JP2007188553A - Optical element, optical pickup system, and optical element manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an objective lens which can maintain the focused spot properly on a disk even if the inside of the objective lens is heated unevenly. <P>SOLUTION: This optical element is molded by unevenly mixing a first materials consisting of a resin which has a refractivity n<SB>1</SB>in room temperature and a refractivity change rate of dn<SB>1</SB>/dT for the change of a temperature T and a second materials consisting of a resin which has a refractivity n<SB>2</SB>in room temperature and a refractivity change rate of dn<SB>2</SB>/dT for the change of a temperature T. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical element, an optical pickup device using the optical element, and a method for manufacturing the optical element.

  Conventionally, an optical pickup device is known as means for irradiating a signal recording surface of an optical disc with a light beam to read information recorded on the optical disc or write predetermined information on the optical disc.

  This optical pickup device uses a semiconductor laser or the like as a light source, and condenses the light beam from the light source on the signal recording surface of the optical disc through an optical device such as a collimator lens or a beam splitter and an objective lens. The light beam reflected from the recording surface is detected, and information is written to and read from the signal recording surface.

  In these optical pickup devices, an objective lens support member that supports an objective lens is driven to be displaced in two directions, ie, an optical axis direction (focus direction) and a direction orthogonal to the optical axis (tracking direction) to record signals on an optical disk. The recording track is accurately scanned by focusing the light beam on the surface.

  As an actuator for displacing and driving the objective lens support member, an electromagnetic driving force is generally used with a coil and a magnet as a pair. In use, these coils generate heat when supplied with power, and this heat travels through the objective lens support member to the objective lens, and the temperature distribution of the objective lens becomes non-uniform.

  When the objective lens is made of a plastic material with a large change in refractive index with respect to temperature, this non-uniform temperature distribution (also referred to as a heat-biased state) causes the refractive index of the objective lens to change non-uniformly, resulting in astigmatism. There are known problems to exacerbate.

In order to solve this problem, there is a technique in which a through hole is provided in an objective lens support member to reduce the amount of heat conduction and equalize the temperature distribution of the objective lens (for example, see Patent Document 1). In addition, there is a technique in which a gap is provided between the objective lens and the support member in a direction orthogonal to the tracking coil to eliminate the anisotropy of heat inflow and to equalize (for example, see Patent Document 2).
JP-A-11-353675 JP-A-10-162407

  The objective lens used in the optical pickup device is lightweight when formed of a plastic material, and does not require the driving force of the above displacement drive as much as that of an objective lens formed of a glass material. Many objective lenses are used.

  On the other hand, in recent years, there are some that write and read information on an ultra-high-density optical disk having a high recording capacity using not only a CD and a DVD but also a blue-violet laser. Various optical pickup devices having compatibility with these plural types of discs have been proposed, and for achieving this compatibility, for example, FIG. There is one in which a plurality of types of objective lenses are mounted on an objective lens support member as described in FIG. 44 of the 2003/091764 pamphlet.

  When multiple types of objective lenses are mounted on the same support member, it is difficult to arrange the objective lenses at an equal distance from the coil that is a heat source. Therefore, there is a problem of worsening astigmatism.

  In addition, the amount of heat generated by the coil, which is a heat source, is further increased by operating focusing and tracking at higher speeds in order to increase the speed of data reading and recording. This increase in the amount of generated heat further deteriorates the degree of the above-mentioned heat deviation state, and makes the problem more serious.

  In view of the above problems, an object of the present invention is to obtain an objective lens capable of maintaining a good converging spot formed on a disk even when the inside of the objective lens is in a heat-biased state.

  The above object is achieved by the invention described below.

1. A first material made of a resin having a refractive index n ₁ at normal temperature and a refractive index change rate dn ₁ / dT with respect to a change in temperature T; and a refractive index n ₂ at normal temperature, An optical element formed by unevenly distributing a second material made of a resin having a refractive index change rate of dn ₂ / dT with respect to a change in temperature T.

2. _2. The optical element according to 1, wherein the refractive index n _{1 of} the first material at room temperature and the refractive index n 2 of the second material at room temperature are substantially equal.

In the present invention, the refractive index at room temperature of the first material n ₁ and the second refractive index n ₂ at room temperature of the material are substantially equal, n ₁ is relative to n _2, 100 ± 0. Represents within 5%. Furthermore, it is preferably within 100 ± 0.3%, more preferably within 100 ± 0.2%.

  3. 3. The optical element according to 1 or 2, wherein at least one of the first material and the second material is a mixture of inorganic fine particles.

  4). The optical element according to any one of 1 to 3, wherein the first material and the second material are unevenly distributed in a radial direction.

  5. The optical element according to any one of 1 to 3, wherein the first material and the second material are unevenly distributed in the optical axis direction.

  6). The optical element according to any one of 1 to 5, wherein the first material and the second material are thermosetting resins.

  7). The optical element according to any one of 1 to 5, wherein the first material and the second material are thermoplastic resins.

  8). The optical element according to any one of claims 1 to 7, wherein an index indicating the uneven distribution direction of the first material and the second material is provided on the flange portion.

  Light having the optical element according to any one of 9.1 to 8, an actuator for driving the optical element in at least one of an optical axis direction and a direction perpendicular to the optical axis, a light source, and a photodetector. Pickup device.

  10. 10. The optical pickup device according to 9, wherein the actuator is disposed on an outer periphery of the optical element, and the first material and the second material are unevenly distributed in a radial direction of the optical element.

  11. An optical pickup device according to 9, comprising at least two optical elements according to any one of 11.1 to 8.

12 A first material made of a thermosetting resin having a refractive index n ₁ at room temperature and a refractive index change rate dn ₁ / dT with respect to a change in temperature T, and a refractive index n ₂ at room temperature. And a second material made of a thermosetting resin having a refractive index change rate of dn ₂ / dT (dn ₁ / dT> dn ₂ / dT) with respect to a change in temperature T is unevenly distributed in the mold. An optical element manufacturing method for molding, wherein the mold part corresponding to the position of the second material is installed vertically downward, the second material is allowed to flow into the mold, An optical element manufacturing method comprising: a step of flowing a first material; and a step of heating the mold.

13. A first material made of a thermoplastic resin having a refractive index n ₁ at room temperature and a refractive index change rate dn ₁ / dT with respect to a change in temperature T, and a refractive index n _{2 at} room temperature. Then, a second material made of a thermoplastic resin having a refractive index change rate of dn ₂ / dT (dn ₁ / dT> dn ₂ / dT) with respect to a change in temperature T is unevenly distributed in the mold. An optical element manufacturing method comprising: a step of placing the pre-formed second material at a predetermined position in the mold; and a step of flowing the melted first material. An optical element manufacturing method.

