JP2000123405A - Optical head and information reproducing device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to execute recording and reproducing, etc., at a recording density higher than the recording density determined by a diffraction threshold and to suppress the heat generation in microapertures, the deformation accompanying the same, etc. SOLUTION: The optical head having the constitution to make the light from a light source 101 incident on a slider formed of a translucent material via an optical path 102 has light shielding means 104a to 104c which are disposed on the circumference of this slider and shield the light exclusive of evanescent light. The coefficient of thermal expansion of the material constituting the slider is set below the coefficient of thermal expansion of the material constituting these light shielding means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head for optically recording, erasing or reproducing information by irradiating an information recording medium with light, and an information reproducing apparatus using the same.
The present invention relates to an optical head capable of recording, erasing, or reproducing at high density by using evanescent light, and an information reproducing apparatus using the same.

[0002]

2. Description of the Related Art A conventional technique will be described below.

[0003] In general, the recording density on a recording medium is determined by the diameter of a condensed spot, but with a conventional optical head, the diameter of the condensed spot cannot be made smaller than the diffraction limit determined by the numerical aperture of the objective lens and the wavelength of the light source. Therefore, a recording density higher than the diffraction limit could not be obtained.

[0004] Therefore, in order to form a light spot below the diffraction limit and dramatically improve the recording density of a recording medium,
For example, Applied. Physics. Letter (Appl.P
hys. Lett. ), 61.142 (1992), the tip of an optical fiber is sharpened, and a small aperture having a diameter equal to or less than the wavelength is provided at the tip, and recording / reproducing to / from a recording medium is performed using evanescent light generated in the opening. , A technique that exceeds the diffraction limit is disclosed.

[0005]

However, according to the conventional method of generating evanescent light by providing a minute aperture at the tip of an optical fiber, light is transmitted to the minute aperture provided by sharpening the tip of the optical fiber. Concentration and the temperature of the minute opening becomes very high. For this reason, disadvantages such as expansion and deformation of the minute opening due to the heat generated therein and deformation of the recording medium provided in the vicinity occur, and the optical head and the information reproducing apparatus using the same. There is a problem that the reliability of the device is lowered.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and can perform recording / reproducing at a recording density higher than the recording density determined by the conventional diffraction limit. It is an object of the present invention to provide a highly reliable optical head capable of suppressing heat generation and accompanying deformation thereof, and an information reproducing apparatus using the same.

[0007]

According to the present invention, there is provided an evanescent light generating means for generating evanescent light from light guided by an optical system for guiding light from a light source to a predetermined position, and holding the evanescent light generating means. Holding means;
An optical head comprising: a driving unit that moves a holding unit to a predetermined position on a recording medium; and a light blocking unit that is provided around the evanescent light generating unit and blocks light other than the evanescent light. Is made to have a coefficient of thermal expansion equal to or less than the coefficient of thermal expansion of the material forming the light shielding means.

[0008] Further, an intermediate layer is provided between the evanescent light generating means and the light shielding means for reducing heat generated by the evanescent light generating means or the light shielding means.

Further, an area through which light guided from an optical system for guiding light from a light source to a predetermined position passes is formed of a translucent material, and slides or floats on the recording medium by rotation of the recording medium. A slider that moves, and a driving unit that moves the slider to a predetermined position on a recording medium; and a light-shielding unit having a minute opening formed in the medium facing surface is provided on the slider, and evanescent light is generated from the minute opening. It has the structure of.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is a light source, an optical system for guiding light from the light source to a predetermined position, and an evanescent light for generating evanescent light from the light guided by the optical system. Light generating means, holding means for holding the evanescent light generating means, driving means for moving the holding means to a predetermined position on a recording medium, and light provided around the evanescent light generating means, other than evanescent light. A light-shielding means for shielding light, an intermediate layer provided between the evanescent light generating means and the light-shielding means, for reducing heat generated by the evanescent light generating means or the light-shielding means, and recording of the evanescent light and the recording medium. Light receiving means for receiving the light generated by the interaction with the surface, the evanescent light generating means or the shielding The heat generated in the unit, it is possible to alleviate the thermal stress generated between the evanescent light generating means and light shielding means.

[0011] The second aspect of the present invention is to further improve the thermal expansion coefficient of the intermediate layer by setting the thermal expansion coefficient of the material forming the evanescent light generating means to be equal to or higher than the thermal expansion coefficient of the material forming the light shielding means. Thermal stress generated between the evanescent light generating means and the light shielding means can be efficiently reduced.

According to a third aspect of the present invention, a light source, an optical system for guiding light from the light source to a predetermined position, and at least a region through which the light guided from the optical system passes are formed of a translucent material. A slider that slides or floats on the recording medium due to the rotation of the recording medium to move, a driving unit that moves the slider to a predetermined position on the recording medium, and a mutual movement between the evanescent light and the recording surface of the recording medium. Light receiving means for receiving light generated by the action, light shielding means having a fine opening formed in the slider, an optical head for generating evanescent light from the fine opening, the slider and the light shielding means, Provided between the slider and the intermediate layer for reducing the heat generated by the slider or the light shielding means, by the heat generated by the slider or the light shielding means, It is possible to reduce thermal stress generated between the rider and the light shielding means.

According to a fourth aspect of the present invention, the slider is more efficiently provided that the coefficient of thermal expansion of the intermediate layer is not less than the coefficient of thermal expansion of the material forming the slider and not more than the coefficient of thermal expansion of the material forming the light shielding means. Thermal stress generated between the light-shielding means and the light-shielding means can be reduced.

According to a fifth aspect of the present invention, the heat generated by the thermal conductivity of the intermediate layer is not less than the thermal conductivity of the material forming the slider and not more than the thermal conductivity of the material forming the light shielding means. It can be efficiently diverged.

According to a sixth aspect of the present invention, the heat release of the intermediate layer into the air is higher than the heat release from the slider and lower than the heat release from the light shield. Thus, it is possible to significantly suppress the deterioration of the light shielding characteristics due to the temperature change and the breakage of the light shielding means.

