WO2006057181A1

WO2006057181A1 - Optical information recording carrier

Info

Publication number: WO2006057181A1
Application number: PCT/JP2005/020937
Authority: WO
Inventors: Seiji Nishino; Teruhiro Shiono; Hiroaki Yamamoto
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2004-11-24
Filing date: 2005-11-15
Publication date: 2006-06-01
Also published as: JP2008059616A

Abstract

An optical information recording carrier comprising a plurality of recording films onto which information is recorded by being irradiated with light having one pulse length of l pico sec through 10 nano sec from a light source, and separating films separating the recording films, wherein the recording film has in-film light loss of up to about 2% with respect to the light wavelength and mainly contains as a recording material a reaction matter between a first inorganic compound and a second inorganic compound, wherein the first inorganic compound is at least one kind selected from a group consisting of tellurium dioxide, bismuth oxide and zinc sulfide, and the second inorganic compound is an inorganic compound that acts to increase the refractive index of the recording film by forming the reaction matter with the first inorganic compound or reduce a melting point temperature or a sublimating temperature.

Description

Specification

Optical information record carrier

Technical field

[0001] The present invention relates to an optical information record carrier.

Background art

In recent years, there has been a strong demand for higher density optical information recording carriers (for example, disc carriers) as the amount of information increases.

[0003] The recording density of the optical information record carrier is proportional to (NAZ λ) ² (where λ is the recording / reproducing light source wavelength, ， is the numerical aperture of the objective lens). Therefore, in recent years, using a GaN laser with a λ force of 05 nm and an objective lens with an aperture power of 0.85, a recording density (25 GByte) that is about 6 times that of a DVD (Digital Versatile Disc) has been achieved with a 5-inch diameter disc. The technology to do is proposed.

However, methods for increasing the numerical aperture of the objective lens as much as possible and methods for increasing the recording density by shortening the recording / reproducing light source wavelength as much as possible have reached the limit.

That is, when the wavelength of the light source is shorter than 405 nm, the light transmittance of the polycarbonate substrate that has been used as the resin substrate of the conventional optical information recording carrier is rapidly lowered. In addition, composition decomposition of the resin substrate occurs due to long-time irradiation, which further reduces the light transmittance.

[0006] When the numerical aperture of the objective lens is larger than 0.85, the distance (WD) between the objective lens and the optical information recording carrier is further reduced. For this reason, the thickness of the protective film formed on the recording film is 100 m or less from the viewpoint of the WD limitation and the tilt margin of the optical information recording carrier. Therefore, when the numerical aperture of the objective lens increases, the optical information recording carrier and the objective lens easily collide. Furthermore, when the protective film is thin, the distance between the protective film surface and the signal surface of the recording film is very short, so that a little dirt on the protective film causes deterioration of the reproduction signal.

[0007] As described above, there is the above-mentioned problem when high density is achieved simply by shortening the wavelength of the light source or increasing the numerical aperture of the objective lens.

[0008] Therefore, in order to further increase the density of the future optical information record carrier, it is important to make the recording film multilayer. FIG. 6 shows a conventionally proposed optical information record carrier 100 having a multilayer recording film. It is a figure. In this optical information recording carrier 100, a three-layer light-absorbing translucent recording film 151 is formed on a substrate 153. A protective film 150 is provided on the uppermost layer, and a separation film 152 that separates the recording films 151 is formed between the recording films 151 adjacent to each other. A parallel light beam 105 from a light source (not shown) is collected by the objective lens 101, and recording is performed by irradiating the converging light 103 onto the light condensing unit 156 of a predetermined recording film 151.

Therefore, according to the optical information recording carrier on which such a multilayer recording film 151 is formed, information is recorded three-dimensionally, so that the recording density can be improved.

However, recording on the translucent recording film 151 used in this type of optical information recording carrier 100 is caused by the recording material absorbing the recording light and generating heat. Using the deformation, pits are formed in the recording film. Therefore, in the conventional optical information recording carrier 100, since the recording light is directly absorbed by the recording film 151, when the number of the recording films 151 is 4, 5 or more, the attenuation of the light increases in the lower layer, and the objective lens 101 In the lower recording layer where the surface force of the optical information recording carrier on the side is also separated, it becomes difficult to record information, and the recording capacity is limited.

