Adhesive sheet

Abstract

An adhesive sheet comprising a base material and an adhesive agent layer that is layered on one surface of the base material, wherein the base material is formed from a material comprising a polyester resin, and the polyester resin has an alicyclic structure and a heat of fusion of at least 2J / g as measured with a differential scanning calorimeter when the temperature is increased at a rate of 20°C / min. The adhesive sheet enables the suppression of manufacturing costs while also inhibiting the occurrence of chips from cutting.

Description

Technical Field

[0001] The present invention relates to an adhesive sheet that can be suitably used as a work processing sheet for processing works such as semiconductor wafers.

Background Art

[0002] Semiconductor wafers such as silicon and gallium arsenide and various packages are manufactured in a large-diameter state, cut (diced) into chips, peeled off (picked up), and then transferred to the next process, the mounting process. At this time, a work such as a semiconductor wafer is in a state of being attached to an adhesive sheet having a base material and an adhesive layer (hereinafter sometimes referred to as a "work processing sheet"), and is processed such as back grinding, dicing, washing, drying, expanding, picking up, and mounting.

[0003] As one of the above-described dicing methods, there is a method of cutting a work with a rotating round blade (dicing blade). In this method, in order to surely cut the work, it is common to also partially cut the work processing sheet to which the work is attached, together with the work.

[0004] Thus, when the work processing sheet is cut together with the work, cutting chips made of the materials constituting the adhesive layer and the base material may be generated from the work processing sheet. In particular, such cutting chips are usually generated in the vicinity of the line (kerf line) through which the round blade has passed, on the chips obtained by cutting and the work processing sheet.

[0005] When the chip is sealed with a large amount of cutting chips still attached to it, the cutting chips attached to the chip are decomposed by the heat of the sealing, and this thermal decomposition product may destroy the package or cause malfunction in the resulting device. Since it is difficult to remove this cutting chip by washing, the yield of the dicing process is significantly reduced due to the generation of cutting chips. Therefore, when dicing is performed with a rotating round blade, it is required to prevent the generation of cutting chips.

[0006] For the purpose of suppressing the generation of such cutting chips, Patent Document 1 discloses an invention in which a polyolefin-based film irradiated with 1 to 80 Mrad of electron beam or γ (gamma) ray is used as the base film of the dicing sheet. In this invention, it is considered that cross-linking by covalent bonds is formed in the resin constituting the base film by irradiation with electron beam or γ ray, and the generation of cutting chips is suppressed.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, in the invention of Patent Document 1, since irradiation with radiation such as electron beam or γ ray is performed after once forming the resin into a film as described above, the manufacturing process increases by one, and the manufacturing cost tends to be higher than that of a general base film.

[0009] The present invention has been made in view of such a situation, and an object thereof is to provide an adhesive sheet that can suppress the generation of cutting chips while being manufacturable at a reduced manufacturing cost.

Means for Solving the Problems

[0010] In order to achieve the above object, firstly, the present invention provides an adhesive sheet comprising a base material and an adhesive layer laminated on one side of the base material, wherein the base material is made of a material containing a polyester resin, and the polyester resin has an alicyclic structure and a heat of fusion measured by differential scanning calorimetry at a heating rate of 20 ° C / min of 2 J / g or more (Invention 1).

[0011] The adhesive sheet according to the above invention (Invention 1) is such that the base material is made of a material containing a polyester resin, and the polyester resin has an alicyclic structure and exhibits the above-described heat of fusion. Therefore, even when used for dicing using a rotating round blade, the generation of cutting chips can be favorably suppressed.

[0012] In the above invention (Invention 1), it is preferable that the polyester resin contains a dicarboxylic acid having the alicyclic structure as a monomer unit constituting the polyester resin (Invention 2).

[0013] In the above inventions (Inventions 1 and 2), it is preferable that the polyester resin contains a diol having the alicyclic structure as a monomer unit constituting the polyester resin (Invention 3).

[0014] In the above inventions (Inventions 1 to 3), it is preferable that the alicyclic structure has 6 or more and 14 or less carbon atoms forming the ring (Invention 4).

[0015] In the above inventions (Inventions 1 to 4), the polyester resin contains a dimer acid formed by dimerizing an unsaturated fatty acid as a monomer unit constituting the polyester resin, and the carbon number of the unsaturated fatty acid is preferably 10 or more and 30 or less (Invention 5).

[0016] In the above invention (Invention 5), the ratio of the dimer acid as a monomer unit constituting the polyester resin to all dicarboxylic acids as monomer units constituting the polyester resin is preferably 2 mol% or more and 25 mol% or less (Invention 6).

[0017] In the above invention (Inventions 1 to 6), the tensile modulus of the base material at 23°C is preferably 100 MPa or more and 800 MPa or less (Invention 7).

[0018] In the above invention (Inventions 1 to 7), the elongation at break of the base material at 23°C is preferably 200% or more and 800% or less (Invention 8).

[0019] In the above invention (Inventions 1 to 8), the thickness of the base material is preferably 20 μm or more and 600 μm or less (Invention 9).

[0020] In the above invention (Inventions 1 to 9), the pressure-sensitive adhesive layer is preferably composed of an acrylic pressure-sensitive adhesive (Invention 10).

[0021] In the above invention (Inventions 1 to 10), it is preferably used as a sheet for work processing (Invention 11).

[0022] In the above invention (Invention 11), the sheet for work processing is preferably a dicing sheet (Invention 12).

