JP2976225B2 - Carbon black for capacitance type information recording medium and information recording medium of the same type - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Object of the Invention (Industrial Application Field) The present invention relates to a capacitance-type information recording medium, for example, a high-density information recording medium such as a video disk and a digital audio disk, in particular, information The signal is recorded as a change in the geometrical shape of the surface portion, and the recorded information is stored in accordance with the change in the geometrical shape when the capacitance between the electrode of the reproducing needle that relatively scans the surface is changed. The present invention relates to a carbon black used for manufacturing a capacitance type disk or the like which reproduces as an information signal by utilizing the change of the information, and a capacitance type information recording medium using the carbon black.

(Prior art) A video disc disc is manufactured by forming a resin composition in which a high concentration of carbon black is blended with a thermoplastic resin such as polyvinyl chloride by pressure forming fine pits on the surface. Is well known (Japanese Patent Application Laid-Open
140518, 60-63745, etc.). Such a video disk board has, firstly, that the video disk board itself containing carbon black has a sufficiently low volume resistivity and the necessary conductivity, and secondly, it has fine pits. It is premised that the material has sufficient moldability to be formed (JP-A-59-194818,
No. 60-186557).

Further, the resin composition containing the carbon black before the molding of the video disk should not contain coarse particles or metal salts having high hygroscopicity. When they are contained, they cause deformation of the shape of the molded product and cause swelling with time (Japanese Patent Laid-Open Nos. 61-252270 and 60-24).
No. 973).

That is, a video disk of the capacitance reproduction method is a conductive plastic formed by mixing a conductive material such as carbon black with a vinyl chloride resin, for example, and has a width of 1 μm and a depth of 1 μm on the surface of the video disk. 0.3
Small pits of about μm are formed.
Then, on the pit of such a video disc,
For example, scanning is performed with a fine diamond stylus having a bottom surface of about 5 μm × 6 μm, the capacitance between the electrode of the diamond stylus and the video disk is detected, and an information signal is reproduced by a change in the detected capacitance. .

Incidentally, a certain amount of a liquid additive (stabilizer or the like) is blended in such a resin composition for molding a video disc or the like in order to impart thermal stability and surface lubricity to the video disc or the like. Therefore, at the time of processing and molding a video disk or the like, the liquid additive is leached in a very small amount and migrates to the surface of a mold (stamper).
Therefore, when the number of molded articles increased, the pit shape of the molded article collapsed due to the liquid additive transferred to the surface of the stamper,
If Y-S / N is degraded and becomes worse, adjacent pits are linked together, resulting in crosstalk that picks up signals of adjacent pits during reproduction, resulting in disturbance of the screen or sound.

Then, when the attached matter of the video disk was actually analyzed, absorption of carbonyl was confirmed by an infrared spectrophotometer, and an electron probe microanalyzer (EP
MA) confirmed the spectrum of tin. Therefore, the deposit is presumed to be a tin-based liquid additive (stabilizer) blended in the resin composition before molding.

For these reasons, in order to keep the performance of video disc products above a certain level, there has been a limitation on the number of discs that can be formed by a stamper, and this has caused a significant reduction in disc forming productivity. In order to prevent the transfer of the additive to the surface of the stamper and the occurrence of crosstalk caused thereby, it was considered to adjust the amount and type of the liquid additive, but a sufficient effect was not obtained. (JP-A-59-195355).

(Problems of the Invention) The present invention relates to carbon black used for manufacturing a capacitance type information recording medium such as a video disk, which effectively prevents leaching of a liquid additive during pressure molding of the recording medium,
In addition, the present invention provides a carbon black for the recording medium capable of increasing the number of moldings of the recording medium that can be molded without occurrence of crosstalk and increasing the productivity of the molding, and a capacitance information recording using the carbon black. It is intended to provide a medium.

