JP2000285506A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a constant and stable distance between a near-field light generator and a medium regardless to the changes in the ambient temp. by forming a recording layer to record information and a surface layer having higher hydrophobicity than the recording layer on the surface of the recording layer. SOLUTION: A recording layer 52 comprising a cyanine dye to record information is formed by a spin coating method on a glass substrate 51, and a surface layer 53 comprising a poly-methyl methacrylate having higher hydrophobicity than the recording layer 52 is formed on the recording layer 52. A near-field light emitting part is disposed in the proximity of the surface side of an optical recording medium 5. When the information is recorded, reproduced or erased in the optical recording medium 5, the distance between the near-field light emitting part and the optical recording medium 5 is detected and controlled while the optical recording medium 5 is rotated and driven. Since the surface layer 53 is hard, the surface 5a of the optical recording medium is hardly damaged by collision with the near-field light emitting part, and thereby, inhomogeneous state of hydrophobicity of the surface 5a is hardly caused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium for performing near-field optical recording, reproduction, and / or erasing of information using near-field light.

[0002]

2. Description of the Related Art When an optical recording medium is irradiated with light, information is recorded on the medium, information is reproduced (read) from the medium, and / or information on the medium is erased. In some cases, near-field light is used for recording, reproducing, and / or erasing such information. Since near-field light recording, reproduction and / or erasing of information uses near-field light which is not restricted by the “diffraction limit of light”, recording, reproducing and erasing of information in units smaller than the wavelength of light is performed. It is noted that it can be done. For example, Applied Physics Letters: 61,1
42,1992 (published by the American Institute of Physics) describes recording information on a magneto-optical recording medium using near-field light. No. 5,288,99.
No. 8 describes a photoresist process using near-field light.

[0003] By the way, "near-field light exists only in the vicinity of the near-field light generator, and the intensity of the near-field light largely depends on the distance from the near-field light generator."
It has the characteristic. Therefore, information is recorded (or information is recorded) in order to stably record, reproduce, and erase information on a medium using near-field light.
It is necessary to maintain the distance between the surface of the optical recording medium and the near-field light generator at a constant distance in the area near the near-field light generator.

[0004] The following two methods are known as typical methods for controlling the distance between the medium surface and the near-field light generator to be constant within a region near the near-field light generator. That is, the first method detects the distance between the near-field light generating device and the surface of the medium, and feeds back the driving means for changing the position of the near-field light generating device or the medium based on the detected value. This is a method for controlling the distance between the near-field light generating device and the medium surface. As means for detecting the distance between the near-field light generating device and the medium surface, there are a tunnel current method (for example, US Pat. No. 5,138,159), an atomic force method (for example, JP-A-8-106646), The shear force method (see, for example, US Pat. No. 5,254,854)
No.) is known.

The second method is the same as the method used for controlling the distance between a recording head and a magnetic recording medium in a hard disk device (magnetic recording device), and the medium surface is moved at a constant speed. It is operated (moved), and the distance between the near-field light generator and the medium surface is controlled by the levitation force of the near-field light generator due to the air flow generated between the near-field light generator and the medium surface at that time. is there. In most cases, this air flow method does not require a means for detecting the distance between the near-field light generating device and the medium surface.

[0006]

However, in either of the above two methods, a near-field light generating device and a near-field light generating device are used when near-field light recording, reproduction and erasing of information on an optical recording medium by near-field light are performed. Since the surface of the medium must be very close to the medium, the change in the surface state of the medium has a great effect on distance control. According to the study by the present inventor, the first method has a problem that the distance detected by the distance detecting means varies (including an error) due to ambient environmental fluctuations, especially ambient humidity fluctuations, and the distance cannot be controlled properly. Occurs.
In the latter second method, the flow of air generated between the near-field light generating device and the medium surface fluctuates due to ambient environmental fluctuations, particularly ambient humidity fluctuations. There is a problem that the distance cannot be controlled properly. Such a problem arises because the distance between the near-field light generating device and the surface of the medium must be very short, and when the distance between the two may be relatively large, If the order is larger than the wavelength of
The influence of the change in the surface state of the medium on the distance control is small.

Accordingly, the present invention is directed to an optical recording medium for performing near-field optical recording, reproduction, and / or erasing of information by using near-field light. Stabilize and stabilize the distance between the near-field light generating device and the medium irrespective of environmental fluctuations, especially ambient humidity fluctuations, and perform near-field optical recording, reproduction and / or erasure of information stably. An object of the present invention is to provide an optical recording medium that can perform the above-described operations.

[0008]

Means for Solving the Problems The inventors of the present invention have repeatedly studied to solve the above-mentioned problems, and have been concerned with performing near-field optical recording, reproduction and / or erasing of information on an optical recording medium using near-field light. However, since the near-field light generator and the medium surface must be very close to each other, where the surface condition of the medium greatly affects the distance control, the surrounding environment, especially the surrounding environment, is improved by improving the hydrophobicity of the medium surface. Has been found to be less susceptible to the effects of humidity. This is presumably because the amount of water adsorbed on the surface of the medium, which has been affected by fluctuations in the surrounding environment, particularly, the surrounding humidity, is hardly affected by the surrounding environment, particularly, the surrounding humidity.

The present invention is based on this finding,
In order to solve the above problems, the following first and second optical recording media are provided. (1) First optical recording medium Near-field optical recording, reproduction and / or information using near-field light
An optical recording medium for erasing, comprising a recording layer for recording information, and a surface layer having a higher hydrophobicity than the recording layer is provided on a surface of the recording layer. Medium. (2) Second optical recording medium Near-field optical recording, reproduction and / or information using near-field light
An optical recording medium for erasing, comprising a recording layer for recording information, wherein the recording layer is a layer having enhanced hydrophobicity. The "optical recording medium for performing near-field optical recording, reproduction and / or erasing of information" includes an optical recording medium capable of performing near-field optical recording, reproducing and erasing of information, and information already recorded in near-field optical recording. And any optical recording medium capable of near-field light reproduction of the information.