Effect of the Invention

[0023] The pressure-sensitive adhesive sheet according to the present invention can be manufactured while suppressing the manufacturing cost, and can further suppress the generation of cutting chips.

Embodiment for Carrying Out the Invention

[0024] Hereinafter, embodiments of the present invention will be described. The pressure-sensitive adhesive sheet according to this embodiment includes a base material and a pressure-sensitive adhesive layer laminated on one side of the base material. Although the pressure-sensitive adhesive sheet can be used for various applications like a general pressure-sensitive adhesive sheet, it is particularly preferably used as a sheet for workpiece processing used for processing workpieces such as semiconductor wafers, and especially preferably used as a dicing sheet used for dicing workpieces.

[0025] 1. Configuration of the pressure-sensitive adhesive sheet (1) Base material The base material in this embodiment is made of a material containing a polyester resin. The polyester resin has an alicyclic structure and a heat of fusion measured by differential scanning calorimetry at a heating rate of 20 °C / min of 2 J / g or more. Since the base material is made of a material containing a polyester resin having an alicyclic structure and exhibiting the above heat of fusion, the pressure-sensitive adhesive sheet according to this embodiment can favorably suppress the generation of cutting chips when used for dicing workpieces using a rotating round blade.

[0026] The following reasons are expected for obtaining such a cutting chip suppression effect. However, it is not excluded that the above effect is obtained by a combination of the following reasons and other reasons, and it is not excluded that the above effect is obtained by reasons other than the following reasons.

[0027] First, it is expected that when a dicing force is applied to a base material made using the polyester resin, the polyester resin is likely to be cut at the position of the ester bond. Furthermore, as described above, the polyester resin in the present embodiment has an alicyclic structure and exhibits the above-mentioned heat of fusion, so that it moderately has a structure (lamellar structure) in which a part of its polymer chain is regularly folded. Therefore, when a dicing force is applied, it is expected that the polyester resin is also likely to be cut at the position of the lamellar structure. Thus, the polyester resin in the present embodiment is more likely to be cut at a specific position when a dicing force is applied, compared to the resins used in conventional base materials.

[0028] Here, as a mechanism for generating cutting chips from the base material of a general dicing sheet, it is considered that the base material is softened by the frictional heat generated during dicing, and then a force is applied by the rotating round blade contacting and pulling the cut portion of the base material, so that the cut portion of the base material is scraped off while being stretched. In particular, many of the cutting chips generated in this way will have a filamentous form.

[0029] On the other hand, in the base material of the present embodiment, it is considered that the generation of cutting chips is suppressed as a result of effective cutting occurring in the vicinity of the ester bond and the lamellar structure before being stretched as described above.

[0030] Such an effect of suppressing cutting chips is exhibited without irradiating the base material of the present embodiment with radiation such as electron beams or γ-rays. Therefore, the adhesive sheet provided with the base material can keep the manufacturing cost low compared to a conventional dicing sheet manufactured by a method including a radiation irradiation step.

[0031] In addition, the base material made of the above polyester resin is likely to exhibit good flexibility. Therefore, in the pressure-sensitive adhesive sheet according to the present embodiment, effects such as the effect (expandability) of easily expanding the pressure-sensitive adhesive sheet well in the expansion process and the effect (pick-up property) of easily pushing up from the back surface of the chip in the pick-up process, thereby easily picking up the chip well, can be obtained. Furthermore, since the base material made of the above polyester resin also has good transparency, visual recognition and inspection of the workpiece through the pressure-sensitive adhesive sheet are also easily performed.

[0032] From the viewpoint of more easily achieving the above-described cutting chip suppression effect, the heat of fusion measured by differential scanning calorimetry at a heating rate of 20 °C / min in the above polyester resin 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 value of the heat of fusion is not particularly limited, and for example, it may be 150 J / g or less, may be 100 J / g or less, particularly may be 70 J / g or less, more preferably may be 50 J / g or less, and especially may be 30 J / g or less. The details of the measurement method of the heat of fusion described above are as described in the column of the examples described later.

[0033] (1-1) Polyester resin The specific composition of the above polyester resin is not particularly limited as long as it has an alicyclic structure and the polyester resin satisfies the condition of exhibiting the above-described heat of fusion.

[0034] From the viewpoint of more easily obtaining a better cutting chip suppression effect, the alicyclic structure of the above polyester resin preferably has 6 or more carbon atoms constituting the ring. Also, the number of carbon atoms is preferably 14 or less, particularly preferably 10 or less. Especially, 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 one consisting of three or more rings.

[0035] From the perspective of being more likely to satisfy the above two conditions, it is preferable that the polyester resin contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting the polyester resin. Also, from the same perspective, it is preferable that the polyester resin contains a diol having an alicyclic structure as a monomer unit constituting the polyester resin. Although only one of such dicarboxylic acid and diol may be contained in the polyester resin, from the perspective of being more likely to satisfy the above conditions, it is preferable that the polyester resin contains both such dicarboxylic acid and diol.

[0036] The structure of the above-mentioned dicarboxylic acid is not particularly limited as long as it has an alicyclic structure and two carboxy groups. For example, the dicarboxylic acid may have a structure in which two carboxy groups are bonded to the alicyclic structure, or may have a structure in which an alkyl group or the like is further inserted between such an alicyclic structure and the carboxy group. Preferred examples of such dicarboxylic acids include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,4-decahydronaphthalenedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid, 2,7-decahydronaphthalenedicarboxylic acid, etc. Among these, it is preferable to use 1,4-cyclohexanedicarboxylic 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 to 10 carbon atoms. More specific examples include dimethyl ester, diethyl ester, etc., and dimethyl ester is particularly preferable.

