JPH0296942A - Rewritable optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain the recording medium which allows rewriting with a compact disk player by providing a recording layer consisting of a light absorbent and a thermoplastic resin having a specific softening point temp. and number average mol.wt. between a substrate and a light reflecting layer. CONSTITUTION:The optical disk is formed by laminating the recording layer 2, the light reflecting layer 3 and a protective layer 4 on the light transparent substrate 1. This layer 2 is formed by uniformly dispersing a material mixture composed of the light absorbent which absorbs laser light and the thermoplastic resin having 50 to 150 deg.C softening point temp. and 500 to 25,000 number average mol.wt. Recording to this disk is executed by irradiating the layer 2 with laser light and softening the thermoplastic resin by the heat energy and pressure of the light absorbent to induce local deformation to recessed shapes, thereby forming pits 5. The recording medium having the high reflectivity and modula tion percentage of the laser light conforming to compact disk formats is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording medium in which data can be rewritable and can conform to the compact disc format.

[Prior art] Data is recorded by irradiating laser light, and the recorded data can be reproduced using a laser light whose power is weaker than that of the laser light used for recording, and the power is almost equal to or weaker than the light used to record data. As a so-called rewritable optical information recording medium in which data can be erased with a laser beam stronger than the reproduction light, a recording layer of a magneto-optical material such as Gdx Tbs Fe is provided on one main surface of the substrate, and a A structure in which a metal layer having a high reflectance is provided and a protective layer is further formed on the upper surface of the metal layer is already known. The pit type formed in the recording layer in this case is a domain inversion type. Other types of bits formed in the recording layer include a type that repeats amorphous and crystalline forms, a type that is made of organic material, and a pre-stabilized type, depending on the type of recording material that forms the recording layer.

[Problems to be Solved by the Invention] The above-mentioned rewritable optical information recording media that have been developed or put into practical use in the past are compatible with compact disc players (CD players) that play compact discs (CDs), which are now in widespread use. ) is difficult to play.

That is, the first type, which uses domain reversal of magneto-optical materials, is a method of reproducing by reading changes in the reversal rate due to the Kerr effect, but the reversal rate is low and cannot be reproduced in a CD player. The second type, which repeats amorphous and crystalline states, is the reflected light i? of the laser beam at pits (marks) formed in the recording layer due to phase change. L,!
- The difference from the reflected light m at other parts is small.

For this reason, since the degree of modulation of the reproduced signal is low and the disc reflectance is also low, it cannot conform to the CD format defined for CDs and cannot be reproduced on a CD player. The third type, which is based on photoisomerization of organic materials, is similar to the type that repeats crystallization from amorphous, and cannot meet the CD format for the same reasons as the second type. Playback on a player is not possible.

The present invention has been made to solve the above-mentioned conventional problems. It is in the seventh place that provides the medium.

[Means for Solving the Problems] That is, the gist of the first means adopted in the present invention to achieve the above-mentioned [Object 1] is that the light-transmitting substrate l and the light-reflecting layer 3 that reflects laser light are In between, a recording layer 2 is provided in which a light absorbing material that absorbs laser light is mixed with a thermoplastic resin having a softening point temperature of 50 to 150°C and a number average molecular weight of 1 to 25,000. It is a replaceable optical information recording medium.

Furthermore, the gist of the second means is that in the first means, the real part nrea of the complex refractive index of the recording layer 2 and its partial thickness d. . and the wavelength λ of the reproduction light ρ = n r
e. d, , , /λ is 0.05≦p≦0°6, and the imaginary part 1 of the above complex refractive index is

is 0. It is a rewritable optical information recording medium with a power of 3 or less.

Furthermore, the gist of the third means is that the softening point temperature is between 50 and 1
50'C, a thermoplastic resin layer 2b with a number average molecular toxicity in the range of 500 to 25,000, absorbs laser light to generate heat, and this heat deforms the thermoplastic resin layer 2b. This is a rewritable optical information recording medium in which a light absorption layer 2a is formed.

