阅读说明：本技术 背面研磨带 (Back grinding belt ) 是由 龟井胜利 于 2019-08-07 设计创作，主要内容包括：本发明提供在切割之后进行的背面研磨工序中使用的背面研磨带,其是在防止背面研磨时会产生的芯片缺损的同时对凹凸面的追随性优异的背面研磨带。本发明的背面研磨带依次具备粘合剂层、中间层和第1基材,构成该中间层的材料为具有羧基且未交联的丙烯酸类树脂,该中间层在23℃下的储能模量E’为200MPa以下,将该粘合剂层粘贴在Si镜面晶圆上时的初始粘合力为1N/20mm～30N/20mm。(The invention provides a back grinding tape used in a back grinding process after cutting, which is a back grinding tape with excellent followability to concave and convex surfaces while preventing chip defect generated in back grinding. The back grinding tape comprises a pressure-sensitive adhesive layer, an intermediate layer and a1 st base material in this order, wherein the intermediate layer is made of an uncrosslinked acrylic resin having a carboxyl group, the intermediate layer has a storage modulus E' at 23 ℃ of 200MPa or less, and the pressure-sensitive adhesive layer has an initial adhesive force of 1N/20mm to 30N/20mm when bonded to an Si mirror wafer.)

1. A back grinding tape comprises an adhesive layer, an intermediate layer and a1 st base material in this order,

the material constituting the intermediate layer is an uncrosslinked acrylic resin having a carboxyl group,

the intermediate layer has a storage modulus E' at 23 ℃ of 200MPa or less,

the initial adhesive force when the adhesive layer is pasted on a Si mirror wafer is 1N/20mm to 30N/20 mm.

2. The backgrinding tape of claim 1, wherein the No. 1 substrate is comprised of polyethylene terephthalate.

3. The back-grinding tape according to claim 1 or 2, wherein the thickness of the 1 st base material is 35 to 200 μm.

4. The back-grinding tape according to claim 1 or 2, wherein the adhesive layer has a thickness of 1 μm to 50 μm.

5. The back-grinding tape according to claim 1 or 2, wherein the thickness of the intermediate layer is 20 μm to 300 μm.

6. The back-grinding tape according to claim 1 or 2, wherein the acrylic resin has a constituent unit derived from a carboxyl group-containing monomer,

the content ratio of the constituent unit derived from the carboxyl group-containing monomer is 2 to 30 parts by weight based on 100 parts by weight of the acrylic resin.

7. The back-grinding tape of claim 1, used in back-grinding stealth diced semiconductor wafers.

8. The backgrinding tape of claim 7, wherein the semiconductor wafer has a convex surface.

Technical Field

The present invention relates to a back-grinding tape. More specifically, the present invention relates to a back grinding tape suitably used in a back grinding step performed after a dicing step.

Background

A workpiece (e.g., a semiconductor wafer) as an aggregate of electronic components is manufactured in a large diameter, cut (diced) into small component pieces, and then transferred to a mounting process. In the dicing step, the workpiece is cut into small pieces. In order to fix the cut workpiece, it is common to attach an adhesive tape (dicing tape) to the workpiece and then cut the workpiece (for example, patent document 1). As one of the methods of cutting, a method of cutting a workpiece with a laser is known. As such a cutting method, a method of cutting a workpiece after forming a groove on the surface of the workpiece by condensing a laser beam on the surface of the workpiece is often used. On the other hand, in recent years, stealth dicing has been proposed in which a laser beam is condensed inside a workpiece, the workpiece is reformed in the condensed laser beam, and then the workpiece is cut.

In general, in the processing of a semiconductor wafer, back grinding is performed until a predetermined thickness (for example, 100 to 600 μm) is reached (back grinding step). Conventionally, after a pattern is formed on the front surface of a semiconductor wafer, the front surface is fixed to a back grinding tape to perform back grinding (backsgrind), and then a dicing step is performed. The back-grinding tape is required to have fixability of the semiconductor wafer, and also, bumps are sometimes formed on the surface of the semiconductor wafer, so that excellent fixability to appropriately fill the irregularities due to the bumps, and to be able to prevent the intrusion of grinding water are required.

On the other hand, in recent years, in order to improve the usefulness of the stealth dicing, a technique of performing a back grinding step by fixing the front surface to a back grinding belt after the stealth dicing is performed has been studied.