According to the seventh aspect of the present invention, since the intermediate layer is formed of a translucent material, the position where the evanescent light is generated can be located near the interface between the intermediate layer and the light shielding means.

According to an eighth aspect of the present invention, in the optical head according to any one of the first to seventh aspects, the recording medium being rotated by a medium driving unit that holds and drives the recording medium. By irradiating evanescent light to reproduce information, it is possible to provide an information reproducing apparatus with high reliability especially against heat.

(Embodiment 1) Next, an optical head and an information reproducing apparatus according to Embodiment 1 will be described.

FIG. 1 is a diagram showing an information reproducing apparatus according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 101 denotes a light source. As the light source 101, it is preferable to use a light source having a relatively large light amount such as a laser or a light emitting diode. In particular, a device made of a semiconductor is small in size and low in price, so that it is suitable for use in an information reproducing device having a small volume.

An optical path 102 is composed of a waveguide such as an optical fiber, an optical system using a lens or the like, and has a function of guiding light emitted from the light source 101 to a predetermined position. are doing.

Numeral 103 denotes a slider. The slider 103 is partially or entirely formed of a light-transmitting material. The slider 103 floats or slides on the recording medium 106 to record at a predetermined position on the recording medium 106. It has a function of moving light used for reproduction, and light guided through the optical path 102 is configured to be incident on the slider 103.

Reference numeral 104 denotes a light blocking means.
The slider 103 is provided on a surface of the slider 103 facing the recording medium 106, and a small opening 104 a having a diameter smaller than the wavelength of light emitted from the light source 101 is formed in a part of the slider 103. A slider 103 from a light source 101 via an optical path 102
Enters a small aperture 104a formed in the light shielding means 104 and takes the form of an evanescent wave. Normal,
Light waves cannot pass through the small aperture 104a smaller than the wavelength, but only when the distance between the small aperture 104a and the recording medium 106 is sufficiently small (（100 nm).
The evanescent light 113 from the minute opening 104a can interact with the recording medium 106. Therefore, it is very important to accurately detect and control the distance between the minute opening 104a and the recording medium 106. The configurations of the slider 103 and the light blocking means 104 will be described later in detail.

Reference numeral 105 denotes a support member. One end 105 a of the support member 105 is
Is connected to the end face on the opposite side to the face on which is provided, and the other end 105b is connected to the driving means 107. The operation of the driving means 107 is such that the evanescent light 113 transmitted from the slider 103 via the support member 105 and generated at the minute opening 104 a provided on the medium facing surface of the slider 103 is moved to a predetermined position on the recording medium 106. Then, information recording and / or reproduction can be performed. Here, as the driving unit 107, a unit that rotates around an axis such as a voice coil motor or a unit that linearly moves in the XY directions such as an actuator can be used.

Reference numeral 108 denotes a light-condensing member.
It is provided on the opposite side of the slider 103 with the recording medium 106 interposed therebetween, and the evanescent light 113 generated in the minute opening 104 a condenses a part of the propagation light generated by interacting with the recording surface 106 a of the recording medium 106. Has a function.

Reference numeral 109 denotes a light receiving member.
It has a function of receiving the reproduction light corresponding to the information on the recording surface 106a condensed by the condensing member 108 and converting it into an electric signal.

Reference numeral 111 denotes a medium driving unit.
Reference numeral 11 includes a medium holding unit and a medium driving unit, and has a function of holding and rotating the recording medium 106. As the medium holding unit, a known mechanism for holding a medium using a nail, a ball, or the like can be used. In addition, it is preferable to use a spindle motor using a fluid bearing as the medium drive unit, because silence can be improved and a long life can be achieved.

Next, recording on the phase change type recording medium 106 will be described. Light emitted from the light source 101 at a predetermined output enters the slider 103 via the optical path 102,
Evanescent light 113 is generated in the vicinity of the minute aperture 104a of the light shielding means formed on the medium facing surface of the slider 103. The evanescent light 113 is locally applied to the phase change type recording medium 106 to heat a predetermined position of the recording medium 106. In the portion of the recording medium 106 that has been heated by light irradiation to a temperature equal to or higher than the melting point, the portion that was in a crystalline state is temporarily melted and changes to an amorphous state in the course of a rapid temperature drop. Information is recorded based on the change between the crystalline state and the amorphous state.

Next, reproduction of information on the phase change recording medium 106 will be described. Since the amorphous portion and the crystalline portion of the recording medium 106 have different structures even if they have the same composition, they have different optical constants. Therefore, the minute opening 104
Even if the distance between a and the recording medium 106 is constant, the optical coupling efficiency between the minute opening 104a and the recording medium 106 changes between the amorphous state and the crystalline state. The intensity of light transmitted through the recording medium 106 changes according to the change in the optical coupling efficiency. That is, propagating light generated by the interaction between the evanescent light 113 generated in the minute opening 104 a by the light emitted from the light source 101 and the recording medium 106 passes through the recording medium 106, passes through the light collecting member 108, and passes through the light receiving member 109. Is different between the crystalline state and the amorphous state. Therefore, by detecting the difference in intensity with the light receiving member 109, the recording medium 10
6 can be reproduced.

Although the light source 101 and the optical path 102 are provided separately from the slider 103 in the present embodiment, the light source 101 and the optical path 102 may be provided on the slider 103. Further, the light source 101 and the optical path 102 are provided on the support
03 may be linked. By providing the light source 101 and the optical path 102 in the slider 103, the support member 105, and the driving means 107 in this manner, light from the light source 101 can be surely made to enter a predetermined position of the moving slider 103, so that information Reproduction is reliable, the seek time can be shortened, and a mechanism for causing the light source 101 and the optical path 102 to follow the operation of the slider 103 can be simplified, so that productivity is high. An optical head having high reliability can be obtained.

