Sheet for workpiece processing

Abstract

To provide a workpiece processing sheet which has excellent adhesiveness between a substrate and an adhesive layer while exhibiting excellent antistatic properties.SOLUTION: There is provided a workpiece processing sheet 1 which comprises a substrate 11 having a layer containing an antistatic agent and an adhesive layer 12 formed from an adhesive composition comprising an acrylic polymer (A) in which an active energy ray-curable group is introduced into the side chain and an isocyanate-based crosslinking agent (B), wherein the content of the crosslinking agent is 2 pts.mass or more and 10 pts.mass or less, the polymer (A) is obtained by reacting a (meth)acrylic acid ester polymer (AP) having a functional group with an active energy ray-curable group-containing compound (A3) in the presence of an organometallic catalyst and the polymer (AP) contains at least one of a predetermined (meth)acrylic acid alkyl ester (A1) and an alkoxy alkyl group-containing (meth)acrylic acid ester (A2).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a work processing sheet used 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 step, the mounting step. At this time, a work such as a semiconductor wafer is laminated on an adhesive sheet having a base material and an adhesive layer (hereinafter sometimes referred to as a "work processing sheet"), and processing such as back grinding, dicing, cleaning, drying, expanding, picking up, and mounting is performed.

[0003] When the above-described work processing sheet is peeled off from the processed work after a predetermined processing step is completed, static electricity called peeling electrification may be generated between the work processing sheet and the adherend. Such static electricity causes dust and the like to adhere to the work and the device, and also causes damage to the work and the like. Therefore, the work processing sheet is required to have antistatic properties.

[0004] Patent Documents 1 and 2 disclose that, for the purpose of providing a work processing sheet having antistatic properties, a base material containing a predetermined antistatic agent is used.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, as the work processing sheet, a sheet having an adhesive layer formed of an active energy ray-curable adhesive may be used. In this case, after performing work processing on the work processing sheet, before separating the processed work from the work processing sheet, the adhesive layer may be irradiated with active energy rays. The adhesive layer irradiated with the active energy rays is cured, whereby the adhesion to the processed work is reduced. Therefore, it becomes possible to easily separate the processed work from the work processing sheet.

[0007] However, the adhesive layer cured by irradiation with active energy rays may have reduced adhesion not only to the processed work but also to the base material. In particular, the reduction in adhesion is remarkable with respect to a base material containing an antistatic agent as disclosed in Patent Documents 1 and 2, and there has been a problem that the adhesive layer is easily peeled off from the base material when separating the processed work from the work processing sheet.

[0008] The present invention has been made in view of such a situation, and an object thereof is to provide a work processing sheet having excellent antistatic properties and excellent adhesion between the base material and the adhesive layer.

Means for Solving the Problems

[0009] In order to achieve the above object, first, the present invention provides a sheet for workpiece processing, comprising a base material and an adhesive layer laminated on one side of the base material, wherein the base material includes a surface layer positioned proximal to the adhesive layer, a back surface layer positioned distal to the adhesive layer, and an intermediate layer positioned between the surface layer and the back surface layer. At least one of the surface layer, the intermediate layer, and the back surface layer contains an antistatic agent. The adhesive layer is composed of an active energy ray-curable adhesive formed from an adhesive composition containing an acrylic polymer (A) having an active energy ray-curable group introduced into its side chain and an isocyanate crosslinking agent (B). The content of the isocyanate crosslinking agent (B) in the adhesive composition is 2 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the acrylic polymer (A). The acrylic polymer (A) is obtained by reacting a (meth)acrylic acid ester polymer (AP) having a functional group in the presence of at least one organometallic catalyst selected from organotin compounds, zirconium complexes, zinc complexes, and zirconium-containing metal soaps, with an active energy ray-curable group-containing compound (A3) having a functional group capable of reacting with the functional group. The (meth)acrylic acid ester polymer (AP) includes, as monomer units constituting the polymer, at least one of a (meth)acrylic acid alkyl ester (A1) having a glass transition temperature (Tg) of the homopolymer of -20°C or lower and a carbon number of the alkyl group of 4 or less, and an alkoxyalkyl group-containing (meth)acrylic acid ester (A2) having a glass transition temperature (Tg) of the homopolymer of -20°C or lower and a carbon number of the alkoxyalkyl group of 4 or less. (Invention 1)

[0010] The sheet for workpiece processing according to the above invention (Invention 1) has a base material provided with the above-described three layers, and any one of the layers contains an antistatic agent, thereby exhibiting excellent antistatic properties. On the other hand, since the adhesive layer satisfies the above-described conditions, even after the adhesive layer is cured by irradiation with active energy rays, the adhesion between the base material and the adhesive layer is excellent.

[0011] In the above invention (Invention 1), it is preferable that the surface layer and the back surface layer contain the antistatic agent, and the intermediate layer either does not contain the antistatic agent or contains the antistatic agent in a content (unit: mass%) less than that of each of the surface layer and the back surface layer (Invention 2).

[0012] In the above invention (Inventions 1 and 2), it is preferable that the antistatic agent is a polyether polyolefin block copolymer (Invention 3).

[0013] In the above invention (Inventions 1 to 3), the organometallic catalyst is the organotin compound, and the content of the organotin compound in the pressure-sensitive adhesive composition is preferably 0.001 part by mass or more and less than 0.13 part by mass with respect to 100 parts by mass of the acrylic polymer (A) (Invention 4).

[0014] In the above invention (Inventions 1 to 4), it is preferable that the thickness of the surface layer is 1 μm or more and 10 μm or less (Invention 5).

[0015] In the above invention (Inventions 1 to 5), it is preferably a dicing sheet (Invention 6).

Advantages of the Invention

[0016] The sheet for workpiece processing according to the present invention exhibits excellent antistatic properties and also has excellent adhesion between the base material and the adhesive layer.

Brief Description of the Drawings

[0017]

Figure 1

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described. FIG. 1 shows a cross-sectional view of a sheet for workpiece processing according to an embodiment. The sheet for workpiece processing 1 shown in FIG. 1 includes a base material 11 and an adhesive layer 12 laminated on one side of the base material 11.

[0019] As shown in FIG. 1, the base material 11 includes a surface layer 111 located proximal to the adhesive layer 12, a back surface layer 113 located distal to the adhesive layer 12, and an intermediate layer 112 located between the surface layer 111 and the back surface layer 113. And in the base material 11, at least one of the surface layer 111, the intermediate layer 112, and the back surface layer 113 contains an antistatic agent.

[0020] As described above, since the base material 11 includes a layer containing an antistatic agent, the sheet for workpiece processing 1 according to the present embodiment has excellent antistatic properties. Therefore, it is possible to favorably suppress peeling electrification when separating a release sheet or a workpiece from the sheet for workpiece processing 1.

[0021] Furthermore, in the sheet for workpiece processing 1 according to the present embodiment, the adhesive layer 12 is composed of an active energy ray curable adhesive formed from an adhesive composition containing an acrylic polymer (A) having an active energy ray curable group introduced into a side chain and an isocyanate crosslinking agent (B).

[0022] And the content of the isocyanate crosslinking agent (B) in the above adhesive composition is 2 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the acrylic polymer (A).

[0023] In addition, the acrylic polymer (A) is obtained by reacting a (meth)acrylic acid ester polymer (AP) having a functional group with an active energy ray curable group-containing compound (A3) having a functional group capable of reacting with the functional group in the presence of at least one organometallic catalyst selected from an organotin compound, a zirconium complex, a zinc complex, and a zirconium-containing metal soap.

[0024] Furthermore, the above-mentioned (meth)acrylic acid ester polymer (AP) contains, as monomer units constituting the polymer, at least one of an alkyl (meth)acrylate (A1) having a glass transition temperature (Tg) of a homopolymer of -20°C or lower and 4 or less carbon atoms in the alkyl group, and an alkoxyalkyl group-containing (meth)acrylate (A2) having a glass transition temperature (Tg) of a homopolymer of -20°C or lower and 4 or less carbon atoms in the alkoxyalkyl group.

