Blade for microtomes

Abstract

Provided is a blade for microtomes which suppresses chipping, has excellent sharpness and durability, and can cut satisfactorily, regardless of the hardness of a sample to be cut out.　This blade for microtomes comprises a blade main body having a flat plate-shaped base portion and a pointed portion 1B formed in a tip portion of the base portion, and a water-repellent DLC thin film 2 formed on the pointed portion 1B, wherein: the contact angle of the water-repellent DLC thin film 2 with respect to water is 90° or more; a radius of curvature (R1) of a tip end E of the pointed portion 1B is 15-150 nm inclusive; a radius of curvature (R2) of a tip end F of a cutting edge including the water-repellent DLC thin film 2 is 30-250 nm inclusive and is greater than the radius of curvature (R1) of the tip end E of the pointed portion 1B; and a film thickness (d) of the water-repellent DLC thin film 2 is 15-150 nm inclusive.

Description

Microtome blades

[0001] The present invention relates to a blade for a microtome.

[0002] A microtome is a device used to thinly slice materials to prepare samples for use in optical microscope observations, etc. To improve the sharpness and durability of microtome blades, coatings are often applied to the blade surface. For example, Patent Document 1 discloses a durable cutting blade whose cutting edge is coated with a hard carbon film of several micrometers thick by a physical vapor deposition (PVD) method.

[0003] Japanese Patent Application Publication No. 02-041195

[0004] In recent years, particularly in the fields of medicine and biology, a large number of extremely thin samples have been produced each day using microtomes, creating a demand for improved cutting speed and further improvements in durability.

[0005] Although water repellency has been imparted to the cutting edge to reduce the frictional resistance of the blade surface and prevent the cut sample from sticking to the blade surface, the durable cutting blade of Patent Document 1 does not have sufficient water repellency at the cutting edge, and further improvement in water repellency was necessary to extract thin samples without damaging them. When cutting out samples as thin as a few micrometers, the cutting edge lacks sharpness and durability, which can lead to variations in the film thickness of the cut sample, leaving room for improvement.

[0006] Furthermore, the objects cut using a microtome range from soft tissues such as kidneys, hearts, livers, lungs, brains, mammary glands, and fat to hard tissues such as bones, teeth, calcified lungs, and calcified kidneys, and the methods for fixing these tissues vary widely. However, when using a microtome blade designed for cutting soft samples to cut hard samples, problems such as chipping and variations in the thickness of the cut ultrathin samples can easily occur. Therefore, conventional microtomes require different blades with different cutting angles to minimize chipping depending on the sample being cut. Microtome blades designed for cutting hard samples have a larger cutting angle to prevent chipping (chipping) at the cutting edge. For example, microtome blades designed for soft samples have a cutting angle of 22°, while microtome blades used for cutting hard samples such as water-soluble resin blocks and frozen blocks have cutting angles of 35° and 45°. However, this was still not enough to prevent chipping, and there was a demand for microtome blades that were less susceptible to chipping.In addition, microtome blades suitable for cutting hard samples tend to have a large cutting angle, and their sharpness tends to decrease when cutting soft samples, so improvements were needed.

[0007] The present invention has been made in consideration of the above circumstances, and aims to provide a microtome blade that suppresses chipping, has excellent sharpness and durability, and can cut well, regardless of the hardness of the sample (object to be cut) being cut.

[0008] The present inventors have conducted extensive research to solve the above problems and have found that the following inventions meet the above objectives, thereby completing the present invention.

[0009] <1> A microtome blade comprising: a blade body having a flat base and a pointed portion formed at the tip of the base; and a water-repellent DLC thin film formed on the pointed portion, wherein the water-repellent DLC thin film has a contact angle with water of 90 degrees or more, a radius of curvature (R1) of the tip of the pointed portion of 15 nm to 150 nm, a radius of curvature (R2) of the tip of the cutting edge including the water-repellent DLC thin film of 30 nm to 250 nm and is larger than the radius of curvature (R1) of the tip of the pointed portion, and a film thickness (d) of the water-repellent DLC thin film of 15 nm to 150 nm. <2> The microtome blade according to <1>, wherein the blade angle θ is 15 to 50 degrees. <3> The microtome blade according to <1> or <2>, wherein the water-repellent DLC thin film contains fluorine and / or silicon. <4> The microtome blade according to any one of <1> to <3>, wherein the blade body is made of cemented carbide. <5> The microtome blade according to <4>, wherein the cemented carbide has a binder content of 0% by mass or more and 24% by mass or less. <6> The microtome blade according to any one of <1> to <3>, wherein the blade body is made of stainless steel. <7> The microtome blade according to any one of <1> to <6>, wherein the water-repellent thin film has a contact angle with water of 90 degrees or more and 135 degrees or less. <8> The microtome blade according to any one of <1> to <7>, wherein the water-repellent DLC thin film is a thin film in which water-repellent properties are imparted to the DLC film itself, or a thin film in which a water-repellent layer is formed on the surface of the DLC film. <9> The microtome blade according to <8>, wherein the water-repellent layer is a water-repellent monomolecular film.

[0010] According to the present invention, a microtome blade is provided that suppresses chipping, has excellent sharpness and durability, and is capable of cutting well regardless of the hardness of the sample being cut out.

