JPH024064B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a conductive disk-type record carrier used in capacitive video disks, etc., and in particular, by using a resin material that has excellent processability, impact resistance, and abrasion resistance, and has a high heat distortion temperature. The present invention aims to provide a disk-type record carrier with excellent mass productivity and reliability. Traditionally, in the field of the record industry, disc records have been produced by compression molding a copolymer of vinyl chloride and vinyl acetate using, for example, a stamper with information signals applied to the surface. There is. On the other hand, conductive disk-type record carriers such as capacitive video disks are manufactured by almost the same method, but with a sufficient amount of conductive particles to enable capacitive reading from the disk, e.g. A considerable amount of carbon black had to be mixed into the resin material, which caused various problems in the disk manufacturing method and physical properties. In other words, since a large amount of conductive material is added to the molding material, the melt viscosity of the molding material increases, requiring extremely high compression pressure or making molding almost impossible, and the molded disk becomes brittle. It had increased significantly. One possible solution to this problem is to lower the melt viscosity of the molding material and improve its processability by using large amounts of plasticizers, processing aids, and the like. However, this also lowers the heat distortion temperature of the molded product, making the dimensions and shape of the disk unstable in high-temperature climatic conditions, resulting in the disk waving or shrinking and becoming unrecyclable. or In addition, the use of large amounts of plasticizers, processing aids, etc., tends to cause stains on the disk surface and stamper surface during molding due to their embossment, making it impossible to perform continuous molding with the same stamper. Even on discs that appear clean at first glance, as time passes after molding, excessive plasticizers, processing aids, etc. migrate to the disc surface, resulting in the problem of not being able to obtain good signals. . Therefore, the amount of plasticizers, processing aids, etc. used needs to be as small as possible within the range in which the effects are expected, and excessive expectations cannot be placed on these. For this reason, conductive disk-type record carriers such as capacitive video disks require resin materials that not only have a high heat deformation temperature but also have good processability even in the presence of a relatively large amount of conductive particles. is strongly desired. Furthermore, in the disk-type record carrier that is the subject of the present invention, the rotational speed of the disk during reproduction is significantly higher than that of a conventional piezoelectric audio-only disk using guide grooves, and in a disk intended for image reproduction, During still image playback, the playback needle is designed to run on the same circumference of the high-speed rotating disk, and the disk material, especially the resin material, has greater wear resistance than conventional materials. is required. The present invention has been made in view of these points, and it is an object of the present invention to provide a conductive disk-type record carrier that satisfies the above-mentioned conditions. That is, in a conductive disk-type record carrier that is constructed using at least a thermoplastic resin and conductive particles, and in which pits corresponding to information signals are formed in a spiral or concentric manner at predetermined intervals, the thermoplastic resin , among the resins in which vinyl chloride is graft-polymerized to the ethylene-vinyl acetate copolymer resin, the proportion of the ethylene-vinyl acetate copolymer resin and the vinyl chloride to be graft-polymerized as the constituent units of this resin is 2 to 10% by weight, respectively. Use a resin material consisting of two types, graft polymer and chlorinated polyethylene, which are 98 to 90% by weight, and whose mixing ratio is 1 to 10% by weight of chlorinated polyethylene to 99 to 90% by weight of the graft polymer. It has been discovered that this makes it possible to manufacture a disk that has excellent workability, impact resistance, and abrasion resistance, and has a high heat deformation temperature. Hereinafter, the conductive disk type record carrier of the present invention will be explained in detail. The constituent resin of the conductive disk-type recording carrier according to the present invention is a mixture of two resins: a resin obtained by graft polymerizing vinyl chloride onto an ethylene-vinyl acetate copolymer resin, and chlorinated polyethylene, and The composition ratios of the ethylene-vinyl acetate copolymer resin, which is a constituent component of the combination, and the vinyl chloride to be graft-polymerized thereto are 2 to 10% by weight and 98 to 90% by weight, respectively, and that the graft polymer and chlorinated polyethylene The resin mixture system is characterized by having a mixing