JPH0267179A - Rewritable optical recording medium and erasure method thereof - Google Patents

Abstract

PURPOSE:To make the size of a pit (recording data part) stable and to reduce the remainder at the time of erasure by constituting the first layer of a recording layer of a porous layer and the second layer thereof of a layer held in a form of a pit by thermal deformation due to light energy. CONSTITUTION:A glass substrate having a guide groove formed thereto is used as a substrate 11 and a layer 12 consisting of an org. dye and a binder is formed on the substrate 12 by spin coating and a porous layer 13 is next formed on the layer 12 using silicone rubber. When the optical recording medium thus constituted is rotated and irradiated with laser beam to perform recording, the layer 12 being the second layer is thermally deformed to generate a layer 21 of the org. dye and the binder having a pit formed thereto. At this time, in the porous layer 13, the edge built up on the circumference of the pit is forcibly fixed in a cooled state and a porous layer 22 having a dome-shape protruberance formed thereto is held. Regeneration is performed by projecting laser power beam and reding the intensity change of reflected beam and erasure is performed by the irradiation with laser power beam and the recording layer smoothly returns to the original flat shape.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to rewritable optical recording such as optical disks, optical cards, and optical tapes used for data files and digital audio disks that record, reproduce, and erase information using light. It is about media and how to eliminate them.

2. Description of the Related Art In recent years, optical disks have been increasingly being applied to data files due to their advantages such as high density, large capacity, and high speed access.

Furthermore, it is being used in the form of optical power-1 and optical tape for recording data. Although the present invention relates to any of these optical recording media, the optical disc will be described below.

There are three main types of optical discs: the WO type, which only plays back pre-written information; the write-once type, which allows new information to be written in addition to the pre-written information; and the rewritable type, which can be repeatedly written and erased. It is. The most needed type is the rewritable type, and the present invention also relates to this type.

There are several types of rewritable types.

1. Phase change type that uses the heat of light to cause a phase transition (crystalline amorphous phase) in the optical recording medium and read the change in light reflectance.The magnetic film is heated with laser light above the Curie temperature. Pit (information recording section) created by applying a magnetic field
A magneto-optical type that changes the magnetization direction and reads changes in polarization angle due to the Kerr effect.

There are photochromic types that use software in the absorption wavelength range due to the light absorption of organic dyes, and two-layer types that use the heat of laser light to create and erase dome-shaped bumps and hole-shaped deformations. .

The phase change type has the disadvantage that when the linear velocity is slow, the thermal conductivity of the optical recording medium is high, so that the pits become smudged. The magneto-optical type has the disadvantage that the optical cost is high and the optical system is complicated, and the photochromism type has the disadvantage that the signal deteriorates over time. The present invention relates to a two-layer type.

This type of recording layer includes a two-layer recording layer in which the second layer is a polymer layer containing an organic dye and the first layer is an inorganic ceramic layer. For example, JP-A-60-253035
It is disclosed in the publication No.

A conventional two-layer recording device having two recording layers will be described below with reference to the drawings. FIGS. 4 and 5 show an unrecorded state and a recorded state in the conventional three-day type. In FIG. 4, 41 is a substrate, 42 is a polymer layer made of a binder containing an organic dye, 43 is an inorganic ceramic layer, 51 is a space, and 52 is a dome-shaped structure. A polymer layer 42 having a glass transition temperature higher than room temperature is formed on a substrate 41 made of glass or resin, and silicon oxide is formed on the polymer layer 42 having a glass transition temperature higher than room temperature.

An inorganic ceramic 1143 such as aluminum oxide is formed.

When a laser beam is focused and irradiated onto the required location of the polymer layer 42 of the recording layer, the second polymer layer 42 absorbs the light energy of the selected wavelength and is melted by the heat generated.
A thermally deformed pit is created in the form of a displaced substance, forming a space 51. At this time, the first thin inorganic ceramic layer traps the material extruded from the polymer layer 42 and forming the pits, forming a dome-like structure 52 over the pits.

During erasing, by reirradiating the laser beam, the displaced substance of the second polymer layer is reheated and made plastic and poured into the space 51 within the pit.

At this time, the stress of the inorganic ceramic layer 43 attempts to erase and flatten the dome-shaped structure 52.

Problems to be Solved by the Invention However, with the above configuration, when pit spaces are formed by thermal deformation during recording, the inorganic ceramic layer is essentially a dense material, so there is no place for the displaced substances to escape, and the material collapses. It is easy for pits to form in different shapes, and it is difficult for the pits to be uniform in size. Furthermore, during erasing, when the material that was displaced by reheating flows back into the space, the inorganic ceramic layer is dense, so there is no place for the gas present in the space to escape, and as a result, the pit space is not completely filled. This method has the disadvantage that erasing tends to be incomplete, resulting in unerased areas.

In view of the above-mentioned problems, the present invention provides a rewritable optical recording medium that has a stable pinot size and leaves little unerased data during erasing, and a method for erasing the same.

