JP2007140195A - Resin composition for optical element, optical element, beam condensing apparatus and optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition for an optical element enhancing optical stability and capable of maintaining the optical characteristics for a long time, to provide the optical element, to provide a beam condensing apparatus and to provide an optical pickup device. <P>SOLUTION: The resin composition for the optical element contains an alicyclic hydrocarbon based polymer. The alicyclic hydrocarbon based polymer is obtained by performing addition polymerization of a polymerizable solution containing at least an alicyclic olefinic monomer and having ≤100 ppm oxygen concentration under an atmosphere of an inert gas or an addition polymerizable monomer gas. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resin composition for optical elements, an optical element, a condensing device, and an optical pickup device.

  2. Description of the Related Art Conventionally, recording devices such as a player, a recorder, and a drive that read and record information on an optical information recording medium (hereinafter abbreviated as a medium) such as MO, CD, and DVD are provided with an optical pickup device. The optical pickup device includes an optical element unit that irradiates a medium with light having a predetermined wavelength emitted from a light source, and receives the reflected light with a light receiving element. The optical element unit receives the light from a reflection layer or a light receiving medium of the medium. An optical element such as a lens for condensing light by the element is included.

The optical element of the optical pickup device is preferably made of plastic as a material in that it can be manufactured at low cost by means such as injection molding. As plastics to which optical elements can be applied, cyclic olefins and optical element resin compositions-olefin copolymers (for example, Patent Document 1) are known.
By the way, in the case of an information device capable of reading and writing information on a plurality of types of media such as a CD / DVD player, for example, the optical pickup device responds to differences in the shape of both media and the wavelength of light to be applied. It is necessary to make it the structure. In this case, it is preferable from the viewpoint of cost and pickup characteristics that the optical element unit is common to any medium.

In recent years, as a medium capable of recording information at a higher density than CD and DVD, Blu-ray which records and reproduces information at a shorter wavelength than that used in CD (λ = 780 nm) and DVD (λ = 635, 650 nm). Development of a medium such as a ray disk and an information device that reads and writes information on these mediums are newly performed.
JP 2002-105131 A

  However, since so-called next-generation DVDs such as Blu-ray Disks use light with a short wavelength of around 400 nm for recording and reproducing information, the optical element described in Patent Document 1 is irradiated with the light. In this case, optical characteristics (light stability) such as white turbidity of the optical element itself, fluctuation of the refractive index, and deformation of the optical surface are lowered, and the optical element may need to be replaced.

  Therefore, the present invention provides a resin composition for an optical element, an optical element, a condensing device, and an optical pickup device that can improve the light stability and maintain the characteristics for a long time. Objective.

In order to solve the above problems, the resin composition for an optical element of the invention according to claim 1 is:
An alicyclic hydrocarbon-based polymer, wherein the alicyclic hydrocarbon-based polymer contains at least an alicyclic olefin-based monomer, and an inert gas atmosphere using a polymerizable solution having an oxygen concentration of 100 ppm or less. Or obtained by addition polymerization in an addition polymerizable monomer gas atmosphere.

The resin composition for an optical element of the invention according to claim 2 is:
A resin composition for an optical element containing an alicyclic hydrocarbon-based polymer,
The alicyclic hydrocarbon-based polymer contains at least an aromatic vinyl monomer and is subjected to addition polymerization in an inert gas atmosphere or an addition-polymerizable monomer gas atmosphere using a polymerizable solution having an oxygen concentration of 100 ppm or less. After that, it is obtained by further adding hydrogen.

Invention of Claim 3 in the resin composition for optical elements of Claim 1 or Claim 2,
It contains at least one selected from hindered amine stabilizers, phenol stabilizers, phosphorus stabilizers, and sulfur stabilizers, or two or more stabilizers.

Invention of Claim 4 in the resin composition for optical elements as described in any one of Claims 1-3,
A melt index (MI) value measured under conditions of a temperature of 260 ° C. and a load of 2.16 kg is in a range of 20 <MI (g / 10 minutes) <60.

Invention of Claim 5 is an optical element obtained by shape | molding the resin composition for optical elements as described in any one of Claims 1-4,
The light transmittance at a wavelength of 400 nm is 85% or more at a thickness of 3 mm.

The invention according to claim 6 is the optical element according to claim 5,
A predetermined optical path difference providing structure is provided on at least one optical surface.

The invention according to claim 7 is a light collecting device having a light collecting function,
It has the optical element of Claim 5 or Claim 6, It is characterized by the above-mentioned.

The invention according to claim 8 is an optical pickup device for reproducing and / or recording information on an optical information recording medium,
A light source that emits light;
An optical element unit that irradiates the optical information recording medium with the light emitted from the light source and / or collects the light reflected by the optical information recording medium,
The optical element unit includes the optical element according to claim 5 or 6.

The invention according to claim 9 is the optical pickup device according to claim 8,
The light source emits light having a wavelength of 390 nm to 420 nm.

  The resin composition for an optical element according to the first and second aspects of the present invention undergoes addition polymerization in an inert gas atmosphere or an addition polymerizable monomer gas atmosphere using a monomer solution having an oxygen concentration of 100 ppm or less. It is characterized by containing an alicyclic hydrocarbon-based polymer obtained in this way, and has a high stabilizing effect against light irradiation. For example, even when continuously irradiated with light having a short wavelength of around 400 nm, white turbidity or refractive index And the deformation of the optical surface can be suppressed. That is, the light stability of the resin composition for optical elements can be improved, and the characteristics can be maintained for a long time. The cause of light stabilization of the resin composition for optical elements is not yet clear, but by regulating the oxygen concentration during polymerization, radical by-products that trigger the resin degradation reaction and oxidation degradation products It is conceivable that the production amount of can be controlled.

  According to the invention of claim 3, by appropriately selecting from hindered amine stabilizers, phenol stabilizers, phosphorus stabilizers, and sulfur stabilizers, and adding them to the resin composition for optical elements, The fluctuation | variation of the optical characteristic of the resin composition for optical elements can be suppressed more effectively.

  According to invention of Claim 4, the melt index (MI) value of the resin composition for optical elements measured on condition of temperature 260 degreeC and load 2.16kg is 20 <MI (g / 10min) < When the optical element is molded using the melted resin composition, the resin composition has appropriate fluidity and is in a state suitable for a molding method such as injection molding. Is possible.

According to the fifth aspect of the present invention, an optical element molded to a thickness of 3 mm using the resin composition for an optical element has high shape stability and transmits light having a high energy wavelength of around 400 nm. However, it is possible to suppress the occurrence of white turbidity, refractive index fluctuation, deformation, and the like in the element. Thereby, the light transmittance of the element in the vicinity of a wavelength of 400 nm can be 85% or more.
Accordingly, the optical element can be suitably used for an optical information recording medium having a high information density such as a Blu-ray Disc.

According to the invention described in claim 6, the optical element is provided with a predetermined optical path difference providing structure on at least one optical surface. For example, when the optical element is molded by injection molding or the like, the optical element is melted. The resin composition for optical elements can reach the tip of the portion corresponding to the optical path difference providing structure, and the optical path difference providing structure formed with high accuracy can be provided.
Furthermore, in an optical element, the deformation | transformation which arises in an optical path difference providing structure can be suppressed by the high shape stability which the resin composition for optical elements has.

  According to the seventh aspect of the present invention, even if an optical element is used in a condensing device having a condensing function, the optical element has high shape stability, so that the optical characteristics of the optical element are deteriorated. Such a thing disappears. In other words, even when high energy is applied to the optical element by focusing, the high shape stability of the optical element makes it possible to suppress deformation of the optical element over a long period of time. It is possible to prevent deterioration of characteristics.

According to the invention described in claim 8, the addition is performed in an inert gas atmosphere or an addition polymerizable monomer gas atmosphere using a polymerizable solution containing at least an alicyclic olefin monomer and having an oxygen concentration of 100 ppm or less. An alicyclic hydrocarbon polymer obtained by polymerization, or a polymerizable solution containing at least an aromatic vinyl monomer and having an oxygen concentration of 100 ppm or less, in an inert gas atmosphere, or an addition polymerizable monomer gas atmosphere Since it is an optical element produced using a resin composition for an optical element containing an alicyclic hydrocarbon-based polymer obtained by further hydrogenation after addition polymerization, the effect of stabilizing against light irradiation is high. For example, even when irradiation with light having a short wavelength of around 400 nm is continuously performed, white turbidity and refractive index fluctuations can be suppressed, and deformation of the optical surface can be suppressed. That is, the light stability of the optical element can be improved, and the characteristics can be maintained for a long time.
Therefore, for example, an optical information recording medium having a high information density such as a Blu-ray Disc can be read and written with good pickup characteristics over a long period of time, and an optical pickup device with high reliability can be obtained. Obtainable.

