Method for manufacturing adhesive sheets

Abstract

To provide a method for producing an adhesive sheet which exhibits excellent adhesive force before ultraviolet irradiation and can be peeled off from an adherend without adhesive residue after irradiation.SOLUTION: There is provided a method for producing an adhesive sheet which comprises: polymerizing a monomer composition containing a (meth)acrylic monomer having a hydroxyl group in a polyol to obtain a reaction solution containing a (meth)acrylic polymer having a hydroxyl group; adding a compound having a radiation-polymerizable carbon-carbon double bond into the reaction solution and introducing a radiation-polymerizable carbon-carbon double bond into the polyol and the (meth)acrylic polymer having a hydroxyl group to obtain a reaction solution containing a polyol derivative into which the double bond is introduced and a (meth)acrylic polymer into which the double bond is introduced; forming an adhesive layer on a base material by preparing an adhesive solution by adding a polyisocyanate and a photopolymerization initiator into the reaction solution; and subjecting the polyisocyanate in the adhesive layer, the polyol derivative into which a radiation-polymerizable carbon-carbon double bond is introduced and the introduced (meth)acrylic polymer to urethanization reaction.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing an adhesive sheet. [Background Art]

[0002] Adhesive sheets are widely used for the purposes of surface protection and fixing of adherends. For example, in the processing step of semiconductor wafers, they are used to appropriately hold a semiconductor wafer, which is an adherend, during the back grinding step and dicing step. In recent years, chips have been miniaturized and thinned, and adhesive strength that can appropriately hold a semiconductor wafer even when the semiconductor wafer is thinly ground during processing is required. In addition, in recent years, as the performance of semiconductor chips has improved, the surface structure of semiconductor chips has become more complex. Therefore, there is a demand for an adhesive sheet that can follow more complex surface shapes and has adhesive strength capable of fixing a semiconductor wafer during processing. However, an adhesive sheet with high adhesive strength may damage the wafer during peeling. Therefore, there is a demand for an easily peelable adhesive sheet that can be easily peeled from an adherend after processing. As such a pressure-sensitive adhesive composition, an adhesive sheet using an ultraviolet-curable pressure-sensitive adhesive has been proposed (for example, Patent Document 1). As the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer, pressure-sensitive adhesives using a solvent are widely used. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-31620 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a method for producing an adhesive sheet that exhibits excellent adhesive strength before ultraviolet irradiation and can be peeled from an adherend without adhesive residue after ultraviolet irradiation. [Means for Solving the Problem]

[0005] 1. The method for producing an adhesive sheet according to an embodiment of the present invention is a method for producing an adhesive sheet having a substrate and an active energy ray curable adhesive layer, comprising: polymerizing a monomer composition containing a hydroxyl group-containing (meth)acrylic monomer in a polyol to obtain a reaction solution (1) containing a hydroxyl group-containing (meth)acrylic polymer; adding a compound having a radiation-polymerizable carbon-carbon double bond to the reaction solution (1) to introduce a radiation-polymerizable carbon-carbon double bond into the polyol and the hydroxyl group-containing (meth)acrylic polymer; and introducing a radiation-polymerizable carbon-carbon double bond. The method comprises: obtaining a reaction solution (2) containing a polyol derivative and a (meth)acrylic polymer into which a radiation-polymerizable carbon-carbon double bond has been introduced; adding a polyisocyanate and a photopolymerization initiator to the reaction solution (2) to prepare an adhesive solution; forming an adhesive layer on a substrate using the adhesive solution; and urethane-forming the polyisocyanate contained in the adhesive layer, the radiation-polymerizable carbon-carbon double bond-introduced polyol derivative, and the radiation-polymerizable carbon-carbon double bond-introduced (meth)acrylic polymer. 2. In the method for producing the adhesive sheet described in item 1 above, the content ratio of the hydroxyl group-containing (meth)acrylic monomer to the total amount of all monomer components contained in the monomer composition may be 30% by weight or less. 3. In the method for producing an adhesive sheet as described in 1 or 2 above, the weight ratio of the polyol contained in the reaction solution (1) to the (meth)acrylic polymer having a hydroxyl group may be 30:70 to 70:30. 4. In the method for manufacturing an adhesive sheet described in any of items 1 to 3 above, the number average molecular weight of the polyol may be 3000 or less. 5. In the method for producing an adhesive sheet described in any of items 1 to 4 above, the polyol may have secondary hydroxyl groups. 6. In the method for manufacturing an adhesive sheet described in any of items 1 to 5 above, the polyol may contain polypropylene glycol units. 7. In the method for producing an adhesive sheet described in any of items 1 to 6 above, radiation-polymerizable carbon-carbon double bonds may be introduced into the total of 50 mol% to 90 mol% of the hydroxyl groups of the polyol and the (meth)acrylic polymer having hydroxyl groups contained in the reaction solution (2). 8. In the method for manufacturing an adhesive sheet described in any of items 1 to 7 above, the adhesive sheet may be an adhesive sheet for semiconductor wafer processing. [Effects of the Invention]

[0006] According to the manufacturing method of the embodiment of the present invention, an adhesive sheet can be provided that exhibits excellent adhesive strength before ultraviolet irradiation and can be peeled off from the adherend without leaving any adhesive residue after ultraviolet irradiation. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic cross-sectional view of an adhesive sheet according to one embodiment of the present invention. [Modes for carrying out the invention]

