JP2015001666A - Lens unit, and camera module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens unit capable of holding even a compact and thin lens in other members such as a holder in a good adhesion state.SOLUTION: A lens unit 200 has a plurality of lenses L1-L5. At least the fifth lens L5 closest to the image side is made of a thermoplastic resin composition, and is fixed to a lens barrel part 54 as other member by using a resin adhesive. The thermoplastic resin composition has: an alicyclic skeleton; and a polar group having a hetero atom in a side chain of a molecular chain.

Description

  The present invention relates to a lens unit incorporating a plurality of lenses in a holder and a camera module incorporating the lens unit.

  A lens unit such as an imaging lens incorporated in a cellular phone or the like has a structure in which an imaging lens is fitted and fixed in a holder so as to be held from the periphery. Mobile phones and the like are becoming smaller and thinner, and lens units are similarly being made smaller and thinner.

  In general, a cycloolefin polymer is used as a material of a lens constituting the lens unit in consideration of moldability and hygroscopicity. Here, it is known that the cycloolefin polymer has poor adhesion. For this problem, improvement of the adhesive (for example, see Patent Documents 1, 2, 3, and 4), modification of the adhesive surface (for example, see Patent Documents 5 and 6), introduction of a functional group into the resin material (for example, Patent) Reference 7), and a method for securing adhesiveness by taking sufficient adhesive area and the like has been adopted.

  However, when the lens is reduced in size and thickness, a sufficient adhesion area cannot be secured. In addition, even if the adhesive is improved or the adhesive surface is modified, the lens may be peeled off from the holder by an environmental test or an impact test because a sufficient adhesion area cannot be secured. In addition, when a functional group is introduced into the resin material, the adhesiveness is improved, but the hygroscopicity is increased due to the influence of the functional group, and the optical performance may be deteriorated by changing the refractive index.

International Publication WO2008 / 149766 JP-A-5-301915 JP 2012-144661 A JP 2010-53283 A JP 2002-200720 A JP 2008-174791 A JP 2013-47341 A

  An object of the present invention is to provide a lens unit that can hold a lens in another member such as a holder with a good adhesion state even if the lens is reduced in size and thickness.

  It is another object of the present invention to provide a camera module incorporating the lens unit.

  In order to solve the above problems, a lens unit according to the present invention is a lens unit having a plurality of lenses, and at least the most image-side lens is formed of a thermoplastic resin composition and uses a resin adhesive. The thermoplastic resin composition has an alicyclic skeleton and a polar group having a hetero atom in the side chain of the molecular chain.

  In the lens unit, a lens formed of a resin material having a functional group on the most image side is disposed and fixed by adhesion. That is, a thermoplastic resin composition having a polar group that is compatible or adhesive with the adhesive is selectively used as the most image-side lens material that is relatively unaffected by the overall optical performance. Thereby, optical performance and impact resistance due to refractive index fluctuations due to moisture absorption can be increased.

  In a specific aspect of the present invention, in the lens unit, the heteroatom is oxygen. In this case, it is possible to improve the adhesiveness while reducing the deterioration of the optical performance.

  In another aspect of the invention, the polar group is an ester group. In this case, it is possible to improve the adhesiveness while reducing the deterioration of the optical performance.

  In still another aspect of the present invention, the thickness of the thinnest portion in the optical axis direction of at least the most image side lens is 0.05 mm or more and 0.15 mm or less. In the case of a lens having such a thinnest portion, the thickness of the flange on the outer periphery of the lens becomes thin, and the bonding area becomes narrow. Therefore, the adhesiveness can be improved even if the adhesion area is small by making at least the lens closest to the image side with the above composition.

  In still another aspect of the present invention, at least the most image side lens has a diameter of 3 mm or more and 8 mm or less. In the case of a lens having such a diameter size, since the thickness of the flange on the outer periphery of the lens becomes thin, the bonding area may be narrowed. Therefore, the adhesiveness can be improved even if the adhesion area is small by making at least the lens closest to the image side with the above composition.

  In still another aspect of the present invention, at least one lens excluding the most image side lens is formed of a resin composition having no polar group. In this case, even if the lens other than the most image side lens is not compatible or adhesive with the adhesive, it is fixed to another member by bonding and fixing the most image side lens while maintaining the optical performance of the lens unit. It is easy to ensure.

