JP2541847B2 - Optical recording medium disk - Google Patents

Description

The present invention relates to an optical recording medium disc, and more particularly to a write-once type optical recording medium disc that is compatible with compact discs.

(Prior Art) With the increasing demand for recording various information signals at a high recording density, an information signal has been recently formed using an information recording medium made on the basis of various construction principles and operation principles. It is well known that high-density recording / reproduction has been performed. For example, information signals are recorded by forming irregularities corresponding to information signals on a signal surface of an information recording medium, and the recorded information is recorded. A recording / reproducing apparatus that reproduces a signal by optical means or reproduces a signal by detecting a change in capacitance value has already been practically used for recording and reproducing a video signal and an audio signal.

In order to meet the demand for high-density recording and reproduction in various technical fields, the recording layer of the information recording medium is irradiated with a beam whose intensity is modulated by the information signal, so that the recording layer of the information recording medium responds to the information signal. Studies have also been conducted on information recording media in which information signals are recorded by causing physical or chemical changes, but in recent years, it has become easier to obtain semiconductor lasers that operate stably. As a result, various optical recording media (optical discs) capable of high-density recording and reproduction using laser light have already been put into practical use, or research and development for practical use have been conducted. It is well known that the current situation is.

That is, a recorded optical disk (optical disk dedicated for reproduction) copied in large quantities from an original master on which information signals are recorded by pits formed as geometric concave or convex portions is, for example, a video disk or a compact disk. In addition, it has begun to spread to ordinary households.
Optical discs (write-once optical discs) that can be additionally recorded by a user only once, erasable optical discs, and the like are being actively researched and developed for practical use in, for example, office file memories and other applications.

By the way, when an information signal is reproduced from an information recording medium in which the information signal is recorded at a high density, a reproducing element or a reproducing beam is always made to accurately pass through a recording mark where the information signal is recorded by tracking control. Thus, for example, a spot of light with a minute diameter is projected onto the signal surface of the information recording medium, and reflected light whose intensity is modulated by pits formed on the signal surface is produced. As a tracking error detection method used in tracking control in an optical information signal reproducing device that reproduces an information signal based on
The tracking error detection method by the so-called push-pull method, in which the intensity distribution of the light reflected from the information recording medium is biased by the tracking error, is used to detect the tracking error. In addition to being widely used because it is simple and cost effective, it also projects a first light spot for signal reading onto a signal surface of an information recording medium, and the first light described above. On the straight line including the spot, the second and third light spots for tracking are projected at symmetrical positions with the first light spot as the center of symmetry, and the second and third light spots described above are projected.
It is well known that a tracking error detection method for detecting a tracking error based on reflected light generated on a signal surface of an information recording medium by a light spot is also conventionally used. In general, the reproduction operation is performed under the tracking control operation even when reproducing the information signal recorded on the information recording medium at a high density.

By the way, a compact disc known as one of the information recording media in which the information signals are recorded at a high density by the arrangement of pits corresponding to the information signals on the signal surface of the information recording medium is An information signal is recorded on the signal surface by an array of pits having a depth set in a specific relationship with the wavelength, and the entire signal surface is covered with a thin film of aluminum or the like. Therefore, the reflectance of the land portion on the signal surface is regulated to 70% to 90% with respect to the light having the wavelength of 780 nm, and the reading of the information signal from the signal surface of the information recording medium is controlled by the wavelength. The light spot of 780 nm is used.

Then, when reading the information signal from the compact disc, the amount of the reflected light from the pit portion on the signal surface of the compact disc is the same as that of the reflected light from the land portion as a result of the light interference occurring at the pit portion. It is performed by making use of the fact that the amount of light is smaller than the amount of light, and tracking error information also uses the difference between the amount of light reflected from the recorded mark and the amount of light reflected from the land. It is supposed to be obtained.

Now, with the spread of the compactor discs mentioned above,
As an optical disc compatible with a compact disc that can be played back using a compact disc playback device, for example, additional recording of a configuration form in which a recorded area dedicated to playback and a recording area usable as a write-once optical disc are provided. -Type optical discs, or various proposals for optical discs with the entire recording area being made,
The optical disc having the configuration in which the recording area is provided as described above has a configuration in which a guide groove for tracking is provided on the transparent substrate so that tracking control can be performed even at the time of recording.

(Problems to be Solved by the Invention) By the way, as an optical disc having compatibility with a compact disc, naturally, various standards relating to reproduction defined for the compact disc, that is, reflectance, high-frequency signal It must satisfy the standard values concerning the modulation degree, symmetry of high frequency signals, tracking signal output, crosstalk, etc.,
The standards for reproduction on compact discs, which are particularly problematic when trying to obtain a write-once optical disc having satisfactory compatibility with the standards for reproduction on compact discs, include reflectance and high frequency. The modulation degree of the signal, the output of the tracking signal, and the like are included.

