JPH04325932A - Objective lens drive mechanism for optical pickup - Google Patents

Abstract

PURPOSE:To make the device light in weight and compact and to improve workability and reliability by using one part of the element wire of a driving coil as the supporting member of an objective lens, utilizing it as a spring member and interposing silicone gell for fixing the element wire to a bobbin holder. CONSTITUTION:In a drive device 1, driving coils 4 for tracking control are arranged in front and rear of an objective lens 2 for a bobbin 3 directly holding the lens 2. A drive coil 5 for focus control is arranged between the coils 4 just under the lens 2, the end parts of element wires 6 constituting the coils 4 and 5 are pulled out, and the end parts are fixed to a bobbin holder 7. Among the pulled-out element wires 6, the element wire fed out in one direction is mounted on an electronic substrate 8 at one end of the bobbin holder 7, and the other element wire 6 is inserted to a small hole 9 at the end part of the holder 7. Then, silicone gell 10 is filled and set. For the gell 10, the penetration is 5-250 and the loss coefficient at a shearing frequency 0.01-10Hz is 0.1-2 by the consistency measuring method of JIS K2220.

Description

[Detailed description of the invention]

0001

[Purpose of the invention]

[Field of Industrial Application] The present invention relates to an optical pickup applied to a drive unit that drives an optical disk such as a DAD (digital audio disk), a video disk, or a CD-ROM. and a drive mechanism for an objective lens that performs tracking adjustment.

0002

BACKGROUND OF THE INVENTION Optical pickups for detecting information recorded on optical discs such as DADs (generally called compact discs), video discs, and CD-ROMs include the three-spot method, the astigmatism method, and the two-axis device. Various types have been developed based on differences in detection methods and drive systems for objective lenses such as focus servo and tracking servo. As shown in FIG. 7, an optical pickup with a characteristic drive system for the objective lens has drive coils 4' and 5' for focusing and tracking around the objective lens 2'.
A structure has been developed in which the objective lens 2' is held by a spring member 6'.

Furthermore, in this type of objective lens drive mechanism, focus and tracking adjustments are made by the amount of deflection by the spring member 6', so vibrations transmitted from the external housing are sometimes amplified, and the objective lens After the movement, swinging back occurs. Therefore, some type of vibration damping mechanism is required to prevent the transmission of these vibrations and to converge the vibrations in a short time.

[0004] Therefore, recently, attempts have been made to hold the spring member supporting the objective lens through a suitable vibration absorbing member rather than directly holding it. Since this vibration absorbing member is required to have stable characteristics such as temperature characteristics, it is conceivable to use silicone gel. Moreover, since the objective lens is lightweight and supported by the spring member as described above, the silicone gel used must have a material with excellent damping properties, that is, a material with a large tan δ.

[0005] Furthermore, since electronic circuits are naturally built into the surrounding area (silicone gel is also a highly insulating material), there is a risk that volatile matter from the silicone gel may cause poor contact at these contacts. The gel material is required to have a reduced content of volatile low molecular weight substances. Furthermore, if the viscosity of the silicone gel stock solution is too low, there is a risk that it will penetrate into fine details due to capillary action, and it may also flow out before it hardens. On the other hand, if the viscosity is too high, there is a risk that it will not be able to fully cover the entire filling area, and workability will also deteriorate. For this reason, it is desired that the viscosity is suitably low and the thixotropy (the extent to which the phenomenon of thixotropy appears) is high.

[0006]Therefore, it is desired to develop and improve a silicone gel material with excellent vibration absorption properties that can fully demonstrate the characteristics of this type of objective lens drive mechanism and meet the various demands mentioned above. .

[0007]

[Technical matters attempted to be developed] The present invention was made in view of this background, and aims to reduce the size of optical pickups,
This is an attempt to develop an objective lens drive mechanism for a new optical pickup that has improved vibration absorption characteristics while making weight reduction substantially possible.

