JP4621441B2 - Polishing tool and method for manufacturing polishing tool - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a polishing tool for finishing hard and brittle materials such as glass, ceramics, and silicon, and a method for manufacturing the polishing tool, and in particular, high processing without impairing excellent processing surface quality (mirror surface). It is an object of the present invention to provide a polishing tool that achieves efficiency and has a long service life and a method for manufacturing the polishing tool.

  Fixed grinding that can achieve excellent finish surface roughness equivalent to polishing finish using loose abrasive grains for final finishing process of parts made of various hard and brittle materials such as silicon wafers and glass discs Grain processing tools are being actively developed in various directions. In order to obtain a good surface roughness in abrasive processing, it is usually advantageous to use fine abrasive grains, and the same applies to fixed abrasive processing tools.

  However, for the purpose of obtaining an excellent machining surface such as a mirror surface, if a fixed abrasive processing tool using abrasive grains having a particle size of several μm or less is used, contact between the abrasive binder and the workpiece is likely to occur during processing. As a result, there was a sudden increase in machining resistance, loss of abrasive grains, etc., and in the worst case not only fell into a state where machining was possible, but clogging due to chips etc. was reduced and the machining efficiency was reduced. There is a problem that the mirror surface is scratched or scratched again.

  In order to solve these problems, there is a fixed abrasive processing tool that forms fine abrasive grains and uses agglomerated powder as abrasive grains. For example, Patent Document 1 and Patent Document 2 disclose an invention related to a polishing tool in which agglomerated granules are fixed on a base material with a binder resin. Further, Patent Document 3 focuses on the bonding state between fine primary particles, elucidates the relationship between the bonding force (cohesive force) between primary particles and the processing efficiency, and improves the processing efficiency. It is disclosed that the optimization of the bonding force between each other is effective.

  However, as described in Patent Document 3, there is a limit to improving the machining efficiency without impairing the quality of the machined surface. This is because if the binding force (cohesive force) between the primary particles is too weak, the aggregated granules (secondary particles) themselves are destroyed, the processing efficiency is extremely low, and the pre-processed surface of the workpiece can be completely removed. Can not. On the other hand, the higher the bond strength (cohesive force) between primary particles, the less the original characteristics of the agglomerated granules, the closer to normal large particle size single-grain abrasive grains, and the better the processing efficiency, but scratches, etc. It tends to occur and the quality of the machined surface is greatly degraded.

  Further, as can be seen from the characteristics of the abrasive grains described in Patent Documents 1 to 3, since the abrasive grains are inevitably worn with the progress of the polishing process, a decrease in processing efficiency with time is also a problem. sell.

  Furthermore, the inventions described in Patent Documents 1 to 3 all focus on a single type of abrasive grain, and consideration is given to the relationship between the abrasive grain material and its processing characteristics. Not.

On the other hand, as an invention using two or more kinds of abrasive grains, there are, for example, Patent Document 4 and Patent Document 5. According to the description of Patent Document 4, a grindstone provided with a coarse polishing layer and a fine polishing layer at the same time, and by roughing the coarse polishing layer in order in the cutting direction of the grindstone, rough machining and I am trying to achieve finishing at the same time. According to the description of Patent Document 5, a first abrasive grain that has a polishing layer on a base film and exists as fixed abrasive grains in the polishing layer, and a second abrasive grain that functions as a free abrasive grain during polishing. Have
JP 2000-190228 A Japanese Patent Laid-Open No. 2000-237962 JP 2003-105324 A JP 7-246564 A Japanese Patent Application Laid-Open No. 2002-239921

  However, the method described in Patent Document 4 is merely a mechanical removal action, and there is a limit to the quality of the processed surface to be obtained, and the disadvantages of the conventional fixed abrasive tools described above, for example, fine grinding It is impossible to solve defects such as clogging in grains.

  Moreover, according to the invention described in Patent Document 5, the first particles are 0.5 to 5 μm, and the second abrasive grains are 1 to 500 nm. It is very difficult to maintain the protruding amount, and contact between the abrasive grain binder (binder) and the workpiece is likely to occur during machining, resulting in a rapid increase in machining resistance and loss of abrasive grains. In the worst case, machining is impossible. There is a risk of falling into the state of. In addition, according to the invention described in Patent Document 5, since it is assumed to be the final finishing of a processed surface with little polishing margin, it is not a polishing tool with a lot of polishing margin and capable of processing for a long time.

  The present invention has been made in view of the above problems, and its object is to achieve higher polishing efficiency and longer life than conventional polishing tools without impairing the quality of the excellent processed surface of the nanometer order. It is another object of the present invention to provide a polishing tool and a method for manufacturing the polishing tool that can be realized at low cost and can be easily manufactured.

