JPH071556B2 - Disc information recording method - Google Patents

Description

The present invention relates to an information recording plate, particularly a disc such as a video disc and a PCM audio disc, and a method for manufacturing the disc.

Conventionally, photoresists have been used to manufacture information recording plates. That is, a master made of glass or the like whose surface is polished is prepared, and this master is washed and cooled (step of about 1 hour). A photoresist is thinly coated on this master, and it is prebaked and then cooled (step of about 1 hour). A master beam coated with this photoresist is irradiated with a laser beam or the like modulated by a signal to be recorded, and the signal is recorded (a step of about 1 to 2 hours). The exposed master is developed, washed with water, drained, afterbaked and then cooled (step of about 1 hour). As a result, a master having pits corresponding to recording signals formed on the surface is obtained. Then, a metal reflection film is coated on the recording surface on which the pits are formed (step of about 45 minutes). The master coated with the reflective film is regenerated by a regenerator for inspection and inspected for dropout or the like (a process of about 1 to 2 hours). Only masters that have passed this inspection will be sent to the step of manufacturing stampers for mass-producing replicas.

However, in such a conventional method, it takes about 4 to 5 hours from the start of recording a signal to the end of the inspection, and the good product and the defective product cannot be distinguished unless the time elapses. Therefore, when it was found that the product was defective after about 4 to 5 hours, it was necessary to manufacture the information recording plate again from the beginning over the same time, which was extremely inefficient. This is because the photoresist is used as a recording film, and so-called monitoring cannot be performed so that the recording signals are simultaneously reproduced immediately after signal recording or at the time of signal recording. Further, even if the signal recording itself can be performed accurately, if the developing time or the like is mistaken in the subsequent developing process, not only will the product eventually become defective, but the photoresist may also be exposed to natural light. Therefore, there is a drawback that handling in a bright room becomes difficult and yield is extremely poor. Therefore, the natural manufacturing cost was also high.

In consideration of such drawbacks, a method of using a monitorable material as a recording film has been proposed in, for example, US Pat. No. 4097895. In this method, a reflection film of aluminum is formed on a glass master, and a recording film made of a dye (fluorescein) having a marked absorption property for a predetermined wavelength is formed on the reflection film. When it is irradiated with an argon laser,
Since this dye has a marked absorption for the wavelength of the argon laser, it sublimes and pits are formed. When the recording film on which pits are formed is irradiated with an argon laser having a power that is sufficiently smaller than during recording and does not sublime the dye, the laser beam is reflected at the portions where the pits are formed and the reflective film is exposed, forming pits. Since the laser beam is not absorbed (or the reflectance is sufficiently small) in the portion where the dye is not applied and the dye remains, it is possible to reproduce the signal depending on the presence or absence of pits due to the difference in the light amount.

According to this method, monitoring is possible, a wet development step is not necessary, and since it has absorptivity only for a predetermined wavelength, it can be handled even in a bright room. However, this method has the drawback that the sublimation speed of the dye is slow, the pit shape is not properly arranged, and an information recording plate having a sufficient SN cannot be obtained.

Methods improved on this are described, for example, in Japanese Patent Laid-Open No. 55-87595 and "Technical Report of Technical Report of IEICE (CPM79-59)" issued on November 22, 1979, "Real-time laser recording using dye evaporation recording material". It is disclosed. That is, on a transparent film such as polyester or polyethylene, or a substrate such as acrylic, a dye sensitizer (dye) such as ethyl red, methylene blue or brilliant green, and nitrocellulose (polymerization degree about 80) are used as a ketone solvent. The melted material is coated, and a signal is recorded by irradiating a laser beam having a wavelength at which the dye sensitizer has a marked absorption property.

In this method, not only the dye (dye sensitizer) but also nitrocellulose is mixed, so the sublimation speed is fast due to its self-oxidation effect, and recording at low temperature (low power) is possible, and the pit shape Has an advantage that it can be prepared neatly as compared with the case of using only the dye. However, in this method, not only is the pit shape not sufficiently adjusted as compared with the case where the above-mentioned photoresist is used, but the reaction residue is left and remains as dust-like foreign matter on the recording surface, resulting in sufficient SN. It was not possible to manufacture the information recording plate having it. Therefore, this method goes beyond the experimental stage, and in order to manufacture a large number of information recording plates as commercial products, the method using the above-mentioned photoresist has to be adopted.

