JP2009244586A - Optical element, optical element unit, and imaging unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the reduction of light transmittance and the occurrence of cracks of an antireflection film. <P>SOLUTION: An optical element is to include a lens body 23, constituted of a thermosetting resin and an antireflection film 6, formed on the lens body 23. A contact layer 61 in contact with the lens body 23, of the antireflection film 6 is made of SiO<SB>x</SB>, wherein x lies within a range from 1.5 to 1.8. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical element, an optical element unit, and an imaging unit.

  Conventionally, from the viewpoint of excellent optical characteristics, mechanical strength, etc., inorganic glass materials are generally used as constituent materials of optical elements (mainly lenses). As the manufacturing process proceeds, it is necessary to reduce the size of the optical element. With inorganic glass materials, it is becoming difficult to manufacture a material having a large curvature (R) or a complicated shape due to the problem of workability. For this reason, plastic materials that are easy to process have been studied and used. Examples of plastic materials that are easy to process include thermoplastic resins having good transparency, such as polyolefin, polymethyl methacrylate, polycarbonate, and polystyrene, and are usually manufactured by injection molding using a metal mold.

  On the other hand, when an IC (Integrated Circuits) chip or other electronic component is mounted on a circuit board, a metal paste (for example, solder paste) is applied (potted) in advance to a predetermined position on the circuit board, and the electronic component is placed at that position. A technology for manufacturing an electronic module at a low cost has been developed by a technique in which the circuit board is subjected to a reflow process (heating process) in a state where the circuit board is placed, a metal paste is melted, and an electronic component is mounted on the circuit board. (For example, patent document 1). In recent years, in addition to electronic components, an optical element is mounted on a circuit board, and the reflow process as described above is performed, so that the electronic component and the optical element are simultaneously mounted on the circuit board. An optical module (imaging unit) that integrates the above has also been produced.

Of course, in an optical module manufactured by a production system incorporating the above-described reflow process, it is desired to use a plastic optical element that can be manufactured at low cost rather than a high-cost glass optical element. . However, the thermoplastic resin that has been used as a resin material for conventional optical elements is soft and melts at a relatively low temperature, so the processability is good, but the molded optical element is easily deformed by heat. Has drawbacks. When an electronic component incorporating an optical element is mounted on a substrate by reflow processing, the optical element itself is also exposed to heating conditions of about 260 ° C. However, in an optical element made of a thermoplastic resin having low heat resistance, This causes a problem of shape deterioration. Therefore, it is conceivable to use a thermosetting resin as a plastic material for an optical element to be subjected to reflow treatment, and by heating and curing this (a monomer component is polymerized by heat), an optical element for reflow is prepared. Can be produced.
JP 2001-24320 A

  Here, it is desirable to form an antireflection film for suppressing light reflection on the surface of the optical element (optical element body) made of a thermosetting resin. However, when this antireflection film is formed, it can withstand a reflow process. In order to form a film that can be formed, it is necessary to deposit the film material in a high temperature environment. In this case, an uncured monomer component may remain in the thermosetting resin. In this case, an uncured monomer may be used during the deposition period (during the lamination period when a multi-layer film is formed). The phenomenon that C (carbon atom) in the component diffuses or permeates through the film occurs, and the antireflection film itself has light absorption and becomes the original function of the optical element. There is a disadvantage that the permeability is lowered. Furthermore, when the optical element is mounted on the circuit board, it is exposed to a high temperature environment due to the reflow process, so that the above phenomenon may occur and light transmittance may be reduced. Further, since the optical element is exposed to a high temperature environment during the reflow process, it is assumed that a crack (so-called film cracking) occurs in the formed antireflection film.

  Therefore, a main object of the present invention is to provide an optical element that can suppress a decrease in light transmittance and further suppress the occurrence of cracks in the antireflection film. Another object is to provide an optical element unit and an imaging unit using the optical element.

