JP5113324B2 - Lens holder and optical recording / reproducing apparatus - Google Patents

Description

  The present invention relates to a molding material for a lens holder used for manufacturing a lens holder used in an optical recording / reproducing apparatus or the like. The present invention further relates to a lens holder manufactured using the lens holder molding material, and an optical recording / reproducing apparatus using the lens holder.

  In an optical recording / reproducing apparatus such as a CD, MD, and DVD, an optical pickup is used for recording and reproducing information. The optical pickup has an objective lens held by a lens holder. The objective lens collects light incident from the light source on the optical disc to record and reproduce information, and reflects light from the optical disc. Enters the light receiving element through the objective lens and is converted into an electric signal. At present, various optical pickups have been proposed and described in, for example, Japanese Patent Application Laid-Open No. 2005-92949.

  FIG. 1 is a perspective view showing an example of such an optical pickup. This optical pickup comprises a lens holder 1 and a suspension holder 2, and two suspension wires 3, 3 'are provided on both sides of the lens holder 1, respectively.

  One end of the suspension wires 3, 3 ′ is embedded in the lens holder 1, and the other end is embedded in the suspension holder 2, and is electrically connected to control means (not shown). . The suspension wires 3 and 3 'are made of an elastic conductive material, and the lens holder 1 is supported by the suspension holder 2 so as to be displaceable by the elasticity of the suspension wires 3 and 3'.

  The lens holder 1 has a circular through hole 4 at the center thereof, and an objective lens 5 is attached to the through hole 4. Further, the lens holder 1 is provided with rectangular through holes 6 and 6 ′.

  Further, the lens holder 1 is provided with coils 7, 8 and 8 'for moving the objective lens 5 in the focus direction and the tracking direction. The end portions of the coils 7, 8 and 8 'are joined to the suspension wires 3 and 3' by soldering or the like, although not shown.

  The suspension holder 2 is fixed to a yoke (not shown), and a plurality of magnets (not shown) are fixedly provided on the yoke, and these magnets are installed at positions close to the coil 7. Also, they are inserted into the through holes 6 and 6 ', that is, into the coils 8 and 8', respectively. Accordingly, the control means allows a current to flow selectively through the suspension wires 3 and 3 ', thereby causing a current to flow through each coil, and the objective lens 5 is moved in the focus direction and / or tracking direction by the action of the generated magnetic field and magnet. Move to.

  A lens holder which is a movable part of such an optical pickup is formed by molding a material excellent in moldability and insulation, and the following characteristics are desired for this material.

1. In order to achieve a high response of the lens holder (moving with high sensitivity by a small signal), it is desired to reduce the weight of the lens holder. Therefore, a material having a low specific gravity is desired as a material for forming the lens holder. .

2. Higher-order resonance that is difficult to resonate due to vibration caused by rotation of an optical disk or the like is desired. This resonance can usually be avoided by adjusting the rigidity of the suspension wire. However, when the response is further improved, the resonance also occurs due to the elastic modulus of the lens holder itself. Accordingly, since the resonance resistance is proportional to (elastic modulus / specific gravity) ^1/2 , a material having a high elastic modulus (rigidity) is desired.

3. In the manufacture of an optical pickup, the lens holder is exposed to a high temperature of 360 to 380 ° C. for about 0.5 to 3 seconds in order to thermally dissipate the coating of the winding after mounting the lens holder and the like. Even in this case, high temperature heat resistance that does not cause distortion or deformation is desired.

Therefore, conventionally, in order to satisfy such requirements, a liquid crystal polymer has been widely used as a material for forming a lens holder, and is described in JP-A-2005-50466 (paragraph 0003).
JP 2005-92949 A Japanese Patent Laying-Open No. 2005-50466 (paragraph 0003)

  However, in order to meet the demand for higher recording density and higher response in recent years, the demand for lens holders has become higher. In particular, a material having no anisotropy of elastic modulus and linear expansion coefficient has been demanded.

