as) United States
`a2) Patent Application Publication 10) Pub. No.: US 2006/0128869 A1
`
` Taima (43) Pub. Date: Jun. 15, 2006
`
`
`US 20060128869A1
`
`(54) THERMOPLASTIC COMPOSITE MATERIAL
`AND OPTICAL ELEMENT
`
`(30)
`
`Foreign Application Priority Data
`
`(75)
`
`Inventor: Yasuo Taima, Tokyo (JP)
`
`Correspondence Address:
`FINNEGAN, HENDERSON, FARABOW,
`GARRETT & DUNNER
`LLP
`901 NEW YORK AVENUE, NW
`WASHINGTON, DC 20001-4413 (US)
`
`Dec. 10, 2004
`
`(IP) vn eeeccececsssscneseneessenee JP2004-358369
`oo.
`,
`,
`Publication Classification
`
`51)
`(1)
`
`Int. Cl
`Cl.
`Int.
`(2006.01)
`CO8K 3/34
`(2006.01)
`CO8K 3/00
`52) US. CD.
`ceeccescsescsccseceseeseecseesuesonssaessnerseensenes 524/493
`62)
`(57)
`
`ABSTRACT
`
`(73) Assignee: KONICA MINOLTA OPTO,INC.
`
`(21) Appl. No.:
`
`11/295,488
`
`(22)
`
`Filed:
`
`Dec. 7, 2005
`
`A thermoplastic composite material comprising: (i) a ther-
`moplastic resin comprising an organic polymer; and (11)
`particles having an average diameter of 1-30 nm dispersed
`in the thermoplastic resin, wherein the particles contain two
`or more kinds of inorganic particles having differentrefrac-
`tive indexes.
`
`APPLE 1020
`
`APPLE 1020
`
`1
`
`

`

`Patent Application Publication Jun. 15, 2006
`
`US 2006/0128869 Al
`
`FIG. 1
`
`2
`
`

`

`US 2006/0128869 Al
`
`Jun. 15, 2006
`
`THERMOPLASTIC COMPOSITE MATERIAL AND
`OPTICAL ELEMENT
`
`[0001] This application is based on Japanese Patent Appli-
`cation No. 2004-358369 filed on Dec. 10, 2004 in Japanese
`Patent Office, the entire content of which is hereby incor-
`porated by reference.
`
`FIELD OF THE INVENTION
`
`[0002] The present invention relates to a thermoplastic
`composite material which has small thermal variation ratio
`in the refractive index and is suitably applied for a lens,
`filter, grating, optical fiber and planar light conducting path,
`and an optical element using the material.
`
`BACKGROUND OF THE INVENTION
`
`[0003] An optical pickup is installed in information appa-
`ratus such as a player, a recorder and a drive for leading out
`or recording information from or to an optical information
`recording medium, referred also to as simply a medium,
`such as an MO, CD and DVD. Theoptical pickup apparatus
`has an optical element such as a lens for irradiating light
`generated from a light source having a prescribed wave-
`length to the medium,andfor receiving the reflected light by
`a light receiving element unit, and a lens for condensing the
`light on the reflective surface of the medium orthe light
`receiving element.
`
`[0004] A plastic is preferably applied for the material of
`the optical element of the optical pickup apparatus because
`the optical element can be produced with low cost by a
`meanssuch as an injection molding. A copolymerof a cyclic
`olefin and an a-olefin is known as the plastic capable for
`applying the optical element (for example, refer to Patent
`Document1).
`
`In an information apparatus capable of leading and
`[0005]
`writing information to plural kinds of recording media such
`as a CD/DVDplayer, it is necessary that the optical pickup
`has a constitution capable of corresponding to the wave-
`length of the light to be applied to each of the media and the
`shape thereof. In such the case,
`the optical element
`is
`preferably one commonly applicable to both of the media
`from the viewpoint of cost and picking up property.
`
`In the optical element unit using plastic as a
`[0006]
`material, it is desirable that the plastic is a material having
`optical stability similar to that of a glass lens. The optical
`plastic material such as the cyclic olefin, for example, has
`sufficiently improved stability in the refractive index with
`respect to humidity, but the improvementin the stability of
`the refractive index is not fully sufficient in the present stage.
