JPH0434201B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method of manufacturing a record disc used for music listening and the like. [Prior art] Record discs for music listening, so-called LP records, are basically made of hard vinyl chloride resin, but with an emphasis on transferability during stamper molding, the average degree of polymerization is 400~400. 600, which has a relatively low degree of polymerization, is used. [Problems to be Solved by the Invention] The record disc obtained as described above has low hardness and has the following problems. (1) Hard vinyl chloride is a soft material due to its low degree of polymerization, causing slight jamming between the stylus and the sound groove when playing records.
This jamming appears as a strain on the cantilever supporting the stylus, causing strain release at the next signal. This repeated operation causes deterioration of sound quality as extremely slow phase distortion. (2) When cleaning with a brush, the surface of the record disc is scraped by the frictional force with the brush, which not only remains as deposits on the surface, but also damages the shape of the grooves and causes deterioration of sound quality. The present invention has been made to solve the problems of the prior art described above, and aims to provide a manufacturing method that can realize a record disc with high hardness. [Means for Solving the Problems] The manufacturing method of the present invention involves molding a resin composition containing 1 to 10 parts by weight of a polyfunctional monomer to 100 parts by weight of a vinyl chloride resin to produce a record disc. 1 step and a second step of repeating the operation of irradiating one side of the record disc with ionizing radiation and then irradiating the other side with ionizing radiation two or more times, and the ionizing property in the second step is It is characterized in that the total irradiation dose of radiation is 0.5 to 4 Mrad. [Function] The vinyl chloride resin used in the present invention includes not only vinyl chloride resin but also copolymer resins mainly composed of vinyl chloride, such as vinyl chloride-based resins.
Examples include vinyl acetate copolymer resin, vinyl chloride-maleic anhydride copolymer resin, vinyl chloride-methacrylic acid copolymer resin, and vinyl chloride-vinylidene chloride copolymer resin. It is preferable to use such a vinyl chloride resin having an average degree of polymerization in the range of 400 to 800 in consideration of strength after molding and transferability during stamper molding. In the present invention, a polyfunctional monomer is contained in the vinyl chloride resin in order to enhance the irradiation crosslinking reaction during ionizing radiation irradiation after molding. If polyfunctional monomers are not included, the irradiation dose will be reduced.
A sufficient degree of crosslinking cannot be achieved unless the exposure is 5 Mrad or more, and when exposed to such a large amount of irradiation, the record disc becomes deformed due to heat generation. The microbubbles contained in the record disc become ionized, producing grains and irregularities on the surface. It has been confirmed by the inventor's previous prototype experiments that such a phenomenon occurs. Therefore, in the present invention, vinyl chloride resin 100
The polyfunctional monomer is contained in the range of 1 to 10 parts by weight based on the weight part. If it is less than 1 part by weight, there is no effect in reducing the irradiation dose, and if it exceeds 10 parts by weight, the polyfunctional monomer bleeds and accumulates in the sound groove, hardens during irradiation crosslinking, changes the waveform of the sound groove, and actually impairs the sound quality. It turns out. Examples of polyfunctional monomers include triallyl isocyanurate, diallyl phthalate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene dalycol dimethacrylate, diallyl phthalate, diallyl fumarate, trimethylolpropane trimethacrylate, etc. . In the present invention, in addition to the above-mentioned ingredients, stearate metal soaps such as lead stearate, cadmium stearate, barium stearate, etc. are used to impart thermal stability, fluidity, mold release properties, etc. during molding. It is also possible to add heat stabilizers. The vinyl chloride resin composition containing a polyfunctional monomer as an essential component is molded into a record disc by stamper molding or the like, and then crosslinked by irradiation with ionizing radiation such as an electron beam. In this crosslinking, irradiation is performed not only on one side of the record disc but also on the other side, and if irradiation from (one side) to (other side) is made into one cycle (irradiation twice), more than two cycles are applied. , that is, at least (one side) → (other side) → (one side) →
It is necessary to perform irradiation four times (on the other side). Irradiation of only one side cannot improve the surface hardness of the other side, and irradiation for less than two cycles increases the irradiation dose per time.
This may cause the record disc to bend, or cause grains or irregularities to appear on the surface. It is preferable that the irradiation dose be the same each time. In the present invention, the total irradiation dose is 0.5-4 Mrad
If it is less than 0.5 Mrad, there is no effect on improving the surface hardness, and if it exceeds 4 Mrad, as mentioned above, the record disc may be bent, grains or unevenness may occur on the surface, or the sound groove may be deformed. wake up [Examples] Examples 1 to 3, Comparative Examples 1 and 2 Vinyl chloride-vinyl acetate copolymer resin (vinyl acetate amount 10% by weight, average degree of polymerization 450)
100 parts by weight, lead stearate 1.5 parts by weight, epoxidized soybean oil 1.0 parts by weight, furnace black 0.2 parts by weight, nonionic surfactant 0.1 parts by weight The above ingredients contain a polyfunctional monomer (trimethylolpropane trimethacrylate) as a first component. Record discs were prepared by stamper molding resin composition parts containing the amounts shown in each example in the table, and then two cycles of electron beam irradiation were performed at an irradiation dose of 1 Mrad/time (total irradiation dose 4 Mrad). The surface hardness of the record disc in each example (shareD
The results of measuring the hardness are shown in Table 1. In addition, when the same song was played 25 times using the record disc of each example, Examples 1 to 3
In addition to obtaining extremely good sound quality in subjective measurements, there is almost no change in sound quality,
Even when I cleaned it with a brush, it didn't get scratched. The sound quality of Comparative Example 1 was good at first, but the sound quality gradually deteriorated, and the surface was found to be scraped when cleaned with a brush. In Comparative Example 2, bleeding of the polyfunctional monomer was observed, and deterioration of sound quality was observed from the start of performance.

[Table] Examples 4 to 7, Comparative Examples 3 to 5 The same resin composition as in Example 2 (polyfunctional monomer content: 5 parts by weight) was molded with a stamper to create record discs, and then as shown in Table 2. In this way, the electron beam was irradiated. The discs of Examples 4 to 7 had excellent sound quality like the record discs of Examples 1 to 3. In Comparative Example 3, the irradiation dose was small and the sound quality gradually deteriorated. In Comparative Example 4, the irradiation dose was too high and the record disc was deformed, and in Comparative Example 5, the irradiation dose was too high and the record disc was deformed, and grains and unevenness were observed on the surface. This caused tracking noise.

[Table] [Effects of the Invention] As explained above, according to the present invention, it is possible to obtain a record disc with high hardness,
The following remarkable effects can be obtained. (1) Improved hardness of the record material improves compliance between the stylus and the sound groove during performance, significantly reducing mechanical phase distortion. Therefore, it is possible to obtain a natural sound that is faithful to the original sound and full of realism. (2) When cleaning with a brush, the surface is not scraped, so deformation of the important sound groove can be prevented.

Claims (1)

[Claims] 1 A first step of forming a record disc by molding a resin composition containing 1 to 10 parts by weight of a polyfunctional monomer based on 100 parts by weight of a vinyl chloride resin, and irradiating one side of the record disc with ionizing radiation. and a second step of repeating the operation of irradiating the other side with ionizing radiation twice or more, and the total dose of ionizing radiation in the second step is 0.5 to 4 Mrad. Method of manufacturing record discs.