JPS59195353A - High density information signal recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled recording medium reducing remarkably drop-out during reproduction by delaying the initiation of the dehydrochlorination reaction of vinyl chloride resin contg. an electrically conductive substance as a material for a recording medium by thermal decomposition in a molten state. CONSTITUTION:When heat is generated locally and abnormally in a high performance kneader in a stage for working vinyl chloride resin contg. an electrically conductive substance as a material for a recording medium, the decomposition of the composition is caused at a locally abnormal heat generating part or staying part, and the dehydrochlorination reaction of the composition proceeds, At the same time, the composition is cross-linked while holding carbon black, the volume is reduced, and hardened particles produced by the decomposition disperse in the composition. Projections causing drop-out are formed in accordance with the sizes and positions of the particles. The initiation of the dehydrochlorination reaction is delayed by this invention, and the reaction is initiated practically after the lapse of 4min in a molten state, so the reaction is not initiated during pelletizing with the kneader, and the production of hardened particles is remarkably reduced. As a result, drop-out is remarkably reduced.

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. In a capacitive 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, this recording medium is at least It is made of vinyl chloride resin containing a conductive substance, and when this material is in a molten state, the dehydrochloric acid reaction due to thermal decomposition does not start until about 4 minutes or more have elapsed. It is an object of the present invention to provide a high-density information signal recording medium that exhibits significantly less dropout when reproducing the obtained high-density 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. There is a so-called electrostatic capacitance reproduction method that reproduces recorded information signals by utilizing changes in the magnetic field.

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, hundreds of thin metal films are deposited on top of the electrodes to protect the metal thin film, prevent short circuits between electrodes, and increase the dielectric constant between the electrodes. A recording medium with a dielectric thin film attached has been proposed, but this glazed recording medium requires many manufacturing processes, such as a press molding process for the recording medium body, a metal thin film attachment process, and a dielectric thin film attachment process. However, it has disadvantages such as being complicated and troublesome to manufacture, requiring heavy-duty manufacturing equipment, and extremely high manufacturing cost.

Therefore, vinyl chloride resin, vinyl chloride/vinyl acetate copolymer, vinyl chloride/ethylene copolymer, -vinyl chloride
Stare is applied to thermoplastic resins such as propylene copolymers, vinyl chloride/acrylic acid alkyl ester copolymers, acrylonitrile/styrene copolymers, and graft copolymers of ethylene and vinyl acetate copolymers and vinyl chloride. Metallic soaps such as calcium phosphate, organotin stabilizers, lubricants such as higher alcohols, fatty acids, fatty acid esters, or polysaccharide esters, and lubricants such as dimethylpolysiloxane are used with conductive carbon. The carbon black is blended with black using a high-speed mixer such as a Henschel mixer, and the carbon black is sufficiently dispersed.Then, the carbon black is melted into a gel using a highly kneading extruder, and then pelletized. Means for molding video discs have been proposed. In other words, in this way, since capacitance is formed between the recording medium itself and the reproducing needle electrode, there is no need for the process of attaching a metal thin film or the process of attaching a dielectric thin film, which greatly reduces the manufacturing process. Easy and low cost.

However, when attempting to reproduce the capacitive information signal recording medium obtained in this way by installing it in a reproducing apparatus, dropouts often occur.

The inventor of the present invention investigated the cause of this dropout and found that it was caused by protrusions on the surface of the capacitive information signal recording medium. As a result of further investigation into this matter, various types of protrusions (hereinafter referred to as "tsukurami") have been introduced, but most of them are decomposition products of the capacitive information signal recording medium composition. I stopped myself. That is, the conductive carbon blank contained has a DBP oil absorption of 280rnI2/
Due to its extremely high weight of around 100g and its structure with developed struts, the composition itself generates a large amount of heat during the process of gelling, melting, and dispersing in a high-speed kneading machine, sometimes causing decomposition phenomena. This caused the Tsukurami that is the cause of dropouts.

Therefore, various stabilizers and plasticizers were added to suppress such decomposition phenomena. However, simply increasing the thermal stability of the composition in this way was insufficient at the stage of processing with a high-performance kneader. In other words, a decomposition phenomenon of the composition occurs in local abnormal heat generation parts or stagnation parts inside the high kneading machine, and as the dehydrochloric acid reaction progresses from the composition, the composition is crosslinked while still containing carbon black, and the volume shrinks. is caused, and the hardened particles, which are decomposition products, change in composition.
It has been determined that the hardened particles are dispersed throughout the material and that blackheads occur depending on the size and position of the hardened particles.

Therefore, in order to prevent this kind of blackness from occurring, it would be best to prevent the dehydrochloric acid reaction from occurring due to the thermal decomposition of the PVC resin, but it is virtually impossible to do so. It is possible.

