JP2005292184A - Optical unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical unit having two or more plastic lenses having high resolution and corrected color aberration. <P>SOLUTION: The optical unit comprises at least a first plastic lens and a second plastic lens and is characterized in that: (1) the first plastic lens is obtained by molding a composition containing polycarbonate which has structural units expressed by specified formula (A), formula (B) and formula (C) with the structural unit of formula (A) included by 5 to 40 mol% in the entire structural units and which has 0.30 to 0.50 dl/g intrinsic viscosity; and (2) the second plastic lens has 45 to 50 Abbe number. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-resolution optical unit used for a silver salt camera, a digital camera, a video camera, a small camera for incorporation into a mobile phone, and the like. Specifically, the optical unit has two or more plastic lenses and has a high resolution. The chromatic aberration is corrected with respect to the optical unit.

  Due to the rapid increase in resolution and cost reduction of imaging semiconductors in recent years, the optical unit used therefor is required to have higher resolution, smaller size, lighter weight, and lower cost. In order to reduce the size and weight and reduce the cost, it is desirable to use a plastic lens as the lens used in the optical unit. For low-resolution applications, an optical unit in which all the lenses are plastic lenses is used. It is popular.

  However, the plastic material has a larger birefringence than glass, and when used as a lens of an optical unit, this has a problem of adversely affecting the resolution. In low-resolution applications, the required resolution is low, which is not a problem. However, high resolution (for example, a spatial frequency (MTF) with a contrast of 20% and a resolution of 150 lines / mm or more, or about 200 lines / mm) As described above, since the desired resolution cannot be obtained in applications, it is not possible to make all the lenses constituting the optical unit plastic lenses.

In the optical design of the optical unit, it is known to correct chromatic aberration by using a combination of a plurality of lenses having different Abbe numbers. In the case of an optical unit for high-resolution applications, there is no known combination of plastic lenses that can solve the above-mentioned problem of birefringence of plastic lenses with a combination of appropriately different Abbe numbers.
Therefore, chromatic aberration is corrected by combining a plastic lens and a glass lens having different Abbe numbers.

Alicyclic polyolefin resins, commercially Nippon Zeon Zeonex (ZEONEX) ^TM, JSR ARTON Co., Ltd. (ARTON) ^TM, manufactured by Mitsui Chemicals, Inc. of APEL (APEL) ^TM and the like are known, optical Used for unit lenses.
Further, the correction of chromatic aberration is performed by combining a lens made of an alicyclic polyolefin resin having an Abbe number of 45 to 60 and a lens made of a bisphenol A type polycarbonate resin having a lower Abbe number (for example, about 30). It has been broken. However, the polycarbonate resin has a large intrinsic birefringence of 0.106 (see Non-Patent Document 1), and cannot be applied to a high-resolution optical unit.

  On the other hand, a small imaging module mounted on a mobile phone, a PDA (Personal Digital Assistant), or a small digital camera usually has a holding member (hereinafter referred to as a CCD holder) that holds an imaging element (usually a CCD sensor); It is configured by combining with a lens barrel that holds an imaging lens.

  Such a small imaging module generally uses a CCD holder having a through hole, and a CCD sensor is fixed to one end of the through hole of the CCD holder, and a lens barrel holding an imaging lens is inserted / inserted from the other end side. It is assembled by fixing.

  An imaging lens having high resolution is difficult to realize with a single lens. Therefore, normally, an imaging lens having a desired resolution and accuracy is realized as a combined lens in which a plurality of lenses are combined.

Such an imaging lens (optical unit) formed by combining a plurality of lenses usually has a plurality of lenses having different outer diameters and a lens holding portion having a size corresponding to each lens diameter in a stepped manner. In accordance with the lens diameter, each lens is sequentially incorporated in the lens barrel, and each lens is fixed to the lens barrel.
Fumio Ide, “Transparent Resins That Have Been Here”, Industrial Research Committee, p. 29, 2001.

In the case of an optical unit for high-resolution applications, there is no known combination of plastic lenses that can solve the above-mentioned problem of birefringence of plastic lenses with a combination of appropriately different Abbe numbers.
In addition, in order to capture a high-quality image, it is necessary that the optical axes of the lenses incorporated in the lens barrel are properly matched. In particular, in a small imaging unit, the optical unit is required to have high resolution as described above. Therefore, if there is even a slight shift in the optical axis between lenses (hereinafter referred to as decentering between lenses), a very large image quality is obtained. Causes deterioration.
However, there is a gap (clearance) between the lens barrel and the lens for incorporating the lens into the lens barrel. Therefore, in this, the incorporated lens moves, and the inter-lens eccentricity occurs.

An object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a high-resolution optical unit with a combination of plastic lenses having appropriately different Abbe numbers.
In addition, by simply combining plastic lenses, the optical axes of the lenses can be aligned with each other in the direction orthogonal to the optical axis, and the optical axes are not shifted from each other thereafter. The object is to provide an optical unit (lens unit).

In order to achieve the above object, the present invention provides the following inventions.
[1] An optical unit comprising at least a first plastic lens and a second plastic lens,
(1) The first plastic lens has structural units represented by the following formula (A), formula (B), and formula (C), and the structural unit of formula (A) is 5 in all structural units. Obtained by molding a composition containing polycarbonate having a viscosity of ˜40 mol% and an intrinsic viscosity of 0.30 to 0.50 dl / g,
(2) An optical unit in which the Abbe number of the second plastic lens is 45-60.
[2] The optical unit according to [1], wherein a molecular terminal of the polycarbonate is derived from a monohydric phenol represented by the formula (D) described later.
[3] The first and second plastic lenses each have a flange portion around the lens portion having an optical action, and the flange portions of the first and second plastic lenses are respectively The flange portion of the second and first plastic lenses or a spacer provided between the first and second plastic lenses can be fitted, and the first and second lenses can be fitted with the flange portion. The optical unit according to the above [1] or [2], which has a shape in which the optical axes coincide with each other in a state of being combined by mutual fitting or by fitting the spacer and the flange portion.
[4] The lens has a shape in which the positions in the optical axis direction of each other are appropriate in a state of being combined with another lens by fitting the flange portion or the spacer and the flange portion. The optical unit according to [3].
[5] The optical unit according to any one of [1] to [4], wherein at least the first plastic lens has a moisture-proof coating on the entire surface thereof.
[6] The optical unit according to [5], wherein the moisture-proof coating is a Si—O-based film formed by a sputtering method.
[7] The optical unit according to [5], wherein the moisture-proof coating is a film having vinylidene chloride.

  In such a lens unit of the present invention, it is preferable that the lens has a shape in which the position in the optical axis direction of each other is appropriate in a state where the lens is combined with other lenses by fitting the flange portions. Further, the lens is formed by injection molding, and in contact with the other lens in the optical axis direction in the combined state, and in contact with the other lens in the direction perpendicular to the optical axis in the combined state. Preferably, at least one of the surfaces does not have a nested score line.

