Electrical discharge machining oil composition

Abstract

There has been a need for an electrical discharge machining oil composition which is improved in terms of viscosity increase during electrical discharge machining and has improved cooling properties. Provided is an electrical discharge machining oil composition which contains a base oil (A) and a succinimide compound (B), wherein: the kinematic viscosity of the electrical discharge machining oil composition at 40°C is 1.00-5.00 mm2 / s; and the nitrogen atom content is 220-7,000 mass ppm on the basis of the total amount of the electrical discharge machining oil composition.

Description

Electric discharge machining oil composition

[0001] The present invention relates to an electrical discharge machining fluid composition, a method for processing brittle materials, and a method for manufacturing wafers.

[0002] As a method for cutting wafers from ingots of SiC and the like, slicing technology using wire discharge with an aqueous processing solution is known (for example, Patent Documents 1-2, Non-Patent Document 1).

[0003] Japanese Patent Publication No. 2010-179381, Japanese Patent Publication No. 2014-659

[0004] Study on discharge slicing of SiC and its performance improvement, Proceedings of the 2010 Spring Conference of the Japan Society for Precision Engineering

[0005] Generally, electrical discharge machining (EDM) using water-based machining fluid is considered to have a faster machining speed but lower machining accuracy than EDM using oil-based machining fluid. On the other hand, EDM using oil-based machining fluid has the problem of lower machining speed, although it offers superior machining accuracy. This can be due to the aggregation of machining debris, which increases the viscosity of the machining fluid, and consequently worsens the cooling performance of the machining fluid, making it difficult for the machining debris to be discharged from the gap between the electrode and the workpiece. Under these circumstances, there has been a need for an EDM fluid composition that improves the viscosity increase during EDM using oil-based machining and also improves the cooling performance.

[0006] As a result of diligent research, the present inventors have found that an electrical discharge machining (EDM) oil composition containing a base oil and a succinimide compound, with its kinematic viscosity at 40°C adjusted to a predetermined range, can solve the above problems, and have completed the present invention. That is, one aspect of the present invention is provided as follows: [1] An EDM oil composition comprising a base oil (A) and a succinimide compound (B), wherein the kinematic viscosity of the EDM oil composition at 40°C is 1.00 to 5.00 mm². ２[1] An electrical discharge machining oil composition having a nitrogen content of 220 to 7000 ppm by mass on a total basis of the electrical discharge machining oil composition. [2] The electrical discharge machining oil composition according to [1], which substantially contains no water. [3] The electrical discharge machining oil composition according to [1] or [2], wherein the base oil (A) content is 70% by mass or more on a total basis of the electrical discharge machining oil composition. [4] The electrical discharge machining oil composition according to any one of [1] to [3], wherein the base oil (A) comprises one or more selected from the group consisting of paraffinic oils, esteric oils, and mineral oils. [5] The electrical discharge machining oil composition according to any one of [1] to [4], wherein the succinimide compound (B) comprises one or more selected from the group consisting of succinic monoimide compounds (B1), succinic bisimide compounds (B2), and boron-modified products thereof (B3). [6] The electrical discharge machining oil composition according to any one of [1] to [5], wherein the characteristic temperature of the electrical discharge machining oil composition is 350°C or higher. [7] The electrical discharge machining oil composition according to any one of [1] to [6], wherein the volume resistivity of the electrical discharge machining oil composition is 50 TΩ·m or less. [8] The electrical discharge machining oil composition according to any one of [1] to [7], wherein the flash point of the electrical discharge machining oil composition is 70°C or higher. [9] The electrical discharge machining oil composition according to any one of [1] to [8], used for machining brittle materials.

[10] The electrical discharge machining oil composition according to [9], wherein the brittle material comprises a semiconductor material.

[11] The electrical discharge machining oil composition according to

[10] , wherein the semiconductor material comprises one or more selected from the group consisting of silicon carbide (SiC) and gallium nitride (GaN).

[12] The electrical discharge machining oil composition according to

[11] , wherein the semiconductor material is a single crystal.

[13] A method for processing a brittle material, comprising applying the electrical discharge machining oil composition described in any one of [1] to

[12] to a workpiece that is a brittle material.

[14] A method for manufacturing a wafer, comprising performing electrical discharge machining using the electrical discharge machining oil composition described in any one of [1] to

[12] .

[0007] A preferred embodiment of the present invention provides an electrical discharge machining fluid composition that can suppress viscosity increase during electrical discharge machining and improve cooling performance. Another preferred embodiment of the present invention, by combining these properties, can facilitate the discharge of machining chips and improve the machining speed in electrical discharge machining using an oil-based machining fluid.