[0011] In order to overcome this problem, a recording method using multiphoton absorption such as two-photon absorption is attracting attention, as opposed to the conventional recording film absorbing one photon of recording light as it is ( Non-patent literature 1, 2).

[0012] Regarding the mechanism of this recording method, the force detailed in Non-Patent Document 1 is outlined below.

[0013] In multiphoton absorption recording, since light is simply absorbed and recording pits are not formed by the heat, sensitivity is inferior to that of one-photon absorption. For this reason, a conventional semiconductor laser used as a light source for optical disc recording has insufficient output light amount, and a femtosecond (10 to ¹⁵ seconds) pulse laser is usually used. According to this femtosecond pulse laser, ultrashort pulse light with very high peak light output is output.

[0014] For example, if the oscillation pulse length is 100 femtoseconds and the pulse repetition frequency is 100 MHz, the photons are stored in the oscillation cavity as much as the time during which light is emitted is shorter than the normal continuous oscillation output. Therefore, the pulsed light output of the pulse is 10 ⁵ times higher than that of the continuous wave output Become.

Therefore, according to the femtosecond pulse laser, a very high photon density state is created.

If light in such a high photon density state is used, the nonlinear effect can be easily used. For example, the two-photon absorption generation efficiency, in which two photons are simultaneously absorbed by a substance to excite the substance, is proportional to the square of the peak light output of the light pulse. Therefore, if a short pulse laser with a peak light output of 10 ⁵ times is used, the generation efficiency of two-photon absorption is 10 ^{1 (>} times higher).

[0017] Therefore, in an optical memory in which bit data is recorded in multiple layers, data is recorded on the multilayer recording film by utilizing two-photon absorption by the femtosecond pulse laser. In normal one-photon absorption, electrons in the ground state absorb one photon with the angular frequency ω and are excited to the excited state. Data is recorded by changes in the recording material due to heat generated when returning from the excited state to the ground state, for example, refractive index change, phase change, thermal drilling, and the like. In contrast, the two-photon absorption recording material does not absorb (excites) at the optical angular frequency ω, and uses a material that absorbs at the optical angular frequency ω (ω = ω / 2). Now space

twenty two

When the photon density increases (the light output increases), the ground state electrons in the recording material absorb light of the optical angular frequency ω twice at the same time and are excited by ω. At this time, the material absorbs light

2

Force to be generated Excited state force When returning to the ground state, heat is generated in the same way as one-photon absorption, and data is recorded.

Therefore, the structure of the optical information record carrier using multiphoton absorption is the same as the structure of the multilayer optical information record carrier shown in FIG. 6, but the recording film with respect to the wavelength of one photon of the recording light. Is almost transparent. In the recording using the conventional light absorption described above, light is absorbed by the recording film to generate heat. In multiphoton absorption recording, a recording light condensing portion (a portion where the electric field strength of light is high) Only at the focal point of the recording light and in the vicinity thereof, electrons of the recording material are excited by a plurality of photons and light absorption occurs. In addition, multiphoton absorption does not occur except in the condensing part. As described above, in the case of multiphoton absorption recording, the recording film is substantially transparent to the wavelength of one photon of the recording light. The recording light reaches the film sufficiently. For this reason, according to the recording method using multiphoton absorption, the number of recording films is much larger than that of a multilayer optical information recording carrier using conventional recording films. It is possible to use an optical information record carrier. For example, in the conventional multilayer optical information record carrier, the maximum number of recording films is about 8, but in an optical information record carrier using a recording material for multiphoton absorption recording, about 20-50 layers are recorded. A membrane is also possible.

[0019] Therefore, various organic materials and inorganic materials shown in Non-Patent Document 1 have been studied as recording materials for such multiphoton absorption recording. Among these materials, inorganic materials can be produced with a simple film-forming device, and many of them are relatively highly sensitive to two-photon absorption recording, so they are actively researched and developed. .

