JPH02185737A - Optical recording medium disk - Google Patents

Abstract

PURPOSE:To obtain the DRAW type optical disk having interchangeability with a compact disk by sticking an org. material film which is decreased in refractive index by laser light for recording having a determined wavelength on a transparent substrate having guide grooves for tracking and providing a metallic film for reflection thereon. CONSTITUTION:This disk is constituted by laminating the light transparent org. material film 2 which is decreased in refractive index by absorbing the proper quantity of the laser light when irradiated with the laser light for recording having the predetermined wavelength and the metallic film 3 for light reflection on the transparent substrate 1 having the guide grooves G for tracking. The reproduction mechanism of the optical disk is executed substantially by the phase structure in this way and the optical disk of the DRAW type satisfying various requirements relating to the reflectivity, modulation percentage of high-frequency signals, tracking signal output, etc., regulated for the compact disk is easily obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical recording medium disk, particularly a write-once optical recording medium disk which is also compatible with compact discs.

(Prior Art) As the demand for recording various information signals at high recording densities has increased, in recent years, information recording media created based on various structural and operating principles have been used to record information signals at high recording densities. It is well known that high-density recording and reproduction of information has become possible. For example, information signals are recorded by forming irregularities on the signal surface of an information recording medium according to the information signal, Recording and reproducing devices that reproduce signals by optical means or by detecting changes in capacitance values are already in practical use for recording and reproducing video signals and audio signals.

In addition, in order to meet the demands for high-density recording and reproduction in various technical fields, by irradiating the recording layer of the information recording medium with a beam whose intensity is modulated by the information signal, the recording layer of the information recording medium can respond to the information signal. Research has also begun on information recording media that record information signals by causing physical or chemical changes, but in recent years it has become easier to obtain semiconductor lasers that operate stably. Along with this, various optical recording media (which use laser light for high-density recording and reproduction)
It is well known that optical discs) have already been put into practical use, or research and development is currently underway to put them into practical use.

In other words, recorded optical discs (read-only optical discs), which are mass-copied from master discs on which information signals are recorded using pits formed as geometrical concave or convex parts, can be used, for example, as video discs or compact discs. etc., and are beginning to become popular in ordinary households.
Optical discs that allow the user to record data only once (write-once optical discs) and erasable optical discs are being actively researched and developed for practical use in, for example, office file memories and other uses.

By the way, when reproducing information signals from an information recording medium on which information signals are recorded at high density, tracking control is used to ensure that the reproducing element or the reproducing beam always accurately follows the recording trace where the information signals are recorded. For example, a spot of light with a minute diameter is projected onto the signal surface of an information recording medium,
As a tracking error detection method used for tracking control in an optical information signal reproducing device that reproduces information signals based on reflected light whose intensity is modulated by pits formed on the signal surface, The so-called push-pull tracking error detection method uses the fact that the intensity distribution of the reflected light is biased by the tracking error to detect the tracking error, but the optical system has a simple configuration. In addition, it is widely used because it is advantageous in terms of cost.In addition, a straight line that projects a first light spot for signal reading onto the signal surface of an information recording medium and includes the first light spot described above. A second light spot for tracking is placed at a symmetrical position with the first light spot as the center of symmetry.
．． By projecting the third light spot, the second light spot described above is projected. It is well known that a tracking error detection method that detects a tracking error based on the reflected light generated on the signal surface of the information recording medium by the third light spot has also been used. Even when reproducing information signals recorded at high density on various formats of information recording media,
The reproduction operation is normally performed under tracking control operation.

Now, a compact disc is known as an information recording medium in which information signals are recorded at high density by an array of pits corresponding to the information signals on the signal surface of the information recording medium. The information signal is formed on the signal surface by an arrangement of pits with a depth set in a specific relationship with respect to the wavelength, and the reflectance of the land portion on the signal surface is 70% to 70% for light with a wavelength of 780 nm. 90
%, and the information signal is read out from the signal surface of the information recording medium using a spot of light with a wavelength of 780 nm.

When reading an information signal from the above-mentioned compact disc, the amount of light reflected from the pit portion on the signal surface is greater than the amount of light reflected from the land portion as a result of light interference occurring at the pit portion. This is done by taking advantage of the fact that the amount of light is reduced compared to the amount of light, and the tracking error information is also based on the amount of light reflected from the recorded trace.
It is obtained by using the difference between the amount of light reflected from the land portion and the amount of light reflected from the land portion.

Now, with the spread of the above-mentioned compact disc, there are optical discs compatible with compact discs that can be played using a compact disc player. Various proposals have been made for write-once optical discs that have a configuration that provides a recording area that can be used as a storage area, or for optical discs that have a recording area that covers the entire surface. The optical disc of this type has a structure in which a guide groove for tracking is provided on a transparent substrate so that tracking control can be performed even during recording.

(Problem M to be solved by the invention) By the way, as an optical disc that is compatible with compact discs, it goes without saying that compact discs are compatible with compact discs.
Various standards regarding playback established for discs,
In other words, it must satisfy standard values for reflectance, modulation degree of high-frequency signals, symmetry of high-frequency signals, tracking signal output, crosstalk, etc., but it must also satisfy standards for playback on compact discs. When trying to obtain a write-once optical disc with sufficient compatibility, the various standards related to playback of compact discs, which are particularly problematic, include reflectance, modulation degree of high-frequency signals, tracking signal output, etc. Can be mentioned.

