JP4131774B2 - Optical pickup device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup device.
[0002]
[Prior art]
An optical pickup device is used for a CD player, a CD-ROM device, and the like for reading and reproducing information recorded on an optical disk. This optical pickup device irradiates a signal recording surface of an optical disc with a laser beam having a wavelength of about 700 nanometers emitted from a laser light source, and detects a reflected beam reflected from a pit row composed of minute irregularities with a photodetector. , Convert to electrical signal. At this time, if the laser light emitted from the laser light source is not accurately and vertically focused on the pit row, the reflected beam is distorted due to aberration or the like, and noise is mixed or reading error occurs.
[0003]
Therefore, an objective lens that guides laser light is prepared, and an apparatus that controls the position of an actuator equipped with this objective lens in the tracking direction and the focus direction by electromagnetic force has been developed (Japanese Patent Laid-Open No. 5-266507). In addition, an optical pickup device having a structure in which the actuator is supported by four metal wires so that the optical axis of the laser beam is always perpendicular to the pit row formation surface is also developed by such actuator position control. (JP-A-5-266507). Since the metal wire for supporting the actuator is required to be flexible and elastic, beryllium copper alloy or phosphor bronze is used.
[0004]
[Problems to be solved by the invention]
By the way, the conventional techniques as described above have the following problems to be solved.
The metal wire that supports the actuator is always subjected to the gravity of the actuator, and even if it is initially a straight line, the curve becomes significant over time, the home position changes, and the position control performance and accuracy deteriorate. there were. In particular, phosphor bronze alloys have a problem that such a tendency is remarkable as compared with beryllium alloys.
[0005]
One end of the metal wire is soldered to the actuator, and the other end is soldered to the control board. As for solderability, beryllium copper alloy has poorer solderability than phosphor bronze. In order to improve the solderability, surface treatment such as silver plating is necessary, and there is a problem that the price of the metal wire is increased. Furthermore, the beryllium copper alloy is toxic, and there is a problem in that special attention is required for management in manufacturing operations, recycling treatment and environmental impact.
[0006]
[Means for Solving the Problems]
The present invention adopts the following configuration in order to solve the above points.
<Configuration 1>
An actuator including a laser light source, an objective lens that guides the laser light emitted from the laser light source, and a position control drive coil; and a plurality of suspension wires that movably support the actuator. An optical pickup device comprising 2% by weight or more and 24% by weight or less of silver, the balance being made of a copper-silver alloy which is copper except for a small amount of impurities which cannot be removed in production .
[0007]
<Configuration 2>
An actuator including a laser light source, an objective lens that guides the laser light emitted from the laser light source, and a position control drive coil; and a plurality of suspension wires that movably support the actuator. An optical pickup device comprising 3% by weight to 14% by weight of silver, the balance being made of a copper-silver alloy which is copper except for a small amount of impurities which cannot be removed in production.
[0008]
<Configuration 3>
3. The optical pickup device according to claim 1, wherein one end of the suspension wire is soldered to the actuator and the other end is connected to the control board side.
[0009]
<Configuration 4>
A plurality of actuators including a laser light source, an objective lens that guides the laser light emitted from the laser light source, and a position control drive coil; a plurality of position control signals that supply the drive coil to the drive coil; A suspension wire, and the suspension wire contains 2 wt% or more and 24 wt% or less of silver, and the remainder is copper except for a small amount of impurities that cannot be removed in production. An optical pickup device comprising an alloy.
[0010]
<Configuration 5>
A plurality of actuators including a laser light source, an objective lens that guides the laser light emitted from the laser light source, and a position control drive coil; a plurality of position control signals that supply the drive coil to the drive coil; The suspension wire contains 3 wt% or more and 14 wt% or less of silver, and the remainder is copper except for a small amount of impurities that cannot be removed in production. An optical pickup device comprising an alloy.
[0011]
<Configuration 6>
6. The optical pickup device according to claim 4, wherein one end of the suspension wire is soldered to a drive coil signal input terminal of the actuator, and the other end is soldered to a control signal output terminal of the control board. An optical pickup device.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described using specific examples.
FIG. 1A is a perspective view showing a specific example of the optical pickup device of the present invention, and FIG. 1B is a side view of the main part for showing the operation of the suspension wire.
In the figure, a laser light source 1 indicated by a broken line frame is composed of a laser diode or the like. In order to guide the laser beam 2 irradiated by the laser light source 1, an actuator 3 shown in the figure is provided. The actuator 3 is mounted with an objective lens 4 and a drive coil for position control (not shown).
[0013]
The actuator 3 includes four suspension wires 5 for supplying a position control signal to the drive coil. One pair is used for control in the tracking direction (direction of arrow X), and the other pair is used for position control in the focus direction (direction of arrow Y). One end of these suspension wires 5 is soldered to the drive coil signal input terminal 6 of the actuator 3. The other end of the suspension wire 5 is soldered to the control signal output terminal 8 of the control board 7.
