JPH0150978B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a capacitive information signal recording medium,
In a capacitive information signal recording medium, in which an information signal is recorded as a change in geometrical shape, and the recorded signal is reproduced by a change in capacitance between the electrode of a scanning and reproducing needle, a conductive material and an affinity for the same are used. The purpose of the present invention is to provide various types of capacitive information signal recording media with good stability, which are molded from materials containing specific polymers with good properties. Conventionally, an information signal recording medium is obtained by forming pits in a plane or groove according to an information signal and recording the information signal as a change in geometric shape, and electrodes are provided on the recording track of this information signal recording medium. The recorded information signal is detected by scanning the reproducing needle relative to each other, and utilizing the fact that the capacitance formed between the electrode of the reproducing needle and the information signal recording medium changes in accordance with the change in the geometrical shape. There is a so-called capacitance regeneration method that regenerates . Capacitive information signal recording media used in this type of capacitance reproducing method have conventionally been press-molded with a geometric shape change on the surface of the recording medium main body, and between the electrode of the reproducing needle and the For example, a thin metal film of several hundred angstroms is deposited as an electrode to form capacitance, and on top of that a thin metal film of several hundred angstroms is deposited to protect the thin metal film, prevent short circuits between the electrodes, and increase the dielectric constant between the electrodes. It had a structure in which a dielectric thin film of 1.5 Å was attached. However, in order to manufacture this conventional capacitive information signal recording medium, as mentioned above, many manufacturing processes are required, such as a press molding process for the recording medium body, a process for attaching a metal thin film, a process for attaching a dielectric thin film, It has drawbacks such as being complicated and troublesome to manufacture, requiring large-scale manufacturing equipment, and resulting in extremely high manufacturing costs. Therefore, a new capacitive information signal recording medium which eliminates the above-mentioned drawbacks of the conventional method was proposed in Japanese Patent Application Laid-Open No. 119017/1983. The previously proposed capacitive information signal recording medium is press-molded from a conductive plastic made by mixing vinyl chloride/vinyl acetate copolymer with, for example, several tens of parts by weight of carbon black, which is a conductive substance. The information signal is recorded as a change in geometric shape. According to this, since an electrostatic capacitance is formed between the recording medium itself and the reproducing needle electrode, there is no need for the metal thin film adhesion process as in the conventional example, and the carbon black fine powder particles themselves are made of resin. Since it is covered with a thin film, there is no need for the process of attaching a dielectric thin film as in the conventional example, and the manufacturing process is extremely simple, and it has the advantage that it can be manufactured at an extremely low cost. However, the previously proposed capacitive information signal recording medium uses vinyl chloride/vinyl acetate copolymer, which has traditionally been used in audio records, as a polymer, and several tens of parts by weight of carbon black are mixed with this. ing. For this reason, there is a particular problem in that large internal heat generation occurs during material processing due to molecular friction between carbon particles and polymer molecules, which tends to cause thermal decomposition of the polymer during processing. Furthermore, due to the poor affinity between carbon particles and polymer molecules, the melt viscosity of the material is high, resulting in the problem that it cannot be molded well using conventional molding equipment. Therefore, in order to improve these problems, increasing the amount of lubricant and plasticizer components added to the polymer may cause the molded recording medium to deform when exposed to even the slightest high temperature, resulting in poor environmental stability. Moreover, new problems arise such as performance deterioration and stability over time due to the migration phenomenon of plasticizers and the like. The present invention provides a conventional capacitive recording medium that essentially does not require a plasticizer that impairs the thermal stability of the recording medium and uses a material that can be stably and easily processed. It provides: The capacitive information signal recording medium according to the present invention includes:
60-65% by weight of vinyl chloride and 5-25% by weight of maleic acid alkyl ester and/or fumaric acid alkyl ester having an alkyl group having 4 or more carbon atoms
and 0 to 15% by weight of other monomers copolymerizable with these, with a specific viscosity of 0.16 to 0.31 (JIS K-6721)
It is obtained by molding a material with a softness temperature (JIS K-6745) of 45°C or higher, which is made by blending a conductive substance with a copolymer. A copolymer consisting of the above vinyl chloride, an alkyl maleate and/or an alkyl fumarate, and another monomer copolymerizable with these (hereinafter sometimes referred to as a vinyl chloride/ester copolymer)
The alkyl group of the maleic acid alkyl ester and fumaric acid alkyl ester constituting the ester may be linear or branched, but the number of carbon atoms thereof is 4.