[0008] The numerical ranges described herein can be any combination of upper and lower limits. For example, if the numerical range is described as "preferably 30 to 100, more preferably 40 to 80," the ranges of "30 to 80" and "40 to 100" are also included in the numerical range described herein. Similarly, if the numerical range is described as "preferably 30 or more, more preferably 40 or more, and also preferably 100 or less, more preferably 80 or less," the ranges of "30 to 80" and "40 to 100" are also included in the numerical range described herein. In addition, for example, if the numerical range described herein is described as "60 to 100," it means the range is "60 or more (60 or greater than 60), and 100 or less (100 or less than 100)." Furthermore, in the provisions for upper and lower limits described herein, the numerical range from the lower limit to the upper limit can be defined by appropriately selecting and combining the options from each set of choices. In addition, multiple combinations of the various requirements described as preferred embodiments described herein are possible.

[0009] [Composition of the electrical discharge machining oil composition] A lubricating oil composition according to one aspect of the present invention is an electrical discharge machining oil composition comprising a base oil (A) (hereinafter also referred to as "component (A)") and a succinimide compound (B) (hereinafter also referred to as "component (B)"), wherein the kinematic viscosity of the electrical discharge machining oil composition at 40°C is 1.00 to 5.00 mm². ２ / s, and the nitrogen atom content is 220 to 7000 mass ppm based on the total amount of the electric discharge machining oil composition. The electric discharge machining oil composition according to one aspect of the present invention contains a succinimide compound (B) together with the base oil (A), and since the nitrogen atom content as a composition is adjusted to a predetermined numerical range, it is possible to enhance the dispersibility of machining chips generated when discharging ingots such as SiC, and it is possible to suppress an increase in the viscosity of the electric discharge machining oil composition. By suppressing the increase in viscosity, the cooling property of the electric discharge machining oil composition can also be maintained. Further, the electric discharge machining oil composition according to one aspect of the present invention is designed to have a kinematic viscosity at 40 °C as low as 1.00 to 5.00 mm ２ / s, and has even better cooling properties. Therefore, the electric discharge machining oil composition according to one aspect of the present invention facilitates the discharge of machining chips, hardly generates short circuits or abnormal discharges, and can improve the machining speed.

[0010] From the viewpoint of improving the cooling property and making a machining oil composition from which machining chips are easily discharged, the kinematic viscosity at 40 °C of the electric discharge machining oil composition according to one aspect of the present invention is 5.00 mm ２ / s or less, 4.50 mm ２ / s or less, 4.00 mm ２ / s or less, 3.80 mm ２ / s or less, 3.70 mm ２ / s or less, 3.50 mm ２ / s or less, 3.20 mm ２ / s or less, 3.00 mm ２ / s or less, 2.70 mm ２ / s or less, 2.50 mm ２ / s or less, 2.40 mm ２ / s or less, 2.30 mm ２ / s or less, 2.20 mm ２ / s or less, 2.10 mm ２ / s or less, or 2.00 mm ２ / s or less is preferable, and also 1.97 mm ２ / s or less, 1.95 mm ２ / s or less, 1.92 mm ２ / s or less, or 1.90 mm ２It may be less than or equal to / s. Furthermore, the kinematic viscosity of the electrical discharge machining oil composition according to one embodiment of the present invention at 40°C is 1.00 mm from the viewpoint of improving the discharge of machining chips. ２ / s or more, 1.05mm ２ / s or more, 1.10mm ２ / s or more, 1.15mm ２ / s or more, or 1.20 mm ２ It is preferable to have a value of 1.25 mm or more. ２ / s or more, 1.30mm ２ / s or more, 1.35mm ２ / s or more, 1.40mm ２ / s or more, 1.45mm ２ / s or more, or 1.50 mm ２ It may be set to 1 / s or higher. In this specification, kinematic viscosity refers to the value measured in accordance with JIS K2283:2000.

[0011] The characteristic temperature of an electrical discharge machining fluid composition according to one aspect of the present invention, measured using an apparatus capable of performing tests according to JIS K2242 and the method described in the examples, is 350°C or higher and 700°C or lower. From the viewpoint of providing an electrical discharge machining fluid composition with improved cooling performance, the characteristic temperature is preferably 350°C or higher, 355°C or higher, 360°C or higher, 365°C or higher, 370°C or higher, 375°C or higher, 380°C or higher, 385°C or higher, 390°C or higher, or 395°C or higher. It may also be 400°C or higher, 420°C or higher, 440°C or higher, 460°C or higher, 480°C or higher, 500°C or higher, 520°C or higher, 540°C or higher, 560°C or higher, 580°C or higher, or 600°C or higher. It may also be 650°C or lower, or 600°C or lower.

