to easily separate the processed workpiece from the workpiece processing sheet.

The active energy ray-curable adhesive constituting the adhesive layer may be one containing an active energy ray-curable polymer as a main component, or a non-active energy ray-curable polymer (active energy ray-curable). The main component may be a mixture of a monomer and/or oligomer having at least one active energy ray-curable group.

Polymers that are curable with active energy rays are (meth)acrylic acid ester polymers (hereinafter referred to as ``active energy ray-curable'') in which functional groups that are curable with active energy rays (active energy ray-curable groups) are introduced into the side chains. (sometimes referred to as "polymer") is preferable. This active energy ray-curable polymer is obtained by reacting an acrylic copolymer having a functional group-containing monomer unit with an unsaturated group-containing compound having a functional group that binds to the functional group. is preferred. In addition, in this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, the concept of "copolymer" is also included in "polymer".

The weight average molecular weight of the 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. Further, the weight average molecular weight is preferably 2.5 million or less, particularly preferably 2 million or more, and even more preferably 1.5 million or less. Note that the weight average molecular weight (Mw) in this specification is a value measured by gel permeation chromatography (GPC method) in terms of standard polystyrene.

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

The weight average molecular weight of the acrylic polymer 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. . Further, the weight average molecular weight is preferably 2.5 million or less, particularly preferably 2 million or more, and even more preferably 1.5 million or less.

In addition, when ultraviolet rays are used as active energy rays for curing an active energy ray-curable adhesive, it is preferable to add a photopolymerization initiator to the adhesive. Further, an active energy ray non-curable polymer component or oligomer component, a crosslinking agent, etc. may be added to the adhesive.

The thickness of the adhesive layer in this embodiment is preferably 1 μm or more, particularly preferably 2 μm or more, and even more preferably 3 μm or more. Further, 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. When the thickness of the adhesive layer is 1 μm or more, the workpiece processing sheet according to this embodiment easily exhibits desired adhesiveness. Moreover, since the thickness of the adhesive layer is 50 μm or less, the adherend can be easily separated from the adhesive layer after being cured.

(2) Release sheet In the workpiece processing sheet according to this embodiment, until the surface of the adhesive layer opposite to the base film (hereinafter referred to as "adhesive surface") is attached to the adherend. During this period, a release sheet may be laminated on the surface for the purpose of protecting the surface.

The structure of the above-mentioned release sheet is arbitrary, and a plastic film subjected to release treatment using a release agent or the like is exemplified. Specific examples of the plastic film include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; and polyolefin films such as polypropylene and polyethylene. As the above-mentioned release agent, silicone type, fluorine type, long chain alkyl type, etc. can be used, and among these, silicone type is preferable because it is inexpensive and provides stable performance.

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 workpiece processing sheet according to the present embodiment, an adhesive layer may be laminated on the opposite side of the adhesive layer to the base film. In this case, the workpiece processing sheet according to this embodiment can be used as a dicing/die bonding sheet. In this sheet, a workpiece is attached to the opposite side of the adhesive layer from the adhesive layer, and the adhesive layer is diced together with the workpiece to obtain chips in which individualized adhesive layers are laminated. be able to. The chip can be easily fixed to the object on which the chip is to be mounted, by means of the individualized adhesive layer. Examples of the material constituting the adhesive layer described above include those containing a thermoplastic resin and a low molecular weight thermosetting adhesive component, and those containing a B-stage (semi-cured) thermosetting adhesive component. It is preferable to use

Further, in the workpiece processing sheet according to the present 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. In such a sheet, a workpiece is pasted on the side of the protective film forming layer opposite to the adhesive layer, and the protective film forming layer is diced together with the work, so that the individualized protective film forming layer is laminated. You can get the chips. The work preferably has a circuit formed on one side, and in this case, a protective film forming layer is usually laminated on the opposite side to the side on which the circuit is formed. By curing the separated 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 made of an uncured curable adhesive.

2. Method for manufacturing a workpiece processing sheet The method for manufacturing a workpiece processing sheet according to the present embodiment is not particularly limited. For example, after forming an adhesive layer on a release sheet, it is preferable to obtain a workpiece processing sheet by laminating one side of a base film on the opposite side of the adhesive layer to the release sheet.