Furthermore, the gist of the fourth means is that in the third means, the real part nabs of the complex refractive index of the light absorption layer 2a and its film thickness (ρ" given by Iabq and the wavelength λ of the reproduction light)
The present invention is a rewritable optical information recording medium in which n abs d ahs/λ satisfies 0.05≦ρ≦0.6, and the imaginary part k abs of these negative prime refractive indices is 0.3 or less.

[Function] The concept of recording, reproducing, and erasing data on an optical information medium using the first and second means described above is shown in FIGS. 2 and 3.

That is, during recording, the recording layer 2 is irradiated with a focused laser beam, and a single change is induced in the light absorber of the recording layer 2 with high laser power.

At this time, the light absorbing material included in the recording layer 2 converts light energy into thermal energy, and at the same time, the light absorbing material contained in the recording layer 2 also transforms into a melting field 11i.
1 Pressure changes due to evaporation, etc. This thermal energy softens the thermoplastic resin contained in the recording layer 2, and at the same time, as the pressure increases due to the light absorbing material, for example,
A local concave deformation as shown in FIG. 3 occurs. Thereafter, the resulting concave deformation is fixed as the resin cools and remains as a pit 5.

During reproduction, the optical pickup 8 irradiates the laser beam 7 with a power such that the light absorbing material contained in the recording ja2 imparts only heat below the softening blackness of the thermoplastic resin, and the light absorption material in the recording pit 5 is The data of the pit 5 is read out based on the difference between the reflected light (1) and the reflected light at other parts. At this time, the pit 5 is not deformed.

Further, during erasing, the light absorbing material itself generates heat in a thermally stable state, and the recording layer 2 is irradiated with a laser beam having a power sufficient to heat the resin to a temperature higher than its softening point. At this time, no pressure increase due to the light absorbing material in record 1 and 2 was observed, and the thermoplastic resin component softened, and due to its surface tension and accumulated stress during deformation, the part that constituted pit 5 became the second Restore to the unrecorded state as shown in the figure.

In the optical information recording media according to the first and second means described above, a light absorbing material and a thermoplastic resin are mixed and dispersed in the recording layer 2;
Optical information recording media according to the third and fourth means provide these as separate layers, a light absorption layer 2a and a thermoplastic resin layer 2b. Recording data on this optical information recording medium,
The principle of reproduction and erasing is basically the same as that of the optical recording medium described above. That is, as shown in FIG. 6, the heat and pressure increase generated in the light absorption layer 2a during recording softens and deforms the thermoplastic resin layer 2b in contact with the light absorption layer 2a, thereby forming pits 5. Furthermore, when data is erased in the same manner as described above, the thermoplastic resin layer 2b that formed the pits 5 is softened and deformed, and the pits 5 become 19 yuan in size, as shown in FIG.

The reason why the thermoplastic resin contained in the recording layer 2 or the softening point temperature and number of the plastic resin forming the thermoplastic resin layer 2b and the uniform molecular weight (2) are limited to the above range is as follows.

In other words, when the softening point temperature is below the above temperature range,
This is because when data is repeatedly reproduced, it becomes difficult to maintain the pits that have already been formed, and it may also be difficult to maintain the pits 5 when the temperature of the atmosphere is high. When the softening point temperature exceeds the above temperature range, it becomes difficult to form pits 5 during recording and erase recorded data, and the C/N value of the reproduced signal becomes low.

On the other hand, regarding the range of the number average molecule m of the thermoplastic resin,
is limited to the above range for the same reason. That is, when the thermoplastic resin contained in the recording layer 2 is below the above range, when the optical recording medium is stored in a normal state,
It is difficult to maintain the pit formed in 111,
This is because the recorded data will be destroyed when subjected to a slight external force. Furthermore, when the number average molecule (2) exceeds the above range, it becomes difficult to form pits 5 during recording and erase recorded data, resulting in a low C/N value of the reproduced signal.

In the optical information recording medium according to the present invention in which data is recorded, reproduced, erased, and re-recorded as described above, the pit shape after recording is similar to the pit shape of a CD formed by means such as a press. This makes it possible to reproduce signals with high laser beam reflectivity and high c/N (compared to conventional rewritable optical information recording media).