  According to invention of Claim 9, the wavelength of the light radiate | emitted from a light source is 390 nm-420 nm. That is, even when transmitting light in the range of 390 to 420 nm corresponding to an optical information recording medium having a high information density such as a Blu-ray Disc, the optical element applied to the optical element of the optical pickup device of the present invention The resin composition for use is obtained by addition polymerization in an inert gas atmosphere or an addition polymerizable monomer gas atmosphere using a polymerizable solution containing at least an alicyclic olefin monomer and having an oxygen concentration of 100 ppm or less. Addition polymerization was performed in an inert gas atmosphere or an addition polymerizable monomer gas atmosphere using a polymerizable solution containing an alicyclic hydrocarbon polymer or at least an aromatic vinyl monomer and having an oxygen concentration of 100 ppm or less. After that, because it contains an alicyclic hydrocarbon polymer obtained by further hydrogenation, white turbidity and refractive index fluctuation It is possible to prevent degradation of said optical element. Thereby, the lifetime of an optical element can be extended and a reliable optical pick-up apparatus can be obtained.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

上記式（１）中、ｎは０又は１であり、ｍは０又は１以上の整数である。 Ｒ¹〜Ｒ²⁰は、それぞれ独立に水素原子、ハロゲン原子又は炭化水素基である。ここでハロゲン原子は、フッ素原子、塩素原子、臭素原子又はヨウ素原子である。 The resin composition for an optical element according to the present invention includes a polymerizable solution containing at least an alicyclic olefin monomer and having an oxygen concentration of 100 ppm or less in an inert gas atmosphere or in an addition polymerizable monomer gas atmosphere. It contains an alicyclic hydrocarbon polymer obtained by addition polymerization, and the cyclic olefin used in producing the alicyclic hydrocarbon polymer is represented by the following formula (1): What is represented is exemplified.

In the above formula (1), n is 0 or 1, and m is 0 or an integer of 1 or more. R ^{1 to} R ²⁰ are each independently a hydrogen atom, a halogen atom or a hydrocarbon group. Here, the halogen atom is a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

Moreover, as a hydrocarbon group, a C1-C20 alkyl group, a C3-C15 cycloalkyl group, and an aromatic hydrocarbon group are mentioned normally each independently. More specifically, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an amyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, and an octadecyl group, and the cycloalkyl group includes a cyclohexyl group. Group, and examples of the aromatic hydrocarbon group include a phenyl group and a naphthyl group. In these hydrocarbon groups, the hydrogen atom may be substituted with a halogen atom. Further, in the above formula (1), R ^{17 to} R ²⁰ may be bonded to each other (in cooperation with each other) to form a monocyclic or polycyclic ring, and the monocyclic or polycyclic ring formed in this way The ring may have a double bond.

で示されるビシクロ［２．２．１］ヘプタ−２−エン（別名ノルボルネン。上記式中において、１〜７の数字は炭素の位置番号を示す。）およびこの化合物に炭化水素基が置換した誘導体が挙げられる。
この置換炭化水素基として、５−メチル、５，６−ジメチル、１−メチル、５−エチル、５−ｎ−ブチル、５−イソブチル、７−メチル、５−フェニル、５−メチル−５−フェニル、５−ベンジル、５−トリル、５−（エチルフェニル）、５−（イソプロピルフェニル）、５−（ビフェニル）、５−（β−ナフチル）、５−（α−ナフチル）、５−（アントラセニル）、５，６−ジフェニル等を例示することができる。 Specific examples of the cyclic olefin represented by the above formula (1) are shown below. As an example,

And bicyclo [2.2.1] hept-2-ene (also known as norbornene, in which the numbers 1 to 7 indicate the position number of carbon) and derivatives in which a hydrocarbon group is substituted for this compound Is mentioned.
As this substituted hydrocarbon group, 5-methyl, 5,6-dimethyl, 1-methyl, 5-ethyl, 5-n-butyl, 5-isobutyl, 7-methyl, 5-phenyl, 5-methyl-5-phenyl , 5-benzyl, 5-tolyl, 5- (ethylphenyl), 5- (isopropylphenyl), 5- (biphenyl), 5- (β-naphthyl), 5- (α-naphthyl), 5- (anthracenyl) 5,6-diphenyl and the like.

で示されるテトラシクロ［４．４．０．１^2,5．１^7,10］ドデカ−３−エン（以後単にテトラシクロドデセンという。上記式中において、１〜１２の数字は炭素の位置番号を示す。）、およびこれに炭化水素基が置換した誘導体が挙げられる。 Still other derivatives include cyclopentadiene-acenaphthylene adduct, 1,4-methano-1,4,4a, 9a-tetrahydrofluorene, 1,4-methano-1,4,4a, 5,10,10a-hexahydro. Bicyclo [2.2.1] hept-2-ene derivatives such as anthracene can be exemplified.
In addition, tricyclo [4.3.0.1 ^2,5 ] dec-3-ene, 2-methyltricyclo [4.3.0.1 ^2,5 ] dec-3-ene, 5-methyltricyclo Tricyclo [4.3.0.1 ^2,5 ] dec-3-ene derivatives such as [4.3.0.1 ^2,5 ] dec-3-ene, tricyclo [4.4.0.1 ^{2, 5]} undec-3-ene, such as 10-methyltricyclo [4.4.0.1 ^{2, 5]} undec-3-en tricyclo [4.4.0.1 ^{2, 5]} undec-3-ene Derivatives,

Tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene (hereinafter simply referred to as tetracyclododecene. In the above formula, the numbers 1 to 12 indicate the position number of carbon), and a derivative substituted with a hydrocarbon group Can be mentioned.

  Examples of the hydrocarbon group for the substituent include 8-methyl, 8-ethyl, 8-propyl, 8-butyl, 8-isobutyl, 8-hexyl, 8-cyclohexyl, 8-stearyl, 5,10-dimethyl, 2, 10-dimethyl, 8,9-dimethyl, 8-ethyl-9-methyl, 11,12-dimethyl, 2,7,9-trimethyl, 2,7-dimethyl-9-ethyl, 9-isobutyl-2,7- Dimethyl, 9,11,12-trimethyl, 9-ethyl-11,12-dimethyl, 9-isobutyl-11,12-dimethyl, 5,8,9,10-tetramethyl, 8-ethylidene, 8-ethylidene-9 -Methyl, 8-ethylidene-9-ethyl, 8-ethylidene-9-isopropyl, 8-ethylidene-9-butyl, 8-n-propylidene, 8-n-propylidene-9-methyl, 8- -Propylidene-9-ethyl, 8-n-propylidene-9-isopropyl, 8-n-propylidene-9-butyl, 8-isopropylidene, 8-isopropylidene-9-methyl, 8-isopropylidene-9-ethyl, 8-isopropylidene-9-isopropyl, 8-isopropylidene-9-butyl, 8-chloro, 8-bromo, 8-fluoro, 8,9-dichloro, 8-phenyl, 8-methyl-8-phenyl, 8- Benzyl, 8-tolyl, 8- (ethylphenyl), 8- (isopropylphenyl), 8,9-diphenyl, 8- (biphenyl), 8- (β-naphthyl), 8- (α-naphthyl), 8- (Anthracenyl), 5,6-diphenyl and the like can be exemplified.

  Examples of addition polymerizable monomers used for copolymerization include ethylene, propylene, but-1-ene, penta-1-ene, hexa-1-ene, octa-1-ene, deca-1-ene, A linear α-olefin having 2 to 20 carbon atoms such as dodec-1-ene, tetradec-1-ene, hexadec-1-ene, octadec-1-ene, eicosa-1-ene; 1-ene, 3-methylpent-1-ene, 3-ethylpent-1-ene, 4-methylpent-1-ene, 4-methylhex-1-ene, 4,4-dimethylhex-1-ene, 4,4 Examples thereof include branched α-olefins having 4 to 20 carbon atoms such as dimethylpent-1-ene, 4-ethylhex-1-ene, and 3-ethylhex-1-ene. Among these, a linear α-olefin having 2 to 4 carbon atoms is preferable, and ethylene is particularly preferable. Such linear or branched α-olefins can be used singly or in combination of two or more.