  As a result of performing various studies and analyzes to achieve the above object, the present inventors have found that there are two types of abrasives: a first abrasive having a chemical action and a second abrasive having a mechanical removal action. Focusing on the joint polishing characteristics of grains, depending on the workpiece, to achieve high processing efficiency while maintaining high processing surface quality, to maintain the processing efficiency for a long time, and to obtain the characteristics that can be processed for a long time Found that it is extremely effective to use the two types of abrasive grains in combination, that is, the first abrasive grains having a chemical action and the second abrasive grains having a mechanical removal action.

  In this case, when the glass is used as an example of the chemical action, a chemical reaction occurs between the abrasive grains, the polishing tool (polisher), the polishing liquid and the glass in the polishing step, and a hydrated layer is formed on the surface of the surface to be polished. It is generally said to occur. In addition, the mechanical removal action is explained by taking the function of a grindstone as an example. Abrasive grains cut into the surface of the surface to be polished as innumerable cutting blades and mechanically remove the surface of the surface to be polished. Point to.

Here, in the polishing layer containing the abrasive grains and the binder on the base material, the first polishing layer containing the first abrasive grains and the protruding portions of the second abrasive grains and the first binder. If there a second two of the polishing layer formed by incorporating a second abrasive grains and a second binder, and the second polishing layer and the second abrasive grains protrude from the second binder, and the The two abrasive grains are disposed on the substrate with a gap between them , and the first polishing layer is disposed at least in the gap between the second abrasive grains on the upper side of the second binder to perform the first polishing. When the surface to be polished is polished, the first binder is gradually dissolved in the polishing liquid by adding a polishing liquid or the like, so that the first abrasive grains are gradually supplied to the surface to be polished. Simultaneously supplying a first abrasive grain having a chemical action and a second abrasive grain having a mechanical removal action to the polishing surface The mechanical action and the chemical action are realized at the same time during polishing, and the machining efficiency can be further improved without losing the quality of the high surface finish. Could be realized.

  Further, by supplying the first abrasive grains having a chemical action and the second abrasive grains having a mechanical removal action to the surface to be polished, the first abrasive grains are chemically bonded to the surface of the object to be polished. When an action is generated to form a soft chemical reaction layer and water is used as a polishing liquid, a soft hydration layer can be formed and mechanically removed by the second abrasive grains. That is, by supplying the first abrasive grains having a chemical action and the second abrasive grains having a mechanical removal action to the surface to be polished at the same time, the chemical reaction layer or the water is obtained by the action of the chemical action and the mechanical action. The generation and removal of the sum layer is repeated, and it is extremely effective in achieving further improvement in machining efficiency without sacrificing the high machined surface quality, which has been difficult in the past. As a result, the life of the polishing tool can be extended.

That is, the polishing tool according to claim 1 is a polishing tool having two polishing layers each containing different abrasive grains and a binder on a base material, wherein the second abrasive grains and the second abrasive grains are included. In the second polishing layer containing a binder, the second abrasive grains protrude from the second binder, and the second abrasive grains are disposed on the base material with a gap provided between them. a first polishing layer formed by incorporating first abrasive grains and a first binder may be disposed on the second abrasive gap between an upper side of at least the second binder, the first The abrasive grains have an average particle diameter of 0.01 μm to 1 μm made of cerium oxide (CeO ₂ ) or silicon dioxide (SiO ₂ ), and the first binder includes glue adhesive, agar, polyvinyl One or a mixture of two or more selected from alcohol resins. It dissolves by supplying a polishing liquid and releases the first abrasive grains to the surface to be polished. The second abrasive grains are particles of zirconium oxide (ZrO ₂ ) without containing a binder. It is characterized in that the average particle diameter made of a material formed by agglomerating is in the range of 20 μm to 200 μm and the compressive fracture strength is in the range of 20 MPa to 160 MPa.

The polishing tool according to claim 2 is the polishing tool according to claim 1, wherein the second abrasive grains are formed by agglomerating the particles without containing a binder, and a bonding point between the particles. It is a porous body formed by heat treatment at a temperature at which a neck is formed .

The polishing tool according to claim 3 is the polishing tool according to claim 1 or 2 , wherein the second abrasive grains protruding from the second binder are present in the first polishing layer. Features.

The polishing tool according to claim 4 is the polishing tool according to any one of claims 1 to 3, wherein the first abrasive grains are 10% by volume to 90% by volume with respect to the entire first polishing layer. In addition, the second abrasive grain is 50% by volume or less based on the entire second polishing layer .