  In still another aspect of the present invention, the thermoplastic resin composition is formed of a cycloolefin resin. In this case, the moldability of the lens can be improved.

  A camera module according to the present invention includes the lens unit described above and an image sensor that detects an image by the lens unit.

  In the camera module described above, by providing a lens unit with high impact resistance while suppressing deterioration of the optical performance due to the refractive index fluctuation due to moisture absorption as described above, it is possible to realize good optical characteristics despite being small.

It is a conceptual diagram explaining the lens unit and camera module of one Embodiment of this invention. (A) is a side sectional view of the lens on the most image side in the lens unit of one embodiment of the present invention, and (B) is a plan view of the lens of (A). (A) is a figure explaining the principal part of the metal mold | die for forming the lens shown to FIG. 2 (A) by injection molding, (B) is a figure explaining supply of molten resin, C) is a conceptual cross-sectional view of a molding die for molding a lens. It is a conceptual diagram explaining the state which incorporated the lens unit in the other member. It is a conceptual diagram explaining the Example of a lens unit.

  Hereinafter, a lens unit and the like according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional conceptual diagram illustrating a camera module or the like including a lens unit according to an embodiment of the present invention.

  The camera module 300 includes a lens unit 200 that forms a subject image, an image sensor 51 that detects a subject image formed by the lens unit 200, and a wiring board 52 that holds the image sensor 51 from behind and has wiring and the like. And a lens barrel part 54 having an opening OP for holding the lens unit 200 and the like and allowing a light beam from the object side to enter. The lens unit 200 has a function of forming a subject image on the image plane or the imaging plane (projected plane) I of the imaging element 51. The camera module 300 is used by being incorporated in an imaging apparatus, but it is also referred to as an imaging apparatus by itself.

  The lens unit 200 includes, in order from the object side, an aperture stop ST, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and an IR cut filter FL. Is provided. Among the lenses L1 to L5 constituting the lens unit 200, at least the fifth lens L5 closest to the image side is bonded and fixed to the lens barrel portion 54 as a holder with an adhesive.

  The image sensor 51 is a sensor chip made of a solid-state image sensor. The photoelectric conversion unit 51a of the image sensor 51 is composed of a CCD (charge coupled device) or a CMOS (complementary metal oxide semiconductor), photoelectrically converts incident light for each RGB, and outputs an analog signal thereof. The surface of the photoelectric conversion unit 51a as the light receiving unit is an image plane or an imaging plane (projected plane) I.

  The wiring board 52 has a role of aligning and fixing the image sensor 51 to other members (for example, the lens barrel portion 54). The wiring board 52 can receive a voltage and a signal for driving the image pickup device 51 and the driving mechanism 55a from an external circuit, and can output a detection signal to the external circuit.

  The lens barrel 54 houses and holds the imaging lens unit 200. The lens barrel portion 54 has, for example, a drive mechanism 55a in order to enable the lens focusing operation by moving the lens constituting the lens unit 200 along the optical axis AX. The drive mechanism 55a includes, for example, a voice coil motor and a guide, and reciprocates a specific lens along the optical axis AX. The lens barrel portion 54 is made of, for example, resin, glass, metal, or the like.

  The imaging apparatus 400 includes a control unit 63, an optical system driving unit 65, an imaging element driving unit 67, an image memory 68, and the like in addition to the camera module 300 described above.

  The control unit 63 controls each unit of the imaging device 400. The control unit 63 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like, and various types of programs are read out from the ROM and expanded in the RAM, in cooperation with the CPU. Execute the process.

  The optical system drive unit 65 operates and controls the drive mechanism 55a when performing focusing, exposure, and the like under the control of the control unit 63. The optical system driving unit 65 operates the driving mechanism 55a to appropriately move along the optical axis AX, thereby causing the lens to perform a focusing operation.

  The image sensor driving unit 67 controls the operation of the image sensor 51 when performing exposure or the like under the control of the control unit 63. Specifically, the image sensor driving unit 67 controls the image sensor 51 by scanning the image sensor 51 based on the timing signal. Further, the image sensor driving unit 67 converts the detection signal output from the image sensor 51 or an analog signal as a photoelectric conversion signal into digital image data. Further, the image sensor driving unit 67 can perform various image processing such as distortion correction, color correction, and compression on the image signal detected by the image sensor 51.