0008]

[Structure of the invention]

[Means for achieving the object] The objective lens driving mechanism in the optical pickup, which is the first invention of the present application, focuses a laser beam onto an optical disk using the objective lens, receives the light reflected back from the optical disk, and In a drive mechanism comprising drive coils for focus adjustment and tracking adjustment for adjusting the position of a laser spot, the objective lens pulls out an end of a wire constituting the drive coil and connects it to a bobbin holder serving as a holding member. A silicone gel is interposed in at least a part of the fixing site of the strand, and the silicone gel is composed of an organopolysiloxane having an alkenyl group and a silicon-bonded hydrogen atom. A crosslinked structure obtained by addition-reacting an organohydrogenpolysiloxane having
The consistency measurement method specified in [or JISK (K-22
-7-1980 50g load)] and penetration is 30
0 or less (or 5 to 250), and the loss coefficient (tan
δ) is in the range of 0.1 to 2.

[0009] In addition to the above requirements, the objective lens drive mechanism in the optical pickup, which is the second invention related to the present application, satisfies the above requirements.
The strands drawn out from the drive coil are drawn out in the direction along the surface of the optical disc, in the tangential direction of the tracks of the optical disc, respectively, in the front and rear directions, and the strands drawn out in one direction are provided directly at the end of the bobbin holder. The strand is mounted on an electronic board, and the wire to be fed out to the other side is inserted into a small hole carved in the other end of the bobbin holder, and the silicone gel is interposed in this small hole. It is.

Furthermore, in addition to the above-mentioned requirements, the objective lens drive mechanism in the optical pickup, which is the third invention according to the present application, satisfies the above requirements.
The organopolysiloxane having an alkenyl group is
Contains two or more silicon-bonded alkenyl groups in one molecule, has a viscosity of 50 to 100,000 centipoise at 25°C, and has a cyclic diorganopolysiloxane content of 4 to 20 weight units. It is characterized by being a diorganopolysiloxane containing 0.5% by weight or less, and is intended to achieve the above object.

[0011]

In the objective lens drive mechanism of the optical pickup of the present invention, a part of the wires constituting each drive coil for focus adjustment and tracking adjustment is used as a spring member to support the objective lens, The drive coil not only drives the objective lens in the optical axis direction and the radial direction of the optical disk, but also supports the objective lens so that it can move within a certain range by using part of the wire of the drive coil. take charge

Furthermore, by applying silicone gel having the structure described below to hold the ends of the wires constituting the drive coil, the drive characteristics of the objective lens are further improved, and contact failures affecting the peripheral electronic circuits are prevented. It can also contribute to prevention and improved workability during filling.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An objective lens drive mechanism in an optical pickup according to the present invention will be described below with reference to the drawings. The reference numeral 1 in the figure is a drive device to which the drive mechanism of the present invention is applied, and this device drives an objective lens 2, which is one of the components of an optical pickup, in the optical axis direction and the radial direction of the optical disc A. work to do. By the way, objective lens 2 is
A laser beam emitted from a laser diode, etc. is focused onto the optical disk A, and recorded signals are detected.

Specifically, the drive device 1 includes a bobbin 3 that directly holds the objective lens 2, and drive coils 4 for tracking adjustment arranged in front and behind the objective lens 2, and a drive coil 5 for focus adjustment. is placed directly below the objective lens 2 and between the drive coils 4 for tracking adjustment, and the ends of the wires 6 constituting these drive coils 4 and 5 are pulled out and viewed in plan. The optical disc A is fed horizontally forward and backward in the tangential direction of the track on the optical disc A, and its ends are fixed to the bobbin holder 7.

Furthermore, among the wires 6 that are fed out, the wires 6 that are fed out to one side are directly mounted on the electronic board 8 located at one end of the bobbin holder 7, and the wires 6 that are fed out to the other side are directly mounted on the electronic board 8 located at one end of the bobbin holder 7. 6 has its tip inserted into a small hole 9 cut in the other end of the bobbin holder 7, and is indirectly held in the bobbin holder 7 by the silicone gel 10 filled in the small hole 9.

[0016] The silicone gel 10 used in the present invention is required to have a reduced content of volatile low molecular weight substances, and furthermore, if the undiluted solution of the silicone gel 10 has too low a viscosity, it will not be possible to form fine particles due to capillary action. There is a risk that it will penetrate and may flow out before it hardens, and on the other hand, if the viscosity is too high, there is a risk that it will not be able to fully cover the entire filling area, which will impair workability. It is necessary to have low viscosity and high thixotropy (the extent to which a thixotropic phenomenon appears).