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

Japanese Patent Laid-Open No. 57-11090 proposes a benzenedithiol nickel complex as a dye sensitizer capable of recording information with a semiconductor laser. However, when an additional test was attempted within the range of the technique disclosed in the above publication, it was not possible to obtain a practicable disc capable of recording information at a high density on the order of at least μm. That is, in order to record information at a high density, the surface stability of the information recording layer should be good in order to reduce dropouts, but when the information recording layer is formed on a substrate having a smooth flat surface, the dye The crystal grains of the sensitizer were deposited and the information recording layer became uneven. Therefore, if the amount of the dye sensitizer mixed with nitrocellulose is reduced, the crystal grains are reduced but the sensitivity is lowered, and it becomes impossible to obtain a sufficient C / N or S / N.

The present invention has been made in view of such a situation, C / N, S / N is good, dropout is small, it is possible to provide a disc capable of accurately recording information and a manufacturing method thereof. To aim.

Hereinafter, the present invention will be described in detail with reference to the drawings. First, a benzenedithiol nickel complex (for example, PA1006 manufactured by Mitsui Toatsu) is prepared as a dye sensitizer, and nitrocellulose is prepared as a binder and a reaction aid. As nitrocellulose, for example, one having DNRS of about 1/8 (nitrification degree of 11.7) can be used. A predetermined amount of nitrocellulose (for example, 32 mg per 1 cc of solvent) is weighed and mixed with the solvent. For example, cyclohexanone is suitable as the solvent. In addition to this, I tried using 10 kinds of other solvents such as acetone, xylene, methyl ethyl ketone, methyl iributyl ketone, methyl cellosolve, cellosolve, cellosolve acetate, diacetone alcohol, ethyl acetate, ethylene dichloride, but when using these, In both cases, many crystal grains appeared and it was difficult to put them to practical use. That is, it was found that the solvent is extremely important when the benzenedithiol nickel complex is used as the dye sensitizer. What melt | dissolved nitrocellulose in a solvent is shaken (incubated) at 40 degreeC for about 4 hours. After that, filtration is performed with, for example, a 0.2 μm filter. On the other hand, a predetermined amount of the benzenedithiol nickel complex (for example, 32 mg per 1 cc of solvent) is weighed and mixed with the filtered solution (thus, in this case, 3 cc per 1 cc of solvent).
2mg nitrocellulose and 32mg of the dye sensitizer will be mixed). This mixed solution is shaken, for example, at room temperature for about 1 hour, and then again filtered by, for example, a 0.2 μm filter. The resulting liquid becomes the stock solution of the information recording layer.

An information recording layer is formed on a substrate by using this undiluted solution. The substrate is glass or cast acrylic (for example, Shimura Kaken Kogyo Co., Ltd., Nitto Plastic Co., Ltd.), and vinyl chloride if smoothness is good. A synthetic resin such as polycarbonate can be used. Glass is preferable when replicas are manufactured using this as a master after recording information on the information recording layer, but cast acrylic is preferable because it is lightweight when it is used as it is as one completed disc. The surface of the substrate needs to be ground to obtain sufficient surface accuracy, but if sufficient surface accuracy cannot be obtained (for example, the surface accuracy is inferior to glass when using acrylic as the base), The smoothing layer may be coated to a predetermined thickness. As the smoothing layer, for example, novolac resin (specifically, positive photoresist OFPR-2 manufactured by Tokyo Ohka Kogyo Co., Ltd.) may be coated to about 1 μm. For example, a solution obtained by diluting 35 cp of OFPR-2 1: 1 with a dedicated thinner is spin-coated on a substrate rotating at about 500 rpm, and baked at 60 ° C. for 15 minutes to evaporate the thinner and solidify it. By forming a thin film as a smoothing layer by applying a liquid synthetic resin and then solidifying it in this manner, the influence of scratches, dust, etc. on the substrate can be reduced and the surface can be made smooth.