  As a manufacturing method of the alicyclic hydrocarbon polymer used in the present invention, a copolymerization reaction is carried out using an α-olefin having 2 to 20 carbon atoms and a cyclic olefin represented by the formula (1). A transition metal compound containing a ligand having a cyclopentadienyl skeleton, a catalyst formed from a vanadium compound and an organoaluminum compound soluble in the hydrocarbon solvent, and an organoaluminum oxy compound Produced by using a catalyst comprising an organoaluminum compound blended if necessary, for example, JP-A-60-168708, 61-120816, 61-115912, 61-115916, 61- In publications such as 271308, 61-272216, 62-252406 and 62-252407 The conditions may be appropriately selected according to the proposed method. In this case, the oxygen concentration of the polymerizable solution is adjusted to a range of 100 ppm or less, preferably 50 ppm by weight or less, more preferably 10 ppm by weight or less. There is a need. If the oxygen concentration of the polymerizable solution at the time of polymerization is within this range, the resin composition for an optical element containing the obtained polymer has a high stabilizing effect against light irradiation, for example, irradiation with light having a short wavelength near 400 nm. Even if the light is continuously received, it is possible to suppress white turbidity and fluctuation of the refractive index, and to suppress deformation of the optical surface. That is, the optical stability of the optical element resin composition can be improved, and an optical element resin composition capable of maintaining the characteristics for a long time can be produced. The cause of the improvement in photostability is not yet clear, but by specifying the oxygen concentration at the time of polymerization as described above, radical by-products that trigger the degradation reaction of the resin and oxidation degradation products It is conceivable that the production amount of can be controlled.

  Although there is no particular limitation on the method of setting the oxygen concentration within this range, a method of bubbling an inert gas such as nitrogen gas or argon gas into the polymerizable solution is usually used. Here, the oxygen concentration can be measured by an oxygen concentration meter.

式（２）、式（３）、式（４）及び式（５）中、Ｒ２１〜Ｒ３３は、それぞれ独立に水素原子、鎖状炭化水素基、ハロゲン原子、アルコキシ基、ヒドロキシ基、エーテル基、エステル基、シアノ基、アミノ基、イミド基、シリル基、及び極性基（ハロゲン原子、アルコキシ基、ヒドロキシ基、エステル基、シアノ基、アミド基、イミド基、又はシリル基）で置換された鎖状炭化水素基等を表す。具体的に、ハロゲン原子としては、フッ素原子、塩素原子、臭素原子、及びヨウ素原子を挙げることができ、極性基で置換された鎖状炭化水素基としては、例えば炭素原子１〜２０、好ましくは１〜１０、より好ましくは１〜６のハロゲン化アルキル基が挙げられる。鎖状炭化水素基としては、例えば炭素原子数１〜２０、好ましくは１〜１０、より好ましくは１〜６のアルキル基：炭素原子数２〜２０、好ましくは２〜１０、より好ましくは２〜６のアルケニル基が挙げられる。 As another optical element resin composition according to the present invention, at least an aromatic vinyl-based monomer is used, and a polymerizable solution having an oxygen concentration of 100 ppm or less is used in an inert gas atmosphere or addition polymerizable monomer gas. It contains an alicyclic hydrocarbon polymer obtained by addition polymerization in an atmosphere and then hydrogenation. As the structure of the alicyclic hydrocarbon copolymer, a repeating unit having an alicyclic structure is represented by the following repeating unit (a) having an alicyclic structure represented by the following general formula (2): (3) and / or a repeating unit (b) having a chain structure represented by the following formula (4) and / or the following formula (5) so that the total content is 90% by mass or more, and Examples are polymers in which the content of the repeating unit (b) is 1% by mass or more and less than 10% by mass.

In formula (2), formula (3), formula (4) and formula (5), R21 to R33 are each independently a hydrogen atom, a chain hydrocarbon group, a halogen atom, an alkoxy group, a hydroxy group, an ether group, Chains substituted with ester groups, cyano groups, amino groups, imide groups, silyl groups, and polar groups (halogen atoms, alkoxy groups, hydroxy groups, ester groups, cyano groups, amide groups, imide groups, or silyl groups) Represents a hydrocarbon group or the like. Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the chain hydrocarbon group substituted with a polar group include, for example, 1 to 20 carbon atoms, preferably The halogenated alkyl group of 1-10, More preferably, 1-6 is mentioned. As the chain hydrocarbon group, for example, an alkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms: 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 2 carbon atoms. 6 alkenyl groups.

  X in the above formula (2) represents an alicyclic hydrocarbon group, and the number of carbon atoms constituting the group is usually 4 to 20, preferably 4 to 10, more preferably 5 to 7. It is. Birefringence can be reduced by setting the number of carbon atoms constituting the alicyclic structure within this range. The alicyclic structure is not limited to a monocyclic structure, and may be a polycyclic structure such as a norbornane ring.

  The alicyclic hydrocarbon group may have a carbon-carbon unsaturated bond, but its content is 10% or less, preferably 5% or less, more preferably 3% or less of the total carbon-carbon bonds. is there. By setting the carbon-carbon unsaturated bond of the alicyclic hydrocarbon group within this range, transparency and heat resistance are improved. The carbon constituting the alicyclic hydrocarbon group includes a hydrogen atom, hydrocarbon group, halogen atom, alkoxy group, hydroxy group, ester group, cyano group, amide group, imide group, silyl group, and polar group ( A chain hydrocarbon group substituted with a halogen atom, an alkoxy group, a hydroxy group, an ester group, a cyano group, an amide group, an imide group, or a silyl group) may be bonded, and among them, the number of hydrogen atoms or carbon atoms 1 to 6 chain hydrocarbon groups are preferable in terms of heat resistance and low water absorption.

  In addition, the above formula (4) has a carbon-carbon unsaturated bond in the main chain, and the above formula (5) has a carbon-carbon saturated bond in the main chain. When heat resistance is strongly required, the content of unsaturated bonds is usually 10% or less, preferably 5% or less, more preferably 3% or less, of all carbon-carbon bonds constituting the main chain.

  In the present invention, the repeating unit (a) having an alicyclic structure represented by the general formula (2) in the alicyclic hydrocarbon copolymer, the general formula (3) and / or the general formula ( 4) and / or the total content with the repeating unit (b) of the chain structure represented by the general formula (5) is usually 90% or more, preferably 95% or more, more preferably 97%, on a weight basis. That's it. By setting the total content within the above range, low birefringence, heat resistance, low water absorption, and mechanical strength are highly balanced.

  As a production method for producing the alicyclic hydrocarbon-based copolymer, an aromatic vinyl-based compound is copolymerized with another monomer that can be copolymerized, and a carbon-carbon unsaturated bond of the main chain and the aromatic ring is formed. The method of hydrogenating is mentioned.

  The molecular weight of the copolymer before hydrogenation is 1,000 to 1,000,000, preferably 5,000 to 500,000 in terms of polystyrene (or polyisoprene) equivalent weight average molecular weight (Mw) measured by GPC. More preferably, it is in the range of 10,000 to 300,000. When the weight average molecular weight (Mw) of the copolymer is excessively small, the strength characteristics of the molded product of the alicyclic hydrocarbon copolymer obtained therefrom are inferior. Conversely, when the copolymer is excessively large, the hydrogenation reactivity is inferior.

  Specific examples of the aromatic vinyl compound used in the above method include, for example, styrene, α-methylstyrene, α-ethylstyrene, α-propylstyrene, α-isopropylstyrene, α-t-butylstyrene, 2- Methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, monochlorostyrene, dichlorostyrene Monofluorostyrene, 4-phenylstyrene and the like, and styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene and the like are preferable.

  These aromatic vinyl compounds can be used alone or in combination of two or more.

  Other monomers that can be copolymerized are not particularly limited, but chain vinyl compounds and chain conjugated diene compounds are used. When chain conjugated dienes are used, the operability in the production process is excellent. The resulting alicyclic hydrocarbon copolymer is excellent in strength properties.

  Specific examples of the chain vinyl compound include chain olefin monomers such as ethylene, propylene, 1-butene, 1-pentene and 4-methyl-1-pentene; 1-cyanoethylene (acrylonitrile), 1-cyano- Nitrile monomers such as 1-methylethylene (methacrylonitrile) and 1-cyano-1-chloroethylene (α-chloroacrylonitrile); 1- (methoxycarbonyl) -1-methylethylene (methacrylic acid methyl ester), 1- (Ethoxycarbonyl) -1-methylethylene (methacrylic acid ethyl ester), 1- (propoxycarbonyl) -1-methylethylene (methacrylic acid propyl ester), 1- (butoxycarbonyl) -1-methylethylene (methacrylic) Acid butyl ester), 1-methoxycarboni (Meth) acrylic acid such as ethylene (acrylic acid methyl ester), 1-ethoxycarbonylethylene (acrylic acid ethyl ester), 1-propoxycarbonylethylene (acrylic acid propyl ester), 1-butoxycarbonylethylene (acrylic acid butyl ester) Ester monomers, 1-carboxyethylene (acrylic acid), 1-carboxy-1-methylethylene (methacrylic acid), unsaturated fatty acid monomers such as maleic anhydride, and the like are mentioned, among which chain olefin monomers are preferable, Most preferred are ethylene, propylene and 1-butene.

  Examples of the chain conjugated diene include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and the like. Of these chain vinyl compounds and chain conjugated dienes, chain conjugated dienes are preferable, and butadiene and isoprene are particularly preferable. These chain vinyl compounds and chain conjugated dienes can be used alone or in combination of two or more.