Disclosure of Invention

Problems to be solved by the invention

As described above, when dicing is performed before the back-grinding step, a new problem arises in that chips formed into small pieces interfere with each other during back-grinding, and chip chipping occurs.

The invention provides a back grinding tape used in a back grinding process after cutting, which prevents chip defects generated during back grinding and has excellent followability to concave and convex surfaces.

Means for solving the problems

The back grinding tape comprises a pressure-sensitive adhesive layer, an intermediate layer and a1 st base material in this order, wherein the intermediate layer is made of an uncrosslinked acrylic resin having a carboxyl group, the intermediate layer has a storage modulus E' at 23 ℃ of 200MPa or less, and the pressure-sensitive adhesive layer has an initial adhesive force of 1N/20mm to 30N/20mm when bonded to an Si mirror wafer.

In one embodiment, the 1 st substrate is made of polyethylene terephthalate.

In 1 embodiment, the thickness of the 1 st base material is 35 to 200. mu.m.

In 1 embodiment, the adhesive layer has a thickness of 1 to 50 μm.

In 1 embodiment, the intermediate layer has a thickness of 20 to 300. mu.m.

In 1 embodiment, the back grinding tape is used for back grinding the stealthy diced semiconductor wafer.

In 1 embodiment, the semiconductor wafer has a bump surface.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a back grinding tape capable of preventing chip chipping that occurs during back grinding can be provided. The back-grinding tape of the present invention is useful as a back-grinding tape used in a back-grinding step performed after dicing (preferably stealth dicing). The back-grinding tape of the present invention is excellent in response following property, and is particularly useful as a back-grinding tape for a semiconductor wafer having a convex surface.

Drawings

Fig. 1 is a schematic cross-sectional view of a back-grinding tape of 1 embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view of a back-grinding tape according to another embodiment of the present invention.

Description of the reference numerals

10 adhesive layer

20 middle layer

31 st base material

32 nd 2 nd base material

100 back side grinding belt

Detailed Description

A. Outline of the Back-grinding tape

Fig. 1 is a schematic cross-sectional view of a back-grinding tape of 1 embodiment of the present invention. The back grinding tape 100 of this embodiment includes a pressure-sensitive adhesive layer 10, an intermediate layer 20, and a1 st base material 31. Although not shown, the back-grinding tape of the present invention may be provided with a release liner (not shown) on the outside of the pressure-sensitive adhesive layer for the purpose of protecting the pressure-sensitive adhesive surface until the tape is used. In addition, the back-grinding tape may further include any other suitable layer as long as the effects of the present invention can be obtained. Preferably, the intermediate layer is disposed directly on the 1 st substrate. Further, the adhesive layer is preferably disposed directly on the intermediate layer.

The back grinding tape of the present invention can be suitably used for fixing a cut semiconductor wafer when back grinding (back grind) is performed on the semiconductor wafer, and can be particularly suitably used when stealth dicing is employed as the dicing. Stealth dicing refers to the formation of a modified layer inside a semiconductor wafer by laser irradiation. The semiconductor wafer can be cut from the modified layer as a starting point.

In the present invention, the pressure-sensitive adhesive layer and the intermediate layer are combined, and the acrylic resin having a carboxyl group and not being crosslinked is used as a material constituting the intermediate layer, whereby the back-grinding tape used in the back-grinding step performed after dicing and capable of preventing chip chipping that may occur at the time of back-grinding can be provided. The back grinding belt of the present invention configured as described above has the following features: the external force relative to the plane direction is not easy to deform, and the original shape is not easy to recover after the deformation. If such a back grinding tape is used, it is possible to prevent chips formed into small pieces after dicing from interfering with each other excessively, and to perform back grinding while preventing the chips from being damaged. The back side grinding tape of the present invention is particularly useful for semiconductor wafer processing including stealth dicing.

Further, the intermediate layer has a specific storage modulus E' (of 0.02GPa or less), and the back-grinding tape provided with the intermediate layer is excellent in the unevenness follow-up property. The back grinding tape of the present invention is useful as a back grinding tape for a semiconductor wafer having a convex surface, and can prevent an undesired positional shift during back grinding and prevent grinding water from infiltrating into the convex surface.