Here, in the case of constructing a write-once optical disc compatible with a compact disc, various standards relating to the reflectance, the modulation degree of a high frequency signal, the tracking signal output, etc. which are prescribed for the compact disc. The problems that occur when a write-once optical disc that can satisfy the above requirements is constructed are as follows.

First, the standard value for the reflectivity of a compact disc is required to have a reflectivity of 70% or more when viewed from the read side of the optical disc when a laser beam with a wavelength of 780 nm is incident from the read side of the optical disc. However, since a reflection loss of about 8% occurs on the surface of the optical disc, in order to make the reflectance on the read side of the optical disc 70% or more, only by considering the reflection loss on the surface of the optical disc, At least 80% or more of the reflectance of the reflective film is required.

It is well known that a compact disc uses an aluminum reflective film having a reflectance of 80% or more, which satisfies the standard value of the reflectance (the reflectance is aluminum Needless to say, it changes depending on the film forming conditions).

However, in a write-once optical disc, since recording is performed on a recording film, energy for recording is absorbed in the recording film. In addition, as described above, a write-once optical disc is used for tracking control during recording. In addition, since the guide groove for tracking control is provided on the transparent substrate, the light loss due to the incident light being diffracted by the guide groove is added, so that the reflectance on the read side of the optical disk is reduced. Conventionally, it has been difficult to set the reflectance to a standard value.

When a write-once optical disk compatible with a compact disk is to be constructed, a write-once optical disk capable of satisfying the standard for the degree of modulation of a high-frequency signal specified for the compact disk is constructed. In this case, there are the following problems.

That is, since the information signal is read out using the diffraction of light by the pit in the compact disc, it is easy to meet the standard value for the modulation degree of the high frequency signal, but it has been proposed in the past. In a general write-once type optical disc, the recording mode on the recording film is, for example, due to perforation or phase change, and the recorded information signal is read by changing the reflectance. Therefore, the difference between the light reflectance of the land and the light reflectance of the recording portion (corresponding to the pit) due to the phase change or the phase change, that is, the modulation degree of the high frequency signal is small, It was not possible to meet the standard for the modulation degree of high frequency signals specified for compact discs.

In order to satisfy the standard value of the compact disk for the modulation degree of the high-frequency signal, a write-once optical disk is different from a compact disk in which information signals are read out by using light diffraction by pits. Similarly, it may be necessary to read out the information signal by means of the phase structure.

Next, in the case of constructing an additional type optical disc compatible with the compact disc, a write-once type optical disc which can satisfy the standard for the output level of the tracking signal defined for the compact disc is constructed. When doing, there are the following problems.

In other words, the output level of the tracking signal on the optical disc is generally determined by the phase structure determined by the shape of the pit or the guide groove for tracking provided on the transparent substrate, but the write-once optical disc also satisfies other characteristics. After that, it is necessary to make the output level of the tracking signal satisfy the standard value.

However, in the case of a general write-once optical disc that has been conventionally proposed, when the recording mode on the recording film is performed by punching, for example, it is determined by the shape of the guide groove for tracking due to the hole. Since the phase structure is disturbed, it is difficult to obtain a tracking signal having a desired output level.

From the above description, when trying to configure a write-once optical disk compatible with a compact disk, the reflectance of light during reproduction, the degree of modulation of a high-frequency signal,
There are many problems in achieving various characteristics such as the output of a tracking signal and the like stipulated for compact discs, and some conventional write-once optical discs are compatible with compact discs. It has been difficult to provide a write-once optical disk.

(Means for Solving the Problem) The present invention is predetermined on a transparent substrate provided with a guide groove for tracking and on the plate surface of the above-mentioned transparent substrate on which the guide groove for tracking is provided. 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 different wavelength,
The transparent substrate is attached such that the film thickness d of the tracking guide groove portion and the film thickness of the portion other than the tracking guide groove of the transparent substrate are (d-Δd), and In the optical recording medium in which the organic material film is provided with a metal film for light reflection, the above-mentioned transparent in the laser light made incident from the plate surface side of the transparent substrate on which the guide groove for tracking is not provided. Compared with the phase difference obtained in the absence of the organic material film, the phase difference generated between the tracking guide groove portion of the substrate and the portion of the transparent substrate other than the tracking guide groove is compared with the organic material described above. By using the change in the optical path length due to the difference Δd in the film thickness, the actual phase difference is reduced more than the phase difference value determined by the groove shape in the transparent substrate. An optical system that reduces the size of the laser light and uses the phase advance caused by the change in the refractive index of the organic material film in the recorded portion to substantially advance the optical phase of the laser light as compared with the unrecorded portion. To provide a dynamic recording medium disc.

(Operation) On the plate surface of the transparent substrate having the tracking guide groove provided with the tracking guide groove,
When a recording laser beam having a predetermined wavelength is irradiated, the organic material film attached to the transparent substrate absorbs an appropriate amount of the laser beam and the refractive index decreases.