The polishing tool according to claim 5 is the polishing tool according to any one of claims 1 to 4, wherein the thickness of the first polishing layer containing the first abrasive grains is at least the second polishing. The second abrasive grains in the layer have a thickness protruding from the second binder .

The polishing tool according to claim 6 is the polishing tool according to claim 2 , wherein the temperature at which the neck is formed is in the range of 600 degrees to 1600 degrees .

The polishing tool according to claim 7 is the polishing tool according to claim 1 , wherein the surface to be polished is a substrate of a brittle material such as glass, ceramics, silicon, silicon oxide film, a wafer, or an end face of an optical fiber. It is characterized by.

The polishing tool according to claim 8 is a porous body in which particles are aggregated without containing a binder to form an aggregate, and the aggregate is heated to form a neck at a bonding point between the particles. A step of generating a second abrasive grain, a step of applying a second coating liquid containing the second abrasive grain and a second binder on the substrate, and the application A step of drying the second coating liquid to form a second polishing layer; and a first coating liquid containing first abrasive grains and a first binder on the second polishing layer. It is manufactured by a manufacturing method including a step of applying, and a step of drying the applied first coating solution to form a first polishing layer.

  According to the polishing tool of the present invention, it is possible to supply abrasive grains having different functions to the surface to be polished, and achieve both high processing surface quality and high processing efficiency, which are difficult for conventional fixed abrasive processing tools. It is possible to improve the machining efficiency while maintaining high quality.

  In the polishing tool of the present invention, the first abrasive grains have a function of generating a chemical reaction layer or a hydration layer on the surface to be polished, and the second abrasive grains remove the chemical reaction layer or the hydration layer. Therefore, when polishing the surface to be polished, a chemically reactive layer or a hydrated layer is generated on the surface to be polished, and the generated chemically reactive layer or hydrated layer protrudes from the second polishing layer. Since it is mechanically removed by the second abrasive grains, the chemical action and the mechanical removal action are simultaneously applied to the surface to be polished, and the surface of the object to be polished can be processed in a balanced and uniform manner. The processing efficiency can be improved without impairing the quality of the surface.

  In the polishing tool of the present invention, when the polishing process is performed on the surface to be polished, when the first abrasive grains are supplied to the surface to be polished, the first binder moves along with the progress of the polishing process. By gradually dissolving in the polishing liquid or lubricating liquid, the first abrasive grains are supplied to the surface to be polished, and the chemical action can be surely applied to the workpiece during the polishing process, which is linked to the mechanical removal action. In addition, since the chemical action can be reliably performed, the surface of the object to be polished can be processed more uniformly.

In the polishing tool of the present invention, the first abrasive grains are CeO ₂ and / or SiO ₂ having a strong chemical action, and the second abrasive grains are ZrO ₂ having a strong mechanical removing action and contain a binder. In the case of a porous body formed by heat-treating an aggregate formed by agglomerating particles at a temperature at which a neck is formed at the bonding point between the particles, the second abrasive Since the grains gradually wear out, always supply two types of abrasive grains, the first abrasive grains with strong chemical action and the second abrasive grains with strong mechanical removal action, to the surface to be polished. Can do.

In the polishing tool of the present invention, when the second abrasive grains are present on the surface of the first polishing layer, for example, the maximum thickness of the first polishing layer containing the first abrasive grains is The second abrasive is not only capable of supplying the first abrasive grains having a strong chemical action to the surface to be polished, but also having a mechanical removal action, which is substantially equal to the protruding amount of the second abrasive grains in the second polishing layer. to become the particle also can be more reliably supplied, well-balanced surface to be polished at the same time can be uniformly polished without compromising the quality of the polished surface, it is possible to further improve the processing efficiency.

  In the polishing tool of the present invention, when the average particle diameter of the first abrasive grains is 0.01 to 1 μm and the particle diameter of the second abrasive grains is 20 μm to 300 μm, in the second polishing layer, The protrusion amount of the second abrasive grains can be reliably ensured, and the first polishing layer containing the first abrasive grains can be reliably disposed between the second abrasive grains.

  In the polishing tool of the present invention, when the content rate of the second abrasive grains is 50% by volume or less, a gap can be surely provided between the second abrasive grains, and the first A first polishing layer containing abrasive grains can be disposed. Moreover, when the content rate of a 1st abrasive grain is 10 volume% or more and 90 volume% or less, a 1st abrasive grain can be reliably supplied to a to-be-polished surface.

  According to the method for manufacturing an abrasive tool of the present invention, it is possible to reliably realize both high processing surface quality and high processing efficiency, and to manufacture an extremely inexpensive abrasive tool.