[0008] A. Method for manufacturing adhesive sheets The method for producing an adhesive sheet according to an embodiment of the present invention is a method for producing an adhesive sheet having a substrate and an active energy ray curable adhesive layer, and comprises the following steps: (A-1) Polymerizing a monomer composition containing a (meth)acrylic monomer having a hydroxyl group in a polyol to obtain a reaction solution (1) containing a (meth)acrylic polymer having a hydroxyl group; (A-2) Adding a compound having a radiation-polymerizable carbon-carbon double bond to the reaction solution (1) to introduce a radiation-polymerizable carbon-carbon double bond into the polyol and the (meth)acrylic polymer having a hydroxyl group, thereby introducing a radiation-polymerizable carbon-carbon double bond into the polyol and the (meth)acrylic polymer having a hydroxyl group. (A-3) A reaction solution (2) is obtained containing an ol derivative (hereinafter also called a polyol derivative) and a (meth)acrylic polymer into which a radiation-polymerizable carbon-carbon double bond has been introduced; (A-4) A polyisocyanate and a photopolymerization initiator are added to the reaction solution (2) to prepare an adhesive solution; (A-5) An adhesive layer is formed on a substrate using the obtained adhesive solution; (A-6) The polyisocyanate contained in the adhesive layer, the polyol derivative into which a radiation-polymerizable carbon-carbon double bond has been introduced, and the (meth)acrylic polymer into which a radiation-polymerizable carbon-carbon double bond has been introduced are subjected to a urethane reaction. In the production method of the embodiment of the present invention, a radiation-polymerizable carbon-carbon double bond is introduced to the polyol that functions as a solvent in step (A-1) in step (A-2). The resulting reaction solution (2) contains a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond, a polyol derivative in which a carbon-carbon double bond has been introduced to at least one of the hydroxyl groups of the polyol, and a polyol. A polyisocyanate and a photopolymerization initiator are added to this reaction solution (2) to prepare an adhesive solution, and an adhesive layer is formed on a substrate or release liner using the obtained adhesive solution. Next, a urethane reaction is carried out in the formed adhesive layer. Through the urethane reaction, unreacted hydroxyl groups of polyols, (meth)acrylic polymers, and polyol derivatives can react with the polyisocyanate in the adhesive layer.The adhesive layer after the urethane reaction may contain an active energy ray curable component in which the above-mentioned (meth)acrylic polymer is the main chain and polyols, polyol derivatives, or (meth)acrylic polymers are introduced via urethane bonds in the side chains and / or terminals, and an active energy ray curable component that is an oligomer in which polyols or polyol derivatives are linked via urethane bonds. These can be cured by irradiating the adhesive layer with ultraviolet light. Since the polyol, which is the solvent used in the polymerization of the (meth)acrylic polymer, also becomes a curing component in the adhesive layer, the amount of solvent (polyol) contained in the adhesive layer can be significantly reduced. As a result, it can contribute to reducing the environmental burden due to residual solvent. Furthermore, since the formed adhesive layer is flexible and has excellent step-following properties, it can be suitably used for processing semiconductor wafers with more complex surface structures. In this specification, (meth)acrylic means acrylic and / or methacrylic.

[0009] A-1. Polymerization of monomer compositions containing (meth)acrylic monomers having hydroxyl groups. In the manufacturing method of the embodiment of the present invention, first, a monomer composition containing a (meth)acrylic monomer having a hydroxyl group is polymerized in a polyol to obtain a reaction solution (1) containing a (meth)acrylic polymer having a hydroxyl group. In this step, the polyol can function as a solvent. The (meth)acrylic polymer can function as a base polymer of the adhesive that forms the adhesive layer. As described above, since the polyol used as a solvent can become an ultraviolet curing component in a later step, the amount of solvent contained in the resulting adhesive sheet can be significantly reduced.

[0010] A-1-1. Polyol Any suitable polyol can be used as the polyol. Examples include polyhydric alcohols, amines, alkanolamines, and polyhydric phenols. Specifically, examples include polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, diethylene glycol, glycerin, hexanetriol, trimethylolpropane, and pentaerythritol; amines such as ethylenediamine and hexamethylenediamine; alkanolamines such as ethanolamine and propanolamine; and polyhydric phenols such as resorcinol and bisphenols. More specifically, examples include polyether polyols such as polytetramethylene glycol, polyethylene glycol, polypropylene glycol, polyoxypropylene glycol, and polyoxybutylene glycol; polyolefin polyols such as polybutadiene polyol and polyisoprene polyol; and other polyols such as adipate polyols, lactone polyols, and polyester polyols such as castor oil. Only one type of polyol may be used, or two or more types may be used in combination.

[0011] The number-average molecular weight (Mn) of the polyol is preferably 3000 or less, more preferably 400 to 3000, even more preferably 600 to 3000, and particularly preferably 600 to 2000. If the number-average molecular weight of the polyol is within the above range, an adhesive solution that can be coated at room temperature can be obtained when using a (meth)acrylic polymer with a weight-average molecular weight of 100,000 or less. Furthermore, it can exhibit excellent adhesive strength for fixing Si wafers during semiconductor wafer processing. The number-average molecular weight can be determined by gel permeation chromatography (solvent: tetrahydrofuran, polystyrene equivalent).

