JPS6214893B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel structure of a removable optical recording disk in which recording is performed by evaporating or melting the light incident portion of the recording film using the thermal energy of light, particularly a laser beam. be.

FIG. 1 shows the basic structure and function of a conventional optical recording disk. In Figure 1a, reference numeral 101 is a substrate for supporting the disk and resisting rotation, and it needs to have the required mechanical strength and flatness, as well as low thermal conductivity, and a polymer flat plate is generally used. . Reference numeral 102 denotes a recording film provided on the substrate, which requires a material with low thermal conductivity, high thermal diffusivity, and low melting point, and a metal thin film such as Bi or Te is used. By irradiating the optical recording disk with the above structure with recording light focused on a fine focus to increase the energy density and adding a change corresponding to the required information, generally an ON-OFF modulation, As shown in FIG. 1b, the recording light 103
The recording film at the position corresponding to the ON state is melted and evaporated to form recording pits 104. When playing back records, we use the same laser beam as when recording.
The recorded information is reproduced by irradiating the recording film with such weak energy that the recording film is not affected by the change, and by detecting reflected light or transmitted light from the recording film.

FIG. 2 shows the basic structure and function of another type of optical recording disk. In FIG. 2a, 201 is the same substrate as 101 in FIG. An interferometric reflective filter is used. Recording film 202
In this case, a metal thin film similar to that shown in FIG. 1 102 is used. Recording is performed by forming recording pits 204 in accordance with the ON state of the recording light 203 in FIG. 2B, similar to FIG. 1B. During reproduction, a laser beam similar to that used during recording is applied at a weakened level to prevent re-recording, and the reflected light from the disk is detected. When the recording film is a thin metal film, in order to emphasize the change in the reproduction light caused by the recording pit, the thickness of the recording film is made to be about 1/4 wavelength, so that the incident light and reflected light interfere with each other in opposite phases. The following measures will be taken. Note that in order to prevent information from being lost due to dust or the like, a light-transmissive protective layer may be provided at a non-focal position of the light beam on the incident light side of the recording film 202.

In the optical recording disk as described above, since the recording pits can be about 1 .mu.m or less, the pitch of the recording tracks can be about 2 .mu.m, and extremely high-density recording can be performed.
However, when using such an optical recording disk, the shape of the beam spot of the reproduction light is detected during reproduction so that the beam spot of the reproduction light is correctly positioned on the recording track.
A tracking servo function is added to control the position of the optical system, but track setting during recording depends on the feeding mechanism of the optical system. For this reason, the mechanism to correctly hold track pitches of about 2 μm requires extremely high precision, and special care is required to handle and maintain precision, making it inevitable that the recording equipment will become larger and more expensive. .

To solve this problem, a guide signal for the tracking servo is recorded on the optical recording disk, and during recording, the tracking servo is used to set and follow the track in the same way as during playback, and the information is transferred to the above guide. One possible method is to record in the blank part of the signal. FIG. 3 shows a theoretical sectional view along the track of the optical recording disk with guide signals and the corresponding recording signals. In Figure 3 a, 301, 30
2, 303, and 304 are 101 and 101 in Fig. 1, respectively.
These are a substrate, a recording film, a recording light, and a recording pit corresponding to 102, 103, and 104. A section 310 on the track is a section in which guide signals are recorded in advance, and 311 is a section where information is recorded. Section 3
The guide signal No. 10 is recorded on a track determined by a recording device having a highly accurate optical system feeding mechanism, and the waveform of the recorded signal is shown in b. When recording information, the recording light 303 is weakened to the extent that re-recording is not performed for the section 310 and used as reproduction light, and the guide signal is reproduced to operate the tracking servo of the recording device to set and track the track. Then, for the section 311, the intensity of the recording light 303 is increased, and the recording pit 30 is
form 4. According to the above-mentioned optical recording disk with a guide signal, a highly accurate original recording device is required for recording the guide signal, but for information recording, it has a track servo similar to the playback device, and has a track setting,
Since the tracking accuracy can depend more on the servo system than on the accuracy of the optical system feeding mechanism, it is possible to provide an optical recording/reproducing device that is small and easy to handle. The guide signal includes
Data synchronization signals, address signals, etc. can be used.