[0025] The work processing sheet 1 according to the present embodiment has an adhesive layer 12 that satisfies the above-described conditions, and thus has excellent adhesion between the base material 11 and the adhesive layer 12. In particular, even after the adhesive layer 12 is cured by irradiation with active energy rays, the base material 11 and the adhesive layer 12 exhibit high adhesion. Therefore, when separating the processed work from the work processing sheet 1, even if the adhesive layer 12 is cured by irradiation with active energy rays, the adhesive layer 12 does not separate from the base material 11, and the processed work can be satisfactorily separated from the work processing sheet 1.

[0026] Generally, when dicing a wafer on the work processing sheet 1, the adhesive layer 12 may be cut together with the wafer. In this case, when picking up the obtained chip from the work processing sheet 1, the possibility that the divided adhesive layer 12 is picked up in a state of adhering to the chip is extremely increased. However, according to the work processing sheet 1 according to the present embodiment, even in such a case, adhesion of the adhesive layer 12 to the chip can be satisfactorily suppressed.

[0027] 1. Configuration of Work Processing Sheet (1) Base Material As described above, the base material 11 in the present embodiment includes a surface layer 111, an intermediate layer 112, and a back surface layer 113. Regarding the composition of these layers, there is no particular limitation as long as at least one of the surface layer 111, the intermediate layer 112, and the back surface layer 113 contains an antistatic agent.

[0028] As materials other than the antistatic agent in each layer constituting the base material 11, there is no particular limitation as long as they can form those layers, and for example, it is preferable to use a resin. In particular, from the viewpoint of easily exhibiting the performance required for a work processing sheet such as expandability and suppression of cutting pieces, it is preferable to use at least one of a polyolefin-based resin and a thermoplastic elastomer as the main material. Note that the surface layer 111 and the back surface layer 113 may have different compositions or may have exactly the same composition.

[0029] (1-1) Polyolefin-based resin Specific examples of the above-mentioned polyolefin-based resin are not particularly limited. In this specification, the polyolefin-based resin refers to a homopolymer or copolymer having an olefin as a monomer, or a copolymer having an olefin and a molecule other than an olefin as monomers, and the mass ratio of the portion based on the olefin unit in the resin after polymerization is 1.0% by mass or more.

[0030] The polymer constituting the above polyolefin-based resin may be linear or may have side chains. Further, the polymer may have an aromatic ring or an aliphatic ring.

[0031] Examples of the olefin monomer constituting the polyolefin-based resin include olefin monomers having 2 to 8 carbon atoms, α-olefin monomers having 3 to 18 carbon atoms, and olefin monomers having a cyclic structure. Examples of the olefin monomer having 2 to 8 carbon atoms include ethylene, propylene, 2-butene, octene, etc. Examples of the α-olefin monomer having 3 to 18 carbon atoms include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-octadecene, etc. Examples of the olefin monomer having a cyclic structure include norbornene, cyclopentadiene, cyclohexadiene, dicyclopentadiene, and tetracyclododecene and their derivatives, etc.

[0032] The polyolefin resin can be used alone or as a mixture of two or more kinds.

[0033] Among the specific examples of the above-mentioned polyolefin resin, it is preferable to use at least one of polyethylene containing ethylene as a main polymerization unit and polypropylene containing propylene as a main polymerization unit.

[0034] As the above-mentioned polypropylene, for example, it is preferable to use homopolypropylene, random polypropylene and block polypropylene. These can be used alone or as a mixture of two or more kinds. In particular, it is preferable to use a mixture of homopolypropylene and random polypropylene.

[0035] As the above-mentioned homopolypropylene, random polypropylene and block polypropylene, commercially available products on the market may be used respectively. Examples of commercially available products of homopolypropylene include product names "Prime Polypro E111G", "Prime Polypro E-100GV", "Prime Polypro E-100GPL", "Prime Polypro E-200GP", etc. manufactured by Prime Polymer Co., Ltd. Examples of commercially available products of random polypropylene include product names "Prime Polypro B221WA", "Prime Polypro B241", "Prime Polypro E222", "Prime Polypro E-333GV", etc. manufactured by Prime Polymer Co., Ltd. Examples of commercially available products of block polypropylene include product names "Prime Polypro E701G", "Prime Polypro E702G", "Prime Polypro E702MG", etc. manufactured by Prime Polymer Co., Ltd.

[0036] As the above-mentioned polyethylene, it may be any of high-density polyethylene, medium-density polyethylene, low-density polyethylene, ultra-low-density polyethylene and linear low-density polyethylene, or a mixture of two or more of these.

[0037] In particular, as the polyethylene, it is preferable to use low-density polyethylene. Examples of commercially available products include "Novatec LL" manufactured by Mitsubishi Chemical Corporation, the Neozex series and the Ultra Zex series manufactured by Prime Polymer Co., Ltd., and the like.

[0038] When any of the layers constituting the base material 11 contains a polyolefin resin, the content of the polyolefin resin in the layer is preferably 10% by mass or more, particularly preferably 15% by mass or more, and more preferably 20% by mass or more. Further, the content is preferably 100% by mass or less, particularly preferably 95% by mass or less, and more preferably 90% by mass or less. When the content of the polyolefin resin is within the above range, the work processing sheet 1 according to the present embodiment is likely to have better expandability.

[0039] (1-2) Thermoplastic elastomer The above-mentioned thermoplastic elastomer is not particularly limited as long as it is other than the above polyolefin resin and enables the formation of the base material 11. Examples of the thermoplastic elastomer include, for example, olefin-based elastomers, rubber elastomers, urethane-based elastomers, styrene-based elastomers, acrylic-based elastomers, vinyl chloride-based elastomers, and the like. These may be used alone or in combination of two or more.

[0040] Among the above-mentioned elastomers, olefin-based elastomers are preferable from the viewpoint of easily obtaining good expandability. In particular, it is preferable that at least one of the surface layer 111 and the back surface layer 113 contains an olefin-based elastomer. In the present specification, the "olefin-based elastomer" means a copolymer containing a structural unit derived from an olefin or its derivative (olefin-based compound), having rubber-like elasticity in a temperature range including room temperature, and having thermoplasticity.

[0041] Examples of the olefin-based elastomer include those containing at least one resin selected from the group consisting of ethylene-propylene copolymers, ethylene-α-olefin copolymers, propylene-α-olefin copolymers, butene-α-olefin copolymers, ethylene-propylene-α-olefin copolymers, ethylene-butene-α-olefin copolymers, propylene-butene-α-olefin copolymers, and ethylene-propylene-butene-α-olefin copolymers. Among these, ethylene-propylene copolymers are preferred.

[0042] When any of the layers constituting the base material 11 contains an olefin-based elastomer, the content of the olefin-based elastomer in the layer is preferably 1% by mass or more, particularly preferably 10% by mass or more, and still more preferably 15% by mass or more. Also, the above content is preferably 90% by mass or less, particularly preferably 80% by mass or less, and still more preferably 70% by mass or less. By the content of the olefin-based elastomer being within the above range, the work processing sheet 1 according to the present embodiment is more likely to obtain good expandability.

[0043] Also, from the viewpoint of easily obtaining good expandability, it is also preferable to use a styrene-based elastomer. In particular, it is preferable that the intermediate layer 112 contains a styrene-based elastomer. In this specification, the "styrene-based elastomer" means a copolymer containing a structural unit derived from styrene or its derivative (styrene-based compound), having rubber-like elasticity in a temperature range including room temperature, and having thermoplasticity.

[0044] Examples of styrenic elastomers include styrene-conjugated diene copolymers and styrene-olefin copolymers, among which styrene-conjugated diene copolymers are preferred. Specific examples of styrene-conjugated diene copolymers include unhydrogenated styrene-conjugated diene copolymers such as styrene-butadiene copolymers, styrene-butadiene-styrene copolymers (SBS), styrene-butadiene-butylene-styrene copolymers, styrene-isoprene copolymers, styrene-isoprene-styrene copolymers (SIS), and styrene-ethylene-isoprene-styrene copolymers; hydrogenated styrene-conjugated diene copolymers such as styrene-ethylene / propylene-styrene copolymers (SEPS: hydrogenated product of styrene-isoprene-styrene copolymers) and styrene-ethylene-butylene-styrene copolymers (SEBS: hydrogenated product of styrene-butadiene copolymers). The styrenic thermoplastic elastomer may be a hydrogenated product (hydrogenated material) or an unhydrogenated material, but a hydrogenated product is preferred. Among the above, from the viewpoint of easily obtaining good expandability, hydrogenated styrene-conjugated diene copolymers are preferred, and particularly styrene-ethylene-butylene-styrene copolymers (SEBS) are preferred.