In the first and second optical recording media according to the present invention, when information is recorded, reproduced, and / or erased by near-field light, the near-field light emitting portion of the near-field light generating device is arranged in proximity. You. Then, information is recorded, reproduced and / or erased by near-field light generated in a region near the light emitting portion. According to the first optical recording medium of the present invention, the surface layer of the recording layer for recording information is provided with a surface layer having a higher hydrophobicity than the recording layer. According to the recording medium, the hydrophobicity of the recording layer for recording information is enhanced, so that the influence of ambient environmental fluctuations, particularly ambient humidity fluctuations, on the surface state of the medium is suppressed, and the surface state of the medium is made uniform. Thus, the distance between the near-field light generating device, particularly the near-field light emitting unit, and the near-field light emitting unit can be made constant and stable. This records information,
When reproducing and / or erasing, the distance between the near-field light generating device, particularly the near-field light emitting unit, and the medium is kept constant and stable irrespective of changes in the surrounding environment, particularly, changes in the ambient humidity. And the near-field optical recording, reproduction and / or erasure of information can be performed stably.

In the second optical recording medium of the present invention, the hydrophobicity of the recording layer can be increased to such an extent that such advantages can be obtained. As a scale representing the degree of hydrophobicity, for example, a water contact angle can be mentioned. When the degree of hydrophobicity is expressed using a water contact angle, the degree of hydrophobicity of the recording layer can be exemplified by a water contact angle of 50 degrees or more.

The water contact angle is defined as an angle between a water droplet attached to a flat surface of a layer to be evaluated for hydrophobicity and a tangent to a water droplet at a point where the water droplet intersects the surface of the layer with the surrounding gas. Of these, the angle on the water drop side is defined as the water contact angle. In this case, the water contact angle is represented by 0 to 180 degrees, and the larger the angle, the higher the hydrophobicity.

In the first and second optical recording media of the present invention,
When information is recorded, reproduced, and / or erased by near-field light, a near-field light generating device is arranged close to the device. Therefore, in some cases, the near-field light generating device may collide with the medium surface. If the surface of the medium is damaged by the collision, the degree of hydrophobicity of the surface becomes non-uniform, and if the influence of the damage is transmitted to the recording layer, errors in recording, reproducing, and erasing of information are caused by the influence. Easy to cause. Therefore, it is desirable that the surface of the medium, that is, the surface layer in the first optical recording medium and the recording layer in the second optical recording medium are as hard as possible.

In the first optical recording medium of the present invention, materials usable for the surface layer include polymethyl methacrylate, polyethylene, polystyrene, polyimide, diamond-like carbon and the like from the viewpoint of hydrophobicity and hardness. Can be exemplified. In addition, in the second optical recording medium of the present invention, examples of a material that can be used for the recording layer include a material in which a cyanine dye is dispersed in a polyethylene resin from the viewpoint of hydrophobicity and hardness.
Comparing the materials of the surface layer and the recording layer, the surface layer is harder than the recording layer. This can provide a surface protection effect in a general sense.

A control method for maintaining the distance between the near-field light generating device applicable to the first and second optical recording media according to the present invention and the surface of the medium at a constant distance in the vicinity of the near-field light generating device. And means for detecting the distance between the near-field light generating device and the medium surface, and applying feedback to the driving means for changing the near-field light generating device position or the medium position based on the detected value. A method and means for controlling the distance between the near-field light generating device and the medium surface, and moving the medium surface at a constant speed, and the proximity by the air flow generated between the near-field light generating device and the medium surface A method and means for controlling the distance between the near-field light generating device and the medium surface by the levitation force of the field light generating device can be exemplified. In the method and means for controlling the distance between the near-field light generating device and the medium surface based on the detected distance value, the distance detecting device for detecting the distance between the two includes a tunnel current method, an atomic force method,
An example of a distance detection device using a shear force method or the like can be given.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an optical recording / reproducing apparatus for accommodating an example of an optical recording medium according to the present invention. The optical recording / reproducing apparatus shown in FIG.
00, the optical recording medium storage unit 200, the distance detection device 300,
Near-field light generator drive unit 400, reproduction information detection device 50
0a, 500b, a control unit CONT, etc., to perform any of near-field optical recording, reproduction, and erasure of information with the near-field light L on the optical recording medium 5 accommodated in the optical recording medium accommodation unit 200. Can be. That is, at the time of information recording or erasing, the near-field light L for information recording or the near-field light L for information erasing based on the recording information from the control unit CONT is transmitted from the light emitting unit 4 of the near-field light generating device 100 to the medium 5. To the surface 5a of the medium 5 to record or erase information on the medium 5. In reproducing information, near-field light L for reproducing information is irradiated from the light emitting unit 4 of the near-field light generating device 100 to the surface 5a of the medium 5 by an instruction signal from the control unit CONT, and reflected by the surface 5a of the medium 5. The reflected light 9 or transmitted light 6 transmitted through the medium 5 is detected by the reproduction information detecting device 500a or 500b, and the information is reproduced. In any case of recording, reproducing, and erasing of information, the distance between the medium 5 and the light emitting unit 4 of the near-field light generating device 100 described later is controlled by the control unit CONT based on the value detected by the distance detecting device 300. Is controlled.