Here, when attempting to configure a write-once optical disc that is compatible with compact discs, it is necessary to refer to the various standards regarding reflectance, modulation degree of high-frequency signals, tracking signal output, etc. stipulated for the above-mentioned compact discs. The problems that arise when constructing a write-once optical disc that satisfies the requirements are as follows.

First, the standard value for reflectance on compact discs is that the wavelength is 780 nm from the readout side of the optical disc.
The optical disc is required to have a reflectance of 70% or more when viewed from the readout side when a laser beam of Even if we consider only the reflection loss at
In order to achieve 0% or more, the reflectance of the metal reflective film must be at least 80% or more.

As is well known, compact discs use an aluminum reflective film that exhibits a reflectance of 80% or more, and that they meet the reflectance standards mentioned above. (Needless to say, it changes depending on the film formation conditions).

However, in write-once optical discs, since recording is performed on the recording film, energy for recording is absorbed into the recording film, and as mentioned above, in write-once optical discs, recording is performed for tracking control during recording. In addition, since the transparent substrate is provided with guide grooves for tracking control, the incident light is diffracted by the guide grooves, resulting in a loss of light quantity, which reduces the reflectance on the read side of the optical disc to a level similar to that of a compact disc. Conventionally, it was considered difficult to set the reflectance to a standard value.

Furthermore, when constructing a write-once optical disc that is compatible with compact discs, it is necessary to construct a write-once optical disc that satisfies the standards for the degree of modulation of high-frequency signals stipulated for compact discs. In this case, there are the following problems.

In other words, compact discs use light diffraction by bits to read information signals, so it is easy to meet the standard value for the degree of modulation of high-frequency signals, but this method has not been proposed in the past. In general write-once optical discs, the mode of recording on the recording film is as follows.
For example, it is based on perforation or phase change, and readout of recorded information signals is performed by change in reflectance. The difference between the optical reflectance of the recording part (corresponding to the bit) due to the change, that is, the degree of modulation of the high-frequency signal, is small, so it meets the standards for the degree of modulation of high-frequency signals stipulated for compact discs. It wasn't a vine.

In order to satisfy the compact disc standard value for the degree of modulation of high-frequency signals, even in write-once optical discs, it is necessary to read out information signals using diffraction of light by bits. It is considered necessary that the information signal be read out using a one-phase structure as well.

Next, when trying to configure a write-once optical disc that is compatible with compact discs.

There are the following problems when constructing a write-once optical disc that can meet the standards regarding the output level of the tracking signal stipulated for the above-mentioned compact disc.

In other words, the output level of the tracking signal on an optical disc is generally determined by the phase edge structure determined by the bit or the shape of the tracking guide groove provided on the transparent substrate, but even in write-once optical discs, it is determined by the phase edge structure determined by the shape of the tracking guide groove provided on the transparent substrate. It is necessary to make the output level of the tracking signal satisfy the standard value while satisfying the following.

However, in the general write-once optical discs that have been proposed in the past, the mode of recording on the recording film is limited.

For example, if this is done by drilling holes, the holes disrupt the phase structure determined by the shape of the tracking guide groove.

It is difficult to obtain a tracking signal with a desired output level.

Based on the explanation so far, if you are trying to configure a write-once optical disc that is compatible with compact discs,
There are many problems in ensuring that various characteristics such as light reflectance, modulation degree of high-frequency signals, and tracking signal output 1 meet the standards specified for compact discs during playback, and conventional For some write-once optical discs, it has been difficult to provide a write-once optical disc that is compatible with compact discs.

(Means for Solving Problem No. 111) The present invention provides a transparent substrate provided with a guide groove for tracking, and a transparent substrate provided with a guide groove for tracking. An organic material film that absorbs an appropriate amount of the laser light and decreases the refractive index when it is irradiated with a recording laser light having a specific wavelength is attached to the organic material film. An optical recording medium disc provided with a metal film, a transparent substrate provided with a guide groove for tracking, and a predetermined material on the surface of the transparent substrate on which the guide groove for tracking is provided. The film thickness d of the guide groove portion for tracking in a transparent substrate comprising an organic material film that absorbs an appropriate amount of the laser light and reduces the refractive index when it is irradiated with a recording laser light having a wavelength of And the film thickness of the part of the transparent substrate other than the guide groove for tracking is (d - Δd)
In addition, in the optical recording medium in which a metal film for light reflection is provided on the organic material film, the transparent substrate described above has no guide groove for tracking. The phase difference that occurs between the tracking guide groove portion of the transparent substrate and the portion of the transparent substrate other than the tracking guide groove in the laser beam incident from the plate surface side is determined by the state in which the organic material film is not present. Compared to the retardation obtained by By making use of the phase advance caused by the change in the refractive index of the organic material film in the recorded area, the optical phase of the laser beam is substantially advanced compared to the unrecorded area. An optical recording medium disc is provided.

(Function) When a laser beam for recording having a predetermined wavelength is irradiated onto the surface of the transparent substrate on which the guide groove for tracking is provided, the transparent substrate has a guide groove for tracking. An organic material film attached to the substrate absorbs an appropriate amount of the laser light, and its refractive index decreases.