According to one aspect of the invention,
An optical element body composed of a thermosetting resin;
An antireflection film formed on the optical element body;
Have
An optical element is provided in which the contact layer of the antireflection film that contacts the optical element body is SiO _x and 1.5 ≦ x ≦ 1.8.

  Preferably, the contact layer has a thickness of 10 to 100 nm.

Preferably, in addition to the contact layer, the antireflection film is composed of a layer composed of a low refractive index material having a refractive index of less than 1.7 and a layer composed of a high refractive index material having a refractive index of 1.7 or more. Has a multi-layer structure in which and are alternately laminated,
The low refractive index material is SiO ₂ ;
The high refractive index material is Ta ₂ O ₅ , a mixture of Ta ₂ O ₅ and TiO ₂ , or a mixture of ZrO ₂ , ZrO ₂ and TiO ₂ .

  Preferably, the thermosetting resin is an acrylic resin.

According to another aspect of the invention,
The optical element;
A diaphragm for adjusting the amount of light incident on the optical element;
A spacer for adjusting the arrangement position of the optical element;
An optical element unit is provided.

According to another aspect of the invention,
An optical element unit comprising: the optical element; a diaphragm for adjusting the amount of light incident on the optical element; and a spacer for adjusting an arrangement position of the optical element;
A sensor device that receives light transmitted through the optical element unit;
A casing covering the optical element unit and the sensor device;
An imaging unit is provided.

According to the present invention, the contact layer that contacts the optical element body of the antireflection film is made of SiO _x , and the value of x falls within a certain range of 1.5 ≦ x ≦ 1.8. A decrease in transmittance can be suppressed, and further, the occurrence of cracks in the antireflection film can be suppressed even in the reflow process.

  Next, preferred embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, an imaging unit 1 according to a preferred embodiment of the present invention mainly includes a lens unit 2, an IR cut filter 3, a sensor device 4, and a casing 5, and the lens unit 2, IR cut filter 3. The sensor device 4 is covered with a casing 5.

  The casing 5 includes a cylindrical cylindrical portion 51 and a rectangular parallelepiped base portion 53. The cylindrical portion 51 and the base portion 53 are integrally formed, and the cylindrical portion 51 is erected on the base portion 53. The lens unit 2 is disposed inside the cylindrical portion 51. A circular light transmission hole 51 a is formed in the top plate portion of the cylindrical portion 51. The IR cut filter 3 and the sensor device 4 are disposed in the base portion 53 (bottom portion).

  As shown in the enlarged view of FIG. 1, the lens unit 2 mainly includes a diaphragm 21, a lens body 23, and a spacer 25. These members are overlapped with each other in a state in which the lens body 23 is disposed between the diaphragm 21 and the spacer 25. The central portion of the lens portion 23 has a convex shape on both the front and back surfaces, and this serves as the lens portion 23a to exhibit an optical function. The diaphragm 21 is a member that adjusts the amount of light incident on the lens body 23, and a circular opening 21a is formed at a portion corresponding to the lens portion 23a. The spacer 25 is a member for adjusting the arrangement position (height position) of the lens unit 2 in the cylindrical portion 51 of the casing 5, and a circular opening 25 a (upper part of FIG. 1) is also provided at a portion corresponding to the lens portion 23 a. Reference) is formed.

  In the imaging unit 1 described above, external light is incident on the lens unit 2 through the light transmission hole 51a, and the amount of incident light is adjusted by the opening 21a of the diaphragm 21, transmitted through the lens portion 23a of the lens body 23, and spacers. The light is emitted from the 25 openings 25 a toward the IR cut filter 4. Thereafter, the infrared rays of the emitted light are cut by the IR cut filter 4 and finally enter the sensor device 4.

  The lens body 23 of the lens unit 2 is made of a thermosetting resin, and specifically includes the following (1) acrylic resin, (2) a resin having an adamantane skeleton, and (3) an acrylate compound / allyl ester compound. Resin, (4) silicone resin, and (5) epoxy resin can be used.

