JP2008285550A - Plastic optical element material, plastic optical element and optical pick-up device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic material which is improved in photostability and maintains optical characteristics for a long time, while keeping the excellent transparency. <P>SOLUTION: An object lens 10 as a plastic optical element is constituted of a special plastic optical element material. The plastic optical element material comprises a polycarbonate resin, at least one of hindered amine-based stabilizers and at least one of phenol-based stabilizers, wherein the molar ratio of the number (A) of moles of the whole piperidyl groups in the hindered amine-base stabilizer and the number (B) of moles of the whole hydroxyphenyl groups in the phenol-based stabilizer satisfy the inequality: 1<(A)/(B)<20, and the total amount of the contained stabilizers based on 100 pts.mass of the polycarbonate resin is 0.01-5 pts.mass. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a plastic optical element material suitably used for a plastic optical element and the like, a plastic optical element using the same, and an optical pickup device to which the plastic optical element is applied.

  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 element of the medium. And an optical element such as a lens for condensing light.

  The optical element of the optical pickup device is preferably made of plastic as a material because it can be manufactured at low cost by means such as injection molding. As plastics to which optical elements can be applied, copolymers of cyclic olefins and α-olefins (see Patent Document 1) are known.

  On the other hand, when designing the optical element, if the refractive index of the optical material is increased, for example, the curvature of the lens can be reduced and the optical system can be reduced in size, and the aberration can be further reduced. A high polycarbonate resin has a large birefringence and is difficult to apply. In contrast, an aromatic polycarbonate resin obtained by reacting a carbonate precursor with 9,9-bis (4-hydroxyphenyl) fluorenes as a polycarbonate resin with reduced birefringence has a high refractive index and birefringence. For example, a lens molded body made of a polycarbonate resin having a fluorene derivative as a structural unit is disclosed (see Patent Documents 2 and 3).

  By the way, for example, 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, the optical pickup device has a configuration corresponding to the difference in the shape of both media and the wavelength of light to be applied. It is necessary to. 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 new media such as ray discs and information devices for reading and writing information on these media is underway.

However, in so-called next-generation DVDs such as Blu-ray Discs, light having a wavelength of around 400 nm is used for recording and reproducing information. Conventionally proposed polycarbonate resins are UV absorbers such as benzotriazoles and phenolic resins. It is a resin composition composed of a stabilizer formulation combining a stabilizer, a phosphite stabilizer, and the like, and has the following problems. That is, when an optical element is manufactured from a resin composition containing an ultraviolet absorber, the optical element absorbs light in the ultraviolet region near a wavelength of 400 nm, and thus it is difficult to exhibit the original optical function of the optical element. In addition, when an optical element for a pickup device used for recording / reproduction of a next-generation DVD is manufactured using a resin composition composed of a phenol-based stabilizer, a phosphite-based stabilizer alone, or a stabilizer formulation combining them, It has been found that the optical element is not sufficiently durable against light and heat when irradiated with light of a short wavelength, and there arises a problem that the light transmittance is lowered or the optical characteristics are changed.
JP 2002-105131 A JP-A-6-25398 JP 2007-57916 A

  Therefore, the main object of the present invention is to improve the light stability of polycarbonate resin with high refractive index and low birefringence, which is superior in optical design, and maintain its characteristics for a long time while having excellent transparency It is an object of the present invention to provide a plastic optical element material that can be used. Another object of the present invention is to provide a plastic optical element and an optical pickup device using such a plastic optical element material.

According to the present invention,
A polycarbonate resin composed of structural units represented by the following general formula (1) and general formula (2);
At least one hindered amine stabilizer;
At least one phenolic stabilizer;
Have
1 <(A) / (B) <20 moles with respect to the number of moles (A) of all piperidyl groups in the hindered amine stabilizer and the number of moles (B) of all hydroxyphenyl groups in the phenol stabilizer. Ratio
A plastic optical element material is provided which is a resin composition containing 0.01 to 5 parts by mass of the total amount of the stabilizer with respect to 100 parts by mass of a polycarbonate resin.