In the organic material film, the film thickness of the guide groove portion for tracking on the transparent substrate is d, and the film thickness of the portion other than the guide groove for tracking on the transparent substrate is (d−
Δd), and 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 light incident from the plate surface side of the transparent substrate where the tracking guide groove is not provided, and the tracking guide groove of the transparent substrate Compared with the phase difference obtained in the state where the organic material film does not exist, the phase difference caused in other portions is reduced by the change in the optical path length due to the difference Δd in the film thickness of the organic material film, and the laser light The phase difference caused by the change in the refractive index of the organic material film in the recorded portion is made smaller than the value of the retardation determined by the groove shape in the transparent substrate, and the recorded portion described above is The optical phase of the laser beam at is substantially advanced as compared with the unrecorded portion.

(Examples) Hereinafter, detailed contents of the optical recording medium disc of the present invention will be specifically described 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 disc of the present invention, and FIGS. 2 and 3 are used for explaining the configuration principle and operation principle of the optical recording medium disc of the present invention. 4 is a side sectional view of the recording medium, FIG. 4 is an example of characteristic curves used for explaining the optical recording medium disc of the present invention, and FIG. 6 is a perspective view showing a specific example of the guide groove of the board with the guide groove, and FIG. 7 is a view for explaining the action of the phase structure by the guide groove of the board with the guide groove. It is a characteristic curve example figure.

In the side sectional view showing the schematic constitution of an example of the optical recording medium disc of the present invention shown in FIG. 1, 1 is a transparent substrate, and this transparent substrate 1 has a depth H1 for tracking. Guide grooves G, G ... Are provided.

Transparent substrate 1 with guide groove for tracking described above
Are made of polycarbonate resin, for example. Two
Is a guide groove for tracking in the transparent substrate 1 described above.
An organic material film (recording layer, recording film) attached on the plate surface on which G, G ... Is provided, and the organic material film 2 has a predetermined wavelength (for example, 780 nm). An organic material film that absorbs an appropriate amount of the laser light and has a reduced refractive index when irradiated with the recording laser light. The organic material film 2 is a guide groove G for tracking in the transparent substrate 1. , G ... Is applied and formed on the surface of the plate provided with the spin coating method.

The above-mentioned organic material film 2 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, and a photon using an organic dye or a material in which an organic dye is dispersed in an organic material. Mode optical recording material, or an optical recording material selected from organic dyes that operate in both heat mode and photon mode or materials in which organic dyes are dispersed in an organic material. Thus, the organic material film 2 suitable for implementing the optical recording medium disc of the present invention is formed.

In the organic material film 2, the film thickness of the portion of the tracking guide groove G on the transparent substrate 1 is d, and the film thickness of the portion other than the tracking guide groove G on the transparent substrate is (d−Δd). The portion of the tracking guide groove G on the transparent substrate 1 in the laser light incident from the plate surface side of the transparent substrate on which the tracking guide groove G is not provided, and the transparent substrate Compared with the phase difference obtained in the state where the organic material film 2 does not exist, the phase difference caused in the portion other than the tracking guide groove G in 1 described above is different from the film thickness difference Δd of the organic material film 2 described above. To reduce the substantial phase difference to be smaller than the phase difference value determined by the shape of the tracking guide groove G in the transparent substrate 1, and The phase advance caused by the change in the refractive index of the organic material film 2 in the recorded portion is utilized to substantially advance the optical phase of the laser light as compared with the unrecorded portion. .

That is, in the optical recording medium disk (optical disc) of the present invention shown in the first figure, the recording laser light having a predetermined wavelength is formed on the transparent substrate 1 having the guide grooves G for tracking. Of a light-transmissive organic material film 2 which absorbs an appropriate amount of the laser light and has a reduced refractive index when irradiated with a metal film 3 for light reflection. A write-once optical disc that can meet various standards regarding reflectance, modulation of high-frequency signals, tracking signal output, etc., which are specified for compact discs, is made easy by making the reproduction mechanism substantially by the phase structure. I was able to obtain it.

Next, the optical recording medium disc (optical disc) of the present invention described with reference to FIG. 1 is used to obtain the reflectance, the modulation factor of a high frequency signal, and the tracking signal output specified for the compact disc. The reason why a write-once type optical disc that satisfies the standards for .., etc. and is compatible with a compact disc can be easily obtained will be described in detail with reference to FIG.

The optical recording medium disk (optical disk) of the present invention shown in the first illustration, that is, the guide grooves G, G for tracking ...
Guide groove G for tracking in the transparent substrate 1 provided with
The organic material film 2 that absorbs an appropriate amount of the laser light and reduces the refractive index when the recording laser light having a predetermined wavelength is irradiated is attached to the plate surface on which is provided. Further, the optical recording medium disc having the above-mentioned organic material film provided with the metal film 3 for light reflection has a reflectance, a modulation degree of a high frequency signal, a tracking signal output, etc. which are specified for a compact disc. Assuming that the various standards concerning the above are satisfied, the organic material film 2 in the optical recording medium disc (optical disk) of the present invention shown in the first illustration is made into a recorded state as described later, and then transparent. When the reproducing laser beam focused on the guide groove G by the condenser lens is incident from the plate surface 1a side of the substrate 1 on which the guide groove G for tracking is not provided, the recording is performed on the organic material film 2. Has been The reproduction signal obtained based on the information is a high-frequency signal with the same output level as when reproducing the information signal from the compact disc, and with the same degree of modulation as when reproducing the information signal from the compact disc. At the same time, a tracking signal output of the same magnitude as when reproducing the information signal from the compact disc is obtained.