Fig. 2 is a schematic cross-sectional view of a back-grinding tape according to another embodiment of the present invention. The base material of the back surface polishing tape 200 of this embodiment is 2-layer structure, and further includes the 2 nd base material 32. The 2 nd substrate 32 is disposed on the 1 st substrate 31 on the opposite side of the intermediate layer 20. That is, the back side polishing tape 200 includes the pressure-sensitive adhesive layer 10, the intermediate layer 20, the 1 st base material 31, and the 2 nd base material 32 in this order. As the 2 nd substrate, a substrate softer (for example, lower in elastic modulus) than the 1 st substrate is preferably used. The back-grinding tape of the present embodiment can prevent defects such as chip chipping during back-grinding. In semiconductor wafer processing including stealth dicing, a semiconductor wafer is diced by generating a crack (so-called BHC) that propagates from a modified layer formed by laser to the wafer surface, and in an embodiment in which the crack is generated before back grinding, even in an embodiment in which processing is considered to be more difficult, that is, even in an embodiment in which the crack is generated at the time of back grinding, it is possible to prevent disadvantages such as chip chipping. The substrate may have a structure of 3 or more layers.

The initial adhesive force when the adhesive layer of the back grinding tape of the present invention is bonded to an Si mirror wafer is preferably 1N/20mm to 30N/20mm, more preferably 5N/20mm to 25N/20mm, still more preferably 8N/20mm to 22N/20mm, and particularly preferably 14N/20mm to 22N/20 mm. If the amount is within this range, a back grinding tape can be obtained which can satisfactorily fix the semiconductor wafer during back grinding and prevent chipping. In the back-grinding tape of the present invention, a tape whose adhesive force is reduced by irradiation with active energy rays (for example, ultraviolet rays) may be used, and the "initial adhesive force" refers to the adhesive force before irradiation with active energy rays. In the present invention, the adhesive force is according to JIS Z0237: 2000 the assay was performed. Specifically, the adhesive force was measured using a tensile tester (TENSILON, manufactured by Shimadzu corporation) at 23 ℃, a peel speed of 300mm/min, a peel angle: the measurement was carried out under conditions of 180 ℃.

The thickness of the back grinding tape is preferably 35 μm to 500. mu.m, more preferably 60 μm to 300. mu.m, and still more preferably 80 μm to 200. mu.m.

B. Base material

B-1. No. 1 base Material

The 1 st substrate is preferably a resin film. Examples of the resin constituting the resin film include: polyester resins such as polyethylene terephthalate (PET), polyolefin resins such as polypropylene (PP), Polyimide (PI), polyether imide (PEI), Polyphenylene Sulfide (PPs), Polysulfone (PSF), polyether ether ketone (PEEK), Polyarylate (PAR), and the like. Among them, polyester resins are preferable, and polyethylene terephthalate is particularly preferable. If the No. 1 base material composed of polyethylene terephthalate is used, a back grinding tape which can prevent defects such as chip chipping during back grinding can be obtained.

The tensile modulus of the 1 st base material at 23 ℃ is preferably 50MPa to 10000MPa, more preferably 100MPa to 5000 MPa. Measurement of tensile modulus of the No. 1 base material (and each layer constituting the back-grinding tape (described later)) was measured using a tensile tester (manufactured by Shimadzu corporation, "AG-IS") at a chuck pitch: 50mm, drawing speed: 300mm/min, sample width: 10 mm.

The thickness of the first substrate 1 is preferably 35 to 200. mu.m, more preferably 38 to 150. mu.m, and still more preferably 50 to 120. mu.m. When the amount is within this range, a back surface polishing tape having excellent unevenness follow-up properties can be obtained.

The 1 st substrate may further contain any suitable additive. Examples of additives include: lubricants, antioxidants, ultraviolet absorbers, processing aids, fillers, antistatic agents, stabilizers, antibacterial agents, flame retardants, colorants, and the like.

B-2. 2 nd base Material

The 2 nd substrate is preferably a resin film. Examples of the resin constituting the resin film include: polyester resins such as polyethylene terephthalate (PET), polyolefin resins such as polypropylene (PP), Polyimide (PI), polyether imide (PEI), Polyphenylene Sulfide (PPs), Polysulfone (PSF), polyether ether ketone (PEEK), Polyarylate (PAR), and the like. Among them, polyolefin-based resins are preferable.