  The image memory 68 receives the digitized image signal from the image sensor driving unit 67 and stores it as readable and writable image data.

Hereinafter, the fifth lens L5 closest to the image in the lens unit 200 will be described.
As shown in FIGS. 2 (A) and 2 (B), the fifth lens L5 has a circular outline in a plan view and has a lens body 10 that exhibits an optical function, and is supported around the lens body 10. And a flange portion 20 used for the above. The lens body 10 is a biconcave element as a whole, and has a first optical surface 11 and a second optical surface 12. Both optical surfaces 11 and 12 are both aspherical surfaces. In particular, the first optical surface 11 has a concave shape at the central portion 10a and an annular convex shape at the peripheral portion 10b. The flange portion 20 has a relatively large thickness, but has a narrow radial width. That is, the outermost edge 10c is thinner again. The fifth lens L5 has the thinnest portion 14a having the smallest thickness in the optical axis AX direction at the central portion 10a and the thickest portion 14b having the largest thickness in the optical axis AX direction at the peripheral portion 10b. The thinnest part 14a is provided on the optical axis AX, and the thickest part 14b is provided between the central part 10a and the outer edge part 10c. That is, the lens body 10 is thin at the central portion 10a and thick at the peripheral portion 10b. The thickness H of the thinnest portion 14a in the optical axis AX direction of the fifth lens L5 is 0.05 mm or more and 0.15 mm or less. The diameter D of the fifth lens L5 is 3 mm or more and 8 mm or less. The fifth lens L5 has a relatively larger diameter than the other lenses L1 to L4.

  The fifth lens L5 is formed by injection molding using a thermoplastic resin composition. The thermoplastic resin composition has an alicyclic skeleton and a polar group having a hetero atom in the side chain of the molecular chain. Specifically, the thermoplastic resin composition is formed of, for example, a cycloolefin resin. Cycloolefin resin is based on cyclic olefin polymer (COP) resin and cyclic olefin copolymer (COC) resin, and is used to improve the performance of additives and products to facilitate molding as required. Additives can be included. Cyclic olefin polymer (COP) is an amorphous polymer synthesized from cycloolefins such as norbornene. Cyclic olefin copolymer (COC) resin is an amorphous polymer obtained by copolymerizing cycloolefins such as norbornene and other monomers such as ethylene. The hetero atom is, for example, oxygen, nitrogen, sulfur, etc. The polar group is, for example, an ester group, hydroxy group, carboxyl group, aldehyde group, acyl group, acetyl group, amino group, cyano group, azo group, isocyanate Group, nitro group, sulfo group, thiol group and the like.

式（１）中のＲ_１及びＲ_２のいずれかはヘテロ原子を持つ極性基であり、極性基以外の場合は水素原子、ハロゲン原子（フッ素、塩素、臭素又はヨウ素）を含む連結基を有してもよい置換基又は非置換の炭素原子数１〜３０の炭化水素基である。
また、シクロオレフィン系の樹脂組成物のうち環状オレフィン・コポリマー（ＣＯＣ）樹脂は、一般に下式（２）で示される構造骨格を有するものである。

式（２）中のＸは独立に式「−ＣＨ＝ＣＨ−」で表される基又は式「−ＣＨ_２−ＣＨ_２−」で表される基である。 Among cycloolefin-based resin compositions, cyclic olefin polymer (COP) resins generally have a structural skeleton represented by the following formula (1).

Either R ₁ or R ₂ in the formula (1) is a polar group having a hetero atom, and in the case other than the polar group, it has a linking group containing a hydrogen atom and a halogen atom (fluorine, chlorine, bromine or iodine). Or a substituted or unsubstituted hydrocarbon group having 1 to 30 carbon atoms.
Of the cycloolefin-based resin compositions, the cyclic olefin copolymer (COC) resin generally has a structural skeleton represented by the following formula (2).

X in the formula (2) is independently a group represented by the formula “—CH═CH—” or a group represented by the formula “—CH ₂ —CH ₂ —”.

