JP2004261945A - Polishing abrasive grain and polishing tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide abrasive grains to realize polishing performance higher than conventional one without spoiling excellent worked surface quality in a nanometer order, a polishing tool manufacturable at low cost and easily and its manufacturing method, by taking notice of polishing characteristics of the abrasive grains forming composite particles by mixing fine oxide particles of more than two kinds having first oxide particles strong in mechanical removing action and second oxide particles strong in chemical action. <P>SOLUTION: The abrasive grains 1 are mode of particular porous bodies in which a large number of primary particles 11, 12 provided by heat treatment of secondary particles formed by coagulation of a large number of the primary particles 11, 12 at temperature to form a neck at at connecting points of the primary particles are partly connected to each other in a state where cavities are formed among them. The primary particles are the composite particles simultaneously using more than two kinds of the oxide particles having the first oxide particles strong in the mechanical removing action and the second oxide particles strong in the chemical action against a work, respectively. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
[Industrial applications]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing tool for finishing hard and brittle materials such as silicon and glass, and metal materials such as steel and aluminum, and a method for manufacturing the same. And a polishing film having a long service life and a method for producing the same.
[0002]
[Prior art]
Polishing using an abrasive slurry has been used for final finishing of parts made of various hard and brittle materials and metal materials, such as silicon wafers and glass disks. In this processing method, excellent finished surface roughness can be easily obtained because fine abrasive grains are easily used, and stable processing characteristics can be maintained by using a large amount of abrasive slurry, It is used in many processing sites.
However, in the polishing process, a large amount of abrasive slurry is required and a large amount of waste liquid is discharged, so that the burden on the environment is extremely high and the processing efficiency cannot be particularly improved. For this reason, research and development of a fixed abrasive processing tool that is excellent in polishing efficiency and obtains excellent finished surface roughness has been actively conducted.
[0003]
In order to obtain good machined surface roughness in abrasive grain machining, it is usually advantageous to use fine abrasive grains, as is the case with fixed abrasive machining tools. However, in order to obtain an excellent machined surface such as a mirror surface, if abrasive grains having a grain size of several μm or less are used in a fixed abrasive tool, contact between the abrasive binder and the workpiece tends to occur at the time of machining. As a result, a sharp increase in the processing resistance, dropping of the abrasive grains, etc. occur, and in the worst case, the state falls into a state in which processing is impossible. In addition, clogging due to chips or the like not only lowers the processing efficiency but also causes problems such as scratching, scratching, and the like on the warped polished surface.
[0004]
As a means for solving these problems, there is a fixed abrasive processing tool in which fine abrasive grains are granulated and a powder in an agglomerated state is used as abrasive grains, and Japanese Patent Application Laid-Open Nos. 2000-190228 and 2000-237962. Japanese Patent Application Publication No. 2001-221811 discloses a polishing tool in which aggregated abrasive grains are fixed on a base material with a binder resin. In these fixed abrasive processing tools, excellent processing surface roughness is obtained by the action of fine primary particles, and at the same time, high processing efficiency is realized by agglomerated abrasive grains. Further, Japanese Patent Application No. 2001-221811 describes the relationship between the bonding force (cohesion) between the primary particles and the processing efficiency. In order to improve the processing efficiency without deteriorating the processing surface quality, It is described that it is effective to optimize the bonding force between particles.
[0005]
However, as described in Japanese Patent Application No. 2001-221811, there is a limit in improving the processing efficiency without deteriorating the quality of the processed surface. This is because if the bonding force (cohesion) between the primary particles is too weak, the coagulated abrasive grains (secondary particles) themselves are destroyed, the processing efficiency is extremely low, and the pre-processed surface of the workpiece is completely removed. Can not. On the other hand, the higher the bonding force (cohesion) between the primary particles, the more the inherent characteristics of the cohesive abrasive grains are lost and approach the above-mentioned ordinary large-size single-particle abrasive grains, and the processing efficiency is improved. In addition, scratches and the like are likely to occur, and the quality of the machined surface is greatly deteriorated.
