JPH04134738A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To prevent the reproduction defect of information and off-tracking by selectively forming reflection films only in the ROM region in such a manner that the reflectivity of the ROM region attains the reflectivity equal to or higher than the reflectivity of a RAM region. CONSTITUTION:The optical disk is formed by being divided to the RAM region 1 and the ROM region 2. Pregrooves 3 are formed in the RAM region 1 and prepits 4 are formed in addition to the pregrooves in the ROM region 2. A recording film 6 is formed on the surface of a substrate 5 across such RAM region 1 and ROM region 2. Further, the Ni films as the reflection layers 7 are laminated on the surface of the recording film 6 where the reflectivity of the RAM region 1 corresponds to the ROM region 2 in such a manner as to attain the reflectivity equal to or higher than the reflectivity of the RAM region 1. The stability of the tracking control and focus control is improved in this way and the troubles, such as the reproduction defect of information and the offtracking, are eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical information recording medium having an R'AM area capable of recording and reproduction and a ROM area capable of only reproduction.

Conventional technology Conventionally, ISO (International O
organization for S standardi
zation) compliant 130mm write-once optical information recording medium, a control track called SFP that records the conditions for playing the user area is located inside the user area R29.5 to 2'9.7mm. exists. Information necessary for reproduction is preformatted in the control track area, and information such as data and programs is preformatted in areas other than the control track area. As a result, some optical disks have both a read-only area (ROM, SFP area) and an area for recording and playback (RAM, user area) (existence of both areas). (This is called a partial ROM).

Problems to be Solved by the Invention FIG. 3 shows a part of the cross-sectional shape of an optical disk in which the RAM area 1 and ROM area 2 are formed. In this case, in RAM area 1 there is only a groove for tracking control called pregroup 3, whereas
In the ROM area 2 in which information is preformatted in advance, there are pre-pits 4 for recording information in addition to the pre-groups 3, which causes problems such as a decrease in reflectance and a decrease in tracking signal. Note that these pre-groups 3 and pre-pits 4 are formed on a substrate 5, and a recording film 6 is formed over the entire surface of this substrate 5.

FIG. 4 shows the relationship between the track error signal (bush pull signal) and the pit density in the case where pre-groups 3 and pre-pits 4 as shown in FIG. 5 are present. It can thus be seen that the track error signal decreases significantly as the pit density increases.

That is, in the ROM area 2 in which information has been preformatted, the tracking tends to become unstable because the tracking error signal is small, which causes problems such as errors in information reproduction due to tracking deviations and tracking disturbances. In addition, such optical discs are
Since the ROM area 2 is frequently moved to the ROM area 2, there is a problem in that tracking tends to deviate at the start of tracking. Furthermore, as described above, since the amount of reflected light decreases due to the pre-pits 4, there is a problem in that when the light goes back and forth between the RAM area 1 and the ROM area 2, focus control becomes unstable due to the difference in reflectance.

As a method for preventing such a decrease in reflectance in the ROM area 2, there is a method disclosed in, for example, Japanese Unexamined Patent Publication No. 137744/1983. This is the RAM area and RO
The RAM area of the information recording layer is in an unrecorded state and the ROM area is in a recorded state, so that the reflectance of the RAM area and the ROM area is made equal. It is something. In this way, the reflectance problem can be solved by recording the information recorded in the ROM area in the same way as writing information in the RAM area instead of preformatting, but in this case, There is a problem that productivity is poor because it is not possible to duplicate the data.

Means for Solving the Problems Therefore, in order to solve such problems, the present invention provides a RAM area for recording and reproducing information and a ROM area in which information is previously formed as a pit string and only for reproduction. In the optical information recording medium provided, a reflective film is selectively formed only in the ROM area so that the reflectance of the ROM area is equal to or higher than that of the RAM area.

Further, the reflective film was provided on the surface of the recording film formed on the substrate located in the ROM area.

Furthermore, a reflective film was provided between the substrate located in the ROM area and the recording film formed on this substrate.

Effect By providing a reflective film only in the ROM area in this way, it is possible to obtain a reflectance equivalent to that in the RAM area, and this prevents the reflectance and tracking error signal from decreasing in the ROM area, making tracking control easier. It is now possible to perform stable focus control at all times.
This can eliminate problems such as poor information reproduction and tracking errors.

Further, by providing a reflective film on the surface of the recording film formed on the substrate located in the ROM region, it is possible to further improve the stability of tracking control and focus control in the ROM region.

Furthermore, by providing a reflective film between the substrate located in the ROM area and the recording film formed on this substrate,
The stability of tracking control and focus control in the ROM area can be further improved, and since no new manufacturing process is required after forming the recording film, the influence of dust and the like can be minimized.

Embodiment A first embodiment of the present invention will be explained based on FIG. Note that the same reference numerals are used for the same parts as in the prior art (see FIG. 3).