式（３）中のｍは１以上の整数、ｐは０又は１以上の整数である。また、Ｘは独立に式「−ＣＨ＝ＣＨ−」で表される基又は式「−ＣＨ_２−ＣＨ_２−」で表される基である。また、Ｒ１〜Ｒ４の少なくとも１つはヘテロ原子を持つ極性基であり、極性基以外の場合は水素原子、ハロゲン原子（フッ素、塩素、臭素又はヨウ素）を含む連結基を有してもよい置換基又は非置換の炭素原子数１〜３０の炭化水素基である。 Moreover, a nobornene-type resin composition is generally represented by the following Formula (3) (refer Unexamined-Japanese-Patent No. 2003-14901).

M in the formula (3) is an integer of 1 or more, and p is 0 or an integer of 1 or more. X is independently a group represented by the formula “—CH═CH—” or a group represented by the formula “—CH ₂ —CH ₂ —”. In addition, at least one of R1 to R4 is a polar group having a hetero atom, and in the case other than the polar group, a substituent which may have a linking group containing a hydrogen atom or a halogen atom (fluorine, chlorine, bromine or iodine) Group or an unsubstituted hydrocarbon group having 1 to 30 carbon atoms.

  In the lens unit 200, at least one of the other lenses L1 to L4 other than the fifth lens L5 is different from the fifth lens L5 in that the resin composition does not have a polar group or does not have an alicyclic skeleton. It is formed of things. Examples of the resin composition having no polar group include COP and COC having no polar group (see JP-A-2003-73559). Examples of the resin composition having no alicyclic skeleton include acrylic and polycarbonate.

  Hereinafter, a method for manufacturing the fifth lens L5 will be described. FIGS. 3A and 3B are diagrams illustrating a mold for molding the fifth lens L5. The mold apparatus 70 includes a first mold 71 and a second mold 72. The first mold 71 and the second mold 72 are mold-matched at the mold-matching surface PL, and a cavity 70 a is formed between the molds 71 and 72. A transfer surface 71a for transferring the shape of the first optical surface 11 of the fifth lens L5 is formed on the first mold 71 so as to face the cavity 70a, and a fifth lens is formed on the second mold 72. A transfer surface 72a for transferring the shape of the second optical surface 12 of L5 is formed. The transfer surfaces 71 a and 72 a are also portions for transferring the surface of the flange portion 20. In the mold apparatus 70, a gate GA communicating with the cavity 70a is formed. In this case, the gate GA is disposed not on the center of the transfer surfaces 71a and 72a but on the side, and injection molding is performed by a side gate method.

  FIG. 3C is a cross-sectional view illustrating the entire structure of the mold apparatus 70. A runner RA is connected to the cavity 70a shown in FIG. 3A and the like via a gate GA, and the runner RA is connected to a sprue SP on the resin supply side. As a result, the molten resin J from the sprue SP obtained by melting the thermoplastic resin fills the runner RA and fills the cavity 70a through the gate GA. By separating the first mold 71 and the second mold 72 after cooling the molten resin J, a sprue portion 81 corresponding to the sprue SP, a runner portion 82 corresponding to the runner RA, and a gate corresponding to the gate GA. A molded product 80 including the portion 83 and a molded product main body 84 corresponding to the cavity 70a is formed. Here, the gate part 83 is subjected to a gate cut process, and the fifth lens L5 is obtained by the molded product body 84 at the end of the gate part 83.

  Hereinafter, with reference to FIG. 4, a method of attaching to the lens barrel portion 54 which is another member of the first to fifth lenses L1 to L5 will be described. As already described, the fifth lens L5 is bonded and fixed to the lens barrel portion 54 using the adhesive B. The lenses L1 to L5 are incorporated into the lens barrel portion 54 in the order of the relatively small first lens L1 to the relatively large fifth lens L5. The first to fourth lenses L1 to L4 are sealed in the lens barrel portion 54 by covering the lens barrel portion 54 with the fifth lens L5 that is the final built-in lens.