The drawback of the above-mentioned optical recording disc is that it is necessary to record a guide signal in advance for each disc using a high-precision original recording device.To solve this problem, records are manufactured from the optical recording disc with a guide signal. A disk may be considered in which a stamper with surface irregularities of opposite polarity is prepared, a substrate with a guide signal is obtained by pressing, and a metal recording film is provided on this. FIG. 4 shows a cross section along the track of a disk having this configuration. In the figure, 401 to 404, 410, and 411 correspond to 301 to 304, 310, and 311 in FIG.
It is used as a guide signal by forming similarly uneven pits on the surface of the recording film on the substrate.

As shown in FIG. 4, an optical recording disk suitable for recording and reproducing information by an optical recording and reproducing device having a relatively low-precision track feeding mechanism and a track servo function is provided with a guide signal by pressing technology. It can be provided by mass-produced means. A problem with conventionally proposed optical recording disks, such as the one shown in FIG. 4, lies in the recording sensitivity. In other words, in conventional recording films, thin films of metals such as Bi or Te are used to provide extremely high recording sensitivity, and in order to improve sensitivity, improvements such as multilayer films that increase absorption of laser beams have been added. However, recording energy of 100 to 30 mJ/cm ² is required, and 10 Mbit/sec data recording practically requires a laser light source with an output of 20 mW or more. This output can be adequately accommodated by a gas laser, but in this case it is necessary to provide information to the laser beam using an expensive optical modulator. On the other hand, the practical output of semiconductor lasers that can be directly modulated is less than 10 mW, and in order to increase the output, it is necessary to expand the radiation area, and the energy density decreases due to the expansion of the beam spot on the recording film, which is the limit. There is.

As mentioned above, since the conventional removable recording film made of a metal thin film is insufficient for the high-speed recording targeted by the present invention, the use of an organic thin film is considered. FIG. 5 shows a cross section along a track of an optical recording disk in which a guide signal is applied to a substrate and an organic thin film is used as a recording film. In the figure, 501 is a substrate provided with guide signal pits 506, and 505 is a reflective film whose upper surface has the same unevenness as the surface of the substrate. 5
02 is a recording film made of an organic thin film, and 503 is a laser beam, which has a guide signal reproduction level intensity in a guide signal section 510 and a recording level intensity in an information recording section 511. However, there are great difficulties in realizing an optical recording disk with this structure.
That is, the organic thin film recording film as described above is generally prepared by applying a solution of an organic substance and evaporating the solvent. However, in the guide signal section 510, such a solution not only fills the concave pits on the reflective thin film, but also is formed so that the surface of the recording film is flattened by surface tension. The recording sensitivity of the recording film increases as the absorption rate for the laser beam increases. Therefore, when it is formed flat on the guide signal section, it depends on the intensity of the reflected light necessary for this section, that is, the guide signal reproduction light and the guide signal pit. The modulation is significantly reduced and the desired tracking servo cannot be operated.

The present invention provides an optical recording disk with a guide signal that eliminates the above-mentioned drawbacks and enables high-speed information recording even with a low-power laser.

The configuration of an embodiment of the present invention will be explained in detail below.

FIG. 6 shows a cross section along a track of an optical recording disk with a guide signal according to the invention. Board 601
The material is required to have the required mechanical strength, flatness, and low thermal conductivity, so a polymer flat plate or the like is used. Board 6
01, a highly accurate guide signal is formed in a convex direction with a polarity opposite to that of the information pits recorded on the recording film by a method such as press molding, and forms the base of the guide signal pit 607. On the substrate 601, a metal thin film such as A1 is deposited to prevent transmission and diffusion of recording light energy toward the substrate and to increase recording sensitivity, or a reflective film 605 such as an interference reflection filter is provided on the substrate 601, and a recording film is formed on the substrate 601. 602 is configured. FIG. 7 shows an enlarged example of the configuration of the present invention, showing a cross section along the track. 70
1,702,703,704,705,707,
710 and 711 are respectively 601 and 60 in Figure 6
2,603,604,605,607,610,
This corresponds to 611.

For example, if the recording film is an organic recording film, the organic recording film will fill the recesses on the reflective film, but it can be formed so that it is not formed on the convex parts of the guide signal pits or is formed very thinly. Therefore, the intensity modulation of the guide signal reproduction light is sufficiently performed.