  These chain vinyl compounds can be used alone or in combination of two or more.

  The polymerization reaction is not particularly limited, such as radical polymerization, anionic polymerization, and cationic polymerization. However, the polymerization operation, the ease of the hydrogenation reaction in the post-process, and the mechanical properties of the finally obtained hydrocarbon copolymer are not limited. In view of strength, the anionic polymerization method is preferable.

  In the case of radical polymerization, methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be used in the presence of an initiator, usually at 0 ° C to 200 ° C, preferably 20 ° C to 150 ° C. In particular, bulk polymerization and suspension polymerization are desirable when it is necessary to prevent impurities from being mixed into the resin. As radical initiators, benzoyl peroxide, lauroyl peroxide, organic peroxides such as t-butyl-peroxy-2-ethylhexanoate, azoisobutyronitrile, 4,4-azobis-4-cyanopentanoic acid An azo compound such as azodibenzoyl, a water-soluble catalyst typified by potassium persulfate and ammonium persulfate, a redox initiator, and the like can be used.

  In the case of anionic polymerization, bulk polymerization, solution polymerization, slurry polymerization, etc. in the temperature range of usually 0 ° C. to 200 ° C., preferably 20 ° C. to 100 ° C., particularly preferably 20 ° C. to 80 ° C. in the presence of an initiator. However, solution polymerization is preferable in view of removal of reaction heat. In this case, an inert solvent capable of dissolving the polymer and its hydride is used. Examples of the inert solvent used in the solution reaction include aliphatic hydrocarbons such as n-butane, n-pentane, iso-pentane, n-hexane, n-heptane, and iso-octane; cyclopentane, cyclohexane, methylcyclopentane, Examples include alicyclic hydrocarbons such as methylcyclohexane and decalin; aromatic hydrocarbons such as benzene and toluene. Among them, when aliphatic hydrocarbons and alicyclic hydrocarbons are used, hydrogenation reaction is also performed. It can be used as it is as an inert solvent. These solvents can be used alone or in combination of two or more, and are usually used at a ratio of 200 to 10,000 parts by mass with respect to 100 parts by mass of all the monomers used.

  Examples of the initiator for the anionic polymerization include monoorganolithium such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, and phenyllithium, dilithiomethane, 1,4-diobane, and 1,4-dilithio. A polyfunctional organolithium compound such as 2-ethylcyclohexane can be used.

  When carrying out these polymerization reactions, the oxygen concentration of the polymerizable solution is 100 ppm or less, preferably 50 ppm by weight or less, more preferably 10 ppm by weight, as in the case of producing the alicyclic hydrocarbon-based polymer described above. The polymerization reaction may be performed after adjusting to the following.

  When conducting hydrogenation reactions such as carbon-carbon double bonds of unsaturated rings such as aromatic rings and cycloalkene rings of the copolymer before hydrogenation, and unsaturated bonds of the main chain, the reaction method and reaction form are special. There is no particular limitation, and it may be carried out according to a known method, but a hydrogenation method that can increase the hydrogenation rate and has little polymer chain scission reaction that occurs simultaneously with the hydrogenation reaction is preferable, for example, in an organic solvent, nickel, The method is performed using a catalyst containing at least one metal selected from cobalt, iron, titanium, rhodium, palladium, platinum, ruthenium, and rhenium. As the hydrogenation catalyst, either a heterogeneous catalyst or a homogeneous catalyst can be used.

  The heterogeneous catalyst can be used in the form of a metal or a metal compound or supported on a suitable carrier. Examples of the carrier include activated carbon, silica, alumina, calcium carbide, titania, magnesia, zirconia, diatomaceous earth, silicon carbide and the like. The supported amount of the catalyst is usually 0.01 to 80% by weight, preferably 0. The range is from 05 to 60% by weight. The homogeneous catalyst is a catalyst in which a nickel, cobalt, titanium or iron compound and an organometallic compound (for example, an organoaluminum compound or an organolithium compound) are combined, or an organometallic complex catalyst such as rhodium, palladium, platinum, ruthenium or rhenium. Can be used. Examples of the nickel, cobalt, titanium, or iron compound include acetylacetone salts, naphthene salts, cyclopentadienyl compounds, cyclopentadienyl dichloro compounds, and the like of various metals. As the organic aluminum compound, alkylaluminum such as triethylaluminum and triisobutylaluminum, aluminum halide such as diethylaluminum chloride and ethylaluminum dichloride, alkylaluminum hydride such as diisobutylaluminum hydride and the like are preferably used.

  As an example of the organometallic complex catalyst, a metal complex such as a γ-dichloro-π-benzene complex, a dichloro-tris (triphenylphosphine) complex, a hydrido-chloro-triphenylphosphine) complex of each of the above metals is used. These hydrogenation catalysts can be used alone or in combination of two or more, and the amount used is usually 0.01 to 100 parts, preferably on the basis of weight with respect to the polymer. 0.05 to 50 parts, more preferably 0.1 to 30 parts.

  The hydrogenation reaction is usually 10 ° C. to 250 ° C., but preferably 50 ° C. to 200 ° C. because the hydrogenation rate can be increased and the polymer chain scission reaction occurring simultaneously with the hydrogenation reaction can be reduced. More preferably, it is 80 degreeC-180 degreeC. The hydrogen pressure is usually 0.1 MPa to 30 MPa, but in addition to the above reasons, from the viewpoint of operability, it is preferably 1 MPa to 20 MPa, more preferably 2 MPa to 10 MPa.

The hydrogenation rate of the hydride obtained in this way is determined by ¹ H-NMR, as determined by carbon-carbon unsaturated bond of the main chain, carbon-carbon double bond of aromatic ring, carbon of unsaturated ring All of the carbon double bonds are usually 90% or more, preferably 95% or more, more preferably 97% or more. When the hydrogenation rate is low, the low birefringence, thermal stability, etc. of the resulting copolymer are lowered.

  The method for recovering the hydride after completion of the hydrogenation reaction is not particularly limited. Usually, after removing the hydrogenation catalyst residue by a method such as filtration or centrifugation, the solvent is removed directly from the hydride solution by drying, the hydride solution is poured into a poor solvent for the hydride, and the hydride A method of coagulating can be used.

(Combination agent)
In the resin composition for an optical element of the present invention, compounding agents such as various stabilizers, surfactants, and plasticizers can be blended with the alicyclic hydrocarbon-based copolymer as necessary. These compounding agents can be used alone or in admixture of two or more, and the compounding amount is appropriately selected within a range not impairing the object of the present invention.

(Stabilizer)
In the resin composition for an optical element of the present invention, one or more stabilizers selected from hindered amine stabilizers, phenol stabilizers, phosphorus stabilizers, and sulfur stabilizers may be additionally added. Good. By appropriately selecting these stabilizers and adding them to the alicyclic hydrocarbon-based copolymer, for example, white turbidity when irradiated with light having a short wavelength such as 400 nm, or fluctuations in optical properties such as refractive index fluctuations. Can be suppressed to a higher degree.

  As a preferable phenol-based stabilizer, conventionally known ones can be used, 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-tert-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 [ie, 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-triazine What triazine group-containing phenol compound; and the like.

  Preferred hindered amine stabilizers include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) succinate, bis ( 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (N-octoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (N-benzyloxy-2, 2,6,6-tetramethyl-4-piperidyl) sebacate, bis (N-cyclohexyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6) -Pentamethyl-4-piperidyl) 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-butylmalonate, bis (1-acryloyl-2,2,6,6-teto Methyl-4-piperidyl) 2,2-bis (3,5-di-t-butyl-4-hydroxybenzyl) -2-butylmalonate, bis (1,2,2,6,6-pentamethyl-4- Piperidyl decandioate, 2,2,6,6-tetramethyl-4-piperidyl methacrylate, 4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -1- [2 -(3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy) ethyl] -2,2,6,6-tetramethylpiperidine, 2-methyl-2- (2,2,6 , 6-tetramethyl-4-piperidyl) amino-N- (2,2,6,6-tetramethyl-4-piperidyl) propionamide and the like.

  Further, the preferable phosphorus stabilizer is not particularly limited as long as it is a substance usually used in the general resin industry. For example, triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (nonyl). Phenyl) phosphite, tris (dinonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, 10- (3,5-di-t-butyl-4-hydroxybenzyl) -9 , 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and the like; 4,4′-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecyl) Phosphite), 4,4 'isopropylidene-bis (phenyl-di-alkyl (C12-C15) phosphine) Ito), and the 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.

Preferred sulfur stabilizers include, for example, dilauryl 3,3-thiodipropionate, dimyristyl 3,3′-thiodipropionate, distearyl 3,3-thiodipropionate, lauryl stearyl 3,3- Thiodipropionate, pentaerythritol-tetrakis- (β-lauryl-thio-propionate, 3,9-bis (2-dodecylthioethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane, etc. Is mentioned.