  According to the present invention, it is possible to obtain an objective lens capable of maintaining a good condensing spot formed on the disk even when the objective lens is in a heat-biased state.

  Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not limited thereto.

  FIG. 1 is a diagram illustrating an example of an optical system of the optical pickup device according to the present embodiment.

  The figure shows a state in which an ultra-high density optical disk 12 having a substrate thickness of 0.1 mm, an optical disk (DVD) 13 having a substrate thickness of 0.6 mm, and an optical disk (CD) 14 having a substrate thickness of 1.2 mm are recorded and reproduced. For convenience of explanation, they are drawn in the same place.

  The optical system of this example includes a light source 1 having a wavelength of 380 nm to 420 nm (λ1), a light source 2 having a wavelength of 630 nm to 680 nm (λ2), and a light source 3 having a wavelength of 780 nm to 820 nm (λ3).

  When recording / reproducing the ultra-high-density optical disc 12, the light beam having the wavelength λ1 emitted from the light source 1 is transmitted through the prisms 4, 5, and 6 to be converted into a parallel light beam by the collimator lens 7 and reflected by the reflecting surface 67a of the dichroic mirror. Then, the light is condensed as a light spot on the recording surface of the ultra-high density optical disk 12 by the objective lens 39. The reflecting surface 67a is formed of, for example, a dielectric multilayer film so as to reflect the light beams having the wavelengths λ1 and λ2 and transmit the light beam having the wavelength λ3. Note that a phase plate or the like may be disposed on the light source side of the objective lens 39.

  The light beam reflected by the recording surface of the ultra-high density optical disk 12 passes through the objective lens 39 again, is reflected by the reflecting surface 67a, passes through the collimator lens 7, is reflected by the prism 6, and enters the detector 15. The detector 15 has a plurality of light detection areas, and the plurality of light detection areas output signals according to the received light quantity.

  When recording / reproducing the DVD 13, the light beam having the wavelength λ 2 emitted from the light source 2 is reflected by the prism 4, passes through the prisms 5 and 6, then becomes a parallel light beam by the collimator lens 7, and is reflected by the reflection surface 67 a of the dichroic mirror. The light is reflected and condensed as a light spot on the recording surface of the DVD 13 by the objective lens 39.

  The light beam reflected by the recording surface of the DVD 13 passes through the objective lens 39 again, is reflected by the reflecting surface 67a, passes through the collimator lens 7, is reflected by the prism 6, and enters the detector 15.

  When recording / reproducing the CD 14, the light beam having the wavelength λ 3 emitted from the light source 3 is reflected by the prism 5, passes through the prism 6, then becomes a parallel light beam by the collimator lens 7, and passes through the reflection surface 67 a of the dichroic mirror. Then, the light is reflected by the reflecting surface 67 b and is condensed as a light spot on the recording surface of the CD 14 by the objective lens 45.

  The light beam reflected by the recording surface of the CD 14 passes through the objective lens 45 again, is reflected by the reflecting surface 67 b, passes through the collimator lens 7, is reflected by the prism 6, and enters the detector 15.

  In other words, the optical system of the optical pickup device shown in the same figure uses the objective lenses 39 and 45 mounted on the objective lens support member 33 properly, so that each of the ultra high density optical disc 12, DVD 13 and CD 14 is used. Information is recorded and reproduced.

  FIG. 2 is a perspective view schematically showing an optical head portion on which an objective lens of the optical pickup device according to the present embodiment is supported.

  In the figure, two objective lenses 39 and 45 are bonded and supported by an objective lens support member 33. The objective lens support member 33 is supported by four flexible wires 26 extending from the support holder 27, and the objective lens support member 33 can move within a predetermined range using the wires 26 as a suspension.

  A focus drive coil 23 is wound around the outer periphery of the objective lens support member 33, and a tracking drive coil 22 (not shown) is disposed in a magnetic circuit composed of an outer yoke 24, an inner yoke 25, and a magnet 21. Has been. By supplying power to these coils, which are actuators, the objective lens support member 33 can swing in two directions, ie, the optical axis direction of the two objective lenses 39 and 45 and the direction orthogonal to the optical axis. These coils are supplied with power via a wire 26.

  FIG. 3 is a diagram showing the objective lenses 39 and 45 according to the present embodiment. 2A is a cross-sectional view of the optical head section shown in FIG. 2 taken along the line FF, and FIG. 2B is a view of the objective lenses 39 and 45 viewed from the optical disc side. .

  The objective lenses 39 and 45 shown in the figure are formed of different materials on the side closer to and far from the focus driving coil 23. Further, the different materials are unevenly distributed in the radial direction as shown in the figure.

  The objective lens 39 is formed of the first material A on the side far from the focus driving coil 23 and is formed of the second material B on the side close to the focus driving coil 23. Similarly, the objective lens 45 is also formed of the first material A on the side far from the focus driving coil 23 and the second material B on the side close to the focus driving coil 23.

The first material A is made of a resin having a refractive index n ₁ at room temperature and a refractive index change rate dn ₁ / dT with respect to a change in temperature T, and the second material B is refractive index at normal temperature an n _2, of dn ₂ / dT refractive index change rate with respect to changes in temperature T, a resin, which refractive index change rate with respect to changes in temperature T are different, i.e., dn is a _{1 / dT ≠ dn 2 / dT} . Further, the refractive indexes n ₁ and n ₂ of the materials A and B at room temperature are n ₁ ≈n ₂ .

  As the first material A and the second material B constituting the objective lens according to the present embodiment, for example, a resin material in which inorganic fine particles are dispersed can be used. When using a resin material in which inorganic fine particles are dispersed, a resin material in which inorganic fine particles are dispersed in one of the resin material of the first material A and the resin material of the second material B may be used. A resin material in which inorganic fine particles are dispersed in both the resin material of the material A and the resin material of the second material B may be used.

  In addition, the inorganic fine particles dispersed in the resin are not particularly limited, and may be arbitrarily selected from the inorganic fine particles so that the refractive index change dn / dT depending on the temperature of the resin material to be obtained becomes the structure of the present invention. Can do. Specifically, oxide fine particles, metal salt fine particles, semiconductor fine particles, and the like are preferably used. Of these, those that do not generate absorption, light emission, fluorescence, etc. in the wavelength region used as an optical element are appropriately selected and used. Is preferred.

  Furthermore, as the resin material of the first material A and the second material B, a thermoplastic resin, a thermosetting resin, or the like can be used.

In this way, the objective lens, which is an optical element, has a radius by using a material having a refractive index that is substantially equal to room temperature and having a different refractive index change with respect to a temperature change (in the above example, dn ₁ / dT> dn ₂ / dT). In order to eliminate the difference in refractive index between the high-temperature part and the relatively low-temperature part in the objective lens against the heat-biased state caused by the heat generated by the actuator of the optical pickup device in the radial direction of the objective lens. Accordingly, it is possible to obtain an objective lens capable of maintaining a good focused spot formed on the disk without deteriorating astigmatism.