The optical unit of the present invention is composed of a combination of two or more plastic lenses, corrects chromatic aberration, does not adversely affect resolution due to birefringence, and is excellent as an optical unit for high resolution applications.
The optical unit of the present invention is suitable for applications that require a reduction in size and weight if all the lenses are made of plastic lenses.

In addition, since the first plastic lens material is a specific polycarbonate material excellent in fluidity, the optical unit of the present invention can be injection-molded at a lower temperature and can be molded at the time of injection molding. Is excellent. Therefore, the productivity of the lens is excellent, and the cost of the optical unit can be reduced.
In addition, this specific polycarbonate material has sufficient mechanical strength as a lens constituting the optical unit, despite being excellent in fluidity.

  Moreover, since it is excellent in moldability at the time of injection molding, lenses having various shapes can be molded and used. By using a lens having an optical axis alignment structure of the lens or an alignment structure in the optical axis direction of the lens as such a lens, the optical axis alignment of the lens or the optical axis direction of the lens when assembling the optical unit. Can be easily aligned. Further, if the gate mark, which is a characteristic of a lens manufactured by injection molding, is used as a mark for optical axis alignment, the optical axis alignment can be easily performed.

  In the optical unit of the present invention in which a moisture-proof coating is formed on the entire surface of at least the second plastic lens, the optical performance of the lens changes due to changes in the environment, more specifically, changes in the humidity of the environment where the optical unit is placed. Can be prevented.

<Optical unit>
Hereinafter, an example of the optical unit of the present invention will be described with reference to the drawings.
FIG. 1 is a side sectional view of one embodiment of the optical unit of the present invention. The optical unit of the present invention includes at least a first plastic lens 2 and a second plastic lens 3. The plastic lens may be two or more lenses having specific characteristics described later. By combining multiple lenses with the same characteristics or having other lenses, any combination such as 3, 4, 5 or more may be used. If necessary, a glass lens and two or more plastic lenses can be combined. good. The optical unit 1 shown in FIG. 1 has two plastic lenses 2 and 3 housed in a cylindrical lens barrel 5.

  Hereinafter, in the description of the drawings, the incident side of the optical unit 1 with respect to the photographing light is a front part, and the opposite side is a rear part. Reference numeral 2 denotes a first plastic lens located on the incident side of the photographing light, that is, the front part, and 3 denotes a second plastic lens located on the rear part. In the lens barrel 4, the two lenses 2 and 3 are fixed via a spacer 6. The spacer 6 properly aligns the positions of the lenses 2 and 3 in the optical direction. The lens 2 located on the front side is fixed by a lens presser 7 to prevent the lens 2 from dropping off.

<First plastic lens>
In the optical unit of the present invention, the first plastic lens has structural units represented by the following formulas (A) to (C), and the structural unit of the formula (A) is 5 to 40 mol in all the structural units. % And obtained by molding a composition containing a polycarbonate having an intrinsic viscosity of 0.30 to 0.50 dl / g.

｛（Ｃ）式中Ｗは、

{W in formula (C)

R _{1 to} R ₄ are each independently hydrogen, fluorine, chlorine, bromine, iodine, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, An alkoxy group having 1 to 5 carbon atoms or an aralkyl group having 7 to 17 carbon atoms. However, when these groups have carbon, they are selected from an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, fluorine, chlorine, bromine and iodine. Also included are those substituted with halogen, dimethylpolysiloxy groups, and alkylarylpolysiloxy groups.
Y is

Wherein R ₅ and R ₆ are each independently hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Represents a group, or R ₅ and R ₆ are bonded together to form a carbocyclic or heterocyclic ring. However, when these groups contain carbon, they are substituted with an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, fluorine, chlorine, bromine, and iodine. Including those that have been. a represents an integer of 0 to 20, and b represents an integer of 1 to 100. )

  The polycarbonate contained in the composition of the present invention is a known method used in producing a polycarbonate from bisphenol A, for example, a direct reaction of a dihydric phenol and phosgene (phosgene method), or a dihydric phenol and bisaryl. It can be produced by a method such as transesterification with carbonate (transesterification method).

  In the former phosgene method, usually in the presence of an acid binder and a solvent, 1,1′-bi-2-naphthol for deriving the formula (A) in the present invention and 4,4 ′ for deriving the formula (B) are used. -[1,3-phenylenebis (1-methylethylidene)] bisphenol and a dihydric phenol derived from formula (C) are reacted with phosgene. Examples of the acid binder include pyridine and alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. As the solvent, for example, methylene chloride, chloroform, chlorobenzene, xylene and the like are used. Further, in order to accelerate the polycondensation reaction, a tertiary amine catalyst such as triethylamine and a catalyst such as a quaternary ammonium salt are used, and phenol, pt-butylphenol, p-cumylphenol are used for adjusting the degree of polymerization. A monofunctional group compound such as phenols represented by the formula (D) is added as a molecular weight regulator.

（式中、Ｒ₇ は炭素数４〜２０のアルキル基を示し、Ｒ₈ 〜Ｒ₉は各々独立に、水素、炭素数１〜６のアルキル基、炭素数２〜６のアルケニル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表す。Ｚはエステル基、エーテル基、カルボニル基を表すか、単に結合を表す。）

(Wherein R ₇ represents an alkyl group having 4 to 20 carbon atoms, and R _{8 to} R ₉ each independently represents hydrogen, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or a carbon number. Represents an alkoxy group having 1 to 6 or an aryl group having 6 to 12 carbon atoms, Z represents an ester group, an ether group, a carbonyl group, or simply represents a bond.)

  In addition, antioxidants such as sodium sulfite and hydrosulfite, phloroglucin, isatin bisphenol, 1,1,1-tris (4-hydroxyphenyl) ethane, α, α ', α "-tris (4 A small amount of a branching agent such as -hydroxyphenyl) -1,3,5-triisopropylbenzene may be added, and the reaction is usually in the range of 0 to 150 ° C., preferably 5 to 40 ° C. Although the reaction time depends on the reaction temperature, it is usually 0.5 minutes to 10 hours, preferably 1 minute to 2 hours, and it is desirable to maintain the pH of the reaction system at 10 or more during the reaction. .

  On the other hand, in the transesterification method, 1,1′-bi-2-naphthol, 4,4 ′-[1,3-phenylenebis (1-methylethylidene)] bisphenol and a dihydric phenol derived from the formula (C) And bisaryl carbonate are mixed and reacted at high temperature under reduced pressure. At this time, a monofunctional compound such as pt-butylphenol, p-cumylphenol, or a phenol represented by the formula (D) may be added as a molecular weight regulator. The reaction is usually carried out at a temperature in the range of 150 to 350 ° C., preferably 200 to 300 ° C., and the degree of vacuum is preferably 1 mmHg or less, and is derived from the bisaryl carbonate produced by the transesterification reaction. The phenols to be distilled out. The reaction time depends on the reaction temperature and the reduced pressure, but is usually about 1 to 6 hours. The reaction is preferably carried out in an inert gas atmosphere such as nitrogen or argon. Moreover, you may react by adding antioxidant and a branching agent as needed.