Next, a detailed configuration of the slider and the light shielding means in the present embodiment will be described with reference to the drawings. FIG. 2 is a diagram showing a configuration of the slider according to the first embodiment of the present invention.

In FIG. 2, rail surfaces 103a, 103b and 103c are formed on the slider 103 at the medium facing surface side, and a light shielding means 104 is formed on the rail surface 103b.

The slider 103 has a function of smoothly moving the optical head on the recording medium 106. As the type of the slider 103, a sliding type used in contact with the recording medium 106 or a floating type used while flying above the recording medium 106 may be used. Further, among the floating types, a contact start / stop method for starting and stopping the apparatus while the slider is in contact with the recording medium 106, a self-loading type floating head slider mechanism for starting and stopping without contact, a slider lifting and lowering Mold loading / unloading mechanism,
There is a non-contact type such as a ramp load type load / unload mechanism.

The height of the rail surface of the slider 103 is
It is preferable that the light shielding means 104 be different from the light shielding means provided with the light shielding means 104. When the slider 103 is of a sliding type or a CSS type, the light shielding means 10
In order to prevent breakage of the light shielding means 104 due to contact between the recording medium 106 and the recording medium 106, the rail surface 103b provided with the light shielding means 104 is different from the other rail surfaces 103a, 103.
c, and the medium facing surface of the light shielding means 104 is preferably formed lower than the other rail surfaces 103a, 103c.

In the case of the floating type, in which the starting and stopping are performed in a non-contact manner, the medium facing surface of the light shielding means 104 is formed higher than the other rail surfaces 103a and 103c. Since the distance (flying height) between the small aperture 106a and the minute opening 104a formed in the light shielding means 104 can be made smaller, the recording medium 1 is not affected by external vibration or the like.
Since the evanescent light 113 can more reliably come into contact with the recording medium 106 even when the light-shielding means 104 is slightly separated from the light-shielding means 06, extremely stable recording or reproduction characteristics can be realized.

The surface of the slider 103 is
The light incident from the slider 103 and the portion other than the minute opening 104a are shielded by light-shielding means having light absorption and reflection characteristics. This means that light (stray light) leaked from the slider 103 and not related to recording or reproduction (stray light). This is preferable because it is possible to prevent the S / N ratio from being degraded by being incident on the light receiving member 109 as noise.

The light shielding means 104 has a minute opening 104a, an intermediate layer 104b, and a light shielding layer 104c. The minute opening 104a generates the evanescent light 113 as described above. On the other hand, the intermediate layer 104b and the light shielding layer 104
c indicates that the light other than the light that contributes to the generation of the evanescent light 113 is blocked by the minute aperture 104a and the recording medium 10
It has a function of suppressing generation of light (stray light) leaking in six directions.

Here, the light-shielding layer 104c has an absorption property,
It has the function of absorbing incident light and converting it into heat. Therefore, the light shielding layer 104c is
High thermal conductivity and heat release are required to prevent the destruction of the material. Further, the size of the minute opening 104a changes due to thermal stress strain generated due to a temperature difference or a difference in thermal expansion coefficient between the intermediate layer 104b and the intermediate layer 104b.
In order to prevent the light-shielding layer 104c from being destroyed, it is necessary to pay attention to thermal expansion and the like.

The intermediate layer 104b is provided with a minute opening 104a.
Is provided between the light-shielding layer 104c where the light is concentrated and the temperature is high and the slider 103 which is a relatively low temperature to absorb the temperature difference and the difference of the expansion coefficient between the light-shielding layer 104c and the slider 103, It has a function of alleviating the stress caused by heat and suppressing the occurrence of inconveniences such as a change in the shape of the minute opening 104a and the destruction of the light shielding layer 104c.

Therefore, when the characteristic values of the intermediate layer 104b, the light shielding layer 104c and the slider 103 are compared and examined, it is preferable that the characteristic values are set as follows.

First, the thermal conductivity (rate) is determined by the minute opening 104a.
Light is concentrated in order to define
c is the highest, adjacent to the light shielding layer 104c,
4a and the intermediate layer 104b in contact with the light-shielding layer 104c and the slider 103 in contact with the intermediate layer 104b become lower in this order, so that the generated heat can be efficiently dissipated.
This is preferable because the occurrence of inconveniences such as deformation and melting of the light shielding means 104 due to heat can be suppressed. In addition, by using a material whose thermal conductivity increases with an increase in temperature, the heat dissipation of a portion where heat is generated can be improved with an increase in temperature. Breakage of the light shielding means 104 can be suppressed more efficiently, and a more reliable optical head can be obtained.

Next, it is also preferable to reduce the heat release into the air in the order of the light-shielding film 104c, the intermediate layer 104b adjacent to the light-shielding film 104c, and the slider 103, which generate a large amount of heat. In particular, the heat release property of the light-shielding film 104c should be at least twice as large as that of the intermediate layer 104b and the slider 103, so that the temperature rise of the light-shielding film 104c can be suppressed. This is preferable because breakage can be greatly suppressed.

Finally, it is preferable that the thermal expansion (linear expansion coefficient) of both the light shielding means 104 and the slider 103 is small, and that the difference is small. Also, the intermediate layer 104
b corresponds to the linear expansion coefficient of the slider 103 and the light-shielding layer 1.
04c can be set during the linear expansion coefficient of the slider 10c.
3 and the difference in linear expansion coefficient between the intermediate layer 104b and the intermediate layer 10b.
Since the difference in the coefficient of linear expansion between 4b and the light-shielding layer 104c can be reduced, inconveniences such as cracks caused by the difference in the respective coefficients of expansion can be suppressed, which is a more preferable configuration. .