Now, the depth (which may be height, provided in the specification) of the transparent substrate 1 in the optical recording medium disk (optical disc) of the present invention shown in the first illustration is
It is assumed that the guide grooves G, G, for tracking of H1 are continuous groove shapes having a rectangular cross section as shown in FIG. 6 for easy explanation (when manufactured, The guide grooves G, G ... Actually formed on the transparent substrate 1 have a trapezoidal cross section like the guide grooves G, G ... shown in FIG. 2 and 3, in order to simplify the description, the tracking guide grooves G, G ... Are assumed to have a rectangular cross section, and the transparent substrate 1 , N2, the refractive index of the organic material film 2 in the unrecorded state is n2, the refractive index of the organic material film 2 in the recorded state is n2r, and the guiding groove G for tracking in the transparent substrate 1, G ...
Where d is the thickness of the organic material film 2 in the portion of the transparent substrate 1 and (d-Δd) is the thickness of the organic material film 2 in the portion of the transparent substrate 1 other than the portions for the guide grooves G, G. A guide groove G is formed by a condenser lens from the plate surface 1a side on which the tracking guide groove G is not provided.
A case will be described in which a reproducing laser beam focused on is incident on the organic material film 2 at the portions of the guide grooves G for tracking in the transparent substrate 1 as described above. , The organic material film 2 in the portion other than the portions of the tracking guide grooves G, G ... In the transparent substrate 1.
Is set to different predetermined thicknesses such as d and (d−Δd), as described above, the organic material film 2 is formed on the transparent substrate 1 by the guide groove G for tracking, Since the spin coating method is applied to the plate surface on which G ... Is provided to form the film, it can be realized very easily by changing the viscosity of the organic material or the rotation speed of the transparent substrate 1.

FIG. 5 shows a guide groove for tracking on the transparent substrate 1.
The thickness of the organic material film 2 in the portions G, G ... and the thickness of the organic material film 2 in the portions other than the portions of the guide grooves G, G ... for tracking in the transparent substrate 1 are shown in FIG. But the same), d and (d-
FIG. 5A is a diagram used for explaining that different thicknesses such as Δd) are produced, and FIG. 5A is a vertical cross-sectional view of a part of the transparent substrate 1, and FIG. b) is the transparent substrate 1
And the thickness of the organic material film 2 in the portion other than the tracking guide grooves G, G, Go ... in the transparent substrate 1. FIG. 5C is a view showing a case of equal do, and further, FIG. 5C shows that the thickness of the organic material film 2 in the guide groove G for tracking on the transparent substrate 1 is d. , The organic material film 2 in the portion other than the portions of the tracking guide grooves G, G ... In the transparent substrate 1.
FIG. 4 is a diagram showing that the cross-sectional shape of the tracking guide groove G in the transparent substrate 1 is rectangular when the thickness is (d−Δd), which corresponds to FIGS. 2 and 3, and 5 (d), the thickness of the organic material film 2 at the tracking guide grooves G, G ... In the transparent substrate 1 is d, and the tracking guide grooves G, G ... In the transparent substrate 1 are shown. The case where the thickness of the organic material film 2 in the portion other than the portion is (d−Δd) is shown as a trapezoidal cross-sectional shape like the guide groove G for tracking in the transparent substrate 1 shown in FIG. FIG.

The position shown by the dotted line in (c) of FIG. 5 (and FIG. 2) is the organic material film in the tracking guide grooves G, G ... In the transparent substrate 1 in FIG. 2 and the distance between the position shown by the dotted line in FIG. 5 (c) (and FIG. 2) and the bottom of the tracking guide groove G on the transparent substrate 1 is It is the same as the thickness do of the organic material film 2 in FIG.

The depth H1 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 tracking guide groove G of the transparent substrate 1 Thickness d of 2 and (c) of FIG. 5 (and FIG. 2)
At the position indicated by the dotted line in FIG. 1 and the bottom of the guide groove G for tracking on the transparent substrate 1 (transparent substrate 1
Thickness of the part without the guide groove G for tracking in
And the groove depth H2 of the organic material film 2 itself in the portion of the guide groove G for tracking described above and the difference Δd between d and do described above are H1 + do = d + H2 = do + Δd + H2 Because of the above equation, the thickness do of the organic material film 2 in the portion of the transparent substrate 1 where the tracking guide groove G is not present is shown as do = d−Δd.

Now, the guide groove G for tracking on the transparent substrate 1
If the wavelength of the laser beam incident on the optical disc is λ, the depth H1 of the is approximately any value within the range smaller than the value obtained by the following equation λ / 4n1 when the refractive index of the transparent substrate 1 is n1. (H1 may be larger than the value of λ / 4n1 shown in the above equation, but it is preferable that it be smaller than the value determined by the equation λ / 4n1).