[0006]
In addition, JP-A-2000-190228, JP-A-2000-237962, and those described in Japanese Patent Application No. 2001-221811 each have a single abrasive component, and the abrasive material is No consideration is given to how it relates to its processing characteristics.
As a result of repeated trials and analyzes, it was found that the material of the primary particles was a very important factor, depending on the workpiece, and the secondary particles were composed of single-component oxide primary particles. Instead of the above, two or more types of fine oxide particles each having a first oxide particle having a strong mechanical removal action and a second oxide particle having a strong chemical action are mixed with a workpiece. It has been found that the composite particles are more effective for further improving the processing efficiency without deteriorating the quality of the high processing surface.
[0007]
[Patent Document 1] JP-A-2000-190228
[Patent Document 2] JP-A-2000-237962
[Patent Document 2] Japanese Patent Application No. 2001-221811
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide an abrasive in which two or more types of fine oxide particles having a first oxide particle having a strong mechanical removal action and a second oxide particle having a strong chemical action are mixed to form composite particles. Focusing on the polishing characteristics of the grains, it is an object to provide abrasive grains that can achieve higher polishing efficiency than before without impairing the excellent processed surface quality on the order of nanometers, and are inexpensive and easy to manufacture polishing tools And a method for producing the same.
[0009]
[Measures taken to solve the problem]
SOLUTION: (corresponding to claim 1)
Means taken to solve the above problems, a number of secondary particles formed by aggregation of a large number of primary particles obtained by heat treatment at a temperature at which a neck is formed at the bonding point of the primary particles, a large number of Assuming that the primary particles are partially and abrasive grains made of a granular porous material bonded in a state in which a void is formed therebetween, the primary particles are mechanically It is characterized in that it is a composite particle using two or more kinds of oxide particles simultaneously having a first oxide particle having a strong removal action and a second oxide particle having a strong chemical action.
[0010]
[Action]
Since the large number of primary fine abrasive particles are partially, and a porous body in which voids are formed therebetween, excellent processing surface roughness is obtained by the action of the fine primary particles, and they are simultaneously bonded. High processing efficiency is realized by the porous body. In addition, the chips are easily separated from the processing surface together with the ultrafine abrasive particles, and the possibility of processing damage due to clogging or the like is significantly reduced. Further, the primary particles are provided with a first oxide particle having a strong mechanical removal action and a second oxide particle having a strong chemical action with respect to a workpiece, whereby the second oxide particles are processed. A chemical reaction occurs with the surface of the object, a soft chemical reaction layer or a hydrated layer is generated, and the first oxide particles having a strong mechanical removal action can be removed mechanically (mechanically). Also, by combining the oxide particles having two functions, the oxide particles having two functions can be supplied at the processing point during the processing, and the two functions can be simultaneously performed. In addition, the workpiece surface can be uniformly processed. This method is extremely effective in improving the processing efficiency, which is difficult with the above-mentioned conventional technology. That is, the processing efficiency can be remarkably improved without impairing the quality of the high processing surface as in the related art.
[0011]
Embodiment 1 (corresponding to claim 2)
Embodiment 1 is a solution, wherein the oxide particles of the composite particles are a mixture of zirconium oxide, cerium oxide, and silica.
[Action]
Metal oxides have long been used as abrasive grains, depending on the workpiece. For example, Al₂O₃, CeO₂, ZrO₂, SiO , Fe₂O₂, TiO₂, Cr₂O₃and so on. Cerium oxide is known to have the highest chemical action on glassy works such as glass, quartz, and oxide films of Si. Here, by mixing zirconium oxide with the first oxide particles having a strong mechanical removal action and cerium oxide with the second oxide particles having a strong chemical action, high machining surface quality can be ensured in the processing of glassy workpieces. Can be obtained with extremely high polishing efficiency. Similarly, SiO has a known chemical action on Si.₂To ZrO₂By mixing with the particles, it is possible to reliably obtain a high processed surface quality with a high polishing efficiency.
[0012]
Embodiment 2 (corresponding to claim 3)
The second embodiment is that the second oxide particles having a strong chemical action are not dissolved in the first oxide particles having a strong mechanical removal action.