  Furthermore, as shown in the figure, indicators 39h and 45h (circular dents in the figure) indicating the direction in which the second material is unevenly distributed are formed on the flange portions of the objective lenses 39 and 45, respectively. By doing in this way, it is possible to embed without making a mistake in the direction at the time of incorporation.

  FIG. 4 is a cross-sectional view showing another example of the objective lens according to the present embodiment.

The objective lenses 39 and 45 shown in FIG. 5A have a first material A made of a resin having a refractive index n ₁ at room temperature and a refractive index change rate dn ₁ / dT with respect to a change in temperature T; A second material B made of a resin having a refractive index of n ₂ at normal temperature and a refractive index change rate of dn ₂ / dT (dn ₁ / dT ≠ dn ₂ / dT) with respect to a change in temperature T is provided on the optical axis. It is formed by uneven distribution in the O direction. This example is applied when, for example, the actuator is disposed so as to be shifted downward relative to the objective lens in the figure and is in a heat-biased state in the optical axis direction of the objective lens.

  FIG. 4B shows the first material A and the second material B that are formed so as to be unevenly distributed in both the radial direction and the optical axis O direction. This example is applied to a case where the heat is shifted in both directions of the optical axis direction and the radial direction of the objective lens.

  That is, the objective lens, which is an optical element according to the present embodiment, uses a material having a different refractive index change with respect to a temperature change so as to correspond to the thermal deviation state of the optical head portion of the optical pickup device arranged. This eliminates the difference in refractive index between the high temperature portion and the relatively low temperature portion in the lens, and makes it possible to maintain a good condensing spot formed on the disk.

  In the above example, two objective lenses are mounted on the optical head unit, and both are described as being formed of a resin material. However, the present invention is not limited to this, and when one is formed of glass, This is applied to the one formed of the other resin material. In addition, even when one lens is mounted on the optical head unit, the present invention can be applied corresponding to the generated thermal deviation state.

  FIG. 5 is a diagram showing a process of forming an objective lens, which is an optical element according to the present embodiment, using a thermosetting resin. The case where the objective lens 45 shown in FIG. 3 is formed will be described as an example with reference to FIGS.

  A mold 50 shown in the figure includes a mold part 52 on which a surface that forms one optical effective surface of the objective lens 45 is formed, and a mold part 51 that forms one surface of the flange part and a side surface of the flange part. And the mold part 53 on which the other optically effective surface of the objective lens 45 and the surface forming the flange surface are formed. The mold is opened with the parting line PL as a boundary, and the objective lens 45 as a molded product can be taken out. It is like that.

  As shown in FIG. 5A, the mold 50 is provided with a mold part corresponding to the position of the second material B (part corresponding to the index 45h) vertically below.

  First, the second material B is introduced from the gate portion 45g. At this time, the second material B is in a state of being stored downward due to gravity as shown in FIG.

  Next, as shown in FIG. 4B, after the first material A is caused to flow from the gate portion 45g, it is heated to cure the first material A and the second material B, which are thermosetting resins. . By doing so, in the vicinity of the boundary line between the first material A and the second material B, they are mixed and hardened in a state where the boundary line is ambiguous, and the objective lens 45 according to the present embodiment is formed.

  After curing, as shown in FIG. 5C, the mold parts 51 and 52 are opened apart from the mold part 53 with the parting line PL of the mold 50 as a boundary, and the mold 52 is projected. Then, the objective lens 45 is released.

  Thereafter, the gate portion 45g is deleted, and the objective lens 45 is completed.

  FIG. 6 is a diagram illustrating a process of forming an objective lens, which is an optical element according to the present embodiment, using a thermoplastic resin. The case where the objective lens 45 shown in FIG. 3 is formed will be described as an example with reference to FIGS.

  The mold 50 shown in the figure also includes a mold part 52 on which a surface that forms one optical effective surface of the objective lens 45 is formed, and a mold part 51 that forms one surface of the flange part and a side surface of the flange part. And the mold part 53 on which the other optically effective surface of the objective lens 45 and the surface forming the flange surface are formed. The mold is opened with the parting line PL as a boundary, and the objective lens 45 as a molded product can be taken out. It is like that.

  First, as shown in FIG. 5A, the mold 50 is opened, and a portion 45p constituting a part of the objective lens 45, which is previously molded using the second material B, is arranged at a predetermined position. To do.

  Next, as shown in FIG. 5B, the mold 50 is closed, the first material A is caused to flow from the gate portion 45g, and the mold temperature is lowered.

  Thereafter, as shown in FIG. 5C, the mold parts 51 and 52 are opened apart from the mold part 53 with the parting line PL of the mold 50 as a boundary, and the mold 52 is projected. Then, the objective lens 45 is released.

  Thereafter, the gate portion 45g is removed, and the objective lens 45 is completed.

  In the insert molding using this thermoplastic resin, the second material B can be molded in advance into a desired shape, the degree of freedom of the shape occupied by the second material B is high, and the conditions of the optical head portion It is possible to increase the ability to cope with various heat deviation states corresponding to the above.

  Next, the first material and the second material according to the present embodiment will be described.

  Specifically, oxide fine particles, metal salt fine particles, semiconductor fine particles, and the like are preferably used as the inorganic fine particles dispersed in the resin material used in the present embodiment.

As oxide fine particles, the metal constituting the metal oxide is Li, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb. 1 selected from the group consisting of Sr, Y, Nb, Zr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, La, Ta, Hf, W, Ir, Tl, Pb, Bi and rare earth metals A metal oxide that is a seed or two or more metals can be used. Specifically, for example, silicon oxide, titanium oxide, zinc oxide, aluminum oxide, zirconium oxide, hafnium oxide, niobium oxide, tantalum oxide, oxide Magnesium, calcium oxide, strontium oxide, barium oxide, indium oxide, tin oxide, lead oxide, double oxides composed of these oxides, lithium niobate and potassium niobate , Lithium tantalate, the aluminum magnesium oxide (MgAl ₂ O _4), and the like. In addition, rare earth oxides can also be used as oxide fine particles used in the present invention, specifically, scandium oxide, yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide. Terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide and the like. Examples of the metal salt fine particles include carbonates, phosphates, sulfates, and the like, specifically, calcium carbonate, aluminum phosphate, and the like.