[0012] The volume resistivity of an electrical discharge machining fluid composition according to one embodiment of the present invention at 50°C is 1.0 × 10⁻⁶ －１０ The volume resistivity is between TΩ·m and 50TΩ·m. From the viewpoint of providing an electrical discharge machining fluid composition that can improve the machining speed, the values ​​are 50TΩ·m or less, 40TΩ·m or less, 30TΩ·m or less, 20TΩ·m or less, 10TΩ·m or less, 1TΩ·m or less, and 1.0 × 10 －１ TΩ・m or less, 8.0×10 －２ TΩ・m or less, 5.0×10 －２TΩ・m or less, 1.0×10 －２ TΩ・m or less, 8.0×10 －３ TΩ・m or less, 6.0×10 －３ TΩ・m or less, 4.0×10 －３ TΩ・m or less, 2.0×10 －３ TΩ・m or less, 1.0×10 －３ TΩ・m or less, 8.0×10 －４ TΩ・m or less, 6.0×10 －４ TΩ・m or less, 4.0×10 －４ TΩ・m or less, 2.0×10 －４ TΩ・m or less, 1.0×10 －４ TΩ・m or less, 8.0×10 －５ TΩ・m or less, 6.0×10 －５ TΩ・m or less, 4.0×10 －５ TΩ・m or less, 2.0×10 －５ TΩ·m or less, or 1.0 × 10⁻⁶ －５ It is preferable that the coefficient be TΩ·m or less, and also 1.0 × 10 －１０ TΩ・m or more, 1.0×10 －９ TΩ・m or more, 1.0×10 －８ TΩ·m or greater, or 1.0 × 10⁻⁶ －７ It may be set to TΩ·m or higher. In this specification, volume resistivity refers to the value obtained from the current value after 1 minute has elapsed since applying a voltage of 250 V / mm at an oil temperature of 50°C, in accordance with JIS C2101.

[0013] The flash point of the electrical discharge machining fluid composition according to one embodiment of the present invention is 70°C or higher, from the viewpoint of providing an electrical discharge machining fluid composition with excellent chip evacuation properties. The flash point is preferably 70°C to 200°C, more preferably 70°C to 150°C, even more preferably 70°C to 100°C, and particularly preferably 70°C to 80°C. In this specification, the flash point refers to the value measured in accordance with JIS K2265-3.

[0014] An electrical discharge machining oil composition according to one aspect of the present invention may contain additives other than components (A) and (B). In an electrical discharge machining oil composition according to one aspect of the present invention, from the viewpoint of providing an electrical discharge machining oil composition that facilitates the discharge of machining chips and can further improve the machining speed, the total content of components (A) and (B) may be 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 93% by mass or more, 95% by mass or more, 97% by mass or more, 99% by mass or more, or 100% by mass, based on the total amount (100% by mass) of the electrical discharge machining oil composition, or it may be less than 100% by mass, 100% by mass or less, 99% by mass or less, or 98% by mass or less.

[0015] In one embodiment of the present invention, the electrical discharge machining oil composition preferably contains substantially no water from the viewpoint of further improving its insulating properties. Here, "substantially no water" means excluding electrical discharge machining oil compositions that intentionally contain water, and does not exclude embodiments in which trace amounts of water are inevitably added, but it is preferable that such water content be as low as possible. In one embodiment of the present invention, the specific water content in the embodiment that "substantially no water" is preferably less than 0.05% by mass, more preferably less than 0.03% by mass, even more preferably less than 0.01% by mass, and particularly preferably less than 0.001% by mass, based on the total amount (100% by mass) of the electrical discharge machining oil composition.

[0016] The details of each component contained in the electrical discharge machining fluid composition according to one embodiment of the present invention will be described below.

[0017] <Component (A): Base Oil> Component (A) used in one aspect of the present invention may be one or more selected from mineral oils and synthetic oils. Examples of mineral oils include atmospheric residues obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate base crude oil, and naphthenic crude oil; distillates obtained by vacuum distillation of these atmospheric residues; and refined oils obtained by subjecting the distillates to one or more refining treatments such as solvent delamination, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining. Examples of synthetic oils include normal paraffins; isoparaffins; α-olefins; poly-α-olefins such as α-olefin homopolymers or α-olefin copolymers (e.g., 8-14 carbon olefin copolymers such as ethylene-α-olefin copolymers); polyalkylene glycols; ester oils such as polyol esters and dibasic acid esters; ether oils such as polyphenyl ethers; alkylbenzenes; alkylnaphthalenes; and synthetic oils (GTL) obtained by isomerizing waxes produced from natural gas by the Fischer-Tropsch process, etc. (GTL waxes (Gas To Liquids Wax)).

[0018] Among these, from the viewpoint of providing an electrical discharge machining oil composition that facilitates the discharge of machining chips and improves the machining speed, component (A) used in one embodiment of the present invention is preferably one or more selected from paraffinic oils, esteric oils, and mineral oils, and more preferably one or more selected from isoparaffins, normal paraffins, polyol esters, dibasic acid esters, and mineral oils. Furthermore, from the viewpoint of providing an electrical discharge machining oil composition with low viscosity, a high flash point, and excellent safety, isoparaffins and normal paraffins having 10 to 30 carbon atoms are preferred.