  The amount of these stabilizers is appropriately selected within a range not to impair the purpose of the present invention, but is usually 0.01 to 2 parts by mass, preferably 100 parts by mass with respect to 100 parts by mass of the alicyclic hydrocarbon copolymer. Is 0.01 to 1 part by mass.

(Surfactant)
A surfactant is a compound having a hydrophilic group and a hydrophobic group in the same molecule. The surfactant prevents white turbidity of the optical element resin composition by adjusting the rate of moisture adhesion to the resin surface and the rate of moisture evaporation from the surface.

  Specific examples of the hydrophilic group of the surfactant include a hydroxy group, a hydroxyalkyl group having 1 or more carbon atoms, a hydroxyl group, a carbonyl group, an ester group, an amino group, an amide group, an ammonium salt, a thiol, a sulfonate, and phosphoric acid. Examples include salts and polyalkylene glycol groups. Here, the amino group may be primary, secondary, or tertiary. Specific examples of the hydrophobic group of the surfactant include an alkyl group having 6 or more carbon atoms, a silyl group having an alkyl group having 6 or more carbon atoms, and a fluoroalkyl group having 6 or more carbon atoms. Here, the alkyl group having 6 or more carbon atoms may have an aromatic ring as a substituent. Specific examples of the alkyl group include hexyl, heptyl, octyl, nonyl, decyl, undecenyl, dodecyl, tridecyl, tetradecyl, myristyl, stearyl, lauryl, palmityl, cyclohexyl and the like. Examples of the aromatic ring include a phenyl group. The surfactant only needs to have at least one hydrophilic group and hydrophobic group as described above in the same molecule, and may have two or more groups.

  More specifically, examples of such surfactants include myristyl diethanolamine, 2-hydroxyethyl-2-hydroxydodecylamine, 2-hydroxyethyl-2-hydroxytridecylamine, 2-hydroxyethyl-2-hydroxy. Tetradecylamine, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate, di-2-hydroxyethyl-2-hydroxydodecylamine, alkyl (8 to 18 carbon atoms) benzyldimethylammonium chloride, ethylene bis Examples include alkyl (carbon number 8 to 18) amide, stearyl diethanolamide, lauryl diethanolamide, myristyl diethanolamide, palmityl diethanolamide, and the like. Of these, amine compounds or amide compounds having a hydroxyalkyl group are preferably used. In the present invention, two or more of these compounds may be used in combination.

  The surfactant is added in an amount of 0.01 to 10 parts by weight with respect to 100 parts by weight of the alicyclic hydrocarbon polymer. When the addition amount of the surfactant is less than 0.01 parts by weight, the white turbidity of the molded product accompanying fluctuations in temperature and humidity cannot be effectively suppressed. On the other hand, when the addition amount exceeds 10 parts by weight, the light transmittance of the molded product becomes low, and application to the optical pickup device becomes difficult. The addition amount of the surfactant is preferably 0.05 to 5 parts by weight and more preferably 0.3 to 3 parts by weight with respect to 100 parts by weight of the alicyclic hydrocarbon-based polymer.

(Plasticizer)
The plasticizer is added as necessary to adjust the melt index of the cyclic olefin resin.
Plasticizers include bis (2-ethylhexyl) adipate, bis (2-butoxyethyl) adipate, bis (2-ethylhexyl) azelate, dipropylene glycol dibenzoate, tri-n-butyl citrate, tri-citrate -N-butylacetyl, epoxidized soybean oil, 2-ethylhexyl epoxidized tall oil, chlorinated paraffin, tri-2-ethylhexyl phosphate, tricresyl phosphate, t-butylphenyl phosphate, tri-2-ethylhexyl phosphate Diphenyl, dibutyl phthalate, diisohexyl phthalate, diheptyl phthalate, dinonyl phthalate, diundecyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, diisodecyl phthalate, ditridecyl phthalate, butylbenzyl phthalate, dicyclophthalate Known materials such as xylyl, di-2-ethylhexyl sebacate, tri-2-ethylhexyl trimellitic acid, Santizer 278, Paraplex G40, Drapex 334F, Plastolein 9720, Mesamoll, DNODP-610, HB-40 are applicable. . The selection of the plasticizer and the addition amount are appropriately performed under the condition that the permeability of the cyclic olefin and the resistance to environmental changes are not impaired.
Such cyclic olefin resins are transparent, low birefringence, heat resistance, heat aging resistance, chemical resistance, solvent resistance, dielectric properties, various mechanical properties, precision moldability, moisture resistance (low water absorption) Excellent). In particular, the cyclic olefin-based resin according to the present invention contains a structural unit derived from a bulky cyclic olefin and a surfactant having a hydrophilic group and a hydrophobic group in the same molecule at a specific ratio. Excellent transparency can be maintained even when the environment changes from an environment such as humidity to normal temperature and humidity.

  In the present invention, in addition to the above-mentioned compounding agents, other resins can be further compounded into the cyclic olefin polymer. Other resin to be blended is added within a range not impairing the object of the present invention.

Here, other resins that can be added to the cyclic olefin polymer are exemplified below.
(1) A polymer derived from a hydrocarbon having one or two unsaturated bonds, specifically, for example, polyethylene, polypropylene, polymethylbut-1-ene, poly-4-methylpent-1-ene, polybuta Examples include polyolefins such as -1-ene and polystyrene. These polyolefins may have a crosslinked structure.
(2) Halogen-containing vinyl polymer, specifically, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polychloroprene, chlorinated rubber, etc. (3) From α, β-unsaturated acid and its derivatives Derived polymers, specifically polyacrylates, polymethacrylates, polyacrylamides, polyacrylonitriles, or copolymers with monomers constituting the polymers, such as acrylonitrile / butadiene / styrene copolymers, acrylonitrile / Examples thereof include styrene copolymers and acrylonitrile / styrene / acrylic acid ester copolymers.
(4) Polymers derived from unsaturated alcohols and amines, or acyl derivatives or acetals of unsaturated alcohols, specifically polyvinyl alcohol, polyvinyl acetate, polyvinyl stearate, polyvinyl benzoate, vinyl polymaleate , Polyvinyl butyral, polyallyl phthalate, polyallyl melamine, or a copolymer with a monomer constituting the polymer, such as an ethylene / vinyl acetate copolymer.
(5) A polymer derived from an epoxide, specifically, a polymer derived from polyethylene oxide or bisglycidyl ether.
(6) Polyacetals, specifically, polyoxymethylene, polyoxyethylene, polyoxymethylene containing ethylene oxide as a comonomer, and the like.
(7) polyphenylene oxide (8) polycarbonate (9) S polysulfone (10) polyurethane and urea resin (11) polyamides and copolyamides derived from diamines and dicarboxylic acids and / or aminocarboxylic acids or corresponding lactams, Specifically, nylon 6, nylon 66, nylon 11, nylon 12, etc. are mentioned.
(12) Polyesters derived from dicarboxylic acids and dialcohols and / or oxycarboxylic acids, or corresponding lactones, such as polyethylene terephthalate, polybutylene terephthalate, poly 1,4-dimethylol / cyclohexane terephthalate. .
(13) A polymer having a cross-linked structure derived from aldehyde and phenol, urea or melamine, and specifically includes phenol-formaldehyde resin, urea-formaldehyde resin, melamine-formaldehyde resin and the like.
(14) Alkyd resin, and specific examples include glycerin / phthalic acid resin.
(15) Unsaturated polyester resins and halogen-containing modified resins derived from copolyesters of saturated and unsaturated dicarboxylic acids and polyhydric alcohols and obtained using vinyl compounds as crosslinking agents.
(16) Natural polymer, specifically, cellulose, rubber, protein, or derivatives thereof such as cellulose acetate, cellulose propionate, and cellulose ether.
(17) Soft polymer, for example, a soft polymer containing a cyclic olefin component, a resin composition for an optical element-olefin copolymer, a resin composition for an optical element-olefin / diene copolymer, an aromatic vinyl series Examples thereof include a hydrocarbon / conjugated diene-based soft copolymer, a soft polymer or copolymer composed of isobutylene or isobutylene / conjugated diene, and the like.

  What is necessary is just to mix an alicyclic hydrocarbon-type copolymer, another resin component, an additive, etc., when shape | molding the resin composition for optical elements mentioned above. As a mixing method of the alicyclic hydrocarbon copolymer and other resin components and additives, any method may be used as long as each component is sufficiently dispersed, such as mixing each component simultaneously. Known methods can be applied. For example, a method of kneading a resin in a molten state with a mixer, a twin-screw kneader, a roll, a brabender, an extruder, or the like, or a method of dissolving and dispersing in an appropriate solvent and solidifying the resin can be used. When a twin-screw kneader is used, it is often used as a molding material that is usually extruded after being kneaded into a rod shape in a molten state, cut into an appropriate length with a strand cutter, and pelletized.

