JP2009166231A - Polishing material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polishing material excellent in workability (productivity), capable of attaining high-grade flatness and surface roughness, and ensuring less scratching in grinding and polishing work of glass, ceramics and metal. <P>SOLUTION: The polishing material includes particles comprising graphite-based carbon and diamond with 30-250 nm median size and 2.63-3.38 g/cm<SP>3</SP>gravity, or includes mixed particles comprising particles comprising graphite-based carbon and diamond with 30-250 nm median size and particles comprising nano-sized diamond with 30-250 nm median size wherein the average gravity of the mixed particles is 2.63-3.38 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a material with less scratching and excellent grinding and polishing characteristics. Specifically, in the processing of glass, ceramics, metals, etc., a grinding (lapping) process that adjusts the flatness and surface roughness of the work piece to finish it into a predetermined shape and size, and requires a ground work piece at the nanometer level. The present invention relates to a grinding / polishing material used in a process of polishing with high accuracy.

  Conventionally, for grinding (lap) of glass, ceramics, metal, etc., abrasive sand as loose abrasive grains, diamond tools as fixed abrasive grains, and for polishing (polishing), cerium oxide, colloidal silica, etc. as loose abrasive grains are used. A polishing pad is used as another processing form.

  In the precision instrument field, glass, ceramics and metals are used for various purposes. For example, crystallized glass, amorphous glass, aluminum, etc. are used as hard disk substrates, synthetic quartz glass, blue plate glass, etc. as photomask substrates, sapphire, gallium nitride (GaN), silicon carbide (SiC), zinc oxide (ZnO), etc. LED backlight used as a light emitting diode substrate (LED substrate) for signals, display boards, lighting, etc.Non-alkali glass is used as a flat panel on a liquid crystal television, blue plate glass, high strain point glass, etc. is used as a display glass substrate (PDP glass substrate) As a plasma television, mobile phone, game machine, personal computer, etc., crystal, PZT, barium titanate, lithium niobate, etc. as a vibrator, as a vibrator, as a communication device, mobile phone, watch, etc., optical glass, crown glass, flint glass, etc. Single lens reflex cameras, digital cameras, astronomical telescopes, and optical drive pick-up lenses These glasses, ceramics, and metals are precision processed by a lapping and polishing process using a double-sided machine.

  However, a grinding / polishing material excellent in workability is required from the viewpoint of improving productivity in response to a demand for cost reduction. In recent years, it has been recognized that the excellent hardness of diamond is excellent in workability and increases productivity. Fortunately, the diamond obtained by the explosion method has a nanometer size particle size of 4 to 7 nm for primary particles and 50 to 200 nm for secondary particles, and is excellent in workability and extremely productive. It is attracting attention as a material that can obtain a high-quality processed surface (high flatness and surface roughness) that is high in demand and has been increasingly required in recent years.

  However, when nanometer-sized diamond, which is hard, excellent in workability, and high in productivity, is used as a grinding / polishing material, it often occurs due to high flatness and surface roughness required in recent years. A wide and deep scratch called a so-called scratch was a problem. The cause is a minute amount of coarse particles having a size of micron which is extremely large compared to the nanometer size and remains in the nanosize diamond of nanometer size. The hardness, which is a characteristic of diamond, is adversely affected and the presence of a minute amount of micron-sized coarse diamond causes scratches. Although efforts have been made to remove these coarse particles, they cannot be completely removed at the industrial production level.

  Accordingly, an object of the present invention is a polishing material that is excellent in workability (productivity), can achieve high flatness and surface roughness, and has few scratches on scratches in glass, ceramics and metal grinding and polishing processes. Is to provide.

  As a result of earnest research in view of the above object, the present inventor has used nanometer-size particles composed of graphite-based carbon and diamond, or mixed particles obtained by adding nanosize diamond to the nanometer-size particles. The present inventors have found that the generation of scratches can be significantly reduced without degrading the workability of glass, ceramics, etc., the flatness and surface roughness of the processed surface, and have arrived at the present invention.

That is, the abrasive of the present invention is characterized by having particles having a median diameter of 30 to 250 nm and specific gravity of 2.63 to 3.38 g / cm ³ made of graphite-based carbon and diamond.

The specific gravity is preferably 2.75 to 3.25 g / cm ³ .

Another abrasive of the present invention has mixed particles composed of particles having a median diameter of 30 to 250 nm composed of graphite-based carbon and diamond, and particles having a median diameter of 30 to 250 nm composed of nano-sized diamond. The average specific gravity of the mixed particles is 2.63 to 3.38 g / cm ³ .

The average specific gravity is preferably 2.75 to 3.25 g / cm ³ .

  The abrasive of the present invention is preferably used for polishing glass, ceramics and aluminum.