[0020] However, as described above, the multiphoton absorption recording has a very low sensitivity because it is not a method of recording by simply absorbing light and generating heat unlike the conventional light absorption recording. Therefore, the biggest drawback of multiphoton absorption recording is that a femtosecond pulse laser having a high output is required as a recording light source.

For example, when quartz glass is used as a recording material, a pulse length of 120 femtoseconds and an optical output on the recording film of 1.33 MW are required. Therefore, a recording film containing such a recording material can be recorded only with a titanium sapphire laser, and is a recording method with little practical use for consumer use. This is because the femtosecond pulse laser has a short oscillation time, but the optical electric field strength at the time of oscillation is very strong (peak light output 45 MW), and the semiconductor laser itself is easily broken at that electric field strength.

[0022] Therefore, the present inventors have proposed an optical information record carrier comprising a recording film containing an inorganic compound such as tellurium dioxide for the purpose of recording with a low-power laser such as a semiconductor laser ( Patent Document 1).

[0023] However, for high-density recording, a recording material that is further excellent in sensitivity of multiphoton absorption recording is desired. In addition, when multiphoton absorption recording using a low-power laser is used, the amount of light in the lower layer portion of the multilayered recording film is insufficient, so it is necessary to consider light loss in the upper layer portion.

Non-Patent Document 1: "3D optical memory using femtosecond laser", Yoshimasa Kawada, OPTRONIC S (2001) No.l l, PP138-142

Non-patent document 2: Three-Dimensional uptical Data Storage in Vitreous bilica, Watan abe, Misawa et.al, JJAP Vol.37 (1998) PP.L 1527- L1530 Patent Document 1: Publication of WO2004Z030919

Disclosure of the invention

[0024] In the multiphoton absorption recording described above, the present invention uses light having a pulse length of 1 picosecond or more and 10 nanoseconds or less when a femtosecond pulse laser is used as recording light, and on the recording film during recording. It is an object of the present invention to provide an optical information recording medium capable of recording with high sensitivity even with a low-power laser whose optical output is about 1 W or less.

[0025] The present invention provides a plurality of recording films on which information is recorded by irradiating light having a pulse length of 1 picosecond or more and 10 nanoseconds or less from a light source, and a separation film that separates the recording films An optical information recording carrier, wherein the recording film has an in-film light loss of about 2% or less with respect to the wavelength of the light, and the first inorganic compound and the second inorganic component as main components A reaction product of a compound is contained as a recording material, and the first inorganic compound is at least one selected from the group force of tellurium dioxide, bismuth oxide, and zinc sulfate, and the second inorganic compound is An optical information recording carrier, which is an inorganic compound that functions to increase the refractive index of the recording film by forming the reaction product with the first inorganic compound or to lower the melting point temperature or the sublimation temperature. is there.

The objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

Brief Description of Drawings

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing the recording sensitivity evaluation results of the recording material.

[FIG. 3] FIG. 3 is a diagram showing a state of an experiment conducted for confirming recording on an optical information record carrier.

[Fig. 4] Fig. 4 shows the electron microscope observed from the direction of the SiO film after recording the experiment shown in Fig. 3.

2

It is a mirror photo.

FIG. 5A and FIG. 5B are diagrams showing the relationship between the recording film thickness and the transmittance of the optical information record carrier.

FIG. 6 is a diagram showing an example of a conventional optical information record carrier.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention has a light output on a recording film of about 1 W or less that can be easily realized with a low-power light source such as a semiconductor laser without using a femtosecond pulse laser that has been used in conventional multiphoton absorption recording. This is the result of a study to obtain a recording film that can be recorded with light having a pulse length of 1 picosecond or more and 10 nanoseconds or less.

FIG. 1 is a schematic view showing an embodiment of an optical information record carrier according to the present invention. The optical information recording carrier 10 of the present embodiment has a multilayer recording film 51 (20 to 50 layers) on a substrate 53 and a UV film having a thickness of 2 for separating the recording film 51 between the adjacent recording films 51. A separation membrane 52 made of resin is formed, and a protective membrane 50 is formed as the uppermost layer.

