CN100403068C - optical low pass filter - Google Patents

Abstract

The optical low-pass filter provided by the present invention can improve moisture resistance even when it is constituted by bonding a retardation film with an adhesive. A retardation film 10 made of a polymer film as a 1/4 wavelength plate is pasted together with adhesives 4, 5 between crystal plates 2, 3 as birefringent plates, and at least the adhesive layer 4 is included. The sealing portion 20 is formed in the region of the entire outer periphery 4 a , the entire outer periphery 5 a of the adhesive layer 5 , and the entire outer periphery 10 a of the retardation film 10 . The sealing portion 20 can be composed of a physical film-forming layer, a chemical film-forming layer, an adhesive tape, and a resin composition.

Description

optical low pass filter

technical field

The present invention relates to optical low-pass filters that suppress high-pass components of spatial frequencies.

Background technique

An imaging device such as a digital still camera or a digital video camera includes an imaging element such as a CCD or a CMOS, and converts an optical image into an electronic signal with limited pixels arranged at a certain distance to capture an image. In this camera device, if the spatial frequency of the optical image is less than or equal to 1/2 of the sampling frequency determined by the arrangement pitch of the pixels, false signals such as moiré will not be generated; but if the spatial frequency of the optical image exceeds the sampling frequency 1/2 of that, false signals will be generated to degrade the picture quality.

In order to suppress the generation of spurious signals such as moiré, in conventional imaging devices, an optical filter (so-called optical low-pass filter) that suppresses high-pass components of the spatial frequency of an optical image is mounted on the front of the imaging element.

As the structure of such an optical low-pass filter, there are generally three birefringent plates, a phase plate sandwiched between two birefringent plates, and a phase plate sandwiched between two birefringent plates. The vertical attachment type of the structure of the 1/4 wavelength plate is known for its high performance.

In recent years, it has been proposed to use a polymer film formed by a uniaxial stretching method as a 1/4 wavelength plate (for example, refer to Patent Document 1). Thinning and manufacturing cost can be reduced by using a polymer film. A crystal plate is generally used as a birefringent plate.

[Patent Document 1] JP-A-7-152035

Contents of the invention

However, an optical low-pass filter formed by laminating two birefringent crystal plates and a polymer film sandwiched between them with an adhesive layer or an adhesive layer will suffer from prolonged exposure to high temperature and high humidity. After the durability test under the conditions, it was found that peeling phenomenon (hereinafter referred to as peeling phenomenon) along the outer circumference to the center occurred between the polymer film and the crystal plate, and there was a quality problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a high-quality optical low-pass filter that is less prone to peeling even under high-temperature and high-humidity conditions.

In order to achieve the above object, the present invention provides the first optical low-pass filter, which is characterized in that, the optical low-pass filter is made by pasting the phase plate of the polymer film on two double sheets through an adhesive layer or an adhesive layer. Formed between the refracting plates, a sealing portion is provided on the entire outer peripheral surface of the optical low-pass filter.

The inventors of the present invention have recognized that since the adhesive layer or the adhesive layer used for bonding the birefringent plate and the polymer film phase plate absorbs water under high temperature and high humidity conditions, the adhesion or cohesive force decreases, becoming a peeling phenomenon and found that preventing moisture from entering the interior from the outer periphery of the adhesive layer or the adhesive layer is effective for preventing the peeling phenomenon, and for this reason, the adhesive layer or the entire outer periphery of the adhesive layer It is effective to prevent the occurrence of the peeling phenomenon by providing a sealing portion blocking the inside and the outside on the outer peripheral surface of the optical low-pass filter.

The present invention provides a second optical low-pass filter, which is the same as the first optical low-pass filter, wherein the sealing portion is formed by a film-forming layer formed by a physical film-forming method or by a chemical film-forming method. The film-forming layer constitutes.

By selecting appropriate materials and film-forming methods, the film-forming layer formed by physical film-forming methods such as vapor deposition or chemical film-forming methods such as CVD can be configured as a sealing part that prevents moisture from penetrating from the outside to the inside.

The present invention provides a third optical low-pass filter as described in the first optical low-pass filter, wherein the sealing portion is formed of an adhesive tape.

By wrapping a tape using a moisture-resistant resin film or metal film on the outer peripheral surface to form a sealing portion covering the adhesive layer or the outer periphery of the adhesive layer, moisture can be blocked from the outside to effectively prevent peeling.

The present invention provides a fourth optical low-pass filter as described in the first optical low-pass filter, wherein the sealing portion is made of a resin composition.

For example, the peeling phenomenon can be effectively prevented by covering the adhesive layer or the entire outer periphery of the adhesive layer with a resin composition capable of forming an adhesive or a coating film to form a seal portion that blocks moisture from the outside.

The present invention provides a fifth optical low-pass filter, which is the same as the first optical low-pass filter, characterized in that an infrared absorption filter plate is attached to the two birefringent sheets through an adhesive layer or an adhesive layer. On the light incident side of the birefringent plate located on the light incident side of the plate, the sealing part covers the entire outer peripheral surface of the infrared absorption filter plate and the adhesive layer or adhesive layer.