  The polishing tool of the present invention will be described with reference to FIG. The polishing tool 1 has a polishing layer 10 containing abrasive grains and a binder on a base material 15, and the polishing layer 10 is disposed on the surface to be polished, and includes first and second abrasive grains 11 and 2. The first polishing layer containing the abrasive grains 12 and the first binder 13, and the second polishing disposed on the substrate side and containing the second abrasive grains 12 and the second binder 14. Consists of layers.

  The second abrasive grains 12 are formed by agglomerating particles without containing a binder, and have a compressive fracture strength of 20 MPa to 160 MPa.

The particles formed by aggregating particles without containing the binder may be aggregates formed by aggregating the particles without containing the binder, and the aggregates are the bonding points between the particles. It may be a porous body formed by heat treatment at a temperature at which a neck is formed. For example, when ultrafine ZrO ₂ powder composed of 50 to 60 nm is made muddy with water and sprayed with a spray dryer, a size of 1 μm to 300 μm is generally obtained. If the particle size distribution is not sharp, a classification process may be added.

  The compressive fracture strength of the second abrasive grain 12 needs to be in the range of 20 MPa to 160 MPa. When the compressive fracture strength of the second abrasive grain 12 is smaller than 20 MPa, the second abrasive grain is This is because the undesired polished surface before being polished cannot be completely removed because it is crushed during the polishing process. Conversely, when the compressive fracture strength is greater than 160 MPa, the mechanical removal action is strong. This is because the wear of the abrasive grains does not proceed too much, and damage such as new scratches is brought about by the polishing process. Moreover, it is because the 2nd abrasive grain into which the compressive fracture strength falls within the range of 20 MPa to 160 MPa gradually wears so that the first binder 13 is dissolved in the polishing liquid as the polishing process proceeds.

  It is preferable that the polishing tool 1 supplies the first abrasive grains 11 to the surface to be polished when the surface to be polished is polished. This is because the chemical action can be effectively exerted on the surface to be polished.

  The first binder 13 is dissolved in the polishing liquid during the polishing process to release the first abrasive grains having a strong chemical action. The first binder 13 is preferably one or a mixture of two or more selected from glue adhesive, agar, and polyvinyl alcohol resin. The glue is in a solution state (sol) when heated, and becomes a jelly state (gel) when cooled. It has been used as an adhesive for a long time, and is mainly a protein collagen hydrolyzate. This is preferable because it has the property of being dissolved again in water, and it is preferable to use agar or low-polymerization polyvinyl alcohol in addition to glue adhesive, after drying and solidifying, This is because the effect of dissolving in water is obtained, which is preferable.

The first abrasive grains 11 depend on the object to be polished, but may be metal oxides that have been used for a long time. For example, Al ₂ O ₃ , CeO ₂ , ZrO ₂ , SiO ₂ , Fe ₂ O ₃ , TiO ₂ , MnO and the like can be mentioned.

The first abrasive grains 11 are preferably cerium oxide (CeO ₂ ) or silicon dioxide (SiO ₂ ). This is because cerium oxide (CeO ₂ ) is preferred because it is known to have the highest chemical action on glassy workpieces such as glass, quartz, and silicon oxide films. Silicon dioxide (SiO ₂ ) Is preferable because it has a strong mechanical chemical action against silicon.

  The average grain size of the first abrasive grains 11 is preferably 0.01 to 1 μm from the viewpoint that the effect of adding the first abrasive grains is sufficiently exhibited.

  It is preferable that the 1st abrasive grain 11 is 10 volume% thru | or 90 volume% with respect to the whole 1st polishing layer. If the content rate of the 1st abrasive grain 11 is 10 volume% or more and 90 volume% or less, while the 1st abrasive grain can be reliably supplied to a to-be-polished surface, content of the 1st abrasive grain 11 is included. If the rate is less than 10% by volume, the effect of adding the first abrasive grains may not be sufficiently obtained, which is not preferable. Conversely, if the rate exceeds 90% by volume, the polishing tool 1 This is because the amount of the binder is too small, the abrasive grain holding strength is remarkably lowered, and the first polishing layer is lost all at once, and there is a possibility that the characteristic of gradually dissolving cannot be maintained.

  The second abrasive grains 12 are preferably present on the surface of the first polishing layer. Not only can the first abrasive grains 11 with a strong chemical action be supplied to the surface to be polished, but also the second abrasive grains 12 with a strong mechanical removal action can be supplied, so that the surface of the surface to be polished is balanced and processed uniformly. This is because it is possible to improve the processing efficiency without impairing the quality of the polished surface and at the same time. In this case, it is more preferable that the maximum thickness of the first polishing layer containing the first abrasive grains 11 is substantially equal to the protruding amount of the second abrasive grains 12 in the second polishing layer.