  The abrasive having nanometer-sized particles composed of graphite-based carbon and diamond of the present invention, or mixed particles obtained by adding nanosized diamond to the nanometer-sized particles is a workability of glass, ceramics, metal, etc. Excellent hard surface with high flatness and surface roughness, and few scratches occur. Hard disk substrates such as crystallized glass, amorphous glass, and aluminum (with Ni-P thin film), synthetic quartz Glass, blue plate glass and other photomask substrates, non-alkali glass flat panels (liquid crystal televisions), light emitting diode substrates (LED substrates), blue plate glasses, high strain point glass and other display glass substrates (PDP glass substrates: plasma televisions, mobile phones) Used for grinding and polishing of telephones, game machines, personal computers and the like).

[1] abrasives
(1) Nanometer-sized particles composed of graphite-based carbon and diamond Nanometer-sized particles composed of graphite-based carbon and diamond (hereinafter also referred to as “graphite-diamond particles”) are produced by the explosion method. The These particles are considered to have a core / shell structure in which the surface of diamond is covered with graphite-based carbon, and the surface of graphite-based carbon has many hydrophilic functional groups such as -COOH, -OH, It has very good affinity with solvents having —OH groups such as water, alcohol, ethylene glycol, etc., and disperses quickly in these solvents. Of these, water dispersibility is the best.

  The graphite-diamond particles are preferably used as an aqueous dispersion having a concentration of about 0.001 to 0.1% by mass. While this aqueous dispersion is dripped onto a nonwoven fabric or the like in a lapping / polishing process using a double-sided machine, the surface of glass, ceramics, aluminum (with Ni-P thin film), etc., is precisely polished.

Graphite-diamond particles have good processability and the occurrence of scratches when the specific gravity is 2.63 to 3.38 g / cm ³ . The specific gravity of the graphite-diamond particles is preferably 2.75 to 3.25 g / cm ³ . When the specific gravity of diamond is 3.50 g / cm ³ and the specific gravity of graphite is 2.25 g / cm ³ and the ratio of diamond to graphite is calculated, the specific gravity of 2.63 g / cm ³ has a composition of 30% by volume of diamond and 70% by volume of graphite. Corresponding to particles, a specific gravity of 3.38 g / cm ³ corresponds to particles having a composition of 90% diamond by volume and 10% by volume graphite. Similarly, a specific gravity of 2.75 g / cm ³ corresponds to a particle having a composition of 40% by volume of diamond and 60% by volume of graphite, and a specific gravity of 3.25 g / cm ³ corresponds to a particle having a composition of 80% by volume of diamond and 20% by volume of graphite. The specific gravity of 2.87 g / cm ³ corresponds to particles having a composition of 50% by volume of diamond and 50% by volume of graphite. When the specific gravity is less than 2.63 g / cm ³ , scratches hardly occur, but the workability is inferior because the amount of diamond is small. On the other hand, when the specific gravity exceeds 3.38 g / cm ³ , the workability is very good, but many scratches are generated.

  The graphite-diamond particles have a good workability when the median diameter is 30 to 250 nm, and the generation of scratches can be suppressed.

(2) Nano-sized diamond Nano-sized diamond is obtained by further purifying the graphite-diamond particles to remove graphite, and has a specific gravity greater than 3.38 g / cm ³ . The specific gravity of the nano-sized diamond is preferably 3.45 g / cm ³ or less. The median diameter of the nano-sized diamond is preferably 30 to 250 nm, and more preferably 50 to 150 nm.

When nano-sized diamond is used alone, scratching becomes a problem. Therefore, graphite-diamond particles and nano-sized diamond particles are mixed and used so that the average specific gravity of the mixed particles is 2.63 to 3.38 g / cm ³ . The average specific gravity of the mixed particles is preferably 2.75 to 3.25 g / cm ³ . The amount of the nano-sized diamond particles used may be any amount as long as the average specific gravity of the mixed particles with the graphite-diamond particles is within the above range, but is 0 to 100% by volume with respect to the graphite-diamond particles. Is preferable, 0 to 50% by volume is more preferable, and 0 to 10% by volume is most preferable.

(3) Applications Abrasives containing graphite-diamond particles or mixed particles obtained by adding nano-sized diamond to graphite-diamond particles are preferably used for polishing glass, ceramics, metals, etc., especially crystallized glass, amorphous glass, Hard disk substrate such as aluminum (with Ni-P thin film), photomask substrate such as synthetic quartz glass and blue plate glass, non-alkali glass flat panel (liquid crystal television), light emitting diode substrate (LED substrate), blue plate glass, high strain point It is suitably used for polishing a display glass substrate (PDP glass substrate) such as glass.