In examining the present invention, first, the recording sensitivity of a recording film containing various inorganic compounds for multiphoton absorption recording as a recording material was evaluated. For the evaluation, a YAG laser with a second harmonic wavelength of 532 nm (pulse length: 6 nanoseconds, repetition frequency: 10 Hz) was used as the recording light source. Then, as shown in FIG. 1, the parallel light beam 5 emitted from this laser (not shown) is focused on the condensing part 6 of the predetermined recording film 51 by the objective lens 1 having a numerical aperture of 0.8. Irradiated to collect light. After pits are recorded on the recording film 51 with recording light of various light outputs by drilling type gradation recording, the recording state of the formed pits is observed, and the optimum light output for recording of each recording material is measured. It was done.

[0031] FIG. 2 shows the evaluation results of the recording sensitivity of the inorganic compound used for the representative multiphoton absorption recording selected for this experiment.

[0032] The MgF film is almost as low as the TeO film!

twenty two

However, as shown in Fig. 2, such a phenomenon was not observed in this experiment. Of the inorganic compounds measured, the most sensitive film was ZnS. According to measurements, ZnS had the highest refractive index of 2.35 among the selected materials. ZnS is characterized by a high melting point (1700 ° C) but a low sublimation temperature (1180 ° C). For this reason, the temperature plotted as V for ZnS in FIG. 2 is the sublimation temperature.

[0033] From this experimental result, in the abrasion recording for the recording film containing the inorganic compound for multiphoton absorption recording as the recording material, the low refractive index, low melting point or low sublimation point shown in the direction of the broken line arrow in FIG. It became clear that the higher the sensitivity, the more inorganic compounds. [0034] The reason is considered as follows. In other words, it is speculated that the higher the refractive index material, the higher the sensitivity tends to be because the main absorption heat source is thermally relaxed by two-photon absorption excitation. Although there are few published examples of the two-photon absorption cross-section for incident light with a wavelength of 532 nm, the third harmonic has an intensity proportional to the third-order nonlinear constant (% ^(¾ ) due to the electric field of the incident light acting on the recording material. Is assumed to be absorbed in the recording film and generate heat, the third-order nonlinear constant (χ ⁽³⁾ ) is proportional to the fourth power of the first-order nonlinear constant ( ⁽¹⁾ ) from Miller's equation. Therefore, if the first-order nonlinear constant () that depends on the refractive index increases, the third-order nonlinear constant (c ( ³ )), which is the light absorption characteristic, increases. It is considered that a recording material having a high two-photon absorption cross section is selected.

[0035] The melting point and sublimation point can be considered as follows. When light with a pulse length of 1 picosecond or more and 10 nanoseconds or less used in this experiment is used as recording light, free electrons excited by two-photon absorption are more continuous than when using a femtosecond pulse laser. It is thought that it is accelerated by the optical electric field. Because it collides with electrons in the impurity level while having this accelerated energy, it is assumed that free electrons multiply even more than recording with a femtosecond pulse laser despite the use of low-power light. . Therefore, unlike the conventional way of thinking, it is considered that the recording with the light of the nanosecond pulse which is the object of the present invention is much more sensitive than the recording with the femtosecond pulse.

[0036] Next, the applicability to abrasion recording by perforating a recording film having such a recording material force was examined. In order to clarify the recording mechanism of the recording film, as shown in Fig. 3, the stress in the recording film due to the abrasion phenomenon is used instead of the separation film made of UV resin on the 250 nm thick diacid / tellurium film. 200 nm thick SiO

2 A sample with a film formed on it. FIG. 4 is an electron micrograph of the sample observed from the SiO film side after recording with the same recording light as described above, with the light output changed. Copy of Figure 4

2

The crack and large shape pit shown by B in the middle of the center show the area recorded with excessive light output, and one shape shown by A in the upper part shows the expansion of the recorded pit with the optimum light output. Showing In Fig. 4, the swelling of the SiO film seen in the optimal recording part of A is about 30η.

