JP2000048408A - Draw type optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DRAW type information optical recording medium which improves reproduction in an information reproducing device, etc., for CD-ROM by obtaining a diagonal sum phase difference signal detected by the use of a phase difference trucking method at a same output level as that of the CD-ROM. SOLUTION: In the DRAW type optical information recording medium 1, in which information is recorded by forming a pit 7 in a recording layer 3 on a guiding groove 6 provided in a substrate 2, reproduction in the information reproducing device, etc., for CD-ROM is improved by setting the optical depth of the pit 7 to be <=λ/7 and obtaining the diagonal sum phase difference signal detected by the use of the phase difference trucking method at the same output level as the output level at the time of reproduction of the CD-ROM. Where, λrepresents the wavelength of a laser beam irradiated on the recording layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a write-once optical information recording medium capable of recording and reproducing information by irradiating an optical information recording medium with a laser beam.

[0002]

2. Description of the Related Art As a type of optical information recording medium, a write-once optical information recording medium capable of recording and reproducing information by irradiating a laser beam is widely known today. As such a write-once optical information recording medium, Compac
t There is Disc-Recordable (CD-R). CD-R is
It has a disk shape and has a multilayer structure in which a recording layer, a reflective layer, and a protective layer are sequentially formed on a transparent substrate. Also,
For example, a guide groove (hereinafter, referred to as a pre-groove) for causing a laser beam from an information recording / reproducing device to follow a tracking is formed in advance on the transparent substrate in a spiral shape. By irradiating the recording layer on the pre-groove with a laser beam having a high output, pits are formed in the irradiated portion, and information is recorded.

In order to improve the recording and reproduction of digital data on such a CD-R, a tracking error signal of a laser beam emitted from an information recording / reproducing device following a pre-groove is detected and a track shift is performed. There is a tracking control method that corrects for As a method of detecting a tracking error signal of such a tracking control method, a push-p signal using a push-pull signal (difference signal) is used.
There is a ull method. In the push-pull method, a light receiving element provided in an information recording / reproducing apparatus is divided into two parts, and a pu signal which is a difference signal between signals obtained by photoelectrically converting these two light receiving areas is obtained.
The tracking error signal is obtained by comparing the symmetry of the sh-pull signal. Push-pull like this
By optimizing the output level of the signal, the reproduction of digital data is improved and the Compact Disc-Digital Audio (C
D-DA) and Compact Disc-ReadOnly Memory (CD-
For example, Japanese Unexamined Patent Publication (Kokai) No. 3-230330 discloses a pre-groove having a characteristic value conforming to a standard (red book standard, yellow book standard) that can be reproduced by an information reproducing apparatus for a ROM, and the thickness of a recording layer. It is described in the gazette.

[0004] In recent years, the specification of a write-once optical information recording medium has been defined in "Orange Book part2ve."
r.2.0 ", a method of detecting a tracking error signal by a phase difference tracking method, which has been mainly used for a read-only optical information recording medium such as a CD-ROM, has been described.

FIG. 4 shows a configuration of a detection system for detecting the tracking error signal TE by employing the phase difference tracking method. In this detection system, the light receiving section 8 is provided with a four-divided light receiving element 9. The detection signals obtained by photoelectric conversion from the light receiving areas 9a, 9b, 9c, 9d of the four-division light receiving element 9 are A1, A2, A3, A4, respectively.
It has become. Further, the light receiving area 9 of the four-divided light receiving element 9
a and a diagonal sum signal (A) of the detection signal A2 obtained from the light receiving region 9b of the four-divided light receiving element 9
1 + A2) and a diagonal sum signal (A3 + A4) of a detection signal A3 obtained from the light receiving area 9c of the four-division light receiving element 9 and a detection signal A4 obtained from the light receiving area 9d of the four-division light receiving element 9 An adder 11 is provided. Note that A1 and A3 are provided with delay circuits D1 and D2, respectively, as a countermeasure against tracking offset fluctuation. These delay circuits D1 and D2 are
The tangential phase difference ((A1 + A3) and (A2 + A
4) is set to “0” during on-track.

A comparator 12 is connected to each of the adders 10 and 11 via a capacitor C, and outputs a binarized signal. Each signal output from the comparator 12 is input to a phase comparator 13, where the phase difference between the diagonal sum signal (A1 + A2) and the diagonal sum signal (A3 + A4) is compared. , A diagonal sum phase difference signal is generated. This diagonal sum phase difference signal is the tracking error signal T
Detected as E.