In formula (1), R ₁ , R ₂ , R ₃ and R ₄ each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a cycloalkyl group, a cycloalkoxyl group, an aryl group or an aryloxy group. A represents an alkylene group, a cycloalkylene group or an arylene group. n, m, o, and p represent an integer of 1 to 4, and q and r represent an integer of 0 to 5.

  In formula (2), B represents an alkylene group, a cycloalkylene group or an arylene group.

  According to the present invention, since the hindered amine stabilizer and the phenol stabilizer are contained in a specific ratio with respect to the polycarbonate resin, the light stability is improved, and the characteristics are improved for a long time while being excellent in transparency. (See the examples below).

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  The plastic optical element material used as a preferred embodiment of the present invention includes a polycarbonate resin composed of structural units represented by the following general formula (1) and general formula (2), and at least one hindered amine stabilizer: And at least one phenol-based stabilizer. The plastic optical element material has 1 <(A) / (B) with respect to the number of moles (A) of all piperidyl groups in the hindered amine stabilizer and the number of moles (B) of all hydroxyphenyl groups in the phenol stabilizer. ) <20 molar ratio, and a resin composition in which the total amount of the stabilizer is 0.01 to 5 parts by mass with respect to 100 parts by mass of the polycarbonate resin.

In formula (1), R ₁ , R ₂ , R ₃ and R ₄ each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a cycloalkyl group, a cycloalkoxyl group, an aryl group or an aryloxy group. A represents an alkylene group, a cycloalkylene group or an arylene group. n, m, o, and p represent an integer of 1 to 4, and q and r represent an integer of 0 to 5.

  In formula (2), B represents an alkylene group, a cycloalkylene group or an arylene group.

  Polycarbonate resin is a resin with excellent optical properties such as transparency and high refractive index. However, in recent years, with the advancement of functions of optical equipment, the physical properties of optical elements and the higher reliability have been achieved. It has been demanded. In particular, environmental fluctuations in optical characteristics are a major issue, and improvement in physical properties such as improvement in light resistance and heat resistance is required in addition to reduction in birefringence.

  In contrast, the polycarbonate resin having a fluorene structure has at least one hindered amine stabilizer and at least one phenol stabilizer, and the number of moles of all piperidyl groups in the hindered amine stabilizer; An optical element manufactured using a resin composition including a stabilizer composition in which the ratio of moles of all hydroxyphenyl groups in the phenol-based stabilizer is controlled has high light transmittance and is stable against light irradiation. For example, even when continuously irradiated with light having a short wavelength of around 400 nm, white turbidity and fluctuations in refractive index are suppressed, and further, for example, deformation of the optical surface in a high temperature environment around 85 ° C. It was found that it can be suppressed for a long time. That is, it has been found that the optical stability and thermal stability of the optical element can be improved, and an element capable of maintaining the characteristics for a long time can be manufactured.

  According to another preferred embodiment of the present invention, there is provided a first plastic optical element manufactured using the plastic optical element material and having a fine structure on the optical surface.

  According to the first plastic optical element, at least one optical surface is provided with a fine structure, and is manufactured using the plastic optical element material, so that it has high shape stability against environmental fluctuations such as light and heat. It can suppress appropriately that a fine structure deform | transforms.

  Preferably, in the first plastic optical element, when the plastic optical element material is used to form a molded body having a thickness of 3 mm, the second plastic optical element has a light transmittance of 85% or more at a wavelength of 400 nm. An element is provided.

  According to the second plastic optical element, the molded body having a thickness of 3 mm formed using the plastic optical element material has high shape stability and transmits light having a wavelength of about 400 nm with high energy. In addition, it is possible to suppress the occurrence of white turbidity, refractive index variation, deformation, and the like in the molded body. Thereby, the light transmittance in the vicinity of a wavelength of 400 nm can be 85% or more. Therefore, for example, it can be suitably used as an optical element for an optical information recording medium having a high information density such as Blu-ray Disc.

  More preferably, in the first or second plastic optical element, a third plastic optical element used for a light condensing device having a light condensing function is provided.