ratio of 1 to 10% by weight with respect to 99 to 90% by weight of the former, and satisfying the above conditions. By using the above resin mixture system, it not only has a high heat distortion temperature, but also has good workability even in the presence of a relatively large amount of conductive particles, and has excellent wear resistance and impact resistance. It becomes possible to manufacture a conductive disk-type record carrier having these characteristics. On the other hand, if the amount of chlorinated polyethylene to be mixed is less than 1 part by weight based on 100 parts by weight of the disk-constituting resin, the effect of mixing the chlorinated polyethylene will hardly be observed. In other words, the heat deformation temperature is high, and it has good properties in terms of processability and wear resistance, similar to when a resin made by graft polymerizing vinyl chloride to an ethylene-vinyl acetate copolymer resin is used alone as the disk constituent resin. Although it is possible to obtain a conductive disk-type record carrier having the above-mentioned characteristics, it is only obtained that has insufficient impact resistance. On the other hand, if the amount of chlorinated polyethylene to be mixed exceeds 10% by weight, the rubber properties of the resin will increase too much, making it difficult to form accurate pits that correspond to information signals on the surface of the molded product, making it difficult to obtain information from the disk. The playback quality will also drop significantly, so
This would be inappropriate as a resin composition for disk materials, which is the object of the present invention. In addition, as a resin composition in which vinyl chloride is graft-polymerized to an ethylene-vinyl acetate copolymer resin, if the amount of vinyl chloride to be grafted in the graft polymer exceeds 98% by weight,
The physical properties of the resulting graft polymer approach those of vinyl chloride homopolymer, and a mixed system of this resin and chlorinated polyethylene can only produce disks that are inferior in terms of wear resistance among the various properties required for disk manufacturing. Therefore, it is not suitable as a resin for disk construction. On the other hand, if the amount of vinyl chloride to be grafted in the graft polymer is less than 90% by weight, the rubber elasticity of the resulting graft polymer will increase and problems will arise in terms of processability, such as a decrease in compatibility with lubricants. . As the conductive particles mixed in the disk constituent resin, metal powders such as nickel, silver, gold, etc. or conductive carbon black can be used. Carbon black particles are preferable in terms of performance and price. The amount of carbon black particles added must be sufficient to enable capacitive reading from the disk, and the guideline for this is when the volume resistivity of the molded product is 500 Ωcm or less, preferably 100 Ωcm or less. Good. The appropriate amount of carbon black to be added as a conductive particle suitable for satisfying these conditions varies depending on the conductivity of the carbon black, but the more carbon black is mixed, the more brittle the composition becomes. It is generally becoming more difficult to manufacture disks, so it is desirable to take the above points into consideration when selecting carbon black. It goes without saying that when blending a predetermined amount of the disk-constituting resin and carbon black as conductive particles, a heat stabilizer, plasticizer, lubricant, etc. may be used together with these as necessary. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto. In addition, all the parts mentioned in the following examples show parts by weight. Vinyl chloride (VC) graft polymer (EVA vs.
VC = 5:95, average degree of polymerization 380) ... 95 parts chlorinated polyethylene (Elastlene 303B: manufactured by Showa Denko K.K., chlorine content 30%) ... 5 parts carbon black (Ketsuchen Black EC: Lion Corporation) )
Made in Japan, oil absorption amount, approx. 360c.c./100g, average particle size 30μm,
Apparent specific gravity approximately 0.16) ... 20 parts heat stabilizer (N-2000K: manufactured by Nitto Kasei Kogyo Co., Ltd., butyltin malate type) ... 3 parts lubricant (Wax OP: manufactured by Hoechst Co., Ltd., partially stabilized from montanic acid) chemical ester wax)
...0.3 part lubricant (Conol 1670: manufactured by Shin Nihon Rika Co., Ltd., high alcohol type) ...1.0 part lubricating oil (SH-200: manufactured by Toray Silicon Co., Ltd., dimethyl silicone) ...0.7 part After thoroughly mixing the mixture with a high-speed stirrer, it was heated and melt-kneaded with a kneader, and then extruded and compression molded to prepare a sample. The samples thus obtained were evaluated for processability, heat distortion temperature, reproduced image quality, impact resistance, and abrasion resistance. The results are shown in No. 1 of Table 3. Next, a vinyl chloride (VC) graft polymer to ethylene-vinyl acetate copolymer (EVA) with the above composition (EVA to VC = 5 to 95, average polymerization degree
380) as shown in Table 1.
A sample was prepared using the same composition and method as above.