In 1 embodiment, the 2 nd base material contains a polyethylene resin or a polypropylene resin. Examples of the polyethylene resin include: low density polyethylene, linear polyethylene, medium density polyethylene, high density polyethylene, ultra low density polyethylene, and the like. The content ratio of the ethylene-derived constituent unit in the polyethylene resin is preferably 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more. Examples of the constituent units other than the constituent units derived from ethylene include constituent units derived from monomers copolymerizable with ethylene to form a copolymer, and examples thereof include: propylene, 1-butene, isobutylene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and the like.

In 1 embodiment, a substrate made of polyethylene terephthalate is used as the 1 st substrate, and a substrate made of a polyolefin resin (preferably the polyethylene resin or the polypropylene resin) is used as the 2 nd substrate. When these base materials are used, defects such as chip chipping during back grinding can be prevented more favorably.

The tensile modulus of the 2 nd base material at 23 ℃ is preferably 50MPa to 2000MPa, more preferably 100MPa to 1000 MPa.

The tensile modulus at 23 ℃ of the above-mentioned 2 nd substrate is preferably smaller than the tensile modulus at 23 ℃ of the above-mentioned 1 st substrate. The tensile modulus at 23 ℃ of the 2 nd base material is preferably 0.5% to 100%, more preferably 0.5% or more and less than 100%, and further preferably 1% to 50% of the tensile modulus at 23 ℃ of the 1 st base material.

The thickness of the 2 nd substrate is preferably 25 to 200. mu.m, more preferably 30 to 150. mu.m, still more preferably 40 to 100. mu.m, and particularly preferably 40 to 80 μm.

The 2 nd substrate may further contain any suitable additive. Examples of additives include: lubricants, antioxidants, ultraviolet absorbers, processing aids, fillers, antistatic agents, stabilizers, antibacterial agents, flame retardants, colorants, and the like.

The 1 st base material and the 2 nd base material may be laminated via any suitable adhesive layer. The thickness of the adhesive layer between these substrates is, for example, 2 μm to 10 μm.

C. Intermediate layer

The intermediate layer is made of an acrylic resin having a carboxyl group and not being crosslinked (for example, being epoxy-crosslinked). Such an intermediate layer can be formed by an intermediate layer-forming composition containing an acrylic resin having a carboxyl group in a side chain and not containing a crosslinkable compound such as a crosslinking agent. The acrylic resin constituting the intermediate layer is obtained by polymerizing monomer components containing an alkyl (meth) acrylate and a carboxyl group-containing monomer, and contains a constituent unit derived from the alkyl (meth) acrylate and a constituent unit derived from the carboxyl group-containing monomer (a constituent unit having a carboxyl group in a side chain). The presence or absence of crosslinking in the acrylic resin can be confirmed by thermal cracking GC/MS analysis.

Examples of the alkyl (meth) acrylate include: n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, tert-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth, And alkyl (meth) acrylates having a linear or branched alkyl group having 4 to 20 carbon atoms such as nonadecyl (meth) acrylate and eicosyl (meth) acrylate. Among these, from the viewpoint of adhesiveness to an adherend and adhesion workability, an alkyl (meth) acrylate having an alkyl group with 5 to 12 carbon atoms is preferable, and n-butyl acrylate or 2-ethylhexyl acrylate (2EHA) is more preferable. The alkyl (meth) acrylate may be used alone in 1 kind or in combination of 2 or more kinds.

In the acrylic resin, the content of the constituent unit derived from the alkyl (meth) acrylate is preferably 70 to 98 parts by weight, and more preferably 85 to 96 parts by weight, based on 100 parts by weight of the acrylic resin.

Examples of the carboxyl group-containing monomer include: ethylenically unsaturated monocarboxylic acids such as Acrylic Acid (AA), methacrylic acid (MAA) and crotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and citraconic acid. The acrylic resin has a carboxyl group in a side chain, and the back grinding tape having the intermediate layer made of the acrylic resin can prevent chip chipping during back grinding. The carboxyl group-containing monomers may be used alone in 1 kind or in combination of 2 or more kinds.

In the acrylic resin, the content of the constituent unit derived from the carboxyl group-containing monomer is preferably 2 to 30 parts by weight, more preferably 4 to 15 parts by weight, and particularly preferably 4 to 8 parts by weight, based on 100 parts by weight of the acrylic resin. The content of the constituent unit derived from the carboxyl group-containing monomer is preferably 2 to 30 parts by weight, more preferably 5 to 20 parts by weight, and still more preferably 5 to 10 parts by weight, based on 100 parts by weight of the constituent unit derived from the alkyl (meth) acrylate.