[0012] In one embodiment, the polyol preferably has secondary hydroxyl groups. Using a polyol having secondary hydroxyl groups, radiation-polymerizable carbon-carbon double bonds can be preferentially introduced to the primary hydroxyl groups of the side chains of the (meth)acrylic polymer in step (A-2). In step (A-3), the polyol can be incorporated into the main chain skeleton of the (meth)acrylic polymer via urethane bonds. As a result, sufficient adhesive strength can be achieved to fix Si wafers during semiconductor wafer processing. The polyol may have one secondary hydroxyl group or two or more.

[0013] The polyol preferably contains polypropylene glycol units. Using a polyol containing polypropylene glycol units, an adhesive solution with a viscosity suitable for coating at room temperature can be obtained. Furthermore, the hydroxyl groups of the polyol are secondary hydroxyl groups, allowing for sufficient adhesive strength to fix Si wafers during semiconductor wafer processing. The polyol may contain one or two or more polypropylene glycol units.

[0014] Preferably, polypropylene glycol or polypropylene triol is used as the polyol. Using these polyols, an adhesive solution with a viscosity that can be applied at room temperature can be obtained. Furthermore, the hydroxyl groups of the polyol are secondary hydroxyl groups, which can exhibit sufficient adhesive strength to fix Si wafers during semiconductor wafer processing.

[0015] The viscosity of the polyol at 25°C is preferably 1000 mPa·s or less, more preferably 800 mPa·s or less, and even more preferably 600 mPa·s or less. Alternatively, the viscosity of the polyol at 25°C may be, for example, 50 mPa·s or more. If the viscosity is within the above range, an adhesive solution that can be coated at room temperature can be obtained. Furthermore, it can exhibit sufficient adhesive strength to fix Si wafers during semiconductor wafer processing. The viscosity of the polyol at 25°C can be measured by any suitable method. For example, it can be measured using a B-type viscometer.

[0016] Commercially available products may be used as the polyol. Examples include the Sannix PP series manufactured by Sanyo Chemical Industries, Ltd. under the trade names "Sannix PP-600", "Sannix PP-1000", "Sannix PP-2000", etc., the Sannix GP series manufactured by Sanyo Chemical Industries, Ltd. under the trade name "Sannix GP-1000", etc., and those manufactured by AGC Inc. under the trade names "EXCENOL 1020F", "EXCENOL 1030F", "EXCENOL 2020F", "EXCENOL 903", etc.

[0017] A-1-2. Monomer Composition Examples of monomers included in the monomer composition include hydroxyl group-containing (meth)acrylic monomers, any appropriate (meth)acrylic monomers other than hydroxyl group-containing (meth)acrylic monomers, and any monomers copolymerizable with these. Only one type of these monomers may be used, or two or more types may be combined.

[0018] Any appropriate monomer can be used as the (meth)acrylic monomer having a hydroxyl group. Examples include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyhexyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl acrylate, polypropylene glycol mono(meth)acrylate, N-hydroxyethyl (meth)acrylamide, N-hydroxypropyl (meth)acrylamide, and the like. Preferable examples include 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl acrylate. By using these monomers, a (meth)acrylic polymer having good compatibility with polyols can be obtained. Further, it is possible to provide a pressure-sensitive adhesive sheet that exhibits excellent adhesive force before ultraviolet irradiation and can have a sufficiently reduced adhesive force after ultraviolet irradiation. Only one type of (meth)acrylic monomer having a hydroxyl group may be used, or two or more types may be used in combination.

[0019] The content ratio of the (meth)acrylic monomer having a hydroxyl group relative to the total of all monomer components contained in the monomer composition is preferably 30% by weight or less, more preferably 20% by weight or less, and still more preferably 15% by weight or less. The content ratio of the (meth)acrylic monomer having a hydroxyl group relative to the total of all monomer components contained in the monomer composition is, for example, 5% by weight or more. When the content ratio of the (meth)acrylic monomer having a hydroxyl group falls within the above range, the pressure-sensitive adhesive layer formed from the obtained pressure-sensitive adhesive solution exhibits excellent adhesive force before ultraviolet irradiation, and can be peeled from an adherend without adhesive residue after ultraviolet irradiation.

[0020] Aside from (meth)acrylic monomers having hydroxyl groups, alkyl (meth)acrylates are typically used as (meth)acrylic monomers. Specific examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, and (meth) Examples of C1-20 alkyl esters of (meth)acrylate include nonyl 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, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. Only one alkyl ester of (meth)acrylate may be used, or two or more may be used in combination. The content ratio of alkyl (meth)acrylate to the total monomer components contained in the monomer composition can be adjusted to any appropriate ratio. The content ratio of alkyl (meth)acrylate to the total amount of monomer components contained in the monomer composition is preferably 50% to 95% by weight, and more preferably 50% to 80% by weight.