Further, the semiconductor fine particles mean fine particles having a semiconductor crystal composition, and specific examples of the semiconductor crystal composition include a simple substance of group 14 element of periodic table such as carbon, silicon, germanium, tin, phosphorus (black). A group consisting of a group 15 element such as phosphorus), a group 16 element such as selenium or tellurium, a compound composed of a plurality of group 14 elements such as silicon carbide (SiC), tin oxide (IV) ) (SnO ₂ ), tin sulfide (II, IV) (Sn (II) Sn (IV) S ₃ ), tin sulfide (IV) (SnS ₂ ), tin sulfide (II) (SnS), tin selenide (II) ) (SnSe), tin telluride (II) (SnTe), lead (II) sulfide (PbS), lead selenide (II) (PbSe), lead telluride (II) (PbTe) group 14 Compounds of elements and group 16 elements of the periodic table, boron nitride (BN), boron phosphide (BP), arsenic Arsenic (BAs), aluminum nitride (AlN), aluminum phosphide (AlP), aluminum arsenide (AlAs), aluminum antimonide (AlSb), gallium nitride (GaN), gallium phosphide (GaP), gallium arsenide (GaAs) Of periodic table group 13 elements such as gallium antimonide (GaSb), indium nitride (InN), indium phosphide (InP), indium arsenide (InAs), indium antimonide (InSb), etc. Compound (or III-V compound semiconductor), aluminum sulfide (Al ₂ S ₃ ), aluminum selenide (Al ₂ Se ₃ ), gallium sulfide (Ga ₂ S ₃ ), gallium selenide (Ga ₂ Se ₃ ), tellurium gallium (Ga ₂ Te _3), indium oxide (In ₂ O _3), indium sulfide In ₂ S _3), indium selenide (In ₂ Se _3), telluride, indium (In ₂ Te ₃₎ Periodic Table compounds of a Group 13 element and Periodic Table Group 16 element such as, thallium chloride (I) ( TlCl), thallium bromide (I) (TlBr), thallium iodide (I) (TlI) and other compounds of group 13 elements of the periodic table and elements of group 17 of the periodic table, zinc oxide (ZnO), zinc sulfide ( ZnS), zinc selenide (ZnSe), zinc telluride (ZnTe), cadmium oxide (CdO), cadmium sulfide (CdS), cadmium selenide (CdSe), cadmium telluride (CdTe), mercury sulfide (HgS), selenium Compounds of Group 12 elements of the periodic table and Group 16 elements of the periodic table (or II-VI group compound semiconductors) such as mercury halide (HgSe) and mercury telluride (HgTe), arsenic sulfide (III) ( s ₂ S _3), selenium arsenic _{(III) (As 2 Se 3} ), telluride arsenic _{(III) (As 2 Te 3} ), antimony sulfide _{(III) (Sb 2 S 3} ), selenium antimony (III) (Sb ₂ Se ₃ ), antimony telluride (III) (Sb ₂ Te ₃ ), bismuth sulfide (III) (Bi ₂ S ₃ ), bismuth selenide (III) (Bi ₂ Se ₃ ), bismuth telluride (III ) (Bi ₂ Te ₃ ) and the like, compounds of periodic table group 15 elements and periodic table group 16 elements, copper oxide (I) (Cu ₂ O), copper selenide (Cu ₂ Se), etc. Compounds of Group 11 elements and Group 16 elements of the periodic table, copper (I) (CuCl), copper (I) (CuBr), copper (I) (CuI), silver chloride (AgCl) ), Silver bromide (AgBr) and the like, compounds of Group 11 elements of the periodic table and elements of Group 17 of the periodic table, nickel oxide (II Compound of periodic table group 10 element and periodic table group 16 element such as (NiO), periodic table group 9 element such as cobalt oxide (II) (CoO), cobalt sulfide (II) (CoS) and periodic table Compounds with Group 16 elements, compounds of Group 8 elements of the periodic table such as triiron tetroxide (Fe ₃ O ₄ ) and iron (II) sulfide (FeS), and Group 16 elements of the periodic table, manganese oxide (II ) (MnO) periodic table group 7 elements and periodic table group 16 elements, molybdenum sulfide (IV) (MoS ₂ ), periodic table group 6 elements such as tungsten oxide (IV) (WO ₂ ) And compounds of Group 16 elements of the periodic table, Group 5 elements of the Periodic Table such as vanadium oxide (II) (VO), vanadium oxide (IV) (VO ₂ ), tantalum oxide (V) (Ta ₂ O ₅ ), etc. the compounds of the periodic table group 16 element, titanium oxide _{(TiO 2, Ti 2 O 5} , Ti 2 O 3, Ti 5 _9, etc.) Group 4 of the periodic table element and the periodic table compounds of Group 16 elements such as magnesium sulfide (MgS), a Group 2 element and Periodic Table Group 16 element such as magnesium selenide (MgSe) , Cadmium oxide (II) chromium (III) (CdCr ₂ O ₄ ), cadmium selenide (II) chromium (III) (CdCr ₂ Se ₄ ), copper sulfide (II) chromium (III) (CuCr ₂ S ₄ ) ), Chalcogen spinels such as mercury (II) selenide (III) (HgCr ₂ Se ₄ ), barium titanate (BaTiO ₃ ), and the like. In addition, G. Schmid et al .; Adv. Mater. 4, 494 (1991) (BN) 75 (BF2) 15F15 and D.C. Fenske et al .; Angew. Chem. Int. Ed. Engl. 29, page 1452 (1990), a semiconductor cluster having a fixed structure such as Cu ₁₄₆ Se ₇₃ (triethylphosphine) ₂₂ reported in the same manner is also exemplified.

In general, dn / dt of a resin has a negative value, that is, has a property that the refractive index becomes smaller as the temperature rises. Therefore, in order to efficiently reduce the absolute value of dn / dt of the resin material, that is, the magnitude of the refractive index change due to the temperature change by dispersing the inorganic fine particles, it is necessary to disperse the fine particles having a large dn / dt. preferable. When using inorganic fine particles having the same sign value as the dn / dt of the resin, the absolute value of the dn / dt of the inorganic fine particles is preferably smaller than the dn / dt of the resin serving as the base material. Furthermore, fine particles having a dn / dt of the opposite sign to the dn / dt of the resin as the base material, that is, fine particles having a positive value of dn / dt are preferably used. By dispersing such fine particles in the resin, the size (absolute value) of the dn / dt of the resin material can be effectively reduced with a small amount. The dn / dt of the fine particles to be dispersed can be appropriately selected depending on the value of the dn / dt of the resin as a base material. However, when the fine particles are dispersed in a resin generally preferably used for an optical element, dn / dt is preferably larger than −20 × 10 ^{−6, and} more preferably larger than −10 × 10 ⁻⁶ .

  Examples of the fine particles having a large dn / dt include gallium nitride, zinc sulfide, zinc oxide, lithium niobate, and lithium tantalate.