[0019] The kinematic viscosity of component (A) used in one aspect of the present invention at 40°C is 0.90 mm, from the viewpoint of providing an electrical discharge machining fluid composition that improves cooling performance, facilitates the discharge of machining chips, and can improve machining speed. ２ / s or more, 1.00mm ２ / s or more, 1.10mm ２ / s or more, 1.20mm ２ / s or more, 1.22mm ２ / s or more, 1.25mm２ / s or more, 1.27mm ２ / s or more, 1.30mm ２ / s or more, 1.32mm ２ / s or more or 1.35 mm ２ It is preferable to have a value of 4.00 mm or more. ２ / s or less, 3.50mm ２ / s or less, 3.20mm ２ / s or less, 3.00mm ２ / s or less, 2.70mm ２ / s or less, 2.50mm ２ / s or less, 2.20mm ２ / s or less, 2.00mm ２ / s or less, 1.90mm ２ / s or less, 1.80mm ２ / s or less, 1.70mm ２ / s or less, or 1.60 mm ２ It is preferable to keep it below / s.

[0020] In an electrical discharge machining oil composition according to one aspect of the present invention, from the viewpoint of providing an electrical discharge machining oil composition with high machining accuracy, the content of component (A) is preferably 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 92% by mass or more, 94% by mass or more, 96% by mass or more, or 98% by mass or more, based on the total amount (100% by mass) of the electrical discharge machining oil composition, and is also preferably 100% by mass or less, 99.99% by mass or less, 99.95% by mass or less, 99.90% by mass or less, 99.80% by mass or less, 99.70% by mass or less, 99.60% by mass or less, or 99.50% by mass or less.

[0021] <Component (B): Succinimide compound> As the component (B) used in one embodiment of the present invention, succinimide compounds having an alkyl group or an alkenyl group can be mentioned. By blending the succinimide compound (B), the dispersibility of machining chips can be improved. As a result, an increase in the viscosity of the electrical discharge machining oil composition can be suppressed, and the cooling property of the electrical discharge machining oil composition can be maintained. Therefore, the discharge of machining chips becomes easy, and the machining speed can be improved. The component (B) used in one embodiment of the present invention is preferably at least one selected from the group consisting of a succinic monoimide compound (B1), a succinic bisimide compound (B2), and their boron-modified products (B3). More specifically, at least one selected from the group consisting of a succinic monoimide compound (b1) represented by the following general formula (b-1), a succinic bisimide compound (b2) represented by the following general formula (b-2), and their boron-modified products (b3) can be mentioned.

[0022]

[0023] In the general formula (b-1), R １ is an alkenyl group or an alkyl group, R ２ is an alkylene group having 1 to 6 carbon atoms, and m is an integer of 1 to 20. When m is 2 or more, the plurality of R ２ may be the same or different. In the general formula (b-2), R ３ and R ４ are each independently an alkenyl group or an alkyl group, R ５ and R ６ are alkylene groups having 1 to 6 carbon atoms, and n is an integer of 1 to 20. When n is 2 or more, the plurality of R ５ may be the same or different.

[0024] R １ 、R ３ and R ４The alkenyl group or alkyl group has a mass-average molecular weight of 500 or more, more preferably 700 or more, even more preferably 800 or more, and also preferably 3,000 or less, more preferably 2,000 or less, and even more preferably 1,500 or less. Using such an alkenyl group or alkyl group improves solubility in the base oil (A), resulting in better suppression of viscosity increase and improved cooling performance. １ , R ３ and R ４ Examples of alkenyl groups include polybutenyl groups, polyisobutenyl groups, and ethylene-propylene copolymers, while examples of alkyl groups include those obtained by hydrogenation of these groups. For polybutenyl groups, a mixture of 1-butene and isobutene or a polymer of high-purity isobutene is preferred. Among these, polybutenyl groups and polyisobutenyl groups are preferred as alkenyl groups, and examples of alkyl groups include those obtained by hydrogenation of polybutenyl groups and polyisobutenyl groups. Furthermore, component (B) used in one embodiment of the present invention is preferably one or more selected from the group consisting of alkenyl succinate monoimide compounds (B11), alkenyl succinate bisimide compounds (B21), and boron-modified products thereof (B31). Examples of alkenyl groups include those described above.

[0025] R ２ , R ５ and R ６ The alkylene group having 1 to 6 carbon atoms is preferably 2 or more carbon atoms, preferably 5 or fewer carbon atoms, more preferably 4 or fewer carbon atoms, and even more preferably 3 or fewer carbon atoms, from the viewpoint of improving solubility in the base oil (A), better suppression of viscosity increase, and improved cooling performance. Examples of alkylene groups include methylene groups, 1,1-ethylene groups, 1,2-ethylene groups, 1,3-propylene, 1,2-propylene, 2,2-propylene and other propylene groups, various butylene groups, various pentylene groups, and various hexylene groups.

[0026] m and n are each an integer from 1 to 20, and from the viewpoint of improving solubility in the base oil (A), suppressing viscosity increase more effectively, and improving cooling performance, a value of 2 or more is preferred, 3 or more is more preferred, 15 or less is preferred, 10 or less is more preferred, and 5 or less is even more preferred.