The near-field light generating device 100 includes an Ar ion laser light source 1, an optical coupling device 3, and a near-field light emitting unit 4. The laser light source 1 is connected to the control unit CONT, and can emit a laser beam 2 (a laser beam having a wavelength of 514 nm and an output power of 10 mW in this example) to the optical coupling device 3 under the instruction of the control unit CONT. The optical coupling device 3 can irradiate the light emitting unit 4 with the laser light 2 from the laser light source 1. The light emitting unit 4 can convert the laser light 2 from the optical coupling device 3 into near-field light L.

FIG. 2 is a sectional view of the near-field light emitting section 4.
The near-field light emitting section 4 is composed of an optical fiber 4a having a core section 41 and a clad section 42 in this example. As shown in FIG. 2, the optical fiber 4a has a coating 4c formed by evaporating aluminum around the tip 4b after sharpening the tip 4b by chemical etching. Then, only the aluminum at the tip of the sharpened portion is removed by chemical etching, so that in this example, an opening 4d having an opening diameter of about 100 nm is formed. Thereby, the near-field light emitting unit 4 is connected to the optical coupling device 3.
Is incident on the non-sharpened side 4e of the optical fiber 4a, so that the near-field light L can be emitted from the sharpened opening 4d.

As shown in FIG. 1, the medium storage unit 200
A rotation drive device (not shown) is provided, and can accommodate a disk-shaped optical recording medium 5. The medium surface 5a of the medium 5 is moved by the rotation of the rotation drive device. The distance detecting device 300 includes a distance detecting laser light source 12 different from the laser light source 1, a two-part photodiode 17, and a focusing lens 1.
4. Includes a condenser lens 16. The laser light source 12 is connected to the control unit CONT. Under the instruction of the control unit CONT, the distance detection laser beam 13 (in this example, the wavelength 780)
nm, laser light having an output power of 1 mW), and the light can be applied to the near-field light emitting unit 4 via the lens 14. In this case, the spot diameter of the light in the light irradiating section is made larger than the width of the portion of the near-field light emitting section 4 where the laser light 13 is irradiated.

The two-division photodiode 17 includes photodiodes 17a and 17b, and is connected to the control unit CONT. Light 15 having a shadow of the near-field light emitting unit 4 after being applied to the near-field light emitting unit 4 is incident on the photodiodes 17a and 17b via the lens 16, and the incident light to each photodiode is It is converted into an electric signal (photoelectric conversion) according to the amount of light. This signal is detected as an amount of light by the electric circuits 17a 'and 17b' and sent to the control unit CONT. The control unit CONT
By comparing the light amounts detected via the photodiodes 17a and 17b, the position of the near-field light emitting unit 4 in a predetermined direction (x direction in FIG. 1) is detected in the form of a relative value to the irradiation beam position. And position detecting means capable of detecting the position.

The near-field light generating device driving unit 400 drives the near-field light emitting unit 4, and includes a driving element (driving unit) 18 in the x direction in FIG. 1 and an ascending and descending direction in the light emitting unit (z direction in FIG. 1).
A driving element (driving unit) 19 is included. The driving element 18 is connected to the control unit CONT, and can apply vibration in the x direction to the light emitting unit 4 under the instruction of the control unit CONT. In this example, the vibration frequency applied to the light emitting unit 4 is approximately equal to the resonance frequency of the light emitting unit 4 and 10 kHz.
z, amplitude is 50 nm. The driving element 19 is a control unit CO
The light emitting unit 4, which is connected to the NT and is oscillated by the drive element 18 under the direction of the control unit CONT, can be moved closer to or away from the medium 5.

When the light emitting section 4 vibrated by the driving element 18 is brought closer to the medium 5, when the distance between them approaches a certain distance, the amplitude and phase of the vibration of the light emitting section 4 change.
The cause is considered to be the influence of the water adsorbed on the medium surface 5a. Under the influence, the amplitude gradually decreases, and the phase shifts as compared with the initial stage (when the distance between the two is long). By utilizing this fact, a relative distance between the two can be determined by detecting a change in amplitude or a shift in phase through the two-division photodiode 17 described above. That is, the control unit CONT gives feedback to the drive element 19 that drives in the z direction in FIG. 1 based on the relative distance change in the x direction detected by the two-division photodiode 17. Accordingly, the distance between the light emitting unit 4 and the medium 5 can be adjusted to the target value by controlling the driving element 19.

The reproduction information detecting device 500a is an optical recording medium 5
And includes a condenser lens 10 and a photodiode 11 for detecting the amount of reflected light. Condensing lens 1
0 can collect the reflected light 9 from the medium 5 to the photodiode 11. The photodiode 11 is connected to the control unit CONT, and can convert incident light from the lens 10 into an electric signal (photoelectric conversion). This signal is detected as a light amount by the electric circuit 11 'and sent to the control unit CONT.

The reproduction information detecting device 500b is an optical recording medium 5
And includes a condenser lens 7 and a photodiode 8 for detecting the amount of transmitted light. The condenser lens 7 can condense the transmitted light 6 from the medium 5 to the photodiode 8. The photodiode 8 is connected to the control unit CONT, and can convert incident light from the lens 7 into an electric signal (photoelectric conversion). This signal is detected as a light amount by the electric circuit 8 'and sent to the control unit CONT.

The control unit CONT is mainly composed of a computer and controls the entire optical recording / reproducing apparatus. As described above, the control unit CONT is connected to the laser light source 1, the distance detection device 300, the near-field light generation device driving unit 400, and the reproduction information detection devices 500a and 500b. Control unit C
The ONT controls the emission timing of the laser light 2 from the laser light source 1 or, based on the detection value of the distance detection device 300, between the optical recording medium 5 and the near-field light emission unit 4 by the drive unit 400. Distance control and reproduction information detection device 50
Reproduction of information or the like is performed based on the detection values by 0a and 500b.