Furthermore, in the second means and the fourth means, ρ” n r
*. d, , /λ or ρ= n abs d ab
The reason why s/λ is set to 0.05≦ρ≦0.6 and the imaginary part 1 (1,. or 1. is set to 0.3 or less of the above complex refractive index) is that this range is The reason for this is that the reflectance of the laser beam is the highest, the degree of modulation of the reproduced signal is also high, and recording errors are reduced.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 schematically shows the structure of an optical information recording medium according to the first and second means described above.

That is, the recording layer 2 is formed on a transparent substrate l made of resin such as polycarbonate. Further, a light reflecting layer 3 made of a metal film is formed on this, and a protective layer 4 made of resin or the like is provided on this, thereby constructing an optical disk as shown in the figure.

As already mentioned, the recording layer 2 includes a light absorption layer that absorbs laser light, a softening point temperature of 50 to 150°C, and a number average molecule f? f M 500 to 25,000 (This is a layer formed from a mixed material of a thermoplastic resin layer in the D range, and in which these materials are uniformly dispersed.

FIG. 2 is an enlarged view of section A in FIG. 1, showing the state before recording or after erasing recording.

Moreover, FIG. 3 shows the recorded state of the same part.

FIG. 4 schematically shows the structure of an optical information recording medium according to the third and fourth means described above.

That is, on a transparent substrate 1 made of a resin such as polycarbonate, a thermoplastic resin layer 2b made of a thermoplastic resin having a softening point temperature of 50 to 150°C and a number average molecular weight of 500 to 25,000 is formed. A light absorption layer 2a made of a light absorption material that absorbs laser light is formed thereon. FIG. 5 is an enlarged view of section B in FIG. 4, showing the state before recording or after erasing recording. Also, Figure 6 shows
Shows the recorded state of the same part.

In the optical information recording media according to the third and fourth means, the thermoplastic resin layer 2b may contain a light absorbing material. Further, in order to prevent deformation of the substrate and reflective layer during recording) 1 (a hard layer may be provided between the plate and reflective layer and the eyebrows having a light absorbing material).

Note that the softening point temperature of the thermoplastic resin forming the thermoplastic resin layer 2b is preferably 80 to 150°C, and the number rlz average molecular weight is more preferably in the range of 1,000 to 20,000.

Next, examples of the present invention will be specifically described.

(Example 1) Pellet-like polycarbonate (from Teijin Chemicals (manufactured by Takagi, Panlite), width 0.8 μm, depth area 12 μm) pitch 1. Thickness 1 to irradiate 8 μm spar-shaped pregrooves A transparent substrate I made of polycarbonate and having a thickness of 2 mm was formed by injection molding.

In order to form a recording layer 2 in which a thermoplastic resin and a light absorbing material are mixed and dispersed on this substrate I, a styrene acrylic resin (
Softening point 105°c1 Number of average molecular weight meter 2500) 1.0
Dissolve 8 g in 30 ml of diisobutyl ketone and add 0.542 g of 1.1' dibutyl 3.3.3'3 to this solution.
'Tetramethyl4.5.4°5'dibenzoindica-
Bocyanin verchlorate (manufactured by Ichiki photosensitive dye C stock),
NK3219) was added, and this was coated onto the above substrate by the spin coat I method to form a recording layer 2 with a film thickness of 210 nm. In this recording layer 2, ρ=0.44, k r
e. ~0.025.

Next, on this recording layer 2, 1
A light-reflecting layer 3 made of a Cu film with a thickness of 60 nm was provided, and an ultraviolet curable resin (Daikure Clear, manufactured by Dainippon Ink and Chemicals Co., Ltd.) was spin-coated on the light-reflecting layer 3. The protective layer 4 with a thickness of 1 μm was provided by irradiating and curing ultraviolet rays.

For the optical disc manufactured in this way, λ=78
Using a 0nm semiconductor laser, linear velocity 1゜2m/S
eC&! Recording power 8.5mW 4.501<)1
z (7) The Hals signal was recorded. This disk is 1
．． Reproduction was performed using a 0 mW semiconductor laser, and when the reflected light was detected, a reproduced signal with a CNR value of 50 dB was obtained. Further, the reflectance at this time was 72.8%.

