JPH0427614B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an optical recording medium and information recording medium that has areas with different recording sensitivities and allows information to be recorded only in high sensitivity areas without recording information in low sensitivity areas. Regarding the body.

U.S. Pat. No. 4,097,895 discloses a two-layer ablative optical recording medium consisting of a reflective layer and an absorbing layer covering the reflective layer, the thickness of the absorbing layer being selected to reduce the overall reflectance. has been done. This absorbing layer is melted or ablated during recording, changing the reflectance of the recording medium, and the difference in reflectance between the changed and unchanged areas of the recording medium is optically detected during reading. Convert it into an electrical signal representing the recorded information.

Further, US Pat. No. 4,216,501 discloses a three-layer optical recording medium having a transparent intervening layer between the reflective layer and the absorbing layer of the optical recording medium. The thickness of this absorption layer works together with the thickness of the intervening layer and the optical constants (refractive index and extinction coefficient) of the reflective layer, intervening layer, and absorption layer to reduce the reflectance of the recording medium. selected. During recording, the absorbing layer is melted or ablated to create holes in the layer, changing the reflectance of the recording medium, but instead of forming holes, the absorbing layer is deformed or the optical properties of the absorbing layer are changed. It is also possible to change the reflectance.

In all of the above cases, the recording sensitivity of the optical recording medium is substantially uniform between each point on it, and therefore the deformation of the absorbing layer, e.g. the geometry of the aperture, is the geometry of the recording light beam. Depends on.

US Pat. No. 4,176,377 discloses that although it is highly sensitive to recording along a spiral recording track,
A video disk structure is disclosed in which there is no recording sensitivity in the areas between adjacent tracks. This is achieved by thermally removing unnecessary surface portions of an unrecorded record with uniform sensitivity using an unmodulated high power laser.
Further, by using this deletion record as a mask, a disk having a vortex track with recording sensitivity can be manufactured by photolithography. This additional step is undesirable because faithful reproduction of recorded information requires a high degree of integrity of the sensitive surface.

A recording body of an optical recording medium is provided in which the recording sensitivity changes locally so that the recorded change in the absorbing layer is independent of the geometry of the recording light beam, and in which no processing is required after the formation of the absorbing layer. It has been desired.

The recording medium according to the present invention comprises a substrate having a first region with high recording sensitivity and a second region with lower recording sensitivity on the main surface, and the main surface of this substrate has the first and second regions. A recessed portion and a plateau are formed corresponding to the region or the second and first regions, and the main surface has a substantially flat surface that fills the recessed portion and is photodevelopable. There is a medium formed of layers including a layer of light-absorbing material adjacent to the flat surface.
The photodevelopable medium will be described later.

The present invention also provides an information recording medium in which information tracks are recorded in the first area so as to form a series of areas having different optical characteristics from the rest and the second area.

In FIG. 1, an optical recording medium 10 includes a substrate 12 having a main surface 14, an absorption layer 16 on the main surface 14, and a first region 18 and an absorption rate at the wavelength of the recording light beam. and a lower remaining second region 19. For illustrative purposes, the first area 18 is arranged in the form of concentric rings 20 or in the form of a grid 22, but as will be described later, this first area 18 is used to record information on the optical recording medium by the user. It goes without saying that they can be arranged in any desired shape. Since this region has a higher absorption rate, even if the recording light beam incident on the optical recording medium 10 overlaps the second region 19, the first region 18
Information is successfully recorded in a manner that changes the optical properties of the medium. This change may be irreversible recording, such as the formation of apertures in the light absorption layer 16, or it may be reversible recording, such as a change in the crystallinity of the absorption layer 16. As mentioned above, media on which information can be recorded by the incidence of a recording light beam, such as light-absorbing materials, can be used to open holes without any special development treatment after being irradiated with a light beam for recording. Because stable records of shapes such as deformation or changes in crystallinity can be obtained, it is distinguished from photosensitive materials that can only be developed by the action of a reducing agent after exposure, such as silver halide emulsions in conventional photographic technology. Let's call it a photodevelopable medium.