  In the phosgene method and the transesterification method, the phosgene method is preferred in consideration of the reactivity of the compound that induces the structure of formula (A) and the compound that induces the structure of formula (B).

  Specific examples of the dihydric phenol derived from the formula (C) used for the production of polycarbonate include 4,4′-biphenyldiol, bis (4-hydroxyphenyl) methane, bis (4-hydroxyphenyl) ether, Bis (4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfoxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) ketone, 1,1-bis (4-hydroxyphenyl) ethane, 2 , 2-bis (4-hydroxyphenyl) propane (bisphenol A; BPA), 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) cyclohexane (bisphenol Z) BPZ), 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4- Droxy-3-bromophenyl) propane, 2,2-bis (4-hydroxy-3-chlorophenyl) propane, 2,2-bis (4-hydroxy-3-methylphenyl) propane (dimethylbisphenol A; DMBPA), 2 , 2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane (bisphenol AP; BPAP), bis (4-hydroxyphenyl) diphenylmethane, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, 2,2-bis (4-hydroxy-3-allylphenyl) propane, α, ω-bis [2- (p-hydroxyphenyl) ethyl] polydimethyl Siloxane, α, ω-bis [3- (o-hydroxyphenyl) propyl] polydimethylsiloxane, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, 2,2-bis (4-hydroxy-3 -A Ruphenyl) propane, 3,3,5-trimethyl-1,1-bis (4-hydroxyphenyl) cyclohexane, 6,6'-dihydroxy-3,3,3 ', 3'-tetramethyl-1,1'- Spirobiindane, 1,1,3-trimethyl-3- (4-hydroxyphenyl) -indan-5-ol, 6,6′-dihydroxy-4,4,4 ′, 4′7,7′-hexamethyl-2, Examples include 2'-spirobichroman. These can be used in combination of two or more.

  Among these, 1,1-bis (4-hydroxyphenyl) cyclohexane, bis (4-hydroxyphenyl) diphenylmethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 9,9- Bis (3-methyl-4-hydroxyphenyl) fluorene, 3,3,5-trimethyl-1,1-bis (4-hydroxyphenyl) cyclohexane, 6,6'-dihydroxy-3,3,3 ', 3' It is preferably selected from -tetramethyl-1,1'-spirobiindane. Two or more of these may be used in combination.

  Furthermore, as a molecular weight regulator, the monohydric phenol represented by the formula (D) that can be expected to improve the fluidity is preferable, and specifically, n-butylphenol, octylphenol, nonylphenol, decanylphenol, tetradecanyl. Long chain alkyl-substituted phenols such as phenol, heptadecanylphenol, octadecanylphenol; hydroxybenzoic acid long chains such as butyl hydroxybenzoate, octyl hydroxybenzoate, nonyl hydroxybenzoate, decanyl hydroxybenzoate, heptadecanyl hydroxybenzoate Alkyl esters; butoxyphenol, octyloxyphenol, nonyloxyphenol, decanyloxyphenol, tetradecanyloxyphenol, heptadecanyloxyphenol, octadecanyloxyphenol Long-chain alkyloxy phenols such as Nord are exemplified.

  When employing the phosgene method, it is preferable to add a small amount of a quaternary ammonium salt in order to efficiently carry out the reaction after the completion of phosgene blowing. Specific examples include tetramethylammonium chloride, trimethylbenzylammonium chloride, triethylbenzylammonium chloride, tetraethylammonium bromide, and tetra-n-butylammonium iodide. Of these, trimethylbenzylammonium chloride and triethylbenzylammonium chloride are preferred. This quaternary ammonium salt is generally preferably used in an amount of 0.0005 to 5 mol% based on the total bisphenol used. It is preferable to polymerize by adding a tertiary amine such as triethylamine and a molecular weight regulator 3 to 10 minutes after the addition of the quaternary ammonium salt. The amount of tertiary amine added is 0.01 to 1.0 mol% with respect to the total bisphenols. Moreover, the addition amount of the molecular weight regulator is 3 to 10 mol% with respect to all bisphenols.

  The polycarbonate polymer synthesized by these reactions can be molded by a known molding method such as extrusion molding, injection molding, blow molding, compression molding, wet molding, etc., but injection molding is preferred, and the intrinsic viscosity is 0.30 to 0.50. A range of dl / g is preferred.

  In addition, the structural unit of the formula (A) of the present invention is preferably 5 to 40 mol% in the total structural units in consideration of moldability, heat resistance and low birefringence. When the structural unit of the formula (A) is less than 5 mol%, the birefringence improving effect is small.

  Furthermore, the structural unit of the formula (B) is preferably 10 to 90 mol% in all the structural units. If the formula (B) is less than 10 mol%, the fluidity improving effect is small, and if it exceeds 90 mol%, the fluidity is excessively increased and the moldability is deteriorated.

The composition containing polycarbonate is preferably molded by injection molding, but if the fluidity at that time is too large or too small, there is a problem in moldability. For example, in the Koka type flow tester (280 ° C., 160 kgf / cm ² , nozzle diameter 1 mm × 10 mm) measurement, a range of 15 to 90 × 10 ⁻² cc / sec is preferable. If it is less than 15 × 10 ^-2 cc / sec, the fluidity may be poor and filling defects or flow marks may occur in the mold. If it exceeds 90 × 10 ^-2 cc / sec, mold peeling failure or warping is likely to occur. .

The composition containing polycarbonate is preferably highly purified. Specifically, dust having a diameter of 50 μm or more is substantially not detected, dust having a diameter of 0.5 to 50 μm is 3 × 10 ⁴ or less, inorganic and organic residual chlorine is 2 ppm or less, residual alkali metal is 2 ppm or less, residual hydroxyl group Refinement is performed so as to satisfy the criteria of 200 ppm or less, residual nitrogen amount of 5 ppm or less, and residual monomer of 20 ppm or less as much as possible. Further, post-treatment such as extraction may be performed for removing low molecular weight substances and removing solvents.

  A composition containing a polycarbonate ensures hindered phenol-based or phosphite-based antioxidants; silicon-based, fatty acid ester-based, as required, in order to ensure the stability and release properties required during extrusion and injection molding. Fatty acid, fatty acid glyceride, beeswax and other natural oils and mold release agents; benzotriazole, benzophenone, dibenzoylmethane, salicylate, and other light stabilizers; polyalkylene glycol, fatty acid glycerides and other antistatic agents Etc. may be used in combination as appropriate. Further, from the viewpoint of cost and the like, general general-purpose polycarbonate can be arbitrarily mixed and used within a range not impairing the performance. The molding temperature in the case of injection molding is not limited, but is preferably 250 to 360 ° C from the viewpoint of fluidity, more preferably 250 to 260 ° C, and the mold temperature is 90 to 120 ° C. The in-mold cooling and holding time is preferably 30 seconds to 5 minutes.