[Action]
In order to further process the work efficiency without deteriorating the high processed surface quality, it is more effective that the chemical and mechanical actions are selectively performed by the respective oxide particles depending on the work. However, if both particles do not exist alone in the porous body but form a solid solution, each metal oxide particle cannot fulfill its original role.
[0013]
Embodiment 3 (corresponding to claim 4)
A third embodiment is that, in the solution or the first embodiment, the primary particles of the composite particles are bonded to each other without a binder.
[Action]
Since a binder for bonding the primary particles is not included, it is possible to avoid an increase in polishing resistance due to contact between the binder and the surface of the workpiece at the time of processing, or deterioration of a processed surface quality due to chips being attached to the binder. be able to. In addition, since it does not contain a binder, the bonding force between primary particles is easier to adjust, abrasive grains are surely worn during polishing, and a new cutting edge is reliably supplied to the processing point, so that the height is more reliably improved. Achieves high surface quality with high processing efficiency.
[0014]
Embodiment 4 (corresponding to claim 5)
Embodiment 4 is that the average particle diameter of the primary particles of the solving means, Embodiment 1 and Embodiment 2 is 5 μm or less.
[Action]
Since the average particle size of the primary particles is 5 μm or less, higher processed surface quality can be obtained. When particles larger than 5 μm are used, processing damage such as scratches may be newly caused by processing on the processing surface.
[0015]
Embodiment 5 (corresponding to claim 6)
A fifth embodiment is the solution 1, the first to third embodiments, wherein the composite particles have a compressive breaking strength of 20 MPa to 300 MPa.
[Action]
Since the compression fracture strength of the composite particles is 20 MPa or more and 300 MPa or less, it is possible to achieve both high processing surface quality and high processing efficiency. If the compressive fracture strength is less than 20 MPa, the composite particles themselves are crushed during processing, and the pre-processed surface of the work cannot be completely removed. On the other hand, when the compressive breaking strength is greater than 300 MPa, the mechanical removal action is too strong, which causes damage such as new scratches due to processing.
[0016]
Embodiment 6 (corresponding to claim 7)
Embodiment 6 is that the compressive breaking strength of the solution means or Embodiment 1 is 20 MPa to 160 MPa.
[Action]
Since the compressive fracture strength is from 20 MPa to 160 MPa, it is possible to more reliably realize both high processing surface quality and high processing efficiency.
[0017]
Embodiment 7 (corresponding to claim 8)
A seventh embodiment is a polishing tool having a solution, the abrasive grains of the first to sixth embodiments on a polishing surface.
[Action]
By processing using a polishing tool having abrasive grains on the polishing surface, a highly efficient and high-quality processed surface can be obtained, and the polishing tool also has a long life. In addition, the use of the fixed abrasive polishing tool eliminates the need for slurry, and greatly reduces the environmental burden.
[0018]
Embodiment 8 (corresponding to claim 9)
Embodiment 8 is the embodiment 6 in which the content of the composite particles is 10% by volume to 90% by volume.
[Action]
When the content of the composite particles is 10% by volume or more and 90% by volume or less, it is possible to particularly effectively attain a highly efficient and high-quality processed surface. When the addition rate of the composite particles is less than 10% by volume, the effect of the addition is ineffective. Can not.
[0019]
Embodiment 9 (corresponding to claim 10)
Embodiment 9 is that the polishing tool is a polishing film, and the thickness of a binder layer for fixing the abrasive grains to the base film is smaller than the maximum diameter of the abrasive grains.
[Action]
Since the thickness of the binder layer for fixing the abrasive grains to the base film is smaller than the maximum diameter of the abrasive grains, the protrusion amount of the abrasive grains is guaranteed, and the binder is hardly brought into contact with the processing surface, and the processing is performed. It is possible to prevent a decrease in surface quality.
[0020]
Embodiment
Hereinafter, embodiments of the present invention will be described.
The abrasive grains, although depending on the object to be processed, are generally hard inorganic materials, and a fine powder of primary particles having an average particle diameter of 5 μm or less is aggregated to have an average particle diameter of about 10 to 300 μm, more preferably Those having secondary particles having an average particle size of about 40 to 100 μm are suitable. The oxide material used for ordinary abrasive grains is silica, ceria, alumina, zirconium oxide, titanium oxide, or the like. Aggregates can be formed by means such as a sol-gel method or a spray dryer.