[0027] Furthermore, the boron-modified succinic acid monoimide compounds and succinic acid bisimide compounds described above can be obtained by reacting these succinic acid imide compounds with boron compounds such as boric acid, borate salts, and borate esters.

[0028] In one embodiment of the present invention, the content of succinimide compound (B) in terms of nitrogen atoms is such that, from the viewpoint of providing an electrical discharge machining oil composition that improves the dispersibility of machining chips, facilitates their discharge, and improves the machining speed, the total amount of the electrical discharge machining oil composition is 220 ppm or more, 250 ppm or more, 280 ppm or more, 300 ppm or more, 350 ppm or more, 400 ppm or more, 600 ppm or more, 800 ppm or more, 1000 ppm or more, 1400 ppm or more. It is preferable to have 2000 ppm by mass or more, and may also be 7000 ppm by mass or less, 6500 ppm by mass or less, 6000 ppm by mass or less, 5500 ppm by mass or less, 5000 ppm by mass or less, 4500 ppm by mass or less, 4000 ppm by mass or less, 3500 ppm by mass or less, 3000 ppm by mass or less, 2500 ppm by mass or less, 2000 ppm by mass or less, 1800 ppm by mass or less, 1600 ppm by mass or less, 1400 ppm by mass or less, 1200 ppm by mass or less, or 1000 ppm by mass or less. In this specification, the nitrogen atom content refers to the value measured in accordance with JIS K2609.

[0029] Furthermore, in an electrical discharge machining oil composition according to one aspect of the present invention, the nitrogen atom content is such that, from the viewpoint of providing an electrical discharge machining oil composition that improves the dispersibility of machining chips, facilitates their discharge, and improves the machining speed, the nitrogen atom content is 220 ppm or more by mass, 250 ppm or more by mass, 280 ppm or more by mass, 300 ppm or more by mass, 350 ppm or more by mass, 400 ppm or more by mass, 600 ppm or more by mass, 800 ppm or more by mass, 1000 ppm or more by mass, 1400 ppm or more by mass, or 2000 ppm or more by mass. It is preferable to have a quantity of ppm or more, and it may also be 7,000 ppm by mass or less, 6,500 ppm by mass or less, 6,000 ppm by mass or less, 5,500 ppm by mass or less, 5,000 ppm by mass or less, 4,500 ppm by mass or less, 4,000 ppm by mass or less, 3,500 ppm by mass or less, 3,000 ppm by mass or less, 2,500 ppm by mass or less, 2,000 ppm by mass or less, 1,800 ppm by mass or less, 1,600 ppm by mass or less, 1,400 ppm by mass or less, 1,200 ppm by mass or less, or 1,000 ppm by mass or less.

[0030] In an electrical discharge machining oil composition according to one aspect of the present invention, when succinimide compound (B) is a boron-modified product, the content in terms of boron atoms is such that, from the viewpoint of providing an electrical discharge machining oil composition that improves the dispersibility of machining chips, facilitates their discharge, and improves the machining speed, the total amount of the electrical discharge machining oil composition is 10 ppm or more, 30 ppm or more, 50 ppm or more, 70 ppm or more, 90 ppm or more, 100 ppm or more, 150 ppm or more, and 200 ppm. Preferably, the boron content is 250 ppm by mass or more, 300 ppm by mass or more, 350 ppm by mass or more, or 400 ppm by mass or more. It may also be 2000 ppm by mass or less, 1800 ppm by mass or less, 1600 ppm by mass or less, 1500 ppm by mass or less, 1200 ppm by mass or less, 1050 ppm by mass or less, 1000 ppm by mass or less, 800 ppm by mass or less, 600 ppm by mass or less, 500 ppm by mass or less, 450 ppm by mass or less, or 400 ppm by mass or less. In this specification, the boron atom content refers to the value measured in accordance with JPI-5S-38-03.

[0031] Furthermore, in an electrical discharge machining oil composition according to one aspect of the present invention, the content of boron atoms is such that, from the viewpoint of providing an electrical discharge machining oil composition that improves the dispersibility of machining chips, facilitates their discharge, and improves the machining speed, the total amount of the electrical discharge machining oil composition is 10 ppm or more, 30 ppm or more, 50 ppm or more, 70 ppm or more, 90 ppm or more, 100 ppm or more, 150 ppm or more, 200 ppm or more, and 250 ppm or more. Preferably, the concentration is 300 ppm by mass or more, 350 ppm by mass or more, or 400 ppm by mass or more, and may also be 2000 ppm by mass or less, 1800 ppm by mass or less, 1600 ppm by mass or less, 1500 ppm by mass or less, 1200 ppm by mass or less, 1050 ppm by mass or less, 1000 ppm by mass or less, 800 ppm by mass or less, 600 ppm by mass or less, 500 ppm by mass or less, 450 ppm by mass or less, or 400 ppm by mass or less.