(1) Acrylic resin A typical example of an acrylic resin is a (meth) acrylate resin. There is no restriction | limiting in particular in (meth) acrylate used in this embodiment, The mono (meth) acrylate and polyfunctional (meth) acrylate manufactured by the general manufacturing method can be used. Although it is preferable to use (meth) acrylate having an alicyclic structure such as tricyclodecane dimethanol acrylate or isobornyl acrylate, general alkyl acrylate or polyethylene glycol diacrylate can also be used.

  Moreover, as other reactive monomers, if it is mono (meth) acrylate, for example, methyl acrylate, methyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, Examples include isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, phenyl acrylate, phenyl methacrylate, benzyl acrylate, benzyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate.

  Examples of the polyfunctional (meth) acrylate include trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta ( (Meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, tripentaerythritol octa (meth) acrylate, tripentaerythritol septa (meth) acrylate, tripentaerythritol hexa (meth) acrylate, tri Pentaerythritol penta (meth) acrylate, tripentaerythritol tetra (meth) acrylate, tripentaerythritol And tri (meth) acrylate.

  When the (meth) acrylate resin is used, examples of the polymerization initiator include hydroperoxide, dialkyl peroxide, peroxyester, diacyl peroxide, peroxycarbonate, peroxyketal, and ketone peroxide. . Specifically, 1,1-di (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-hexylperoxy) cyclohexane, 1,1-di (t-butyl) Peroxy) -2-methylcyclohexane, 1,1-di (t-butylperoxy) cyclohexane, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, di (2-t-butyl) Peroxy) benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, t-butylcumyl peroxide, di-t-butyl peroxide, dilauryl peroxide, Dibenzoyl peroxide, di (4-t-butylcyclohexyl) peroxycarbonate, di (2-ethylhexyl) per Oxycarbonate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanate, t-hexylperoxy-2-ethylhexanate, t-butylperoxy-2-ethylhexanate, t-hexyl Peroxyisopropyl monocarbonate, t-butyl peroxylaurate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-hexyl peroxybenzoate, 2,5-dimethyl-2 , 5-di (benzoylperoxy) hexane, t-butylperoxybenzoate and the like.

(2) Curable resin having an adamantane skeleton 2-alkyl-2-adamantyl (meth) acrylate (see JP 2002-193883 A), 3,3′-dialkoxycarbonyl-1,1 ′ biadamantane (JP 2001-253835), 1,1′-biadamantane compound (see US Pat. No. 3,342,880), tetraadamantane (see JP 2006-169177), 2-alkyl-2-hydroxyadamantane, 2 Curable resins having an adamantane skeleton having no aromatic ring such as alkylene adamantane and di-tert-butyl 1,3-adamantane dicarboxylate (see JP 2001-322950 A), bis (hydroxyphenyl) adamantanes and bis (Glycidyloxyphenyl) adamantane (JP-A-11) -35522 and JP-A-10-130371) can be used.

(3) Resin containing acrylate compound and allyl ester compound Bromine-containing (meth) allyl ester not containing an aromatic ring (see JP-A-2003-66201), allyl (meth) acrylate (see JP-A-5-286896) ), Allyl ester resins (see JP-A-5-286896 and JP-A-2003-66201), copolymers of acrylic acid ester and an epoxy group-containing unsaturated compound (see JP-A-2003-128725), acrylates A compound (see JP-A No. 2003-147072), an acrylic ester compound (see JP-A No. 2005-2064) or the like can be preferably used.

(4) Silicone Resin A silicone resin having a siloxane bond with Si—O—Si as the main chain can be used. As the silicone resin, a silicone resin made of a predetermined amount of polyorganosiloxane resin can be used (for example, see JP-A-6-9937).

  The thermosetting polyorganosiloxane resin is not particularly limited as long as it becomes a three-dimensional network structure with a siloxane bond skeleton by a continuous hydrolysis-dehydration condensation reaction by heating. It exhibits curability and has the property of being hard to be re-softened by heating once cured.