Therefore, such a silicone gel 10 is made of, for example, diorganopolysiloxane (hereinafter referred to as component A) which is a silicone gel stock solution represented by the following formula [1]: RR1
2SiO-(R22SiO)nSiR12R…[1][
However, R is an alkenyl group, R1 is a monovalent hydrocarbon group having no aliphatic unsaturated bond, and R2 is a monovalent aliphatic hydrocarbon group (at least 50 mol% of R2 is a methyl group). and when it has an alkenyl group, its content is 10 mol% or less), and n is a number such that the viscosity of this component at 25 °C is 100 to 100,000 cSt], and 25 °C The viscosity at 500
0 cSt or less, and at least two Si in one molecule
It consists of organohydrogenpolysiloxane (component B), which is a silicone gel stock solution having hydrogen atoms directly bonded to atoms, and in component A relative to the total amount of hydrogen atoms directly bonded to Si atoms in component B. The ratio (mole ratio) of the total amount of alkenyl groups contained in is 0.1 to 2.
An addition reaction type silicone copolymer obtained by curing a mixture adjusted to have a
Consistency measurement method specified in JISK2220 [or JISK2220]
ISK (K-22-7-1980 50g load)
], the penetration is 300 or less (or 5 to 250), and the loss coefficient (tan δ) at a shear frequency of 0.01 Hz to 10 Hz is within the range of 0.1 to 2.

To explain this silicone gel 10 in more detail, the A component has a linear molecular structure, and the alkenyl groups R at both ends of the molecule are connected to the Si in the B component.
It is a compound that can form a crosslinked structure by adding to a hydrogen atom that is directly bonded to an atom. The alkenyl group present at the end of the molecule is preferably a lower alkenyl group, and in consideration of reactivity, a vinyl group is particularly preferred.

Furthermore, R1 present at the end of the molecule is a monovalent hydrocarbon group having no aliphatic unsaturated bonds, and specific examples of such groups include methyl, propyl, and hexyl groups. Mention may be made of alkyl groups, phenyl groups and fluoroalkyl groups.

In the above formula [1], R2 is a monovalent aliphatic hydrocarbon, and specific examples of such groups include:
Mention may be made of alkyl groups such as methyl, propyl and hexyl, and lower alkenyl groups such as vinyl. However, at least 50 mol% of R2 is a methyl group, and when R2 is an alkenyl group, the amount of the alkenyl group is preferably 10 mol% or less. If the amount of alkenyl groups exceeds 10 mol %, the crosslinking density becomes too high and the viscosity tends to increase. Also, n is
The viscosity of this A component at 25°C is usually 100 to 10
0,000cSt, preferably 200-20,000c
It is set within the range of St.

The above component B is a crosslinking agent for component A, and S
The hydrogen atom directly bonded to the i atom adds to the alkenyl group in component A to harden component A. Component B only needs to have the above-mentioned action, and component B can have various molecular structures such as linear, branched, cyclic, or network.

[0022] In addition to a hydrogen atom, an organic group is bonded to the Si atom in component B, and this organic group is usually a lower alkyl group such as a methyl group. Furthermore, 2 of component B
The viscosity at 5°C is usually 5000 cSt or less, preferably 500 cSt or less. Examples of such component B include organohydrogenpolysiloxane in which both molecular ends are capped with triorganosiloxy groups, copolymers of diorganosiloxane and organohydrogensiloxane, and tetraorganotetrahydrogencyclotetrasiloxane. , HR12SiO 1/2 unit and S
Copolymer siloxane consisting of iO 4/2 units, and HR12SiO 1/2 units and R13SiO 1
Copolymer polysiloxane consisting of /2 units and SiO 4/2 units can be mentioned. However, in the above formula, R1 has the same meaning as above.

The ratio of the total molar amount of alkenyl groups in component A to the total molar amount of hydrogen atoms directly bonded to Si in component B is usually 0.1 to 2.0;
It is produced by mixing and curing component A and component B so that the ratio preferably falls within the range of 0.1 to 1.0.

The curing reaction in this case is usually carried out using a catalyst. The catalyst used here is preferably a platinum-based catalyst, such as crushed elemental platinum,
Mention may be made of chloroplatinic acid, platinum oxide, complex salts of platinum and olefins, platinum alcoholates, and complex salts of chloroplatinic acid and vinylsiloxic acid. Such a complex salt consists of component A and component B.
It is usually used in an amount of 0.1 ppm or more (in terms of platinum, hereinafter the same), preferably 0.5 ppm or more, based on the total weight of the components. There is no particular restriction on the upper limit of the amount of catalyst, but for example, if the catalyst is in a liquid state or can be used as a solution, 200 p.
An amount of pm or less is sufficient.