`
`[0007] Various methods have been proposed for compen-
`sating the refractive index of such the plastic lens by using
`a particlefiller.
`
`[0008] The particle filler is employed for compensating
`the refractive index of the optical plastic. The plastic can
`hold sufficient transparency for the lens without light scat-
`tering caused by the filler by the use of the filler of
`sufficiently small particle size. Technology for enhancing the
`refractive index of the plastic by the addition ofthe particles
`is described in Non-patent Documents 1 and 2, for example.
`
`materials are lighter in the weight and lowerin the cost when
`compared with glass. However, the plastic is inferior to the
`glass in the stability in the refractive index against changes
`in temperature and humidity. Therefore,
`improvement is
`desired in this point of view for the plastic materials.
`
`[0010] The refractive index of an organic polymer
`decreases with increasing temperature almost without
`exception (temperature dependencyofthe refractive index:
`dn/dT<0). As described below,
`for example, dn/dT of
`organic polymer materials (thermoplastic resins)
`to be
`applied for the optical use is generally almost -10-*/K.
`
`[0011] A method for reducing the absolute value of dn/dT
`has been proposed, in which a substance having a dn/dT of
`more than 0 is mixed in the thermoplastic resin host material
`which has a dn/dT of less than 0. Among inorganic sub-
`stances, known are the ones showing a dn/dT of more than
`0, which is a result of the variation in the intramolecular
`coordination with varing temperature. It has been expected
`that the absolute value of dn/dT is reduced by mixing an
`organic polymerthermoplastic resin of which a dn/dTis less
`than 0 with inorganic particles having a dn/dT of more than
`0. Accordingly, an optical product reduced in thermal sen-
`sitivity of an optical property, containing a thermal sensitive
`thermoplastic polymerresin and particles dispersed therein
`has been proposed in Patent Documents 2 through 8, for
`example.
`
`[0012] Various proposals have been submitted regarding
`the composite materials each containing inorganic particles.
`Composite materials containing particles of a semi-conduc-
`tive substance and a resin composition in which semi-
`conductive particles are bonded with the polymer chain by
`a covalent bondare disclosed, for example, in Patent Docu-
`ment 9, and a resin composition containing zinc sulfide
`particles is disclosed, for example, in Patent Document 10.
`
`[0013] Patent Document 6, for example, describes that the
`mixing of 40% by weight or more of aluminum oxide or
`magnesium oxide is necessary to reduce by 50% of the
`dn/dT of the thermoplastic resin.
`
`[0014] However, when a composite material contains inor-
`ganic particles having high refractive index in such the high
`ratio, the following problems may occur, for example, (i)
`transparency of the composite material largely decreases;
`and (ii) the property of the composite material varies during
`prolonged storage due to coagulation of the inorganic par-
`ticles dispersed in the resin. Accordingly, composite mate-
`rials suitable for practical use as an optical element have
`hardly been obtained.
`
`In the methods disclosed in Patent Documents 9
`[0015]
`and 10, particles having high refractive index, namely
`semi-conductive particles are added to increase the refrac-
`tive index of the resin composition. However, a sufficiently
`high transparency as an optical element cannot be obtained
`in the resin composition obtained by such a method. These
`Patent Documents do not describe the use of two or more
`kinds of particles having different refractive indexes such as
`that described in the present invention, and no composite
`material having high transparency and small temperature
`dependencyin the refractive index as obtained in the present
`invention has been known until now.
`
`transparent plastic materials have been
`[0009] The
`employedfor various uses in the optical systems since those
`
`[0016] Non-patent Document1: C. Becker, P. Mueller and
`H. Schmidt, “Optical and thermomechanical investigations
`
`3
`
`3
`
`

`

`US 2006/0128869 Al
`
`Jun. 15, 2006
`
`on thermoplastic nanocomposites with surface-modified
`silica nanoparticles”, SPIE Proceedings, July 1998, vol.
`3469, p.p. 88-98
`
`[0017] Non-patent Document2: B. Braune, P. Mueller and
`H. Schmidt, “Tantalum oxide nanomers for optical applica-
`tions”, SPIE Proceedings, July 1998, vol. 3469, p.p. 124-132
`
`[0018] Patent Document 1: Japanese Patent Publication
`Open to Public Inspection (hereafter referred to as JP-A) No.