It is empirically believed that the infrared absorbing filter board is easy to absorb moisture, which is regarded as an important reason for the peeling phenomenon. And it has been recognized that the adhesive layer or adhesive layer used for bonding the birefringent plate and the infrared absorbing filter plate absorbs moisture under high-temperature and high-humidity conditions to reduce the adhesion or cohesive force and become the cause of the peeling phenomenon. Therefore, on the outer peripheral surface of the optical low-pass filter including the infrared absorbing filter plate and the adhesive layer or the entire outer periphery of the adhesive layer, the peeling phenomenon can be effectively prevented by blocking moisture from the outside through the sealing portion.

The present invention provides a sixth optical low-pass filter, which is the same as the first optical low-pass filter, wherein at least a part of the outer periphery of the phase plate is located on at least one of the two birefringent plates A step or a depression is formed inside the outer periphery of the birefringent plate, and the sealing portion is formed at the step or depression.

The thick sealing portion can be easily formed by using the step or the depression, and the adhesive layer or the outer periphery of the adhesive layer can be accurately blocked from the outside.

The present invention provides a seventh optical low-pass filter, which is characterized in that the optical low-pass filter is formed by attaching a phase plate of a polymer film between two birefringent plates through an adhesive layer or an adhesive layer. , wherein the entire outer peripheral surface of the formed optical low-pass filter was treated with a water-repellent treatment agent.

By treating the exposed adhesive layer or the outer periphery of the adhesive layer with a water repellent treatment agent, the adhesive force between the adhesive layer or the adhesive layer and the birefringent plate and the polymer film phase plate can be improved , and make it difficult for moisture to penetrate from the outer periphery of the adhesive layer or adhesive layer to the inside, thereby preventing peeling.

The present invention provides an eighth optical low-pass filter as described in the seventh optical low-pass filter, wherein the water-repellent treatment agent is a silane coupling agent.

The silane coupling agent can improve the adhesive force between the adhesive layer or adhesive layer and the birefringent plate and the phase plate, even if the adhesive layer or adhesive layer absorbs moisture to a certain extent, it can effectively prevent peeling .

Description of drawings

FIG. 1( a ) is a plan view of the optical low-pass filter 1 in the first embodiment, and FIG. 1( b ) is a cross-sectional view of the optical low-pass filter 1 .

2 is a cross-sectional view schematically showing another example of the optical low-pass filter of the first embodiment.

3 is a cross-sectional view schematically showing a schematic configuration of an optical low-pass filter according to a second embodiment.

4( a ) is a plan view of the optical low-pass filter 1 in Example 1 of the third embodiment, and FIG. 4( b ) is a cross-sectional view of the optical low-pass filter 1 .

5( a ) is a plan view of the optical low-pass filter 1 in Example 2 of the third embodiment, and FIG. 5( b ) is a cross-sectional view of the optical low-pass filter 1 .

6( a ) is a plan view of the optical low-pass filter 1 in Example 3 of the third embodiment, and (b) is a cross-sectional view of the optical low-pass filter 1 .

FIG. 7 is a cross-sectional view of the optical low-pass filter 1 and the solid-state imaging device 130 in the imaging device.

Symbol Description

1 optical low pass filter

2, 3 crystal plate

2a, 2b, 2c, 2d Concavity (gap)

3a, 3b, 3c, 3d step slope

4, 5, 6 Adhesive layers

7 Infrared absorption filter board

4a, 5a, 10a outer periphery

10 phase difference film

20 sealing part

21 waterproof treatment department

100 cameras

110, 111 anti-reflection film

120 infrared absorption filter

130 solid-state imaging elements

131 External connection wiring

132 bonding wire

140 packs

140a opening

A arrow

Detailed ways

Embodiments of the optical low-pass filter of the present invention will be described below, but the present invention is not limited to the following embodiments.

[the first embodiment]

FIG. 1( a ) is a plan view of the optical low-pass filter 1 in the first embodiment, and FIG. 1( b ) is a cross-sectional view of the optical low-pass filter 1 .

A retardation film 10 made of a polymer film as a 1/4 wavelength plate is pasted together with adhesive layers 4, 5 between the crystal plates 2, 3 as birefringent plates, and a sealing portion 20 is provided, so that at least The entire area including the outer periphery 4 a of the adhesive layer 4 , the outer periphery 5 a of the adhesive layer 5 , and the outer periphery 10 a of the retardation film 10 are covered.

The crystal plate 2 and the crystal plate 3 as birefringent plates may be crystal plates having birefringence, and may be lithium niobate (LiNbO ₃ ) or the like in addition to crystal. It may be that only crystal plates are used for both plates, or a combination of crystal and lithium niobate or a combination of birefringent plates made of other materials may be used. Birefringence refers to a phenomenon in which incident light is separated into two types of light rays, ordinary rays and extraordinary rays whose vibration directions are perpendicular to each other. Birefringent crystals other than crystal and lithium niobate include Chilean saltpeter, ferrocalcite, rutile, KPD (KH ₂ PO ₄ ), APD (NH ₄ H ₂ PO ₄ ), and the like.