  The lens barrel portion 54 is formed with recesses R1 to R4 for fitting the first, third to fifth lenses L1, L3 to L5. In the lens barrel portion 54, the lenses L1, L3 to L5 are sequentially fitted into the corresponding recesses R1 to R4 from the object side, that is, the first lens L1. In the present embodiment, a convex portion for alignment with the first lens L1 is formed on the flange portion of the second lens L2. In assembling the lens into the lens barrel portion 54, the position of the second lens L2 is defined by this convex portion. After the fifth lens L5 closest to the image side is fitted, the adhesive B is applied to the image side, that is, the exposed side of the fifth lens L5. The adhesive B is applied in a scattered manner at several places (for example, five places) on the outer edge portion 10c of the fifth lens L5 so that the fifth lens L5 is securely fixed. As a material of the adhesive B, for example, a photocurable resin is used. Examples of the photocurable resin include acrylic resins, silicon resins, urethane resins, polyester resins, and epoxy resins. When the adhesive B is a photocurable resin, the adhesive B is cured by irradiating ultraviolet rays after the adhesive B is applied. As a result, the fifth lens L5 is bonded and fixed to the lens barrel portion 54, and the first to fourth lenses L1 to L4 are fixed inside the lens barrel portion 54. That is, the first lens L1 is pressed by the second lens L2, the second lens L2 is pressed by the third lens L3, the third lens L3 is pressed by the fourth lens L4, and the fourth lens L4 is pressed by the fifth lens L5. And the entire first to fifth lenses L1 to L5 are fixed. Since the thermoplastic resin composition having a polar group compatible with adhesive B or having good adhesiveness is used as the material of the fifth lens L5, the fifth lens L5 is securely fixed to the lens barrel portion 54. In the present embodiment, the flanges of the adjacent lenses are not in contact with each other except for the first and second lenses L1 and L2, but the flanges of the adjacent lenses are also in contact with the other lenses L3 to L5. Good.

  According to the lens unit described above, the fifth lens L5 formed of a resin material having a functional group on the most image side is disposed and fixed by adhesion. That is, a thermoplastic resin composition having a polar group having compatibility or good adhesiveness with the adhesive B is selectively used as the material of the fifth lens L5 on the most image side that is relatively less affected by the overall optical performance. Thereby, optical performance and impact resistance due to refractive index fluctuations due to moisture absorption can be increased.

表１からわかるように、実施例の第５レンズＬ５の材料としてエステル基を側鎖に持つシクロオレフィンを用いると、いずれのサンプルにおいても剥離力が２０Ｎ以上となり、衝撃強度が良好であった。 〔Example〕
Specific examples will be described below. In the example, the fifth lens L5 was manufactured using a cycloolefin having an ester group in the side chain as a material. The diameter of the fifth lens L5 is 4.66 mm, and the thickness of the outer edge portion 10c of the flange portion 20 is 0.5 mm. The fifth lens L5 was fitted into the holder HR, and five adhesives B were applied from the image side to the outer edge portion 10c of the fifth lens L5 closest to the image side, and the fifth lens L5 was adhered and fixed to the holder HR. In this embodiment, as shown in FIG. 5, for convenience, one lens is bonded and fixed to the holder HR, and a force is applied in a direction parallel to the optical axis AX from the object side, that is, the side where the adhesive B is not provided. It was. At this time, the force (peeling force) at which the fifth lens L5 was peeled from the holder HR was measured. Table 1 below summarizes the peel force of the sample of the example. If the peeling force is 20 N or more, the impact strength is good. In Samples 1 to 3, three different adhesives are used.
[Table 1]

As can be seen from Table 1, when a cycloolefin having an ester group in the side chain was used as the material of the fifth lens L5 of the example, the peel strength was 20 N or more in any sample, and the impact strength was good.

表２からわかるように、比較例のレンズの材料として極性基を持たない無官能シクロオレフィンを用いると、いずれのサンプルにおいても剥離力が２０Ｎを下回り、衝撃強度が不良であった。 [Comparative Example]
Hereinafter, a comparative example will be described. In the comparative example, a lens was produced using non-functional cycloolefin as a material. The method for measuring the size of the lens, the peeling force, and the like are the same as in the above-described embodiment. Table 2 below summarizes the peel force of the comparative sample. In Samples 4 to 6, three different adhesives are used.
[Table 2]

As can be seen from Table 2, when a non-functional cycloolefin having no polar group was used as the material for the lens of the comparative example, the peel strength was less than 20 N and the impact strength was poor in any sample.

