JPS59177746A - Production of disc - Google Patents

Abstract

PURPOSE:To produce a disc which does not require a wet process by developing, permits monitoring and has a substantial S/N by using a dye sensitizing agent and a binder as a material for constituting a recording layer, dissolving both in a solvent, coating the soln. on a substrate and using cyclohexanone as a solvent. CONSTITUTION:A benzene thiol nickel complex is used as a dye sensitizing agnet and nitrocellulose is prepd. as a reaction assistant. DNRS 1/8 or equiv. is used for the latter and is mixed with a solvent at 32mg for each 1cc of the solvent. For example, cyclohexanone is preferable as the solvent. After the soln. is shaped for about 4hr at 40 deg.C, the soln. is passed through, for example, 0.2mum filter. The benzene thiol nickel complex is mixed with the soln. at 32mg for each 1cc of the solvent. The soln. is shaked and is filtered to prepare an original liquid for the recording layer. The formation of a recording layer 4 on a reflection film 3 is accomplished by dropping 10cc the above-mentioned original liquid on the reflection film, rotating the substrate for 7sec at 250 r.p.m. to coat the soln. over the entire surface and rotating further the substrate for 120sec at 600 r.p.m.

Description

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

Conventionally, 7-otoresists have been used to manufacture information recording plates. That is, a master disc made of glass or the like with a polished surface is prepared, and this master disc is cleaned and cooled (a process that takes about one hour). This master is coated with a thin layer of photoresist,
Prebaked and then cooled (about 1 hour process). The master disc 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 with pits corresponding to the recording signal formed on its surface is obtained, and a metal reflective film is further coated on the recording surface where the focus is 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 products and defective products until that 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 amount of time, which is extremely inefficient.

This is because a photoresist is used as a recording film, so it is not possible to perform so-called monitoring in which recorded signals are simultaneously reproduced immediately after signal recording or during signal recording. 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, sublimated pits are formed because this dye has a significant absorption property for the wavelength of the argon laser.

The pits are formed on the recording film, which is much smaller than when recording.
When irradiating with an argon laser with a power that does not sublimate the dye, the laser beam is reflected in areas where pits are formed and the reflective film is exposed, and the laser beam is reflected in areas where pits are not formed and the dye remains. Since the light is absorbed and not reflected (or the reflectance is sufficiently small), it is possible to determine the presence or absence of pits and reproduce the signal based on the difference in light amount.

If this method is used, it can be monitored, a wet developing step is not required, and since it has absorbency only for a predetermined wavelength, it can be handled even in a bright room.

However, this method has the disadvantage that the dye sublimation rate is slow, the pits are not well formed, and an information recording plate with a sufficient SN cannot be obtained.

An improved method of this is disclosed, for example, in Japanese Patent Application Laid-Open No. 55-87595, and in the Institute of Electronics and Communication Engineers Technical Report (CPM79-59) published on November 22, 1979, "Real-time laser recording using dye evaporation recording material." has been disclosed.

t A dye sensitizer such as ethyl red, methylene blue, brilliant green, etc. (
The dye is coated with a solution of nitrocellulose (degree of polymerization: 80) dissolved in a ketone solvent, and a signal is recorded by irradiating the dye with a laser beam at a wavelength for which the dye sensitizer has significant absorption. It is.

This method uses not only a dye (dye sensitizer) but also nitrocellulose, so its self-oxidation effect allows the sublimation rate to be fast (and enables recording at low temperatures (low power), resulting in the formation of pits. This method has the advantage that the shape is more precisely aligned than the case of using only the dye mentioned above.However, compared to the case of using the photoresist mentioned above, this method not only has the shape of the focus not well arranged, but also the reaction Residues were produced and remained as dust-like foreign matter on the recording surface, making it impossible to manufacture information recording plates with sufficient SN.Therefore, this method remained at the experimental stage and was not suitable for 1n reporting as a commercial product. In order to mass-produce sickle plates, it was necessary to adopt the method using photoresist as 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 benzenethiol nickel complex as a dye sensitizer capable of recording information with a semiconductor laser. 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 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, when the amount of dye sensitizer mixed with nitrocellulose is reduced, the number of crystal grains decreases, but the sensitivity decreases, making it impossible to obtain sufficient O/N or S/N.