In particular, the size such as the opening diameter of the minute opening 104a defined by the light-shielding layer 104c slightly changes according to the expansion and contraction of the light-shielding layer 104c. Especially small aperture 1
In the state where the evanescent light 113 is generated from the light-shielding layer 104c, the light-shielding layer 104
If the minute aperture 104a becomes small due to the expansion of c, the reaching distance of the generated evanescent light 113 also becomes short. Therefore, it is difficult to form the evanescent light 113 to the extent that the evanescent light 113 comes into contact with the recording medium 106. As a result, recording or reproduction cannot be performed. Therefore, the range of the linear expansion coefficient to be satisfied by the light shielding layer 104c is required to be a range in which the change in the size of the minute opening 104a can record and reproduce information using the evanescent light 113. At the time of light irradiation, that is, when the light-shielding layer 104c has a higher temperature,
The use of a material having a fluctuation rate within 20% when 4c is compared with the linear expansion coefficient at a lower temperature state minimizes a change in the shape change amount of the light shielding layer 104c due to the temperature state. It is preferable because it can be suppressed.

The slider 10 satisfying the above characteristics
3 and the following materials can be considered as the materials of the intermediate layer 104b and the light shielding layer 104c.

First, the slider 103 is formed of a material having a light-transmitting property such as resin or glass, in particular, a material having a transmittance of 90% or more at the wavelength of the light from the light source 101 here. It is preferable because the evanescent light 113 can be generated without lowering the light emission. In particular, since glass has a large strength, by using it as a material for forming the slider 103 which is considered to have a possibility of contact with the recording medium, it is less likely to be damaged even if it contacts the recording medium. This is preferable because a slider with high performance can be realized. In particular, among glass materials, it has a sufficient strength, a small coefficient of thermal expansion, and
Quartz glass, which has almost no change in coefficient of thermal expansion from low to high temperatures, is the most suitable material.

Next, the intermediate layer 104b is located between the slider 103 and the light-shielding layer 104c, and is often formed mainly of a material such as glass, resin, or metal. It is often determined accordingly. For example, when the slider 103 is formed of a glass material and the light shielding layer 104c is formed of a metal material,
4b is made of a glass material or a metal material, so that the difference in the coefficient of thermal expansion can be suppressed to a minimum. Therefore, inconveniences such as cracks are generated between each of the slider 103 and the light shielding layer 104c and the intermediate layer 104b. Can be suppressed. As an optimal combination, when quartz glass is used for the slider 103, lead glass or borosilicate glass should efficiently absorb the difference in thermal expansion between the slider 103 and the light-shielding layer 104c particularly at a high temperature. Is preferred. The middle layer 1
The film thickness of 04b is preferably about 10 nm to 1000 nm because a difference in thermal expansion between the slider 103 and the light shielding layer 104c can be efficiently absorbed. Further, the intermediate layer 104b is also preferably formed of a light-transmitting material. By forming the intermediate layer 104b from a translucent material, the position where the evanescent light 113 is generated can be changed.
It can be near the interface between b and the light shielding layer 104c.
Therefore, compared with the case where the light is generated on the lower surface of the slider 103, the recording medium 1 is generated from the portion where the evanescent light 113 is generated.
It is preferable that the distance to the recording medium 106 and the slider 103 can be more easily controlled because the distance up to 06 can be reduced.

Next, the light shielding layer 104c is mainly made of Au, Ag, A
Metal materials such as l and Cu, SIO ₂ and TiO ₂
In many cases, it is formed of a material having a property of reflecting light, such as a combination of dielectric materials such as, or a material having a property of absorbing light due to a combination of a Si layer and a Ti layer. When the film thickness is about 10 nm to 100 nm, light can be prevented from leaking from a portion other than the minute opening 104a, and the evanescent light 113 generated in the minute opening 104a faces the recording medium 106 of the light shielding layer 104c. This is a preferable configuration because the recording medium 106 can be reliably projected to the recording medium 106 side from the surface, and information can be recorded and / or reproduced by the projected evanescent light 113 reliably.

In the present embodiment, since the intermediate layer 104b has high translucency, the minute opening 104a is
04c. Intermediate layer 104
b has a light-shielding characteristic,
Is preferably formed so as to penetrate through the intermediate layer 104b and the light shielding layer 104c.

Further, the light-shielding means 104 has a two-layer structure of the intermediate layer 104b and the light-shielding layer 104c. However, the light-shielding means 104 may have a three-layer or more layer structure. Intermediate layer 104 using functionally graded material
b can be eliminated.

As described above, in the present embodiment, a part or the whole of the slider 103 is formed of a translucent member, and the minute opening 104a for generating the evanescent light 113 is formed in the medium facing surface. With such a configuration, the slider 103 itself can be used as a means for generating the evanescent light 113. Therefore, compared to a case where the evanescent light 113 generating means such as a probe is provided separately, Positioning becomes unnecessary, and the number of parts and the number of assembling steps can be reduced, so that an optical head with extremely high product accuracy and high productivity can be realized.

The whole or a part of the slider 103 is formed of a translucent member, so that strict positioning between the optical path 102 and the minute opening 104a,
Even if a hole for transmitting light is not provided in the small aperture 10,
Since the light can be guided to the slider 4a, the configuration of the optical head can be simplified.
The optical head can be installed anywhere as long as it is the medium facing surface, so that the degree of freedom in designing the optical head can be ensured.

(Embodiment 2) Hereinafter, Embodiment 2 of the present invention will be described with reference to the drawings.

FIG. 3 is a diagram showing an information reproducing apparatus according to Embodiment 2 of the present invention. In FIG. 3, reference numeral 201 denotes a light source, and as the light source 201, it is preferable to use a light source having a relatively large light amount such as a laser or a light emitting diode. In particular, a device made of a semiconductor is small in size and low in price, so that it is suitable for use in an information reproducing device having a small volume.

Reference numeral 202 denotes an optical path. In the present embodiment, the optical path 202 is constituted by an optical system using a lens 211 and a reflection mirror 212, and converts light emitted from the light source 201 into convergent light by the lens 211. Convert to the reflection mirror 212
And has a function of guiding to a predetermined position via the.