  According to the third plastic optical element, even if the 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 another preferred embodiment of the present invention, there is provided an optical pickup device that performs either reproduction or recording of information on an optical information recording medium, the light source emitting light, and the light emitted from the light source An optical element unit that performs either irradiation of the optical information recording medium or condensing of light reflected by the optical information recording medium, and the optical element unit is any one of the first to third There is provided a first optical pickup device including one plastic optical element.

  According to the first optical pickup device, since the optical element unit has the specific plastic optical element described above, the stabilization effect against light irradiation is high. For example, irradiation with light having a short wavelength near 400 nm is continued. Even if it receives it, the cloudiness and the fluctuation of the refractive index can be suppressed.

  Further, for example, the deformation of the optical surface in a high temperature environment of around 85 ° C. can be suppressed for a long time. 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, information can be read / written with good pickup characteristics over a long period of time on an optical information recording medium having a high information density such as a Blu-ray Disc, and the optical pickup device is reliable. You can get something expensive.

  Preferably, in the first optical pickup device, a second optical pickup device is provided in which the light source emits light having a wavelength of 390 to 420 nm.

  According to the second optical pickup device, the wavelength of light emitted from the light source is 390 to 420 nm. That is, for example, 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 Blu-ray Disc, the resin applied to the optical element in the preferred embodiment of the present invention The composition comprises at least one hindered amine stabilizer and at least one phenol stabilizer relative to the polycarbonate resin having a fluorene structure, the number of moles of all piperidyl groups in the hindered amine stabilizer and the above Since the resin composition includes a stabilizer composition in which the molar ratio of the total number of hydroxyphenyl groups in the phenol-based stabilizer is controlled, deterioration of the optical element such as white turbidity and refractive index fluctuation can be prevented. Thereby, the lifetime of the optical element can be extended, and a highly reliable optical pickup device can be obtained.

  The plastic optical element material used for the plastic optical element according to a preferred embodiment of the present invention is a polycarbonate resin having a fluorene structure, and at least one hindered amine stabilizer and at least one phenol stabilizer. A resin composition comprising a stabilizer composition in which the ratio of the number of moles of all piperidyl groups in the hindered amine stabilizer to the number of moles of all hydroxyphenyl groups in the phenol stabilizer is controlled. It is said. In general, when compared with inorganic materials such as glass and ceramics, plastic optical materials have a large problem of fluctuations in optical characteristics of elements in optical systems using a light source of 390 to 420 nm and applications used in a high temperature environment.

  On the other hand, as a result of intensive studies to solve the above problems, the present inventors can suppress fluctuations in optical properties under a high temperature environment of, for example, about 85 ° C. by using the plastic optical element material described above, and For example, it has high stabilization effect against light irradiation, such as maintaining transparency and suppressing white turbidity and refractive index fluctuations even when continuously irradiated with light having a short wavelength of around 400 nm. Thermal stability of optical elements It has been found that a device capable of improving the light stability and capable of maintaining the characteristics for a long time can be manufactured.

  In the following, preferred embodiments of the present invention will be described in more detail.

(Polycarbonate resin)
The polycarbonate resin used in a preferred embodiment of the present invention has a chemical structure in which the structural unit represented by the general formula (1) and the structural unit represented by the general formula (2) are alternately bonded.

  The structural unit represented by the general formula (1) forming the polycarbonate resin is obtained from a dihydroxy compound having a fluorene skeleton, specifically, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis. 9,9-bis (4-hydroxyphenyl) fluorenes such as (3-methyl-4-hydroxyphenyl) fluorene, 9,9-bis (3-ethyl-4-hydroxyphenyl) fluorene, and 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-methylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy)- 3,5-dimethylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-tert-butylphenyl) fur 9,9 such as lenene, 9,9-bis (4- (2-hydroxyethoxy) -3-isopropylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-cyclohexylphenyl) fluorene -Bis (4-hydroxyalkoxyphenyl) fluorenes and the like are exemplified.

