JP2001009693A - Grinding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide high surface roughness using a grinding tool having high grinding efficiency by interposing a colloidal silica liquid on a surface of a fragile material, and performing grinding by using a grinding wheel having either of aluminum, zinc, nickel, magnesium or copper as a bond material. SOLUTION: An aluminum bond grinding wheel 1 using a diamond abrasive grain and high purity aluminum as a bond material is installed in an existing curve generator, and optical glass 3 is ground while blowing out a colloidal silica liquid 2 to a work part from a nozzle 2a instead of a water soluble grinding liquid. The colloidal silica liquid 2 has high silica purity and is used for gringing a semiconductor, and a silica ultrafine particle in the silica liquid 2 is used by being negatively electrified. A grinding wheel may be a grinding wheel having either of aluminum, zinc, nickel, magnesium and copper as a bond material besides an aluminum bond grinding wheel to thereby improve grinding efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for grinding a brittle material such as an optical element made of glass such as a lens and a prism.

[0002]

2. Description of the Related Art Grinding is performed from glass (optical glass), which is a brittle material, to manufacture optical elements such as lenses and prisms. This grinding includes a curve generating process as a rough process for creating a spherical surface and a planar shape on the surface of a brittle material, and a smoothing process by rubbing (lapping) with a diamond pellet or the like. 5A and 5B show a curve generating process described in “Optical Component Processing Terminology” (issued by the Optical Industrial Technology Association). FIG. 5A illustrates a case where a convex shape is ground from the optical glass 102, and FIG. This is a case where a concave shape is ground.

An optical glass 102 is a work holder 103.
The cup-shaped diamond grindstone 101 is inclined and ground at an angle α at which a desired spherical shape can be created with respect to the optical glass 102. The angle α is an angle formed between the grindstone shaft 110 of the grindstone holder 105 and the work shaft 120 of the workpiece holder 103. While the angle α is maintained, both the grindstone 101 and the optical glass 102 are rotated to perform the creation.

[0004]

Generally, since the grinding efficiency for grinding an object to be ground and the quality of the obtained surface roughness are in an opposite relationship, when the grinding efficiency is increased, the obtained surface roughness is reduced. When the surface roughness is reduced and the surface roughness is improved, the grinding efficiency is reduced. That is, in order to improve the grinding efficiency, it is necessary to increase the abrasive grain size of the grindstone to secure a large cutting depth. However, if the abrasive grain size increases and the cutting depth increases, the obtained surface roughness decreases. In addition, when the cut amount is large as described above, in the case of a brittle material such as glass, a crack (crack) occurs, and a crack, which is a crack, progresses to the inside of the material. Have.

Accordingly, an object of the present invention is to provide a grinding method capable of simultaneously obtaining a high surface roughness while using a grinding tool having a high grinding efficiency.

[0006]

In order to achieve the above object, the grinding method of the present invention utilizes the interfacial potential double layer of ultrafine silica particles contained in a colloidal silica liquid to adsorb silica particles on the surface of a grinding wheel. Thus, the surface of the workpiece, which is a brittle material, is simultaneously polished and polished.

[0007] That is, the invention of claim 1 is a method of grinding a brittle material such as an optical element with a grindstone, wherein a colloidal silica liquid is interposed on the surface of the brittle material, and any one of aluminum, zinc, nickel, magnesium and copper is used. The grinding is performed using a grindstone having the bonding material as a bonding material.

The ultrafine silica particles contained in the colloidal silica liquid, which is an alkaline liquid, are negatively charged by adsorbing hydroxyl groups, and adsorb to the metal surface with a very small force. On the other hand, it is known that metals such as aluminum, zinc, copper, nickel and magnesium are attacked in an alkaline solution. When grinding a brittle material using a grindstone that uses such a metal as a bonding material in a colloidal silica liquid that is an alkaline liquid, the bonding material of the grinding stone is eroded by the alkali liquid and It elutes as a positively charged metal ion. By this elution, the negatively charged silica ultrafine particles having hydroxyl groups attached thereto react with metal ions on the surface layer of the grindstone to produce a gelled product (silica gel) and adhere to the grindstone surface.