[0025] Component A, component B and catalyst as described above are mixed and allowed to stand at room temperature or are cured by heating to produce the silicone gel used in the present invention. The silicone gel thus obtained is JISK
(K-2207-198050g load) The penetration is usually 5 to 250. The hardness of such a silicone gel varies depending on the crosslinked structure formed by the above-mentioned components A and B.

The viscosity of the silicone gel 10 before curing and the penetration degree after curing of the silicone oil having methyl groups at both ends are 5 to 7 with respect to the resulting silicone gel 10.
It can be adjusted by adding in advance an amount within the range of 5% by weight. Silicone gel 10 like this
can be adjusted as described above, or a commercially available one can be used. Examples of commercially available products that can be used in the present invention include CF5027,
TOUGH-3, TOUGH-4, TOUGH-5, T
Examples include OUGH-6 and TOUGH-7 (manufactured by Toray Dow Corning Silicone).

[0027] In addition to the above-mentioned A component, B component and catalyst, thixotropy imparting agents, pigments, curing retarders, flame retardants, fillers, etc. may be added within the range that does not impair the properties of the silicone gel. Alternatively, a silicone gel containing a filler of micro hollow spheres may be used. Examples of such materials include Fillite (registered trademark) manufactured by Nippon Fillite Co., Ltd. and Expancel (registered trademark) sold by the same company. can be exemplified.

A more suitable silicone gel 10 is a silicone gel manufactured using diorganopolysiloxane, which is a silicone gel stock solution, with a reduced content of low molecular weight substances. That is, as the A component, 1
Contains two or more silicon-bonded alkenyl groups in the molecule, has a viscosity of 50 to 100,000 centipoise at 250°C, and has a cyclic diorganopolysiloxane content of 4 to 20 weight bodies, 0.5% by weight
The following diorganopolysiloxane is used. Incidentally, by using the silicone gel 10 having such characteristics, even when the drive mechanism of the present invention is incorporated into an electric circuit, it is possible to prevent conduction failure of the electrical switching contacts caused by the organopolysiloxane gas. In addition to this, it is preferable to further incorporate a thixotropy imparting agent into these compositions, and such a thixotropy imparting agent has a specific surface area of 5.
Examples include fine silica powder of 0 m2/g or more. An example of a commercially available silicone gel 10 is EMX-
008 (manufactured by Toray Dow Corning Silicone Company), etc.

Next, the principle of operation of the objective lens drive mechanism in the optical pickup of the present invention constructed as described above will be explained. When the optical pickup accesses a predetermined position on the optical disc A, the drive coil 4 for tracking adjustment in the drive device 1 is activated in order to accurately focus the laser beam on a track consisting of pits carved on the optical disc A. The bobbin 3 holding the objective lens 2 is moved in the radial direction of the optical disc A to perform tracking adjustment.

Next, power is supplied to the drive coil 5 for focus adjustment, and the bobbin 3 holding the objective lens 2 is moved in the optical axis direction to adjust the focus. Note that during these adjustments, the bobbin 3 holding the objective lens 2 is connected to the drive coil 4.
, 5, it is supported by the strands 6 drawn out from the strands 6, so it is affected by the swinging back that occurs as the strands 6 curve. However, in the present invention, since the vibration of the wire 6 is attenuated by the silicone gel 10, the vibration converges in a short time and does not interfere with the focus and tracking adjustments of the objective lens 2. do not have.

[0031] Then, while repeating the same operation,
The information recorded on the optical disc A is read one after another. Next, another embodiment of the objective lens drive mechanism in the optical pickup of the present invention will be described.

In the embodiment shown in FIG. 4, only the strands 6 on one side of the strands 6 drawn out in the tangential direction forward and backward of the optical disc A in the embodiments shown in FIGS. In addition to this, the wire 6 on the other side, which is directly mounted on the electronic board 8, is also held with a silicone gel 10 interposed therebetween. In this case, further vibration absorption efficiency can be expected.

Further, in the embodiment shown in FIG. 5, the bobbin 3 holding the objective lens 2 in the embodiments shown in FIGS. 1 to 3 and the embodiment shown in FIG. The bobbin 3, which holds the objective lens 2, is supported in a cantilevered manner. In this case, the wire diameter of the strands 6 at the ends of the drive coils 4 and 5, which act as spring members, is made somewhat larger.
In some cases, reinforcement may be necessary.

