JPS59177740A - Disc - Google Patents

Abstract

PURPOSE:To decrease drop-out, etc. and to enable exact recording of information in a disc provided with an information recording layer formed on guide tracks by forming the pits corresponding to information on the part on which the information recording layer is thinly formed. CONSTITUTION:1 is a substrate, 2 is a smoothing layer consisting of a photoresist, 3 is a reflection film consisting of silver, 4 is an information recording layer consisting of a mixture composed of nitrocellulose and benzene dithiol nickel complex, and 6 is a transparent protective plate. Guide tracks 9 are formed on the layer 2. An information signal can be recorded on the tracks 9 or intermediate parts 10 with the disc formed with the tracks 9. There is a possibility of generating the place where a recording material is not thoroughly filled in the bottom angle part of the tracks 9 formed as grooves if the dynamic viscosity of the original liquid forming the layer 4 is large and therefore, drop-out, etc. are decreased by recording information in the parts 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to information recording plates, particularly discs such as video discs and PCM audio discs.

Photoresists have traditionally been used to manufacture information storage plates. That is, a master disk made of glass or the like with a polished surface is prepared, and this master disk is washed and cooled (a process of about 1 hour). This master is coated with a thin layer of photoresist,
Prebaked and then cooled (about 1 hour process). The master coated with this photoresist is irradiated with a laser beam modulated by the signal to be recorded to record the signal (
process (approximately 1 to 2 hours). This exposed master is developed, washed with water, drained, and then afterbaked and cooled (a process that takes about 1 hour). As a result, a master disc having pits corresponding to recording signals formed on its surface is obtained. Further, a metal reflective film is coated on the recording surface on which the pits have been formed (a process of about 45 minutes). The master disc coated with the reflective film is played back using a testing playback machine and inspected for dropouts, etc. (a process that takes about 1 to 2 hours). Only master discs that pass this inspection will be sent to the process of manufacturing stampers for producing large quantities of replicas.

However, in this conventional method, it takes about 4 to 5 hours from the start of signal recording to the end of the inspection, and it is not possible to distinguish between good and defective products until this time has elapsed. Therefore, if the product is found to be defective after about 4 to 5 hours, it is necessary to manufacture the information recording plate again from the beginning over the same one hour period, which is extremely inefficient.

This is because, since a photoresist is used as a recording film, monitoring cannot be performed by simultaneously reproducing the recorded signal immediately after recording the signal or at the time of recording the signal. Furthermore, even if the signal recording itself is accurate, if the developing time etc. are incorrect in the subsequent development process, not only will the product end up being defective, but there is a risk that the photoresist will be exposed to natural light. In order to be
It has the disadvantage that handling in a bright room becomes difficult and the yield becomes extremely poor. Therefore, the natural manufacturing cost was also high.

In consideration of these drawbacks, a method of using a material that can be monitored as a recording film has been proposed, for example, in US Pat. No. 4,097,895. In this method, an aluminum reflective film is formed on a glass master disk, and a recording film made of a dye (fluorescene) that has a remarkable absorption property for a predetermined wavelength is formed thereon. When this is irradiated with an argon laser, this dye sublimes and forms bits because it has a significant absorption property for the wavelength of the argon laser. When recording or film in which pits are formed is irradiated with an argon laser that is sufficiently smaller than during recording and has a power that does not sublimate the dye, the laser beam is reflected in the areas where bits are formed and the reflective film is exposed, causing the pits to disappear. In areas where no dye is formed and the dye remains, the laser beam is absorbed and not reflected (or the reflectance is sufficiently small).
Based on the difference in the amount of light, it is possible to reproduce the signal according to the presence or absence of pits.

In this method, monitoring is possible, a wet developing process is not necessary, and since the material has absorbency only for a predetermined wavelength, it is possible to conduct a link even in a bright room.

However, this method has the disadvantage that the sublimation rate of the dye is slow, the shape of the bits is not neatly arranged, and an information recording plate with a sufficient SN cannot be obtained.