The retardation film 10 is a transparent plate introduced into the optical system in order to introduce a retardation, and is a polymer film capable of passing linearly polarized light components vibrating in mutually perpendicular principal axis directions, and introducing a necessary retardation into these two components, Retardation films include 1/2 wavelength plate and 1/4 wavelength plate, etc. In the optical low-pass filter 1 , a combination of a 1/2 wavelength plate and a 1/4 wavelength plate or a 1/4 wavelength plate alone is used as the retardation film 10 .

In the optical low-pass filter 1 of the present invention, it is preferable to use, as the 1/4 wavelength plate, a polymer film having wavelength dispersion characteristics such that the phase difference increases as the wavelength of incident light increases. A polymer film functioning as such a 1/4 wavelength plate is commercially available. The polymer film sold is made of uniaxially stretched polycarbonate with a glass transition temperature greater than or equal to 200°C.

By making the phase plate into the polymer film 10, not only can the optical low-pass filter 1 be formed thinly, but also have the wavelength dispersion characteristic that the phase difference increases as the wavelength of the incident light increases, and it is possible to cover a large wavelength range. The polarization state of the incident light is converted from linearly polarized light to circularly polarized light. Therefore, it is possible to constitute a high-performance optical low-pass filter 1 that functions as a 1/4 wavelength plate with respect to incident light having a wide wavelength range.

In addition, the optical low-pass filter 1 shown in the sectional view of FIG. 2 has the same basic structure as the optical low-pass filter 1 shown in FIG. Plate 7 is sandwiched between birefringent plate 2 and retardation film 10 or between birefringent plate 3 and retardation film 10 . The infrared absorption filter plate 7 is a filter that absorbs infrared components added to the glass substrate, and is used to block infrared components and prevent solid-state imaging elements that are also sensitive to infrared rays from being exposed to infrared rays. Preferably, the arrangement structure of the infrared absorption filter plate 7 is such that the infrared absorption filter plate 7 is bonded to the birefringent plate 2 or the birefringent plate on the light incident side among the two birefringent plates 2 and 3 through an adhesive layer or an adhesive layer. 3 and the polymer film 10.

It is empirically believed that the infrared absorbing filter plate 7 tends to absorb moisture, which is considered to be an important cause of the peeling phenomenon. Therefore, as shown in FIG. 2 , it is preferable that the sealing portion 20 also covers the entire outer peripheral surface of the infrared absorption filter plate 7 so as to block moisture from the outside.

The sealing portion 20 may be formed of a film-forming layer formed by a physical film-forming method, a film-forming layer formed by a chemical film-forming method, an adhesive tape, or a resin composition. The physical film-forming method can be a vacuum evaporation method, an ion-assisted evaporation method, an ion plating method, a sputtering method, and the like. The vacuum evaporation method is a method of heating and evaporating thin film materials under high vacuum conditions and depositing these evaporated particles on the substrate to form a thin film. The ion-assisted evaporation method is to ionize the evaporated particles and make them adhere to the substrate after being accelerated by an electric field. It is divided into APS (Advanced Plasma Source), EBEP (Electron Beam Excited Plasma) method, RF (Radio Frequency) direct substrate The Indo method (the method of reactive vacuum evaporation in the state of generating high-frequency gas plasma in the film-forming chamber) and other methods. The sputtering method is a method in which ions accelerated by an electric field collide with the thin film material, and the thin film material is evaporated by knocking the sputtering of the thin film material, and the evaporated particles are deposited on the substrate to form a thin film. As the chemical film forming method, CVD (Chemical Vapor Deposition), electroless plating, or the like can be used.

Materials that can be deposited by physical or chemical deposition methods include metals such as aluminum, nickel, copper, chromium, silver, and gold, and carbides, nitrides, oxides, and borides of metals. The thickness of the film is not particularly limited, as long as it can prevent moisture from penetrating inside, and it is generally about 50 nm to 1 μm.

For example, when forming a film using silicon oxide as a metal oxide by a vacuum deposition method, it can be performed as follows. Several optical low-pass filters are stacked, and a deposited layer formed by vapor deposition is provided to prevent scratches on the surface and to prevent adsorption of impurities. Scratches or adsorption of impurities will affect the moisture-proof effect. For example, a SiO ₂ layer is deposited on the side of a stacked optical low-pass filter in a vacuum evaporation device. The film thickness of SiO ₂ is preferably about 50 nm to 1 μm. If the film thickness is too thick, productivity will be poor, and if the film thickness is too thin, sufficient barrier effect will not be obtained. Evaporation can be performed on each side, or a structure capable of rotating the overlapped optical low-pass filter can be installed in the evaporation device, and evaporation can be performed on each side continuously or simultaneously.

When forming the sealing portion 20 with an adhesive tape, a resin film such as PEN (polyethylene naphthalate) having excellent gas barrier properties, or a metal foil is used as a base material of the adhesive tape, and one side thereof is treated to make a silicone adhesive. To enable adhesion, apply a silicone adhesive on the surface, and then wrap the outer peripheral surface of the optical low-pass filter for at least one turn with a tape that imparts water-impermeability to the base material and the adhesive.