The organic material film described above has a film thickness of d in the tracking guide groove portion of the transparent substrate, and a film thickness of the transparent substrate in a portion other than the tracking guide groove (d−Δ
d) and also.

A metal film for light reflection is attached to the organic material film.

Then, the tracking guide groove portion of the transparent substrate in the laser beam incident from the side of the plate where the tracking guide groove is not provided in the transparent substrate, and the tracking guide groove in the transparent substrate. The phase difference generated in the other parts is compared to the phase difference obtained in the absence of the organic material film described above.
The optical path length is decreased due to the change in the optical path length due to the difference Δd in the film thickness of the organic material film described above, and the substantial phase difference of the laser beam is made smaller than the value of the phase difference determined by the groove shape in the transparent substrate, and the recorded Due to the phase advance caused by the change in the refractive index of the organic material film in the portion, the optical phase of the laser beam in the recorded portion is substantially advanced compared to the unrecorded portion.

(Example) Hereinafter, detailed contents of the optical recording medium disk of the present invention will be specifically explained with reference to the accompanying drawings.

FIG. 1 is a side sectional view showing a schematic configuration of an example of the optical recording medium disk of the present invention, and FIGS. 2Wi and 3 are used to explain the principle of construction and operation of the optical recording medium disk of the present invention. 4 is a side sectional view of a characteristic curve used to explain the optical recording medium disk of the present invention, and FIG. 5 is a side sectional view for explaining the thickness of a recording film attached to a substrate with guide grooves. 6 is a perspective view showing a specific example of the guide groove of a substrate with guide grooves, and FIG. 7 is a characteristic for explaining the effect of the phase structure due to the guide grooves of the substrate with guide grooves. It is a curve side view.

In the side sectional view showing the schematic structure of an example of the optical recording medium disk of the present invention shown in FIG. Guide grooves G, G... are provided.

The transparent substrate 1 with the guide groove for tracking described above is
For example, it is made from polycarbonate resin. 2 is a guide groove G for tracking in the transparent substrate 1 described above;
G... is an organic material film (recording layer, recording film) deposited on the plate surface on which it is provided, and the organic material M2 is
An organic material film whose refractive index decreases by absorbing an appropriate amount of the laser light when irradiated with a recording laser light having a predetermined wavelength (for example, 780 nm); 2 is deposited and formed on the surface of the transparent substrate 1 on which the tracking guide grooves G, G, . . . are provided by applying a spin code method.

The organic material film 2 described above is, for example, a heat mode optical recording material using an organic dye or a material in which an organic dye is dispersed in an organic material, or a photon recording material using an organic dye or a material in which an organic dye is dispersed in an organic material. mode optical recording material,
Alternatively, the optical recording medium of the present invention may be produced using an optical recording material selected from among optical recording materials using organic dyes that operate in both heat mode and photon mode, or materials in which organic dyes are dispersed in organic materials. Thus, an organic material film 2 suitable for implementation as a recording medium disc is constructed.

The organic material film 2 has a film thickness of d at a portion of the tracking guide groove G on the transparent substrate 1, and a film thickness of (d) at a portion of the transparent substrate other than the tracking guide groove G.
−Δd), and the portion of the tracking guide groove G in the transparent substrate 1 in the laser beam incident from the side of the plate where the tracking guide groove G in the transparent substrate is not provided. and transparent substrate 1
The phase difference generated in the portion other than the tracking guide groove G in the organic material film 2 described above is compared with the phase difference obtained in the absence of the organic material film 2 described above.
The change in the optical path length due to the film thickness difference Δd is used to reduce the substantial phase difference to be smaller than the value of the phase difference determined by the shape of the tracking guide groove G in the transparent substrate 1, and the recording By utilizing the phase advance caused by the change in the refractive index of the organic material film 2 in the recorded portion, the optical phase of the laser beam is substantially advanced compared to the unrecorded portion.

That is, in the optical recording medium disk (optical disk) of the present invention shown in FIG. 1, the tracking guide grooves G, G...
a light-transmissive organic material film that absorbs an appropriate amount of the laser beam and reduces its refractive index when it is irradiated with a recording laser beam having a predetermined wavelength; 2 and a metal film 3 for light reflection are laminated, so that the playback mechanism of the optical disc is substantially performed by a phase structure, and the reflectivity and high frequency signal specified for compact discs are achieved. This makes it possible to easily obtain a write-once optical disc that satisfies various standards regarding modulation degree, tracking signal output, etc.

Next, by adopting the configuration of the optical recording medium disk (optical disk) of the present invention as explained with reference to FIG. The reason why it is possible to easily obtain a write-once type optical disc that satisfies various standards related to 1st grade and is compatible with compact discs will be explained in detail with reference to FIG. 2 and the following figures.

