JP2000357334A - Optical head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical head of a low cost of which the movable part having an objective lens slides and turns smoothly with respect to an optical information recording and reproducing medium under a central shaft which is highly resistant to flawing and is easy in production stages. SOLUTION: The central shaft 13 which is formed with composite nickel plating 18 dispersed with particulates 17 of polytetrafluoroethylene, on the surface of a base material shaft 15 to a thickness of 3±0.5 μm by a method of electroless plating is erected in the central part of a yoke 52 constituting a frame of a main body 51 of an optical head 1. The central shaft 13 is inserted into a sleeve 63 of a movable part 61. Drive coils 64 and 65 for focusing error correction and tracking error correction of the movable part 61 having the objective lens 62 are disposed to face magnets 54 and 55 for focusing error correction and tracking focusing error correction disposed at the main body 51 together with neutral iron pieces 66 disposed in their central positions.

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 recording and reproducing information on and from an optical information recording / reproducing medium such as a compact disk (CD) and a magneto-optical disk, and more particularly, to an optical head. And a semiconductor laser for the optical information recording / reproducing medium.
When the objective lens for focusing and irradiating the light beam is moved in the focusing error correction direction and / or the tracking error correction direction, the objective lens does not tilt, and thus the optical axis with respect to the surface of the optical information recording / reproducing medium does not tilt, The present invention relates to an optical head on which information is accurately recorded and reproduced.

[0002]

2. Description of the Related Art An optical head comprises a movable portion on which an objective lens is mounted, and a main body for supporting the movable portion. To correct a focusing error and a tracking error, the movable portion is made of a spring, a wire, or the like. The movable part is moved by sliding along the central axis and rotating around the central axis so that the objective lens does not tilt.

(Conventional Example 1) FIG. 4 is a perspective view showing an example of an optical head in which a movable portion is suspended and supported. FIG. 5 is a side view taken along the line [5]-[5] in FIG. 4, and is shown together with the optical disc 31 set on a spindle of a chassis (not shown). Referring to FIGS. 4 and 5, the optical head 2 of the related art 1 includes a main body 21 and a movable portion 41 supported by the main body 21, and the main body 21 has a rectangular cylindrical laser extending downward. A coupler mounting section 23 is provided, and a laser coupler 24 that houses a semiconductor laser, a microprism, and a photodetector is mounted at the lower end thereof. Further, a feed gear 25 is attached to the main body 21, and a driving force is transmitted to the feed gear 25 by a DC motor and a rack and pinion mechanism (not shown), and the optical head 2 is moved in a chassis (not shown) in a direction indicated by an arrow n. Reciprocated.

Referring to FIG. 5, an objective lens 42 of a movable portion 41 is located above the laser coupler 24 and directly below the optical disk 31. That is, laser coupler 2
The light beam from the semiconductor laser in 4 is
The light focused on the optical disk 31 and radiated on the surface of the rotating optical disk 31 and reflected by the surface of the optical disk 31 returns to the laser coupler 24 again through the objective lens 42, is separated by the microprism, and is incident on the photodetector. Thus, the error of the irradiation position of the light beam on the surface of the optical disk 31 is detected. In FIG. 5, the direction in which the optical head 2 is moved is a direction perpendicular to the paper surface.

[0005] Referring to FIG. 4, a magnet 34 a and a core 3 are located on both sides of a movable portion 41 in a main body 21.
7a, a magnet 34b and an iron core 37b are attached, and a magnetic circuit is formed between them. The magnets 34a and 34b are polarized in the thickness direction and have opposite poles. That is, when the surface of one magnet 34a on the movable portion 41 side has the N pole, the surface of the movable portion 41 of the other magnet 34b is magnetized so as to have the S pole.

