JPS6320668B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a knife for an ultramicrotome made of an artificial single crystal of sapphire, and particularly to a method for final polishing the knife.

[Conventional technology]

Currently, diamond knives and glass knives are mainly used as knives for ultramicrotomes. The former has no problems in terms of quality, but it has the disadvantages of price and the fact that there are few manufacturing engineers and it is difficult to obtain.The latter is cheap, but has a short lifespan.
Another drawback is that the experimenter must make his own knife each time. In order to eliminate these drawbacks, a knife for an ultramicrotome has recently been developed and commercially available using artificial sapphire single crystal as a material (Japanese Patent Laid-Open No. 57-46141).

The key point of the manufacturing method is that the two surfaces that make up the cutting edge of the ultramicrotome knife, which is made of high-quality artificial sapphire single crystal, have low index surfaces, such as (11
00), the knife is shaped and polished using a diamond tool, then so-called mechanochemical polishing (mechanochemical polishing) is performed using fine silica particles as a wrapping material, and then chemical polishing (chemical polishing) is performed at 320°C for 10 minutes using an aqueous phosphoric acid solution. ).

When a blot of biological tissue embedded in epoxy resin is sliced with this saphire knife, ultrathin sections with a so-called silver thickness (600 to 900 Å thick) are obtained.

When this ultra-thin section is closely observed with a transmission electron microscope, defects in the striped pattern, which is thought to be due to the chattering phenomenon of the striped pattern perpendicular to the direction of blade movement, called chatter, or the blade edge called a sag-like scalpel mark are observed. The frequency of small streak-like scratches that occur parallel to the direction of movement of red blood cells, which are often seen in red blood cells, is slightly higher than in ultra-thin sections obtained with an expertly finished diamond knife of the highest quality. It is inferior in this respect.

The reason for this phenomenon is that during the manufacturing process of sapphire knives, so-called chemical polishing is performed to dissolve the sapphire using chemicals, so the rounding radius of the tip of the cutting edge reaches an equilibrium within a certain limit, and this rounding radius This seems to be because it is larger than that of the highest quality diamond knife.

[Means for solving problems]

An object of the present invention is to provide a polishing method for reducing the rounding radius of the cutting edge of a sapphire knife without damaging the cutting edge.

That is, in the present invention, an ultramicrotome knife made of artificial sapphire single crystal is attached to the cutting edge by placing a spherical or cylindrical elastic body close to the surface immediately behind the cutting edge in a solution in which fine abrasive particles are suspended. The cutting edge is rotated toward the grinding surface, and fine abrasive particles are slid from behind the cutting edge parallel to the grinding surface, and at least one surface of the cutting edge forming surface is elastically released and polished to reduce the rounding radius of the cutting edge. The present invention relates to a method for manufacturing a knife for an ultramicrotome.

〔Effect of the invention〕

According to the method of the present invention, elastic emission machining (EEM) in which fine abrasive particles are slid from behind the cutting edge parallel to the grinding surface of the cutting edge can be used to eliminate damage to the cutting line of the cutting edge. The rounding radius of the cutting edge can be reduced with an extremely smooth finished surface without causing distortion to the polished surface, making the blade sharp. As a result, a sapphire knife capable of reducing chatter and sagging scalpel marks to the same level as a first-class diamond knife is obtained.

The present invention will be specifically explained below.

FIG. 1 schematically shows the method of the present invention, in which 1 is a sahuaiya knife, 2 is its cutting edge,
3 is its polished surface, 4 is an elastic cylinder or sphere, and 5 is 4
, 6 is an abrasive fine particle solution, 7 is an abrasive fine particle, and 8 is an abrasive removal section. The arrows indicate the direction of rotation of the cylinder or sphere and the direction of movement of the particles.

As the abrasive material, fine particles of silica, alumina, zirconia, etc. are used. Among these, silica fine particles are preferred. Its average particle size is about 0.5~0.01μm
Preferably.

The abrasive particles are used by being suspended in a liquid, especially water. Although the concentration of fine particles in the solution is not particularly specified, it must be avoided if it is too high, as this will make it difficult to perform EEM polishing. A range of about 1-5% by weight is preferred.

The material of the rotating elastic body should be one with suitable rubber-like elasticity, for example, an equivalent elastic modulus of about 10,500 g/mm ² ,
Any material having the following properties may be used, but polyurethane rubber, which can be easily heat-molded and exhibits appropriate rubber-like elasticity at room temperature, is advantageous.