[0011] 1A and 1B are diagrams of a blade according to an embodiment of the present invention, in which (A) is a diagram showing the entire blade, and (B) is a diagram showing a partial enlargement of the blade. FIG. 1B is a diagram showing the vicinity of the tip of the cutting edge of the blade shown in FIG. 1. FIG. 1C is a diagram showing the vicinity of the tip of the cutting edge of a blade body of another embodiment. FIG. 1D is a diagram for explaining the rake angle and clearance angle of the blade shown in FIG. 1D. FIG. 1E is a diagram for explaining the movement of a sliding microtome blade in a thin-sectioning test of an example, as viewed from above. FIG. 1F is an image of thin sections sliced ​​using the microtome blades of Example 1 and Comparative Example 1, enlarged 500 times. FIG. 1A is an image of a thin section cut using Comparative Example 1, and FIG. 1B is an image of a thin section cut using Example 1. FIG. 1F is a diagram of a blade according to another embodiment of the present invention, in which (A) is a diagram showing the entire blade, and (B) is a diagram showing a partial enlargement of the blade.

[0012] The following describes in detail an embodiment of the present invention, but the following description of the constituent elements is one example (typical example) of an embodiment of the present invention, and the present invention is not limited to the following content unless the gist of the present invention is changed. Note that when the expression "~" is used in this specification, it is used as an expression including the numerical values ​​or physical property values ​​before and after it.

[0013] [Microtome Blade of the Present Invention] The microtome blade of the present invention (hereinafter sometimes referred to as the "microtome blade of the present invention") is a microtome blade comprising a blade body having a flat base and a pointed portion formed at the tip of the base, and a water-repellent DLC thin film formed on the pointed portion, wherein the water-repellent DLC thin film has a contact angle with water of 90 degrees or more, the radius of curvature (R1) of the tip of the pointed portion is 15 nm or more and 150 nm or less, the radius of curvature (R2) of the tip of the cutting edge including the water-repellent DLC thin film is 30 nm or more and 250 nm or less and is larger than the radius of curvature (R1) of the tip of the pointed portion, and the film thickness (d) of the water-repellent DLC thin film is 15 nm or more and 150 nm or less.

[0014] Here, the radius of curvature (R1) of the tip of the pointed portion and the radius of curvature (R2) of the tip of the cutting edge including the water-repellent DLC thin film can be calculated from an image of the width-thickness cross section of the blade (the b-c cross section in Figure 1) taken using an SEM. The radius of curvature (R1) of the tip of the pointed portion and the radius of curvature (R2) of the tip of the cutting edge including the water-repellent DLC thin film are the average values ​​of the radii of curvature calculated at three points on the left, center, and right sides of the cutting edge in the longitudinal direction. The film thickness (d) of the water-repellent DLC thin film is the distance from the tip of the pointed portion to the tip of the cutting edge including the water-repellent DLC thin film, and is the value obtained by subtracting the radius of curvature (R1) of the tip of the pointed portion from the radius of curvature (R2) of the tip of the cutting edge including the water-repellent DLC thin film. Details will be described later in the Examples.

[0015] The microtome blade of the present invention has a water-repellent DLC thin film formed on the pointed portion of the blade body, which has a contact angle with water of 90 degrees or more. This makes it easy to peel off the cut sample from the blade surface, and the cutting ability does not change regardless of the hardness of the cut sample, resulting in excellent chipping resistance and durability.

[0016] The microtome blade of the present invention has a radius of curvature (R1) of 15 nm or more and 150 nm or less at the tip of the pointed portion of the blade body. If R1 is less than 15 nm, chipping is likely to occur, resulting in scalpel scratches on the cut sample. On the other hand, if R1 exceeds 150 nm, the blade will not be sharp enough, the cutting load will be large, and the sample cannot be cut thinly at the level of several microns. R1 is preferably 30 nm or more, more preferably 50 nm or more, more preferably 60 nm or more, and even more preferably 70 nm or more. Furthermore, R1 is preferably 130 nm or less, more preferably 120 nm or less, and even more preferably 110 nm or less.

[0017] The microtome blade of the present invention has a curvature radius (R2) of 30 nm or more and 250 nm or less at the tip of the cutting edge including the water-repellent DLC thin film, and is larger than the curvature radius (R1) at the tip of the pointed portion. If R2 is less than 30 nm, chipping is likely to occur and the water-repellent DLC thin film is likely to peel off. On the other hand, if R2 exceeds 250 nm, the cutting performance is poor, the cutting load is large, and it is not possible to slice the sample thinly at the level of several microns. R2 is preferably 50 nm or more, more preferably 60 nm or more, more preferably 75 nm or more, and even more preferably 90 nm or more. Furthermore, R2 is preferably 200 nm or less, more preferably 180 nm or less.