[0037] When the polyester resin in the present embodiment contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting the same, the ratio of the dicarboxylic acid monomer to all the monomer units constituting the polyester resin is preferably 20 mol% or more, more preferably 25 mol% or more, particularly preferably 30 mol% or more, and still more preferably 35 mol% or more. Also, the ratio is preferably 60 mol% or less, more preferably 55 mol% or less, particularly preferably 50 mol% or less, and still more preferably 45 mol% or less. By being within these ranges, the polyester resin is likely to exhibit the above-described heat of fusion, and as a result, the pressure-sensitive adhesive sheet according to the present embodiment is likely to achieve a more excellent effect of suppressing cutting chips.

[0038] Further, when the polyester resin in the present embodiment contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting the same, the ratio of the dicarboxylic acid having an alicyclic structure to the total amount of the dicarboxylic acids having a ring structure constituting the polyester resin is preferably 60% or more, more preferably 70% or more, particularly preferably 80% or more, and still more preferably 90% or more. By the above ratio being 60% or more, the pressure-sensitive adhesive sheet according to the present embodiment is likely to achieve a more excellent effect of suppressing cutting chips. Note that the upper limit value of the ratio is not particularly limited, and may be, for example, 100% or less. Note that the dicarboxylic acid having a ring structure includes, in addition to the dicarboxylic acid having an alicyclic structure, a dicarboxylic acid having an aromatic ring structure and the like.

[0039] The structure of the diol described above is not particularly limited as long as it has an alicyclic structure and has two hydroxy groups. For example, the diol may have a structure in which two hydroxy groups are bonded to the alicyclic structure, or may have a structure in which an alkyl group is further inserted between such an alicyclic structure and the hydroxy group. Preferred examples of such diols include 1,2-cyclohexanediol (particularly 1,2-cyclohexanedimethanol), 1,3-cyclohexanediol (particularly 1,3-cyclohexanedimethanol), 1,4-cyclohexanediol (particularly 1,4-cyclohexanedimethanol), 2,2-bis-(4-hydroxycyclohexyl)-propane, etc. Among these, it is preferable to use 1,4-cyclohexanedimethanol.

[0040] When the polyester resin in the present embodiment contains a diol having an alicyclic structure as a monomer unit constituting it, the ratio of the diol monomer to all the 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. Also, the ratio is preferably 65 mol% or less, particularly preferably 60 mol% or less, and even more preferably 55 mol% or less. By being within these ranges, the polyester resin is likely to exhibit the above-mentioned heat of fusion, and as a result, the pressure-sensitive adhesive sheet according to the present embodiment is likely to achieve a more excellent effect of suppressing cutting chips.

[0041] From the perspective that the base material of the polyester resin in this embodiment is likely to have a desired flexibility, it is also preferable that the monomer units constituting the polyester resin include dimer acid formed by dimerizing an unsaturated fatty acid. Here, the number of carbon atoms of the unsaturated fatty acid is preferably 10 or more, particularly preferably 15 or more. Also, the number of carbon atoms is preferably 30 or less, particularly preferably 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 dicarboxylic acids with 44 carbon atoms obtained by dimerizing unsaturated fatty acids with 22 carbon atoms such as erucic acid. When obtaining the above dimer acid, a small amount of trimer acid formed by trimerizing the above-mentioned unsaturated fatty acid may also be generated. The polyester resin in this embodiment may contain such trimer acid together with the above dimer acid.

[0042] When the polyester resin in this embodiment contains the above dimer acid as a monomer unit constituting it, the ratio of the dimer acid to all the dicarboxylic acid units constituting the polyester resin is preferably 2 mol% or more, particularly preferably 5 mol% or more, and even more preferably 10 mol% or more. Also, the ratio is preferably 25 mol% or less, particularly preferably 23 mol% or less, and even more preferably 20 mol% or less. Being within these ranges makes it easier for the polyester resin to have the desired flexibility, and as a result, it is also possible for the pressure-sensitive adhesive sheet according to this embodiment to achieve excellent expandability and pick-up properties.

[0043] The polyester resin in this embodiment may contain monomers other than the above-mentioned dicarboxylic acids, diols, and dimer acids 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, 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. Also, a diol component other than the diol having an alicyclic structure may be contained. For example, it may contain ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, decanediol; ethylene oxide adducts such as bisphenol A and bisphenol S; trimethylolpropane, etc.

[0044] However, in the polyester resin in this embodiment, from the viewpoint of easily achieving an excellent cutting chip suppressing effect, monomers having an alicyclic structure (the above-mentioned dicarboxylic acids having an alicyclic structure and diols having an aliphatic structure) are preferably contained more than monomers having an aromatic ring structure. In particular, among the monomer units constituting the polyester resin in this embodiment, 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, more preferably 0.5 or less, still more preferably 0.2 or less, even more preferably 0.1 or less, yet more preferably 0.05 or less, still more preferably 0.03 or less, even more preferably 0.01 or less, particularly preferably 0.005 or less, and most preferably 0.

[0045] The method for producing the polyester resin in this embodiment is not particularly limited, and a polyester resin can be obtained by polymerizing the above-mentioned monomer components using a known catalyst.