The first plastic lens material is a specific polycarbonate material with excellent fluidity, which can be injection-molded at a lower temperature than conventional bisphenol A-type polycarbonate, and has excellent moldability during injection molding. ing.
The molding temperature is 240 to 260 ° C., and the shear rate is 100 to 1000 s ⁻¹ . In this temperature range, the relationship between the shear rate and the viscosity is close to that of Newtonian fluid. Since low temperature molding is possible, there is little thermal deterioration (coloring) of the polymer and less energy is required for molding. Therefore, the productivity of the lens is excellent, and the cost of the optical unit can be reduced. In addition, this specific polycarbonate material has sufficient mechanical strength for the lens application constituting the optical unit, despite being excellent in fluidity.

The first plastic lens has an Abbe number of 23 to 35 and can be used as a low Abbe number lens.
The retardation of the first plastic lens is, for example, about 0 to 120 nm when a lens having an optical surface radius of 9 mm and a central portion thickness of 2.5 mm is injection-molded. It can be seen that the birefringence is low considering that the retardation in the case of injection molding with a bisphenol A type PC) material is 200 to 400 nm. Here, the retardation is obtained by comparing the interference color with a reference sample sandwiched between polarizing plates (crossed Nicols).
The water absorption of the first plastic lens is about 0.3% or less, and the water absorption of a general-purpose polycarbonate (bisphenol A type PC) material is about 0.25% compared to about 0.3%. is there.

  The first and second plastic lenses constituting the optical unit of the present invention are preferably manufactured by injection molding. A plastic lens molded by injection molding has a shape called a gate mark at a position corresponding to a gate of a mold. Since the positional relationship between the gate trace and the optical axis of the lens can be specified from the optical design of the lens and the injection molding apparatus / injection molding conditions, the two gate traces of the first and second plastic lenses can be identified. It is preferable to set injection molding conditions at the time of manufacturing the first and second plastic lenses so that the optical axes of the two lenses can be aligned as an index. In this way, by combining the gate traces of the first and second plastic lenses as a mark, the optical axis of the lens can be relatively easily adjusted. By devising the shape of the gate, it is possible to easily identify the gate mark as a mark.

<Second plastic lens>
The second plastic lens of the optical unit of the present invention is a lens having an Abbe number of 45-60. The plastic material to be used is preferably a transparent plastic material having low birefringence and water absorption and excellent dimensional stability. Examples of such plastic materials include methacrylic resin (PMMA), diethylene glycol bisallyl carbonate, alternating olefin / maleimide copolymer, poly (1,3-cyclohexanediene), poly (cyclohexane), and alicyclic polyolefin resin. It is done.

  Among these, alicyclic polyolefin resin is preferable because it has preferable characteristics as a lens of an optical unit for high-resolution applications. The alicyclic polyolefin resin has a molecular skeleton formed from a bulky alicyclic structure, has a low birefringence like PMMA, and is superior to PMMA in terms of low water absorption and heat resistance.

Specific examples of such alicyclic polyolefin resins include JP-A-5-279554, JP-T-2001-072870, JP-A-6-107735, JP-A-6-136035, and JP-A-9-263627. Norbornene-based alicyclic polyolefin resins disclosed in Japanese Patent Application Laid-Open Nos. 2004-51949, 2003-313177, 2003-327630, 2004-51949, and Japanese Patent Application No. 2002-293492 are disclosed. An alicyclic polyolefin resin obtained by ring-opening polymerization of a norbornene derivative having a methacrylic group in the side chain with a metallocene catalyst or the like and then hydrogenating, JP-A Nos. 2001-26693, 2001-26682, 2003 -321591, JP2003-313247, JP2002-3323 No. 2, JP-A No. 2002-275314, JP-A No. 2002-105131, and alicyclic polyolefin resins made of a copolymer of ethylene and cycloolefin, and commercially available products include ZEONEX manufactured by ZEON Corporation. (ZEONEX ^™ ), ARTON ^™ manufactured by JSR Corporation, and APEL ^™ manufactured by Mitsui Chemicals, Inc.

The second plastic lens preferably has the following characteristics suitable as a lens material for an optical unit for high resolution applications.
The above-described alicyclic polyolefin resin is characterized by low birefringence. Specifically, for example, when a lens having an optical surface radius of 6.4 mm and a central portion thickness of 2.9 mm is injection-molded, the retardation is about 0 to 150 nm and low birefringence. Even when used in combination with the first plastic lens to correct chromatic aberration, the resolution is not adversely affected.

The saturated water absorption measured according to JIS K7209 is preferably 0.4% or less, and more preferably less than 0.01%. It is preferable that the refractive index change due to humidity hardly occur and that the lens has excellent dimensional stability.
In addition, the alicyclic polyolefin resin has a low optical elastic modulus. Specifically, the optical elastic modulus is 7.0 × 10 ⁻¹³ cm ² / dyne or less. A molded body injection-molded using a material with a low optical elastic modulus is more complex than a molded body molded from a material with a high optical elastic modulus, even if the molecular strains in the molded body are similar. It has the characteristic that refraction is less likely to appear in the molded body. Therefore, a material having a low optical elastic modulus is preferable for obtaining a molded body having a low birefringence.
The second plastic lens can be molded by a known molding method such as extrusion molding, injection molding, blow molding, compression molding, or wet molding. Injection molding is preferable, and the injection molding conditions are, for example, a polymer temperature of 240 to 240. 290 ° C., mold temperature of 100 to 130 ° C., and in-mold cooling and holding time of 30 seconds to 5 minutes are preferable.

Since the optical unit of the present invention combines a first plastic lens and a second plastic lens with an Abbe number of 45 to 60, chromatic aberration is appropriately corrected. Although the Abbe number of the first plastic lens is not limited, it is preferable that the Abbe number is smaller than that of the second lens (for example, about 23 to 30 Abbe number). The number of lenses to be combined is not limited to one each, and any number of combinations is possible.
The optical unit may have other mechanisms preferable for its use, that is, a silver salt camera, a digital camera, a video camera, a small camera for incorporation into a mobile phone, and the like. Specific examples of such a mechanism include a focusing mechanism and a zoom mechanism.

<Lens with flange>
Said 1st and 2nd plastic lens may have a flange part around the lens part which has an optical effect | action. The flange portions of the first and second plastic lenses can be fitted with the flange portions of the second and first plastic lenses, respectively, or with the spacer provided between the first and second plastic lenses. Furthermore, the first and second lenses have shapes that match the optical axes of each other in a state where they are combined by the mutual fitting of the flange portions or the fitting of the spacer and the flange portion. The spacer can be preferably configured as a flange portion having no lens portion.
In the optical unit of the present invention, since the lens constituting the optical unit is made of plastic, a structure useful for optical axis alignment described below can be easily manufactured.
According to the present invention having the above-described configuration, in an optical unit having a plurality of lenses, the position in the direction perpendicular to the optical axis is determined simply by fitting and combining the flange portions of each lens or the flange portion as a spacer. By aligning the optical axes with each other and preferably determining the position in the optical axis direction, an imaging lens or the like can be obtained. In addition, since it can be handled in the same way as one lens after the combination, it is possible to prevent the optical axis from being shifted between the lenses after the combination.