[2] Manufacturing method Particles composed of graphite-based carbon and diamond (graphite-diamond particles) are obtained by purifying crude diamond (hereinafter also referred to as “blended diamond” or “BD”) synthesized by the explosion method. can get. Nano-sized diamond [hereinafter referred to as UDD (Ultra Dispersed Diamonds). ] Can be obtained by further purifying the rough diamond. As the explosion method, Science, Vol. 133, No. 3467 (1961), pp 1821-1822, JP-A No. 1-234311, JP-A No. 21-14414, Bull. Soc. Chim. Fr. Vol. 134 (1997) pp.875-890, Diamond and Related materials Vol. 9 (2000), pp 861-865, Chemical Physics Letters, 222 (1994) pp 343-346, Carbon, Vol. 33, No. 12 (1995), pp 1663-1671, Physics of the Solid State, Vol. 42, No. 8 (2000), PP1575-1578, Carbon Vol. 33, No. 12 (1995), pp1663-1671, K.Xu.Z.Jin, F. Wei and T Jiang, Energetic Materials, 1,19 (1993) (in Chinese), JP-A-63-303806, JP-A-56-26711, British Patent No. 1154633, JP-A-3-271109, JP-T-3-271109 -505694 (WO93 / 13016), Carbon, Vol. 22, No.2, 189-191 (1984), Van Thiei. M. & Rec., FH, J. Appl. Phys. 62, pp. 1761-1767 (1987), JP 7-505831 (WO94 / 18123), US Pat. No. 5,861,349, and the like. The specific gravity of the graphite-diamond particles can be adjusted by adjusting the explosion conditions and the purity of the BD.

(1) Control of the ratio of graphite to diamond by blasting conditions To convert carbon atoms from the graphite structure to the diamond structure, high temperature and high pressure conditions are required. Explosive bombardment easily generates the high pressure and high temperature conditions necessary to convert the carbon source placed in the reaction system into a diamond structure. In the diamond synthesis operation, when the applied pressure is released instantaneously, if the heat (temperature) remains, the generated diamond structure is returned to the graphite structure. The temperature at which the generated diamond structure in the reaction system returns to the graphite structure is, for example, typically about 2000 ° C. at normal pressure when the high pressure is released, so it is necessary to quickly cool below this temperature. .

Since the propagation speed of shock waves due to explosives is usually about 0.8 to 12 km / sec, the time during which the reaction system of normal thickness and size is maintained at high pressure is at most 10 ^-5 to 10 ^-6 sec. It is a short time, and the time during which the minimal reaction unit is maintained at a high pressure is only 10 ⁻⁸ to 10 ⁻⁹ sec. In order to maintain the generated diamond structure, it is necessary to instantly open the sealed state of the reaction system and rapidly cool to below the temperature (about 2000 ° C) at which the diamond structure is converted to the graphite structure. It is difficult to accurately control the temperature in a short time. Therefore, it is difficult to produce graphite-diamond particles in which the ratio of graphite carbon and diamond is appropriately changed at an industrial level by controlling only the explosion conditions.

  A technique for rapidly cooling the inside of the reaction vessel after the explosion and adjusting the amount of graphite is described in JP 7-505831 (WO94 / 18123). Special Table No. 7-505831 (WO94 / 18123) includes the explosion temperature when trinitrotoluene (TNT) / cyclotrimethylenetrinitroamine (RDX) = 60/40 is used as the explosive (3500 to 4000 K) When the product is cooled to 350 K at a rate of about 7000 degrees / min after explosion, the carbon phase contains 70-80% by mass of cubic phase (diamond), and the cooling rate is It is stated that if it is lower than 200 degrees / minute, the product reacts with carbon dioxide and water vapor to completely turn into CO. That is, the composition ratio of graphite and diamond in the blended diamond can be controlled by adjusting the cooling rate of the gas in the container after the reaction by explosion. The cooling rate can be adjusted using different outgassing conditions, changing the explosion volume and explosion chamber volume, and changing the amount of ice or water in the reaction vessel.

  Furthermore, as a method for controlling the ratio of graphite-based carbon to diamond in the graphite-diamond particles, the refined UDD (superdispersed diamond) of the final step obtained by the method described in Patent Publication 2003-146637 is partially used. There is a way to change to graphite. By heating at 700 to 1200 ° C. for 1 to 30 minutes under an inert gas such as nitrogen, in an oxygen atmosphere, or under vacuum, graphite-diamond particles with varying amounts of graphite covering the diamond surface can be obtained. .

  However, the methods described in JP 7-505831 (WO94 / 18123) and Patent Publication 2003-146637 are possible in principle, but it is difficult to ensure the stability of the quality at the industrial level. The production cost is also high. In the present invention, the amount of graphite can also be adjusted by these methods, but the method is not limited to these methods, and a method of adjusting the amount of graphite during BD purification after explosion synthesis described below is preferable.