[0045] The content (styrene ratio) of the structural unit derived from styrene or a styrene-based compound in the styrenic elastomer is preferably 1% by mass or more, particularly preferably 5% by mass or more, and even more preferably 10% by mass or more. Also, from the viewpoint of film-forming properties, the content of the above structural unit is preferably 80% by mass or less, particularly preferably 70% by mass or less, and even more preferably 60% by mass or less. This makes it easier to achieve excellent expandability.

[0046] When any of the layers constituting the base material 11 contains a styrene-based elastomer, the content of the styrene-based elastomer in the layer is preferably 1% by mass or more, particularly preferably 10% by mass or more, and more preferably 15% by mass or more. Also, the content is preferably 90% by mass or less, particularly preferably 80% by mass or less, and more preferably 70% by mass or less. By the content of the styrene-based elastomer being within the above range, the work processing sheet 1 according to the present embodiment is likely to obtain better expandability.

[0047] (1-3) Antistatic agent The antistatic agent in the present embodiment is not particularly limited, and known ones can be used. Examples of the antistatic agent include low molecular weight antistatic agents and high molecular weight antistatic agents. From the viewpoint of being likely to suppress the generation of cutting pieces, being less likely to cause bleed-out from the base material 11, and thereby being more likely to achieve higher adhesion between the base material 11 and the adhesive layer 12, a high molecular weight antistatic agent is preferred.

[0048] Examples of the high molecular weight antistatic agent include copolymers having a polyether unit such as polyether ester amide and polyether polyolefin block copolymer. These copolymers may contain metal salts such as alkali metal salts and alkaline earth metal salts, and ionic liquids. Among these, from the viewpoint of achieving sufficient antistatic properties while being more likely to achieve high adhesion between the base material 11 and the adhesive layer 12, a polyether polyolefin block copolymer is preferred.

[0049] The polyether polyolefin block copolymer is a copolymer having units of a polyether moiety and a polyolefin moiety respectively. The antistatic property is exhibited by the polyether moiety showing ionic conductivity, and the polyolefin moiety makes it excellent in dispersibility with polyolefin-based resins.

[0050] Examples of commercially available polyether polyolefin block copolymers include product names such as "Pelestat 300", "Pelestat 230", "Perektron PVH", "Perektron PVL", "Perektron HS", "Pelestat 201", "Perektron UC", etc. manufactured by Sanyo Chemical Industries, Ltd., and product names such as "Sunconol TBX-310" manufactured by Sanko Chemical Industries Co., Ltd.

[0051] In the base material 11 in the present embodiment, as described above, although at least one of the surface layer 111, the intermediate layer 112, and the back surface layer 113 contains an antistatic agent, in particular, it is preferable that each of the surface layer 111 and the back surface layer 113 contains an antistatic agent. Thereby, the work processing sheet 1 according to the present embodiment is likely to have excellent antistatic properties, and it is possible to favorably suppress peeling electrification when separating the peeling sheet or the work from the work processing sheet 1.

[0052] Although the intermediate layer 112 may also contain an antistatic agent, from the viewpoint of easily suppressing the generation of cutting pieces during dicing, the intermediate layer 112 preferably does not contain an antistatic agent, or the intermediate layer 112 contains an antistatic agent at a content (unit: mass%) less than that of each of the surface layer 111 and the back surface layer 113. Thus, when the intermediate layer 112 that does not contain an antistatic agent or has a low content thereof exists between the surface layer 111 and the back surface layer 113, when the dicing blade reaches the intermediate layer 112 during dicing, it is possible to favorably suppress the generation of cutting pieces from the intermediate layer 112.

[0053] The content of the antistatic agent in the surface layer 111 is preferably 3% by mass or more, particularly preferably 5% by mass or more, and even more preferably 10% by mass or more. When the content of the antistatic agent is 3% by mass or more, it is easier to exhibit good antistatic properties. Also, the content of the antistatic agent in the surface layer 111 is preferably 40% by mass or less, particularly preferably 35% by mass or less, and even more preferably 30% by mass or less. When the content of the antistatic agent is 40% by mass or less, it is easier to further improve the adhesion between the base material 11 and the adhesive layer 12.

[0054] The content of the antistatic agent in the back surface layer 113 is preferably 10% by mass or more, particularly preferably 20% by mass or more, and even more preferably 30% by mass or more. When the content of the antistatic agent is 10% by mass or more, it is easier to exhibit good antistatic properties. Also, the content of the antistatic agent in the back surface layer 113 is preferably 50% by mass or less, particularly preferably 45% by mass or less, and even more preferably 40% by mass or less. When the content of the antistatic agent is 50% by mass or less, it is easier to further improve the adhesion between the base material 11 and the adhesive layer 12.

[0055] As described above, the intermediate layer 112 preferably does not contain an antistatic agent, or the intermediate layer 112 contains an antistatic agent in a content (unit: mass%) less than that of each of the surface layer 111 and the back surface layer 113. When the intermediate layer 112 contains an antistatic agent, the content thereof in the intermediate layer 112 is preferably 10% by mass or less, particularly preferably 5% by mass or less, and even more preferably 3% by mass or less. When the content of the antistatic agent in the intermediate layer 112 is 10% by mass or less, it is easier to suppress the generation of cutting pieces. Note that, as the lower limit value of the above content, for example, it may be 0.01% by mass or more.

[0056] (1-4) Acid-modified resin Each layer constituting the base material 11 preferably contains an acid-modified resin. In particular, it is preferable that the surface layer 111 contains an acid-modified resin. In this specification, the "acid-modified resin" means a resin in which a structure derived from an acid component is added to the polymer chain. The structure derived from the acid component may be in the form of an acid anhydride or may have a carboxy group. By the surface layer 111 containing the acid-modified resin as described above, the adhesion between the base material 11 and the adhesive layer 12 is further improved, and it is possible to further suppress the adhesive remaining on the chip side during pickup.

[0057] As the main chain of the acidic resin, for example, ethylene-acrylic copolymers such as ethylene-(meth)acrylic acid copolymer and ethylene-(meth)acrylate copolymer are preferably mentioned. According to such a resin, it becomes easy to improve the adhesion between the surface layer 111 and the adhesive layer 12. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms.

[0058] As the above (meth)acrylate, (meth)acrylate alkyl esters having 1 to 4 carbon atoms in the alkyl group are preferable. For example, (meth)methyl acrylate, (meth)ethyl acrylate, (meth)propyl acrylate, (meth)n-butyl acrylate, etc. are preferably mentioned. Among them, (meth)ethyl acrylate is more preferable, and ethyl acrylate is particularly preferable.

[0059] The content of the structure derived from the (meth)acrylate in the ethylene-(meth)acrylate copolymer is preferably 1% by mass or more, particularly preferably 3% by mass or more. Further, the content is preferably 20% by mass or less, particularly preferably 15% by mass or less, and more preferably 10% by mass or less.

[0060] To acid-modify the resin, it is preferable to react the resin with an unsaturated carboxylic acid. Examples of the unsaturated carboxylic acid include maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, tetrahydrophthalic acid, aconitic acid, maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, aconitic anhydride, norbornenedicarboxylic anhydride, tetrahydrophthalic anhydride, and the like. These can be used alone or in combination of two or more. Among these, maleic anhydride is particularly preferable from the viewpoint of adhesion to the adhesive layer 12.

[0061] The amount of the acid component (the amount of the structure derived from the acid component) in the above acid-modified resin is preferably 1% by mass or more, particularly preferably 2% by mass or more. Also, the amount of the acid component is preferably 7% by mass or less, particularly preferably 5% by mass or less. When the amount of the acid component is within the above range, the adhesion between the surface layer 111 and the adhesive layer 12 is further improved.

