JPS59177741A - Disc and its production - Google Patents

Abstract

PURPOSE:To obtain a disc which has good C/N and C/N and less drop-out by forming a smoothing layer consisting of a synthetic resin which is solidified from a liquid state on a substrate consisting of a synthetic resin and forming a reflection film thereon. CONSTITUTION:Synthetic resins such as cast acryl and, if smoothness is good, vinyl chloride, polycarbonate, etc. are usable as a substrate 1. A smoothing layer 2 can be formed simply by coating, for example, a novolak resin to about 1mum on the substrate. A soln. prepd. by diluting, for example, ''OFR-2'' having 35cp to 1:1 with a thinner to be used exclusively with the same is spin coated on the substrate rotating at about 500r.p.m. and is baked for 15min at 60 deg.C to evaporate the thinner and to solidify the resin. The influence of flaw, dust, etc. on the substrate is decreased and the surface is smoothed by forming the layer 2 in the above-mentioned way. A prescribed thickness of a reflection film 3 consisting of silver, aluminum, etc. is formed on the layer 2. For example, silver is sputtered to 400Angstrom thickness as the reflection film.

Description

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

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 original fa is thinly coated with photoresist, prebaked, and then cooled (a process of about 1 hour). A laser beam or the like modulated by the signal to be recorded is irradiated onto the master disc coated with this photoresist to record the signal (a process of about 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. Then, a metal reflective film is further coated on the recording surface on which the focus has 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 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 pattern 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 will sublime and form pits because it 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 an argon laser with a power that does not sublimate the dye, the laser beam will be reflected in the areas where pits are formed and the reflective spots are exposed, and the laser beam will be reflected in the areas where no tips are formed and the dye remains. is not absorbed (or its reflectance is sufficiently small), so it is difficult to reproduce the signal based on the difference in light intensity depending on the presence or absence of pits.
It becomes f-ability.

In the case of this method, monitoring is possible, a wet developing step is not necessary, and since the material has absorbency only for a predetermined wavelength, non-driving is possible 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 Technical Report of the Institute of Electronics and Communication Engineers (OPM79-59) ``Real-time laser recording using dye evaporation recording material'' published on November 22, 1979. Disclosed. That is, on a transparent film such as polyester or polyethylene or on a substrate such as acrylic, a dye sensitizer (dye) such as ethyl red, methylene blue, brilliant green, etc.
The film is coated with nitrocellulose (Polymerized Tomozuri 80) dissolved in a ketone solvent, and a signal is recorded by irradiating it with V-the beam at a wavelength in which the dye sensitizer has significant absorption.

This method mixes not only a dye (dye sensitizer) but also nitrocellulose (y), which has a high sublimation rate due to its self-oxidation effect, and enables recording at low temperatures (low power). It has the advantage that the shape is more neatly arranged than in the case of using only the dye mentioned above. However, with this method, the shape of the pits is not as well prepared as compared to the case of using the photoresist described above, and reaction residues are generated and remain as dust-like foreign matter on the recording surface, resulting in insufficient SN. It was not possible to Q-build the information recording board that it had. Therefore, this method remains at the experimental stage, and in order to mass-produce information display boards as commercial products, the method using the photoresist described above had to be adopted.

Furthermore, when forming an information recording layer using nitrocellulose and a dye sensitizer, the semiconductor laser 1 having a wavelength of 800 to 900 nm (as opposed to the dye sensitizer that exhibits significant absorption has not been found, It has been difficult to create a disk that can record and play back.If semiconductor lasers could be used, the recording and playback device could be made simple and extremely compact, making it possible to record as well as play. It becomes possible to realize consumer equipment.

JP-A-57-11111190 proposes a benzenedithiol 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 dye 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 a/N or s/N.

The present invention was made in view of this situation, and it
An object of the present invention is to provide a disk that has a good /N ratio, has little dropout, and can accurately record information, and a method for manufacturing the same.