  That is, if there is anisotropy, the lens holder is distorted due to heating or the like in the manufacture of the optical pickup, causing problems such as a decrease in the accuracy of the position of the objective lens. In particular, this problem is significant when the position where the objective lens is provided is not at the center of the lens holder but is biased to one side. However, the liquid crystal polymer is a material having a large anisotropy due to the flow direction at the time of molding, and this requirement cannot be satisfied.

  The present invention provides a molding material for a lens holder having the above characteristics, that is, excellent heat resistance at high temperature, high-order resonance, light weight and low anisotropy, and excellent moldability. The issue is to provide. The present invention further provides a lightweight lens holder manufactured using this lens holder molding material, having excellent high-temperature heat resistance, having high-order resonance, and an optical recording / reproducing apparatus using the lens holder. This is the issue.

  As a result of the study, the present inventor gives a lens holder which is a cross-linked resin and has excellent high-temperature heat resistance and high-order resonance by using a resin having a dynamic viscoelastic modulus at a high temperature of a predetermined value or more. And the present invention has been completed. Further, the present inventor has also found that the use of a specific cross-linked resin can also achieve the object of providing a lens holder that is lighter and has less anisotropy.

  The invention according to claim 1 is a molding material for a lens holder comprising a crosslinked resin and comprising a material having a dynamic viscoelastic modulus at 360 ° C. of 1 MPa or more after crosslinking.

  Here, the cross-linked resin refers to a resin having a portion (cross-linking site) capable of forming a cross-link in its main chain or side chain, that is, a resin capable of causing a cross-linking reaction by heating or radiation irradiation. It is distinguished from collapsible resins such as polyisobutylene and polyvinylidene chloride, which are broken by heat and radiation. After molding this crosslinked resin, a crosslinked molded product can be obtained by heating or radiation irradiation.

  A molded product obtained by crosslinking a crosslinked resin is excellent in heat resistance and rigidity, and has good creep resistance. In addition, the use of a material having a smaller orientation than the liquid crystal polymer reduces the problem of anisotropy that occurs when the liquid crystal polymer is used. Further, by using a crosslinked resin having a low specific gravity and excellent insulating properties, the lens holder can be reduced in weight and high insulative properties. Furthermore, molding is easy at the stage before the crosslinked resin is crosslinked, and molding having excellent characteristics is easily performed by performing predetermined molding at this stage and crosslinking by heating or irradiation after molding. You can get a body.

  Examples of the molding method include LIM molding, mold molding, blow molding, transfer molding, and injection molding. When a cyclic polyolefin or semi-aromatic polyamide, which will be described later, is used as the crosslinked resin, injection molding is preferably used.

  The molding material for lens holder of the present invention is characterized in that the dynamic viscoelasticity at 360 ° C. after the crosslinking is 1 MPa or more. That is, the material can have a dynamic viscoelastic modulus at 360 ° C. of 1 MPa or more by crosslinking within a range of practical crosslinking conditions (such as radiation dose). By using a material having this characteristic, it is possible to obtain excellent high-temperature heat resistance and rigidity (high-order resonance) that can sufficiently satisfy recent requirements. Here, the dynamic viscoelastic modulus is a value of a real part (E ′ storage elastic modulus) of a complex elastic modulus measured under conditions of a frequency of 10 Hz and a temperature rising rate of 20 ° C./min.

  As the cross-linked resin, use of general-purpose cross-linked resins such as polyethylene, polyvinyl chloride, polypropylene, polystyrene, natural rubber, epoxy resin, phenol resin, melamine resin, etc. is possible, but high temperature heat resistance, high rigidity and low specific gravity are also considered. In order to obtain, an aliphatic polyamide such as polyamide 6 or polyamide 66, a polyester resin having an aromatic ring such as polybutylene terephthalate (PBT), a cyclic olefin such as cyclopentene, 2-norbornene, or a cyclotetradodecene monomer. Preferred examples include semi-aromatic polyamides such as cyclic polyolefins obtained by polymerizing monomers, polyamide 6T, and polyamide 9T.