The shape of the rotational elastic body may be spherical or cylindrical.
If it is spherical, the rotating ball or blade must be moved parallel to the blade line while rotating to polish the entire blade line. In the case of a cylindrical shape, the surface is polished over the entire blade line, so there is no need to move the rotating body or the blade.

The size of the rotating elastic body is not particularly limited either, but since the sapphire knife itself is small, it can be extremely small, and those with a diameter of 30 to 60 mm are preferably used, and the rotation speed is 2000 to 3000 mm/sec. The rotation speed must be determined as follows.

In order to perform EEM polishing, the rotating elastic body must not be brought into contact with the polishing surface under a large load. A preferable example is to use a rotating elastic body as a balance with one pole and the other pole so that an extremely slight load is applied.
It is best to approach the surface to be polished from below to the rotating body and stop at a constant load. For example, this load is approximately
Ideally it should be around 200g. Under such a load, while the rotating body is rotating, deformation occurs near the polishing surface of the rotating body due to the dynamic pressure generated by the fluid wedge due to its elasticity, and the rotating body itself does not directly touch the polishing surface. Approximately 1 ~ between and the polished surface
A 3μm fluid film is created and there is no contact. The pressure exerted on the polishing surface by the advanced abrasive particles in the aqueous solution becomes very light, so that atomic-order peeling occurs without any strain on the polishing surface. As a result, the polished surface becomes an extremely smooth mirror surface.

To give a specific example, the fine particles used are colloidal silica particles with a diameter of 60 Å dispersed in pure water at a rate of 2 to 3%. The polishing rate by this method is 1700 Å per hour or about 30 Å/min, and the surface roughness is about 20 Å as measured by Talystep.

The surface processed by this method was evaluated by comparative light reflectance spectrometry, and the results showed that:
The surface is as perfect as a chemically polished surface,
This meets the purpose of the present invention.

Furthermore, since the abrasive fine particles move in parallel in one direction from behind the cutting edge toward the cutting edge, chipping of the cutting edge line does not occur.

The cutting edge may be polished on one side or on both sides. In the case of one surface, either surface may be used, but it is more common to polish the so-called scooped angle surface.

In the method of the present invention, it is possible to polish the knife by just EEM polishing immediately after forming the cutting edge of the knife, but it is also possible to polish the knife using only EEM polishing, but it is also possible to polish the knife after mechanical polishing, then after mechanical chemical polishing, and then after chemical polishing. This EEM polishing can also be applied to knives. The edge of a nearly finished sahuaiya knife, for example,
According to the method disclosed in JP-A No. 57-46141, it is preferable to finish the cutting edge by EEM polishing, which has been finished by forming polishing with a diamond tool, mechanochemical polishing with silica powder, chemical polishing with phosphoric acid treatment, etc. be. This makes the cutting edge sharper, making it possible to obtain a sahuaiya knife that is comparable to a first-class diamond knife.

Next, examples will be shown.

Example 1 A rotating shaft of a polyurethane cylinder with a radius of 28 mm was set 0.75 mm from the cutting edge of a sapphire knife manufactured by the method described in JP-A No. 57-46141, and the rotating speed was set at 3000 mm/sec in the direction of rotation. Drives the cutting edge to cut particles by sliding them from behind. The polishing liquid is a liquid in which 2% by weight of silica particles with a diameter of 70 Å are suspended in pure water, and the cutting edge is polished in this liquid. The required polishing time is 10 minutes.

Ultra-thin sections were cut using the thus obtained saphire knife, and were examined using a transmission electron microscope (×3000).
When inspected at 100% accuracy, both chatter and sag-like scalpel marks were reduced compared to those without such polishing, and a knife comparable to a high-quality diamond knife was obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing the method of the present invention. 1...Sahuaia knife, 2...blade tip, 3...
Polishing surface, 4... Elastic cylinder or sphere, 5... Rotating shaft, 6... Abrasive particle solution, 7... Abrasive particle, 8... Polishing removal section.

Claims (1)

[Scope of Claims] 1. An ultramicrotome knife made of artificial sapphire single crystal is prepared by holding a spherical or cylindrical elastic body close to the surface immediately behind the cutting edge in a solution containing fine abrasive particles. Rotate it towards the
For use in an ultramicrotome, characterized in that fine particles of abrasive material are slid from behind the cutting edge parallel to the polishing surface, and at least one surface of the cutting edge forming surface is subjected to elastic release polishing to reduce the rounding radius of the cutting edge. How to make a knife. 2. The method for manufacturing a knife for an ultramicrotome according to claim 1, wherein the abrasive material is fine particles of silica.