Peeling method

Abstract

To provide a sand blast treatment method which can remove a photosensitive resin layer after sand blast treatment from a carbon fiber-reinforced plastic without residues.SOLUTION: A sand blast treatment method includes: stacking a photosensitive resin layer which contains (A) an alkali-soluble cellulose derivative, (B) a photopolymerization initiator and (C) an urethane (meth)acrylate compound, and does not substantially contain (D) a carboxy group-containing acrylic resin, on a treated body made of a carbon fiber-reinforced plastic; imagewise exposing the photosensitive resin layer with light; removing a non-exposure part with an alkali developer and thereby forming a resist pattern on the treated body; and then subjecting the treated body to sand blast treatment through the resist pattern.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a sandblasting method.

Background Art

[0002] Conventionally, carbon fiber reinforced plastics are known as materials having properties such as high specific stiffness, low density, and low coefficient of thermal expansion. Carbon fiber reinforced plastics are composite materials in which carbon fibers are placed in resins (polyester resins, vinyl ester resins, epoxy resins, phenolic resins, and thermoplastic resins) to improve strength, and are used in a wide range of fields such as daily necessities, sports goods, automobiles, and aerospace industry applications.

[0003] Conventionally, as methods for microfabricating carbon fiber reinforced plastics, laser processing, cutting using tools such as drills, and sandblasting have been used. Sandblasting is a process in which a resist pattern is provided as a mask material on a workpiece, and then an abrasive is sprayed to selectively cut non-masked portions. When there are many processing sites for each workpiece, processing by sandblasting is advantageous from the viewpoint of productivity. Patent Document 1 describes a method for drilling a workpiece made of carbon fiber reinforced plastic using a resist layer having sandblast resistance. Patent Document 2 also describes a processing method for suppressing fluffing and peeling of a workpiece made of carbon fiber reinforced plastic in a sandblast process by adjusting the opening diameter of a resist layer having sandblast resistance.

[0004] As a photosensitive resin layer used as a mask material for this sandblasting process, it is common to include an alkali-soluble resin, urethane (meth) acrylate, and a photoinitiator. As the alkali-soluble resin, cellulose derivatives or carboxyl group-containing acrylic resins are known (for example, see Patent Document 3).

[0005] In sandblasting, it is necessary to remove the resist pattern from the workpiece after sandblasting. As described in Patent Document 4, a method is known in which an aqueous solution of an alkali metal hydroxide such as sodium hydroxide, or a basic compound such as N-methyldiethanolamine, pyridine, or piperidine is used as a stripping solution.

[0006] On the other hand, the photosensitive resin layer used as a masking material is highly adhesive, and after sandblasting, the surface layer of the resist pattern is coated with fine abrasives, which can make it difficult for the stripping solution to penetrate the photosensitive resin layer. In such cases, methods such as directly removing the resist pattern using hands or adhesive tape, or burning off the resist pattern at high temperatures can also be used (see Patent Document 5).

[0007] However, carbon fiber reinforced plastics have high adhesion to the photosensitive resin layer after curing, and even with removal using a stripping solution, residue of the resist pattern sometimes remained on the treated object. Furthermore, even with methods of direct removal by hand, the resist pattern sometimes fractured before peeling off the treated object, making removal difficult. In addition, methods involving high heat to burn off the resist pattern are undesirable because they may degrade the resin that makes up the carbon fiber reinforced plastic. For these reasons, there has been a need for a sandblasting method for carbon fiber reinforced plastics that can remove the resist pattern from the treated object without leaving any residue after sandblasting. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2012-196751 [Patent Document 2] International Publication No. 2018-062101 [Patent Document 3] Japanese Patent Publication No. 2012-27357 [Patent Document 4] Japanese Patent Publication No. 2006-78868 [Patent Document 5] International Publication No. 2007-091476 [Overview of the project] [Problems that the invention aims to solve]

[0009] The object of the present invention is to provide a sandblasting method that can remove the resist pattern from carbon fiber reinforced plastic without leaving any residue after sandblasting. [Means for solving the problem]