(2) Control of the ratio of graphite and diamond by purification conditions BD obtained by the explosion method consists of UDD (superdispersed diamond) having a diameter of several tens to several hundreds of nanometers and non-graphite. It is an agglomerate in which diamond units with a nanometer size of nanometer size (diameter of nanometer size) are strongly aggregated. In other words, it is a strong agglomerate of at least four diamonds, usually a few dozen to a few hundred, and sometimes a few thousand nanometers. BD contains very small amounts of fine (less than 1.5 nm) amorphous diamond, graphite and non-graphitic carbon ultrafine particles.

  BD impurities include (i) water-soluble electrolytes (ionized), (ii) hydrolyzable groups and ionic substances (such as salts of functional surface groups) chemically bonded to the diamond surface, and (iii) water-insoluble substances. It can be divided into substances (impurities attached to the surface, insoluble salts, insoluble oxides), (iv) volatile substances, (v) substances contained or encapsulated in the diamond crystal lattice.

  The above (i) and (ii) are formed in the UDD purification process. Although the water-soluble electrolyte (i) can be removed by washing with water, it is preferably treated with an ion exchange resin for more effective removal. The water-insoluble impurities (iii) are composed of separated microparticles such as metals, metal oxides, metal carbides, metal salts (sulfates, silicates, carbonates), surface salts that cannot be separated, surface metal oxides, and the like. . To remove these, it is preferable to convert them to a soluble form with acid. The volatile impurities (iv) can be removed by heat treatment at 250 to 400 ° C. in a vacuum of usually about 0.01 Pa.

  The graphite-diamond particles used in the present invention do not necessarily need to completely remove impurities, but it is preferable to remove 40 to 95% of the impurities (i) to (iii). The ratio of graphite to diamond can be adjusted by changing the blasting conditions and / or changing the BD purification conditions.

  An example of the process for producing graphite-diamond particles is schematically shown in FIG. 1, but is not limited to these methods. The method for producing graphite-diamond particles in this example is (A) a step of producing an explosive initial BD by explosive explosives, (B) an electric detonator or the like by recovering the generated initial BD and oxidatively decomposing it. Oxidative decomposition process for decomposing contaminants such as mixed metals and carbon, (C) BD purified by oxidative decomposition process is oxidized by etching to remove hard carbon mainly covering the BD surface and graphite-diamond Oxidative etching treatment step to form particles, (D) Addition of basic material which is volatile or its decomposition reaction product is volatile to nitric acid aqueous solution containing graphite-diamond particles formed by oxidative etching treatment. Neutralizing reaction step to neutralize graphite-diamond aggregates as secondary aggregates into individual graphite-diamond particles as primary particles, (E) Grad formed through neutralization reaction step Phyto-gradient process in which the reaction suspension of diamond particles is fully decanted with water, (F) Graphite that has undergone the gradient process--Nitrate is added to the diamond particle suspension, washed, and left to stand- A washing step of extracting the lower layer suspension containing diamond particles from the upper layer drainage, (G) a step of centrifuging the washed graphite-diamond particle suspension, and (H) a centrifuged graphite-diamond particle dispersion. Is prepared to a desired pH and a desired concentration. The dispersion of graphite-diamond particles usually has a pH of 4.0 to 10.0, preferably 5.0 to 8.0, more preferably 6.0 to 7.5.

(A) Explosive type initial BD manufacturing process Explosive 5 equipped with an electric detonator 6 in a pressure vessel 2 made of pure titanium filled with water and a large amount of ice 1 [in this example TNT (trinitrotoluene) / HMX (cyclotetra (Methylenetetranitramine) = 50/50] is used. The steel pipe 4 with a single-sided plug that can be stored in the body is submerged horizontally, and the steel helmet 4 is covered with the steel pipe 4 to explode the explosive 5. The initial BD as a reaction product is recovered from the water and ice in the container 2.

(B) BD Oxidative Decomposition Process The recovered initial BD is oxidatively decomposed with 55 to 56 mass% concentrated HNO ₃ for 10 to 30 minutes in an autoclave 7 at 14 atm 150 to 180 ° C., for example. Decomposes impurities such as impurities, inorganic impurities and residual metals.

(C) Oxidative Etching Process The oxidative etching process removes hard carbon that covers the surface of the BD that has been subjected to the oxidative decomposition process as much as possible. 240 ℃). When treated for 10 to 30 minutes under such conditions, the hard carbon that coats the BD surface, that is, graphite, can be thoroughly removed. In the present invention, the purpose is not to thoroughly remove the graphite covering the surface of the BD, but to adjust the amount of residual graphite. Therefore, the processing conditions of temperature and pressure are relaxed. For example, graphite-diamond with a non-diamond carbon (graphite) amount adjusted as appropriate by slowing the rate of removal of hard carbon by oxidative etching under conditions of 13 atm, 120-150 ° C., 0.5-3 hours Particles can be made. The solution after the oxidative etching treatment is usually acidic at pH 2 to 6.95.