On the other hand, a movable part 41 having an objective lens 42
Is supported by a support member 29 of the main body 21 via two upper and lower support plates 27 made of synthetic resin (the lower support plate 27 is not shown in FIG. 4). That is, an extremely fine concave portion 27a in the width direction of the front end portion of the support plate 27 is connected to the central portion of the movable portion 41, and an extremely fine concave portion 27b in the width direction of the rear end portion of the support plate 27 is connected to the support member 29. It is connected to. Further, a horizontally long rectangular through hole 28 is provided near the front end and the rear end of the support plate 27, and on both sides thereof, an extremely fine concave portion 28t is formed in a horizontal line shape in the thickness direction. (The tip portion 28t is not shown). Then, the movable portion 41 provided with the objective lens 43 is moved up and down with the deformed portion 28t as a deformed portion, and is rotated in a horizontal plane about the deformed portion 27a located at an intermediate position between the magnet 34a and the magnet 34b. ing.

The movable part 41 includes an iron core 37a of the main body 21,
Focusing error correcting drive coils 44a and 44b wound in a rectangular tube shape are attached to both side edges so as to surround 37b. These are connected and wound in the same direction, and the focusing error correction drive coils 44a and 44b are moved up and down depending on the direction of the current flowing, and move the movable unit 41 up and down together with the objective lens 42. Further, two tracking error correction drive coils 45a are mounted side by side on the magnet 34a side surface of the focusing error correction drive coil 44a, and similarly, the focusing error correction drive coil 44b is mounted on the magnet 34b side. Also, two tracking error correcting drive coils 45b (not shown in FIG. 4) are mounted side by side in the horizontal direction.
The drive coil 45a and the drive coil 45b are connected with their winding directions reversed, and rotate the movable portion 41 clockwise and counterclockwise in a horizontal plane about the concave portion 27a depending on the direction of the flowing current. .

In the optical head 2 of the conventional example 1, the movable portion 41 is supported by the support member 29 of the main body 21 via the support plate 27. Therefore, even if two support plates 27 are provided up and down, When the movable part 41 is moved up and down together with the objective lens 42 and rotated, the objective lens 42 tilts, the optical axis of the semiconductor laser with respect to the surface of the optical disk 31 is tilted, so-called dynamic skew is generated, and information recording and reproduction is performed. Is liable to lower the accuracy.

(Conventional Example 2) In recent years, a semiconductor laser having a short wavelength and an objective lens having a large numerical aperture have been adopted in order to increase the recording density. In this case, an optical system is used. The allowable margin width of the optical axis with respect to the surface of the information recording / reproducing medium, that is, the skew tolerance is reduced. In order for the optical head to operate within a small dynamic skew tolerance, it is necessary to improve the assembly accuracy of the entire optical head, but the method of supporting the movable part prevents the tilt of the objective lens The effect of doing is great.

FIG. 6 is a perspective view of an optical head 3 of a second conventional example with improved dynamic skew. FIG.
7A is an exploded perspective view, FIG. 7A is a perspective view of the movable portion 61, and FIG. 7B is a perspective view of the main body 51. That is, the optical head 3 is connected to the yoke 52
The central shaft 53 erected at the center of the bobbin 69 is inserted through the sleeve 63 at the center of the bobbin 69 that is the main body of the movable portion 61, and the movable portion 61 slides vertically along the central axis 53, It rotates clockwise and counterclockwise about a central axis 53 in a horizontal plane. In such an optical head 3, as long as the accuracy of mounting the center shaft 53 and the accuracy of the clearance between the center shaft 53 and the sleeve 63 are ensured, the inclination of the objective lens 62 is prevented and the dynamic skew is relatively reduced. There is an advantage that it can be easily maintained at a predetermined accuracy.