[0062] When the surface layer 111 contains the acid-modified resin, the content of the acid-modified resin in the surface layer 111 is preferably 5% by mass or more, particularly preferably 10% by mass or more. Thereby, the adhesion between the surface layer 111 and the adhesive layer 12 is further improved. Also, the content is preferably 30% by mass or less, particularly preferably 25% by mass or less, and more preferably 20% by mass or less.

[0063] (1-5) Other components The layer constituting the base material 11 may contain other components in addition to the above-described components. In particular, the resin composition may contain components used for the base material of a general work processing sheet.

[0064] 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.

[0065] (1-6) Surface treatment of the substrate On the surface of the substrate 11 where the adhesive layer 12 is laminated, in order to enhance the adhesion with the adhesive layer 12, surface treatments such as primer treatment, corona treatment, plasma treatment, roughening treatment (mat processing), etc. may be performed. Examples of the roughening treatment include, for example, embossing method, sandblasting method, etc. Among these, it is preferable to perform corona treatment.

[0066] (1-7) Manufacturing method of the substrate The manufacturing method of the substrate 11 in the present embodiment is not particularly limited. For example, melt extrusion methods such as T-die method and round die method; calendar method; solution methods such as dry method and wet method can be used. Among these, from the viewpoint of efficiently manufacturing the substrate, it is preferable to adopt the melt extrusion method, and particularly preferable to adopt the T-die method.

[0067] Also, when manufacturing the substrate 11 by the melt extrusion method, the components constituting each layer are kneaded respectively, and directly from the obtained kneaded product, or after once manufacturing pellets, a plurality of layers can be simultaneously extruded and formed into a film using a known extruder.

[0068] (1-8) Physical properties of the substrate, etc. The surface resistivity of the surface on the surface layer 111 side of the substrate 11 is preferably 1.0×10 13 Ω / sq or less, particularly preferably 1.0×10 12 Ω / sq or less, and more preferably 1.0×10 11 Ω / sq or less. When the above surface resistivity is 1.0×10 13 Ω / sq or less, the work processing sheet 1 according to the present embodiment is likely to have good antistatic properties. Note that the lower limit value of the above surface resistivity is not particularly limited. For example, it may be 1.0×10 8 Ω / sq or more, particularly 1.0×10 9 Ω / sq or more. The details of the measurement method of the above surface resistivity are as described in the test examples described later.

[0069] In the present embodiment, the thickness of the surface layer 111 is preferably 1 μm or more, particularly preferably 2 μm or more, and even more preferably 4 μm or more. Also, the thickness of the surface layer 111 is preferably 10 μm or less, particularly preferably 8 μm or less, and even more preferably 4 μm or less. When the thickness of the surface layer 111 is within the above range, the work processing sheet 1 is likely to achieve excellent expandability, and it is easy to impart desired performance to the work processing sheet 1. Further, when the thickness of the surface layer 111 is 10 μm or less, it is easier to further improve the adhesion between the base material 11 and the adhesive layer 12.

[0070] In the present embodiment, the thickness of the intermediate layer 112 is preferably 40 μm or more, particularly preferably 50 μm or more, and even more preferably 60 μm or more. Also, the thickness of the intermediate layer 112 is preferably 100 μm or less, particularly preferably 90 μm or less, and even more preferably 80 μm or less. When the thickness of the intermediate layer 112 is within the above range, the work processing sheet 1 is likely to achieve excellent expandability, and it is easy to impart desired performance to the work processing sheet 1.

[0071] In the present embodiment, the thickness of the back surface layer 113 is preferably 2 μm or more, particularly preferably 4 μm or more, and even more preferably 8 μm or more. Also, the thickness of the back surface layer 113 is preferably 40 μm or less, particularly preferably 30 μm or less, and even more preferably 25 μm or less. When the thickness of the back surface layer 112 is within the above range, the work processing sheet 1 is likely to achieve excellent expandability, and it is easy to impart desired performance to the work processing sheet 1.

[0072] (2) Adhesive layer In the present embodiment, as described above, the adhesive layer 12 is composed of an active energy ray curable adhesive formed from an adhesive composition containing an acrylic polymer (A) having an active energy ray curable group introduced into the side chain and an isocyanate crosslinking agent (B).

[0073] (A) Acrylic polymer in which an active energy ray curable group is introduced into the side chain As described above, the acrylic polymer (A) in which an active energy ray curable group is introduced into the side chain is obtained by reacting a (meth)acrylic acid ester polymer (AP) having a functional group with an active energy ray curable group-containing compound (A3) having a functional group capable of reacting with the functional group in the presence of at least one organometallic catalyst selected from organotin compounds, zirconium complexes, zinc complexes, and zirconium-containing metal soaps.

[0074] The (meth)acrylic acid ester polymer (AP) contains at least one of an alkyl (meth)acrylate (A1) having a glass transition temperature (Tg) of a homopolymer of -20°C or lower and 4 or less carbon atoms in the alkyl group and an alkoxyalkyl group-containing (meth)acrylate (A2) having a glass transition temperature (Tg) of a homopolymer of -20°C or lower and 4 or less carbon atoms in the alkoxyalkyl group as a monomer unit constituting the polymer.

[0075] By the (meth)acrylic acid ester polymer (AP) containing at least one of the above alkyl (meth)acrylate (A1) and the above alkoxyalkyl group-containing (meth)acrylate (A2), the resulting pressure-sensitive adhesive can maintain good adhesion to the substrate even when cured by irradiation with active energy rays. The glass transition temperature (Tg) in this specification is a calculated value obtained from Fox's equation.

[0076] Examples of the above alkyl (meth)acrylate (A1) include n-butyl acrylate (Tg = -54°C), ethyl acrylate (Tg = -22°C), isobutyl acrylate (Tg = -26°C), etc. Among these, it is preferable to use n-butyl acrylate.

[0077] When the (meth)acrylic acid ester polymer (AP) contains the above (meth)acrylic acid alkyl ester (A1), the mass ratio of the structural part derived from the above (meth)acrylic acid alkyl ester (A1) in the (meth)acrylic acid ester polymer (AP) is preferably 30% by mass or more, particularly preferably 40% by mass or more, and still more preferably 50% by mass or more. When the above ratio is 30% by mass or more, the resulting adhesive can maintain better adhesion to the base material 11. Also, the above ratio is preferably 90% by mass or less, particularly preferably 80% by mass or less, and still more preferably 70% by mass or less. When the above ratio is 90% by mass or less, it becomes easier to secure the ratio of other desired monomers, and the resulting adhesive is more likely to have the desired performance.

[0078] Examples of the above alkoxyalkyl group-containing (meth)acrylic acid ester (A2) include methoxymethyl acrylate (Tg = -50°C). Among these, it is preferable to use methoxymethyl acrylate.

[0079] When the (meth)acrylic acid ester polymer (AP) contains the above alkoxyalkyl group-containing (meth)acrylic acid ester (A2), the mass ratio of the structural part derived from the above alkoxyalkyl group-containing (meth)acrylic acid ester (A2) in the (meth)acrylic acid ester polymer (AP) is preferably 5% by mass or more, particularly preferably 10% by mass or more, and still more preferably 15% by mass or more. When the above ratio is 5% by mass or more, the resulting adhesive can maintain better adhesion to the base material 11. Also, the above ratio is preferably 70% by mass or less, particularly preferably 60% by mass or less, and still more preferably 50% by mass or less. When the above ratio is 70% by mass or less, it becomes easier to secure the ratio of other desired monomers, and the resulting adhesive is more likely to have the desired performance.

[0080] Further, it is also preferable that the above (meth)acrylic acid ester polymer (AP) contains a functional group-containing monomer having a reactive functional group. The functional group can be used for the reaction with the above-mentioned active energy ray curable group-containing compound (A3).

[0081] As the above functional group-containing monomer, those having a reactive functional group capable of reacting with the functional group of the active energy ray curable group-containing compound (A3) are preferable. Examples of the functional group include a hydroxyl group, a carboxy group, an amino group, a substituted amino group, an epoxy group, etc. Among them, a hydroxyl group or a carboxy group is preferable, and a hydroxyl group is particularly preferable. When an isocyanate-based crosslinking agent (B) is used, it is also preferable that the reactive functional group of the functional group-containing monomer reacts with the isocyanate-based crosslinking agent (B).