Generally, when a film is formed by applying a spin coat method onto a plate provided with grooves, the thickness of the film formed on the plate is The thickness is larger than the thickness of the groove in the non-groove portion, which can be understood by considering the function of surface tension.

Then, the thickness d of the organic material film 2 at the guide groove G for tracking in the transparent substrate 1 shown in FIG. 5C (and FIG. 2) and FIG. The same applies to (c)} transparent substrate 1 for tracking
Thickness of the part without the guide groove G for tracking in
Setting each of (or Δd) to a predetermined thickness can be independently controlled by setting the viscosity of the organic material used for spin coating and the rotation speed of the transparent substrate 1 ( The viscosity of the organic material can be adjusted to a desired value by adjusting the amount of solvent).

The tracking guide groove G to be provided on the transparent substrate 1 is actually manufactured by the optical recording medium illustrated in FIG. 1 even if it is manufactured to have a rectangular cross section. The cross-sectional shape of the guide groove G for tracking the transparent substrate 1 in the disk (optical disk) is trapezoidal, and the groove width of the organic material film 2 deposited by spin coating on the transparent substrate 1 is transparent. Although it is narrower than the groove width of the tracking guide groove G of the substrate 1, the analysis becomes very complicated when the optical disk having the cross-sectional shape as shown in FIG. 1 is analyzed. Therefore, as described above, in order to simplify the analysis, in the following explanation, the cross-sectional shape of the tracking guide groove G to be provided in the transparent substrate 1 as shown in FIGS. Is rectangular In addition, an optical disk in which the groove width of the organic material film 2 deposited on the transparent substrate 1 by spin coating is also equal to the groove width of the tracking guide groove G of the transparent substrate 1 is targeted for analysis. It .

The analysis is performed assuming that the optical disc has the cross-sectional shape as shown in FIGS. 2 and 3, and the optical disc having the cross-sectional shape shown in FIG. As a matter of course, a deviation occurs in the analysis result of the case where the analysis is performed by using the second method, but the deviation can be corrected by slightly changing many parameters.
The optical disc shown in FIG. 1 may be analyzed using the model illustrated in FIGS.

As described above, the optical disc of the present invention is a write-once disc that is compatible with compact discs, satisfying various standards concerning reflectance, modulation of high frequency signals, tracking signal output, etc., which are stipulated for compact discs. Since it is intended to obtain an optical disc of the above, a compact disc constructed by coating a light reflection film on the surface of the transparent substrate on which the pits are provided Various characteristics such as the degree of modulation of the high frequency signal, the output of the tracking signal, and the like will be described.

FIG. 7 shows how the tracking signal output and the reflected light level on the compact disk change with respect to the pit depth, and the horizontal axis shows the pit depth. Note that n1 is the refractive index of the transparent substrate, and CD on the horizontal axis represents the pit depth in the compact disc.

The modulation degree of the high frequency signal is represented by the difference in the reflected light level between the pit portion and the non-pitted portion. Therefore, the modulation degree of the high frequency signal on the compact disc is shown in FIG. It is obtained as the difference between the reflected light level at the position of 0 in and the reflected light level at the position of CD on the horizontal axis.

Also, the tracking signal output on the compact disc is approximately half the tracking signal output at the CD position on the horizontal axis in the tracking signal output chart in FIG. 7 (see FIG. 7 for pits). Since it is about the part, the pit part and the part without the pit are about 1 / thick like an actual compact disc.
If there are two, the size of the tracking signal output in FIG. 7 is approximately half the size in the diagram). The maximum value of the tracking signal is obtained when the phase difference between the reflected light from the pit portion and the reflected light from the non-pit portion is π / 2.

For compact discs, the refractive index of the transparent substrate
Let n1 be the depth of the pits provided on the transparent substrate, and let H1 be the reflected light from the pits when laser light is incident from the side of the transparent substrate opposite to the side where the pits are provided. As is well known, the phase difference between the reflected light from the pitless part and the reflected light is 2H1 · n1. When the phase difference is π radians, the amount of returned light is minimized and the degree of modulation is maximized due to the interference effect of light.

Compact discs are specified so that the amount of light returned from the pits is extremely small, but in order to comply with such specifications, the part where the light phase is advanced in the pits, There is a need for a phase structure in which the amount of reflected light can be reduced by the effect of interference with light in the pitless portion.

In an ordinary compact disc, the tracking signal output and the modulation factor of the high frequency signal are defined by a standard, and the center of the range of the standard is shown by CD in FIG.