The above-described adhesive layer can be formed by a known method. For example, a coating liquid containing an adhesive composition for forming an adhesive layer and, if desired, a solvent or a dispersion medium is prepared. Then, the coating liquid is applied to the releasable surface of the release sheet (hereinafter sometimes referred to as "release surface"). Subsequently, an adhesive layer can be formed by drying the obtained coating film.

The coating liquid described above can be applied by a known method, such as a bar coating method, a knife 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 in its properties as long as it can be applied, and may contain components for forming the adhesive layer as a solute or as a dispersoid. . Further, the release sheet may be peeled off as a process material, or may protect the adhesive layer until it is attached to an adherend.

When the adhesive composition for forming the adhesive layer contains the above-mentioned crosslinking agent, the coating can be improved by changing the drying conditions (temperature, time, etc.) or by separately providing heat treatment. It is preferable to allow a crosslinking reaction between the polymer component within the film and the crosslinking agent to proceed, and to form a crosslinked structure at a desired density within the adhesive layer. Furthermore, in order to allow the above-mentioned crosslinking reaction to proceed sufficiently, after bonding the adhesive layer and the base film, curing may be performed, for example, by leaving it in an environment of 23° C. and 50% relative humidity for several days. good.

3. How to use the workpiece processing sheet The workpiece processing sheet according to the present embodiment can be used for processing a workpiece such as a semiconductor wafer. In this case, after the adhesive surface of the workpiece processing sheet according to this embodiment is attached to the workpiece, the workpiece can be processed on the workpiece processing sheet. Depending on the processing, the workpiece processing sheet according to the present embodiment can be used as a workpiece processing sheet such as a back grinding sheet, a dicing sheet, an expanded sheet, and a pickup sheet. Here, examples of the work include semiconductor members such as semiconductor wafers and semiconductor packages, and glass members such as glass plates.

Since the workpiece processing sheet according to the present embodiment is constructed using the base film according to the embodiment described above, it exhibits excellent antistatic properties and good mechanical strength, especially elongation at break. be able to. Therefore, the workpiece processing sheet according to the present embodiment is particularly suitable as an expandable sheet or a dicing sheet used in the process from dicing to expansion.

In addition, when the workpiece processing sheet according to the present embodiment includes the above-described adhesive layer, the workpiece processing sheet can be used as a dicing/die bonding sheet. Furthermore, when the workpiece processing sheet according to the present embodiment includes the above-mentioned protective film forming layer, the workpiece processing sheet can be used as a protective film forming and dicing sheet.

Further, when the adhesive layer in the workpiece processing sheet according to the present embodiment is composed of the above-mentioned active energy ray-curable adhesive, the following active energy rays may be irradiated during use. is also preferable. That is, when processing of a workpiece is completed on the workpiece processing sheet and the processed workpiece is separated from the workpiece processing sheet, the adhesive layer may be irradiated with active energy rays before the separation. preferable. As a result, the adhesive layer is cured, the adhesive strength of the workpiece processing sheet to the processed workpiece is favorably reduced, and separation of the processed workpiece is facilitated.

The embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design changes and equivalents that fall within the technical scope of the present invention.

Hereinafter, the present invention will be explained in more detail with reference to examples, but the scope of the present invention is not limited to these examples.

[Example 1]
(1) Preparation of base film In a reactor equipped with a stirrer, a distillation tube, and a pressure reducing device, 12.90 kg of dimethyl 1,4-cyclohexanedicarboxylate (trans isomer ratio 98%), 1,4-cyclohexanedicarboxylate, 11.47 kg of methanol, 0.3 kg of ethylene glycol, and 0.11 kg of an ethylene glycol solution containing 10% Mn acetate tetrahydrate were charged, heated to 200°C under nitrogen flow, and then raised to 230°C over 1 hour. It was warm. After holding as it was for 2 hours to perform a transesterification reaction, 10.30 kg of erucic acid-derived dimer acid (carbon number 44, manufactured by Croda, product name "PRIPOL1004") and 0.11 kg of an ethylene glycol solution containing 10% trimethyl phosphate were added. was introduced into the system, followed by an esterification reaction at 230°C for 1 hour. Subsequently, after adding and stirring 300 ppm of germanium dioxide as a polycondensation catalyst, the pressure was reduced to 133 Pa or less in 1 hour, and during this time the internal temperature was raised from 230°C to 270°C, and the predetermined viscosity was achieved under high vacuum of 133 Pa or less. The polycondensation reaction was carried out by stirring until the temperature reached 100 mL. The obtained polymer was extruded into strands into water and cut into pellets.