[Table] Furthermore, in the above composition, the mixing ratio of vinyl chloride graft polymer to ethylene-vinyl acetate copolymer and chlorinated polyethylene, 95 parts to 5 parts, was
All compositions are the same as above, except for the changes shown in the table.
A sample was prepared by the method.

[Table] The samples whose compositions are shown in Tables 1 and 2 were also evaluated for processability, heat distortion temperature, reproduced image quality, impact resistance, and abrasion resistance, and the results are shown in Table 3. It was shown to. The volume eigenvalues of the samples shown in Table 3 were all 3 to 4 Ω·cm. In Table 3, the processability of the samples was evaluated based on the extrusion torque and stability of the extrusion amount when the kneaded material was extruded and compression molded, and the presence or absence of warpage of the molded product. The heat distortion temperature of the sample was evaluated using the sample's flexibility temperature using the Kratschberg test method. The reproduction image quality of the sample disk was evaluated by performing standard reproduction from the outer circumference to the inner circumference, and visually determining whether the image quality was good or bad. The impact resistance of the sample disk was evaluated by dropping a steel ball of a certain weight onto a sample piece using a falling ball impact tester, and measuring the falling distance of the steel ball when the sample piece broke. Regarding the abrasion resistance of the sample, when reproducing the image of the sample disk, only a certain part (middle circumference) was repeatedly reproduced for 5 times.
The evaluation was made by comparing the initial image quality and the image quality after 5 hours.

[Table] * Comparative example In the above table, (1) The heat distortion temperature is JIS (Japanese Industrial Standard) K-6745.
Measured values by the Kratschberg method shown in (load 50 g). (2) Impact resistance was evaluated by the method shown below. Measuring machine: No. 621 Falling ball impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.) Steel ball weight: 50 g Sample shape: 100 x 65 x 1.2 mm plate Measurement/evaluation: Both ends of the long side of the test piece are horizontally spaced by 18 mm After dropping the steel ball from a predetermined height, observe whether the test piece is broken or not. The measured data (cm) indicates the height at which failure of the specimen begins. As is clear from the table, the present invention not only has excellent processability and heat deformation temperature, but also has excellent playback image quality, impact resistance, abrasion resistance, and conductivity, and has a disk-type recording carrier. It becomes possible to manufacture

Claims (1)

[Claims] 1. A conductive disk-type record carrier made of at least a thermoplastic resin and conductive particles, in which pits corresponding to information signals are formed spirally or concentrically at predetermined intervals. and the thermoplastic resin is a resin obtained by graft polymerizing vinyl chloride to an ethylene-vinyl acetate copolymer resin,
The constituent units of this resin are 2 to 10% by weight of ethylene-vinyl acetate copolymer resin and 98 to 90% by weight of vinyl chloride to be grafted, which is a graft polymer and chlorinated polyethylene. 1. A conductive disk-type recording carrier characterized in that the volume resistivity of the forming composition is 1 to 10% by weight based on 99 to 90% by weight of chlorinated polyethylene and 500 Ωcm or less. 2. The conductive disk type record carrier according to claim 1, characterized in that carbon black is used as the conductive particles.