[0046] In the present embodiment, the proportion of the polyester resin with respect to all components constituting the base material is preferably 50% or more, particularly preferably 60% or more, and even more preferably 70% or more. When the above proportion is 50% or more, the pressure-sensitive adhesive sheet according to the present embodiment is likely to achieve a more excellent cutting chip suppressing effect. Note that the upper limit value of the above proportion is not particularly limited, and may be, for example, 100% or less.

[0047] (1-2) Other components The material for producing the base material in the present embodiment may contain other components other than the above-described polyester resin. In particular, the material may contain components used for a base material of a general pressure-sensitive adhesive sheet (particularly, a base material of a general sheet for workpiece processing).

[0048] Examples of such components include various additives such as flame retardants, plasticizers, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, and ion scavengers. Although the content of these additives is not particularly limited, it is preferably within a range in which the base material exhibits a desired function.

[0049] (1-3) Configuration of the base material As the layer configuration of the base material in the present embodiment, as long as it includes a layer made of a material containing the above-described polyester resin (hereinafter, may be referred to as a "polyester resin layer"), it may be a single layer or a plurality of layers. From the viewpoint of reducing manufacturing costs, the base material in the present embodiment is preferably a single layer (only the polyester resin layer).

[0050] On the other hand, in the case of a plurality of layers, a plurality of polyester resin layers may be laminated, or a polyester resin layer and other layers may be laminated. In the latter case, in the layer configuration of the base material, it is preferable that the polyester resin layer is a layer on which the pressure-sensitive adhesive layer is laminated. In this case, it is possible to achieve both the cutting chip suppressing effect by the polyester resin layer and the desired effect by other layers.

[0051] In addition, the surface of the substrate on which the adhesive layer is laminated may be subjected to surface treatments such as primer treatment, corona treatment, plasma treatment, etc. to enhance the adhesion to the adhesive layer.

[0052] (1-4) Manufacturing method of the substrate The manufacturing method of the substrate in this embodiment is not particularly limited as long as the material containing the above-described polyester resin is used. For example, melt extrusion methods such as the T-die method and the round-die method; the calendar method; solution methods such as the dry method and the wet method can be used. Among these, from the viewpoint of efficiently manufacturing the substrate, it is preferable to adopt the melt extrusion method or the calendar method.

[0053] When manufacturing a single-layer substrate by the melt extrusion method, the material of the substrate (the material containing the above-described polyester resin) is kneaded, and then directly from the obtained kneaded product or after once manufacturing pellets, a film is formed using a known extruder.

[0054] When manufacturing a multi-layer substrate by the melt extrusion method, the components constituting each layer are kneaded respectively, and then directly from the obtained kneaded products or after once manufacturing pellets, a multi-layer film is formed by simultaneously extruding using a known extruder.

[0055] (1-5) Physical properties of the substrate, etc. In the present embodiment, the tensile elastic modulus of the base material at 23°C is preferably 800 MPa or less, particularly preferably 600 MPa or less, and even more preferably 500 MPa or less. Further, the above tensile elastic modulus is preferably 100 MPa or more, particularly preferably 200 MPa or more, and even more preferably 300 MPa or more. When the above tensile elastic modulus is 800 MPa or less, the base material in the present embodiment is likely to have a desired flexibility, and the pressure-sensitive adhesive sheet according to the present embodiment is likely to achieve excellent expandability and pick-up properties. Further, when the above tensile elastic modulus is 100 MPa or more, the base material in the present embodiment is likely to have appropriate strength, the pressure-sensitive adhesive sheet has good handleability, and it becomes easier to perform desired work processing well. Incidentally, the details of the method for measuring the above tensile elastic modulus are as described in the test examples described later.

[0056] In the present embodiment, the breaking point stress of the base material at 23°C is preferably 60 MPa or less, particularly preferably 50 MPa or less, and even more preferably 40 MPa or less. Further, the above breaking point stress is preferably 15 MPa or more, particularly preferably 20 MPa or more, and even more preferably 25 MPa or more. When the above breaking point stress is 60 MPa or less, the base material film according to the present embodiment has better processability. Further, when the above breaking point stress is 15 MPa or more, the base material in the present embodiment is likely to have appropriate strength, the pressure-sensitive adhesive sheet has good handleability, and it becomes easier to perform desired work processing well. Furthermore, when the above breaking point stress is 15 MPa or more, the base material film according to the present embodiment has good expandability. Incidentally, the details of the method for measuring the above breaking point stress are as described in the test examples described later.

[0057] In the present embodiment, the elongation at break of the base material at 23°C is preferably 200% or more, more preferably 250% or more, particularly preferably 300% or more, and even more preferably 350% or more. When the elongation at break is 200% or more, the base material in the present embodiment is likely to have a desired extensibility, and the pressure-sensitive adhesive sheet according to the present embodiment is likely to achieve excellent expandability and pick-up properties. Further, the elongation at break is preferably 800% or less, more preferably 700% or less, particularly preferably 600% or less, and even more preferably 500% or less. When the elongation at break is 800% or less, the processability of the base material becomes more excellent, and it becomes easier to manufacture a desired sheet for workpiece processing. The details of the method for measuring the elongation at break are as described in the test examples described later.