Since this state occurs on the surface layer of the grindstone, the polishing action of the ultrafine silica particles adhered to the surface is added in accordance with the ordinary grinding processing using abrasive grains such as diamond and cBN of the grindstone, and the water-soluble grinding is performed. Surface roughness higher than ordinary grinding using a liquid can be obtained.

Also, since the ultrafine silica particles adhere to the surface of the grindstone, the amount of protrusion of the abrasive grains protruding from the surface of the grindstone is reduced, so that the cutting depth of the abrasive grains of the grindstone is reduced, and a higher surface roughness is obtained. Can be. At the same time, the gelled ultra-fine particle film intervenes at the interface between the grindstone and the object to be ground, and also plays a role of a cushioning material that absorbs vibrations caused by the processing of both, so that high surface roughness can be obtained.
In addition to this effect, even if a gelled film intervenes,
Since the grinding is still performed by the abrasive grains, the grinding efficiency does not decrease.

According to a second aspect of the present invention, in a grinding method for grinding a brittle material such as an optical element with a grindstone, a colloidal silica liquid mixed with a water-soluble grinding fluid is interposed on the surface of the brittle material, and aluminum, zinc, The grinding is performed using a grindstone having any one of nickel, magnesium and copper as a bonding material.

According to the present invention, since the water-soluble grinding fluid is mixed in the colloidal silica fluid, an activating action acts on the interface between the grinding wheel and the object to be ground, so that the sludge generated by the grinding is discharged. As a result, the surface roughness can be improved by preventing the occurrence of grinding scratches (scratch). Further, the grinding resistance can be reduced by the lubricating action of the grinding fluid, vibration and heat generated by the grinding can be suppressed, and higher surface roughness and higher stability of the shape can be secured.

According to a third aspect of the present invention, there is provided a grinding method for grinding a brittle material such as an optical element with a grindstone, wherein a colloidal silica liquid containing metal ions is interposed on the surface of the brittle material, and aluminum, zinc, nickel, magnesium Alternatively, grinding is performed using a grindstone having either copper as a bonding material.

According to the present invention, by containing metal ions in the colloidal silica solution, the contained metal ions and ultrafine silica particles adhere to form a gel having a size corresponding to the charge and amount of the metal ions. It is produced and intervenes in the liquid. Since the gel has further attached hydroxyl groups in the liquid, the gel gradually softens to become a liquid and adheres to the surface of the grindstone. In this way, a gel having a certain size is generated by previously containing metal ions in the colloidal silica liquid, and the gel is attached to the surface of the grindstone. Since the adhesion of the ultrafine silica particles to the surface of the silica fine particles can be promoted, the high polishing ability of the ultrafine silica particles can be secured.

According to a fourth aspect of the present invention, in the grinding method for grinding a brittle material such as an optical element with a grindstone, a colloidal silica liquid containing a metal ion and mixed with a water-soluble grinding fluid is interposed on the surface of the brittle material. The grinding is performed using a grindstone having any of aluminum, zinc, nickel, magnesium and copper as a bonding material.

In the present invention, since the grinding method according to the second and third aspects is combined, the activating action of the grinding fluid and
The promotion of the adhesion action of the ultrafine silica particles by the metal ions can be achieved at the same time, and the workpiece can be processed quickly.

[0017]

(Embodiment 1) FIGS. 1 and 2
(A) and (b) show Embodiment 1 of the present invention, and FIG.
(A) shows the results of surface roughness measurement when grinding optical glass using colloidal silica liquid as an aluminum bond grinding wheel, and (b) grinds the aluminum bond grinding wheel using existing water-soluble grinding fluid. The result of the surface roughness measurement when processing is performed is shown.