[0021]
Embodiment 1
Next, examples of the present invention will be described.
First, ultrafine particles ZrO of 50-90 nm₂And CeO₂Powder (CeO₂Is mixed in a ratio of 10 mol%), without using an organic binder, for example, a resin, etc., and pulverized with water and sprayed with a spray drier to obtain a desired size, for example, the average of the primary particles 11 and 12 described above. 50 μm particle size ZrO₂ZrO based on₂-CeO₂(In general, a size of 1 μm to 300 μm is obtained (when the particle size distribution is not sharp, a classification process is added)). The average particle size was measured dry using a laser diffraction / scattering type particle size distribution analyzer LA-920 manufactured by Horiba, Ltd. As the value of the average particle diameter, a particle diameter at a frequency integration of 50% was used (usually also referred to as a median diameter). However, the bonding force between the primary particles of granules usually produced without a binder by a spray dryer may be too weak. Therefore, if necessary, ZrO₂-CeO₂The composite particles were placed in an electric furnace and fired.
[0022]
Although the primary particles grow by heat treatment, not only the primary particles grow due to mass transfer of the constituent material, but also the bonding points between the particles become thicker due to the mass transfer of the constituent material of the particle, and there are no discontinuities. It becomes a gentle curved surface, and becomes a so-called "neck" shape which is constricted in a one-lobe hyperboloidal shape (a drum shape) (see FIG. 8). The growth of primary particles and the formation of a “neck” due to mass transfer during this heat treatment are described in “2. Ceramic Materials Technology Gathering” (published on April 10, 1979, first edition, first edition) published by the Industrial Technology Center. 3. Model of mass transfer mechanism and sintering. In this firing step, the degree of the heating temperature and the holding time are the most important factors.
[0023]
FIG. 9 is a schematic diagram showing the relationship between the firing temperature and the bonding force between the primary particles. As the firing temperature increases, sintering of the primary particles progresses, voids between them disappear, the porous structure is lost, and the sintered body becomes a complete sintered body, so that the bonding force increases. In addition, since there are two or more types of primary particles, a heating step is further set according to a phase diagram to obtain CeO.₂Is ZrO₂It is most important to devise a solution so that it does not form a solid solution. In order to evaluate the bonding strength of the composite secondary particles obtained by firing, each particle was picked up and subjected to a compression fracture test. This compression breaking 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 10 to 1000 mN, the load speed is 0.446 mN / sec, and the composite secondary particles to be measured are compressed using a plane indenter, and the composite secondary particles are compressed and fractured. Measure the strength of
[0024]
Further, after sintering, measurement was performed using X-rays.₂CeO with strong chemical action with particles 11₂It was confirmed that Compound 12 was present alone and did not form a solid solution with each other.
[0025]
Next, the composite secondary particles 1 according to the present invention (FIG. 1) having a compressive breaking strength of 67 MPa and an average particle size of 50 μm obtained as described above were mixed with a liquid so that the volume ratio of the particles was 35% by volume. , And after adding an organic solvent to adjust the solution viscosity, the mixture was mixed and stirred for about 10 minutes using a stirrer to prepare a mixture. The stirring was performed at room temperature and at a rotation speed of 50 rpm so as not to break the abrasive grains.
This mixture is applied on a base material (PET film having a thickness of about 75 μm) 22 using a wire bar coater, and then dried for 1 hour in a constant temperature bath maintained at 60 ° C. to obtain a polishing film A as a polishing tool. (FIG. 2). The maximum thickness of the obtained coating layer (portion having abrasive grains) 2 is substantially equal to the maximum diameter of the abrasive grains (composite secondary particles 1) according to the present invention having a particle size distribution (as described above). By using a solvent together, it becomes easy to reduce the thickness of the binder layer 21). An optical glass disk (borosilicate crown glass (equivalent to BK7)) in which the polishing film A thus produced is mounted on the lapping plate 32 of the processing apparatus shown in FIG. 3 and the maximum height roughness Ry is adjusted to 2 μm ) 31 was polished (processing conditions: platen rotation speed 120 rpm, processing pressure 50 kPa). As a result, it was possible to obtain a mirror surface having a maximum height roughness Ry of 30 nm or less without scratches in one minute.
