JPS5925288B2 - information record body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in lubricants for high-density information recording media such as video disks, and particularly to the purification and fractionation of methylalkylsiloxane lubricants that exhibit excellent performance as lubricants for video disks.

U.S. Pat. No. 3,833,408, cited herein, describes the use of methylalkylsiloxane compositions as lubricants for conductive video discs having audio and visual information recorded in the form of geometric variations on the inner surface of the spiral grooves. is listed.

The video disc is first coated with a conductive material to serve as the first electrode, then a dielectric material, and finally a coat of lubricant.A storage needle with a metal point serves as the second electrode of the capacitor. When information in the form of irregularities passes under the storage needle, the storage needle detects the change in capacitance between it and the disk surface and monitors the information. Polyvinyl chloride (P) containing carbon and elementary particles
VC) consisting of a conductive plastic material, such as a copolymer resin, which surrounds the carbon particles and forms a dielectric surface layer on the surface of the conductive particles, the disk being capable of capacitive readout. A video disk was developed. This development eliminates the need for separate metal and dielectric coatings on plastic discs. Accumulator needles, which had previously been made of metallized sapphire, have been improved to allow the use of metallized diamond.

Since diamond is a harder and less abrasive material than sapphire, it requires good lubrication of the disk surface. Video discs have also evolved to eliminate the need for guiding or grooved surfaces.

That is, the storage needle is held in synchronization with the information pattern track by an electrical signal instead of by the groove wall. This change in video disk and stylus materials has slightly changed the requirements for lubricants, and commercially available methylalkylsiloxane lubricants are now unsatisfactory in certain respects.

One commercially available methylalkylsiloxane has the following chemical formula. Here, R is a linear decyl group, and n is an integer.

This material has a molecular weight of approximately 1500 and is manufactured by General Electric Co.
It is commercially available under the trade name SF-1147. The composition also contains about 1.5% antioxidant compounds. When current video disks molded from carbon-filled PVC compositions are sprayed with SF-1147 lubricant and regenerated with a diamond stylus, the regeneration performance and stability are unsatisfactory, so it is desirable to improve the performance of this type of lubricant. This invention arose while conducting research.

That is, it has been discovered that methylalkylsiloxane represented by the following formula has excellent lubricity for use in video discs, high stability at high temperatures and high and low humidity, and high resistance to changes over time. However, Rl and R2 are each an alkyl group having 4 to 20 carbon atoms, x is an integer 2,
3 or 4, y is an integer 0, 1 or 2, and the sum of X and y is 4 or less.

The methylalkylsiloxane composition of this invention has a pressure of 10
-5m77! Distillation temperature in Hg is about 100-205
℃, the molecular weight range is about 500 to 8001, and the polydispersity ratio, which is the ratio of weight average molecular weight to number average molecular weight, is about 1.07 or less.

The fraction useful here can be obtained by molecularly distilling a mixed siloxane raw material represented by the following formula under high vacuum and low temperature conditions to obtain a fraction with a narrow molecular weight range. However, as mentioned above, M and p are integers for URLl and R2.

Molecular fractions are well known and are published in Analytical Chemistry (October 1964).
istry), Volume 36, No. 11 blank (Frank
) and others, “Molecular Distillation of Superthermosensitive Liquids”
arDistillatiOnOfTherma-11
ySupersensitive Liquids), this method will now be described in detail with reference to FIG. 1, which shows a molecular still 10.

The material to be distilled is passed through a conduit 16 through a liquid nitrogen trap 18.
via a diffusion pump 14 to a supply reservoir 12 which is evacuated. This reservoir 12 has a glass coil 24
It is connected to a distillation chamber 20 that includes a glass tube 22 having a tank 26 at one end of which is wound a tank 26 for storing a high-temperature liquid. The distillation chamber 20 also has two further vessels, a retentate vessel 28 and a distillate vessel 30. The feed pipe 32 is for flowing material from the feed reservoir 12 through the valve 34 into the distillation chamber 20. Distillation chamber 20 is maintained at high vacuum via conduit 36 that communicates with diffusion pump 14 . In operation, the device is evacuated to an initial pressure of approximately 10-7 MmHg. When boiling water is placed in the tank 26, it rises up the glass tube 22, and the glass coil 2 wound around the tube rises.
4 to about 100°C. Control valve 34 is opened to allow the material to be distilled to trickle down from reservoir 12 onto heated glass tube 22, whereupon the material flows into glass coil 24.
It forms a smooth thin film that is spread out by the coil 24 and periodically reversed as it moves along the coil 24, evaporating volatile components. Materials that evaporate at temperatures below 100°C evaporate from the heating tube 22 and condense on the wall surface of the distillation chamber 20,
The remaining material flows down the wall and collects in the distillate tank 30, while the remaining material collects in the residue tank 28.