Next, a 780 nm, 2.5 mW elliptical beam is scanned over the recording pit at 1.2 m/s to erase the recorded data, and then the wavelength is 780 nm again at a linear velocity of 1°2 m/S% and a power of 8.5 mW. m semiconductor laser, 7
When five pulse signals of 20 kHz were recorded, a reproduced signal with a CNR value of 48 dB was obtained.

(Example 2) In Example 1 above, except that the transparent plate 1 was formed of polymethyl methacrylate 1 instead of polycarbonate, and the light reflective layer 3 was formed of an AI film with a thickness of 60 nm. An optical disc was manufactured in the same manner as in Example 1 above.

Note that ρ in the recording layer 2 of this optical disc is 0.44.
, k r. . =0.025.

On this optical disc, a pulse signal was recorded in the same manner as in Example 1, and when the pulse signal was reproduced and the reflected light was detected, the CNR value of the reproduced signal was 48 dB, and the reflectance was 70.5%. there were. Next, after erasing the recorded data in the same manner, the pulse signal was recorded again.
A reproduced signal with a CNR value of 48 dB was obtained.

(Example 3) In the above Example 1, record) r! The film thickness of J2 is 130
nm, that a 1100 nm thick SiO2 layer was formed between the recording layer 2 and the light reflective layer 3 by sputtering, and that the light reflective layer 3 was formed of a 60 nm thick Au film. An optical disc was manufactured in the same manner as in Example 1 above. Note that ρ in the recording layer 2 of this optical disc is 0.44, c. . =0. ．． It is 025.

On this optical disc, a pulse signal was recorded at a recording power of 8.5 mW in the same manner as in Example 1, and when the pulse signal was reproduced and the reflected light was detected, the C of the reproduced signal was
The NR value is 50 dB.

The reflectance was 76.5%. Next, after erasing the recorded data in the same manner, a pulse signal was recorded again at a recording power of 8.5 mW, and a reproduced signal with a CNR value of 47 dB was obtained.

(Example 4) In Example 1 above, a SiO2 layer with a thickness of 50 nm was formed by sputtering between the transparent substrate 1 and the optical recording layer 2, and as a light absorbing material to be included in the recording layer 2. , 0.261 g tl t' diethyl 3.3.3'
The addition of 3'tetramethylindotricapodianine barchlorate (Nippon Kanko Shokuryo 1, NK2885), the film thickness of the same recording JtP12 being set to loonm, and the difference between the recording layer 2 and the light reflecting layer 3. S with a film thickness of 1100n
An optical disc was manufactured in the same manner as in Example 1 above, except that the light layer was formed by sputtering and the light reflection layer 3 was formed of an Ag film with a thickness of 60 nm.

Note that this optical disc record II'! ρ at V2 =
0.22.1<r. . =0.200.

On this optical disc, a pulse signal was recorded at a recording power of 9.0 mW in the same manner as in Example 1, and when the pulse signal was reproduced and the reflected light was detected, the C of the reproduced signal was
The NR value is 48 dB.

The reflectance was 70.4%. Next, after erasing the recorded data in the same manner, a pulse signal was recorded again at a recording power of 9.0 mW, and a reproduced signal with a CNR value of 45 dB was obtained.

(Example 5) In the above Example 1, 1 for forming the recording layer 2
Melt plastic resin 5W 1. 0.360g of light absorbing material was added to the coating agent, and the thickness of the recording layer 2 was increased to 14.
An optical disc was manufactured in the same manner as in Example 1, except that the thickness was 0 nm. Note that ρ and krec in the recording layer 2 of this optical disc are ρ and 1 (r6° is ρ
=0.32, k ra. =0.020.

On this optical disc, a pulse signal was recorded at a recording power of 10.0 mW in the same manner as in Example 1, and when the pulse signal was reproduced and the reflected light was detected, the CNR value of the reproduced signal was 48 dB1, and the reflectance was 74. It was .4%.

Next, after erasing the recorded data in the same manner, a pulse signal was recorded again at a recording power of 10.0 mW.
A reproduced signal with a CNR value of 48 dB was obtained.