[0082] When using a monomer having a hydroxyl group (hydroxyl group-containing monomer) as the functional group-containing monomer, examples thereof include (meth)acrylic acid hydroxyalkyl esters, and specific examples thereof include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc. Among these, 2-hydroxyethyl (meth)acrylate is preferable. These may be used alone or in combination of two or more.

[0083] When using a monomer having a carboxy group (carboxy group-containing monomer) as the functional group-containing monomer, examples thereof include ethylenically unsaturated carboxylic acids, and specific examples thereof include acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, etc.

[0084] When the (meth)acrylate polymer (AP) contains a functional group-containing monomer, the proportion of the mass of the structural part derived from the functional group-containing monomer in the (meth)acrylate polymer (AP) is preferably 10% by mass or more, particularly preferably 15% by mass or more, and even more preferably 20% by mass or more. Also, the proportion is preferably 70% by mass or less, particularly preferably 60% by mass or less, and even more preferably 50% by mass or less. By the proportion of the mass of the structural part derived from the functional group-containing monomer being within the above range, the amount of the active energy ray-curable group-containing compound (A3) introduced into the acrylic polymer (A) having an energy ray-curable group introduced into the side chain can be made to be within a suitable range. Further, when using an isocyanate-based crosslinking agent (B) to react the functional group-containing monomer with the isocyanate-based crosslinking agent (B), the degree of crosslinking by the isocyanate-based crosslinking agent (B), that is, the gel fraction, can be made to be within a suitable range, and it becomes easy to control physical properties such as the cohesive force of the adhesive layer 12.

[0085] The (meth)acrylate polymer (AP) may be a copolymer of the above-described monomers and other monomers. For example, the (meth)acrylate polymer (AP) may contain, as monomer units constituting the polymer, other (meth)acrylate alkyl esters other than the above (meth)acrylate alkyl ester (A1).

[0086] As the other (meth)acrylate alkyl ester, those having an alkyl group with 1 to 18 carbon atoms are preferred, and particularly those having 1 to 4 carbon atoms are preferred.

[0087] Specific examples of the above-mentioned other (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl methacrylate, propyl (meth)acrylate, n-butyl methacrylate, isobutyl methacrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, and the like. Among these, methyl methacrylate is preferred. These may be used alone or in combination of two or more.

[0088] When the (meth)acrylic acid ester polymer (AP) contains the above-mentioned other (meth)acrylic acid alkyl esters, the mass ratio of the structural part derived from the above-mentioned other (meth)acrylic acid alkyl esters in the (meth)acrylic acid ester polymer (AP) is preferably 1% by mass or more, particularly preferably 5% by mass or more, and even more preferably 10% by mass or more. Also, the ratio is preferably 60% by mass or less, particularly preferably 50% by mass or less, and even more preferably 40% by mass or less. When the mass ratio of the structural part derived from the above-mentioned other (meth)acrylic acid alkyl esters is within the above range, the resulting adhesive is likely to have desired performance.

[0089] In addition, the (meth)acrylic acid ester polymer (AP) may contain other alkoxyalkyl group-containing (meth)acrylic acid esters other than the above-mentioned alkoxyalkyl group-containing (meth)acrylic acid ester (A2) as monomer units constituting the polymer. Examples thereof include methoxymethyl methacrylate, (meth)acrylic acid methoxyethyl, (meth)acrylic acid ethoxymethyl, (meth)acrylic acid ethoxyethyl, and the like.

[0090] Furthermore, the (meth)acrylate polymer (AP) may include, as monomer units constituting the polymer, (meth)acrylate esters having an aliphatic ring such as cyclohexyl (meth)acrylate; (meth)acrylate esters having an aromatic ring such as phenyl (meth)acrylate; monomers having a nitrogen-containing heterocyclic ring such as N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, and N-(meth)acryloylpyrrolidone; non-crosslinkable acrylamide such as (meth)acrylamide and N,N-dimethyl(meth)acrylamide; (meth)acrylate esters having a non-crosslinkable tertiary amino group such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate; vinyl acetate; styrene; and the like.

[0091] The polymerization mode of the (meth)acrylate polymer (AP) may be a random copolymer or a block copolymer. Also, the polymerization method is not particularly limited, and it can be polymerized by a general polymerization method, for example, a solution polymerization method.

[0092] On the other hand, the active energy ray curable group-containing compound (A3) contains a functional group capable of reacting with the functional group of the (meth)acrylate polymer (AP) and an active energy ray curable group containing a carbon-carbon double bond that cleaves upon irradiation with active energy rays.

[0093] Examples of the functional group capable of reacting with the functional group of the (meth)acrylate polymer (AP) include an isocyanate group, an epoxy group, etc. Among them, an isocyanate group having high reactivity with a hydroxyl group is preferable.

[0094] As the active energy ray curable group containing a carbon-carbon double bond, a (meth)acryloyl group etc. are preferable. The carbon-carbon double bond that cleaves upon irradiation with active energy rays is preferably present in 1 to 5, particularly preferably 1 to 3, per molecule of the active energy ray curable group-containing compound (A3).

[0095] Examples of the active energy ray curable group-containing compound (A3) include 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate; acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with hydroxyethyl (meth)acrylate; acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with a polyol compound and hydroxyethyl (meth)acrylate, and the like. Among these, 2-methacryloyloxyethyl isocyanate is particularly preferred. The active energy ray curable group-containing compound (A3) may be used alone or in combination of two or more.

[0096] In the resulting acrylic polymer (A), the amount of the active energy ray curable group-containing compound (A3) relative to the amount of the functional groups possessed by the (meth)acrylate polymer (AP) is preferably 60 mol% or more, particularly preferably 70 mol% or more. Also, the amount of the active energy ray curable group-containing compound (A3) is preferably 99 mol% or less, particularly preferably 95% or less, and more preferably 90 mol% or less.

[0097] In preparing the acrylic polymer (A), the preparation of the (meth)acrylate polymer (AP) and the reaction of the (meth)acrylate polymer (AP) with the active energy ray curable group-containing compound (A3) can be carried out by conventional methods. In this reaction step, the reactive functional groups derived from the functional group-containing monomer (A2) in the (meth)acrylate polymer (AP) react with the functional groups in the active energy ray curable group-containing compound (A3). Thereby, an acrylic polymer (A) having an energy ray curable group introduced into the side chain is obtained.

[0098] Incidentally, as described above, the reaction between the (meth)acrylic acid ester polymer (AP) and the active energy ray curable group-containing compound (A3) is carried out in the presence of at least one organometallic catalyst selected from organotin compounds, zirconium complexes, zinc complexes, and zirconium-containing metal soaps. Since the acrylic polymer (A) is produced by the action of such an organometallic catalyst, the resulting adhesive exhibits better adhesion to the substrate 11.

[0099] Examples of the above organotin compounds include dibutyltin dilaurate (DBTDL), dioctyltin dilaurate (DOTDL), dibutyltin diacetate (DBTDA), dioctyltin diacetate (DOTDA), dioctyltin maleate (DOTM), dibutyltin maleate (DBTM), and the like. Among these, it is preferable to use dibutyltin dilaurate (DBTDL).

[0100] When an organotin compound is used as the above organometallic catalyst, the content of the organotin compound in the pressure-sensitive adhesive composition is preferably 0.001 part by mass or more, particularly preferably 0.01 part by mass or more, and even more preferably 0.02 part by mass or more with respect to 100 parts by mass of the acrylic polymer (A). Further, the content is preferably less than 0.13 part by mass, particularly preferably 0.1 part by mass or less, and even more preferably 0.07 part by mass or less. When the organotin compound is used within these ranges, the resulting adhesive exhibits better adhesion to the substrate 11.

[0101] Examples of the above zirconium complexes include zirconium(IV) acetylacetonate, zirconium acetate, zirconium(IV) isopropoxide isopropanol, zirconium(IV) ethoxide, zirconium(IV) butoxide, zirconium(IV) propoxide, zirconium acrylate, zirconium carboxyethyl acrylate, and the like. Among these, it is preferable to use zirconium(IV) acetylacetonate.