Referring to FIG. 7A, an objective lens 62 is provided on the bobbin 69 of the movable portion 61, and a pair of focusing error corrections for moving (vertically moving) the objective lens 62 in the focusing error correction direction. A drive coil 64 for tracking and a pair of drive coils for tracking error correction 65 for moving (rotating) the objective lens 62 in the tracking error correction direction are mounted at symmetrical positions about the sleeve 63. When the error correction is not required, a neutral iron piece 66 is attached to the center position of each of the drive coils 64 and 65 so that the movable portion 61 maintains the neutral position in the focusing error correction direction and the tracking error correction direction. And a pair of focusing error correcting magnets 54 and a pair of tracking error correcting magnets 55 of the main body 51 to be described later. That is, the magnetic attractive force acting between each neutral iron piece 66 and each of the magnets 54 and 55 facing each other becomes a force for restoring the movable portion 61 to the neutral position when the movable portion 61 is displaced from the neutral position. The movable part 61 is the central axis 5
3 and can be positioned at the neutral position in a floating state. The bobbin 69 is provided with a balancer 67 corresponding to the objective lens 62 so that the center of gravity coincides with the center of movement. A flexible printed wiring board (FPC) 68 is fixed to the balancer 67 and the bobbin 69 so that the driving coils 64, 6
5 is supplied with a current for correcting a focusing error and / or a tracking error as necessary.

Referring to FIG. 7B, the main body 51 is configured with the yoke 52 as a frame. As described above, the center shaft 53 is erected at the center of the yoke 52, and , Four rising portions 5 on the periphery of the yoke 52
2a, a pair magnet (N pole piece 54n, S pole piece 5), which is arranged in the thickness direction and oppositely arranged in opposite directions to the focusing error correction drive coil 64 of the movable portion 61.
4s), a pair of focusing error correcting magnets 54 are fixed, and similarly, the opposite pole pieces are arranged in the thickness direction opposite to the tracking error correcting drive coil 65 of the movable portion 61 and are polarized in the thickness direction. Pair magnet (N
A pair of tracking error correcting magnets 55 composed of a pole piece 55n and an S pole piece 55s) is fixed, and a magnetic field is formed between each pair of magnets. It should be noted that an integral two-pole magnetized magnet may be used instead of the paired magnet.

That is, horizontal portions 64a and 64b of the focusing error correcting drive coil 64 shown in FIG.
Are the N pole piece 54n and the S pole piece 5 of the pair magnet of the focusing error correcting magnet 54 shown in FIG.
4s, and similarly, vertical portions 65a, 65a of the tracking error correction drive coil 65 in FIG.
b is an N pole piece 55n and an S pole piece 5 of a pair magnet of the tracking error correction magnet 55 shown in FIG.
5s. Then, depending on the direction of the current flowing through the focusing error correction drive coil 64, a force to move the coil 64 in the vertical direction acts to slide the movable portion 61 in the vertical direction along the central axis 53 together with the objective lens 62, Due to the direction of the current flowing through the tracking error correction drive coil 65, a force for moving the coil 65 in the horizontal direction acts to rotate the movable portion 61 together with the objective lens 62 around the central axis 53.

In the optical head 3, the movable portion 61 slides smoothly along the central axis 53,
The bobbin 69 including the sleeve 63 is manufactured by molding a material having a small frictional resistance so that the bobbin 69 including the sleeve 63 is smoothly rotated around the bobbin. FIG. 8 shows a central shaft 53.
FIG. 4 is a perspective view showing a state before fixing to a yoke 52 of a main body 51, such that a movable portion 61 slides and rotates smoothly.
Except for the lower end portion 57e of the metallic base shaft 57 inserted under pressure into the yoke 52, the surface 58 of the base shaft 57 is coated with a coating of ethylene tetrafluoride resin 15 μm to 20 μm.
It is formed to a thickness and has a reduced friction coefficient.

Japanese Patent Laid-Open Publication No. Hei 10-172151 discloses an optical pickup for supporting a movable portion provided with an objective lens for converging and irradiating a light beam onto an optical disk so as to be able to slide on an axis. There is disclosed an optical pickup in which a magnetic body is attached to a sleeve of a movable portion into which a shaft of a magnetic material is fitted. In this optical pickup, the inclination of the movable portion with respect to the axis is prevented by a magnetic material to prevent the inclination of the objective lens, but this does not improve the axis itself. Japanese Patent Application Laid-Open No. Hei 9
Japanese Patent Application Laid-Open No. 18020/220 discloses a two-axis actuator that moves a current by flowing a current by arranging a tracking coil or a focusing coil in a magnetic field formed between a magnet and a yoke, that is, a movable part. In the above, for example, a cross-shaped magnetic body of a size at least partially coinciding with the height and width of the magnet is attached to the coil of the movable part, and the midpoint is held when the biaxial actuator is moved. There is disclosed a biaxial actuator that does not generate a large frictional force when pressed against a sliding shaft. This two-axis actuator is intended to smoothly slide the sliding shaft and the two-axis actuator, but does not improve the sliding shaft itself.