[0026]
FIG. 4 shows a surface photograph and a roughness chart of the work. Further, even if 10 BK7s were subsequently polished, no significant reduction in the processing efficiency or the processed surface roughness was observed.
The high efficiency and high processed surface quality were obtained because of the ZrO constituting the composite secondary particles.₂And CeO₂Is considered to be due to each contribution. CeO₂Is the most widely used abrasive grain type. CeO₂Is known to have much lower hardness than glass and to have the greatest chemical action with glass. The composite particles of the present invention are CeO₂Particles are ZrO₂Independently of the solid solution, a chemical reaction layer is formed on the surface of the BK7 glass during the polishing process, and the chemical reaction layer is formed in the ZrO 2 present in the composite particles.₂It is considered that since the particles were mechanically removed by the fine particles or the composite particles themselves, high processed surface roughness could be obtained with extremely high processing efficiency.
[0027]
[Comparative Example 1 and Comparative Example 2]
Composite particles were produced in the same manner as in Example 1 above, but the compressive breaking strength was 16.2 MPa (Comparative Example 1) and 310.2 MPa (Comparative Example 2), respectively. Then, polishing films B and C were produced, respectively. In the same manner as in Example 1, an optical glass disk (borosilicate crown glass (BK7 equivalent)) 31 attached to the lapping plate 32 and adjusted to have a maximum height roughness Ry of 2 μm was processed for 1 minute ( Processing conditions: platen rotation speed 120 rpm, processing pressure 50 kPa). In the case of the polishing film B, the processed surface roughness was slightly improved (0.23 μmRy), but did not reach the mirror surface. On the other hand, in the case of the polishing film C, scratches were newly generated by the processing, and the processed surface roughness was deteriorated (2.5 μmRy). From this result, if the compressive breaking strength is too low, the composite particles themselves will be crushed, the cut into the work will be weakened, and the physical (mechanical) removal action will be lost, and the pre-processed surface cannot be completely removed. On the other hand, if the compressive breaking strength is too high, it is presumed that the cut on the work surface is too strong, and a new scratch is caused by the working.
Therefore, it is considered that only abrasive grains composed of secondary particles having an appropriate bonding force between primary particles can achieve high machining surface quality (mirror surface) with high efficiency. Then, the sintering conditions are adjusted, and the ZrO 2 having different compressive fracture strengths is adjusted.₂-CeO₂When composite particles were prepared, processed into a polishing film and applied to BK7 glass, the results shown in FIG. 6 were obtained.
[0028]
Since the compression fracture strength of the composite particles is 20 MPa or more and 300 MPa or less, it is possible to achieve both high processing surface quality and high processing efficiency. If the compressive fracture strength is less than 20 MPa, the composite particles themselves are crushed during processing, and the pre-processed surface of the work cannot be completely removed. On the other hand, when the compressive breaking strength is greater than 300 MPa, the mechanical removal action is too strong, which causes damage such as new scratches due to processing.
[0029]
[Comparative Example 3]
The same component composition as in Example 1 was used, but CeO₂To ZrO₂To prepare a composite particle β completely dissolved. Moreover, when the compressive breaking strength was measured in the same manner as in Example 1 above, it was 96.5 MPa. Then, a polishing film D was produced with the same configuration using the same as in Example 1. Then, as a result of applying the same method to the BK7 work using the processing apparatus of FIG. 3, no mirror surface was obtained. The same result was obtained even if the processing time was further extended to 10 minutes. FIG. 7 shows a pre-processed surface of BK7 and a photograph of the surface after processing for 10 minutes. From these results, it can be seen that CeO, which has strong chemical action,₂Is ZrO with strong mechanical action₂Is completely dissolved in CeO₂Since the original chemical action is lost, it does not react with the surface of the BK7 glass during processing, a soft reaction layer is not generated or reduced, the function of the composite particles is lost, and the polishing efficiency is reduced as a whole. It was understood that the pre-processed surface could not be completely removed.