FIG. 3 is a sectional view of a part of the optical recording medium 5. As shown in FIG. 3, in the optical recording medium 5, a recording layer 52 for recording information composed of a cyanine dye is formed on a substrate 51 composed of glass by a spin coating method. A surface layer 53 made of highly hydrophobic polymethyl methacrylate is formed. In this case, the near-field light emitting unit 4 is arranged close to the surface layer 53 of the medium 5. The thickness of the recording layer 52 is about 5 here.
0 nm, and the layer thickness of the surface layer 53 is about 10 n here.
m. Further, a water contact angle was adopted as a scale indicating the degree of hydrophobicity of the recording medium surface 5a, and the angle was measured.

Hereinafter, a method of measuring the water contact angle will be described. FIG. 4 shows a diagram for describing a method of measuring the water contact angle. As shown in FIG. 4, a water droplet D is adhered on the flat surface F ′ of the hydrophobic evaluation target layer F, and a water droplet tangent line E at a point P where the water droplet D, the layer surface F ′, and the surrounding gas intersect.
And the layer surface F ′, the angle θ on the water droplet D side is defined as the water contact angle. In this case, the water contact angle is represented by 0 to 180 degrees, and the larger the angle, the higher the hydrophobicity.

In the medium 5 shown in FIGS. 1 and 3, the water contact angle was 66 degrees. Note that optical recording media 5A to 5A to be described later.
All the water contact angles on the 5D surface were measured by this method.
According to the optical recording / reproducing apparatus described above, when recording, reproducing, and erasing information on the optical recording medium 5, the medium 5
Is driven to rotate, and first, the distance between the near-field light emitting unit 4 and the medium 5 is detected and controlled. Note that the method of detecting the distance between the near-field light emitting unit 4 and the medium 5 applied to this example is known as a shear force method.

The near-field light generating device driving section 400 applies vibration in the x-direction in FIG. 1 to the near-field light emitting section 4 by the driving element 18 mounted on the near-field light emitting section 4. Near-field light emitting unit 4 vibrated in the x direction by the driving element 18
Is brought closer to the medium surface 5a by the drive element 19. In the distance detection device 300, the laser light source 1 for distance detection is used.
The near-field light emitting unit 4 is irradiated with the distance detecting laser light 13 emitted from the light source 2. At this time, the light spot diameter of the irradiating part is larger than the width of the laser light irradiating part of the near-field light emitting part 4. The light 15 after irradiating the near-field light emitting unit 4 has a shadow of the near-field light emitting unit 4. This light is photoelectrically converted by the two-division photodiode 17 and the amount of light is detected, and the detection signal is sent to the control unit CONT. The control unit CONT compares the light amounts detected by the photodiodes 17a and 17b to change the amplitude (or phase) of the vibration of the near-field light emission unit 4 and further changes the light emission unit 4 and the medium surface 5
Find the distance to a. Then, feedback is applied to the drive element 19 based on the detected relative distance between the near-field light emitting unit 4 and the medium 5. As a result, the distance between the two is adjusted to the target value.

Next, a laser beam 2 is emitted from the laser light source 1. The laser light 2 emitted from the laser light source 1 enters the near-field light emitting unit 4 via the optical coupling device 3 and is converted into near-field light L here. The converted near-field light L is irradiated onto the medium surface 5a. As a result, information is recorded, reproduced, and deleted on the medium 5. According to the optical recording medium 5, a surface layer 53 having a higher hydrophobicity than the recording layer 52 is provided on the surface of the recording layer 52 for recording information (FIG. 3).
), Medium 5 for ambient environmental fluctuations, especially ambient humidity fluctuations
Of the surface layer 53 (mainly a state affected by the amount of adsorbed water on the medium surface 5a), and the uniformity of the surface state of the surface layer 53 is easily maintained. As a result, variation in the detected value of the relative distance from the near-field light emitting unit 4 is suppressed, and the distance can be kept constant and stably. Accordingly, the distance between the near-field light generating device 100, particularly, the light emitting unit 4 and the medium 5 is made constant and stable irrespective of the fluctuation of the surrounding environment, particularly, the fluctuation of the surrounding humidity. Field light recording, reproduction, and erasing can be performed.

In the optical recording medium 5, the near-field light emitting section 4 is arranged close to the near-field light recording, reproducing, and erasing information.
May collide with the medium surface 5a. However, since the surface layer 53 is hard, the collision hardly damages the medium surface 5a, and the degree of hydrophobicity of the surface 5a does not easily become uneven. As a result, the influence of the damage is not easily transmitted to the recording layer 52, and an error at the time of recording, reproducing, and erasing information is unlikely to occur due to the influence.

Next, when the optical recording medium 5 is accommodated in an optical recording / reproducing apparatus in which the distance between the optical recording medium and the near-field light generating device is controlled by a method different from that of the optical recording / reproducing apparatus shown in FIG. Will be described with reference to FIG. The optical recording / reproducing apparatus shown in FIG. 5 includes a near-field light generating device 100 ′, an optical recording medium housing unit 200 ′, a reflected light amount detecting device 600 and a control unit CONT ′. Any of near-field optical recording, reproduction, and erasing of information by the light L can be performed. That is, at the time of information recording or erasing, the near-field light L for information recording or the near-field light L for information erasing based on the recording information from the control unit CONT 'is transmitted from the near-field light generating device 100' to the medium housing unit 200 '. The information is recorded or erased on the medium 5 by irradiating the surface 5a of the medium 5 stored in the medium 5. At the time of information reproduction, the control unit CONT ′
Irradiates near-field light L for information reproduction from the near-field light generating device 100 ′ to the surface 5 a of the medium 5 according to an instruction signal from the controller 5, and detects a change in the amount of reflected light 36 reflected on the surface 5 a of the medium 5 by a reflected light amount detecting device. At 600, information is read out (reproduced).