Now, as described above, on the transparent substrate provided with the tracking guide groove and the plate surface of the transparent substrate provided with the tracking guide groove, the recording substrate having the predetermined wavelength is recorded. Of the present invention, wherein an organic material film that absorbs an appropriate amount of the laser light to reduce the refractive index when irradiated with the laser light is attached, and a metal film for light reflection is provided on the organic material film. 2 and 3 used for analyzing the optical disc of FIG. 2, the refractive index of the transparent substrate 1 is n1, and the depth of the tracking guide groove G provided in the transparent substrate 1 is H1. Further, the refractive index of the organic material film in the unrecorded state is n2 (the organic material film absorbs light, so the refractive index thereof is a complex number, but in the organic material film used in the present invention, the real refractive index is Since the part greatly contributes to the change of the phase of light, In the analysis it is assumed refractive index of the organic material film is only the real part. Note that the analysis result performed with only the real part of the refractive index of the organic material film,
The deviation from the actual value can be corrected at the time of manufacturing the organic material film), and the light reflection film 3 is a compact disc for the wavelength of light used for reading information signals (780n).
A metal material having a high reflectance in m) is formed by a vacuum deposition method or a sputtering method. It is a preferred embodiment that a gold film having a reflectance of 95% or higher at the wavelength of light (780 nm) used for reading an information signal in a compact disc is used as the reflection film 3.

In FIG. 2, when a laser beam having a wavelength of λ is incident from the surface side of the transparent substrate 1 opposite to the surface on which the tracking signal guide groove G is provided, the center of the guide groove G in the width direction. The phase difference Δθ between the reflected light from the portion and the reflected light from the portion without the guide groove G is the thickness d of the organic material film 2 itself in the guide groove G for tracking.
In addition, with the surface including the bottom surface of the guide groove G for the tracking signal on the transparent substrate 1 as a reference surface, the optical distance from the reference surface in the guide groove G to the bottom surface of the organic material film 2 is L1, When the light distance from the reference surface to the bottom surface of the organic material film 2 in the portion without the guide groove G is L2, the phase difference Δθ of the reflected light is the optical path length 2L2 of the round trip of the light distance L2 and 2 round-trip optical path length of L1
The difference from L1 is calculated from 2L2−2L1 as follows.

2L1 = 2 (2π / λ) d · n2 (1) 2L2 = 2 (2π / λ) {n2 (H2 + d−H1) + n1 · H1…
(2) Δθ = 2L2-2L1 = (4π / λ) {n2 (H2-H1) + n1 · H
1} = (4π / λ) {n1 · H1 + n2 (H2-H1)} (3) Note that H2 in the formula (3) is H1−Δd as shown in FIGS. 2 and 5. is there.

Now, let n1 · H1 shown in the first term in the curly braces in the equation (3) be A, and nd (H2− in the second term in the braces in the equation (3). If H1) is B, the A (4π / λ) described above is on the surface of the transparent substrate 1 on which the guide groove G for the track is provided, similar to the structure of the compact disc. The phase difference characteristics are the same as those obtained when the reflective film 3 is directly formed.

In addition, the transparent substrate 1 provided with the guide groove G for tracking
Even if the organic material film 2 is deposited on the surface of the track guide groove G in FIG.
= 0, the phase difference Δθ of the reflected light in this case
Is A (4π / λ), but as described above, Δd is not 0 in the optical disc of the present invention, and therefore B (4π / λ) causes a phase reduction.

Then, as can be seen from the above formula (3), the phase of the reflected light from the portion of the transparent substrate 1 on which the tracking signal guide groove G is provided is from the portion of the transparent substrate 1 on which the tracking signal guide groove G is not provided. Will be later than the phase of the reflected light. The phase of the reflected light when the organic material film 2 is not deposited on the transparent substrate 1 is A in the formula (3).
Since it is (4π / λ), it is shown by the point V in FIG. 4, but the phase of the reflected light from the portion of the guide groove G for the tracking signal in the transparent substrate 1 depends on the effect of the organic material film 2. Since the phase is delayed by B (4π / λ) in the equation (3), the phase at point W is delayed by B from the phase indicated by point V in FIG.

As described above, the phase of the reflected light from the portion of the guide groove G for the tracking signal on the transparent substrate 1 is delayed from the phase of the reflected light from the portion of the transparent substrate 1 without the in-hospital groove G for the tracking signal. The following advantages are brought about.

(1) The depth of the guide groove G for the tracking signal to be provided in the transparent substrate 1 is set to be relatively deep so as to be easily manufactured, and the depth of the optical guide groove is substantially made by the effect of the organic material film 2. It is possible to increase the reflectance of the light in the unrecorded portion and to easily set the tracking signal output level to the standard value for the compact disc as described later with reference to FIG. .

(2) The depth H1 of the guide groove G for the tracking signal to be provided on the transparent substrate 1 can be freely set in relation to Δd generated by spin coating.

(3) In the case of an optical disc in which a recorded portion (ROM) and a random access memory (RAM) portion are mixed, the depth H1 of the guide groove G for the tracking signal to be provided on the transparent substrate 1 is set to a normal value. It can be the same as the pit depth on a compact disc.