In order to separate materials with a boiling point of 100°C or higher and 205°C or lower that are useful in this invention, for example,
When distillation is repeated by filling the feed reservoir 12 with benzyl alcohol from the first fractionation, the required distillate will collect in the distillate tank 30 as described above, increasing the boiling point. The higher the molecular weight, the more the high molecular weight fraction collects in the residual distillate tank. By using this separation method. The liquid material simply comes into contact with the heated glass tube without heating the entire material, resulting in collisionless evaporation at the lowest temperature without damaging the heat-sensitive molecules. This molecular distillation process for methylalkylsiloxane feed material It has been found that it is possible to not only fractionate the feedstock, but also to purify it by removing all antioxidant compounds and chromophores as well as silicon hydride to produce a very good lubricant for video discs.

The results of this purification were unexpected, surprising, and highly desirable since hydrides are chemically active and can result in gelation that causes dropouts and noise during video disc playback. Metal aromatic complex chromophores and antioxidant compounds are also highly disadvantageous because they react with the video disc surface and contribute to a deterioration of playback quality over time. Antioxidants commonly added to methylalkylsiloxane compounds are both of the free antioxidant type and of the chemically bound antioxidant type. The free antioxidant is represented by the following formula: Moreover, the chemically bonded antioxidant is represented by the following formula.

Since the concentration of unbound antioxidants varies from batch to batch, resulting in non-uniformities in video disc playback performance, this unbound lubricant can be removed by dissolving it in acetone and fractionating the acetone layer from the methylalkylsiloxane. I can do it.

However, the presence of chemically bound antioxidants often renders video discs unplayable within a few weeks, so the presence of aromatic impurities and antioxidant compounds in current lubricants for video discs is simply unacceptable. . The removal of silicon hydride by this molecular distillation process, particularly to the bottom fraction or high molecular weight fraction, was highly unexpected since silicon hydride is generally a low boiling point compound. Even at relatively low temperatures, if silicon hydride is present, it is thought to react with the methylalkylsiloxane compound to form a high molecular weight fraction or cause gelation, which in turn consumes the low molecular weight fraction over time and forms a gel. This is extremely inconvenient, as it causes a large amount of information to be lost during playback of the video disc. The fractionated methylalkylsiloxane of this invention can be dissolved in a suitable solvent inert to the video disk surface, such as heptane or isopropanol, and typically the methylalkylsiloxane solution is about 0.2 to 2.0% by weight.
It is.

This solution is then sprayed onto the disk surface to a thickness of approximately 200 mm.
300 people form a siloxane coating. This lubricant coating can also be vapor deposited. The lubricant fraction of the present invention does not change over time, is stable in the atmosphere, provides a high degree of uniformity and reproducibility to video discs, and also provides low wear on the stylus and disc, as well as improved initial replay performance. It shows excellent lubricity as evidenced by the improved lubricity.

The invention will now be further explained by way of example, without restricting the invention to its details. In the examples, percentages indicate weight ratios unless otherwise noted. Example 1 When n is an integer from 1 to about 8, it is expressed by the formula, exhibits a viscosity of 49.4 centistokes at 22°C, a number average molecular weight of 1239, a weight average molecular weight of 15
A methylalkylsiloxane feed having a polydispersity of 1.57, thus a polydispersity of 1.26 and a refractive index of 1.4463, was molecularly distilled using the distillation apparatus shown in FIG.

FIG. 2 shows the percentage of distillate weight relative to the feed weight as a function of temperature. The fractions distilled at 100-205°C were collected.