An improved method of this is disclosed in, for example, Japanese Patent Application Laid-Open No. 55-87595 and the Institute of Electronics and Communication Engineers Technical Report (CPM79-59) ``Real-time laser recording using dye evaporation recording material'' published on November 22, 1979. Disclosed. In other words, a pigment sensitizer (dye) such as ethyl red, methylene blue, brilliant green, etc. is applied to a transparent film such as polyester or polyethylene or a substrate H such as acrylic.
and nitrocellulose (polymerization time: about 80%) dissolved in a ketone solvent is coated, and a signal is recorded by irradiating the dye with a laser beam at a wavelength for which the dye sensitizer has significant absorption. .

This method uses not only a dye (dye sensitizer) but also a mixture of nitrocellulose, which has a high sublimation rate due to its self-oxidation effect, enables recording at low temperatures (low power), and allows for the formation of bit shapes. It has the advantage of being more neatly arranged than in the case of using only the dye mentioned above. However, compared to using the photoresist described above, this method not only does not form the pits sufficiently, but also leaves reaction residues on the recording surface as dust-like foreign matter, resulting in insufficient SN. It was not possible to manufacture an information recording board with this. Therefore, this method remained at the experimental stage, and in order to mass-produce information recording plates as commercial products, it was necessary to adopt the method using the photoresist described above.

Furthermore, when forming an information recording layer using nitrocellulose and a dye sensitizer, there is no dye sensitizer that exhibits significant absorption to a semiconductor laser having a wavelength of 800 to 900 nm, and information is recorded using a semiconductor laser. It has been difficult to realize a disc that can be played. If a semiconductor laser can be used, a recording/reproducing device can be easily and extremely miniaturized, and it becomes possible to realize a consumer device that is capable of recording as well as reproducing.

JP-A-57-11090 proposes a dye sensitizer capable of recording information using a semiconductor laser and a benzenedithiol nickel complex.

However, when additional tests were attempted within the scope of the technology disclosed in the above-mentioned publication, it was not possible to obtain a practically usable disk capable of recording information at high density, at least on the order of μm. In other words, in order to record information at high density, the information recording layer should have good surface flatness in order to reduce dropouts, etc., but when the information recording layer is formed on a smooth flat substrate, the pigment Crystal grains of the sensitizer precipitate, resulting in an uneven information recording layer. Therefore, if the amount of dye sensitizer mixed with nitrocellulose is reduced, the number of crystal grains will be reduced, but the sensitivity will be lowered, and sufficient C/N or S/N
I am no longer able to obtain it.

The present invention was made in view of this situation, and it
An object of the present invention is to provide a disc that has a good /N ratio, has few dropouts, and can accurately record information.

The present invention will be explained in detail below with reference to the drawings. First, a benzenedithiol nickel complex (for example, PA1006 manufactured by Mitsui Toatsu Co., Ltd.) is prepared as a dye sensitizer, and nitrocellulose is prepared as a binder and a reaction aid. For example, nitrocellulose having a DNR of about 81/8 (nitrification degree 117) can be used.

Add a certain amount of nitrocellulose (e.g. 5 to 1 vol of solvent)
2 mg) and mix with the solvent.

For example, cyclohexanone is suitable as the solvent. In addition to the above, we used 10 other solvents: acetone, xylene, methyl ethyl ketone, methyl yliptyl ketone, methyl cellosolve, cellosolve, selonlube acetate, diacetone alcohol, ethyl acetate, and ethylene dichloride. However, many crystal grains were produced in both cases, making it difficult to put them to practical use. That is, it has been found that when a benzenedithiol nickel complex is used as a dye sensitizer, the solvent is extremely important. A solution of nitrocellulose in a solvent is incubated at, for example, 40° C. for about 4 hours.

After that, filtration is performed using a 0.2#+ filter, for example. On the other hand, weigh out a predetermined amount of benzenedithiol nickel complex (52 mg for 1 w of solvent) and mix it with the previously filtered solution (therefore, in this case, 52 mg of nitrocellulose is used for 1 cc of solvent). and 62 mg of dye sensitizer). This mixture is photographed at night at room temperature for about an hour, and then filtered again using a 0.2 am filter.

The resulting liquid becomes the stock solution for the information recording layer.