It is desirable that the number is at least 1. That is, the number of carbon atoms is 3
Below this, the effect of improving the processability and physical properties of the obtained material is small. Generally, the higher the number of carbon atoms, the better the processability, and the more thermally stable and flexible the material can be obtained. The maleic acid alkyl ester and/or the fumaric acid alkyl ester referred to in the present invention may be monoester or diester, and may be used alone or in combination of two or more. Examples of maleic acid alkyl esters and fumaric acid alkyl esters include (di)butyl maleate, (di)n-octyl maleate, (di)2-ethylhexyl maleate, and (di) maleate.
Examples include dodecyl, (di)isobutyl fumarate, (di)octyl fumarate, and the like. Other monomers that can be copolymerized with vinyl chloride, maleic acid alkyl esters and/or fumaric acid alkyl esters include olefins such as ethylene and propylene, and vinyl fatty acids having 3 or less carbon atoms such as vinyl acetate. Alkyl, unsaturated acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, unsaturated acid esters such as methyl acrylate, unsaturated acid anhydrides such as maleic anhydride, nitrile compounds such as acrylonitrile, methyl vinyl ether, etc. Examples include alkyl vinyl ethers having 3 or less carbon atoms and vinylidene chloride compounds. Furthermore, in the present invention, instead of the vinyl chloride/ester copolymer, the monomer components constituting the polymer mixture include 60 to 95% by weight of vinyl chloride, 5% by weight of an alkyl maleate, and/or an alkyl fumarate. The specific viscosity (JIS K-6721) obtained by mixing at least two types of polymers is 0.16 to 25% by weight, and 0 to 15% by weight of other monomers copolymerized with at least one of these. ~0.31 polymer mixture (hereinafter sometimes referred to as a vinyl chloride/ester polymer mixture) can be used. Here, this vinyl chloride/ester polymer mixture refers to vinyl chloride homopolymer, or vinyl chloride and a monomer copolymerizable therewith (as mentioned above as an example that can be used for the vinyl chloride/ester copolymer). copolymers with maleic acid alkyl esters and/or fumaric acid alkyl esters and monomers copolymerizable with these monomers (for example, vinyl chloride, olefin,
It is a mixture of copolymers with vinyl esters, unsaturated acids or their derivatives, acrylonitrile, vinylidene chloride, etc.), and in short, the monomer components constituting the polymer mixture are mixed in the proportions mentioned above. It can be prepared by selecting and mixing at least two kinds of arbitrary polymers. The proportion of maleic acid alkyl ester and/or fumaric acid alkyl ester in the vinyl chloride/ester copolymer or vinyl chloride/ester polymer mixture is 5 to 25% by weight. That is, if these amounts are less than 5% by weight, the affinity with the conductive substance is poor, and as a result, heat generation during processing is large and there is a risk of decomposition, and the mechanical properties, particularly the toughness, are poor. If a necessary amount of plasticizer or lubricant is used to avoid these drawbacks, the resulting recording medium will have poor environmental stability and thermal stability, which is not preferable. Moreover, if it exceeds 25% by weight, the material containing the conductive substance will have a softening temperature substantially below 45° C., which is not preferable because the recording medium will lack thermal stability. Further, the proportion of other monomers in the vinyl chloride/ester copolymer or the vinyl chloride/ester polymer mixture is 0 to 15% by weight. That is, if it exceeds 15% by weight, either or both of the mechanical properties and thermal stability during processing of the material will deteriorate, which is not preferable. Furthermore, depending on the ratio of each component above, vinyl chloride
60-95% by weight is used. In addition, if the specific viscosity of these copolymers or polymer mixtures is less than 0.16, the mechanical strength of the molded information recording medium will be poor, and preferably if the specific viscosity is more than 0.31, it will be obtained as a copolymer. Not only is it difficult to process, but the moldability of the mixture is also poor, making it undesirable. Examples of the conductive substance used in the present invention include carbon black, as well as fine powders of metals such as silver, copper, and aluminum. In order for an information signal recording medium obtained by molding a material in which this conductive substance is blended with a vinyl chloride ester copolymer or a vinyl chloride ester polymer mixture to perform good capacitance regeneration, this molding is necessary. The recorded recording medium has a predetermined DC volume resistivity (hereinafter simply referred to as volume resistivity).
