JPH11175999A - Supporting shaft for optical pickup and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain dimensional accuracy of not larger than a specific value and also to smoothly perform the assembling work of the actuator of an optical pickup by forming lubricative thin films on all surfaces of supporting shafts of the optical pickup in which the driving system of a focusing drive system uses sliding bearings. SOLUTION: Supporting shafts 2 are attachingly placed in upper end parts of auxiliary metallic bodies 3 which are fixed to a fixing tool 5 and are magnetized with a magnet 4. Next, after the whole of this assembly is dipped into dispersion liquid 7 consisting of polyorgano siloxane and at least one resin polymer selected from fluoropolymers with low mol.wt. by using an elevating/ lowering device 6, lubricative thin films 8 are coated on all surfaces of the supporting shafts 2 by pulling up the whole of the assembly at a constant speed. Then, the supporting shafts 2 coated with the lubricative thin films 8 are subjected to heat treatment in an electric furnace while they are kept being attachingly placed in the auxiliary metallic bodies 3. Thus, the lubricative thin films 8 having the film thickness of <=5 μm are formed on the surfaces of the supporting shafts 2 uniformly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an actuator and a support shaft for an optical pickup and a method of manufacturing the same. In particular, the present invention relates to an actuator and a support shaft of an optical pickup in an optical information recording / reproducing apparatus, and a method of manufacturing the same.

[0002]

2. Description of the Related Art As an optical information recording / reproducing device, a video disk player, a digital audio player, an optical disk file and the like are known. In recent years, a digital video disk (DVD) has been developed as a device capable of recording and reproducing a large amount of information. Also, a DVD device having two objective lenses is known in order to provide compatibility with a conventional model. The optical pickup for performing focus control and tracking control of these devices focuses the light beam that has passed through the objective lens on the disk surface, and compensates for the defocus due to the shake of the disk surface to detect information. The beam needs to be imaged on the disk surface. In addition, if there is a deviation (displacement in the radial direction of the optical axis) between a signal track (information pit row) on the disk and the optical axis of the objective lens, accurate reading becomes impossible. It is necessary to compensate to make the optical axis of the objective lens coincide with the signal track. Such a focus shift is compensated by a focusing servo, and a signal track shift is compensated by a tracking servo.

There are many types of structures of a focusing drive system and a tracking drive system, and one of them is illustrated in FIG. FIG. 2 is a cross-sectional view of an actuator in which a drive unit supporting system of a focus drive system uses a slide bearing. In this method, the driving unit is guided by a fixed support shaft 2 and moves in the focusing direction, and at the same time, the support shaft 2
1 shows a drive system of an optical pickup that also rotates around and performs tracking control. That is, the support shaft 2 is fixed to the base 1 together with the magnetic core 16 around the support shaft 2, and the lens holder 10 in which the bearing hole 12 is provided in the shaft core of the lens holder main body 11 is rotatable. A driving coil 13 is provided on the outer peripheral surface of the lens holder body 11 and a lens mounting hole 14 is provided at an eccentric position of the bearing hole 12. An objective lens 15 is mounted in the lens mounting hole 14. Here, the drive coil 13 has a focus coil wound around the axis of the bearing hole 12, and a plane wound around an axis perpendicular to the axis and including the axis of the lens holder main body 11. And a tracking coil (not shown) arranged at the opposing position. The amount of axial movement and rotation of the lens holder body 11 is controlled according to the amount of current flowing through the focus coil and the tracking coil.

Therefore, better sliding properties between the bearing hole 12 and the support shaft 2 are required. Conventionally, the sliding properties are improved by providing a lubricating coating such as a fluororesin composition on the sliding surface. (Japanese Patent Laid-Open No. 62-20444)
No. 0, Japanese Patent Publication No. 7-43836, Patent No. 256
No. 6598). Alternatively, after forming a fluorine-based resin layer thicker, centerless polishing or grinding is performed as an outer diameter finish to improve roundness and outer diameter dimensional accuracy (Japanese Utility Model Application Laid-Open No. 63-40812).