The near-field light generating device 100 ′ includes a laser light source 31, an optical coupling device 33, and a near-field light emitting unit 34. The laser light source 31 is connected to the control unit CONT ′, and can emit a laser beam 32 for recording information or detecting a reflected light amount toward the optical coupling device 33 under the instruction of the control unit CONT ′. The optical coupling device 33 includes the laser light source 31.
Can be applied to the near-field light emitting unit 34. The near-field light emitting section 34 can convert the laser light 32 from the optical coupling device 33 into near-field light L.

FIG. 6 is a more detailed side view of the near-field light emitting section 34 shown in FIG. The near-field light emitting section 34 is provided with a minute opening 34b in a head 34a which floats by a floating force caused by an air flow generated by rotation of the optical recording medium 5. The head 34a has an opening entrance 34c (opening diameter 600 nm in this example) on the wide side of the minute opening 34b and an opening exit 34d (opening diameter 2 in this example) on the narrow side of the minute opening 34b.
00 nm). Thereby, the near-field light emitting unit 34 can emit the near-field light L from the opening exit 34d by the laser light 32 from the optical coupling device 33 being incident on the opening entrance 34c.

The medium accommodating section 200 'is provided with a rotation driving device (not shown), and can accommodate the disk-shaped optical recording medium 5. The medium surface 5a of the medium 5 is moved by the rotation of the rotation drive device. In this case, the surface layer 5 of the medium 5
The near-field light emitting unit 34 is arranged close to the third side. The reflected light amount detection device 600 includes a photodiode 38 and a condenser lens 37. The condensing lens 37 can condense the reflected light 36 converted into normal propagation light at the time of irradiating the medium surface 5a to the photodiode 38. The photodiode 38 is connected to the control unit CONT ′, and can convert light collected by the condenser lens 37 into an electric signal (photoelectric conversion) in accordance with the amount of light. This signal is transmitted to the electric circuit 38 '.
, And is sent to the control unit CONT ′. The control unit CONT ′ obtains the record information from the difference in the amount of reflected light from the information recording portion and the unrecorded portion of the medium 5 detected via the photodiode 38, that is, the difference in the amount of reflected light due to the difference in the reflectance between the two portions. It includes information reproducing means that can be read (reproduced).

The control unit CONT 'is composed mainly of a computer, and controls the entire optical recording / reproducing apparatus. The control unit CONT ′ is connected to the laser light source 31 and the reflected light amount detection device 600 as described above. Control unit CON
T ′ controls the emission timing of the laser light 32 from the laser light source 31 and reads information from the medium 5 based on the detection result of the reflected light amount detection device 600.

In the optical recording / reproducing apparatus shown in FIG. 5, the distance between the near-field light emitting section 34 and the medium 5 is not detected.
The medium surface 5a is moved at a constant speed, and the levitation force of the near-field light emitting unit 34 caused by the airflow generated between the near-field light emitting unit 34 and the medium surface 5a at that time causes the near-field light emitting unit 34 to move.
And the distance between the medium and the medium surface 5a. According to the optical recording / reproducing apparatus shown in FIG.
In performing reproduction and erasing, the medium 5 is driven to rotate.
The near-field light emitting unit 34 floats by a levitation force due to the airflow generated by the rotation of the medium 5, and the distance between the near-field light emitting unit 34 and the medium surface 5 a is controlled.

Next, laser light 32 is emitted from the laser light source 31. Laser light 32 emitted from laser light source 31
Is incident on the near-field light emitting unit 34 via the optical coupling device 33, and is converted into near-field light L here. The converted near-field light L is irradiated onto the medium surface 5a. Thus, the medium 5
Information is recorded and erased. Alternatively, the reflected light 36 from the medium 5 is detected by the reflected light amount detection device 600,
The signal is sent to the control unit CONT 'as the light amount. The control unit CONT ′ reads recorded information from the difference in the amount of reflected light sent from the detection device 600 due to the difference in reflectance between the information recording unit and the information non-recording unit of the medium 5.

According to the optical recording medium 5, a surface layer 53 having a higher hydrophobicity than the recording layer 52 is provided on the surface of the recording layer 52 for recording information.
In particular, the influence of the ambient humidity fluctuation on the surface state of the medium 5 is suppressed, and the uniformity of the surface state of the surface layer 53 is easily maintained. As a result, variation in the detected value of the relative distance from the near-field light emitting unit 34 is suppressed, and the distance can be maintained constant and stably.

Next, another embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. Note that the optical recording medium shown in FIGS. 7 and 8 can be accommodated in the optical recording / reproducing apparatus shown in FIGS.
Playback and deletion can be performed. FIG. 7 shows another example 5A of the optical recording medium according to the present invention.

As shown in FIG. 7, in the optical recording medium 5A, a recording layer 52A for recording information composed of a cyanine dye is formed on a substrate 51A composed of glass by a spin coating method. A surface layer 53A made of polyethylene having a higher hydrophobicity than 52A is formed. In this case, the near-field light emitting units 4 and 34 are arranged close to the surface layer 53A side of the medium 5A. Here, the layer thickness of the recording layer 52A is about 50 nm here, and the layer thickness of the surface layer 53A is about 10 nm here. In addition, the recording medium 5A
The water contact angle on the surface was 101 degrees.