(Example 6) In Example 1 above, 1.0% of the light absorbing material was added to the coating agent in which the thermoplastic resin for forming the recording layer 2 was dissolved.
An optical disc was manufactured in the same manner as in the above example except that 0.8 g was added and the thickness of the recording layer 2 was 140 nm.

Note that ρ and kre in the recording layer 2 of this optical disc
c is p=0. 38, k ra. =0.030.

On this optical disc, a pulse signal was recorded at a recording power of 7.5 mW in the same manner as in Example 1, and when the pulse signal was reproduced and the reflected light was detected, the C of the reproduced signal was
The NR value is 54 dB.

The reflectance was 70.3%. Next, after erasing the recorded data in the same manner, a pulse signal was recorded again at a recording power of 7.5 mW, and a reproduced signal with a CNR value of 45 dB was obtained.

(Example 7) In Example 1 above, 2.0% of the light absorbing material was added to the coating agent in which the thermoplastic resin for forming the recording layer 2 was dissolved.
16g was added, and the thickness of the recording layer 2 was 40 nm.
An optical disc was manufactured in the same manner as in Example 1 above, except for the above.

Note that ρ and k r in the recording layer 2 of this optical disc
ec is ρ=0.41, k re. =0. It is 040.

On this optical disc, a pulse signal was recorded at a recording power of 7.0 mW in the same manner as in Example 1, and when the pulse signal was reproduced and the light was detected at inverse q, the CNR value of the reproduced signal was 55 d. B.

The reflectance was 70.9%. Next, after erasing the recorded data in the same manner, a pulse signal was recorded again at a recording power of 7.0 mW, and a reproduced signal with a CNR (direction of 42 dB) was obtained.

(Example 8) In the above Example 1, 1.08 g of polyamide resin (softening point 105° C., number average molecular weight fft 1500) was dissolved and used as the Ci-containing thermoplastic resin in the recording layer 2; An optical disc was manufactured in the same manner as in Example 1 above, except that the thickness of the recording layer 2 was 130 nm.

Note that ρ and l<r in the recording layer 2 of this optical disc
ec is ρ=0.37.1<,. . =0.026.

On this optical disc, a pulse signal was recorded at a recording power of IO 15 mW in the same manner as in Example 2 above, and the r
4 raws and detected the reflected light, the CNR of the reproduced signal (RA is 50 dB1, reflectance is 73.2%)
Met. Next, after erasing the recorded data in the same manner, a pulse signal was recorded again at a recording power of 10.5 mW, and a reproduced signal with a CNR value of 49 dB was obtained.

(Example 9) In the above Example I, polypropylene (softening point 130°C, number average molecular m 3000) was used as the thermoplastic resin contained in the recording layer 2, and the film thickness of the recording layer 2 was 1
An optical disc was manufactured in the same manner as in Example 1 above, except that the thickness was 40 nm and the light reflection layer 3 was formed of a Cu film with an IIQ thickness of 60 nm. Note that ρ and krec in the recording layer 2 of this optical disc are ρ=0.35, Ha2
．． . =0.026.

On this optical disc, a pulse signal was recorded at a recording power of 10.0 mW in the same manner as in Example 1, and when the pulse signal was reproduced and the reflected light was detected, the CNR value of the reproduced signal was 49 dB1, and the reflectance was 72. It was .4%. Next, after erasing the recorded data in the same manner, a pulse signal was recorded again at a recording power of 10.0 mW, and a reproduced signal with a CNR value of 47 dB was obtained.

(Example 10) A polycarbonate substrate (manufactured by Teijin Kasei Ltd., Panlite) with a thickness of 1.2 mm was used to form spiral pregrooves with a width of 0.8 μm, a depth of 0.12 μm, and a pitch of 1°6 μm. It was formed by the Shiyama Sei L() method.

On this substrate, 0.52 g of polyamide resin (softening point 105°C, average molecular size 1500) was dissolved in 20 ml of butanol, and this was spin-coated onto the above substrate 1 to a film thickness of 50 nm. A thermoplastic resin layer 2b was formed.