Conventionally, a lubricating film is formed by heat treatment after dip coating. FIG. 3 shows a conventional method of forming a lubricating film, and FIG.
Shown in One end of the cylindrical support shaft 2 is held by a fixture 9, and a part of the support shaft 2 is immersed in a dispersion 7 in which a lubricant such as a fluororesin composition is dispersed in a solvent. After the immersion, the support shaft 2 having the lubricant layer formed on the pulling surface at a constant speed is subjected to a heat treatment. In this manner, a support shaft for an optical pickup having an uncoated portion on which one end portion held by the fixture 9 is not coated with a lubricating coating is obtained.

[0006]

However, a DV using a medium in which a track width and a pit diameter on an optical disk are reduced by a digital signal compression technique.
In a high-density information recording / reproducing device such as a D device, higher dimensional accuracy between the bearing hole 12 and the outer diameter of the support shaft 2 is required. Depending on the type of DVD device actuator, there are cases where two objective lenses are rotated and switched around the support shaft. Further, the dimensional accuracy of the support shaft is required, for example, between the support shaft 2 and the bearing hole 12. It is becoming more severe, for example, the gap must be kept to around 5μm.

[0007] The conventional lubricating coating has a problem that it is excellent in productivity and cannot meet the requirement of this dimensional accuracy. For example, in FIG. 3, when the support shaft 2 is pulled up,
There is a problem that the thickness of the coating is increased in the lowermost region 2a of the support shaft 2 due to the influence of the surface tension. Also, the support shaft 2
The lubricating film of the second embodiment is formed by the boundary region 2 c with the dispersion 7 and the dispersion 7.
In the internal region 2b, there is a problem that the thickness of the coating tends to vary, and particularly when a dispersion is used, the coating thickness in the boundary region 2c becomes large. As a result, as shown in FIG. 4, there is a problem that a uniform thickness of the lubricating film after the heat treatment cannot be obtained.

Further, in the conventional coating method shown in FIG. 3, an uncoated portion which is not coated always occurs. When the thickness of the lubricating film is 5 μm or less, the color becomes almost transparent, and it is difficult to distinguish between the coated portion and the uncoated portion. When fixing the support shaft 2 to the base 1 of the actuator, it is necessary to press-fit the uncoated portion to the main body, but since the lubricating coating is transparent,
It is very difficult to identify the uncoated portion, it takes time and cost, and there is a problem that the operation of assembling the actuator of the optical pickup cannot be performed smoothly.

SUMMARY OF THE INVENTION The present invention has been made to address such a problem, and a support for an optical pickup capable of maintaining a dimensional accuracy of 5 μm or less and smoothly performing an actuator assembly operation of the optical pickup. An object of the present invention is to provide an optical pickup actuator using a shaft, a manufacturing method thereof, and a support shaft for the optical pickup.

[0010]

The support shaft for an optical pickup according to the present invention is a support shaft for an optical pickup using a sliding drive as a driving system of a focusing drive system, and at least the entire surface of the side surface of the support shaft is lubricated. Characterized in that a conductive thin film is formed.

Further, the lubricating thin film is formed by immersing the entire support shaft in a dispersion of at least one resin polymer selected from polyorganosiloxane and a fluoropolymer, and then heating the formed surface film. It is characterized by being obtained by processing.

The polyorganosiloxane or the fluorine-containing polymer is a resin polymer having a functional group having a high affinity for the surface of the support shaft.

[0013] The lubricating thin film according to the present invention is characterized in that the thickness thereof is 5 µm or less.

The actuator of the optical pickup according to the present invention is characterized in that the driving unit supporting system of the focusing drive system uses a slide bearing, wherein the slide bearing is the above-described support shaft for the optical pickup.

In the method of manufacturing a support shaft for an optical pickup according to the present invention, at least one end face of the columnar metal body is magnetically applied through an auxiliary metal body having an outer diameter equal to or less than the outer diameter of the columnar metal body. The step of holding, and dispersing the entire end of the held cylindrical metal body in a dispersion of at least one resin polymer selected from a polyorganosiloxane and a fluorinated polymer, the end face opposite to the one end face It is characterized by comprising a step of immersing the liquid as the liquid surface side and a step of heat-treating the surface film formed by pulling up after the immersion.