[0018] In the microtome blade of the present invention, the thickness (d) of the water-repellent DLC thin film is 15 nm or more and 150 nm or less. If d is less than 15 nm, it becomes difficult to form a uniform water-repellent DLC thin film, which makes the cut sample prone to scalpel scratches, insufficient hardness, and the water-repellent DLC thin film prone to peeling due to friction, resulting in low durability. On the other hand, if d is more than 150 nm, the cutting performance deteriorates, the water-repellent DLC thin film peels off in a cracking manner, and durability is low. d is preferably 20 nm or more, more preferably 30 nm or more, more preferably 40 nm or more, and even more preferably 50 nm or more. d is preferably 130 nm or less, more preferably 110 nm or less.

[0019] The microtome blade configuration of the present invention is not significantly affected by the hardness of the sample being cut, and it is possible to maintain cutting quality while suppressing chipping and improving the life of the blade.

[0020] The blade angle of the microtome blade of the present invention is appropriately selected depending on the type and purpose of the sample to be cut, but the blade angle θ is preferably 15 to 50 degrees, and more preferably 15 to 35 degrees. A blade angle θ of 15 to 50 degrees ensures good cutting quality even when thinly slicing a sample.

[0021] The microtome blade of the present invention can have a blade body made of a cemented carbide alloy. By forming the blade body from a cemented carbide alloy, the phenomenon of rippling of the sliced ​​sample can be suppressed even when the sample is sliced ​​thinly.

[0022] The microtome blade of the present invention has a blade body made of a cemented carbide alloy, and the cemented carbide alloy preferably has a binder content of 0% by mass or more and 24% by mass or less. The use of such a cemented carbide alloy facilitates precise machining, and the tip of the pointed portion of the blade body can be easily shaped into a desired shape.

[0023] From the viewpoint of adhesion between the blade body and the water-repellent DLC thin film, it is preferable that the cemented carbide constituting the blade body of the microtome blade of the present invention contains tungsten carbide (WC) and cobalt (Co), and that the cobalt content in the cemented carbide is 14 mass% or more.

[0024] In the microtome blade of the present invention, the contact angle of the water-repellent DLC thin film with water is preferably 90 to 135 degrees, more preferably 95 to 130 degrees, more preferably 100 to 125 degrees, and even more preferably 105 to 120 degrees. Having such a contact angle makes it difficult for the sample to stick to the blade surface, improving sharpness.

[0025] In the microtome blade of the present invention, the contact angle of the water-repellent thin film with water is preferably 90 to 135 degrees, more preferably 95 to 130 degrees, more preferably 100 to 125 degrees, and even more preferably 105 to 120 degrees, R1 is 15 to 150 nm, preferably 30 to 145 nm, more preferably 40 to 140 nm, more preferably 50 to 130 nm, more preferably 60 to 120 nm, more preferably 70 to 110 nm, and even more preferably 75 to 100 nm, R2 is 30 to 250 nm, preferably 30 to 200 nm, more preferably 50 to 180 nm, more preferably 60 to 175 nm, more preferably 75 to 170 nm, more preferably 80 to 160 nm, and even more preferably 90 to 150 nm, and d is 15 nm to 150 nm, preferably 20 nm to 130 nm, more preferably 25 nm to 125 nm, more preferably 30 nm to 120 nm, more preferably 40 nm to 100 nm, and even more preferably 50 nm to 80 nm.

[0026] The microtome blade of the present invention can be used to cut out objects (cutting materials) such as kidneys, hearts, livers, lungs, brains, mammary glands, fat, bones, teeth, calcified lungs, and calcified kidneys. The microtome blade configuration of the present invention allows for good cutting regardless of the hardness of the object being cut out. Furthermore, the microtome blade of the present invention can be used in both sliding and rotary cutting methods.

[0027] [Embodiment 1] A blade according to an embodiment of the present invention will be described below with reference to Figures 1 to 3. Figure 1 shows the entire blade according to an embodiment of the present invention and a partially enlarged view of the blade. Figure 2 shows the vicinity of the tip of the cutting edge of the blade shown in Figure 1. Figure 3 shows the vicinity of the tip of the cutting edge of a blade body of another embodiment.

[0028] 1, a blade 10 according to an embodiment of the present invention is a flat blade made of cemented carbide and having a linear cutting edge. The blade 10 is used as a replaceable blade for a microtome, which slices specimens such as bones or paraffin-embedded tissues into extremely thin sections having thicknesses on the order of micrometers to several tens of nanometers (e.g., about 1 to 3 μm).

[0029] The blade body 1 of the blade 10 shown in Figure 1 is formed to have a blade length L of approximately 80 mm, a thickness t of approximately 0.25 mm, and a width W of approximately 8 mm. The blade body 1 has a base 1A with a width W1 of approximately 7.3 mm and a pointed portion 1B extending from the base 1A to the tip and having a width W2 of approximately 0.7 mm.

[0030] Both ends of the cutting edge of the blade body 1 are chamfered (chamfered) with triangular notches. In this embodiment, the four corners are chamfered. The C-faces are formed by cutting out an isosceles triangle with equal sides of approximately 2 mm. Even if a 45° shear angle is applied to a workpiece (e.g., a thin-sectioned specimen) with a blade length L of approximately 80 mm using a sliding microtome, the length of the blade body 1 is approximately 1 / cos 45° (1.4114) times the length, or approximately 42 mm, and therefore the four corners of the blade 10 with the C-faces formed are non-cutting portions.

