JPS5856243A - Recording medium of high-density information signal - Google Patents

Abstract

PURPOSE:To produce a recording medium which is free from a drop-out or a stylus jump, by limiting the diameter to a specific value or less for the particles of the powder which is added to the base material of a recording medium of high-density information signal. CONSTITUTION:For instance, the carbon black is put into an aqueous solution or an organic solvent to be turned into a slurry-like matter having about <=10,000 cps viscosity. This slurry matter is filtered by means of a proper filtering material of <=20mum mesh space. Then a filtrate containing only a powder additive like the carbon black that has a small grain size is dried. A matter thus obtained is used to a conductive material which is mixed into the base material of the polyvinyl chloride resin, etc. Thus a factor which causes a defect of screen is eliminated. In such way, the grain size is reduced for the powder additive which is added into the base of a recording medium. This can prevent the shrinkage distortion produced on the surface of the base material after the recording medium is pressed. Thus a drop-out or a styluse jump is avoided for the recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-density information signal recording medium such as a video disc or a digital audio disc, and in particular, information signals are recorded as changes in the geometrical shape of the surface, and the surface is relatively Added to the resin base of the recording medium in capacitive recording media in which information signals are reproduced by changing the capacitance between the electrode and the electrode of the reproducing needle that scans according to the change in geometric shape. For example, by using carbon black or other powder additives with a particle size of approximately 20 μm or less, dropouts and needle skipping phenomena are almost eliminated when scanning and reproducing electrodes, thus improving both image quality. It is an object of the present invention to provide a high-density information signal recording medium that is extremely superior in terms of performance, etc.

"Conventional": Forming pits in a plane or groove according to the information signal, recording the information signal as a change in geometric shape to obtain an information signal recording medium, and recording the information signal on the recording track of the information signal recording medium. By relatively scanning a reproducing needle provided with an electrode, it was found that the capacitance formed between the electrode of the reproducing needle and the information signal recording medium changes in response to changes in the geometrical shape. There is a so-called electrostatic capacitance reproduction method that utilizes this method to reproduce recorded information signals.

A capacitive information signal recording medium used in this type of capacitance reproduction method has, for example, a capacitive capacitance between the surface of the recording medium body, which is press-molded with a geometrical change, and the electrode of the reproduction needle. For example, a metal thin film of several hundred times the thickness is deposited as an electrode to form a dielectric layer of several hundred A to protect the metal thin film, prevent short circuits between the electrodes, and increase the dielectric constant between the electrodes. A recording medium with a structure in which a body thin film is attached has been proposed, but a recording medium with this structure requires many manufacturing processes such as press molding of the recording medium body, metal thin film attachment process, dielectric thin film attachment process, etc. is complicated and troublesome,
This method has drawbacks such as requiring extensive manufacturing equipment and extremely high manufacturing costs.

Therefore, a conductive plastic made by mixing several tens of parts by weight of a conductive substance such as carbon black with a resin such as vinyl chloride-vinyl acetate copolymer is press-molded as a raw material, and the information signal is shaped into a geometric shape. A capacitance type information signal recording medium has been proposed as a change in the recording medium, and since a capacitance is formed between the recording medium itself and the playback needle electrode, the process of attaching a metal thin film is required. Moreover, since the carbon black fine powder particles themselves are coated with resin, there is no need for a process for attaching a dielectric thin film, making manufacturing extremely simple and low cost.

However, recording media made by forming predetermined pits with carbon black-containing resin as described above often suffer from dropouts and needle skipping phenomena when played back by scanning the playback needle, such as video discs. The reproduced image has screen defects and is not in good condition.

As a result of studying why fatal defects such as playback screen defects occur, the inventor of the present invention found that powder additives added to vinyl chloride resins, such as carbon black, vanadium, nickel contained in carbon black, etc. ,
We found that the particle size of impurities such as iron, glue, copper, aluminum, magnesium, calcium, sodium, chromium, or graphitized carbon is the main factor that causes dropouts and needle skipping, and we developed these powder additives. They found that by taking the size of the needle into consideration, dropouts and needle skipping phenomena could be significantly eliminated, resulting in a much better playback screen. Furthermore, they have found that the quality of the reproduced image deteriorates depending on the hardness and high reactivity of impurities contained in conductive carbon such as carbon black.

Therefore, the inventor of the present invention prepared a conductive material such as Carpump Sic, which is mixed into a base material such as a vinyl chloride resin, in an aqueous solution or an organic solvent for approximately 100 minutes.
A slurry having a viscosity of 00 cps or less, preferably about 3000 cps or less is prepared, and this slurry is passed through a suitable pore opening of, for example, 20 ttm or less, preferably about 10 μm or less, particularly preferably about 5 μm or less. The particle size of the powder additive such as carbon black is reduced to, for example, about 2071 m or less, preferably about 0 μm or less, particularly preferably about 5 μm or less, and then the particle size of the powder particles is By using dried oral fluid containing only small particles, factors that could cause screen defects were removed.

In other words, by keeping the particle size of the powder additive added to the resin base of the recording medium small, it is possible to increase the particle size of the particles in the layer near the surface of the resin base of the recording medium. "There is no problem": By keeping it
This prevents shrinkage distortion from occurring on the surface of the base material after the recording medium is pressed, prevents swelling of the recording medium surface caused by shrinkage distortion, and prevents dropouts and needle-flying phenomena from occurring.