[0010] As a result of diligent research, the inventors have found that the above problems can be solved by the invention described below. A sandblasting method comprising: laminating a photosensitive resin layer on a carbon fiber reinforced plastic workpiece containing (A) an alkali-soluble cellulose derivative, (B) a photopolymerization initiator, and (C) a urethane (meth)acrylate compound, and (D) substantially free of carboxyl group-containing acrylic resin; exposing the photosensitive resin layer to an image-like state; removing the unexposed areas with an alkaline developer to form a resist pattern on the workpiece; and then sandblasting the workpiece through the resist pattern. [Effects of the Invention]

[0011] The present invention provides a sandblasting method that can remove the resist pattern from carbon fiber reinforced plastic without leaving any residue after sandblasting. [Modes for carrying out the invention]

[0012] The sandblasting method of the present invention will be described in detail below.

[0013] In the present invention, the photosensitive resin layer laminated on a carbon fiber reinforced plastic substrate contains (A) an alkali-soluble cellulose derivative as an alkali-soluble resin. Examples of (A) alkali-soluble cellulose derivatives include cellulose acetate phthalate, hydroxypropyl methylcellulose phthalate, hydroxypropyl methylcellulose acetate phthalate, and hydroxypropyl methylcellulose acetate succinate.

[0014] (A) The acid value of the alkali-soluble cellulose derivative is preferably 30 to 500 mg KOH / g, and more preferably 100 to 300 mg KOH / g. If this acid value is less than 30 mg KOH / g, the alkaline development time tends to be longer, while if it exceeds 500 mg KOH / g, the blast resistance may decrease.

[0015] Furthermore, the mass-average molecular weight of (A) the alkali-soluble cellulose derivative is preferably 10,000 to 200,000, and more preferably 10,000 to 150,000. If the mass-average molecular weight is less than 10,000, it may be difficult to form the photosensitive resin composition used in the present invention into a film state, while if it exceeds 200,000, the solubility in alkaline developer tends to deteriorate.

[0016] The photosensitive resin layer in the present invention contains (B) a photopolymerization initiator. (B) Examples of photopolymerization initiators include aromatic ketones such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one; 2-ethylanthraquinone, phenanthrenequinone, 2-tert-butylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2-phenylanthraquinone, and 2,3-diphenyl Quinones such as ruanthraquinone, 1-chloroanthraquinone, 2-methylanthraquinone, 1,4-naphthoquinone, 9,10-phenanthaquinone, 2-methyl-1,4-naphthoquinone, and 2,3-dimethylanthraquinone; benzoin ether compounds such as benzoin methyl ether, benzoin ethyl ether, and benzoin phenyl ether; benzoin compounds such as benzoin, methylbenzoin, and ethylbenzoin; benzyldimethyl ketal, 1-hydroxycyclohex Alkaline compounds such as silphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methylpropan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, etc. Kilphenones; acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide; oxime esters such as 1,2-octanedione, 1-[4-(phenylthio)phenyl-,2-(o-benzoyl oxime)], ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-,1-(o-acetyl oxime);2,4,5-triarylimidazole dimers such as 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-bis(methoxyphenyl)imidazole dimer, 2-(o-fluorophenyl)-4,5-diphenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, and 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer; acridines such as 9-phenylacridine and 1,7-bis(9,9′-acridinyl)heptane. Derivatives; N-phenylglycine, N-phenylglycine derivatives; Coumarin compounds; Benzophenone compounds such as benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylic benzophenone, 4-benzoyl-4′-methyldiphenyl sulfide, 3,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone, 4,4′-bis(dimethylamino)benzophenone, and 4,4′-bis(diethylamino)benzophenone are examples. The substituents on the aryl groups of the two 2,4,5-triarylimidazole dimers may be identical and symmetrical, or they may be different and asymmetrical. Furthermore, thioxanthone compounds and tertiary amine compounds may be combined, such as the combination of diethylthioxanthone and dimethylaminobenzoic acid. These can be used alone or in combination of two or more.