! ! l! Means for Solving the Problems In order to solve the above problems, the optical recording medium of the present invention has at least two recording layers, the first layer is a porous surface, and the second layer is heated by light energy heat. Via with deformation 1-
It is made up of layers that hold it in the shape of. Further, by focusing laser light on the recording layer ζ, thermally deformed pits forming information recording elements that need to be erased are flattened and erased.

Function The present invention has the above-described structure, in which a layer consisting of an organic dye that absorbs the wavelength of laser light and a polymer material Fl as a binder is formed, and a porous polymer layer having a flat surface is formed on this layer. is in an unrecorded (first jlJl) state.

For recording, the recording layer is irradiated with a recording laser beam, and the second layer has a glass transition temperature higher than the room temperature and lower than the thermal temperature generated by the irradiation of the recording laser beam, and has a low thermal conductivity. The binder is heated by light absorption of the organic dye. As a result, the second layer consisting of the organic dye and binder is thermally deformed, forming pits with spaces in the form of displacing the material, and then being cooled without irradiation, and the pits are fixed. The displaced material simultaneously pushes up the first layer, which is a porous rubbery polymer layer, forming a tom-like bulge. Since the first layer is porous, the pressure in the space does not decrease, and smooth space pits can be formed.

11. When reproducing, a low power laser beam is applied to the recording layer. (The reflectance changes due to diffraction and reflection from the pit are read.

Erasing means erasing. - By irradiating the recording layer with light, the material trapped on the edge of the pier formed in the second layer is reheated and becomes a plastic layer. Due to the elastic force of the layer of rubbery polymer ribs, the displaced material flows back into the pit space. At this time, since the second part i is porous, the gas in the space flows out into the pit, and the inside of the pit is filled with material and flattened, completing the erasing.

The second layer is made by dissolving an organic dye that has a light absorption band in almost the same wavelength range as the laser light wavelength into a binder polymer material, and the movement of the organic dye absorbs the laser light well during recording and converts it into heat. There is no need to cause a change in the optical absorption wavelength band. As a binder, a material with low thermal conductivity is required. If the thermal conductivity is low, the size of the pit formed will be small (and the height of the edge of the pit can be increased, resulting in the height of the dome being increased. Therefore, a signal with a high CN ratio can be obtained with a small laser power. The thermal conductivity is preferably 4×10 IW/m− or less.

The first layer has a higher thermal deformation temperature due to the thermal temperature generated when the recording/erasing laser beam is irradiated to the binder of the second layer, is transparent at the wavelength of light used, and exerts stress on the second layer. Furthermore, it is a porous polymer.

The organic dye used in the second layer is ethylene l.

2-dithiol metal (Ni) fit bodies, cyanine dyes such as phthalocyanine, squalirium dyes, methine dyes, naphthoquinone dyes, quinone imine dyes, quinone diimine dyes, and other dyes with absorption bands in the near-infrared region. It is effective.

As the binder, polymethyl methacrylate, polystyrene, polyvinyl alcohol, polyvinyl acetate, polyvinyl chloride 7 nylon, 21-cellulose ethyl cellulose polycarbonate, and polymeric materials of these types can be used.

As the porous material used for the first layer, silicone rubber 2 polyethylene, polypropylene, etc. can be used.

71) -Layer, -The second layer of \1''Ngu's seven notes is heat deformation temperature, gas, PL transfer temperature, etc. i:j:
tft joint service was selected from IJii).

1'J's 1.1+j4 formation operation allows recording with relatively low-power Rayleigh light, and has a high heat resistance that allows for erasing and erasing. Thus, an optical disc can be obtained with a high number of repeated recording and erasing operations.

'P8i! EXAMPLE 1 A removable optical recording medium and its rt' according to an embodiment of the present invention will now be described with reference to the drawings.

FIG. 1 shows an optical recording medium in an uninvented embodiment.
This shows a Tii diagram. In Fig. 1, 11 is an olfactory layer, 12 is a layer of pigment and binder, and 13 is a porous layer. Fig. 2 shows a cross-sectional view during recording. In Fig. 2, 21 is a thermal layer. A layer of organic dye and binder is deformed to form pits, 22 is a porous layer with dome-shaped protuberances, and 23 is radar light.

In cases 11 and 1, glass substrates on which indoor grooves were formed by dry etching were used. On top of this, 700 ~
Using tradedehydrocholine, which has an absorption band at 900 nm, and polymethyl methacrylate as a binder, the organic dye and binder layer 12 was coated with a spin cord (rotation speed: 150 nm).
orpm).

Next, a porous layer 13 was formed on the organic dye and binder 112 using silicone rubber.

Membrane 17 was 0.3 μm.

The thermal conductivity of the organic dye and binder layer in this example is 1.
4 x 10'' W7/m -K. The glass transition temperature of polymethyl methacrylate was above room temperature, and the heat distortion temperature of the porous layer was around 300°C.