  The second abrasive grain 12 depends on the object to be polished, but is not particularly limited as long as it is a hard inorganic material. Examples thereof include silica, diamond, CBN, alumina, silicon carbide, zirconium oxide, and the like. A fine powder of primary particles having an average particle size of 5 μm or less is aggregated to have an average particle size of about 10 to 300 μm, more preferably a secondary particle size of about 20 to 200 μm. Agglomerates of fine powder can be produced by means such as a sol-gel method or a spray dryer.

  Since the second abrasive grain 12 has an action of removing the chemical reaction layer or the hydrated layer, the generated chemical reaction layer or hydrated layer is more than the second abrasive grain 12 protruding from the second polishing layer. When mechanically removed, not only chips are discharged smoothly, but also scratches due to clogging are suppressed, and generation and removal of the chemical reaction layer or hydrated layer are repeated, the first binder 13 As a result, the first abrasive grains 11 are continuously supplied to the surface to be polished, and high processing efficiency can be maintained for a long time.

  The second abrasive grain 12 is a porous body formed by heat-treating an aggregate formed by aggregating particles without containing a binder at a temperature at which a neck is formed at a bonding point between the particles. Is preferred. The porous body formed by heat treatment is suitable for strength because the binding force between the particles of the aggregate formed by aggregating particles with a spray dryer without containing a binder may be too weak. Because it becomes.

  Although the primary particles grow by heat treatment, the primary particles grow not only by the mass transfer of the constituent substances, but also the bonding sites between the particles become thicker due to the mass transfer of the constituent substances of the particles, and there are no discontinuities. It has a gentle curved surface and a so-called “neck” shape constricted in a one-leaf hyperboloid shape (a drum shape). Regarding the growth of primary particles and the formation of “neck” by mass transfer during the heat treatment, for example, “Ceramic Materials Technology Collection” issued by the Industrial Technology Center Co., Ltd. It is described in detail in “2.3 Mechanism of Mass Transfer and Model of Sintering”. The firing may be performed in a pressurized state in order to shorten the firing time or to further increase the hardness. The firing temperature range is preferably 600 to 1600 ° C.

The second abrasive grains 12 are preferably zirconium oxide (ZrO ₂ ). This is because zirconium oxide has long been adopted as one of abrasive grains for glass polishing. From the results of various experiments, it is considered that zirconium oxide is most effective in the present invention.

  The particle size of the second abrasive grains 12 is preferably 20 μm to 300 μm. Combined with the average grain size of the first abrasive grains 11 being 0.01 to 1 μm, in the second polishing layer, the protruding amount of the second abrasive grains 12 can be reliably ensured. This is because the first polishing layer containing the first abrasive grains 11 can be reliably disposed between the abrasive grains 12.

  It is preferable that the 2nd abrasive grain 12 is 50 volume% or less with respect to the whole 2nd polishing layer. This is because it is preferable because a gap can be provided between the second abrasive grains 12 with certainty and the first polishing layer containing the first abrasive grains 11 can be reliably arranged.

  The second binder 14 is not particularly limited as long as the second abrasive grains 12 can be fixed, and examples thereof include a urethane resin added with an organic solvent. Can do.

  In the manufacturing method of the polishing tool of the present invention, the second coating liquid containing the second abrasive grains 12 and the second binder 14 is applied on the base material 15, and then dried. A polishing layer is formed, and then a first coating liquid containing the first abrasive grains 11 and the first binder 13 is applied on the second polishing layer, and then dried to obtain the first A polishing layer is formed. As for the coating method of the coating solution, a gravure coater, a reverse roll coater, a knife coater, etc. can be used in addition to the wire bar coater.

  The surface to be polished of the polishing tool 1 of the present invention is preferably a substrate of a hard and brittle material such as glass, ceramics, silicon, or silicon oxide film, a wafer, or an end face of an optical fiber.

  Hereinafter, the present invention will be supplemented by examples.

Example 1
Ultrafine ZrO ₂ powder (ultrafine particles) consisting of ₅₀ to 60 nm was made muddy with water and sprayed with a spray dryer to obtain secondary particles (granules) having an average particle diameter D ₅₀ of 60 μm. The average particle diameter was measured by a dry method using a laser diffraction / scattering particle size distribution measuring apparatus LA-920 manufactured by Horiba. As the average particle size, the particle size at a frequency integration of 50% was used (usually also referred to as median diameter).

The ZrO ₂ granules of the secondary particles were placed in an electric furnace and fired by a conventional method. By this firing step, a granular porous body was obtained in which necks were formed at the bonding points between the primary particles, and the primary particles were bonded partially and with voids formed.