[0031] The pointed portion 1B is formed in a tapered shape that gradually becomes thinner from the base portion 1A. In the shape of the pointed portion 1B shown in FIG. 1, the angle formed by the front and back surfaces of the pointed portion 1B is constant from the base portion 1A to the tip E of the cutting edge. Note that the shape of the pointed portion 1B is not limited to this, and it may be configured as a multi-stage blade having multiple regions between the base portion 1A and the tip E of the cutting edge where the angles formed by the front and back surfaces of the pointed portion 1B are different. Furthermore, although the pointed portion 1B has a symmetrical shape on the front and back, it may also have an asymmetrical shape on the front and back.

[0032] As shown in Figure 2, the tip E of the cutting edge of the pointed portion 1B is formed with a blade angle (blade edge angle) θ of 15 to 50 degrees. The blade angle θ of the pointed portion 1B of the blade 10 is the angle (blade edge angle) that forms the tip E of the pointed portion 1B, and is the angle at the intersection formed when the blade faces (blade surfaces) on both the front and back sides of the pointed portion 1B are extended. A smaller blade angle θ improves cutting quality, but chipping becomes more likely to occur, shortening the lifespan. On the other hand, if the blade angle θ is too large, cutting quality deteriorates.

[0033] The blade angle θ is the angle between the rake face and the flank of the blade when cutting a sample using the blade 10. As shown in FIG. 4 , the clearance angle β1 is the angle between the flank 12 and a reference line H parallel to the direction in which the blade moves (the cutting direction), and the rake angle β2 is the angle between the rake face 11 and a reference line V perpendicular to the direction in which the blade moves, and the sum of the blade angle θ, the clearance angle β1, and the rake angle β2 is 90 degrees. The clearance angles β1 and β2 are set appropriately depending on the blade angle θ. For example, when cutting a sample using a blade 10 with a blade angle θ of 20 to 35 degrees, the clearance angle β1 can be 10 to 25 degrees, and the rake angle β2 can be 60 to 30 degrees (β2 = 90 degrees - β1 - θ).

[0034] The blade 10 has a high-hardness, water-repellent DLC thin film and is excellent in durability and ease of peeling off cut samples, so it is possible to maintain cutting quality even when the blade angle θ is increased compared to conventional microtome blades for soft samples, and by increasing the blade angle θ, chipping is less likely to occur even when cutting hard samples. From these perspectives, the shear angle of the microtome is also taken into consideration, but in order to maintain cutting quality, suppress chipping, and improve service life without being greatly affected by the hardness of the cut sample, the blade angle θ is preferably 15 degrees to 45 degrees, and more preferably 18 degrees to 40 degrees, 20 degrees to 35 degrees, 22 degrees to 34 degrees, 23 degrees to 33 degrees, 25 degrees to 31 degrees, 26 degrees to 30 degrees, or 27 degrees to 29 degrees.

[0035] 1 and 2, the shape of the tip E of the pointed portion 1B is a shape that slopes linearly from both sides of the base portion 1A toward the tip E of the cutting edge so as to approach each other, but as shown in Fig. 3, the pointed portion 1B may be a shape that curves from a straight line to connect to the tip E of the cutting edge. In this case, the radius of curvature (R1) of the tip E and the cutting edge angle θ are as shown in Fig. 3.

[0036] The radius of curvature (R1) of the tip E of the pointed portion 1B is 15 nm to 150 nm.

[0037] As shown in Figure 2, a water-repellent DLC thin film 2 is formed on the pointed portion 1B. The radius of curvature (R2) of the tip F of the cutting edge including the water-repellent DLC thin film 2 is larger than the radius of curvature (R1) of the tip E of the pointed portion 1B and is 30 nm to 250 nm. The thickness (d) of the water-repellent DLC thin film 2 is 15 nm to 150 nm.

[0038] The cemented carbide (Cemented Carbide) forming the blade body 1 is a composite material in which metal particles made of carbides of metals from Groups IVa, Va, and VIa of the periodic table are sintered with a binder made of an iron-based metal such as Fe, Co, or Ni. There are no particular limitations on the cemented carbide forming the blade body 1, but examples that can be used include WC—Co alloys, WC—TiC—Co alloys, WC—TaC—Co alloys, WC—TiC—TaC—Co alloys, WC—Ni alloys, and WC—Ni—Cr alloys.

[0039] For example, a cemented carbide material containing WC and Co can be obtained by sintering a mixture containing WC particles and Co. While various particle sizes can be used for the WC particles, from the viewpoint of preventing chipping during machining of the cutting edge, the particle size of the WC particles is preferably 0.1 μm to 0.7 μm, and more preferably 0.3 μm to 0.7 μm. The "particle size" refers to the average particle size measured by the Sub Sieve Sizer method. The average particle size measured by the Sub Sieve Sizer method is calculated by passing air through a sample, measuring the flow rate and pressure drop, and then determining the specific surface area. The permeation method can use the Fischer method or the Blaine method.