An information recording layer is formed on the substrate using this stock solution, and the substrate is glass or cast acrylic (
For example, synthetic resins such as those manufactured by Shimura Kaken Kogyo Co., Ltd. and Nitto Jushi Co., Ltd.), vinyl chloride, and polycarbonate can be used as long as they have good smoothness. Glass is preferable if information is recorded on the information recording layer and then used as a master disk to produce a burr, but if it is used as a single completed disk, cast acrylic is preferable because it is lightweight.The surface of the base needs to be polished to obtain sufficient surface precision, but sufficient surface precision cannot be obtained (for example, if the base is made of acrylic, the surface precision is inferior to that of glass)
In this case, a smoothing layer may be coated on the substrate to a predetermined thickness. As a smoothing layer, for example, a novolac tree Ji& (specifically, for example, positive photoresist 0FPR-2 manufactured by Tokyo Ohka Co., Ltd.) may be coated to a thickness of about 1 μm. For example, a solution in which 35 cp of 0FPR-2 is diluted 1:1 with a dedicated sinker is spin-coded onto a substrate rotating at about 500 rpm and 6 m, and baked at 60'C for 15 minutes to evaporate the sinker and solidify. . By applying a liquid synthetic resin and then solidifying it to form a thin film as a smoothing layer, the effects of scratches, dust, etc. on the substrate can be reduced and the surface can be made smooth.

A reflective film made of silver, aluminum, etc. with a predetermined thickness is formed on the substrate or the smoothing layer formed on the substrate.

As the reflective film, for example, silver is sputtered to a thickness of 400A0. Sufficient film strength and anchoring can be obtained by sputtering silver on the smoothing layer rather than directly sputtering silver on the hexagonal acrylic substrate.

To form an information recording layer on this reflective film, 10 cc of the above stock solution is filtered through a 0,451 Irn filter and dropped onto the reflective film, and the substrate is
Rotate at 60 Or, p, m for 7 seconds to coat the entire surface with this liquid, and further rotate at 60 or, p, m for 120 seconds.

Thereafter, the mixture is baked at, for example, 60° C. for 20 minutes to evaporate the solvent, solidify, and return to room temperature.

Table 1 shows the properties of the stock solution and the information recording layer when the mixing amount of the dye sensitizer and binder and the rotational speed of the spin code were varied.

In Table 1, the properties of the stock solution are 1 times when diluted 500 times, and the properties of the coated state are the values when the thickness of the information recording layer is about 1,000 to 5,000.

The light transmittance is for a semiconductor laser with a wavelength of 850 nm, and is the average value of several types of sample disks. Furthermore, the light transmittance in the coated state is the value when the laser beam passes through the information recording layer once, and during reproduction, as will be described later, the laser beam that once passed through the information recording layer is reflected by the reflective film and passes through the information recording layer again. Since it passes, it becomes the square (7) value (if it is 80 chi, it becomes 64 chi (=082)).

As is clear from the above table, by increasing the amount of dye sensitizer, the value of the residual dye a remaining in the information recording layer can be increased (lowering the light transmittance in the coated state), and therefore the sensitivity can be increased. (allowing signals with higher frequencies to be recorded). However, if it is increased too much, crystal grains of the dye sensitizer that cause noise will appear and the coated surface will deteriorate (NG). 64 m
gAl: At above, a good (OK) flat surface was hardly obtained. In addition, increasing the amount of binder improves the uniformity of the information recording layer, but the kinematic viscosity of the solution increases, and it is necessary to increase the spin code rotation speed to obtain the same pi thickness. .

Increasing the rotational speed not only reduces the residual color density but also leads to the appearance of crystal grains.

The information recording layer formed in this way has a density of 800 to 90%.
It was confirmed that the transmittance was minimum (absorption rate was maximum) for light with a wavelength of 0 nm, and that it had a large transmittance for light with other wavelengths in the visible light region.

FIG. 1 represents an embodiment of the structure of a disc having such information recording jω. 1 is a base made of cast acrylic with a thickness of 1.2 mm, 2i"t is a smoothing layer made of photoresist formed to a thickness of 1 m, and 6 is made of silver formed to a thickness of 600 to 500 A'. 4 is a reflective film, 4 is an information recording layer made of a mixture of nitrocellulose and benzenedithiol nickel complex, 5 is a 0.1 mm thick layer arranged on the outer and inner peripheries of 1 of a substantially circular base;
6 is a protection plate made of transparent cast acrylic with a thickness of 12 mm, 7 is an air layer formed by the spacer 5, and 8 is a center hole. The spacer 5 may have its lower end in direct contact with the base 1 or may be integrally molded with the base 1 or the protection plate 6.