On the other hand, as the structural unit represented by the general formula (2) forming the polycarbonate resin, tricyclo [5.2.1.0 ^2,6 ] decanedimethanol, cyclohexane-1,4-dimethanol, norbornane dimethanol, It can be obtained from dihydroxy compounds such as pentacyclopentadecane dimethanol, cyclopentane-1,3-dimethanol and 1,4-butanediol.

  The polycarbonate resin is produced by an interfacial polycondensation method using phosgene or the transesterification reaction using a carbonic acid diester.

(Resin composition)
The plastic optical element is molded using a resin composition containing various stabilizers in the polycarbonate resin.

  As the stabilizer, a hindered amine stabilizer and a phenol stabilizer are used, and together with these, a phosphorus stabilizer may be appropriately added. By adding these stabilizers to an appropriate amount of resin, a high temperature is added. It is possible to synergistically enhance the effect of suppressing deterioration of optical characteristics with respect to light irradiation with a short wavelength under the environment, and a more reliable optical pickup device can be obtained.

  Specifically, among the hindered amine stabilizer and the phenol stabilizer, the number of moles of all piperidyl groups in the hindered amine stabilizer (A) and the number of moles of all hydroxyphenyl groups in the phenol stabilizer ( In the case of B), the molar ratio is 1 <(A) / (B) <20.

  That is, when ensuring the stability of various resins to light, heat, etc., when using a hindered amine stabilizer and a phenol stabilizer together, it is based on the basicity of the hindered amine stabilizer and the acidity of the phenol stabilizer. Since antagonism due to salt formation occurs, the radical species scavenging ability is more efficiently exhibited by optimizing the amount of hindered amine stabilizer and phenol stabilizer so that they are within the above ranges. be able to.

  Examples of 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-t-butyl-4-hydroxybenzyl) -2-butyl malonate, bis (1-acryloyl-2,2,6,6-tetra Til-4-piperidyl) 2,2-bis (3,5-di-t-butyl-4-hydroxybenzyl) -2-butylmalonate, bis (1,2,2,6,6-pentamethyl-4- Piperidyl) decanedioate, 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, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) ) 1,2 3,4-butane tetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) 1,2,3,4-butane tetracarboxylate, and the like.

  In this embodiment, at least one hindered amine stabilizer selected from the above is added to the resin composition.

  Conventionally known phenol-based stabilizers can be used, such as 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, etc. JP-A 63-179953 and JP-A 1-168643 Acrylate compounds described in the publication: octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 2,2′-methylene-bis (4-methyl-6-tert-butylphenol) 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di- t-butyl-4-hydroxybenzyl) benzene, tetrakis (methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenylpropionate) methane [ie, pentaerythrmethyl-tetrakis (3 Alkyl substitution such as-(3,5-di-t-butyl-4-hydroxyphenylpropionate)), triethylene glycol bis (3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate) Phenolic compounds; 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, etc. Triazine group-containing phenol compounds.

  In this embodiment, at least one phenol-based stabilizer selected from the above is added to the resin composition.

  Among these, a compound having a bulky substituent such as a t-butyl group at the ortho position with respect to the hydroxyl group in the hydroxyphenyl skeleton is preferably used.

  The 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 (nonylphenyl) phosphine. Phyto, tris (dinonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, 10- (3,5-di-t-butyl-4-hydroxybenzyl) -9,10- Monophosphite compounds such as dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; 4,4′-butylidene-bis (3-methyl-6-tert-butylphenyl-di-tridecyl phosphite) 4,4 'isopropylidene-bis (phenyl-di-alkyl (C12-C15) phosphite), etc. Diphosphite compounds and the like. 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.

  In the present embodiment, at least one phosphorus-based stabilizer selected from the above may be added to the resin composition.

  The blending amount of these stabilizers is appropriately selected within a range that does not impair the object of the preferred embodiment of the present invention, but with respect to 100 parts by mass of the polycarbonate resin, a stabilizer of a hindered amine stabilizer and a phenol stabilizer ( When a phosphorus stabilizer is added, the total amount of hindered amine stabilizer, phenol stabilizer and phosphorus stabilizer) is 0.01 to 5 parts by mass, preferably 0.01 to 1 part by mass.