[0016]

In manufacturing the center shaft 53 coated with the tetrafluoroethylene resin 58 in the optical head 3 of the second prior art in order to slide and rotate the movable part, the coating 58 is not used. In order to increase the thickness, a mask is applied to the lower end portion 57e of the base material shaft 57 inserted into the yoke 52 so that the coating 58 is not formed, and the surface of the unmasked portion is coated with a coating solution of tetrafluoroethylene resin. After applying and drying, 400 ° C
It is fired at a temperature before and after. Thereafter, the center axis 53 is set to ± 2μ.
The coating film is polished by a centerless polisher so as to obtain an outer diameter accuracy of m, and the above-mentioned film thickness of 15 μm to 20 μm is obtained, so that the manufacturing cost of the central shaft 53 is high. Further, the obtained coating film 58 of the central shaft 53 is obtained.
Has a problem that it requires a great deal of caution and caution when handling transport and assembly because the surface hardness is about B, which is indicated by the hardness of the pencil lead and is easily damaged.

The present invention has been made in view of the above problems, and does not tilt the objective lens when the movable portion slides and rotates around the center axis, so that dynamic skew does not occur, and the center axis has a surface. An object of the present invention is to provide an optical head which has high hardness, is hardly damaged, and is therefore easy to handle, and has a simple manufacturing process and can be manufactured at low cost.

[0018]

Means for Solving the Problems The above-mentioned problems are solved by the structure of claim 1. To solve the problem, the optical head of claim 1 is applicable to an optical information recording / reproducing medium such as an optical disk. A movable part equipped with an objective lens that focuses and irradiates the light beam is erected on the main body and is slidable along a central axis that passes through the movable part in the direction of the light beam, and is rotatable around the central axis. Further, a focusing error correction drive coil and a tracking error correction drive coil attached to the movable portion are arranged in a magnetic field formed in the main body, and the focusing error correction drive coil and / or Depending on the direction of the current flowing through the tracking error correction drive coil, the direction in which the focusing error is corrected for the optical information recording / reproducing medium and / or the tracking error is corrected. So as to move the objective lens in a direction to correct, sliding and based on the central axis of the movable part /
Alternatively, in the optical head to be rotated, the central axis is such that the surface of the base material axis is covered with a composite metal plating film in which fine particles of a lubricity imparting material are dispersed. In such an optical head, the movable part having the objective lens slides smoothly around the central axis to rotate and does not generate dynamic skew, and the central axis has a large surface hardness and is damaged. It is difficult and does not require much attention and caution during handling, the manufacturing process is simple, and the manufacturing cost is reduced.

In the optical head according to the first aspect, the volume ratio of the fine particles of the lubricity-imparting material in the composite metal plating film on the central axis is in the range of 10% to 30%. Such an optical head has a high surface hardness of the central axis but a low coefficient of friction, so that the optical axis imparts resistance to scratches on the central axis, and slides along the central axis of the movable portion, and rotates around the central axis. To smooth out. The optical head according to claim 3 is dependent on claim 1, wherein the fine particles of the lubricity imparting material dispersed in the composite metal plating film on the central axis are fine particles of ethylene tetrafluoride resin or ethylene tetrafluoride copolymer resin. And the particle size is in the range of 0.01 μm to 1 μm. Such an optical head has a low friction coefficient due to the low friction coefficient of the fine particles of the tetrafluoroethylene resin or the tetrafluoroethylene copolymer resin exposed on the surface of the central axis, and smoothly moves and rotates the movable portion. . The optical head according to claim 4 is dependent on claim 3, wherein fine particles of an ethylene tetrafluoride resin or an ethylene tetrafluoride copolymer resin are spherical and independently dispersed in the composite metal plating film on the central axis. is there. In such an optical head, fine particles of ethylene tetrafluoride resin or ethylene tetrafluoride copolymer resin work most efficiently and effectively, and the central axis has a low friction coefficient close to that of ethylene tetrafluoride resin alone. While exhibiting high surface hardness.