When a semiconductor laser with a wavelength of 850 nm is directly modulated by a recording signal and the laser beam is irradiated onto the rotating disk through the protective plate 6, the exposed portion of the information storage Ek layer 4 sublimates, melts, or evaporates (- 1. As shown in FIG. 2, bit A corresponding to the recorded information is formed.

When the laser beam emitted from the semiconductor laser of the information recording stage is irradiated onto the information recording 1 m d through the plate 6, (
At this time, the power of the laser beam is attenuated compared to that during recording to prevent new bits from being formed in the non-information storage area), and the laser beam is scattered in the area where bit A is located, and the reflective film 3 The amount of reflected light that is captured after being reflected by the information recording layer 4 decreases, and the amount of reflected light that is captured without being scattered is large in the part where A is not present. Therefore, recorded information can be reproduced by detecting the amount of reflected light using a photodiode or the like.The configuration of the recording/reproducing apparatus may be the same as a known one.

A disk having a structure as shown in Fig. 2 (mixed amount of dye sensitizer and binder with respect to solvent is vc 52 mg) was rotated at a linear speed U of 1.25 m/s, and a fixed frequency of 20 m/s was rotated.
A rectangular wave signal of 0 KHz, wavelength 850 nm, NA
When the optical system of O15 was used for recording and reproduction, the characteristics shown in FIG. 3 could be obtained. In the figure, the horizontal axis indicates the peak power of the laser beam emitted from the objective lens during recording (therefore, the average power is approximately 1/1/2 of the indicated value).
2) The vertical axis represents the level and C/N of the reproduction signal obtained when the disc was reproduced. Approximately 2 mw at peak power
It was possible to record a signal from (average power 1 mW). C/N reaches its maximum peak when the peak power is around 4 mw.

Table 2 shows the results obtained by varying the recording power and frequency for the same disk as in FIG. In Table 2, the rightmost column shows the case where the recording track pitch is 2.3 μm, and the four columns to the left show the case where the recording track pitch is 402 m.
Each is represented. Note that the numbers in parentheses represent decibel values when the level of the reproduced signal at 100 KHz is set to 0.

FIG. 4 shows a structure in which guide tracks are formed on the disk shown in FIG. 1. Portions corresponding to those in FIG. 1 are denoted by the same reference numerals, so a detailed description thereof will be omitted (the same applies to the following figures). That is, the hole 8 is formed in a concentric or spiral shape (C guide track 9 is formed on the smoothing layer 2 (therefore, in this case, the smoothing layer 2 also functions as a guide track forming layer). Since the smoothing layer 2 is removed in the portion where the number 9 is formed, the information recording layer 4 is thicker than the middle portion 10 of the track.

The guide track 9 can be formed by continuously irradiating a positive resist coated on the substrate 1 as a smoothing layer 2 with laser light and then developing it. In addition, a master disk on which guide tracks are formed by irradiating a glass substrate with photoresist and developing it with a laser beam is prepared in advance, and a smoothing layer 2 made of ultraviolet curing resin is applied to the substrate 1 using a spin cord. The smoothing layer 2 can also be formed by pressing the master disk onto the smoothing layer 2 and irradiating it with ultraviolet rays to harden the smoothing layer 2 from a liquid state to a solid state. Alternatively, it can also be formed by integrally molding the guide track with the base 1, such as by transferring the guide track onto a synthetic resin by injection or the like from a stamper on which the guide track is formed.

Of course, the mixture of the dye sensitizer and binder according to the present invention can also be used in place of the photoresist in the master disc or stamper for transferring guide tracks onto the disc.

When forming the smoothing layer 2 made of photoresist on the substrate 1 and forming the guide track 9 on the smoothing layer 2, the back side of the substrate 1 (the surface opposite to the surface on which the smoothing layer 2 is formed) absorbs light well. If you draw letters or pictures with ink (for example, black ink), or place paper with letters, pictures, etc. on it against the back side of the substrate 1, the photoresist side will be exposed to light. When the beam is irradiated, the reflected light is smaller in areas where characters, pictures, etc. are drawn than in other areas. Therefore, when developed, the width of the pit or guide track becomes narrower in the area where there was ink than in other areas, and when the ink, paper, etc. on the back side is removed and viewed from the back side or front side, the characters, pictures, etc. It looks like you put it in. Even if the width of the pit or guide track is slightly changed in this way, it has almost no effect on the signals that are originally recorded and reproduced.