`2002-105131, (p. 4)
`
`[0019] Patent Document 2:
`(Claims)
`
`[0020] Patent Document 3:
`(Claims)
`
`[0021] Patent Document 4:
`(Claims)
`
`[0022] Patent Document
`(Claims)
`
`[0023] Patent Document
`(Claims)
`
`5:
`
`6:
`
`[0024] Patent Document 7:
`(Claims)
`
`[0025] Patent Document
`(Claims)
`
`[0026] Patent Document
`(Claims)
`
`8:
`
`9:
`
`[0027] Patent Document
`(Claims)
`
`10:
`
`JP-A No. 2003-73563,
`
`SUMMARYOF THE INVENTION
`
`[0028] An object of the present invention is to provide a
`thermoplastic composite material having considerably small
`thermal variation in the refractive index and an optical
`element employing the composite material.
`
`[0029] One of the aspects of the present inventionto attain
`the above object
`is a thermoplastic composite material
`containing: (i) a thermoplastic resin containing an organic
`polymer; and (ii) particles having an average diameter of
`1-30 nm dispersed in the thermoplastic resin, wherein the
`particles contain two or more kinds of inorganic particles
`having different refractive indexes.
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`[0030] FIG. 1 shows a schematic drawing of constitution
`of optical pickup apparatus 1.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`[0031] The above object of the present
`achieved by the following structures.
`
`invention is
`
`[0032]
`
`(1) Athermoplastic composite material containing:
`
`(i) a thermoplastic resin containing an organic
`[0033]
`polymer; and
`
`(i) the particles contain two or more kinds of
`[0049]
`inorganic particles having different refractive indexes; and
`
`(ii) particles having an average diameter of 1-30
`[0034]
`nm dispersed in the thermoplastic resin,
`
`(ii) nh and np1 satisfy Formula (A), provided that
`[0050]
`nh represents a refractive index of the thermoplastic organic
`
`
`
`JP-A No. 2002-207101,
`
`JP-A No. 2003-240901,
`
`JP-A No. 2002-241560,
`
`JP-A No. 2002-241569,
`
`JP-A No. 2002-241592,
`
`JP-A No. 2002-241612,
`
`JP-A No. 2002-303701,
`
`JP-A No. 2002-105325,
`
`
`
`wherein the particles contain two or more kinds of inorganic
`particles having different refractive indexes.
`
`(2) The thermoplastic composite material of Item
`[0035]
`(1), wherein
`
`nh and np! satisfy Formula (A), provided that nh
`[0036]
`represents a refractive index of the thermoplastic resin and
`np1 represents a smallest refractive index amongrefractive
`indexes of the two or more kinds of inorganic particles.
`nh-0.1 Snp1 Snht+0.1
`Formula (A)
`
`(3) The thermoplastic composite material of Item
`[0037]
`(2), wherein
`
`np1 and np2 satisfy Formula (B), provided that np2
`[0038]
`represents one of the refractive indexes of the two more
`kinds of inorganic particles other than np1.
`0.1 Snp2-np151.0
`
`Formula (B)
`
`(4) The thermoplastic composite material of Item
`[0039]
`(3), wherein
`
`a weight content of inorganic particles having the
`[0040]
`refractive index of np1 is not less than a content of inorganic
`particles having the refractive index of np2.
`
`(5) The thermoplastic composite material of Item
`[0041]
`(3), wherein
`
`a weight content of inorganic particles having the
`[0042]
`refractive index of np1 is not more than a content of
`inorganic particles having the refractive index of np2.
`
`(6) The thermoplastic composite material of any
`[0043]
`one of Items (1) to (5), wherein
`
`a total content of the two or more kinds of inor-
`[0044]
`ganic particlesis in the range of 20-70% by weight based on
`a weight of the thermoplastic resin.
`
`(7) An optical element formed by using the ther-
`[0045]
`moplastic composite material of any one of Items (1) to (6).