  The cyclic olefin resin prepared as described above preferably has a melt index (MI) measured at a temperature of 260 ° C. and a load of 2.16 kg in a range of 20 <MI (g / 10 min) <60. Here, the measuring method of MI is based on ASTM D1238. The MI is more preferably 40 <MI (g / 10 min) <60.

  Here, the MI can be adjusted by a known method such as control of crystallinity by selection of the composition ratio of monomers, control of molecular weight by selection of a polymerization method or polymerization conditions, or addition of a plasticizer.

  Since the MI of the cyclic olefin resin is within the above-described range, when the optical element is molded by a method such as injection molding, the molten cyclic olefin resin is a ring-shaped lens surface, a diffracting ring zone, or a ring-shaped shape described later of the mold. Since it reaches to the tip of the part corresponding to the concave part and the ring-shaped convex part, the part can be formed with high accuracy. Therefore, it is possible to manufacture an optical element that can irradiate the medium with light or collect the light reflected by the medium with high reliability.

(Optical element)
The optical element according to the present invention is obtained by molding the above-described resin composition for an optical element. The molding method is not particularly limited, but melt molding is preferable in order to obtain an optical element excellent in characteristics such as low birefringence, mechanical strength, and dimensional accuracy. Examples of the melt molding method include press molding, extrusion molding, and injection molding, and injection molding is preferable from the viewpoints of moldability and productivity. The molding conditions are appropriately selected depending on the purpose of use or the molding method. For example, the resin temperature in the injection molding is usually appropriately selected in the range of 150 to 400 ° C, preferably 200 to 350 ° C, more preferably 230 to 330 ° C. The If the resin temperature is too low, fluidity will deteriorate, causing sink marks and distortion in the molded product. If the resin temperature is too high, silver streaks will occur due to thermal decomposition of the resin, and the optical element will turn yellow. Defects may occur.

  The optical element according to the present invention can be used in various forms such as a spherical shape, a rod shape, a plate shape, a cylindrical shape, a tubular shape, a tubular shape, a fibrous shape, a film shape or a sheet shape, and has a low birefringence and a transparency. It has excellent properties, mechanical strength, heat resistance, and low water absorption.

Specific examples of the optical element include the following. As an optical lens and an optical prism, an imaging lens of a camera; a lens such as a microscope, an endoscope, a telescope lens; an all-light transmission lens such as a spectacle lens; a CD, a CD-ROM, a WORM (recordable optical disk), an MO (Optical optical discs that can be rewritten; magneto-optical discs), pickup lenses for optical discs such as MD (mini discs), DVDs (digital video discs); laser scanning system lenses such as fθ lenses and sensor lenses for laser beam printers; Examples include finder type prism lenses. Examples of optical disc applications include CD, CD-ROM, WORM (recordable optical disc), MO (rewritable optical disc; magneto-optical disc), MD (mini disc), DVD (digital video disc), and the like. Other optical applications include light guide plates such as liquid crystal displays; optical films such as polarizing films, retardation films and light diffusing films; light diffusing plates; optical cards;
Among these, the optical element is preferably applied to a condensing device having a condensing function, and is particularly suitable as an optical system lens or a laser scanning system lens constituting an optical pickup device that requires low birefringence. It is most suitable for an optical system lens of a pickup device.

  As an optical system lens of the optical pickup device, for example, an objective lens, an objective lens unit, a coupling lens (collimator), a beam expander, a beam shaper, a correction plate, and the like can be used.

  The objective lens unit is a lens group formed by integrally combining a plurality of single lens optical lenses in the optical axis direction, and the optical element of the present invention includes at least one single lens optical lens among the plurality of single lens optical lenses. It is preferable to use it as a ball optical lens.

(Optical pickup device)
Next, an optical pickup device incorporating a light collecting device to which the optical element according to the present invention is applied will be described with reference to FIGS.

  The optical pickup device 1 according to the present invention includes a current DVD that applies light having a wavelength of 650 nm (hereinafter referred to as current DVD) and a so-called next-generation DVD that applies light having a wavelength of 405 nm (hereinafter referred to as next-generation DVD). This is an apparatus for reproducing and recording information on two types of optical information recording media 5.

  The optical pickup device 1 allows laser light (light) emitted from a light source 2 to pass through a single lens optical element such as a collimator lens 3 and an objective lens (optical element) 10 having an optical path difference providing structure, which will be described later. 4 is collected on the information recording surface 6 of the optical information recording medium 5 to form a condensed spot, the reflected light from the information recording surface 6 is taken in by the deflecting beam splitter 7, and the beam spot is again incident on the light receiving surface of the detector 8. Is formed.

  The light source 2 includes a laser diode, and is configured to be able to select and emit light of two types of wavelengths of 650 nm and 405 nm by a known switching method. Here, the collimator lens 3, the objective lens (optical element) 10, and the deflection beam splitter 7 constitute an optical element unit.

  The objective lens 10 according to the present invention is an optical element having an optical path difference providing structure, and is created by molding the above-mentioned cyclic olefin resin by injection molding. As shown in FIG. 2, the objective lens 10 is a single-sided optical element having a double-sided aspheric surface, and is predetermined on the optical surface 11 on one side (light source side) for predetermined light passing through the optical surface 11. The optical path difference providing structure 20 for providing the optical path difference is provided.

  The optical path difference providing structure 20 includes three annular lens surfaces whose optical surfaces 11 are centered on the optical axis 4 (hereinafter, a first annular lens surface 21, a second annular lens surface 22, and a third annular zone in order from the inside). Of the three annular lens surfaces 21 to 23, the adjacent annular lens surfaces 21 to 23 have different refractive powers.

The first annular lens surface 21 and the third annular lens surface 23 are on the same optical surface 11, and the second annular lens surface 22 is a surface translated from the optical surface 11.
The first annular lens surface 21 transmits light having both wavelengths of 650 nm and 405 nm, the second annular lens surface 22 transmits light having a wavelength of 650 nm corresponding to the current DVD, and the third annular lens surface 23 The light of wavelength 405nm corresponding to next-generation DVD is allowed to pass through. The light that has passed through each of the annular lens surfaces 21 to 23 is collected at the same position on the information recording surface 6.

  In FIG. 2, the first annular lens surface 21 and the third annular lens surface 23 are provided on the same optical surface 11, but the first and third annular lens surfaces 21 and 23 are different from each other. The second annular lens surface 22 does not have to be provided on the same optical surface, and the second annular lens surface 22 is a surface translated from the optical surface 11, but it need not be a particularly translated surface. Further, the number of the three annular lens surfaces 21 to 23 may be five or at least three.

  Since the objective lens 10 uses the above-described cyclic olefin resin, when the objective lens 10 is melted and injected into a mold, the first annular lens surface 21, the second annular lens surface 22, The resin has surely spread to the portion corresponding to the boundary portion of the three-band lens surface 23. Therefore, the objective lens 10 is provided with the optical path difference providing structure 20 with high accuracy.

  By the action of the optical path difference providing structure 20 formed in this way, the objective lens 10 collects the light emitted from the light source 2 on the information recording surface 6 with respect to a plurality of types of optical information recording media 5 such as the current DVD and the next generation DVD. Condensing light and light reflected by the information recording surface 6 toward the detector 8 can be performed with high reliability. Further, since the cyclic olefin resin forming the objective lens 10 has a high light transmittance of 85% or more, the above-described light collection can be performed with high efficiency. Therefore, since the power consumption of the light source 2 can be reduced, the power consumption of the entire optical pickup device 1 can be reduced.

  Further, since the cyclic olefin resin contains an antioxidant, even when light of 405 nm for reproducing and recording information of the next generation DVD is transmitted, white turbidity and refractive index fluctuation hardly occur. Therefore, the optical pickup device 1 can be operated with high pickup characteristics over a long period of time.

  The objective lens 10 according to the present invention is not limited to the one having the optical path difference providing structure 20 described above, and may be, for example, objective lenses 10a to 10e having optical path difference providing structures 20a to 20d shown in FIGS.

  The optical path difference providing structure 20a in FIG. 3 includes a plurality of diffraction ring zones 21a with the optical axis 4 as the center, the plurality of diffraction ring zones 21a have a sawtooth cross section, and the optical surface of each diffraction ring zone 21a. 11a is a discontinuous surface. Further, the plurality of diffraction ring zones 21 a are formed so that the thickness increases as the distance from the optical axis 4 increases. The objective lens 10a shown in FIG. 3 is a so-called diffractive lens.