However, the present inventor believes that if the start point of this dehydrochlorination reaction is delayed, that is, if the dehydrochlorination reaction is started after substantially 4 minutes have elapsed in the molten state,
For example, it has been found that if the dehydrochloric acid reaction is prevented from starting in the step of pelletizing with a kneader PR-46'), the generation of hardened particles is significantly reduced, and dropout is significantly reduced.

The present invention has been made based on the above viewpoint, and specific examples thereof will be described below.

Example 1 100 parts by weight of an ethylene-vinyl chloride copolymer (VE'-N manufactured by Tokuyama Sekisui Dot Gyogyo ■) with an average degree of polymerization of 430 and an ethylene content of 1.5 parts, a dibutyltin mercaptoester stabilizer (Three-copyrite synthesis ■) 5 parts by weight of 5TANNJF-95), fatty acid glycerin ester lubricant (RIKEN VITAMIN RES-21)
0) 2.0 parts by weight, fatty acid alkyl ester lubricant (Kao Soap ■Splendor E-10) 0.5 parts by weight, dimethylpolysiloxane (Shin-Etsu Chemical ■R, ES-42)
1) 1.0 part by weight was blended at 110°C in a 20t Henschel mixer, cooled at low speed to 70°C, and then washed with water or pickled conductive carbon black (08X manufactured by Cabot, USA). -150A1DBL
) Oil absorption amount 320m/! /100g, I2 adsorption amount 1269
7 #g/g) was added thereto, the temperature was again raised to 110°C, the mixture was stirred at high speed for 15 minutes, and then cooled to room temperature.

Thereafter, the pellets are pelleted using a kneader PR-46 manufactured by Swissbus (no dehydrochloric acid reaction occurs in this pelleting process), and the resulting pellets are molded, for example, in a press machine exclusively used for video discs. to obtain a video disc.

Example 2 was added to 7 parts by weight, and a video disc was obtained in the same manner. However, no dehydrochloric acid reaction occurs during the pelleting process.

Example 3 In Example 1, the amount of 5TANNJF-95 added was 3
parts by weight, the amount of 08X-1,50A added was 16 parts by weight, and 5 TANNBL (a dibutyltin laurate stabilizer manufactured by Sankyoki Synthesis ■) was used as a stabilizer, and a video disc was prepared in the same manner. obtain.

Note that no dehydrochloric acid reaction occurs in the pelleting process.

Comparative Example 1 The same procedure as in Example 3 was carried out using 2 parts by weight of 5TANNBL and 20 parts by weight of 08X-15OA, but it could not be made into a pellet and could not be molded into a video disc. Incidentally, in the kneader PR, -46, a dehydrochloric acid reaction occurred during crosstalk.

Comparative Example 2 A video disc is obtained in the same manner as in Example 3 except that 20 parts by weight of 08X-15OA is used. Note that a dehydrochloric acid reaction occurs in the pelleting process.

Prepare 50 of each of the video discs made as described above, load them into a playback device at least 72 hours after molding, and calculate the incidence of dropouts of 3H or more as shown in the table. It was on the street. Visit,
Since a dropout of 3H or less can be dealt with by electrical correction, the dropout that becomes a problem is a dropout of 3H or more.

In addition, 1'60 g of each element was preheated to 150 to 152°C using PLv-151 and W-50E manufactured by West German Brabender.
After placing it in an O-type rotor mixer and preheating it for 3 minutes, the rotor speed was increased to 60 rpm, and the temperature rise and torque change of the material at this time were automatically recorded, and the measurement was performed for 30 seconds immediately after the start of measurement. At each time, using a commercially available Congo Red test paper, check for discoloration of the Congo Red test paper due to the gas generated from the open part of the rotor mixer, and measure the point at which the dehydrochloric acid reaction begins, and this is shown in the table.

In other words, when producing a video disc, for example, if the dehydrochloric acid reaction occurs within 3 minutes after the constituent material of the video disc is melted, the dropout rate is high, whereas the dehydrochloric acid reaction occurs after about 4 minutes. Among those that did occur, the incidence of dropout was significantly lower.

As mentioned above, the high-density information signal recording medium according to the present invention includes:
In a high-density information signal recording medium made of a vinyl chloride resin containing a conductive substance that records information signals by forming pits, a dehydrochloric acid reaction due to thermal decomposition of the vinyl chloride resin of the high-density information signal recording medium is performed after melting. Since it is configured so that it does not occur until approximately 4 minutes or more have elapsed, it has the advantage that the occurrence of dropout is significantly reduced.

Patent applicant: Victor Japan Co., Ltd. Agent Katsumi Utaka

Claims (1)

[Claims] In a high-density information signal recording medium made of a vinyl chloride resin containing a conductive substance that records information signals by forming pits, a dehydrochloric acid reaction due to thermal decomposition of the vinyl chloride resin of the high-density information signal recording medium is performed after melting. A high-density information signal recording medium characterized in that it is configured such that it does not occur until approximately 4 minutes or more have elapsed.