The viscosity of the distillate is about 14 centistokes at 25 C, and the weight average molecular weight is 660, which corresponds to the general formula (1) where y=01X=3 and R1 is a decyl group, The dispersion rate was 1.06 and the refractive index was 1.435.
The color of this distillate was determined by measuring the optical density at various wavelengths of a 107 nm thick sample and comparing this with the color of the feed material and the color of the residue after molecular distillation.

This data is summarized and shown in Table 1. The distillate thus contains less color-forming material than the feed and the residue at all wavelengths tested. The hydride content of the distillate was also significantly reduced compared to the feed.

A sample with a thickness of 1.0 mm was heated at a wave number of 2150/CTn (SlH
), the infrared absorption analysis showed that the feed material was approximately 5~
It contained 12/Cm of silicon hydride, but the distillate contained 0.
It contained less than 1/2 hydrides. The infrared spectrum of this feed is shown by curve 1 in FIG. 3, and that of the distillate by curve 2.

In this way, methylalkylsiloxane is fractionated and purified by molecular distillation.

Example 2 The feedstock of Example 1 was molecularly distilled into five fractions using appropriate heating fluids and various measurements were made.

This data is shown in Table 2, where fraction 1 is at 4'C, fraction 2 at 100 °C, fraction 3 at 153 °C, fraction 4 at 211 °C, and fraction 5 at 239 °C. Each was collected at ℃.
The table above shows that methylalkylsiloxanes can be fractionated into fractions with narrow molecular weight ranges by molecular distillation.

Example 3 A series of video discs were tested by depositing various lubricant compositions and distillates by vapor deposition or spraying and regenerating them with titanium-plated Diacent accumulators.

Lubricant A is a methyldecylsiloxane of the formula having a molecular weight range given in Example 1, i.e. a number average molecular weight of 1239 and a heavy molecular weight of 1557, containing no antioxidants and deposited by vacuum evaporation. It was done.

Lubricant B is the same lubricant but was applied by spraying a 1% solution of heptane. Lubricant C is a fraction obtained by molecular distillation at 100 to 205°C, and corresponds to methylalkylsiloxane in which x-3, y-0, and R1 are decyl groups in formula (1), and has a weight average molecular weight of 660. It was also applied by spraying. The thickness of these lubricant coatings was approximately 200λ. The quality of the video disc during playback was evaluated by measuring the carrier wave degradation time, which is the time (in seconds) during which the radio frequency output of the arm falls below the peak-to-peak value of 150 m during the entire playback period of the disk. (times shorter than 10 microseconds are rounded down) and the time indicating a defect where the frequency of the radio frequency output is about 8.6 MHz or more or 3.1 MHz or less.

Such defects are observed by the viewer as signal dropouts. The acceptance criteria for a video disc is a maximum of 3 seconds in a 30 minute playback time, and if the video quality is good, it is considered to be 0.3 seconds or less in a 30 minute playback time. Twelve disks using the above lubricant were tested, and the percentage of disks that passed each criterion was calculated as shown in Table 3.

3 on the same 20 minute zone for the above 12 disks.
The needle and disk surface were tested for wear by measuring the degree of wear on the needle before and after five plays and inspecting the disk surface for severe visible wear and significant damage visible to the naked eye or microscopically.

This data is shown in Table 4. The effect of low humidity on the lubricant fraction of Example 1 was tested by measuring the carrier wave degradation time of 12 video disks at a temperature of about 24.5 DEG C. and a relative humidity of 18%. This disc has 30 plays
The carrier wave degradation time was less than 0.3 seconds per minute. Next, when this was stored at a temperature of approximately 18.8°C and a relative humidity of 6% for 72 hours and then played, all discs were successfully played and the carrier wave deterioration time was less than 0.3 seconds per 30 minutes of playback. .
When the supplied lubricant was applied to video disks and tested as described above, 42% of the disks showed a carrier wave degradation time of less than 0.3 seconds per 30 minutes of playback, and 75% also showed a carrier wave degradation time of less than 3 seconds. It was shown that.

This remained unchanged even after storage at low humidity. Example 5 The effect of low temperatures on the lubricant of this invention was tested by measuring the carrier wave degradation time of 12 video discs coated with the lubricant fraction of Example 1 at a temperature of about 24.5°C and 20% relative humidity. As a result, the carrier wave deterioration time for all disks was less than 0.3 seconds per 30 minutes of playback.