2A and 2B show an embodiment of a first plastic lens having an optical axis alignment structure that is a flange portion. FIG. 2A is a plan view of the lens, and FIG. 2B is a side sectional view of the lens. is there.
A lens 28 shown in FIGS. 2A and 2B includes a lens portion 28 a that is positioned at the center and performs an optical action, and a flange portion 28 b provided around the lens 28. The flange portion 28b can be fitted with a flange portion provided in another lens constituting the optical unit, and forms an optical axis alignment structure with the flange portion of the other lens.

As shown in FIG. 3, the optical unit 1 is formed by three lenses: a lens 26, a lens 28, and a lens 30.
The lens 26 includes a lens portion 26a and a flange portion 26b, the lens 28 includes a lens portion 28a and a flange portion 28b, and the lens 30 includes a lens portion 30a and a flange portion 30b, both of which are circular (in the optical axis direction). Shape seen from above).
In the illustrated example, the flange portion 26 b of the lens 26 can be fitted (inserted) inside (on the optical axis side) above the flange portion 28 b of the lens 28, and the flange portion 30 b of the lens 30 is the flange portion of the lens 28. It can be fitted inside the lower part of the part 28b.

In the optical unit 1, the flange portion 26b of the lens 26 is fitted to the flange portion 28b of the lens 28 from above, and the flange surface (surface in the optical axis direction) of the flange portion 28b is brought into contact with the upper surface of the lens portion 28a. The flange portion 30b of the lens 30 is fitted to the flange portion 28b of the lens 28 from below, and the flange surface of the flange portion 30b is brought into contact with the lower surface of the lens portion 28a to be assembled.
In a state in which the lenses are assembled by fitting the flange portions in this way, the respective lenses have the same optical axis, and in the illustrated example, as a preferable aspect, a shape in which the mutual positional relationship in the optical axis direction is also appropriate. Have.
Since the optical unit of the present invention has such a configuration, it is possible to align the optical axes of the respective lenses or to perform positioning in the optical axis direction only by fitting and assembling the flange portions of each other. Furthermore, it is possible to prevent misalignment between the optical axes (hereinafter referred to as inter-lens eccentricity).

In order to capture a high-quality image using the combined lens, it is natural that the optical axes of all the lenses need to be properly positioned.
Usually, a small imaging module used for a mobile phone or the like uses a glass lens because a high resolution is required. Glass lenses cannot be used to mold lenses with complex shapes. Therefore, in a conventional small-sized imaging module, as disclosed in Japanese Patent Application Laid-Open No. 2002-82272, a plurality of circular lenses having different diameters are combined to form a stepped shape having lens housing portions having different diameters in stages. It is built into the lens barrel.
However, since a normal lens unit has a play for incorporating a lens into a lens barrel, the optical axis of the lens shifts during assembly, making it difficult to match the optical axes.

In the present invention, even with a lens having a complicated shape that cannot be molded with glass, a lens having the above-described resolving power can be produced by molding with high accuracy.
The optical unit of the present invention utilizes this, and the lens can be combined by fitting with the flange portion, and the optical axis is matched in the state where the flange portion is fitted and combined, Preferably, the thickness of the flange portion (thickness in the optical axis direction) is also a thickness corresponding to the position in the optical axis direction of the lens to be combined, and the flange portion is fitted and combined in the optical axis direction. The optical unit 1 is formed by combining these lenses with an appropriate shape.
Therefore, according to the present invention, the lenses 26, 28, and 30 are combined with each other by fitting the flanges, and the positions in the direction orthogonal to the optical axis (hereinafter referred to as the xy direction) are determined to each other. The optical unit 1 can be matched, and preferably the position in the direction of the optical axis is also determined, so that the optical unit 1 as an imaging lens can be obtained. Further, after combination, it can be handled in the same way as one lens. Therefore, eccentricity between the lenses after the combination can be prevented.

Here, the lenses 26, 28, and 30 have a nesting score line (a parting of the mold) on a surface that abuts in the optical axis direction and a surface that abuts in the xy direction, that is, a reference surface that determines the position of the lens. Preferably there is no parting line. In other words, it is preferable that each lens is molded by creating a lens mold by creating a split surface at a position away from the reference surface so that no split line exists on the reference surface.
In particular, positioning in the optical axis direction is performed such as a contact surface between the flange portion 26b of the lens 26 and the lens portion 28a of the lens 28, or a contact surface between the flange portion 30b of the lens 30 and the lens portion 28a of the lens 28. It is preferable that each lens is molded so that no dividing line exists on the surface to be performed (reference surface).

As described above, in the optical unit 1 including the lenses 26, 28, and 30, the flange portions of the lenses are fitted, and the flange portions and the lens portions are brought into contact with each other between the lenses so that the optical axis direction and x− By positioning in the y direction, the optical axes are aligned with each other and positioning in the optical axis direction is performed. Therefore, if a dividing line exists on the reference surface, an error occurs in the positional relationship between the lenses, and there is a possibility that a position in the optical axis direction or an eccentricity between the lenses may occur.
In other words, since there is no dividing line on the reference plane, it is possible to produce a highly accurate imaging lens of a combined lens.

When there is a high possibility that the lens shape is complicated as described above, it is often advantageous to form a split surface of the mold in a portion continuous with the reference surface for the sake of molding accuracy and manufacturing.
In this case, the corner continuous to the reference plane is a curved surface (R is attached), a means for forming a split plane at this position, and the split plane is formed at this position as a shape with the corner continuous to the reference plane cut away. A method of releasing the dividing line from the reference plane is preferably used depending on the means for forming.

In the illustrated example, the optical unit 1 includes three lenses 26, 28, and 30, but the present invention is not limited to this, and the number of lenses may be two or less or four or more.
In addition, the shape of the lens (lens portion and flange portion) is not limited to a circle as long as they can be fitted to each other, and various shapes can be used.
Furthermore, in the illustrated example, as a preferable aspect, the thickness of the flange portion is set to a thickness corresponding to the position of each lens in the optical axis direction, so that the flange portion and the lens portion are brought into contact with each other in the optical axis direction. Positioning is also performed. However, the present invention is not limited to this. For example, the positioning of each lens in the optical axis direction is performed by a method such as arranging a positioning member in the optical axis direction such as a spacer between the contact portions. Also good.

<Lens with moisture barrier film>
The first or second plastic lens may further have a moisture-proof coating on the entire surface. In FIG. 2B, the moisture-proof coating 14 is exaggerated.
The moisture-proof coating 14 is preferably provided on the entire surface of the lens 28 including not only the lens portion 28a but also the flange portion 28b.
Here, the moisture-proof coating 14 may be a single layer film or a multilayer film. The single layer film may be an inorganic film or an organic film. Furthermore, the multilayer film may be an inorganic film multilayer film, an organic film multilayer film, or a composite film of an inorganic film and an organic film.