The optical recording medium disk (optical disk) of the present invention shown in the first figure described above, that is, the guide grooves G for tracking, G.
When a recording laser beam having a predetermined wavelength is irradiated onto the surface of the transparent substrate 1 on which the tracking guide groove G is provided, an appropriate amount of the laser beam is applied. An organic material film 2 whose refractive index decreases by absorbing light is attached, and a metal film 3 for light reflection is attached to the organic material film.
Assuming that the optical recording medium disc having the configuration satisfies various standards regarding reflectance, modulation degree of high-frequency signal, tracking signal output, etc. stipulated for compact discs, the optical recording medium disk configured as shown in Figure 1. After the organic material film 2 in the optical recording medium disc (optical disk) of the present invention is brought into a recorded state as described later, the transparent substrate 1 on the side of the transparent substrate 1 where the guide groove G for tracking is not provided is When a reproduction laser beam is focused on the guide groove G by a condensing lens from the plate surface 1a side, a reproduction signal obtained based on the information recorded on the organic material film 2 is generated from the compact disc. A high frequency signal having the same output level as when reproducing the information signal from the compact disc and the same modulation degree as when reproducing the information signal from the compact disc can be obtained. A tracking signal output of the same magnitude can be obtained.

Now, in the optical recording medium disk (optical disk) of the present invention shown in FIG.
Guide groove G for tracking l.

For ease of explanation, when G... was manufactured as having a continuous groove shape with a rectangular cross-sectional shape as shown in FIG. The guide grooves G, G, . . . to be formed are similar to the guide grooves G, G, . . . shown in FIG.

The cross-sectional shape is trapezoidal. Note that FIGS. 2 and 3 are also used to simplify the explanation.

It is assumed that the tracking guide grooves G, G, etc. have a rectangular cross-sectional shape), and the refractive index of the transparent substrate 1 is nl, and the refractive index of the organic material film 2 in an unrecorded state is n2. The refractive index of the organic material film 2 in the recording state is n2r, the thickness of the organic material film 2 at the tracking guide grooves G, G, etc. on the transparent substrate 1 is d, and the tracking on the transparent substrate 1 is Guide groove G.

Assuming that the thickness of the organic material film 2 in the part other than the part G is (d-Δd), the condenser lens is inserted from the plate surface 1a side of the transparent substrate 1 on which the guide groove G for tracking is not provided. We will explain the case where a reproducing laser beam focused on the guide groove G is incident on the guide groove G.
As mentioned above, the thickness of the organic material film 2 at the tracking guide grooves G, G... on the transparent substrate 1,
Guide grooves G for tracking in the transparent substrate 1, G...
The thickness of the organic material film 2 in the part other than the part .
Setting different predetermined thicknesses such as d and (d - Δd), respectively, means that the organic material film 2 is set to the guide groove G for tracking in the transparent substrate 1, as described above.
Since the spin code method is applied to deposit and form G... on the side of the plate surface where G... is provided, it can be realized extremely easily by changing the viscosity of the organic material and the rotation speed of the transparent substrate 1. obtain.

FIG. 5 shows a guide groove G for tracking in the transparent substrate 1.
, G... and the thickness of the organic material film 2 in the portions of the transparent substrate 1 other than the tracking guide grooves G, G...
This is a diagram used to explain that the thicknesses are different, such as d and (d - Δd), respectively, as shown in the figure (the same applies to Figure 3), and is a diagram (a of Figure 5). ) is a longitudinal sectional view of a part of the transparent substrate 1, and FIG. 5(b) is a longitudinal sectional view of a part of the transparent substrate 1, and FIG.
The thickness of the organic material film 2 in the portion marked with d is equal to the thickness of the organic material film 2 in the portions of the transparent substrate 1 other than the tracking guide grooves G, G, Go...
(Q) in FIG. 5 is a diagram showing for reference the case where the thickness of the organic material film 2 at the tracking guide grooves G, G... Then, the guide grooves G for tracking in the transparent substrate 1, G.
The thickness of the organic material film 2 in the part other than the part is (
d-Δd) is shown assuming that the cross-sectional shape of the tracking guide groove G in the transparent substrate 1 is rectangular in correspondence with FIGS. 2 and 3, and furthermore,
(d) in FIG. 5 shows the organic material in the tracking guide grooves G, G... in the transparent substrate 1! [The thickness of 12 is d, and the organic material film 2 in the portions of the transparent substrate 1 other than the tracking guide grooves G, G...
When the thickness of the transparent substrate 1 shown in the first figure is (d-Δd),
FIG. 3 is a diagram showing a case where the cross-sectional shape is trapezoidal, like the tracking guide groove G in FIG.

The positions indicated by dotted lines in FIG. 5(C) (and FIG. 2) are the locations of the tracking guide grooves G, G... in the transparent substrate 1 in FIG. 5(b). This is the position of the upper surface of the material film 2, and therefore the position indicated by the dotted line in FIG. 5C (and FIG. 2) and the tracking guide groove G in the transparent substrate 1.
The distance from the bottom of the organic material film 2 in FIG. 5(b) is
is the same as the thickness dO.

The depth Hl of the tracking guide groove G of the transparent substrate 1 shown in FIG. 5(C) (and FIG. 2) and the organic material film in the portion of the tracking guide groove G of the transparent substrate 1. The thickness d of 2 and (C) in Figure 5 (and Figure 2)
The distance do between the position indicated by the dotted line and the bottom of the tracking guide groove G in the transparent substrate 1 (equal to the thickness do of the portion of the transparent substrate 1 without the tracking guide groove G), and Guide groove G for tracking
The relationship between the depth Hl of the groove of the organic material film 2 itself in the part and the difference Δd between d and do described above is H1+d
o=d+H2=d o+Δd+H2 Since the above formula is as follows, the guide groove G″ for tracking in the transparent substrate 1
The thickness dO of the organic material film 2 in the portion without is expressed as d o −d−Δd.