[0021] Copolymerizable monomers include, for example, carboxyl group-containing monomers such as acrylic acid and methacrylic acid; acid anhydride monomers such as maleic anhydride and eicotanoic anhydride; sulfonic acid group-containing monomers such as styrene sulfonic acid and allyl sulfonic acid; nitrogen-containing monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, and acryloylmorpholine; aminoalkyl (meth)acrylate monomers such as aminoethyl (meth)acrylate; alkoxyalkyl (meth)acrylate monomers such as methoxyethyl (meth)acrylate; maleimide monomers such as N-cyclohexylmaleimide and N-isopropylmaleimide; itaconimide monomers such as N-methylitaconimide and N-ethylitaconimide; succinimide monomers Examples of monomers include vinyl monomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone, and methylvinylpyrrolidone; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth)acrylate; glycol-based acrylic ester monomers such as polyethylene glycol (meth)acrylate and polypropylene glycol (meth)acrylate; acrylic ester monomers having heterocycles, halogen atoms, silicon atoms, etc., such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, and silicone (meth)acrylate; olefin monomers such as isoprene, butadiene, and isobutylene; and vinyl ether monomers such as vinyl ether. These monomer components may be used individually or in combination of two or more. The content ratio of copolymerizable monomers to the total monomer components in the monomer composition can be adjusted to any appropriate ratio. For example, the content ratio of copolymerizable monomers is used such that the total of hydroxyl-containing (meth)acrylic monomers and alkyl (meth)acrylates is 100% by weight. The content of copolymerizable monomers relative to the total monomer components in the monomer composition is preferably 50% by weight or less, and more preferably 10% to 50% by weight.

[0022] A-1-3. Other ingredients The composition used for polymerization of (meth)acrylic monomers having hydroxyl groups may further contain a polyol and any suitable additives other than the monomer composition. Examples include chain transfer agents and polymerization initiators.

[0023] Any suitable polymerization initiator can be used as the polymerization initiator. For example, azo polymerization initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane)dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis(2-methylpropionamidine)disulfate, and 2,2'-azobis(N,N'-dimethyleneisobutylamidine); persulfates such as potassium persulfate and ammonium persulfate. Examples of peroxide-based polymerization initiators include benzoyl peroxide, t-butyl hydroperoxide, and hydrogen peroxide; and redox polymerization initiators that combine peroxides with reducing agents, such as combinations of peroxides with ascorbic acid (e.g., hydrogen peroxide solution and ascorbic acid), combinations of peroxides with iron(II) salts (e.g., hydrogen peroxide solution and iron(II) salts), and combinations of persulfates with sodium bisulfite. A single polymerization initiator may be used, or two or more may be used in combination.

[0024] The polymerization initiator can be used in any appropriate amount depending on the type of polymerization initiator used and the composition of the monomer composition. The content of the polymerization initiator is, for example, 0.01 parts by weight to 1 part by weight, preferably 0.02 parts by weight to 0.5 parts by weight, per 100 parts by weight of the monomer composition.

[0025] Any suitable chain transfer agent can be used. Examples include mercaptans such as dodecyl mercaptan (dodecanethiol), lauryl mercaptan, glycidyl mercaptan, 2-mercaptoethanol, mercaptoacetic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, and α-methylstyrene dimer. One chain transfer agent may be used alone, or two or more may be used in combination. The content of the chain transfer agent is, for example, 0.001 to 0.5 parts by weight per 100 parts by weight of the monomer composition.

[0026] A-1-4. Polymerization reaction Polymerization of hydroxyl-containing (meth)acrylic polymers can be carried out by any suitable method. For example, it can be carried out by adding any suitable additives such as a polyol, a monomer composition containing a hydroxyl-containing (meth)acrylic monomer, a polymerization initiator, and a chain transfer agent to a polymerization reaction vessel and heating while stirring. The reaction time and reaction temperature can be set to any suitable values. The reaction time is, for example, 4 to 8 hours, preferably 6 to 8 hours. The reaction temperature is, for example, 60°C to 80°C, preferably 60°C to 70°C.

[0027] By carrying out the above polymerization reaction, a reaction solution (1) containing a hydroxyl-containing (meth)acrylic polymer is obtained. In reaction solution (1), the polyol may exist as a solvent in an unreacted state. The weight ratio of the polyol to the hydroxyl-containing (meth)acrylic polymer in reaction solution (1) is preferably 30:70 to 70:30, more preferably 35:65 to 65:35, and even more preferably 40:60 to 60:40. If the weight ratio of the polyol to the hydroxyl-containing (meth)acrylic polymer in reaction solution (1) is within the above range, radiation-polymerizable carbon-carbon double bonds can be introduced into both the polyol and the hydroxyl-containing (meth)acrylic polymer in an appropriate proportion. As a result, the adhesive layer formed from the obtained adhesive solution exhibits excellent adhesive strength before UV irradiation and can be peeled off from the adherend without leaving any residue after UV irradiation.

[0028] A-2. Preparation of reaction solution (2) Next, a compound having a radiation-polymerizable carbon-carbon double bond is added to the obtained reaction solution (1), and a radiation-polymerizable carbon-carbon double bond is introduced into the polyol and the (meth)acrylic polymer having a hydroxyl group, thereby obtaining a reaction solution (2) containing a polyol derivative into which a radiation-polymerizable carbon-carbon double bond has been introduced and a (meth)acrylic polymer into which a radiation-polymerizable carbon-carbon double bond has been introduced.

[0029] A-2-1. Compounds containing a carbon-carbon double bond that are radiopolymerizable. Any suitable compound can be used as the compound having a radiation-polymerizable carbon-carbon double bond. Examples of functional groups having a radiation-polymerizable carbon-carbon double bond include acryloyl groups, methacryloyl groups, vinyl groups, allyl groups, and acetylene groups. As described above, polyols and (meth)acrylic polymers have hydroxyl groups. Compounds having an isocyanate group and a polymerizable carbon-carbon double bond are preferably used because they are reactive with hydroxyl groups and the reaction can be easily tracked. Specifically, examples include 2-isocyanate ethyl methacrylate, methacryloisocyanate, 2-methacryloyloxyethyl isocyanate (2-isocyanate ethyl methacrylate), and m-isopropenyl-α,α-dimethylbenzyl isocyanate. These polymerizable carbon-carbon double bond compounds may be used individually or in combination of two or more.