  The lens unit 200 and the like as the present embodiment have been described above, but the imaging lens according to the present invention is not limited to the above. For example, the shape of the lens unit 200 is not limited to that illustrated in FIG. 1 and the like, and may have various surface shapes determined by optimizing the optical design. For example, the fifth lens L5 is not limited to the thinnest portion 14a provided on the optical axis AX of the central portion 10a, and the thinnest portion 14a is provided on the outer side adjacent to the central portion 10a. It may be what was made.

  In the above embodiment, the fifth lens L5, which is the most image side lens (final ball) in the lens unit 200, is assumed to be injection-molded with a resin material having a functional group. Any of the other lenses L1 to L4 that are not can be made to have the same properties as the fifth lens L5. The configuration of the lens unit 200 shown in FIG. 1 is merely an example, and the number of lenses constituting the lens unit 200 can be three, four, six or more.

  Moreover, in the said embodiment, the shape of recessed part R1-R4 of the lens-barrel part 54 is an illustration, and can be suitably changed with the lens shape and lens structure of the lens unit 200. FIG.

  The manufacturing method of the lens unit 200 and the like described in the above embodiment is merely an example, and various methods not illustrated can be used.

  In the above embodiment, a light-shielding diaphragm may be provided between the lenses L1 to L5.

  In the above embodiment, the IR cut filter FL is provided between the fifth lens L5 and the image sensor 51. However, a parallel plate other than the IR cut filter may be provided. Further, the IR cut filter FL may not be provided.

  Although the fifth lens L5 is bonded and fixed to the lens barrel portion 54, other members other than the lens barrel portion 54 may be used as other members for fixing the lens.

  In the above embodiment, the fifth lens L5 is bonded and fixed to the lens barrel portion 54. However, any one of the first to fourth lenses L1 to L4 may be bonded and fixed to the lens barrel portion 54. In this case, even if the adhesive strength of any of the first to fourth lenses L1 to L4 is weak, the adhesive strength of the fifth lens L5 that is adhesively fixed as a final stop is relatively high, so that the impact resistance of the lens unit 200 is improved. Can keep.

  DESCRIPTION OF SYMBOLS 10 ... Lens body, 10a ... Center part, 10b ... Peripheral part, 10c ... Outer edge part, 11, 12 ... Optical surface, 14a ... Thinnest part, 14b ... Thickest part, 20 ... Flange part, 51 ... Imaging element, 52 DESCRIPTION OF SYMBOLS ... Wiring board 54 ... Lens barrel part 65 ... Optical system drive part 67 ... Image sensor drive part 70 ... Mold apparatus 70a ... Cavity 71, 72 ... Mold, 71a, 72a ... Transfer surface 80 ... Molded article, 82 ... runner part, 83 ... gate part, 84 ... molded article main body, 200 ... lens unit, 300 ... camera module, 400 ... imaging device, AR ... opposite side area, AX ... optical axis, B ... adhesive, FL ... IR cut filter, I ... Imaging surface, L1-L5 ... Lens

Claims (8)

A lens unit having a plurality of lenses,
At least the most image-side lens is formed of a thermoplastic resin composition, and is fixed to another member using a resin adhesive,
The thermoplastic resin composition has an alicyclic skeleton and a polar group having a hetero atom in a side chain of a molecular chain.   The lens unit according to claim 1, wherein the heteroatom is oxygen.   The lens unit according to claim 1, wherein the polar group is an ester group.   4. The lens according to claim 1, wherein a thickness of a thinnest portion in the optical axis direction of the at least image-side lens is 0.05 mm or more and 0.15 mm or less. 5. unit.   5. The lens unit according to claim 1, wherein a diameter of the at least image-side lens is 3 mm or more and 8 mm or less.   6. The lens unit according to claim 1, wherein at least one lens excluding the most image side lens is formed of a resin composition having no polar group.   The lens unit according to any one of claims 1 to 6, wherein the thermoplastic resin composition is formed of a cycloolefin resin.   A camera module comprising: the lens unit according to claim 1; and an image sensor that detects an image by the lens unit.

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