Next, a case where recording is performed on the optical disc of the present invention will be described with reference to FIG. Transparent substrate 1 provided with a guide groove G for tracking in the optical disc of the present invention
When the recording laser light having a predetermined wavelength is irradiated onto the plate surface on which the guide groove G for tracking is provided, the organic material film 2 absorbs an appropriate amount of the laser light. Refractive index n with a relationship of n2 to n2> n2r
Change to 2r.

Therefore, the phase difference Δθr between the reflected light from the central portion in the width direction of the guide groove G having the recorded organic material film 2 and the reflected light from the portion without the guide groove G is the tracking on the transparent substrate 1. Using the surface including the bottom surface of the signal guide groove G as a reference surface, the reciprocal optical path length from the reference surface in the guide groove G to the bottom surface of the organic material film 2 is 2L3, and in the portion without the guide groove G. When the light distance from the reference surface to the bottom surface of the organic material film 2 is L2, the phase difference Δθ of the reflected light is the reciprocal optical path length 2L2 of the light distance L2,
From the difference 2L2-2L3 from the above-mentioned optical path length 2L3, it is obtained as follows.

2L3 = 2 (2π / λ) d · n2r (4) 2L2 = 2 (2π / λ) {n2 (H2 + d−H1) + n1 · H1…
(2) Δθr = 2L2−2L3 = (4π / λ) {n2 (H2 + d−H1) + n1 · H1−d · nr}) = (4π / λ) {n2 (H2-H1) + n1 · H1 + d (n2-n2r )} (5) Now, n2 (H2-H1) + n1 · H1 shown in the first term in the curly braces in the equation (5) is set as C, and in the curly braces in the equation (5). (N2-n2r) d shown in the third term
Letting D be D, since the above-mentioned C shows the formula (1), the phase change due to recording is shown in the third term in the curly braces in the formula (5) (n2- n2r) d =
It is D. The organic material film 2 absorbs an appropriate amount of the laser light described above, and the refractive index changes from n2 to n2r in the relationship of n2> n2r. Therefore, the phase of the reflected light from the recorded portion is reflected from the unrecorded portion. It will be ahead of the phase of light.

This corresponds to a state in which the phase of the pit portion is advanced as compared with the phase of the land portion in the compact disc, and the phase of the reflected light in the recording portion in the optical disc of the present invention is shown in FIG. Although the phase advances by D to point X, the modulation degree of the high frequency signal in the optical disc of the present invention can easily obtain a high value of modulation degree determined by the phase at point X described above.

Further, since the tracking signal output from the optical disc of the present invention is generated based on the continuous guide groove for the tracking signal, 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 is within the standard of the compact disc.

The tracking signal is 2π as shown in FIG.
Therefore, when the phase at point W in FIG. 4 is Δφ, the phase at point X is (π−
If it is set to φ), the tracking signal outputs can be made equal before and after recording, which is convenient in the configuration of the tracking control system to be provided in the recording / reproducing apparatus.

Next, a configuration example in the case of configuring the optical disc of the present invention as an optical disc capable of recording on the entire surface of the recording / reproducing area will be described.

The organic material film 2 having a refractive index n2 before recording of 2 and a refractive index of 1.7 after recording is used, and the depth H1 of the guide groove G for tracking in the transparent substrate 1 having a refractive index of 1.58 is about 40.
nm (this depth is an example) and the wavelength of the laser light is 78
The value of (4π / λ) n1 · H1 in the equation (3) (4π / λ) {n1 · H1 + n2 (H2-H1)} (3) showing the phase difference of the reflected light described above is 0.32π. Is required as.

Here, when the organic material film is applied to the surface of the transparent substrate 1 on which the guide groove G for tracking is provided so that H2 is 0.65H1, the above-mentioned (3) is performed. The value of (4π / λ) n2 (H2-H1) in the formula is 0.14
Therefore, in this case, the phase difference Δθ obtained by the equation (3) is 0.18π.

As described above, the optical disc that causes the phase difference Δθ of 0.18π in the state where the organic material film 2 is deposited on the surface of the transparent substrate 1 on which the guide groove G for tracking is provided is the transparent substrate 1 Guide groove G for tracking
The presence of the organic material film 2 causes the fourth
As is clear from the point indicated by W in the figure,
It can be seen that it has a high reflectance and a large tracking signal output.

Now, under the condition that the tracking signal is in the same state as before recording due to recording, the above-mentioned equation (5) (4π / λ) {n2 (H2-H1) + n1 · H1 + d (n2-n2r)} (5) (4π / λ) (n2-n2r) = π-2Δθ in the formula
Since {= 4π (n2-n2r) d / λ}, the thickness d of the organic material film 2 in the tracking guide grooves G, G ... In the transparent substrate 1 is 416 nm.

Then, the phase difference Δθr generated in the optical disc in this configuration example is 0.82π, which shows 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 example satisfies the standards regarding the reflectance, the modulation factor of the high frequency signal, the output of the tracking signal, etc. which are stipulated for the compact disc, and additionally has the compatibility with the compact disc. It is made as a type of optical disc.