It is necessary to have Generally, when fine powder of a conductive substance is sufficiently mixed and dispersed in a resin, in order for this material to exhibit a certain degree of conductivity, the fine powder particles must be present at a distance of less than a certain distance (for example, 100 Å or less) or must be in contact with each other. This itself is
It is widely known from literature describing the electron tunneling effect, the conduction mechanism of conductive materials, etc. However, in order to perform good capacitive reproduction using the capacitive information signal recording medium obtained as described above, the volume resistivity of this recording medium must be
It needs to be 0.5Ω·cm to approximately 1kΩ·cm.
Here, if the amount of the conductive substance to be mixed is too small and the volume resistivity is too large, good capacitance regeneration will not be possible. On the other hand, even if the amount of conductive material is increased and the volume resistivity is lowered, below a certain value, the capacitive regeneration performance will almost reach a plateau and will not improve indefinitely; on the contrary, the molded product will deteriorate. The disadvantage is that it becomes brittle. Therefore, it is impractical to use too much conductive material. Therefore, the conductive substance to be mixed is used in an amount of, for example, 10 to 60 parts by weight per 100 parts by weight of the polymer or polymer mixture so that the volume resistivity is within the above range. This is almost the same whether the conductive material is carbon black or other fine metal powder. In the present invention, the material obtained by blending a conductive substance with the polymer or polymer mixture is molded at a relatively high temperature (for example, 130° or higher), so the molding process is similar to that used for general vinyl chloride resin. Preferably, additives such as stabilizers and lubricants are included, and plasticizers and the like may also be included. Further, for the purpose of preventing wear of the regenerated needle, a lubricant such as a silicone-based or fluorine-based lubricant may be included. However, according to the present invention, PVC
Ester copolymers or vinyl chloride/ester polymer mixtures are used, and because the polymer molecules and conductive material particles have good compatibility, the above-mentioned lubricants, plasticizers, etc. may impair the stability of the molded product. It is not necessary to use such a large amount, and the problems of the previously proposed recording medium as described above do not occur. In addition, in order to improve the processability, mechanical properties, especially brittleness and electrical properties of the material, acrylonitrile-butadiene rubber, thermoplastic polyurethane,
Mainly contains elasticity-imparting polymers such as ethylene-vinyl acetate copolymer, vinyl chloride graft polymer on ethylene-vinyl acetate copolymer, methyl methacrylate-butadiene-styrene resin, and chlorinated polyolefin, and methyl methacrylate. A processability-improving polymer such as a copolymer may be added as a copolymer.
In this case, the amount used is, for example, 0 to 30 parts by weight per 100 parts by weight of the vinyl chloride/ester copolymer or vinyl chloride/ester polymer mixture. The above-mentioned conductive substance and the above-mentioned various additives may be blended into the polymer during processing using a normal ribbon blender, Banbury mixer, high-speed stirrer, etc., or they may be added to the polymerization machine together with monomers during the production of the polymer. Furthermore, it may be added and mixed into the slurry of the polymer or polymer mixture before drying. It is necessary that the material thus obtained has a softening temperature of 45°C or higher. Information recording media using materials with a softness temperature of less than 45° C. tend to be easily deformed due to temperature changes during storage and tend to have poor environmental stability. Next, examples of materials used for molding a so-called video disk recording a video signal as an example of a capacitance type information signal recording medium according to the present invention will be described together with a compounding method and a molding method.