(Other ingredients)
If necessary, the resin composition may contain other additives such as UV absorbers, light stabilizers, near-infrared absorbers, coloring agents such as dyes and pigments, lubricants, plasticizers, antistatic agents, and fluorescent whitening. An agent or the like can be blended, and these can be used alone or in admixture of two or more, and the blending amount is appropriately selected within a range that does not impair the object of the preferred embodiment of the present invention.

(Molding material)
The resin composition can be obtained by appropriately mixing the above components. The mixing method is not particularly limited as long as each component is sufficiently dispersed in the hydrocarbon polymer. For example, the resin is melted in a mixer, a twin-screw kneader, a roll, a Brabender, an extruder, or the like. And a method of dissolving and dispersing in a suitable solvent and solidifying. 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.

(Plastic optical element)
The plastic optical element according to this embodiment is obtained by molding a molding material made of the resin composition. 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 injection molding is usually 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 plastic optical element according to the present embodiment 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 or a sheet shape, and has a low birefringence. Excellent in transparency, transparency, mechanical strength, and heat resistance.

  Specific examples of the plastic 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 made of plastic is suitable for use as an optical system lens or a laser scanning system lens constituting an optical pickup device requiring low birefringence, and used as an optical system lens of the optical pickup device. Most preferably.

  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 this embodiment is used as at least one single lens optical lens among the plurality of single lens optical lenses. It is preferable to use a plastic optical element.

(Optical pickup device)
Next, the optical pickup device according to this embodiment will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of the overall configuration of the optical pickup device, and FIG. 2 is a side view of the main part showing the structure of the objective lens.

  The optical pickup device 1 has two types, a current DVD that applies light with a wavelength of 650 nm (hereinafter referred to as current DVD) and a so-called next-generation DVD that applies light with a wavelength of 390 to 420 nm (hereinafter referred to as next-generation DVD). This is an apparatus for reproducing and recording information on the optical information recording medium 5.

  The optical pickup device 1 passes laser light (light) emitted from a laser oscillator (light source) 2 through a collimator lens 3 and an objective lens (plastic optical element) 10 to be described later, and optical information on the optical axis 4. A light collecting spot is formed by collecting on the information recording surface 6 of the recording medium 5, reflected light from the information recording surface 6 is taken in by the deflecting beam splitter 7, and a beam spot is formed again on the light receiving surface of the detector 8. is there.

  The light source 2 includes a laser diode, and is configured to be able to select and emit light having two types of wavelengths of 650 nm and 390 to 420 nm by a known switching method.

  The objective lens 10 is produced by molding the above resin composition by injection molding. As shown in FIG. 2, the objective lens 10 is a single lens having a double-sided aspheric surface, and is predetermined for a predetermined light beam passing through the optical surface 11 on one (light source side) optical surface 11. The optical path difference providing structure (fine 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 390 to 420 nm, and 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. No. 23 transmits light having a wavelength of 390 to 420 nm corresponding to the next generation DVD. 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 lens 10 is applied with the resin composition described above, when the lens 10 is melted and injected into a mold and molded, the first annular lens surface 21, the second annular lens surface 22, and the third lens surface of the mold are used. The resin has surely spread to the portion corresponding to the boundary portion of the annular lens surface 23. Therefore, the 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 lens 10 focuses 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. Then, the light reflected from the information recording surface 6 toward the detector 8 can be condensed with high reliability.

  Further, since the resin composition contains the stabilizer having the above composition, even when light of 390 to 420 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 embodiment is not limited to the one having the optical path difference providing structure 20, and may be lenses 10a to 10e having the 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 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 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 lens 10 has the same structure as the lens 10 shown in FIG. 2). Also, in FIG. 4, the annular concave portion 21b is concentrically formed, but as shown in FIG. 5, the lens 10c having the convex portion 23b on the third annular lens surface 23 of FIG. Good (in FIG. 5, components similar to 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.

  Note that the optical pickup device 1 may reproduce and record information 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.