On the other hand, the first material and the second material that are unevenly distributed in the optical element of the present embodiment have the same refractive index at the reference temperature. Therefore, when fine particles are dispersed in the resin, it is necessary to appropriately select and disperse the fine particles so that the first material and the second material have the same refractive index at the reference temperature. For example, the same resin is used as the base material of the first material and the second material (materials having the same refractive index are used), and fine particles are dispersed in one of them to change the refractive index change dn ₁ / When dt ₁ and dn ₂ / dt ₂ are made different, fine particles having a refractive index equal to that of the resin serving as a base material can be dispersed. In addition, when different resins are used as the base materials for the first material and the second material (different refractive indexes), the fine particles are dispersed so that the refractive indexes of the first material and the second material are equal. It is necessary to appropriately adjust the type and amount of addition.

  When dispersing the fine particles, it is desirable that the difference in refractive index between the resin as the base material and the fine particles is small. As a result of investigations by the inventors, it was found that if the difference in refractive index between the resin and the dispersed fine particles is small, scattering is difficult to occur when light is transmitted. When the fine particles are dispersed in the resin, the larger the particles, the easier it is to cause scattering when light is transmitted. However, if the difference in refractive index between the resin and the fine particles to be dispersed is small, relatively large fine particles can be used. It was discovered that the degree of light scattering is small. The difference in refractive index between the resin and the dispersed fine particles is preferably in the range of 0 to 0.3, and more preferably in the range of 0 to 0.15.

  The refractive index of a resin preferably used as a material for an optical element is often about 1.4 to 1.6, and examples of the material dispersed in these thermoplastic resins include silica (silicon oxide) and calcium carbonate. Aluminum phosphate, aluminum oxide, magnesium oxide, aluminum / magnesium oxide and the like are preferably used.

  Further, the inventors' research has revealed that the absolute value of dn / dt of the resin material can be effectively reduced by dispersing fine particles having a relatively low refractive index. Although the details of the reason why the absolute value of dn / dt of the resin material in which fine particles having a low refractive index are dispersed are small are not known, the temperature change of the volume fraction of inorganic fine particles in the resin composition indicates that the refractive index of the fine particles It is considered that the lower the value, the smaller the absolute value of dn / dt of the resin composition works. As fine particles having a relatively low refractive index, for example, silica (silicon oxide), calcium carbonate, and aluminum phosphate are preferably used.

  The fine particles to be dispersed in the resin are dn / dt of the fine particles themselves, the difference between the dn / dt of the fine particles and the dn / dt of the base resin, and the refractive index of the fine particles depending on the characteristics required for the resin material. It can be appropriately selected in consideration of the above. In addition, it is preferable to appropriately select and use fine particles which are compatible with the thermoplastic resin as a base material, that is, dispersibility with respect to the thermoplastic resin and hardly cause scattering, and are used.

  For example, when a cyclic olefin polymer that is preferably used in an optical element is used as a base material, silica is preferably used as the fine particles that reduce dn / dt while maintaining light transmittance.

  As the fine particles, one kind of inorganic fine particles may be used, or a plurality of kinds of inorganic fine particles may be used in combination. By using a plurality of types of fine particles having different properties, the required characteristics can be improved more efficiently.

  Further, the inorganic fine particles mixed with the material of the optical element according to the present embodiment preferably have an average particle diameter of 1 nm or more and 30 nm or less, more preferably 1 nm or more and 20 nm or less, and further preferably 1 nm or more and 10 nm or less. is there. When the average particle diameter is less than 1 nm, it is difficult to disperse the inorganic fine particles and the desired performance may not be obtained. Therefore, the average particle diameter is preferably 1 nm or more, and the average particle diameter exceeds 30 nm. In addition, the resulting thermoplastic material composition may become turbid, resulting in a decrease in transparency and a light transmittance of less than 70%. Therefore, the average particle diameter is preferably 30 nm or less. The average particle diameter here refers to the volume average value of the diameter (sphere converted particle diameter) when each particle is converted into a sphere having the same volume.

  Further, the shape of the inorganic fine particles is not particularly limited, but spherical fine particles are preferably used. Specifically, the minimum diameter of the particle (minimum value of the distance between the tangents when drawing two tangents in contact with the outer periphery of the fine particle) / maximum diameter (the value in drawing two tangents in contact with the outer periphery of the fine particle The maximum value of the distance between tangents) is preferably 0.5 to 1.0, and more preferably 0.7 to 1.0.

  Further, the particle size distribution is not particularly limited, but in order to achieve the effect of the present invention more efficiently, a particle having a relatively narrow distribution is preferably used rather than a particle having a wide distribution. Used.

(Resin used as base material)
Next, a resin serving as a base material of a resin material used for the optical element according to the present embodiment will be described.

  As a resin that is a base material of the resin material used in the optical element according to the present embodiment, a thermoplastic resin, a thermosetting resin, a photocurable resin, or the like that is generally used as an optical material can be used without limitation. it can.

  In consideration of processability as an optical element, the thermoplastic resin is preferably an acrylic resin, a cyclic olefin resin, a polycarbonate resin, a polyester resin, a polyether resin, a polyamide resin, or a polyimide resin. The compounds described in -73559 can be mentioned, and preferred compounds are shown in Table 1.

  The thermoplastic resin used in the optical element according to the present embodiment is an olefin-based resin having a cyclic structure obtained by hydrogenating a copolymer of an α-olefin having 2 to 20 carbon atoms and a cyclic olefin. JP-A-7-145213, paragraphs [0032] to [0054], which are polymers, and alicyclic hydrocarbon copolymers comprising repeating units having an alicyclic structure It is preferable that Examples of the cyclic olefin resin preferably used include, but are not limited to, ZEONEX (Nippon Zeon), APEL (Mitsui Chemicals), Arton (JSR), and TOPAS (Chicona).

  An example of the thermosetting resin is a thermosetting polyorganosiloxane resin. The thermosetting polyorganosiloxane resin is not particularly limited as long as it becomes a three-dimensional network structure with a siloxane bond skeleton by a continuous hydrolysis-dehydration condensation reaction by heating. It exhibits curability and has the property of being hard to be re-softened by overheating once cured.

  Such a polyorganosiloxane resin includes the following general formula as a structural unit, and the shape thereof may be any of a chain, a ring, and a network.

((R ¹ ) (R ² ) SiO) _n
Here, R ¹ and R ² represent the same or different substituted or unsubstituted monovalent hydrocarbon groups, and examples of R ¹ and R ² include alkyl groups such as a methyl group, an ethyl group, a propyl group, and a butyl group, Alkyl groups such as vinyl and allyl groups, aryl groups such as phenyl and tolyl groups, cycloalkyl groups such as cyclohexyl and cyclooctyl groups, or hydrogen atoms bonded to carbon atoms of these groups are halogen atoms, cyano groups A group substituted with an amino group, such as a chloromethyl group, a 3,3,3-trifluoropropyl group, a cyanomethyl group, a γ-aminopropyl group, an N- (β-aminoethyl) -γ-aminopropyl group, etc. Illustrated. R ¹ and R ² may be a group selected from a hydroxyl group and an alkoxy group. N represents an integer of 50 or more.