[0017] The photosensitive resin layer in the present invention contains (C) a urethane (meth)acrylate compound. (C) A urethane (meth)acrylate compound is a reaction product of a compound having terminal isocyanate groups, obtained by the reaction of a compound having a polyvalent hydroxyl group with a polyvalent isocyanate compound, and a (meth)acrylate compound having a hydroxyl group. Examples of compounds having a polyvalent hydroxyl group include polyesters and polyethers having hydroxyl groups at the terminals. Examples of polyesters include polyesters obtained by ring-opening polymerization of lactones, polycarbonates, and polyesters obtained by the condensation reaction of alkylene glycols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and dipropylene glycol with dicarboxylic acids such as maleic acid, fumaric acid, glutaric acid, and adipic acid. Examples of the aforementioned lactones include δ-valerolactone, ε-caprolactone, β-propiolactone, α-methyl-β-propiolactone, β-methyl-β-propiolactone, α,α-dimethyl-β-propiolactone, and β,β-dimethyl-β-propiolactone. Examples of the aforementioned polycarbonates include reaction products of diols such as bisphenol A, hydroquinone, and dihydroxycyclohexanone with carbonyl compounds such as diphenyl carbonate, phosgene, and succinic anhydride. Examples of the aforementioned polyethers include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polypentamethylene glycol.

[0018] Specific examples of the polyvalent isocyanate compound that reacts with the compound having a polyvalent hydroxy group include aliphatic or alicyclic diisocyanate compounds such as dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, 2,2-dimethylpentane-1,5-diisocyanate, octamethylene diisocyanate, 2,5-dimethylhexane-1,6-diisocyanate, 2,2,4-trimethylpentane-1,5-diisocyanate, nonamethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate, decamethylene diisocyanate, isophorone diisocyanate, etc. A single one of these compounds or a mixture of two or more thereof can be used.

[0019] Furthermore, specific examples of the (meth)acrylate compound having a hydroxy group include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, and compounds obtained by adding 1 to 10 mol of ε-caprolactone to 1 mol thereof. A single one of these compounds or a mixture of two or more thereof can be used.

[0020] Component (C) may contain a carboxy group. By containing a carboxy group, the solubility in an alkali developer tends to be improved. Component (C) containing a carboxy group can be obtained by first reacting a diisocyanate compound with a diol compound having a carboxy group so that isocyanate groups remain at both ends, and then reacting the terminal isocyanate groups of this reaction product with a (meth)acrylate compound having a hydroxy group.

[0021] The mass average molecular weight of component (C) is preferably 1,000 to 40,000.

[0022] The photosensitive resin layer in the present invention substantially does not contain a (D) carboxyl group-containing acrylic resin as an alkali-soluble resin. Examples of the (D) carboxyl group-containing acrylic resin include acrylic polymers obtained by copolymerizing (meth)acrylates such as methyl (meth)acrylate and ethyl (meth)acrylate with ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid. Further included are polymers obtained by copolymerizing dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid, their anhydrides and half esters, and monomers having other copolymerizable ethylenically unsaturated groups such as styrene, (meth)acrylonitrile, and (meth)acrylamide. Here, the term "substantially" means that the content of the carboxyl group-containing acrylic resin is less than 5% by mass based on the total mass of the photosensitive resin layer, preferably 2% by mass or less, and more preferably 0% by mass. This allows adjustment of the adhesion between the resist pattern and the carbon fiber reinforced plastic, and enables the resist pattern after sandblast treatment to be removed from the carbon fiber reinforced plastic without residue. When the content of the carboxyl group-containing acrylic resin is 5% by mass or more based on the total mass of the photosensitive resin layer, phase separation occurs in the coating liquid of the photosensitive resin composition used for producing the dry film resist described later, and shape defects and peeling defects of the resist pattern occur.

[0023] The photosensitive resin layer may contain, if necessary, components other than the above components (A) to (C). Examples of such components include photopolymerizable monomers, solvents, thermal polymerization inhibitors, plasticizers, colorants (dyes, pigments), photochromic agents, photobleaching agents, thermal discoloration inhibitors, fillers, defoamers, flame retardants, adhesion promoters, leveling agents, peeling accelerators, antioxidants, fragrances, thermosetting agents, water repellents, and oil repellents, etc., and each can be contained in an amount of about 0.01 to 20% by mass based on the total amount of the above components (A) to (C). These components can be used alone or in combination of two or more.

