JPS59214624A - Manufacture of information signal recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled product in which the carbon is dispersed favorably, by mixing and dispersing a resin that will serve as a matrix, electroconductive carbon black, and various additives in a solvent whose amount is down to the amount that will be absorbed into said carbon black, then removing the solvent, and molding the mixture. CONSTITUTION:100pts.wt. resin that will serve as a matrix of an information signal recording medium such as a vinyl chloride resin and 300pts.wt. solvent for said resin such as tetrahydrofuran are charged into a dissolving tank 13 from a resin tank 11 and a solvent tank 12 respectively and are made into a uniform solution, and the solution is led via a filter 14 to a dispersion tank 15. At the same time, 5-10pts. additive such as a heat stabilizer from a tank 16 and 20pts. electroconductive carbon black (whose absorption is 350ml/100g) are charged into the dispersion tank 15 and are mixed to prepare a dispersion, the dispersion is introduced into a low pressure dryer 18, where the solvent is removed to produce a compound in the form of a block, then the block is ground in a grinder 19 into particles having a suitable particle diameter, and the particles are press molded to obtain the desired item.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an information signal recording medium such as a video disc or a digital audio disc, and particularly relates to a method for manufacturing an information signal recording medium such as a video disc or a digital audio disc. As a manufacturing process of a capacitive information signal recording medium in which an information signal is reproduced by changing the capacitance between a relatively scanning reproducing needle and an electrode according to a change in geometrical shape, After mixing and dispersing the base material resin, conductive carbon black, and various additives in a resin-soluble solvent in an amount greater than the oil absorption of the carbon black, the solvent is removed, and then processes such as molding are performed. It is an object of the present invention to provide a manufacturing method that can improve the dispersion of various additives, especially carbon black, and produce an excellent information signal recording medium.

Conventionally, pits are formed spirally or concentrically in a plane or groove according to an information signal, and the information signal is recorded as a change in geometrical shape to obtain an information signal recording medium. A playback needle made of diamond or the like with an electrode provided on the recording track is relatively scanned, and the capacitance formed between the electrode of the playback needle and the information signal recording medium changes according to the change in the geometrical shape. The so-called capacitance reproduction method reproduces recorded information signals by taking advantage of the changes in It is made by press-molding a thermoplastic resin such as vinyl chloride resin mixed with a conductive substance and additives such as a heat stabilizer.

Such a manufacturing method includes, for example, as shown in FIG. 1, a tank 1 containing a thermoplastic resin such as a vinyl chloride resin,
From a tank 2 containing various additives such as heat stabilizers and a tank 3 containing conductive carbon black, the thermoplastic resin, various additives, and carbon black are respectively transferred to a high-speed stirrer 4 such as a Henzoel mixer. After that, the mixture is introduced into a cooling mixer 5 to be cooled, and then processed into a pellet-like compound by a kneading extruder 6, and sent to a product compound tank 7. After that, it is transferred to a press and molded.

However, such a manufacturing method makes it difficult to produce a video disc in which, for example, carbon black is uniformly dispersed. In other words, since the blending performed using a high-speed stirrer is a tri-blend, it is difficult to disperse it on a scale smaller than the particle size of the resin, and in order to improve dispersibility, a cross-wire extruder is used. Carbon black and decomposition products due to the heat resistance of the resin are generated, which causes protrusions on the surface of the molded video disc, significantly deteriorating the playback characteristics.

Furthermore, if the carbon black is not uniformly dispersed in the molded video disc, even if the pits have the same shape, the configured capacitance may differ, and in this case, the specified information is not recorded. As a result, it cannot function as a recording medium. Moreover, if the dispersibility of carbon black is poor, thermal decomposition is likely to occur during processing.

The present invention eliminates the above-mentioned drawbacks, and examples thereof will be described below.

That is, when mixing and dispersing various additives such as conductive carbon black and heat stabilizers with olefin polymers such as vinyl chloride resins or thermosetting glasstics such as epoxy resins, conventional By using wet dispersion instead of tri-blending, the dispersibility of carbon black is improved and partial thermal decomposition during processing can be prevented, resulting in molding defects, especially protrusions on the surface. We have made sure that this does not happen.

However, if such wet dispersion and other methods are used, for example, even if foreign matter is mixed in the vinyl chloride resin material, the vinyl chloride resin material can be dissolved with a solvent to form a solution, and this solution can be passed through a filter. By passing it through, it is possible to remove the foreign matter contained therein, greatly extending the life of the master during press molding, and also preventing the occurrence of distortions and protrusions after molding.