From the above comparison, the first phase (ZrO 2) constituting the composite secondary particles was₂) And the second phase (CeO₂) Do not form a solid solution with each other, but only when they exist independently, can play the role of each of the two components, and it is clear that a high processed surface quality can be achieved with extremely high processing efficiency.
[0030]
[Comparative Example 4 and Comparative Example 5]
ZrO₂A polishing film E of a single component (compression breaking strength was 64 MPa) was produced in the same manner as in Example 1 (Comparative Example 4). The optical glass disk (borosilicate crown glass (equivalent to BK7)) 31 adjusted to have a maximum height roughness Ry of 2 μm under the same conditions as in Example 1 described above was polished (processing conditions: platen rotation speed 120 rpm) , Processing pressure 50 kPa). As a result, it was possible to obtain a mirror surface having a maximum height roughness Ry of 30 nm or less without scratching in 2 minutes. However, it is inferior to Example 1 in terms of processing efficiency. In other words, in the case of Example 1 using the composite particles, by using both the chemical action and the mechanical removal action, the polishing efficiency is high without deteriorating the quality of the processed surface, and in the case of Comparative Example 4, the processing efficiency is high. Is approximately の of that of the first embodiment.
[0031]
In addition, using this polishing film E, 5 wt% CeO₂The processing was performed while flowing the slurry on the polishing film (Comparative Example 5). As a result, almost the same polishing efficiency as in Example 1 was obtained, however, occurrence of scratches on the processed surface was confirmed.
In the case of abrasive grains of composite particles, since the oxide particles having two functions are surely supplied simultaneously to the processing point at the same time, the reaction layer due to the chemical action is instantaneously and appropriately removed to particles having strong mechanical action. However, when free abrasive grains are added as in Comparative Example 5, oxide particles having a strong chemical action are not uniformly supplied to the processing point between the abrasive grains and the work. When supplied, a soft reaction layer is formed on the entire surface of the work, and it is considered that particles having strong mechanical action are more likely to cause scratching more easily. And, as described in the section of the related art, much time is required for the cleaning step after processing. In other words, the use of oxide particles with strong mechanical action as a fixed abrasive tool and the addition of oxide particles with strong chemical action as free abrasive grains, rather than the form of composite particles, is, in the end, the conventional loose abrasive Therefore, the merit of the fixed abrasive cannot be obtained.
[0032]
Embodiment 2
First, ultrafine particles ZrO of 50-90 nm₂And SiO consisting of 70 to 90 nm₂Ultrafine particles (SiO₂In a proportion of 40 mol%), without organic binders, such as resins, etc., slurried with water and sprayed with a spray drier to obtain ZrO having the desired size, for example 30 μm in average particle size.₂ZrO based on₂-SiO₂Obtain composite secondary particles (granules). As in Example 1 above, the average particle size was measured by a dry method using a laser diffraction / scattering type particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.). Diameter, ie, the particle size at 50% frequency integration).
And, similarly, ZrO₂-SiO₂The composite secondary particles were placed in an electric furnace and fired. In this firing step, the heating temperature and the holding time are also the most important, so the heating step is basically set according to the phase diagram.₂Is the first layer, ZrO₂It is most important to devise a solution so that it does not form a solid solution. When the calcined composite secondary particles were measured by X-ray, both products, ZrSiO₄Does not exist and SiO₂Exists alone and ZrO₂It was confirmed that no solid solution was formed. Then, in the same manner as in Example 1 above, the compressive breaking strength of the fired composite secondary particles was measured.
[0033]
The composite secondary particles β according to the present invention having a compressive breaking strength of 112.5 MPa and an average particle diameter of 30 μm thus obtained are mixed with a liquid urethane resin so that the volume ratio thereof is 40% by volume, Further, after adding an organic solvent to adjust the solution viscosity, the mixture was mixed and stirred for about 10 minutes using a stirrer to prepare a mixture. The stirring was performed at room temperature and at a rotation speed of 50 rpm at which the abrasive grains were not destroyed. Then, in the same manner as in Example 1 described above, this mixture was applied onto a substrate (a PET film having a thickness of about 75 μm) using a wire bar coater, and then placed in a thermostat kept at 60 ° C. After drying for an hour, a polishing film F as a polishing tool was obtained. The maximum thickness of the obtained coating layer (portion having abrasive grains) is substantially equal to the maximum diameter of the abrasive grains according to the present invention having a particle size distribution (the binder layer is formed by using a solvent together as described above). Can be easily reduced).