[0024] The above-mentioned photopolymerizable monomers are compounds other than component (C) urethane (meth)acrylate that have at least one polymerizable ethylenically unsaturated group in their molecule. Examples include compounds obtained by reacting a polyhydric alcohol with an α,β-unsaturated carboxylic acid; bisphenol A-based (meth)acrylate compounds; compounds obtained by reacting a glycidyl group-containing compound with an α,β-unsaturated carboxylic acid; nonylphenoxypolyethylene oxyacrylate; phthalic acid compounds such as γ-chloro-β-hydroxypropyl-β′-(meth)acryloyloxyethyl-o-phthalate and β-hydroxyalkyl-β′-(meth)acryloyloxyalkyl-o-phthalate; alkyl (meth)acrylates, EO-modified and / or PO-modified nonylphenyl (meth)acrylate, etc. Here, EO and PO represent ethylene oxide and propylene oxide, and the nonylphenyl (meth)acrylate has a block structure of ethylene oxide and / or a block structure of propylene oxide. These photopolymerizable monomers can be used individually or in combination of two or more types.

[0025] Furthermore, as the above-mentioned photopolymerizable monomer, a compound having three or more polymerizable ethylenically unsaturated groups in its molecule may be used. Examples of photopolymerizable compounds having three or more polymerizable ethylenically unsaturated groups in their molecule include trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane triglycidyl ether tri(meth)acrylate, etc., and these can be used individually or in combination of two or more.

[0026] In the photosensitive resin layer of the present invention, the content of (A) is preferably 20 to 50% by mass, and more preferably 25 to 35% by mass, relative to the total amount of (A), (B), and (C). If the content of (A) is less than 20% by mass, the film-forming properties may be poor or the developability may be reduced. If the content of (A) exceeds 50% by mass, the resolution of the resist pattern may be reduced.

[0027] The content of (B) is preferably 0.1 to 10% by mass, and more preferably 0.2 to 5% by mass, relative to the total amount of (A), (B), and (C). If the content of (B) is less than 0.1% by mass, the photopolymerization may be insufficient. On the other hand, if it exceeds 10% by mass, absorption on the surface of the photosensitive resin layer increases during exposure, which may result in insufficient photocrosslinking inside the photosensitive resin layer.

[0028] The content of (C) is preferably 40 to 75% by mass, and more preferably 55 to 70% by mass, relative to the total amount of (A), (B), and (C). If the content of (C) is less than 40% by mass, the crosslinking properties may decrease and the photosensitivity may become insufficient. On the other hand, if it exceeds 75% by mass, the tackiness of the film surface of the photosensitive resin layer may increase.

[0029] The photosensitive resin layer in the present invention is a layer containing a photosensitive resin composition comprising the above-mentioned components (A) to (C) and other components. As a method for laminating the photosensitive resin layer on a carbon fiber reinforced plastic workpiece, the photosensitive resin composition can be directly applied to the workpiece and dried to laminate the photosensitive resin layer. However, from the viewpoint of obtaining a more uniform photosensitive resin layer, a dry film resist (DFR) is prepared by coating the photosensitive resin composition onto a support (carrier film) and drying it to form a photosensitive resin layer, and the surface of the photosensitive resin layer of the DFR is laminated onto the workpiece. The DFR may also have a cover film on top of the photosensitive resin layer.

[0030] A transparent film that transmits active light is preferred as the support for the photosensitive resin layer. Regarding the thickness of the support, a thinner film is preferable because it reduces light refraction, while a thicker film offers superior coating stability; therefore, a thickness of 10 to 100 μm is preferred. Examples of such films include polyethylene terephthalate and polycarbonate.

[0031] As a cover film, it is sufficient to be able to peel off the uncured photosensitive resin layer, and a resin film with high release properties is used. Examples include polyethylene film, polypropylene film, and polyethylene film coated with a release agent such as silicone.

[0032] The surface processing method for a carbon fiber reinforced plastic workpiece according to this embodiment includes the steps of: attaching the above-mentioned photosensitive resin layer onto the workpiece using a laminator or the like; exposing the attached photosensitive resin layer to a mask pattern to form a cured portion at a predetermined location; removing the uncured photosensitive resin layer with a developer to form a resist pattern; sandblasting the carbon fiber reinforced plastic workpiece in areas where the resist pattern has not been formed by spraying an abrasive; and peeling the resist pattern from the cut carbon fiber reinforced plastic workpiece after the sandblasting step.