In this embodiment, as shown in FIG. 1, an aluminum bond grindstone 1 is attached to an existing curve generator (hereinafter referred to as a CG machine), and a colloidal silica liquid 2 is jetted from a nozzle 2a instead of a water-soluble grinding liquid. The optical glass 3 is ground while being applied to the processing portion. The aluminum bond whetstone 1 is a whetstone using diamond abrasive grains and high-purity aluminum as a bonding material. In this embodiment,
An aluminum bond whetstone (# 600, concentration 100) manufactured and sold by Shin Nissan Diamond Industrial Co., Ltd. was used.

The colloidal silica liquid 2 has a high silica purity and is used for polishing semiconductors and the like. Snowtex 30 (trade name, manufactured by Nissan Chemical Industries, Ltd., Snowtex is a colloidal silica liquid containing 30% by weight of ultrafine silica particles). .)
Was diluted to 6% by weight with pure water. This silica liquid 2
The ultrafine silica particles inside are negatively charged. Two types of FPL51 (trade name) and BSL7 (trade name) manufactured and sold by OHARA Co., Ltd. were used as the optical glass 3 as a brittle material as an object to be ground.

The grinding machine uses an existing curve generator, and in this embodiment, K-Ritsu Seiki Co., Ltd.
CG-3 type (trade name) was used. The aluminum bond whetstone 1 is attached to the whetstone holder 1a of this curve generator,
The optical glass 3 was attached to the workpiece holder 3a, and grinding was performed with a total cutting amount of about 1 mm while rotating the aluminum bond grindstone 1 and the optical glass 3 respectively. At this time, the peripheral speed of the aluminum bond grindstone 1 is 10 m / sec, and the peripheral speed of the optical glass 3 is 0.1 m / sec. Also, in this grinding,
The colloidal silica liquid 2 was supplied from the nozzle 2a.

FIGS. 2A and 2B show the optical glass 3.
Shows the measurement results of the surface roughness when FPL51 is used. As shown in FIG. 2 (b), the average surface roughness Ra when grinding was performed with the aluminum bond grindstone 1 using the existing water-soluble grinding fluid under the same grinding conditions was 0.320 μm.
In contrast, the aluminum bond whetstone 1 of this embodiment
When the grinding was performed while supplying the colloidal silica liquid 2, the average surface roughness Ra was improved to 0.052 μm, which corresponds to about ６, as shown in FIG. The same tendency was observed in other optical glasses.

The reason for this is as follows. When a colloidal silica liquid having negatively charged silica ultrafine particles is supplied to the aluminum-bonded grindstone 1, the silica ultrafine particles are adsorbed to the aluminum-bonded grindstone, although the force is very weak. Further, since the colloidal silica liquid 2 is an alkaline liquid, aluminum is attacked and trivalent aluminum ions are eluted.
In this elution, the ultrafine silica particles adsorbed in a negatively charged state with hydroxyl groups attached thereto are more strongly adsorbed on the surface layer with aluminum ions, gelled and adhered to the surface of the grindstone. Since this state occurs on the surface layer of the grinding wheel, in addition to the normal grinding process using diamond abrasive grains of the grinding wheel, the polishing of the ultrafine silica particles adhered acts, and it is more than the normal grinding process using a water-soluble grinding fluid. Surface roughness was obtained.

[0023] Therefore, compared with the surface roughness when processing with a normal water-soluble grinding fluid containing no ultrafine silica particles, the polishing effect of the ultrafine particles acts, so that a better surface roughness can be obtained. Can be. In addition, since the silica ultrafine particles adhere to the surface of the grindstone, the amount of the diamond abrasive particles protruding from the surface of the grindstone decreases. For this reason, the cutting depth of the abrasive grains of the aluminum bond grindstone itself is also reduced, and higher surface roughness can be obtained.