An optical recording medium with such a configuration has a linear velocity of 1.4 m, -'se
Rotate at c and laser beam 23 (wavelength 830 nm)
．． Recording was performed by irradiating from the 2h plate side with a power of 2 mW.

By the laser irradiation, the second layer of organic dye and binder absorbs the laser light and becomes heated, and is thermally deformed to form a layer 21 of organic dye and binder in which pits are formed. At this time, after the first layer, the ash layer builds up around the pit caused by the thermal deformation of the second layer. The formed porous layer 22 is retained.

For reproduction, light with a power of 1.0 mW was inputted from a sea 4 node, and changes in the intensity of the reflected light were read out. Linear speed 1.4m/
It was found that it is optimal to change the recording power by about 4 mW for each second, and the CN ratio becomes 53tjB.

For erasing, irradiation was performed with a laser power of 9 mW. By kneading 2, the recording layer smoothly returned to its original flat 1u shape. The number of times of repeating and erasing was 104 times or more in the system of tetradehydrocholine and polymethorutacrylate, and it was found that the repeatability was superior to that of the type with an inorganic ceramic layer and a polymer layer. This is thought to be because the first porous layer is physically porous, so it forms pits with stable sized spaces during recording, and the pit spaces disappear smoothly during erasing.

Figure 3 shows a cross-sectional view of the completed optical y' isk.

In FIG. 3, 31 is an optical recording medium, 32 is an air gear knob, 33 is a protective board, and 34 is a center hole. An optical recording medium 31 consisting of a first layer and a second layer was formed by the method described above, and an aI-retaining substrate 33 made of polymethylpentene was bonded to the disk via an air gear knob 32 in order to improve durability. This optical disc is 80'C809i
When subjected to an accelerated RH test, it showed no C even after 1000 hours.
No deterioration of the N ratio was observed.

As described above, by using an organic dye and a binder with low thermal conductivity as the second layer and a porous layer as the first layer, an excellent optical disk with a high CN ratio and a high number of repeated recording/erasing cycles was obtained.

In the above embodiment, an example is shown in which the recording layer is composed of two layers, but an Al film or the like may be provided to increase the reflectance to form a multilayer structure.

Effects of the Invention As described above, the present invention is composed of a second layer made of an organic dye with low thermal conductivity and a binder, and a porous first layer. The present invention provides an excellent optical disc with a small number of discs.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an optical recording medium at t3 according to an embodiment of the present invention], FIG. 2 is a cross-sectional view during recording, No. 3121 is a cross-sectional view of a completed optical disc, and FIGS. FIG. 3 is a cross-sectional view showing an unrecorded state and a recorded state in a two-layer type. 11...Substrate, 12...Organic dye and binder layer,
13... Porous layer, 21... Layer of organic dye and binder that is thermally deformed to form pits, 22... Porous layer that has dome-shaped protuberances formed, 23... Laser light, 31
...Optical recording medium, 32...Air gear, Bu, 33...
Protection board, 34...center hole. Name of agent: Patent attorney Shigetaka Awano is Rikishi name 1--
i T25 [

Claims (1)

[Claims] (1) It has a recording layer made of a recording material that can be deformed by light and a substrate that supports the recording layer, and data can be written using optical energy;
In order to erase data or optically read data, the recording layer has at least two layers, the first layer is a porous layer, and the second layer is held in the form of pits by thermal deformation due to light energy heat. A rewritable optical recording medium characterized by comprising a layer of (2) A rewritable optical recording medium characterized in that by focusing an erasing laser beam on the recording layer, the pits generated by thermal deformation that form the information recording element that needs to be erased are flattened and erased. Elimination method. (3) The first layer of the recording layer has a significantly high heat deformation temperature,
The rewritable optical recording medium according to claim 1, characterized in that it is made of a polymer layer that is transparent at the wavelength of light used. (4) The rewritable optical recording medium according to claim (1), wherein the first layer of the recording layer is made of a porous rubbery polymer layer that allows gas to pass through. (5) The second layer of the recording layer contains an organic dye that absorbs light at a desired wavelength, and a polymeric material that is a binder and has a glass transition temperature higher than room temperature and lower than the thermal temperature generated by laser light irradiation. Claim (1)
The rewritable optical recording medium described above. (6) Claim characterized in that the second layer of the recording layer is heated and cooled without irradiation with recording laser light to form and fix thermally deformed pits, and shows plastic deformation when reheated with erasing laser light. 1) The rewritable optical recording medium described above. (7) The rewritable optical recording medium according to claim (1), wherein the second layer of the recording layer has a low thermal conductivity. (8) The material in the second layer, which has become plastic due to reheating by the erasing laser beam irradiated to the recording layer, is pressed down by the elastic force of the first layer and flows into the pit again, and the gas in the pit becomes porous. 3. The method of erasing a rewritable optical recording medium according to claim 2, wherein the thermally deformed pits are flattened through the first layer to easily complete the erasing process.