JPH05180736A - Manufacturing method of diamond knife for microtome - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for producing a diamond knife for a microtome, which has high cutting performance and hydrophilicity. [Structure] A step of mechanical polishing parallel to the cutting edge,
A step of making an ion beam incident perpendicularly from the ridge direction of the tip of the cutting edge to be sharpened to process the two flat surfaces of the included cutting edge smoothly, and a step of removing the graphite structure layer on the surface graphitized by the ion beam processing. The step of bonding oxygen to the surface of the diamond from which the graphite structure layer has been removed by heating at a temperature of 600 ° C. or lower in an oxygen atmosphere is continuously performed. The diamond knife surface according to the invention is hydrophilic and has very good performance for microtomes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting tool used for a microtome (a thin section cutting device for a speculum) and an ultramicrotome, and more particularly to a method for manufacturing a diamond knife for a microtome having a cutting edge formed of diamond.

[0002]

2. Description of the Related Art A diamond knife for a microtome is used as a cutting tool for producing thin specimens to be observed with an electron microscope for analysis of tissue structure or elemental analysis of biological tissues, plastics, metals and the like. Conventionally, a diamond knife for a microtome is manufactured only by mechanical polishing, and there is variation in cutting performance as a cutting blade, and it takes a lot of time to manufacture it.

In general, a microtome collects thin slices by suspending them in water. Ultra thin section deforms,
In order to collect without shrinking, it is necessary that the surface of the slice absorbs water immediately after cutting to swell and maintain its shape. Therefore, it is important for this purpose to always be swollen with water up to the sharp edge of the knife. Conventional diamond knives make the knife surface hydrophilic,
Alternatively, in order to provide a moist atmosphere, a wetting liquid containing a surfactant is applied, or a diamond knife is immersed in pure water to give pseudo hydrophilicity. It has been known from the experience of glass knives used for the same purpose and application that the hydrophilicity of the knife surface is important as a good cutting condition for diamond knives. It has been difficult to modify. In this regard, JP-A-59-1122
In Japanese Patent Publication No. 49, it is described that those having a hydrophilic surface characteristic are preferable as a diamond knife, and the cutting edge surface is defined as the two lowest reference planes of a diamond crystal, that is, (100) and (110), oxygen. It is stated that by constructing the surface with the strongest and most stable binding property to other hydrophilic species, it contributes to the wettability of the knife and minimizes the capture of dust and debris during use. However, this only uses a surface that is more likely to form a hydrophilic bond than other surfaces, and does not specifically make the surface hydrophilic.

[0004]

When mechanical polishing is generally used as a conventional method for manufacturing a diamond knife for a microtome, diamond has hydrophilicity in addition to the above-mentioned variation in cutting performance and time-consuming production. It was difficult to get the surface. The surface of the diamond knife may be oxidized to make it hydrophilic, but the surface of diamond cannot normally bond with oxygen. Therefore, a positive means must be used to bond oxygen. I have to. As one of the methods of bonding oxygen to the diamond surface, there is a method of heating at 1000 ° C. or higher in a vacuum to perform degassing, and then reacting at 400 ° C. in an oxygen atmosphere.
This is a method in which diamond is heated to 600 ° C. or higher in the atmosphere to graphitize the surface structure of diamond, and then oxygen is bonded to graphite structure carbon. Each of the above methods requires a step of removing other elements that are easily bonded from the diamond structure surface and then reacting the graphite structure carbon with oxygen. Since the microtome diamond knife is a tool for obtaining an ultrathin section having a thickness of about 0.01 μm by cutting, the surface and the cutting edge thereof should not have surface irregularities of 0.01 μm or shape defects. The change in the diamond structure of the diamond surface caused by oxygen bonding by the conventional method occurs with etching, and the shape of the etching pit due to this etching is a regular triangular pyramid shape on the (111) plane, which is deep and sharply removed. It is widely known that, in the case of diamond, this etching pit is called a trigon. When applying the conventional surface oxygen bonding method to the diamond knife processing method, this Trigon depression is
The thickness was 0.01 μm or more, and the conventional method could not be used for cutting. The present invention has been made in view of such a current situation, and an object thereof is to provide a method for stably and reliably producing a novel microtome diamond knife having excellent cutting performance and having a hydrophilic surface. Is to provide.