The present invention has been made in view of the above situation, and utilizes a dye sensitizer that can be used with the semiconductor laser to eliminate the need for a wet development process, enable monitoring, and provide a practical product that can be used as a commercial product. It is an object of the present invention to provide a method for manufacturing a disk having a sufficient S/N ratio and capable of recording and reproducing high-density 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 is about tq RS i/8 (nitrification degree 1t7
) can be used. A specified amount of nitrocellulose (for example, 32 songs per 1 cc of solvent)
Weigh and mix into solvent. For example, nclohexanone is suitable as the solvent. In addition to this, acetone is used as a solvent.
I tried using 10 types of xylene, methyl ethyl ketone, methyl iributyl ketone, methyl selonulp, cellosolve, cellosolve acetate, diacetone alcohol, ethyl acetate, and ethylene dichloride, but when I used these, there were many crystal grains. It was difficult to put it into practical use. In other words, when using a benzenedithiol nickel complex as a dye sensitizer, it has been found that the solvent is extremely important1-
is. A solution of nitrocellulose in a solvent is incubated at, for example, 40° C. for about 4 hours. Thereafter, filtration is performed using a 0.2 μm filter, for example. On the other hand, weigh out a predetermined amount of benzenedithiol nickel complex (for example, 32 mg for 1 cc of solvent) and mix it with the filtrated solution (therefore, in this case, 32 mg for solvent I QC) is weighed.
1] 1g of 2)o cellulose and 32fl1g of dye sensitizer were mixed).

This mixed solution is allowed to stand for about 1 hour at room temperature, for example, and then filtered again through a 0.2 μm 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. If information is recorded on the information recording layer and then a replica is manufactured using this master disc, glass is preferable, but if the disc is to be used as a completed disc as it is, cast acrylic is preferred 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, when the base is made of acrylic, the surface precision is inferior to that of glass).
If so, coat the base with a smoothing layer to a predetermined thickness. The smoothing layer may be coated with, for example, novolak wood@ (specifically, for example, positive photoresist 0FPR-2 manufactured by Tokyo Ohka Co., Ltd.) to a thickness of about 1 μm.

For example, 0FPR-2 with 3scp 1:1 with special thinner
The solution diluted to
Bake for a minute to evaporate and solidify the thinner. By applying a liquid synthetic resin and then solidifying it to form a thin film as a smoothing layer in this manner, the influence of scratches, dust, etc. on the substrate can be reduced<1-1 and the surface can be smoothed.

A reflective film made of silver, aluminum, etc. and having 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. In this case, sufficient film strength and anchoring can be obtained by sputtering silver on the smoothing layer rather than directly sputtering silver on the acrylic substrate.

In order to form an information recording layer on this reflective film, the above-mentioned stock solution is filtered using a 045 μm filter, for example, and a drop of jOQc is dropped onto the reflective film, and the substrate is heated to 25 μm.
, p, m for 7 seconds to coat the entire surface with this solution.
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 the values when diluted 500 times, and the properties of the coated state are the values when the thickness of the information recording layer is 10 times.
This is the value when it is set to about 00 to 3000A0. Further, the light transmittance is for a semiconductor laser having a wavelength of 830 nm, and is an average value of several types of sample disks. In addition, the light transmittance in coat state 1 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 has passed through the information recording layer is reflected by the reflective film and the information is recorded again. Since it passes through the layers, it becomes the squared value (S
If it is Ochi, it will be 64% (=o, s2)).

As is clear from the table above, increasing the amount of the dye sensitizer can increase the concentration of the residual dye remaining in the information recording layer (lower the light transmittance in the coated state), and therefore increase the sensitivity ( This makes it possible to record higher frequency signals. 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). 6410g/
When it was cc or more, a good (OX) plane was hardly obtained. Increasing the amount of binder will improve the uniformity of the information recording layer, but the kinematic viscosity of the solution will increase, and the spin code rotation speed will need to be increased to obtain the same film thickness. .

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

The information recording layer formed in this way has a density of 80υ to 90υ.
It was confirmed that the transmittance was the minimum (the absorption rate was the 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 shows an embodiment of the structure of a disk having such an information recording layer. 1 is a base made of cast acrylic with a thickness of 12 μm, 2 is a smoothing layer made of photoresist formed to a thickness of 1 μm, and 3 is a 300 to 5 μm thick base.
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 peripheries of the substantially circular base 1. A spacer of about 0.1 volts,
6 is a protective plate made of transparent cast acrylic having a thickness of 12, 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 830 nm is directly modulated by a recording signal and the rotating disk is irradiated with laser light through the protection &6, the exposed portion of the information recording layer 4 sublimes.
It is melted or evaporated, and Pino) A corresponding to the recorded information is formed as shown in FIG.

After information recording, when the laser beam emitted from the semiconductor laser is irradiated onto the information recording layer 4 through the protection plate 6 (at this time, the power of the laser beam is attenuated from that during recording, and the information recording layer 4 is The laser beam is scattered in the part where there is Pino)A, and the amount of reflected light that is captured after being reflected by the reflective film 3 is reduced. In areas where there is no light, the information recording layer 4 absorbs the reflected light, but since the surface is smooth, it is not scattered and is captured by a large amount of reflected light.Therefore, the recorded information is reproduced by detecting the amount of reflected light with a photodiode or the like. be able to. The configuration of the recording/reproducing device may be the same as a known one.