  As described above, the plastic optical element of the present embodiment is molded using a resin composition in which a hindered amine stabilizer that functions as a light-resistant stabilizer and a phenol stabilizer are mixed with a polycarbonate resin having a fluorene structure. In the resin composition, the ratio (A) / (B) of the number of moles (A) of all piperidyl groups in the hindered amine stabilizer to the number of moles (B) of all hydroxyphenyl groups in the phenol stabilizer is 1 Since each stabilizer is added so that <(A) / (B) <20, the synergistic effect on the radical species scavenging ability is more efficiently exhibited based on the coexistence of these stabilizers. It will be. As a result, even if irradiation with light having a short wavelength such as 390 to 420 nm is continuously received, deterioration such as white turbidity and refractive index fluctuation of the optical element can be effectively suppressed. That is, the light stability of the optical element can be improved, and the characteristics can be maintained for a long time.

  Therefore, by using the plastic optical element according to the present embodiment for the optical pickup device, the optical information recording medium having a high information density such as Blu-ray Disc can be recorded with good pickup characteristics over a long period of time. Reading and writing can be performed, and a highly reliable optical pickup device can be obtained.

  Furthermore, by adding at least one stabilizer selected from among phosphorus-based stabilizers to the resin composition, for example, the effect of suppressing deterioration against light irradiation with a short wavelength can be enhanced more synergistically.

  In addition, this invention is not limited to the said embodiment, You may perform a various improvement and change in the range which does not deviate from the meaning of this invention.

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

(Production Example 1)
According to the method described in JP-A-10-101786, A: 9,9-bis (4- (2-hydroxyethoxy) phenyl) as a dihydroxy compound in a reaction layer equipped with a stirrer, a distiller and a decompressor. Fluorene, B: Tricyclo [5.2.1.0 ^2,6 ] decanedimethanol was charged so that the molar ratio was A / B = 10/1, and polymerization was performed to obtain “polycarbonate resin A”. The obtained polycarbonate resin A had Mw (molecular weight) = 65,100 and Tg (glass transition temperature) = 150 ° C.

(Production Example 2)
In Production Example 1, A: 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, B: 2,2-bis (4-hydroxyphenyl) propane as a dihydroxy compound in the reaction layer in a molar ratio. Polymerization was carried out in the same manner except that it was charged so that A / B = 1/1, and “polycarbonate resin B” was obtained. Obtained polycarbonate resin B was Mw = 62,100 and Tg = 154 degreeC.

[Example 1]
Tetrakis (2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butanetetra as a hindered amine stabilizer with respect to 100 parts by mass of the polycarbonate resin A obtained in Production Example 1. Carboxylate (ADK STAB LA-57, manufactured by Asahi Denka Co., Ltd.) 1.0 part by mass, and n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate ( 2.3 parts by weight of ADK STAB AO-50, manufactured by Asahi Denka Co., Ltd., and a twin-screw kneader (manufactured by Toshiba Machine, TEM-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.

  At this time, the composition ratio of the hindered amine stabilizer to the phenol stabilizer is the mole number of the piperidyl group in the hindered amine stabilizer (A) and the number of moles of the hydroxyphenyl group in the phenol stabilizer (B). The ratio is (A) / (B) = 1.17. The total amount of the hindered amine stabilizer and the phenol stabilizer relative to the polycarbonate resin A (100 parts by mass) is 3.3 parts by mass (= 1.0 + 2.3).

  The obtained pellets were dried at 70 ° C. for 2 hours using a hot air dryer in which air was circulated to remove moisture, and then the cylinder temperature was 280 ° C. and the mold was molded by an injection molding machine (AUTOSHOTOMODE 30A manufactured by FANUC). Injection molding was performed at a temperature of 80 ° C., a primary injection pressure of 98.1 MPa, and a secondary injection pressure of 78.4 MPa to obtain a plate-like “plastic optical element 1” having a resin substrate, Φ30 mm, and a thickness of 3 mm.

[Example 2]
In Example 1, n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Adekastab AO-50, manufactured by Asahi Denka Co., Ltd.) 0.5 mass as a phenol-based stabilizer Parts (molar ratio of moles of piperidyl groups in hindered amine stabilizer (A) to moles of hydroxyphenyl groups in phenol stabilizer (B), (A) / (B) = 5.37). A “plastic optical element 2” was obtained in the same manner as above.