The acrylic resin may contain a constituent unit derived from another monomer copolymerizable with the alkyl (meth) acrylate, if necessary. Examples of the other monomers include the following monomers. These monomers may be used alone in 1 kind or in combination of 2 or more kinds.

Hydroxyl group-containing monomer: hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether and diethylene glycol monovinyl ether;

amino group-containing monomers: such as aminoethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate;

a cyano group-containing monomer: such as acrylonitrile, methacrylonitrile;

a ketone group-containing monomer: such as diacetone (meth) acrylamide, diacetone (meth) acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate;

monomer having nitrogen atom-containing ring: such as N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N- (meth) acryloylmorpholine;

alkoxysilyl group-containing monomer: for example, 3- (meth) acryloyloxypropyltrimethoxysilane, 3- (meth) acryloyloxypropyltriethoxysilane, 3- (meth) acryloyloxypropylmethyldimethoxysilane, 3- (meth) acryloyloxypropylmethyldiethoxysilane.

In the acrylic resin, the content of the constituent unit derived from another monomer is preferably 40 parts by weight or less, more preferably 20 parts by weight or less, and still more preferably 10 parts by weight or less, based on 100 parts by weight of the acrylic resin.

The weight average molecular weight of the acrylic resin is preferably 20 to 300 ten thousand, and more preferably 25 to 150 ten thousand. The weight average molecular weight can be measured by GPC (solvent: THF).

The intermediate layer-forming composition may further contain any suitable additive. Examples of the additives include: plasticizers, tackifiers, anti-aging agents, fillers, colorants, antistatic agents, surfactants, and the like. The above additives may be used alone or in combination of 2 or more. When 2 or more additives are used, 1 additive may be added at a time, or 2 or more additives may be added simultaneously. The amount of the additive to be blended may be set to any appropriate amount.

The thickness of the intermediate layer is preferably 20 to 300. mu.m, more preferably 40 to 200. mu.m, and still more preferably 60 to 150. mu.m. When the amount is within this range, a back-grinding tape can be obtained which can prevent defects such as chipping during back-grinding and which has particularly excellent conformability to uneven surfaces.

The thickness of the intermediate layer is preferably 5 to 30 times, more preferably 8 to 25 times, and still more preferably 10 to 20 times the thickness of the pressure-sensitive adhesive layer. If the intermediate layer and the pressure-sensitive adhesive layer are formed in such a thickness relationship, a back-grinding tape can be obtained which is less likely to deform due to external force in the surface direction and which is less likely to return to its original shape even after deformation. Further, a back surface polishing tape particularly excellent in followability to uneven surfaces can be obtained.

The storage modulus E' of the intermediate layer at 23 ℃ is preferably 200MPa or less, more preferably 30MPa to 180MPa, and still more preferably 50MPa to 160 MPa. When the amount is within this range, a back surface polishing tape having particularly excellent conformability to uneven surfaces can be obtained. The storage modulus E' can be determined by nanoindentation. The measurement conditions were as follows.

(measurement apparatus and measurement conditions)

The device comprises the following steps: hysitron Inc. manufacture of Tribo Inder

Using a pressure head: berkovich (triangular pyramid type)

The determination method comprises the following steps: single indentation assay

Measuring temperature: 23 deg.C

Setting the pressing depth: about 300nm

Pressing-in speed: about 10nm/sec

Frequency: 100Hz

And (3) measuring atmosphere: in the air

Sample size: about 1cm by about 1cm

The tensile modulus of the intermediate layer at 23 ℃ is preferably 0.05MPa to 1MPa, more preferably 0.1MPa to 0.5MPa, and still more preferably 0.15MPa to 0.3 MPa. If the amount is within this range, the use of a specific material as the material constituting the intermediate layer can prevent defects such as chip chipping during back grinding.

D. Adhesive layer

The adhesive layer may be formed of any suitable adhesive. Examples of the binder include: acrylic adhesives, rubber adhesives, silicone adhesives, polyvinyl ether adhesives, and the like. The adhesive may be a curable adhesive such as a thermosetting adhesive or an active energy ray curable adhesive, or may be a pressure-sensitive adhesive. Preferably, a curable adhesive is used. If a curable adhesive is used, a back-grinding tape can be obtained which can satisfactorily fix a semiconductor wafer during back-grinding and can be easily peeled off by curing the adhesive layer when peeling is required later.