[0014]
For example, the control board 7 is fixed to the main body of a CD player, and the actuator 3 is supported by being suspended directly above the optical disk by four suspension wires 5. Thereby, the laser beam 2 irradiated from the laser light source 1 is accurately condensed on the pit row forming surface 11 by the objective lens.
[0015]
The position of the actuator 3 is controlled in the tracking direction (in the direction of arrow X) and the focus direction (in the direction of arrow Y) by the force of an electromagnet (not shown). The details of this position control mechanism are known, for example, from Japanese Patent Laid-Open No. 5-266507, and therefore illustration and description thereof are omitted. In this position control, the suspension wire 5 that supports the actuator 3 is freely curved in a direction that allows the actuator to move. For example, when the actuator 3 moves in the focus direction (the direction of the arrow Y), the suspension wire 5 is bent as indicated by the broken line shown in FIG.
[0016]
In order to mechanically protect the connection portion (fixed end portion) between the suspension wire 5 and the control board 7, a damper 9 made of rubber or the like closely attached to the control board 7 side is provided. When the electromagnetic force for position control is extinguished, the free single side of the suspension wire 5 returns to the position of the solid line again. At this time, since the suspension wire 5 has appropriate elasticity and hardness, a device with little secular change can be realized.
[0017]
In the present invention, for this purpose, for example, a copper-silver alloy having a wire diameter of 0.1 mm is used for the suspension wire. This copper-silver alloy contains 2% by weight or more and 24% by weight or less of silver, and the remainder is preferably copper. It should be noted that a very small amount of impurities that cannot be removed in manufacturing is ignored. The reason why the silver content is 2% by weight or more is to increase the hardness due to the silver content and to ensure sufficient strength and elasticity. Note that the sag phenomenon refers to a phenomenon in which bending becomes significant with the passage of time. The reason why the silver content is 24% by weight or less is to secure a certain degree of flexibility and enable processing into a thin wire. Further, if the silver content is further increased, the price becomes too high. Such a copper alloy is disclosed, for example, in the development of a high-strength, high-conductivity copper-silver alloy and its application (Showa Electric Wire Review VOL.48, No.2, 1998).
[0018]
In terms of characteristics, the copper-silver alloy preferably contains 3% by weight or more and 14% by weight or less of silver, and the remainder is copper. This is because the strength and workability are balanced, and the price is sufficiently low. In order to process the suspension wire, for example, a copper-silver alloy wire is repeatedly thinned to a wire diameter of 0.1 mm by alternately repeating cold working and heat treatment using a continuous casting machine. In the present invention, a copper-silver alloy having the above structure is continuously cast to create a supersaturated eutectic structure, and a precipitation heat treatment is performed to finely precipitate silver and copper in the alloy. This is further drawn into a filament by cold working.
[0019]
This cold working is desirably performed at a working degree of 99% or more. By applying such high cold working, the eutectic structure is stretched into fine filaments to form a dense fiber reinforced structure. Further, by applying a high cold working after the precipitation heat treatment, the pinning effect of fine precipitates on the accumulation of dislocations due to the working is exhibited, and a high tensile strength of 1000 MPa or more can be obtained. Thus, it is considered that an alloy wire having high strength and excellent conductivity can be obtained, and high characteristics against sag can be obtained when applied to a suspension wire as will be described later. Moreover, since it consists of silver and copper, soldering connectivity is very good. In addition, since it is made of a binary material of silver and copper, it has excellent recyclability and environmental friendliness.
[0020]
2A and 2B are explanatory views of the suspension wire characteristic test of the optical pickup device of the present invention. FIGS. 2A and 2B are explanatory views of test conditions, and FIG. 2C is an explanatory view showing test results.
This test was conducted with the aim of comparing the suspension wire sag phenomenon with the conventional one. For the sample shown in (a), a rod-shaped sample having a wire diameter of 1 mm and a length L = 200 mm was used. In each sample, one end was supported by a damper 9 and the other end was a free end. A load F was repeatedly applied from the other end to W = 3 mm, and bending motion with an amplitude H = 5 mm was performed 1 million times. After completion of the test, as shown in (b), the displacement of the free end due to the sag phenomenon appears. This width Z was measured.
[0021]
The comparative phosphor bronze alloy used in the test contains 6.1% by weight of tin (Sn) and 0.1% by weight of phosphorus (P) in copper (Cu). Moreover, a beryllium copper alloy contains 1.9 weight% of beryllium (Be) in copper (Cu). The copper-silver alloy which is an example of the present invention contains 10% by weight of silver (Ag) in copper (Cu). In the example of (c) in FIG. 1 to No. Three tests were conducted up to 3.