According to the optical recording medium 5A, since polyethylene having higher hydrophobicity than the recording layer 52A is used as the material of the surface layer 53A, polymethacrylic acid having higher hydrophobicity than the recording layer 52 is used as the material of the surface layer 53. There are advantages similar to those of the optical recording medium 5 using methyl. FIG. 8 shows still another example 5B of the optical recording medium according to the present invention. In the optical recording medium 5B, the hydrophobicity of the recording layer 52B itself is improved. That is,
As shown in FIG. 8, in the optical recording medium 5B, a recording layer 52B for recording information in which a cyanine dye is dispersed in a polyethylene resin is formed on a substrate 51B made of glass by a spin coating method. In this case, the near-field light emitting units 4 and 34 are arranged close to the recording layer 52B side of the medium 5B. The recording layer 52B has a thickness of about 50 nm here.
And the weight ratio between the cyanine dye and the polyethylene resin is 1: 1. The water contact angle on the surface of the recording medium 5B was 92 degrees.

According to the optical recording medium 5B, since the hydrophobicity of the recording layer 52B for recording information is enhanced, the surface condition of the medium 5B due to ambient environmental fluctuation, particularly, ambient humidity fluctuation (mainly, the surface of the medium 5B The influence on the amount of adsorbed water) is suppressed, and the uniformity of the surface state of the recording layer 52B is easily maintained. As a result, variation in the detected value of the relative distance between the near-field light emitting units 4 and 34 is suppressed, and the distance can be kept constant and stably. This stabilizes and stabilizes the distance between the near-field light emitting units 4 and 34 and the medium 5B regardless of fluctuations in the surrounding environment, especially fluctuations in the surrounding humidity, and stably records and reproduces near-field light of information. , Can be erased.

In the optical recording medium 5B, when information is recorded, reproduced, and erased by the near-field light, the near-field light emitting units 4 and 34 are arranged close to each other. 34 may collide with the surface of the medium 5B. However, since the recording layer 52B is hard, the surface of the medium 5B is hardly damaged by this collision, and the degree of hydrophobicity of the surface is hardly uneven. As a result, the influence of the damage is hardly transmitted to the recording layer 52B, and the information recording,
Errors during playback and erasure are unlikely.

Next, a performance evaluation experiment was performed on the optical recording medium of the present invention, which will be described below along with a comparative experiment.
In the experiment, the optical recording media 5, 5A, and 5B according to the present invention and the optical recording media 5C and 5D for a comparative experiment described later were used in Experimental Example 1.
Were stored in the optical recording and reproducing apparatus shown in FIG. 1 respectively, and as Experimental Example 2, they were respectively stored in the optical recording and reproducing apparatus shown in FIG. (Experimental Example 1) In the optical recording / reproducing apparatus shown in FIG. 1, the near-field light emitting section 4, the mediums 5, 5A and 5B, and the comparative experimental medium 5
With respect to the relative distance between C and 5D, the detection value of the divided photodiode 17 by the shear force method, that is, the amplitude of the vibration of the near-field light emitting unit 4 in the x direction in FIG.
When the ambient temperature and humidity are 25 ° C, 30% and 25 ° C,
The difference in the effect of humidity between 70% and 70% was examined. (Experimental example 2) In the optical recording / reproducing apparatus shown in FIG. 5, while rotating the mediums 5, 5A, 5B and the comparative experimental mediums 5C, 5D on which no information is recorded by a rotation driving device (not shown), The medium emits near-field light L for detecting the amount of reflected light to each medium from a near-field light emitting unit 34 that floats by the buoyancy of the airflow generated by the rotation. When the ambient temperature and the humidity environment are 25 ° C. and 30%, the detection value of the reflected light 36 reflected from each medium by the irradiation of the near-field light L by the reflected light amount detection device 600, that is, the reflected light amount of the reflected light 36, is 25. The difference in the effect of humidity between 70 ° C. and 70% was examined.

The amount of the reflected light 36 varies depending on the state of the surface of each medium, but is considered to be greatly affected by the distance between the near-field light emitting section 34 and the surface of each medium.
The details of the configurations of the media 5, 5A, and 5B used in Experimental Example 1 and Experimental Example 2 are as already described, but are collectively shown below. Optical recording medium 5 A recording layer 52 composed of a cyanine dye is formed on a glass substrate 51 by spin coating (the thickness of the recording layer 52 is about 5
0 nm), and a surface layer 53 of about 10 nm thick made of polymethyl methacrylate was formed thereon (see FIG. 3). The water contact angle on the surface of the recording medium 5 was 66 degrees. -Optical recording medium 5A Recording layer 52 made of cyanine dye on glass substrate 51A
A was prepared by spin coating (the thickness of the recording layer 52A was about 50 nm), and a surface layer 53A of polyethylene having a thickness of about 10 nm was further formed thereon (see FIG. 7).
The water contact angle on the surface of the recording medium 5A was 101 degrees. Optical recording medium 5B A recording layer 52B in which a cyanine dye was dispersed in a polyethylene resin was formed on a glass substrate 51B by spin coating (the thickness of the recording layer 52B was about 50 nm, and the weight ratio of the cyanine dye to the polyethylene resin was 1). 1) (see FIG. 8).
The water contact angle on the surface of the recording medium 5B was 92 degrees.

Next, the comparative experimental media 5C and 5D used in Experimental Examples 1 and 2 will be described. FIGS. 9 and 10 show partial cross-sectional views of optical recording media 5C and 5D, respectively. -Optical recording medium 5C Recording layer 52 made of cyanine dye on glass substrate 51C
C was produced by spin coating (the thickness of the recording layer 52C was about 50 nm). The water contact angle on the surface of the recording medium 5C is 3
7 degrees. In this case, the near-field light emitting portions 4 and 34 were arranged close to the recording layer 52C side of the medium 5C. Optical recording medium 5D A recording layer 52D was formed on a glass substrate 51D, and a surface layer 53D made of silicon dioxide having a thickness of about 10 nm was formed thereon. The water contact angle on the surface of the recording medium 5D was 28 degrees. In this case, the near-field light emitting units 4 and 34 are arranged close to the surface layer 53D side of the medium 5D. (Experimental Results) The results of Experimental Example 1 are shown in FIGS.