Such a polyorganosiloxane resin includes the following general formula (A) as a structural unit, and the shape thereof may be any of a chain, a ring, and a network.
((R ₁ ) (R ₂ ) SiO) _n (A)

In the general formula (A), “R ₁ ” and “R ₂ ” represent the same or different substituted or unsubstituted monovalent hydrocarbon groups. Specifically, as “R ₁ ” and “R ₂ ”, an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, an alkenyl group such as a vinyl group or an allyl group, an aryl group such as a phenyl group or a tolyl group Group, a cycloalkyl group such as a cyclohexyl group or a cyclooctyl group, or a group in which a hydrogen atom bonded to a carbon atom of these groups is substituted with a halogen atom, a cyano group, an amino group, or the like, such as a chloromethyl group, 3, 3, Examples include 3-trifluoropropyl group, cyanomethyl group, γ-aminopropyl group, N- (β-aminoethyl) -γ-aminopropyl group, and the like. “R ₁ ” and “R ₂ ” may be a group selected from a hydroxyl group and an alkoxy group. In the general formula (A), “n” represents an integer of 50 or more.

  The polyorganosiloxane resin is usually used after being dissolved in a hydrocarbon solvent such as toluene, xylene or petroleum solvent, or a mixture of these with a polar solvent. Moreover, you may mix | blend and use what differs in a composition in the range which mutually melt | dissolves.

  The method for producing the polyorganosiloxane resin is not particularly limited, and any known method can be used. For example, it can be obtained by hydrolysis or alcoholysis of one or a mixture of two or more organohalogenosilanes, and polyorganosiloxane resins generally contain hydrolyzable groups such as silanol groups or alkoxy groups. A group is contained in an amount of 1 to 10% by weight in terms of a silanol group.

  These reactions are generally performed in the presence of a solvent capable of melting the organohalogenosilane. It can also be obtained by a method of synthesizing a block copolymer by cohydrolyzing a linear polyorganosiloxane having a hydroxyl group, an alkoxy group or a halogen atom at the molecular chain terminal with an organotrichlorosilane. The polyorganosiloxane resin thus obtained generally contains the remaining HCl, but in the composition of the present embodiment, the storage stability is good, so that the one having 10 ppm or less, preferably 1 ppm or less is used. Is good.

(5) Epoxy resin Examples of the epoxy compound include novolak phenol type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin, bisphenol F diglycidyl ether, bisphenol A diglycidyl ether, 2,2′-bis (4 -Glycidyloxycyclohexyl) propane, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, vinylcyclohexene dioxide, 2- (3,4-epoxycyclohexyl) -5,5-spiro- (3 4-epoxycyclohexane) -1,3-dioxane, bis (3,4-epoxycyclohexyl) adipate, 1,2-cyclopropanedicarboxylic acid bisglycidyl ester, triglycidyl isocyanurate, monoallyl Triglycidyl isocyanurate, mention may be made of diallyl monoglycidyl isocyanurate and the like.

  As the curing agent, an acid anhydride curing agent, a phenol curing agent, or the like can be preferably used. Specific examples of the acid anhydride curing agent include phthalic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, 3-methyl-hexahydrophthalic anhydride, 4-methyl-hexahydrophthalic anhydride. Examples thereof include an acid, a mixture of 3-methyl-hexahydrophthalic anhydride and 4-methyl-hexahydrophthalic anhydride, tetrahydrophthalic anhydride, nadic anhydride, methyl nadic anhydride and the like. Moreover, a hardening accelerator is contained as needed. The curing accelerator is not particularly limited as long as it has good curability, is not colored, and does not impair the transparency of the thermosetting resin. For example, 2-ethyl-4-methylimidazole Imidazoles such as (2E4MZ), tertiary amines, quaternary ammonium salts, bicyclic amidines such as diazabicycloundecene and their derivatives, phosphines, phosphonium salts, etc. can be used, Two or more kinds may be mixed and used.