  Of these, cyclic polyolefins and semi-aromatic polyamides are particularly preferred, and claims 2 and 3 correspond to this particularly preferred embodiment.

  That is, the invention of claim 2 is the lens holder molding material, wherein the cross-linked resin is a cyclic polyolefin. A resin obtained by crosslinking a cyclic polyolefin is preferable because it has high rigidity and particularly low specific gravity. In addition, the cyclic polyolefin is excellent in moldability and is low in anisotropy because it is an amorphous resin. Further, when irradiated with radiation, a molded product having excellent high temperature heat resistance can be easily obtained.

  The invention of claim 3 is the lens holder molding material, wherein the cross-linked resin is a semi-aromatic polyamide. The semi-aromatic polyamide is, for example, a polyamide obtained by condensing an aliphatic diamine such as hexamethylene diamine and an aromatic dicarboxylic acid such as terephthalic acid and having an aliphatic chain and an aromatic ring in the molecule. And polyamide 9T.

  Semi-aromatic polyamide has low specific gravity and high rigidity. Moreover, it is excellent in moldability, and a molded article having excellent high temperature heat resistance can be easily obtained by irradiation with radiation.

  The molding material for lens holder of the present invention preferably further contains a filler as a reinforcing material in addition to the crosslinked resin. By containing the filler, it is possible to reduce the amount of the crosslinking agent and the amount of radiation necessary for setting the dynamic viscoelasticity at 360 ° C. after crosslinking to 1 MPa or more.

  When a filler is contained, the filler is kneaded with a cross-linked resin, then molded, and further subjected to cross-linking by radiation irradiation or the like to obtain a lens holder.

  The addition amount of the filler is preferably 5 to 100 parts by weight with respect to 100 parts by weight of the cross-linked resin. When the content of the filler is less than 5 parts by weight, it is necessary to increase the amount of the crosslinking agent or increase the irradiation amount of the radiation, which tends to become brittle. When the filler content exceeds 100 parts by weight, the fluidity is lowered, and it may be difficult to mold into a precise lens holder shape.

  Examples of fillers include glass fibers, hollow materials such as hollow glass particles and foamed metals, inorganic whiskers such as basic magnesium sulfate whiskers, zinc oxide whiskers, and potassium titanate whiskers, montmorillonite, synthetic smectite, wholly aromatic polyamide fibers, etc. Is mentioned.

  Among them, glass fiber is preferably used because it has a high reinforcing effect and is inexpensive. A hollow substance is also preferably used in terms of excellent resonance characteristics. Examples of the hollow material include Glass Bubbles (registered trademark) manufactured by Sumitomo 3M.

  The present invention provides a lens holder obtained from the molding material for lens holder, in addition to the molding material for lens holder. That is, the invention according to claim 4 is a lens holder obtained by using the molding material for a lens holder, wherein the dynamic viscoelasticity at 360 ° C. after crosslinking is 1 MPa or more. A holder is provided.

  The lens holder of the present invention can be obtained by molding and crosslinking the lens holder molding material. The dynamic viscoelastic modulus after cross-linking varies depending on the type of cross-linked resin, the degree of cross-linking, the presence or absence and type of filler. Therefore, after the type of the crosslinked resin, the presence or absence of the filler, and the type are determined, the degree of crosslinking is adjusted so that the dynamic viscoelastic modulus at 360 ° C. after crosslinking of the molded product is 1 MPa or more. That is, the range of the degree of crosslinking differs depending on the type of the crosslinked resin and cannot be specifically determined, but is defined as a range in which the dynamic viscoelasticity at 360 ° C. is 1 MPa or more. The specific range of the degree of cross-linking can be easily determined by an experiment in which the amount of radiation irradiation is varied, for example, when cross-linking is performed by radiation irradiation.