Next, in the recording / playback area of the inner circumference of the optical disc, a recorded portion (RO
In the case of configuring the optical disc of the present invention by configuring M) and providing a recording area for additional recording on the outer peripheral portion of the recorded portion, the organic material is formed only on the outer peripheral portion of the recorded portion of the optical disc. Is applied to form an organic material film 2 to form a recording area for additional recording.

This can be easily done by adjusting the dropping start position of the organic material on the board surface. In this case, the depth of the tracking guide groove G on the transparent substrate 1 is set to be the same as that of the compact disc so that the reproduction characteristic of the recorded portion on the inner circumference of the optical disc is the same as that of the compact disc. Since the depth of the pit is the same as that of the pit, the depth is deeper than the depth of the guide groove G in the case of the above-described configuration example.

Therefore, in this case, in order to cancel the phase difference caused by the deep guide groove G, the value of (4π / λ) n2 (H2-H1) in the above-mentioned equation (3) is increased to a predetermined value. Try to get a phase difference. Even in the case of this configuration example, the guide groove G for tracking on the transparent substrate 1,
The thickness d of the organic material film 2 in the portion G ... may be the same as in the case of the configuration example described above.

(Effects of the Invention) As is clear from the above description, the transparent substrate provided with the tracking guide groove of the present invention and the transparent substrate provided with the tracking guide groove of the above-mentioned transparent substrate On the plate surface, an organic material film whose refractive index is reduced by absorbing an appropriate amount of the laser light when irradiated with a recording laser light having a predetermined wavelength is used for tracking in the transparent substrate. The film thickness d of the guide groove portion and the film thickness of the portion other than the guide groove for tracking on the transparent substrate are made to be (d-Δd), and the organic material film is used for light reflection. In the optical recording medium provided with the metal film, the transparent substrate in the transparent substrate in the laser light incident from the plate surface side of the transparent substrate on which the guide groove for tracking is not provided. Compared with the phase difference obtained in the absence of the organic material film, the phase difference generated between the tracking guide groove portion and the portion of the transparent substrate other than the tracking guide groove is The change in the optical path due to the film thickness difference Δd 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 refraction of the organic material film in the recorded portion. An optical recording medium disk which is configured to substantially advance the optical phase of a laser beam as compared with an unrecorded portion by utilizing a phase advance caused by a change in the ratio. As a recording medium, it is easy to provide a write-once optical disc that can meet various standards such as reflectance of compact discs, modulation of high frequency signals, and output of tracking signals. You can

[Brief description of drawings]

FIG. 1 is a side sectional view showing a schematic configuration of an example of the optical recording medium disc of the present invention, and FIGS. 2 and 3 are used for explaining the configuration principle and operation principle of the optical recording medium disc of the present invention. 4 is a side sectional view of the recording medium, FIG. 4 is an example of characteristic curves used for explaining the optical recording medium disk of the present invention, and FIG. 5 is a diagram showing the thickness of a recording film attached to a substrate having guide grooves. 6 is a perspective view showing a specific example of the guide groove of the board with the guide groove, and FIG. 7 is a view for explaining the action of the phase structure by the guide groove of the board with the guide groove. It is a characteristic curve example figure. 1 ... Transparent substrate, 2 ... Organic material film (recording layer, recording film), 3 ... Light reflecting metal film, G ... Tracking guide groove,

Claims (2)

(57) [Claims] 1. A laser for recording having a predetermined wavelength on a transparent substrate provided with a guide groove for tracking and on a plate surface of the transparent substrate on which the guide groove for tracking is provided. An organic material film whose refractive index is reduced by absorbing an appropriate amount of the laser light when irradiated with light,
The film thickness d of the guide groove portion for tracking on the transparent substrate and the film thickness of the portion other than the guide groove for tracking on the transparent substrate are set to (d−Δd), and the film is attached. Optical recording medium disk comprising an organic material film and a metal film for light reflection 2. A laser for recording having a predetermined wavelength on a transparent substrate provided with a guide groove for tracking and a plate surface of the transparent substrate on which the guide groove for tracking is provided. An organic material film whose refractive index is reduced by absorbing an appropriate amount of the above-mentioned laser light when irradiated with light,
The transparent substrate is attached such that the film thickness d of the tracking guide groove portion and the film thickness of the portion other than the tracking guide groove of the transparent substrate are (d-Δd), and In the optical recording medium in which the organic material film is provided with a metal film for light reflection, the above-mentioned transparent in the laser light made incident from the plate surface side of the transparent substrate on which the guide groove for tracking is not provided. Compared with the phase difference obtained in the absence of the organic material film, the phase difference generated between the tracking guide groove portion of the substrate and the portion of the transparent substrate other than the tracking guide groove is compared with the organic material described above. By using the change in the optical path length due to the difference Δd in the film thickness, the actual phase difference is reduced more than the phase difference value determined by the groove shape in the transparent substrate. An optical system that reduces the size of the laser light and uses the phase advance caused by the change in the refractive index of the organic material film in the recorded portion to substantially advance the optical phase of the laser light as compared with the unrecorded portion. Recording medium disk