In the optical head according to the first aspect of the present invention, the composite metal plating film on the central axis is formed by electroless plating using nickel (Ni) or another nickel alloy, or cobalt (Co) or a cobalt alloy as a metal component. It was formed. In such an optical head, since the composite metal plating film is formed as a thin film on the surface of the base material shaft and has a uniform outer diameter accuracy, for example, with a film thickness of 3 ± 0.5 μm, it is inserted into the yoke on the center shaft. There is no need for a mask for preventing the formation of the composite metal plating film on the portion, and the formed composite metal plating film does not require finish polishing. The optical head according to claim 6 is dependent on claim 5, wherein the metal component of the composite metal plating film on the central axis is an alloy of 85 to 95% by weight of nickel and 5 to 15% by weight of phosphorus or boron. Things. Heat treatment after composite metal plating can increase the surface hardness of the central axis to the same level as hard chrome plating.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the optical head of the present invention has a movable portion provided with an objective lens for focusing and irradiating an optical information recording / reproducing medium such as an optical disk with a light beam. The unit is slidable along a central axis that passes through the unit in the direction of the light beam, and is rotatable about the central axis. Further, a focusing error correction drive coil attached to the movable unit and tracking An error correction drive coil is disposed in a magnetic field formed in the main body, and the objective lens is moved to the optical information recording medium by a direction of a current flowing through the focusing error correction drive coil and / or the tracking error correction drive coil. The movable part is slid along the center axis so that the moving part moves in the direction of correcting the focusing error and / or the direction of correcting the tracking error. In and / or optical head to pivot, in which the central axis is covered with dispersed composite metal plating film of fine particles of lubricity providing material to the surface of the base axis.

The metal film as a matrix in the composite metal plating film on the central axis may be formed by an electroplating method, or may be formed by using sodium hypophosphite, borohydride, hydrazine or the like as a reducing agent. It may be formed by an electrolytic plating method. The fine particles of the lubricity-imparting material added to and mixed with these plating solutions are co-precipitated with the metal to form a composite metal plating film. However, the electroless plating method is preferred from the viewpoint of the throwing power of the metal plating and the uniformity of the thickness of the formed composite metal plating film.

The kind of metal of the metal plating film is not particularly limited as long as the hardness of the metal plating film to be formed is high, and nickel (Ni) that can be electrolessly plated is suitable in that respect. N
i may be a simple substance or an alloy containing Ni as a main component. Ni alloys include NiP (phosphorus) alloy, NiB (boron) alloy, and NiCo (cobalt).
Alloys, Ni-Co-P alloys, Ni-Co-B alloys and the like can be used. Those containing 5% to 15% by weight of P or B increase the surface hardness of the central axis by heat treatment, but those containing 8% to 10% by weight are more preferable from the viewpoint of the effect. By subjecting such a Ni alloy to a heat treatment at a temperature of 350 ° C. or higher for about one hour, it has a hardness comparable to hard chromium (Cr). Also, instead of Ni, Co can be electrolessly plated.
A simple substance or an alloy containing Co as a main component can also be used as the matrix metal of the composite metal plating film.

The amount of the fine particles of the lubricity imparting material dispersed in the composite metal plating film is preferably in the range of 10% by volume to 30% by volume. When the volume ratio is less than 10% by volume, the lubricating property of the central axis is insufficient and the friction coefficient does not decrease as expected. When the volume ratio exceeds 30% by volume, the strength of the composite metal plating film becomes insufficient, and Fine particles of the application material easily fall off the composite metal plating film. A more preferred range is 15
It is in the range from 25% by volume to 25% by volume.