  The optical path difference providing structure 20b in FIG. 4 has a plurality of annular zone-shaped recesses 21b that cause a phase difference around the optical axis 4 in a concentric manner. The ring-shaped concave portions 21b are formed in five on one surface (upper and lower optical surfaces around the optical axis 4 in FIG. 4) of the optical surface 11b with the optical axis 4 as the center. Adjacent ring-shaped recesses 21b are continuously integrated with each other, and the entire cross-section of each ring-shaped recess 21b is stepped. Moreover, the optical surface 22b which forms each annular zone-shaped recessed part 21b is a surface translated with respect to the optical surface 11b. The objective lens 10b shown in FIG. 4 is a so-called phase difference lens.

In FIG. 4, adjacent annular recesses 21 b are continuous and integrated, and the entire cross section is stepped. However, the annular recesses 21 b are simply provided on the optical surface 11 b individually. (In this case, for example, the structure is the same as that of the objective lens 10 shown in FIG. 2). In FIG. 4, the annular concave portion 21b is concentrically formed. However, as shown in FIG. 5, the objective lens having the annular convex portion 23b on the third annular lens surface 23 of FIG. 10c may be used (in FIG. 5, the same components as those in FIG. 2 are given the same reference numerals).

  The optical path difference providing structure 20d in FIG. 6 includes a plurality of diffraction ring zones 21d centered on the optical axis 4, the plurality of diffraction ring zones 21d have a sawtooth cross section, and the optical surface of each diffraction ring zone 21d. 11d is a discontinuous surface. The cross section of each diffraction ring zone 21d is a stepped shape of three steps 22d along the optical axis direction, and the optical surface 12d of each step 22d is a discontinuous surface and is a surface orthogonal to the optical axis 4. Yes.

The lens 10d shown in FIG. 6 may have, for example, a hologram optical element (HOE) 10e having an optical path difference providing structure 20d similar to FIG. 6 and an objective lens 10f as shown in FIG. . In this case, the hologram optical element 10e uses a plate-like optical element, and the optical path difference providing structure 20d is provided on the surface of the objective lens 10f of the optical element.
The optical pickup device 1 according to the present invention may perform information reproduction and recording on three types of optical information recording media 5, for example, a CD, a current DVD, and a next-generation DVD. The combination of the optical information recording medium 5 for reproducing and recording information with the optical pickup device 1 is a design matter and is set as appropriate.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these.

(Production Example 1)
In a stainless steel autoclave, 1000 parts by mass of dry cyclohexane, tetracyclo [4.4.0.1 ^2,5 . 200 parts by mass of 1 ^7,10 ] -3-dodecene (hereinafter abbreviated as “TD”) was added, and nitrogen was circulated for 1 hour at a flow rate of 40 ml / min. With respect to this polymerizable monomer solution, the oxygen concentration in liquid at 25 ° C. was measured with a submerged oxygen concentration meter (TOX-90, manufactured by Toko Chemical Laboratories). As a result, the oxygen concentration was 1.8 ppm. Next, after replacing the inside of the autoclave with ethylene gas, 0.073 parts by mass of methylaluminoxane (MAO) in terms of aluminum atoms and 0.003 parts by mass of bis (cyclopentadienyl) zirconium dichloride were added, and 50 parts of ethylene gas was added. The polymerization reaction was carried out at 25 ° C. and normal pressure for 10 hours while circulating at a flow rate of liter / hr, and then the polymerization was stopped by adding a small amount of isobutyl alcohol. The reaction solution was added to an acetone / methanol mixed solvent to precipitate the whole amount of the polymer, and then the copolymer was collected by filtration and dried under reduced pressure at 80 ° C. for 48 hours to obtain Resin 1.

(Production Example 2)
Resin 2 was obtained in the same manner as in Production Example 1, except that the flow time of nitrogen to the polymerizable monomer solution was shortened and a polymerizable monomer solution having an oxygen concentration of 95 ppm was used.

(Production Example 3)
Resin 3 was obtained in the same manner as in Production Example 1, except that no nitrogen flow was performed in the polymerizable monomer solution and a polymerizable monomer solution having an oxygen concentration of 106 ppm was used.

(Production Example 4)
The inside of the stainless steel reactor equipped with a stirrer was sufficiently dried and purged with nitrogen, and then charged with 300 parts by mass of dehydrated cyclohexane, 60 parts by mass of styrene, and 0.38 parts by mass of dibutyl ether, and 40 ml / min. Nitrogen was passed at the flow rate for 1 hour. About this polymerizable monomer solution, when the oxygen concentration in liquid at 25 degreeC was measured with the liquid oxygen concentration meter (the Toko Chemical Laboratories make; TOX-90), oxygen concentration was 1.2 ppm. To this polymerizable monomer solution, 0.36 parts by mass of an n-butyllithium solution (15% hexane solution) was added while stirring at 60 ° C. to initiate a polymerization reaction. After carrying out the polymerization reaction for 1 hour, a mixed monomer composed of 8 parts by mass of styrene and 12 parts by mass of isoprene was added to the reaction solution, and after further carrying out the polymerization reaction for 1 hour, isopropyl alcohol 0.2 was added to the reaction solution. The reaction was stopped by adding parts by weight.
Next, 300 parts by mass of the polymerization reaction solution was transferred to a pressure-resistant reactor equipped with a stirrer, and as a hydrogenation catalyst, a silica-alumina supported nickel catalyst (manufactured by JGC Chemical Industry Co., Ltd .; E22U, nickel supported amount 60%). ) 10 parts by mass were added and mixed. The inside of the reactor was replaced with hydrogen gas, hydrogen was further supplied while stirring the solution, the temperature was set to 160 ° C., and a hydrogenation reaction was performed at a pressure of 4.5 MPa for 8 hours.
After completion of the reaction, the reaction solution was filtered to remove the hydrogenation catalyst. After diluting by adding 800 parts by mass of cyclohexane, the reaction solution was poured into 3500 parts by mass of isopropanol to precipitate a copolymer. Next, this copolymer was collected by filtration and dried under reduced pressure at 80 ° C. for 48 hours to obtain Resin 4.

(Production Example 5)
Resin 5 was obtained in the same manner as in Production Example 4 except that the polymerizable monomer solution was used in which the nitrogen flow time to the polymerizable monomer solution was shortened and the oxygen concentration was 92 ppm.

(Production Example 6)
In Production Example 4, resin 6 was obtained by the same operation except that the polymerizable monomer solution was not subjected to nitrogen flow and the polymerizable monomer solution having an oxygen concentration of 110 ppm was used.

Example 1
100 parts by weight of the resin 1 obtained in Production Example 1, 0.2 parts by weight of tetrakis (1,2,2,6,6, -pentamethylpiperidyl) butanetetracarboxylate, 2,2′-methylenebis (4 The composition ratio of 6-ditert-butylphenyl) -2-ethylhexyl phosphite 0.05 parts by mass and 0.5 parts by mass of pentaerythritol distearate as a surfactant, -35B, screw diameter 37 mm, L / D = 32, screw rotation speed 150 rpm, resin temperature 240 ° C., feed rate 10 kg / hour), kneaded, and pelletized. The obtained pellets were dried at 70 ° C. for 2 hours to remove moisture, and then the cylinder temperature was 280 ° C., the mold temperature was 80 ° C., and the primary injection pressure was 98.1 MPa using an injection molding machine (ATOSHOT MODEL 30A manufactured by FANUC). Then, injection molding was performed at a secondary injection pressure of 78.4 MPa to obtain a molded plate 1 (corresponding to an optical element) having a resin substrate with a diameter of 30 mm and a thickness of 3 mm.

(Example 2)
In Example 1, the same operation was performed except that the resin 2 obtained in Production Example 2 was used instead of the resin 1, and a molded plate 2 was obtained.

(Example 3)
In Example 1, the same operation was performed except that the resin 4 obtained in Production Example 4 was used instead of the resin 1, and the molded plate 3 was obtained.

Example 4
In Example 1, the same operation was performed except that the resin 5 obtained in Production Example 5 was used instead of the resin 1, and the molded plate 4 was obtained.

(Comparative Example 1)
In Example 1, the same operation was performed except that the resin 3 obtained in Production Example 3 was used instead of the resin 1, and a molded plate 5 was obtained.

(Comparative Example 2)
In Example 1, the same operation was performed except that the resin 6 obtained in Production Example 6 was used instead of the resin 1, and a molded plate 6 was obtained.

  Next, for the molded plates obtained in Examples 1 to 4 and Comparative Examples 1 and 2, melting characteristics (melt index) and optical characteristics (light transmittance and light durability) were obtained by the following methods. ) Was evaluated.

(Melt index measurement)
For each molded plate, the melt index at a temperature of 260 ° C. and a load of 2.16 kg was measured according to the method defined in ASTM D1238. The results are shown in Table 1.

(Measurement of light transmittance)
About each shaping | molding board, the light transmittance by wavelength 400nm was measured, and the coloring property and transparency of a molded article were evaluated. The results are shown in Table 1.
As a result, each of the molded plates of Examples 1 to 4, Comparative Example 1 and Comparative Example 2 had a light transmittance of 90% or higher and a high transmittance.