[0040] Furthermore, if the particle size of the WC particles used is larger than the diameter (R1 x 2) of the intended circle of curvature of the tip E of the pointed portion 1B, the WC must be cut to achieve the desired radius of curvature (R1) for the tip E. It is important that the cutting stress at this time is smaller than the bonding strength with the Co that connects the WC. If the cutting stress exceeds this bonding strength, the WC particles will peel off and the cutting edge will become chipped. From the perspective of strength, the hardness of the cemented carbide material is preferably 85 (HRC) or higher, the transverse rupture strength of the cemented carbide material is preferably 3.0 GPa to 4.0 GPa, and the Young's modulus of the cemented carbide material is preferably around 570 GPa.

[0041] Considering the balance between hardness, wear resistance, chipping resistance, adhesion of the water-repellent DLC thin film, and formability of the water-repellent DLC, the content of the binder in the cemented carbide is preferably 14% by mass to 30% by mass, more preferably 16% by mass to 27% by mass, more preferably 17% by mass to 25% by mass, still more preferably 17% by mass to 24% by mass, and even more preferably 18% by mass to 22% by mass.

[0042] Among these, the cemented carbide alloy forming the blade body 1 is preferably a cemented carbide alloy containing WC and Co, and preferably the cobalt content in the cemented carbide alloy is 14% by mass or more. Here, it is generally believed that water-repellent DLC thin films have a high affinity with carbon-containing substrates because they contain carbon atoms, and it has been commonly believed that the lower the amount of Co (cobalt), known as a binder, the easier it is for a cemented carbide alloy to adhere a DLC coating. For cemented carbide alloys containing WC and Co, a higher WC content increases the alloy's hardness, resulting in a blade with less wear and is also considered preferable for suppressing waviness in cut samples. However, the inventors discovered that increasing the WC content increases the susceptibility of the blade to chipping and reduces the adhesion of the water-repellent DLC thin film, making it more susceptible to peeling. Conversely, increasing the Co content improves the adhesion of the water-repellent DLC thin film. By increasing the amount of Co in a cemented carbide alloy containing WC and Co to a certain level or more, the adhesion between the blade body and the water-repellent DLC thin film is improved, making chipping less likely.

[0043] The content of cobalt in the cemented carbide containing WC and Co is preferably 14% by mass or more, more preferably 16% by mass or more, still more preferably 17% by mass or more, and even more preferably 18% by mass or more, in order to improve the adhesion of the water-repellent DLC thin film and the bonding strength between WC and Co.

[0044] On the other hand, if the proportion of WC is low, the material is prone to wear and is not suitable for cutting tools, so the cobalt content in the cemented carbide is preferably 30 mass% or less, more preferably 27 mass% or less, more preferably 25 mass% or less, more preferably 24 mass% or less, and even more preferably 22 mass% or less.

[0045] Considering the balance between hardness, wear resistance, chipping resistance, adhesion of the water-repellent DLC thin film, and formability of the water-repellent DLC, the content of cobalt in the cemented carbide is preferably 14% by mass to 30% by mass, more preferably 16% by mass to 27% by mass, more preferably 17% by mass to 25% by mass, still more preferably 17% by mass to 24% by mass, and even more preferably 18% by mass to 22% by mass.

[0046] The cemented carbide of the blade body 1 is not limited to a composite material of a carbide of a metal from Groups IVa, Va, or VIa of the periodic table and a binder of an iron-based metal such as Fe, Co, or Ni. It may also be made of a binderless material (a binderless material) made by sintering a carbide of a metal from Groups IVa, Va, or VIa of the periodic table. The microtome blade of the present invention has a water-repellent DLC thin film of a specific thickness formed on the sharpening portion, thereby suppressing chipping even when the blade body is made of a binderless cemented carbide or a cemented carbide with a low binder content. From the perspective of ease of machining the tip shape of the sharpening portion of the blade body, the binder content of the cemented carbide is preferably 0% to 24% by mass, and more preferably 6% to 24% by mass.

[0047] Furthermore, the blade body 1 is not limited to being made of cemented carbide, but may be made of stainless steel or special steel.

[0048] (Water-repellent DLC thin film) The water-repellent DLC thin film 2 is a thin film that has been given water-repellency by incorporating fluorine, silicon, etc. DLC is an abbreviation for Diamond-Like Carbon, and is a film with an amorphous structure whose main component is carbon that has the carbon-carbon bonds of both diamond and graphite.

[0049] The water contact angle of the water-repellent DLC thin film 2 is 90 degrees or more. Higher water repellency reduces the likelihood of the cut sample adhering to the blade surface, improving sharpness. Therefore, the water contact angle of the water-repellent DLC thin film 2 is preferably 95 degrees or more, more preferably 100 degrees or more, and even more preferably 105 degrees or more. The "water contact angle" is the average value of water contact angles measured at three points on the left, center, and right sides of the water-repellent DLC thin film 2 in the longitudinal direction (the direction of arrow a in FIG. 1 ).

[0050] There is no particular upper limit to the contact angle of the water-repellent DLC thin film 2 with respect to water, but taking into consideration productivity and the like, it can be set to, for example, 135 degrees or less, 130 degrees or less, 125 degrees or less, or 120 degrees or less.