(B) Configuration of the Invention (Means for Solving the Problems) The present inventors have conducted various studies to solve the above-mentioned problems, and as a result, in this type of recording medium, a liquid additive (liquid stabilizer or the like) has been used. The addition is necessary to maintain the thermal stability of the polymer, etc., and the addition amount cannot be extremely reduced or can be completely absent. It has been found that the leaching of the liquid additive during pressure molding can be extremely effectively prevented by selecting a carbon black having a high adsorption performance having a good performance. As a result of further research, the carbon black for a recording medium has remarkably excellent adsorption performance for the liquid additive in addition to the physical properties (conductivity and processability) required for the carbon black for a recording medium. The present inventors have found a specific carbon black having the above characteristics, and have reached the present invention.

In other words, capacitive carbon black for an information recording medium of the present invention, the volume of pores 20Å by N ₂ adsorption method
0.30cc / g or more, ash content is 0.02% by weight or less, coarse particles remaining on 44 μm sieve is 0.0002% by weight or less, dibutyl phthalate absorption is 270-350m / 100g, and body area average primary particle size Is 15 to 20 nm.

Further, capacitive type information recording medium of the present invention, in a resin matrix, the volume of pores 20Å by N ₂ adsorption method
0.30cc / g or more, ash content is 0.02% by weight or less, coarse particles remaining on 44 μm sieve is 0.0002% by weight or less, dibutyl phthalate absorption is 270-350m / 100g, and body area average primary particle size Is a recording medium characterized by being formed by dispersing and molding carbon black having a thickness of 15 to 20 nm.

Carbon black in the present invention, thus, N ₂
The pore volume of 20 mm or less by the adsorption method is 0.30 cc / g or more, the ash content is 0.02% by weight or less, and the coarse particles remaining on the 44 μm sieve are 0.00
02% by weight or less, the absorption amount of dibutyl phthalate (hereinafter “DB
P absorption amount) is 270-350m / 100g, and the body area average primary particle size is 15-20nm, but the alkaline earth metal content is 20ppm by weight or less, and the specific surface area is Those which are 1400-1600 m < ² > / g are preferable.

When volume of pores 20Å by N ₂ adsorption method of carbon black is less than 0.30 cc / g, the adsorption performance of the liquid additive is decreased, the effective leaching of the additives in the molding of the recording medium It cannot be prevented. On the other hand, if the ash content exceeds 0.02% by weight, swelling tends to occur during molding, which is not preferable because it causes dropout. Further, if the amount of coarse particles remaining on the 44 μm sieve exceeds 0.0002% by weight, poor swelling is liable to occur, which also causes inconvenience.

Carbon black or less of the pore volume of 20Å by such N ₂ adsorption method of the present invention has 0.30 cc / g or more pore structure is easily produced by the method disclosed in JP-A-61-148270 be able to. The ash content and coarse particle content of carbon black can be easily controlled by the method disclosed in JP-A-61-89262.

As the matrix resin for the recording medium of the present invention, various resins such as polyvinyl chloride can be used, and further, the matrix resin includes a heat stabilizer, a lubricant and other various processing aids, and furthermore, a disk or the like. Silicone lubricant etc. for imparting surface lubricity is compounded,
Since these matrix resins and compounding agents such as processing aids are known per se, detailed description thereof is omitted.

In order to produce the recording medium of the present invention, a matrix resin such as polyvinyl chloride, the carbon black of the present invention (the compounding ratio of carbon black is about 10 to 30% by weight based on the resin composition), and the necessary Heat stabilizers, lubricants, and processing aids are added in predetermined amounts, and a silicone-based lubricant added to maintain the lubricity of the disk surface is put into a high-shear stirrer (for example, a Henschel mixer) and mixed. The resulting compound is kneaded using a kneader such as a kneader or a Banbury mixer, and then granulated to obtain pellets. Next, the obtained pellet is supplied to a molding machine provided with a mold (referred to as a stamper) on the surface of which an information signal has been applied, and is molded by a replica into a molded body (recording medium) on which double-sided information recording is cut.

When a recording medium such as a video disk is molded from the resin composition in which the specific carbon black is dispersed in accordance with the present invention, the stamper life (the number of disk disks obtained with one stamper) is higher than in the conventional case. It is greatly improved.