(Evaluation of light durability)
In a constant temperature and humidity chamber of 90 ° C. and 55% RH, the optical pickup device shown in FIG. 1 is used, and light having a wavelength of 405 nm from the laser diode of the light source 2 is formed as a circular spot light having a diameter of 1 mm on each molded plate. After continuous irradiation over time, the laser irradiation spot was visually observed, and (1) transparency (coloring degree) due to cloudiness and (2) shape stability were evaluated according to the following criteria. The results are shown in Table 1.
(1) coloring degree;
A: After the continuous irradiation, no cloudiness is observed at the laser irradiated portion.
○: Slight turbidity is observed at the laser irradiation site after continuous irradiation, but is practically acceptable.
Δ: After continuous irradiation, turbidity is observed at the laser irradiation site, but it is in a practically acceptable range.
X: After continuous irradiation, a white turbidity phenomenon is observed at the laser irradiation site, which is problematic in practical use.
(2) Shape stability;
(Double-circle): After a continuous irradiation, a deformation | transformation is not recognized at the laser irradiation location at all.
○: After continuous irradiation, slight laser beam deformation is observed, but it is practically acceptable.
(Triangle | delta): Although a deformation | transformation is recognized slightly in the laser irradiation location after continuous irradiation, it exists in a practically allowable range.
X: After continuous irradiation, deformation was observed at the laser irradiation site, and there was a problem in practical use.

  As shown in Table 1, the molded plates produced in Examples 1 to 4 do not cause coloring or white turbidity even when continuously irradiated with light having a short wavelength for a long time, and are not deformed and have high shape stability. I was able to maintain sex.

(Example 5)
In Example 1, instead of obtaining the molded plate 1 by injection molding the pellets, the objective lens 1 having the configuration shown in FIG. 2 was obtained.

(Example 6)
In Example 2, instead of obtaining the molding plate 2 by injection molding the pellets, the objective lens 2 having the configuration shown in FIG. 2 was obtained.

(Example 7)
In Example 3, instead of obtaining the molding plate 3 by injection molding the pellets, the objective lens 3 having the configuration shown in FIG. 2 was obtained.

(Example 8)
In Example 4, instead of obtaining the molding plate 4 by injection molding the pellets, the objective lens 4 having the configuration shown in FIG. 2 was obtained.

(Examples 9 to 13)
In Example 5, instead of obtaining the objective lens 1 by injection molding the pellets, objective lenses having the configurations shown in FIGS. 3 to 7 were obtained.

(Example 14 to Example 18)
In Example 6, instead of obtaining the objective lens 2 by injection molding the pellets, the objective lenses having the configurations shown in FIGS. 3 to 7 were obtained.

(Example 19 to Example 23)
In Example 7, instead of obtaining the objective lens 3 by injection molding the pellets, objective lenses having the configurations shown in FIGS. 3 to 7 were obtained.

(Example 24 to Example 28)
In Example 8, instead of obtaining the objective lens 4 by injection molding the pellets, the objective lenses having the configurations shown in FIGS. 3 to 7 were obtained.

(Comparative Example 3)
In Comparative Example 1, instead of obtaining the molded plate 5 by injection molding the pellets, the objective lens 5 having the configuration shown in FIG. 2 was obtained.

(Comparative Example 4)
In Comparative Example 2, instead of obtaining the molded plate 6 by injection molding the pellets, the objective lens 6 having the configuration shown in FIG. 2 was obtained.

(Comparative Example 5 to Comparative Example 9)
In Comparative Example 3, instead of obtaining the objective lens 5 by injection molding the pellets, objective lenses having the configurations shown in FIGS. 3 to 7 were obtained.

(Comparative Example 10 to Comparative Example 14)
In Comparative Example 4, instead of obtaining the objective lens 6 by injection molding the pellets, objective lenses having the configurations shown in FIGS. 3 to 7 were obtained.

  Next, the pickup characteristics of the objective lenses obtained in Examples 5 to 28 and Comparative Examples 3 to 14 were evaluated by the following method.

(Evaluation of pickup characteristics)
Changes in the physical properties of the objective lenses produced in Examples 5 to 28 and Comparative Examples 3 to 14 were evaluated in the same manner as described above (evaluation of light durability), and the objective lenses were used. Each of the optical pickup devices having the structure shown in FIG. Next, using each optical pickup device, recording and reproduction on a DVD were performed using light having a wavelength of 405 nm by a laser diode, and the pickup characteristics at that time were evaluated. The results are shown in Table 2.
(1) Pickup characteristics;
The pickup characteristics are evaluated based on the laser irradiation time at which a reading error occurs, and the laser irradiation time at which a reading error occurs is performed according to the following criteria.
○: No reading error even after continuous laser irradiation for 250 hours or more.
Δ: Read error occurs after continuous laser irradiation for 200 hours or more and less than 250 hours.
X: Read error occurs in continuous laser irradiation for less than 200 hours.

  Upon evaluating the pickup characteristics, the obtained objective lens was examined for changes in physical properties, and it was confirmed that the same result as that of the corresponding molded plate was obtained. When a pickup device is manufactured using this objective lens, in the optical pickup device using the objective lens of Examples 5 to 28, no reading error occurs even if continuous laser irradiation is performed for 250 hours or more. It showed good pickup characteristics. On the other hand, in the optical pickup device using the objective lenses of Comparative Examples 3 to 14, a reading error occurred even if the continuous laser irradiation was less than 200 hours, and the pickup characteristics were deteriorated. Further, in this optical pickup device, it was observed that the element itself was more deformed as the optical surface structure (optical path difference providing structure) was made finer (complex).

1 is a side view showing an outline of an optical pickup device 1 according to the present invention. It is a cutaway side view of the objective lens concerning the present invention. It is a cutaway side view of the objective lens concerning the present invention. It is a cutaway side view of the objective lens concerning the present invention. It is a cutaway side view of the objective lens concerning the present invention. It is a cutaway side view of the objective lens concerning the present invention. It is a sectional side view of a hologram optical element and an objective lens according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical pick-up apparatus 2 Light source 3 Collimator lens 4 Optical axis 5 Optical information recording medium 6 Information recording surface 7 Polarizing beam splitter 8 Detector 10, 10a, 10b, 10c, 10d, 10f Objective lens (optical element)
11, 11a, 11d, 12d, 22b Optical surfaces 20, 20a, 20b, 20c, 20d Optical path difference providing structure 21 First annular lens surface (annular lens surface)
21a, 21d Diffraction zone 21b Zone-like recess 22 Second zone-like lens surface (zone-like lens surface)
23 Third annular lens surface (annular lens surface)
23b Ring-shaped convex part

Claims (9)

A resin composition for an optical element containing an alicyclic hydrocarbon-based polymer,
The alicyclic hydrocarbon polymer is added in an inert gas atmosphere or an addition polymerizable monomer gas atmosphere using a polymerizable solution containing at least an alicyclic olefin monomer and having an oxygen concentration of 100 ppm or less. A resin composition for an optical element obtained by polymerization. A resin composition for an optical element containing an alicyclic hydrocarbon-based polymer,
The alicyclic hydrocarbon-based polymer contains at least an aromatic vinyl monomer and is subjected to addition polymerization in an inert gas atmosphere or an addition-polymerizable monomer gas atmosphere using a polymerizable solution having an oxygen concentration of 100 ppm or less. After that, a resin composition for optical elements obtained by further adding hydrogen. In the resin composition for optical elements according to claim 1 or 2,
A resin composition for optical elements, comprising at least one stabilizer selected from a hindered amine stabilizer, a phenol stabilizer, a phosphorus stabilizer, and a sulfur stabilizer, or two or more stabilizers. In the resin composition for optical elements as described in any one of Claims 1-3,
A resin composition for an optical element, wherein a melt index (MI) value measured under conditions of a temperature of 260 ° C. and a load of 2.16 kg is in a range of 20 <MI (g / 10 minutes) <60. An optical element obtained by molding the resin composition for an optical element according to any one of claims 1 to 4,
An optical element having a thickness of 3 mm and a light transmittance of 85% or more at a wavelength of 400 nm. The optical element according to claim 5, wherein
An optical element, wherein a predetermined optical path difference providing structure is provided on at least one optical surface. A light collecting device having a light collecting function,
A condensing device comprising the optical element according to claim 5. An optical pickup device for reproducing and / or recording information on an optical information recording medium,
A light source that emits light;
An optical element unit that irradiates the optical information recording medium with the light emitted from the light source and / or collects the light reflected by the optical information recording medium,
The optical element unit includes the optical element according to claim 5 or 6. The optical pickup device according to claim 8,
An optical pickup device characterized in that the light source emits light having a wavelength of 390 nm to 420 nm.

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