For a specific method of wrapping the tape, for example, apply a silicone adhesive (10 μm) on one side of the PEN film, form a tape, and then wrap it around the side of the optical low-pass filter for at least one turn. The winding method is to fix the optical low-pass filter on a rotary table equipped with a vacuum chuck, and stick one end of the adhesive tape to the side of the optical low-pass filter. Winding can be performed by cutting the tape after rotating the turntable at least one turn. As a result, the adhesive tape that prevents moisture absorption can be wound evenly and without gaps.

The resin composition constituting the sealing portion 20 may, for example, be an adhesive or a sealing resin usable as a sealing material. The adhesives may, for example, be epoxy adhesives, acrylic adhesives, hot melt adhesives, or silicone adhesives excellent in moisture resistance. The resin for sealing can be exemplified by materials that are not easily permeable to water, such as epoxy resin, silicone resin, polypropylene, methacrylic resin, polyethylene terephthalate, polyethylene terephthalate, etc., used for sealing semiconductors. Butylene glycol diformate, vinyl chloride resin, vinylidene chloride resin, polyamide, fluorine-containing resin, etc.

According to the type of adhesive, the adhesive is applied to the outer peripheral surface of the optical low-pass filter and cured according to the prescribed coating methods such as brushing, molding, spraying, scraper, and roller. The method is to form the sealing portion 20 . The epoxy-based adhesive may, for example, be CS2340-5 (trade name, manufactured by Cemedine Co., Ltd.) of a two-component mixing type. Furthermore, the acrylic UV-curable adhesive can be exemplified by OPTOKLEB UT20 manufactured by Adell Co., Ltd. which is excellent in water and moisture resistance. After the UT20 is coated on the peripheral surface of the optical low-pass filter, it is cured after being irradiated with ultraviolet rays under nitrogen gas.

When forming the sealing portion 20 with a sealing resin, the resin can be diluted with an appropriate solvent, and the solution can be applied to the outer peripheral surface of the optical low-pass filter with a brush, and then dried in an oven at 100°C for 1 hour to evaporate the solvent. , forming the sealing portion 20 . In addition to the brush coating method, the coating method may also be a die-press method, a spray method, a doctor blade method, and a roller method.

The thickness of the sealing portion 20 formed of the resin composition is not particularly limited, but is preferably in the range of 0.001 μm to 50 μm. If the thickness is too thin, a sufficient moisture blocking effect cannot be obtained, and if the thickness is too thick, productivity will be poor.

In the optical low-pass filter of the first embodiment, in the optical low-pass filter 1 including at least the entire outer periphery 4a of the adhesive 4, the entire outer periphery 5a of the adhesive 5, and the retardation film 10 The outer peripheral area of the entire outer periphery 10a forms a sealing portion 20, which can prevent the adhesive 4, 5 or the retardation film 10 and the infrared absorption filter plate from absorbing moisture, and prevent the crystal plates 2, 3, the retardation film 10 from contacting the adhesive. Peeling phenomenon between layers 4 and 5.

[the second embodiment]

3 is a cross-sectional view schematically showing a schematic configuration of an optical low-pass filter according to a second embodiment. The basic structure of the optical low-pass filter is basically the same as in FIG. 2 , so the same symbols are used for the same parts and their descriptions are omitted. The difference from the optical low-pass filter shown in FIG. 2 is that a waterproof treatment part 21 is provided instead of the sealing part 20, and the waterproof treatment part 21 is bonded in the outer peripheral surface of the optical low-pass filter with a waterproof treatment agent. The exposed parts of the outer peripheries of the adhesive layers 4, 5, 6 are formed to cover the entire outer peripheries of the adhesive layers 4, 5, 6 and the phase difference film 10, and the entire outer peripheral surface of the infrared absorption filter plate 7. The waterproof treatment part 21 has covered the entire outer periphery of the adhesive layer 4, 5, 6 and the phase difference film 10 and the entire outer peripheral surface of the infrared absorption filter plate 7, thus these adhesive layers 4, 5, 6 and the phase difference film The entire outer periphery of the differential film 10 and the entire outer peripheral surface of the infrared absorbing filter plate 7 are subjected to waterproof treatment.

By treating the outer peripheries of the adhesive layers 4, 5, 6 exposed to the outside, the outer peripheries of the phase difference film 10, and the outer peripheries of the infrared absorption filter plate 7 with a water repellant, the birefringent plates 2, 3 and the phase can be improved. The adhesion of the difference film 10 and the infrared absorption filter plate 7 to the adhesive layer 4, 5, 6, and the water resistance has been obtained due to the waterproof treatment, making it difficult for moisture to escape from the adhesive layer 4, 5, 6 or the retardation film 10 Or the outer peripheral surface of the infrared absorption filter plate 7 penetrates into the inside, which can effectively prevent the peeling phenomenon.

The water repellent agent may, for example, be a silane coupling agent, a fluorine-containing silane compound, a fluorine-containing resin, or a fluorine-containing surfactant.

The silane coupling agent referred to here refers to a carbon functional (carbofunctional) silane having an organic group having a substituent bonding with an organic material and a hydrolyzing group reacting with an inorganic material in the same molecule. Specifically, it is a compound represented by R ¹ SiX ¹ _m X ² _(3-m) , wherein R ¹ represents an organic group, X ¹ represents -OR ² , -Cl, X ² represents -R ² , R ² represents an alkyl group having 1 to 4 carbon atoms, and m is 2 or 3.