The first optical recording medium of the present invention shown in FIG.
Embodiment 30 includes a substrate 12 having a main surface 14, a plurality of recesses 32 recessed into the substrate 12 from the main surface 14, and forming a plurality of plateaus 34 therebetween;
It includes an absorbent layer 36 that fills the concave portion 32 and further covers the plateau 34 therebetween, or may not cover it. The absorbent layer 36 further consists of two parts, the first part 40 filling the recesses 32 and being thicker than the second part 42 covering the plateaus 34 between the recesses. Upper surface 4 of light absorption layer 36
4 is flat and covered with an overcoat 46, but may not be covered.

Elements of the second embodiment 50 of the invention shown in FIG. 3 that are common to the first embodiment 30 are given the same reference numerals. The second embodiment 50 of the present invention differs from the first embodiment 30 in that the main surface 14 including the depressions 32 and the plateau 34 between them is covered with a reflective layer 52, and the absorption layer 54 is covered with the depressions 32. , and also covers the part of the reflective layer 52 that covers the plateau 34 between them. However, the reflective layer 52 on the plateau portion 34 may not be covered. At this time, the absorbent layer consists of two parts, the first part 56 is a part that fills the depressions, and the second part 56 covers the plateau between the depressions.
It is thicker than the portion 58 of . Flat upper surface 6 of absorption layer 54
0 is covered with an overcoat layer 46, but may not be covered.

Elements of the third embodiment 70 of the invention shown in FIG. 4 that are common to the second embodiment 50 are designated by the same reference numerals. This third embodiment 70 differs from the second embodiment 50 in that the intervening layer 72 is
It fills in the recessed part 32 and further covers the reflective layer 52 on the plateau part 34. The interlayer thus comprises a first portion in the area of the recesses of the main surface 14 and a second portion 76 which is thinner and covers the plateau 34 between the recesses. This second portion 76
may not be provided. On the surface 80 of the intervening layer 72 is an absorbent layer 78 of substantially uniform thickness. The third embodiment 70 of the present invention is different from the second embodiment 50 in that a cover layer 82 is also provided on the surface 84 of the light absorption layer 78.
There is. There is a top coat layer 46 on top of the cover layer 82, and when there is no cover layer 82, there is a top cover layer 46 on the absorbent layer 78. However, a top coat is not always necessary.

Substrate 12 may be formed of a plastic material, such as polyvinyl chloride or polymethyl methacrylate, which is generally disc-shaped. The recesses on the main surface 14 of the substrate 12 can be formed by pressing a master having irregularities corresponding to the recesses on the surface 14, but they can also be formed during pressure molding or pressure casting of the disk. You can also do that. The depth of this recess is generally about 5-200 nm.

Although the main surface is described as having depressions, it should be noted that this includes both surface pores and ridges. The functions of pores and ridges are the same in providing photosensitive coatings of varying thickness.

In the first embodiment of FIG. 2, the depth of the recess 32 is approximately equal to or preferably the thickness of the absorption layer 36 filling it is approximately equal to the thickness required to achieve absorption-reflection balance in order to increase the sensitivity. It is chosen to be slightly thinner than that. If the depth is less than the thickness required to achieve the equilibrium, the thickness above the recess is increased further to achieve the required thickness. The depth of the recess 32 in the first embodiment 30 is typically about 5-40 nm.

In the second and third embodiments shown in FIGS. 3 and 4, the thickness of the layer filling the recesses is approximately equal to or preferably the thickness required to minimize the local reflectance of the optical recording medium. The depth of the recess is selected so that it is slightly thinner than this. If the recess is shallower than this thickness, the required thickness will depend on the thickness of the layer stacked above the recess. Generally, the depth of the recess 32 is about 20 to 80 nm for the double layer structure of the second embodiment 50 of FIG. 3, and about 30 to 200 nm for the triple layer structure of the third embodiment 70 of FIG. The preferred thicknesses of the absorbent layer and the intervening layer depend on the nature of the material of that layer, as discussed below.