[Example 3]
In Example 1, n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (ADK STAB AO-50, manufactured by Asahi Denka Co., Ltd.) 0.14 mass as a phenol-based stabilizer Parts (molar ratio of moles of piperidyl group in hindered amine stabilizer (A) to moles of hydroxyl group of phenolic stabilizer (B), (A) / (B) = 19.0) A “plastic optical element 3” was obtained in the same manner as above.

[Example 4]
In Example 2, 0.5 parts by mass of tris (2,4-di-t-butylphenyl) phosphite (Adeka Stub 2112, manufactured by Asahi Denka Co., Ltd.) is additionally added as a phosphorus stabilizer during kneading. Except for the above, the same operation was performed to obtain “plastic optical element 4”.

[Example 5]
In Example 2, the same operation was performed except that the polycarbonate resin B was used instead of the polycarbonate resin A, to obtain “plastic optical element 5”.

[Example 6]
In Example 3, the same operation was performed except that the polycarbonate resin B was used instead of the polycarbonate resin A to obtain “plastic optical element 6”.

(Comparative Example 7)
In Example 1, n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Adeka Stub AO-50, manufactured by Asahi Denka Co., Ltd.) 3.0 mass as a phenol-based stabilizer Parts (molar ratio of moles of piperidyl group in hindered amine stabilizer (A) to moles of hydroxyphenyl group in phenol stabilizer (B), (A) / (B) = 0.9) A “plastic optical element 7” was obtained in the same manner as above except for adding.

(Comparative Example 8)
In Example 1, n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Adeka Stub AO-50, manufactured by Asahi Denka Co., Ltd.) 0.12 mass as a phenol-based stabilizer Parts (molar ratio of moles of piperidyl group in hindered amine stabilizer (A) to moles of hydroxyl group of phenolic stabilizer (B), (A) / (B) = 2.38) A “plastic optical element 8” was obtained in the same manner as above.

(Comparative Example 9)
In Example 1, do not add n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Adeka Stab AO-50, manufactured by Asahi Denka) as a phenol-based stabilizer. Except for the above, the same operation was performed to obtain “plastic optical element 9”.

(Comparative Example 10)
In Example 1, n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Adekastab) was used as a phenol stabilizer without adding a hindered amine stabilizer during kneading. AO-50 (manufactured by Asahi Denka Co., Ltd.) was subjected to the same operation except that 1.0 part by mass was added to obtain “plastic optical element 10”.

<< Evaluation of plastic optical elements >>
Next, for the obtained plastic optical elements 1 to 10, each optical characteristic was evaluated according to the following method, and the obtained results are shown in Table 1.

(Colorability and transparency evaluation)
About each said plastic optical elements 1-10, the light transmittance by wavelength 400nm was measured, the color tone through the transmitted light was visually observed, and coloring property and transparency were evaluated. As a result, each of the plastic optical elements 1 to 10 had a light transmittance of 86% or more 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 is emitted from the laser diode of the light source 2 onto each plastic optical element 1 to 10 with a diameter of 1 mm. After continuous irradiation for 1500 hours as a circular spot light, the laser irradiation spot was visually observed, and transparency (coloring degree) and shape stability due to white turbidity were evaluated according to the following criteria.

<Evaluation of coloring>
○: Slight turbidity is observed at the laser irradiation location after continuous irradiation △: Turbidity is observed at the laser irradiation location after continuous irradiation ×: White turbidity is observed at the laser irradiation location after continuous irradiation If it is “Δ” or more (if it is ◯, Δ), it is practically acceptable.

<Evaluation of shape stability>
◎: After the continuous irradiation, no deformation of the laser irradiated portion is observed. ○: After the continuous irradiation, the laser irradiated portion is slightly deformed. Δ: After the continuous irradiation, the laser irradiated portion is slightly deformed. After the irradiation, deformation is observed in the laser irradiation portion. In this evaluation, if it is “Δ” or more (in the case of ◎, ○, Δ), it is within a practically acceptable range.