Since the surface of the support shaft for an optical pickup of the present invention has a lubricating thin film formed on at least the entire side surface of the support shaft, there is no boundary between the coated portion and the uncoated portion. Therefore, a support shaft for an optical pickup having excellent dimensional accuracy can be obtained. In addition, since it is not necessary to identify the uncoated portion, the operation of assembling the actuator of the optical pickup can be performed smoothly. As a result, an actuator of an optical pickup having excellent productivity and excellent sliding characteristics can be obtained.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A support shaft for an optical pickup of the present invention is a columnar metal body having a lubricating thin film formed on at least the entire side surface of the support shaft, and the metal body is a metal having magnetism. . Further, the above metal is preferable because the corrosion resistant metal does not cause corrosion due to the occurrence of rust and the like,
A metal having magnetism and corrosion resistance, for example, SUS420 series metal as stainless steel, preferably S
US420J2 is good. The lubricating thin film may be formed on the entire support shaft made of a cylindrical metal body. The lubricating thin film is obtained by immersing the entire support shaft in a dispersion of at least one resin polymer selected from a polyorganosiloxane and a fluorine-containing polymer, followed by heat treatment. Therefore,
The lubricating thin film may be a thin film made of a polyorganosiloxane alone, a thin film made of a fluoropolymer, a thin film in which these are laminated, or a thin film made of a mixed resin polymer of a polyorganosiloxane and a fluoropolymer. . Fluoropolymers are preferred because of their good lubricity.

The dispersion of the polyorganosiloxane polymer according to the present invention will be described. The polyorganosiloxane is, for example, a homopolymer or a copolymer of two or more of dimethylsiloxane, methylphenylsiloxane, trimethylfluoropropylsiloxane, etc., and a support shaft for an optical pickup for forming a thin film of these organopolysiloxanes. Polymers having a structural unit containing a functional group having a high affinity for the surface of the polymer are preferred. This is because such a polyorganosiloxane thin film prevents peeling from the sliding surface of the support shaft and significantly improves the durability of the thin film. , An amino group, a carboxyl group, a hydroxyl group, and a mercapto group.

Specific examples of such a polyorganosiloxane are shown below.

Embedded image (R represents an alkylene group or the like, m is 5 to 10,000, n is
Represents an integer from 2 to 100)

The above-mentioned polyorganosiloxanes can be used alone or in combination without any problem. Incidentally, a polyorganosiloxane whose functional group is an epoxy group may be used in combination with a compound having an active hydrogen such as various phenols or tertiary amines. Preferred are combinations of polyorganosiloxanes that react with each other to increase the molecular weight. This is because a polyorganosiloxane thin film having an increased molecular weight has a higher coating strength and a remarkably improved abrasion resistance. As specific examples thereof, a combination of a polyorganosiloxane having a unit containing an epoxy group and a polyorganosiloxane having a unit containing at least one group selected from an amino group, a carboxyl group, a hydroxyl group, and a mercapto group, Alternatively, a combination of a polyorganosiloxane having a unit containing a carboxyl group and a polyorganosiloxane having a unit containing at least one group selected from an amino group and a hydroxyl group can be given.

The dispersion of the fluoropolymer according to the present invention will be described. As the fluorinated polymer, a fluorinated polymer such as a polyfluoroalkyl polymer (PFAE) or a fluoropolyether polymer is preferable. Here, the polyfluoroalkyl polymer is, for example, CF ₃ (CF ₂ )
_{7 -, H (CF 2)} 6 -, CF 2 Cl (CF 2) 11 -,
_{(CF 3) 2 CF (CF} 2) 7 -, CF 2 Cl (C
_{F 3) CF (CF 2)} 7 - is a polymer having a polyfluoroalkyl group, such as, fluoropolyether polymer have the general formula, -C _x F _2x -O- _(x is an integer from 1 to 4) Is the main structural unit and the number average molecular weight is 100
It is a polymer of 0 to 50,000. Such a fluorine-containing polymer contains a functional group having a high affinity for the material of the support shaft, such as an epoxy group, an amino group, a carboxyl group, a hydroxyl group, a mercapto group, an isocyanate group, a sulfone group, an ester group, and the like. Are preferred.