[0030] A-2-2. Introduction of radiation-polymerizable carbon-carbon double bonds Any suitable method can be used to introduce radiation-polymerizable carbon-carbon double bonds into polyols and (meth)acrylic polymers having hydroxyl groups. For example, one method involves condensing or adding a compound having radiation-polymerizable carbon-carbon double bonds to a polyol or (meth)acrylic polymer while maintaining the radiation polymerizability of the carbon-carbon double bonds.

[0031] The introduction of a radiation-polymerizable carbon-carbon double bond is carried out by adding a compound having a radiation-polymerizable carbon-carbon bond to the reaction solution (1) and reacting it in the presence of any suitable catalyst. The reaction temperature and reaction time are set to any suitable values. The reaction time is, for example, 6 to 72 hours, preferably 8 to 12 hours. The reaction temperature is, for example, 23°C to 60°C, preferably 40°C to 60°C.

[0032] Through the above reaction, the hydroxyl groups of the polyol and / or the hydroxyl groups of the (meth)acrylic polymer having hydroxyl groups react with the functional groups (e.g., isocyanate groups) of the compound having a radiation-polymerizable carbon-carbon double bond, and a radiation-polymerizable carbon-carbon double bond may be introduced into the polyol and the (meth)acrylic polymer. As a result, a polyol derivative in which a radiation-polymerizable carbon-carbon double bond has been introduced into the polyol and a (meth)acrylic polymer in which a radiation-polymerizable carbon-carbon double bond has been introduced (hereinafter also referred to as a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond) can be obtained. In the polyol derivative in which a radiation-polymerizable carbon-carbon double bond has been introduced, the radiation-polymerizable carbon-carbon double bond may be introduced into one hydroxyl group or into two or more hydroxyl groups. In the (meth)acrylic polymer in which a radiation-polymerizable carbon-carbon double bond has been introduced, the radiation-polymerizable carbon-carbon double bond may be introduced into one hydroxyl group or into two or more hydroxyl groups.

[0033] In one embodiment, radiation-polymerizable carbon-carbon double bonds are introduced to preferably 50 mol% to 90 mol%, more preferably 55 mol% to 85 mol%, and even more preferably 60 mol% to 80 mol% of the total hydroxyl groups of the polyol and the (meth)acrylic polymer having hydroxyl groups. If the proportion of hydroxyl groups to which radiation-polymerizable carbon-carbon double bonds are introduced, out of the total hydroxyl groups of the polyol and the (meth)acrylic polymer having hydroxyl groups, is within the above range, the adhesive layer formed from the resulting adhesive solution will exhibit excellent adhesion before UV irradiation and will peel off from the adherend without leaving any residue after UV irradiation.

[0034] The weight-average molecular weight of the (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond is preferably 100,000 or less, and more preferably 80,000 or less. Furthermore, the weight-average molecular weight of the (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond is, for example, 10,000 or more. If the weight-average molecular weight of the (meth)acrylic polymer containing the radiation-polymerizable carbon-carbon double bond is within the above range, an adhesive solution that can be applied at room temperature can be obtained. The weight-average molecular weight can be determined by gel permeation chromatography (solvent: tetrahydrofuran, polystyrene equivalent).

[0035] A-3. Preparation of adhesive solution Next, polyisocyanate and a photopolymerization initiator are added to the reactive solution (2) obtained above to prepare an adhesive solution.

[0036] A-3-1. Polyisocyanates Any suitable polyisocyanate can be used as the polyisocyanate. Examples of polyisocyanates include aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and dimers and trimers of these diisocyanates. Specifically, tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, butane-1,4-diisocyanate, 2,2,4-trimethylhexa Examples include methylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, 1,3-bis(isocyanate-methyl)cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate, and the like, as well as their dimers and trimers, and polyphenylmethane polyisocyanate. Examples of the above trimers include isocyanurate type, biuret type, and allophanate type. Polyisocyanates may be used individually or in combination of two or more types.

[0037] Commercially available polyisocyanates may be used. Examples of commercially available products include "Takenate D101A" and "Takenate D165N" from Mitsui Chemicals, and "Coronate L," "Coronate HL," and "Coronate HX" from Tosoh Corporation.

[0038] The polyisocyanate content in the adhesive solution can be set to any appropriate value. Preferably, the equivalent ratio of polyisocyanate to hydroxyl groups in the reaction solution (2) is NCO / OH = 0.5 to 5.0, more preferably 1.0 to 3.0, and even more preferably 1.5 to 3.0. If the equivalent ratio is within the above range, the adhesive layer formed from the resulting adhesive solution will exhibit excellent adhesion before UV irradiation and will peel off from the adherend without leaving any residue after UV irradiation.

[0039] A-3-2. Photopolymerization Initiators Any suitable initiator can be used as the photopolymerization initiator. Examples of photopolymerization initiators include: acylphosphine oxide-based photopolymerization initiators such as ethyl 2,4,6-trimethylbenzylphenylphosphine and (2,4,6-trimethylbenzoyl)-phenylphosphine oxide; α-ketol compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and 1-hydroxycyclohexylphenyl ketone; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1; benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether, and anisoin methyl ether; and benzyldimethyl ketal. Examples include ketal compounds such as 2-naphthalenesulfonyl chloride; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; benzophenone compounds such as benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone; camphorquinone; halogenated ketones; acylphosphonates; and α-hydroxyacetophenones such as 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropane-1. A single photopolymerization initiator may be used, or two or more may be used in combination.