A disk with a structure as shown in Figure 2 (the amount of dye sensitizer and binder mixed in the solvent is 52111 g/cc)
was rotated at a linear velocity of 1.25 m/s, and a rectangular wave signal with a fixed frequency of 200 KHz was transmitted at a wavelength of 830 nm.

When recording and reproducing were performed using an optical system of NAO.5, characteristics as shown in FIG. 6 could be obtained. In the figure, the horizontal axis is the peak power of the laser beam emitted from the objective lens during recording (therefore, the average power is approximately 1/2 of the indicated value), and the vertical axis is the reproduced signal obtained when the disc is reproduced. level and A/N. It was possible to record a signal from approximately 277LW (average) at a peak power of 1TrLW).

a/N reaches its maximum peak when the peak power is around 477LW.

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 represents the case where the recording track pitch is 2.3 μm, and the four columns to the left thereof represent the case where the recording track pitch is 4.02 μm. The number in parentheses is 100K.
It represents the decibel value when the level of the reproduced signal at l(z is O).

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, a guide track 9 is formed concentrically or spirally around the hole 8 on the smoothing layer 2 (therefore, in this case, the smoothing layer 2 also functions as a guide trunk 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 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 the smoothing layer 2 with ultraviolet rays to harden the smoothing layer 2 from a fluid 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 exposure beam will be emitted from the photoresist side. When irradiated, areas where characters, paper, etc. are drawn will reflect less light than other areas. Therefore, when developed, the width of the bit or guide track becomes narrower in the area where the ink was than in other areas, and if you remove the ink, paper, etc. from the back side and look at it from the back side or the 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 bits. can. Therefore, even when a photoresist is applied on a substrate, a signal is directly recorded without forming a guide track, it is developed to make pits appear, a stamper is made from it, and a large number of replica disks are manufactured from the stamper. , characters, pictures, etc. can be transferred 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.

In addition, in a disc on which a guide track 9 is formed, the optical system for recording and reproducing can be made to follow the guide track 9, or it can be made to follow the intermediate portion 10 narrowed 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, the bottom corners of the guide tracks 9 formed as grooves will not be filled with the recording material sufficiently. 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, an information recording layer 4 is formed on a transparent substrate 1 (which can also be considered as a protective plate 6), and a pair of spacers are formed on which a reflective film 6 made of aluminum is formed. We are in touch through 5. In this embodiment, the reflective film 3 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, and recording and reproduction can be performed from both sides of the disc. In this embodiment, as shown in FIG. 6, the reflective film 3 may be sublimated, melted or evaporated together with the information recording layer 4 to form a layer A.
In this case, the thickness of the reflective film 3 is preferably 3[]OA' or less). Further, the reflective film 3 is made of a metal such as aluminum with good ductility, and the pits B are formed by expanding the reflective film 3 into a bubble shape by the pressure generated when the information recording layer 4 sublimates, melts, or evaporates. Good too. Pit A
The level of the reproduced signal will be higher when formed as shown in B) than when formed as shown in 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, in the present invention, cyclohexano/ is used as a solvent when dissolving a mixture of a dye sensitizer and a binder in a solvent and coating it on the base of a disk to form an information recording layer. Therefore, it is possible to ensure flatness, to manufacture a disc at a low cost that can be monitored, and has a practically sufficient S/N or a/N that can be offered as a commercial product.

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. 3 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 third embodiment, FIG. 6 is a sectional view showing the pit 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...Foundation 2...River/Smoothing layer 3
...Reflective film 4...Old information recording layer 5...
...Shesa 6...Protection plate 7...
・・Air layer 8・River・・Central hole 9・・・・Guide track 1o・・Former middle part Patent applicant Pioneer Co., Ltd.

Claims (3)

[Claims] (1) A method for manufacturing a disc in which an information recording layer is formed on a substrate and high-density information is recorded by irradiating the information recording layer with a laser beam, and the method uses dye-enhanced material as the material constituting the information recording layer. A method for producing a disk, characterized in that a sensitizer and an inder are prepared, the dye sensitizer and binder are dissolved in a solvent and applied onto the substrate, and cyclohexanone is used as the solvent. . (2) The method for manufacturing a disk according to claim 1, wherein the dye sensitizer is a benzenedithiol nickel complex. (3) Claim 1, characterized in that the WjE binder contains at least nitrocellulose.
2. Method for manufacturing a disk according to paragraph 2 or paragraph 2.