Furthermore, 1.1' diptyl 3.3.3'3'tetramethyl 4.5.4'5'dibenzoindinonovocyanine iodide (manufactured by Nippon Kanko Shiki Co., Ltd., NK3251)
195 mg was dissolved in 3 ml of 2-=1-ropropane, and this was applied onto the plastic resin layer 2b to give a thickness of 1 ml.
A 30 nm light absorption layer 2a was formed. This light absorption layer 2a
ρ and krec are ρ=0.45, k abs
: o, 50.

Next, on this light absorbing layer 2a, a 60 nm thick Ag film is formed as a light reflecting layer 3 by vacuum evaporation, and then on the top surface of this layer is coated with an ultraviolet curable resin (Dainippon Ink & Chemicals Co., Ltd.).
A 10-μm-thick protective layer was formed by irradiating ultraviolet rays to cure the coating.

For the disc created in this way, λ=780
A pulse signal of 450 kHz was recorded using a nm semiconductor laser at a linear velocity of 1.2 m/see and a recording power of 11.5 mW. About this disc Recording power 1. 0mW
% When reproduction was performed using a semiconductor laser with a wavelength of 7800 m and reflected light was detected, a reproduced signal with a CNR value of 52 dB was obtained. Also, the reflectance at this time is 71,
It was 5%.

After erasing the recorded data by scanning a 780 nm 2.5 mW elliptical beam at 1.2 m/s over this recording pit, the line a 1.2 m / 8% recording power 11
．． 720kHz with 5mW wavelength 780nm semiconductor laser
When I recorded 5 pulse signals of z, the CNR value was 51 dB.
A reproduced signal was obtained.

(Example 11) In the above Example IO, the transparent substrate l was formed of polymethyl methacrylate instead of polycarbonate, and 1.1' was used as the light absorbing material forming the light absorbing layer 2a.
Dibutyl 3.3.3'3"Tetramethyl4.5.4'
5” dibenzoindodicarbocyanine perchloride-1.
An optical disc was manufactured in the same manner as in Example 1, except that NK3219 (manufactured by Nippon Kanko Shiki Co., Ltd.) was used and the light reflection layer 3 was formed of an Au film. Note that ρ and k rec in the light absorption layer 2a of this optical disc
is ρ = 0.46, k abs = 0°05.

On this optical disk, a pulse signal was recorded at a recording power of 11.0 mW in the same manner as in Example IO, and when the pulse signal was reproduced and the reflected light was detected, the CNR value of the reproduced signal was 53 dB, and the reflectance was It was 72.0%. Next, after erasing the recorded data in the same manner, pulses were recorded again at a recording power of 11.0 mW.
A reproduced signal with a CNR value of 50 dB was obtained.

(Example 12) In the above Example 13, a Sio2 layer with a film thickness of 1100 nm was formed by sputtering between the light absorption layer 2a and the light reflection layer 3, and the light reflection layer 3 was formed of a Cu film. Except for this, an optical disc was manufactured in the same manner as in Example 10 above.

On this optical disc, a pulse signal was recorded at a recording power of 12.5 mW in the same manner as in Example 10, and when the pulse signal was reproduced and the reflected light was detected, the CNR value of the reproduced signal was 48 dB, and the reflectance was It was 75.6%. Next, the recorded data is d! i After leaving,
When the pulse signal was recorded again at a recording power of 12.5 mW, a reproduced signal with a CNR value of 46 dB was obtained.

(Example 13) Width 0.8μm Depth 0. 12μm Pi Tsuchi I.

Thickness 1.2 with 6μm spiral pregroove
mm polycarbonate plate (manufactured by Teijin Kasei Ltd.,
Panlite) was formed by injection molding.

0.75 g of polyamide resin was dissolved in 20 ml of butanol, Rhodamine B was added thereto, and the above substrate 1 was prepared.
A thermoplastic resin layer 2b having a thickness of 70 nm was formed on top of the substrate.

Furthermore, 1.1' dibutyl 3.3.3'3'tetramethyl 4.5.4"5'dibenzoindodicarbocyanine iodide (Nippon Kanko Shikicho Co., Ltd., NK3251) 1
50 mg was dissolved in 3 ml of 2-nitropropane and applied onto the plastic resin layer 2b to form a light absorption layer 2a with a thickness of 95 nm.