The reflective layer 52 of FIG. 3 preferably reflects a significant portion, preferably at least 50%, of the incident light at the wavelength of the recording and reading light beams, and is typically made of aluminum or metal, which has a high reflectance at this wavelength. made of metals such as The reflective layer 52 is typically about 30-60 nm thick and can be applied to the recessed substrate surface 14 by vacuum deposition. Alternatively, a single-layer or multi-layer dielectric reflective layer may be used.

The absorption layer 36 of the first embodiment 30 of FIG. 2 and the absorption layer 54 of the second embodiment 50 of FIG.
Alternatively, it is formed of a material that can be deposited on the reflective layer 52 so as to preferentially fill the recesses 32 thereon. When the recesses 32 are filled, the excess material forms a thin layer over the recesses 32 and the plateaus 34 therebetween, forming a smooth, continuous upper surface of the absorbent layer. In all embodiments, the absorbing layer may be a spin-applied organic dye dissolved in a solvent. A suitable dye and binder mixture is Sibley's 1350B of 4 phenyl azo and 1 naphthylamine.
type photoresist in a 4.8% weight-to-volume solution,
This was diluted 25:1 with dimethoxyethyl acetate and applied by rotation. This material is useful for recording and reading light sources at a wavelength of about 488 nm.

The overcoat layer 46 is comprised of a material that is substantially transparent at the wavelengths of the recording and reading light beams and has a thickness of about 0.05 mm.
~1 mm is useful. As a result, dust particles adhering to the upper surface of the overcoat are far away from the focal point of the recording and reading optical system, and are significantly less likely to affect the recording and reading of information. A useful material for this layer is silicone resin, which can be applied by a rotational method.

The thickness of the absorbing layer 54 of the second embodiment 50 of FIG. The relationship is such that it is preferably non-reflective. For example, in 1965, Dover
Heavens (OS) published by Publications Inc.
Heavens) in his book “Optical Properties of Thin Solid Films”, Vol.
The optimal thickness of this absorbing layer can be calculated using the matrix method described on page 69; the thickness of the absorbing layer with low reflectance is about 20-100 nm.

The thickness of this absorption layer 54 varies depending on each part of the surface of the optical recording medium, and is thicker than the plateau part 34 and the thickness of the recessed part 32.
thick in the area. The lowest reflectance at the recording and reading wavelengths initially occurs over the recess, but once the recess is filled, the second portion 58 on the plateau 34
increases by the same amount as the thickness of the first portion 56 above the recessed portion 32, and as the thickness of the second portion increases, the reflectance of this portion decreases, but the reflectance of the first portion passes through the minimum. and begins to increase. By controlling the coating thickness of the second portion in this way, it is possible to place a region with low reflectance and high sensitivity on the recessed portion 32 or the plateau portion 34, but it is possible to place a region with low reflectance and high sensitivity on the recessed portion 32 or the plateau portion 34, but the thickness of the second portion may be extremely thin. It is preferable that the portion above the concave portion 32 be a region of low reflectance and high sensitivity.

In a third embodiment 70 of the invention shown in FIG.
The interlayer 72 has a varying thickness. This interposer layer is substantially transparent at the wavelengths of the recording and reading light beams and is placed over the reflective layer 52 so that the recesses 32 in the substrate surface are preferentially filled to form a first portion of the interposer layer. It is made of a material that can be deposited. After the depression is filled, the first portion 74 and the second portion 76 on the plateau 34
increases in thickness. A suitable material for this interlayer is a solution of polymethylstyrene in toluene, which is applied by a rotational method.

The absorbing layer 78 on the intervening layer 72 is made of a material that absorbs light at the wavelengths of the recording and reading light beams. Suitable materials for this layer include titanium, rhodium, tellurium, selenium, tellurium or selenium alloys, arsenic trisulfide, arsenic triselenide, etc., which can be deposited by vacuum evaporation. Some of these materials oxidize when exposed to the atmosphere, leaving an absorbing layer that is much thinner than the original deposited layer. This effect can be compensated for by depositing a layer thicker than the required thickness and then oxidizing it to bring the effective thickness to the required thickness.