[0040] Commercially available photopolymerization initiators may be used. Examples include "Omnirad TPO-L," "Omnirad 500," and "Omnirad MBF" from IGM Resins.

[0041] The photopolymerization initiator can be used in any appropriate amount. The amount of photopolymerization initiator is preferably 0.5 to 20 parts by weight, and more preferably 1 to 10 parts by weight, per 100 parts by weight of the (meth)acrylic polymer containing radiation-polymerizable carbon-carbon double bonds in the reaction solution (2). If the amount of photopolymerization initiator is less than 0.5 parts by weight, the polymer may not cure sufficiently upon UV irradiation.

[0042] A-3-3. Coating The adhesive solution may contain any suitable additives as needed. Examples of additives include crosslinking agents, catalysts (e.g., platinum catalysts), tackifiers, plasticizers, pigments, dyes, fillers, antioxidants, conductive materials, UV absorbers, light stabilizers, release modifiers, softeners, flame retardants, and solvents. Additives are used in any appropriate amount depending on the purpose.

[0043] A-4. Formation of the adhesive layer Next, an adhesive layer is formed on the substrate using the obtained adhesive solution. The adhesive layer can be formed by any suitable method. For example, the adhesive solution obtained above can be applied to a release liner and heated to form an adhesive layer on the release liner, and then the adhesive layer can be transferred to the substrate to form an adhesive layer on the substrate. Alternatively, the adhesive solution can be applied to the substrate and heated to form an adhesive layer.

[0044] Various methods can be used to apply the adhesive solution, including bar coating, air knife coating, gravure coating, gravure reverse coating, reverse roll coating, lip coating, die coating, dip coating, offset printing, flexographic printing, and screen printing. Any suitable heating method can be used.

[0045] The base material can be composed of any suitable resin. Specific examples of resins constituting the base material include polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polybutylene naphthalate (PBN); polyolefin resins such as ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, polyethylene, polypropylene, and ethylene-propylene copolymer; polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyamide, polyimide, celluloses, fluorine resins, polyethers, polystyrene resins such as polystyrene; polycarbonate, polyethersulfone, and polyetheretherketone. Preferably, the resin is a polyolefin resin or a polyester resin. Since these resins transmit ultraviolet light, an adhesive sheet with easy peelability can be obtained by ultraviolet irradiation.

[0046] The base material may further contain other components, to the extent that it does not impair the effects of the present invention. Examples of other components include antioxidants, ultraviolet absorbers, light stabilizers, heat stabilizers, and antistatic agents. The type and amount of other components used can be any appropriate amount depending on the purpose.

[0047] A-5. Urethane formation reaction Next, the polyisocyanate contained in the adhesive layer, a polyol derivative into which a radiation-polymerizable carbon-carbon double bond has been introduced, a (meth)acrylic polymer into which a radiation-polymerizable carbon-carbon double bond has been introduced, and the polyol are subjected to a urethane reaction. Through the urethane reaction, unreacted hydroxyl groups contained in the polyol, polyol derivative, and (meth)acrylic polymer can be bonded to the urethane. As a result, the unreacted polyol contained in the adhesive layer can be bonded to the side chains or ends of the (meth)acrylic polymer. Alternatively, it can be bonded with the unreacted polyol and / or polyol derivative to form an active energy ray-curable oligomer. As a result, the adhesive layer may contain an active energy ray-curable (meth)acrylic polymer and an active energy ray-curable oligomer. Through the urethane reaction, the polyol used as a solvent becomes the above-mentioned active energy ray-curable component, and the amount of solvent remaining in the adhesive layer can be reduced.

[0048] In one embodiment, it is preferable to apply the adhesive solution to a substrate or a release liner and heat it to carry out the urethane reaction. By carrying out the urethane reaction in this manner, the productivity of the adhesive sheet can be improved. In this embodiment, the urethane reaction may be carried out in an adhesive layer formed on the substrate or an adhesive layer transferred to the substrate, or the urethane reaction may be carried out in an adhesive layer formed on a release liner and then the adhesive layer may be transferred to the substrate.

[0049] The urethane reaction can be carried out by any suitable method. For example, the urethane reaction can be carried out by placing the material in a light-shielded state at any suitable temperature for any suitable time. The reaction time is, for example, 1 to 10 minutes, preferably 2 to 5 minutes. The reaction temperature is, for example, 110°C to 150°C, preferably 120°C to 140°C.

[0050] B. Adhesive sheet B-1. Overall structure of the adhesive sheet Figure 1 is a schematic cross-sectional view of an adhesive sheet according to an embodiment of the present invention. The adhesive sheet 100 obtained by the manufacturing method of the above embodiment of the present invention comprises a base material 20 and an adhesive layer 10 in this order. As described above, the adhesive layer contains a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond, an oligomer having a radiation-polymerizable carbon-carbon double bond, and a photopolymerization initiator. Therefore, it exhibits excellent adhesion to the adherend before ultraviolet irradiation, and after ultraviolet irradiation, it suppresses adhesive residue on the adherend and can be easily peeled off the adherend. The adhesive sheet 100 may further contain any suitable layer. For example, an intermediate layer (not shown) may be formed between the base material 20 and the adhesive layer 10. When an intermediate layer is included, the ability to conform to adherends having irregularities on the surface may be improved.