`
`[0046] A thermoplastic composite material having consid-
`erably small temperature dependenceofthe refractive index
`can be obtained by the present invention, and further an
`optical element having small temperature dependenceof the
`refractive index and high light transmittance which is not
`degraded during storage for a prolonged period can be
`obtained by employing the thermoplastic composite material
`of the present invention.
`
`[0047] Preferred embodiments of the present invention are
`described below. Though various technical limitations pref-
`erable for carrying out the present invention are described in
`the followings, the present invention is not limited thereto.
`
`[0048] An optical element exhibiting small temperature
`dependence of the refractive index and high transparency
`whichis not degraded during storage for a prolonged period
`can be realized by a thermoplastic composite material con-
`taining a thermoplastic organic polymer resin as a host
`material and particles having an average diameter of 1-30
`nm dispersed in the thermoplastic organic polymer resin,
`wherein
`
`4
`
`

`

`US 2006/0128869 Al
`
`Jun. 15, 2006
`
`polymer resin and np1 represents a refractive index of one
`of the two or more kinds of inorganic particles.
`nh-0.1 Snp1 Snht+0.1
`
`Formula (A)
`
`phosphate, magnesium carbonate, calcium carbonate, stron-
`tium carbonate, zinc sulfate and copper sulfate are also
`preferably employed.
`
`[0051] The above mentioned effects of the present inven-
`tion are further enhanced whenthe thermoplastic composite
`material containing particles having an average diameter of
`1-30 nm dispersed in the thermoplastic organic polymer
`resin satisfy one of the following conditions (1) to (4):
`
`(1) np1 and np2satisfy Formula (B), wherein np1
`[0052]
`and np2 represent refractive indexes of two kinds of inor-
`ganic particles and np2 is larger than np1;
`0.1 Smp2-np1=1.0
`
`Formula (B)
`
`(2) The content of inorganic particles having the
`[0053]
`refractive index of np1 is not
`less than the content of
`inorganic particles having the refractive index of np2;
`
`(3) The content of the inorganic particle having the
`[0054]
`refractive index of np1 is not more than the content of the
`inorganic particle having the refractive index of np2; and
`
`(4) The total content of the two or more kinds of
`[0055]
`inorganic particles is in the range of 20-70% by weight
`based on a weight of the thermoplastic organic polymer
`resin.
`
`[0056] The embodiments of the present invention will now
`be described in detail below.
`
`<<Inorganic Particle>>
`
`[0057] The averagesize of the inorganic particles is pref-
`erably from 1 nm to 30 nm, morepreferably 1 nm to 20 nm,
`and further preferably from 1 nm to 10 nm. When the
`average diameter is less than 1 nm,there is the possibility
`that the desired property cannot be obtained because the
`particles are difficultly dispersed. When the average diam-
`eter exceeds 30 nm, there is the possibility that the light
`transparency becomes less than 70% by the lowering in the
`transparency due to the turbid of the thermoplastic material
`composition. The average particle diameter is the value in
`the terms of the diameter of the sphere having the same
`volume.
`
`[0058] Though the shape of the inorganic particle is not
`specifically limited,
`a spherical particle is preferably
`employed. Thedistribution ofthe particles is also not limited
`but ones havingrelatively narrow distribution are preferable
`than ones having relatively wide distribution for enhancing
`the effects of the present invention.
`
`[0059] The dn/dT of the inorganic particle is preferably
`not
`less than 0, more preferably from 0 to 0.01, and
`specifically preferably from 5x10-° to 5x107°.
`
`[0060] As inorganic particles, oxide particles are employ-
`able,
`for example.