(Examples, etc.) Hereinafter, the present invention is not limited by these examples and the like, which will be described in more detail with reference to examples and comparative examples.

Examples 1 to 3 (Production of carbon black) Carbon black was produced according to the method disclosed in JP-A-61-148270.

That is, using the carbon black production furnace having the structure shown in Figure 1 of the accompanying, fuel having the composition shown in Table 2 below in the first zone 8 (coal gas) 190 Nm ³ / hr, and fuel air 1000 Nm ³
/ hr is supplied from nozzles 2 and 3 and burned, and a raw material oil (creosote oil) having physical properties shown in Table 2 below is shown in the obtained high temperature gas stream from nozzle 1 in Table 3. The carbon black particles were generated in the second zone 9 by supplying each at each flow rate. Next, in the third zone 10, steam is introduced from the nozzle 4 and auxiliary fuel (coal gas having the composition shown in Table 2) and air or oxygen are introduced from the nozzle 7 at the respective flow rates shown in Table 3. The carbon black produced in the zone was activated in the third zone while maintaining the activation temperature and activation (residence) time shown in Table 3. Then
At the latter stage of the third zone, the reaction stop cooling water was sprayed from the nozzles 5 and 6 to stop the reaction and at the same time cool the produced carbon black, and then collected the produced carbon black with a bag filter. Adjustment of the residence time (activation time) was performed by changing the spray position of the cooling water for stopping the reaction. Further, the cooling water for stopping the reaction was sprayed in such an amount that the temperature of the product at the outlet of the carbon black production furnace became about 500 ° C.

(Purification of Carbon Black) Each of the obtained carbon blacks was subjected to a purification treatment for controlling ash and coarse particles in accordance with the method described in JP-A-61-89262.

That is, each produced carbon black was first mixed with water so as to be 4% by weight, and vigorously stirred to obtain a high-concentration carbon black water slurry having a viscosity of 50 poise. Then
Each slurry was diluted with water to 2.5% by weight and stirred until the equilibrium viscosity at the same concentration was reached. Then, each of the obtained slurries was pressurized to an overpressure of 0.2 kg / cm ² using a slurry pump, and the oscillation frequency was increased. 19.5kHz, oscillation input 30W / cm ³ , oscillation amplitude 20μm, clearance between the oscillator and the sieve mesh 3.0mm, transferred to the ultrasonic vibration sieve device set to 28μm mesh opening,
A water-insoluble solid foreign matter was removed. Next, hexane, an organic solvent, was added to the obtained carbon black water slurry in an amount of 300 m / 100 g-carbon black and stirred, and the carbon black was transferred to the hexane phase and granulated at the same time. Next, the obtained hexane-containing granular carbon black was separated from water and dried with a steam dryer at 180 ° C. for about 5 hours.

The physical properties of each of the obtained carbon blacks after the purification treatment are as shown in Table 3.

Comparative Examples 1 to 4 The production conditions were changed as shown in Table 3, respectively. Other than that, each carbon black was produced in accordance with Examples 1 to 3, and each produced carbon black was used in Examples 1 to 3.
Purification was performed in the same manner as described above. The physical properties of each of the obtained carbon blacks are as shown in Table 3.

The conditions for setting the residence temperature (activation temperature) and residence time (activation time) in the production of the carbon black of the comparative example are based on the method disclosed in JP-A-61-76554. As shown in Table 3, the carbon blacks obtained in the respective comparative examples had a smaller micropore amount than the carbon blacks obtained in Examples 1 to 3.

Examples I-III Comparative Examples I-IV Using each of the carbon blacks produced in Examples 1-3 and Comparative Examples 1-4, an information recording medium (video disc) was produced by the following method.