A reflective film made of silver, aluminum or the like having a predetermined thickness is formed on the base or the smoothing layer formed on the base.
As the reflective film, for example, silver is sputtered to a thickness of 400 A °. In this case, it is possible to obtain sufficient film strength and anchoring by sputtering silver on the smoothing layer rather than directly sputtering silver on the acrylic substrate.

To form an information recording layer on this reflective film, 10 cc of the above stock solution filtered with a filter of 0.45 μm is dropped on the reflective film, and the substrate is rotated at 250 rpm for 7 seconds. Apply the liquid to the entire surface, and at 600r.pm
Rotate for 120 seconds. Then, for example, baking is performed at 60 ° C. for 20 minutes to evaporate the solvent, solidify, and return to normal temperature.

Table 1 shows the characteristics of the stock solution and the information recording layer when the mixing amount of the dye sensitizer and the binder and the spin coating rotation speed were changed.

In Table 1, the characteristics of the stock solution are the values when diluted 500 times, and the characteristics of the coated state are the values when the thickness of the information recording layer is about 1000 to 3000 A °. The light transmittance is for a semiconductor laser having a wavelength of 830 nm and is an average value of several kinds of sample disks. Further, the light transmittance in the coated state is a value when the light passes through the information recording layer once, and at the time of reproduction, the laser light which once passed through the information recording layer is reflected by the reflection film and again passes through the information recording layer as described later. Since it passes, it will be a squared value (80% is 46%
A (= 0.8 ^2)).

As is clear from the above table, increasing the amount of the dye sensitizer can increase the value of the residual dye concentration remaining in the information recording layer (decrease the light transmittance in the coated state), thus increasing the sensitivity ( Higher frequency signals can be recorded). However, if the amount is increased too much, the crystal grains of the dye sensitizer, which causes noise, appear and the surface in the coated state deteriorates (becomes NG). When it was 64 mg / cc or more, a good (OK) flat surface was hardly obtained. Further, when the amount of the binder is increased, the uniformity of the film of the information recording layer is improved, but the kinematic viscosity of the solution is increased, and it is necessary to increase the spin coating rotation speed to obtain the same film thickness. . Increasing the rotation number not only lowers the residual dye concentration, but also leads to the appearance of crystal grains.

The information recording layer thus formed has a minimum transmittance (maximum absorptance) for light with a wavelength of 800 to 900 nm and a large transmittance for light with other visible wavelengths. It was confirmed to have a rate.

FIG. 1 shows an embodiment of the structure of a disc having such an information recording layer. 1 is a 1.2 mm thick cast acrylic substrate, 2 is a 1 μm thick photoresist smoothing layer, and 3 is 300 to 500 A
Reflection film made of silver formed to a thickness of 4 °, 4 is an information recording layer made of a mixture of nitrocellulose and benzenedithiol nickel complex, and 5 is a thickness arranged on the outer and inner circumferences of a substantially circular base 1. A spacer having a thickness of about 0.1 mm, 6 is a protective plate made of transparent cast acrylic having a thickness of 1.2 mm, 7 is an air layer formed by the spacer 5, and 8 is a central hole.
The lower end of the spacer 5 may be in direct contact with the base 1, or may be integrally formed with the base 1 or the protective plate 6.

When a semiconductor laser having a wavelength of 830 nm is directly modulated by a recording signal and a rotating disk is irradiated with the laser beam through the protective plate 6, the exposed portion of the information recording layer 4 is sublimated, melted or evaporated, and FIG. A pit A corresponding to the recorded information is formed as shown in FIG.