[0051] The adhesive sheet preferably has an adhesive strength of 0.5 N / 20 mm or more to the Si wafer before UV irradiation, more preferably 0.75 N / 20 mm or more, and even more preferably 1.0 N / 20 mm or more. If the adhesive strength to the Si wafer before UV irradiation is within the above range, it has excellent adhesion to the adherend. The adhesive strength to the Si wafer is, for example, 15 N / 20 mm or less. In this specification, the adhesive strength to the Si wafer refers to the adhesive strength measured by the following method. The adhesive sheet is cut to a width of 20 mm and a length of 80 mm, and pressed onto the mirror surface of a silicon mirror wafer by moving a hand roller back and forth once in an atmosphere of 23°C, and left at 23°C for 30 minutes. After that, the force required to peel off the adhesive sheet is measured by performing a 180° peel test at a tensile speed of 300 mm / min in an atmosphere of 50% RH at 23°C.

[0052] The adhesive sheet has an accumulated light intensity of 460 mJ / cm². 2The adhesive strength of the adhesive sheet to the Si wafer after irradiation with ultraviolet light is preferably 0.20 N / 20 mm or less, more preferably 0.15 N / 20 mm or less, and even more preferably 0.10 N / 20 mm or less. If the adhesive strength to the Si wafer after ultraviolet irradiation is within the above range, it has easy peelability. A smaller adhesive strength after ultraviolet irradiation is preferable. In this specification, the integrated light amount is 460 mJ / cm². 2 The adhesive strength of the adhesive sheet to the Si wafer after irradiation with ultraviolet light is measured using the following method: Cut the adhesive sheet to a width of 20 mm and a length of 80 mm, and press it onto the mirror surface of a silicon mirror wafer by moving a hand roller back and forth once in an atmosphere of 23°C, and leave it at 23°C for 30 minutes. After that, irradiate with ultraviolet (UV) light until the integrated light intensity is 460 mJ / cm². 2 The adhesive sheet is irradiated from the side so that the wavelength is (equivalent to 365 nm). Next, the force required to peel off the adhesive sheet is measured by performing a 180° peel test under the conditions of 23°C, 50% RH atmosphere, and a tensile speed of 300 mm / min.

[0053] The thickness of the adhesive sheet obtained by the manufacturing method of the embodiment of the present invention can be set to any appropriate thickness. The thickness of the adhesive sheet is preferably 30 μm to 400 μm, more preferably 40 μm to 300 μm, and even more preferably 50 μm to 200 μm.

[0054] The thickness of the substrate can be set to any appropriate value. Preferably, the thickness of the substrate is 30 μm to 200 μm, more preferably 40 μm to 180 μm, and even more preferably 45 μm to 180 μm.

[0055] The thickness of the adhesive layer can be set to any appropriate value. Preferably, the thickness of the adhesive layer is 2 μm to 200 μm, more preferably 3 μm to 150 μm, and even more preferably 5 μm to 100 μm. If the thickness of the adhesive layer is within the above range, it can exhibit excellent adhesion to the adherend.

[0056] C. Uses of adhesive sheets The adhesive sheet obtained by the manufacturing method of the embodiment of the present invention can be suitably used in the semiconductor wafer manufacturing process. For example, it can be used as an adhesive sheet for semiconductor wafer processing, such as a dicing tape and a backgrinding tape. The adhesive sheet obtained by the manufacturing method of the embodiment of the present invention can have excellent conformability. Therefore, it can be suitably used for processing semiconductor wafers with more complex surface structures. [Examples]

[0057] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the examples, unless otherwise specified, "parts" and "%" are based on weight.

[0058] [Example 1] A composition was prepared by mixing 32.9 parts by weight of 2-ethylhexyl acrylate (2EHA), 8.4 parts by weight of acryloylmorpholine (ACMO), 8.6 parts by weight of 4-hydroxybutyl acrylate (4HBA), 0.1 parts by weight of 1-dodecanethiol (LSH), 50 parts by weight of polyol (manufactured by Sanyo Chemical Industries, Ltd., trade name "Sannix PP-600"), and 0.1 parts by weight of azobisisobutyronitrile (AIBN). The obtained composition was placed in a 1 L round-bottom separable flask into a polymerization apparatus equipped with a separable cover, separatory funnel, thermometer, nitrogen inlet tube, Liebig condenser, vacuum seal, stirring rod, and stirring blade, and nitrogen was purged at room temperature for 1 hour while stirring. Subsequently, polymerization was carried out under nitrogen inflow and stirring at 62°C for 4 hours, and then at 78°C for 2 hours to obtain a resin solution. The flask containing the obtained resin solution was then cooled to room temperature. Subsequently, 28 parts by weight of a radiation-polymerizable carbon-carbon double bond compound (manufactured by Showa Denko, trade name "Kalenz MOI") and 0.08 parts by weight of a catalyst (dibutyltin IV dilaurate) were added to the resin solution, and the mixture was stirred at 50°C for 8 hours under an air atmosphere to obtain a polymer solution. To the obtained polymer solution, 21.6 parts by weight of polyisocyanate (manufactured by Mitsui Chemicals, trade name "Takenate D-101A") and 4.5 parts by weight of a photopolymerization initiator (manufactured by IGM Resins BV, trade name "Omnirad TPO-L") were added and mixed to prepare an adhesive solution. A 50 μm thick PET film (Toray Industries, Ltd., product name "Lumirror S105") with one side corona-treated was coated with an adhesive solution onto the corona-treated side and heated in a dryer at 130°C for 3 minutes to form a 30 μm thick adhesive layer. Then, the formed adhesive layer and the release-treated side of a PET release liner (Mitsubishi Chemical Industries, product name "Diafoil MRF38") were bonded together using a hand roller. Next, the sheet was left in a dryer set to 50°C for 48 hours in a light-shielded environment, and then removed from the dryer to obtain an adhesive sheet.