In 1 embodiment, an acrylic adhesive is used as the adhesive. The acrylic pressure-sensitive adhesive is preferably a curable type.

The acrylic adhesive contains an acrylic polymer as a base polymer. The acrylic polymer may have a constituent unit derived from an alkyl (meth) acrylate. Examples of the alkyl (meth) acrylate include: n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, tert-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth, And alkyl (meth) acrylates having a linear or branched alkyl group having 4 to 20 carbon atoms such as nonadecyl (meth) acrylate and eicosyl (meth) acrylate. Among these, from the viewpoint of adhesiveness to an adherend and adhesion workability, an alkyl (meth) acrylate having an alkyl group with 5 to 12 carbon atoms is preferable, and n-butyl acrylate or 2-ethylhexyl acrylate (2EHA) is more preferable. The alkyl (meth) acrylate may be used alone in 1 kind or in combination of 2 or more kinds.

The acrylic polymer may contain a constituent unit derived from another monomer copolymerizable with the alkyl (meth) acrylate, if necessary. Examples of the other monomers include the following monomers. These monomers may be used alone in 1 kind or in combination of 2 or more kinds.

Carboxyl group-containing monomer and anhydride thereof: ethylenically unsaturated monocarboxylic acids such as Acrylic Acid (AA), methacrylic acid (MAA) and crotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and citraconic acid, and anhydrides thereof (such as maleic anhydride and itaconic anhydride);

hydroxyl group-containing monomer: hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether and diethylene glycol monovinyl ether;

amino group-containing monomers: such as aminoethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate;

epoxy group-containing monomer: such as glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether;

a cyano group-containing monomer: such as acrylonitrile, methacrylonitrile;

a ketone group-containing monomer: such as diacetone (meth) acrylamide, diacetone (meth) acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate;

monomer having nitrogen atom-containing ring: such as N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N- (meth) acryloylmorpholine;

alkoxysilyl group-containing monomer: such as 3- (meth) acryloyloxypropyltrimethoxysilane, 3- (meth) acryloyloxypropyltriethoxysilane, 3- (meth) acryloyloxypropylmethyldimethoxysilane, 3- (meth) acryloyloxypropylmethyldiethoxysilane;

isocyanate group-containing monomers such as (meth) acryloyl isocyanate, 2- (meth) acryloyloxyethyl isocyanate and m-isopropenyl- α -dimethylbenzyl isocyanate.

In the acrylic polymer, the content of the constituent unit derived from the other monomer is less than 50 parts by weight, more preferably 2 to 40 parts by weight, and still more preferably 5 to 30 parts by weight, based on 100 parts by weight of the acrylic polymer.

The weight average molecular weight of the acrylic polymer is preferably 20 to 300 ten thousand, and more preferably 25 to 150 ten thousand.

The above-mentioned binder may further contain any suitable additive. Examples of the additives include: photopolymerization initiators, crosslinking agents, plasticizers, adhesion promoters, anti-aging agents, fillers, colorants, antistatic agents, surfactants, and the like. The above additives may be used alone or in combination of 2 or more. When 2 or more additives are used, 1 additive may be added at a time, or 2 or more additives may be added simultaneously. The amount of the additive to be blended may be set to any appropriate amount.

In 1 embodiment, the adhesive further contains a photopolymerization initiator, and any suitable initiator can be used as the photopolymerization initiator, for example, acylphosphine oxide photoinitiators such as ethyl 2,4, 6-trimethylbenzylphenylphosphinate and 2,4, 6-trimethylbenzoyl-phenylphosphine oxide, α -ketol compounds such as 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, α -hydroxy- α' -dimethylacetophenone, 2-methyl-2-hydroxypropiophenone and 1-hydroxycyclohexylphenylketone, benzoin ether compounds such as methoxyacetophenone, 2-dimethoxy-2-phenylacetophenone, 2-diethoxyacetophenone, 2-methyl-1- [4- (methylthio) -phenyl ] -2-morpholinopropane-1, benzoin ether, benzoin isopropyl ether and anisole ether, ketals such as benzoin dimethyl ketal, ketals such as 2-naphthalene sulfonyl chloride, and the like, aromatic ketone compounds such as 2-naphthoyl sulfonyl chloride, and the like, preferably, benzoin ether ethers such as benzoin ether, benzoin isopropyl ether, benzoin ether ketone ethers such as benzoin dimethyl benzophenone, 2-1-phenyl ketone, 2-1-dichlorothioxanthone, and the like, preferably, and the photopolymerization initiator is used in an amount of 100 parts by weight of a halogenated benzophenone, preferably, and the amount of a 2-methoxy benzophenone, and the photopolymerization initiator is preferably, and the amount of 2-1-ethoxybenzophenone, and the same, and the amount of a halogenated benzoylacetone, and the same amount of a photoinitiator, and the photopolymerization initiator is preferably, and the amount of a photoinitiator, and the amount of 2-ethoxybenzophenone, and the amount of the photoinitiator, and the photoinitiator.