`In concrete, examples of the oxide
`include:silicon oxide, titanium oxide, zinc oxide, aluminum
`oxide, zirconium oxide, hafnium oxide, niobium oxide,
`tantalum oxide, magnesium oxide, calcium oxide, strontium
`oxide, barium oxide, yttrium oxide,
`lanthanum oxide,
`cerium oxide, indium oxide, tin oxide, lead oxide, and a
`double oxide composed of these oxides such as lithium
`niobate, potassium niobate and lithium tantalate. Phos-
`phates, carbonates and sulfates formed by the combination
`of these oxides such as aluminum phosphate,
`tantalum
`
`[0061] As inorganic particles, particles of a semi-conduc-
`tor crystal are also preferably utilized. Though the compo-
`sition of the semi-conductor crystal is not specifically lim-
`ited, desirable are those exhibiting no absorption, no light
`emission and no fluorescence within the range of the wave-
`length of light applying to the optical element. Examples of
`the composition include: elements of Group 14 of periodic
`table such as carbon, silicon, germanium andtin; elements
`of Group 15 of periodic table such as phosphorus (black
`phosphorous); elements of Group 16 of periodic table such
`as selenium and tellurium; compounds composed of ele-
`ments of Group 14 of periodic table such as silicon carbide
`SiC; compounds composed of an element of Group 14 and
`that of Group 16 of periodic table such as tin oxide(IV)
`SnO,,
`tin sulfide(II, IV) Sn(dDSn(IV)S,, tin sulfide (IV)
`SnS,, tin(]) selenide SnSe, tin(I]) telluride SnTe, lead(II)
`sulfide PbS,
`lead(II) selenide PbSe and lead(1]) telluride
`PbTe; compounds of an element of Group 13 and that of
`Group 15 of periodic table (or semi-conductor compounds
`of Group III-V) such as boron nitride BN, boron phosphide
`BP, boron arsenide BAs, aluminum nitride AIN, aluminum
`phosphide AIP, aluminum arsenide AlAs, aluminum anti-
`monide AlSb, gallium nitride GaN, gallium phosphide GaP,
`gallium arsenide GaAs, gallium antimonide GaSb, indium
`nitride InN, indium phosphide InP, indium arsenide InAs
`and indium antimonide InSb; compounds of an element of
`Group 13 and that of Group 16 of periodic table such as
`aluminum sulfide Al,S,, aluminum selenide Al,Se,, gallium
`sulfide Ga,S,, gallium selenide Ga,Se,, gallium telluride
`Ga,Te;, indium oxide In,O,, indium sulfide In,S,, indium
`selenide In,Se, and indium telluride In,Te,; compounds of
`an element of Group 13 and that of Group 17 of periodic
`table such as thallium(]) chloride TIC], thallium() bromide
`T1Br andthallium(1) iodide TI; compoundsof an element of
`Group 12 and that of Group 16 of periodic table (or
`semiconductor compounds of Group II to VI) such as 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, mercury selenide HgSe and mercury telluride;
`compounds of an element of Group 15 and that of Group 16
`of periodic table such as arsenic(III)
`sulfide As.S,,
`arsenic(III) selenide As,Se,, arsenic(III) telluride As,Te,,
`antimony(II]) sulfide Sb,S,, antimony selenide Sb,Se,, anti-
`mony(III) telluride Sb,Te,, bismuth(II]) sulfide B1,S,, bis-
`muth(III) selenide Bi,Se, and bismuth(III) telluride Bi,Te,;
`compoundsof an element of Group 11 and that of Group 16
`of periodic table such as copper(I) oxide Cu,O and copper(I)
`selenide Cu,Se; compounds of an element of Group 11 and
`that of Group 17 of periodic table such as copper(I) chloride,
`copper(I) bromide CuBr, copper(I) iodide Cul, silver chlo-
`ride AgCl and silver bromide AgBr; compounds of an
`element of Group 10 and that of Group 16 of periodic table
`such as nickel(IT) oxide NiO; compounds of an element of
`Group 9 and that of Group 16 of periodic table such as
`cobalt(II) oxide CoO and cobalt(II) sulfide CoS; compounds
`of an element of Group 8 and that of Group 16 of periodic
`table such as iron(IJ) diiron(III) oxide Fe,O, and iron(II)
`sulfide FeS; compoundsof an element of Group 7 andthat
`of Group 16. of periodic table such as manganese(I]) oxide;
`compounds of an element of Group 6 and that of Group 16
`
`5
`
`

`

`US 2006/0128869 Al
`
`Jun. 15, 2006
`
`<<Production Method and Surface Modification of Inor-
`ganic Particle>>
`
`[0066] Any known methods can be applied for producing
`the inorganic particles without any limitation. For example,