  As is clear from the results shown in Table 1, the plastic optical element molded using the resin composition according to the example of the present invention is obtained by continuously irradiating light of a short wavelength for a long time with respect to the comparative example. No coloration or white turbidity occurred, and no deformation occurred, and high shape stability could be maintained.

<Production of optical pickup device>
An optical element (objective lens) having the same composition as that of the plastic optical elements 1 to 10 described in Example 1 and the structure illustrated in FIGS. 2 to 7 is manufactured by injection molding, and the structure illustrated in FIG. Thus, optical pickup devices 1 to 6 according to examples of the present invention and optical pickup devices 7 to 10 of comparative examples were produced. Next, using each of the optical pickup devices 1 to 10, recording and reproduction on a DVD were performed using light of a wavelength of 405 nm by a laser diode.

<Evaluation of optical pickup device>
The optical pickup devices 1 to 6 manufactured using the plastic optical elements 1 to 6 according to the examples of the present invention showed good pickup characteristics even after continuous irradiation for a long time.
On the other hand, in the optical pickup devices 7 to 10 manufactured using the plastic optical elements 7 to 10 of the comparative example, the pickup characteristics deteriorate as the optical surface structure is formed more finely (complex). It was.

1 is a side view schematically showing an optical pickup device according to an embodiment of the present invention. It is a cutaway side view of the objective lens concerning the embodiment of the present invention. It is a cutaway side view of the objective lens concerning the embodiment of the present invention. It is a cutaway side view of the objective lens concerning the embodiment of the present invention. It is a cutaway side view of the objective lens concerning the embodiment of the present invention. It is a cutaway side view of the objective lens concerning the embodiment of the present invention. It is a sectional side view of a hologram optical element and an objective lens according to an embodiment of 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 (Plastic optical element, objective optical element )
11, 11a, 11d, 12d, 22b Optical surface 20, 20a, 20b, 20c, 20d Optical path difference providing structure 21 First annular lens surface (annular lens surface)
22 Second annular lens surface (annular lens surface)
23 Third annular lens surface (annular lens surface)
23b Ring-shaped convex part

Claims (6)

A polycarbonate resin composed of structural units represented by the following general formula (1) and general formula (2);
At least one hindered amine stabilizer;
At least one phenolic stabilizer;
Have
1 <(A) / (B) <20 moles with respect to the number of moles (A) of all piperidyl groups in the hindered amine stabilizer and the number of moles (B) of all hydroxyphenyl groups in the phenol stabilizer. Ratio
A plastic optical element material, which is a resin composition in which the total amount of the stabilizer is 0.01 to 5 parts by mass with respect to 100 parts by mass of the polycarbonate resin.

(In formula (1), R ₁ , R ₂ , R ₃ and R ₄ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a cycloalkyl group, a cycloalkoxyl group, an aryl group or an aryloxy group. A represents an alkylene group, a cycloalkylene group, or an arylene group, n, m, o, and p represent an integer of 1 to 4, and q and r represent an integer of 0 to 5.)

(In formula (2), B represents an alkylene group, a cycloalkylene group or an arylene group.)   A plastic optical element manufactured using the plastic optical element material according to claim 1 and having a fine structure on an optical surface.   3. The plastic optical element according to claim 2, wherein when the plastic optical element material is used to form a molded body having a thickness of 3 mm, the light transmittance at a wavelength of 400 nm is 85% or more.   4. The plastic optical element according to claim 2, wherein the plastic optical element is used in a light collecting device having a light collecting function. An optical pickup device that performs either reproduction or recording of information on an optical information recording medium,
A light source that emits light;
An optical element unit that performs either irradiation of the light emitted from the light source onto the optical information recording medium or condensing of the light reflected by the optical information recording medium,
The said optical element unit is equipped with the plastic optical element as described in any one of Claims 2-4, The optical pick-up apparatus characterized by the above-mentioned.   The optical pickup device according to claim 5, wherein the light source emits light having a wavelength of 390 to 420 nm.

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