Specifically, as shown in the following chemical formula 2, a perfluoropolyether polymer (PFPE) having an isocyanate group at the terminal is excellent in adhesion to a substrate such as a support shaft, and The formed fluoropolyether polymer is excellent in non-adhesiveness and sliding properties, and it is easy to form such a coating layer. Cutting such as polishing is not particularly required. It is preferable because it is generally excellent in terms of price and price.

[0023]

Embedded image

(In the formula, m and n represent integers.) Examples of such a substance include Fomblin Z-DISOC (manufactured by Montefluos) (number average molecular weight: about 2000). In addition, any fluorine-containing polymer, resin, or the like containing a fluorine atom may be used.

The dispersion comprising at least one resin polymer selected from the group consisting of polyorganosiloxanes and low molecular weight fluoropolymers according to the present invention is prepared by dissolving the polymer in an organic solvent, for example, a highly fluorinated solvent such as a fluorocarbon detergent. It can be obtained by dispersing it in an organic solvent to a concentration of 0.1 to 10% by weight to a concentration of 1 to 5% by weight in consideration of the effective thin layer, the liquid yield, the cost and the like. As the dispersion liquid, hydrofluorocarbon (C ₅ H) which is a cleaning liquid alternative to CFCs is used.
Preferably in terms _{of 2} F ₁₀₎ to protect the environment, for example, Du Pont-Mitsui Fluorochemicals Co., Ltd. trade name: Vertrel FX
And the like.

A method of manufacturing a support shaft for an optical pickup according to the present invention will be described with reference to FIG. FIG. 1 is a view showing a method for forming a lubricating film according to the present invention, and FIG.
Fig. 1 (b) shows a state before immersion in the dispersion, Fig. 1 (c) shows a state immediately after being pulled up from the dispersion, and Fig. 1 (d) shows a state after heat treatment. Are respectively shown. The magnet 4 is arranged at the lower end of the auxiliary metal body 3 fixed by the fixture 5. Since the auxiliary metal member 3 is made of a magnetic material, the support shaft 2 can be held vertically by magnetically seating the support shaft 2 on the upper end of the auxiliary metal member 3 magnetized by the magnet 4. (FIG. 1A).

The auxiliary metal body 3 has an outer diameter smaller than the outer diameter of the support shaft 2 which is a cylindrical metal body. If the outer diameter of the support shaft 2 is exceeded, a liquid pool will be generated on the seating surface between the support shaft 2 and the auxiliary metal body 3, so that a lubricating thin film cannot be formed uniformly on the side surface of the support shaft. The lower limit of the outer diameter of the auxiliary metal body 3 varies depending on the magnitude of the magnetic force of the magnet 4, the length of the support shaft 2, and the like, but may be any diameter as long as the support shaft 2 can be held vertically. The length of the auxiliary metal body 3 is
Is fixed in such a manner that the seating side is always protruded from the fixture 5. By setting the outer diameter and the length of the auxiliary metal body 3 as described above, it is possible to prevent a liquid pool from being generated on the seating surface between the support shaft 2 and the auxiliary metal body 3. In addition,
If the support shaft 2 can be held vertically,
The auxiliary metal body 3 and the support shaft 2 can be arranged alternately from the bottom like the auxiliary metal body 3 that is fixed by the fixture 3 -the support shaft 2 -the auxiliary metal body 3 that is not fixed and the support shaft 2. In addition, the auxiliary metal body 3 and the magnet 4 can be formed as an integrated body.

The magnet 4 is preferably a ferromagnetic material and a magnetic material whose magnetic force does not change even when the heat treatment is repeated at room temperature and up to about 400 ° C. This is magnet 4
This is because it is necessary to repeat the heat treatment in a state where the auxiliary metal body 3 is further seated on the support metal 2 and the support shaft 2 is further seated thereon. Specifically, rare earth magnets exhibiting a high maximum energy product (BH) max are preferred. An example of such a rare earth magnet is a NEOMAX-based rare earth magnet (trade name of Sumitomo Special Metals)
There is.