`desired oxide particles can be produced by hydrolyzing a
`metal halide or a metal alkoxide as a raw material in a
`
`of periodic table such as molybdenum(IV)sulfide MoS, and
`tungsten(IV) oxide. WO,; compounds of an element of
`Group 5 and that of Group 16 of periodic table such as
`vanadium(II) oxide VO, vanadium(IV) oxide VO, andtan-
`talum(V) oxide Ta,O,; compounds of an element of Group
`4 and that of Group 16 of periodic table such as titanium
`oxide TiO, Ti,0;, Ti,0;, and Ti;0,; compounds of an
`reaction system containing water. On such the occasion, an
`element of Group 2 and that of Group 16 of periodic table
`organic acid or an organic amine may be employed for
`such as magnesium sulfide MgS and magnesium selenide
`stabilizing the inorganic particles. In concrete, the known
`MgSe; charcogen spinel such as cadmium(I]) chromium(III)
`method described in “Journal of Chemical Engineering of
`
`oxide CdCr,O,, chromium(III)\selenidecadmium(II])
`
`Japan” vol. 31, No. 1, PP. 21-28, 1998, can be applied for
`
`CdCr,Se, chromium(III)_selenideand mercury(I)
`
`titanium dioxide particles and that described in “Journal of
`HgCr,Se,; and barium titanate BaTiO,. Furthermore, a
`Physical Chemistry” vol. 100, P.P. 468-471, 1996 can be
`applied for zinc sulfide. According to the methods, for
`semi-conductor cluster having a confirmed structure such as
`example, titanium oxide particles having an average diam-
`(BN),;(BF,),5F,; described in G. Schmid et al., Adv.
`eter of 5 nm canbe easily produced by hydrolyzing titanium
`Mater.,
`vol
`4,
`p.
`494,
`1991
`and
`tetraisopropoxide or titanium tetrachloride as the raw mate-
`Cu,Se,,(triethylphosphine),, described in D. Fenskeetal.,
`rial in a suitable solvent in the presence of a suitable surface
`CHEM.
`Int. Ed. Engl., vol. 29, P. 1452, 1990 is also
`modifier agent. Zinc sulfide having an average particles
`exemplified.
`diameter of 40 nm can be produced by sulfurization of
`dimethyl zine or zine chloride as the raw material by using
`hydrogen sulfide or sodium sulfide in the presence of the
`surface modifier agent.
`
`[0062] Among them, two or more kinds of the inorganic
`particles having different refractive indexes are employed in
`the present invention. The refractive index is an average
`value of the refractive indexes nd25 measured by using
`d-line of light at 25° C. Regarding the compound showing
`anisotropic refractive index such as calctum carbonate, the
`refractive index is an average of the refractive index values
`of normallight and that of extraodinary light. The refractive
`index nd25 correspondsto the refractive index measured by
`Abbe refractmeter according to ASTM Test Method D542,
`and valued described in various documents can be applied.
`
`inorganic
`[0063] The refractive index np1 of the first
`particles are preferably near that of the thermoplastic resin,
`and preferably employed are inorganic particles having a
`refractive index of which difference with the refractive index
`
`of the thermoplastic resin is not more than 0.1 as shown in
`Formula (A). The refractive index of the inorganic particle
`is preferably from 1.4 to 2.0, and more preferably from 1.45
`to 1.7 even though it may be varied depending on the
`composition of the thermoplastic resin. In concrete, silicon
`dioxide, calcium carbonate, magnesium carbonate, stron-
`tium carbonate and aluminum phosphate are preferably
`employed.
`
`[0064] The refractive index of the second inorganic par-
`ticles are preferably higher than that of the thermoplastic
`resin, and preferable are inorganic particles having a refrac-
`tive index of not
`less than the refractive index of the
`
`thermoplastic resin, but not more than 4.0. The refractive
`index of the second inorganic particle is preferably higher
`than that of the first inorganic particle. The refractive index
`of the second inorganic particle is preferably from 1.6 to 4.0,
`and more preferably from 1.7 to 3.0 even though the
`refractive index may be varied depending on the composi-
`tion of the thermoplastic resin. In concrete, aluminum oxide,
`zinc oxide, zine sulfide, titantum oxide, magnesium oxide,
`niobium oxide andlithium niobate are preferably employed.