[0051] The water-repellent DLC thin film 2 is formed on the pointed portion 1B. The water-repellent DLC thin film 2 may be formed at least on the tip E side of the pointed portion 1B (for example, a region of 1 μm to 20 μm including the tip E of the pointed portion 1B), but it is preferably formed over the entire pointed portion 1B so that the cut sample does not stick to the pointed portion 1B and can be easily peeled off.

[0052] [Embodiment 2] The microtome blade 30 shown in Figure 7 is made of cemented carbide and has a two-stage cutting edge. The blade body 3 of the blade 30 includes a base 3A and a pointed portion 3B. The pointed portion 3B has a first region A1 including the tip of the cutting edge and a second region A2 extending from the first region A1 to the base 3A, which is a third region A3. The second region A2 is wider than the first region A1. The water-repellent DLC thin film (not shown) formed on the pointed portion 3B of the blade body 3 of the blade 30 includes a DLC thin film and a water-repellent layer formed on the surface of the DLC thin film, and has a thickness (d) (i.e., the total thickness of the DLC thin film and the water-repellent layer) of 15 nm to 150 nm. The water-repellent layer constituting the water-repellent DLC thin film of the blade 30 is a water-repellent coating layer formed by applying a water-repellent coating agent. For example, the water-repellent layer can be a fluorine-based monomolecular film with a thickness of about 10 nm that is coated with a fluorine-based coating agent, but the water-repellent layer is not limited to this.

[0053] The blade 30 is similar to the blade 10 except for the shape of the blade body and the configuration of the water-repellent DLC thin film. The contact angle of the water-repellent DLC thin film of the blade 30 with water, the radius of curvature (R1) of the tip of the pointed portion, the radius of curvature (R2) of the tip of the cutting edge, the film thickness (d) of the water-repellent DLC thin film, and the blade angle θ are similar to those of the blade 10, and the preferred ranges are also similar.

[0054] The water-repellent DLC thin film is not particularly limited as long as it has an amorphous structure containing carbon and the surface of the thin film is water-repellent, but preferably contains carbon and fluorine and / or silicon. Also, the thin film may contain fluorine or silicon throughout, or only the surface of the DLC thin film may be modified with fluorine or silicon to be water-repellent.

[0055] Specifically, the water-repellent DLC thin film constituting the microtome blade of the present invention can be a thin film in which the DLC film itself has been given water-repellent properties, or a thin film in which a water-repellent layer has been formed on the surface of the DLC film. Examples of thin films in which the DLC film itself has been given water-repellent properties include thin films in which the DLC film itself contains fluorine, silicon, or the like. Examples of thin films in which a water-repellent layer has been formed on the surface of the DLC film can include thin films in which a water-repellent layer has been formed on the surface of a DLC film that has not been given water-repellent properties, or thin films in which a water-repellent layer has been formed on the surface of a DLC film that has been given water-repellent properties. Examples of water-repellent layers include water-repellent monomolecular films.

[0056] (Method for Manufacturing Microtome Blade of the Present Invention) The microtome blade of the present invention can be manufactured by, for example, forming a water-repellent DLC film on the cutting edge side of the pointed portion of a blade body made of cemented carbide or stainless steel. There are no particular limitations on the method for forming the DLC thin film, and known methods can be used, such as plasma CVD, pulsed plasma CVD, and thermal electron impact ionization deposition, which use hydrocarbon gases as the carbon source, and arc ion plating, magnetron sputtering, and ion beam sputtering, which use solid carbon (graphite) as the carbon source.

[0057] For example, by using a hydrocarbon gas containing fluorine or silicon, it is possible to form a water-repellent DLC film containing fluorine or silicon throughout the DLC film.

[0058] Furthermore, a water-repellent DLC thin film having a water-repellent layer on its surface can be formed, for example, by depositing a DLC thin film or a DLC thin film containing fluorine or silicon, and then dipping the film in a fluorine-based water-repellent coating agent.

[0059] Furthermore, when the tip of the cutting edge is sharpened (i.e., the radius of curvature R1 of the tip E is set to a predetermined thickness) as in the blade body 1, deposition by the PVD (physical vapor deposition) method may cause chipping due to damage to the cutting edge, making the deposition conditions and control more complicated. CVD method makes it easy to deposit a water-repellent DLC thin film while reducing damage to the cutting edge, and is therefore one of the preferred methods for depositing DLC ​​thin films.

[0060] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not changed.

[0061] [Evaluation] (Measurement of Water Contact Angle) The water contact angles of the cutting edges of the blades coated with the water-repellent DLC thin film of this example and a comparative microtome blade were measured using a NICK LSE100T. 0.01 to 0.12 μL of pure water was dropped onto the cutting edge of each blade at room temperature at three points along its length: the left side (10 mm from the left end of the blade), the center (40 mm from the left end of the blade), and the right side (70 mm from the left end of the blade). The contact angles (static contact angles) were measured approximately 1000 ms later according to the θ / 2 method, and the average of these three points was taken as the water contact angle.