The polyester resin pellets thus obtained were dried at 85° C. for 4 hours or more. Thereafter, 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 a carbon nanotube kneaded material (A). Obtained.

Next, 85 parts by mass of the above polyester resin pellets, 10 parts by mass of a polyether ester amide polymer type antistatic agent (manufactured by Sanyo Chemical Industries, Ltd., product name "Pellectron AS"), and the above carbon nanotube kneaded product (A). 5 parts by mass were kneaded using a twin-screw kneader (240°C, 12 minutes) to obtain pellets. Note that the content of carbon nanotubes in the pellet was 0.05% by mass.

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

The above polyester resin contains about 50 mol% of 1,4-cyclohexanedimethanol, about 40.5 mol% of dimethyl 1,4-cyclohexanedicarboxylate, and a dimer derived from erucic acid as monomers constituting the resin. It contained 9.5 mol% of acid. Further, the proportion of the dimer acid to all dicarboxylic acid units constituting the polyester resin was 19.1 mol%. Furthermore, when the heat of fusion of the polyester resin was measured by the method described later, it was 20 J/g.

Further, the 5% weight loss temperature of the polymer type antistatic agent was measured by the method described below, and was found to be 260° C. under an air atmosphere and 333° C. under a nitrogen atmosphere.

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

100 parts by mass of the (meth)acrylic acid ester polymer obtained as described above (in terms of solid content, the same applies hereinafter), 120 parts by mass of urethane acrylate oligomer (Mw: 8,000), and 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., product name "Omnirad 184") to prepare an energy ray-curable adhesive composition. I got it.

(3) Formation of adhesive layer The adhesive composition obtained in step (2) above is applied to a release sheet (manufactured by Lintec, product: The resulting coating film was dried at 100° C. for 1 minute. Thereby, a laminate was obtained in which a 10 μm thick adhesive layer was formed on the release surface of the release sheet.

(4) Preparation of sheet for workpiece processing By bonding one side of the base film obtained in the above step (1) and the surface on the adhesive layer side of the laminate obtained in the above step (3), A workpiece processing sheet was obtained.

(5) Various measurement methods The heat of fusion of the polyester resin described above was measured using a differential scanning calorimeter (DSC, manufactured by TA Instruments, product name "DSC Q2000") in accordance with JIS K 7121:2012. did. Specifically, first, heat from room temperature to 250 °C at a temperature increase rate of 20 °C/min, hold at 250 °C for 10 minutes, lower the temperature to -60 °C at a temperature decrease rate of 20 °C/min, and heat at -60 °C for 10 minutes. Hold for minutes. Thereafter, it was heated again to 250° C. at a heating rate of 20° C./min to obtain a DSC curve, and the melting point was measured.

The 5% weight loss temperature of the polymeric antistatic agent mentioned above was determined in accordance with JIS K7120:1987 using a simultaneous differential thermal and thermogravimetric measuring device (manufactured by Shimadzu Corporation, product name "DTG-60"). Ta. Specifically, thermogravimetry was performed by raising the temperature from 40°C to 550°C at a gas inflow rate of 100 ml/min and a temperature increase rate of 20°C/min using air or nitrogen as the inflowing gas. From the obtained thermogravimetric curve, the temperature at which the mass decreases by 5% with respect to the mass at a temperature of 100° C. (5% weight loss temperature) was determined.