Furthermore, the direction in which the strands 6 are pulled out from the drive coils 4 and 5 is not limited to the horizontal direction, but can be changed as appropriate depending on the mounting direction of the optical disc A, etc. Further, in the embodiment shown in FIG. 6, the wire 6 is pulled out vertically from the drive coil 4 for tracking adjustment, while the wire 6 is pulled out horizontally from the drive coil 5 for focus adjustment.
Each strand 6 can also be used for the sole purpose of tracking adjustment or focus adjustment. In the embodiment shown in FIG. 6, the silicone gel 10 is provided not only at the fixed site to the bobbin holder 7 but also at the fixed site on the bobbin 3 side that is driven.

[0035]

[Effects of the Invention] The present invention has the above-described structure, and by having such a structure, the following effects can be achieved. That is, a part of the wires 6 of the drive coils 4 and 5 is used as a support member for the objective lens 2, and is made to function as a spring member. On the other hand, since the silicone gel 10 is provided to fix the wire 6 to the bobbin holder 7, the attenuation efficiency is increased, stable characteristics are always obtained without being affected by temperature changes, and the driving of the objective lens 2 is ensured. Facilitates tightening, focus, and tracking adjustments. Moreover, the volatile matter from the silicone gel 10 is suppressed, and the volatile matter does not cause contact failure in the surrounding electronic circuits.
When filling the supporting portion of the liquid, there is no problem with liquid penetration or outflow, so the workability of the filling work is improved and it is possible to substantially reduce the weight and size of the optical pickup.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a drive device to which an objective lens drive mechanism in an optical pickup of the present invention is applied.

FIG. 2 is a plan view of the same as above.

FIG. 3 is a longitudinal cross-sectional side view of the same as above.

FIG. 4 is a longitudinal sectional side view showing another embodiment same as the above.

FIG. 5 is a longitudinal sectional side view showing still another embodiment of the same.

FIG. 6 is a longitudinal sectional side view showing still another embodiment of the same.

FIG. 7 is a skeletal explanatory diagram showing an objective lens drive mechanism in a conventional optical pickup.

[Explanation of symbols]

1 Drive device 2 Objective lens 3 Bobbin 4 Drive coil 5 for tracking adjustment
Drive coil for focus adjustment 6 Wire 7 Bobbin holder 8 Electronic board 9 Small hole 10 Silicone gel A Optical disk

Claims (3)

[Claims] Claim 1: A drive coil for focus adjustment and tracking adjustment that focuses a laser beam onto an optical disk using an objective lens, receives light reflected back from the optical disk, and adjusts the position of the laser spot. In the drive mechanism, the objective lens is supported by pulling out an end of a wire constituting the drive coil and stretching it between a bobbin holder, which is a holding member, and a fixing portion of the wire. A silicone gel is present in at least a portion of the silicone gel, and the silicone gel is obtained by adding an organopolysiloxane having an alkenyl group and an organohydrogenpolysiloxane having a silicon-bonded hydrogen atom in the presence of a platinum-based catalyst. A cross-linked structure consisting of
0g load)] and penetration is 300 or less (or 5 to 250)
An objective lens drive mechanism in an optical pickup, characterized in that the cured product has a loss coefficient (tan δ) of 0.1 to 2 at a shear frequency of 0.01 Hz to 10 Hz. 2. The strands of wire drawn out from the drive coil are drawn out in the direction along the surface of the optical disk, and in the tangential direction of the tracks of the optical disk, respectively, and the strands drawn out in one direction are directly drawn out. The wire mounted on the electronic board provided at the end of the bobbin holder and fed out to the other end is inserted into a small hole carved in the other end of the bobbin holder, and the silicone gel is interposed in this small hole. An objective lens drive mechanism in an optical pickup according to claim 1. 3. The alkenyl group-containing organopolysiloxane contains two or more silicon-bonded alkenyl groups in one molecule, and has a viscosity of 50 to 1 at 25°C.
00,000 centipoise, and from 4 weight to 2
3. The objective lens drive mechanism in an optical pickup according to claim 1, wherein the diorganopolysiloxane contains 0.5% by weight or less of cyclic diorganopolysiloxane up to 0 weight.