2

It is m-convex and pits with clear outlines are formed. It was also confirmed that clear recording pits were formed with optimum light output even in samples with the same structure and a UV resin layer as the separation film. It was.

[0037] From this result, when a signal is recorded on the recording film with recording light having a wavelength transparent to the recording film having a pulse length of 6 nanoseconds (in this example, light of 532 nm), the recording film Ablation occurred due to heat scattering, which confirmed the recording of pit-like signals. In addition, this abrasion phenomenon has the power to distort the SiO film.

2

4 is understood. Therefore, the recording of the signal on the recording film by the abrasion phenomenon is a phenomenon in which the surface material of the recording film is scattered by a strong light beam. If there is a separation film on the recording film, the scattering is suppressed and the recording sensitivity is lowered. Previously conceived, this experiment has shown that the recording sensitivity does not drop significantly even if there is a resin layer that separates the recording film on the recording film. For this reason, the ablative recording of the recording material used in the above experiment has sufficient practicality as a recording method for a multilayer optical information record carrier.

[0038] Based on the above knowledge, the recording material used in the optical information recording carrier of the present invention is at least one inorganic material selected from the group consisting of tellurium dioxide, bismuth oxide, and zinc sulfate. A second inorganic compound that acts as a first inorganic compound and increases the refractive index of the recording film or lowers the melting point or sublimation point when used in combination with the first inorganic compound as the main component. If the reaction product obtained from the above is used as a recording material, a highly sensitive recording film with multiphoton absorption can be obtained, and the recording density can be reduced by using a semiconductor laser with a low nanosecond pulse without using an ultrashort pulse laser. It has been found that a higher density can be achieved.

[0039] Such a second inorganic compound is preferably an inorganic compound having at least the function of increasing the refractive index of the recording film, as long as it is an inorganic compound having one of the functions described above. Preferable examples of the second inorganic compound specifically include at least one selected from, for example, lead oxide, bismuth oxide, zinc sulfate, vanadium oxide, and acid cadmium power. The second inorganic compound includes one overlapping with the first inorganic compound. In that case, a different kind of inorganic compound is used as the second inorganic compound. In the present invention, the first and second inorganic compounds may be a mixture of inorganic oxides having different valences. For example, acid lead is in the form of PbO, PbO, etc.

3 4

It can be used alone! /, Or two or more can be combined. [0040] Among the combinations of the first inorganic compound and the second inorganic compound, the first inorganic compound has a high refractive index and a low melting point, dihydrogen tellurite, and the second inorganic compound has a large refractive index. A combination of lead oxides that is expected to increase is preferable. In addition, glass materials to which lead oxide is added have a lower melting point, so a lower melting point is also expected.

[0041] The reason why the recording film is made highly sensitive by using a reaction product obtained by using the second inorganic compound in combination with the first inorganic compound as a recording material is not necessarily clear. However, it is presumed that the electron density of the reaction product obtained is higher than the electron density of the first inorganic compound alone. For example, since lead oxide is a higher density material than tellurium dioxide and is a dielectric material that generates more free electrons when an electric field with a higher electron density is applied, the reaction product of tellurium dioxide and lead oxide is better than tellurium dioxide. It is considered that the refractive index is high. Therefore, when light is applied to the reaction product of the first inorganic compound and the second inorganic compound having a high electron density and an electric field of light is applied, electric charges are likely to be generated. It is speculated that it will become a material!

In the present invention, the amount of the second inorganic compound for forming the reactant as the recording material improves the characteristics such as the refractive index necessary for achieving high sensitivity. When the total amount of the inorganic compound 1 and the second inorganic compound is 100 parts by mass, 10-40 parts by mass is preferable, and 15-20 parts by mass is more preferable. When the amount of the second inorganic compound is 50 parts by mass or more, the reaction product obtained does not vitrify and tends to crystallize, which is not preferable as a recording film for an optical information recording carrier.