[0005]

As means for solving the above-mentioned problems, the present invention comprises a step of mechanically polishing in parallel to a cutting edge to form a cutting edge of a diamond knife, and a cutting to be sharpened. Using an ion beam processing device perpendicularly from the ridge direction of the blade tip, a step of smoothing the two planes of the included cutting edge by applying an ion current, and removing the graphite structure layer on the surface graphitized by the ion beam processing It is characterized in that the processing step and the step of bonding oxygen to the surface of the diamond from which the graphite structure layer has been removed are successively performed. In the present invention, the step of bonding oxygen to the surface of the diamond from which the graphite structure layer has been removed following the ion beam processing step includes heating in an oxygen atmosphere at a temperature of 600 ° C. or lower,
Alternatively, a particularly preferable embodiment is to immerse the oxidizing molten salt in the oxidizing molten salt in a state where oxygen is generated by heating.

[0006]

As described above, in order to oxidize the surface of the diamond itself to make it hydrophilic, it is necessary to perform heat treatment at a temperature higher than 600 ° C. At such a temperature, it can be graphitized and used for cutting purposes. Disappear. Therefore, the conventional method has not been able to realize a diamond knife for a microtome in which oxygen is bound over 50% or more of the surface area of the cutting edge. The present invention further comprises a graphite layer formed on the diamond surface by the ion beam processing,
It is based on the finding that the graphite layer can be removed and oxygen is bonded to the diamond surface by heating in an oxygen atmosphere at a temperature lower than 0 ° C or lower. The present inventors have studied the technical factors in manufacturing that determine the cutting performance of the diamond knife for microtome.
The diamond knife of the present invention can be realized reliably and stably by the process of developing into one elemental technology and continuously processing these two elemental technologies.

The first elemental technique of the present invention smoothes the cutting edge flat surface in order to minimize the frictional resistance of the cutting edge, especially the mechanical cutting edge shape of the diamond knife, particularly the flow direction of the cutting edge. That is. Generally, a cutting tool makes an edge in parallel with the cutting direction, but a diamond knife cannot make such an edge because it is difficult to polish the diamond and the diamond is easily chipped. It was The first elemental technique of the present invention is to use an ion beam processing machine as the blade setting means. The ion beam processing (also referred to as ion milling or ion showering) referred to in the present invention is an ionized state in which a gas containing oxygen introduced into the apparatus is ionized by being discharged in a vacuum apparatus. Then, only positively charged ions (oxygen ions) in the ionized state gas are accelerated by the electric field to form a convergent ion flow in the direction of the electric field acceleration, which is then guided to the processing chamber, where it is exposed to the ion flow. An ion stream is made incident on the diamond surface by allowing the workpiece (diamond) to stand. It is possible to remove minute amounts of carbon atoms from the diamond surface by the reactive ion etching by the active species oxygen incident as an ion stream. The angle dependence of the diamond plane on the surface roughness due to ion processing is from an incident angle of 5 ° to 85 °.
Shows a tendency for continuous improvement. Incident angle is 15 °
Low incidence angles of -40 ° are preferred, with 20 being particularly preferred.
It is between 30 and 30 degrees. Experiments by the inventor have shown that a minimum surface roughness can be obtained at low incident ion angles of 20 °. Further, the diamond surface processed by ion incidence at a low incidence angle of 20 ° to 30 ° with respect to the two planes forming the cutting edge is subjected to smooth and homogeneous removal processing and is uniform in proportion to the acceleration voltage of the ions. It was found that a graphite structure layer having a uniform thickness was formed. As the ion source used for the ion beam processing, in addition to the above oxygen ions, an inert gas such as argon and nitrogen ions are effective. Particularly, for the processing of the diamond surface, activation reaction ion etching with oxygen ions can easily perform processing with higher efficiency than other ion species.

In the case of the ion beam processing apparatus used in Examples 1 and 2 which will be described later, since the ion source is an electrodeless discharge by an ionization mechanism utilizing ECR (cyclotron resonance in a magnetic field), an active gas ion species is generated. It has the feature that it can be used. With this apparatus, when the oxygen cations ionized by introducing oxygen gas were subjected to electric field acceleration at 500 V to irradiate the diamond flat plate vertically, the diamond could be removed at a rate of 0.015 μm / min. In this case, the depth at which the diamond structure on the surface is structurally changed to the graphite structure is 0.001 μm. It was also confirmed that when the diamond plate was tilted and irradiated with oxygen cations, the diamond removal processing efficiency per time correlated with the tilt angle of the diamond plate was obtained. Further, it was also found that the surface roughness change of the diamond surface to be processed correlates with the inclination angle of the diamond flat plate.

FIG. 1 is a schematic view showing the state of a diamond knife edge in each step of the present invention in the order of steps, which will be described below with reference to the drawings. FIG. 1 (a) shows a state in which a cutting edge free from chipping and chipping is formed by mechanical polishing parallel to the edge line of the diamond, and FIG. 1 (b) shows a state of a diamond knife using an ion processing device. It shows a state in which ion processing is performed so that it is smooth in the flow discharge direction of the cutting pieces during actual use.