The thicknesses of the intervening layer 72 and the absorbing layer 78 are selected to reduce the reflectivity of the first and second portions of the optical recording medium, respectively;
It is calculated taking into account the optical properties of the absorbing layer, the capping layer if present, the overcoating layer, and the wavelengths of the recording and reading light beams. Generally, the thickness of the intervening layer that reduces the reflectance is about 20 to 200 nm, and the thickness of the absorption layer is about 3 to 50 nm. At this time, the change in sensitivity on the surface of the information recording medium depends on the thickness of the intervening layer. The interlayer is thicker in the depression 32 than in the plateau 34. For the absorbing layer of the second embodiment 50 of FIG. 3, the first minimum in reflectance may occur over the recess. When the recess is filled with the interposer layer, the thickness of the second portion 76 of the interposer layer on the plateau 34 increases with the thickness of the first portion 74 above the recess. As the thickness of this second part increases, the local reflectance in this region of the optical recording medium decreases, while the reflectance of the first part reaches a minimum value and then begins to increase. By controlling the thickness of the intervening layer on the portion, the region with lower reflectance and higher sensitivity can be made into the recessed portion 32 or the plateau portion 34.
It can be placed on either. The thickness of the second portion of the intervening layer is minimized so that the thickness of the first portion on the recessed portion 32 is minimized.
Preferably, the area of portion 74 is a low reflectance, high sensitivity area.

A cover layer 82 may also be provided on the upper surface 84 of the absorbent layer 78 . The function of this cover layer 78 is that the absorption layer 7
The purpose is to prevent damage to the overcoat layer 46 when a high melting point material such as titanium or rhodium is used for the absorption layer 78, but when a low melting point material such as tellurium, selenium or an alloy thereof is used for the absorbing layer 78, the overcoat layer It is not necessary to use a capping layer to prevent thermal damage to layer 46.

However, if the cover layer 82 and the intervening layer 72 are formed of a material that prevents the formation of holes or other permanent deformations in the absorbent layer 78, reversible recording, or erasable and rewritable recording, can be achieved on the absorbent layer. It can be carried out. Suitable materials for absorbing layer 78 in this embodiment include tellurium, selenium, tellurium or selenium alloys, arsenic trisulfide, arsenic triselenide, and the like. Suitable materials for use in the capping layer that prevent the formation of reversible records include:
These include silicon trioxide, silicon monoxide, titanium dioxide, and tellurium dioxide. These materials can be deposited by electron beam evaporation. Generally, the thickness of the capping layer suitable for preventing the formation of holes or other deformations in the absorbing layer is about 50 to 500 nm.

When you want to record information reversibly, the upper layer 46
It is also necessary for the cover layer 82 to be substantially transparent to the wavelength of the erasing light beam, and for the absorbing layer 78 to be absorbent at the wavelength of the erasing light beam.

The recesses in the main surface of the disk substrate can be arranged in a variety of formats, as illustrated in FIG. The recesses are in the form of continuous recessed circular or spiral grooves on the main surface of the substrate of the disk, so that the photoelectric recording medium is thicker above the grooves than on the plateaus between the grooves. At this time, if the optical recording medium has higher sensitivity in the area above the groove than in the area above the plateau, even if the light beam overlaps both the groove and the plateau surrounding it, priority will be given to the area in the groove. Information is recorded on the surrounding plateau, but not on the surrounding plateau.

Alternatively, the series of depressions can be arranged in separate circular or spiral tracks, with depressions and plateaus alternating along the direction of the track. In this case, the concave portions can be of equal length on each track, or can be of equal angular length and become longer as they are farther from the center of the disk. Thus, in the first case, information is recorded and read from the disk with a variable frequency and constant recording element size, and in the second case, information is recorded and read out with a constant frequency and variable recording element size. If the sensitivity of this optical recording medium is higher on the depression than on the plateau, a light beam that spans both the depression and the plateau along the track will give priority to information only in the area of the depression. recorded.