[0102] When using a zirconium complex as the above-mentioned organometallic catalyst, the content of the zirconium complex in the pressure-sensitive adhesive composition is preferably 0.001 part by mass or more, particularly preferably 0.01 part by mass or more, and even more preferably 0.02 part by mass or more, based on 100 parts by mass of the acrylic polymer (A). Also, the content is preferably 0.2 part by mass or less, particularly preferably 0.15 part by mass or less, and even more preferably 0.1 part by mass or less. By using the zirconium complex within these ranges, the resulting pressure-sensitive adhesive exhibits better adhesion to the substrate 11.

[0103] Examples of the above-mentioned zinc complex include zinc(II) acetylacetonate monohydrate, zinc acetate, trifluoroacetic acid, zinc methacrylate, etc. Among these, it is preferable to use zinc(II) acetylacetonate monohydrate.

[0104] When using a zinc complex as the above-mentioned organometallic catalyst, the content of the zinc complex in the pressure-sensitive adhesive composition is preferably 0.01 part by mass or more, particularly preferably 0.03 part by mass or more, and even more preferably 0.05 part by mass or more, based on 100 parts by mass of the acrylic polymer (A). Also, the content is preferably 0.5 part by mass or less, particularly preferably 0.3 part by mass or less, and even more preferably 0.2 part by mass or less. By using the zinc complex within these ranges, the resulting pressure-sensitive adhesive exhibits better adhesion to the substrate 11.

[0105] Examples of the above-mentioned zirconium-containing metal soap include zirconium(IV) oxide (2-ethylhexanoate), zirconium octylate, zirconium laurate, zirconium oleate, etc. Among these, it is preferable to use zirconium(IV) oxide (2-ethylhexanoate).

[0106] When using a zirconium-containing metal soap as the above-mentioned organometallic catalyst, the content of the zirconium-containing metal soap in the pressure-sensitive adhesive composition is preferably 0.01 part by mass or more, particularly preferably 0.03 part by mass or more, and more preferably 0.05 part by mass or more, based on 100 parts by mass of the acrylic polymer (A). Further, the content is preferably 0.5 part by mass or less, particularly preferably 0.3 part by mass or less, and more preferably 0.15 part by mass or less. By using the zirconium-containing metal soap within these ranges, the resulting pressure-sensitive adhesive exhibits better adhesion to the substrate 11.

[0107] The weight-average molecular weight (Mw) of the acrylic polymer (A) is preferably 100,000 or more, particularly preferably 200,000 or more, and more preferably 300,000 or more. Further, the weight-average molecular weight (Mw) is preferably 1,200,000 or less, particularly preferably 1,000,000 or less, and more preferably 800,000 or less. When the weight-average molecular weight (Mw) of the acrylic polymer (A) is within the above range, the resulting pressure-sensitive adhesive is easily adjusted to a viscosity suitable for coating and easily exhibits appropriate pressure-sensitive adhesive physical properties.

[0108] (2-2) Isocyanate-based crosslinking agent (B) As the isocyanate-based crosslinking agent (B), it is preferable to use a compound having two or more isocyanate groups per molecule. Specific examples include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate and pentamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. Furthermore, biuret compounds, isocyanurate compounds, adduct compounds, etc. of these are included. Examples of the adduct compound include reaction products with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, it is preferable to use at least one of trimethylolpropane-modified hexamethylene diisocyanate and trimethylolpropane-modified tolylene diisocyanate.

[0109] The isocyanate-based crosslinking agent (B) can be used alone or in combination of two or more. Also, it may be used in combination with other crosslinking agents. Examples of other crosslinking agents include epoxy compounds, metal chelate compounds, polyimine compounds such as aziridine compounds, melamine resins, urea resins, dialdehydes, methylol polymers, metal alkoxides, metal salts, etc.

[0110] The content of the isocyanate-based crosslinking agent (B) in the pressure-sensitive adhesive composition is 2 parts by mass or more, preferably 3 parts by mass or more, particularly preferably 4 parts by mass or more, based on 100 parts by mass of the acrylic polymer (A). Also, the above content is 10 parts by mass or less, preferably 9 parts by mass or less, particularly preferably 8 parts by mass or less. When the content of the isocyanate-based crosslinking agent (B) is within the above range, the resulting pressure-sensitive adhesive exhibits better adhesion to the base material 11.

[0111] (2-3) Photoinitiator (C) When ultraviolet rays are used as the active energy rays for curing the active energy ray-curable pressure-sensitive adhesive, it is also preferable that the above-described pressure-sensitive adhesive composition further contains a photopolymerization initiator (C). By containing the photopolymerization initiator (C) in this way, the acrylic polymer (A) having an energy ray-curable group introduced into the side chain can be efficiently polymerized and cured, and the polymerization curing time and the irradiation amount of the active energy rays can be reduced.

[0112] Examples of the photopolymerization initiator (C) include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin benzoic acid methyl, benzoin dimethyl ketal, 2,4-diethylthioxanthone, 1-hydroxycyclohexyl phenyl ketone, benzyldiphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β-chloroanthraquinone, (2,4,6-trimethylbenzyl diphenyl)phosphine oxide, 2-benzothiazole-N,N-diethyldithiocarbamate, oligo{2-hydroxy-2-methyl-1-[4-(1-propenyl)phenyl]propanone}, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, and the like. These may be used alone or in combination of two or more.

[0113] The content of the photopolymerization initiator (C) in the pressure-sensitive adhesive composition is preferably 0.1 part by mass or more, particularly preferably 0.5 part by mass or more, based on 100 parts by mass of the acrylic polymer (A) having an energy ray-curable group introduced into the side chain. Also, the content of the photopolymerization initiator (C) is preferably 10 parts by mass or less, particularly preferably 8 parts by mass or less, based on 100 parts by mass of the acrylic polymer (A) having an energy ray-curable group introduced into the side chain.

[0114] (2-4) Other components As long as the effects of the pressure-sensitive adhesive composition P in the present embodiment and the pressure-sensitive adhesive sheet 1 for workpiece processing according to the present embodiment are not impaired, desired additives such as antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, fillers, etc. can be added. It should be noted that the diluting solvent described later is not included in the additives constituting the pressure-sensitive adhesive composition P.

[0115] (2-5) Preparation of pressure-sensitive adhesive composition The pressure-sensitive adhesive composition in the present embodiment can be produced by producing an acrylic polymer (A) and mixing the obtained acrylic polymer (A) with an isocyanate-based crosslinking agent (B), and optionally a photopolymerization initiator (C) and additives. At this time, a diluting solvent may be added as desired to obtain a coating solution of the pressure-sensitive adhesive composition.

[0116] Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and ethylene chloride, alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve-based solvents such as ethyl cellosolve.

[0117] The concentration and viscosity of the coating solution prepared in this way may be within a coatable range and are not particularly limited, and can be appropriately selected according to the situation. For example, it is diluted so that the concentration of the pressure-sensitive adhesive composition is 10% by mass or more and 60% by mass or less. In addition, when obtaining the coating solution, the addition of a diluting solvent or the like is not a necessary condition, and as long as the pressure-sensitive adhesive composition has a viscosity that can be coated, the diluting solvent does not need to be added. In this case, the pressure-sensitive adhesive composition becomes a coating solution using the polymerization solvent of the acrylic polymer (A) as the diluting solvent as it is.

[0118] (2-6) Thickness of adhesive layer In the present embodiment, the thickness of the adhesive layer 12 is preferably 1 μm or more, particularly preferably 3 μm or more, and even more preferably 5 μm or more. Also, the thickness of the adhesive layer 12 is preferably 70 μm or less, particularly preferably 30 μm or less, and even more preferably 15 μm or less. When the thickness of the adhesive layer 12 is within the above-described range, the work processing sheet 1 according to the present embodiment is likely to exhibit a desired adhesiveness and has excellent adhesion to the base material 11.

[0119] (3) Release sheet In the work processing sheet 1 according to the present embodiment, a release sheet may be laminated on the surface of the adhesive layer 12 on the side opposite to the base material 11 (hereinafter sometimes referred to as the "adhesive surface") for the purpose of protecting the surface until it is attached to the work.

[0120] The configuration of the release sheet is arbitrary, and examples 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, rubber-based, etc. can be used, and among these, silicone-based is preferred because it is inexpensive and provides stable performance.