  The conditions for the BD oxidative decomposition treatment (14 atmospheres, 150 to 180 ° C., 10 to 30 minutes) and the conditions for the oxidative etching treatment (13 atmospheres, 120 to 150 ° C., 0.5 to 3 hours) are limited. Instead, it can be changed as appropriate. The conditions for the oxidative etching treatment may vary depending on the combination of temperature, pressure, and time, and are not particularly limited, but are preferably 12 to 18 atmospheres, 120 to 150 ° C., and 0.5 to 3 hours.

(D) Neutralization reaction step The neutralization reaction step is one of the characteristic operations not found in conventional methods. For example, 200-220 ° C., 20 atm under conditions of adding a basic substance which is volatile or its decomposition reaction product is volatile to an aqueous nitric acid solution containing graphite-diamond particles subjected to oxidative etching. so
Reflux for 10-30 minutes to neutralize. The pH of the liquid to be treated increases from 2 to 6.95 to 7.05 to 12 by adding the basic substance. In this neutralization reaction, cation (generally smaller in ionic radius than the anion) penetrates into the agglomerated graphite-diamond particles, attacking the nitric acid remaining in the particles, and intense neutralization with a small explosion Reaction, decomposition reaction, impurity elimination and dissolution reaction, gas generation reaction and surface functional group generation reaction occur, and as a result, the graphite-diamond aggregate is disassembled into individual graphite-diamond particles by the generation of gas and the increased temperature and pressure. This process seems to form a large specific surface area and pore adsorption space of graphite-diamond particles.

  Basic materials include ammonia, hydrazine, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethanolamine, propylamine, isopropylamine, dipropylamine, allylamine, aniline, N, N-dimethylaniline, diisopropylamine. And polyalkylene polyamines such as diethylenetriamine and tetraethylenepentamine, 2-ethylhexylamine, cyclohexylamine, piperidine, formamide, N, N-methylformamide, urea and the like. For example, when ammonia is used as a basic material, nitric acid and the following various gas generation reactions proceed.

HNO ₃ + NH ₃ → NH ₄ NO ₃ → N ₂ O + 2H ₂ ON ₂ O → N ₂ + (O) 3HNO ₃ + NH ₃ → NH ₄ NO ₂ + N ₂ O ₃ + H ₂ O + O ₂ + (O) NH ₄ NO ₂ → N ₂ + 2H ₂ ON ₂ O ₃ + NH ₃ → 2N ₂ + 3H ₂ ON ₂ O ₃ → N ₂ + O ₂ + (O) NH ₄ NO ₂ + 2NH ₃ → 2N ₂ + H ₂ O + 3H ₂ H ₂ + (O) → H ₂ O HCl + NaOH → Na ⁺ + Cl ⁻ + H ₂ O HCl + NH ₃ → NH ₄ ⁺ + Cl ⁻ NH ₄ ⁺ → NH ₃ + H ⁺ H ₂ SO ₄ + 2NH ₃ → N ₂ O + SO ₂ + NO ₂
Since the generated N ₂ , O ₂ , N ₂ O, H ₂ O, H ₂ , and SO ₂ gases are released out of the system, there is almost no influence on the system by the residue.

(E) Inclination Step Water is added to the reaction suspension of graphite-diamond particles produced through the neutralization reaction step, and decantation is repeated as many times as necessary (for example, three times or more).

(F) Washing step Nitric acid is added to the graphite-diamond particle suspension that has been subjected to the tilting step, stirred (for example, using a mechanical magnetic stirrer), washed and allowed to stand, and separated into an upper layer drainage solution and a lower layer suspension. The underlayer suspension containing graphite-diamond particles is withdrawn. For example, when 50 kg of water is added to 1 kg of graphite-diamond particle-containing liquid, the upper layer drainage and the lower layer suspension are not clearly separated into layers, but the volume of the lower layer suspension containing graphite-diamond particles is It is about 1/4 of the capacity of the upper layer drainage.

(G) Centrifugation step The graphite-diamond particle suspension recovered from the bottom of the tank is centrifuged by, for example, a 20,000 rpm ultracentrifuge. The graphite-diamond particle dispersion concentrated by centrifugation is optionally adjusted in (H) graphite-diamond particle dispersion preparation step or (J) graphite-diamond particle fine powder preparation step.