  Antireflection films 6 (see the enlarged portion in the upper part of FIG. 2) are formed on both the front and back surfaces of the lens body 23 made of the resin. The antireflection film 6 has a three-layer structure. A first layer 61 is formed directly on the lens body 23, and a second layer 62 and a third layer 63 are formed thereon.

The first layer 61 is a contact layer that comes into direct contact with the lens body 23. Specifically, the first layer 61 is made of SiO _x (1.5 ≦ x ≦ 1.8), which is a low refractive index material, and the composition ratio of O atoms (value of x) is within a specific range. . The first layer 61 has a thickness of 10 to 100 nm, preferably 50 to 100 nm.

The second layer 62 is a layer made of a low refractive index material having a refractive index of less than 1.7, and is preferably made of SiO ₂ . The third layer 63 is a layer made of a high refractive index material having a refractive index of 1.7 or more, preferably Ta ₂ O ₅ , a mixture of Ta ₂ O ₅ and TiO ₂ , ZrO ₂ , ZrO ₂ and TiO _2. And is composed of any mixture. The third layer 63 may be composed of TiO ₂ , Nb ₂ O ₃ , and HfO ₂ .

  In the lens unit 2, two layers of the second layer 62 and the third layer 63 are formed on the first layer 61, and layers similar to these are further formed on the second layer 62 and the third layer 63. May be laminated alternately. Further, the antireflection film 6 may be formed only on the surface of the lens body 23 and on the light incident surface (upper surface in FIG. 1).

  In general, when light is incident on a boundary surface having a different refractive index, a part of the incident light is reflected according to the refractive index ratio on both sides of the boundary surface. As the refractive index ratio of the boundary surface increases, the amount of light reflected at the boundary surface increases. For example, a thermoplastic plastic (thermoplastic resin) used as an optical component has a refractive index in the range of about 1.5 to 1.6. Therefore, when light enters from a medium such as air, 4 to 4 of the incident light. 5% will be reflected.

  This surface reflection phenomenon is not only that the amount of transmitted light is simply reduced, but if such an optical component is used as it is in a camera lens or the like, it causes a great cause of ghosts and flares. Therefore, in order to reduce this surface reflection, a thin dielectric film of the order of the wavelength of light is provided as an antireflection film on the surface of the optical component, and the reflected light is reduced by the interference effect of light in the film. Well done. Many high-performance antireflection film structures have been proposed in which several layers of two or more types of dielectric films are stacked to achieve low reflectance in a wide wavelength range.

  Moreover, in the imaging unit 1 having the above-described configuration, an aspect in which the antireflection film 6 is formed on the lens body 23 as an example of an optical element is illustrated. The lens body 23 is illustrated as an example of the optical element body. The lens unit 2 is shown as an example.

  Next, a method for manufacturing the imaging unit 1 will be described with reference to FIG.

  As shown in the upper part of FIG. 2, a lens array 27 having a plurality of lens portions 23a, a diaphragm array 26 having the same number of openings 21a as the lens portions 23a, and an opening 25a having the same number as the lens portions 23a are formed. Prepared spacer array 28 is prepared.

  The lens array 27 is obtained by injection-molding a thermosetting resin, and then forming the antireflection film 6 over the entire front and back surfaces. The aperture array 26 and the spacer array 28 are formed by mixing a thermosetting resin with carbon and coloring it black, and molding the resin by an injection molding method.

Here, the antireflection film 6 in the lens array 27 is formed as follows. First, the lens array body 27a (the lens array 27 without the antireflection film 6) is mounted in the vacuum evaporation apparatus, and the pressure in the apparatus is reduced to a predetermined pressure (for example, 2 × 10 ⁻³ Pa), The lens array body 27a is heated by a heater at the top of the vacuum evaporation apparatus until the temperature reaches a predetermined temperature (for example, 240 ° C.).