[0033] In the process of laminating a photosensitive resin layer onto a workpiece, the layers are laminated on the workpiece in the order of the photosensitive resin layer followed by the support, starting from the workpiece side.

[0034] Lamination methods include those in which a photosensitive resin layer is heated and pressed onto a workpiece using a laminator or the like.

[0035] The heating temperature of the photosensitive resin layer during the lamination process described above is preferably 70 to 130°C, and the bonding pressure is preferably 0.1 to 1.0 MPa, but there are no particular restrictions on these conditions. Furthermore, if the photosensitive resin layer is heated to 70 to 130°C as described above, it is not necessary to preheat the workpiece beforehand, but preheating the workpiece can be performed to further improve adhesion.

[0036] After forming a photosensitive resin layer on the workpiece in this manner, the attached photosensitive resin layer is exposed to light through a mask material to form photocured areas at predetermined locations. In this case, if the support present on the photosensitive resin layer is transparent, the active light can be irradiated directly; however, if it is opaque, it is preferable to remove the support before irradiating the photosensitive resin layer with the active light.

[0037] As the light source for exposure, known light sources that effectively emit ultraviolet light can be used, such as carbon arc lamps, mercury vapor arc lamps, ultra-high pressure mercury lamps, high-pressure mercury lamps, xenon lamps, etc. The amount and duration of ultraviolet irradiation can be appropriately set according to the photosensitive resin layer. Examples of exposure methods include contact exposure, in which the mask pattern is in close contact with the dry film and exposed, and non-contact exposure, in which the mask pattern is exposed using parallel light without being in close contact with the dry film.

[0038] If a support is present on the photosensitive resin layer after exposure, the support is removed, and then in the development process, the photosensitive resin layer other than the cured area is removed by wet development, dry development, etc., to form a resist pattern. In this invention, wet development is preferred because it is cost-effective.

[0039] In wet development, a developer solution such as an alkaline aqueous solution is used, and development is carried out by known methods such as spraying, agitation immersion, brushing, and scraping. The developer solution used should be safe, stable, and easy to handle, such as a dilute solution of sodium carbonate (0.2% by mass aqueous solution) at 20-50°C.

[0040] In the sandblasting process, the obtained resist pattern is used as a mask material, and an abrasive is blasted onto it to cut away the areas of the carbon fiber reinforced plastic workpiece where the resist pattern has not been formed. Various known abrasives (blasting materials) can be used for sandblasting, such as inorganic compounds like silica and glass; metallic compounds like steel, stainless steel, zinc, and copper; ceramics like garnet, zirconia, silicon carbide, alumina, and boron carbide; and particles mainly composed of dry ice, with an average particle size of about 2 to 100 μm.

[0041] After the workpiece is cut with an abrasive, a stripping step is performed to remove the resist pattern from the carbon fiber reinforced plastic workpiece using a stripping solution. Examples of stripping solutions used in the stripping step include aqueous solutions of alkali metal hydroxides such as sodium hydroxide, and basic compounds such as N-methyldiethanolamine, pyridine, and piperidine. Alternatively, instead of using a stripping solution, there are methods to directly remove the photosensitive resin layer using hands or adhesive tape, or to burn off the photosensitive resin layer at high temperatures. [Examples]

[0042] The present invention will be described in more detail by the following examples, but the present invention is not limited to these examples.

[0043] (Examples 1-4, Comparative Examples 1-3) A coating solution for the photosensitive resin layer was prepared by mixing the components shown in Table 1. The units for the amount of each component in Table 1 are parts by mass. The obtained coating solution was applied to a polyethylene terephthalate (PET) film (product name: R310, 25 μm thick, manufactured by Mitsubishi Chemical Corporation, support) using an applicator, dried at 80°C for 8 minutes to evaporate the solvent components, and a photosensitive resin layer (dry film thickness: 70 μm) was formed on one side of the PET film. A polyethylene film (product name: GF1, 30 μm thick, manufactured by Tamapoly Co., Ltd.) was then laminated on the photosensitive resin layer as a cover film to obtain DFRs for Examples 1-4 and Comparative Examples 1-3. In Comparative Example 1, the coating solution underwent phase separation and could not be mixed uniformly, so a DFR with good surface quality could not be obtained.