  In order to evaluate the bonding strength in the granular porous body obtained by firing, the granular porous body was picked up and subjected to a compression fracture test. The compressive fracture strength test was performed using a micro compression tester MCTM500PC manufactured by Shimadzu Corporation based on a report by Hiramatsu, Oka and Kiyama (Journal of the Japan Mining Association, 81, 1024 (1965)). As test conditions, the test load is set to 10 to 1000 mN, the load speed is set to 0.446 mN / sec, and the first abrasive grains having a strong mechanical removal action to be measured are compressed using a flat indenter, and the abrasive grains are compressed. The strength when destroyed was measured. In this way, those having a compressive fracture strength of 67 MPa were employed as the second abrasive grains having a strong mechanical removal action.

ZrO ₂ with a compressive fracture strength of 67 MPa adopted as the second abrasive grains is mixed with a liquid urethane resin as the second binder so that the volume ratio of the particles becomes 40% by volume, and an organic solvent is added to the solution. After adjusting the viscosity, the mixture was stirred for about 10 minutes using a stirrer to prepare a mixture. Stirring was performed at 50 rpm at room temperature and with a rotational speed that did not destroy the abrasive grains.

Thereafter, as shown in FIG. 2, a coating liquid 22 containing ZrO ₂ abrasive grains was applied onto a substrate (for example, PET Film having a thickness of about 75 μm) using a wire bar coater. And the apply | coated polishing tool 1 was dried for about 30 minutes by the thermostat (made by Yamato Scientific) at about 60 degreeC. Through the above steps, a second polishing layer (B) containing second abrasive grains having a strong mechanical removal action of ZrO ₂ as shown in FIG. 3 was formed.

CeO ₂ was adopted as the first abrasive grain having a strong chemical action (SHOROX manufactured by Showa Denko). The average particle diameter D50 was about _0.5 to 1.0 μm. The CeO ₂ abrasive grains are added to a liquid glue adhesive (manufactured by Nitta Gelatin Co., Ltd.) which is a first binder heated to 60 ° C. so that the volume ratio of the particles becomes 50% by volume. In addition, after adjusting the solution viscosity, the mixture was stirred for about 10 minutes using a stirrer to prepare a mixture.

Then, as shown in FIG. 2 again, the base material having the second polishing layer (B) containing ZrO ₂ is set on the base of the coating machine 2, and the wire bar coater is again placed on the polishing layer (B). The coating liquid 22 containing CeO ₂ abrasive grains was applied. The glue was allowed to cool to room temperature and the glue was solidified to form a first polishing layer (A) containing CeO ₂ abrasive grains on the second polishing layer (B). And in order to raise the adhesive force of glue, the water | moisture content contained in glue was dried with cold wind etc., and the grinding | polishing tool (alpha) was produced.

  The polishing tool α thus prepared is attached to the surface plate 4 of the processing apparatus shown in FIG. 4, pure water is supplied as a polishing liquid at a rate of 20 ml / min, and the polishing target 3 has a mirror surface with a surface roughness of about 30 nm Ry. As a result of processing the adjusted BK7 optical glass disk of φ50 mm (processing conditions: surface plate rotation speed 60 rpm, processing pressure 25 kPa), processing marks (scratches, processing scratches, etc.) are free in 30 minutes and a mirror surface of 30 nmRy or less can be maintained. At the same time, a high processing efficiency of 0.7 μm / min could be maintained. The surface roughness was evaluated with Foam Talysurf S4C manufactured by Taylor Hopson. Further, when 10 glass disks were subsequently processed, not only the generation of scratches was observed, but also the processing efficiency was not deteriorated.

(Comparative Example 1)
A polishing tool β was produced by repeating the same operation as in Example 1 except that the polishing layer was composed of the second polishing layer using only the second ZrO ₂ abrasive grains having a strong mechanical removing action.

  The thus produced polishing tool β is attached to the surface plate 4 of the polishing apparatus (FIG. 4), pure water is supplied as a polishing liquid at 20 ml / min, and the surface to be polished 3 is adjusted to a mirror surface with a surface roughness of about 30 nm Ry. Results of processing a Φ50mm BK7 optical glass disk (processing conditions: surface plate rotation speed 60rpm, processing pressure 25kPa), processing marks (scratch, processing scratches, etc.) free in 30 minutes and a mirror surface of 30nmRy or less could be maintained As compared with Example 1, the processing efficiency was reduced to about half as a whole, and the processing efficiency gradually deteriorated as the processing progressed. The surface roughness was evaluated with Foam Talysurf S4C manufactured by Taylor Hopson.

(Comparative Example 2)
The same operation as in Example 1 was repeated except that ZrO ₂ (manufactured by Nippon Denko Co., Ltd.) having a normal single particle large particle size was used as the second abrasive grain having a strong mechanical removal action, thereby producing a polishing tool γ. did. The average particle size was 60 μm as in Example 1, but the compressive fracture strength was 325 MPa.