Thereafter, the first layer 61 (SiO _x film (1.5 ≦ x ≦ 1.8)) is formed on the lens array body 27a. Specifically, the SiO ₂ used as a raw material of the membrane, to form a SiO _x film on the lens array body 27a by evaporation of the SiO ₂ by an electron gun heating. SiO ₂ raw material in the film during the evaporation is in a state of being dissociated into Si and O _2, the lens array body 27a formed on the film is in a state in which oxygen is deficient, O ₂ gas into the vacuum deposition apparatus It is possible to adjust the value of x of SiO _x by replenishing. Specifically, the value of x can be controlled by the amount of O ₂ gas introduced and the film formation rate, and can be adjusted in the range of 1.3 to 2.2.

For example, when the value of x of the SiO _x film as the first layer 61 is 1.65, the pressure inside the vacuum vapor deposition apparatus before the vapor deposition is set to 2 × 10 ⁻³ Pa, and 5 × 10 ^−3. A SiOx (x = 1.65) film can be formed by evaporating at a deposition rate of 5 liters / sec while introducing O ₂ gas to a pressure of Pa.

  Thereafter, in order to form the first layer 61 on both surfaces of the lens array main body 27a, the lens array main body 27 is reversed by a reversing mechanism inside the vapor deposition apparatus, and the first layer 61 is also formed on the back surface in the same manner as described above ( The same applies to the film formation on the back surfaces of the second and third layers).

Thereafter, the second layer 62 and the third layer 63 are formed on the first layer 61 by a vacuum deposition method according to a predetermined film thickness. For example, in the case of forming a (Ta ₂ O ₅ + TiO ₂ (5%)) film as the second layer 62, OA600 manufactured by Optran Co., Ltd. is used as the evaporation source up to a pressure of 1.0 × 10 ⁻² Pa inside the vacuum evaporation apparatus. It can be realized by evaporating under the condition of 5 liters / sec while introducing O ₂ gas. For example, when forming a SiO ₂ film as the third layer 63, it is realized by evaporating under a condition of 5 liters / sec while introducing O ₂ gas up to a pressure of 1.2 × 10 ⁻² Pa inside the vacuum vapor deposition apparatus. can do. The lens array 27 can be manufactured through the above steps.

  When the lens array 27 is manufactured, the lens array 27 is arranged in the same arrangement as the lens array 23a and the lens array 23a by using an adhesive to restrict the light beam arranged above the lens having the same arrangement as the lens portion 23a. The spacer array 28 for adjusting the height arranged below the lens is joined to manufacture the lens unit array 29. Thereafter, as shown in the middle and lower parts of FIG. 2, the lens unit array 29 is individually separated for each lens part 23 a by an end mill to produce a plurality of lens units 2, and each lens unit 2 is a cylindrical part 51 of the casing 5. The imaging unit 1 is manufactured.

  After the imaging unit 1 is manufactured, when the imaging unit 1 and other electronic components are simultaneously mounted on the circuit board, a predetermined mounting position on the circuit board on which a conductive paste such as solder has been applied (potted) in advance. The imaging unit 1 is placed together with other electronic components. Thereafter, the circuit board on which the imaging unit 1 and other electronic components are placed is transferred to a reflow furnace (not shown) by a belt conveyor or the like, and the circuit board is heated at a temperature of about 230 to 270 ° C. for about 5 to 10 minutes. (Reflow processing). As a result, the conductive paste is melted and the imaging unit 1 is mounted on the circuit board together with other electronic components.

According to the above embodiment, the first layer 61 of the antireflection film 6 formed on the lens main body 23 of the lens unit 2 is made of SiO _x (1.5 ≦ x ≦ 1.8), and contains O atoms. Since the composition ratio (the value of x) is within a specific range, it is possible to suppress a decrease in the light transmittance of light incident on the imaging unit 1, and even when the antireflection film 6 is subjected to reflow processing. Generation of cracks can be suppressed (see the following examples).