[0062] (Thin-section test) A microtome blade manufactured under the conditions of this example was attached to a microtome and subjected to a thin-section test. As shown in FIG. 5, a sliding microtome was used. The cutting edge of the blade attached to a holder (not shown) was positioned at a predetermined angle (α was 27.5° in this example) relative to the reference line L11, and the blade was moved back and forth perpendicular to the reference line L11 to slice the workpiece into sections. One end of the microtome blade was provided with a mark M (see FIG. 5) to distinguish between the front and back sides. During the thin-section test, the cutting edge was inclined relative to the reference line L11, and the workpiece moved back and forth perpendicular to the reference line L11, ensuring that the position where the cutting edge first contacted the workpiece remained the same. A mark line was provided across the width of the blade so that the initial position would be the same when the blade was removed and reattached to the workpiece.

[0063] (Adhesion Evaluation) Cutting debris generated when sawing a pig femur was degreased with ethanol and then dried. Pieces of debris less than 1 mm in size (selected mainly from 0.5 mm diameter) were grasped with tweezers and embedded in the viscera to be embedded, and this was used as the cutting object. Using the prepared cutting object, thin-section tests of 2 μm to 4 μm thickness were repeatedly performed using the method described in the thin-section test above. If the water-repellent DLC thin film on the cutting edge peels off, the thin-sectioned pieces will no longer curl, so the curling state of the thin-sectioned pieces was checked on the first and 20th times to evaluate adhesion. Adhesion was evaluated according to the following criteria: ○: Curls at a diameter of 1 mm or less. △: No curl, or the entire thin-sectioned piece curls but the curl diameter is large (2 mm or more). ×: Cannot be cut.

[0064] (Evaluation of Sharpness) Using paraffin-embedded specimens of pig stomach, brain, kidney, liver, and lung, each specimen was sliced ​​500 times using the method described in the thin sectioning test above. The curling state of each sliced ​​specimen was checked and evaluated according to the following criteria: ○: Curled at a diameter of 1 mm or less; △: No curl, or the entire slice curled but the curl diameter was large (2 mm or more); ×: Unable to cut.

[0065] (Chipping evaluation) A thin-slicing test was conducted in the same manner as the sharpness evaluation, and the first time (initial performance) was checked, and thereafter, the presence or absence of scalpel scratches on the thin-sliced ​​sample was checked every 100 times. If scalpel scratches were found on the thin-sliced ​​sample, the test was stopped temporarily and the microtome blade was checked. The location of the microtome blade that was thought to be the cause of the scalpel scratches was observed under a microscope capable of magnification of 500 to 2500 times, and the depth and width of the chipping were confirmed and evaluated according to the following criteria. ○: Less than 2 μm in both depth and width direction △: 2 μm or more in both depth and width direction ×: Unable to cut

[0066] (Measurement of R1, R2, and d of Microtome Blade) The cutting edge of the microtome blade of this example was observed at a magnification of 20,000 times using an electron microscope (Electron Beam Cutting Edge Analysis Device ERA-8900 manufactured by Elionix Co., Ltd.), and the surface condition was observed. Using the blade body before the water-repellent DLC thin film was formed, the radius of curvature (R1) of the tip E was measured at three points along the length of the cutting edge: the left side (10 mm from the left end of the blade), the center (40 mm from the left end of the blade), and the right side (70 mm from the left end of the blade), and the average was calculated. Next, after the water-repellent DLC thin film was formed on the blade body, the radius of curvature (R2) of the tip F was measured at three points along the length of the cutting edge: the left side (10 mm from the left end of the blade), the center (40 mm from the left end of the blade), and the right side (70 mm from the left end of the blade), and the average was calculated. The thickness (d) of the water-repellent DLC thin film was determined by calculating the difference between the radius of curvature (R2) of tip F and the radius of curvature (R1) of tip E at each of the three points and averaging the results.

[0067] Comparative Example 1 A blade body made of the following material and shape was installed in the chamber of a plasma CVD deposition device, and a DLC thin film was formed. It was then dipped into a fluorine-based water-repellent coating agent to form a water-repellent monomolecular film, resulting in a water-repellent DLC thin film containing carbon and fluorine. Blade body: WC-Co alloy (Co content 19% by mass) Blade length L: 80 mm Thickness t: 0.25 mm Width W: 8 mm, width W1: 7.3 mm, width W2: 0.7 mm Blade angle θ: 28 degrees Radius of curvature (R1) of the tip E of the pointed portion: 40 nm

[0068] When the cutting edge after the water-repellent DLC thin film was formed was observed with an optical microscope, it was found that the water-repellent DLC thin film was significantly uneven, with the film formation condition particularly variable at the tip (ridge line) of the cutting edge, and the film thickness (d) of the formed film was greater than 150 nm.

[0069] Example 1: A blade body similar to that of Comparative Example 1 was installed in the chamber of a plasma CVD deposition device, and a DLC thin film was formed. The blade was then dipped in a fluorine-based water-repellent coating agent to form a water-repellent monomolecular film, resulting in a water-repellent DLC thin film containing carbon and fluorine. The radius of curvature (R2) of the tip F of the blade, including the water-repellent DLC thin film, was 150 nm.

[0070] When the cutting edge after the water-repellent DLC thin film was formed was observed with an optical microscope, it was found that the water-repellent DLC thin film on the microtome blade of Example 1 had almost no irregularities and was formed uniformly.

[0071] When the contact angles of the cutting edge of the microtome blade of Example 1 with water were measured, they were 116.1 degrees on the left side, 120.1 degrees in the center, and 116.3 degrees on the right side, with an average of 117.5 degrees.