[0034]
Then, the polishing film F was attached to the lap surface plate of the processing apparatus shown in FIG. 3, and a silicon wafer having a diameter of 50 mm ground by a grinding stone of # 2000 was polished. As a result, the processing mark (scratch) was formed in a processing time of 5 minutes. No mirror surface having a processed surface roughness of 20 nm Ry or less was obtained. In addition, even if 10 silicon wafers were continuously polished, no reduction in processing efficiency or processed surface roughness was observed.
In addition, the present invention is limited to the above-described examples in the types of abrasive grains that are primary particles, the granulation and aggregation method, the types of additives, the types of abrasive bonding materials, the types of processing tools, and the objects to be processed. is not.
[0035]
【The invention's effect】
The effects of the present invention are as follows, organized for each invention according to each claim.
1. Effect of the invention according to claim 1
The composite secondary particles are granular porous bodies in which a large number of primary particles are partially bonded and voids are formed therebetween, and the primary particles use at least two or more types of oxide particles. Since it is a composite secondary particle, when polishing using this, the primary particle may function as a component, that is, one may have a function of a chemical action and the other may have a function of a mechanical removal action. The combination of these functions can provide high efficiency and excellent processed surface quality.
[0036]
2. Advantageous Effects of the Inventions According to Claims 2 and 3
The oxide particles constituting the composite secondary particles are a mixture of zirconium oxide, cerium oxide and silica, and the oxide particles having a strong chemical action are not dissolved in the other oxide particles having a strong mechanical action, Since each property is maintained, each function of each oxide particle can be reliably achieved. For example, in glass processing, ZrO₂-CeO₂In the case of composite particles, CeO₂The particles mainly form a chemical reaction layer with glass, and ZrO₂Is a function that causes a mechanical removal action. In processing silicon wafers, ZrO₂-SiO₂In the case of composite secondary particles, SiO₂Particles are chemically active, ZrO₂The particles will exert a mechanical removal action.
By the way, if an oxide having a strong chemical action is dissolved in an oxide having a strong mechanical removal action, the intrinsic properties of each particle are not maintained, so that a function based on each property cannot be exhibited.
[0037]
3. Effect of the invention according to claim 4
Since a binder for bonding the primary particles is not included, it is possible to avoid an increase in polishing resistance due to contact between the binder and the surface of the workpiece at the time of processing, or deterioration of a processed surface quality due to chips being attached to the binder. be able to. In addition, since it does not contain a binder, the bonding force between primary particles can be adjusted more easily, causing abrasion during polishing, and supplying a new cutting edge to the processing point to improve the quality of the high processed surface. High processing efficiency is surely achieved.
[0038]
4. Effect of the invention according to claim 5
Since the average particle size of the primary particles is 5 μm or less, higher processed surface quality can be obtained. When particles larger than 5 μm are used, processing damage such as scratches may be newly caused on the processing surface by processing.
[0039]
5. Effect of the invention according to claim 6
Since the composite secondary particles have a compressive fracture strength of 20 MPa or more and 300 MPa or less, both high processing surface quality and high processing efficiency can be realized. If the compressive breaking strength is less than 20 MPa, the composite secondary particles are crushed during processing, and the pre-processed surface of the work cannot be completely removed. On the other hand, when the compressive breaking strength is greater than 300 MPa, the mechanical removal action is too strong, which causes damage such as new scratches due to processing.
[0040]
6. Effect of the invention according to claim 7
Since the composite secondary particles have a compressive breaking strength of 20 MPa or more and 160 MPa or less, both high working surface quality and high working efficiency can be more reliably realized.