[0032] Furthermore, in order to provide an electrical discharge machining oil composition according to one aspect of the present invention that can improve the dispersibility of machining chips, facilitate their discharge, and improve the machining speed, it is preferable that the ratio of boron atoms to nitrogen atoms (B / N) in component (B) is 0.1 or more, 0.2 or more, 0.3 or more, or 0.4 or more, and may also be 1.5 or less, 1.0 or less, 0.8 or less, or 0.6 or less.

[0033] <Other Additives> The electrical discharge machining oil composition according to one embodiment of the present invention may further contain other additives other than the above components (A) and (B), as necessary, as long as they do not impair the effects of the present invention. Examples of such other additives include thickeners, oil-soluble resins, rust inhibitors, defoamers, antioxidants, metal deactivators, and the like. These additives may be used individually or in combination of two or more.

[0034] Examples of thickeners used in one aspect of the present invention include polybutene, polyisobutylene, polyvinyl acetate, polyalkyl acrylate, ethylene-propylene copolymer, and polyalkylene glycol. In the electrical discharge machining oil composition of one aspect of the present invention, the content of the thickener may be 0.1% by mass or more, 0.5% by mass or more, or 1.0% by mass or more, based on the total amount (100% by mass) of the electrical discharge machining oil composition. Furthermore, the electrical discharge machining oil composition of one aspect of the present invention may have a limited content of the thickener from the viewpoint of improving the effect of suppressing viscosity increase. Specifically, the content of the thickener may be less than 5.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, less than 0.0001% by mass, or less than 0.00001% by mass, based on the total amount (100% by mass) of the electrical discharge machining oil composition.

[0035] Examples of oil-soluble resins used in one aspect of the present invention include polymers of dipentene, tetraterpenes, and polyterpenes, or hydrogenated versions thereof; cyclopentadiene-dicyclopentadiene copolymer petroleum resins or hydrogenated versions thereof; rosin esters; coumarone resins; coumarone-indene resins, etc. The number average molecular weight of the oil-soluble resin used in one aspect of the present invention may be 200 or more, 300 or more, 400 or more, or 500 or more, or 5000 or less, 4000 or less, 3000 or less, or 2000 or less. In the electrical discharge machining oil composition of one aspect of the present invention, the content of the oil-soluble resin may be 0.1% by mass or more, 0.5% by mass or more, or 1.0% by mass or more, or 5.0% by mass or less, 3.0% by mass or less, or 2.0% by mass or less, based on the total amount (100% by mass) of the electrical discharge machining oil composition.

[0036] On the other hand, the electric discharge machining oil composition of one embodiment of the present invention may substantially contain no terpene resin and petroleum resin having a number average molecular weight of 400 to 1200. "Substantially containing no terpene resin and petroleum resin having a number average molecular weight of 400 to 1200" means excluding an electric discharge machining oil composition obtained by intentionally blending the terpene resins and petroleum resins, and does not mean excluding even a mode in which a trace amount of terpene resin and petroleum resin is inevitably blended. However, it is preferable that the content of such terpene resin and petroleum resin is as small as possible. In the electric discharge machining oil composition of one embodiment of the present invention, the content of the terpene resin and petroleum resin in an embodiment substantially containing no terpene resin and petroleum resin is preferably less than 0.05% by mass, more preferably less than 0.03% by mass, still more preferably less than 0.01% by mass, and particularly preferably less than 0.001% by mass based on the total amount (100% by mass) of the electric discharge machining oil composition. Examples of the terpene resin include polymers of hemiterpenes, monoterpenes such as dipentene, sesquiterpenes, diterpenes, sesterterpenes, triterpenes, tetraterpenes, polyterpenes, or hydrogenated products and modified resins thereof. Examples of the petroleum resin include those made from C4-5 hydrocarbon fractions, C8- 10 hydrocarbon fractions of petroleum cracking distillates, those made from both, or modified resins thereof, cyclopentadiene-dicyclopentadiene copolymer-based petroleum resins, or hydrogenated products and modified resins thereof.

[0037] Examples of the rust inhibitor used in one embodiment of the present invention include alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic ester, polyhydric alcohol ester, and the like. In the electric discharge machining oil composition of one embodiment of the present invention, the content of the rust inhibitor may be 0.01% by mass or more, 0.05% by mass or more, or 0.10% by mass or more, and may be 5.0% by mass or less, 3.0% by mass or less, or 2.0% by mass or less based on the total amount (100% by mass) of the electric discharge machining oil composition.

[0038] Examples of defoaming agents used in one aspect of the present invention include silicone-based defoaming agents, fluorosilicone-based defoaming agents, fluoroalkyl ether-based defoaming agents, and polyacrylate-based defoaming agents. In the electrical discharge machining oil composition according to one aspect of the present invention, the content of the defoaming agent may be 0.001% by mass or more, 0.005% by mass or more, or 0.01% by mass or more, based on the total amount (100% by mass) of the electrical discharge machining oil composition, or it may be 3.0% by mass or less, 1.0% by mass or less, or 0.50% by mass or less.