FIGS. 11 to 15 show the near-field light emitting section 4 and the mediums 5, 5A and 5B and the mediums 5C and 5C for comparison experiments, respectively.
9 is a graph showing a relationship between a relative distance between the light emitting element D and the amplitude of a near-field light emitting unit 4. In the graphs of FIGS. 11 to 15, the solid line indicates the case where the ambient temperature and the humidity environment are 25 ° C. and 30%, and the broken line indicates the case where the ambient temperature and the humidity environment are 25 ° C. and 70%. Medium 5,
5A and 5B show the results of FIGS.
2. As shown in FIG. 13, there is no significant difference in the two detection results between the case of the solid line and the case of the broken line, and the near-field light emitting unit 4 and the mediums 5, 5A, 5
It can be seen that the relative distance to B can be detected. On the other hand, in the experimental results using the comparative experimental media 5C and 5D,
As shown in FIGS. 14 and 15, respectively, there is a difference between the two detection results for the case of the solid line and the case of the broken line, and the near-field light emitting unit 4 and the medium 5C, It can be seen that the detected values of the relative distance to 5D are different. That is, it can be seen that the sensitivity of distance detection by the shear force method increases when the surface of the medium is highly hydrophobic, and the dynamic range of distance detection by the shear force method increases when the surface is highly hydrophilic. The results of Experimental Example 2 are shown in FIGS.

FIG. 16 to FIG.
6 is a graph showing the amount of reflected light 36 at each predetermined rotation angle of A and 5B and comparative experimental media 5C and 5D. FIG.
In the graphs of FIGS. 6 to 20, the solid line indicates the case where the ambient temperature and the humidity environment are 25 ° C. and 30%, and the broken line indicates the case where the ambient temperature and the humidity are 25 ° C. and 7%.
This is the case of 0%. As shown in FIGS. 16, 17, and 18, the experimental results using the media 5, 5A, and 5B, respectively,
In each case, there is no large difference between the two detection results of the solid line and the broken line, and it can be seen that the reflected light amount detection device 600 detects the amount of the reflected light 36 without being affected by the humidity of the surrounding environment. That is, it can be seen that the distance between the near-field light emitting unit 34 and the surfaces of the media 5, 5A, and 5B is constant and stable without affecting the humidity of the surrounding environment. In contrast,
As shown in FIGS. 19 and 20, respectively, in the experimental results using the comparative experiment media 5C and 5D, there is a difference between the two detection results in the case of the solid line and the case of the dashed line. It can be seen that the amount of the reflected light 36 fluctuates due to the influence. That is, it is considered that the distance between the near-field light emitting unit 34 and the surfaces of the media 5C and 5D fluctuates due to the influence of the humidity of the surrounding environment.

The above results can be said to be related to the degree of hydrophobicity of the surface of the optical recording medium. That is, the mediums 5 and 5 provided with a surface layer having a higher hydrophobicity than the recording layer on the recording layer surface.
In the case of A, since the amount of adsorbed water on the medium surface is hardly affected by the humidity of the surrounding environment, the apparatus shown in FIG. 1 enables stable relative distance detection by the shear force method. I can imagine. In addition, it is considered that the apparatus shown in FIG. 5 can stably maintain the interval by the rotational levitation force. When a large amount of adsorbed water is present on the medium surface, it is considered that the flow of air generated by rotation of the medium, that is, the movement of air molecules is disturbed by the influence of the adsorbed water molecules.

Further, by comparing the results of the mediums 5C and 5B, it can be seen that even in the case of the medium 5B in which the surface layer is not provided, that is, the hydrophobicity of the recording layer itself is improved, the recording layer which is originally low in hydrophobicity has a hydrophobic property. A medium 5 having a surface layer having a higher hydrophobicity than the recording layer on the surface of the recording layer by improving the degree of hydrophobicity of the recording layer by mixing a resin having high hydrophobicity,
It can be seen that there is the same advantage as in the case of 5A. Therefore,
It is preferable to improve the hydrophobicity of the recording layer itself. However, since the recording layer needs to meet many requirements including information recording sensitivity, if the hydrophobicity of the recording layer itself cannot be improved, the recording layer It is effective to provide a surface layer having a higher hydrophobicity than the recording layer on the surface of the recording medium.

[0052]

According to the present invention, there is provided an optical recording medium for performing near-field optical recording, reproduction, and / or erasing of information using near-field light, wherein information is recorded, reproduced, and / or erased. Stabilize and stabilize the distance between the near-field light generating device and the medium irrespective of the fluctuation of the surrounding environment, especially the fluctuation of the surrounding humidity, and stably record, reproduce and / or erase the near-field light of information. An optical recording medium capable of performing the following can be provided. Further, according to the present invention, when a surface layer having a higher hydrophobicity than the recording layer is provided on the surface of the recording layer, the surface layer can be formed of a material harder than the recording layer. An optical recording medium that is hardly damaged can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an optical recording / reproducing apparatus accommodating an example of an optical recording medium according to the present invention.

FIG. 2 is a cross-sectional view of the near-field light emitting unit shown in FIG.

FIG. 3 is a sectional view of a part of the optical recording medium shown in FIG.

FIG. 4 is a diagram for explaining a method of measuring a water contact angle.

FIG. 5 is a diagram showing a schematic configuration of an optical recording / reproducing apparatus that performs distance control between an optical recording medium and a near-field light generating apparatus by a method different from that of the optical recording / reproducing apparatus shown in FIG. 1;

6 is a more detailed side view of the near-field light emitting unit shown in FIG.

