JPS6044724B2 - Method for manufacturing cantilevers in record playback cartridges - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention combines ligrin, which is a major component of wood along with cellulose and is abundantly present in nature, and inorganic powders such as ceramic powder, glass powder, and carbon powder (carbon black, graphite powder). The present invention relates to a method for manufacturing a cantilever in a record reproducing cartridge, in which the mixture is mixed, formed into a desired shape such as a rod or pipe to become a cantilever, and heated and carbonized.

What is desired for a cantilever for a record playback cartridge is that the Young's modulus E is large enough to prevent splitting vibrations in order to extend the playback frequency band to high frequencies, and that the material can be easily processed to reduce the equivalent mass of the needle tip. A uniform and structurally robust finish is required.

By the way, aluminum, titanium, etc. have been used as materials for this type of cantilever in the past, but these materials have excellent workability and have a density ρ of 2.69 (yld) for aluminum and 4.69 (yld) for titanium. 54(y
Id) is relatively small, but the Young's modulus E is small, making it difficult to produce a high-performance cantilever.

On the other hand, beryllium is a typical material with a large Young's modulus E and a small density ρ, but beryllium is mechanically brittle and therefore extremely difficult to process into thin tubes and is toxic. Therefore, preventive measures at the manufacturing stage are expensive, resulting in high product costs. Therefore, the present inventor focused on carbon as a material that is lightweight, has high rigidity, and has a large ratio E/ρ between Young's modulus E and density ρ, and previously proposed a cantilever made of carbonized or graphitized synthetic resin. It has been confirmed that in the carbonization and graphitization processes of synthetic resins, the material undergoes severe shrinkage and deformation, causing cracks and other problems.

That is, lignin and inorganic powder are mixed, molded into a desired shape to form a cantilever, and then this molded product is carbonized to obtain a cantilever having the above characteristics.

Lignin, along with cellulose, is a major component of wood and is one of the substances that exist abundantly in nature.

Although the chemical structure of lignin is not clear, its structural unit is a propylbenzene derivative having a substituent such as a hydroxyl group or a methoxyl group on an aromatic ring. Various methods are known for separating lignin from plants, but when wood chips are steamed at high temperature and pressure when pulping wood, wood is heated to 170'C with sodium hydroxide and sodium sulfide. The Kraft method (KP method) uses bisulfite (calcium or sodium salt), and the sulfide method (SP method) uses bisulfite (calcium or sodium salt). The lignin used in the present invention may be obtained by any method such as the KP method or the SP method, regardless of the method for producing it.

Additionally, when carbonizing a carbonaceous material, large deformations are generally involved, which is a disadvantage if the molded product obtained after carbonization requires structural uniformity or has a complicated shape. There are many.

Therefore, when lignin is used alone, it tends to be deformed when it is formed into the shape of a cantilever and carbonized, so the inventor considered adding solid powder. By the way, when carbonizing lignin, temperatures of 1000'C or more are experienced, so it is necessary that the process does not easily deform or melt even at that temperature, and inorganic powders such as ceramic powder, glass powder, and carbon powder have been derived. The most preferred of these inorganic powders is graphite powder (scaly graphite), and by adding graphite powder, (1) shrinkage and deformation that occur during pre-firing and carbonization can be prevented; 2) When forming a mixture of lignin and graphite powder into the shape of a cantilever, the graphite powder is oriented, improving the elastic modulus and mechanical strength; (3) During carbonization, the graphite powder forms crystal nuclei. Therefore, effects such as the ability to obtain carbon with good crystallinity, the ability to greatly improve the elastic modulus and mechanical strength after carbonization, and (4) the ability to process up to graphitization (at 2000° C. or higher) can be expected. The cantilever manufacturing process of the present invention is shown in the figure, and the process shown in the figure will be explained below.

Kneading process Inorganic powder with a particle size of 0.1 to 10 μm is added to lignin, mixed and kneaded using a roller or roller.