That is, a graft copolymer of vinyl chloride and the same copolymer having an average degree of polymerization of 500 and containing 3.2% by weight of a copolymer of ethylene and vinyl acetate as a graft component (Tosease GK, trade name of Tokuyama Sekisui Kogyo Co., Ltd.) 5 parts by weight of a dibutyltin mercapto-based stabilizer (trade name: RES-1) and 100 parts by weight of a fatty acid glycerin ester-based lubricant (trade name: RES-21, manufactured by Riken Vitamin Co., Ltd.)
0) 2 parts by weight, fatty acid alkyl ester-based lubricant (trade name: RES-310, Kao Soap Co., Ltd.), 0.5 parts by weight, and dimethylpolysiloxane (trade name: RE, Shin-Etsu Chemical Co., Ltd.)
S-421) 1.0 part by weight was added through a 0.2 μm filter, put into a Henschel mixer, and stirred at high speed to 110 ° C.
After the temperature was raised to the level shown in Table 4, each carbon black was blended, heated to 110 to 120 ° C again, stirred at a high temperature for 20 minutes with a Henschel mixer, and then cooled to room temperature. Next, each of the obtained compounds was sufficiently kneaded using an extruder (manufactured by Bus Inc.) and granulated. Each of the obtained pellets was placed in a φ50 mm single screw extruder, and a cylinder temperature of 150
After molding into a preform at a temperature of ° C., it was further supplied to a compression molding machine equipped with a stamper and molded into each video disc.

The melt index of each obtained pellet at 210 ° C,
Physical properties such as conductivity of each molded product (video disc), dropout occurrence rate, Y when 300 sheets were compression molded
-Disc characteristics such as S / N and crosstalk deterioration rate, and productivity were compared. The results were as shown in Table 4.

Notes to Table 4 * 1 (Melt index) Load of 19.9 kg with a nozzle of 2 mm diameter * 2 (Conductivity) Volume resistivity, Japan Rubber Association Standard SRIS2301-19
According to 69.

* 3 (Dropout occurrence rate) According to the method described in JP-A-59-195354, a dropout counter (defect checker) of 1000 completed discs shows a dropout of 3H or more. It is a comparison based on the rate of occurrence.

Note that the dropout 1H corresponds to the loss of one scanning line on the television screen, and a dropout of less than 3H can be completely corrected by processing it with an electric signal in a reproducing apparatus, and thus is treated as an allowable level.

* 4 (S / N deterioration rate) First, the specified mold (technical stamper) was mounted on the compression molding machine, and the specified number of disks (300) were continuously formed (1,5,10,15,20,25) , 50,75,100,150,175,
The 200th, 250th, and 300th sheets) Measure the Y-S / N value of the signals recorded at 0 ', 30', 45 ', and 56' (50IRE gray in the NTSC system). It was confirmed that the relationship was almost linear.

Next, when the deterioration amount (dB) at each time of the conventional product (comparative example) was set to 100, the deterioration ratios of Examples 1 to 3 and Comparative Examples 1 to 3 were displayed as S / N deterioration rates.

Table 4 shows data of 0 '(outer peripheral portion) and 56' (inner peripheral portion).

* 5 (Crosstalk degradation index) In the same way as the S / N degradation rate, a specified mold (technical stamper) is attached to a compression molding machine, and a predetermined number (300) of continuously formed discs (1,5,10,15) , 20,25,50,75,10,1
The following stroke values (* 6) recorded at 0 ', 29', 44 ', and 56' were measured for the 50th, 175th, 200th, 250th, and 300th sheets, and it was confirmed that the deterioration of the crosstalk value was almost linearly related to the number of pressed sheets. .

Next, the percentage of deterioration in Examples 1 to 3 and Comparative Examples 1 to 3 when the amount of deterioration (dB) at each time of the conventional product (Comparative Example 4) was set to 100 was displayed as a crosstalk deterioration index. . Table 4 shows 0 '(outer peripheral part) and 56'
(Inner circumference) data is shown.

* 6 (Crosstalk) Indicates the degree of S / N deterioration due to the influence of adjacent tracks. In the capacitance reproduction method (VHD method), the video signal is
The track next to the recorded track (one round =
1/15 second before and after). This effect appears as noise (roughness on the screen).