All amounts added in the formulations of the following examples are shown in parts by weight. First, before explaining each example, various measurement items for each example material will be explained. "Flexibility temperature"...Measurement was carried out using the flexibility temperature measurement method for hard vinyl chloride plates according to JIS K6745. "Melt viscosity"... 10mm x with Koka type flow tester
Using a 1mmφ nozzle, temperature 160℃, shear rate
Melt viscosity was measured using a 5 mm square pellet sample under conditions of 10 ³ sec ^-1 . "Dynamic thermal stability"... Prabender Plastograph has a chamber capacity of 60 c.c., spindle rotation speed of 60 rpm,
Prepare 68g of 5mm square pellet sample under the conditions of rotor rotation ratio 2:3 and chamber temperature 170℃ 3
The dynamic thermal stability was determined by preheating the chamber for a minute and then rotating it, at which point the torque began to increase and the concore test paper moistened with glycerin held 3 cm above the chamber inlet became colored by the hydrochloric acid gas caused by decomposition. The decomposition time was used as an index of Materials whose decomposition time is less than 15 minutes are undesirable because they may decompose depending on the molding conditions. "Stiffness"...Weight 5 inches by Olsen stiffness tester based on ASTM D-747
Jn, measured under conditions of 1/4 inch span spacing. The sample is a 1 cm x 3 cm x 5 mm square pellet sample obtained from a plate obtained by pressing it with a 75 ton press machine.
A 0.1 cm sample piece was cut out and used. The bending angle is preferably 20 degrees or more, and at least
10deg or higher is required. Discs obtained by molding materials with a diameter of 10 degrees or less tend to break when removed from the molding machine, and are also easily damaged in the deburring process after molding, which is undesirable. "Reproduction C/N"...The ratio between the sync chip output of the synchronizing signal in the reproduced video signal and the residual noise at 2 MHz when the disc is reproduced by a reproducer is calculated and expressed in dB. "Volume resistivity"...A sample of 1.5 cm x 8 cm was cut out from the obtained disk in a tandem shape in the diameter direction, and silver paint was applied to both ends of the sample in a width of 5 mm to serve as an electrode. The distance between the electrodes was measured using a carbanometer, and the DC resistance value was calculated using the following formula. Volume resistivity (Ω cm) = Resistance value (Ω) × Width (cm) × Thickness (cm) / Length (cm) “Reproduction stability”…Recycle the obtained disc with a reproduction machine and play it. Check whether playback can be performed without serious problems such as the playback signal being interrupted for a short time due to needle skipping or the playback needle being lifted up by debris generated from the disk, and whether playback can be performed stably in still image playback mode. It was measured. "Environmental stability": We measured whether the product could be regenerated stably after being left in an atmosphere of 35°C and 80% relative humidity for 24 hours. "Thermal stability": After press-molding a disk, it was left in an atmosphere at a temperature of 45°C for 3 hours, and the degree to which the disk deformed was measured. Example 1 A Henschel mixer was charged with a specific viscosity of 85% by weight vinyl chloride and 15% by weight dioctyl maleate.