[0058] In the present embodiment, the thickness of the base material is preferably 20 μm or more, particularly preferably 40 μm or more, and even more preferably 60 μm or more. Also, the thickness of the base material 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 material is 20 μm or more, the pressure-sensitive adhesive sheet is likely to have appropriate strength and is likely to support well the workpiece fixed on the pressure-sensitive adhesive sheet. As a result, it becomes possible to effectively suppress the occurrence of chipping during dicing. Further, when the thickness of the base material is 600 μm or less, it becomes easier to achieve the above-described elongation at break. Furthermore, when the thickness of the base material film is 600 μm or less, the base material film has better processability.

[0059] (2) Adhesive layer As the adhesive that constitutes the adhesive layer in the present embodiment, it is not particularly limited as long as it can exhibit sufficient adhesive force to the adherend (particularly, the adhesive force to the work sufficient for processing the work). Examples of the adhesive that constitutes the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, polyvinyl ether adhesives, and the like. Among these, from the viewpoint of being likely to exhibit a desired adhesive force, it is preferable to use an acrylic adhesive.

[0060] The adhesive that constitutes the adhesive layer in the present embodiment may be an adhesive that does not have active energy ray curability, but it is preferably an adhesive having active energy ray curability (hereinafter, may be referred to as "active energy ray curable adhesive"). 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 force of the adhesive sheet to the adherend can be easily reduced. In particular, when the adhesive sheet according to the present embodiment is used as a work processing sheet, the processed work can be easily separated from the adhesive sheet by irradiation with active energy rays.

[0061] The active energy ray curable adhesive that constitutes the adhesive layer may be mainly composed of a polymer having active energy ray curability, or may be mainly composed of a mixture of an active energy ray non-curable polymer (a polymer that does not have active energy ray curability) and at least one monomer and / or oligomer having an active energy ray curable group.

[0062] 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 bonded to the functional group. In the present specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Further, the concept of "copolymer" is also included in "polymer".

[0063] The weight average molecular weight of the above active energy ray curable polymer is preferably 10,000 or more, particularly preferably 150,000 or more, and more preferably 200,000 or more. Also, the weight average molecular weight is preferably 2.5 million or less, particularly preferably 2 million or less, and more preferably 1.5 million or less. The weight average molecular weight (Mw) in the present specification is a value in terms of standard polystyrene measured by gel permeation chromatography (GPC method).

[0064] On the other hand, when the active energy ray curable pressure-sensitive 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 or more active energy ray curable groups, as the active energy ray non-curable polymer component, for example, the above acrylic copolymer before reacting an unsaturated group-containing compound can be used. Also, as the monomer and / or oligomer having active energy ray curability, for example, esters of polyhydric alcohols and (meth)acrylic acid can be used.

[0065] 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 more preferably 200,000 or more. Also, the weight average molecular weight is preferably 2.5 million or less, particularly preferably 2 million or less, and more preferably 1.5 million or less.

[0066] When ultraviolet rays are used as the active energy rays for curing the active energy ray curable pressure-sensitive adhesive, it is preferable to add a photopolymerization initiator to the pressure-sensitive adhesive. Further, an active energy ray non-curable polymer component or oligomer component, a crosslinking agent, etc. may be added to the pressure-sensitive adhesive.

[0067] The thickness of the pressure-sensitive adhesive layer in the present embodiment is preferably 1 μm or more, particularly preferably 2 μm or more, and more preferably 3 μm or more. Also, the thickness of the pressure-sensitive adhesive layer is preferably 50 μm or less, particularly preferably 40 μm or less, and more preferably 30 μm or less. When the thickness of the pressure-sensitive adhesive layer is 1 μm or more, the pressure-sensitive adhesive sheet according to the present embodiment is likely to exhibit a desired adhesiveness. Also, when the thickness of the pressure-sensitive adhesive layer is 50 μm or less, it becomes easy to separate the adherend from the cured pressure-sensitive adhesive layer.

[0068] (3) Release sheet In the pressure-sensitive adhesive sheet according to the present embodiment, a release sheet may be laminated on the surface of the pressure-sensitive adhesive layer on the side opposite to the base material (hereinafter sometimes referred to as the "adhesive surface") for the purpose of protecting the surface until the surface is attached to the adherend.

[0069] The configuration of the release sheet is arbitrary, and examples thereof include those obtained by subjecting a plastic film to a release treatment with a release agent or the like. Specific examples of the plastic film include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; and polyolefin films such as polypropylene and polyethylene. As the release agent, silicone-based, fluorine-based, long-chain alkyl-based, etc. can be used, and among these, silicone-based which can obtain inexpensive and stable performance is preferable.

[0070] There is no particular limitation on the thickness of the release sheet, and for example, it may be 20 μm or more and 250 μm or less.

[0071] (4) Others In the adhesive sheet according to this embodiment, an adhesive layer may be laminated on the surface of the adhesive layer opposite to the base material. In this case, the adhesive sheet according to this embodiment can be used as a dicing and die-bonding sheet. In the sheet, a work is attached to the surface of the adhesive layer opposite to the adhesive layer, and by dicing the adhesive layer together with the work, a chip with the individualized adhesive layer laminated thereon can be obtained. The chip can be easily fixed to the object on which the chip is mounted by the individualized adhesive layer. As the material constituting the above-described adhesive layer, those containing a thermoplastic resin and a low molecular weight thermosetting adhesive component, those containing a B-stage (semi-cured state) thermosetting adhesive component, etc. are preferably used.