FIG. 7 shows another example of the optical recording medium according to the present invention.

FIG. 8 shows still another example of the optical recording medium according to the present invention.

FIG. 9 is a cross-sectional view of a part of an optical recording medium for a comparative experiment.

FIG. 10 is a cross-sectional view of a part of an optical recording medium for a comparative experiment.

FIG. 11 is a graph showing the results of Experimental Example 1, showing the relationship between the relative distance between the near-field light emitting unit and the medium shown in FIGS. 1, 3 and 5 and the amplitude of the near-field light emitting unit. It is a graph shown.

12 is a graph showing the results of Experimental Example 1, and is a graph showing the relationship between the relative distance between the near-field light emitting unit and the medium shown in FIG. 7 and the amplitude of the near-field light emitting unit.

13 is a graph showing the results of Experimental Example 1, and is a graph showing the relationship between the relative distance between the near-field light emitting unit and the medium shown in FIG. 8 and the amplitude of the near-field light emitting unit.

14 is a graph showing the results of Experimental Example 1, and is a graph showing the relationship between the relative distance between the near-field light emitting unit and the medium shown in FIG. 9 and the amplitude of the near-field light emitting unit.

15 is a graph showing the results of Experimental Example 1, and is a graph showing the relationship between the relative distance between the near-field light emitting unit and the medium shown in FIG. 10 and the amplitude of the near-field light emitting unit.

FIG. 16 is a graph showing the results of Experimental Example 2, and FIG.
FIG. 6 is a graph showing a reflected light amount of reflected light for each predetermined rotation angle of the medium shown in FIGS. 3 and 5.

17 is a graph showing the results of Experimental Example 2, and is a graph showing the amount of reflected light of the reflected light at each predetermined rotation angle of the medium shown in FIG.

FIG. 18 is a graph showing the results of Experimental Example 2, and is a graph showing the amount of reflected light of the reflected light at each predetermined rotation angle of the medium shown in FIG.

19 is a graph showing the results of Experimental Example 2, and is a graph showing the amount of reflected light at each predetermined rotation angle of the medium shown in FIG. 9;

FIG. 20 is a graph showing the results of Experimental Example 2, and FIG.
5 is a graph showing the amount of reflected light of the reflected light for each predetermined rotation angle of the medium shown in FIG.

[Explanation of symbols]

Reference Signs List 1 Ar ion laser light source 2 Laser light emitted from laser light source 1 3 Optical coupling device 4 Near-field light emitting portion 4a Optical fiber 4b Tip of optical fiber 4a 4c Coating film 4d Opening 4e The optical fiber 4a is sharpened. No side 41 Core part 42 Cladding part 5, 5A, 5B, 5C, 5D Optical recording medium 51, 51A, 51B, 51C, 51D Glass substrate 52, 52A, 52C Recording layer 52B composed of cyanine dye 52B Cyanine dye in polyethylene resin Dispersed recording layer 52D Recording layer 53 Surface layer composed of polymethyl methacrylate having higher hydrophobicity than recording layer 52 53A Surface layer composed of polyethylene having higher hydrophobicity than recording layer 52A 53D Surface layer composed of silicon dioxide 5a Light Surface of recording medium 5 6 Light transmitted through optical recording medium 7 Condensing lens 8 Transmission Amount detecting photodiode 8 'Electric circuit of photodiode 8 9 Light reflected from optical recording medium 10 Condensing lens 11 Photodiode for detecting reflected light amount 11' Electric circuit of photodiode 11 12 Laser light source for distance detection 13 For distance detection Laser light 14 Focusing lens 15 Light after irradiating near-field light emitting unit 4 16 Condensing lens 17 Two-part photodiodes 17a, 17b Photodiodes 17a ', 17b' Photodiodes 17a, 17b
18 x-direction drive element (drive section) 19 light-emitting section ascending / descending direction (z-direction) drive element (drive section) 31 laser light source 32 laser light 33 optical coupling device 34 near-field light emission section 34a head 34b minute aperture 34c Opening entrance 34d Opening exit 36 Reflected light 37 Condensing lens 38 Photodiode 38 'Electric circuit of photodiode 38 100, 100' Near-field light generator 200 Optical recording medium accommodating unit 200 'Optical recording medium accommodating unit 300 Distance detecting device 400 Near-field light generator driving unit 500a, 500b Reproduction information detecting device 600 Reflected light amount detecting device CONT, CONT 'Control unit D Water droplet E Water droplet tangent F Hydrophobicity evaluation target layer F' Layer surface L Near-field light P Water droplet D, layer The angle between the surface F ′ and the surrounding gas θ The angle between the water droplet tangent E and the layer surface F ′ Angle of

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Hiroyuki Yamazaki, Inventor Hiroshi Yamazaki 2-3-13, Azuchicho, Osaka-shi Osaka International Building Minolta Co., Ltd. (72) Inventor Daisuke Nishino 2-3-3, Azuchicho, Chuo-ku, Osaka No.13 Osaka International Building Minolta Co., Ltd. F-term (reference) 5D029 JA04 JC09 NA12

Claims (4)

[Claims] An optical recording medium for performing near-field light recording, reproduction and / or erasing of information using near-field light, comprising a recording layer for recording information, and recording the information on a surface of the recording layer. An optical recording medium comprising a surface layer having a higher hydrophobicity than a layer. 2. The optical recording medium according to claim 1, wherein said surface layer is a layer made of polymethyl methacrylate. 3. The optical recording medium according to claim 1, wherein said surface layer is a layer made of polyethylene. 4. An optical recording medium for performing near-field optical recording, reproduction, and / or erasing of information using near-field light, comprising a recording layer for recording information, wherein the recording layer has an increased hydrophobicity. An optical recording medium characterized in that it is a layer.