Reference numeral 203 denotes a slider. The slider 203 is partially or entirely formed of a light-transmitting material. The slider 203 floats or slides on the recording medium 206 to record at a predetermined position on the recording medium 206. And / or has the function of moving light used for reproduction. A lens surface 203a is formed on a surface of the slider 203, on the side opposite to the medium facing surface, on which the light guided from the optical path 202 is incident, and condenses the incident light at a predetermined position. In the present embodiment, the lens surface 203a is formed as a part of the slider 203, but may be provided as a separate member.

The light shielding means 204 comprises an intermediate layer 204b and a reflection layer 204c.
6, a small opening 204a having a diameter smaller than the wavelength of light emitted from the light source 201 is formed in a part of the reflection layer 204c.

The light beam 210 incident on the slider 203 from the light source 201 via the optical path 202 is condensed on the lens surface 203a and condensed near the minute opening 204a formed in the reflection layer 204c constituting the light shielding means 204. At this time, the maximum angle between the optical axis and the condensed light is determined by the intermediate layer 20.
4b is larger than the total reflection angle at the end face. Then, part of the light that is totally reflected leaks out as evanescent light 216 from the end of the intermediate layer 204b. Normal,
Since the light wave cannot pass through the aperture smaller than the wavelength, only the evanescent light 216 can pass through the minute opening 204a formed in the recording medium 206 rather than the intermediate layer 204b. 204
Unnecessary light having the form of normal propagation light transmitted without being reflected at the end face b cannot pass through the minute aperture 204a. Therefore, ordinary propagation light, which is only stray light, does not enter the recording medium 206, so that the S / N ratio of light used for recording and / or reproduction can be improved from the minute aperture 204a, and recording or / and reproduction quality can be improved. And an information reproducing apparatus using the same can realize an information reproducing apparatus having good recording and / or reproducing characteristics.

Further, since the light beam 210 is converged on the lens surface 203a in the vicinity of the minute aperture 204a, the light beam 210 is converted into the evanescent light 216 as compared with the case where no light is condensed.
It is possible to increase the amount of light leaking from 4a, that is, to improve the light use efficiency.

Reference numeral 205 denotes a support member. One end 205 a of the support member 205 is
Is connected to the end face opposite to the face on which the is provided, and the other end 205 b is connected to the driving means 207. The operation of the driving means 207 is such that the evanescent light 216 transmitted from the slider 203 via the support member 205 and generated at the minute opening 204 a provided on the medium facing surface of the slider 203 is moved to a predetermined position on the recording medium 206. Then, information can be recorded or reproduced. Here, as the driving unit 207, a unit that rotates around an axis such as a voice coil motor or a unit that linearly moves in the XY directions such as an actuator can be used.

Reference numeral 208 denotes a light collecting member.
The evanescent light 216 generated in the minute opening 204 a is provided on the opposite side of the slider 203 with the recording medium 206 interposed therebetween, and condenses a part of the propagation light generated by interacting with the recording surface 206 a of the recording medium 206. Has a function.

Reference numeral 209 denotes a light receiving member.
It has a function of receiving the reproduction light corresponding to the information on the recording surface 206a condensed by the condensing means 208 and converting it into an electric signal.

Reference numeral 213 denotes a light source.
1 is provided separately from the light source 201 and emits light having a wavelength different from that of the light source 201. The light is emitted onto the recording medium 206 via an optical path 214 formed of an optical fiber or the like, and is recorded on the recording medium 206. It has the function of erasing the information. Although not shown here, at least the optical path 214 is configured to be movable from the innermost circumference to the outermost circumference of the recording surface 206a of the recording medium 206. Although not shown, a minute projection or a minute opening is formed at the tip of an optical fiber or the like constituting the optical path 214, and the structure is configured to irradiate the evanescent light 216 therefrom.

Next, a photochromic recording medium 206
Will be described. Recording layer 206a of recording medium 206
Is formed of a photochromic material having a thermally irreversible property in which color changes reversibly between two states by light irradiation, and both states are thermally stable. Examples of the photochromic material having heat irreversibility include a diarylethene derivative, a fulgide derivative, and a cyclophane derivative, and a diarylethene derivative is more preferable in terms of thermal stability, repetition durability, and long wavelength range sensitivity. Among them, a symmetric or asymmetric diarylmaleimide having a substituted benzothiophene or a substituted indole as an aryl group, a symmetric or asymmetric diaryl anhydride, or a symmetric or asymmetric diarylperfluorocyclopentene is particularly preferable.

The recording medium 206 is preferably formed by dispersing these photochromic materials in a polymer. These photochromic materials, if necessary, together with a solvent such as carbon tetrachloride, benzene, cyclohexane, methyl ethyl ketone, tetrachloroethane, polyester resin, polystyrene resin, polyvinyl butyral resin, polyvinylidene chloride, polyvinyl chloride, polymethyl methacrylate, The recording medium 2 is dispersed or dissolved in a polymer such as polybutyl methacrylate, polyvinyl acetate, cellulose acetate, epoxy resin, and phenol resin.
06.

Further, these photochromic materials are dispersed or dissolved in the above-mentioned polymer medium or solvent and applied on an appropriate substrate to form a recording layer, and the recording medium
It can also be 6. Furthermore, a photochromic compound is formed on a suitable substrate by a known evaporation method or a co-evaporation method with another compound to form a recording layer, or a photochromic material is dissolved in a solvent as described above,
What is enclosed in a glass cell or the like can be used as the recording medium 206.

As the substrate, glass, plastic,
Examples of the support include a general support for a recording medium such as paper, a plate-like or foil-like metal. When a recording layer is formed on a substrate, layers such as a lubricating layer, a reflective layer, and a protective layer can be provided as necessary.