[0072] (Thin Sectioning Test 1) Figure 6 shows 500x magnification images of tissue obtained by attaching the manufactured blade to a sliding microtome and slicing an object containing embedded pig liver cells to a thickness of 2 µm. Figure 6(A) is an image of a thin section cut using the microtome blade of Comparative Example 1, and Figure 6(B) is an image of a thin section cut using the microtome blade of Example 1. When the microtome blade of Comparative Example 1 was used, scalpel scratches were generated, but the microtome blade of Example 1 suppressed the generation of scalpel scratches, and a good sample was obtained.

[0073] (Thin Sectioning Test 2) A thin sectioning test was conducted using the microtome blade of Example 1. Before cutting out the bone, which was the object to be cut, paraffin was used as the object to be cut, and the object was sliced ​​10 times at 2 μm. After slicing the bone 90 times, paraffin was used as the object to be cut, and the object was sliced ​​at 2 μm. For comparison, a similar experiment was conducted using a fluororesin-coated microtome blade (steel blade, blade body: stainless steel, R2: approximately 25 nm, blade angle: 35 degrees, contact angle of coating film with water (average of three points): 88.6 degrees). The results are shown in Table 1. As shown in Table 1, it can be seen that the microtome blade of Example 1 produced thin sections with a more stable thickness than the comparative example.

[0074]

[0075] (Thin-section test 3) Using the microtome blade of Example 1, a thin-section test was conducted on a human lung as the cut object, following the procedures of an ethical committee, etc. Human lungs are densely packed with blood vessels, many of which are calcified, making them one of the cut objects prone to chipping. The comparative steel blade was used in three separate positions, and had to be replaced 50 times at each position, for a total of 150 times, whereas the microtome blade of Example 1 was able to slice more than 660 times at one position without any problems.

[0076] Examples 2 and 3: Blade bodies made of WC—Co alloys with a Co content of 12% by mass or 19% by mass and having the same shape as in Example 1 were used. Blades with a water-repellent DLC thin film and a tip F with a radius of curvature (R2) of 120 μm and 140 μm were manufactured in the same manner as in Example 1, except that the film formation conditions were changed.

[0077] Table 2 shows the results of the evaluation of the adhesion of the water-repellent DLC thin film.

[0078]

[0079] A water-repellent DLC thin film with the thickness shown in Table 3 was formed in the same manner as in Example 1, except that a blade body made of the following material and shape was attached to a plasma CVD deposition device and the film formation conditions were changed. Blade body: WC-Co alloy (Co content 24% by mass) Blade length L: 80 mm Thickness t: 0.25 mm Width W: 8 mm, width W1: 7.3 mm, width W2: 0.7 mm Blade angle θ: 20° to 35° Table 3 shows the results of evaluating the adhesion, sharpness, and chipping of the manufactured blades.

[0080]

[0081] The microtome blade of the present invention can be attached to a microtome used for slicing various tissues, and is therefore industrially useful.

[0082] 1, 3 Cutting tool body 11 Rake face 12 Flank face 1A, 3A Base portion 1B, 3B Point portion 2 Water-repellent DLC thin film 10, 30 Cutting tool A1 First region A2 Second region A3 Third region E, F Tip R1 Radius of curvature of tip E R2 Radius of curvature of tip F d Film thickness t Thickness of cutting tool body θ Cutting tool angle L Cutting length W, W1, W2 Width V, H Reference line

Claims

1. A microtome blade comprising: a blade body having a flat base and a pointed portion formed at the tip of the base; and a water-repellent DLC thin film formed on the pointed portion, wherein the water-repellent DLC thin film has a contact angle with water of 90 degrees or more, the radius of curvature (R1) of the tip of the pointed portion is 15 nm or more and 150 nm or less, the radius of curvature (R2) of the tip of the blade edge including the water-repellent DLC thin film is 30 nm or more and 250 nm or less and is larger than the radius of curvature (R1) of the tip of the pointed portion, and the thickness (d) of the water-repellent DLC thin film is 15 nm or more and 150 nm or less.

2. A microtome blade as claimed in claim 1, wherein the blade angle θ is 15 to 50 degrees.

3. A microtome blade according to claim 1 or 2, wherein the water-repellent DLC thin film contains fluorine and / or silicon.

4. A microtome blade as claimed in claim 1 or 2, wherein the blade body is made of cemented carbide.

5. A microtome blade as described in claim 4, wherein the binder content in the cemented carbide is equal to or greater than 0 mass % and equal to or less than 24 mass %.

6. A microtome blade as claimed in claim 1 or 2, wherein the blade body is made of stainless steel.

7. A microtome blade as claimed in claim 1 or 2, wherein the water-repellent DLC thin film has a contact angle with water of 90 degrees or more and 135 degrees or less.

8. A microtome blade as claimed in claim 1 or 2, wherein the water-repellent DLC thin film is a thin film in which the DLC film itself has been given water-repellency, or a thin film in which a water-repellent layer is formed on the surface of the DLC film.

9. The microtome blade of claim 8, wherein the water-repellent layer is a water-repellent monolayer.

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