(1) Preparation of sample (1.1) Preparation of samples 1 to 6 Injection using A-DCP (tricyclodecane dimethanol diacrylate monomer) and perbutyl O (polymerization initiator, one kind of peroxide ester) A plurality of 2 mm thick acrylic flat plates were produced by molding. In producing the acrylic flat plate, after injecting the resin into the mold heated to the molding temperature while keeping the cylinder at 10 ° C. by water cooling so that the resin does not harden in the cylinder, The mold was opened, and the molded product (acrylic flat plate) was collected.

Then, 5 layers of antireflection films were formed on both front and back surfaces of each acrylic flat plate by vacuum deposition. Specifically, each acrylic flat plate is mounted in a vacuum vapor deposition apparatus, the pressure in the apparatus is reduced to 2 × 10 ⁻³ Pa, and each acrylic flat plate is brought to a temperature of 240 ° C. by a heater at the top of the vacuum vapor deposition apparatus. Until heated.

Thereafter, a SiO _x film was formed directly on the surface of the acrylic flat plate as the first layer film. SiO ₂ was used as a raw material for the film, and SiO ₂ was evaporated by electron gun heating to form a SiO _x film on the acrylic flat plate. During evaporation, the raw material SiO ₂ is in a state of being separated from Si and O _2, and the film formed on the acrylic flat plate is in a state of oxygen deficiency, but O ₂ gas is introduced into the vacuum evaporation apparatus. The value of x of SiO _x was adjusted by replenishment. Specifically, the value of x can be controlled by the amount of O ₂ gas introduced and the film formation rate, and is adjusted in the range of 1.3 to 2.2 here. For example, when the value of x is 1.65, when the pressure inside the vacuum vapor deposition apparatus before vapor deposition is 2 × 10 ⁻³ Pa, O ₂ gas is introduced up to a pressure of 5 × 10 ⁻³ Pa. Then, a film of SiO _x (x = 1.65) was vapor-deposited by evaporating at a deposition rate of 5 liters / sec.
Thereafter, the acrylic flat plate was reversed by the reversing mechanism inside the vapor deposition apparatus, and the SiOx film was formed on the back surface in the same manner as described above (the same applies to the second to fifth layer films on the back surface). is there.).

Thereafter, as the second to fifth layer films, a (Ta ₂ O ₅ + 5% TiO ₂ ) film and a SiO ₂ film were alternately formed on the _first layer film by a vacuum deposition method. (Ta ₂ O ₅ + 5% TiO ₂ ) As an evaporation source, OA600 manufactured by Optran Co., Ltd. is evaporated under the condition of 5 kg / sec by introducing O ₂ gas up to a pressure of 1.0 × 10 ⁻² Pa inside the vacuum evaporation system. Was formed. On the other hand, the SiO ₂ film was formed by introducing O ₂ gas up to a pressure of 1.2 × 10 ⁻² Pa inside the vacuum evaporation apparatus and evaporating it under the condition of 5 Å / sec. Through the above steps, “Samples 1 to 6” shown in Table 1 were produced (Sample No. is distinguished by the value of x of the first layer SiO _x film). Table 1 shows the characteristics of the samples 1 to 6 such as the antireflection film and the value of x of SiO _x .

(1.2) Preparation of Samples 3A to 3D Based on Sample 3 above, the thickness of the first-layer SiOx film was varied within a range of 10 to 150 nm, and the other items of (1.1) above “Samples 3A to 3D” were produced in the same manner as described above (the alphabet after Sample No. is distinguished by the film thickness of the SiO _x film). Table 1 shows the characteristics of the samples 3A to 3D such as the antireflection film and the value of x of SiO _x . The “sample 3” and the “sample 3B” are substantially the same sample.

(2) Evaluation of samples In order to investigate the characteristics of the antireflection film of each sample 1 to 6, 3A to 3D, each sample 1 to 6, 3A to 3D is heated at 260 ° C for about 5 to 10 minutes (reflow treatment is executed) The degree of light loss and the presence or absence of cracks were examined for each of the samples 1 to 6, 3A to 3D after the heating, and the resistance to temperature was evaluated.