In 1 embodiment, the adhesive further comprises a crosslinking agent. As the crosslinking agent, any suitable crosslinking agent can be used. Examples thereof include: isocyanate crosslinking agents, epoxy crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, carbodiimide crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, amine crosslinking agents, and the like. Only 1 kind of the crosslinking agent may be used, or 2 or more kinds may be used in combination. The amount of the crosslinking agent to be used may be set to any appropriate value depending on the use application. The amount of the crosslinking agent to be used is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, and still more preferably 1 to 3 parts by weight, based on 100 parts by weight of the acrylic polymer.

In 1 embodiment, an isocyanate-based crosslinking agent is preferably used. An isocyanate-based crosslinking agent is preferable in that it can react with various functional groups. Specific examples of the isocyanate-based crosslinking agent include: lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; aromatic isocyanates such as 2, 4-tolylene diisocyanate, 4' -diphenylmethane diisocyanate, and xylylene diisocyanate; isocyanate adducts such as trimethylolpropane/tolylene diisocyanate trimer adduct (trade name "CORONATE L" manufactured by Nippon polyurethane industries Co., Ltd.), trimethylolpropane/hexamethylene diisocyanate trimer adduct (trade name "CORONATE HL" manufactured by Nippon polyurethane industries Co., Ltd.), and isocyanurate of hexamethylene diisocyanate (trade name "CORONATE HX" manufactured by Nippon polyurethane industries Co., Ltd.); and so on. It is preferable to use a crosslinking agent having 3 or more isocyanate groups.

The thickness of the pressure-sensitive adhesive layer is preferably 1 to 50 μm, more preferably 1 to 25 μm, and still more preferably 1 to 5 μm. When the amount is within this range, defects such as chip chipping during back grinding can be prevented more effectively.

The storage modulus E' of the pressure-sensitive adhesive layer at 23 ℃ is preferably 15MPa to 200MPa, more preferably 20MPa to 150MPa, and still more preferably 30MPa to 120 MPa. When the amount is within this range, a back surface polishing tape having particularly excellent conformability to uneven surfaces can be obtained.

The tensile modulus of the pressure-sensitive adhesive layer at 23 ℃ is preferably 0.01 to 2MPa, more preferably 0.05 to 1MPa, and still more preferably 0.1 to 0.5 MPa. When the amount is within this range, defects such as chip chipping during back grinding can be prevented more effectively. When the pressure-sensitive adhesive layer is a curable pressure-sensitive adhesive layer, the tensile modulus of the pressure-sensitive adhesive layer before curing is preferably in the above range.

The adhesive layer preferably has a viscosity value at 23 ℃ of 340gf or less, more preferably 100 to 340 gf. When the amount is within this range, a back surface polishing tape having particularly excellent conformability to uneven surfaces can be obtained. The above-mentioned viscosity value was measured by a probe tack method using a tack tester manufactured by RHESCA co.

E. Method for manufacturing back grinding belt

The back-side grinding tape may be produced by any suitable method. The back-grinding tape can be obtained, for example, by applying (coating and drying) the composition for forming an intermediate layer on a base material (1 st base material) to form an intermediate layer, and then applying (coating and drying) the pressure-sensitive adhesive on the intermediate layer to form a pressure-sensitive adhesive layer. As the coating method, various methods such as bar coater coating, air knife coating, gravure coating, reverse roll coating, lip coating, die coating, dip coating, offset printing, flexographic printing, screen printing, and the like can be employed. In addition, a method of separately forming an adhesive layer and an intermediate layer on a release liner, and then transferring and bonding them may be employed.