Now, the depth Hl of the tracking guide groove G in the transparent substrate 1 can be roughly calculated by the following equation when the wavelength of the light incident on the optical disk is λ and the refractive index of the transparent substrate 1 is nl. (Hl may be larger than the value of λ/4n1 shown in the above formula, but it is better to set it smaller than the value determined by the formula λ/4n1. desirable).

Generally, when a coating is applied to a plate with grooves by applying a spin code method, the thickness of the coating formed on the plate is larger than that at the groove part. The thickness is greater than the thickness of the film in the area without grooves, but this can be understood by considering the effect of surface tension.

The thickness d of the organic material film 2 at the portion of the tracking guide groove G in the transparent substrate 1 shown in FIG. 5(C) (and FIG. 2) and of(,
), the thickness of the portion of the transparent substrate 1 for tracking without the guide groove G for tracking do(
or Δd) to predetermined thicknesses can be independently controlled by setting the viscosity of the organic material used in the spin cord and the rotational speed of the transparent substrate 1. The viscosity of the material can be adjusted to the desired value by adjusting the amount of solvent).

Now, even if an attempt is made to manufacture a tracking guide groove G to be provided in the transparent substrate 1 with a rectangular cross-sectional shape, the one actually manufactured is the optical recording medium illustrated in FIG. The cross-sectional shape of the guide groove G for tracking on the transparent substrate 1 in a disk (optical disk) is trapezoidal, and the groove width of the organic material film 2 deposited on the transparent substrate 1 by a spin cord is transparent. Although it is narrower than the groove width of the tracking guide groove G of the substrate L, when analyzing an optical disk with a cross-sectional shape as shown in Figure 1, the analysis is extremely complicated. Therefore, as mentioned above, in order to simplify the analysis, in the following explanation, the guide grooves for tracking that should be provided in the transparent substrate 1 as shown in FIGS. 2 and 3 will be used. G
It is assumed that the cross-sectional shape of is rectangular, and the groove width of the organic material film 2 deposited on the transparent substrate 1 by a spin cord is also equal to the groove width of the tracking guide groove G of the transparent substrate 1. The optical discs that are stored are targeted for analysis.

In addition, when the analysis is performed assuming that the optical disk has the cross-sectional shape shown in FIGS. 2 and 3 as described above, and when the optical disk has the cross-sectional shape shown in FIG. Naturally, there will be a discrepancy in the analysis results compared to when the analysis was performed, but this discrepancy can be corrected by slightly changing many parameters. 1st by model
There is no problem even if the analysis is performed on the illustrated optical disc.

As mentioned above, the optical disc of the present invention is a write-once type that satisfies various standards regarding reflectance, modulation degree of high-frequency signals, tracking signal output, etc. stipulated for compact discs, and is compatible with compact discs. Since we are trying to obtain an optical disc of
The degree of modulation of a high frequency signal in a compact disc, which is constructed by coating a light reflective film on the side of a transparent substrate on which bits are provided,
We will discuss various characteristics such as tracking signal output.

FIG. 7 shows how the tracking signal output and reflected light level in a compact disc change with respect to the bit depth, and the horizontal axis represents the bit depth. Note that nl is the refractive index of the transparent substrate, and CD on the horizontal axis indicates the bit depth in the compact disc.

The degree of modulation of a high-frequency signal is expressed by the difference in the level of reflected light between a bit part and a part without bits, so the degree of modulation of a high-frequency signal on a compact disc is shown in the graph of reflected light level in Figure 7. 0 at
It is obtained as the difference between the reflected light level at the position CD and the reflected light level at the position CD on the horizontal axis.

Furthermore, the tracking signal output on a compact disc is approximately 1/2 the size of the tracking signal output at the CD position on the horizontal axis in the chart of tracking signal output in Figure 7 (Figure 7 shows the bit size). Since it is about the tracking signal output chart in Fig. 7, if there are approximately 1/2 bit parts and 1/2 parts without bits, as in an actual compact disc, Note that the maximum value of the tracking signal is obtained when the phase difference between the reflected light from the bit part and the reflected light from the non-bit part is π/2.

In a compact disc, the refractive index of the transparent substrate is n
Let Hl be the depth of the bit provided on the transparent substrate.
Then, when a laser beam is incident on the side of the transparent substrate opposite to the side where the bit is provided, the phase difference between the reflected light from the bit part and the reflected light from the non-bit part is as follows. It becomes 2Hnl as follows. When the above-mentioned phase difference is π radian, the amount of returned light is minimized and the modulation degree is maximized due to the light interference effect.

Compact discs are regulated so that the amount of light returned from the bit area is extremely small, but in order to meet these regulations, it is necessary to A phase structure is required that can reduce the amount of reflected light due to the interference effect with light in areas where there are no bits.

In a normal compact disc, the tracking signal output and the modulation degree of the high frequency signal described above are determined by a standard, and the center of the range of the standard is indicated by CD in FIG.

Now, as mentioned above, there is a transparent substrate provided with a guide groove for tracking, and a recording medium having a predetermined wavelength on the surface of the transparent substrate on which the guide groove for tracking is provided. An organic material film is deposited which absorbs an appropriate amount of the laser beam and reduces its refractive index when it is irradiated with the laser beam.