Silane coupling agent and crystal plate 2,3, the hydroxyl group on the surface of adhesive 4,5,6 and retardation film 10 carries out chemical adsorption, improves adhesive and retardation film 10 and with crystal plate 2,3 The bonding strength between them is also waterproof, so even if the adhesives 4, 5, and 6 have some moisture absorption, they can prevent peeling. Among these silane coupling agents, especially the fluorine-containing silane coupling agent in which R ¹ is perfluoroalkyl C _n F _2n+1 or perfluoroalkyl ether C _p F _2p+1O (C _p F _2p O) _r In the case of a combination agent, since the surface free energy of the solid surface is lower than 25mJ/m ² , the affinity with polar materials becomes smaller, and the water repellency can be further improved, so it is suitable for use.

Specifically, examples of the silane coupling agent include CF ₃ -CH ₂ CH ₂ -Si(OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₃ -CH ₂ CH ₂ -Si(OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₅ -CH ₂ CH ₂ -Si(OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₅ -CH ₂ CH ₂ -Si(OC ₂ H ₅ ) ₃ , CF ₃ (CF ₂ ) ₇ -CH ₂ CH ₂ -Si(OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₁₁ -CH ₂ CH ₂ -Si(OC ₂ H ₅ ) ₃ , CF ₃ (CF ₂ ) ₃ -CH ₂ CH ₂ -Si(CH ₃ ) (OCH ₃ ) ₂ , CF ₃ (CF ₂ ) ₇ -CH ₂ CH ₂ -Si(CH ₃ )(OCH ₃ ) ₂ , CF ₃ (CF ₂ ) ₈ -CH ₂ CH ₂ -Si(CH ₃ )(OC ₂ H ₅ ) ₂ , CF ₃ (CF ₂ ) ₈ -CH ₂ CH ₂ -Si(C ₂ H ₅ )(OC ₂ H ₅ ) ₂ , CF ₃ O(CF ₂ O) ₆ -CH ₂ CH ₂ -Si (OC ₂ H ₅ ) ₃ , CF ₃ O(C ₃ F ₆ O) ₄ -CH ₂ CH ₂ -Si(OCH ₃ ) ₃ , CF ₃ O(C ₃ F ₆ O) ₂ (CF ₂ O) ₃ - CH ₂ CH ₂ -Si(OCH ₃ ) ₃ , CF ₃ O(C ₃ F ₆ O) ₈ -CH ₂ CH ₂ -Si(OCH ₃ ) ₃ , CF ₃ O(C ₄ F ₉ O) ₅ -CH ₂ CH ₂ -Si(OCH ₃ ) ₃ , CF ₃ O(C ₄ F ₉ O) ₅ -CH ₂ CH ₂ -Si(CH ₃ )(OC ₂ H ₅ ) ₂ , CF ₃ O(C ₃ F ₆ O) ₄ -CH ₂ CH ₂ -Si(C ₂ H ₅ )(OCH ₃ ) ₂ and so on. But it is not limited to these structures.

The coating method of the silane coupling agent may, for example, be a brush coating method, a press method, a spray method, a doctor blade method, a roller method or the like. The coating film thickness is not particularly limited, but is preferably in the range of 0.001 μm to 50 μm. If the thickness is too thin, sufficient waterproofness cannot be obtained, and if the thickness is too thick, productivity will be poor.

As an example, the optical low-pass filter was subjected to water-repellent treatment using a silane coupling agent. For example, Shin-Etsu Chemical Co., Ltd. product named KBM603 was used as a silane coupling agent, and diluted with ethanol to a concentration of 3 wt%. This solution was applied to the outer periphery of the optical low-pass filter with a brush, and dried in an oven at 100°C for 1 hour. Thereby, the water-repellent treatment agent for preventing the adhesive from absorbing moisture can be provided uniformly and without gaps. In addition, the optical low-pass filter can be coated one by one, but when mass production is required, it is preferable to stack several sheets together and apply the above-mentioned method at the same time to improve efficiency.

The fluorine-containing silane compound may, for example, be a compound represented by the following general formula (1).

[Compound 1]

R _f in the general formula (1) is a linear or branched perfluoroalkyl group having 1 to 16 carbon atoms, preferably CF ₃ -, C ₂ F ₅ - and C ₃ F ₇ -. X is iodine or hydrogen, Y is hydrogen or lower alkyl, and Z is fluorine or trifluoromethyl. R ¹ is a group capable of hydrolysis, preferably halogen, -OR ³ , -OCOR ³ , -OC(R ³ )=C(R ⁴ ) ₂ , -ON=C(R ³ ) ₂ , -ON=CR ⁵ . More preferred are chlorine, -OCH ₃ , -OC ₂ H ₅ . Here, R ³ is an aliphatic hydrocarbon group or an aromatic hydrocarbon group, R ⁴ is hydrogen or a lower aliphatic hydrocarbon group, and R ⁵ is a divalent aliphatic hydrocarbon group having 3 to 6 carbon atoms. R ² is hydrogen or an inactive monovalent organic group, preferably a monovalent hydrocarbon group having 1 to 4 carbon atoms. a, b, c, and d are integers of 0-200, preferably 1-50, and e is 0 or 1. m and n are integers of 0-2, preferably 0. p is an integer greater than or equal to 1, preferably an integer of 1-10. And, the molecular weight is 5×10 ² to 1×10 ⁵ , but preferably it is 5×10 ² to 1×10 ⁴ .