`
`[0065] The difference between the refractive index of the
`first inorganic particles and that of the second inorganic
`particles is preferably from 0.1 to 1.0 as shown in Formula
`(B). Three or more kinds of the inorganic particle may be
`employed byselecting from the above-described two kinds
`and another kind of the inorganic particles.
`
`[0067] A method for forming oxide particles having a
`diameter of from 5 to 100 nm is disclosed in JP-A No.
`
`60-255602, in which a metal powder of a suitable amount
`for forming dust cloud is thrown into a chemical flame and
`burned in an oxygen containing atmosphere which is fre-
`quently employed for forming oxide particles.
`
`[0068] Besides the above mentioned methods for forming
`inorganic nanoparticles using clusters which are referred to
`as bottom up processes, a top down process has been
`proposed in which inorganic particles are further pulverized
`to form nonaparticles. Concrete examples of a pulverizer
`include: Ultra-Apex Mill manufactured by Kotobuki Engi-
`neering & Manufacturing Co., Ltd.; Counter Jet Mill,
`Micronjet and Inomizer, each manufactured by Hosokawa
`Micron Corp.; IDS Mill and PJM Jet Crusher manufactured
`by Nippon Pneumatic Mfg. Co., Ltd.; Cross Jet Mill manu-
`factured by Kurimoto Ltd.; Ulmax manufactured by Nisso
`Engineering Co., Ltd.; SK Jet-o-Mill manufactured by
`Seishin Enterprise Co., Ltd.; Kryptron manufactured by
`Kawasaki Heavy Industries, Ltd.; Turbo Mill manufactured
`by Turbo Kogyo Co., Ltd.; and Super Rotor manufactured
`by Nisshin Engineering Inc.
`
`[0069] Any known method can be applied for the surface
`modification without any limitation. For example, a method
`can be applied in which the surface of each particle is
`modified by hydrolysis of the modifier agent in the presence
`of water. In such the method, an acid or an alkali is suitably
`applied as a catalyst.
`It
`is generally considered that a
`hydroxyl group at the surface of the particle and a hydroxyl
`group formed by hydrolysis of the modifier agent are
`combined to form a bond by dehydration.
`
`[0070] The inorganic particles relating to the present
`invention is preferably subjected to the surface treatment.
`
`[0071] Examples of the surface modifier agent to be used
`for the surface treatment include: tetramethoxysilane, tetra-
`ethoxysilane,
`tetraisopropoxysilane,
`tetrephenoxysilane,
`methyltrimethoxysilane, ethyltrimethoxysilane, propyltri-
`methoxysilane, methyltriethoxysilane, methyltriphenoxysi-
`
`6
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`

`US 2006/0128869 Al
`
`Jun. 15, 2006
`
`lane, ethyltriethoxysilane, phenyltrimethoxysilane, 3-meth-
`ylphenyltrimethoxysilane,
`dimethyldimethoxysilae,
`diethyldiethoxysilane, diphenyldimethoxysilane, diphenyl-
`diphenoxysilane, trimethylmethoxysilane, triethylethoxysi-
`lane, triphenylmethoxysilane and triphenylphenoxysilane.
`
`[0072] These compoundsare each different from the oth-
`ers in the properties such as reaction rate, and the compound
`suitable for the condition of surface modification can be
`
`selected to be used. The compounds may be employed
`singly or in combination of two or more kinds thereof. The
`properties of the surface of the surface modified particle is
`varied sometimes depending on the compound employed for
`the surface modification, and the affinity with the thermo-
`plastic resin to be employed for formation of the material
`composition can be increased by the selection of the com-
`pound employed for the surface modification. Though the
`ratio of the surface modification is not specifically limited,
`the ratio of the surface decoration is preferably from 10 to
`99% by weight, and more preferably from 30 to 98% by
`weight.