[0007] The output level of such a diagonal sum phase difference signal, which is the tracking error signal TE, is determined by factors such as pits, pregrooves, and recording layers.

[0008]

When a CD-R is reproduced by a CD-ROM information reproducing apparatus or the like using the phase difference tracking method using the detection system as shown in FIG. It is necessary to obtain the output level of the diagonal sum phase difference signal, which is the signal TE, at the same level as when reproducing the CD-ROM.

However, conventionally, a CD-ROM
When reproducing a CD-R by an information reproducing apparatus for reproducing a CD-R, an output level of a diagonal sum phase difference signal detected by a phase difference tracking method is obtained to be approximately the same as an output level at the time of reproducing a CD-ROM. No standards are defined for pits, pregrooves, recording layers, etc.

In particular, in order to obtain a diagonal sum phase difference signal at an output level substantially equal to that at the time of reproduction of a CD-ROM, the optical depth of a pit, the optical depth of a pre-groove, and the recording layer It is important to properly select the film thickness and the like.

An object of the present invention is to obtain a diagonal sum phase difference signal detected by using a phase difference tracking method at an output level similar to that of a CD-ROM, so that an information reproducing apparatus for a CD-ROM can use the same. The object of the present invention is to provide a write-once type optical information recording medium which makes the reproduction of data good.

Another object of the present invention is to provide a write-once optical information recording medium capable of stabilizing the signal quality of a diagonal sum phase difference signal used in the phase difference tracking method.

[0013]

According to the first aspect of the present invention,
In a write-once optical information recording medium that records information by forming pits in a recording layer on a guide groove provided in a substrate, the optical depth of the pits determines the wavelength of a laser beam applied to the recording layer. When λ, it is λ / 7 or less.

Therefore, a diagonal sum phase difference signal, which is a tracking error signal detected by using the phase difference tracking method, can be obtained at an output level substantially equal to that at the time of reproducing a CD-ROM.

According to a second aspect of the present invention, in the write-once optical information recording medium according to the first aspect, the thickness of the recording layer on the guide groove is 300 to 3000 °.

Therefore, the thickness of the recording layer on the guide groove is set to 3
Since the optical depth of the pit is formed to be λ / 7 or less by setting the angle between 00 ° and 3000 °, the diagonal sum phase difference signal detected by using the phase difference tracking method is a CD-R
An output level similar to that during OM reproduction can be obtained.

According to a third aspect of the present invention, in the write-once optical information recording medium according to the first or second aspect, the optical depth of the guide groove is 600 ° or less.

Therefore, the diagonal sum phase difference signal detected by using the phase difference tracking method can be obtained at the same output level as when reproducing the CD-ROM, without causing distortion in the RF signal.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. In this embodiment, a write-once optical information recording medium is applied to a CD-R. The same parts as those shown in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1A shows a CD according to an embodiment of the present invention.
FIG. 3B is a cross-sectional view schematically showing the structure of R-R1, and FIG.
FIG. 3 is a plan view partially showing one recording layer 3. CD-R1
Although not shown here, has a disk shape with a diameter of 120 mm, and has a multilayer structure in which a recording layer 3, a reflective layer 4, and a protective layer 5 are sequentially laminated on a transparent substrate 2. The transparent substrate 2 is formed of a polycarbonate resin having a refractive index of 1.532 to a thickness of 1.2 mm. A pregroove 6 having a rectangular cross section for causing a laser beam to follow tracking is formed in a spiral shape on the transparent substrate 2. The width of the pregroove 6 is 0.5 μm, and the pitch thereof is 1.6 μm according to the standard. As a material for forming the recording layer 3, a material whose state changes only once upon irradiation with a laser beam (for example, an organic dye material such as phthalocyanine) is used. Further, as a material for forming the reflective layer 4, gold (A
u), an ultraviolet curable resin is used as the material of the protective layer 5.

In such a CD-R1, an information recording / reproducing device (not shown) irradiates the recording layer 3 on the pre-groove 6 with a laser beam having a high output, whereby the refractive index of the dye material at the irradiated portion is irradiated. , The absorption coefficient changes, and pit 7
Is formed. Since the pits 7 and the other portions of the recording layer 3 have different return intensities when irradiated with a laser beam, the information recording / reproducing apparatus irradiates and receives a laser beam with a low output during reproduction to receive those return intensities. Is read, and digital data "1" and "0" are recognized.

Normally, this type of CD-R1 can be reproduced by a CD-ROM information reproducing apparatus or the like, but in this case, it is a tracking error signal detected during reproduction of the CD-R1. CD of diagonal sum phase difference signal
-It is necessary to obtain at the same output level as at the time of reproducing the ROM.