[0039] Examples of antioxidants used in one aspect of the present invention include amine-based antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; phenol-based antioxidants such as 2,6-di-t-butylphenol, 4,4'-methylenebis(2,6-di-t-butylphenol), isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. In the electrical discharge machining oil composition according to one aspect of the present invention, the content of the antioxidant may be 0.01% by mass or more, 0.05% by mass or more, or 0.10% by mass or more, based on the total amount (100% by mass) of the electrical discharge machining oil composition, or it may be 7.0% by mass or less, 5.0% by mass or less, or 3.0% by mass or less.

[0040] Examples of metal deactivators used in one aspect of the present invention include benzotriazole, imidazoline, pyrimidine derivatives, thiadiazole, and the like. In the electrical discharge machining oil composition according to one aspect of the present invention, the content of the metal deactivator may be 0.01% by mass or more, 0.05% by mass or more, or 0.10% by mass or more, or 2.0% by mass or less, 1.0% by mass or less, or 0.50% by mass or less, based on the total amount (100% by mass) of the electrical discharge machining oil composition.

[0041] Furthermore, the electrical discharge machining oil composition according to one embodiment of the present invention may have a limited content of metal-based detergents or organic acid metal salts. Specifically, the content of these may be less than 5.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, less than 0.0001% by mass, or less than 0.00001% by mass, based on the total amount (100% by mass) of the electrical discharge machining oil composition. The content of metal atoms can be measured in accordance with JPI-5S-38-92. Examples of metal-based detergents or organic acid metal salts include metal sulfonates, metal salicylates, metal phenates, and organic acid zinc salts.

[0042] Furthermore, the electrical discharge machining oil composition according to one embodiment of the present invention may have a limited content of compounds containing molybdenum atoms. Specifically, the content of such compounds may be less than 5.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, less than 0.0001% by mass, or less than 0.00001% by mass, based on the total amount (100% by mass) of the electrical discharge machining oil composition. The content of molybdenum atoms can be measured in accordance with JPI-5S-38-03. Examples of compounds containing molybdenum atoms include molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybdic acid.

[0043] [Method for Manufacturing an Electrical Discharge Machining Oil Composition] The method for manufacturing an electrical discharge machining oil composition according to one embodiment of the present invention is not particularly limited, but it is preferable to have a step of blending component (A) with component (B) and, if necessary, other additives. The order in which each component is blended can be set as appropriate.

[0044] [Uses of the Electrical Discharge Machining Oil Composition] One embodiment of the present invention provides an electrical discharge machining oil composition that suppresses viscosity increase during machining and has excellent cooling properties, thereby facilitating the discharge of machining chips and improving the machining speed in electrical discharge machining. For this reason, one embodiment of the present invention provides an electrical discharge machining oil composition that can be suitably used for machining brittle materials (especially wire electrical discharge machining). The brittle material may be a semiconductor material, and more specifically, the semiconductor material may be one or more selected from the group consisting of silicon carbide (SiC) and gallium nitride (GaN). Furthermore, these semiconductor materials may be single crystals or polycrystalline, but single crystals are preferred.

[0045] Based on the characteristics described above, the following [1] and [2] can also be provided as embodiments of the present invention: [1] A method for processing a brittle material, wherein the electrical discharge machining oil composition of the above-described embodiment of the present invention is applied to a workpiece that is a brittle material. [2] A method for manufacturing a wafer, comprising performing electrical discharge machining using the electrical discharge machining oil composition of the above-described embodiment of the present invention.

[0046] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples. In the following examples, the methods for measuring and calculating the following physical properties are as follows: (1) Kinematic viscosity, viscosity index Measured and calculated in accordance with JIS K2283:2000. (2) Nitrogen atom content Measured in accordance with JIS K2609. (3) Boron atom content Measured in accordance with JPI-5S-38-03. (4) Flash point Measured in accordance with JIS K2265-3. (5) Volume resistivity Calculated in accordance with JIS C2101, by applying a voltage of 250 V / mm at an oil temperature of 50°C and taking the current value after 1 minute. (6) Cooling test Evaluated using an apparatus capable of measuring cooling performance in accordance with JIS K 2242. Specifically, the heat-treated object heated to 700°C was immersed in a sample solution at a liquid temperature of 40°C, and the time (seconds) it took for the temperature to cool from 700°C to 150°C without stirring was measured, and the cooling performance was evaluated based on the cooling time. (7) Evaluation test of viscosity change (thickening rate) Sample oils and carbon black (average particle size 24 nm) for each example and comparative example were weighed out so that the total amount of evaluation oil was 40 g. Then, ultrasonic waves were continuously irradiated for 5 minutes using an ultrasonic instrument (SFX250, manufactured by BRANSON) with an amplitude of %A = 20%. After that, the viscosity was evaluated at a rotational speed of 100 rpm using a B-type rotational viscometer (VISCOMETER TVB-10, manufactured by Toki Sangyo Co., Ltd.). Viscosity was measured for 5 minutes, and the average value of the viscosity at 1, 2, 3, 4, and 5 minutes was used. The liquid temperature during evaluation was within 23°C ± 2°C. Note that carbon black was added as a quasi-processed material.