The fine particles of the lubricity-imparting material preferably have a particle diameter in the range of 0.01 μm to 1 μm. Further, those in which they are dispersed as independent spherical fine particles are more preferable, and they work most efficiently and effectively. Particles having a particle size of less than 0.01 μm have too small a particle size and are cumbersome to manufacture and handle, and particles having a particle size of more than 1 μm have a large sedimentation velocity in a plating solution, making it difficult to expect uniform co-precipitation. Even if the fine particles are not independent and are aggregated, or the fine particles are not spherical, lubricity is provided, but the lubricating effect is slightly reduced.

As the fine particles of the lubricity-imparting material dispersed in the composite metal plating film on the central axis, various inorganic and organic fine particles are used. As an inorganic lubricity imparting material, for example, graphite,
Fine particles such as graphite fluoride and molybdenum disulfide can be used, and fine particles such as, for example, ethylene tetrafluoride resin and ultrahigh molecular weight polyethylene are used as the organic lubricity imparting material. Among them, fine particles of ethylene tetrafluoride resin and ethylene tetrafluoride as main components, propylene hexafluoride, ethylene trifluoride monochloride, perfluoroalkyl vinyl ether (alkyl group having 1 to 3 carbon atoms), ethylene Fine particles of a tetrafluoroethylene copolymer resin containing at least one copolymer component are preferably used.

(Embodiment) An optical head according to the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of an optical head 1 according to the embodiment. Since the overall configuration is the same as that of the optical head 3 of the conventional example 2 shown in FIG. 6, the corresponding components are denoted by the same reference numerals and description thereof will be omitted. The optical head 1 according to the first embodiment is different from the optical head 3 according to the second conventional example in that the optical head 3 according to the second conventional example has a center shaft 53 and a surface 58 of a base material shaft 57 coated with a tetrafluoroethylene resin coating 58. On the other hand, the optical head 1 according to the embodiment is such that the central axis 13 is obtained by applying a composite nickel electroless plating 18 on the surface of the base material axis. Compared with the center shaft 53 in the conventional example 2, the center shaft 13 by the composite nickel electroless plating 18 can be manufactured at a high dimensional accuracy while having a simple manufacturing process, so that it can be manufactured at low cost without the need for finish polishing. Is done. Further, the hardness is high, the scratch is hard to be made, and a great deal of attention and caution is not required for handling. These will be described below.

Optical head 1 according to an embodiment of the present invention
As shown in FIG. 1, a center shaft 13 erected on a yoke 52 forming a frame of a main body 51 is inserted through a sleeve 63 provided at a center portion of a bobbin 69 serving as a main body of a movable portion 61. Slides vertically along the central axis 13 and rotates clockwise and counterclockwise around the central axis 13. FIG. 2 is a perspective view of the center shaft 13, and FIG. 3 is a partial cross-sectional view schematically showing a surface portion indicated by a circle in FIG. That is, the central shaft 13 is formed on the surface of the base material shaft 15 having a diameter of 1.5 mmφ by electroless plating in the nickel-phosphorus alloy plating film 16 in a polytetrafluoroethylene resin (polytetrafluoroethylene, PTFE).
The composite nickel plating film 18 is formed to a thickness of 3 μm in which spherical fine particles 17 having a particle diameter of 0.01 μm to 1 μm protrude from the surface and are also uniformly dispersed in the thickness direction. In addition, fine particles 1 of ethylene tetrafluoride resin
7 is 20% by volume to 2% in the composite nickel plating film 18.
5% by volume, nickel-phosphorus alloy plating film 1
6 contains nickel 90% to 92% by weight and phosphorus 8% by weight
-10% by weight of nickel alloy is used.

The center axis 13 as described above has fine particles 17 of ethylene tetrafluoride resin projecting from the surface of the composite nickel plating film 18 giving the center axis 13 a low friction coefficient close to that of the ethylene tetrafluoride resin alone. Provides lubricity. That is, the dynamic friction coefficient measured with stainless steel as the counterpart material is in the range of 0.08 to 0.10. The movable portion 61 slides very smoothly under the center shaft 13 to rotate. Then, the nickel-phosphorus alloy plating film 16 gives the central axis 13 a surface hardness of Vickers hardness of 250 to 350. The nickel-phosphorus alloy plating film 16 is subjected to a heat treatment at 350 ° C. for one hour as described above,
The surface hardness of the central shaft 13 is set to a Vickers hardness of 400 to 500.
Enhance.