  Examples of the crosslinking method include a heating method using a crosslinking agent and a crosslinking method using an electron beam or other radiation. However, when a normal thermosetting resin such as a phenol resin is used as the crosslinked resin, so-called burrs are likely to occur during molding, and it may be difficult to mold a precise lens holder. On the other hand, the method of crosslinking using an electron beam or other radiation is preferable because such problems are unlikely to occur and the temperature and fluidity are not limited during molding. A fifth aspect of the invention corresponds to this preferred embodiment, and provides a lens holder obtained by molding the molding material for the lens holder and radiation-crosslinking the crosslinked resin. Examples of radiation include γ rays in addition to electron beams.

  As described above, the radiation dose required for crosslinking varies and is not limited depending on the type of crosslinking resin, the presence or absence and type of crosslinking aid, the presence or absence and type of filler, but the dynamic viscosity at 360 ° C. after crosslinking is not limited. Irradiation is performed in an amount necessary for the elastic modulus to be 1 MPa or more.

  Circuit formation can be performed on the molded article after crosslinking by plating or the like. This makes it possible to provide an MID type optical pickup.

  The present invention further provides an optical recording / reproducing apparatus using the lens holder (claim 6). Since this optical recording / reproducing apparatus uses the lens holder having the above-mentioned excellent characteristics, it is an optical recording / reproducing apparatus having excellent reliability.

  The dynamic viscoelastic modulus at 360 ° C. after crosslinking of the material forming the lens holder is 1 MPa or more, more preferably 5 MPa or more. Moreover, the thing whose elasticity modulus in room temperature is 5 GPa or more is preferable.

  The molding material for lens holder of the present invention is excellent in moldability, and a molded product having a dynamic viscoelastic modulus at 360 ° C. of 1 MPa or more can be obtained by crosslinking the molded product of this material. The lens holder of the present invention made of the molded product thus obtained is excellent in high-temperature heat resistance and has high-order resonance. Furthermore, by using a material with low anisotropy, a lens holder that is excellent in the accuracy of the position of the objective lens without being distorted by heating during the formation of the pickup is obtained, and by using a material with a low specific gravity. Thus, a lens holder having an excellent characteristic that it is lightweight and has high response can be obtained. Therefore, the optical recording / reproducing apparatus of the present invention using this lens holder is a highly reliable optical recording / reproducing apparatus, and is suitably used as a CD, MD, DVD or the like.

  Next, specific modes for carrying out the invention will be described.

  In addition to the method of crosslinking using radiation, the method of crosslinking the crosslinked resin includes a method by heating using a crosslinking agent. Examples of the crosslinking agent include sulfur compounds, dialkyl peroxides, and peroxyketals; Peroxyesters; organic peroxides such as hydroperoxides are exemplified. In the case of using a crosslinking agent, a sulfur compound or an organic peroxide is blended in the crosslinking resin, and a crosslinking aid is blended and heated as necessary to carry out a crosslinking reaction.

  Both the method of heating using a crosslinking agent and the method of crosslinking using radiation are preferred because crosslinking is promoted by using a crosslinking aid in combination, and excellent heat resistance and rigidity can be obtained. . Examples of the crosslinking aid include vulcanization accelerators, vulcanization acceleration aids (when sulfur is used as the crosslinking agent), oximes; acrylates or methacrylates; vinyl monomers; allyl compounds; maleimide compounds, and the like.

  When a cyclic polyolefin is used as the cross-linked resin, the cyclic olefin monomer that is a raw material thereof includes 2-norbornene, 5-methyl-2-norbornene, 5,5-dimethyl-2-norbornene, and 5-ethyl-2-norbornene. , 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, 5-methoxycarbonyl-2-norbornene, 5-cyano-2-norbornene, 5-methyl-5-methoxycarbonyl-2-norbornene, 5-phenyl 2-norbornene monomers such as 2-norbornene and 5-phenyl-5-methyl-2-norbornene, cyclopentene monomers such as dicyclopentadiene and 2,3-dihydrodicyclopentadiene, tetracyclo-3- Dodecene, 8-methyltetracyclo-3-dodecene, 8-ethyltetra Tetracyclododecene monomers such as chloro-3-dodecene, 8-hexyltetracyclo-3-dodecene, 2,10-dimethyltetracyclo-3-dodecene, and 5,10-dimethyltetracyclo-3-dodecene Illustrated.