[0043] In the production of the recording film of the present invention, a known method for producing a recording film is used. Specifically, for example, a mixture in which a first inorganic compound and a second inorganic compound are mixed at a predetermined ratio is prepared, and the reactant is coated on the substrate by sputtering, vapor deposition, or the like using this mixture as a target. Is applied to form a recording material. In this case, the first and second inorganic compounds may be different targets. Deposition conditions for the recording film formed by evaporation, to the extent of the order of the degree of vacuum is 10 ^_6 mmTorr, the evaporation rate is 0. 1 to 0. 5 nm Z seconds, substrate heating temperature is 15 to 60 ° C Is preferred. Note that the obtained recording material is a reaction product of the first inorganic compound and the second inorganic compound, as observed by observation with an electron microscope or the like. This is confirmed by the fact that the formed recording material is amorphous. For example, in the lead tellurium dioxide monooxide system, crystals of acid lead are confirmed in the recording film obtained by the vapor deposition method.

. In the film formation, other optional components may be added. However, in order to increase the sensitivity of two-photon absorption, the recording can be obtained by substantially using only the first inorganic compound and the second inorganic compound. A membrane is preferred.

[0044] Although a recording material was selected based on the above results, recording light is condensed on an optical information recording carrier having a plurality of recording films containing such a recording material, and ablative recording is performed on the recording film. In this case, it is necessary to consider the optical loss in the recording film, the diffraction loss due to the perforated recording pits, and the reflection loss at the interface between the recording film and the separation film. That is, in order to obtain high transmittance in multiphoton absorption, a recording material that is transparent to the wavelength of one photon is desired. However, depending on the raw material, the film formation environment, the obtained recording film is slightly smaller than the wavelength of one photon. Has absorption. Further, in the present invention, a recording film of 20 layers or more is multilayered for high-density recording, and a low-power light source is used. Therefore, recording pits are formed in the upper recording film on the light source side. When formed, light is diffracted in the recording pit portion, so that the intensity of the light reaching the lower recording layer is weakened. Furthermore, the intensity of light reaching the lower layer is also reduced by reflection at the interface between the recording film and the separation film. Multi-photon absorption recording requires a high amount of light at the condensing part, so it is necessary to reduce the light loss as described above and secure a sufficient amount of light for multi-photon absorption to occur in the lower layer part. There is.

On the other hand, when an apparatus for recording / reproducing an optical information record carrier is considered, the intensity of the recording light required for the lowermost recording film or the light output of the reproducing light is about that of the uppermost recording film. If it is 70% or more, it has been found that the variation in the amount of light in this range can be sufficiently adjusted by a conventional optical disc recording / reproducing apparatus. Therefore, if the thickness of the recording film is set so as to satisfy the above relationship, the amount of light necessary for two-photon absorption recording is secured in the lower layer portion. In addition, the above optical information record carrier can provide complete compatibility with conventional optical discs.

[0046] FIGS. 5A and 5B show the results of studies on the thickness and transmittance of the recording film based on the above findings. Each figure shows the degree of optical loss per layer when ablative recording is performed on each recording film having a different refractive index. The effect of the presence or absence of recording pits is that there is an optical electric field in the track groove direction between recording films without recording pits (without pits) and recording films with recording pits. It was evaluated by the transmittance in the case (TE) and the case where the optical electric field is perpendicular to the track groove (TM).

FIG. 5A shows the evaluation result of the optical information recording carrier in which the refractive index of the recording film is 2.35 and the refractive index of the UV resin of the separation film is 1.55, and FIG. This is an evaluation result of an optical information recording carrier in which the refractive index is 2.15 and the refractive index of the UV resin of the separation membrane is set to 1.55. When light reaches the lowermost recording film with a multilayer optical information record carrier, the total optical loss is higher than that, so the total loss is 30% or less (i.e., transmission through the 20th layer). If the rate is 70% or higher)

[0048] Therefore, in the 20th recording film, ²⁰ f (0.7) is obtained, so that the transmittance per layer is required to be 98.2% or more. For this reason, the in-film optical loss per recording film layer is set to about 2% or less. From FIG. 5A, it can be seen that the film thickness of the recording film that can obtain this transmittance is about lOnm or less. Therefore, for example, in the case of performing recording on a recording film containing zinc sulfate as a recording material, the thickness of the recording film per layer is set to about lOnm or less.