[0121] There is no particular limitation on the thickness of the release sheet, and for example, it may be 16 μm or more and 250 μm or less.

[0122] (4) Others In the work processing sheet 1 according to this embodiment, an adhesive layer may be laminated on the surface of the adhesive layer 12 opposite to the base material 11. In this case, the work processing sheet 1 according to this embodiment can be used as a dicing and die bonding sheet. In this sheet, a work is attached to the surface of the adhesive layer opposite to the adhesive layer 12, and the adhesive layer is diced together with the work, whereby chips with the individualized adhesive layers laminated thereon can be obtained. The chips can be easily fixed to the object on which the chips are mounted by the individualized adhesive layers. As the material constituting the above-described adhesive layer, it is preferable to use those containing a thermoplastic resin and a low molecular weight thermosetting adhesive component, those containing a B-stage (semi-cured state) thermosetting adhesive component, and the like.

[0123] Also, in the work processing sheet 1 according to this embodiment, a protective film forming layer may be laminated on the adhesive surface of the adhesive layer 12. In this case, the work processing sheet 1 according to this embodiment can be used as a protective film forming and dicing sheet. In such a sheet, a work is attached to the surface of the protective film forming layer opposite to the adhesive layer 12, and the protective film forming layer is diced together with the work, whereby chips with the individualized protective film forming layers laminated thereon can be obtained. As the work, it is preferable to use one having 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 individualized 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.

[0124] 2. Manufacturing Method of Work Processing Sheet The manufacturing method of the work processing sheet 1 according to this embodiment is not particularly limited. For example, after forming the adhesive layer 12 on the release sheet, it is preferable to obtain the work processing sheet 1 by laminating one side of the base material 11 on the surface of the adhesive layer 12 opposite to the release sheet.

[0125] The formation of the above-described adhesive layer 12 can be performed by a known method. For example, an adhesive composition for forming the adhesive layer 12 and, if desired, a coating solution further containing a solvent or a dispersion medium are prepared. Then, the coating solution is applied to the surface having peelability of the release sheet (hereinafter sometimes referred to as the "release surface"). Subsequently, the obtained coating film is dried to form the adhesive layer 12.

[0126] The application of the above-described coating solution can be performed by a known method, for example, by a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like. The properties of the coating solution are not particularly limited as long as it can be applied. It may contain the components for forming the adhesive layer 12 as a solute or as a disperse phase. Further, the release sheet may be peeled off as a process material, or may protect the adhesive layer 12 until it is attached to the adherend.

[0127] When the adhesive composition for forming the adhesive layer 12 contains the above-described crosslinking agent, by changing the above drying conditions (temperature, time, etc.) or by separately providing a heat treatment, the crosslinking reaction between the polymer component in the coating film and the crosslinking agent is advanced, and it is preferable to form a crosslinked structure at a desired density of existence in the adhesive layer 12. Further, in order to sufficiently advance the above-described crosslinking reaction, after bonding the adhesive layer 12 and the base material 11, curing may be performed, for example, by leaving it standing in an environment of 23°C and a relative humidity of 50% for several days.

[0128] 3. Method of using the sheet for workpiece processing The work processing sheet 1 according to this embodiment can be used for processing works such as semiconductor wafers. That is, after the adhesive surface of the work processing sheet 1 according to this embodiment is attached to the work, the work can be processed on the work processing sheet 1. Depending on the processing, the work processing sheet 1 according to this embodiment will be used as a back grinding sheet, a dicing sheet, an expand sheet, a pick-up sheet, or the like. Here, examples of the work include semiconductor members such as semiconductor wafers and semiconductor packages, and glass members such as glass plates.

[0129] As described above, the work processing sheet 1 according to this embodiment has excellent adhesion between the base material 11 and the adhesive layer 12, and when separating the processed work from the work processing sheet 1, it is possible to effectively suppress the adhesive layer 12 from peeling off from the base material 11 and adhering to the work. Therefore, the work processing sheet 1 according to this embodiment is particularly suitable for use as a dicing sheet and a pick-up sheet among the above-described work processing sheets.

[0130] Furthermore, as described above, the work processing sheet 1 according to this embodiment has excellent antistatic properties. The work processing sheet 1 according to this embodiment can suppress peeling electrostatic charge when separating the release sheet or when separating the work.

[0131] When the work processing sheet 1 according to this embodiment includes the above-described adhesive layer, the work processing sheet 1 can be used as a dicing and die bonding sheet. Furthermore, when the work processing sheet 1 according to this embodiment includes the above-described protective film forming layer, the work processing sheet 1 can be used as a protective film forming and dicing sheet.

[0132] In addition, since the pressure-sensitive adhesive layer 12 in the workpiece processing sheet 1 according to the present embodiment is composed of the above-described active energy ray-curable pressure-sensitive 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 workpiece processing sheet 1 and the processed workpiece is separated from the workpiece processing sheet 1, it is preferable to irradiate the pressure-sensitive adhesive layer 12 with active energy rays before the separation. Thereby, the pressure-sensitive adhesive layer 12 is cured, the adhesive force of the adhesive sheet to the processed workpiece is favorably reduced, and the separation of the processed workpiece becomes easy.

[0133] The embodiments described above are described for facilitating the understanding of the present invention and are not described for limiting 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.

[0134] For example, another layer may be laminated between the base material 11 and the pressure-sensitive adhesive layer 12 in the workpiece processing sheet 1 according to the present embodiment, or on the surface of the base material 11 opposite to the pressure-sensitive adhesive layer 12. Further, other layers may be laminated on the surface of the surface layer 111 opposite to the intermediate layer 112, between the surface layer 111 and the intermediate layer 112, between the intermediate layer 112 and the back surface layer 113, and on the surface of the back surface layer 113 opposite to the intermediate layer 112, respectively.

Example

[0135] 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.

[0136] [Production of Base Material A] 45 parts by mass of random polypropylene resin (manufactured by Japan Polypropylene Corporation, product name "Novatec FX3B"), 16 parts by mass of olefin thermoplastic elastomer (manufactured by Japan Polypropylene Corporation, product name "Wellnex RFX4V"), 15 parts by mass of acid-modified resin (manufactured by SK functional polymer, product name "Bondine LX4110", ethyl acrylate content: 5% by mass, acid component amount: 3% by mass), and 25 parts by mass of antistatic agent (manufactured by Sanyo Chemical Industries, product name "Perektron PVH") were each dried and then kneaded in a twin-screw kneader to obtain pellets for the surface layer.

[0137] Also, 28 parts by mass of random polypropylene resin (manufactured by Japan Polypropylene Corporation, product name "Novatec FX3B"), 39 parts by mass of olefin thermoplastic elastomer (manufactured by Japan Polypropylene Corporation, product name "Wellnex RFX4V"), and 33 parts by mass of styrene thermoplastic elastomer (manufactured by Asahi Kasei Corporation, product name "Taftec H1041", styrene / ethylene-butylene-styrene copolymer, styrene ratio: 30 wt%) were each dried and then kneaded in a twin-screw kneader to obtain pellets for the intermediate layer.

[0138] Furthermore, 70 parts by mass of olefin thermoplastic elastomer (manufactured by Japan Polypropylene Corporation, product name "Wellnex RFX4V") and 30 parts by mass of antistatic agent (manufactured by Sanyo Chemical Industries, product name "Perektron PVH") were each dried and then kneaded in a twin-screw kneader to obtain pellets for the back layer.

[0139] Using the three types of pellets obtained as described above, coextrusion molding was performed with a small T-die extruder (manufactured by Toyo Seiki Seisakusho, product name "Laboplastmill") to obtain a base material A having a three-layer structure in which a surface layer with a thickness of 4 μm, an intermediate layer with a thickness of 64 μm, and a back layer with a thickness of 12 μm were laminated in this order.

[0140] [Production of Base Material B and Base Material C] Pellets for each layer prepared by changing the composition as shown in Table 1 were used, and except that the thickness of each layer was changed as shown in Table 1, base materials B and C were produced in the same manner as base material A.

[0141] [Example 1] (1) Preparation of the pressure-sensitive adhesive composition 62 parts by mass of n-butyl acrylate, 10 parts by mass of methyl methacrylate, and 28 parts by mass of 2-hydroxyethyl acrylate were polymerized by solution polymerization to obtain a (meth)acrylate polymer (AP) having a functional group (hydroxyl group).