The crosstalk value is the S / N value of the gray part (= CTY) of the signal in which black (7.5 IRE) and gray (50 IRE) are recorded alternately, and the S / N value of the continuous gray part in the vicinity. (Y−S / N) [Expression (1) below].

(Crosstalk) = (Y−S / N) − (CTY) (1) Comparing Examples 1 to 3 with Comparative Examples 1 to 4, the pore volume of 20 ° or less by the N ₂ adsorption method was 0.30 cc / When g or more, S / N
The deterioration rate, and especially the crosstalk deterioration rate, is a remarkably low value, and the reproduction characteristics are improved. Example 1
When carbon black having an ash content of 0.02% by weight or less and a coarse particle remaining on a 44 μm sieve of 0.0002% by weight or less is compared with Comparative Example 3, a defect on a disc surface represented by dropout ( That is, scanning line defects on the screen) are significantly reduced.

As described above, the pore volume, the ash content and the coarse particle content of the carbon black having the specific values specified in the present invention are excellent in regenerating characteristics, and extremely excellent in productivity during molding represented by a stamper life. A recording medium was obtained.

(Effects of the Invention) In the present invention, by using a specific carbon black having a large pore volume and an extremely small amount of ash and coarse particles as a conductive material for a capacitive recording medium, dropout and crosstalk can be achieved. As a result, it is possible to obtain the same recording medium having excellent reproduction performance in which image quality degradation is greatly improved, and the productivity of the recording medium can be significantly increased.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing an example of a carbon black production furnace. Each symbol in the figure is as follows. 1 ... feed oil supply nozzle, 2 ... fuel supply nozzle, 3 ...
... Oxygen-containing gas supply nozzle, 4 ... Activator introduction nozzle,
5: 1st cooling water introduction nozzle, 6: 2nd cooling water introduction nozzle, 7: High-temperature gas supply nozzle for auxiliary heating, 8: 1st zone, 9: 2nd zone, 10: 3rd Band, 11 ... Chalk (furnace narrowing part), 12 ... Flue.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hideyuki Hisa 2447 Fujita, Yawatanishi-ku, Kitakyushu-shi, Fukuoka Prefecture 1 within the Kurosaki Plant of Mitsubishi Kasei Co., Ltd. No. 1 Inside the Kurosaki Plant of Mitsubishi Kasei Co., Ltd. (72) Inventor Toshiaki Hamaguchi 3-12 Moriyacho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Within Victor Company of Japan, Ltd. (72) Toshiki Kasai Moriya, Kanagawa-ku, Yokohama, Kanagawa 3-12, Chocho, Japan Victor Company, Ltd. (72) Inventor Toshio Akai 3-12, Moriyacho, Kanagawa-ku, Yokohama, Kanagawa Prefecture, Japan Victor Company of Japan, Ltd. (56) References JP-A-61-73773 (JP, A) JP-A-61-252270 (JP, A) JP-A-58-105445 (JP, A) JP-A-57-200954 (JP, A) 194818 (JP, A) JP Akira 61-89262 (JP, A) JP Akira 61-148270 (JP, A) (58 ) investigated the field (Int.Cl. ^6, DB name) C09C 1/48

Claims (2)

(57) [Claims] (1) a pore volume of not more than 20 ° by an N ₂ adsorption method is 0.30
cc / g or more, ash content is 0.02% by weight or less, coarse particles remaining on 44 μm sieve is 0.0002% by weight or less, dibutyl phthalate absorption is 270 to 350m / 100g, and body area average primary particle size is Carbon black for a capacitance type information recording medium, having a thickness of 15 to 20 nm. _{2. The} method according to claim 2, wherein the resin matrix contains 20
細孔 Pore volume of less than 0.30cc / g and ash content of 0.02% by weight
Below, the coarse fraction remaining on the 44 μm sieve is 0.0002% by weight or less, and the dibutyl phthalate absorption amount is 270 to 350 m / 100 g,
A capacitance type information recording medium characterized by being formed by dispersing and molding carbon black having a body area average primary particle diameter of 15 to 20 nm.