Of course, when creating a master disc etc. for transferring guide tracks, even if you apply the same treatment to the back side of the base, it will not be possible to transfer the above-mentioned characters, pictures, etc. to the disc together with the guide tracks or pits. can. Therefore, when a photoresist is applied on a substrate, a signal is directly recorded without forming a guide track, it is developed to form pits, a stamper is made, and a large number of replica discs are manufactured from the stamper. Even when you are abroad, you can transfer letters, pictures, etc. in the same way.

It goes without saying that address data and the like may be recorded on the disk in addition to a mere guide track.

Furthermore, in a disc on which guide tracks 9 are formed, the optical system for recording and reproduction can be made to follow the guide tracks 9, or to follow the intermediate portion 10 between adjacent guide tracks 9. Therefore, information signals can be recorded on the guide track 9 or on the intermediate part 10. Although it depends on the amount of nitrocellulose mixed as a binder, if the kinematic viscosity of the stock solution forming the information recording layer 4 increases, there will be places where the recording material is not sufficiently filled at the bottom corners of the guide tracks 9 formed as grooves. In such a case, recording information in the intermediate section 10 is more advantageous in preventing dropouts and the like.

FIG. 5 shows another embodiment of the structure of the disk.

In this embodiment, a pair of spacers are formed, in which an information recording layer 4 is formed on a transparent substrate 1 (which can also be considered as a protection plate 6), and a reflective film 3 made of aluminum is formed thereon. We are in touch through 5. In this embodiment, the reflective film 6 is connected to the substrate 1 through the information recording layer 4.
Since the information recording layer 4 functions as a kind of smoothing layer, a special smoothing layer can be omitted. Further, recording and reproduction are possible from both sides of the disc. Further, in this embodiment, as shown in FIG. 6, the bit A may be formed by sublimating, melting or evaporating the reflective film 6 together with the information recording layer 4.
In this case, the thickness of the reflective film 5 is preferably 500A0 or less), and the reflective film 5 is made of a metal such as aluminum, which has good ductility, and the pressure generated when the information recording layer 4 sublimates, melts, or evaporates. The bit B may be formed by expanding the reflective film 3 into a bubble shape. When formed like bit A, the level of the reproduced signal becomes higher than when formed like bit B.

FIG. 7 shows a structure in which guide tracks 9 are formed on the disk shown in FIG. In this case, the smoothing layer 2 has a function as a smoothing layer and a guide track forming layer.

As described above, the present invention includes a base, a guide track layer formed on the base, a guide track formed concentrically or spirally on the guide track layer, and a guide track formed as the guide track. A disk comprising a groove and an information recording layer that covers the space between the grooves and is formed so that the thickness is thick in the groove portion and thinner between the grooves, Since the bits corresponding to the information are formed in the thin portion of the information recording layer, it is possible to realize a disc that has fewer dropouts and can accurately record information.

Table 1 Table 2 The figures are all related to the present invention; FIG. 1 is a sectional view showing the disk structure of the first embodiment, FIG. 2 is a sectional view showing the bit shape, and FIG. 6 is a sectional view showing the characteristics of the disk. Characteristic diagram shown, 4th
The figure is a sectional view of the disk of the second embodiment, FIG. 5 is a sectional view of the disk of the fifth embodiment, FIG. 6 is a sectional view showing the bit shape, and FIG. 7 is a sectional view of the disk of the fourth embodiment. 2A and 2B each represent a cross-sectional view of a disk.

1... Base 2... Smoothing layer 6... Reflective film 4... Information recording layer 5... Spacer 6.
・・Protective plate 7・Air layer 8・Center hole 9・Guide track 10・Middle part Patent applicant Pioneer Co., Ltd. figure

Claims (1)

[Claims] A disc that records and reproduces information at a relatively high density by forming bits corresponding to recorded information,
A base, a guide track layer formed on the base, a guide track formed as a concentric or spiral groove on the guide track layer, a groove formed as the guide track, and the groove and the groove. - an information recording layer formed to cover between the grooves and have a thickness that is thick in the grooves and thinner between the grooves; A disc characterized in that the bit is formed in a thinly formed part.