[0041]
7. Effect of the invention according to claim 8
By processing using the polishing tool having the abrasive grains according to any one of claims 1 to 7 on the polishing surface, it is possible to obtain a high-efficiency and high-quality processed surface, and the polishing tool Also has a long life. In addition, the use of a fixed abrasive polishing tool eliminates the need for a slurry, thereby greatly reducing the environmental burden.
[0042]
8. Effect of the invention according to claim 9
When the content of the composite secondary particles is 10% by volume to 90% by volume, high efficiency and high quality of the processed surface can be achieved, and a practical polishing tool can be realized. That is, when the addition ratio of the composite secondary particles is less than 10% by volume, the effect of adding the composite secondary particles is almost negligible. As a result, the polishing function is remarkably reduced, and the tool cannot be put to practical use.
[0043]
9. Effect of the invention according to claim 10
The polishing tool is a polishing film, the thickness of the binder layer for fixing the abrasive grains to the base film is smaller than the maximum diameter of the abrasive grains, so that the binder is in direct contact with the processing surface. By avoiding this, it is possible to prevent the quality of the processed surface from deteriorating due to the direct contact of the binder layer.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a cross-sectional structure of a composite secondary particle.
FIG. 2 is a sectional view of an example schematically showing a sectional structure of a polishing film in which composite secondary abrasive grains are fixed to a film substrate.
FIG. 3 is a cross-sectional view schematically showing a polishing apparatus.
FIG. 4A is a photograph showing a surface shape of a polished test piece before processing, and FIG. 4B is a view showing a measurement result of the surface roughness.
FIG. 5 (a) is a photograph of the surface shape of the same test piece after polishing test processing, and FIG. 5 (b) is a view showing the results of surface roughness measurement.
FIG. 6 is a graph showing the relationship between the breaking compressive strength of the composite secondary particles and the surface roughness of the surface to be processed.
FIG. 7 shows CeO having strong chemical action.₂Has strong mechanical removal action₂(A) is a photograph showing the surface shape of the polished test piece before processing, and (b) is a photograph after processing for 10 minutes.
FIGS. 8A and 8B are schematic diagrams showing a state in which primary particles grow by heat treatment, wherein FIG. 8A shows a pattern before heat treatment, and FIG. 8B shows a pattern after heat treatment.
FIG. 9 is a graph schematically showing a relationship between a heat treatment and a bonding force between primary particles of abrasive grains.
[Explanation of symbols]
1: Composite secondary abrasive
2: Coating layer (part having abrasive grains)
11, 12: primary particles
21: Binder layer
22: Substrate
31: Optical glass disk
32: Lap surface plate

Claims (10)

Secondary particles formed by aggregation of a large number of primary particles are abrasive grains obtained by heat treatment at a temperature at which a neck is formed at a bonding point between the primary particles, and the large number of primary particles are partially And, abrasive grains made of a granular porous body that is bonded in a state where voids are formed therebetween,
The primary particles are composite particles using two or more types of oxide particles each having a first oxide particle having a strong mechanical removal action and a second oxide particle having a strong chemical action with respect to a workpiece. Abrasive grains characterized by being present. 2. The abrasive grain according to claim 1, wherein the oxide particles of the composite particles are a mixture of zirconium oxide, cerium oxide, and silica. 2. The abrasive grain according to claim 1, wherein the second metal oxide particles having a strong chemical action of the composite particles are not dissolved in the first metal oxide particles having a strong mechanical removal action. The abrasive grain according to claim 1 or 2, wherein the primary particles of the composite particles are bonded to each other without passing through a binder. 4. The abrasive grain according to claim 1, wherein the primary particles have an average particle size of 5 μm or less. The abrasive grain according to any one of claims 1 to 4, wherein the composite particles have a compressive breaking strength of 20 MPa to 300 MPa. The abrasive grain according to claim 1 or 2, wherein the compressive breaking strength is from 20 MPa to 160 MPa. A polishing tool having the abrasive grains according to claim 1 on a polishing surface. The polishing tool according to claim 7, wherein the content of the composite particles is 10% by volume to 90% by volume. 9. The method according to claim 8, wherein the abrasive grains are fixed to a base film, and a thickness of a binder layer for fixing the abrasive grains to the base film is smaller than a maximum diameter of the abrasive grains. Polishing tool.

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