In this embodiment, the aluminum bond whetstone 1 is used. However, any whetstone using a bonding material made of a metal which is eluted with an alkali solution may be used. Any of zinc, copper, nickel and magnesium can be used. Or can be used. The content of ultrafine silica particles is 6% by weight.
Although the colloidal silica liquid 2 was used, the present invention is not limited to this, and the concentration can be appropriately selected within the range of 3 to 30% by weight. The selection in this case can be determined in consideration of the workability of processing, the degree of damage to the CG machine, and the like.

In such an embodiment, since the grinding is performed by adding the polishing action of the ultrafine silica particles, a ground surface having a higher surface roughness can be obtained.

(Embodiment 2) FIGS. 3 (a) and 3 (b) show Embodiment 2 of the present invention, and FIG. 3 (a) shows the surface roughness obtained by the grinding method of this embodiment. (B) shows the increase in the current value of the motor that rotates the aluminum bond grinding wheel 1 during the grinding process. In the characteristic diagram of FIG. 3B, each lens is ground with the current value of the motor on the grindstone side (motor for rotating the grindstone) as a reference (0.00) when no grinding is performed on the vertical axis (so-called idling). The amount of increase in the motor current is plotted on the horizontal axis, and the number of ground lenses (the number of ground lenses when the optical glass is ground to create 30 lenses) is plotted on the horizontal axis. The characteristic curve A in this (b) shows the grinding using only the colloidal silica liquid, and the curve B shows the grinding when the colloidal silica liquid and the grinding liquid are mixed.

The feature of this embodiment is that a slightly water-soluble grinding liquid is mixed in the colloidal silica liquid 2. That is, in this embodiment, the first embodiment
An aluminum bond grindstone 1 is attached to an existing curve generator (GC machine) similar to the above, and grinding is performed. A slightly water-soluble grinding fluid is mixed with a colloidal silica fluid 2 supplied during the grinding process. For grinding the optical glass 3. As the colloidal silica liquid 2, a liquid obtained by diluting Snowtex 30 manufactured by Nissan Chemical Industries, Ltd. to 6% by weight with pure water was used.

In this embodiment, the aluminum bond grindstone 1, the colloidal silica liquid 2, the optical glass 3, and the curve generator are the same as those in the first embodiment. As a water-soluble grinding fluid, Green Cut (trade name) sold by Mabuchi S & T Co., Ltd. was used, and this grinding fluid was added to the colloidal silica solution 2 at a concentration of 1.5 vol%.
In addition, the colloidal silica liquid 2 was mixed with a water-soluble grinding liquid in 6 vol.
%, The effect of the polishing action by the ultrafine silica particles was hardly obtained, and the surface roughness was close to the surface roughness at the time of grinding using only the water-soluble polishing liquid, so that a desired result was not obtained.

As shown in FIG. 3 (a), when grinding is performed while supplying a colloidal silica liquid 2 mixed with a water-soluble grinding liquid to an aluminum bond grinding wheel 1, the aluminum shown in FIG. It can be seen that 0.043 μm, which is a high surface roughness accuracy of about ８, is secured as compared with 0.320 μm when grinding is performed while supplying only the water-soluble grinding fluid to the bond grindstone. Further, by mixing the water-soluble grinding fluid into the colloidal silica fluid, as shown in FIG. 3 (b), the current flowing through the motor for rotating the grindstone during grinding is reduced to about 1/3 to 1
/ 5.

According to such an embodiment, as in the first embodiment, the grinding action of the ultrafine silica particles attached is taken into account, and at the same time, the grinding fluid is mixed by adding a small amount of a water-soluble grinding fluid. Has the effect of surface active action,
Better surface roughness can be obtained. The colloidal silica liquid itself (containing 30% by weight of silica ultrafine particles or a colloidal silica liquid diluted 5 times as in Embodiment 1) contains silica ultrafine particles as an abrasive, but is originally ground. Since it does not have the function as a liquid, it is a sludge (cutting waste) of ground glass.
And the lubrication action in the grinding region between the workpiece and the grinding wheel is extremely low.