(2.1) Light loss The light of wavelength 405nm was permeate | transmitted with respect to each sample 1-6, 3A-3D, and the light loss at that time was calculated | required. Specifically, the transmittance (%) and the reflectance (%) are measured with the amount of incident light as 100%, and the measured value is the amount of light loss (%) = 100− (transmittance + reflectance). The value of the amount of light loss was determined by substituting into this equation, and the value was used as the evaluation target for the amount of light loss. Table 1 shows the amount of light loss and the evaluation results.

In Table 1, the criteria of “◯” and “Δ” of the “light loss” of the evaluation are as follows.
“◯”: Light loss is less than 3% “△”: Light loss is 3% or more and less than 5%

(2.2) Crack after reflow Each sample 1 to 6, 3A to 3D is visually observed with a 40-fold actual microscope, and the temperature resistance of the antireflection film is determined based on the presence or absence of cracks based on the observation result. Evaluated.

In Table 1, the criteria of “◯” and “Δ” of “crack after reflow” in the evaluation are as follows.
“○”: There is no crack in the antireflection film and there is no problem in actual use. “△”: Although there are several cracks in the antireflection film, there is no problem in actual use.

(3) Summary As shown in Table 1, in Samples 1 to 6, Samples 2 to 4 had a smaller light amount loss than Samples 1, 5, and 6, and no cracks were generated. As a result, it can be seen that it is useful in terms of light quantity loss and crack suppression to specify the value of x of SiO _x of the first layer of the antireflection film as 1.5 ≦ x ≦ 1.8. Among samples 3A to 3D, samples 3A to 3C have better results than sample 3D, and it is particularly useful that the thickness of the first anti-reflection film SiO _x is 10 to 100 nm. I understand that.

It is a disassembled perspective view which shows schematic structure of the imaging unit which concerns on preferable embodiment of this invention. 5 is a diagram for explaining a schematic manufacturing method of an imaging unit according to a preferred embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging unit 2 Lens unit 21 Aperture 21a Opening 23 Lens body 23a Lens part 25 Spacer 25a Opening 26 Aperture array 27 Lens array 27a Lens array body 28 Spacer array 3 IR cut filter 4 Sensor device 5 Casing 51 Cylindrical part 51a Light transmission Hole 53 Base portion 6 Antireflection film 61 First layer 62 Second layer 63 Third layer

Claims (6)

An optical element body composed of a thermosetting resin;
An antireflection film formed on the optical element body;
Have
An optical element in which a contact layer of the antireflection film contacting the optical element main body is SiO _x and 1.5 ≦ x ≦ 1.8. The optical element according to claim 1,
An optical element having a thickness of the contact layer of 10 to 100 nm. The optical element according to claim 1 or 2,
In addition to the contact layer, the antireflection film includes layers composed of a low refractive index material having a refractive index of less than 1.7 and layers composed of a high refractive index material having a refractive index of 1.7 or more. Having a multi-layer structure laminated to
The low refractive index material is SiO ₂ ;
An optical element in which the high refractive index material is Ta ₂ O ₅ , a mixture of Ta ₂ O ₅ and TiO ₂ , or a mixture of ZrO ₂ , ZrO ₂ and TiO ₂ . In the optical element as described in any one of Claims 1-3,
An optical element in which the thermosetting resin is an acrylic resin. The optical element according to any one of claims 1 to 4,
A diaphragm for adjusting the amount of light incident on the optical element;
A spacer for adjusting the arrangement position of the optical element;
An optical element unit. An optical element comprising: the optical element according to claim 1; a diaphragm for adjusting a light amount of light incident on the optical element; and a spacer for adjusting an arrangement position of the optical element. Unit,
A sensor device that receives light transmitted through the optical element unit;
A casing covering the optical element unit and the sensor device;
An imaging unit comprising:

Images