As a result of the above, it is possible to provide an organic recording film having a large absorption rate for the recording laser beam on the substrate and the reflective film layer having the guide signal pits having the opposite polarity to the information pits recorded on the removable recording film. According to the present invention, the above absorption rate can be increased without considering the guide signal pits. Therefore, next, an invention for increasing the absorption rate of nitrocellulose collodion, which has a low evaporation temperature and is suitable for obtaining a thin film, but has a low absorption rate for laser light, will be described. For example, a collodion solution containing ethyl alcohol or ether as the main solvent, polymethine dye, etc.
For example, 1,1′-Dieth1-2,2′-tricarbocyanine
A solution of 1 mg of i-odide dissolved in 20 ml of alcohol was added and mixed at a ratio of 1:1, and this was dropped onto a transparent substrate and dried to a thickness of approximately 0.75 μm.
The absorption rate of the obtained thin film is shown in FIG. The absorption rate of this organic thin film is 30% of the peak value at the semiconductor laser wavelength of 0.83 μm, including the 5% substrate.
shows. Therefore, combined with the effect of the reflective film, 50% of the laser beam in the recording film is absorbed during the round trip.
Therefore, the specific gravity of the nitrocellulose membrane is 1.67,
Since the specific heat is 0.03ca1/g·deg, if the thickness of the film is 1 μm, the input light energy to heat the film to the vaporization temperature of 180° C. is 3.78 mJ/cm ² .

If the absorption rate due to the above dye mixture is 50% round trip, the required input energy of the recording film is 7.56 mJ/cm ² ,
When the efficiency of the optical system is 50%, the output of the semiconductor laser is 15.12 mJ/cm ² . When using a typical semiconductor laser with a radiation area of about 2 μm ² , the required optical output is 3 mW at an information rate of 10 Mbit/sec, which is fully achievable.

If the mixing ratio of the collodion liquid and the dye liquid is 1:2, the absorption rate will be 50% one way and 75% round trip, and a film with even higher recording sensitivity can be obtained. This thin film appears pale blue-gray to the naked eye and exhibits absorption in the long wavelength region.

A recording film with similar effects can be obtained by using isoamyl acetate or butyl acetate as the main solvent for collodion.

As described above, according to the present invention, a highly sensitive optical recording disk with a guide signal can be obtained and its basic structure has been shown, but in practice, it is necessary to protect the recording film and prevent information errors caused by dust. A light-transmitting protective layer can also be provided on the non-focal plane of the recording film on the laser beam incident side.

Furthermore, since the recording thin film has a color fading property with respect to ultraviolet light, the stability is improved by reducing the transmittance of the protective layer in the short wavelength range.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic structure and function of a conventional optical recording disk. FIG. 2 is a diagram showing the basic structure and function of another type of conventional optical recording disk. FIG. 3 is a diagram showing a theoretical sectional view along a track of a conventional optical recording disk with a guide signal and a corresponding recording signal. FIG. 4 is a sectional view along a track of a conventional optical recording disk with a guide signal. FIG. 5 is a sectional view along a track of a conventional optical recording disk using an organic thin film as a recording film. FIG. 6 is a sectional view along a track of an optical recording disk with a guide signal according to the present invention. FIG. 7 is an enlarged cross-sectional view along the track of an optical recording disk with a guide signal, showing an example of the configuration of the present invention. FIG. 8 is a diagram showing the light absorption rate of the recording thin film of the present invention. 01 is the substrate, 02 is the recording film, 03 is the recording light, 0
4 is a recording pit, 05 is a reflective film, 06 is a guide signal pit, 07 is a guide signal pit, 10 is a guide signal section, and 11 is an information recording section. The third digit indicates the drawing number.

Claims (1)

[Claims] 1. A substrate having a guide signal pit portion and a blank portion on a track, a reflective thin film provided along the irregularities on the substrate, and a removable recording thin film uniformly formed on the substrate surface. In an optical recording disk that has a layered structure and is provided with a guide signal for setting and tracking the track during recording, the track of the information recording portion on the substrate is lower than the surface of the convex part of the guide signal pit on the substrate. An optical recording disk characterized by being formed at a deep position. 2. The optical recording disk according to claim 1, wherein the recording film is an organic thin film. 3. The optical recording disk according to claim 1, wherein the recording film is an organic thin film with enhanced light absorption rate for recording light. 4. The optical recording disk according to claim 3, wherein the recording film is a mixture of nitrocellulose and polymethine dye. 5 Claims 1, 2, and 3, wherein a light-transmitting protective layer is provided on the non-focal plane on the incident light side of the recording film.
The optical recording disk according to item 3 or 4. 6. The optical recording disk according to claim 5, wherein the protective layer has a transmittance that decreases in the short wavelength region of light.