`
`<<Mixing of Resin and Inorganic Particles>>
`
`[0073] The thermoplastic composite material contains the
`thermoplastic resin as the host material and the inorganic
`particles, and the production method thereof is not specifi-
`cally limited. Examples of the applicable method include a
`method in which the thermoplastic resin and the inorganic
`particles which are each independently prepared are mixed
`thereafter, a method in which the thermoplastic resin is
`produced in the presence of the preliminary prepared inor-
`ganic particles, a method in which the inorganic particles are
`formed in the presence of the preliminary prepared thermo-
`plastic resin, and a method in which the thermoplastic resin
`and the inorganic particles are simultaneously formed. In
`concrete, for example, a methodis suitably applied in which
`a solution of the thermoplastic resin and a uniform disper-
`sion of the inorganic particles are uniformly mixed and the
`resultant mixture is poured into a solvent having low dis-
`solvability to the thermoplastic resin, but the methodis not
`limited to this method.
`
`[0074] Though the degree of mixing of the thermoplastic
`resin and the inorganic particles is not specifically limited in
`the present invention, it is preferable that they are uniformly
`mixed for enhancing the effects of the present invention.
`Whenthe mixing degreeis insufficient, the optical properties
`such as refractive index, Abbe constant and the light trans-
`parency may be degraded and the processing suitability of
`the resin such as thermoplastic ability and the melting
`forming ability is also degraded. It is supposed that the
`mixing degree is influenced by the producing method.
`Therefore, it is important that the method is selected sufii-
`ciently considering the properties of the thermoplastic resin
`and those of the inorganic particle. For further uniformly
`mixing the thermoplastic resin and the inorganic particles, a
`method by directly bonding the thermoplastic resin and the
`inorganic particle can be suitably applied in the present
`invention.
`
`[0075] The content of the inorganic particles is not limited
`as long as the content is within the range in which the effect
`of the present invention can be obtained, and can be option-
`
`ally decided according to the kind of the thermoplastic resin
`and the kind of the inorganic particles. The total content of
`the inorganic particles is preferably from 20% to 70%, more
`preferably from 30% to 60%, and further preferably from
`30% to 50%, based on the weight of the thermoplastic resin.
`The content of the inorganic particles can be determined by
`the observation by a transmission electron microscope
`(TEM) (information regarding the composition of the par-
`ticle can be also obtained by local element analysis by
`EDX), and can be calculated from the containing weight of
`the designated particle component determined by the
`elemental analysis of the ash contained in the resin compo-
`sition and the specific gravity of the crystal of the particle
`component.
`
`Inthe case of the thermoplastic composite material
`[0076]
`containing two or more kinds of the inorganic particles, the
`content of each kind of the inorganic particles also can be
`optionally decided. For example, when the inorganic par-
`ticles having the refractive index np1 near that of the
`thermoplastic resin and the inorganic particles having higher
`refractive index np2 are dispersed in the thermoplastic resin,
`the content of the inorganic particles having the refractive
`index of np1 may be higher or may be lowerthanthat of the
`inorganic particles having the refractive index of np2. The
`contents of the both kinds of the inorganic particles can be
`controlled according to the purpose of the composite mate-
`rial. For obtaining a composite material having a high
`refractive index, the content of the inorganic particles having
`the refractive index of np1 is preferably lower than that of
`the inorganic particles having the refractive index of np2.
`For obtaining a composite material having a high light
`transparency, the content of the inorganic particles having
`the refractive index of np1 is preferably higher than that of
`the inorganic particle having the refractive index of np2.
`
`[0077] High content of inorganic particles having a high
`refractive index is not preferable since the optical properties
`such as the light transparency are degraded due to scattering
`of light. Consequently, the content of the inorganic particles
`having a refractive index higher by 0.5 or more than that of
`the thermoplastic resin is preferably from 1
`to 40%, and
`more preferably from 5 to 30%, based on the weight of the
`thermoplastic resin.
`
`<<Thermoplastic Resin Containing Organic Polymer>>
`
`[0078] The thermoplastic resin containing an organic
`polymer according to the present invention is described
`below.
`
`[0079] Though transparent thermoplastic composite mate-
`rials are usually employed for optical material can be
`employed as the organic polymer host material without any
`limitation, an acryl resin, a cyclic olefin resin, a polycar-
`bonate resin, a polyester resin, a polyether resin, a polya-
`mide resin and a polyimideresin are preferable considering
`the processing suitability of the resin as the optical element.
`The compounds described in JP-A No. 2003-73559 can be
`exemplified. Preferable compoundsare listed in Table 1.
`
`7
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`

`US