  Cyclic polyolefin is, for example, random addition copolymerization with the above-mentioned cyclic olefin monomer and another monomer having an unsaturated group that can be copolymerized with cyclic olefin monomer such as ethylene and acrylate esters. And a method of ring-opening polymerization of a cyclic olefin monomer together with other monomers and hydrogenating the ring-opened polymer. As the polymerization conditions such as the catalyst and solvent to be used, and the reaction temperature, known conditions described in JP-A-8-20692 can be employed.

  The lens holder of the present invention is manufactured by, for example, the following method. That is, first, the cross-linked resin, a filler added if necessary, a cross-linking aid and the like are kneaded. The obtained uniform mixture is molded into the shape of a lens holder by means such as injection molding, and then heated or irradiated with radiation, and the crosslinked resin is crosslinked to obtain the lens holder of the present invention. The lens holder thus obtained may be used as it is for an optical pickup of an optical recording / reproducing apparatus, but may be used after being processed by cutting, polishing, or the like.

  Next, the present invention will be described with reference to examples. In addition, this invention is not limited to this Example, The change to another form is also possible unless the meaning of this invention is impaired.

Examples 1-4 and Comparative Examples 1-4
[Crosslinked resin]
As the cross-linked resin, the following commercially available products (1) to (3) were used.
(1) Apel 6013T: COC (cyclic polyolefin) manufactured by Mitsui Chemicals, Inc. Tg = 125 ° C .: MFR15 (260 ° C.)
(In Table 1, "Apel" is displayed.)
(2) Grivory GV-1H: Semi-aromatic polyamide / GF 40% manufactured by EMS Shodensha Co., Ltd. (In Table 1, "Grivory" is indicated.)
(3) Toraycon 1301G: Polybutylene terephthalate (PBT) manufactured by Toray Industries, Inc. (In Table 1, "Torcon" is displayed.)
For comparison, the same experiment was performed using the following liquid crystal polymer.
Sumika Super 5008: manufactured by Sumitomo Chemical Co., Ltd. (In Table 1, "LCP" is displayed.)

  Each of the above-mentioned crosslinked resins (or liquid crystal polymers) was blended with the following crosslinking aid and filler at the blending ratio shown in Table 1, and a plate of 5 cm × 7 cm × thickness 1 mm was molded by injection molding.

[Crosslinking aid]
DA-MGIC: diallyl monoglycidyl isocyanurate (manufactured by Shikoku Kasei Co., Ltd., melting point 50 ° C.) (In Table 1, “DAMGIC” is indicated.)
TAIC: triallyl isocyanurate (manufactured by Nippon Kasei Co., Ltd.) (indicated as “TAIC” in Table 1)

[filler]
ECS03T-289 / PL: Aminosilane-treated chopped glass fiber manufactured by Nippon Electric Glass Co., Ltd. (In Table 1, "ECS" is displayed.)
Glass Bubbles S60H (registered trademark): Hollow glass manufactured by Sumitomo 3M
(In Table 1, “S60H” is displayed.)
Vulcan 9A32: carbon for coloring (indicated as “carbon” in Table 1)

  After molding, the electron beam having the irradiation amount shown in Table 1 was irradiated for crosslinking. Thereafter, the elastic modulus at room temperature, the dynamic viscoelastic modulus at 360 ° C., the workability of the lens holder, the deformation of the lens holder, and the anisotropy were measured by the following method, and the results are shown in Table 1.