[0044] [Table 1]

[0045] In Table 1, the components are as follows: (A-1); Cellulose acetate phthalate (mass-average molecular weight 61000, acid value 200 mgKOH / g) (A-2); Hydroxypropyl methylcellulose phthalate (manufactured by Shin-Etsu Chemical Co., Ltd., mass-average molecular weight 45000, acid value 120 mgKOH / g) (B-1)2-(o-chlorophenyl)-4,5-diphenylimidazole dimer (B-2)4,4′-Bis(diethylamino)benzophenone (C-1) Shiko (registered trademark) UV-3000B (urethane acrylate manufactured by Mitsubishi Chemical Corporation) (C-2)DURA-167 (Carboxylate-containing urethane acrylate manufactured by Kyoeisha Chemical Co., Ltd.) (D-1); Copolymer resin obtained by copolymerizing methyl methacrylate / n-butyl acrylate / methacrylic acid in a mass ratio of 58 / 15 / 27 (mass-average molecular weight 30000)

[0046] Next, a sheet of dry carbon made of pitch-based carbon fiber, 3 mm thick and measuring 15 cm x 15 cm, was prepared as the carbon fiber reinforced plastic workpiece to be sandblasted. On one side of this dry carbon, the cover film of the DFR obtained in Examples 1-4 and Comparative Examples 2 and 3 was peeled off and the photosensitive resin layer surface was laminated using a laminator at a temperature of 100°C and a pressure of 0.2 MPa. Next, the DFR attached to the dry carbon was subjected to high-pressure mercury lamp (85 mJ / cm²) through a photomask having nine circular patterns with a diameter of 1 mm. 2 The samples were exposed to light. Next, the PET film of the DFR was peeled off and alkaline development was performed with a 0.2% sodium carbonate aqueous solution to remove the photosensitive resin layer in the unexposed areas. Subsequently, using 100-mesh silicon carbide, holes were drilled (sandblasted) on top of the resist pattern of the plate-shaped dry carbon of Examples 1-4 and Comparative Examples 2 and 3 at a cutting speed of 1 second / mm by sandblasting, creating 9 holes.

[0047] For the plate-shaped dry carbon samples of Examples 1-4 and Comparative Examples 2 and 3 after sandblasting, OPP adhesive tape (manufactured by Nitto Denko CS Systems Co., Ltd., product name "EA-3925") was applied, and an attempt was made to remove the resist pattern. As a result, the resist pattern could be removed in Examples 1-4, but in Comparative Examples 2 and 3, removal was extremely difficult, and the resist pattern fractured before it could be removed from the dry carbon, making it impossible to completely remove the resist pattern.

[0048] The present invention provides a method for processing a carbon fiber reinforced plastic workpiece by sandblasting, without leaving any residue on the workpiece.

Claims

1. A photosensitive resin layer containing (A) an alkali-soluble cellulose derivative, (B) a photopolymerization initiator, and (C) a urethane (meth)acrylate compound, and (D) substantially free of carboxyl group-containing acrylic resin, is laminated onto a carbon fiber reinforced plastic substrate by pressing it onto the substrate at a pressure of 0.1 to 1.0 MPa while heating it to a temperature of 70 to 130°C. The photosensitive resin layer is then exposed in an image-like manner, and the unexposed areas are removed with an alkaline developer to form a resist pattern on the substrate. The substrate is then sandwiched through the resist pattern. A stripping method for removing a resist pattern from a carbon fiber reinforced plastic workpiece that has been cut after treatment by a sandblasting method, wherein (B) the photopolymerization initiator is one or more compounds selected from the group consisting of aromatic ketones, quinones, benzoin ether compounds, benzoin compounds, alkylphenones, acyl phosphine oxides, oxime esters, 2,4,5-triarylimidazole dimers, N-phenylglycine, N-phenylglycine derivatives, coumarin compounds, and benzophenone compounds.

2. (B) The stripping method according to claim 1, wherein the photopolymerization initiator comprises a 2,4,5-triarylimidazole dimer.

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