[0142] Subsequently, 2-methacryloyloxyethyl isocyanate (MOI) in an amount corresponding to 80 mol% with respect to 2-hydroxyethyl acrylate constituting the above (meth)acrylate polymer (AP) was added, and dibutyltin dilaurate (DBTDL) as an organometallic catalyst was added in an amount of 0.03 parts by mass with respect to 100 parts by mass of the above (meth)acrylate polymer (AP). Thereafter, by reacting at 50 °C for 24 hours, an acrylic polymer (A) having an active energy ray-curable group introduced into the side chain was obtained. When the acrylic polymer (A) having an active energy ray-curable group introduced into the side chain was measured by the method described below, it was 500,000.

[0143] 100 parts by mass (in terms of solid content, the same applies hereinafter) of the acrylic polymer (A) having an active energy ray-curable group introduced into the side chain obtained above, 2 parts by mass of 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one (manufactured by BASF, product name "Irgacure 127") as a photopolymerization initiator, and 5.7 parts by mass of hexamethylene diisocyanate (manufactured by Tosoh Corporation, product name "Coronate HL") as an isocyanate-based crosslinking agent were mixed in a solvent to obtain a coating solution of the pressure-sensitive adhesive composition.

[0144] (2) Formation of the pressure-sensitive adhesive layer On the release surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031") in which a silicone-based release agent layer is formed on one side of a polyethylene terephthalate film with a thickness of 38 μm, a coating liquid of the pressure-sensitive adhesive composition obtained in the above step (2) is applied and dried at 90°C for 1 minute, so that a laminate in which a pressure-sensitive adhesive layer with a thickness of 5 μm is formed using a comma coater is obtained on the release sheet.

[0145] (3) Preparation of a sheet for workpiece processing After corona treatment was performed on the surface layer side surface of the base material A prepared as described above, the corona-treated surface and the surface on the pressure-sensitive adhesive layer side of the laminate obtained in the above step (2) were bonded together, and then stored in an environment of 23°C and 50% relative humidity for 2 weeks to obtain a sheet for workpiece processing.

[0146] Here, the weight average molecular weight (Mw) described above is the weight average molecular weight in terms of standard polystyrene measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC). <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

[0147] [Examples 2 to 7, Comparative Examples 1 to 2] A sheet for workpiece processing was obtained in the same manner as in Example 1, except that the type of the base material, the composition of the acrylic polymer (A), the type and content of the organometallic catalyst, and the type and content of the isocyanate-based crosslinking agent (B) were changed as described in Table 2.

[0148] [Test Example 1] (Measurement of surface resistivity) The base materials produced in the examples and comparative examples were conditioned at 23°C and 50% relative humidity for 24 hours, and then the surface resistivity of the surface on the surface layer side was measured at an applied voltage of 100 V using a DIGITAL ELECTROMETER (manufactured by ADVANTEST). The results are shown in Table 2.

[0149] [Test Example 2] (Evaluation of Adhesion) With respect to the adhesive layers of the work processing sheets obtained in the examples and comparative examples, using an ultraviolet irradiation device (manufactured by Lintec Corporation, product name "RAD-2000"), ultraviolet rays were irradiated in a nitrogen atmosphere through the base material (light amount 160 mJ / cm 2 ), and the adhesive layer was cured.

[0150] Subsequently, a cross-cut test method according to JIS K5400 was performed on the adhesive layer exposed by peeling off the release sheet, and the number of squares remaining without peeling from the base material (out of 100) was measured. Then, the adhesion was evaluated according to the criteria shown below. The number of squares and the surface results are shown in Table 2. ◎: The number of remaining squares was 100. ○: The number of remaining squares was 80 - 99. △: The number of remaining squares was 50 - 79. ×: The number of remaining squares was 0 - 49.

[0151] The details of the abbreviations and the like described in Table 1 are as follows. <Organometallic Catalyst> DBTDL: Dibutyltin dilaurate Zirconium(IV) acetylacetonate: Zirconium(IV) acetylacetonate (manufactured by Nippon Chemical Industry Co., Ltd., product name "Naccem Zirconium Compound") Zirconium(IV) oxide (2-ethylhexanoate): Zirconium(IV) oxide (2-ethylhexanoate) (manufactured by Fujifilm Wako Pure Chemical Corporation, product name "Bis(2-ethylhexanoate) zirconium(IV) oxide·Mineral spirit solution (Zr: 12%)") Zinc(II) acetylacetonate monohydrate: Zinc(II) acetylacetonate monohydrate (manufactured by Fujifilm Wako Pure Chemical Corporation, product name "Zinc(II) acetylacetonate monohydrate") <Isocyanate-based crosslinking agent> Coronate HL: Trimethylolpropane-modified hexamethylene diisocyanate (manufactured by Tosoh Corporation, product name "Coronate HL") Coronate L: Trimethylolpropane-modified tolylene diisocyanate (manufactured by Tosoh Corporation, product name "Coronate L")

[0152] [Table 1]

[0153] [Table 2]

[0154] As is clear from Table 2, the sheet for work processing manufactured in the examples was excellent in the adhesion between the base material and the adhesive layer even after the adhesive layer was cured by irradiation with active energy rays.

Industrial Applicability

[0155] The sheet for work processing of the present invention can be suitably used for processing works such as semiconductor wafers.

Explanation of Reference Numerals

[0156] 1... Sheet for work processing 11... Base material 111... Surface layer 112... Intermediate layer 113... Back layer 12... Adhesive layer

Claims

1. A sheet for workpiece processing, comprising a base material and an adhesive layer laminated on one side of the base material, wherein the base material includes a surface layer positioned proximal to the adhesive layer, a back surface layer positioned distal to the adhesive layer, and an intermediate layer positioned between the surface layer and the back surface layer, at least one of the surface layer, the intermediate layer, and the back surface layer contains an antistatic agent, the surface layer contains at least one of a polyolefin resin and a thermoplastic elastomer, the adhesive layer is composed of an active energy ray-curable adhesive formed from an adhesive composition containing an acrylic polymer (A) having an active energy ray-curable group introduced into a side chain and an isocyanate crosslinking agent (B), the content of the isocyanate crosslinking agent (B) in the adhesive composition is 2 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the acrylic polymer (A), the acrylic polymer (A) is obtained by reacting a (meth)acrylic acid ester polymer (AP) having a functional group with an active energy ray-curable group-containing compound (A3) having a functional group capable of reacting with the functional group in the presence of at least one organometallic catalyst selected from an organotin compound, a zirconium complex, a zinc complex, and a zirconium-containing metal soap, the (meth)acrylic acid ester polymer (AP) includes, as monomer units constituting the polymer, at least one of a (meth)acrylic acid alkyl ester (A1) having a glass transition temperature (Tg) of a homopolymer of -20°C or lower and an alkyl group having 4 or fewer carbon atoms, and an alkoxyalkyl group-containing (meth)acrylic acid ester (A2) having a glass transition temperature (Tg) of a homopolymer of -20°C or lower and an alkoxyalkyl group having 4 or fewer carbon atoms, characterized in that it is a sheet for workpiece processing.

2. The surface layer and the back surface layer contain the antistatic agent, the intermediate layer does not contain the antistatic agent or contains the antistatic agent in a content (unit: mass%) less than that of each of the surface layer and the back surface layer, characterized in that it is the sheet for workpiece processing according to Claim 1.

3. The sheet for workpiece processing according to Claim 1 or 2, characterized in that the antistatic agent is a polyether polyolefin block copolymer.

4. The organometallic catalyst is the organotin compound, The content of the organotin compound in the pressure-sensitive composition is 0.001 part by mass or more and less than 0.13 part by mass with respect to 100 parts by mass of the acrylic polymer (A). The sheet for work processing according to any one of claims 1 to 3, characterized in that.

5. The sheet for work processing according to any one of claims 1 to 4, characterized in that the thickness of the surface layer is 1 μm or more and 10 μm or less.

6. The sheet for work processing according to any one of claims 1 to 5, characterized in that it is a dicing sheet.

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