Next, on this light absorption layer 2a, a light reflection layer 3 with a thickness of 6
A 0 nm thick Cu film was formed by vacuum evaporation, and then an ultraviolet curable resin (Daichi Yo Ippon Ink Kagaku Kogyo Co., Ltd. yellow, Daicure Clear 5D-17) was spin-coated on this, and then ultraviolet curable resin was applied. was irradiated and cured, and a 10 μm protective layer was provided.

For the optical disc manufactured in this way, λ = 7
Using an 80 nm semiconductor laser, linear velocity 1.2 m/5
ees 450 kHz with recording power of 10.5 mW
The pulse signal was recorded. About this disc 1.0
When reproduction was performed using a semiconductor laser of mWs 780 nm and reflected light was detected, a reproduced signal with a CNR value of 52 dB was obtained. Further, the reflectance at this time was 69.5%.

A circular beam of 780 nm and 2.5 mW is scanned at 1.2 m/s over this recording pit to erase the recorded data, and then again at a linear velocity of 1.2 m/s and a recording power of 10.
．． When a 72.0kHz pulse signal was recorded on the recording layer 1a using a 5mW semiconductor laser with a wavelength of 780nm,
11 with a CNR value of 47dB is 111.

[Effects of the Invention] As described above, according to the present invention, a high reflectance of laser light and a reproduced signal with high C/N can be obtained compared to conventional rewritable optical information recording media. By this, C
Is there a writable optical information recording medium that complies with the D format? j7.

[Brief explanation of drawings]

FIG. 1 is a schematic half-sectional perspective view of an optical disc according to an embodiment of the present invention, enlarged in the thickness direction, and FIG. 2 is a state before recording or after erasing data, showing part A in FIG. 1. FIG. 3 is a schematic enlarged sectional view of the same portion after recording, and FIG. 4 is a schematic perspective view of a half cross section showing an enlarged thickness direction of an optical disc showing another embodiment. 5 is a schematic enlarged cross-sectional view of section B in FIG. 4 in a state before recording or after data erasure, and FIG. 6 is a schematic enlarged cross-sectional view of the same portion in a state after recording. l...Transparent substrate 2...Recording layer 2a...Light absorption layer 2b...Thermoplastic resin finger R? J 3...Light reflective layer 4...Protective layer 5...Pitt patent applicant Taiyo Yuden Co., Ltd. (company agent Patent attorney Kazuyama Hojo)

Claims (4)

[Claims] (1) Between the light-transmitting substrate 1 and the light-reflecting layer 3 that reflects laser light, there is a light-absorbing material that absorbs laser light, and a light-absorbing material that has a softening point temperature of 50 to 150°C and a number average molecular weight of 500 to 25,000 (
7) A rewritable optical information recording medium characterized by comprising a recording layer 2 mixed with a thermoplastic resin within the range. (2) In claim 1, the real part n_r_e_c of the complex refractive index of the recording layer 2 and its film thickness d_r_
ρ=n_r_e_ given by e_c and the wavelength λ of the reproduction light
cd_r_e_c/λ is 0.05≦ρ≦0.6,
A rewritable optical information recording medium characterized in that the imaginary part k_r_e_c of the complex refractive index is 0.3 or less. (3) A thermoplastic resin layer 2b having a softening point temperature of 50 to 150°C and a number average molecular weight of 500 to 25,000, between the transparent substrate 1 and the light reflection layer 3 that reflects laser light; A rewritable optical information recording medium comprising a light absorption layer 2a that absorbs laser light to generate heat and deforms the thermoplastic resin layer 2b by the heat. (4) In claim 3, the light absorption layer 2
The real part n_a_b_s of the complex refractive index of a and its film thickness d_
ρ=n_a given by a_b_s and the wavelength of the reproduction light ^
A rewritable optical information recording medium characterized in that _b_s/λ satisfies 0.05≦ρ≦0.6, and k_a_b_s in the imaginary part of the complex refractive index is 0.3 or less.