Another shape is a checkerboard pattern, in which depressions and plateaus are alternately arranged both along the track direction and in a direction perpendicular thereto.

FIG. 5 shows a two-layer information recording medium 90 on which information tracks are recorded. In this recording body 90, the third
Elements common to the illustrated recording medium 50 are designated by the same reference numerals. In the illustrated information recording body 90, concave portions and plateau portions are alternately arranged along the track. Information is recorded in the form of a series of apertures 92 in the absorbent layer 54;
The presence or absence of the apertures 92 and their spacing represent recorded information. This opening can also be formed in the plateau portion 34.

FIG. 6 shows a three-layer information recording medium 100 on which information tracks are recorded. Elements in this information recording medium 100 that are common to the recording medium 70 in FIG. 4 are designated by the same reference numbers. Information is recorded in the absorbing layer 78 in the form of a series of regions 102 that have different optical properties from the remaining regions. This region can take the form of an irreversible deformation of the optical properties of the absorbing layer 78 or a reversible change thereof, such as due to a change in its crystallinity, where the presence or absence of a change in the optical properties of the absorbing layer affects the reflectance of the recording medium. The length and spacing of this area represent recorded information.

When the recording light beam straddles a region with low sensitivity and its energy density is sufficiently large, changes in the absorption layer representing recorded information may also occur in the second region of low sensitivity.

The optical recording medium of the present invention has regions with different recording sensitivities because the layers have different thicknesses. This change in thickness occurs depending on the presence or absence of recesses on the substrate surface. Information can also be recorded on an optical recording medium by forming recesses with a specific spatial distribution or by varying the depth of the recesses during substrate manufacture. For example, by modulating the depth of a part of the spiral or circular shape, a third region having a different reflectance from the first and second regions can be formed. This information can be used, for example, for track identification to indicate the beginning and end of a track or for generating synchronization data. Similar encoding schemes can be used for other arrangements of recesses. Optical recording medium 11 in FIG.
0 and the optical recording medium 50 of FIG. 3 are designated by the same reference numerals. The depths of the recesses 112 and 114 into the interior of the substrate 12 are different, thereby forming a third region.

During operation of the optical recording/reading/erasing system, the light beam is focused on the center of the information track, and in the above-mentioned photoelectric recording medium, it is focused on the center of the first area of high sensitivity during recording. If there is a difference in reflectance between the first region and the second region, this difference is used to generate a signal proportional to the displacement of the light beam along the width of the track, and this signal is used to move the light beam across the track. The position of the light beam can be modified.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an optical recording medium of the present invention;
FIG. 2 is a sectional view of a portion of the first embodiment of the invention, FIG. 3 is a sectional view of a portion of the second embodiment of the invention, and FIG. 4 is a sectional view of a portion of the second embodiment of the invention. 5 is a sectional view of a part of the information recording medium of the present invention, FIG. 6 is a sectional view of a part of the second embodiment of the information recording medium, and FIG. FIG. 3 is a cross-sectional view of a portion of a photoelectric recording medium having recesses of different sizes. 10... optical recording medium, 12... substrate, 14
... Main surface, 16 ... Absorption layer, 18 ... First region, 19 ... Second region, 32 ... Recessed part.

Claims (1)