[0072] In addition, in the pressure-sensitive adhesive sheet according to the present embodiment, a protective film forming layer may be laminated on the pressure-sensitive adhesive surface in the pressure-sensitive adhesive layer. In this case, the pressure-sensitive adhesive sheet according to the present embodiment can be used as a sheet for forming a protective film and dicing. In such a sheet, a work is attached to the surface of the protective film forming layer opposite to the pressure-sensitive adhesive layer, and the protective film forming layer is diced together with the work, whereby chips with the fragmented protective film forming layers laminated thereon can be obtained. As the work, it is preferable to use one with a circuit formed on one side. In this case, usually, the protective film forming layer is laminated on the surface opposite to the surface on which the circuit is formed. The fragmented protective film forming layer can be cured at a predetermined timing to form a protective film having sufficient durability on the chip. The protective film forming layer is preferably made of an uncured curable adhesive.

[0073] 2. Method for manufacturing a pressure-sensitive adhesive sheet The method for manufacturing the pressure-sensitive adhesive sheet according to the present embodiment is not particularly limited. For example, after forming a pressure-sensitive adhesive layer on a release sheet, it is preferable to obtain a pressure-sensitive adhesive sheet by laminating one side of a base material on the surface of the pressure-sensitive adhesive layer opposite to the release sheet.

[0074] The formation of the pressure-sensitive adhesive layer described above can be performed by a known method. For example, a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer and, if desired, a coating liquid further containing a solvent or a dispersion medium are prepared. Then, the coating liquid is applied to the surface of the release sheet having releasability (hereinafter sometimes referred to as the "release surface"). Subsequently, the obtained coating film can be dried to form a pressure-sensitive adhesive layer.

[0075] The application of the above-mentioned coating liquid can be carried out by known methods, for example, by bar coating method, knife coating method, roll coating method, blade coating method, die coating method, gravure coating method, etc. In addition, the properties of the coating liquid are not particularly limited as long as it can be applied. It may contain components for forming the adhesive layer as a solute in some cases, or as a dispersed substance in other cases. Also, the release sheet may be peeled off as a process material, or it may protect the adhesive layer until it is attached to the adherend.

[0076] When the pressure-sensitive adhesive composition for forming the adhesive layer contains the above-mentioned cross-linking agent, by changing the above drying conditions (temperature, time, etc.) or by providing a separate heat treatment, the cross-linking reaction between the polymer component and the cross-linking agent in the coating film is allowed to proceed, and it is preferable to form a cross-linked structure with a desired density of existence in the adhesive layer. Further, in order to allow the above-mentioned cross-linking reaction to proceed sufficiently, after laminating the adhesive layer and the base material, curing may be performed, for example, by leaving it standing in an environment of 23°C and 50% relative humidity for several days.

[0077] 3. Method of using the adhesive sheet Although the adhesive sheet according to this embodiment can be used for various applications in the same manner as a general adhesive sheet, it is particularly suitable for use as a sheet for workpiece processing used for processing workpieces such as semiconductor wafers. In this case, after attaching the adhesive surface of the adhesive sheet according to this embodiment to the workpiece, the workpiece can be processed on the adhesive sheet. Depending on the processing, the adhesive sheet according to this embodiment can be used as a sheet for workpiece processing such as a back grind sheet, a dicing sheet, an expand sheet, a pick-up sheet, etc. Here, examples of workpieces include semiconductor members such as semiconductor wafers and semiconductor packages, and glass members such as glass plates.

[0078] As described above, the pressure-sensitive adhesive sheet according to the present embodiment can favorably suppress the generation of cutting chips when used for dicing using a rotating round blade. Therefore, among the above-described sheets for workpiece processing, the pressure-sensitive adhesive sheet according to the present embodiment is particularly preferably used as a dicing sheet.

[0079] When the pressure-sensitive adhesive sheet according to the present embodiment includes the above-described adhesive layer, the pressure-sensitive adhesive sheet can be used as a dicing and die-bonding sheet. Further, when the pressure-sensitive adhesive sheet according to the present embodiment includes the above-described protective film forming layer, the pressure-sensitive adhesive sheet can be used as a sheet for forming a protective film and for dicing.

[0080] Also, when the adhesive layer in the pressure-sensitive adhesive sheet according to the present embodiment is composed of the above-described active energy ray curable adhesive, it is also preferable to irradiate the following active energy rays during use. That is, when the processing of the workpiece is completed on the pressure-sensitive adhesive sheet and the processed workpiece is separated from the pressure-sensitive adhesive sheet, it is preferable to irradiate the adhesive layer with active energy rays before the separation. Thereby, the adhesive layer is cured, the adhesive force of the pressure-sensitive adhesive sheet to the processed workpiece is favorably reduced, and the separation of the processed workpiece becomes easy.

[0081] The embodiments described above are described to facilitate the 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 belonging to the technical scope of the present invention.

Example

[0082] Hereinafter, the present invention will be described more specifically by way of examples and the like, but the scope of the present invention is not limited to these examples and the like.