Hereinafter, specific embodiments in which the high-density information signal recording medium according to the present invention is applied to a video disc will be described.

First, to impart conductivity to vinyl chloride resins, such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-cetyl vinyl ether copolymer, vinyl chloride-ethylene copolymer, etc., which serve as the base for video discs. As a pretreatment for Ketjen Black EC (manufactured by Lion Akzo), which is carbon black, as a conductive substance added to the water, for example, Ketjen Black EC is mixed with water, benzene, toluene, etc. in the presence of a suitable surfactant. added to an organic solution,
For example, about 10,000 cps or less, preferably about 3,000 cps
A slurry of approximately cps is prepared, and this slurry is subjected to pressure filtration treatment using a filtration material with a mesh size of about 10 μn1. Through this mouth-filtering treatment, the vanadium, nickel, iron, silica, copper, aluminum, magnesium, calcium contained in Ketjenblack EC,
Most of the impurities with high hardness or high reactivity such as sodium, chromium, and graphitized carbon are removed, and particles with a particle size of about 10/1711 or larger are removed. /1m or less in size only. Then, the sample containing only those having a particle size of about 10 μm or less is dried to form a powder.

Other powder additives added to the base, such as vinyl chloride resin, are also sieved through a sieve with a mesh size of about 10 μm, and only those with a particle size of about 10 μm or less are selected.

After the above-mentioned pretreatment, about 100 parts by weight of a resin base for video discs, about 3 parts by weight of dibutyltin laurate, and about 0.5 parts by weight of evolvated soybean oil are added.
About 0.7 parts by weight of dimethylpolysiloxane were placed in a Henschel type high speed mixer and thoroughly stirred, and then carbon black was added and stirred thoroughly. Then, roll these mixed powders for about 1 hour using a twin 8-inch open roll, for example.
After kneading for 0 minutes, the material is cut into sheets, made into pellets, and passed through an extruder for pre-forming. to create a capacitive video disc. In other words, the video discs were produced by a conventional method using only powder additives with a particle size of approximately 10 μm or less to be added to the base of the video disc.

In addition, as a comparative example, the particle size of the powder additive was approximately 4011 m.
Similarly, a capacitance type video disc is made using a material that includes a large amount of water.

When the capacitive video disc of the present invention produced as described above and the capacitive video disc of the comparative example are mounted on a predetermined playback device and playback is attempted, the capacitive video disc of the present invention becomes the capacitive video disc of the present invention. In the case of a video disc, the number of dropouts is approximately 5 per hour, whereas in the case of a comparative example of capacitive video disc, the number of dropouts is approximately 100 to 200.
In addition, the needle skipping phenomenon is almost non-existent in the case of the present invention, whereas it occurs frequently in the case of the comparative example, that is, the reproduced image of the capacitive video disk of the present invention is good. On the other hand, in the case of the capacitive video disk of Comparative Example 1, the quality was poor, with screen defects occurring. As shown in the electron micrographs in Figures 1 and 2, there are cases where the diameter of the particles added to the base of the video disc is about 40 pm, but when the video disc is molded, There is a difference in the shrinkage rate of the base near the part where particles of about 40I1m are located and other parts, and for this reason, the shrinkage rate of the base is about 4
Swelling occurs on the surface of the video disc in the vicinity of particles of about 0μ711, which causes dropouts and needle skipping during playback, damaging the video disc and causing defects on the playback screen. According to the invention, no swell occurs on the surface of the video disc during molding of the video disc, and therefore no playback screen defects occur.

In addition, many of the impurities with high hardness or high reactivity such as chromium and sodium contained in Ketjen Black EC etc. have been removed, so there is no deterioration in reproduced images caused by these high hardness or high reactivity impurities. I could always get rid of it.

As mentioned above, the high-density information signal recording medium according to the present invention includes:
In a high-density information signal recording medium in which information signals are recorded by forming pits, powder particles added to the base material of the high-density information signal recording medium mainly have a diameter of approximately 20 μm or less, so that no droplets are generated during playback. Out and needle skipping phenomena are significantly reduced compared to conventional ones, and therefore, for example, there are no defects on the reproduced screen, and the reproduced image quality is extremely excellent.
Since only the following are required, it has the advantage that it can be easily carried out, for example, by a mouth-washing method, and can be carried out at extremely low cost.

[Brief explanation of the drawing]

Figure 1 is approximately] Q7. FIG. 2 is an electron micrograph for explaining the particle structure, etc. of a cross-sectional oblique part of a video disc containing particles with a size of approximately 40 μm, and FIG. This is an electron micrograph for explaining. \, -1, -' (11) Figure 1 Figure 2

Claims (1)

[Claims] ■ In a high-density information signal recording medium in which information signals are recorded by forming pits, the diameter of powder particles added to the base material of the high-density information signal recording medium is mainly about 20 μm.
A high-density information signal recording medium characterized in that it uses a medium having a density of less than m. (2) The high-density information signal recording medium according to claim 1, wherein the powder-based particles are limited to those having a diameter of about 20 μm or less by d-filtering.