Further, a second optical disk used for analyzing the optical disc of the present invention in which a metal film for light reflection is provided on the organic material film.
In the figures and FIG. 3, the refractive index of the transparent substrate 1 is nl, the depth of the tracking guide groove G provided in the transparent substrate 1 is Hl, and the refraction of the organic material film in an unrecorded state is nl (Since an organic material film absorbs light, its refractive index is a complex number, but in the organic material film used in the present invention, the real part of the refractive index greatly contributes to changes in the phase of light. Therefore, in the following analysis, it is assumed that the refractive index of the organic material film is only the real part.The difference between the analysis result performed assuming that the refractive index of the organic material film is only the real part and the actual result is corrected by This can be performed when manufacturing the organic material film.

The light reflecting film 3 is made of a metal material that exhibits high reflectivity at the wavelength of light (780 nm) used to read information signals in compact discs, and is formed by vacuum evaporation or sputtering. The wavelength of light used to read the information signal on a compact disc (
It is a preferred embodiment that a gold film having a reflectance of 95% or higher at 780 nm) is used as the reflector 11i3.

In FIG. 2, when a laser beam with a wavelength of λ is incident on the surface of the transparent substrate 1 opposite to the surface on which the guide groove G for tracking signals is provided, the center of the guide groove G in the width direction is The phase difference Δθ between the reflected light from the portion and the reflected light from the portion without the guide groove G is determined by the organic material W!4 in the portion of the tracking guide groove G described above. The thickness of A2 itself is d, and the surface including the bottom surface of the guide groove G for tracking signals on the transparent substrate 1 is used as a reference plane, and the guide groove G
If the optical distance from the reference surface to the bottom surface of the organic material 1II2 in the part is Ll, and the optical distance from the reference surface to the bottom surface of the organic material a2 in the part where there is no guide groove G is Ll, then the reflected light described above is The phase difference Δθ is the round trip optical path length 2L2 of the optical distance L2 described above and the optical distance L2 described above.
It is determined as follows from the difference 2L2-2Ll from the optical path length 2L1 for one round trip.

2L1=2(2π/λ)d−nl−(1)2L2
=2(2g/λ)(nl(H2+d-Hl)+n1-H
1...(2) Δθ−2Ll −2Ll = (4x /λ)(n 2(
H2-Hl,)+nl・Hl) = (4x/λ)(nl・H1+n2(Hl-Hl))−
(3) Note that Hl in formula (3) is shown in Figures 2 and 5.
As shown in the figure, Hl - Δd.

Now, let nl-Hlti-A shown in the first term in the curly brackets in equation (3), and n2(Hl-Hlti-A shown in the second term in the curly brackets in equation (3)). Hl) to B
Then, the above-mentioned A(4π/λ) is similar to the structure of a compact disc, in which the reflective film is directly applied to the surface of the transparent substrate 1 provided with the guide groove G for tracking. This shows the same phase difference characteristic as that obtained when configuring No. 3.

Further, even if the organic material film 2 is adhered to the surface of the transparent substrate 1 provided with the guide groove G for tracking, and the guide groove G for tracking is provided, when Δd is O, Hl- H
Since 1=O, the phase difference of the reflected light in this case becomes A(4π/λ), but as mentioned above, in the optical disc of the present invention, Δd is not 0, so B(4π/λ ) will result in a decrease in phase.

As can be seen from equation (3) above, the phase of the reflected light from the portion of the transparent substrate 1 where the guide groove G for the tracking signal is located is the same as the phase of the reflected light from the portion of the transparent substrate 1 where there is no guide groove G for the tracking signal. The phase of the reflected light lags behind the phase of the reflected light. When the organic material film 2 is not deposited on the transparent substrate 1, the phase of the reflected light is expressed as A(
4π/λ), as shown by the 7 points in FIG. Since the phase is delayed by B (4π/λ) in equation (3), the phase at point W is delayed by B from the phase indicated by 7 points in FIG.

As mentioned above, the phase of the reflected light from the portion of the transparent substrate 1 where the guide groove G for the tracking signal is not delayed from the phase of the reflected light from the portion of the transparent substrate 1 where there is no guide groove G for the tracking signal. The following advantages arise.

(1) The depth of the tracking signal guide groove G to be provided on the transparent substrate 1 is set to a relatively deep depth that is easy to manufacture, and the depth of the optical guide groove is substantially reduced by the effect of the organic material lI2. Taking advantage of the fact that it can be made shallower, it is possible to increase the reflectance of light in the unrecorded area as shown in FIG. .

(2) The depth Hl of the tracking signal guide groove G to be provided on the transparent substrate 1 is determined by Δd caused by the spin code.
It becomes possible to set it freely depending on the relationship.

(3) When creating an optical disc that includes a recorded portion (ROM) and a random access memory (RAM) portion, the depth Hl of the guide groove G for the tracking signal to be provided on the transparent substrate 1 is set to the normal depth Hl. It can be the same as the bit depth on a compact disc.

Next, referring to FIG. 3, the case where recording is performed on the optical disc of the present invention will be described.
When a recording laser beam having a predetermined wavelength is irradiated onto the plate surface on which the tracking guide groove G is provided, the organic material film 2 absorbs an appropriate amount of the laser beam. The refractive index changes from n2 to n2r having the relationship n2)n2r.