[0059] [Examples 2-6] An adhesive solution was obtained in the same manner as in Example 1, except that the composition of the adhesive solution was changed as shown in Table 1. An adhesive sheet was obtained in the same manner as in Example 1, except that the obtained adhesive solution was used.

[0060] (Comparative Example 1) An adhesive solution was obtained in the same manner as in Example 1, except that the composition of the adhesive solution was changed as shown in Table 1. An attempt was made to produce an adhesive sheet using the obtained adhesive solution in the same manner as in Example 1, but an adhesive layer could not be formed, and an adhesive sheet could not be obtained.

[0061] <Rating> The following evaluations were performed using the adhesive sheets obtained in the examples or comparative examples. The results are shown in Table 1. 1. Adhesive strength The obtained adhesive sheet was cut to a size of 20 mm in width and 80 mm in length, and pressed onto the mirror surface of a silicon mirror wafer (manufactured by Shin-Etsu Semiconductor Co., Ltd.) by moving a hand roller back and forth once under a 23°C atmosphere, and left for 30 minutes at 23°C. Subsequently, the force required to peel off the adhesive sheet was measured under the conditions of 23°C, 50% RH atmosphere, 180° peel, and tensile speed of 300 mm / min, and this was defined as the pre-UV adhesive strength. Furthermore, an adhesive sheet was pressed onto a silicon mirror wafer using the same method and left at 23°C for 30 minutes. Subsequently, ultraviolet (UV) light (cumulative light intensity: 460 mJ / cm²) was applied. 2 The adhesive sheet was irradiated with UV light (at 365 nm equivalent) from the adhesive side. Subsequently, the force required to peel the adhesive sheet was measured under the conditions of 23°C, 50% RH atmosphere, 180° peel, and tensile speed of 300 mm / min, and this was defined as the post-UV adhesive strength.

[0062] [Table 1]

[0063] The adhesive sheet of the embodiment of the present invention had high adhesive strength to the adherend before UV irradiation and could be easily peeled off without leaving any adhesive residue after UV irradiation. The adhesive solution of Comparative Example 1 had insufficient cohesive force, and an adhesive sheet could not be obtained. [Industrial applicability]

[0064] The adhesive sheet obtained by the manufacturing method of the embodiment of the present invention can be suitably used in the semiconductor wafer processing process. [Explanation of Symbols]

[0065] 10 Adhesive layer 20 Base material 100 adhesive sheets

Claims

1. A method for producing an adhesive sheet having a base material and an active energy ray curable adhesive layer, Polymerizing a monomer composition containing a (meth)acrylic monomer having a hydroxyl group in a polyol to obtain a reaction solution (1) containing a (meth)acrylic polymer having a hydroxyl group; To obtain a reaction solution (2) containing a polyol derivative with a radiation-polymerizable carbon-carbon double bond and a (meth)acrylic polymer with a radiation-polymerizable carbon-carbon double bond, by adding a compound having a radiation-polymerizable carbon-carbon double bond to the reaction solution (1), thereby introducing a radiation-polymerizable carbon-carbon double bond to a polyol derivative having a radiation-polymerizable carbon-carbon double bond and a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond; A polyisocyanate and a photopolymerization initiator are added to the reaction solution (2) to prepare an adhesive solution; Forming an adhesive layer on a substrate using the adhesive solution; A method for producing an adhesive sheet, comprising: urethane-forming a polyisocyanate contained in the adhesive layer, a polyol derivative into which a radiation-polymerizable carbon-carbon double bond has been introduced, and a (meth)acrylic polymer into which a radiation-polymerizable carbon-carbon double bond has been introduced.

2. The method for producing an adhesive sheet according to claim 1, wherein the content ratio of the hydroxyl group-containing (meth)acrylic monomer to the total amount of all monomer components contained in the monomer composition is 30% by weight or less.

3. A method for producing an adhesive sheet according to claim 1, wherein the weight ratio of the polyol contained in the reaction solution (1) to the (meth)acrylic polymer having hydroxyl groups is 30:70 to 70:

30.

4. The method for producing an adhesive sheet according to claim 1, wherein the number average molecular weight of the polyol is 3000 or less.

5. The method for producing an adhesive sheet according to claim 1, wherein the polyol has a secondary hydroxyl group.

6. The method for producing an adhesive sheet according to claim 1, wherein the polyol comprises a polypropylene glycol unit.

7. A method for producing an adhesive sheet according to claim 1, wherein radiation-polymerizable carbon-carbon double bonds are introduced into 50 mol% to 90 mol% of the total hydroxyl groups of the polyol and the (meth)acrylic polymer having hydroxyl groups.

8. The method for manufacturing an adhesive sheet according to any one of claims 1 to 7, wherein the adhesive sheet is an adhesive sheet for semiconductor wafer processing.

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