  The polyorganosiloxane resin is usually used after being dissolved in a hydrocarbon solvent such as toluene, xylene or petroleum solvent, or a mixture of these with a polar solvent. Moreover, you may mix | blend and use what differs in a composition in the range which mutually melt | dissolves.

  The method for producing the polyorganosiloxane resin is not particularly limited, and any known method can be used. For example, it can be obtained by hydrolysis or alcoholysis of one or a mixture of two or more organohalogenosilanes. Polyorganosiloxane resins generally contain hydrolyzable groups such as silanol groups or alkoxy groups. A group is contained in an amount of 1 to 10% by mass in terms of a silanol group.

  These reactions are generally performed in the presence of a solvent capable of melting the organohalogenosilane. It can also be obtained by a method of synthesizing a block copolymer by cohydrolyzing a linear polyorganosiloxane having a hydroxyl group, an alkoxy group or a halogen atom at the molecular chain terminal with an organotrichlorosilane. The polyorganosiloxane resin thus obtained generally contains the remaining HCl, but since it has good storage stability, it should be 10 ppm or less, preferably 1 ppm or less.

(Other ingredients)
Various additives (also referred to as compounding agents) can be added as necessary during the preparation of the resin and in the molding process of the resin material. There are no particular restrictions on the additives, but stabilizers such as antioxidants, heat stabilizers, light stabilizers, weather stabilizers, UV absorbers and near infrared absorbers; resin modifiers such as lubricants and plasticizers An anti-clouding agent such as a soft polymer or an alcohol compound; a colorant such as a dye or a pigment; an antistatic agent, a flame retardant, or a filler. These compounding agents can be used alone or in combination of two or more, and the compounding amount is appropriately selected within a range not impairing the effects described in the present invention. In the present invention, it is particularly preferable that the polymer contains at least a plasticizer or an antioxidant.

(Plasticizer)
The plasticizer is not particularly limited, however, phosphate ester plasticizer, phthalate ester plasticizer, trimellitic ester plasticizer, pyromellitic acid plasticizer, glycolate plasticizer, citrate ester A plasticizer, a polyester plasticizer, etc. can be mentioned.

  In the phosphate ester plasticizer, for example, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. Trimellitic plasticizers such as diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, butyl benzyl phthalate, diphenyl phthalate, dicyclohexyl phthalate, etc. For pyromellitic acid ester plasticizers such as phenyl trimellitate, triethyl trimellitate, etc. Examples of glycolate plasticizers such as tilpyromelitate, tetraphenylpyromellitate, and tetraethylpyromellitate include triacetin, tributyrin, ethylphthalylethyl glycolate, methylphthalylethyl glycolate, and butylphthalylbutyl glycolate. In the citrate plasticizer, for example, triethyl citrate, tri-n-butyl citrate, acetyl triethyl citrate, acetyl tri-n-butyl citrate, acetyl tri-n- (2-ethylhexyl) citrate, etc. Can be mentioned.

(Antioxidant)
Examples of the antioxidant include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, etc. Among them, phenolic antioxidants, particularly alkyl-substituted phenolic antioxidants are preferable. By blending these antioxidants, it is possible to prevent lens coloring and strength reduction due to oxidative degradation during molding without lowering transparency, heat resistance and the like. These antioxidants can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the object of the present invention, but with respect to 100 parts by mass of the polymer. It is preferably 0.001 to 5 parts by mass, more preferably 0.01 to 1 part by mass.

  A conventionally well-known thing can be used as a phenolic antioxidant, for example, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2 , 4-di-t-amyl-6- (1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl) phenyl acrylate and the like, and JP-A Nos. 63-179953 and 1-168643. Acrylate compounds described in Japanese Patent Publication No. 1; octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 2,2'-methylene-bis (4-methyl-6-tert-butylphenol) ), 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5 Di-t-butyl-4-hydroxybenzyl) benzene, tetrakis (methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenylpropionate)) methane [i.e. pentaerythrmethyl- Tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenylpropionate))], triethylene glycol bis (3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate) Alkyl-substituted phenolic compounds such as 6- (4-hydroxy-3,5-di-t-butylanilino) -2,4-bisoctylthio-1,3,5-triazine, 4-bisoctylthio-1, 3,5-triazine, 2-octylthio-4,6-bis- (3,5-di-t-butyl-4-oxyanilino) -1,3,5-tria Triazine group-containing phenol compounds such emissions; and the like.

  The phosphorus antioxidant is not particularly limited as long as it is usually used in the general resin industry. For example, triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (nonylphenyl) Phosphite, tris (dinonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, 10- (3,5-di-t-butyl-4-hydroxybenzyl) -9,10 Monophosphite compounds such as -dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; 4,4'-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecyl phosphite ), 4,4'-isopropylidene-bis (phenyl-di-alkyl (C12-C15) phosphite) Like diphosphite compounds such as. Among these, monophosphite compounds are preferable, and tris (nonylphenyl) phosphite, tris (dinonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite and the like are particularly preferable.

  Examples of the sulfur-based antioxidant include dilauryl 3,3-thiodipropionate, dimyristyl 3,3′-thiodipropionate, distearyl 3,3-thiodipropionate, lauryl stearyl 3,3-thiodiprote. Pionate, pentaerythritol-tetrakis- (β-lauryl-thio-propionate), 3,9-bis (2-dodecylthioethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane, etc. Can be mentioned.

(Light stabilizer)
Examples of light stabilizers include benzophenone light stabilizers, benzotriazole light stabilizers, and hindered amine light stabilizers. Hindered amine light stabilizers are used from the viewpoint of lens transparency and color resistance. Is preferred. Among hindered amine light-resistant stabilizers (hereinafter also referred to as HALS), those having a polystyrene-equivalent Mn of 1,000 to 10,000 as measured by GPC using tetrahydrofuran (THF) as a solvent are preferable, and 2,000 to What is 5,000 is more preferable, and what is 2,800-3,800 is especially preferable. If Mn is too small, when HALS is blended by heat-melting and kneading into a block copolymer, a predetermined amount cannot be blended due to volatilization, foaming or silver streak occurs during heat-melt molding such as injection molding, etc. Processing stability decreases. Further, when the lens is used for a long time with the lamp turned on, a volatile component is generated as a gas from the lens. Conversely, if Mn is too large, the dispersibility in the block copolymer is lowered, the transparency of the lens is lowered, and the effect of improving light resistance is reduced. Therefore, a lens excellent in processing stability, low gas generation property and transparency can be obtained by setting the MLS of HALS within the above range.