There are no particular limitations on the inorganic film, and various thin films mainly composed of inorganic materials can be used as long as they have sufficient transparency and have low moisture permeability or no moisture permeability. It is.
An example of a suitable inorganic _{materials, SiO 2, SiO, ZrO 2} , TiO 2, TiO, Ti 2 O 3, Al 2 O 3, Ta 2 O 5, CeO 2, MgO, Y 2 O 3, SnO 2, MgF ₂ , WO ₃ , and a mixture composed of a mixed oxide of In and Sn.
In any film, the inorganic film is preferably a film having a structure as dense as possible and having little absorption of light having a target wavelength.
Here, the moisture-proof coating 14 is preferably a glassy membrane made of SiO when an inorganic coating is used. That is, when an inorganic film is used as the moisture-proof film 14 as a single layer film or as a part of a multilayer film or a multilayer composite film, the inorganic film is particularly preferably a glassy film made of SiO.

In addition, the film thickness of the inorganic film is not particularly limited, and it is necessary depending on the composition of the inorganic film, whether it is used as a single layer film or a multilayer film, or combined with an organic film as a multilayer composite film. What is necessary is just to set suitably the film thickness which can ensure transparency and can exhibit the target moisture-proof performance.
The film thickness when an inorganic coating is used as the moisture-proof coating 14 is preferably 10 nm to 1000 nm (1 μm). This film thickness particularly means the film thickness of a single-layer film of an inorganic film or a multilayer film of only an inorganic film, or the total thickness of only an inorganic film in the case of a multilayer composite film with an organic film. This is because if the film thickness is in such a range, the number of pinholes affecting the moisture-proof performance is small. That is, the reason for limiting the film thickness of the inorganic coating to the above range is that there is a concern of pinholes if the film thickness is less than 10 nm, and even if it is thicker than 1000 nm, from the viewpoint of moisture resistance. This is because the contribution is minimal, and when the film thickness is increased, the productivity is lowered, particularly in the dry film forming method, the productivity is lowered, and cracks are easily generated due to residual stress.

There are no particular limitations on the method for forming such an inorganic film, and various dry film forming methods such as vacuum deposition, sputtering, ion plating, and CVD (Chemical Vapor Deposition), and various types of methods such as sol-gel methods. A wet film-forming method can be used, and may be appropriately selected according to the composition, film thickness, etc. of the inorganic film to be formed. In particular, the film thickness of the inorganic film formed by the dry film formation method is more preferably 10 nm to 1 μm as described above. This is because the reason for limitation is more remarkable.
Furthermore, the application method of the solution when using a wet film formation method such as a sol-gel method is not particularly limited, and various application methods such as dip coating, spray coating, and spin coating can be used. Dip coating (dip coating) is preferably exemplified in that a solution can be easily applied to the entire surface of the lens 28, that is, an inorganic film can be formed.
In the case of the sol-gel method, the inorganic coating can be obtained, for example, by hydrolyzing an alkoxysilane compound, and commercially available products such as SolGard ^™ manufactured by Nippon Dacro Shamrock Co., Ltd. can be used.

The organic film is not particularly limited, and various thin films mainly composed of organic materials may be used as long as the film has sufficient transparency and has low moisture permeability or does not exhibit moisture permeability. Is available.
As an example of a suitable organic film, a film mainly composed of polyvinylidene chloride or vinylidene chloride-vinyl chloride copolymer, or a cycloolefin resin such as ZEONEX ^TM manufactured by Nippon Zeon Film, film mainly composed of amorphous fluororesin (amorphous fluoropolymer) such as CYTOP ^TM manufactured by Asahi Glass Co., Ltd. and Teflon AF manufactured by DuPont, Novec manufactured by Sumitomo 3M Examples thereof include a film mainly composed of a fluorine-based resin such as (Novec) ^TM, and a film mainly composed of a silicone-based resin such as Shin-Etsu Silicone KR251, KR400, and KR114A manufactured by Shin-Etsu Chemical.
Here, the moisture-proof coating 14 is preferably a vinylidene chloride film when an organic coating is used. That is, when an organic film is used as the moisture-proof film 14 as a single layer film or as a part of a multilayer film or a multilayer composite film, the organic film is particularly preferably a vinylidene chloride film.

In addition, there is no particular limitation on the film thickness of the organic film, and depending on the composition of the organic film, whether it is used as a single layer film or a multilayer film, or combined with an inorganic film as a multilayer composite film, it is necessary to be transparent The film thickness can be set as appropriate so that the property can be secured and the desired moisture-proof performance can be exhibited.
The film thickness when an organic coating is used as the moisture-proof coating 14 is preferably 100 nm to 10000 nm (10 μm). This film thickness particularly means the film thickness of a single layer film of an organic film or a multilayer film of only an organic film, or the total thickness of only an organic film in the case of a multilayer composite film with an inorganic film. . This is because if the film thickness is in such a range, the number of pinholes affecting the moisture-proof performance is small. That is, the reason for limiting the film thickness of the organic film to the above range is that if the film thickness is less than 100 nm, pinholes are easily formed, and even if it is greater than 10 μm, its contribution is from the viewpoint of moisture resistance. This is because the thickness is not so large, and if it is extremely thick, the thickness tends to be non-uniform, and the optical performance deteriorates.

  Further, as the optical characteristics of the organic coating, it is preferable that the light transmittance is good and the refractive index is low. This is because when the refractive index is low, there is little loss due to surface reflection of incident light, and as a result, the light transmittance is improved. It is also possible to appropriately perform optical design and to provide the moisture-proof film with functions such as functional antireflection and hard coating.

There are no particular limitations on the method for forming such an organic film, and various wet film forming methods such as a film forming method in which a coating formed by dissolving or dispersing a resin component that forms the film is prepared and applied / dried. Various dry film forming methods such as plasma polymerization and CVD can be used, and may be appropriately selected according to the composition and film thickness of the film to be formed.
In the wet film forming method using a paint, the paint application method is not particularly limited, and various methods such as spray coating, brush coating, and dip coating can be used. Dip coating is preferably exemplified in that a solution can be applied to the entire surface of the lens, that is, an organic film can be formed.
In particular, the film thickness of the inorganic film formed by the coating film forming method is more preferably 100 nm to 10 μm as described above. This is because the reason for limitation is more remarkable.

  In the case of using a composite film of an inorganic film and an organic film as the moisture-proof film 14 of the present invention, prior to the formation of the organic film, if necessary, an inorganic film and an organic film In order to improve the adhesion, the surface of the inorganic coating may be subjected to an adhesion improvement treatment such as an anchor coat.

  The film thickness of the moisture-proof film 14, that is, the film thickness of the inorganic film and / or organic film that forms the moisture-proof film is most preferably uniform, but is not particularly limited, and the film is provided over the entire surface. 28, especially if there is moisture resistance that does not cause uneven distribution of moisture inside the lens portion 28a, it is not necessarily uniform, and if the desired moisture resistance is obtained, basically the lens portion 28a. It is sufficient that only the optically acting region has a predetermined film thickness corresponding to the optical characteristics. For example, the film thickness of the edge or end region that does not participate in the light transmission of the flange portion 28b, etc. The structure may be thicker or thinner than the region. In addition, the film thickness of the moisture-proof coating 14 is not necessarily uniform even in the optically acting region such as the lens portion 28a, and has a certain thickness distribution as long as it can meet the required optical characteristics. May be.