  The polishing tool γ thus produced is attached to the surface plate 4 of the polishing apparatus (FIG. 4), pure water is supplied as a polishing liquid at 20 ml / min, and the polishing target 3 has a mirror surface with a surface roughness of about 30 nm Ry. As a result of processing the adjusted φ50 mm BK7 optical glass disk (processing conditions: surface plate rotation speed 60 rpm, processing pressure 25 kPa), the processing efficiency greatly increased to 2.5 μm / min in 30 minutes. However, innumerable new processing marks (scratches) were generated on the processed surface, and the processed surface roughness was significantly deteriorated to 2.8 μmRy or more. The surface roughness was evaluated with Foam Talysurf S4C manufactured by Taylor Hopson.

  The results obtained in Example 1 and Comparative Examples 1 and 2 are shown in Table 1.

  In the case of the comparative example 1, since it is a polishing tool having only a polishing layer containing abrasive grains having a strong mechanical removal action, only mechanical removal can be performed on an object to be polished. A large number of primary fine abrasive particles are porous bodies with voids formed between them, and wear gradually as processing progresses, making it easy for grinding scraps to leave the work surface. The possibility of processing damage due to clogging, etc. has been greatly reduced, but the contact area of the processing point has gradually increased due to abrasive wear, the processing pressure at the processing point has decreased, and the processing efficiency has decreased accordingly. It was.

In contrast, in Example 1, the first abrasive grains having a strong chemical action and the second abrasive grains having a strong mechanical removal action are used in combination, so that the polishing efficiency is improved without impairing the quality of the surface to be polished. I found out. When the surface of the polishing tool α of Example 1 after polishing is observed, the ZrO ₂ abrasive grains are flattened and worn as in Comparative Examples 1 and 2, and the chemical action around the abrasive grains is strong. It was also observed that CeO _2, which is one abrasive grain, was adhered. Thus, since a soft hydrated layer was formed on the surface of the glass due to the presence of CeO _{2 having} a strong chemical action, it was more easily removed by the second ZrO ₂ abrasive grains, and thus high processing efficiency was realized.

ZrO _{2, which} has a strong mechanical removal action, is a porous body in which a number of primary fine abrasive particles are partially formed and voids are formed between them, and gradually wears as the polishing process proceeds. Therefore, the grinding scraps, particularly the first abrasive grains having a strong chemical action, the surface of the object to be polished, and the generated hydrated layer are easily detached from the surface to be polished together with the wear of the second abrasive grains. The possibility of processing damage due to clogging was significantly reduced, and high quality was guaranteed.

Then, as shown in FIG. 1B, simultaneously with the flat wear of the ZrO ₂ abrasive grains, the glue adhesive which is a binder for fixing CeO ₂ is gradually dissolved in water as a polishing liquid, and the first polishing is performed. Since the number of layers is gradually reduced, it is possible to reliably supply abrasive grains having two functions to the surface of the glass, which is the object to be polished, and the generation and removal of a soft hydrated layer is repeated on the surface of the glass. As a result, a decrease in processing efficiency over time was suppressed, and a high processing efficiency could be maintained even for a long time.

  As can be seen from a comparison between Example 1 and Comparative Example 2, even if abrasive grains having two types of functions are used, the abrasive grains having a strong mechanical removal action used in Comparative Example 2 are ordinary single particles. Therefore, since the particles of a large number of primary fine abrasives as described in Example 1 are not porous bodies in which voids are partially formed between them, the machining efficiency is as in a normal fixed abrasive machining tool. However, it was impossible to achieve high surface quality.

(Example 2)
A polishing tool θ was prepared by repeating the same operation as in Example 1 except that the first abrasive grain having a strong chemical action was changed from CeO ₂ to SiO ₂ . The average particle diameter of SiO ₂ was 0.1 μm, and the content in the first polishing layer was 55% by volume.

  Next, as in Example 1, the polishing tool θ is attached to the lapping surface plate 4 of the processing apparatus shown in FIG. 4, and a silicon wafer having a diameter of 50 mm, which is ground by a # 2000 equivalent grindstone as the workpiece 3 is polished. As a result of processing, a mirror surface having a processing surface roughness of 20 nm Ry or less without processing marks (scratches) was obtained in a processing time of 30 minutes, but deterioration of processing efficiency over time was not observed.