Next, specific examples of the present invention will be described.

First, as shown in FIG. 2, a resin tank 11 containing a thermoplastic resin such as a vinyl chloride resin, which is a base material of an information signal recording medium, and a resin tank 11 containing a thermoplastic resin such as a vinyl chloride resin are used to melt the thermoplastic resin, such as tetranohydrofuran. 100 parts by weight of vinyl chloride resin and 300 parts by weight of tetranohydrofuran are put into the dissolving tank 13 from the solvent tank 12, and the vinyl chloride resin is sufficiently dissolved in the tetrahydrofuran.

Then, the solution of tetranohydrofuran in which vinyl chloride resin was dissolved was passed through the r-filter 14 to remove foreign substances, and then
This is carried out in a dispersion tank 1 equipped with dispersion blades having strong shearing force.
Put it in 5.

At the same time, a tank 16 containing additives such as a heat stabilizer, a tank 17 containing conductive carbon black (oil absorption 350 trt/1o0 g), and additives 5 to 10 are added. 10 parts by weight and 20 parts by weight of carbon blank are charged into the dispersion tank 15.

Thereafter, the dispersion tank 15 is operated to perform sufficient wet dispersion to produce a sludge-like or paint-like mixed dispersion.

Next, this mixed dispersion is introduced into, for example, a vacuum dryer 18 and dried under reduced pressure to remove tetrahydrofuran, thereby obtaining a block-shaped compalandra.

Then, the block-shaped combiner, for example, a crusher 19, is put into an appropriate particle size, and the product compound thus obtained is transferred to a product compound tank 2.
0, this is put through a press molding machine to obtain, for example, a capacitive video disc.

A condenser 21 is used to recover and regenerate the tetrahydrofuran removed by the vacuum dryer 18 and send it to the solvent tank 12.

When a video disc is produced as described above, the carbon black has good dispersibility, so local thermal decomposition is less likely to occur during processing of the material, which facilitates production and improves production yield.

For example, when the heat resistance of the above-mentioned compound is examined by the Congo Red test, it is found to be twice as heat resistant as that obtained by the conventional method.

In addition, when a sheet of one thickness was made using two rolls of the above compound and its electrical resistance was measured, the value was approximately 75% of that obtained using the conventional method, indicating that the dispersibility of carbon black is getting better.

In addition, since carbon black is uniformly dispersed in the compound, there are no problems such as fish eyes when molding video discs, and there are no protrusions on the surface, making it possible to obtain high-quality video discs. , the reproduced image is very good.

In the above example, tetrahydrofuran is used as a solvent for dissolving the base material resin, but for example, acetone, kijirol, EDO, etc. may also be used, and any solvent that dissolves the resin may be used. There aren't that many restrictions. Further, the amount of solvent may be at least the oil absorption amount of carbon black, but it is preferably about three times the oil absorption amount of carbon black.

Furthermore, when recovering the solvent from a sludge-like or paint-like mixed dispersion, it is desirable to recover the solvent at a temperature that does not adversely affect the resin contained therein.

As mentioned above, the information signal recording medium manufacturing method according to the present invention includes:
A mixed dispersion solution is prepared by mixing and dispersing a resin serving as a base material for an information signal recording medium, conductive carbon black, and additives in a solvent that dissolves the resin in an amount greater than the oil absorption amount of the conductive carbon black. The method includes a step of removing the solvent from the mixed dispersion solution, and a step of molding the mixture from which the solvent has been removed, so that local thermal decomposition does not occur during the manufacturing process of the information signal recording medium. Become,
An information signal recording medium that does not have problems such as fish eyes on the information signal recording medium, does not suffer from problems such as protrusions on the surface, and can be manufactured at a high manufacturing yield and at low cost. It has features such as extremely good playback quality.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are schematic explanatory diagrams of the steps of the conventional information signal recording medium manufacturing method and the present invention. 11... Resin tank, 12... Solvent tank, 13
...Dissolution tank, 14...1 filter, 15...Dispersion tank,
16, 17... Tank, 18... Vacuum dryer, 1
9...Crusher. Patent Applicant: Japan Victor Co., Ltd. Agent: Katsumi Utaka

Claims (1)

[Claims] A mixed dispersion solution is prepared by mixing and dispersing a resin serving as a base material of an information signal recording medium, conductive carbon black, and additives in a solvent that dissolves the resin in an amount greater than the oil absorption amount of the conductive carbon black. A method for manufacturing an information signal recording tower body, comprising the steps of: removing the solvent from the mixed dispersion solution; and molding a mixture from which the solvent has been removed.