The fluorine-containing silane compound represented by the general formula (1) is used to form an antifouling layer of spectacle lenses, and has very excellent water and oil repellency. As commercial products of fluorine-containing silane compounds, OPTOOL DSX (trade name) manufactured by Daikin Industries, Ltd. and KY-130 (trade name) manufactured by Shin-Etsu Chemical Co., Ltd. may be mentioned.

For the fluorine-containing resin, oligomers or polymers containing fluorine atoms in the molecule can be used, specifically, polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer, hexafluoropropylene-tetrafluoroethylene copolymer, polytetrafluoroethylene Vinylidene fluoride (PVdF), poly(pentadecafluoroheptylethyl methacrylate) (PPFMA), poly(perfluorooctylethyl acrylate) and other ethylene, ester and acrylic acid with long-chain perfluoroalkyl structure Ester, methacrylate, vinyl, urethane, silicone, imide, carbonate polymers. Fluorine-containing resins suitable for water repellent treatment include, for example, DS-3300TH series sold by HERBES Corporation under the trade name DURASURF. The DS-3300TH series, whose trade name is DURASURF, is a fluorine-containing coating that dissolves a fluorine-containing resin in a non-flammable fluorine-containing solvent to form a solution. It can be used for water and oil repellent treatment agents, coatings that reduce reflection, and imparting antifouling properties.

As for the coating method of the fluorine-containing silane compound and the fluorine-containing resin, it is possible to adopt a method of dissolving in an organic solvent, coating the outer peripheral surface of the optical low-pass filter, and then drying to remove the solvent. As the coating method, a dipping method, a spin coating method, a spray method, a flow coating method, a doctor blade method, a roll coating, a gravure coating, a curtain coating, and the like can be used. The organic solvent can be exemplified by perfluorohexane, perfluorocyclobutane, perfluorooctane, perfluorodecane, perfluoromethylcyclohexane, perfluoro-1,3-bis Methylcyclohexane, perfluoro-4-methoxybutane, perfluoro-4-ethoxybutane, m-xylene hexafluoride, and the like. Furthermore, perfluoroether oil and chlorotrifluoroethylene oligomer oil can also be used. In addition, Freon 225 (a mixture of CF ₃ CF ₂ CHCl ₂ and CCIF ₂ CF ₂ CHClF) can also be exemplified. Among these organic solvents, one type may be used alone or at least two types may be used in combination.

Preferably, the concentration when diluted with an organic solvent is 0.03 wt% to 1 wt%. If the concentration is too low, sometimes it will be difficult to form a water-repellent treatment layer 21 with sufficient thickness, and sufficient waterproof effect cannot be obtained; Not worth it.

The thickness of the waterproof treatment layer 21 composed of fluorine-containing silane compound and fluorine-containing resin is not particularly limited, and is generally 0.001 μm to 0.5 μm, preferably 0.001 μm to 0.03 μm. If the film thickness of the water-repellent treatment layer is too thin, the waterproof effect will be insufficient, and if the film thickness is too thick, the surface will be sticky, so it is not preferable.

As an example, a water-repellent treatment layer was formed on the outer peripheral surface of the optical low-pass filter using DS-3300TH series under the trade name DURASURF. The fluorine-containing resin was diluted with a fluorine-containing solvent to have a solid content concentration of 0.2%, and this solution was used as a coating liquid. The outer periphery of the optical low-pass filter was painted with a brush and dried in an oven at 20° C. for 1 hour.

The resulting optical low-pass filter with the water-repellent treatment layer and the optical low-pass filter without the water-repellent treatment layer were exposed for 1000 hours at 60°C and 90%RH, and then the optical low-pass filter was observed using a microscope. Peeling state on the outer peripheral portion. As a result, it was observed that on the outer peripheral portion of the optical low-pass filter on which the water repellent treatment layer was not formed, curved water-trough-shaped peelings were formed from the outer peripheral edge to the center. On the other hand, no peeling was observed on the outer peripheral portion of the optical low-pass filter on which the water-repellent treatment layer was formed.

In addition, the surfactant is a compound represented by R ¹ Y ¹ , where Y ¹ is a hydrophilic polar group, -OH, -(CH ₂ CH ₂ O) _n H, -COOH, -COOK, -COONa, -CONH ₂ , -SO ₃ H, -SO ₃ Na, -OSO ₃ H, -OSO ₃ Na, -PO ₃ H ₂ , -PO ₃ Na ₂ , -PO ₃ K ₂ , -NO ₂ , -NH ₂ , -NH ₃ Cl (ammonium salt), -NH ₃ Br (ammonium salt), ≡NHCl (pyridinium salt), ≡NHBr (pyridinium salt), etc.

