JPS61130094A - Information recording medium and recording regeneration method - Google Patents

Abstract

PURPOSE:To make it possible to obtain a large regeneration signal, by performing the recording of information by the change in the optical density of an information recording layer and the change in the diffraction or interference state generated by the difference in level of the information recording layer and a substrate. CONSTITUTION:A tracking guide groove 2 having a square cross-sectional area is formed to one surface of a substrate 1 comprising a transparent polymer material and the depth (d) of the groove 2 is set to nlambda/16-3nlambda/16 (wherein lambdais the wavelength of a recording regeneration light source and n is the refractive index of the substance for constituting the groove) and the width (w) thereof is set to 0.5-1.2lambda. When an information recording layer 3 is irradiated with laser beam 7, an extremely large modulation degree is obtained by the synergistic effect of the increase in reflectivity of the heated cross-hatched part 8 by phase conversion and the increase in quantity of reflected light due to the reduction in the depth of the groove and, therefor, a large regeneration signal is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is capable of recording information by causing a change in optical density or a step difference in an information recording layer formed on a substrate by irradiating light such as a focused laser beam. The present invention relates to an information recording medium and a recording/reproducing method on which information can be recorded, and the information can be read and reproduced.

Conventional technology Conventional information recording media and recording/reproducing methods involve irradiating a thin film formed on a substrate with a main component such as Te, and removing it by melting and evaporating the thin film due to its thermal effect. This thin film records information by utilizing optical density, that is, changes in refractive index and reflectance due to phase transition from amorphous to crystalline or vice versa, and gas generation on the substrate. A layer, on which a thin metal film is provided, and information is recorded by deforming the thin metal film by gas pressure generated from the gas generating layer heated by laser beam irradiation, for example, JP-A No. 58.
No. 177,538, reproduction is usually carried out by extracting as a signal the difference in reflectance or the difference in the amount of diffracted light between the recorded portion and the unrecorded portion.

Problems to be Solved by the Invention It is an object of the present invention to provide an information recording medium and a recording/reproducing method that can obtain a larger reproduction signal than conventional ones.

Means for Solving the Problems The present invention changes the optical density of the information recording layer provided on the substrate by light irradiation, and also creates a step between the information recording layer and the substrate, thereby increasing the information density. Recording is performed, and reproduction is performed by reading optically changes in the optical density of the information recording layer and changes in the diffraction or interference state of light due to the steps.

Function The present invention uses the above-mentioned configuration to perform recording and reproduction using two changes: a change in the optical density of the information recording layer and a change in the diffraction or interference state of light due to the generation of steps. A comparatively large reproduction signal can be extracted.

Example An embodiment of the present invention will be described based on FIGS. 1 to 4.

In FIG. 2, reference numeral 1 denotes a substrate made of a transparent polymeric material such as acrylic resin or polycarbonate resin, and a tracking guide groove 2 having a rectangular cross section is formed on one surface by injection molding or the like. Usually, this guide nλ 3nλ The depth d of the groove 2 is □~- (where λ is the wavelength of the light source for the recording layer, and n is the refractive index of the material constituting the groove), and the width W is 0.
．． It is set to 6λ to 1.2λ.

Normally, in a recordable and reproducible disk like the present invention, signals indicating track addresses are recorded by providing unevenness in the guide groove 2 for high-speed searching, etc. (not shown). It is normal that this is done. The depth and width of the tracking guide groove 2 depend on the magnitude of the tracking signal obtained from the guide groove,
The setting is made so that the magnitude of the signal provided by the unevenness in the guide groove and the magnitude of the additional recording signal written on the disk by a laser beam or the like to be described later are balanced.

Generally, as the groove becomes shallower and wider within the above range, the diffraction of light in the groove becomes weaker and the tracking signal and unevenness signal become smaller, but the write-once signal written so as to increase the reflectance becomes larger. The opposite is true when the groove becomes deep and narrow. 3 is To
An information recording layer mainly composed of the following is provided on the substrate 1 by a method such as vapor deposition or sputtering. Reference numeral 4 denotes a protection plate bonded with an adhesive 5 made of a polymeric material for the purpose of protecting the information recording layer 3 from external mechanical force and humidity.

Recording is performed by focusing laser light 7 from the substrate 1 side onto the information recording layer 3 of the tracking guide groove 2 using the objective lens 6.

When the focused laser beam 7 is irradiated onto the information recording layer 3 and page 6 is reached, the portion 8 of the information recording layer 3 that has received the irradiation and is shown by the cross-backing is heated and changes from an amorphous state as shown in FIG. The reflectance increases due to phase transition to crystalline state.

Since the intensity of the laser beam 7 is set so that the temperature rises to such an extent that the crosshatch portion softens, the reflectance increases and at the same time softens. At this time, since the crosshatch portion 8 is at a high temperature, the contact portion of the substrate 1 with the crosshatch portion 8 is instantaneously heated to a high temperature by heat conduction or radiation. Then, since the substrate 1 is made of a polymeric material, the heated polymeric material decomposes and generates gas, and the gas pressure indicated by the arrow a acts on the crosshatch portion 8 as shown in FIG. Chromeno Cchi Club 8
Since it has already been heated and softened, it is easily pushed upward by the gas pressure as shown in FIG. 1, and as a result, the groove depth d' becomes shallow.

Of course, at this time, the adhesive 6 in contact with the Chromeno Sochi part 8
Since it is heated and softened, it provides moderate resistance to the displacement of the cross section 8, but it does not strongly block the displacement, but rather allows it to be displaced uniformly over the entire area of the cross section 8. The shape of the action is maintained.