Further, since the composite nickel plating film 18 is formed by an electroless plating method having good throwing power, the composite nickel plating film 18 is formed to a uniform thickness of 3 ± 0.5 μm, and its surface hardness is ± 1.5 μm in combination with the outer diameter accuracy ± 1 μm of the base material shaft 15 before plating.
m is maintained. Therefore, unlike the center shaft 53 coated with the tetrafluoroethylene resin coating 58 of the conventional example 2, the coating 58 does not peel off by press-fitting and no scum is generated, so that a portion to be inserted into the yoke 52 requires a masking. And no polishing treatment for obtaining the outer diameter accuracy is required. Furthermore, since the tetrafluoroethylene resin is not affected by the chemical at all, the composite nickel plating film 1
The corrosion resistance of No. 8 is equivalent to that of a plated film of nickel alone, and is not limited to the atmosphere in which it is used.

Table 1 compares the manufacturing steps of the central shaft 13 of the embodiment and the central shaft 53 of the conventional example 2. As shown in Table 1, in the case of the embodiment, masking is not required for the base material axis in the step, heat treatment is not necessarily required in the step, and outer diameter polishing for finishing the step is not required at all. No inspection of the appearance of the flaw is required in the inspection after the manufacture of the device. As described above, the manufacturing process of the center shaft 13 of the embodiment is greatly simplified, and the manufacturing cost is greatly reduced.

[0032]

[Table 1]

The optical head 1 according to the embodiment of the present invention is constructed and operates as described above. Of course, the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention. It is possible.

For example, in this embodiment, two magnets 54 and 55 and two drive coils 64 and 6 are used.
The focusing error and the tracking error are corrected by correcting the focusing error of the optical head by the combination of four sets of 5 and 5. However, the focusing error and the tracking error are corrected by a combination of other numbers, for example, two sets. It may be a thing. Also, in the present embodiment, the four neutral iron pieces 66 of the movable portion 51 and the main body 51
Of the central shaft 13 by the four magnets 54 and 55
In the above, the optical head 1 that magnetically levitates and supports the movable portion 61 is exemplified. However, the movable portion is supported by a method other than the magnetic support, for example, the movable portion having the center axis inserted therein is easily displaced. The present invention also includes a synthetic resin plate provided with the above, an optical head supported by a spring, a wire, and the like.

In this embodiment, the case in which the number of objective lenses is one is exemplified. However, for example, two objective lenses are provided so as to be able to handle two types of optical discs, a CD and a DVD (digital video disc). The present invention is similarly applied to the provided optical head. Further, in the present embodiment, the composite nickel electroless plating is directly applied to the surface of the base material shaft, but a base film for improving the adhesiveness to the base material shaft before the composite electroless nickel plating, for example, nickel alone is used. A plating film may be formed.

[0036]

The present invention is embodied in the form described above, and has the following effects.

According to the optical head of the first aspect, since the central axis is provided with the composite metal plating in which the fine particles of the lubricity-imparting material are dispersed, the movable portion provided with the objective lens can be moved along the central axis. Smoothly sliding and rotating enables the dynamic skew to be kept within a predetermined accuracy range. Also,
The central shaft has a high surface hardness and is hard to be scratched, so it is easy to handle.In addition, plating does not require masking, and the plating has a high outside diameter accuracy and finish polishing is not required, enabling low-cost manufacturing. To According to the optical head of the second aspect, since the fine particles of the lubricity-imparting material protrude from the surface of the composite metal plating film on the central axis and are uniformly dispersed in the thickness direction of the composite metal plating film, the movable head is movable. The sliding along the central axis of the part and the rotation around the central axis are reduced in friction and performed smoothly and accurately. According to the optical head of claim 3, fine particles having a particle diameter of 0.01 μm to 1 μm of ethylene tetrafluoride resin or ethylene tetrafluoride copolymer resin are used as the lubricity imparting material in the composite metal plating on the central axis. Therefore, the center axis has a low friction coefficient based on the tetrafluoroethylene resin, and smoothly slides and turns the movable portion.