(H) Graphite-diamond particle dispersion preparation step A graphite-diamond particle dispersion concentrated by centrifugation is diluted with a solvent such as water to adjust the concentration.

(J) Graphite-diamond particle fine powder production step The graphite-diamond particle dispersion liquid concentrated by centrifugation is dried to produce graphite-diamond particle fine powder.

  The graphite-diamond particle dispersion is adjusted to pH 4-10, preferably pH 5-8, more preferably pH 6-7.5. Most of the graphite-diamond particles dispersed in the liquid are 2 to 250 nm in size (80% or more on the basis of number, 70% or more on the basis of weight in the range of 2 to 250 nm) and narrow. Distributed. The graphite-diamond particle concentration in the dispersion is 0.05-16%, preferably 0.1-12%, more preferably 1-10%.

  In FIG. 1, for convenience, for example, (B) the BD oxidative decomposition treatment process and (C) the oxidative etching treatment process are shown to be performed in different containers in different containers. May be performed in the same location and / or in the same container. The same applies to the (E) tilting step and the (F) cleaning step. A pressure vessel is used as the container.

[3] Particle Specific Gravity Measurement Method The true specific gravity of graphite-diamond particles or mixed particles of graphite-diamond particles and nanodiamond particles can be measured by the following procedure.
1. Put the sample in a specific gravity bottle and weigh it with the lid on to determine the weight.
2. Add distilled water to the top of the sample and remove bubbles completely by boiling.
3. Add distilled water at 25 ° C and place in a thermostatic bath (25 ° C) for 10 minutes to fill the baseline.
4. Take out the specific gravity bottle from the thermostatic chamber, wipe off the moisture on the outside well, weigh and weigh.
5. Wash the specific gravity bottle thoroughly, add only distilled water at 25 ° C, put it in a thermostatic chamber (25 ° C) for 10 minutes, fill up to the baseline, and measure the weight as in 4.
6. The true specific gravity ρ is obtained from the value obtained by the above operation by the following formula (1).

ρ = [(W−P) · dw] / [(W1−P) − (W2−P)] (1)
here,
W: specific gravity bottle + sample weight,
W1: Weight when specific gravity bottle is filled with distilled water only,
W2: Weight when the specific gravity bottle is filled with sample and distilled water and completely filled with air bubbles (excluding air),
P: weight of specific gravity bottle, and
dw: Specific gravity of water at the temperature at the time of measurement.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Examples 1-5 and Comparative Examples 1-2
Graphite-diamond particles were produced according to the production method shown in FIG. The explosion of (A) is generated by detonating 0.65 kg of explosives containing TNT (trinitrotoluene) and RDX (cyclotrimethylenetrinitroamine) in a ratio of 60/40 in a 3 m ³ explosion chamber. After forming an atmosphere for storing BD, a second explosion occurred under the same conditions to synthesize BD. After the explosion product expanded and reached thermal equilibrium, the gas mixture was allowed to flow out of the chamber for 35 seconds through a supersonic Laval nozzle with a 15 mm cross section. Due to the heat exchange with the chamber walls and the work done by the gas (adiabatic expansion, vaporization), the cooling rate of the mixture was 280 ° C./min. The specific gravity of the product (black powder, BD) captured by the cyclone was 2.55 g / cm ³ . This BD was estimated to be composed of 76% by volume of graphite-based carbon and 24% by volume of diamond, calculated from the specific gravity.

  This BD is mixed with a 60% by mass nitric acid aqueous solution, and after (B) oxidative decomposition treatment is performed at 160 ° C., 14 atm for 20 minutes, only the conditions for (C) oxidative etching treatment are shown. The following changes were made, and neutralization (210 ° C, 20 atm, reflux for 20 minutes), separation by tilting (E), washing (F) [washing with 35% by mass nitric acid], ( Similarly, the centrifugal separation of G) and the BD suspension preparation of (H) were prepared in the same manner to produce graphite-diamond particles having different specific gravities composed of graphite-based carbon and diamond. Comparative Example 2 is nano-sized diamond (UDD), and the other is graphite-diamond particles.

Examples 6-8
Mixed particles were prepared by mixing the graphite-diamond particles of Comparative Example 1 and the nano-sized diamond (UDD) of Comparative Example 2 in the ratios (volume ratios) shown in Table 2.

<Polishing test 1>
To a pure water dispersion containing 0.01% by mass of these graphite-diamond particles, 1% by mass of succinic acid as a processing accelerator was added to the particle weight, and the pH was adjusted to 5.5. Using this dispersion, a polishing test was conducted using a magnetic disk substrate that had been ground (lapped) as follows.