[0022]
As can be seen from the test results, when using the copper-silver alloy of the present invention, the deviation from the home position can be sufficiently reduced even by a large number of bending motions when compared with the phosphor bronze alloy. In addition, even better properties than the beryllium copper alloy.
[0023]
FIG. 3 shows a test result of soldering connectivity.
This test shows the result of observing the surface condition when soldering is performed on the end of the same sample as that used in the above test. In this test, solder in which tin (Sn) and lead (Pb) were adjusted to a ratio of 50:50 was melted and the solder bath temperature was maintained at 250 ° C. The sample was immersed in this solder bath at an immersion time of 1 to 4 seconds, and the solder attached to the end portion was observed. Neither has special surface treatment or pretreatment. As a result, when the immersion time was 2 seconds to 3 seconds, the copper-silver alloy of the present invention was able to be well soldered, whereas the alloys of the comparative examples were partially attached with solder. It does not show satisfactory soldering connectivity.
[0024]
When the immersion time was 4 seconds, all the samples were uniformly soldered. However, if the immersion time in the solder bath is long, the influence on other components connected to the substrate or the like is large, and 4 seconds is too long to be adopted. Therefore, it has been proved that the copper-silver alloy of the present invention, which exhibits good soldering connectivity with an immersion time of 2 to 3 seconds, is suitable.
[0025]
From the above results, according to the copper-silver alloy of the present invention, good soldering connection can be achieved in a short time without costly surface treatment. In the above embodiment, the number of suspension wires supporting the actuator is four, but the number may be increased or decreased as necessary. The suspension wire that supports the actuator and the signal line that supplies the control signal to the position control coil may be different. However, in the apparatus of the present invention, since the suspension wire is extremely excellent in electrical conductivity, there is an effect such as cost reduction when it is also used for supplying a control signal.
【The invention's effect】
In the optical pickup apparatus described above, the suspension wire supporting the actuator is made of a copper-silver alloy, so that the secular change is less than that of phosphor bronze, and the actuator can be supported at the home position for a long time. is there. This also makes it possible to always keep the optical axis of the objective lens mounted on the actuator perpendicular to the pit row formation surface. Therefore, stable signal reading becomes possible. In addition, this suspension wire has an effect that the soldering connectivity is good and the conductivity is excellent as compared with a beryllium copper alloy or the like.
[Brief description of the drawings]
FIG. 1A is a perspective view showing a specific example of an optical pickup device of the present invention, and FIG. 1B is a side view of a main part for illustrating the operation of a suspension wire.
FIGS. 2A and 2B are explanatory diagrams of a suspension wire characteristic test of the optical pickup device of the present invention, wherein FIGS. 2A and 2B are explanatory diagrams of test conditions, and FIG. 2C is an explanatory diagram showing test results;
FIG. 3 is an explanatory view showing a test result of soldering connectivity.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser light source 2 Laser light 3 Actuator 4 Objective lens 5 Suspension wire 6 Drive coil signal input terminal 7 Substrate 8 Control signal output terminal 11 Pit row formation surface

Claims (6)

A laser light source;
An actuator equipped with an objective lens that guides laser light emitted by the laser light source and a drive coil for position control;
A plurality of suspension wires that moveably support the actuator;
The suspension wire contains 2 wt% or more and 24 wt% or less of silver, and the balance is made of a copper-silver alloy that is copper except for a small amount of impurities that cannot be removed in production. Optical pickup device. A laser light source;
  An actuator equipped with an objective lens for guiding the laser light emitted by the laser light source and a drive coil for position control;
  A plurality of suspension wires that moveably support the actuator;
  The suspension wire contains 3 wt% or more and 14 wt% or less of silver, and the balance is made of a copper-silver alloy which is copper except for a small amount of impurities that cannot be removed in production. Optical pickup device. The optical pickup device according to claim 1 or 2,
  One end of the suspension wire is soldered to the actuator, and the other end is connected to the control board side. A laser light source;
  An actuator equipped with an objective lens for guiding the laser light emitted by the laser light source and a drive coil for position control;
  A plurality of suspension wires that movably support the actuator and supply a position control signal to the drive coil;
  The suspension wire contains 2 wt% or more and 24 wt% or less of silver, and the balance is made of a copper-silver alloy which is copper except for a small amount of impurities which cannot be removed in manufacturing. Optical pickup device. A laser light source;
  An actuator equipped with an objective lens for guiding the laser light emitted by the laser light source and a drive coil for position control;
  A plurality of suspension wires that movably support the actuator and supply a position control signal to the drive coil;
  The suspension wire contains 3 wt% or more and 14 wt% or less of silver, and the balance is made of a copper-silver alloy which is copper except for a small amount of impurities that cannot be removed in production. Optical pickup device. The optical pickup device according to claim 4 or 5,
  One end of the suspension wire is soldered to the drive coil signal input terminal of the actuator, and the other end is soldered to the control signal output terminal of the control board.

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