Therefore, the guide groove G having the organic material film 2 where recording was performed
The phase difference Δθr between the reflected light from the central part in the width direction and the reflected light from the part without the guide groove G is determined by using the plane including the bottom surface of the guide groove G for tracking signals in the transparent substrate 1 as a reference plane. , the round trip optical path length from the reference plane to the bottom surface of the organic material film 2 in the part of the guide groove G is 2L3, and the optical distance from the reference plane to the bottom surface of the organic material film 2 in the part without the guide groove G is 2L3. L2, the phase difference Δθ of the reflected light described above is the round trip optical path length 2L of the optical distance L2 described above.
2 and the above-mentioned optical path length 2L3 as follows.

2 L3=2(2x/λ)d−n2r−(4)2
L2=2(2g/λ)(n2(H2+d-Hl)+n
l・H1...(2) Δθr= 2 L2-2 L3=(4yc/λ)(nl
(H2+d −Hl)+ nl・Hl −d−n r)
)=(4z/λ)(nl(H2-Hl)+nl・H1+
d (n 2- n 2r)) - (5) Now, (
5) nl(
Let H2-Hl)+nl・Hl be C, and.

(n
l-n2r) If d is set as D, the above 0 indicates equation (1), so the phase change due to recording is shown in the third term in the curly brackets in equation (5). (n
l−n2r)d=D. The organic material film 2 absorbs an appropriate amount of the laser light and has a refractive index from nl to nl)n2
Since the refractive index changes to n2r in the relationship of r, the phase of the reflected light from the recorded portion leads the phase of the reflected light from the unrecorded portion.

This corresponds to the state in which the phase of the bit part in the compact disc is advanced compared to the phase of the land part, and in the optical disc of the present invention, the phase of the reflected light in the recording part is as shown in FIG. The phase advances by D and reaches point X.

The modulation degree of the high frequency signal in the optical disc of the present invention can easily obtain a high modulation degree value determined by the phase at the above-described X point.

Furthermore, since the tracking signal output from the optical disc of the present invention is generated based on the continuous guide groove for tracking signals, the signal level of the tracking signal output is the average value of the signal level in the recorded portion and the unrecorded portion. becomes. It is also clear from FIG. 4 that the above-mentioned point X falls within the compact disc specifications.

As shown in FIG. 4, the tracking signal is an odd function (sine function) with a period of 2g.

When the phase of point W in FIG. 4 is Δφ, if the phase of point This is convenient in terms of the configuration of the tracking control system to be provided.

Next, a configuration example will be described in which the optical disc of the present invention is configured as an optical disc that can record on the entire surface of the recording/reproducing example.

As the organic material II2, the refractive index n2 before recording is 2, the refractive index after recording is 1.7, and the refractive index is 1.58.
Assuming that the depth Hl of the tracking guide groove G in the transparent substrate 1 is approximately 40 nm (this depth is an example) and the wavelength of the laser beam is 780 nm, the phase difference of the reflected light described above is shown (3) The value of (4π/λ)ni·Hl in Formula 1 (%) (3) is determined as 0.32π.

Here, the guide groove G for tracking in the transparent substrate 1 is adjusted so that H2, which has already been described for the organic material film, is 0.65H1.
When it is deposited on the side where ) The phase difference Δθ obtained by the equation is 0.18π.

In this way, an optical disk that produces a phase difference Δθ of o, 18π in a state in which the organic material film 2 is adhered to the surface of the transparent substrate 1 on which the guide groove G for tracking is provided is formed by using the transparent substrate 1. 1. Tracking guide n
Even if G is provided, the presence of the organic material 112 causes a high reflectance and a large tracking signal output, as is clear from the point W in FIG. I know that there is.

Now, under the condition that the tracking signal is brought into the same state as before recording by recording, (4π/λ) (n 2 - n 2r) =
Since π-2Δθ (=45(nl-n2r)d/λ), the tracking guide IIO on the transparent substrate 1,
(The thickness d of the organic material film 2 in the part 3... is 41
It becomes 8 nm.

The phase difference Δθr generated in the optical disc in this configuration example is o,82π, which indicates a sufficiently high degree of modulation and can generate a sufficiently large tracking output.

The optical disc of the present invention having such a configuration satisfies various standards regarding reflectance, high frequency signal modulation degree, tracking signal output, etc. stipulated for compact discs, and has a postscript compatible with compact discs. It is a type of optical disc.

Next, in the recording/playback area on the inner circumference of the optical disc, a recorded area (RO
M), and when configuring the optical disc of the present invention by providing a recording area for additional writing on the outer periphery of the recorded area, the material is only provided on the outer periphery of the recorded area of the optical disc. A material is applied to form an organic material film 2 to constitute a recording area for additional writing.

This can be easily done by adjusting the starting position of dropping the organic material onto the plate surface. In this case, the depth of the tracking guide groove G in the transparent substrate 1 is set to the depth of the tracking guide groove G in the transparent substrate 1 in order to make the playback characteristics in the recorded area of the inner circumference of the optical disk the same as those of a compact disk. Since the depth of the pit is the same as that of the pit, the depth of the guide groove G is deeper than the depth of the guide groove G in the previously described configuration example.