According to the optical head of claim 4, independent spherical fine particles of ethylene tetrafluoride resin or ethylene tetrafluoride copolymer resin are used as the lubricity imparting material. Low friction is most efficiently and effectively developed, while giving a high surface hardness to the central axis. According to the optical head of the fifth aspect, the composite metal plating film on the central axis is formed by electroless plating with nickel or an alloy mainly containing nickel, or cobalt or an alloy mainly containing cobalt together with fine particles of a lubricity imparting material. Therefore, the thickness of the composite metal plating film is uniform, the finish polishing is not required, and the cost of the central axis is reduced. According to the optical head of the sixth aspect, the alloy of nickel, 85% to 95% by weight, and 5% to 15% by weight of phosphorus or boron is used as the metal of the composite metal plating film. Can be increased in surface hardness, making it difficult to be scratched during handling.

[Brief description of the drawings]

FIG. 1 is a perspective view of an optical head according to an embodiment.

FIG. 2 is a perspective view of a central axis used in the optical head.

FIG. 3 is a partial sectional view of the central axis.

FIG. 4 is a perspective view of an optical head of Conventional Example 1.

FIG. 5 is a side view taken along the line [5]-[5] in FIG. 4, but additionally showing an optical disk.

FIG. 6 is a perspective view of an optical head of Conventional Example 2.

FIG. 7 is an exploded perspective view of the optical head, wherein A is a movable portion, and B is a main body.

FIG. 8 is a perspective view of a central axis used in the optical head.

[Explanation of symbols]

1 optical head of the embodiment, 13 central axis, 1
7: PTFE fine particles, 18: composite nickel plating,
51: body, 54: magnet for correcting focusing error, 55: magnet for correcting tracking error,
Reference numeral 61: movable portion, 62: objective lens, 64: driving coil for correcting a focusing error, 65: driving coil for correcting a tracking error, 69: bobbin.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16H 31/00 F16H 31/00 H

Claims (6)

[Claims] 1. A movable section having an objective lens for converging and irradiating an optical information recording / reproducing medium such as an optical disk with a light beam is provided on a main body, and is provided at a central axis passing through the movable section in the direction of the light beam. Slidable along the center axis, and a focusing error correction drive coil and a tracking error correction drive coil attached to the movable part are attached to the main body. The focusing error and / or the tracking error with respect to the optical information reproducing / recording medium are arranged in the formed magnetic field and depending on the direction of a current flowing through the focusing error correction drive coil and / or the tracking error correction drive coil. The movable part is slid along the center axis so as to move the objective lens in a direction in which An optical head to be rotated, wherein the central axis is formed by coating a surface of a base material axis with a composite metal plating film in which fine particles of a lubricity imparting material are dispersed. 2. The optical head according to claim 1, wherein a volume ratio of the fine particles of the lubricity imparting material in the composite metal plating film is in a range from 10% to 30%. 3. The fine particles of the lubricity-imparting material are fine particles of an ethylene tetrafluoride resin or an ethylene tetrafluoride copolymer resin, and have a particle diameter in the range of 0.01 μm to 1 μm. Alternatively, the optical head according to claim 2. 4. The optical head according to claim 3, wherein the fine particles of the tetrafluoroethylene resin or the tetrafluoroethylene copolymer resin are spherical and are independently dispersed in the composite metal plating film. 5. The composite metal plating film according to claim 1, wherein the composite metal plating film is formed by electroless plating using nickel or a nickel alloy, or cobalt or a cobalt alloy as a metal component. Optical head. 6. The composite metal plating film according to claim 6, wherein the metal component of the composite metal plating film is 85% to 95% by weight of nickel, phosphorus or boron.
6. The optical head according to claim 5, wherein the optical head is an alloy consisting of 15% by weight to 15% by weight.