0.182 copolymer, 2.5 parts by weight of dibutyltin dilaurate as a stabilizer, 0.5 parts by weight of epoxidized die oil, 0.5 parts by weight of dimethylpolysiloxane as a lubricant, and wax manufactured by Hoechst of West Germany as a lubricant. 2 parts by weight of E (trademark) were added and thoroughly stirred. Next, as carbon black, 20 parts by weight of Ketchen Black EC (trademark) (average particle size 30 mμ) manufactured by Akzochemy, Netherlands, was added and further stirred thoroughly. This well-stirred material is rolled into an 8-inch open roll (roll gap 0.2
mm) for about 8 minutes. The surface temperature of the roll at this time was 150°C. After kneading, the pellets were cut into sheets and made into 5 mm square pellets, a portion of which was used as a test sample for melt viscosity, dynamic thermal stability, and rigidity, and the remainder was passed through an extruder for preforming by extrusion. The extruder temperature was 160°C. The preformed material is molded using a compression molding machine equipped with a video disk stamper at a pressure of 140 kg/cm ^2.
Press molding was performed in a 60-second cycle to obtain a video disc. This video disc was directly placed on a playback machine, and the playback C/N was measured. Further, the volume resistivity of this video disc was determined by the method described above. The obtained data are shown in the Example 1 column of Table 1. Example 2 Data obtained using the same method as in Example 1 but with the added amount of carbon black being 15 parts by weight and 25 parts by weight are shown in the columns of Examples 2a and 2b in Table 1. Furthermore, the data obtained by changing the type of carbon black to 35 parts by weight and 40 parts by weight of Vulcan CSX-99 (trademark) manufactured by Cabot Co., Ltd. (average particle size of about 13 mμ) are shown in the columns of Examples 2c and 2d in Table 1. It was shown to. From this example, it can be seen that even if a certain amount or more of carbon black is mixed, the superiority in disk reproduction does not change.

[Table] Example 3 In the same manner as in Example 1, the polymer composition was changed as shown in Table 2 below. However, among the comparative examples in Table 2, when the polymers e and g, excluding f, were passed through an extruder with the same composition as in Example 1, the torque and heat generation were large, and there was a risk that the materials would decompose during processing. Therefore, for Comparative Examples e and g, experiments were conducted using the following formulations in which 3.0 parts by weight of the plasticizer dioctyl phthalate was further added to Example 1. [Music] Polarized part 100 weight part Divotyl tin jirates 2.5 〃 epoxy soybean oil 0.5 〃 dimethyl polychilloxiloxan 0.5 〃 Watsukus E 2.0 〃 Geocylphthalate 3.0 〃 Ketsuchen Bratcsk EC 20 〃 However Regarding stability, ○ indicates good, △ indicates acceptable, and × indicates not acceptable.
This symbol also applies to Tables 3 and 4 below.

[Table] Example 4 The polymer composition was changed in the same manner as in Example 1.
The polymer composition and the data obtained are summarized in Table 3 below.

【table】

[Table] Example 5 Instead of the single polymer used in Example 3, a polymer mixture containing 40 parts by weight and 60 parts by weight of the polymers used in Comparative Examples f and g of Example 3, respectively, was used. When the same experiment as in Example 1 was conducted, the data shown in Table 4 below was obtained.

【table】

[Table] Note that the capacitive information signal recording medium according to the present invention is not limited to a video disk, and may also be a disk on which a PCM audio signal is recorded, for example.
In short, any information signal recording medium may be used as long as it can be reproduced by changing capacitance in response to changes in geometrical shape. Furthermore, it goes without saying that the polymer composition, blending, etc. are not limited to the above examples.

Claims (1)

[Claims] 1 The information signal is recorded as a change in the geometric shape of the surface, and the capacitance between the electrode of the regeneration needle that scans the surface relatively changes according to the change in the geometric shape. In capacitive recording media where information signals are reproduced, (vinyl chloride)
60 to 95% by weight, 5 to 25% by weight of a maleic acid alkyl ester and/or fumaric acid alkyl ester having an alkyl group having 4 or more carbon atoms, and 0 to 15% by weight of other monomers copolymerizable with these. (2) A copolymer with a specific viscosity (JIS K-6721) of 0.16 to 0.31 consisting of A capacitive information signal characterized in that at least the surface portion is formed of a material having a soft temperature (JIS K-6745) of 45°C or higher obtained by blending a conductive substance into a combined mixture. record body.