In the present invention, when a multilayer film using an inorganic film and an organic film in combination is used as the moisture-proof film 14, an excellent moisture-proof property is exhibited. The reason for this is not clear, but both inorganic and organic coatings have different lamination principles and coating configurations, so that they can compensate for or compensate for each other's defects and defects, as well as the moisture-proof performance of each coating. As a result, it is considered that very excellent moisture resistance can be obtained.
In general, inorganic coatings are hard and have many pinholes, cracks, etc. Conversely, organic coatings have a certain degree of elasticity. Therefore, when a multilayer film is used as the moisture-proof coating 14, by providing an inorganic coating on the lower layer and an organic coating on the upper layer, the organic coating suitably fills the pinholes of the inorganic coating, resulting in defects. It is possible to form a non-existing film and to exhibit a very high moisture-proof performance that fully utilizes the moisture-proof performance of the inorganic film. In addition, the organic film having elasticity acts as a protective film that protects the inorganic film against the resistance to external stress and the expansion / contraction of the lens 28 due to heat or the like, so that sufficient strength is ensured. Can exhibit good moisture resistance over a long period of time.

  In the optical unit of the present invention, the first or second plastic lens may have another structure for providing desired characteristics. Specifically, examples of such a configuration include an antireflection film, a hard coat, a dirt prevention film, or a filter that cuts off light having a specific wavelength, such as infrared rays and ultraviolet rays.

The antireflection film is composed of a single layer or multiple layers of an inorganic coating or an organic coating. A multilayer structure of an inorganic coating and an organic coating may be used. The antireflection film can be provided on one side or both sides of the light-transmitting substrate. When provided on both sides, the antireflection films on both sides may have the same configuration or different configurations. For example, the antireflection film on one surface may have a multilayer structure, and the antireflection film on the other surface side may be simplified to have a single layer structure.
As a material of the inorganic _{film, SiO 2, SiO, ZrO 2} , TiO 2, TiO, Ti 2 O 3, Ti 2 O 5, Al 2 O 3, Ta 2 O 5, CeO 2, MgO, Y 2 O 3, Examples thereof include inorganic substances such as SnO ₂ , MgF ₂ , and WO ₃ , and these can be used alone or in combination of two or more. Among these, when the light-transmitting substrate is a thermoplastic resin, SiO ₂ , ZrO ₂ , TiO ₂ , and Ta ₂ O ₅ that can be vacuum-deposited at a low temperature are preferable.
As the multilayer film of the inorganic coating, the total optical film thickness of the ZrO ₂ layer and the SiO ₂ layer from the light-transmitting substrate side is λ / 4, the optical film thickness of the ZrO ₂ layer is λ / 4, and the outermost layer is SiO. A laminated structure in which _two layers having a high refractive index of λ / 4 and a layer having a low refractive index are alternately formed can be exemplified. Here, λ is a design wavelength, and usually 520 nm is used. The outermost layer is preferably made of SiO ₂ having a low refractive index and capable of forming a hard film.
As a method for forming the inorganic film, for example, a vacuum deposition method, an ion plating method, a sputtering method, a CVD method, a method of depositing by a chemical reaction in a saturated solution, or the like can be employed. Examples of the organic coating material include FFP (tetrafluoroethylene-hexafluoropropylene copolymer), PTFE (polytetrafluoroethylene), ETFE (ethylene-tetrafluoroethylene copolymer), and the like. It is selected in consideration of the refractive index of the base material or hard coat film. As a film forming method, a film can be formed by a coating method having excellent mass productivity such as a spin coating method and a dip coating method in addition to a vacuum deposition method.

  For the hard coat, a known ultraviolet curing or electron beam curing acrylic or epoxy resin can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, these examples are for the purpose of explanation, and the present invention is not limited to these examples.

(Manufacture of the first plastic lens PC1)
To 58 liters of 8.8% (w / v) aqueous sodium hydroxide solution, 2.86 kg of 1,1'-bi-2-naphthol (hereinafter abbreviated as BNP, 10 mol) and 4,4 '-[1,3-phenylenebis ( 1-methylethylidene)] bisphenol 6.92 kg (hereinafter abbreviated as BPM, 20 mol), bis (4-hydroxyphenyl) diphenylmethane 3.52 kg (hereinafter abbreviated as BPBP, 10 mol) and 10 g of hydrosulfite were added and dissolved. To this was added 36 liters of methylene chloride, and while stirring at 15 ° C., 5 kg of phosgene was blown in over 50 minutes. After blowing, 5 g (0.022 mol) of triethylbenzylammonium chloride was added and stirred vigorously for 5 minutes to emulsify the reaction solution, and then 360 g of p-tert-butylphenol (hereinafter abbreviated as PTBP, 2.4 mol) was added, and another 20 ml Triethylamine (0.14 mol) was added, and the mixture was stirred for about 1 hour for polymerization. The polymerization liquid was separated into an aqueous phase and an organic phase, the organic phase was neutralized with phosphoric acid, and washed with water until the washing liquid had a conductivity of 10 μS or less, to obtain a purified resin liquid. The obtained purified resin solution was slowly added dropwise to 45 ° C. hot water that was vigorously stirred to solidify the polymer while removing the solvent. The solid was filtered and dried to obtain a white powdery polymer. This polymer had an intrinsic viscosity [η] at a temperature of 20 ° C. of a solution having a concentration of 0.5 g / dl using methylene chloride as a solvent, and was 0.36 dl / g. The results obtained above polymer was analyzed from the infrared absorption spectrum, absorption by carbonyl group at the position in the vicinity of 1770 cm ^-1, observed absorption by ether bond position near 1240 cm ^-1, was confirmed to have a carbonate bond It was. Moreover, almost no absorption derived from a hydroxyl group was observed at a position of 3650 to 3200 cm ⁻¹ . When the monomers in this polycarbonate were measured by GPC analysis, all the monomers were 20 ppm or less. As a result of combining these, this polymer was recognized as a polycarbonate polymer comprising the following structural units.

  300 ppm of stearic acid monoglyceride was added to the obtained polycarbonate powder, and the mixture was extruded at 300 ° C. with a vented 50 mm extruder equipped with a 50 μm polymer filter to form a melt pellet. The obtained pellet was polymerized at a temperature of 250 ° C., a mold temperature of 110 ° C., a holding pressure of 50 MPa, and a cooling holding time of 120 seconds. The radius of the optical surface shown in the first plastic lens 2 of FIG. It was injection-molded into a 2.5 mm lens shape. The retardation of the lens was 0 to 50 nm.

(Manufacture of the first plastic lens PC2)
BNP changed to 4,58Kg (16mol), 1,1-bis (4-hydroxyphenyl) cyclohexane 1.07Kg (abbreviated as BPZ, 4mol) instead of BPBP, p-heptadecanylphenol 797g instead of PTBP (Hereinafter abbreviated as PHPDP, 2.4 mol) The intrinsic viscosity [η] of the obtained polymer was 0.37 dl / g, and this polymer was recognized as a polycarbonate polymer comprising the following structural units by infrared absorption spectrum analysis and the like. The results are shown in Table 1.