(Example 3)
On the PET film that is the base material, a sheet with holes formed in advance is laid, and then the coating liquid 22 containing the _second abrasive grain ZrO ₂ is first applied by the same method as in Example 1. After drying, the coating liquid 22 containing CeO ₂ as the first abrasive grain was re-applied as it was, and after the glue was solidified, the sheet with the pattern of the through holes was peeled off, and the surface of the polishing tool was removed. A polishing tool η having two patterned polishing layers was produced (FIG. 5).

  The polishing tool η thus prepared is similarly attached to the surface plate 4 of the polishing apparatus (FIG. 4), pure water is supplied as a polishing liquid at a rate of 20 ml / min, and the polishing target 3 has a mirror surface with a surface roughness of about 30 nmRy. As a result of processing the adjusted BK7 optical glass disk of φ50 mm (processing conditions: platen rotation speed 60 rpm, processing pressure 25 kPa), the same results as in Example 1 were obtained. Further, there was a tendency that the occurrence of fine scratches, usually called bits, was further suppressed on the surface to be polished. This is considered to be a result of improvement in that the polishing layer was patterned, so that the supply of water as the polishing liquid was more smoothly and smoothly performed, and chip discharge was further promoted.

  Note that the present invention is limited to the above-described embodiments in terms of the type of abrasive grains that are primary particles, the method of granulation and aggregation, the type of additive, the type of abrasive tool binder, the shape of the processing tool, and the object to be polished is not.

(A) is sectional drawing which shows one embodiment of the polishing tool of this invention. (B) is sectional drawing which shows an example of the aspect of the polishing tool of this invention after grinding | polishing. It is a figure explaining the preparation apparatus of the polishing tool used for manufacture of the polishing tool of this invention. It is sectional drawing which shows an example of the base material in which the 2nd grinding | polishing layer containing the 2nd abrasive grain was formed. It is explanatory drawing which shows the use condition of the polishing apparatus using the polishing tool of this invention. It is a figure which shows an example of the patterned grinding | polishing layer in the polishing tool of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polishing tool 2 Application | coating machine 3 To-be-polished object 4 Surface plate 10 Polishing layer 11 1st abrasive grain 12 2nd abrasive grain 13 1st binder 14 2nd binder 15 Base material 21 Wire bar 22 Coating liquid 23 units

Claims (8)

A polishing tool having two polishing layers each containing different abrasive grains and a binder on a substrate,
In the second polishing layer containing the second abrasive grains and the second binder, the second abrasive grains protrude from the second binder, and a gap is provided between the second abrasive grains. Arranged on the substrate,
The first polishing layer containing the first abrasive grains and the first binder is disposed in a gap between the second abrasive grains that is at least above the second binder,
The first abrasive grains have an average particle diameter of 0.01 μm to 1 μm made of cerium oxide (CeO ₂ ) or silicon dioxide (SiO ₂ ),
The first binder is one or a mixture of two or more selected from glue adhesives, agar, and polyvinyl alcohol resin. The first binder is dissolved by supplying a polishing liquid to cover the first abrasive grains. Which is released to the polished surface,
The second abrasive grains are formed by agglomerating zirconium oxide (ZrO ₂ ) particles without containing a binder. A polishing tool characterized by being within the range of.   The second abrasive is a porous body formed by heat-treating an aggregate formed by agglomerating the particles without containing a binder at a temperature at which a neck is formed at a bonding point between the particles. The polishing tool according to claim 1, wherein the polishing tool is provided.   3. The polishing tool according to claim 1, wherein the second abrasive grains protruding from the second binder are present in the first polishing layer. 4.   The first abrasive grains are 10 volume% to 90 volume% with respect to the entire first polishing layer, and the second abrasive grains are 50 volume% or less with respect to the entire second polishing layer. The polishing tool according to claim 1, wherein the polishing tool is provided.   The thickness of the first polishing layer containing the first abrasive grains is such that at least the second abrasive grains in the second polishing layer protrude from the second binder. The polishing tool according to any one of claims 1 to 4.   The polishing tool according to claim 2, wherein a temperature at which the neck is formed is in a range of 600 degrees to 1600 degrees.   2. The polishing tool according to claim 1, wherein the surface to be polished is a substrate of a brittle material such as glass, ceramics, silicon, or silicon oxide film, a wafer, or an end face of an optical fiber. A step of aggregating particles without containing a binder to form an aggregate;
Heat-treating the agglomerates to produce second abrasive grains that are porous bodies with necks formed at the bonding points of the particles;
Applying a second coating liquid containing the second abrasive grains and the second binder on the substrate;
Drying the applied second coating solution to form a second polishing layer;
Applying a first coating liquid containing a first abrasive grain and a first binder on the second polishing layer;
Drying the applied first coating solution to form a first polishing layer;
The polishing tool according to any one of claims 1 to 7, which is manufactured by a manufacturing method comprising:

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