The support shaft 2 seated on the auxiliary metal body 3 is entirely immersed in the above-mentioned dispersion liquid 7 with the seating surface down using a lifting device 6 (FIG. 1 (b)). . afterwards,
The whole is pulled up again at a constant speed using the lifting device 6, whereby the lubricating thin film is applied to the entire surface of the support shaft 2 (FIG. 1 (c)). As described above, it is preferable to immerse the support shaft 2 in such a posture that the axial direction of the support shaft 2 is substantially perpendicular to the immersion liquid level, since a uniform thin layer is easily formed on the side surface of the support shaft 2. .

The support shaft 2 coated with the lubricating thin film is detached from the lifting device 6 while being seated on the auxiliary metal body 3 and the magnet 4, and is heated in an electric furnace or the like. The heat treatment conditions are, for example, a temperature of 50 to 350 ° C., preferably 100 to 200 ° C., for about 1 minute to 3 hours, preferably about 3 minutes to 3 hours. Specifically, it is preferable to carry out the reaction for 2 to 3 hours at 100 ° C., 20 to 40 minutes at 150 ° C., and 3 to 7 minutes at 200 ° C.

By the heat treatment, the surface of the support shaft 2 is uniformly formed.
A lubricating thin film 8 having a thickness of 0.001 to 5 μm is formed. When the film thickness is in this range, good sliding characteristics can be maintained for a long period of time, and good control of the gap dimensional accuracy between the support shaft 2 and the lens holder body 10 or the base 1 and the lens holder body Ten smooth rotation / swing / reciprocation operations can be obtained. Finally, the support shaft 2 is demagnetized to obtain an optical pickup support shaft (FIG. 1D).

By using the above-described support shaft 2 for an actuator of an optical pickup using a sliding bearing as a driving unit supporting system of a focusing drive system, it is not necessary to distinguish between a coated portion and an uncoated portion. The actuator assembly work of the optical pickup can be performed smoothly. Also, since the actuator of the optical pickup uses the support shaft 2 having excellent dimensional accuracy, when used in an optical information recording / reproducing apparatus, a reproduced image without distortion can be obtained.

[0033]

Example 1 As a support shaft 2 for an optical pickup, stainless steel (SUS420J2) having a diameter of 1.5 mm and a length of 9.0 mm was prepared. As shown in FIG. 1, the auxiliary metal body 3 and the magnet 4 (both NEOMAX-32EH, a trade name of Sumitomo Special Metals) having the same diameter as the support shaft 2 are attached to the lower end of the support shaft 2, as shown in FIG. Further, a magnet 4 is arranged at the lower end,
The entire surface was immersed in the dispersion liquid 7 by the lifting device 6. Dispersion 7
As the lubricating polymer, Fomblin Z-DISOC (trade name, manufactured by Montefluos) was used. Thereafter, a lubricating thin film was applied to the entire surface of the lifting support shaft 2 at a constant speed by the lifting device 6. Next, the support shaft 2 was detached from the elevating device 6 while adsorbing the auxiliary metal body 3 and the magnet 4, and was heated in an electric furnace at 150 ° C. for 30 minutes. The support shaft 2 was removed from the auxiliary metal body 3, and the magnetic force of the magnetized support shaft was removed by a demagnetizer to obtain a support shaft for an optical pickup. In the obtained support shaft, a uniform lubricating thin film was formed on the entire surface except a part of one end surface, that is, on the outer diameter surface which is the side surface of the support shaft. When the actuator of the optical pickup was assembled using the obtained support shaft, the assembly work could be performed smoothly.

Example 2 A lubricating polymer was replaced with a lubricating polymer of silicone oil X22-160C manufactured by Shin-Etsu Chemical Co., Ltd.
A support shaft for an optical pickup was obtained under the same conditions as in Example 1. In the obtained support shaft, a uniform lubricating thin film was formed on the entire surface except a part of one end surface, that is, on the outer diameter surface which is the side surface of the support shaft. When the actuator of the optical pickup was assembled using the obtained support shaft, the assembly work could be performed smoothly.