Therefore, in this case, in order to cancel the phase difference caused by the deep guide groove G mentioned above, the value of (4π/λ)n2(H2-)(1) in the equation (3) mentioned above is increased to a predetermined value. to obtain a phase difference of . In addition, even in the case of this configuration example, the thickness d of the organic material film 2° at the portions of the tracking guide grooves G, G, etc. in the transparent substrate 1 may be the same as in the case of the already described configuration example. .

(Effects of the Invention) As is clear from the detailed explanation above, one of the transparent substrates provided with the tracking guide grooves of the present invention;
When a recording laser beam having a predetermined wavelength is irradiated onto the surface of the transparent substrate on which the tracking guide groove is provided, an appropriate amount of the laser beam is absorbed. An optical recording medium disk on which an organic material film having a decreasing refractive index is attached, and a metal film for light reflection is provided on the organic material film, and a transparent substrate provided with a guide groove for tracking. When a recording laser beam having a predetermined wavelength is irradiated onto the surface of the transparent substrate on which the tracking guide groove is provided, an appropriate amount of the laser beam is absorbed. The film thickness d of the tracking guide groove portion of the transparent substrate including the organic material film whose refractive index decreases and the film thickness of the portion of the transparent substrate other than the tracking guide groove are (d−Δd). In addition, in the optical recording medium in which a metal film for light reflection is provided on the organic material film, from the side of the transparent substrate on which the guide groove for tracking is not provided. The phase difference generated between the tracking guide groove portion of the transparent substrate and the portion of the transparent substrate other than the tracking guide groove in the incident laser beam can be obtained in the absence of the organic material film. Compared to the phase difference, the change in the optical path length due to the difference Δd in the film thickness of the organic material film described above is used to reduce the substantial phase difference to be smaller than the value of the phase difference determined by the groove shape in the transparent substrate, and,
An optical recording medium disk that utilizes the phase advance caused by the change in the refractive index of an organic material film in recorded areas to substantially advance the optical phase of laser light compared to unrecorded areas. In the optical recording medium of the present invention, the reflectance of a compact disc.

It is possible to easily provide a write-once optical disc that satisfies various standards such as the degree of modulation of high-frequency signals and the output of tracking signals.

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view showing a schematic configuration of an example of the optical recording medium disk of the present invention, and FIGS. 2 and 3 are for explaining the principle of construction and operation of the optical recording medium disk of the present invention. FIG. 4 is a side sectional view of the characteristic curve used to explain the optical recording medium disc of the present invention, and FIG. 5 is a side view of the characteristic curve used to explain the optical recording medium disk of the present invention. FIG. 5 shows the thickness of the recording film attached to the substrate with guide grooves. 6 is a perspective view showing a specific example of the guide groove of a substrate with guide grooves, and FIG. 7 is a side sectional view for explaining the effect of the phase structure due to the guide grooves of the substrate with guide grooves. FIG. DESCRIPTION OF SYMBOLS 1... Transparent substrate, 2... Organic material film (recording layer, recording film), 3... Metal film for light reflection, G... Guide groove for tracking. Patent applicant: Victor Company of Japan Ltd. 4044 No. 2, Name of the invention Relationship to the case of a person who makes a 3° correction for an optical recording medium disk Patent Applicant Office Address: 3-12 Moriya-cho, Kanayō-ku, Yokohama-shi, Kanagawa Prefecture Name (432) Victor Company of Japan Co., Ltd. 4 , Agent 5, the date of the amendment order (voluntary) (2) Amend "Can do" on page 33 of the specification, line 10, to "can do". (3) Amend page 40, line 20 of the specification, "side" to "F area"
Correct to.

Claims (1)

[Claims] 1. A transparent substrate provided with a guide groove for tracking;
When a recording laser beam having a predetermined wavelength is irradiated onto the surface of the transparent substrate on which the tracking guide groove is provided, an appropriate amount of the laser beam is absorbed and refracted. Depositing an organic material film that reduces the rate of
Further, an optical recording medium disc 2 comprising a metal film for light reflection provided on the organic material film, when irradiated with a recording laser light having a predetermined wavelength, The organic material film whose refractive index decreases by absorption has a film thickness d at the tracking guide groove portion on the transparent substrate and a film thickness at the portion other than the tracking guide groove on the transparent substrate (d - Δd). an optical recording medium disk 3 according to claim 1, comprising: a transparent substrate provided with a guide groove for tracking;
When a recording laser beam having a predetermined wavelength is irradiated onto the surface of the transparent substrate on which the tracking guide groove is provided, an appropriate amount of the laser beam is absorbed and refracted. The film thickness d of the tracking guide groove portion of the transparent substrate and the film thickness of the portion of the transparent substrate other than the tracking guide groove are (d - Δd). In addition, in the optical recording medium in which a metal film for light reflection is provided on the organic material film, the light is incident from the side of the transparent substrate on which the guide groove for tracking is not provided. The phase difference that occurs between the tracking guide groove portion of the transparent substrate and the portion of the transparent substrate other than the tracking guide groove in the laser beam generated by the laser beam is the phase difference obtained in the absence of the organic material film. The difference in film thickness of the organic material film described above Δd
The change in optical path length is used to reduce the substantial retardation to be smaller than the value of the retardation determined by the groove shape in the transparent substrate, and the change in the refractive index of the organic material film in the recorded area is used to reduce the substantial retardation. An optical recording medium disk that utilizes phase advance to substantially advance the optical phase of laser light compared to unrecorded areas.