At this time, one or more of carboxymethylcellulose, sodium carboxymethylcellulose (hereinafter both referred to as CMC), and polyvinyl alcohol (hereinafter referred to as PVA) is added to the mixture of lignin and inorganic powder. is desirable. In addition, as an additive, 10
If aluminum chloride is kneaded at the same time in an amount of Wt% or less, good crystalline carbide can be obtained during carbonization. Some lignins are soluble in water and others are soluble in alkaline solutions.
Either can be used, but if you are using a water-soluble product, add water during kneading, and if you are using a product that is soluble in an alkaline solution, add sodium hydroxide to water and mix thoroughly. Knead. The mixture of lignin and inorganic powder ranges from 10 to 90 wt% inorganic powder, but 3
Good results can be obtained with 0 to M%, and the particle size of the inorganic powder varies depending on the shape and size of the cantilever, but in general, the smaller the better, and preferably 0.1 to several μm or less. It should be noted that if the amount of inorganic powder added is less than 10%, the effect described above is almost lost, and if it is more than 90%, the mechanical strength after carbonization decreases. Also, when adding CMC and PVA, the appropriate weight ratio to lignin is about 5 to 60%, and by adding CMC and PVA,
This has the advantage that the kneaded material can be easily formed into a cantilever in the next step, and the mechanical strength of the formed product is increased.

Furthermore, since shrinkage increases in the drying process after molding, it is desirable to reduce the amount of water and alkaline solution to the extent that the diaphragm can be molded. Molding process The mixed and kneaded lignin and inorganic powder then enters the molding process.

In this forming step, the kneaded material obtained in the previous step is formed into the desired shape of the cantilever, such as a rod shape or a pipe shape. It is desirable to press and mold the material by holding it in a shaped press die.

In addition, in the molding process, instead of molding using a press mold, extrusion molding may be used.

It is also preferable to take into consideration the stylus attachment hole when forming the stylus attachment hole. Drying process This process is the process of drying the molded product formed into the shape of the cantilever. At this time, in order to maintain the shape of the cantilever, a wire mesh or punching metal is placed on a jig formed into the shape of the cantilever. and dry.

It is preferable to use hot air at 90°C for drying, but it is also possible to dry using an oven or the like, and the drying time must be at least 2 hours, preferably about 100 hours.

Carbonization Step The molded product that has undergone the drying step is carbonized by heating to 1000 to 1500'C in a non-oxidizing atmosphere such as nitrogen or argon gas.

In this carbonization step, it is necessary to slow down the initial temperature increase rate. That is, the heating rate is 1 to 20'C/hour up to 400°C, and 10 to 100'C/hour above 400°C.
It is preferable to carry out the heating at a heating rate of 1 hour. This is because if the initial heating rate is increased, the carbon material will have a rough structure and both Young's modulus and mechanical strength will decrease.
When the temperature is 00'C or higher, it is carried out at a suitably fast speed in consideration of economic efficiency. Since the molded product is deformed during carbonization, it is preferable to carry out carbonization by placing or holding the molded product on a jig formed into the shape of a cantilever and made of carbon or a high-melting point metal. In addition, before starting the carbonization process, the molded product obtained in the drying process is heated to 300°C in an oxidizing atmosphere such as air.
Heating at a heating rate of ~40°C/hour, heating at 300°C for 5~(
) The properties after carbonization are improved by holding it for a long time.

The steps of the present invention have been described in detail above, and one embodiment of the present invention will be described below. Graphite powder 45Wt. %, aluminum chloride 5wt%, CMc2OWt%, and lignin 30wt% were kneaded in a kneader, molded into a rod shape, and dried in air at a temperature of 100°C for 20 hours. and then heated to 1250°C in nitrogen gas,
Carbonize.

The cantilever thus obtained has a Young's modulus of 18
000k91?2, density 1.6q1c! It has physical properties of l.

The physical properties of the cantilever of the present invention according to this example and the cantilever made of conventionally used materials (aluminum, beryllium) are shown in the table below.

As shown in the table, those using lignin have a specific elastic modulus E/ρ that is about four times that of aluminum, which is slightly inferior to beryllium, but the internal loss is about 100% higher than that of beryllium. Therefore, the Q of resonance in the high frequency range (high frequency resonance frequency FH) is low, resulting in flat characteristics, and overall it is possible to obtain characteristics superior to beryllium.

As explained above, by mixing lignin and inorganic powder and carbonizing the molded product, a lint lever with a large specific elastic modulus and a large internal loss can be manufactured at low cost through a simple process.

[Brief explanation of drawings]

The figures are process diagrams for explaining the manufacturing method of the present invention.

Claims (1)

[Claims] 1. A record reproducing cartridge characterized in that lignin and inorganic powder are mixed and kneaded, molded into a shape to become a cantilever, dried, and then heated in a non-oxidizing atmosphere to carbonize it. How to make a cantilever.