When the information recording layer 4 is irradiated with laser light emitted from the same semiconductor laser after information recording through the protective plate 6 (at this time, the power of the laser light is attenuated more than in the case of recording, and the information recording layer 4 is newly added. The laser light is scattered at the portion where the pit A exists, and the amount of reflected light captured after being reflected by the reflective film 3 is not small. In the portion where there is no pit A, the amount of reflected light that is absorbed by the information recording layer 4 but is not scattered because of the smooth surface is captured. Therefore, the recorded information can be reproduced by detecting the amount of reflected light with a photodiode or the like. The structure of the recording / reproducing apparatus may be the same as the known one.

A disk with a structure as shown in Fig. 2 (mixing amount of dye sensitizer and binder to the solvent is both 32 mg / cc) was applied at a linear velocity of 1.2.
When a fixed rectangular wave signal having a frequency of 200 KHz was rotated at 5 m / s and recorded and reproduced using an optical system having a wavelength of 830 nm and NA of 0.5, the characteristics shown in FIG. 3 were obtained. In the figure, the horizontal axis is the peak power of the laser light emitted from the objective lens during recording (the average power is therefore about 1/2 of the indicated value), and the vertical axis is the reproduction signal obtained when the disc is reproduced. Is the level and C / N. The signal could be recorded from about 2 mw at peak power (1 mw at average power). The C / N peaks when the peak power is around 4 mw.

Table 2 shows the results obtained by changing 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 pits are 2.3 μm, and the four columns on the left side show the case where the recording track pitch is 4.02 μm. The numbers in parentheses represent decibel values when the level of the reproduced signal at 100 KHz is 0.

FIG. 4 shows a structure in which a guide track is formed on the disk shown in FIG. The parts corresponding to those in FIG. 1 are designated by the same reference numerals, and thus detailed description thereof will be omitted (the same applies to the following drawings). That is, the guide track 9 is formed on the smoothing layer 2 in a concentric or spiral shape around the hole 8 (thus, in this case, the smoothing layer 2 also has a function as a guide track forming layer). Since the smoothing layer 2 is removed in the portion where the guide track 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 the piji type resist applied as the smoothing layer 2 on the substrate 1 with laser light and then developing it. In addition, a glass substrate coated with a photoresist is irradiated with laser light and developed to prepare a master disc on which guide tracks are formed, and a smoothing layer 2 made of an ultraviolet curable resin is spin-coated on the substrate 1. It can also be formed by pressing the master disk against the smoothing layer 2 and irradiating it with ultraviolet rays to cure the smoothing layer 2 from a fluid state to a solid state. Alternatively, it can also be formed by integrally molding with the base 1 by transferring the guide track to a synthetic resin by injection or the like from a stamper on which the guide track is formed. Of course, a mixture of the dye sensitizer and the binder according to the present invention can be used instead of the photoresist in the master disk or stamper for transferring the guide track to the disk.

When the smoothing layer 2 made of photoresist is formed on the substrate 1 and the guide track 9 is formed 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. Or draw a character or picture with the ink (for example, black ink)
Alternatively, when a paper or the like on which letters or pictures are drawn is applied to the back side of the base 1, when the exposure beam is irradiated from the photoresist side, the pits or The width of the guide track becomes thin, and when the ink, paper, etc. on the back side are removed and viewed from the back side or front side, the characters, pictures, etc. appear to have a sharpness. Even if the width of the pit or the guide track is slightly changed in this way, there is almost no influence on the signal originally recorded and reproduced. Of course, when creating a master board to transfer the guide track, even if the same processing is performed on the back side of the base, it is possible to transfer the above-mentioned characters, pictures, etc. together with the guide track or pit to the disc. it can. Therefore, even in the case of coating photoresist on the substrate, recording signals directly without forming guide tracks, developing it to make pits appear, then making stampers, and making a large number of replica disks from stampers. ,
Similarly, characters, pictures, etc. can be transferred.

It goes without saying that address data or the like may be recorded on the disc in addition to the simple guide track.

Further, in the disc having the guide track 9 formed therein, the optical system for recording / reproducing can be made to follow the guide track 9 or the intermediate portion 10 sandwiched between the adjacent guide tracks 9. As such, the information signal can be recorded on the guide track 9 or on the intermediate portion 10. Depending on the mixing amount of nitrocellulose as a binder, when the kinematic viscosity of the stock solution forming the information recording layer 4 increases, there is a place where the recording material is not sufficiently filled in the bottom corner portion of the guide track 9 formed as a groove. In such a case, it is more advantageous to record the information in the intermediate section 10 against dropout or the like.