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. A predetermined amount of nitrocellulose (for example, 62 cm to the solvent ICC) is weighed and mixed with the solvent. For example, cyclohexanone is suitable as the solvent. Other solvents include acetone, xylene, methyl ethyl ketone, methyl iributyl ketone, methyl cellosolve, cellosolve, celonorp acetate,
Ten types of diacetone alcohol, ethyl acetate, and ethylene dichloride were used, but when these were used, many crystal grains were produced, 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 inked at, for example, 40° C. for about 4 hours. After that, filtration is performed using a 0.2 μm filter, for example. On the other hand, weigh out a predetermined amount (for example, 32 cm per 1 cc of solvent) of benzene ditheol nickel complex,
This is mixed with the filtered solution (so in this case, 32111 g of nitrocellulose and 32 mg of dye sensitizer were mixed for 1 ee of solvent). After this mixed solution is allowed to stand for about 1 hour at room temperature, it is filtered again using a 0.2 μm filter, for example. 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 as a master, glass is preferred, but if the disc is used as a complete disc, cast acrylic is preferred because it is lightweight. The surface of the base needs to be polished to obtain sufficient surface precision, but if sufficient surface and roughness cannot be obtained (for example, when the base is made of acrylic, the surface precision is inferior to that of glass), A smoothing layer may be coated thereon to a predetermined thickness. The smoothing layer may be coated with a novolak resin (specifically, for example, positive photoresist 0FPR-2 manufactured by Tokyo Ohka Co., Ltd.) to a thickness of about 1 μm.

For example, 1:1 350p 0FPR-2 with special thinner.
The diluted solution is spin-coded onto a substrate rotating at about 500 r, p, m, and baked at 60° C. for 15 minutes to evaporate the thinner and solidify it. 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. 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 40 OA'. 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.

To form an information recording layer on this reflective film, 10 CC of the above-mentioned stock solution is filtered through a 045 μm filter, for example, and then dropped onto the reflective film.
, p, m for 7 seconds to coat the entire surface with this solution.
Further, rotate at 600r and plm for 120 seconds. Thereafter, the solvent is evaporated by baking at, for example, 60° C. for 20 minutes, solidified, and then returned 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 and smooth solution are the values when the thickness of the information recording layer is reduced by 1.
This is the value when it is set to about 000 to 5000A0. Further, the light transmittance is for a semiconductor laser having a wavelength of 550 nm, and is the average value of a sample disk. 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 through, it becomes the squared value (8
If the ratio is 0, it will be 64% (=0.82)).

As is clear from the above table, increasing the amount of dye sensitizer increases the residual dye concentration remaining in the information recording layer (lowers the light transmittance in the coated state), and therefore increases the sensitivity. (higher frequency signals can 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). 64mg/
When it was cc or more, a good (OK) plane was hardly obtained. In addition, increasing the amount of binder improves the uniformity of the information recording layer, but this increases the kinematic viscosity of the solution and requires an increase in the spin code rotation speed 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 800 to 90%.
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 t2 Trm, 2 is a smoothing layer made of photoresist formed to a thickness of 1 μm, and 6 is a 600
A reflective film made of silver formed to a thickness of 500 A′,
4 is an information recording layer made of a mixture of nitrocellulose and benzenedithiol nickel complex; 5 is a substantially circular base 1;
6 is a protective plate made of transparent cast acrylic with a thickness of t 2 , 7 is an air layer formed by the spacer 5, 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 protective plate 6, the exposed portion of the information recording layer 4 sublimes.
It melts or evaporates, forming a pip A corresponding to the recorded information as shown in FIG.

When the laser beam emitted from the semiconductor laser after information recording 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 (To prevent new bits from being formed), Pino) The laser light is scattered in the part where A is present, and the amount of reflected light that is captured after being reflected by the reflective film 6 is not small. In the part +c where bit A is not present, the information recording layer 4 absorbs the light, but since the surface is smooth, the amount of reflected light that is captured without being scattered increases. 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 device may be the same as a known one.

A disk having a structure as shown in Fig. 2 (mixing amounts of dye sensitizer and binder in solvent are both 32Q/cc) was rotated at a linear velocity of t 25' m/s, and a rectangular wave signal with a fixed frequency of 200 KHz was generated. , wavelength 830 nm, N
When the optical system of AO.5 was used for recording and reproduction, the characteristics shown in FIG. 3 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 0/N. Approximately 2 at peak power
It was possible to record signals from mw (1 mw at average power).

0/N reaches its maximum peak when the peak power is around 4rnw.

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 2.5 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 Hz 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 trunk 9 is formed, the information recording layer 4 is thicker than the middle portion 10 of the track.