Polishing conditions
(a) Workpiece: φ2.5 inch crystallized glass disk
(b) Number of processed sheets: 15
(c) Polishing machine: Double-side polishing machine (plate diameter φ700 mm)
(d) Polishing pad: BELLATRIX N0048 (manufactured by Kanebo Corporation)
(e) Load: 100 g / cm ²
(f) Upper surface plate rotation speed: 24 rpm
(g) Lower platen rotation speed: 16 rpm
(h) Abrasive dispersion supply: 150 cc / min.
The processing time was the time when the machining allowance was 3 μm (both sides) when the dispersion of Comparative Example 2 was used in Examples 1 to 5 and Comparative Example 1. Specifically, the polishing rate was obtained in advance by the following method using the dispersion liquid of Comparative Example 2, and the polishing rate was set so that the machining allowance was constant (3 μm for both surfaces).

<Measurement of polishing rate>
After cleaning and drying the magnetic disk substrate after the polishing test, the weight of the magnetic disk substrate is measured before and after the polishing process, and the polishing rate is calculated based on the difference (weight reduction), the area of the magnetic disk substrate, and the processing time. Was measured.

<Measurement of scratch>
Measurement was performed using MicroMAX OSA6100, a micro defect visualization inspection device manufactured by Vision Cytec Co., Ltd.

  The workability was shown as a relative value with the amount of work taken as 1.00 when using the UDD (super-dispersed diamond, about 93% by volume of diamond and 7% by volume of graphite) of Comparative Example 2. As for the occurrence of scratches, the average value (number) of the number of scratches generated at the recording locations on both sides of the hard disk substrate and the average value (number) of one surface of a long scratch of 5 mm or more were evaluated. The results are shown in Tables 1 and 2.

注(1)：比較例2の分散液を用いたときの加工量を1.00とした相対値。
注(2)：ハードディスク基板の1面辺りに発生したスクラッチの平均値。
注(3)：ハードディスク基板の1面辺りに発生した５ mm以上のスクラッチの平均値。

Note (1): Relative value with 1.00 as the processing amount when using the dispersion of Comparative Example 2.
Note (2): Average value of scratches generated on one side of the hard disk substrate.
Note (3): The average value of scratches of 5 mm or more generated around one surface of the hard disk substrate.

注(1)：比較例2の分散液を用いたときの加工量を1.00とした相対値。
注(2)：ハードディスク基板の1面辺りに発生したスクラッチの平均値。
注(3)：ハードディスク基板の1面辺りに発生した５ mm以上のスクラッチの平均値。
注(4)：比較例1のグラファイト-ダイヤモンド粒子及び比較例2のナノサイズダイヤモンドの混合比

Note (1): Relative value with 1.00 as the processing amount when using the dispersion of Comparative Example 2.
Note (2): Average value of scratches generated on one side of the hard disk substrate.
Note (3): The average value of scratches of 5 mm or more generated around one surface of the hard disk substrate.
Note (4): Mixing ratio of graphite-diamond particles of Comparative Example 1 and nano-sized diamond of Comparative Example 2

  The results shown in Tables 1 and 2 are evaluated according to the following criteria and shown in Table 3. In addition, Table 3 shows the median diameter measured by HORIBA LB-500. The median diameter (d50) indicates a diameter in which the large side and the small side are equivalent when the powder is divided into two from a certain particle size. Here, the quality was regarded as important, and a reduction within 10% of the processing amount (evaluation of）) was regarded as an acceptable range.

Machinability ◎; Machining amount 0.90 or more and 1.00 or less ○; Machining amount 0.75 or more and less than 0.90 ×;

Scratch property ◎; Number of scratches is less than 50 ○; Number of scratches is 50 or more and less than 100 ×: Number of scratches is 100 or more

It can be seen that when the specific gravity of the graphite-diamond particles is 2.63 to 3.38 g / cm ³ , the workability is good and the generation of scratches is suppressed. The specific gravity of the graphite-diamond particles is preferably 2.75 to 3.25 g / cm ³ . When the specific gravity is less than 2.63 g / cm ³ , scratches are very small and very good, but the amount of diamond is small and the workability is poor. Further, it is understood that when the specific gravity exceeds 3.38 g / cm ³ , the workability is very good, but the generation of scratches is increased, which is not preferable. In addition, abrasives using mixed particles composed of graphite-diamond particles and nano-sized diamond particles also have an average specific gravity in the range of 2.63 to 3.38 g / cm ³ , similar to abrasives composed of graphite-diamond particles. It can be seen that the processability is good and the occurrence of scratches is suppressed.