Such a diagonal sum phase difference signal is output from the pit 7
Of optical depth. Here, the relationship between the optical depth of the pit 7 and the diagonal sum phase difference will be described with reference to FIG. FIG. 2 shows the relationship between the optical depth of the pit 7 and the diagonal sum phase difference when the depth of the pre-groove 6 is 0 ° (corresponding to a CD-ROM) and when the depth of the pre-groove 6 is 400 °. The results of the measurements for and are shown respectively. The laser wavelength (λ) of the irradiated laser beam is 790 nm. According to the characteristics shown in FIG. 2, the pits 7 when the depth of the pregroove 6 is 400 °
Is less than λ / 7, the CD-
It can be seen that a diagonal sum phase difference signal having the same output level as that of the ROM is obtained.

The optical depth of the pit 7 is calculated by the following formula: optical depth of pit = (film thickness of absorbing layer on pregroove) × (refractive index of light absorbing layer). In order to make the optical depth of λ / 7 or less, the material properties and thickness of the recording layer (light absorbing layer) 3 are adjusted. That is, main forming materials (for example, phthalocyanine, cyanine, etc.) used for the recording layer (light absorbing layer) 3
It can be seen from the change in the refractive index that the thickness of the recording layer 3 on the pre-groove 6 is in the range of 300 to 3000 degrees.

The diagonal sum phase difference signal is a detection signal A1, A2, A3, A4 obtained by photoelectric conversion from each of the light receiving areas 9a, 9b, 9c, 9d of the quadrant light receiving element 9 shown in FIG.
, Where these detection signals A
The relationship between the RF signal, which is the sum signal of A1, A2, A3, and A4, and the depth of the pregroove 6 will be described with reference to FIG. FIG.
2 shows a simulation of the relationship between the RF signal and the depth of the pre-groove 6 when the depth of the pre-groove 6 is changed stepwise (0 °, 400 °, 800 °, 1600 °). Further, as another simulation in this case, the optical depth of the pit 7 is λ / 7. According to the characteristics shown in FIG. 3, when the depth of the pre-groove 6 becomes 400 ° or more, distortion occurs in the RF signal. That is, the data signal HF
In order to obtain a diagonal sum phase difference signal having the same output level as that of a CD-ROM without generating a signal distortion, 400
わ か る The following is found to be appropriate. The optical depth of the pre-groove 6 is calculated by the following formula: optical depth of the pre-groove 6 = depth of the pre-groove 6 × refractive index of the transparent substrate 2. Therefore, since the transparent substrate 2 is formed of a polycarbonate resin having a refractive index of 1.532, the optical depth of the pregroove 6 is set to 600Å (400Å1.532 ≒ 600).
Å) By setting the following, a diagonal sum phase difference signal having an output level similar to that of a CD-ROM can be obtained with stable signal quality.

Therefore, by setting the optical depth of the pre-groove 6 to 600 ° or less, a diagonal sum phase difference signal having the same output level as that of the CD-ROM can be obtained without distortion of the HF signal. Become.

[0027]

An embodiment of the present invention will be described. The transparent substrate 2 has a diameter of 120 mm, a thickness of 1.2 mm, and a refractive index of 1.
A pre-groove 6 having a depth of 1500 °, a width of 0.5 μm and a pitch of 1.6 μm is spirally formed on the surface of the transparent substrate 2 using a 532 polycarbonate resin. On the transparent substrate 2, a recording layer 3 having a thickness of 1500 ° (groove, land portion average thickness) is formed by applying a phthalocyanine compound solution by a spinner. The reflective layer 4 is formed on the recording layer 3 by providing Au of 800 ° by sputtering. Then, an ultraviolet-curable resin was formed on the reflective layer 4 to a thickness of 5 μm to obtain a CD-R1. A laser wavelength of 790 nm is applied to the CD-R1 thus created.
The diagonal sum of the diagonal sum phase difference voltage detected at the time of recording / reproduction of information by irradiating the laser beam and the diagonal sum phase difference voltage detected at the time of reproduction of the CD-ROM As a result of the measurement with the phase difference voltage measuring device, the measured value of CD-R1 was 76 times the measured value of CD-ROM.
%Met. That is, during reproduction of CD-R1, C
A diagonal sum phase difference signal having the same output level as that of the D-ROM is obtained. Also, the cross section of the CD-R1 was SEM
As a result, the groove portion film thickness was 1900 ° and the land portion was 1000 °. Therefore, the change in the refractive index of phthalocyanine forming the recording layer 3 is 0.3
When the optical depth of the pit 7 is calculated, the optical depth of the pit 7 is equal to or less than λ / 7.
D-R1 was created. The optical depth of the pre-groove 6 is the depth 1 of the polycarbonate resin substrate.
500 °, difference 900 between light absorption layer of groove and land
Å, calculated from the refractive index 2.3 of the absorbing layer is 230 °.