[0083] 〔Example 1〕 (1) Production of base material Into a reactor equipped with a stirrer, a bleed pipe, and a decompression device, 12.90 kg of dimethyl 1,4-cyclohexanedicarboxylate (trans isomer ratio 98%), 11.47 kg of 1,4-cyclohexanedimethanol, 0.3 kg of ethylene glycol, and 0.11 kg of an ethylene glycol solution containing 10% manganese acetate tetrahydrate were charged. After heating to 200 °C under a nitrogen flow, the temperature was raised to 230 °C over 1 hour. After holding at this temperature for 2 hours to carry out a transesterification reaction, 10.30 kg of dimer acid derived from erucic 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 to the system, and subsequently, an esterification reaction was carried out at 230 °C for 1 hour. Subsequently, 300 ppm of germanium dioxide was added as a polycondensation catalyst and stirred, then the pressure was reduced to 133 Pa or less in 1 hour. During this time, the internal temperature was raised from 230 °C to 270 °C, and the polycondensation reaction was carried out by stirring until a predetermined viscosity was reached under a high vacuum of 133 Pa or less. The obtained polymer was extruded into strands into water and cut to form pellets.

[0084] The pellets of the polyester resin thus obtained were dried at 85 °C for 4 hours or more and then charged into the hopper of a single-screw extruder equipped with a T-die. Then, under the conditions of a cylinder temperature of 220 °C and a die temperature of 220 °C, the above resin was extruded from the T-die in a state of being melt-kneaded and cooled by a cooling roll to obtain a sheet-like substrate with a thickness of 80 μm.

[0085] The above polyester resin contained about 50 mol% of 1,4-cyclohexanedimethanol, about 40.5 mol% of dimethyl 1,4-cyclohexanedicarboxylate, and 9.5 mol% of dimer acid derived from erucic acid as monomers constituting the resin. Also, the ratio of the dimer acid to all dicarboxylic acid units constituting the above polyester resin was 19.1 mol%. Furthermore, when the heat of fusion of the above polyester resin was measured by the method described later, it was 20 J / g.

[0086] (2) Preparation of the 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)acrylate polymer. When the weight average molecular weight (Mw) of this acrylic polymer was measured by the method described below, it was 500,000.

[0087] 100 parts by mass (in terms of solid content, the same applies hereinafter) of the (meth)acrylate polymer obtained as described above, 120 parts by mass of urethane acrylate oligomer (Mw: 8,000), 5 parts by mass of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L"), and 4 parts by mass of a photopolymerization initiator (manufactured by IGM Resins B.V., product name "Omnirad184") were mixed to obtain an energy ray-curable pressure-sensitive adhesive composition.

[0088] (3) Formation of the pressure-sensitive adhesive layer The pressure-sensitive adhesive composition obtained in the above step (2) was applied to the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031") in which one side of a polyethylene terephthalate film with a thickness of 38 μm was release-treated with a silicone-based release agent, and the obtained coating film was dried at 100 °C for 1 minute. Thereby, a laminate in which a pressure-sensitive adhesive layer with a thickness of 10 μm was formed on the release surface of the release sheet was obtained.

[0089] (4) Production of the pressure-sensitive adhesive sheet A pressure-sensitive adhesive sheet was obtained by bonding one side of the base material obtained in the above step (1) and the surface on the pressure-sensitive adhesive layer side of the laminate obtained in the above step (3).

[0090] Here, 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.

[0091] Specifically, first, it was heated from room temperature to 250°C at a heating rate of 20°C / min, held at 250°C for 10 minutes, cooled to -60°C at a cooling rate of 20°C / min, and held at -60°C for 10 minutes. Then, 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.

[0092] In addition, the weight-average molecular weight (Mw) described above is the weight-average molecular weight in terms of standard polystyrene measured under the following conditions using gel permeation chromatography (GPC) (GPC measurement). <Measurement conditions> · Measuring device: HLC-8320 manufactured by Tosoh Corporation · GPC column (passing in the following order): manufactured by Tosoh Corporation TSK gel superH-H TSK gel superHM-H TSK gel superH2000 · Measuring solvent: Tetrahydrofuran · Measuring temperature: 40°C

[0093] [Comparative Example 1] An adhesive sheet was obtained in the same manner as in Example 1 except that a polyvinyl chloride resin sheet with a thickness of 80 μm was used as the base material. The heat of fusion of the above polyvinyl chloride resin was measured by the method described above and found to be 0 J / g.

[0094] [Comparative Example 2] An adhesive sheet was obtained in the same manner as in Example 1 except that a base material (thickness: 80 μm) made of ethylene-methacrylic acid copolymer (EMAA) and having one surface subjected to electron beam irradiation treatment was used, and an adhesive layer was laminated on the surface of the base material that had been irradiated with the electron beam. The heat of fusion of the above ethylene-methacrylic acid copolymer was measured by the method described above and found to be 81 J / g.

[0095] [Comparative Example 3] Using a substrate made of EMAA with one surface electron beam irradiated (thickness 80 μm) as the substrate, and laminating an adhesive layer on the surface of the substrate that has been irradiated with electron beam, an adhesive sheet was obtained in the same manner as in Example 1 except for this. Note that the irradiation amount of the electron beam in the substrate used in this Comparative Example 3 is twice the irradiation amount of the electron beam in the substrate used in Comparative Example 2. Further, when the heat of fusion of the above ethylene-methacrylic acid copolymer was measured by the method described above, it was 79 J / g.

[0096] 〔Comparative Example 4〕 An adhesive sheet was obtained in the same manner as in Example 1 except for using a resin sheet with a thickness of 80 μm manufactured using a glycol-modified polyester resin having a structure represented by the following general formula (1) as the substrate. Note that when the heat of fusion of the above glycol-modified polyester resin was measured by the method described above, it was 0 J / g.