FIG. 5 shows another embodiment of the disc structure. In this embodiment, a pair of spacers having an information recording layer 4 formed on a transparent substrate 1 (which can also be considered as a protective plate 6) and a reflective film 3 made of aluminum formed thereon is a spacer. They are associated with each other through 5. In this embodiment, the reflective film 3 is formed on the substrate 1 via the information recording layer 4, and since the information recording layer 4 functions as a kind of smoothing layer, a special smoothing layer can be omitted. Recording and reproduction can be performed from both sides of the disc. In the case of this embodiment, as shown in FIG.
The reflective grease 3 may be sublimated, melted or evaporated together with the information recording layer 4 to form the pit A (in this case, the thickness of the reflective film 3 is preferably 300 A ° or less). The reflective film 3 is formed of a metal such as aluminum having good spreadability, and the pit B is formed by expanding the reflective film 3 into a bubble shape by the pressure generated when the information recording layer 4 is sublimated, melted or evaporated. Good. The level of the reproduced signal is higher in the case of forming like the pit A than in the case of forming like the pit B.

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

As described above, according to the present invention, there is provided a disc on which information is recorded and reproduced by forming pits corresponding to recorded information, which comprises a transparent substrate and an information recording layer formed on the transparent substrate. A reflective film is formed on the recording layer so as to be flat over the entire surface, and the reflective film is made of a metal having good spreadability. The information recording layer is sublimated, melted or evaporated to expand the reflective film. Since the semiconductor laser for forming and recording or reproducing is irradiated from the transparent substrate side, the reflectance is constant, a disc with a short optical path length and a high reflectance can be obtained, and further, because of the simple structure, A cost disc can be provided.

[Brief description of drawings]

All of the figures relate to the present invention, FIG. 1 is a sectional view showing the disc structure of the first embodiment, FIG. 2 is a sectional view showing the pit shape thereof, and FIG. 3 is a characteristic diagram showing the characteristics of the disc. Fourth
FIG. 5 is a sectional view of the disk of the second embodiment, FIG. 5 is a sectional view of the disk of the third embodiment, FIG. 6 is a sectional view showing its pit shape, and FIG. 7 is a sectional view of the fourth embodiment. A cross-sectional view is shown on each disc. 1 ... Base, 2 ... Smoothing layer 3 ... Reflective film, 4 ... Information recording layer 5 ... Spacer, 6 ... Protective plate 7 ... Air layer, 8 ... Center hole 9 ... Guide track, 10 ...... Middle part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiyuki Kakuda 4-2610 Hanazono, Tokorozawa-shi, Saitama Pioneer Co., Ltd. Tokorozawa Plant (72) Inventor Fumio Matsui 4-2610 Hanazono, Saitama Prefecture Pioneer shares Company Tokorozawa factory (56) Reference JP-A-52-154603 (JP, A) JP-A-57-12426 (JP, A) JP-A-55-132536 (JP, A) JP-A-55-87595 (JP , A) JP 57-11090 (JP, A) JP 52-114306 (JP, A) JP 56-124135 (JP, A) JP 56-127937 (JP, A) JP 56-155940 (JP, A)

Claims (1)

[Claims] 1. A transparent substrate, a recording layer formed on the transparent substrate, the recording layer containing an organic compound excellent in light absorption for a recording light wavelength, and the entire surface of the recording layer. An information recording method for a disc having a metal film made of a metal having good spreadability, the method irradiating a recording light from a substrate side through the substrate to a recording layer, and changing the optical energy of the recording light. The recording layer absorbs the light energy, and then the recording layer that absorbs the light energy is deformed so as to expand the metal film by the force generated by sublimation, melting or evaporation, and the pit is also formed on the recording layer itself. A method for recording information on a disc, characterized by performing information recording.