Next, the temperature is about 15.0 to 22.2℃, and the relative humidity is 25℃.
When the disks were regenerated immediately after being stored in a low-temperature chamber for 72 hours, all disks showed good performance both before and after storage, and carrier wave deterioration times were all less than 3 seconds per 30 minutes of playback. This result remained unchanged before and after low temperature storage. EXAMPLE 6 The effect of high temperature and high humidity on the lubricant of this invention was determined after 12 video discs coated with the lubricant fraction of Example 1 were stored for 24 hours in a room at about 35° C1 and about 75% humidity. It was tested by measuring the carrier wave degradation time.

Data on this carrier wave deterioration time is shown in Table 5. It is expressed by the formula. A hybrid methylalkylsiloxane in which M and p are integers from 2 to 7 is produced, and this is molecularly distilled to give 10
Fractions between 0 and 205°C were collected.

A 1% heptane solution of this lubricant fraction was sprayed onto a video disc as in Example 1. High temperature and high humidity conditions (35℃, 75%
Table 6 shows the playback data before and after storage in ). Example 8 A series of methylalkylsiloxanes represented by the formula, where R is a hexyl group, an octyl group, or a decyl group, and m is an integer of 2 to 7, are prepared, and then molecularly distilled to obtain a 100 to 20
Fractions at 5°C were collected.

This was sprayed onto eight video records and the carrier wave deterioration time was measured. This data is shown in Table 7. The discs were then stored at 35° C. and 75% for 72 hours and retested. This carrier wave deterioration time data is shown in Table 8. A needle wear test was also conducted, and it was found that the degree of wear of the needle was 0.04 μ3/hour or less in all tests.

Comparative Test 1 Commercially available methylalkylsiloxane composition SF-1147
was treated to remove free antioxidants as follows.

When the lubricant is shaken twice with equal amounts of acetone and layered, the free antioxidant is dissolved into the acetone along with some low molecular weight silicone oil. Collect the siloxane layer and 80℃ in vacuum.
and evacuated to 10 mm Hg at 8'C to remove all free antioxidant while leaving the chemically bound antioxidant and molecular weight distribution of the feedstock intact. This composition was further subjected to molecular distillation as in Example 1, and the fraction between 100 and 205°C was collected. A fraction of this lubricant was sprayed onto the video disc in the form of a heptane solution.

Initial playback data was good, with 84% of the 12 sheets showing a carrier wave deterioration time of 0.3 seconds or less per 30 minutes of playback. When the disks were then stored under ambient conditions for one week, all disks exhibited extremely high carrier degradation times of about 100 seconds to about 1000 seconds per 30 minutes of playback. This lubricant was found to be fading in places, indicating that the presence of chemically bound antioxidants in the lubricant changes over time and is not compatible with current disk equipment.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a molecular distillation apparatus useful for producing the composition of the present invention, Fig. 2 is a chart showing temperature changes in the amount of distillate, and Fig. 3 is an infrared ray of the methylalkylsiloxane composition before and after distillation. It is a figure showing a spectrum. 10... Molecular distillation device, 12... Feed material reservoir, 14... Diffusion pump, 20...
... Distillation tube, 22 ... Heating tube, 24 ...
...Glass coil, 26,28,30... Distillation tank.

Claims (1)

[Claims] 1 When used with a reproducing needle and setting a relative movement at the required speed between the needle and the needle, it reproduces a signal that occupies a bandwidth of at least several MHz, and is made up of an uneven pattern on the surface. comprising a disc of conductive material having an information track suitable for reproducing a signal of said bandwidth upon setting of relative motion of said velocity and coated with a methylalkylsiloxane lubricant coating, said lubricant comprising: R_1
, R_2 is an alkyl group having 4 to 20 carbon atoms, x is an integer 2, 3 or 4, y is an integer 0, 1 or 2, and the sum of x and y is 4 or less, chemical formula ▲ mathematical formula, chemical formula , there are tables, etc. It is represented by ▼, and the pressure is 10^-^5
An information recording medium having a distillation temperature range of 100 to 205°C in mmHg and containing no antioxidant.