(Manufacture of second plastic lens ZEO)
The material of the second plastic lens, an Abbe number 56.2 (25 ° C., catalog value), using a water absorption of less than 0.01% Zeonex (ZEONEX) ^TM 480R (manufactured by Nippon Zeon Co., Ltd.), polymer temperature Injection molding was performed at 280 ° C., a mold temperature of 125 ° C., a holding pressure of 80 MPa, and a cooling holding time of 130 seconds to obtain the lens 3 of FIG. 1 (optical surface radius 6.4 mm, center thickness 2.9 mm). The retardation of the lens was 0 to 150 nm.

(Examples 1 and 2)
Using the first and second plastic lenses obtained by injection molding, the optical unit 1 shown in FIG. 1 was assembled, and the influence of the birefringence of the lens on the resolution was evaluated by the following procedure.

(1) Evaluation of influence on resolution by birefringence FIG. 4 is a schematic diagram of an apparatus used for evaluation. In FIG. 4, the parallel light beams emitted from the collimated light source 8 pass through the imaging chart 10 and enter the optical unit 1. As shown in FIG. 5, the chart 10 is a transparent glass plate having no birefringence with lines drawn in a grid pattern. However, as a pattern used for evaluating the influence on the resolution due to birefringence, a chart other than the chart shown in FIG. 5 can be used. For example, the chart shown in FIG. 6 or 7 can also be used. The selection of the imaging chart to be used can be appropriately selected according to the use of the optical unit and the required resolution.
This chart 10 is imaged and imaged on a CCD camera 12 using the optical unit 1 shown in FIG. The optical unit 1 and the CCD camera 12 are connected by an adapter 11 having a focal length adjustment mechanism and a diaphragm mechanism. An image taken by the CCD camera 12 is taken into the computer 13 as electronic data. The computer 13 stores reference data of zero birefringence in advance. The reference data and the captured image data are compared using an image calculation program, and image degradation relative to the reference data is evaluated according to the following criteria. did. The reference data is created on a computer as theoretically birefringence zero image data. The results are shown in Table 2.
○ When there is almost no image degradation.
△ When image degradation is recognized to some extent.
× When image degradation is clearly observed.

(Comparative Example 1)
As the first plastic lens material, a bisphenol A type polycarbonate resin (AD-5503 (manufactured by Teijin Kasei Co., Ltd.)), Abbe number 30 (25 ° C, catalog value), polymer temperature 280 ° C, mold temperature Except that the BPA type PC was injection-molded at 130 ° C., holding pressure 60 MPa, and cooling holding time 240 seconds, it was carried out in the same manner as in Example 1. Table 2 shows the results of evaluation of the influence of the birefringence of the lens on the resolution.

Abbreviations described in Table 1 are as follows.
1,1'-bi-2-naphthol BNP
4,4 '-[1,3-phenylenebis (1-methylethylidene)] bisphenol BPM
Bis (4-hydroxyphenyl) diphenylmethane BPBP
1,1-bis (4-hydroxyphenyl) cyclohexane BPZ

FIG. 1 is a side sectional view of one embodiment of the optical unit of the present invention. FIG. 2A is a plan view of a first or second plastic lens having an optical axis alignment structure, and FIG. 2B is a side sectional view of the lens. FIG. 3 is a side sectional view of another embodiment of the optical unit of the present invention, in which a lens having an optical axis alignment structure is used. FIG. 4 is a schematic diagram of an apparatus for evaluating the influence of birefringence of a lens on an image. FIG. 5 is a plan view of an imaging chart that is a component of the apparatus of FIG. FIG. 6 is a plan view showing another example of the photographing chart. FIG. 7 is a plan view showing another example of the photographing chart.

Explanation of symbols

1: Optical unit 2, 3, 4: Lens 5: Lens barrel 6: Spacer 7: Lens holder 8: Collimated light source 10: Chart for photographing 11: Connection adapter 12: CCD camera 13: Computer 14: Dampproof film 26, 28, 30 Lens 26a, 28a, 30a Lens part 26b, 28b, 30b Flange part

Claims (7)

An optical unit comprising at least a first plastic lens and a second plastic lens,
(1) The first plastic lens has structural units represented by the following formulas (A), (B), and (C), and the structural unit of the formula (A) is 5 to 5 in all the structural units. Obtained by molding a composition containing a polycarbonate having an intrinsic viscosity of 40 mol% and an intrinsic viscosity of 0.30 to 0.50 dl / g,
(2) The optical unit characterized in that the Abbe number of the second plastic lens is 45-60.

{W in formula (C)

R _{1 to} R ₄ are each independently hydrogen, fluorine, chlorine, bromine, iodine, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, An alkoxy group having 1 to 5 carbon atoms or an aralkyl group having 7 to 17 carbon atoms. However, when these groups have carbon, they are selected from an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, fluorine, chlorine, bromine and iodine. Also included are those substituted with halogen, dimethylpolysiloxy groups, and alkylarylpolysiloxy groups.
Y is

Wherein R ₅ and R ₆ are each independently hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Represents a group, or R ₅ and R ₆ are bonded together to form a carbocyclic or heterocyclic ring. However, when these groups contain carbon, they are substituted with an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, fluorine, chlorine, bromine, and iodine. Including those that have been. a represents an integer of 0 to 20, and b represents an integer of 1 to 100. } The optical unit according to claim 1, wherein the molecular terminal of the polycarbonate is derived from a monohydric phenol represented by the following formula (D).

(Wherein R ₇ represents an alkyl group having 4 to 20 carbon atoms, and R _{8 to} R ₉ each independently represents hydrogen, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or a carbon number. Represents an alkoxy group having 1 to 6 or an aryl group having 6 to 12 carbon atoms, Z represents an ester group, an ether group, a carbonyl group, or simply represents a bond.)   The first and second plastic lenses each have a flange portion around a lens portion having an optical action, and the flange portions of the first and second plastic lenses are respectively second and first. It can be fitted to each flange portion of one plastic lens or a spacer provided between the first and second plastic lenses, and the first and second lenses can be fitted to each other. 3. The optical unit according to claim 1, wherein the optical units have a shape in which the optical axes coincide with each other in a state where the optical axes are combined with each other or by fitting between the spacer and the flange portion.   4. The lens according to claim 3, wherein the lenses have a shape in which the positions in the optical axis direction of each other are appropriate in a state where the lenses are combined with each other by fitting the flanges or the spacers and the flanges. The optical unit described.   5. The optical unit according to claim 1, wherein at least the first plastic lens has a moisture-proof coating on the entire surface thereof.   The optical unit according to claim 5, wherein the moisture-proof coating is a Si—O-based film formed by a sputtering method.   The optical unit according to claim 5, wherein the moisture-proof coating is a film having vinylidene chloride.

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