Chemical formula

[0097] 〔Comparative Example 5〕 An adhesive sheet was obtained in the same manner as in Example 1 except for using a resin sheet with a thickness of 80 μm manufactured using an amorphous polyester resin having a structure represented by the following general formula (2) as the substrate. Note that when the heat of fusion of the above amorphous polyester resin was measured by the method described above, it was 0 J / g.

Chemical formula

[0098] 〔Test Example 1〕(Measurement of Tensile Physical Properties of Substrate) The substrates prepared in the examples and comparative examples were cut into test pieces of 15 mm × 150 mm. At this time, the cutting was performed such that the 150 mm side was parallel to the MD direction (the flow direction during the manufacture of the substrate) of the substrate, and the 15 mm side was parallel to the TD direction (the direction perpendicular to the above MD direction) of the substrate film. Then, for the said test piece, the tensile modulus of elasticity, elongation at break, and breaking point stress were measured in accordance with JIS K7127:1999.

[0099] Specifically, after setting the above test piece in a tensile testing machine (manufactured by Shimadzu Corporation, product name "Autograph AG-Xplus 100N") with a chuck distance of 100 mm, a tensile test was performed to pull the test piece in the MD direction of the base film at a speed of 200 mm / min under an environment of 23°C, and the tensile elastic modulus (MPa), elongation at break (%), and stress at break point (MPa) were measured. The results are shown in Table 1.

[0100] 〔Test Example 2〕(Measurement of the number of cutting chips) The release sheet was peeled off from the pressure-sensitive adhesive sheets manufactured in the examples and comparative examples, and the exposed surface of the exposed pressure-sensitive adhesive layer was attached to one side of a silicon wafer with a thickness of 40 μm. Then, a dicing ring frame was attached to the peripheral portion of the exposed surface in the pressure-sensitive adhesive sheet (a position that does not overlap with the silicon wafer). Next, dicing of the silicon wafer was performed under the following conditions using a dicing saw (manufactured by DISCO Corporation, product name "DFD6362"). ·Workpiece (adherend): Silicon wafer ·Workpiece size: 6 inches in diameter, 40 μm thick ·Dicing blade: Manufactured by DISCO Corporation, product name "27HECC", diamond blade ·Blade rotation speed: 50,000 rpm ·Dicing speed: 100 mm / sec ·Cutting depth: Cut to a depth of 20 μm from the substrate surface ·Dicing size: 8 mm × 8 mm

[0101] After dicing, while the chips formed by fragmenting the silicon wafer were still attached to the adhesive sheet, the number of cutting chips generated on the kerf line (the cutting line formed by the passage of the dicing blade) was counted using a digital microscope (manufactured by Keyence Corporation, product name "VHX-5000", magnification: 500 times). At this time, for the kerf lines, among the plurality of kerf lines existing in the vertical and horizontal directions respectively, the number of cutting chips existing on 3 lines near the center in the vertical direction and 3 lines near the center in the horizontal direction was counted. The counted results are shown in Table 1.

[0102]

Table 1

[0103] As is clear from Table 1, the adhesive sheet manufactured in the examples was able to effectively suppress the generation of cutting chips during dicing.

Industrial Applicability

[0104] The adhesive sheet of the present invention can be suitably used as a workpiece processing sheet used for processing workpieces such as semiconductor wafers.

Claims

Claim 1 An adhesive sheet comprising a base material and an adhesive layer laminated on one side of the base material, wherein the base material is made of a material containing a polyester resin, the polyester resin has an alicyclic structure and a heat of fusion measured by differential scanning calorimetry at a heating rate of 20 °C / min is 2 J / g or more, the polyester resin contains, as monomer units constituting the polyester resin, a dicarboxylic acid having the alicyclic structure, a diol having the alicyclic structure, and a dimer acid obtained by dimerizing an unsaturated fatty acid, the ratio of the dicarboxylic acid having the alicyclic structure to all monomer units constituting the polyester resin is 20 mol% or more, the ratio of the dicarboxylic acid having the alicyclic structure to the total dicarboxylic acids having a ring structure constituting the polyester resin is 60% or more, the ratio of the diol having the alicyclic structure to all monomer units constituting the polyester resin is 35 mol% or more, the number of carbon atoms of the unsaturated fatty acid is 10 or more and 30 or less An adhesive sheet characterized by the above. Claim 2 The adhesive sheet according to claim 1, wherein the alicyclic structure is characterized in that the number of carbon atoms constituting the ring is 6 or more and 14 or less. Claim 3 The adhesive sheet according to claim 1 or 2, wherein the ratio of the dimer acid as a monomer unit constituting the polyester resin to all dicarboxylic acids as monomer units constituting the polyester resin is 2 mol% or more and 25 mol% or less. Claim 4 The adhesive sheet according to any one of claims 1 to 3, wherein the tensile modulus of the base material at 23 °C is 100 MPa or more and 800 MPa or less. Claim 5 The adhesive sheet according to any one of claims 1 to 4, wherein the elongation at break of the base material at 23 °C is 200% or more and 800% or less. Claim 6 The adhesive sheet according to any one of claims 1 to 5, wherein the thickness of the base material is 20 μm or more and 600 μm or less. Claim 7 The adhesive sheet according to any one of claims 1 to 6, wherein the adhesive layer is composed of an acrylic adhesive. Claim 8 The adhesive sheet according to any one of claims 1 to 7, characterized in that it is used as a sheet for workpiece processing. Claim 9 The adhesive sheet according to claim 8, wherein the sheet for workpiece processing is a dicing sheet.

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