When this ion processing is carried out, as shown in FIG. 1 (c), the crystal structure of the two planes of the diamond cutting edge is changed into a graphite structure having a thickness of about 10Å. Since this graphite layer has no wear resistance and is easily worn during cutting, it cannot be used as a knife as it is. Therefore, as a result of examining the means for positively removing the graphite structure layer for use as a diamond knife, the present inventors conducted ion beam processing as described above, and immediately followed by oxygen treatment of the surface continuously. It was found that the maximum effect can be obtained by doing. Specific examples of the surface oxygen treatment include a method of heating in an oxidizing furnace in an oxygen atmosphere, or a method of immersing the oxidizing molten salt in the molten salt in a state where oxygen is generated by heating.

That is, according to the second elemental technology of the present invention, the graphite structure layer thus produced is continuously heated to 600 ° C. or lower, preferably 350 ° C. to 550 ° C. in an oxygen atmosphere after the cutting process using an ion processing machine. Particularly preferably 400 ° C
It is to be removed by heating and holding at about 450 ° C., specifically about 420 ° C. This treatment causes no change in the diamond structure layer below the graphite layer. Further, the diamond structure layer exposed on the surface of the diamond knife by this treatment can be in a state in which oxygen atoms are bonded only to the surface layer. That is, as shown in FIG. 1D, only the outermost surface of the diamond surface is surrounded by oxygen. Due to the bonded oxygen atoms, the diamond surface does not have the general property of water repellency and is modified to a hydrophilic surface. As described above, the hydrophilically modified diamond surface is
When cutting with a microtome, it is an important functional element. Further, as described above, oxygen treatment may be performed by a method of heating an oxidizing molten salt such as potassium chlorate and immersing it in the molten salt in a state where oxygen is generated.

According to the present invention, the diamond surface strongly bonded to oxygen can maintain this water swelling property, and thus is the most effective surface treatment method. This treatment method can maintain a permanent hydrophilic surface. In the present invention, the diamond layer in which oxygen is bonded to the diamond surface needs to be 50% or more of the diamond surface. If it is less than 50%, unreacted carbon that is not bonded to oxygen is easily bonded to a hydrogen atom having antihydrophilicity, resulting in a marked decrease in hydrophilicity.
FIG. 2 shows a state in which a diamond knife cutting edge having oxygen bound to the surface of the present invention is wet to the tip. Also, FIG.
In the conventional diamond knife, the tip is not wet because the surface is lipophilic (water repellent).

[0013]

【Example】

Example 1 A pre-finished diamond knife whose sharp edge was made to be 45 ° by mechanical polishing was positioned vertically with respect to the ion source of an ion beam processing device (equipped with an ECR ion source). Place it on the worktable and fix it. 45
° Two small planes of the cutting edge pre-finished on the cutting edge and each small plane are processed by this fixing method at a low incident angle from the direction of the ion incident angle of 22.5 °. The processing conditions of this example are as follows: ECR excitation of oxygen gas, ionization,
As a result of irradiating the diamond to be processed with an electric field at 500 V and irradiating the diamond plate vertically with oxygen ions,
When the processing time was set to 1 minute, the removal processing amount of the diamond surface was 0.015 μm and was equivalent to the thickness. At this time, the roughness of the diamond surface is R _max 0.01 before ion processing.
What was 2 μm was improved to R _max 0.008 μm. By performing this ion processing, the crystal structure of the two planes of the diamond cutting edge changed to a graphite structure having a thickness of about 10Å. Immediately after the ion processing, the graphite structure layer was removed by heating at 420 ° C. in an oxygen gas atmosphere and holding for 1 hour. No change occurred in the lower diamond structure layer. Further, it was confirmed by photoelectron spectroscopy that oxygen was bonded only to the diamond surface.

Example 2 A diamond knife having a width of 3 mm, which was finished by a mechanical polishing method into a knife cutting edge having an included angle of 45 °, was subjected to a magnetic field from the vertical direction on the axis of the blade edge of the knife. Nitrogen ions extracted from the ion source using ionization by electron cyclotron resonance are accelerated to 500 V between the ion source and the diamond knife and irradiated, and the diamond surface is removed at a rate of 50 Å per minute. As a result, a new smooth plane is created, and at the same time, a 10Å graphite structure layer (calculated value from acceleration voltage and atomic weight) is always formed on the outermost surface. By performing this ion beam processing for 1 minute, the minimum surface roughness can be obtained, and the maximum surface roughness before ion processing (R _max 0.1 μm) can be obtained.
m was less than or equal to m). The 10 Å graphite layer formed by ion beam processing was heated at a temperature of 420 by an atmospheric pressure oxidation furnace in a pure oxygen atmosphere.
It is removed by treating at 60 ° C. for 60 minutes. The contact angle of water on the outermost surface of diamond with only the diamond structured carbon to water is 90 ° or more, whereas one atom is present on the outermost surface of the diamond structured layer exposed from the lower part of the graphite layer removed by oxygen according to the present invention. Oxygen chemical bonding layer, and the bonding angle of the surface to water is less than 60 °, which shows good water wettability.