Similarly, in the recording film of FIG. 5B, the thickness of the recording film per layer is set to about 15 nm or less. For example, in the system of diacid-tellurite-lead-based (82% by mass of TeO and 18% by mass of PbO) produced in the experimental example, the refractive index is 2.15. Recording film is laminated

2 3 4

In this case, the thickness of each recording film is set to about 15 nm or less.

[0050] If the film thickness of each recording film is set, the optical loss in the film can be almost ignored even when the recording film has 20 layers or more. In addition, if such a thin recording film is used, the residual stress caused by the multi-layered recording film is also reduced, and when the disk carrier is used, the warp of the disk can be suppressed to an allowable range. In consideration of the manufacturing method, the thickness of the recording film is preferably about 5 nm or more.

[0051] As described above, the present invention uses a reaction product obtained from a specific inorganic compound as a recording material, so that a recording film having a high sensitivity of two-photon absorption even with a nanosecond pulsed low light source. And an optical information recording carrier having a high recording density can be obtained. Furthermore, if the recording film is very thin per layer, the loss of transmitted light is reduced, and the recording film below the multilayered recording film has a sufficient amount of light for two-photon absorption. As well as ensuring, the distortion caused by the residual stress of the recording film is suppressed. The recording film of the present invention is a sputtering method. In addition, since it can be manufactured by a conventional method such as a vapor deposition method, the manufacturing cost is also reduced.

[0052] This application claims priority based on Japanese Patent Application No. 2004-338423 filed on November 24, 2004, the contents of which are incorporated herein by reference.

[0053] Hereinafter, the present invention will be described in more detail by way of experimental examples. However, the following experimental examples are not intended to limit the present invention, and it is not possible to change the design in accordance with the gist of the preceding and following descriptions. Is also included in the technical scope of the present invention.

Experimental example

As a recording film for comparison, a pure TeO film was produced. Diacid gel as a target

2

Le was used. In order to prevent oxygen deficiency during film formation, a TeO recording film was formed on a glass substrate by an oxygen reactive sputtering method with a film formation time of 20 minutes. This recording film has a wavelength of 53

2

The refractive index is 2.07 so that the optical loss in the recording film is negligible for 2 nm light. The recording film thickness was set to 200 nm in order to evaluate the loss for about 20 layers.

[0055] Next, a separation film having a UV resin layer strength of 10 m in thickness was formed on the TeO recording film.

2

A specific sample was made. A YAG laser with a second harmonic wavelength of 532 nm (pulse length: 6 nanoseconds, repetition frequency: 10 Hz) was used as the light source. The light from the light source was focused on the separation film side force recording film of the contrast sample by the objective lens (number of apertures: 0.8), and a recording experiment was conducted.

[0056] The light output on the recording film necessary for recording of this recording film was 2W.

[0057] Next, in order to further increase the sensitivity of the TeO recording film, Pb 2 O is mixed as the second inorganic compound.

2 3 4 A recording film was fabricated using the combined target. As a target, a mixture in which 82 parts by mass of Te 2 O and 18 parts by mass of Pb 2 O were mixed well in a mortar was prepared.

2 3 4

[0058] The prepared mixture was placed in a lOcc crucible vessel made of alumina. The container was heated in vacuum using a tungsten coil, and vapor deposition was performed on a glass substrate at a rate of about 0.1 nm per second for about 30 minutes to produce an amorphous recording film having a thickness of 200 nm. When the refractive index of the recording film and the optical loss in the film were measured with an ellipsometer, the refractive index increased by 0.8 from the contrasting TeO film to 2.15 for light with a wavelength of 532 nm. , Light loss in the film

2

Loss was less than 0.1%. Next, similarly to the comparative sample, a recording film having a UV resin layer strength of 10 m was formed as a separation film on the recording film, and a sample for evaluation was produced. Recording experiments were performed with the same light source as above. As a result, the optical output on the recording film necessary for recording decreases to 0.9 W, and TeO

2 It was confirmed that the sensitivity was higher than that of a single recording film.

In the above experimental example, the present invention can also be applied to a recording method in which recording is performed by changing the refractive index of the recording material by selecting the force recording material in which recording is performed by punching type abrasion recording. .