Therefore, the information recording layer 3 irradiated with the laser beam 7 is the first
As shown by the crosshatch portion 8 in FIG. Due to the synergistic effect of the increase in the amount of reflected light, a very large degree of modulation can be obtained, so that a highly readable signal can be obtained. Therefore, S/
N is improved, and it is also advantageous against contamination on the substrate surface.

Next, other embodiments of the present invention will be described.

In the above embodiments, a configuration was described in which recording is performed by changing the information recording layer from a state of low reflectance to a state of high reflectance, but conversely, recording is performed by changing the state of reflectance from a state of high to a state of low. If the 6th
The configuration shown in the figure may be used.

Components that are the same as those in FIG. 1 of the embodiment described above are indicated by the same numbers.

In FIG. 5, the trunking guide groove 9 is oriented in the opposite direction to that in FIG. 1, that is, it is a concave groove when viewed from the laser light source. In this configuration, when the laser beam 7 is irradiated, the reflectance of the crosshatch portion 1o decreases, and the pressure of the gas generated from the substrate 1 causes the crosshatch portion 1o to decrease as in the case of FIG.
o is pushed up, and as a result, the groove depth d' becomes deeper. Then, due to the synergistic effect of the decrease in the reflectance of the information recording layer and the decrease in the amount of reflected light due to the increase in the groove depth, a large reproduced signal can be obtained as in the previous embodiment.

Note that this case can be applied even when there is no tracking guide groove.

In the embodiment described above, instead of bonding the protective plate 4 with adhesive 6 to protect the information recording layer 3 as shown in FIG. 2, a polymeric material may be applied to the information recording layer 3 to form a protective layer.

Furthermore, the information recording layer is not limited to a thin film containing Tonium as a main component, nor is it limited to a layer whose optical properties change due to phase transition from amorphous to crystalline or vice versa.

9be1] - Furthermore, the method for forming the tracking grooves is not limited to injection molding, and there is no problem in using a method using a photocurable resin called the 2P method. That is, the purpose can be achieved if both sides of the information recording layer are made of polymeric material.

Further, in order to protect the information medium layer from humidity and the like, a dielectric layer such as SiO2 may be provided on both sides or one side of the information medium layer. At this time, the thickness of the dielectric layer is 300 to 500
If it is about the size of a human being, it will not hinder the displacement of the information medium layer so much, and the information medium layer can be sufficiently displaced by slightly increasing the power of the laser beam.

As shown in FIG. 6, the member 13 in the vicinity of the information recording layer 12 of the substrate 11 is made of a polymeric material with a high content of uncrosslinked molecules, and is heated with a laser beam 14 of moderate intensity. Information recording is performed by reducing only the reflectance by phase transition or the like without softening the information recording layer 12, and by crosslinking the uncrosslinked molecules to shrink the volume and forming a step 16 between the information recording layer 12 and the information recording layer 12. It's okay.

10, the -north hatch portion 16 is a portion whose reflectance has decreased due to the irradiation with the laser beam 14.

When reproducing, a laser beam is irradiated, and when focusing on the beam 17 of the laser beam, the light 18 reflected by the step 15 of the beam 17 and the light 19 reflected from the surface of the crosshatch portion 16 are reflected. It becomes a signal light. The light 19 is weaker than the reflected light from the unrecorded area because the reflectance of the crosshatch area 16 is lowered, and is further weakened by interference with the light 18, so the amount of reflected light from the recorded area is extremely large. becomes smaller. At this time, when the distance d'' between the step 16 and the crossbar/chi portion 16 is λ/4, the amount of reflected light becomes the smallest.

In other words, in this case as well, a large reproduced signal can be obtained as in the previous embodiment due to the synergistic effect of the decrease in reflectance and the interference of light due to the step.

In all of the above examples, only the light information recording layer
Alternatively, if recording is performed with two types of irradiation intensities: one that produces only the adult cow on the step, and the other that produces both the shading and the step release, a three-value record representing 0° 11 Be-7 1,-1 is obtained. It is also possible to do this.

Effects of the Invention The present invention records information through two changes: a change in the optical density of the information recording layer and a change in the diffraction or interference state of light caused by the formation of a step between the information recording layer and the substrate. Due to their synergistic effect, a very large degree of modulation can be obtained.

Therefore, it is possible to obtain a larger reproduction signal than ever before, which improves the signal-to-noise ratio, which is advantageous against dirt on the substrate surface, and enables highly reliable recording and reproduction.

[Brief explanation of drawings]

1 and 3 are enlarged sectional views of essential parts of an information recording medium according to an embodiment of the present invention, FIG. 2 is a sectional view of the same embodiment, and FIG.
The figure is a BB' sectional view of FIG. 1, and FIGS. 5 and 6 are enlarged sectional views of essential parts of a disk in other embodiments of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Tracking guide groove, 3... Information recording layer, 4... Protective plate, 5... Adhesive , 6...Objective lens, 7...Laser light.

Claims (4)

[Claims] (1) It is characterized by being composed of a substrate and an information recording layer provided on the substrate, whose optical density changes when irradiated with light, and which creates a step between the layer and the substrate when irradiated with light. information recording medium. (2) The information recording medium according to claim 1, wherein the step is caused by deformation of the information recording layer. (3) The information recording medium according to claim 1, wherein the step is caused by deformation of the substrate. (4) An information recording medium composed of a substrate and an information recording layer provided on the substrate, whose optical density changes when irradiated with light, and which creates a step between the layer and the substrate when irradiated with light. Information is recorded by irradiating the information recording layer with light, changing the optical density of the information recording layer by the light irradiation, and creating a step between the information recording layer and the substrate. A recording and reproducing method characterized in that information is reproduced by reading light and shade changes and changes in light diffraction or interference state due to the step difference using light.