Example 3 With respect to a diamond knife which was finished into a knife cutting edge shape by a mechanical polishing method, argon was extracted from an ion source by a hot filament ionization method from a vertical direction on the axis of the knife edge. Ion beam processing using ions is applied. When argon ions are accelerated to 20 kV in a vacuum of 10 ^-5 Torr and incident on the blade edge of the knife, the included angle by the knife cutting surface mechanically polished to 45 ° by irradiation for 8 hours becomes the minimum, and 48 °. Becomes Full width of blade 3 by ion processing that forms the included angle of cutting edge that is closest to mechanical polishing
It shows a uniform cutting edge angle and flatness over a range of mm. Then, after ion processing, etching is performed in an oxidizing molten salt in order to remove the graphite structure layer formed on the diamond surface. For example, when potassium chlorate powder is heated to 450 ° C. in a quartz crucible, it is melted and liquefied, and oxygen is separated into an oxidizing atmosphere. When treated in a molten salt under oxygen generation for 1 hour, the graphite is converted into carbon dioxide gas and etching stops at the surface of the diamond structure. Next, the residual potassium chlorate is washed by boiling the diamond knife in pure water.

As described above, according to the manufacturing method of the present invention, a diamond knife can be stably manufactured in a shorter time than ever before and without variation in cutting performance. Further, since the hydrophilic diamond surface of the diamond knife produced according to the present invention recovers the wettability by pouring water into the boat (water tank) immediately after using it even after it is dried and stored, the interface is improved. There is no need for inconvenient pretreatment such as using an activator or soaking the whole in water for a long time.

[0017]

INDUSTRIAL APPLICABILITY The present invention is considered to have the characteristics of an ideal diamond knife, that is, that it can be sharpened in the cutting direction (can be smoothed in the flow discharge direction of cutting pieces) and that the cutting edge surface is hydrophilic. Realized by ion beam processing and heat treatment in an oxygen atmosphere continuous to this.
This facilitates the production of diamond knives, which has been difficult in the past, and the production method of the present invention makes it possible to obtain a diamond knife for microtome having stable cutting edge performance and hydrophilic surface. Conventionally, the cutting performance of a diamond knife as a cutting tool depends on the skill and know-how of a technician who uses the tool, and it has been difficult to perform cutting easily. Moreover, there is no objective index indicating the cutting performance of a diamond knife as a cutting tool, so there is a large difference in how to handle the tool depending on experience. On the other hand, the diamond knife according to the present invention is hydrophilic because oxygen is bound to the surface, is sharpened in the direction of the cutting edge and always provides stable and high cutting performance, and depends on the skill of the operator. No, it is a very advantageous tool that can always be used.

[Brief description of drawings]

FIG. 1 is a schematic view illustrating the state of a diamond cutting edge in each step of the present invention in the order of steps.

FIG. 2 is a schematic explanatory view showing a state where a diamond knife cutting blade having oxygen bonded to the surface of the present invention is wet to the tip.

FIG. 3 is a schematic explanatory view showing a conventional diamond knife in which the tip is not wet because the surface is lipophilic (water repellent).

Claims (3)

[Claims] 1. A step of mechanically polishing in parallel to a cutting edge to form a cutting edge of a diamond knife, and an ion beam processing device which is perpendicular to the ridge direction of the cutting edge to be sharpened. 2 of the included cutting edge by injecting ion current
The step of processing a flat surface, the step of removing the graphite structure layer on the surface graphitized by ion beam processing, and the step of bonding oxygen to the surface of the diamond from which the graphite structure layer has been removed are successively performed. A method for manufacturing a diamond knife for a microtome, which comprises performing. 2. The ion beam processing step is followed by heating in an oxygen atmosphere at a temperature of 600 ° C. or lower to remove the graphite structure layer on the surface and bond oxygen to the surface. A method for producing a diamond knife for a microtome as described above. 3. Following the ion beam processing step, the graphite structure layer on the surface is removed by immersing the oxidizing molten salt in the oxidizing molten salt in which oxygen is generated by heating. The method for producing a diamond knife for a microtome according to claim 1, wherein oxygen is bonded to the surface.