The guide trunk 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 laser light onto a glass substrate coated with photoresist and developing it 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, the width of the pit or guide track becomes narrower than in the area where letters, pictures, etc. are drawn, and when the ink, paper, etc. on the back side is removed and viewed from the back or front side, the letters, pictures, etc. are visible. It looks like a squash was added. 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, even in cases where a photoresist is coated on a substrate, a signal is directly recorded without forming a guide track, 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, 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 information recording layers 4 are formed on a transparent substrate 1 (which can also be considered as a plate 6), and a reflective film 3 made of aluminum is formed thereon. They communicate via Nupesa 5. In this embodiment, the reflective film 3 forms a base IK shadow through the information recording layer 4, and the information recording layer 4 functions as a kind of smoothing layer, so a special smoothing layer is omitted. In addition, recording and reproduction can be performed from both sides of the disk.In addition, in this embodiment, as shown in FIG. (In this case, the thickness of the reflective film 3 is preferably 300A0 or less.) Furthermore, the reflective film 3 may be made of a metal such as aluminum, which has good ductility, and the information recording layer 4 may be sublimated, melted, or Pit B may be formed by expanding the reflective film 3 into a bubble shape due to the pressure generated during evaporation.Pit A
The level of the reproduced signal will be greater if formed as in B) than in the case of 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, a smoothing layer made of synthetic resin is formed on a base made of synthetic resin, a reflective film is formed on the smoothing layer, and an information recording layer is formed on the reflective film. To realize a disc that can reduce the adverse effects of unevenness such as scratches and dust on the base, has few dropouts, has good O/N or S/H, and can accurately record information. I can do it.

Table 1 Table 2

[Brief explanation of the drawing]

The figures are all related to the present invention; FIG. 1 is a cross-sectional view showing the disk structure of the first example, FIG. 2 is a cross-sectional view showing its dot shape, and FIG. 3 is a characteristic diagram showing the characteristics of the disk. FIG. 4 is a sectional view of the disk of the second embodiment, FIG. 5 is a side view of the disk of the third embodiment, FIG. 6 is a sectional view showing the pit shape, and FIG. 7 is the fourth embodiment. Figure 3 shows a cross-sectional view of each disk. 1...Base 2...Smoothing layer 3...Reflection film 4...Information recording layer 5-...Spacer 6...・Protective plate 7... Air layer 8... Center hole 9
......, guide track 10...
Intermediate Patent Applicant Pioneer Co., Ltd. Figure 5 Ring 6 Door 13 8 247-

Claims (9)

[Claims] (1) It has a base, a reflective film that reflects laser light, and an information recording layer that records information formed on the reflective film, and the laser beam is directed from the information recording layer toward the reflective film. A disk on which information is recorded or reproduced on the information recording layer by irradiation with light, which uses a synthetic resin as the base, and which is a synthetic resin that is fixed from a liquid onto the base made of the synthetic resin. 1. A disc characterized in that a smoothing layer is formed to smooth out irregularities such as scratches and dust on the substrate, and the reflective film is formed on the smoothing layer. (2) The disk according to claim 1, wherein the smoothing layer is made of either photoresist or ultraviolet curing resin. (3) The disk according to claim 1 or 2, wherein a guide track is formed on the smoothing layer. (4) The disk according to claim 1, 2 or 6, wherein the information recording layer is made of a mixture of nitrocellulose and a dye sensitizer. (5) Prepare a base made of synthetic resin, form a smoothing layer made of liquid synthetic resin on the base, convert the liquid synthetic resin into an omega form, and place the smoothing layer on the solidified smoothing layer. A method for manufacturing a disc, characterized in that a reflective film that reflects laser light is formed on the disc, and an information recording layer on which a signal corresponding to information is recorded is formed on the reflective film. (6) The method for manufacturing a disk according to claim 5, wherein the synthetic resin forming the smoothing layer is a photoresist, and the liquid photoresist dissolved in thinner is baked and solidified. (7) The disk according to claim 6, characterized in that the solidified photoresist is irradiated with a laser beam and developed to form a guide trunk, and then the vaginal reflection film and the information recording layer are formed. Production method. (8) The synthetic resin forming the smoothing layer is an ultraviolet curable resin, and the liquid ultraviolet curable resin coated on the substrate is solidified by irradiation with ultraviolet rays. 5. The method for manufacturing a disc according to Section 5. (9) Prepare a master master disk on which guide tracks are formed in advance, press the master master disk against the smoothing layer made of the liquid ultraviolet curable resin, and in this state irradiate ultraviolet rays to form the smoothing layer having guide tracks. 9. The method of manufacturing a disk according to claim 8, wherein the vaginal reflection film and the information recording layer are formed after the vaginal reflection film and the information recording layer are formed. ao The method for manufacturing a disk according to any one of claims 5 to 9, characterized in that the information recording layer contains at least a dye sensitizer. αυ The dye sensitizer is a benzenedithiol nickel complex, and a liquid in which the dye sensitizer is dissolved in cyclohexanone as a solvent is spin-coded onto the reflective film and solidified by baking to form the information recording layer. Claim 1e characterized in that