As shown in FIG. 3 (b), the current value of the motor for rotating the aluminum bond whetstone 1 every time each lens is obtained during the grinding process for continuously obtaining 30 lenses, the colloidal silica liquid 2 When a small amount of a green cut grinding fluid is mixed (characteristic curve B), about one-third to one-third of that when grinding is performed only with the colloidal silica liquid 2 (characteristic curve A)
It is about 1/5. This is because, in the present embodiment, a small amount of grinding fluid is mixed in the present embodiment, compared with the first embodiment, in the grinding area, so that sludge discharge and lubricity in the processing area are improved, and The resistance value during the grinding process is reduced, and the value of the current flowing through the motor is reduced.

As a result, in this embodiment, good surface roughness is obtained by the polishing action of the ultrafine silica particles, and the discharge property of the sludge generated by the grinding is improved by the surface active action of the water-soluble grinding fluid. As a result, the grinding and polishing action of the diamond grindstone and the ultrafine silica particles that the grindstone always has can be stably ensured, and high surface roughness can be obtained. Therefore, better surface roughness can be obtained by the polishing action of the ultrafine silica particles and the surface active action of the grinding fluid.

(Embodiment 3) In this embodiment, a small amount of metal ions is added to and contained in the colloidal silica liquid 2 of Embodiment 1. When copper ions are mixed at a concentration of 1 vol% in the colloidal silica liquid 2 and an aluminum bond grindstone is immersed in the liquid, ultrafine silica particles contained in the colloidal silica liquid precipitate on the surface of the aluminum material of the aluminum bond grindstone. Was observed. This is because when the aluminum bond grindstone is immersed in a colloidal silica liquid containing copper ions, the copper ions react with the hydroxyl groups attached to the silica ultrafine particle surface, and a product that gels on the surface of the aluminum bond grindstone is generated. Yes, the gelled product gradually softens to a liquid state, further attaches hydroxyl groups, and binds to aluminum ions eluted with alkali, thereby forming aggregates of ultrafine silica particles on the surface of the aluminum bond grinding wheel. It will adhere.

Also in this embodiment, the first embodiment
When the optical glass 3 was ground using the same aluminum-bonded grindstone 1 and a colloidal silica liquid mixed with copper ions at 1 vol%, the surface roughness was as shown in FIG.
a was 0.048 μm, and the surface roughness was significantly improved from the surface roughness Ra of 0.320 μm when grinding was performed using an existing water-soluble grinding fluid.

According to such an embodiment, by making the colloidal silica liquid 2 contain a small amount of copper ions,
It can increase the deposition rate of ultrafine silica particles. The contained copper ions react with the hydroxyl groups adhering to the surface of the ultrafine silica particles to form a gelled product. Further, the gelled product reacts with the aluminum ions eluted with alkali and the surface of the aluminum bond grindstone 1. This is for reacting and precipitating copper, and for attaching ultrafine silica particles to the surface of the aluminum-bonded grindstone.

Therefore, a local battery is formed between the copper ion and the surface layer of the aluminum-bonded grindstone 1 eluted with the alkali due to the precipitation of the copper ion by the reduction reaction, and the electric energy is smaller than the electric energy obtained only by the elution of the aluminum bond. A higher potential can be obtained, and silica ultrafine particles can be attached and grown faster and more strongly. This copper ion is contained in the colloidal silica liquid at less than 1 vol% (for example,
(0.8 vol%, 0.4 vol%) can increase the deposition rate of ultrafine silica particles on the grindstone surface, and when processing with this grindstone, the existing water-soluble grinding fluid is used. The surface roughness is higher than the surface roughness due to the used grinding. Although copper ions are used as metal ions in this embodiment, calcium ions and sodium ions have the same effect.