An optical disc serving as an optical information recording medium is divided into a RAM area 1 and a ROM area 2. The substrate 5 is made of a transparent member, and has a RAM area area ratio pre-group 3 formed therein, and a ROM area 2 in which a pre-pit 4 is formed in addition to the pre-group 3. And these RAM
A recording film 6 is formed on the surface of the substrate 5 across the area 1 and the ROM area 2. In this case, the transparent substrate 5 can be manufactured from a material such as acrylic or polycarbonate by injection molding, 2P method, or the like. In addition, the recording film 6
can be formed by coating the surface of the substrate 5 with a dye, a low melting point metal such as Te, or the like.

If the recording film 6 is simply formed on the surface of the substrate 5 in this way, the reflectance and track error signal will be smaller in the ROM area 2 than in the RAM area, as explained in the prior art. Therefore, in this embodiment, a reflective film 7 is laminated on the surface of the recording film 6 corresponding to the ROM area 2.

Specifically, if the recording film 6 is made of a dye and the reflectance of the RAM area 1 is 20 to 40%, then the ROM area 2
A Ni film as a reflective film 7 is placed on the surface of the recording film 6 corresponding to R.
The layers are stacked so that the reflectance is equal to or higher than that of the AM region 1.

As mentioned above, the reflective film 7 is selectively laminated only on the ROM area 2, so that the reflectance of the ROM area 2 is equal to that of the RAM area 1.
By setting the reflectance to be equal to that of , it is possible to further improve the stability of comparative tracking control and focus control.

Next, a second embodiment of the present invention will be described based on FIG. 2. In the embodiments described above, the reflective film 7 was formed on the surface of the recording film 6, but here the method of forming it is changed.

That is, the reflective film 7 is laminated on the surface of the substrate 5 on which the pre-format (pre-group 3, pre-pit 4) in the ROM area 2 is formed, and the recording film 6 is formed on the reflective film 7.
was formed, thereby producing an optical disc.

Specifically, a reflective film of N is selectively applied to only the ROM area 2 on the substrate 5 made of preformatted acrylic.
An optical disk is manufactured by stacking 50 to 500 IMs, forming a recording film 6 made of dye on the surface of this N1 film, and setting the reflectance of the ROM area 2 to be almost equal to the reflectance of the RAM area 1. do.

As a result, it is possible to improve the stability of tracking control and focus control in the ROM area 2, and by forming the recording film 6 after laminating the reflective film 7 on the surface of the substrate 5, it is possible to improve the stability of the tracking control and focus control in the ROM area 2. In comparison, since no new manufacturing process is required after the recording film is formed, it is possible to prevent the influence of dust and the like, and it is possible to achieve an excellent product in terms of deterioration of the recording film in the process of applying the reflective film.

In the embodiments described so far, the recording film 6 was formed from a dye and the reflective film 7 was formed from a Ni film, but the invention is not limited to these. For example, the recording film 6 may be formed from a metal, The reflective film 7 may be formed of a material having high reflectance such as AQ, Au, Ag, or the like.

Effects of the Invention The present invention provides an optical information recording medium comprising a RAM area for recording and reproducing information and a ROM area in which information is previously formed as a pit string and only reproduced. Since the reflective film is selectively formed only in the ROM area so that the reflectance is equal to or higher than that of the RAM area, there is no possibility that the reflectance or track error signal will decrease only in the ROM area. Therefore, tracking control and focus control can be performed stably at all times, and in addition, problems such as poor information reproduction and tracking errors can be eliminated.

Furthermore, since the reflective film was provided on the surface of the recording film formed on the substrate located in the ROM area, by providing the reflective film on the surface of the recording film formed on the substrate located in the ROM area, This makes it possible to further improve the stability of tracking control and focus control in the ROM area.

Furthermore, since the reflective film was provided between the substrate located in the ROM area and the recording film formed on this substrate, the ROM
The stability of tracking control and focus control in the area can be further improved, and since no new manufacturing process is required after forming the recording film, the influence of dust and the like can be suppressed as much as possible.

[Brief explanation of the drawing]

Fig. 1 is a side view showing a first embodiment of the present invention, Fig. 2 is a side view showing a second embodiment of the invention, Fig. 3 is a side view showing a conventional example, and Fig. 4 is a side view showing a pit. FIG. 5 is a waveform diagram showing the relationship between the track error signal and the density. FIG. 5 is a side view showing how pre-groups and pre-pits are formed on a conventional substrate. DESCRIPTION OF SYMBOLS 1...RAM area, 2...ROM area, 5...substrate, 6...recording film, 7...reflection film

Claims (1)

[Claims] 1. In an optical information recording medium comprising a RAM area for recording and reproducing information and a ROM area in which information is previously formed as a pit string and only for reproduction, the reflectance of the ROM area is An optical information recording medium characterized in that a reflective film is selectively formed only in the ROM area so that the reflectance is equal to or higher than that of the RAM area. 2. The optical information recording medium according to claim 1, wherein the reflective film is provided on the surface of a recording film formed on the substrate located in the ROM area. 3. The optical information recording medium according to claim 1, wherein the reflective film is provided between the substrate located in the ROM area and the recording film formed on this substrate.