Concrete examples of surfactants include CF ₃ -CH ₂ CH ₂ -COONa, CF ₃ (CF ₂ ) ₃ -CH ₂ CH ₂ -COONa, CF ₃ (CF ₂ ) ₃ -CH ₂ CH ₂ -NH ₃ Br, CF ₃ (CF ₂ ) ₅ -CH ₂ CH ₂ -NH ₃ Br, CF ₃ (CF ₂ ) ₇ -CH ₂ CH ₂ -NH ₃ Br, CF ₃ (CF ₂ ) ₇ -CH ₂ CH ₂ -OSO ₃ Na , CF ₃ (CF ₂ ) ₁₁ -CH ₂ CH ₂ -NH ₃ Br, CF ₃ (CF ₂ ) ₈ -CH ₂ CH ₂ -OSO ₃ Na, CF ₃ O(CF ₂ O) ₆ -CH ₂ CH ₂ - OSO ₃ Na, CF ₃ O(C ₃ F ₆ O) ₂ (CF ₂ O) ₃ -CH ₂ CH ₂ -OSO ₃ Na, CF ₃ O(C ₃ F ₆ O) ₄ -CH ₂ CH ₂ -OSO ₃ Na, CF ₃ O(C ₄ F ₉ O) ₅ -CH ₂ CH ₂ -OSO ₃ Na, CF ₃ O(C ₃ F ₆ O) ₈ -CH ₂ CH ₂ -OSO ₃ Na, etc. But it is not limited to these structures.

[the third embodiment]

In the optical low-pass filter according to the third embodiment, at least a part of the outer periphery of the phase plate is located inside the outer periphery of at least one birefringent plate among the two birefringent plates, so that a step or a depression is formed. The step or depression forms the seal.

4( a ) is a plan view of the optical low-pass filter 1 in Example 1 of the third embodiment, and FIG. 4( b ) is a cross-sectional view of the optical low-pass filter 1 .

The crystal plate 2 serving as a birefringent plate is smaller than the crystal plate 3 serving as a birefringent plate. When the retardation film 10 made of a polymer film as a 1/4 wavelength plate is bonded together with the adhesives 4, 5, the crystal plate 2 is pasted on the inside of the crystal plate 3 so that the presence of the crystal plate 2 Steps 3a, 3b, 3c, 3d formed by different sizes from the crystal plate 3. Steps 3a, 3b, 3c, 3d may not be equal respectively. The above-mentioned sealing portion 20 is formed on the step slopes 3 a , 3 b , 3 c , and 3 d as step portions where the outer peripheral portions of the two crystal plates do not match. The size relationship between the crystal plate 2 and the crystal plate 3 can also be reversed.

In Example 1 of this 3rd embodiment, because the sizes of the two crystal plates 2 and 3 are different, step slopes 3a, 3b, 3c, and 3d are formed between the respective outer peripheral surfaces of the two crystal plates 2 and 3. For the non-uniform step portion of the outer periphery of the crystal plate, the step 3a, 3b, 3c, 3d can be used to simply form the sealing portion 20 with a certain thickness, which also has more stable moisture resistance and can prevent peeling.

Next, Example 2 of the third embodiment will be described, and only matters different from Example 1 will be described, and matters not described will be the same as those of Example 1. FIG.

5( a ) is a plan view of the optical low-pass filter 1 in Embodiment 2, and FIG. 5( b ) is a cross-sectional view of the optical low-pass filter 1 .

The crystal plates 2 and 3 as birefringent plates have the same size. After the crystal plate 2 and the crystal plate 3 are staggered along the direction of the oblique line, the retardation film 10 made of a polymer film as a 1/4 wavelength plate is bonded together with the adhesives 4 and 5. Steps 3a, 3b, 3c, 3d are formed between the crystal plate 2 and the crystal plate 3 . The step slopes 3a, 3d and the step slopes 3b, 3c are step slopes in the same direction. The above-mentioned sealing portion 20 is formed on the step slopes 3 a , 3 b , 3 c , and 3 d as step portions where the outer peripheral portions of the two crystal plates do not coincide. For the method of staggering the positions of the crystal plates 2 and 3, both relative rotation and oblique direction staggering can be performed, and rotation and oblique direction movement can also be performed simultaneously.

In Example 2 of this third embodiment, since the crystal plate 2 and the crystal plate 3 have the same size, they can be manufactured without distinction in the manufacturing process. 2 and the position of crystal plate 3 just can have step 3a, 3b, 3c, 3d, utilize this step 3a, 3b, 3c, 3d to be able to simply form the sealing part 20 that has certain thickness, also have more stable moisture-proof property , can prevent peeling phenomenon.

Next, Example 3 of the third embodiment will be described, and only points that are different from Example 1 will be described, and items that are not described are the same as those in Example 1. FIG.

6( a ) is a plan view of the optical low-pass filter 1 in Embodiment 3, and FIG. 6( b ) is a cross-sectional view of the optical low-pass filter 1 .