[Claims] 1. A substrate having a first region, a second region, and a main surface, wherein the recording sensitivity of the first region is higher than the recording sensitivity of the second region. characterized in that the main surface of the substrate has a recessed part and a plateau, and the recessed part and the plateau are respectively connected to the first and second regions or the second and second regions. 1, and on the major surface there is a photodevelopable medium filling the recess and having a substantially planar surface, the medium including a light absorbing material adjacent to the planar surface. A recordable optical recording medium comprising one or more layers, including a layer. 2. The optical recording medium according to claim 1, wherein the thickness of the photodevelopable medium on the recessed portion is greater than the thickness on the plateau portion. 3. A reflective layer is interposed between the substrate and the absorbing material layer and reflects a considerable portion of the incident light having the wavelengths of the recording and reading light beams, and the thickness of the absorbing material layer is equal to or less than the first thickness. Claim 1 or 2, characterized in that the recording medium is selected such that the reflectance of the recording medium in the region decreases and becomes a non-reflective state.
The optical recording medium described in . 4. The absorbing material layer on the reflective layer has a first region that absorbs light of the wavelength and has a first thickness and a second thickness different from the first thickness. the thickness of the first region of the absorbing material layer is such that the reflectance of the optical recording medium for light of the wavelength in the first region is such that the reflectance of the optical recording medium for light of the wavelength in the first region is such that is chosen to be lower than its reflectance for light of the same wavelength at . The optical recording medium according to claim 3. 5. An intervening layer is provided between the reflective layer and the absorbing material layer and filling the recessed portion, and the thickness of the intervening layer and the absorbing material layer is the same as that of the optical recording medium in the first region. The optical recording medium according to any one of claims 1, 2, 3, or 4, wherein the optical recording medium is selected so that the reflectance is reduced and the medium is in a non-reflective state. 6. Optical recording medium according to claim 5, characterized in that the thickness of the layer of absorbent material provided on top of the intervening layer is substantially uniform. 7. Claims 1, 2, characterized in that the recess extends into the substrate from a distance of 5 nanometers to 200 nanometers from its main surface.
7. The optical recording medium according to any one of 3, 4, 5, or 6. 8. Claims 1, 2, 3, 4, 5, 6, characterized in that the substrate is made of plastic material.
or 7. The optical recording medium according to any one of 7. 9 Claims 1, 2, 3, 4, characterized in that the absorbent material layer is covered with a thick overcoat layer.
9. The optical recording medium according to any one of 5, 6, 7, or 8. 10 A cover layer covers the absorbent material layer, and a thick overcoat layer covers the cover layer.
Claims 1, 2, 3, 4, 5, 6, 7, 8
or 9. The optical recording medium according to any one of 9. 11 Claims 1, 2, 3, characterized in that the absorbing material layer is composed of an organic material.
4. The optical recording medium according to any one of 4, 5, 6, 7, 8, 9, or 10. 12. that the absorbing material layer is composed of a material selected from the group consisting of titanium, rhodium, tellurium, selenium, tellurium-based alloys, selenium-based alloys, arsenic trisulfide and arsenic triselenide; Claims 1, 2,
3. The optical recording medium according to any one of 3, 4, 5, 6, 7, 8, 9, 10, or 11. 13. Claim 1, characterized in that the recessed portion is arranged in the shape of a groove on the main surface of the substrate.
2. The optical recording medium according to any one of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12. 14. Claims 1, 2, 3, 4, 5, characterized in that the recessed portions are arranged so as to form alternating rows of first regions and second regions.
6, 7, 8, 9, 10, 11, 12 or 13. 15 a portion of the recess has a depth that extends into the substrate a different distance than the remainder thereof, thereby
and a third region having a reflectance different from the reflectance in the second region is formed.
6, 7, 8, 9, 10, 11, 12, 13 or 14. 16. A substrate having a main surface having one or more recesses, and an absorbing layer that fills the recesses and is located on the main surface and absorbs light having the wavelength of the recording and reading light beams. A first area and a second area are formed on the substrate so that the recording sensitivity in the first area is higher than the recording sensitivity in the second area, and information tracks are arranged in a row. characterized by the formation of
Optical recording medium as an information recording body or optical disk having an information track. 17. The recessed portion is characterized in that it consists of a substantially continuous recessed groove with a uniform depth, and the recessed groove is formed in a spiral or concentric shape,
The optical recording medium according to claim 16. 18. The optical recording medium according to claim 17, wherein the grooves define radially spaced spiral or concentric track regions. 19. Optical recording according to claim 16, characterized in that a plurality of individual information pores having a substantially uniform depth are formed in said layer approximately in the track area. Medium.