[0061] As described above, the present invention includes a plurality of recording films on which information is recorded by irradiating light having a pulse length of 1 picosecond or more and 10 nanoseconds or less from a light source, and the recording film. An optical information recording carrier comprising a separation film to be separated, wherein the recording film has an in-film light loss of about 2% or less with respect to the wavelength of the light, and is a first inorganic compound as a main component And a reaction product of the second inorganic compound as a recording material, and the first inorganic compound is at least one selected from the group consisting of tellurium dioxide, acid bismuth, and zinc sulfate. The second inorganic compound acts to increase the refractive index of the recording film or to lower the melting point temperature or the sublimation temperature by forming the reaction product with the first inorganic compound. It is an optical information recording carrier that is an inorganic compound.

[0062] According to the present invention, since a highly sensitive recording film can be obtained, an optical information recording carrier in which the recording film is multilayered has a pulse length of 1 picosecond or more and 10 nanoseconds or less, and has a low performance. Even if this laser is used as a light source, high-density recording is possible by multiphoton absorption recording.

[0063] In the present invention, the second inorganic compound is at least different from the first inorganic compound selected from the group consisting of lead oxide, bismuth oxide, zinc sulfide, vanadium oxide, and acid cadmium power. One kind of inorganic compound is preferred.

[0064] Since the second inorganic compound is excellent in improving the above-described characteristics, a highly sensitive recording film can be obtained.

Furthermore, in the present invention, the recording film preferably has a thickness of about 15 nm or less.

[0066] With the above-described thin recording film, even when 20 or more recording films are laminated, the light loss in the upper layer portion is reduced, so that a sufficient amount of light to cause multiphoton absorption in the lower layer portion is achieved. Is secured. In the present invention, recording on the recording film is performed by two-photon absorption recording, which is one of multiphoton absorption.

[0068] According to the recording method described above, three-dimensional recording on a multilayered recording film is possible, and high recording density is achieved.

[0069] In the present invention, a laser having a light output on the recording film of about 1 W or less is used as the light source.

[0070] Since the present invention is an optical information recording carrier having a highly sensitive recording film, high-density recording is possible even with a low-power laser.

Industrial applicability

[0071] According to the optical information recording carrier of the present invention, recording is possible even when a low-power semiconductor laser or the like is used as a light source. Therefore, it can be used for a high recording density optical information record carrier capable of three-dimensional recording.

Claims

The scope of the claims

[1] Optical information comprising a plurality of recording films on which information is recorded by irradiating light having a pulse length of 1 picosecond or more and 10 nanoseconds or less from a light source, and a separation film for separating the recording film A record carrier,

The recording film has an in-film light loss of about 2% or less with respect to the wavelength of the light, and contains a reaction product of a first inorganic compound and a second inorganic compound as main components as a recording material,

The first inorganic compound is at least one selected from the group consisting of tellurium dioxide, bismuth oxide, and zinc sulfide,

The second inorganic compound is an inorganic compound that functions to increase the refractive index of the recording film or to lower the melting point temperature or the sublimation temperature by forming the reaction product with the first inorganic compound. Is,

Optical information record carrier.

[2] The second inorganic compound is at least one inorganic compound different from the first inorganic compound selected from lead oxide, bismuth oxide, zinc sulfide, vanadium oxide, and acid cadmium power. Item 4. The optical information record carrier according to Item 1.

3. The optical information record carrier according to claim 1, wherein the recording film has a thickness of about 15 nm or less.

4. The optical information record carrier according to claim 1, wherein the record is a two-photon absorption record.

5. The optical information record carrier according to claim 1, wherein the light source is a laser having an optical output of about 1 W or less on the recording film.