The crystal plates 2 and 3 as birefringent plates have the same size. The adhesive 4,5 and the retardation film 10 made of a polymer film as a 1/4 wavelength plate are smaller than the crystal plates 2,3, and the entire outer periphery of the retardation film 10 is located in the two crystal plates 2,3 The inner side of the outer periphery of the phase difference film 10 forms depressions (gap) 2a, 2b, 2c, 2d between the outer periphery of the phase difference film 10 and the outer periphery of the two crystal plates 2, 3, forming and filling the depressions 2a, 2b, 2c, 2d The above-mentioned sealing part 20. The depressions 2a, 2b, 2c, and 2d can be different from each other, or can be relatively inclined.

In Example 3 of this third embodiment, since the crystal plate 2 and the crystal plate 3 have the same size, they can be manufactured without distinction in the manufacturing process. Smaller than crystal plate 2 or crystal plate 3, the outer periphery of retardation film 10 is positioned at the inner side of the outer periphery of crystal plate 2 or crystal plate 3, utilizes the outer periphery of retardation film 10 and the outer periphery of crystal plate 2,3 The recesses 2a, 2b, 2c, and 2d between them can simply form a sealing portion 20 with a certain thickness, and also have more stable moisture resistance, and can prevent peeling.

[the fourth embodiment]

Embodiments in which the optical low-pass filter of the present invention is applied to an imaging device will be described below. FIG. 7 is a cross-sectional view of the optical low-pass filter 1 and the solid-state imaging device 130 in the imaging device.

In the imaging device 100 , the light passing through the imaging lens (not shown in the figure) enters from the direction of the arrow A and passes through the anti-reflection film 110 and the infrared absorption filter 120 . Among the light rays passing through the infrared absorption filter 120 , components of high spatial frequency are suppressed by the optical low-pass filter 1 , and the light rays emitted through the antireflection film 111 reach the solid-state imaging device 130 . The light received by the solid-state imaging device 130 is converted into an electronic signal and transmitted to other connected circuits.

This optical low-pass filter 1 has a crystal plate 2 , adhesives 4 and 5 , a retardation film 10 , and a crystal plate 3 , and is integrated with an antireflection film 110 and an infrared absorption filter 120 .

The solid-state imaging device 130 has a structure in which it is composed of a large number of pixels, and the pixels are accurately arranged at a constant distance. The solid-state imaging device 130 is composed of, for example, a CCD (Charge Coupled Device) or a CMOS (Complementary MOS), and has a function of converting received light into an electronic signal.

The solid-state imaging device 130 is enclosed in a concave package 140 as a fixing member. The package 140 has at least an opening 140a capable of housing the optical low-pass filter 1 . Furthermore, external connection wiring 131 connecting the inside and outside of package 140 is provided through the side wall of package 140 , and solid-state imaging device 130 and external connection wiring 131 are electrically connected by bonding wire 132 .

The opening portion 140a as a fixing member and at least the optical low-pass filter 1 are bonded together by a sealing portion 20 made of a resin composition such as fluorine-containing resin, epoxy resin, or acrylic resin. In this imaging device 100 , the optical low-pass filter 1 also serves as a dustproof glass for a package that seals the solid-state imaging device 130 . The sealing part 20 is coated on at least a region including the adhesive layers 4 , 5 and the retardation film 10 . Therefore, in this imaging device 100, the sealing portion 20 covers the entire outer periphery of the adhesive layer 4, 5 and the phase difference film 10 to prevent the penetration of moisture, and also serves as an adhesive material for fixing the optical low-pass filter 1. kick in.

In this imaging device 100, the optical low-pass filter 1 is fixed on the opening 140a as a fixing material through the sealing portion 20 made of an adhesive or a resin composition, and at the same time, the phase difference of the optical low-pass filter 1 can be improved. Moisture resistance of film 10.

In addition, in the above description, an adhesive layer is used for bonding the respective parts constituting the optical low-pass filter, but the same effect can be obtained by using an adhesive layer.

Industrial availability

The optical low-pass filter of the present invention can suppress the high-pass component of the spatial frequency by being installed in front of the imaging device, and thus it can be used in the field of improving the image quality output from the imaging device.

Claims (5)

1. optical low-pass filter, described optical low-pass filter is by adhering agent layer or adhesive phase the phase-plate of polymeric membrane to be attached between 2 birefringent plates to form, it is characterized by, at least a portion of the neighboring of described phase-plate is arranged in the disconnected slope of inboard and formation or the depression of the neighboring of at least 1 birefringent plate of described 2 birefringent plates, is provided with sealing on described disconnected slope or recess.

2. optical low-pass filter as claimed in claim 1 is characterized by, and described sealing is made of film forming layer that forms according to the physical film deposition method or the film forming layer that forms according to the chemical membrane method.

3. optical low-pass filter as claimed in claim 1 is characterized by, and described sealing is made of adhesive tape.

4. optical low-pass filter as claimed in claim 1 is characterized by, and described sealing is made of resin combination.

5. optical low-pass filter as claimed in claim 1, it is characterized by, by adhering agent layer or adhesive phase the infrared ray absorbing filter band is attached to the light light incident side that is positioned at the birefringent plate of light light incident side in described 2 birefringent plates, described sealing is coating whole outer peripheral faces of described infrared ray absorbing filter band and described adhering agent layer or adhesive phase.

Images