Next, a photochromic recording medium 206
The recording of information to the server will be described. Light emitted from the light source 201 is converted into convergent light by a lens 211, reflected by a reflection mirror 212, and converted into a light flux 210 by the slider 2.
03 enters the lens surface 203a. And the luminous flux 210
Is converted into convergent light having a larger NA by the lens surface 203a and is condensed near the minute opening 204a of the light shielding means 204 formed on the medium facing surface of the slider 203.
Then, evanescent light 216 is generated from the minute opening 204a. The evanescent light 216 is locally irradiated to the photochromic recording medium 206 to perform recording. That is, the driving means 207 is driven to
By moving the slider 203 having a to a predetermined position and blinking the light source 201 according to the input information, a change from the colored state to the decolored state is induced in the portion of the recording medium 206 where the evanescent light 216 is irradiated, Information will be recorded.

Next, information reproduction will be described. Light source 2
01 from the slider 2 through the optical path 202.
The evanescent light 216 is condensed near the minute aperture 204a by the lens surface 203a to generate evanescent light 216. At this time, the intensity of the transmitted light generated by the interaction between the evanescent light 216 and the recording surface in the portion changed to the decolored state by the recording has the intensity of the transmitted light in the portion which has not changed in the colored state. Since the intensity differs from the recorded pit, the difference between the recorded pit and the unrecorded pit, that is, the recorded information can be read from the difference in transmitted light intensity. Therefore, the light transmitted through the recording medium 206 is condensed by the light collecting member 20.
At 8 the light is collected and the information is reproduced.

The light source used was the light source 20 used for recording.
Light having a wavelength different from 1 may be introduced and used. Further, the light emitted from the light source 201 may be subjected to intensity modulation or position modulation in a direction perpendicular to the recording medium. Further, in the present embodiment, the configuration is such that the light transmitted through the recording medium 206 is detected.
06, a reflection film is formed on the recording surface 206a, and the recording medium 2
It is good also as a structure which detects the light reflected in 06.

Next, the erasure of information will be described. Light source 2
13 emitted from the recording medium 2 via the optical path 214.
06. Here, the wavelength of light emitted from the light source 213 is shorter than the wavelength of light emitted from the light source 201.
As a result, all the portions of the recording medium 206 to which the light has been irradiated are in a colored state. Thus, the recorded information can be erased.

Although the light source 201 and the light source 213 are provided at different places, they may be provided at the same place and switched to be used, so that the light path 202 and the slider 203 can be shared.

As described above, by using a photochromic material having thermal stability as a recording material and using the evanescent light 216 having a size smaller than the wavelength as a light source, the size (10 to 10) of the evanescent light 216 is obtained.
0 nm), 200 times to 2000 times of the current optical recording.
Recording at a density of 0 times becomes possible.

In the present embodiment, the light source 201 and the optical path 202 are provided separately from the slider 203, but the light source 201 and the optical path 202 may be provided on the slider 203. Further, a light source 201 and an optical path 202 are provided on
03 may be linked. By providing the light source 201 and the optical path 202 in the slider 203, the supporting means 205, or the driving means 207 in this manner, the light from the light source 201 can be surely incident on a predetermined position of the moving slider 203, so that the information Reproduction is reliable and the seek time can be shortened, and the light source 201 and the optical path 202
Since the mechanism for following the operation can be simplified, an optical head with high productivity and high reliability can be obtained.

Next, the slider 203 in the present embodiment
The configuration of the light shielding means 204 will be described in detail.
FIG. 4 is a diagram showing a configuration of a slider according to Embodiment 2 of the present invention. In FIG. 4, rail surfaces 203b and 203c are respectively formed on the medium facing surface side of the slider 203, and a light shielding means 2 is further provided on the rail surface 203b.
04 is formed. The slider 203 has a function of smoothly moving the optical head on the recording medium 206. As a method of the slider 203, the recording medium 20
6 may be used, or a floating type used while floating on the recording medium 206 may be used. Further, among the floating types, a contact start / stop method for starting and stopping the apparatus while keeping the slider in contact with the recording medium 206,
There are non-contact types such as a self-loading type floating head slider mechanism that starts and stops in a non-contact manner, a slider lifting / lowering type load / unload mechanism, and a ramp load type load / unload mechanism.

The surface of the slider 203 is
Light is blocked by a light-shielding means having light-absorbing properties at a portion other than the portion where the light from
Light (stray light) leaking from the slider 203 and having no relation to recording or reproduction enters the light receiving member 209 as noise.
The deterioration of the S / N ratio can be suppressed, and the light reflected by the reflection layer 204c of the light shielding means 204 is repeatedly reflected inside the slider 203, mixed into the optical path 202 and mixed with the light flux 210. Interference or light source 201
This is preferable because it is possible to suppress the occurrence of inconveniences such as instability of the output from the light source 201 due to incidence on the light source.

The light shielding means 204 has a minute opening 204a, an intermediate layer 204b, and a reflection layer 204c. The minute opening 204a generates the evanescent light 216 as described above. On the other hand, the intermediate layer 204b and the reflection layer 204
c indicates that light other than light contributing to the generation of the evanescent light 216 is blocked by the minute aperture 204a, and the recording medium 20
It has a function of suppressing generation of light (stray light) leaking in six directions.

Here, particularly, the reflection layer 204c has a reflection characteristic, and has a function of reflecting incident light. Therefore, the reflection layer 204c is formed of a material having a high reflectance with respect to the wavelength of the light source 201, and is used to prevent the reflection layer 204c from being damaged by light collected around the light shielding unit 204 by the lens surface 203a. , High thermal conductivity and heat release are required. Further, the size of the minute opening 204a changes or the intermediate layer 204b and the reflective layer 204c are destroyed due to thermal stress distortion generated due to a temperature difference or a difference in thermal expansion coefficient between the intermediate layer 204b and the intermediate layer 204b. It is necessary to pay attention to the thermal expansion and the like in order to prevent the occurrence of such a phenomenon.

The intermediate layer 204b is formed with a minute opening 204a.
Is provided between the reflective layer 204c where the light is concentrated and the temperature becomes high and the slider 203 which is a relatively low temperature, and absorbs the difference in temperature and expansion between the reflective layer 204c and the slider 203, It has a function of alleviating the stress caused by heat and suppressing the occurrence of inconveniences such as a change in the shape of the minute opening 204a and breakage of the reflective layer 204c.