  Specific examples of such HALS include N, N ′, N ″, N ′ ″-tetrakis- [4,6-bis- {butyl- (N-methyl-2,2,6,6-tetramethylpiperidine. -4-yl) amino} -triazin-2-yl] -4,7-diazadecane-1,10-diamine, dibutylamine and 1,3,5-triazine and N, N'-bis (2,2,6 , 6-tetramethyl-4-piperidyl) butylamine, poly [{(1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} { (2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}], 1,6-hexanediamine-N, N'-bis (2,2,6,6-tetramethyl- Polypiperidyl) and morpholine-2,4,6-trichloro-1,3,5-triazine, poly [(6-morpholino-s-triazine-2,4-diyl) (2,2, 6,6, -tetramethyl-4-piperidyl) imino] -hexamethylene [(2,2,6,6-tetramethyl-4-piperidyl) imino] and other piperidine rings are bonded via a triazine skeleton. High molecular weight HALS; polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, 1,2,3,4-butanetetracarboxylic acid and 1,2,2 , 6,6-pentamethyl-4-piperidinol and 3,9-bis (2-hydroxy-1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane Such engagement ester, piperidine ring linked to a high molecular weight HALS, and the like via an ester bond.

  Among these, polycondensates of dibutylamine, 1,3,5-triazine and N, N′-bis (2,2,6,6-tetramethyl-4-piperidyl) butylamine, poly [{(1, 1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2 , 2,6,6-tetramethyl-4-piperidyl) imino}], a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol and the like. 5,000 to 5,000 are preferred.

  The blending amount of the optical element according to the present embodiment with respect to the resin material is preferably 0.01 to 20 parts by mass, more preferably 0.02 to 15 parts by mass, particularly preferably 100 parts by mass of the polymer. 0.05 to 10 parts by mass. If the amount added is too small, the effect of improving light resistance cannot be obtained sufficiently, and coloring occurs when used outdoors for a long time. On the other hand, when the blending amount of HALS is too large, a part of the HALS is generated as a gas, or the dispersibility in the resin is lowered, and the transparency of the lens is lowered.

  Further, by blending the resin material of the optical element according to this embodiment with a compound having the lowest glass transition temperature of 30 ° C. or lower, various properties such as transparency, heat resistance, and mechanical strength are lowered. Without being clouded under high temperature and high humidity environment for a long time.

(Mixing of resin and inorganic fine particles)
When the resin material of the optical element according to the present embodiment is obtained by mixing inorganic fine particles with a resin, the method of mixing the base resin and the inorganic fine particles is not particularly limited. That is, a method in which the resin and the inorganic fine particles are separately produced, and then the two are mixed, a method in which the resin is produced in a condition where the pre-made inorganic fine particles exist, and a condition in which the pre-prepared resin is present. Any method can be employed, such as a production method and a method in which both resin and inorganic fine particles are produced simultaneously. Specifically, for example, by mixing two solutions of a solution in which a resin is dissolved and a dispersion in which inorganic fine particles are uniformly dispersed, and meeting them in a solution having poor solubility in the resin, Although the method of obtaining the material composition to perform can be mentioned suitably, it is not limited to this.

  In the resin material of the optical element according to the present embodiment, the degree of mixing of the resin and inorganic fine particles is not particularly limited, but in order to achieve the effect of the present invention more efficiently, it is necessary to mix uniformly. It is desirable. If the degree of mixing is insufficient, there is a concern that it may affect the optical properties such as refractive index, Abbe number, and light transmittance, and it will also adversely affect resin processability such as thermoplasticity and melt moldability. There is a fear. The degree of mixing is considered to be affected by the production method, and it is important to select a method in consideration of the characteristics of the resin and inorganic fine particles used. In order to mix both the resin and the inorganic fine particles more uniformly, a method of directly bonding the resin and the inorganic fine particles can be suitably used in the present invention.

  The content of the inorganic fine particles in the resin material of the optical element according to the present embodiment is not particularly limited as long as the effect of the present invention can be exhibited, and can be arbitrarily determined depending on the types of the resin and the inorganic fine particles. The content of the inorganic fine particles is preferably such that the volume fraction of the inorganic fine particles relative to the total volume of the resin material to be produced is 20% or more and 60% or less, more preferably 20% or more and 50% or less, 30 % Or more and 50% or less is more preferable. The volume fraction of inorganic fine particles here is expressed by the formula (x / a) / Y × 100 when the specific gravity of the inorganic fine particles is a, the content is x grams, and the total volume of the resin material produced is Y milliliters. Desired. The content of the inorganic fine particles can be determined by observing a semiconductor crystal image with a transmission electron microscope (TEM) (information on the semiconductor crystal composition can also be obtained by local elemental analysis such as EDX), or given resin composition It can be calculated from the contained mass of a predetermined composition obtained by elemental analysis of contained ash and the specific gravity of crystals of the composition.

(Production method of inorganic fine particles, surface modification)
The method for producing inorganic fine particles that can be used for the resin material of the optical element according to the present embodiment is not particularly limited, and any known method can be used. For example, desired oxide fine particles can be obtained by using a metal halide or an alkoxy metal as a raw material and hydrolyzing in a reaction system containing water. At this time, a method of using an organic acid, an organic amine or the like in combination is also used for stabilizing the fine particles. More specifically, for example, in the case of titanium dioxide fine particles, Journal of Chemical Engineering of Japan Vol. 31, No. 1, pages 21-28 (1998), and in the case of zinc sulfide, the Journal of Physical. A known method described in Chemistry Vol. 100, 468-471 (1996) can be used. For example, according to these methods, titanium oxide having an average particle diameter of 5 nm is obtained by adding an appropriate surface modifier when hydrolyzed in an appropriate solvent using titanium tetraisopropoxide or titanium tetrachloride as a raw material. It can be manufactured easily. Zinc sulfide having an average particle diameter of 40 nm can be produced by adding a surface modifier when dimethylzinc or zinc chloride is used as a raw material and sulfurized with hydrogen sulfide or sodium sulfide.

In addition, a chemical flame is formed by a burner in an atmosphere containing oxygen, which is often used for making fine oxide particles, and a metal powder is introduced into the chemical flame in an amount capable of forming a dust cloud and burned to form fine oxide particles. A method for synthesizing 5-100 nm is disclosed. (Japanese Patent Laid-Open No. 60-255602)
In addition to the production of inorganic nanoparticles from the above-described bottom-up process from clusters, a top-down process for producing nanoparticles by pulverizing inorganic fine particles has also been proposed. As a pulverizer specifically used, Ultra Apex Mill (manufactured by Kotobuki Giken); Counter Jet Mill, Micron Jet, Inomizer (manufactured by Hosokawa Micron); IDS type mill, PJM jet pulverizer (manufactured by Nippon Pneumatic Industrial Co., Ltd.); Cross jet mill (manufactured by Kurimoto Iron Works); Urmax (manufactured by Nisso Engineering Co., Ltd.); SK jet o mill (manufactured by Seishin Enterprise Co., Ltd.); A super rotor (manufactured by Nisshin Engineering Co., Ltd.) and the like.