[0035]

The support shaft for an optical pickup of the present invention has a lubricating thin film formed on at least the entire side surface of the support shaft, so that there is no uncoated portion on the side surface. As a result, it is possible to assemble without worrying about the directionality of the support shaft, so that automatic assembling becomes possible, and an optical pickup actuator excellent in manufacturing cost can be obtained.

Further, the lubricating thin film is obtained by immersing the entire support shaft in a dispersion of at least one resin polymer selected from polyorganosiloxane and a fluoropolymer, and then subjecting the formed surface film to heat treatment. Thus, a support shaft for an optical pickup having excellent dimensional accuracy can be obtained. In particular, since the polyorganosiloxane or the fluoropolymer is a resin polymer having a functional group having a high affinity with the surface of the support shaft, the optical pickup has excellent adhesion to the support shaft and excellent sliding characteristics. An actuator can be obtained.

Further, since the thickness of the lubricating thin film is 5 μm or less, it can be easily adapted to the dimensional accuracy of a high-density information recording / reproducing apparatus or the like.

Since the actuator of the optical pickup of the present invention uses the above-mentioned support shaft for the optical pickup, it can be easily assembled and manufactured, and excellent reproduced images can be obtained.

According to the method of manufacturing a support shaft for an optical pickup of the present invention, there are provided a step of holding by a magnetic force via an auxiliary metal body having an outer diameter equal to or less than the outer diameter of the cylindrical metal body; A step of immersing the dispersion surface of the columnar metal body in the dispersion of the resin polymer such that the front end surface is on the liquid surface side of the dispersion.
And a step of heat-treating the surface film, so that a uniform lubricating thin film can be formed on at least the entire side surface of the support shaft.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for forming a lubricating film.

FIG. 2 shows a sectional view of an actuator using a plain bearing.

FIG. 3 is a view showing a conventional method of forming a lubricating film.

FIG. 4 is a view showing a state in which a lubricating film is applied to a conventional support shaft.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2 Support shaft 3 Auxiliary metal body 4 Magnet 5 Fixing device 6 Lifting device 7 Dispersion liquid 8 Lubricant thin film 9 Fixing device 10 Lens holder 11 Lens holder main body 12 Bearing hole 13 Drive coil 14 Lens mounting hole 15 Objective lens 16 Magnetic core

Continued on the front page (51) Int.Cl. ⁶ Identification code FI // C10N 40:02 40:06

Claims (6)

[Claims] An optical pickup supporting shaft of an optical pickup using a sliding bearing as a driving system of a focusing drive system, wherein the optical pickup supporting shaft has a lubricating thin film on at least the entire side surface of the supporting shaft. A support shaft for an optical pickup, wherein a support shaft is formed. 2. The surface film formed by dipping the entire support shaft in a dispersion of at least one resin polymer selected from a polyorganosiloxane and a fluorine-containing polymer. 2. A support shaft for an optical pickup according to claim 1, wherein the support shaft is obtained by heat-treating the support shaft. 3. The optical pickup according to claim 2, wherein the polyorganosiloxane or the fluorinated polymer is a resin polymer having a functional group having a high affinity with the surface of the support shaft. Support shaft. 4. The support shaft for an optical pickup according to claim 1, wherein the lubricating thin film has a thickness of 5 μm or less. 5. An optical pickup actuator using a sliding bearing as a driving unit supporting system of a focusing drive system, wherein the sliding bearing is the support shaft for an optical pickup according to claim 4. Pickup actuator. 6. A step of magnetically holding at least one end face of the columnar metal body via an auxiliary metal body having an outer diameter equal to or less than the outer diameter of the columnar metal body, and holding the columnar metal body. A step of immersing the entire body in a dispersion of at least one resin polymer selected from a polyorganosiloxane and a fluorine-containing polymer with the end face opposite to the one end face as the liquid side of the dispersion liquid, Heating the surface film formed by the pulling after the immersion.