Therefore, when the characteristic values of the intermediate layer 204b, the reflective layer 204c and the slider 203 are compared and examined, it is preferable that the characteristic values are set as follows.

First, the thermal conductivity (rate) is determined by the minute opening 204a.
The reflective layer 204, which concentrates light and generates a large amount of heat,
c, which is highest, adjacent to the reflective layer 204c,
4a and the intermediate layer 204b in contact with the reflective layer 204c and the slider 203 in contact with the intermediate layer 204b are reduced in this order, so that the generated heat can be efficiently dissipated.
This is preferable because the occurrence of inconveniences such as deformation and melting of the light shielding means 204 due to heat can be suppressed. In addition, by using a material whose thermal conductivity increases with an increase in temperature, the heat dissipation of a portion where heat is generated can be improved with an increase in temperature. Breakage of the light shielding means 204 can be suppressed more efficiently, and a more reliable optical head can be obtained.

Next, it is also preferable to reduce the heat release into the air in the order of the reflective layer 204c, the intermediate layer 204b adjacent to the reflective layer 204c, and the slider 203, which generate a large amount of heat. In particular, it is possible to suppress the temperature rise of the reflective layer 204c by setting the heat release property of the reflective layer 204c to be at least twice as large as that of the intermediate layer 204b and the slider 203, and it is possible to suppress the deterioration due to the temperature change of the light shielding characteristic and the reflection layer 204c. This is preferable because breakage can be greatly suppressed.

Finally, it is preferable that the thermal expansion properties (linear expansion coefficients) of both the light shielding means 204 and the slider 203 are small, and that the difference is small. Also, the intermediate layer 204
b is the linear expansion coefficient of the slider 203 and the reflection layer 2.
04c can be set between the linear expansion coefficients.
3 and the difference in the coefficient of linear expansion between the intermediate layer 204b and the intermediate layer 20b.
Since the difference in the coefficient of linear expansion between the reflective layer 4b and the reflective layer 204c can be made smaller, it is possible to suppress inconveniences such as cracks caused by the difference in the respective coefficients of expansion. .

In particular, the size such as the opening diameter of the minute opening 204a defined by the reflective layer 204c is slightly changed according to the expansion and contraction of the reflective layer 204c. Especially the small aperture 2
In the state where the evanescent light 216 is generated from the light reflection layer 204a, the reflection layer 204 when the reflection layer 204c is heated to a high temperature.
If the minute opening 204a becomes small due to the expansion of c, the reach of the evanescent light 216, which is considered to change in proportion to the opening diameter, also becomes short, so that the evanescent light 216 comes into contact with the recording medium 206. It is difficult to form the recording medium to such an extent that recording or reproduction cannot be performed. Therefore, the reflection layer 204
The range of the coefficient of linear expansion that c should satisfy is the minute opening 204a.
Is required to be in a range in which information can be recorded / reproduced using the evanescent light 216, and furthermore, when the light is irradiated so that the shape change of the reflective layer 204c becomes large, that is, the temperature of the reflective layer 204c becomes higher. When the coefficient of linear expansion is compared with the coefficient of linear expansion in the non-irradiated state, that is, when the reflective layer 204c is at a lower temperature, the variation rate is 20%.
Using a material within the range can minimize a change in the amount of change in the shape of the reflective layer 204c due to a temperature state, and can stabilize the reach of the evanescent light 216. This is preferable because reproduction and / or recording with stable evanescent light 216 can be performed.

The slider 20 satisfying the above characteristics
3 and the following materials can be considered as materials of the intermediate layer 204b and the reflective layer 204c.

First, the slider 203 is formed of a material having a light-transmitting property such as resin or glass, and in particular, a material having a transmittance of 90% or more at the wavelength of the light from the light source 201 here. This is preferable because the evanescent light 216 can be generated without lowering the light emission. In particular, since glass has a large strength, by using it as a material for forming the slider 203 which is considered to be likely to come into contact with the recording medium, it is less likely that the glass will be damaged even if it comes into contact with the recording medium. This is preferable because a slider with high performance can be realized. In particular, among glass materials, it has a sufficient strength, a small coefficient of thermal expansion, and
Quartz glass, which has almost no change in coefficient of thermal expansion from low to high temperatures, is the most suitable material.

Next, the intermediate layer 204b is located between the slider 203 and the reflection layer 204c, and is often formed mainly of a material such as glass, resin, or metal. It is often determined accordingly. For example, when the slider 203 is formed of a glass material and the reflection layer 204c is formed of a metal material,
4b is made of a glass material or a metal material, so that the difference in the coefficient of thermal expansion can be suppressed to a minimum. Therefore, inconveniences such as cracks are generated between each of the slider 203 and the reflective layer 204c and the intermediate layer 204b. Can be suppressed. As an optimal combination, when quartz glass is used for the slider 203, lead glass or borosilicate glass efficiently absorbs the difference in thermal expansion between the slider 203 and the reflective layer 204c particularly in a high temperature state. Is preferred. The middle layer 2
The thickness of 04b is preferably about 10 nm to 1000 nm, because the difference in thermal expansion between the slider 203 and the reflective layer 204c can be efficiently absorbed. Further, the intermediate layer 204b is also preferably formed of a light-transmitting material. By forming the intermediate layer 204b with a translucent material, the position where the evanescent light 216 is generated can be changed.
It can be near the interface between b and the reflective layer 204c.
Therefore, as compared with the case where the light is generated on the lower surface of the slider 203, the recording medium 2 is generated from the position where the evanescent light 216 is generated.
Since the distance up to 06 can be made shorter, the distance between the recording medium 206 and the slider 203 can be more easily controlled, which is preferable.