In this embodiment, metal ions such as copper ions are contained in order to secure a strong adhesion of ultrafine silica particles and a high growth rate. By including grinding fluid at the same time,
Surfactant action by a water-soluble grinding fluid can be obtained. That is, as described in the second embodiment, since the surface active action of the grinding fluid has an effect of improving the working force in the polishing process, by including the grinding fluid, the deposition rate of the ultrafine silica particles is increased. And the effect of reducing the grinding resistance by the grinding fluid is added, whereby the workpiece can be processed quickly.

In this embodiment, copper ions are mixed in the colloidal silica liquid 2 and an aluminum bond grindstone is immersed in the liquid to elute the aluminum material of the aluminum bond grindstone. An aluminum block material is immersed in a colloidal silica solution containing copper ions to elute aluminum ions from the block material, and then an aluminum bond grindstone is immersed in the colloidal silica solution to form aggregates of ultrafine silica particles on the surface of the aluminum bond grindstone. You may make it adhere.

According to such an embodiment, stronger adhesion of ultrafine silica particles and faster growth can be performed, and a highly efficient polishing action can be secured.

In each of the above embodiments, as a method of interposing the colloidal silica liquid on the surface of the brittle material, the colloidal silica liquid is sprayed from a nozzle. Grinding may be performed by dipping the surface and the colloidal silica liquid between them.

[0041]

According to the first aspect of the present invention, since the grinding is performed by adding the polishing action of the ultrafine silica particles, a ground surface having a higher surface roughness can be obtained.

According to the second aspect of the present invention, a better surface roughness can be obtained by the polishing action of the ultrafine silica particles and the surfactant action of the grinding fluid.

According to the third aspect of the present invention, it is possible to perform stronger adhesion of ultrafine silica particles and faster growth, and it is possible to secure a highly efficient polishing action.

According to the fourth aspect of the present invention, the precipitation rate of the ultrafine silica particles is increased, and the effect of reducing the grinding resistance by the grinding fluid is added, so that the workpiece can be processed quickly.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of an apparatus for processing.

FIGS. 2A and 2B are characteristic diagrams of average surface roughness when a grinding process is performed. FIG. 2A shows the first embodiment, and FIG. 2B shows the case of an existing grinding fluid.

FIG. 3A is a characteristic diagram of average surface roughness when grinding is performed according to the second embodiment, and FIG. 3B is a characteristic diagram of a motor current value during grinding.

FIG. 4 is a characteristic diagram of average surface roughness when grinding is performed according to a fourth embodiment.

FIGS. 5A and 5B are front views showing a conventional grinding process.

[Explanation of symbols]

 1 Aluminum bond whetstone 2 Colloidal silica liquid 3 Optical glass

Claims (4)

[Claims] 1. A method of grinding a brittle material such as an optical element with a grindstone, wherein a colloidal silica liquid is interposed on the surface of the brittle material, and a grindstone having any of aluminum, zinc, nickel, magnesium or copper as a bond material. A grinding method characterized in that grinding is performed by using. 2. A grinding method for grinding a brittle material such as an optical element with a grindstone, wherein a colloidal silica solution mixed with a water-soluble grinding fluid is interposed on the surface of the brittle material to form aluminum, zinc, nickel, magnesium or copper. Grinding using a grindstone having any one of the above as a bonding material. 3. A grinding method for grinding a brittle material such as an optical element with a grindstone, wherein a colloidal silica liquid containing metal ions is interposed on the surface of the brittle material, and any one of aluminum, zinc, nickel, magnesium and copper is used. Grinding using a grindstone having a bond as a bonding material. 4. A grinding method for grinding a brittle material such as an optical element with a grindstone, wherein a colloidal silica solution containing a metal ion and containing a water-soluble grinding fluid is interposed on the surface of the brittle material, and aluminum, zinc Grinding using a grindstone having any one of nickel, magnesium, and copper as a bonding material.