  The method for surface modification is not particularly limited, and any known method can be used. For example, there is a method of modifying the surface of the fine particles by hydrolysis under conditions where water is present. In this method, a catalyst such as an acid or an alkali is preferably used, and it is generally considered that a hydroxyl group on the surface of fine particles and a hydroxyl group generated by hydrolysis of a surface modifier dehydrate to form a bond.

  Examples of the surface treatment method for the inorganic fine particles include surface treatment with a surface modifier such as a coupling agent, polymer graft, and surface treatment with mechanochemical.

  Examples of the surface modifier used for the surface treatment of inorganic fine particles include silane coupling agents, silicone oil, titanate, aluminate and zirconate coupling agents. These are not particularly limited, and can be appropriately selected depending on the type of inorganic fine particles and the thermoplastic resin in which the inorganic fine particles are dispersed. Further, two or more surface treatments may be performed simultaneously or at different times.

  Specifically, for example, as a silane-based surface treatment agent, vinylsilazane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, trimethylalkoxysilane, dimethyldialkoxysilane, methyltrialkoxysilane, hexamethyldisilazane and the like can be mentioned. Trimethylmethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, hexamethyldisilazane and the like are preferably used.

  Silicone oil treatment agents include straight silicone oil such as dimethyl silicone oil, methylphenyl silicone oil, and methylhydrogen silicone oil, amino-modified silicone oil, epoxy-modified silicone oil, carboxyl-modified silicone oil, carbinol-modified silicone oil, and methacryl-modified. Silicone oil, mercapto modified silicone oil, phenol modified silicone oil, one-end reactive modified silicone oil, different functional group modified silicone oil, polyether modified silicone oil, methylstyryl modified silicone oil, alkyl modified silicone oil, higher fatty acid ester modified silicone Oil, hydrophilic specially modified silicone oil, higher alkoxy modified silicone oil, higher fat Acid-containing modified silicone oil, modified silicone oil and fluorine-modified silicone oil can be used.

  These treatment agents may be appropriately diluted with hexane, toluene, methanol, ethanol, acetone water or the like.

  Examples of the surface treatment method using the surface modifier include a wet heating method, a wet filtration method, a dry stirring method, an integral blend method, and a granulation method. In the case of modifying the surface of fine particles of 50 nm or less, the dry stirring method is preferably used from the viewpoint of suppressing particle aggregation, but is not limited thereto.

  These surface modifiers may be used alone or in combination, and the properties of the surface-modified fine particles obtained may vary depending on the surface modifier used, and are used for obtaining a resin composition. Affinity with the thermoplastic resin can also be achieved by selecting a surface modifier. The ratio of the surface modification is not particularly limited, but the ratio of the surface modifier is preferably 10 to 99% by mass and more preferably 30 to 98% by mass with respect to the fine particles after the surface modification. preferable.

  In the above description, the objective lens is described as an example of the optical element. However, the present invention is not limited to this, and the present invention can be applied to an optical element that causes inconvenience when the internal temperature distribution is not uniform. Needless to say.

It is a figure which shows an example of the optical system of the optical pick-up apparatus which concerns on this Embodiment. It is a perspective view which shows typically the optical head part by which the objective lens of the optical pick-up apparatus which concerns on this Embodiment was supported. It is a figure which shows the objective lens which concerns on this Embodiment. It is sectional drawing which shows the other example of the objective lens which concerns on this Embodiment. It is a figure which shows the process of forming the objective lens which is an optical element which concerns on this Embodiment using a thermosetting resin. It is a figure which shows the process of forming the objective lens which is an optical element which concerns on this Embodiment using a thermoplastic resin.

Explanation of symbols

21 Magnet 22 Tracking drive coil 23 Focus drive coil 24 Outer yoke 25 Inner yoke 26 Wire 27 Support member 33 Objective lens support member 39, 45 Objective lens

Claims (13)

A first material made of a resin having a refractive index n ₁ at room temperature and a refractive index change rate dn ₁ / dT with respect to a change in temperature T;
An optical material characterized in that it is formed by unevenly distributing a second material made of a resin having a refractive index n ₂ at normal temperature and a refractive index change rate dn ₂ / dT with respect to a change in temperature T. element. _2. The optical element according to claim ₁ , wherein the refractive index n _{1 of} the first material at normal temperature and the refractive index n 2 of the second material at normal temperature are substantially equal. The optical element according to claim 1, wherein at least one of the first material and the second material is a mixture of inorganic fine particles. The optical element according to claim 1, wherein the first material and the second material are unevenly distributed in a radial direction. The optical element according to claim 1, wherein the first material and the second material are unevenly distributed in the optical axis direction. The optical element according to claim 1, wherein the first material and the second material are thermosetting resins. The optical element according to claim 1, wherein the first material and the second material are thermoplastic resins. The optical element according to any one of claims 1 to 7, wherein an index indicating an uneven distribution direction of the first material and the second material is provided on the flange portion. The optical element according to any one of claims 1 to 8, an actuator for driving the optical element in at least one of an optical axis direction and a direction perpendicular to the optical axis, a light source, and a photodetector, An optical pickup device. The optical pickup device according to claim 9, wherein the actuator is disposed on an outer periphery of the optical element, and the first material and the second material are unevenly distributed in a radial direction of the optical element. The optical pickup device according to claim 9, comprising at least two optical elements according to claim 1. A first material made of a thermosetting resin having a refractive index n ₁ at room temperature and a refractive index change rate dn ₁ / dT with respect to a change in temperature T, and a refractive index n ₂ at room temperature. And a second material made of a thermosetting resin having a refractive index change rate of dn ₂ / dT (dn ₁ / dT> dn ₂ / dT) with respect to a change in temperature T is unevenly distributed in the mold. An optical element manufacturing method for molding,
Installing a mold part corresponding to the position of the second material vertically downward;
A step of causing the first material to flow after flowing the second material into the mold;
And a step of heating the mold. A first material made of a thermoplastic resin having a refractive index n ₁ at room temperature and a refractive index change rate dn ₁ / dT with respect to a change in temperature T, and a refractive index n _{2 at} room temperature. Then, a second material made of a thermoplastic resin having a refractive index change rate of dn ₂ / dT (dn ₁ / dT> dn ₂ / dT) with respect to a change in temperature T is unevenly distributed in the mold. An optical element manufacturing method comprising:
Placing the pre-formed second material in a predetermined position in the mold;
And a step of allowing the melted first material to flow in. An optical element manufacturing method comprising:

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