[0047] Examples 1 to 20 and Comparative Examples 1 to 11: Various components shown in Tables 1 to 4 were added and mixed in the amounts shown in Tables 1 to 4 to prepare electrical discharge machining oil compositions. Details of each component used in the preparation of the electrical discharge machining oil compositions are as follows.

[0048] <Base oil (A)> - 40°C kinematic viscosity = 1.23mm ２ / s normal paraffin. <Succinimide compound (B)> Monoimide: In the above general formula (b-1), R １ is a polyisobutenyl group, R ２A succinic acid monoimide compound in which is an ethylene group and m is a mixture of 2 and 3 (N content = 4.0 mass%). • Bisimide: In the above general formula (b-2), R ３ is a polyisobutenyl group, R ４ is a polyisobutenyl group, R ５ is ethylene, R ６ ethylene, a succinic acid bisimide compound with n = 2 (N content = 2.3% by mass). Boron-modified product: a boron-modified alkenyl succinic acid monoimide compound (N content = 3.0% by mass, B content = 1.0% by mass). <Dispersant> Polybutene

[0049] The kinematic viscosity at 40°C, the nitrogen and boron atom content derived from succinimide compounds, the flash point, and the volume resistivity of the prepared electrical discharge machining fluid composition were measured. The cooling test and viscosity change evaluation test described above were also performed. These properties and test results are shown in Tables 1 to 4. In Table 4, "Not dispersed" indicates a significant decrease in viscosity during the 5-minute viscosity measurement, suggesting that aggregation and precipitation occurred during the measurement.

[0050]

[0051] From the results in Tables 1-4, the kinematic viscosity of the electrical discharge machining fluid composition containing a base oil (A) and a succinimide compound (B) at 40°C was 1.00 to 5.00 mm². ２ Examples 1 to 20, which have a viscosity of 0.5 / s and a nitrogen atom content of 220 to 7000 ppm by mass on a total basis of the electrical discharge machining oil composition, showed little change in viscosity even when 5% carbon black was dispersed, demonstrating high dispersibility and excellent cooling performance as expressed by characteristic temperature. On the other hand, Comparative Examples 1 to 11, which did not meet any of the above requirements, showed high viscosity increase and poor dispersibility when 1%, 3%, and / or 5% carbon black was dispersed, and Comparative Examples 1, 7, 8, 10, and 11 also showed poor cooling performance as expressed by characteristic temperature.

Claims

1. An electrical discharge machining oil composition comprising a base oil (A) and a succinimide compound (B), wherein the kinematic viscosity of the electrical discharge machining oil composition at 40°C is 1.00 to 5.00 mm². ２ An electrical discharge machining oil composition having a density of / s and a nitrogen atom content of 220 to 7000 ppm by mass on a total basis of the electrical discharge machining oil composition.

2. The electrical discharge machining oil composition according to claim 1, which substantially does not contain water.

3. The electrical discharge machining oil composition according to claim 1 or 2, wherein the content of base oil (A) is 70% by mass or more on a total basis of the electrical discharge machining oil composition.

4. The electrical discharge machining oil composition according to any one of claims 1 to 3, wherein the base oil (A) comprises one or more selected from the group consisting of paraffinic oils, esteric oils, and mineral oils.

5. The electrical discharge machining oil composition according to any one of claims 1 to 4, wherein the succinimide compound (B) comprises one or more selected from the group consisting of succinimide monoimide compounds (B1), succinimide bisimide compounds (B2), and boron-modified products thereof (B3).

6. The electrical discharge machining oil composition according to any one of claims 1 to 5, wherein the characteristic temperature of the electrical discharge machining oil composition is 350°C or higher.

7. The electrical discharge machining oil composition according to any one of claims 1 to 6, wherein the volume resistivity of the electrical discharge machining oil composition is 50 TΩ·m or less.

8. The electrical discharge machining oil composition according to any one of claims 1 to 7, wherein the flash point of the electrical discharge machining oil composition is 70°C or higher.

9. An electrical discharge machining fluid composition according to any one of claims 1 to 8, for use in machining brittle materials.

10. The electrical discharge machining fluid composition according to claim 9, wherein the brittle material includes a semiconductor material.

11. The electrical discharge machining oil composition according to claim 10, wherein the semiconductor material comprises one or more selected from the group consisting of silicon carbide (SiC) and gallium nitride (GaN).

12. The electrical discharge machining fluid composition according to claim 11, wherein the semiconductor material is a single crystal.

13. A method for machining a brittle material, comprising applying the electrical discharge machining fluid composition described in any one of claims 1 to 12 to a workpiece that is a brittle material.

14. A method for manufacturing a wafer, comprising performing electrical discharge machining using the electrical discharge machining oil composition described in any one of claims 1 to 12.

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