As a comparative example, a transparent substrate 2 made of a polycarbonate resin having a diameter of 120 mm, a thickness of 1.2 mm, and a refractive index of 1.532 was used. 0.5 μm, pitch 1.6
A pre-groove 6 of μm is formed spirally. A phthalocyanine compound solution is applied on the transparent substrate 2 by a spinner to form a recording layer 3 having a thickness of 2800 ° (groove, land average thickness). The reflective layer 4 is formed on the recording layer 3 by providing Au of 800 ° by sputtering. Then, an ultraviolet curable resin is applied on the reflective layer 4 by 5 μm.
m-thick, and was designated as CD-R1. A diagonal sum phase difference voltage detected at the time of recording / reproducing information by irradiating a laser beam having a laser wavelength of 790 nm to the CD-R1 thus produced, and a diagonal sum phase difference voltage detected at the time of reproducing a CD-ROM. The diagonal sum phase difference voltage was measured by a diagonal sum phase difference voltage measuring device, and the CD-R
The measured value of 1 was 32% of the measured value of the CD-ROM.
When the cross section of CD-R1 was observed by SEM, the thickness of the groove was 3600 °. At the time of reproduction, a CD-R1 in which a diagonal sum phase difference signal having the same output level as that of the CD-ROM cannot be obtained is created.

According to the embodiment and the comparative example, when the optical depth of the pit 7 is λ / 7 or less and the optical depth of the pre-groove 6 is 600 ° or less, when reproducing the CD-R1, It can be seen that a diagonal sum phase difference signal having the same output level as that of the CD-ROM can be obtained. Further, in order to reduce the optical depth of the pits 7 to λ / 7 or less, it is found that the film thickness of the recording layer 3 on the pre-groove 6 is in the range of 300 ° to 3000 °.

[0030]

According to the first aspect of the present invention, since the optical depth of the pit is set to λ / 7 or less, the diagonal sum phase difference signal detected by using the phase difference tracking method is converted to a CD-RO signal.
By obtaining the same output level as during reproduction of M,
Good reproduction by an information reproducing apparatus for a D-ROM or the like can be achieved.

According to the second aspect of the present invention, in the write-once type optical information recording medium according to the first aspect, the film thickness of the recording layer on the guide groove is set to 300 ° to 3000 °, so that the optical depth of the pit is λ. / 7 or less, and the diagonal sum phase difference signal detected using the phase difference tracking method is represented by C
An output level similar to that at the time of reproduction of the D-ROM can be obtained.

According to the third aspect of the present invention, in the write-once optical information recording medium according to the first or second aspect, since the optical depth of the guide groove is set to 600 ° or less, distortion may occur in the RF signal. Therefore, the signal quality of the diagonal sum phase difference signal detected by using the phase difference tracking method can be stabilized.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view schematically illustrating the structure of a CD-R according to an embodiment of the present invention, and FIG. 1B is a plan view partially illustrating a recording layer of the CD-R.

FIG. 2 is a graph showing a relationship between an optical depth of a pit and a diagonal sum phase difference.

3A and 3B are graphs showing a relationship between an RF signal and a pregroove depth, wherein FIG. 3A shows a case where the pregroove depth is 0 °, FIG. 3B shows a case where the pregroove depth is 400 °,
(C), when the depth of the pre-groove is 800 °, (d)
Is a case where the depth of the pre-groove is 1600 °.

FIG. 4 is a block diagram showing a configuration of a detection system for detecting a tracking error signal by employing a phase difference tracking method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Write-once optical information medium 2 Substrate 3 Recording layer 6 Guide groove 7 Pit

Claims (3)

[Claims] 1. A write-once optical information recording medium for recording information by forming pits in a recording layer on a guide groove provided in a substrate, wherein the optical depth of the pits irradiates the recording layer. A write-once optical information recording medium, characterized in that the wavelength of the laser beam to be emitted is λ / 7 or less, where λ is the wavelength. 2. The film thickness of a recording layer on a guide groove is from 300 to 3
2. The write-once optical information recording medium according to claim 1, wherein the angle is 000 °. 3. The write-once optical information recording medium according to claim 1, wherein the optical depth of the guide groove is 600 ° or less.