Comparative Example 4
Example except that (C) oxidizing etching treatment conditions were 150 ° C., 13 atm, 1 hour treatment, and (D) neutralization conditions were 200 ° C., 20 atmospheres, 10 minutes reflux and gentler conditions than before. In the same manner as in 1-5 and Comparative Examples 1-2, a sample having a specific gravity of 2.85 g / cm ³ and a median diameter (d50) of 288 nm was obtained. A specific gravity of 2.85 g / cm ³ corresponds to graphite-diamond particles of 48% by volume of diamond and 52% by volume of graphite.

Comparative Example 3 and Examples 9-13
The sample of Comparative Example 4 was pulverized with a bead mill, and as shown in Table 4, samples of 21 nm, 30 nm, 51 nm, 107 nm, 153 nm, and 250 nm (Comparative Example 3 and Examples 9 to 13, respectively) Was made.

<Polishing test 2>
To the pure water dispersion containing 0.01% by mass of the graphite-diamond particles obtained in Examples 9 to 13 and Comparative Examples 2 to 4, 1% by mass of succinic acid as a processing accelerator is added to the particle weight, and the pH is adjusted. A 3.5-inch diameter 120 GB aluminum hard disk substrate with an aqueous solution adjusted to 3.5 (with an electroless Ni-P plating layer of 8 μm as the base hardened layer. Ni: P = 90: 10) A polishing test was conducted in the same manner as the polishing test 1 except that the supply amount of the polishing dispersion was changed to 300 cc / min.

  Since the area of the 3.5 inch hard disk substrate used in the polishing test 2 is equivalent to twice that of the 2.5 inch substrate used in the polishing test 1, the amount of polishing dispersion supplied is 300 cc / Polishing was performed at min. Further, the processing time was measured by using a 3.5-inch diameter aluminum hard disk substrate for 120 gigabytes when the machining allowance was 3 μm (both sides) when using the dispersion liquid of Comparative Example 2, and Examples 9 to 13 And it applied when the dispersion liquid of Comparative Examples 3-4 was used.

  The median diameter, processability, the number of scratches, and the number of scratches of 5 mm or more were evaluated in the same manner as in Example 1. The results are shown in Table 4.

注(1)：比較例2の分散液を用いたときの加工量を1.00とした相対値。
注(2)：ハードディスク基板の1面辺りに発生したスクラッチの平均値。
注(3)：ハードディスク基板の1面辺りに発生した５ mm以上のスクラッチの平均値。

Note (1): Relative value with 1.00 as the processing amount when using the dispersion of Comparative Example 2.
Note (2): Average value of scratches generated on one side of the hard disk substrate.
Note (3): The average value of scratches of 5 mm or more generated around one surface of the hard disk substrate.

  The results shown in Table 4 are evaluated according to the following criteria, and the median diameter is shown in Table 5. The workability is the same evaluation criteria as in Examples 1 to 5 and Comparative Examples 1 and 2, but the scratch property was doubled in the numerical range because the area of the substrate was doubled.

Machinability ◎; Machining amount 0.90 or more and 1.00 or less ○; Machining amount 0.75 or more and less than 0.90 ×;

Scratch property ◎; Number of scratches is less than 100 ○; Number of scratches is 100 or more and less than 200 ×: Number of scratches is 200 or more

  It was found that if the median diameter (d50) of the graphite-diamond particles is 30 to 250 nm, the workability is good and the generation of scratches is suppressed. The median diameter is preferably 50 to 150 nm. When the median diameter (d50) is less than 30 nm, the generation of scratches is extremely small and very good, but the processability is poor. In addition, it is understood that when the median diameter (d50) exceeds 250 nm, the workability is very good, but the generation of scratches is increased, which is not preferable.

It is a schematic diagram which shows an example of the manufacturing process of the graphite-diamond particle | grains used for the abrasive | polishing material of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ice + water 2 ... Pressure-resistant container 3 ... Helmet 4 ... Steel pipe 5 ... Explosive 6 ... Electric detonator 7 ... Autoclave

Claims (5)

An abrasive comprising particles having a median diameter of 30 to 250 nm and a specific gravity of 2.63 to 3.38 g / cm ^{3 made} of graphite carbon and diamond. The abrasive having nanometer-sized particles according to claim 1, wherein the specific gravity is 2.75 to 3.25 g / cm ³ . A particle having a median diameter of 30 to 250 nm composed of graphite-based carbon and diamond, and a mixed particle composed of particles having a median diameter of 30 to 250 nm composed of nano-sized diamond, and the average specific gravity of the mixed particles is 2.63 to Abrasive material, characterized in that it is 3.38 g / cm ³ . The abrasive having nanometer-sized particles according to claim 3, wherein the average specific gravity is 2.75 to 3.25 g / cm ³ . The abrasive | polishing material which has a nanometer-sized particle | grain in any one of Claims 1-4, It uses for grinding | polishing of glass, ceramics, and aluminum, The abrasive | polishing material characterized by the above-mentioned.

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