Moreover, the weight average molecular weight (Mw) mentioned above is the weight average molecular weight in terms of standard polystyrene measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement).
<Measurement conditions>
・Measuring device: Tosoh Corporation, HLC-8320
・GPC column (passed in the following order): TSK gel superH-H manufactured by Tosoh Corporation
TSK gel superHM-H
TSK gel superH2000
・Measurement solvent: Tetrahydrofuran ・Measurement temperature: 40℃

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

[Test Example 1] (Measurement of surface resistivity)
The surface resistivity of one side of the base films produced in Examples and Comparative Examples was measured. Specifically, a sample obtained by cutting a base film into a size of 100 mm x 100 mm was measured using an ultra-high resistance/micro ammeter (manufactured by ADC Corporation, product name: "Digital ultra-high resistance/micro ammeter 5450"). The surface resistivity (Ω/□) was measured under the conditions of an applied voltage of 100 V and an applied time of 60 seconds. The results are shown in Table 1.

From the above measurement results, surface resistivity (antistatic property) was evaluated based on the following criteria. The results are shown in Table 1.
〇…Surface resistivity is 5×10 ¹¹ Ω/□ or less ×…Surface resistivity is over 5×10 ¹¹ Ω/□

[Test Example 2] (Measurement of elongation at break)
The base films produced in Examples and Comparative Examples were cut into a size of 15 mm x 140 mm to obtain test pieces. At this time, two types of test pieces were obtained: a test piece for the MD direction in which the long side (140 mm side) of the test piece was parallel to the MD direction of the base film, and a test piece for the TD direction in which the long side (140 mm side) of the test piece was parallel to the TD direction.

The elongation at break at 23°C was measured for the above two types of test pieces in accordance with JIS K7127:1999. Specifically, the above test piece was subjected to a tensile test at a speed of 200 mm/min after setting the distance between the chucks to 100 mm in a tensile testing machine (manufactured by Shimadzu Corporation, product name "Autograph AG-XPlus"), The elongation at break (%) when the test piece was cut was measured. At this time, the elongation at break (%) in the MD direction was measured using a test piece for the MD direction, and the elongation at break (%) in the MD direction was measured using a test piece for the TD direction. The elongation at break (%) in the direction was measured.The results are shown in Table 1.

From the above measurement results, the elongation at break (mechanical strength) was evaluated based on the following criteria. The results are shown in Table 1.
〇…Elongation at break is 200% or more ×…Elongation at break is less than 200%

As can be seen from Table 1, the base film of the workpiece processing sheet manufactured in the example has a low surface resistivity and exhibits excellent antistatic properties, as well as a high elongation at break and good mechanical strength. It was something.

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

Claims (13)

A base film comprising a resin layer containing polyester resin, a polymeric 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 50% by mass or less,
The base film according to claim 1, wherein the content of the carbon nanotubes in the resin layer is 0.001% by mass or more and 1% by mass or less. 3. The polyester resin has an alicyclic structure and has a heat of fusion of 2 J/g or more as measured by differential scanning calorimetry at a heating rate of 20° C./min. The base film described. The base film according to claim 3, wherein the polyester resin contains the dicarboxylic acid having the alicyclic structure as a monomer unit constituting the polyester resin. The base film according to claim 3 or 4, wherein the polyester resin contains a diol having the alicyclic structure as a monomer unit constituting the polyester resin. The base film according to any one of claims 3 to 5, wherein the number of carbon atoms constituting the ring of the alicyclic structure is 6 or more and 14 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 base film according to any one of claims 1 to 6, wherein the unsaturated fatty acid has a carbon number of 10 or more and 30 or less. Claim characterized in that the proportion of the dimer acid as a monomer unit constituting the polyester resin with respect to all the dicarboxylic acids as monomer units constituting the polyester resin is 2 mol% or more and 25 mol% or less. 7. The base film according to 7. The polymer type antistatic agent contains a polymer compound,
The base film according to any one of claims 1 to 8, wherein the polymer compound is a polymer containing a polyether segment. The surface resistivity of at least one side of the front base film is 1×10 ⁶ Ω/□ or more and 5×10 ¹¹ Ω/□ or less, according to any one of claims 1 to 9. Base film. The base film according to any one of claims 1 to 10, wherein the base film has a thickness of 20 μm or more and 600 μm or less. The base film according to any one of claims 1 to 11,
A workpiece processing sheet comprising: an adhesive layer laminated on one side of the base film. The workpiece processing sheet according to claim 12, wherein the workpiece processing sheet is a dicing sheet.