Next, the reflection layer 204c is mainly made of Au, Ag, A
Metal materials such as l and Cu, SIO ₂ and TiO ₂
In many cases, it is formed of a material having a property of reflecting light, such as a combination of dielectric materials such as. When the film thickness is about 10 nm to 100 nm, light can be prevented from leaking from a portion other than the minute opening 204a, and the evanescent light 216 generated in the minute opening 204a faces the recording medium 206 of the reflective layer 204c. This is a preferable configuration because the recording medium 206 can be made to protrude more reliably toward the recording medium 206 than the surface, and information can be recorded and / or reproduced with the protruding evanescent light 216 reliably.

In the present embodiment, since the intermediate layer 204b has high translucency, the minute opening 204a is
04c. Middle layer 204
b has a light shielding characteristic,
Is preferably formed to penetrate the intermediate layer 204b and the reflective layer 204c.

Further, the light-shielding means 204 has a two-layer structure of the intermediate layer 204b and the reflective layer 204c. However, the light-shielding means 204 may have a three-layer or more layer structure, and the heat conductivity, the linear expansion coefficient and the like of the reflective layer 204c are optimized. When a functionally graded material is used, or when the difference between the material constituting the slider 203 and the thermal conductivity or the coefficient of linear expansion is small, the intermediate layer 204b can be omitted.

As described above, in this embodiment, a part or the whole of the slider 203 is formed of a translucent member, and the minute opening 204a for generating the evanescent light 216 is formed in the medium facing surface. With this configuration, the slider 203 itself can be used as a means for generating the evanescent light 216. Therefore, compared with a case where the evanescent light 216 generating means such as a probe is provided separately, the distance between the slider 203 and the slider 203 can be reduced. This eliminates the need for alignment, and also reduces the number of parts and the number of assembly steps, so that an optical head with extremely high product accuracy and high productivity can be realized.

Further, since the slider 203 is entirely or partially formed of a translucent member, strict alignment between the optical path 202 and the minute opening 204a and the slider 20 can be achieved.
3. Even if a hole for transmitting light is not provided in
Since the light can be guided to the slider 4a, the configuration of the optical head can be simplified.
The optical head can be installed anywhere as long as it is the medium facing surface, so that the degree of freedom in designing the optical head can be ensured.

[0092]

As described above, according to the present invention, light is concentrated by providing an intermediate layer between light-shielding means, which concentrates light to define a minute aperture, and becomes high in temperature, and evanescent light generating means, which is relatively low in temperature. It absorbs the difference in temperature and expansion coefficient between the means and the evanescent light generating means, and can reduce the stress caused by heat. Can be suppressed. In addition, the thermal conductivity and thermal expansion coefficient of the intermediate layer, the heat release property into the air, and the like are optimized for those of the light blocking means and the evanescent light generating means, respectively, so that the occurrence of inconvenience is suppressed more efficiently. As a result, the reliability of the optical head can be improved, and the reliability of the information reproducing apparatus equipped with the optical head can also be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an information reproducing apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing a configuration of a slider according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an information reproducing apparatus according to Embodiment 2 of the present invention.

FIG. 4 is a diagram showing a configuration of a slider according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Light source 102 Optical path 103 Slider 103a, 103b, 103c Rail surface 104 Light shielding means 104a Micro opening 105 Support member 105a, 105b End 106 Recording medium 107 Driving means 108 Light condensing member 109 Light receiving member 110 Light flux 111 Medium driving means 201 Light source 202 Optical path 203 Slider 204 Light shielding means 204a Micro aperture 204b Intermediate layer 204c Reflective layer 205 Support member 205a, 205b End 206 Recording medium 207 Driving means 208 Condensing member 209 Light receiving member 210 Light flux 211 Lens 212 Reflecting mirror 213 Light source 214 Optical path

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masuki Ogushi 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. Terms (reference) 5D090 AA01 CC04 FF11 KK01 LL03 5D119 AA22 BA01 CA05 CA06 DA05 EB02 JA35 JA44 JA59 JA63 MA03 MA06

Claims (8)

[Claims] A light source, an optical system for guiding light from the light source to a predetermined position, evanescent light generating means for generating evanescent light from light guided by the optical system, and evanescent light generating means. Holding means for holding, driving means for moving the holding means to a predetermined position on a recording medium, light-shielding means provided around the evanescent light generating means for blocking light other than evanescent light, and evanescent light generating means Light generated by an interaction between the evanescent light and the recording surface of the recording medium, and an intermediate layer provided between the evanescent light generating means or the light shielding means and provided between the means and the light shielding means. An optical head comprising: a light receiving unit that receives light. 2. The thermal expansion coefficient of the intermediate layer is not less than the thermal expansion coefficient of the material forming the evanescent light generating means and is not more than the thermal expansion coefficient of the material forming the light shielding means.
The optical head as described. 3. A light source, an optical system for guiding light from the light source to a predetermined position, and at least a region through which light guided from the optical system passes is formed of a translucent material. A slider that slides or floats due to the rotation of the slider, a driving unit that moves the slider to a predetermined position on the recording medium, and receives light generated by an interaction between the evanescent light and the recording surface of the recording medium. An optical head for generating evanescent light from the minute opening, wherein the optical head is provided between the slider and the light shielding unit. An optical head comprising: an evanescent light generating means or an intermediate layer for relaxing heat generated by the light shielding means. 4. The optical head according to claim 3, wherein the coefficient of thermal expansion of the intermediate layer is not less than the coefficient of thermal expansion of the material forming the slider and not more than the coefficient of thermal expansion of the material forming the light shielding means. 5. The optical head according to claim 3, wherein the thermal conductivity of the intermediate layer is higher than the thermal conductivity of the material forming the slider and lower than the thermal conductivity of the material forming the light shielding means. 6. The optical head according to claim 3, wherein the heat release property of the intermediate layer into the air is higher than the heat release property from the slider and lower than the heat release property from the light blocking means. 7. The optical head according to claim 1, wherein the intermediate layer is formed of a translucent material. 8. An optical head according to claim 1, wherein the optical head according to claim 1 irradiates evanescent light to the rotating recording medium by a medium driving means for holding and driving the recording medium. An information reproducing apparatus capable of reproducing information.