[Measurement method]
Elastic modulus at room temperature: Measured according to ISO178. (In Table 1, "room temperature elastic modulus" is displayed and expressed in units of GPa.)

Dynamic viscoelastic modulus: A value of storage elastic modulus measured under conditions of a frequency of 10 Hz and a temperature rising rate of 20 ° C./min by a viscoelasticity measuring device by DVA-200 manufactured by IT Measurement & Control Co., Ltd. (In Table 1, “storage modulus” is displayed, and DMS × 10 ⁶ is displayed.)

  Processability of lens holder: The lens holder was wound, and the deformation of the holder after immersion in lead-free solder at 360 ° C. for 3 seconds was judged visually. The case where no major deformation was observed was marked with ◯, and the case where large deformation was recognized was marked with ×. (In Table 1, “bobbin” is displayed.)

  Deformation of lens holder: When a lens was set in the lens holder, potted with epoxy, and thermally cured at 100 ° C. for 4 hours, it was judged by the presence or absence of deviation of the center of the optical axis of the lens. The case where the deviation occurred was marked as x, and the case where the deviation did not occur was marked as ◯. (In Table 1, “deformed” is displayed.)

  Anisotropy: The deformation of the lens holder is related to the anisotropy of the material. Therefore, the linear expansion coefficient in the flow direction during molding and the linear expansion coefficient in the vertical direction were measured at 40 to 100 ° C. with TMA-50 (manufactured by Shimadzu Corporation), and the ratio thereof (vertical linear expansion coefficient / flow). Direction linear expansion coefficient). When this ratio is large, it is determined that the anisotropy is large.

  As is clear from the results in Table 1, in Examples 1 to 4 which were molded using a crosslinked resin and irradiated with an electron beam, a molded product having a dynamic viscoelasticity of 1 MPa or more at 360 ° C. was obtained. The processability of the lens holder is excellent, and deformation and anisotropy are small. In particular, in Examples 1 and 2 in which a cyclic polyolefin was used as the crosslinked resin and a filler was added, high dynamic viscoelasticity was obtained with a small amount of electron beam irradiation, and the specific gravity was small. It is shown that a lens holder is manufactured.

  On the other hand, in Comparative Examples 1 to 3 in which electron beam irradiation was not performed while using a crosslinked resin, a molded product having a dynamic viscoelasticity of 1 MPa or more at 360 ° C. was not obtained, and the workability of the lens holder was poor. Can not be used as a lens holder. In Comparative Example 4 using LCP instead of the cross-linked resin, dynamic viscoelasticity and processability of the lens holder are excellent, but anisotropy and deformation are large, and in this respect, inferior to Examples 1 to 4. It is.

It is a perspective view which shows an example of a lens holder notionally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens holder 2 Suspension holder 3, 3 'Suspension wire 4 Through-hole 5 Objective lens 6, 6' Through-hole '
7, 8, 8 'coil

Claims (5)

Polymer or copolymer of semi-aromatic polyamide, polyester resin having aromatic ring, and cyclic olefin monomer selected from 2-norbornene monomer, cyclopentene monomer and tetracyclododecene monomer A dynamic viscoelastic modulus at 360 ° C. obtained by molding a molding material obtained by kneading a mixture containing a cross-linking resin selected from the group consisting of cyclic polyolefins and a cross-linking aid and radiation-crosslinking the cross- linking resin. Is a lens holder characterized by being 1 MPa or more.   The crosslinked resin is a cyclic polyolefin that is a polymer or copolymer of a cyclic olefin monomer selected from a 2-norbornene monomer, a cyclopentene monomer, and a tetracyclododecene monomer. The lens holder according to claim 1, characterized in that:   The lens holder according to claim 1, wherein the cross-linked resin is a semi-aromatic polyamide. The lens holder according to any one of claims 1 to 3, wherein the crosslinking aid is diallyl monoglycidyl isocyanurate or triallyl isocyanurate .   An optical recording / reproducing apparatus using the lens holder according to any one of claims 1 to 4.

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